Garments or other items to be washed are placed in the rotatable cylindrical drum, typically through a front opening door to the drum, or alternatively through an opening in the side wall of the drum. In either case, after the items have been put in the drum, the opening of the drum is closed, and the water tank closed.

Water is introduced into the water tank, filling the tank to a predetermined level. The water level is detected by a water level sensor in the form of a pressure sensor which detects the pressure of water in a pipe extending from the bottom of the tank caused by the head of water in the tank. The pipe extending from the bottom of the tank includes a pump downstream of the pressure detector which recirculates the water back to the tank. The recirculation path may include a heater to reheat the water.

Alternatively, the water may be heated either before filling the tank, or may be heated within the tank by a heater. The water within the water tank enters the cylindrical drum through the perforations in the cylindrical drum. The cylindrical drum is then rotated about its axis to agitate the items to be washed and to pass these through the washing water.

After completion of the washing cycle, the washing water is removed from the water tank, and hence from the cylindrical drum via an outlet. The outlet is either in the form of a valve which allows water to drain from the water tank by gravity, or is a pump. Clean water for rinsing is then introduced to the water tank and hence into the cylindrical drum. The drum is again rotated to agitate the items within the drum. The rinsing water is then removed from the water tank in the same way as the washing water.

It is desirable to increase the capacity of drum type washing machines to allow washing of larger loads.

However, washing machines, as with other household appliances, are generally manufactured to a standard size to fit into a standard size space below and between kitchen units. Accordingly, it is desirable that the overall size of the washing machine should remain the same as conventional washing machines. In a conventional washing machine, the size of the cylindrical drum which receives the items to be washed cannot be increased significantly without increasing the size of the water tank in which the drum is provided. The water tank cannot be enlarged without increasing the overall size of the machine, and it is therefore not possible to increase the capacity of a conventional washing machine whilst keeping the overall machine size unchanged.

One solution to this problem is to dispense with the separate water tank and cylindrical rotatable drum, and instead provide a single rotatable drum which both receives the items to be washed and contains all the water for washing and rinsing items. A single drum washing machine is disclosed in US-A-4,941,333.

It is however difficult to accurately determine the level of water in a rotating tank. It is not possible to have a fixed tube from the bottom of the tank in which the pressure due to the head of water in the tank can be determined since the rotation of the tank would mean the tube will continually rotate above and below the level of the water. Whilst it is possible to mount a device, such as a heater or pump, on an arm which is provided on the axis of the drum so that the device remains below the level of the water, a level sensor cannot be provided in this way. If the level sensor is in the form of a pressure sensor, this must be provided on a tube below and connected to the head of water. This is not possible with an axially mounted device. For other types of level sensor, the sensor must be able to determine the position of the top of

the water. This is not possible when the sensor is below the water level. Furthermore, with any sensor provided within the drum in which the items to be washed are contained, there is a danger that the items themselves may affect the determination of the water level for example by resting on the sensor.

Another way in which to determine the volume of water in the drum is to monitor the flow of water into the drum.

However, the optimum amount of water in the drum depends upon the amount of water absorbed by the items in the drum, and this cannot be predetermined. Accordingly it is necessary to measure or monitor the free water in the drum.

Washing machines are used not only for washing items of clothing, but may also be used for dying of garments.

In this case, the washing water is replaced by a suitable dye, but in other respects the washing cycle is unchanged.

SUMMARY OF THE INVENTION According to the present invention, a washing machine includes a rotatable drum with an outlet through which, in use, water is expelled, a recirculation path along which expelled water is returned to the rotatable drum, the recirculation path including a chamber open to the atmosphere, a pressure sensor downstream of or below the water surface in the chamber to determine the volume of water in the chamber and hence to monitor the volume of water in the rotatable drum.

When water is introduced into the drum, the water will initially be absorbed by the clothes. When the clothes are saturated, additional water added to the drum will remain "free"within the drum. It is desirable to saturate the clothes, and have a predetermined, small, free volume of water within the drum. In accordance with the invention, the volume of water in the drum is monitored to ensure the correct amount of water is supplied to the machine to saturate the clothes and give a predetermined volume of free water irrespective of the amount of water absorbed.

Initially, there will be only a small volume of water in the chamber. Water is introduced into the chamber from an external supply, and this water is pumped into the drum.

As this water is absorbed by the items within the drum, the increase in the volume of water within the chamber is due primarily to the water from the external source. When the items within the drum are fully saturated, additional water entering the drum will be"free"and so water will be discharged from the drum to the chamber. Accordingly, when the items are fully saturated, and therefore the desired volume of water has been supplied, the rate of change of the volume of water in the chamber will alter, or a predetermined volume of water in the chamber will be detected. This will give an indication that the correct amount of water is in the drum.

Preferably a cut off means is provided for cutting off the external supply when the required volume of water is detected.

The water expelled from the rotatable tank is introduced to the open chamber from which the recirculation path returns to the rotatable drum. As the chamber is open, it is at atmospheric pressure, and so the detected pressure is not affected by pressure fluctuations which may occur in a closed system. The volume of water can be calculated from the detected pressure.

The recirculation path advantageously includes a pump to recirculate the water, and may include a heater to reheat the water to a required temperature and a temperature sensor.

To expel water from the drum, the drum may include a collector arranged so that, in use, the drum contains water and items to be washed, and the collector collects and lifts water from the drum by rotation of the drum to dispel the water through an outlet. In this case, it is preferred that the drum has an inclined axis, so that water within the drum will be forced, under gravity, towards the back of the drum. The rotation of the drum causes water towards

the back of the drum to be collected by the collector and the continuing rotation of the drum lifts the collected water to a height above that of or level with, an outlet so that, under gravity, the collected water will be dispelled through the outlet. This system of dispelling the water does not require the rotatable drum to be rotated at a high speed.

In this case, the washing machine preferably includes a plurality of collectors angularly displaced with respect to each other around the back of the drum. This increases the rate at which water can be removed from the drum as with a larger number of collectors, the rotations of the drum required to remove the water. The outlet through which water is dispensed is advantageously a hole in the back end of the drum. The hole may be an annular hole around the central axis of the drum, in which case the drum may be connected to the axle by arms. Where there are a plurality of collectors, an outlet associated with each of the collectors is advantageously provided rather than providing a single outlet to be shared between all collectors. In this way, the outlet need not be provided at the centre of the back of the drum. It is preferred that where a plurality of outlets are provided, these are provided in an annular ring centred on the central axis of the drum. In this way, a seal can be provided surrounding all of the outlets.

Where a plurality of outlets or an annular hole are provided, the exterior back end of the drum preferably includes a pair of annular walls together defining an annular trough containing each of the water outlets, the annular walls fitting within an annular groove in a fixed housing, the annular groove having at least one water outlet point. With this arrangement, the drum is rotatable with respect to the housing, with the annular walls on the back end of the drum rotating coaxially within the annular groove in the fixed housing. Water dispensed through the outlet in the back of the drum is contained between the annular walls and within the groove, and is dispensed

through the water outlet point in the groove. Accordingly, this arrangement acts as a seal to preventing leakage of water where the outlets are not provided on the axis of the drum, yet allows rotation of the drum, despite the vibrations which occur during rotation.

The or each collector may be arranged to collect water when the drum is rotated in either direction, or arranged so that water is only collected when the drum is rotated in a predetermined direction, either clockwise or anti- clockwise, and water is not collected when the drum is rotated in the other direction. This is advantageous as it allows the drum to rotate, thereby agitating the items within the drum, either with associated dispensing of water, or with retention of water. This may be achieved by providing cup shaped collectors which lift and collect water to the outlet only when the drum is rotated in one direction.

The collectors may be formed as arms extending generally radially on the interior back end of the drum, as buckets mounted on the back of the drum, or deformations formed in the back of the drum.

It is preferred that a divider is provided in front of the collectors, the divider extending substantially, but not completely, over the back end of the drum. As the back plate does not extend over the entire back end of the drum, water can still pass through the divider to be collected and dispensed by the collectors, however items being washed cannot pass through the divider and become entangled on the or each collector. The divider is preferably formed with apertures provided around the circumference which abuts the side walls of the drum through which the water can pass, or can be formed with perforations through which the water can pass.

Alternatively, the drum may include an outlet arranged so that the drainage point of the drum is below the height of the front opening. With this arrangement, when the water level in the drum reaches the height of the lowest

drainage point of the drum is below the height of the front opening. With this arrangement, when the water level in the drum reaches the height of the lowest drainage point, the water will flow out of the drum through the outlet. As the outlet is below the height of the front opening, this arrangement helps prevent the water from rising to the level of the front opening, and therefore a door with a water tight seal need not be provided to close the drum. This is particularly beneficial as it is difficult to provide a reliable water tight closure for an opening on a rotating drum.

Furthermore, as it is not necessary to provide a water tight door, and indeed the front opening may be left open, it is possible to add items to the wash cycle after commencement of the cycle.

It is preferred that a splash-proof closure is provided over the front opening of the drum. This prevents water splashing out of the front opening of the drum during the washing and rinsing cycles, and stops items being washed from falling out.

The axis of the rotating drum is preferably inclined at an angle of between 5° and 45°.

The side walls of the drum may be tapered with the circumference near the front of the drum being less than the circumference towards the back of the drum. This ensures that the water in the drum descends towards the collectors due to circumferential forces, especially at high rotation speeds.

The washing machine may include a perforated container provided within the rotating drum and closely abutting the inner surface of the drum. In this way, the items to be washed can be placed in the perforated container, and after completion of the washing cycle the perforated container can be removed from the drum together with all the washed items. As the perforated container closely fits the side walls of the drum, the capacity of the washing machine is not reduced significantly. The use of a perforated container allows for easy unloading of the

drum. Where a perforated container is included, the divider and the collectors may be provided in the perforated container rather than in the drum itself.

It will be understood that the machine may be used for purposes other than washing items, for example for dying items, in which case the washing water is replaced by a suitable dye.

BRIEF DESCRIPTION OF DRAWINGS Figure 1 shows a cross-section through an example of a washing machine according to the present invention; Figure 2 shows a perforated container; Figure 3 shows an alternative perforated container provided in the machine of Figure 1; Figure 4 shows a water volume determination system; Figure 5 shows a cross-sectional view through an alternative example of a washing machine drum; Figure 6 shows an axial view of the washing machine drum of Figure 5; Figure 7 shows an axial view of an alternative washing drum; Figure 8 shows an alternative water outlet arrangement; and Figure 9 shows agitators.

DETAILED DESCRIPTION OF PREFERRED EXAMPLES Figure 1 shows a cross-sectional view taken through the axis of a generally cylindrical drum of a washing machine according to the present invention. The cylindrical drum includes side walls 1 and a circular back end wall 7 defining a drum with an open front 8. The drum is mounted on an axial spindle 2 for rotation about its axis which is inclined to the horizontal at an angle of about 20°. The back surface 7 of the drum includes a plurality of outlet holes 5. The lowest outlet hole 5 is below the vertical height of lowest part of the lip defining the front opening 8.

The drum also includes a removable perforated container 3 which is positionable within the drum through

the front opening 8 of the drum, and which is removable through the front opening 8. The perforated container 3 is shaped and dimensioned to correspond closely to the internal walls of the drum so the internal volume of the perforated container 3 is only slightly smaller than that of the drum. The perforated container 3 is generally tapered so that the front end including the opening has a larger diameter than the rear closed end. This assists in the insertion of the perforated container 3 into the drum.

The perforated container 3 has perforations through which water in the drum can pass into the perforated container 3, and through which water in the perforated container 3 can drain into the drum. The perforated container 3 is held within the drum in such a way that the perforated container 3 rotates with the drum. This is achieved by a projection 9 provided on the drum which engages with a recess 10 on the perforated container 3. Where the projection 9 and recess 10 are provided axially, the projection 9 and recess 10 have a non-circular shape to transmit the rotation of the drum to the perforated container 3. The projection 9 and recess 10 may be provided non-axially, and in this case the projection 9 and recess 10 can have any desired shape.

Alternatively, the projection may be provided on the perforated container 3 and the recess on the drum, or, where there is more than one projection and recess, a mixture of recesses and projections may be provided on both the drum and the perforated container 3.

The open end of the perforated container 3 includes an annular ring 4 giving a reduced diameter opening to the perforated container 3. The ring 4 ensures that clothes do not fall out of the perforated container 3 during the washing cycle.

As shown in Figure 2, in one example the perforated container 3 includes a hinged portion extending along the side of the perforated container 3 generally parallel to the longitudinal axis of the perforated container 3. The perforated container 3 also includes a clasp to hold the

perforated container 3 in its generally cylindrical shape.

In this way, the clasp may be undone and the perforated container opened about the hinge to allow easy access to the contents of the perforated container.

In an alternative example, as shown in Figure 3, the perforated container includes a completely closed front end, and an opening 25 in the side wall. As the side wall corresponds closely with the inside of the drum, items contained within the perforated container are not able to fall from the perforated container through the opening into the drum. With this arrangement, items to be washed are added to the perforated container through the opening 25 before the perforated container is placed in the drum.

When full, the perforated container is lifted into the drum, effectively closing the perforated container so all the items to be washed are maintained within the perforated container. With this arrangement, it is not possible to add items after the washing cycle has begun.

A shroud 6, inclined to the horizontal by the same angle as the drum is provided to a vertical front opening of the machine. The opening of the machine is closed by a door 11. This closure does not form a watertight seal but acts merely to prevent splashes during the washing cycle.

In use, clothes are placed into the perforated container 3, either before the filled perforated container 3 is put in the cylindrical drum through the front opening 8, or when the perforated container 3 has been positioned in the drum. Water, which may include washing detergent is introduced to the drum through the spindle 2. The water enters the perforated container 3 through the perforations in the perforated container to wet the clothes.

The lowermost outlet 5 is below the height of the lip of the open front end 8, and due to the inclination of the drum, water entering the drum can rise to the level of the lowermost outlet 5, the lowest drainage point, and any additional water will drain through the lowermost outlet 5.

As the lowest drainage point is below the level of the lip

of the open front end 8, and providing the outlets 5 are of a suitable size the water level will not rise to that of the lip of the open front end 8.

As it is not necessary to close the front end 8 of the drum, it is possible to add garments after the wash cycle has begun.

When the water and clothes are in the perforated container 3 within the cylindrical drum, the drum is rotated about its inclined axis, thereby agitating the clothes in the water to wash them. Due to the inclination of the drum, water passes through the holes 5.

The rear 7 of the drum is positioned within a recess of a water collector 12 which is fixed on the suspension of the machine. As water is discharged through the holes 5 in the back of the drum, this will be collected in the water collector 12, and will fall, under gravity, to the bottom of the water collector to be dispensed through the outlet 13. The rate at which the water is discharged from the drum is such that there is no need to provide a hermatic seal between the edge of the collector 12 and the outside of the drum.

During the washing cycle, the water may be recirculated, and may pass through a heater (not shown) to reheat the water, before being reintroduced to the drum through the inlet 2. This ensures that the water within the drum is maintained at the required temperature. When it is desired to dispense the water, the water from the outlet 13 is not recirculated, but is merely dispensed down a drain.

Figure 4 shows a schematic view of the water volume detector of the present invention which is provided in the recirculation path to determine the amount of water in the drum. In a fixed-tank recycling washing machine, the volume of water in the tank can be determined by measuring the pressure difference in part of the recycling circuit.

The water in the fixed tank is pumped from the tank, around

a recycling path and back into the fixed tank. A pressure sensor provided between the tank and the pump detects the pressure due to the height of water in the tank, and from this the volume of water can be calculated from the measured pressure. The pressure in the drum is at atmospheric pressure as the drum is not perfectly sealed.

Where the water tank is a rotating drum, this system cannot be used unless the outlet is provided at a fixed point below the surface of the water. As previously described this is difficult.

According to the present invention, a system is provided to ensure that sufficient water is added to the drum to saturate the items to be washed completely. Water from an external source is added to a secondary chamber 14 which is open to the atmosphere. The water is pumped from the secondary chamber 14 into the main drum. Water discharged from the drum is introduced into the secondary chamber 14. A pressure detector 15 is provided between the secondary chamber 14 and the pump 16, and by measuring the pressure it is possible to determine the volume of water in the chamber 14. The secondary chamber 14 is open to the atmosphere, so the detected pressure is purely due to the head of water in the secondary chamber 14. If the secondary chamber 14 were closed, the pressure in the tank may vary as the volume of water compresses the air in the tank.

Initially, the water entering the secondary chamber 14 from the external source is pumped into the drum and is absorbed by items in the drum. No or little water will be discharged from the drum. When the items in the drum are completely saturated, additional water will be discharged from the drum into the secondary chamber 14. This additional water will change the rate of change of the volume of water in the secondary chamber 14, or the water in the secondary chamber will reach a predetermined volume.

This is detected by the pressure sensor. When it is

determined that sufficient water has been provided to the drum, the external supply can be cut off.

An alternative example of a washing machine is shown in Figure 5. In this case, collectors 18 are additionally provided at the back of the drum. These collectors 18 are best seen in the axial view of Figure 6, in which the perforated container has been removed for clarity. In this case, the collectors 18 are provided in the form of arms on the rear surface 7 of the drum. Due to the inclination of the drum, the water in the drum will fall, under gravity, to the back of the drum. Anti-clockwise rotation of the drum, when viewed from the front end 8 causes this water to be scooped up by the collectors 18.

The continuing rotation of the drum causes the arms 18 to lift the water collected, and directs the collected lifted water through the outlet holes 5. Accordingly, by continually rotating the drum in an anti-clockwise direction, the water within the drum is expelled through the back 7 of the drum through the holes 5.

Where the drum rotates in a clockwise direction, the water will not be collected by the arms 46 due to their curved shape and therefore the water will remain within the drum.

Figure 7 shows a further alternative arrangement in which the arms 18'are shaped so that water is collect and expelled when the drum rotates in either direction.

Rather than the recessed water collector 12, other systems can be provided to collect the water discharged through the rotating back end of the drum. As shown in Figure 8b, the rear of the drum 7 may be provided with two annular rings 20 and 21 defining a channel 22 containing the outlet orifices 5. As shown in Figure 8a, the housing of the washing machine similarly includes two annular walls 23,24 to define a groove 25, the width of the groove 25 being such that the walls 20 and 21 on the back of the drum 7 may be provided within the groove 25. The groove 25 includes a single outlet 26, although additional outlets may be provided. With this arrangement, the drum is free to rotate, yet as water is dispensed through the dispensing

orifices 5 it is constrained by the grooves 22 and 25 and directed to the single fixed outlet 26.

The drum or perforated container 3 may be provided with agitators to lift the clothes within the drum. As shown in Figure 9 agitators are in the form of a projection 30 which extends from the back of the drum 7 circumferentially around the drum and towards the front of the drum and return to the back of the drum.

The base of the agitator 30 is generally triangular in cross-section, having a maximum height from the side walls 1 near the base 7 of the drum, and a minimum height near the front 8 of the drum. The cross-sectional shape of the agitator 30 may be other than triangular. The agitator 30 has rounded apexes to prevent damage to the clothes. Where the agitators are provided on the inside of the drum, the perforated container 3 is provided with corresponding agitators. In this case the agitators act to hold the perforated container within the drum to prevent relative rotational movement of the drum and perforated container 3 during the washing cycle. Although only one agitator 30 is shown, two or more agitators may be included.

Because the agitator 30 includes components extending towards the front of the drum in both a clockwise and anti- clockwise circumferential direction, on rotation of the drum, articles within the drum are lifted and drawn towards the front of the drum upon rotation of the drum in either direction.