GB2180961A - Washing machines and control systems therefor - Google Patents

Abstract

An automatic washing machine has a control system incorporating a microprocessor for progressing through a number of different selectable wash programmes, in at least one of which it controls electrically energisable means operative to maintain the wash liquid temperature constant at two or more predetermined values, increasing in steps, for respective periods of time, and also controls means for agitating the wash liquid either continuously or intermittently for predetermined times during such periods. <IMAGE>

Description

SPECIFICATION Washing machines and control systemstherefor This invention relatestowashing machines and to control systems therefor. It has particular reference to domestic washing machines of the fully automatic type and relatesto both machinesofthefrontandtop loading types aswell asto machines in which, in addition to providing the normal wash functions, involving agitating clothes and othertextile articles in a wash liquid, i.e. water with a quantity of detergent dissolved within it, followed by rinsing and spinning, has available an additional tumble dry operation.

With the advent of new technology, machines previously controlled by electromechanical means are now being replaced by electronically controlled machines, and especially those in which a microprocessor is incorporated. Such microprocessor controlled machines enable a much wider range of operation and a much finercontrol ofthevarious washing machine functions to be achieved than was hitherto possible.

Automatic washing machines have a control system for progressing the machine through a number of differentselectable programmes, and in particularfor providing a number of different pro grammesselectable by the user according to the nature of and extent of the clothes or other textile articles to be washed. These programmes include a series of controllable steps for the wash, rinse and spin functions.

One important advantage of microprocessor controlled washing machines is the ability to make more economical use of the washing machine, especially as regards the wash function where it is necessaryto heat the wash liquid in orderto achieve a desired level of cleanliness, such heating being relatively expensive. Now that the ability to provide satisfactory wash cleanliness at lower temperatures can be achieved using so called "lowtemperature" detergents, many machines have been adapted to make the best use of these detergents by introducing programmes in which the wash liquid is heated to relatively lowtemperatures, i.e. of the order 40-60 C.

We have now found that a control system can be adapted, for example to make use of detergents having a composition which provides beneficial wash re sults at generally low temperatures, but which needs specific time periods and defined temperatures so as to achieve an optimum wash result.

According, therefore to one aspect of the invention an automatic washing machine incorporates a control system comprising a microprocessor programmed to operate the machine in accordance with a plurality of selected wash programmes, in at least one of which it controls electrically energisable means operative to maintain the temperature of the wash liquid approximately constant at two or more predetermined values, increasing in steps, for respective set periods of time, and also controls means for agitating the wash liquid either continuously or intermittently for predetermined times during said periods.

Such a machine is capable of being programmed to achieve an optimum wash result attemperatures tha# tare generally lowerthanthe normal hightem- perature of 95", depending upon the particular clothes stains and the washing powderemployed.

Moreover by enabling certain wash programmesto be carried out at lower temperatures, the machine can provide a degree of energy saving.

It will be seen that the invention provides a very versatile machine, as the microprocessor may readily be programmed to provide a plurality of differentwash programmes utilising differenttemperature steps, either in terms of the temperatures to which the wash liquid is heated, or the times at which the temperatures are maintained, or alternatively the number oftemperature steps involved.

Forexample,foroneparticularprogrammethe wash liquid may be maintained at a temperature of, say, 40'C, for a first period oftime, and a temperature of, say, 50 C for a second period of time, and a temperature of, say, 600C for a third period of time,the periods for which different temperatures are maintained depending upon the particular programme selected. However for other programmes a different number oftemperature steps and/or differenttemperatures may be more suitable.

This will, in general, depend upon the type of material, nature of stain and the washing powder selected. The invention is particularly applicable for use with washing powders incorporating enzymatic cleaning agents coupled with lowtemperature bleaches. It is well known that the optimum activity of such additives as regards stain removal takes place within certain well-defined temperature ranges, depending upon the particularadditiveem- ployed, this activity gradually decreasing as the temperature is increased above the respective range, until it disappears completely. Different forms of stains are more susceptible to attack by the respective additives at different temperatures, and it has been found that the cleaning effect of certain additives is largely completed within a predetermined period of time.Accordinglythe utilisation of a control system employing a suitable programmed microprocessor enables wash programmes to be readily selected so as to maintain the wash liquid at app ropriatetemperaturesforthe minimum time required to achieve satisfactory stain removal,for any par ticulartypes of stain, thereby enabling an optimum wash result to be achieved.

The wash liquid temperature is conveniently maintained ata required value by activating a heating element as appropriate, the microprocessor con trolling the appropriate function in response to the output of a suitably positioned temperature sensor, which is conveniently in the form of a thermistor.

Preferably the microprocessor is arranged to maintain the temperature within 1 C of the set temperature.

The microprocessor may also be arranged to control the duration of agitation, in a period in which the temperature ofthewash liquid is maintained app roximatelyconstant,whetherthe agitation be continuous or intermittent. In the case of a front loader machine with intermittent agitation the drum is con veniently arranged to be rotated for a set period in one direction, held stationaryforanother set period, followed by rotation for another set period in the opposite direction, the sequence being repeated for a settotal period, or alternatively for a set number of times, the length and/or number of the agitation periods, and possibly the length of the stationary periods, again being controlled by the microprocessor in accordance with the choice of programme.Thus the use of a microprocessor enables the optimum agiation parameters to be be achieved for any selected wash programme, so that, in combination with the various wash temperatures, a wide variety of washing treatments can be achieved providing an optimum wash result according to the nature of the clothes orothertextile articles being washed and the degree of soiling.

One washing machine and control system therefor will now be described bywayofexamplewith reference to the accompanying drawings, in which: Figure 1 illustrates the control system in dia grammaticform, and Figure2 illustrates different time/temperature profiles which may be achieved with different selected wash programmes.

The washing machine in this case comprises an open-fronted perforated drum rotatable about a horizontal axiswithin awash-liquid containermounted within an outer cabinet. The container and cabinet have access openings which register with the open front of the drum, the cabinet being provided in the usual way, with a door which closes the cabinet ac cess opening and in the closed position and seals against a gasketforming a seal between the cabinet and container openings.

In use ofthe machine, the drum is arranged to be driven by a series-wound commutator motor 1, energised via a power board 2 controlled by a control board in the form of a microprocessor3. The micro processor also controls the operation of valves 4,5,6 admitting cold or heated water into the wash-liquid containervia detergentorfabricconditionerdls- pensers, and a pump 7for removing wash liquid from the container at appropriate times during a washing cycle. An immersion heater8 is also en ergised via the power board 2 under the control of the microprocessor 3, a thermistor 9 being used to monitorthewatertemperature and feed backthis information to the microprocessor.The machine also comprises a tachometer 10 which is arranged to feed signals representative of the drum speed, to the mic roprocessor.

Manual controls (not shown) for selecting various wash programmes cause appropriate information to be fed to the microprocessor. Pressure switches 12 are used to control the wash-liquid levels within the container, and a door interlock of any suitable known kind is provided as at 14. On all programmes the first 20 seconds of fill is always with cold water, and after 20 seconds hotwater is fed into the container together with a quantity of cold water until an app ropriate level and temperature is reached. Conveni entlythe initial cold water fill takes place via the pre wash compartmentofthe dispenser, andthesubse- quentintroduction of hot and cold water takes place through the detergent or fabric conditioner dispenser as appropriate.Following the initial cold waterfill the hot water valve 4 is opened con tinuouslywith cold water valve 5 opend or closed as appropriate until the required fill level and temperature are reached according to the temperature needed for the selected wash programme. The drum is then rotated slowly in alternate directions to provide the required agitation, in dependence upon the programme selected, and the wash-liquid heated to an appropriate temperature.

The microprocessor is programmed to provide, not only the usual high temperature wash, for ex ample at around 95"C, but also a selection of low tem- perature wash programmes.

Thus in accordance with the invention a number of programmes are provided in which the wash liquid is heated initiallyto a relatively Iowtemperature e.g.

40and is maintained approximately at this tem- perature for a predetermined length oftime, and then raised to a higher temperature again for a predetermined time, and possibly to a third temperature again for a predetermined time. The temperature is maintained by energising the heating element 8 per iodically under the control of the microprocessor, in response to the output of the thermistor 9. Various temperature/time profiles which can be provided by the microprocessor programme are illustrated in Figure 2, although it will be appreciated that the microprocessor can readily be arranged to provide many alternative temperature/ti me profiles to give wash programmes suited to many different articles and fabrics.

During each time period the drum is periodically rotated alternately in opposite directions to provide agitation ofthewash-liquid with rest periods in between, the speed of rotation, the agitation and rest periods again being accurately controlled by the microprocessor according to the selected wash programme. For example, with a drum speed of between 52 and 60 r.p.m., the drum may be rotated for 5 seconds in one direction, held stationaryforfifteen seconds and rotated another 5 seconds in the opposite direction, the sequence being repeated as many times as are necessary for particularwash programmes selected.However the speed of rotation of the drum, and/orthe periods in which the drum is rotated or held stationary may be differentfordif ferentwash/programmes, or even fordifferentst- ages of the same programme. Conveniently the control system includes means for monitoring the number of periods of rotation ofthe drum, the microprocessor being arranged to terminate a temperature step at which the wash liquid is maintained at a selected temperature after a predetermined number of such periods of rotation, the number and length of such periods together with the length ofthe intervening periods at which the drum is stationary being selected to give the required duration ofthe temperature step.

Rinsing and spinning operations can also be controiled by the microprocessor in accordance with the selected wash programme.

Although for some programmes the wash liquid may be heated in accordance with the invention to different temperature levels, it will be appreciated that the microprocessor can in some instances be programmed to enable the wash to be carried out at a single predetermined low temperature, e.g. 40 C, 50 C or 60 C, as may be desired to provide apart- icularwash programme.

Moreover although the invention has been described by way of example in relation to afront-loaderor "horizontal" washing machine it will be appreciated that it can also have application to automatic top loa- der machines, although it will be appreciated that although, in the case offront-loader machines agitation of the wash liquid is achieved by rotation of the drum, in top loader machines such agitation is produced by means ofagyratororthe like rotatable within a nominally vertical drum.

Claims (18)

1. An automaticwashing machine incorporating a control system incorporating a microprocessor programmed to operate the machine in accordance with a plurality of selected wash programmes, in at least one of which it controls electrically energisable means operative to maintain the temperature ofthe wash liquid approximately constant at two or more predetermined values, increasing in steps, for respective set periods of time, and also controls means for agitating the wash liquid either continuously or intermittently for predetermined times during said periods.

2. An automatic washing machine according to Claim 1, wherein the microprocessor is programmed to provide a selected one of a plurality of different wash programmes utilising different temperature steps.

3. Anautomaticwashing machineaccordingto Claim 2, having at least one wash programme in which the predetermined temperatures at which the wash liquid is maintained constant are differentfrom those of at least one other wash programme.

4. An automatic washing machine according to Claims 2 or3 having at least one wash programme in which the set periods of time forwhich the temperature of the wash liquid is maintained constant are different from those of at least one other wash programme.

5. An automatic washing machine according to any one of Claims 2, 3 or4 having at leastonewash programme in which the number of set periods of time for which the temperature of the wash liquid is maintained constant are different from those of at least one other wash programme.

6. An automaticwashing machine according to any preceding claim including a temperature sensor disposed so as to monitor the temperature of the wash liquid, an electric heating element for heating the wash liquid, switch means operable to energise the heating means underthe control ofthe microprocessor, in response to signals from the tem perature sensorfor maintaining the temperature of the wash liquid approximately constant at said predetermined valuesforsaid set periods of time as determined bythe selected wash programme.

7. An automatic washing machine according to any preceding claim having at least one wash programme during which the temperature of the wash liquid is maintained approximately constantforset periods oftime at th ree different temperatures, such temperatures being held for approximately 25%, 25% and 50% respectively of the total length of such periods.

8. An automatic washing machine according to any preceding claim having at least one wash programme in which the temperature of the wash liquid is maintained at a temperature of approximateiy40 C for a first period of time, is heated to approximately 50"C and maintained atthistemperature for a second period oftime, and is heated to approximately 600C and is maintained atthistemperatureforathird period oftime.

9. An automatic washing machine according to any one of Claims 1 to 6 having at least onewash programme in which the temperature of the wash liquid is maintained at a temperature ofapp- roximately 400C for a first period oftime, and is heated to 500C and maintained at this temperature for a second period oftime.

10. Afrontloaderautomaticwashing machine according to any preceding claim, comprising a rotatable drum, and means for rotating the drum to produce the agitation ofthewash liquid during the periods when the temperature of the wash liquid is maintained approximately constant.

11. Anautomaticwashing machineaccordingto Claim 10, wherein the agitation of the wash liquid is produced by repeatedly rotating the drum in opposite directions.

12. Awashing machine according to Claim 11, wherein the drum is arranged to be held stationary for predetermined periods between the alternate rotations of the drum.

13. Awashing machine according to Claim 12, having at least one wash programme in which, during a set period of time in which the wash liquid temperature is maintained approximately constant, the drum is rotated in one direction for approximately five seconds, held stationary for approximatelyfif- teen seconds and rotated in the opposite direction forapproximatelyfive seconds, the sequence being continuously repeated for said set period oftime.

14. Awashing machine according to Claim, 12 wherein the speed of rotation of the drum, and/orthe periods during which the drum is rotated or is held stationary, are different for different wash programmes or for different stages of the same wash programme.

15. Awashing machine according to any one of Claims 1 otto 14, including means for monitoring the number of agitation periods and terminating at least one temperature step, during which the wash liquid is maintained approximately constant, after a predetermined number of agitation periods.

16. Awashing machine according to any preceding claim wherein the means for agitating the wash liquid is also operative during the heating ofthe wash liquid from one temperature step to another.

17. An automatic washing machine incorporating a control system substantially as shown in and as hereinbefore described with reference to Figure 1 of the accompanying drawings.

18. An automatic washing machine according to Claim 1 in which the microprocessor is programmed to provide at least one of the time/temperature wash profiles illustrated in Figure 2 of the accompanying drawings.