TECHNICAL FIELD

The present invention relates to combination laundry washing and drying machines and in particular, though not solely, to laundry washer dryers including condensing drying functionality.

BACKGROUND TO THE INVENTION

While some combination washing and drying laundry appliances include a heat-pump drying system, currently it is typical for such machines to incorporate a condensing drying system (such machines are referred to hereinafter as "condensing washer dryers"). Typically, condensing tumble dryers have an air-cooled heat exchanger for removing moisture from the process air. The lack of space within the cabinet of a condensing washer dryer, because of the need to house both washing and drying system components within a standard-sized cabinet, means that incorporating a conventional air-cooled heat-exchanger is not feasible.

Most condensing washer dryers therefore include an internal duct that runs, for example, vertically up one of the rear edges of the cabinet. During drying, hot moist process air from the drum flows into the bottom end of the condensing duct (which reduces its moisture content), passes vertically through the duct, exits the upper end of the duct, passes through a fan and over a heater element before returning to the drum to remove further moisture from the clothes load therein. Cold water may be sprayed into the airflow within the duct, or trickled down its inner surface, to encourage condensation of moisture from the process airflow.

Unlike dedicated laundry dryers, most condensing washer dryers do not have a user- serviceable lint filter in the process air flow. For ease of access, such a filter would often be positioned below the door opening but the reduced space in combination washer dryers makes this difficult. Also, providing a lint filter for process air in the same fluid path used to convey washing liquid could risk a blockage or restriction to water flow. When a dedicated, conventional lint filter is not provided in a combination washer dryer, lint often accumulates on moist surfaces, such as within the condensing duct. Eventually, if sufficient lint accumulates in the condensing duct, the duct may become blocked (impeding air flow and therefore reducing drying performance) or it could be drawn into the fan, blocking it. Attempts have been made to utilise the condensation-inducing water spray/trickle within the condensing duct to clear/reduce lint accumulation by temporarily increasing water flow (see, for example, EP2037035A1, EP340403A2, CN1464092A) and extracting the lint and water mixture via the drain, but this has only limited success.

Also, the drying time of the laundry load could be reduced if the condensing duct was capable of extracting moisture from the process airflow more quickly. It is known to add projections to the inner surface of the condensing duct to increase the contact surface area between the airflow and the condensing duct to thereby decrease drying time (see, for example, JP2003135890A) but this can lead to problems with more lint being trapped on the surfaces of the condensing duct. Another option is to add baffles to the condensing duct so that the air flow dwells in the condensing duct for longer (see, for example, JP2008086423A) but this also encourages the deposition of more lint within the duct and can increase airflow resistance, detrimentally affecting moisture extraction from the laundry load and increasing drying times.

SUMMARY OF INVENTION

The present invention seeks to provide a condensing duct for a laundry machine and/or a laundry machine incorporating such a condensing duct, which will go at least some way towards overcoming at least some of the above problems or which will at least provide the public with a useful choice.

In a first aspect the invention may broadly be said to consist in a condensing duct for a laundry drying or combination laundry washing and drying machine, comprising: an air inlet and an air outlet for allowing air containing moisture and lint to flow therethrough, and a lint accumulation region, the lint accumulation region located at or adjacent to the inlet and concentrating lint on surfaces of the condensing duct in this region.

In a second aspect, the invention may broadly be said to consist in a laundry drying or combination laundry washing and drying machine, comprising: a cabinet, a drum for receiving laundry for drying, the drum rotatably supported within the cabinet, a process air path within the cabinet drawing air from the drum and returning processed air to the drum, wherein the process air path includes: a condensing duct according to the first aspect for receiving the air from the drum, a fan for moving air through the process air path, and a heater for heating the process air.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a front-loading combination laundry washing and drying machine incorporating a condensing duct according to an embodiment of the present invention;

Figure 2 is a perspective view of the condensing duct shown in Figure 1 from the rear, a side and above,

Figure 3 is a front elevational view of the condensing duct of Figure 2 in the direction of arrow A,

Figure 4 is a cross-sectional view of the condensing duct of Figure 3 along plane IV-IV, Figure 5 is a side elevational view of the condensing duct of Figure 2 in the direction of arrow B,

Figure 6 is a cross-sectional view of the condensing duct of Figure 5 along plane VI-VI, Figure 7 is a close-up view of region C in Figure 4,

Figure 8 is a close-up view of region D in Figure 6,

Figure 9 is a schematic diagram of the main functional components of the drying system of a condensing dryer, such as a condensing combination washer dryer,

Figure 10 is a cross-sectional view from one side of part of a condensing duct in accordance with a further embodiment of the invention, similar to the view shown in Figure 4, and Figure 11 is a cross-sectional view of the part of the condensing duct further embodiment shown in Figure 10, similar to the view shown in Figure 6.

DETAILED DESCRIPTION OF EMBODIMENT

An exemplary front-loading condensing washing and drying laundry washing machine/appliance 1 is shown in Figure 1. As is well known, machine 1 includes an outer cabinet 2 mounted within which, by a suitable suspension system (not shown), is a generally cylindrical fixed (non-rotating) outer tub or water container 3 (see Figure 9) for containing washing liquid. Within the outer tub, a generally cylindrical, rotatable perforated drum 4 is mounted for holding a load of laundry, such as clothing, for washing and subsequently drying. Access to drum 4 for loading and unloading, is via a circular opening at an axial front end of the drum. A door 5, mounted to cabinet 2, seals against a flexible tub/drum bellows (not shown) spanning between the drum opening and a corresponding tub opening, when the door is in a closed position.

Although Figure 1 illustrates a front-loading (or "horizontal axis") laundry washing machine, it should be understood that the present invention is equally applicable to other forms of laundry washing and drying machine, such as inclined-axis machines.

During operation of laundry washing machine 1, a controller 6 receives input from a user interface ("Ul") or control panel 7. Although not shown, a user may alternatively interact with controller 6 via a wirelessly-connected electronic device such as a "smart" mobile telephone or tablet device executing an applications program. The machine may also be adapted to be connected to the Internet and a user's Internet-connected electronic device may then communicate with machine 1 via a "Cloud" (that is, Internet) -based appliance communication/control system. The user may, via interaction with the controller, be able to select certain predefined operating cycles (e.g., gentle or "heavy duty" washing cycles, or a delicate drying cycle) and/or to set certain wash and/or dry parameters such as washing water temperature or drying time, as is well-known. Machine 1 may also be provided with a sensor within tub 3 for determining when to terminate a drying cycle, such as a conductivity sensor or a humidity sensor for determining when the water content of the laundry load has been sufficiently reduced that the laundry load can be considered to be dry. As is also well known, controller 6 may incorporate a microprocessor and associated memory for storing executable instructions in the form of a computer program controlling operation of laundry machine 1, in one or more user-selectable wash and/or dry cycles. Controller 6 is also connected to control the operation of an electric motor (not shown) which is energised by the controller at appropriate times during a selected operating cycle to rotate drum 4 at a selected speed. During an initial, water-filling part of a "washing" operating cycle, or during the actual washing part of a "washing" operating cycle, the selected speed may be low (less than about 100 rpm) to tumble the laundry load through the detergent and water mixture, and the direction of rotation may be reversed occasionally/regularly. During a spin-drying part of a "washing" operating cycle, near the end of the cycle, the rotational speed is high (above about 1000 rpm). During a "drying" operating cycle the drum may be rotated at a relatively low speed (less than about 100 rpm) and the direction of rotation may be reversed occasionally.

During a washing operating cycle water is provided to the tub/drum via a water inlet valve or valves, under instruction of controller 6, usually via a detergent drawer 8. Detergent drawer

8 is loaded by a user with detergent or other wash additives which are dispensed to water flowing therethrough and on to the outer tub in the known way. Controller 6 is also connected to control the energisation of a fan 8 (see Figure 9) in a process air path connected between an air outlet of tub 3 and an air inlet of the tub. When energised during a drying operating cycle, fan 8 draws moisture-laden process air from the drum into a condensing duct 9 for removing moisture from the process air by lowering its temperature (and whose structure and function will be explained in more detail below), over a heater 10 (whose energisation is also effected by controller 6) and back into the tub/drum for heating the laundry load as it is gently tumbled in the drum to transfer moisture to the process air. Condensing duct 9 may, for example, be blow-moulded from a polymeric material such as polypropylene.

As best shown in Figures 1 and 2, and as schematically indicated in Figure 9, condensing duct

9 has a generally elongated shape such that it has a generally longitudinal axis 11, the longitudinal axis arranged in a generally vertical plane. The condensing duct tapers outwards towards its upper end. A side face 12 of condensing duct 9 that, in use, is adjacent to tub 3 is curved to substantially match the curvature of the tub (see Figures 3 and 6) while front 13 and rear 14 faces of the duct are substantially planar and parallel (see Figures 4 and 5). The combination of the various side, front and rear faces (in particular the inner surfaces thereof) may herein generally be referred to as the duct's side wall. Accordingly, condensing duct 9 is shaped such that it can be located laterally of tub 4, in a rear vertical edge or corner space of cabinet 2 to thereby occupy what would otherwise be wasted space.

A condensing duct air inlet 15 is provided at the lower end of the duct in front face 13 while the upper end of condensing duct 9 flares outwardly, both towards tub 3 and the front of machine 1, providing a generally horizontal upper surface 16 which is provided with an air outlet 17. Extending above upper surface 16 is a water inlet conduit 18, preferably formed integrally with the condensing duct and adapted for connection to a hose receiving a valve- controlled supply of fresh water from the machine's mains water supply. As will be explained in more detail below, the water supplied to conduit 18 both cools the air within, and surfaces of, the condensing duct to thereby encourage water vapour in the process air to condense. It also flushes lint from surfaces of the condensing duct 9.

At selected stages during a washing cycle and/or during a drying cycle, it is necessary to remove liquid from tub 3, such as after a washing or rinsing part of a "washing" cycle to thereby remove soil/detergent-laden washing liquid from tub 3. To achieve this, a drain pump 19 is activated by controller 6 either at an appropriate time during an operating cycle, or in response to a detected water level in tub 3 (for example during a drying operating cycle when the level of condensing/condensed water in tub 3 is at risk of contacting the drum and the drying laundry load therein). Drain pump 19 therefore transfers liquid and any entrained soil or lint from machine 1 to a drain external of the machine.

Condensing Duct - Structure and Function

As the laundry load is tumbled in drum 4 during a drying cycle, it not only releases moisture to the process air but it also gives up small particles and strands of fibre (i.e., lint). Because the inner surfaces of the condensing duct are damp or wet during operation, it will accumulate lint. Existing condensing ducts either accumulate lint substantially over their entire length, or the flow of air pushes lint towards their upper region, above the location where the water inlet conduit 18 injects water. Over time, the amount of accumulated lint in the condensing duct reaches a level where clumps may dislodge and pass through fan 8 and, potentially, on to the heater 10. The present invention aims not only to effectively and efficiently remove moisture from the process air passing through it, but to also create a lint accumulation zone/region C/D on the condensing duct's inner surface, located below the level of the location where water inlet 18 opens into the duct, at or adjacent to or in the proximity of air inlet 15, where lint is concentrated for ease of future removal via a water flush from water inlet conduit 18 or wash water from the next wash cycle.

The above result may be achieved, for example, by the condensing duct design illustrated in Figures 2 to 8 which will be described in detail below.

It can be seen in Figure 3 that water inlet 18 directs supply water substantially vertically downwardly into the upper region of condensing duct 9. Water from inlet 18 is directed against the inner surface of a vertical wall of side face 12 which curves gently toward the horizontal before curving abruptly upwardly at a protruding feature 20 in the water flow's path. Protruding feature 20 may be substantially "ski-ramp"-shaped and is adapted to enable an inlet water flow to be "launched" (preferably sprayed), out of contact with the inner surface of the duct, into the process air flow when the inlet water flow is at a sufficiently high flow rate. When water is sprayed into the process air it will improve the cooling (and therefore condensing) effect on the water vapour in the process air and it will also wet a large area of the inner condensing duct wall, thereby cooling a large area of the condensing duct that can in turn induce additional condensation of moisture in the condensing duct.

In addition, spraying water within the condensing duct (as a result of the aforementioned high water flow rate) has the effect of flushing the internal surface of the duct and any lint accumulated thereon down the condensing duct, out of air inlet 15 to drain pump 19 for removal from the machine. Encouraging lint to accumulate in a lint accumulation zone at a lower portion of condensing duct 9 therefore enables the high flow rate condensing duct water supply to flush a greater proportion of the lint accumulated within the condensing duct and therefore reduce the long-term amount of lint retained in the condensing duct. However, it is desirable to limit the volume of water used by the machine and so, ideally, the duration of water flow at this high flow rate is restricted.

The water flow via water inlet conduit 18 may also be provided at a lower flow rate whereby water effectively trickles onto the inner surface of side face 12, overflows protruding feature 20, and continues alongside face 12 downwardly towards the bottom of the duct. This trickle of inlet water may flow along and substantially within a groove 21 formed in side face 12, on inside of the duct. It has been found that this lower water flow rate through condensing duct 9 provides an acceptable level of condensing effect to dry the laundry load in an acceptable time period although it has little or no effect on accumulated lint on the inner wall of the condensing duct.

Accordingly, the water feed to water inlet conduit 18 is preferably provided from a supply that is capable of at least two water flow rates: a high flow rate (for example, about 3.5 litres per minute) for flushing lint from the side wall of the condensing duct, and a lower flow rate (for example, about 0.3 litres per minute) for causing or inducing water vapour in the process air flow to condense. This could be arranged, for example, by providing a single valve between the machine's inlet water supply and water inlet conduit 18 that is operable, by controller 6, to select either a high or a low flow rate as required. Alternatively, separate flow restrictor valves with differing nominal flow rates could be appropriately energised by the controller to deliver either a high or low water flow rate to water inlet conduit 18. To reduce the number of water valves required, a single valve could be used to supply both the detergent dispenser 8 and water inlet conduit 18 at the same time.

Controller 6 may therefore cause the condensing duct to be fed with a trickle flow (that is, low flow rate) of water either continuously or intermittently during a drying cycle to condense moisture from the process air. Equally, in order to conserve water, the controller could cause water to flow into the condensing duct at the high (flushing) flow rate only at the very end of a drying cycle, only at the very beginning of a drying cycle, or even only during or before a washing cycle preceding the drying cycle, to remove lint accumulated in the condensing duct during that or the previous drying cycle.

A lint accumulation zone of condensing duct 9 is indicated generally by dotted boxes C and D in Figures 4 and 6 and enlarged in Figures 7 and 8. Lint is encouraged to accumulate within the lint accumulation zone by the provision of a number of air redirection and deflection surfaces on the inner surface of the side wall of the duct. In Figures 7 and 8, air flowing through condensing duct 9 is indicated by a series of arrows. As shown in Figure 7, air enters the condensing duct via air inlet 15 in a direction between about 45° - 135°, preferably substantially perpendicularly, to longitudinal axis 11 and is directed against extension portion 22 of rear face 14. Recessed or extension portion 22 is a substantially circular region of rear face 14 that has been moved rearwardly, in the direction of movement of the incoming air flow, out of the plane of rear face 14. A planar circular face of extension portion 22 is offset from the remainder of rear face 14 by a distance between about 5mm and 15mm, most preferably about 10mm. The planar circular face of the extension portion 22 is connected to rear face 14 by a substantially cylindrical wall 23 about its periphery. As an alternative to a planar circular face, extension portion 22 could be bulbous or hemispherical or semi- hemispherical or generally concave-shaped so that airflow tumbling is encouraged.

Without extension portion 22, incoming air to the condensing duct would simply follow a curved path towards the axis of the condensing duct, with minimal turbulence. Extension portion 22 creates a first region of turbulence or tumbling/rotating in the air flow through the condensing duct by forcing the majority of the incoming airflow to turn back on itself in order to leave the extension portion 22 and carry on down the duct, undergoing a change in direction of greater than 90°, and up as much as 180°, while travelling only a small distance in the duct. It will be appreciated that this abrupt change in direction is akin to the action of a cyclonic separator in that more dense constituents (such as water vapour) in the air flow will be thrown towards the outside of the flow, and into contact with the inner wall of the condensing duct.

It will be appreciated that rear face 14 of condensing duct 9 is substantially planar and adjacent to the rear wall of the laundry machine's cabinet 2. Because extension portion 22 extends further rearwardly (relative to the front of machine 1) than the remainder of the condensing duct, it may be put into contact with the rear steel panel of the machine, enabling heat to be transferred from the condensing duct (in particular, the lint accumulation zone of the condensing duct) to the cabinet and its environment. Alternatively, an opening may be formed in the rear panel of the cabinet, commensurate in size, shape and location to extension portion 22 so that the extension portion may protrude through the opening to transfer heat directly to the air surrounding the machine, once suitable user-safety precautions are in place (because the process air may reach a temperature in excess of 65°C. The removal of heat from the condensing duct helps to cool the humid process air flow, thereby condensing more water from it. Additionally, the additional water condensed due to the reduction of temperature at the extension portion increases the dampness of the duct's internal surface within the lint accumulation zone so that this moisture beneficially concentrates trapped lint in the lint accumulation zone.

To increase the direction-changing, turbulence-inducing effect of the extension portion, a raised region or rib 24 may be provided on rear face 14 of the condensing duct, extending around at least a portion of the periphery of extension portion 22. Raised region 24 may be integrally formed with the condensing duct 9 or may be added during a processing step subsequent to formation of the duct, such as by a plastics welding step. The presence of raised region 24 increases the degree to which the incoming air flow must change direction before proceeding up the condensing duct and therefore increases the amount of moisture that condenses out of the air flow. When viewed from the direction of the incoming airflow to air inlet 15, as shown in Figure 8, raised region 24 may be curved or substantially semi-circularly shaped when extension portion 22 is substantially circular in shape. As shown in Figure 7, a cross-section of raised region 24 may also be semi-circular with the raised region extending outwardly from the internal surface of rear face 14, towards axis 11, between about 25% to about 50% of the depth of the condensing duct (that is, across the width of the duct as shown in cross-section in Figure 7). For example, the raised region may extend from the internal surface between about 5mm and about 15mm, preferably about 10mm.

As also shown in Figure 8, raised region 24 spans across much, but not all, of the width of the condensing duct so that a gap 25 exists between either end of the raised region and the adjacent side face of the condensing duct. Preferably the width (the distance from the raised region to the adjacent duct side face, for example face 12) of gaps 25 are, for example, between about 3 mm to about 8 mm and they may both be the same size or may be different in size. Gaps 25 enable air and/or liquid water to pass around the lateral extent of the raised region 24 in addition to the air flowing over the raised region (as shown in Figure 7).

The arrangement so far described encourages air to pass upwards (following arrows R in Figure 8) at one lateral end of raised region 24, laterally over the top surface of raised region 24 and downwardly through the other gap 25 (arrows W). The upward flow indicated by arrow R may effectively be a jetted, high velocity flow through small gap 25. The zone immediately above raised region 24 is another turbulence zone as indicated in Figure 7 by a curved arrow representing airflow rotating or tumbling in this region due to a low pressure created immediately above the raised region from the air flowing axially along the duct. As explained above in relation to extension portion 22, this turbulent zone increases condensation of moisture from the moist process air, wetting the inner surface of the rear face 15 above raised region 24 thereby adhering an increased amount of lint to the duct wall in the turbulent zone. As airflow R passing through gap 25 then flows laterally over the upper surface of raised portion 24 it tends to move some of the lint and condensed water mixture with it, which eventually flows downwards as indicated by arrow W at the opposite end of the raised portion, towards a sump region 26 at the bottom of the condensing duct.

As mentioned above, during a drying cycle of the machine, water will also be added to the condensing duct at a relatively low flow rate via water inlet 18 to cause or initiate condensation to occur. The airflow around raised region 24 will also move at least some of this added water upwards with airflow R and laterally over the top surface of the raised region to further help clear lint from the turbulent zone above it towards sump region 26. High velocity airflow R through gap 25 also returns liquid water (both added water and condensed water) upwards in the duct to coat higher areas of the duct's inner wall with water so as to condense even more water from the process airflow and thereby collect more lint on the duct's inner surface. Some of the liquid water pushed upwards by airflow R will lose contact with the surface of the duct's inner wall and enterthe airflow, mingling with the moist process air thereby cooling it and condensing additional water vapour to liquid water which will eventually be deposited on the duct's inner wall to attract lint deposition. As water and lint accumulate in sump region 26, it may eventually reach a level where it is able to overflow from air inlet 15, enter tub 3 and be drained from the machine via drain pump 19, during the drying cycle. Such draining operations may be timed or in response to sensing a predetermined water level in the tub.

To further improve the rate at which water may be extracted from the process air and the amount of lint that is removed from condensing duct 9, a secondary raised region 26 may be provided on the duct's inner wall, downstream of raised region 24. Secondary raised region 26 functions in a similar manner to raised region 24 and so the above description of raised region 24 is also relevant to secondary raised region 26. The moisture-removal and lint collecting effect of the secondary raised region 26 is enhanced if it is located on an opposing face/wall of the duct to the face/wall on which raised region 24 is located. Accordingly, in the illustrated embodiment, secondary raised region 26 is provided on the inner surface of front face 13, opposing rear face 14 on which raised region 24 is located. In this position, secondary raised portion 26 restricts the process air from easily and quickly passing directly to duct air outlet 17 and so increases the dwell time of air (and therefore liquid water) within condensing duct 9, thereby increasing its condensing effect. The secondary raised portion 26 also forces the process air against the inner duct wall of rear face 14 on the opposite side of the duct so that lint entrained in the process air can be captured by the wet duct inner wall instead of passing directly into fan 8. Eventually the weight of the volume of water held by the duct's inner wall will overcome the upwardly-directed force of the process air and a water/lint mixture will run downwardly towards the sump region.

Secondary raised region 26 may be integrally formed (such as by blow moulding) with a single piece or unitary condensing duct or it may be added to the duct by a post-processing step. Suitable post-processing may involve, subsequent to moulding the condensing duct in two halves, adding the raised region(s) (24 and/or 26) to one or other half of the condensing duct, then joining the two halves of the duct together such as by plastics welding.

Secondary raised region 26 functions in a similar manner to raised region 24 and so the above description of raised region 24 is also relevant to secondary raised region 26. Accordingly, secondary raised region 26 also preferably extends laterally (when viewed as in Figure 8) over much of the width of the condensing duct, leaving gaps 27 at either end to the respective side faces. As shown in Figure 7, after the process air passes raised region 24 it then interacts with secondary raised region 26. As with raised region 24, a turbulent zone is created above the secondary raised region for cyclonically separating liquid water from the process air flow against the duct's inner surface, and for accumulating entrained lint on the thus moistened duct surface. As also previously described in relation to raised region 24, air and/or water flow around secondary raised region 26 through gaps 27 follows arrows R and W such that at least some of the moist process airflow (and any entrained liquid water) passes upwardly through one gap 27 following arrow R, passes laterally over the top surface of the secondary raised region 26 (moving with it some of the lint accumulated in the turbulent zone) and then liquid water and entrained lint moves downwardly (following arrow W) through the other gap 27, eventually reaching sump region 26 for disposal.

Accordingly, there is a rotational flow of air and/or water about the raised regions, in a plane substantially parallel to faces 13 or 14 or axis 11. In the disclosed embodiment as shown in Figure 8 the rotational flow is in a clockwise direction but its direction and effectiveness may be influenced by such factors as the relative widths of gaps 25 (and/or the relative widths of gaps 27) and the start and end angles, about an axis of air inlet 15, that raised region 24 extends (for example, as shown in Figure 8 it can be seen that the raised region's right hand end is at around the 3 o'clock position while its left hand end is at around the 11 o'clock position - the same angular extent and angular orientation factors can also be applied to semi-circular secondary raised region 26 about its centre).

The above-described arrangement of condensing duct 9 includes process airflow- manipulating recessed and raised regions that produce the lint accumulation zone C/D. This increases the amount of liquid water present within the condensing duct at any point in time, thereby improving moisture extraction (via condensation) from the moist process airflow and accumulation of lint on the dampened/wetted duct inner wall. Raised portions 24/26 concentrate lint accumulation in accumulation zone C/D and also aid in removing accumulated lint due to their effect on both air and water flow within the condensing duct. The overall effect of the condensing duct's structure is to create a tortuous path for process air, increasing turbulence in the process air, retaining liquid water in the condensing duct for longer, increasing condensation and increasing lint extraction from the process air flow.

One aspect of the improved lint removal is the concentration of the accumulated lint in the lint accumulation zone C/D rather than at the top of the duct where it cannot be easily removed. Lint captured in the lint accumulation zone, at the lower end of the condensing duct, at or around or adjacent to air inlet 15 may be removed from the machine by the aforementioned high flow rate water spray or flush, preferably at or near the start of the "next" operating cycle of the machine. That is, when a user adds a load of laundry to be dried or washed and dried, one of the first operations in the machine's operating cycle is to feed the high flow rate of water to water inlet conduit 18 for a predetermined time period to flush lint and then, optionally, energisation of drain pump 19 for a period of time to extract the lint/water mixture from the machine. Furthermore, because the lint accumulation zone C/D is at or near air inlet 15 at the lower end of the condensing duct, it is able to be washed or scrubbed from the condensing duct's inner wall by the action of washing water (containing detergent) or rinsing water in tub 3 as it is churned by the action of drum 4 rotating in it during a washing cycle of the machine's operation. Further Modifications

It has also been found that additional modifications to the above-explained arrangements can provide even further improvement in lint removal from the condensing duct (or a reduction of accumulated lint in the condensing duct) and/or an improvement in the duct's ability to condense water from the process air flow through the duct. These additional modifications will now be explained with reference to Figures 10 and 11 which illustrate a further embodiment of condensing duct which is in accordance with a preferred form of the invention.

As illustrated in Figures 10 and 11, raised regions or ribs 24 and 26 have been replaced with raised regions or ribs 29 and 30, respectively. Ribs 29 and 30 have a similar shape and profile to ribs 24 and 26 except that they extend to side face 12 so that one gap 25 and one gap 27 have been closed off. It will be appreciated that ribs 29 and 20 extend only part-way across the duct (as shown in Figure 7) so there is a clear path for air through the duct and the closure of gaps 25, 27 is aimed at controlling the flow of air, water and lint around the ribs to improve lint retention and condensing (i.e., fresh) water reduction.

An additional rib 28 may also be provided, ideally on rear face 14, around mid-way up the height of the duct. Rib 28 may be provided along with rib 30, with or without rib 29. When all three ribs are provided, preferably rib 29 is closer to rib 30 than it is to rib 28. Rib 28 may be angled with its higher end in contact with side face 12 and its lower end in contact with the opposite duct side face. As may be seen in Figure 10, angled rib 28 protrudes only part-way out towards the central axis of the condensing duct and may have a sloped or ramped or inclined upper surface and a substantially flat (that is, substantially perpendicular to rear face 14) lower surface, at least along part of its length or lateral extent (that is, between side face 12 and the opposite side face). The sloped upper surface assists water and lint flowing downwardly over the rib while the flat lower surface helps to restrain the water and lint mixture flowing upward on rear face 14. In this way, a film of water is trapped in a zone between ribs 29 and 28, preventing lint entrained in that water film from being pushed higher in the duct. By maintaining a film of water on rear face 14 the zone also has a lower temperature which leads to further condensing of moisture from the process air flow. Ramps may also be formed on the upper surfaces of ribs 29 and/or 30, at least over a section of their length closest to side face 12 in order to encourage water and lint to flow downwardly over the ribs in those sections towards the outlet. The path of the process air in the plane perpendicular to that shown in Figure 11 is the same as or similar to that shown in Figure 7.

Arrows 'R' in Figure 11 illustrate air flowing upwardly through single gap 25 at the distal end of rib 30, over the top of rib 30 and also upwardly through single gap 27 and over the top surface of rib 29. Arrows 'W' illustrate water moving upwardly in the zone between ribs 29 and 28 and being retained in that zone until falling downward under its accumulated weight, flowing over ribs 29 and 30 (particularly their ramped surfaces) toward the outlet.

Compared to a conventional condensing duct, in some cycles a condensing duct in accordance with embodiments of the invention herein described is capable of drying a laundry load with a reduction of up to 50% or more of added water during the drying cycle. It should also be noted that the benefits described above of the present condensing duct are achieved during normal operation of the machine (drier or washer/drier) that it is installed in. That is, it is not necessary to run a dedicated cleaning cycle to clean the condensing duct. Thus, the most substantial changes required to a product when its conventional condensing duct is replaced by a condensing duct according to an embodiment of the present invention, will be: a reduction in the total volume of water required to be sprayed into the condensing duct (because its effect is at least partially achieved by the increased volume of water condensed by the duct), and/or an increase in the frequency or duration of operation of the drain pump to increase the amount of water removed from the machine, or the rate at which it is extracted.