GB2058148A - Washing machine having drain blockage indicator - Google Patents

Abstract

A washing machine 1 is provided with means to detect when a drain filter 7 connected to the outlet of the washing chamber 2 is blocked. A low- level water sensor 12 used during normal operation of the machine for normal control of the machine is monitored during a drainage operation and a controller 10 is arranged to establish whether the water sensor 12 has operated a predetermined time determined by a timer 18 after the drain pump 6 is started. If the switch 12 does not change state, then it is assumed that the filter is blocked and, either immediately or at the end of the wash programme, a warning light 20 is illuminated. <IMAGE>

Description

SPECIFICATION Washing machine having drain blockage indicator The present invention relates to washing machines.

In conventional clothes washing machines, clothes are agitated in a drum filled with water to remove soil; they are then rinsed with clean water several times before being spun to remove excess water prior to drying. During this process small particles of lint and other material are dislodged from the clothes. Prior to each refilling of the drum, the soiled water is pumped from the drum to an external drain. One of the difficulties which arises is that large pieces of lint and other articles possibly removed during the washing cycle such as buttons, paper, hair pins, etc., may jam or otherwise damage the impellor of the drain pump.

In order to avoid this problem a filter, usually in the form of a plastics mesh, is fitted between the drain pump and the drum of the washing machine. It is necessary periodically to remove this filter and clean away any lint, hair, paper, etc., to allow a free passage for the easy flow of used water to the drain. If periodic cleaning is not carried out, the flow of soiled water to the drain gradually gets restricted and the draining process slows down.

This means that during the time allowed to drain away only a percentage of the soiled soapy wash water is removed prior to rinse water entering the machine. At each rinse stage, dilution of the soapy water takes place but some remains and then an unsatisfactory wash results. In some cases, where the build-up of material is severe, the flow of drain water slows to a trickle and therefore in the time allotted to the draining period, the water level does not drop sufficiently to enable the level sensing switch conventionally provided to operate to admit clean rinse water to the drum. This gives an unsatisfactory wash and is unhygienic. Also, automatic washing machines require a venting arrangement from the drum to allow steam to escape during high temperature washes.When the filter is fouled by excessive lint thus not allowing the drain water to escape as already described, then it is possible for the machine to go into the spin mode with water still in the drum. If this happens, soiled water is then thrown out of the venting arrangement and flooding of the floor will occur.

According to the present invention we avoid the above problem by monitoring the water level during a draining operation and use this to determine whether the washing chamber outlet is blocked, for example because the filter is in need of cleaning. If the water does not drain to a particular level in a given time, it can be taken that the outlet is blocked. Of course, slow drainage may also be due to a faulty pump or a blockage elsewhere in the machine but checking the filter will at least eliminate that as the source of the difficulty.

Thus, according to the present invention we provide a washing machine comprising a washing chamber having an outlet, a water level sensor associated with the washing chamber and a device, operative during a drain step, to monitor the water level sensor and to provide a signal indicating that the outlet is blocked. This signal may be used, for example, to operate an indicator such as a lamp mounted on the fascia of the machine to alert the user to the need to check the filter. The operation of the lamp or whatever other indicator is used may be immediate or it may provide the "check filter" signal at the end of the complete operating cycle of the machine. This latter will be satisfactory where progressive blockages are expected.

In one embodiment, a timer is activated at the same time as the drain pump during the period in which proper drainage or otherwise is to be detected and the level sensor is subsequently monitored. If the level sensor does not indicate that the level has dropped below the operating point of the sensor before the timer times out, this is taken as indicating improper drainage and the "check filter" indicator is activated, either immediately or at the end of the machine cycle.

The invention will be further described with reference to the accompanying drawing in which the sole figure is a somewhat schematic block diagram of one embodiment of the present invention.

In the figure, an automatic washing machine 1 comprises a casing 2 defining a wash chamber in which is mounted a horizontal cylindrical wash tub 3 connected to an appropriate drive (not shown) for the various operations of the machine such as wash, spin, etc. Clothes or other articles to be washed are placed in the wash tub via an access door 4.

Associated with the washing chain within the casing 2 are an electronic water valve 5 and a drain pump 6 to fill and drain the chamber, respectively. As indicated above, between the drain pump 6 and the chamber is located a filter 7 which prevents material which might jam the impellor of the drain pump 6 from reaching it.

Water from the drain pump is pumped via a pipe 8 to an external drain 9.

The operation of the machine is controlled by a controller 10 which may comprise a microprocessor or a more conventional electromagnetic arrangement and this controller controls, inter alia, the drive motor of the wash tub, the water valve 5 and the drain pump 6. The controller is suitably arranged so that the user can select the appropriate one of a number of programmes according to the articles to be washed. At various stages in the wash programme selected by the user, the drain pump 6 is operated to drain the water from the wash chamber and then the water valve 5 opened to refill the wash chamber for a subsequent wash for rinse. Of course, at the end of the wash/rinse part of the programme, the drain pump is operated to drain the wash chamber and the water valve 5 subsequently held closed during the spin operation or operations.

Water levels within the wash chamber are monitored by the controller by means of a pressure switch arrangement 11. Essentially, this comprises a closed housing in which is located a pressure-responsive diaphragm which controls closure of three sets of contacts 12, 13 and 14.

One side of the diaphragm is communicated via a tube 16 with an air bell 17 which is open to the interior of the wash chamber. As the water level changes, the pressure in the wash chamber increases or decreases as appropriate, so the pressure difference acting on the diaphragm changes causes the contacts 12, 13 and 14 to open or close. The contact 12 is arranged to open when the level of water in the wash chamber has increased to a given minimum level while contacts 13 and 14 close, respectively, when the wash chamber is half full and full. There is some hysteresis between the switching level for increasing and decreasing water levels so that, for example, the contacts 13 and 14 open when the water level has decreased to 1and 32 full respectively.

The switch 12 is used by the controller 10 to indicate when a desired minimum level of water is in the wash chamber and, in view of the hysteresis involved in its switching, is also taken to indicate during draining that the wash chamber is empty.

Similarly, the switches 13 and 14 are used by the controller 10 to indicate that the wash chamber is half and completely full respectively during filling to control the operation of the water valve 5.

In operation, the machine operates in a conventional manner except as will be described below.

At the end of the wash/rinse part of the programme, a "pump-out" signal is applied to controller 10 to energise the drain pump 6. This signal also starts a timer 18 within the controller 10. During this period controller 10 monitors the switch 12 and if the latter does not close during the timing period of the timer 18, this indicates that the filter is blocked and a register 19 is set. At the end of the programme, the controller checks the content of the register 1 9 and, if set, illuminates a warning light 20 which indicates that the filter needs to be removed by the user and cleaned.

The controller may alternatively illuminate the lamp immediately or abort the remainder of the programme and continue pumping out past the low level switch operating point, for example countinuing for a predetermined time.

Rather than on completion of the wash/rinse cycles, the controller 10 could operate to start the timer 18 during each drain period.

The "pump-out" signal may be generated by the controller itself, in software in the case of a microprocessor or by an associated, separate programmer.

It will be appreciated that although the invention has been described with a reference to a clothes washing machine it is equally applicable to other washing machines such as dish washers.

Claims (15)

1. A washing machine comprising a washing chamber having an outlet, a water level sensor associated with the washing chamber and a device, operative during a draining step, to monitor the water level sensor and to provide a signal indicating that the outlet is blocked.

2. A machine according to Claim 1 wherein the device is operative to determine whether the outlet is blocked on the basis of the time taken for the chamber to drain.

3. A device according to Claim 1 or 2 wherein the device comprises a timer activated at the start of the draining operation and arranged to produce the signal indicating that the outlet is blocked if draining is not completed within a predetermined amount of time.

4. A washing machine according to Claim 1, 2 or 3 and including a drain filter located in relation to the washing chamber such that the device will indicate whether the filter is blocked.

5. A washing machine according to Claim 4 and including a drain pump located downstream of the drain filter.

6. A washing machine according to any one of the preceding Claims and including a controller defining a number of programme steps of operation of the washing machine.

7. A device according to Claim 6 wherein said controller comprises a microprocessor.

8. A device according to Claim 7 wherein said device is implemented by means of the microprocessor.

9. A washing machine according to Claim 6, 7 or 8 and including a warning light connected to the device to indicate that the outlet is blocked.

10. A washing machine according to Claim 9 wherein the warning light is arranged to be lit at the termination of a wash programme.

11. A machine according to any one of Claims 6 to 9 wherein the programme is caused to abort in the event of the device indicating that the outlet is blocked.

12. A washing machine according to any one of Claims 6 to 11 wherein there are a number of draining operations during a wash programme, the device only being operative during the final draining operation of the programme.

13. A washing machine according to any one of Claims 6 to 12 wherein the controller is arranged to interrupt the draining pump when the water level falls below a predetermined level as sensed by the sensor.

14. A washing machine according to any one of Claims 6 to 13 wherein the controller is so that when the device indicates that the outlet is blocked the pump draining operation will continue for a predetermined time after the water level falls below a predetermined level as sensed by the sensor.

15. A washing machine constructed and arranged to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.