Background to the Invention It would be superfluous to describe in detail conventional boiler designs which the skilled addressee of this application will undoubtedly be familiar with due to their widespread use in today's society. Nevertheless, in order to provide the addressee with exemplary boiler designs, the following patent applications are deemed to be useful as a reference : GB2335266, GB2310711, GB2243205, GB2203531 and GB2169390. Each of these applications was filed in the name of Hedley Roland Micldeburgh.

In conventional boilers, a restriction is usually employed to control the flow rate of combustion air. This restriction is often provided in the form of an adjustable sluice gate that is fixed partly open during the use of the boiler. Most often, arrangements are made so that the opening is manually adjustable, usually in the context of the installation of the boiler or its subsequent annual maintenance. The correct flow of air thereafter depends on the pressure differential across the restriction remaining the same as when the boiler was first correctly adjusted.

In certain conditions such as windy weather, changes in the pressure differential may occur particularly when the boiler is connected to a conventional flue.

Changes of pressure in the flue will cause a deviation from the correct volume of air delivered to the combustion process. This deviation will have the consequence of momentarily reducing the efficiency of the combustion. Repeated momentary inefficient combustion is a serious disadvantage in the context of the modern day quest for more environmentally friendly systems. Furthermore, a momentary excessive supply of air to the combustion process may have the additional undesirable consequence of causing the flame to blow out, resulting in regular manual intervention in order to remedy these situations.

Also in conventional boilers, pressure in the combustion chamber in their start up phases is lower than that found once combustion is established. This temporarily adversely affects the aforementioned pressure differential allowing an excessive flow of air initially to be supplied to the combustion chamber often leading to noisy or even explosive start up phases.

One of the objectives of the present invention is to provide a flow regulating arrangement which may be used in connection with boilers to accurately control the flow of air to the combustion chamber irrespective of the environmental conditions in which the boiler is operating.

A further objective of the present invention is to provide a regulator which improves the overall efficiency of boilers through the accurate control of its air supply.

A further aim of the present invention is to provide a flow regulator which does away with any requirement for two stage firing systems such as those now employed with large industrial boilers, by providing an explosive free start up for the boilers.

An additional aim of the present invention is to provide a flow regulator which may be employed to accurately control the flow rate of the medium with which it operates and in particular to achieve constant output flow in the operating range of a given regulator.

Whilst conventional boilers have been used as a possible starting point for this invention, the invention is however not limited to this context. It is envisaged that such flow regulators as defined and illustrated in this application will have applications in any control of fluid flow.

Summary of the Invention In its broadest aspect, the current invention presents a flow regulating arrangement in which, in use, there is placed within the flow duct a flap which is displaceable in order to achieve variable flow resistance and is linlced operatively to measuring means so that said flap displaces as a function of the flow at the measuring point.

This arrangement is particularly advantageous because it allows the flow in the duct to be accurately controlled by varying the position of a flap. This configuration is particularly advantageous as it permits an essentially constant

output flow from the duct to be achieved irrespective of momentary increases or decreases in the pressure differential across the duct.

In a subsidiary aspect, the measuring means comprises one or more flaps and the rotation of the measuring means translates via an arm into the rotation of the first mentioned flap.

Utilising a simple arm to operatively connect the measuring means to the flap is particularly advantageous because of the reduced number of components this type of system requires. The hydraulic properties of a duct incorporating this particular arrangement are advantageous as the operating means connecting the measuring means to the flap either does not at all interfere with the flow resistance achieved by the flap or only to a limited extent.

This arrangement is also particularly well suited when placed in an elongate duct where the flap and the measuring means would operate in series. This configuration could easily be inserted into narrow elongate spaces in any conventional system.

In a further subsidiary aspect, the measuring means comprises one or more flaps, the first mentioned flap controlled by the measuring means is a butterfly, and the duct incorporates two chambers placed side by side, one chamber receiving the measuring flap and the other chamber receiving the butterfly; the butterfly and the measuring flap being arranged so that the measuring flap and the butterfly pivot about the same axis.

This latest configuration is particularly advantageous because it renders the current inventive arrangement compact and particularly well suited for incorporation in standard units such as the boilers or burners which are currently being manufactured.

In a further subsidiary aspect, one at least of the duct's walls is displaceable.

Constructing the duct walls to be displaceable has the particular advantage of enabling a given arrangement to vary its operating range by simply displacing one of the duct walls. In this situation, there is no need to dismantle the arrangement to access the flaps themselves for adjustment. The operational options are therefore maximised by this system.

In an additional subsidiary aspect, the measuring flap can selectively be lengthened or shortened.

Lengthening or shortening the length of the measuring flap effectively provides the arrangement with increased versatility which will ultimately allow the use of these arrangements within a wide variety of flow rates and with various flow medium.

In an additional subsidiary aspect, there is further provided means to provide a variable aperture bypass in series with the measuring means.

Provision of a variable sized bypass around the measuring means has a particular advantage to allow the apparatus to be set up for a particular operating environment. For example, given a particular air duct layout, the installer can adjust the variable sized aperture to ensure that the flow regulating arrangement operates, at steady-state, at an appropriate position in its range.

In a further subsidiary aspect, the invention presents a boiler incorporating a flow regulator according to any of the aspects defined above.

This invention particularly comes alight when specifically applied to boiler technology and particularly (although not limited to) the configuration where these are installed in the boiler's air intake. When these flow regulators are

inserted in the intake duct, the fuel combustion efficiency is enhanced as the flow rate is maintained essentially constant. Furthermore, the risk of the boiler's flame blowing out is considerably attenuated and even done away with when operating in a given range. In this configuration, the boiler's start up is particularly soft and explosion free which overcomes any requirement for a complex and often costly two stage firing process such as those installed on large boilers.

Brief Description of the Drawings Figure 1 shows a schematic cross-sectional view of a flow regulator in accordance with a first embodiment of the invention.

Figure 2 presents a perspective view of the assembly of a flow regulator according to a second embodiment of the invention.

Figure 3 is a further perspective view of the flow regulator according to the second embodiment of the present invention.

Figure 4 is a perspective view of a variable-gap bypass arrangement.

Detailed Description of the Drawings Figure 1 presents a flow duct generally referenced 1, primarily receiving an intake of flow medium in the direction indicated by the arrow 2. The flow medium as it flows along the duct 1 interacts with flow regulator generally referenced 3.

Flow regulator 3 incorporates a measuring flap 4 which is at pivot point 5 mounted to duct 1 at approximately 4/5 of the flaps length, the flap pivotally engages with an actuating arm 6 whose cross-section is deliberately reduced in order to limit the flow resistance of its surfaces. Actuating arm 6 pivotally engages with a butterfly flap 7 at pivot point 8. The butterfly flap 7 is of

sufficient length to extend across the inner walls of the duct so as to almost completely block the passage of flow medium under certain flow conditions.

Butterfly 7 pivots preferably about its centre point in relation to the duct and about the middle point between the flap's centre point and its extremity in relation to actuating arm 6.

Whilst this particular embodiment illustrates flaps whose dimensions are not variable, the invention envisages measuring flaps which can selectively be lengthened or shortened in order to render the regulator more versatile.

The flap may be constructed in such a way as to facilitate the variation of any other flap dimension if required. The invention also foresees that flaps with varying densities may be employed for any particular application. Furthermore, the flap's weight may be adjustable by for example the insertion of weighting means. The invention may also provide an adjustable by-pass between the measuring means and the butterfly flap which may be adapted for a variety of applications.

Returning to the specific description of the first embodiment of the invention, the broken lines in the drawing illustrate the various positions which may be adopted by the flaps extremities during use. In normal flow medium intake conditions, flap 4 would extend essentially perpendicular to the general axis of flow. Increases in flow would result in the flap displacing in the direction of the flow and transmitting to the butterfly 7 via the actuating arm 6 the movement from an initially almost non-resistive position to a flow medium resistive position, for example that illustrated in the present drawing.

In a boiler system, this flow regulating arrangement is particularly advantageous.

For example, when a negative pressure develops in the flue due to windy weather conditions, the increased pressure differential at the air intake which would normally result in an increase in air flow is effectively controlled and the resulting

air flow into the combustion chamber essentially is maintained constant irrespective of changes in the pressure differential.

In this embodiment, the flow direction is shown to be arrow 2 which translates into the air flowing first past flap 4 then past flap 7. The invention is however not limited to this particular sequence of flaps and envisages the situation where the flow of air first passes around the flow resisting flap such as flap 7 and then onto measuring means such as flap 4. The person skilled in the art would modify the linkage means between the measuring flap and the regulating flap in order to achieve satisfactory flow regulation in this reversed flow scenario without any recourse to inventive thought.

Figure 2 presents a duct generally referenced 9. Duct 9 comprises a central enclosure 10 to which two releasable walls 11 and 12 may be mounted through standard screw means such as that referenced at 13. Central enclosure 10 incorporates a measuring chamber generally referenced 14 and a regulating chamber (not illustrated in this drawing). Chamber 14 has an intake conduit 15 through which in a boiler air would enter. The air would generally follow the constrictions of the enclosure circulating around measuring flap 16 and then crossing over to the regulating chamber (not illustrated in this drawing).

While not illustrated in this drawing it is also envisaged that wall 17 be sufficiently concave to ameliorate the passage of air through chamber 14. It is also envisaged that such a wall would be displaceable towards or away from flap 16 in order to regulate the range at which the flow regulator would operate.

The materials used for the enclosure would typically be hard and heat resistive metal or plastic. It is also envisaged that lids 11 and 12 be manufactured of translucent material since it has been recognised that these lids do not require to be as strong mechanically as enclosure 10 while for aesthetical and maintenance purposes a translucent lid is deemed to be advantageous.

Figure 3 presents duct 9 as discussed with reference to Figure 2, however viewed from the regulating chamber side. The identical elements present in both Figure 2 and Figure 3 are referenced using the same numerals.

The flow medium enters chamber 14 via the conduit 15 and as described previously passes the measuring flap (not illustrated in this drawing) and exits this chamber in order to enter the regulating chamber 18 through opening 19.

Chamber 18 presents a butterfly 20 pivoted essentially about its central axis 21 which is linked through wall 22 to a measuring flap 16 in such a manner that flap 16 rotates together with butterfly 20. Due to clearances on either side of the butterfly, the flow medium controllably progresses past the butterfly and exits chamber 18 at exit 23.

The embodiment described in the context of Figure 2 and Figure 3 is particularly well suited to operation with boilers due to its compact construction. It is particularly well suited for achieving a constant output flow. This in turn contributes to improving the boilers efficiency in terms of fuel consumption and limits the risk of explosive starts and the flame blowing out during operation of the boiler.

Figure 4 illustrates a perspective view of an embodiment of a variable-gap bypass.

For clarity, the flow ducts are not illustrated in this diagram. There is shown a measuring flap 24, pivoting around a point 25, and operatively linked as described above, to a butterfly flap 26, pivoting around the point 27. The variable bypass means is provided by an element 28 having a sloping surface 29. Movement of this element along the line indicated by the arrow A allows the bypass gap 30 to be adjusted. Movement of the element 28 may be effected by a threaded rod 31 passing through a guide hole 32, the thread being advanced by means, eg. of an adjustment knob 33. Other suitable embodiments of such a device, given this

teaching, will be immediately apparent to those skilled in the art, and could equally well comprise sliding slots or lever-actuated means.

The advantages that become apparent when incorporating the above described flow regulators into boilers are also thought to be present when incorporating these flow regulators to burner units.

While these above mentioned applications for the present invention constitute its primary applications, it is however envisaged within the scope of this invention that these flow regulating arrangements may be incorporated into systems such as air conditioning ducts and water transfer systems.