Field of the Invention

This invention relates to fireplaces and associated fireback installations of the type used for open or closed fires, fires with closed glass fronts or traditional non-refractory fireplaces in domestic or residential environments. More particularly, the invention relates to improvements in the design and efficiency of such fireplaces. Background to the Invention

Historically, firebacks were simple slabs of cast iron, which were positioned in front of the masonry back wall of the fireplace to protect the masonry back wall from the intense heat generated by the fire. After the 19th century, the cast iron fireback became unfashionable, as the use of firebrick and tiles in fireplace construction became increasingly popular. Unfortunately, fireplaces constructed from firebrick, concrete, stone or indeed tiles are quite vulnerable to heat damage and as a result are prone to cracking. Such damage demands expensive repairs. Further damage may arise from the accumulation of soot in the cracks or indeed between any protective tiles which eventually leads to deterioration and decay of the fireplace. Furthermore, these materials are not efficient heat conductors. These problems have been lessened somewhat by the return to the use of firebacks which are constructed from a suitable refractory material, such as cast iron or other conductive metals. Thus there is seen a return to use of refractive material firebacks in open fireplaces. Typically a modern fireback includes (i) a back and two side walls (side cheeks) which are usually angled 20 to 30 degrees away from the back and generally are contoured to surround and protect the masonry walls of the fireplace, (ii) a throat lintel which supports the brick work above the breast of the fireplace and connects the fireplace to the exhaust flue or chimney, and reduces turbulent air flow up the chimney, and (iii) means for positioning the solid fuel to be burnt, usually a grate type arrangement situated over the hearth of the fireplace when solid fuels are used. Traditional non-refractory fireplaces sometimes comprise a back wall, which extends vertically upwardly from the hearth and angles forward towards the upper region of the wall before returning to present a rearwardly sloping throat at the entrance or mouth of the chimney flue. In use, the forwardly inclined upper fireplace wall is heated by flames and over time, becomes hot enough to radiate heat back into the room. The lower rear fireback and sidewalls are not struck to the same degree by flames and only acquire heat through radiation transfer from the flames. These parts of the fireback are not efficient radiators of heat. A number of concrete and stone fireplace designs have attempted to overcome this limitation by incorporating of a series of inclined horizontal ribs terminating in a crest portion in the rear fireplace wall. Each rib in the series is usually successively inclined further outward as the fireplace wall extends upwards away from the hearth. The crest and the body of the ribs are all to a degree struck by the flames and thus radiate a greater amount of heat into the room. However, although the improvement has increased efficiency to some degree, further improvements are required.

The purpose of a refractory fireback or a cast iron fireback is to protect the masonry walls of the fireplace from heat deterioration and to radiate heat generated by the fire forward into the room to be heated. Furthermore, the beauty of refractory fireback is that they can reflect heat away from themselves. This is desirable since, in addition to normal heat radiation, reflection of heat energy from the fireback into the room will greatly increase the efficiency of heat transfer into the room to be heated. Heat reflection does not occur to any substantial degree with fireplaces constructed from non-refractory materials. Notwithstanding the protection afforded by cast iron firebacks, intense heat from the fire may eventually lead to damage of the protective fireback itself. In particular, the lower portions of the fireback are susceptible, since this is the area where exposure to heat is most intense. Fireback damage is undesirable since it presents a potential fire hazard, since the seals about the fireplace will be compromised and heat, hot smoke and/or toxic fumes may escape behind the protective fireback and cause unwanted damage, staining, fume release or a fire risk to the surrounding masonry and furnishings of the dwelling. In addition, generally a fireback is an integral piece and thus it is often expensive to replace the whole unit.

Combustion air is taken from the room to be heated and is drawn through or over the fire and exhausted through the chimney. This has the effect of lowering the heating efficiency of the fireplace, since some of the warm air in the room is drawn back into fireplace for combustion and will be lost as exhaust through the chimney. Undesirably, open fireplaces oftentimes may lead to draughts resulting from airflow induced by the "draw" of the chimney and a large amount of heat generated may escape through the chimney. This is a problem as draughts may be present when the fireplace is in use or, indeed, when idle. Thus the passage of air through the chimney results in draw of cooler air into the room and consequent lowering of the temperature.

United States Patent No. 6,941,944, teaches a fireback made from concrete casting, bricks, tiles or blocks and whose walls extend upwardly to a throat and the inner walls slope steadily inwards to decrease the cross sectional area of the fireback as the walls extend upwards. This narrowing effect is said to eliminate smoke and increase the heat radiated into the room, since the sloping fireback and walls may be struck by flames the entire way up the wall and the reduced area to be heated means the fireback becomes hotter and radiates more heat. The document teaches that a fireback that is semicircular in cross section and frustoconical in shape or other arcuate, semicircular, concave cross section are superior since these shapes minimize heat losses into the surrounding walls due to conduction when compared to the more usual trapezoid shape. Additional features include raised surface features provided on the fireback wall which server to increase the surface area of the fireback. The surface features are said to have a preferred wavelength of about 50 mm and height of about 10 mm from trough to peak.

As part of the EU Directive on the Energy Performance of Buildings (EPBD), a Building Energy Rating (BER) certificate, which is effectively an energy label, will be required at the point of sale or rental of a building, or on completion of a new building. The Directive aims to improve the energy performance of residential and non-residential buildings, both new-build and existing. The measures are expected to have an impact on decisions on property transactions. The BER rating will have an impact on the open fireplace, as it is an open space, the inefficiency of an open flue is accounted for when the BER assessment is carried out on a home. To obtain a better BER rating in a dwelling, the owner may decide not to have an open fireplace and settle for an alternative heat source, which could potentially see the end of the traditional open fireplace. Therefore, an improved fireplace, which addresses this problem, would be highly desirable.

A number of prior art fireplaces and firebacks have attempted to address the problems of fireplace damage and lack of efficiency. Fireplace throat restrictors have been used in the past to regulate airflow through the throat portion of the fireplace to the chimney. Such devices are generally found at the throat and some are adjustable, so that the throat restrictors may also be used to control the amount of air drawn through or over the fire to limit the air/exhaust escaping the fireplace to varying degrees. However, existing devices are often complicated, can be comprised of many parts which may be expensive to make and complicated to assemble or install and make chimney and/or fireplace cleaning difficult. Furthermore, many such devices may not be replaceable and require installation of new fireback. In addition, such devices may be unsightly and may detract from the aesthetic appearance of the fireplace. A relatively small number of restrictors can effectively close off the fireplace space and so will not easily solve the problems associated with lack of energy efficiency. United Kingdom Patent No. 813,996 teaches a throat restrictor for an open fire comprising a passageway having a moveable flap valve therein which can swing about a hinge in an arc shape thereby adjusting the size of the passageway as needs be. The device requires complex assembly including a rack and pawl component and is mounted such that many are of the parts are visible in normal use. United Kingdom Patent No. 941,310 describes a regulated damper for domestic flue control. The device comprises a flue damper device for insertion in the chimney of a domestic fireplace above the fireplace throat which comprises a flat rectangular metal frame defining an opening corresponding approximately to the flue opening and including an extension to be held between two courses of brickwork of the chimney to support the device, a damper plate being secured on a spindle mounted near the back or front of the frame and extending beyond the extension where it carries a control lever for setting the angle of opening of the plate. While this device can close off the fireplace space, it is designed to sit in the flue and must be built into the brickwork, which means that the unit is not easily removable. Furthermore, the unit is difficult to install to existing fireplaces since it requires removal of plaster and bricks before installation can be performed. Fireplace screens have been also used to eliminate room draughts and seal off the fireplace space, when the fireplace is not in use.

United States Patent No. 4,194,494 describes a fireplace plug for closing a metal throat of a fireplace during period of non-use. The plug has a body for obstructing the throat, which has magnetic means for securing the body to the metal throat, a handle, and means for indicating that the plug is in an inserted state. However, the device is only suitable for metal chimney flues and risks the spoiling of the user's clothes on insertion or removal of the device.

Swiss Patent No. CH 267 072 describes a chimney and fireplace insert wherein between the lintel and the upper portion of the rear wall of the fireplace, there is smoke exhaust opening into which a feed frame made of angle iron may be inserted. An exhaust control flap is mounted in the frame by means of a pivot axis. The flap may be actuated in by means of a lever disposed in the side of the housing of the fireplace and the flap portion can be withdrawn for cleaning purposes.

US Patent No. 5,080,006 describes a pivotal chimney damper where a damper flap can be used to selectively open and close the outlet from the flue of a chimney by pivotal movement of the flap. A spring is used to urge the damper to a normally open position; the flap can be closed when a pull means is drawn tight. The flap must be forced into the closed position. The pivoting flap is arranged by locating the pivot off centre so that a heavier portion of the flap tends to pivot downward when unrestrained to the open position.

Thus, it is highly desirable to provide improvements to existing fireplaces by providing firebacks suitable for use in an open fireplace which will (i) operate more efficiently than existing fireplaces and will increase heat transfer to a room; and (ii) be less susceptible to heat damage than traditional firebacks; and (iii) will have the capacity to minimize heat loss from such a room when the fireplace is not in operation by controlling air flow created by chimney draw and (iv) will have capacity to substantially create a 'closed' fireplace, if and when the user decides, which will increases the energy efficiency of the home when the fire is inactive. Summary of the Invention

According to the present invention, as set out in the appended claims, there is provided a draught regulator (5) suitable for use with a fireplace having a mouth defined about a chimney flue, the draught regulator comprising: a frame (24) of substantially the same dimension as the mouth and defining an aperture about the mouth for passage of air or exhaust therethrough; at least one baffle (14) pivotally mounted on the frame (24) for movement thereon; a baffle adjustment means (21) coupled to the at least one baffle (14) for baffle (14) movement from an open position for passage of air or exhaust to a closed position to substantially prevent passage of air or exhaust, the draught regulator (5) is insertable into the mouth for removable mounting therein. The term "draught regulator" in the context of this invention is intended to mean a device which can regulate the amount of air and/or exhaust eliminated through a fireplace and chimney flue. By the term "regulation", it is meant that the device can be employed in a number of regulating positions, two extremes of which are fully open when air and/or exhaust may escape the chimney unhindered and fully closed wherein the draught regulator operates to substantially seal off the fireplace space and chimney flue. It will be appreciated that the term "mounting therein" means that unit may be position on the fireback or within the space created by the fireback walls. In this position, the draught regulator effectively closes off the fireplace entirely to avoid heat loss from the room, when the fireplace is not in use.

An added advantage of the draught regulator of the invention arises from the fact that when the baffles are partially closed, the fire burns more efficiently. In particular use of a draught regulator unit results in a slower burning fire which is attractive from the point of reduced fuel consumption, and/or less heat lost through the chimney. Heat emanating from a slow burning fire has greater opportunity to heat a room, rather than be lost up a chimney space. Use of a draught regulator facilitates slower, more efficient burning of solid fuel. The draught regulator of the invention is advantageous since it is removeably mountable within an existing fireplace. This means that the unit can be sold and retrofitted to existing fireplaces by selecting a draught regulator unit of appropriate size for the existing system. The draught regulator of the invention is a significant improvement over existing fireplace inserts or dampers for the reasons provided herein. A removable draught regulator is desirable, since it means that the unit may be conveniently removed when the chimney has to be cleaned, whereas many irremovable chimney flue baffles obstruct correct chimney cleaning. The unit is also easily replaceable in the event of damage or fault and also cleaning of the unit itself is greatly facilitated.

Such a draught regulator is particularly suitable for use with the fireback of the present invention, but the skilled person will appreciate that the draught regulator may advantageously be used with any existing fireplace, chimney flue to provide the beneficial features afforded by this aspect of the invention. The skilled person will also appreciate that the draught regulator may be mounted on a fireback before installation or during construction of the dwelling and to be irremovable. This arrangement negates the advantages associated with a removable unit. However, it will not detract from the ability to the unit to seal off the fireplace and so is still useful where it is desired to have an improved building efficiency rating. The draught regulator of the invention may be of a heat resistant type material such as cast iron or stainless steel which is useful due to its lightness and availability in sheets or roll. However, it is preferred that the unit be fabricated from the same material as that of the fireback of the present invention. The draught regulator may be suitably sized to be insertable into the mouth of the fireplace where it may be mounted on an existing fireback, brickwork, walls or other structure therein. The skilled person will appreciate that the draught regulator may be fitted to or on a bracket or other suitable mounting means which can be easily and inexpensively fitted to an existing fireplace. Such a conveniently installable unit is most welcome since many homes may not afford to install an entire expensive fireback assembly. This means that the draught regulator of the present invention is desirable, since it makes the requirement of making a home more energy efficient more easily attainable, since the draught regulator unit by itself is more affordable than the installation of an entire fireback and regulator assembly. This is an affordable attractive option to households on a budget. The unit will be easily removed for chimney cleaning and the like. In a preferred embodiment, the draught regulator of the invention comprises at least two baffles, which are pivotally mounted on the frame. The draught regulator may comprise between two and ten baffles, depending on the depth of the chimney space it is required for. Desirably, the draught regulator may comprise between three and ten baffles, more desirably still between four and six baffles. In a particularly preferred embodiment, the draught regulator may comprises three baffles pivotally mounted on the frame for baffle movement thereon. It will be appreciated that the number of baffles mounted on the draught regulator will depend on the dimensions of the fireplace, and in particular on the space between the lintel and the flue gatherer. If a single baffle is used and there is a risk that it may become lodged or stuck in a semi open position, there may be a problem with carbon monoxide leakage into the room. For example, if the space is minimal, then a draught regulator having one baffle will not operate correctly (there may not be sufficient space for a the baffle to open fully, or it may get lodged within the tight space), since a single baffle will tend to have longer side edges than the case if more than one baffle is provided. More than one baffle is preferred since this allows shorter edges of baffles to be used. For example, three baffles can have shorter edges than two baffles to close of the same space. An added advantage of three or more baffles, is that if one baffle fails or becomes lodged in the closed position, then two or more remain operable and the entire unit may not have to be replaced and/or the risk of carbon monoxide build up in the room is minimised. Desirably, the at least one baffle is pivotally mounted on the frame along a long edge of the baffle. It will be appreciated that typically rectangular shaped baffle will have two long edges or sides, and two short edges or sides. Typically a pivot axis may be provided along the longer length of the baffle. Suitably, the at least one baffle may be mounted on the frame along a pivot axis provided along a length of the baffle on a lateral side thereof. In other words, the at least one baffle is mounted on the frame at one edge of the baffle, and in particular on a long edge of the baffle so that the baffle may pivot on the frame along a peripheral edge.

In a different embodiment, the at least one baffle may be mounted on the frame along a pivot axis provided along a length of the baffle substantially on a central portion thereof. Desirably, the at least one baffle is pivotally mounted on the frame remote from the edges of the baffle. In other words, the baffle is mounted so that it may pivot around a central line provided intermediate of the baffle edges. The skilled person will appreciate that the baffle may be mounted along a pivot axis positioned off centre without taking from the scope of the invention. In a preferred embodiment, the at least one baffle is pivotally mounted on the frame by at least one hinge means. In another embodiment, the at least one baffle is pivotally mounted on the frame by a support means provided along the length of the baffle and securable to opposing sides of the frame for baffle rotation thereon. Suitably, the support means may be a rod or cable or the like. Eyelets or hooks may be provided on the baffle, along the length of the pivot axis, so that the support means can be threaded or fed through the eyelets or hook before being secured to opposing sides of the frame. The at least one baffle may then pivot about the pivot axis provided by the hinge or the support means. Suitably, the at least one baffle is pivotally mounted to move vertically away the frame in an upwards or downwards direction.

In a preferred embodiment, the draught regulator of the invention is arranged such that the at least one baffle is pivotally mounted to move vertically away the frame in an upwards or downwards direction. The skilled person will appreciate the modifications that would have to be made to the draught regulator frame and baffle adjustment means to allow movement in upwards or downwards direction. Preferably the at least one baffle may move vertically upwards away from the frame. In a desirable arrangement, at an additional baffle may be provided at, at least one of the front and rear ends of a draught regulator unit. The at least one of the front and rear additional baffles may be detached, or disengaged, from the baffle adjustment means. Advantageously, this means that at least one of the front and rear baffle may be disconnected from the normal baffle movement which is generally initiated by engaging the baffle adjustment means. Likewise, the additional baffle may be provide from the outset in a disengaged state, or may be provided separate to the draught regulator for mounting thereon if needs be. Availability of at least one additional disengaged or disconnected baffles is desirable, since in some chimney spaces or fireplaces, there may be additional space located to the rear or towards the front of an installed fireback through which there may be further draughts. A disconnected or disengaged baffle can be suitably positioned to close off this undesirable space without detracting from the proper functioning of the draught regulator unit. In preferred embodiments, the draught regulator may be provided with an additional attachment means for addition of a disengaged baffle as therein described. Suitably, this allows convenient addition of such an additional baffle on installation, if so required. Desirably, attachment means include a tab or a flange on the draught regulator frame which is adapted to cooperatively engage with the at least one additional disengaged baffle. In a particularly preferred embodiment, the at least one baffle may be adapted to comprise a debris trap for collecting soot, dirt, rain and snow or diverting such debris away from the centre of the baffle. The debris trap may provided on the top and/or underneath side of the at least one baffle, depending on the nature of the pivoting arrangement of the baffle on the frame. The advantage of the debris trap becomes clear when it is considered that debris such as dirt, soot, dust or liquids such as rain, sleet, snow, etc., may accumulate on the upper surface of the at least one baffles when they are in the closed position. In order to avoid draughts and unnecessary heat loss from a room, a user would not wish to open the baffles until the fuel for the fire is set, and is ready to ignite. Without the debris trap, when the baffles are opened, soot or worse accumulated water will flow from the now substantially vertical baffle onto the set fire, potentially wetting it and making it more difficult to ignite. Wet fuel also tends to smoke more while burning. Excess soot on the fire, or soot that might later become dislodged while the fire is burning could be dangerous due to its inherent tendency to ignite itself. Accordingly the baffle debris trap is an advantageous feature, since it allows any accumulated debris/fluid to slide down the baffle surface into the trap provided therein. The unit can periodically be removed for cleaning when needs be. In a particularly advantageous arrangement, the central surface of the trap can be raised slightly relative to the surface at opposing ends of the trap, to provide a sloping surface from the centre of the baffle to its opposing sides. This has the effect of directing or diverting any trapped fluid to the sides of the frame where it can discharge into the sides of the fireplace where it will not dampen set fuel. The trap may take the form of an inwardly turned groove or lip which forms a pocket for catching the debris; a channel; a pocket; or drain means. By inwardly it is meant that the baffle edge turns inward on itself. The skilled person will appreciate that the trap may be positioned at any point along the baffle, and that more than one trap may be provide on each baffle, but to ensure that the maximum amount of debris is trapped, it is desirable to position the trap as close to the edge which will extend furthermost into the fireplace space. The skilled person will also appreciate that the trap may be activated when the baffle is moved from a closed position to an open position.

In an embodiment where the at least one baffle is pivotally mounted on the frame at a long edge of the baffle, the trap may suitable be formed from an portion of the baffle surface which may be moulded or fashioned to curve upwardly and inwardly backwards on itself to form a lip or a pocket to trap debris. This is advantageous, since it will trap substantially all debris that may accumulate on the upper baffle surface on opening the baffle to the open position. The provision of such a debris trap is a desirable arrangement, since soot, rain, sleet, etc., will fall back into the trap provided on the baffles which are pivotable on the frame when the baffles are opened rather than into the fireplace and hearth. In an embodiment where the pivot axis is provided remote of the baffle edges, it will be understood that one side of the baffle will move vertically upwards, while the other side will move vertically downwards as the baffle rotates about it pivot axis. This arrangement is desirable in circumstances where there insufficient space in the chimney flue to accommodate a draught regulator where the baffles pivot about an axis on the baffle edge. Several traps could be provided on opposing sides of the baffle in this instance.

In a particularly preferred embodiment, the at least one baffle is pivotally mounted to move away from the frame at an angle in the range of about 1 to about 145 degrees (or negative angle in the case where pivot axis is central to the baffle), more preferably in the range of about 1 to 120 degrees, more preferably still in the range of about 1 to 90 degrees away from horizontal, or from the angle of the plane the baffle lies in, when in the closed (or rest) position on the draught regulator frame. Advantageously, where the maximum opened angle is 90 degrees, this provides for the most unobstructed flow of fire exhaust/air through the draught regulator. At angles greater than 90 degrees, where a trap is provided, it is possible that trapped debris may fall out of the trap or that the trap may not operate sufficiently well. Furthermore, baffle open angles greater than 90 degrees may over reach into the open space of a neighbouring baffle and may interfere with or lessen the air/exhaust flow though. The draught regulator baffles may be pivotally mounted on the draught regulator to move between a position in which the regulator has maximum areas for passage of air or exhaust and a closed position wherein the regulator has is minimal or closed off. In the closed off position, the fireplace is essentially closed off. All in between positions are available to the user. Suitably, from 1 to 10 pivotal baffles may be used in the draught regulator. However, it is preferred to use from 2 to 8 baffles to ensure a good clearance within the fireplace mouth when the unit is in place. The optimum number of baffles will depend on the dimensions of the fireplace mouth and chimney flue arrangement. However, it is most preferred to use at least three pivotal baffles, since this arrangement will be suitable for the majority of spaces. The baffles may be pivotally mounted along the length of the regulator frame or alternatively along the breadth of the regulator frame. The baffles may pivot in the same direction or in opposing directions, for example, the baffles may be mounted along a single central transverse line and may pivot in a butterfly arrangement. In the most preferred embodiment, the baffles may be arranged along three regularly spaced parallel transverse lines whereon they may pivot to the same degree in the same general direction. The skilled person will appreciate that many such pivoting arrangements may be suitably used depending on the space provided in the chimney flue in question or the size of an existing fireback. In a preferred arrangement the at least one baffle may be pivotally mounted to move simultaneously in the same direction. However, there is no bias against a draught regulator wherein the at least one baffles may be pivotally mounted to move simultaneously in the opposite direction. In a related design the baffles may be arranged so that they may incrementally move in a discontinuous or non-concurrent matter relative to each other.

In one embodiment, the at least one baffles, when in the closed position, may lie substantially in the plane of the frame.

In a preferred embodiment, the draught regulator may comprise a frame with edges having at least one sloped portion, so that in the closed position, the at least one baffle lie flat at an angle in the range of about 1 to 75 degrees above the horizontal plane. In other words, the frame, on opposing short edges, may have at least one projecting or jutting portion which extends outwards or upwards beyond the frame, the jutting portion slopes downward toward the frame at an angle of slope in the range of about 1 to 75 degrees. This means that when the at least one baffles are in the closed position, the at least one baffle lies at an angle in the range of about 1 to 75 degrees above the horizontal plane. The preferred angle of slope is 5 to 60 degrees from horizontal, the most preferred angle of slope being 20 to 45 degrees from horizontal. Suitably, a projecting sloped portion may be provide for each baffle provided on the frame, e.g., where three baffles are provided, three sloped portions of the frame may be provided. The frame slope feature is desirably, since it allows the closed (or at rest) baffles to lie against the frame at a predetermined angle away from the horizontal plane. This is useful since it prevents soot/rain/snow, etc., from accumulating on the top side of the baffles when they are closed for sometime, since a sufficient degree of slope will cause the accumulating debris to slide into a debris trap provided on the baffle. It also means that excess weight of debris is avoided, which if left in place, may interference with the operating function of the draught regulator. In a preferred embodiment, the draught regulator may comprise a frame having a peripheral flange extending underneath the frame and being adapted to cooperatively engage with the fireplace mouth or an upper portion of a fireback casing when fitted. This is a desirable arrangement, since it allows the draught regulator to be securing connected or mounted on a suitable fireback casing. In another embodiment, the draught regulator may comprise a frame wherein the frame is substantially wedge shaped. By wedge shaped it is meant that the edges on the underneath side of the frame are shorter in length that the upper edges of the frame. This is desirable where the draught regulator is of the retrofit type. The wedged shaped frame allows the draught regulator to sit into the upper space created by the fireback. The wedge shape may assist maintaining the draught regulator in position on an existing fireback and is particularly advantageous since it allows a good seal to be formed between the upper portion of the existing fireback and the draught regulator itself.

Desirably, the frame may further comprise securing means for securing the draught regulator in the fireplace mouth or in a mounted position on an upper portion of a fireback casing. Suitably, the securing means be a fastener such as a screw or bolt arrangement or the like or any means known to the skilled person. It is preferred that the securing mean not be a permanent one, since it will be required to remove the draught regulator periodically for cleaning, maintenance, replacement or repair.

In a related aspect of the invention, the draught regulator as described herein may be used with a fireback or in a chimney flue or the combination of same.

Accordingly, there is provided a refractory fireback for use with a fireplace and chimney flue comprising: a rear wall; a pair of side walls connected to the rear wall to form a fireback casing, the casing insertable into the fireplace, such that when fitted, the upper periphery of the casing cooperates with the fireplace to define a mouth about the chimney flue; and a draught regulator for controlling air and exhaust entering the chimney flue, characterized in that draught regulator is insertable into the mouth and removeably mounted thereon. The fireback and draught regulator may be provided separately or together as a unit to be assembled and fitted into the fireplace at the time of initial installation. The skilled person will appreciate that in the trade and as intended herein, the side walls may also be known as side cheeks.

In a preferred embodiment, the refractory fireback (1) comprises a draught regulator (5) comprising at least two baffles (14) pivotally mounted on a frame (24) for movement thereon for controlling air and exhaust entering the chimney flue.

In one embodiment, it is preferred that the upper periphery of the fireback casing further comprises an elongate member extending transversely across the upper periphery of the fireback casing. The elongate member is advantageous as it provides further strength and supporting structure to the fireback casing, acts in an additional support role for mounting the draught regulator on the casing and serves as a support for correctly positioning the mantle about the fireplace so as to ensure a good seal can be provided on all sides of the fireback and mantelpiece, when fitted. Preferably, the elongate member is made of the same material as the fireback casing, although another strong heat resistant material may suitably be used. Suitably, the elongate member is integrally joined to the casing and thus the casing and elongate member may be cast in one piece to be formed as an integral part of the fireback. This avoids the necessity for having a multitude of parts to the fireback. However, it will be appreciated that the elongate member (or strut) may be added to a fireback casing and mounted thereon by suitable mounting means, for example, fasteners which include screws, rivets, nuts, bolts and connectors and the like. It will be appreciated that the elongate member may be in the form of a supporting arm, boom, beam, brace, strut, slat, truss, strut or another structure which is suitable for adding strength and stability to the fireback casing and suitable for mounting the draught regulator thereon.

The casing may be dimensioned according to the requirements of the fireplace into which it to be installed. Typically, the fireplace will be of standard dimension and the fireback will be of a complimentary size. It will be appreciated however, that the firebacks of the invention made be made to any desired dimension. Generally, firebacks are available in sizes including 16" (400 mm), 18" (450 mm) and 20" (510 mm) width. The casing is preferably installed to be flush with the fireplace entrance for aesthetic reasons and so that smoke or exhaust leakage is eliminated. The fireback of the invention may be installed in the same manner as a traditional fireback. Likewise, depth of the fireplace will depend on the user requirements and may be installed to fit snugly against the rear fireplace wall, or may be shorter in depth so that a boiler, filling or the like may be located behind the fireback. A suitable filling material is usually provided behind the fireback to fill the cavity between the fireback and the fireplace wall. The skilled person will appreciate that existing methods and protocols for fireback installation are suitable for use with the present invention. The fireback casing of the invention may advantageously be provided in more than one section.

Accordingly, in a further aspect, the invention provides a refractory fireback suitable for use with a fireplace, the fireback being formed in at least two sections, the sections defining at least one channel therebetween to allow for heat expansion, characterized in that a resilient heat resistant material is positioned substantially within the at least one channel thereby providing a seal.

Suitably, the fireback may be provided in two or more sections, which may be assembled together before being installed in the fireplace as a whole unit. Thus, the fireback casing may be moulded as a single piece or may be assembled as a unit from more than one separately cast section. Assembly of two or more sections is advantageous, since it renders installation more convenient, as the fireback sections will weigh less than an entire unit. More importantly, it allows installation of the sections in a way that leaves a channel or a groove or small split space between the installed sections. This is advantageous, since it means that in use there is a degree of room for the sections to safely expand and contract on exposure to heating. This means that the fireback is less susceptible to damage due to heat stress or cracking. In a preferred embodiment, the channel may be provided as a horizontal channel between an upper and lower casing section. It will be appreciated that such a channel may multidirectional, and will dictate the shape of the fireback sections accordingly. For example, the channel may be provided in a vertical or substantially vertical direction, which will allow for widthways expansion and contraction. Equally useful are diagonal channels, zigzag channels or other irregular or non-linear channels or jigsaw channels. In a preferred embodiment, a horizontal channel may be suitably used and will be substantially parallel to the hearth surface. Further advantages arise from positioning a resilient heat resistant material substantially within the channel to provide a resilient seal that is flexible on casing section expansion and contraction. Such a seal is desirable, since it allows use of the beneficial expansion channel feature but still provides a seal ensuring that the fireplace masonry behind the fireback casing is protected from heat damage, smoke access and that draughts do not ensue. There is significant need for such a seal, since damaged masonry may lead to cracking or exhaust leakages, which could present an unsafe fire hazard and be expensive to repair. Examples of suitable resilient heat resistant materials include asbestos fibre materials. Suitably, a resilient ceramic fibre material such as "fire rope" (as it is generally known in the trade) may be used, since it is flexible, relatively inexpensive, readily available and provides a reliable heat resistant seal. The resilience of the fire rope is desirable, since the rope can be prepared for insertion into a channel by squashing the material into a size which facilitates insertion and the resilient nature of the material ensures the rope expands into position to form a good seal between the parts involved. The fireback sections may be held securely together by at least one of a plurality of connecting means. Suitable connecting means include screws, fasteners, adhesives, nuts and bolts or male and female adaptor connectors or combinations thereof. However, it is preferable to use connectors comprising male and female parts, which may be disposed on opposing sections of the fireback casing. The male and female parts may be formed integrally to the fireback casing section when it cast. This is desirable, since it avoids the need to supply additional securing components, such as screws, etc., and reduces the overall cost of the fireback.

In a preferred embodiment, the fireback of the invention may comprise a rear wall which may also have undulations disposed thereon for increases surface area. Desirably, either or both of the sidewalls will have undulations disposed thereon. Accordingly, in a related aspect the invention provides a refractory fireback suitable for use with a fireplace comprising: a rear wall; and side walls connected to the rear wall to form a fireback casing; characterized in that at least one side wall has undulations disposed on the surface thereof to increase the surface area of the wall. It will be appreciated that the term "undulations" is intended to represent any plurality of surface features, which give increased surface area to at least one of the fireback sidewalls. Undulations as a surface feature encompass any surface feature, which may give a wavelike or textured appearance or form to the surface of the fireback walls. Suitably, undulations include surface features such as corrugations, ribbing, bumps, dents, hollows, grooves, notches, recesses and depressions or the like. The undulations or surface features may be arranged vertically, horizontally, or may be arranged in zigzag patterns or lattices or areas of patterns, lattices or devices having bevelled edges. Grid formations or interwoven lattices may all suitably be used. A number of these forms of undulation are preferred, particularly symmetrical features or patterns or fashioned devices such as flowers, pictorial scenes, etc., if aesthetically pleasing qualities are desired. However, it is most preferred that the undulations comprise vertical ribbed lines disposed along surface area of the walls. In one embodiment, the undulations comprise substantially vertical lines or vertical ribbing (having crested pointing), which may be disposed longitudinally across the surface area of the walls. The exact nature, size or form of the undulations is not critical, so long as they have the effect of increasing the surface area of the walls relative to a smooth wall. The effect of increased wall surface area is the provision of increased area for reflection and radiation of heat conducted along the refractory fireback to the walls. The effect is desirably a significant increase in the efficiency of the fireback with respect to heating the room in which the fireplace is situated. The undulations or surface features are preferably formed when the fireback is initially cast or moulded.

The fireback of the invention may further comprises at least one auxiliary heat shield for protecting the casing from heat damage, the at least one auxiliary heat shield being removeably mountable on the fireback wall.

In a further aspect the invention provides a refractory fireback suitable for use with a fireplace, comprising: a rear wall; side walls connected to the rear wall to form a fireback casing; and at least one auxiliary heat shield for protecting the casing from heat damage, characterized in that the at least one auxiliary heat shield is removeably mountable on the fireback wall.

It will be appreciated that the term "auxiliary" is used to differentiate the heat shielding effect of the removable shield to the actual fireback casing wall, which also has a heat shielding effect on the fireplace masonry. The skilled person will appreciate that where more than one auxiliary heat shield is used, the auxiliary heat shields may be removeably mountable on at least one (more than one) fireback wall. The at least one auxiliary heat shield may made of a refractory heat resistant material. Suitably, the at least one auxiliary heat shield be made of the same material of construction as that of the fireback. In one embodiment, it may be of a different material, which ideally would have a higher heat resistance than that of the fireback itself. The use of at least one auxiliary heat shield is advantageous, since it provides additional protection to the fireplace masonry and in particular protects the most heat-exposed areas of the fireback. An important advantage arises from the fact that the at least one auxiliary heat shield is removeably mounted on the fireback. In the event significant heat damage occurs, the at least one auxiliary heat shield will be primarily exposed to the heat and will sacrificially be susceptible to damage in the first instance. This means that the fireback wall (rear and sidewalls) will be protected and is less prone to damage from heat effect. In a preferred embodiment, the auxiliary heat shield may be mounted on the rear fireback wall towards the lower wall area where most heat resistance is required. However, it will be appreciated that auxiliary heat shields may be positioned about the fireback side walls or in any other position where additional protection may be required. In a particularly preferred embodiment, the refractory fireback has at least one additional auxiliary heat shield removeably mountable on at least one sidewall of the fireback. Desirably, both side walls of the fireback casing may be protected by an auxiliary heat shield. Suitably, the auxiliary heat shield may be flat or may be curved or arcuate to a degree, depending on the dimensions and shape of the area of the fireback for which protection is required. In a preferred embodiment, the fireback wall and auxiliary heat shield are fashioned in a complimentary fit manner, so that in operation, when mounted on the fireback, the auxiliary heat shield fits snugly within or abuts tightly up against the fireback wall to form a substantially seamless or flush fit therein. In one particular embodiment, it is preferred that the auxiliary heat shield fits substantially flush against the fireback rear wall. By substantially flush, it is meant that the heat shield is positioned intimately near the rear wall. It will be appreciated that there may be a small gap between the heat shield and the walls in the range of about 0.1 to 5 mm. This sung or flush fit maintains the aesthetically pleasing qualities of the fireback casing or unit and avoids the build up of soot or dust in crevices or spaces around the fitting. The skilled person will appreciate however, that the auxiliary heat shield may be held in position by other means, for example, it may be hung or suspended from pegs or hooks positioned on the upper regions of the fireback walls.

In a preferred embodiment, the at least one auxiliary heat shield (6) forms an air gap between the casing and the at least one auxiliary heat shield (6) when the heat shield is fitted.

Accordingly, in a further aspect there is provided a refractory fireback suitable for use with a fireplace comprising: a rear wall (2); side walls (3, 4) connected to the rear wall (2) to form a fireback casing; and at least one auxiliary heat shield (6) for protecting the casing from heat damage, characterized in an air gap is provided between the casing and the at least one auxiliary heat shield

(6) when the heat shield is fitted.

In a particularly preferred embodiment, the at least one auxiliary heat shield may be fitted against at least one of the fireback rear wall and/or side walls in such a manner as to leave an air gap between the fireback casing wall and the rear of the auxiliary heat shield. This is an advantageous arrangement, since it surprisingly results in a significant increase in fireback efficiency, i.e., refractory efficiency. The air gap between the heat plate and the housing of the fireback unexpectedly increases the insulating value of the air gap and has a substantial increasing effect on the efficiency of the fireback. Desirably, the air gap may be about 1 mm to about 5 mm in depth at its widest point. More preferably, the air gap may be about 2 mm to 3 mm in depth at its widest point. In a preferred embodiment, at least one air cavity may be provided in at least one of the fireback casing rear wall or side walls. Desirably, the air cavity may be about 1 mm to about 5 mm in depth at its widest point. More preferably, the air gap may be about 2 mm to 3 mm in depth at its widest point. The effects are similar to the formation of the air gap formed when at least one auxiliary heat shield is mounted on at least one wall of the fireback casing. Preferable, such an air cavity may be about X to about X mm in depth at its widest point.

In a related aspect there is provided a refractory fireback suitable for use with a fireplace comprising: a rear wall (2); side walls (3, 4) connected to the rear wall (2) to form a fireback casing; and an air cavity provided in the least one of the fireback casing rear wall or side walls.

Increased fireback refractory efficiency is observed if an air gap or an air cavity or a combination of these features, is provided. However, it is preferred that an air gap be provided, rather than an air cavity, since a design having a removable auxiliary heat shield, which provides the air gap when mounted on the casing is superior, since cast iron products will have an increased chance of cracking and having a replaceable heat shield will allow simple replacement of the damaged shield without having to replace the complete fireback.

In a preferred embodiment, fire rope may be provided between the at least one auxiliary heat shield and the at least one fireback wall. Desirably, this ensures that the air gap is maintained, when the at least one auxiliary heat shield is mounted in position against the fireback casing wall.

Further insulating materials may also suitable provided within the air gap or air cavity to improve performance.

In a particularly preferred embodiment, the at least one auxiliary heat shield has a surface on which undulation are disposed on the surface thereof to increase the surface area of the wall. Suitably the undulations are disposed vertically on the front of the at least one auxiliary heat shield. The fireback wall (rear and/or side walls) may be fitted with auxiliary heat shield mounting means, which assist in holding the at least one auxiliary heat shield in position when in use. For example, the fireback wall may be provided with one or more projections, which may be substantially curved, bent, hook or L-shaped type flanges to accommodate the bottom wall of the auxiliary shield. In a preferred embodiment, at least one L-shaped flange in the form of a shield stop may be provided along the grate line of the fireback to support the shield when positioned in place. A single shield stop may be centrally disposed along the fireback or an arrangement comprising two or more shield stops along the fireback wall may be provided. In a preferred embodiment, a pair L-shaped shield stops are disposed on opposing sides of the rear fireback wall along the grate line. It is also advantageous to provide additional securing means on the auxiliary heat shield. For example, securing means comprising at least one projection such as a pip, a nipple or the like, may be provided on the rear surface of shield, preferably along the rear top edge of the shield. At least one complimentary aperture for accommodating said at least one projection may be provided in at least one corresponding position on the fireback wall. The additional securing means are desirable since they ensure the shield can snap into the correct position when the projections engage with the apertures and this ensures the shield does not slip, move or fall from position when heat expansion/contraction of the fireback occurs when in use. In one embodiment, the at least one auxiliary heat shield may be provided with at least one groove or channel along the peripheries of the rear of the shield so that a resilient heat resistant material may be used to substantially fill the groove or channel so that when in position in use, the shield is tightly sealed against the wall. It will be appreciated that the fireback casing wall may comprise the at least one groove. Suitable resilient heat resistant materials include fire rope or other asbestos type material. Desirably, the sealing material will buffer the shield against the fireback wall and will help avoid rattling, grating or other noises, which may occur if the shield is disturbed by draughts or fuel striking it. Suitably, in a preferred embodiment, where it is desired to maintain an air gap between the at least one auxiliary heat shield and the at least one fireback rear and/or sidewall, the resilient heat resistant material is advantageous, since it acts to maintain the air gap between the rear of the auxiliary heat shield and the fireback wall.

Preferably, the at least one auxiliary heat shield may be fitted with a removing means to facilitate removal and insertion of the auxiliary heat shield from its position in the fireback wall. Suitably a handle, a tab, a lug, a projecting tooth, a link or similar projection or an aperture or groove or the like may be provided on or in the front wall of the auxiliary heat shield which may be engaged by hand or with a suitable tool to urge the shield out of position when engaged appropriately. In a preferred embodiment, a handle may be provided on an upper front face portion of the shield to allow the shield to be conveniently removed by hand. In an equally preferred embodiment, a groove many be located towards the bottom of the auxiliary heat shield, the groove being dimensioned to accommodate fingers of a users hand, so as to facilitate removal and fitting of the at auxiliary heat shield.

In one aspect there is provided a refractory fireback for use with a fireplace and chimney flue comprising: a rear wall; a pair of side walls connected to the rear wall to form a fireback casing, the casing insertable into the fireplace, such that when positioned in use, the upper periphery of the casing cooperates with the fireplace to define a mouth about the chimney flue; and a draught regulator for controlling air and exhaust entering the chimney flue; characterized in that draught regulator is insertable into the mouth and removeably mounted therein.

In a preferred embodiment, the refractory fireback (1) comprises a draught regulator (5) comprising at least two baffles (14) pivotally mounted on a frame (24) for movement thereon for controlling air and exhaust entering the chimney flue. In a particularly preferred embodiment, three baffles are pivotally mounted on the frame.

In a preferred embodiment, the baffles pivotally mounted to be movable upwardly away from the frame. Desirably, the at least one baffle pivots upwardly from the frame at an angle in the range of about 1 to 145 degrees, preferably 1 to 120, more preferably 1 to 90 degrees.

In one embodiment, the draught regulator further comprises a baffle adjustment means having: a body mounted on the regulator and having at least one recess therein; an arm coupled to a baffle and moveable relative to the body, the arm comprising at least one detent located thereon and engagable with the recess; such that movement of the arm deploys the baffle from a first position to a second position, wherein engagement of the detent with the recess releasably locks the baffle in the second position.

Thus, the baffle adjustment means is coupled to the at least one baffle for movement from a position for passage of air or exhaust to a closed position to substantially prevent passage of air or exhaust. If more than one recess and detent are provided, the skilled person will appreciate that a number of intermediate positions are available to the user. It is preferred to use three baffles, which are moveable in a series of 15 degree increments. It is preferred to have the recesses and detents numbered and arranged on the appropriate parts so that if the fully closed baffles sit at an angle of 15 degrees to the horizontal plane, a series of 5 increments can be used to bring the baffles to the fully open position, wherein the baffles are disposed at a 90 degree angle to the horizontal plane. For this arrangement, a series of 6 recesses and 6 detents may be provided on the baffles adjustment means body and arm respectively. Thus movement of the first detent on the arm from the first detent of the baffle adjustment body to the first adjacent detent produces a pivotal baffle displacement of 15 degrees to the vertical, wherein the position is held by locking the arm detent into the body recess. Further movement of the arm to later recesses produces movement of further 15 degree increments of the baffle, until the final recess is engaged to lock the baffles in a position which is in the range of 90 to 145 degrees from the horizontal plane, depending on the design provided. This skilled person will appreciate that many variations of this arrangement can be made and movements of 5 to 145 degrees are possible depending on the design of the baffle adjustment means and the number of recesses and detents provided thereon.

It is preferred that the maximum open position is 90 degrees from the plane the baffle lie in, when in the fully closed position.

The baffle adjustment means may further comprise a linking means pivotally coupled to the arm and to the at least one baffle at opposing ends.

The arm may be connected to a handle, which may be located about the frame of the air regulator unit. It is preferred that the handle is positioned towards the front of the air regulator, since this ensures that it is accessible to the user.

In another aspect the invention provides a fireback assembly comprising a kit of parts which include: a fireback casing, and an optional draught regulator, and an optional auxiliary heat shield, and optional heat resistant ceramic fibre, and a set of instructions.

Thus the invention provides a fireback and optionally or additionally a draught regulator suitable for use with a fireplace having a mouth defined about a chimney flue, the draught regulator comprising: a frame of substantially the same dimension as the mouth and defining an aperture about the mouth for passage of air or exhaust there through; at least one baffle pivotally mounted on the frame for movement thereon; a baffle adjustment means coupled to the at least one baffle for movement from an open position for passage of air or exhaust to a closed position to substantially prevent passage of air or exhaust; characterized in the draught regulator is insertable into the mouth for removable mounting therein.

The fireback of the invention may be used in a fireplace. However, the skilled person will appreciate that the features of the various aspects and embodiments described herein may equally well be applied to other refractory heating devices such as solid fuel or gas burning stoves. The fireback of the invention may be used in a stove including the type of stove that sits in front of the fireplace space and has four surrounding walls. The fireback may also be used in a stove of the fire front type where the stove sits back within the fireplace in the position where the fireback would normally sit Accordingly, there is provided a stove comprising: a rear wall (2); side walls (3, 4) connected to the rear wall (2) to form a stove casing; and at least one auxiliary heat shield (6) for protecting the casing from heat damage, characterized in an air gap is formed between the casing and the at least one auxiliary heat shield (6) when the heat shield is fitted.

There is also provided a stove comprising: a rear wall (2); side walls (3, 4) connected to the rear wall (2) to form a stove casing; and an air cavity provided in the least one of the fireback casing rear wall or side walls. The skilled person will appreciate that of the embodiments and features described above in connection with the draught regulator aspect, auxiliary heat shield, air gap, air cavity, surface undulations, sectional fireback with sealing material, use of the fireback of the invention in stoves, etc. of the invention are equally applicable to the each other with or with the draught regulator described in combination with the fireback aspect of the invention. Any or all of the features described in one aspect of the invention, or are described in combination or in isolation relating to one aspect of the invention are to be understood to be applicable to the any other aspect. A specific advantage arises from combinations of features and aspects as described herein. Brief Description of the Drawings:

The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 shows a front top right isometric view of a 3D representation of the assembled fireback of the invention with the draught regulator baffles in the fully open position; Figure 2 shows an exploded front top left isometric view of a 3D representation of the fireback, in which the individual parts are separated;

Figure 3 shows a front elevation view of the fireback shown in a line drawing format; Figure 4 shows a cross section view through section line B-B in Fig 2. Showing the inner surface of a sidewall of the fireback in a line drawing format;

Figure 5A shows a blown up view of a portion of the inner surface of sidewall; Figure 5B shows a blown up portion of a draught regulator of the invention; Figure 6 shows cross section view through line A-A in Fig 2 show, from the bottom, the draught regulator with baffles in the closed position, in a line drawing format;

Figure 7 shows a top perspective view of the draught regulator and baffles in the closed position in a line drawing format; Figure 8 shows a top perspective view of the assembled fireback having the draught regulator mounted on the fireback casing with the baffles in the fully closed position in a line drawing format;

Figure 9(i) shows a front top left isometric view of the upper section of the fireback with draught regulator being inserted in through the fireback in a line drawing format; Figure 9(ii) shows a view where the draught regulator is mounted on the fireback casing (this drawings also shows debris traps positioned on open baffles of the draught regulator);

Figure 10 shows a front top left isometric view of the lower section of the fireback with the auxiliary fire shield being inserted into position on the rear fireback wall;

Figure 11 shows (i) a front top right isometric view of the auxiliary fire shield unit, (ii) a rear elevation view of the auxiliary fire shield unit, (iii) an side elevation view of the auxiliary fire shield unit and a cross section view through section line A-A shown in Figure ll(ii);

Figure 12 shows (i) a snapshot side elevation view of an outer surface of a sidewall of the fireback with the draught regulator being mounted on the upper fireback casing (U) in a line drawing format and (ii) shows a snapshot top perspective view of the assembled fireback snapshot side elevation view of the fireback with the draught regulator being mounted on the upper fireback casing (U) in a line drawing format and (iii) shows a snapshot top perspective view of an existing fireback having a retrofit draught regulator with wedged edges about to be installed;

Figure 13 shows (i) magnification of the upper part of the unit as shown in Figure 4 with the baffles in the fully closed position and (ii) shows the corresponding view wherein the baffles are in the fully deployed or open position. The baffles adjustment mechanism is shown in both figures;

Figure 14 shows a front elevation view of the installed fireback in a fireplace surrounded by a mantelpiece;

Figure 15 shows a left side elevation view of the installed fireplace surrounded to the front by a mantelpiece and to the rear by typical lean mix material used in fireplace installations;

Figure 16 shows (i) a side profile of a fireback of the invention having a draught regulator installed thereon and (ii) a front view of a fireback of the invention having air gaps formed on both sides of the fireback on installation of auxiliary heat shields and (iii) a front perspective view of an existing fireback having a retrofit draught regulator with wedged edges installed; Figure 17 shows a schematic diagram of the test facility;

Figure 18 shows a photograph of test facility showing heater elements and refractory fireback; Figure 19 shows a schematic diagram of set-up with heat absorbing board facing fireback;

Figure 20 shows a sequence of thermal images of a number of test subjects; Figure 21 shows thermal image of back face of firebacks;

Figure 22 shows temperature profiles along vertical (Top) and horizontal (Bottom) lines intersecting at approximately the centre of the hot zone;

Figure 23 shows temperature profiles and thermal images of front of firebacks; Figure 24 shows vertical temperature profiles on front radiating face from top of heater upward; Figure 25 shows heat signatures of different firebacks on heat absorbing board at 1 m for horizontal (Top) and vertical (bottom) sections; Figure 26 shows heat signatures of different firebacks on heat absorbing board at 1 m for horizontal (Top) and vertical (bottom) sections;

Figure 27: shows a simplified thermal model of heat transfer through back of cast iron fireback with a uniform front temperature of 400°C;

Figure 28 shows a simplified thermal model of heat transfer through back of cast iron fireback with a uniform front temperature of 400 ⁰ C;

Figure 29 shows energy consumption to heat up fresh air; Figure 30 shows a plot of power consumption versus ambient temperature; Figure 31 shows a test house for Dickens' study; Figure 32 shows an image of the fireback of the invention; Figure 33 shows surface area calculation. Detailed Description of the Drawings

Referring now to the drawings and specifically Figures 1 to 16 inclusive and initially Figure 1, which shows a front top right isometric view of a 3D representation of the assembled fireback according to the present invention illustrated generally by reference number (1). The assembled fireback (1) is comprised of a rear wall (2) about which is disposed a pair of side walls (3, 4) to form the fireback casing. A draught regulator (5) may be mounted on top of the fireback casing and an auxiliary fire shield (6, 6', 6") may be fitted onto the lower portions of the rear wall (2) and side walls (3, 4) of the fireback assembly (1).

In the embodiment illustrated by Figure 1, the casing comprises an integral strut (7) which is positioned at the top and front of the side walls (3, 4) in parallel position to that of the rear wall (2).

The assembled fireback (1) is comprised of two integral casing sections, an upper casing section (U) and a lower casing section (L). The casing sections may be positioned relative to each other on installation and held by interconnecting complimentary connectors (8), one of which is visible in the embodiment illustrated in Figure 1, and have a male (9) and female (10) part on upper section (U) and the lower section (L), respectively (shown in Figure 2). The connectors (8) may be located in a number of positions disposed about the join of the upper and lower sections

(U, L), the disposition of which in this particular embodiment is more clearly illustrated in Figures 2 and 10. The connectors (8) fit together such that a small space or channel (11) (shown in Figure 2) may be horizontally defined between the upper casing (U) and the lower casing (L). Resilient heat resistant ceramic fibre (18) may be used to seal the groove between these sections (shown in Figure 2).

The upper casing section (U) of rear wall (2) may have series of ribs (12). Ribs (12', 12") are shown in this example, and the ribs (12) may be horizontally disposed parallel to the plane of the floor. The crests (13', 13") of the ribs (12', 12") extend increasingly forward from the lowest rib (12') to the highest rib (12"), so that overall the rear wall (2) is inclined forward from the vertical plane towards the front of the fireback (1).

The draught regulator (5) of this example has a series of three baffles (14', 14", 14'") pivotally attached transversely along the length of the regulator (5) and a handle (15) situated at the front right corner of the regulator (5) for adjusting movement of the baffles thereon. The baffles (14', 14", 14'") are in the fully closed position in Figure 1.

A series of corrugations (16', 16", 16'", etc.) are shown on the inner surface of the left hand side wall (4). The corrugations (16) are vertically positioned along the breadth of the side walls (3, 4) and terminate at the lower end of the walls (3, 4) at the placement position (17) of a firegrate for holding fuel. Referring now to Figure 2, which shows an exploded front top left isometric view of a 3D representation of the fireback (1), in which the individual parts are more clearly visible. The draught regulator (5) is shown mounted on top of the upper casing (U). The pivotal baffles (14) are illustrated in the fully closed position. The male (9) and female (10) parts of a connector (8) are visible in the disconnected position. A handle (15) for adjusting the position of the baffles (14) is visible in this view and is connected to baffle adjustment mechanism (21). Resilient ceramic fire rope (18) are showed in exploded position between the various sections where it is positioned to seal. The plurality of corrugations (16) in side walls (3, 4) are clearly visible, as are the series of forwardly inclined horizontal ribs (12', 12"). This illustration shows a handle (19a) centrally located on the upper front part of auxiliary fire shield (6'). Auxiliary heat shields (6", 6'") for side walls (3, 4) are also shown. The draught regulator (5) is mounted on top the upper casing (U). A handle (15) for adjusting the baffles (14) of the draught regulator (5) is also provided. Sections of resilient heat resistant ceramic fire rope (18) for providing a seal between individual sections are also shown.

Referring now to Figure 3, there is shown a front elevation view of the assembled fireback (1) with the draught regulator (5) and auxiliary heat shields (6', 6", 6'") mounted in position on the fireback (1). A section of resilient heat resistant ceramic fibre (not shown) is provided about the front edge of the upper (U) and lower (L) casing section. The positioning of this fibre (18) ensures a formation good seal between the installed fireback and a mantle piece if one is installed in front of the fireback (1). A handle (19a) positioned on the front of the auxiliary heat shield (6') is also shown, as are two shield stops (not shown) are used to hold the shield (6) in position on the fireback rear wall (2). Side wall auxiliary heat shields (6", 6'") are provided with hand gaps (19b) for facilitating installation and removal of the shield (6).

Referring now to Figures 4 and 5, and Figure 4(i) in particular, which shows a cross section view of the fireback through Section line B-B, as shown in Figure 3. In this view the inner surface (Figure 4(i)) of and outer surface (Figure 4(ii)) of a sidewall (3) of the fireback (1) is visible. Figure 5A is a blown up elevation view of a portion of the inner surface of sidewall (4). In Figures 4 and 5A, the draught regulator unit (5) has baffles (14) in either the fully open position. The cross sectional view of the fireback of Figure 4 illustrates three pivot mountings (22', 22", 22'") about which the baffles (14) move. The auxiliary heat shields (6', 6'") are positioned closely to the fireback rear wall (2) and side wall (4) at the lower portion of the wall that is most susceptible to heat damage. Air gap (G) is shown between the rear wall (2) and the auxiliary heat shield (6'), as is channel (11) for fire rope (18) provided between the heat shield (6') and the fireback rear wall (2). A connector (8) with male and female parts (not shown) is visible in Figure 4(ii), in particular. The cross-sectional view shown in Figure 4 illustrates the baffle adjustment mechanism (21) to which handle (15) connects for adjustment of the baffle (14) position through a hinged connecting linker (21b). The cross-section view illustrates grooves (23), in the form of a channel which form a cavity into which the resilient heat resistant ceramic fire rope (18) may be positioned to form a good seal between the individual parts. Figure 5B shows a blown up drawing of a portion of the draught regulator unit (5) which shows securing flange (25) for holding the draught regulator in position on or within the fireback casing by way of a screw or bolt (B) threaded through an aperture provided on the securing flange (25). Channel (11) is provided in the fireback casing upper surface edge for placement of fire rope (18) therein for a superior seal, if so desired. The sloped or jutting (J) portions of draught regulator frame (24) are shown. Debris traps (T) are shown in position near the pivoting axis of the baffles (14)

Referring now to Figures 6 and 7 show a top and bottom isometric view of the draught regulator (5) with baffles (14', 14", 14'") in the closed position, in a line drawing format, the baffles (14', 14", 14'") on draught regulator (5) are supported by a frame (24) and are pivotally mounted thereon by way of pivots (22) located on the frame (24). Handle (15) for activating baffle adjustment mechanism (21a, 21b) is also shown.

Referring now to Figure 8, which shows a top perspective view of the assembled fireback (1) having the draught regulator (5) mounted on the upper fireback casing (U) with the pivotal baffles (14', 14", 14'") attached to pivot mountings (22) in the fully open position in a line drawing format. Lower casing (L) is connected to upper casing (U) through connectors (8). The plurality of vertical ribbing or undulations (16) on the sidewall (4) are clearly illustrated in this

Figure. Hinged connecting linker (21b) of the baffle adjustment mechanism (21a) is also visible.

Referring now to Figure 9 which shows a front top left isometric view of the upper casing (U) of the fireback with draught regulator (5) being inserted in from underneath the top of the unit and in through the fireback (1) upper casing (U) from the underside position as shown by the directional arrow in the line drawing. Male parts (9) of connector (8) are shown also.

Figure 10 shows a front top left isometric view of the lower section of the fireback with auxiliary fire shields (6) about to be inserted into position on the rear fireback wall (2) and side walls (3, 4), with a handle (19a) disposed on the central top portion of the front face of the auxiliary heat shield (6') and hand gaps (19b) on the bottom of the side wall auxiliary heat shields (6", 6'"). Female (10) parts of connectors (8) are also visible. Auxiliary side wall heat shields (6", 6'") may be adapted to mate also with connectors (8) with nipples (not shown).

Figure 11 shows (i) a front top right isometric view of the auxiliary fire shield (6') with a handle (19a) disposed on the central top portion of the front face of the auxiliary heat shield (6') (ii) a rear elevation view of the auxiliary fire shield unit indicating where the securing nipples (26) are positioned to the rear of the shield, (iii) an side elevation view of the auxiliary fire shield (6), handle (19a) and nipple (26), and (iv) a cross section view through section line A-A shown in Figure H(U) showing a cross section the handle (19) and nipple (26) and resilient heat resistant ceramic fibre channels (23) disposed along the upper and lower edges of the rear of the shield (6') Figure 12 shows (i) shows a snapshot side elevation view of an outer surface of a sidewall

(3) of the fireback (1) with the draught regulator (5) about to be mounted on the upper fireback casing (U). In this particular example, the draught regulator frame (24) further comprises a peripheral dependent skirt (27) which extends down obliquely in this drawing and fits into a groove (28) disposed along the boundary of the upper fireback casing (U) uppermost surface edges and along supporting strut (7) as illustrated in Figure 12(ii). Figure 12(ii) also shows groove or channel (28) into which resilient heat resistant ceramic fibre (18) can be placed to ensure a good seal between the dependent skirt (27) of the draught regulator (5) and the groove (28) of the upper (U) fire back surface edge. Figure 12(iii) shows a retrofit draught regulator (5) with wedge shaped (W) frame (24) about to be position on an existing fire back. Pivotable flange (F) for mounting an additional disconnected baffle is also clearly visible at the front of the draught regulator 5.

Now referring to Figures 13 (i) and (ii), and initially Figure 13 (i) which shows baffles (14) in a fully open position. Linker (30) is coupled to the slider (29) of the baffle adjustment mechanism (21a) for deployment of the baffles through hinged connecting linker (21b) when the handle (15) is activated. Figure 13(ii), there is shown a close up view of the mounted draught regulator (5) of Figure 4 with the baffles (14) in the fully closed position. The drawings more clearly illustrates the baffle adjustment means (21) which is linked to handle (15) which is connected to a slider (29) which is slidably mounted relative to the handle (15) and the baffle adjustment means (21). Locking slot (L) maintains the baffles (14) in position when slider (29) teeth engage therewith.

Referring to Figure 14, there is shown a front elevation view of the installed fireback (1) in a fireplace surrounded by a mantelpiece (32). The chimney flue (33) and flue gatherer (36) is illustrated by the broken lines above the mantle.

Referring now finally to Figure 15, there is shown a left side elevation view of the installed fireplace (1) surrounded to the front by a mantelpiece (32) that is positioned flush with the front edges of the fireback (1) and sealed thereto by placing resilient heat resistant material therebetween. To the rear of the fireback, there is positioned a filling material (35) typically comprising typical lean mix material generally used in fireplace installations to protect the masonry wall (34) from heat and smoke damage, etc.

During installation, the fireback casing (1) may be installed into the fireplace in one integral piece or more conveniently, it may be assembled or installed together from two or more of the sections, as illustrated in Figure 2 above. Both upper (U) and lower (L) casing section of this example have corresponding vertical ribbing features (16) in each of the side walls (3, 4), so that when installed the ribbing forms a neat arrangement (16). The lower casing section (L) is positioned upright and is made ready for connection to the upper casing section (U). A length of resilient heat resistant ceramic fibre (18) is carefully positioned within the channel (11), which is clearly illustrated in Figure 11. The upper casing section (U) may then be connected to the lower casing section (L) by carefully aligning the series of male (9) and female (10) connections which are disposed to the front and rear of the lower and upper edges of the upper (U) and lower (L) casing sections respectively, and snapping into each to other to form the connectors (8). The sections may be further secured together by bolting the sections in place (bolt holes are not shown in this example). The entire fireback is now correctly assembled into a single unitary piece.

The draught regulator (5) may then be installed by positioning the regulator unit (5) on top of the upper fireback casing (U). In the example where the periphery of the top edge of the upper fireback casing is provided with a groove (28) (see Figure 12(i) and 12(ii)), a length of resilient heat resistant ceramic fibre (18) may be fitted into the groove (28), before the dependent skirt (27) of the regulator (5) is lowered to fit snugly into the casing groove (28). This securely mounts the draught regulator (5) in place on top of the fireback casing. If desired, the unit (5) may be further secured by fixing the apertured flange (25) to the inner side wall of the fireback by a screw or the like. The entire unit may then be positioned in the fireplace space as normal.

If the fireback has already been installed or is an existing fireback or fireplace, then the draught regulator (5) may be installed in the correct position by holding the unit in an upright position parallel to the hearth and by sliding it inwardly and upwardly along the upward slope of the fireback rear wall horizontal rib (12'") as indicated by the directional arrow shown in Figure 9.

The draught regulator (5) is suitably dimensioned to be fitted on top of the fireback or to be inserted from the underside of the front of fireback frame where it can be manoeuvred to be delivered into the fireplace mouth to be inserted above the mouth of the fireback, or simply positioned on supporting walls or brackets on a normal stone or concrete fireplace. The regulator may then be gently positioned on top of the upper fireback casing (U) where it may be bolted or screwed into position if so desired using apertured flange (25) (bolts/screws not shown in this example).

The auxiliary heat shield (6) may then be installed by facing the shield in the correct orientation and holding the shield by the handle (19) and positioning the lower edge of the shield (6) into pair of shield stops (20) positioned along the grate line (17) of the fireback (1) as shown in Figure 10. The shield (6) can be secured into the correct position by ensuring the nipples (26) (Figure 19) are aligned with the corresponding fireback rear wall apertures (31) (shown in Figure 9) and snapping the nipples (26) therein. The shield (6) can be removed by gripping the handle (19) and applying sufficient backward pressure to release the nipples (26) from the securing apertures (31). If desired, resilient heat resistant ceramic fibre (18) can be positioned into the grooves to form a heat resistant seal between the shield (6) and the fireback.

In use, when fuel is being burnt, the auxiliary heat shields (6', 6", 6'") will generally be fitted into position on the bottom of the fireback rear wall (2) and sides walls (3, 4). As the fuel is burnt on a grate positioned along the fire line (17), the temperature of the fireback (1) increases as hot flames strike the crests (13) of the plurality of horizontal ribbing (12) of the rear wall (2). The forward inclination of the ribbing (12) ensures that heat is efficiently thrown back or reflected into the room. The refractory material of the fireback (1) ensures that heat is conducted to other areas of the fireback (1) which are not as exposed to flame, e.g. the side walls (3, 4). The plurality of horizontal ribbing (16) provides surfaces where the conducted heat may reflect and radiate back into the room, thereby greatly increasing the efficiency of heat transfer from the fireback (1) of the invention when compared to traditional firebacks.

As need dictates, the user may adjust the position of plurality of baffles (14) by engaging the handle (15) on the draught regulator (5). The baffle adjustment mechanism (21) operates to moveably engage slider (29) to deploy the linker (30) which urges the baffles (14) in the desired positions thereby pivoting the plurality of baffles (14) about the plurality of pivot mountings (22) to fully open position or if so desired, to a partially closed position, so that the draught regulator (5) may act a damper.

When the fire is idle, and the user wishes to conserve heat energy in the room, they may adjust the draught regulator (5) by appropriately engaging the handle (15) so that the baffles (14) are pivoted to the fully closed position whereby draught and heat loss from the room through the chimney are substantially eliminated. This position also prevents entrance of draughts from the chimney entering the alternatively heated room, ensuring that wasteful heat losses are minimised. The device negates the need for unsightly fireplace screens and the like.

The auxiliary heat shield (6) remains in position until it requires replacement or cleaning. Experimental

The fireback of the present invention and an off the shelf standard concrete/refractory fireback were subjected to comparative efficiency testing. The initial stage of this work involved characterising the thermal performance experimentally using IR thermography and then providing some qualitative analysis to compare the performance of the two units. The total radiating surface areas of the two different units have also been compared.

A schematic of the experimental facility is illustrated in Figure 17. It consists of a fireback, a heat source and an infrared thermal imaging camera. In order to provide a controlled thermal environment within which different firebacks could be compared and contrasted, it was decided that consumable fuel (solid/gas) was not appropriate to use. Instead a total of five resistive heater elements with a maximum rating of 1.0 kW each (5 kW combined) were purchased to simulate the hot coals of a solid fuel such as peat or coal. The heaters were arranged in two rows, two on top and three on the bottom, held in place with purpose-built ceramic holders that provide electrical isolation as well as heat shielding, so as not to damage the power cables. The power to the heaters was controlled by three variable transformers and was maintained at 4.5 kW for each test. A photograph of the set up is given in Figure 18.

A second test configuration is illustrated in Figure 19. This configuration involves a 2 meter x 1.5 meter board positioned facing the front of the fireback and a thermal imaging camera positioned such that it can view the front of the board, which is exposed to the radiating front side of the fireback. The board was painted matt-black and was positioned (i) 1.0 m and (ii) 2.0 m from the front of the fireback to gain an indication of the heat spreading characteristics of the respective firebacks.

The test conditions were maintained constant for each test and was as follows: With the heater elements resting on the grate, a fireback was positioned in place. The heat absorbing board was placed 1.0 m from the front of the fireback. The infrared camera was placed behind the fireback. Heat to the elements was turned on and kept at 4.5 kW and a stopwatch was started. The maximum temperature, as indicated by the thermal imaging camera, was monitored along with the time on the stopwatch. Steady state was assumed to be reached when the maximum temperature did not change more than 1°C in 5 minutes. Thermal images were taken in the following order and are depicted in Figure 20: (i) Rear of fireback; (ii) Front of heat absorbing board at 1.0 m; (iii) Front of heat absorbing board at 2.0 m; (iv) Front of fireback (straight on view); (v) Front of fireback (angled view). Results and Discussion

Steady State Tests

One performance indicator which can be use to evaluate the thermal characteristics of a fireback is the unwanted heat leakage through the back of the unit. It is desirable to minimize this leakage as this would mean more energy being dissipated from the front and less wasted through the back. Even with the most sophisticated equipment, measuring this quantity is not a trivial task. However, two indicators which can qualitatively represent the level of heat leakage are (i) the maximum temperature of the back face, as well as (ii) its temperature distribution. In the former, the higher maximum temperature would indicate higher heat leakage. In the later, the smaller the surface area which is 'hot', is desirable from a heat loss standpoint. Figure 21 shows the thermal images of each test subject scenario being tested. Figure 21(i) shows a thermal image of the fireback of the invention fixed with the auxiliary heat shield in position against the back wall; Figure 21(ii) shows a thermal image of the fireback of the invention without the auxiliary heat shield and is meant to give an idea of how a conventional cast iron fireback would behave; and Figure 21(iii) shows a thermal image of a standard refractory fireback. Figures 22(i) and 22(ii) show similar information; however for a better comparison, the temperature distributions along horizontal and vertical lines which intersect roughly at the centre of the hot spot are plotted. From the figures, three things are immediately apparent: (i) the cast iron unit without the reflecting panel is significantly hotter (~100°C) than the other two test subjects, which signifies substantially higher heat losses through the back; (ii) the cast iron fireback shows a more diffuse thermal fields compared with the refractory unit (i.e. a smaller difference from maximum to minimum) which is not surprising, since the thermal conductivity of the cast iron is much higher and should spread the heat more evenly as a result; (iii) the fireback of the invention with the auxiliary heat shield in place has a maximum temperature which is about the same as the refractory unit which signifies that the magnitude of the heat leakage will be comparable. Perhaps the most striking observation with regard to Figure 21 is the drastic change in the vertical thermal profiles for the fireback of the invention, with and without the auxiliary heat shield. When moving upward from the ground, the two profiles (red and green in top graph) are quite similar. However, above approximately 7 cm where the auxiliary heat shield begins, the temperature quickly peaks (~190°C) and then begins to drop off drastically for the scenario with the auxiliary heat shield installed. Without the auxiliary heat shield, which should be similar in nature to a conventional cast iron unit, the temperature continues to rise to about 29O ⁰ C and remains substantially above the test subject with the auxiliary heat shield in place. It can be inferred from this that the fireback of the invention could be expected to have comparable heat leakage compared with a refractory fireback and significantly less heat leakage compared with other cast iron firebacks. From the discussion above it would appear that the presence of the removable auxiliary heat shield has a surprising and advantageous role to play in the thermal characteristics of the unit. Apart from the heat constriction capabilities to be discussed shortly, the thermal images in Figures 23 (i) to (iii), show clearly that the fireback of the invention with the auxiliary heat shield (middle green graph) behaves radically different to the other two test subjects.

Compared with the refractory (Figure 23(i)) and conventional cast iron (Figure 23(iii)), the fireback of the invention comprising the auxiliary heat shield (Figure 23(iii)) tends to be a much more efficient heat absorber, likely due to the fact that it arches over the red hot elements which put it in more direct contact with the hot air issuing upward as well as the electromagnetic radiation emanating the elements. To supplement the obvious from the imbedded thermal images, temperature profiles of the radiating surface for equally spaced horizontal lines above the heater are plotted for each test subject in Figure 23. Accordingly, Figure 24 shows temperature plots for each test subject from the top of the heater upward along the front radiating surfaces of the firebacks. Firstly the figures show that albeit the refractory unit has a higher maximum temperature, it falls off very quickly due partly to the low thermal conductivity of refractory cement which would inhibit heat spreading. In Figure 24, this is apparent from notable drop in the level of the temperature profiles numbered 1-3 whereas in Figure 25, it is the steep negative slope. The fireback of the invention with the auxiliary heat shield in place tends to maintain a high temperature over an extended distance above the heater elements. In Figure 23, this is clear from a much lower drop in temperature from lines 1 to 3 (~125°C) which for the equivalent distance was closer to 275 ⁰ C for the refractory unit. In comparison, the cast iron unit without the auxiliary heat shield shows comparatively poor thermal characteristics as the front surface temperatures are comparatively low due to the heat escaping through the back of this unit.

In order to gauge the radiating characteristics of the firebacks a relatively simple experiment was performed. A large piece of plywood (1.5m x 2m) was painted matt black and placed facing the front side of the fireback. The painted plywood will absorb the thermal radiation emitting from the fireback and different radiating bodies should have different heat signatures on the heat absorbing board. In order to compare the heat emission and spreading of the different fireback scenarios the board was located distances of 1 m and 2 m from the front face. Results for the 1 m and 2 m placements are shown in Figures 25 and 26 respectively. It is clear that the fireback of the invention with the auxiliary heat shield in position tends to provide a more desirable heat signature in the sense that the board at 1 m is notable warmer (3 to 4 ⁰ C) as shown in Figure 25. The refractory and cast iron firebacks without the auxiliary heat shield show heat signatures which are very similar which is not surprising since they are similar in geometry. The 1 m placement can be considered rather close and much of the radiative heat signature being picked up is from the heating elements themselves (hence why they are similar in magnitude and profile). The 2 m spacing should offer a better comparison of the heat spreading characteristics of the different firebacks. As depicted in Figure 26, it is clear that the fireback of the invention with the auxiliary heat shield surprisingly shows far superior output compared with the other two test subject scenarios, in particular the refractory unit. Along the horizontal section the temperature is notably higher which indicates higher output from this unit. The vertical spreading (lower Figure 26(ii)) shows both a higher temperature as well as a very different profile compared with the refractory fireback. This indicates that the design i.e. the undulating surface topology, of the fireback of the present invention improves the radiative heat transfer.

It is believed that the reason the auxiliary heat shield tends to restrict the heat flow through the back of the cast iron fireback, as indicated by the lower maximum temperature compared with the cast iron unit without the auxiliary heat shield, is the that the plate fits quite loosely with the main fireback housing due to the lack of pressure/force (from a mechanical clamp for example) coupled with the fact that there is a fire retardant rope seal between the shield and the casing. It is thought that these together create small air pockets between the auxiliary heat shield and the main casing which could act as surprisingly efficient heat insulation that unexpectedly constricts the heat flow through the back of the fireback.

To confirm the theory, two physical models are proposed; both of which with analytic solutions which can be compared, qualitatively to the experimental observations to give a first approximation confirmation of the proposed mechanism of heat flow constriction. In the first case, a wall of cast iron, 2 cm thick, was heated to the extent that the front surface is maintained at 400 ⁰ C. To simplify the calculation the heat flow is assumed to be one-dimensional, i.e., the entire front face is this temperature. The heat is allowed to flow across the iron slab to the back face whereby the heat is dissipated by natural convection and radiation to an environment maintained at 2O ⁰ C. This is illustrated in Figure 27. If the model is qualitatively feasible the temperature drop from the from to back should be in the region of 45 ⁰ C, which is the approximate measured difference between the maximum front and maximum rear temperatures of the cast iron fireback without the auxiliary heat shield installed. Due to the one-dimensional and steady state assumption it is appropriate to apply the Ohm's law analogy whereby the heat transfer is analogous to the electrical current, the temperature drop analogous to the drop in voltage potential and the thermal resistance analogous to the electrical resistance. In this scenario the equivalent thermal resistance network is illustrated in Figure 27. The relevant equations for the conductive, convective and radiative heat transfer rates are, respectively,

lcomicnon ^~ \ km ~ »M ' tfnuhanoπ ~ ^V lief ^~ * csli '

The solution to this problem requires that,

1 conduction 1 convection 1 radiation

and an iterative approach was implemented to give a front-to-back temperature difference of about 35 ⁰ C, which is close enough to the measured maximum-to-maximum front-to-back temperature difference of 45 ⁰ C. This confirms the usefulness of this simplified model and associated assumptions imposed on it to provide qualitative information.

In the second scenario a small air gap (~1 mm) is situated between a front plate and a back plate. This scenario is illustrated in Figure 28 and once again the front face is kept at 400 ⁰ C and the rear face is exposed to air in an environment at 2O ⁰ C. For this model to be qualitatively valid an overall temperature drop commensurate with the measured 200 ⁰ C should be calculated. Again the solution approach is iterative and results in an estimated 'front-to-back' temperature drop of about 15O ⁰ C which again is close enough to the measured difference that the proposed physical model is reasonable. It is assumed that an air gap caused by the loose fit of the panel formed by the auxiliary heat shield with the main casing can cause a significant enough restriction to heat flow that the heat losses through the back are significantly reduced compared to a design with a solid.

Further tests were carried out by increasing the level of heat constriction of the gap between the auxiliary heat shield and the main housing. First a 5 mm gap was machined in the heat reflector plate with the hope of increasing the size of the air gap and thus the level of insulation. However tests indicated that no notable decrease in the temperature of the back of the fireback occurred. A plausible reason for this is that small gaps offer good insulative properties since the heat must conduct across the air. However, if the size of the air gap is increased to such an extent that buoyancy allows air to circulate within the gap, then this will tend to improve heat transfer across the gap and cause the insulative property to deteriorate. In a second test the 5 mm gap was filled with high temperature insulation. Tests again indicated that no notable improvement was apparent. Utilizing a model similar to those outlined above though discounting radiation across the 5 mm gap which is filled with insulation, a temperature drop of about 200°C was calculated which is larger than with the small air gap. However, testing interestingly showed no significant difference which is surprising, though may be due to type of insulation used which, although is rated for temperature, had an uncertain thermal conductivity and may have been too tightly compressed within the gap. Air Infiltration due to Open Chimney The fireback of the invention comprises an adjustable draught regulator situated at the top of the fireback. The draught regulator baffles can be closed to prevent unwanted energy loss due to air leakage through the open chimney. Quantifying the exact energy savings is not possible since there are so many variables which will affect the actual amount of air infiltration caused by an open chimney, including: type and size of fireplace/chimney, the outdoor temperature and wind speed, the layout and air-tightness of the room & house, the type of ventilation, human factors such as open/closed doors, etc. However, there two journal papers which do provide some scientific measurements and calculations regarding the negative impact of open chimneys. These papers are; (i) Dalicieux, P., Nicolas, C, Ventilation perturbations due to an open fireplace in a house, Energy and Buildings 14 (3), pp. 211-214 (1990).

(H) DJ. Dickson, The work of CIB members: Open fireplace can be installed in a well-insulated draught-tight house provided air flow via chimney is minimized by a removable closure plate, Building Research & Information, 1466-4321, Volume 16, Issue 4, 1988, Pages 237 - 245.

In the Dalicieux and Nicolas study, a sophisticated building thermal simulation model was developed to include predictions of air infiltration through the building shell, the ventilation system as well as what they term the overconsumption due to the presence of the open chimney. The model was developed for a representative test case i.e. a detached house, electrical convectors, mechanical ventilation, with or without an open fireplace, and the outdoor conditions were allowed to vary according the time of year. The simulations indicate that, for the home with a general leakiness of 70 m ³ /h, the average yearly overventilation due to the wind was 20 m ³ /h, and the overventilation due to the open fireplace was 150 m ³ /h, which results in a drastic increase in energy consumption. Figure 29 illustrates this finding where the energy required to heat up the air infiltrating the building is calculated.

What is clear is that the extra fresh air infiltrating the building due to the open fireplace puts very high demand on energy. In particular, during the heating season, the energy consumption due to air change with a chimney flue gate left open is over double that without a chimney. The energy overconsumption is dependent on the outside air temperature. Dalicieux and Nicolas quantified this effect and their results are depicted in Figure 30. As it is shown, the negative effect of the chimney is clear. At an outdoor temperature of 10 ⁰ C the power consumption is roughly doubled (~500W) and this increases with decreasing outdoor temperature i.e. an additional 1.5 kW at -6°C which is about a 2.3 fold increase, which is significant. Dickens experimentally studied air infiltration rates in what can be considered a rather airtight test house (Figure 31) and were performed under moderate wind conditions (~4.5 m/s) and small indoor-to-outdoor temperature difference (~4°C).

The tracer gas method was used to measure the infiltration rates for various test subjects. In this technique a tracer gas (in this case sulphur hexafluoride) is released and uniformly mixed throughout the space of interest. The concentration of the tracer gas is detectable with an appropriate meter and the rate of decay of the concentration with time is related to the air change rate. In this experiment, the lounge area is the area of interest since it is the room in which the fireplace is situated. Measurements were taken in the lounge to measure local air change rate as well as partway up the stairs to gauge the house mean infiltration rate. Obviously, the higher the infiltration rate/air change rate, the higher the rate of energy consumption to heat the excess of fresh air. The test subject scenarios are shown in Figure 32. As Dickens discusses, the whole-house infiltration rate is between 0.15 - 0.2 ac/h (ac/h=air changes per hour) due to general leakiness of the house in mild breezy weather (i.e. fireplace sealed and J-vent closed). This can be considered 'tight'. Opening the J-vent alone increased the whole house infiltration rate slightly (0.15-0.31 ac/h) whilst opening the fireplace alone increased the whole house infiltration rate a similar amount (0.24-0.38 ac/h). In the lounge itself (i.e. with the door to the lounge closed) the effect of having the J-vent or fireplace left open is more substantial with an increase from 0.15 ac/h to 1 ac/h which, as noted, can have negative implications with regard heating requirements of the lounge. For the scenario where the fireplace and J-vent are left open the infiltration rate in the lounge (door closed) shoots up to 1.5-2 ac/h which will have serious implications for heating requirements since the cold fresh air is coming in through the J-vent. Further to this the whole house ventilation rate increased by 0.3 ac/h over that of the sealed house, which is significant. In conclusion, the two studies discussed above show that very severe energy overconsumption will result in the situation where a fireplace chimney is left open. Surface Area

Another aspect of the fireback of the invention is the extended surface area associated with ribs and protrusions as shown in Figure 33. A detailed calculation of the total exposed surface area of the front radiating surface is given above. The total surface area is summarized as: Middle Section Total Surface Area = 0.253673669; Left/Right Section Total Surface Area = 0.055639861 m ² ; Total Surface Area = 0.253673669 + (0.055639861 x 2) = 0.365 m ² . This is about 16% more exposed surface area compared with the standard refractory fireback which has a total surface area of approximately 0.323m ² . Conclusions The fireback of the invention has some particularly advantageous design features, including: Auxiliary Heat Shield

Unexpectedly, the removable auxiliary heat shield drastically reduces heat leakage through the back of the fireback to the extent that the magnitude will be comparable to a refractory fireback and drastically surpasses that of a standard cast iron fireback. The heat restriction is a small air gap between the plate and the housing (which is in the scientific community is coined the contact thermal resistance and is well known to be a severe heat constriction, in particular in electronics thermal management). As this is an extremely promising first prototype, it is my expert opinion that there is significant room for further innovation which may radically improve the efficiency of this fireback, possibly to the extent of being more efficient than the competitors on the market.

The removable auxiliary heat shield is designed in such a way as to absorb the heat from the fire in such a way as to improve the temperature uniformity profile of the front heat radiating face which must, in no small way, improve the discharge of heat into the room.

The fireback of the invention shows a very notable improvement in the heat signature at a distance of 2 m from the fireplace (20% increase in measured maximum temperature) which clearly indicates very much improved radiative heat transfer as is consistent with the previous point above. Although not strictly analogous, this result would, from a human comfort perspective, indicate that the room would feel several degrees warmer at this location. Draught Regulator Thus, the closable vent on the fireback of the invention can be expected to drastically reduce energy overconsumption compared with conventional open firebacks without this capability. Data indicates that if the chimney vent is closed when the fire is not lit, one will save considerable energy and money due to a reduced air exchange rate, i.e., reduced energy burden due to heating the unnecessary infiltration of fresh air. In particular, a test case in what can be considered a relatively mild climate predicts that an annual increase of as much as 30% additional energy usage can result with an open chimney, which is significant. Undulating Surfaces

The fireback of the invention has a surface area which is about 16% greater than that of a conventional refractory unit within the same space-claim of the fireback. Since the heat energy radiated into the room is directly related to the surface area, this combined with the improved heat spreading as discussed above are very likely contributing factors resulting in the much more desirable heat signature.

Improved Burn Efficiency using Draught Regulator The draught regulator also improves efficiency, when the fire is lighting. In this example, using nuggets (Bord Na Mona nuggets are pressed much like a briquette, comprising of peat and coal) and regular briquettes. The same fuel amount was used in each test. The results below indicate improved efficiency (greater than 100%) by using the draught regulator of the invention at different openings (Ignition 50% & Loads 100%) will result in improved efficiency.

NUGGETS BURN TEST

STANDARD 100% OPEN 50% OPEN MEAN RADIATION MEAN RADIATION MEAN RADIATION KW (heat) % KW(heat) % KW(heat)%

The test using Peat Briquette as fuel, shows 18% improved efficiency (over a standard refractory fireback) by having the Damper 50% Open during the ignition phase.

Peat Briquettes BURN TEST

STANDARD 100% OPEN 50% OPEN

MEAN RADIA TION MEAN RADIA TION MEAN RADIATION

Conclusions

The points outlined herein are clear, yet qualitative, indicators that the fireback of the invention has surprisingly efficiency attributes, both from energy efficiency (fire lit) and overall energy consumption (fire lit & not lit) points of view. The words "comprises/comprising" and the words "having/including" when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub- combination. The invention is not limited to the embodiments herein.