GB2164546A

GB2164546A - Dishwashing machine

Info

Publication number: GB2164546A
Application number: GB08419633A
Authority: GB
Inventors: Dan Trevor Clayton
Original assignee: JENKINS PETER WILFRED; PRIEST GORDON JAMES
Current assignee: JENKINS PETER WILFRED; PRIEST GORDON JAMES
Priority date: 1984-08-01
Filing date: 1984-08-01
Publication date: 1986-03-26
Also published as: GB8419633D0

Abstract

In order to overcome the deleterious effects of hot water on the resins 13 in the water softener 1 of a dishwasher and to reduce the overall operating cycle time, water below 38 DEG C is passed through the softener 1 and is then fed, via pipe 18, to a hot tank 14 for pre-heating. Subsequently a controlled amount of heated water leaves the hot-tank 14 and is mixed with a controlled amount of water fed directly from the supply 12 via pipe 17 into the wash chamber 2 to achieve the desired temperature for a particular cycle. Each pipe 17, 18 is provided with a flow control valve 19 connected to a programme timer 20. Alternatively, three separate hot-tanks 14 are provided in addition to the wash-chamber 2 each of which has a similar plumbing system and control valve arrangement to that of Figure 1. <IMAGE>

Description

SPECIFICATION Dishwashing machine This invention relates to dishwashing machines of the kind which operate automatically to a predetermined programme and is particularly, but not exlusively, concerned with domestic dishwashing machines.

Most domestic dishwashing machines incorporate awatersoftenerwhichservesto prevent 'spotting' on crockery and accumulation of lime deposits on the heater elements. As the resins in a water softener will not operate efficiently in hot water, dishwasher manufacturers recommend thatthe watersupplyto the machine is either cold or38"C maximum. Most domestic hot water supplies are above this tempera- ture and if the benefits of the water softener are to be obtained in use the machine should be connected to a cold water supply and the water subsequently heated in the washing chamber of the machine. This procedure will of course lengthen the operating time ofthe machine.

In a typical domestic dishwashing machine a normal wash programmewillcomprisethefollowing stages, each of which uses a fresh charge of two gallons ofwaterwhich has to be brought into the machine, heated to the required temperature if not already atthattemperature, put th rough its task and then pumped away.

Pre-wash at38"C 71/2 minutes + heating time.

Main wash at 55"C 51/2 minutes + heating time.

'Cold' rinse 1 at input temp. 2 minutes.

'Cold' rinse 2 at input temp. 2 minutes.

'Cold' rinse 3 at input temp. 2 minutes.

Hot rinse at 65"C 31/2 minutes + heating time.

The overall wash cycle is therefore 221/2 minutes plus the time taken to heat the water from its input temperature to those indicated above.

On the assumption that water input temperature is 1 0 C the times taken to heat 2 gallons of water using a 2.2K heater, ignoring heat losses, are as follows: To 380C 8 minutes (forPre-wash) 550C 13 minutes (for Main wash) 650C 16 minutes (for Hot rinse) Total 37 minutes The total time of a normal wash, i.e. overall heating times plus wash and rinse cycle times, is therefore 591/2 minutes plus anytime that needs to be added to the water heating times to compensate for heat losses; insofarthatduringthe heating stages the water is being sprayed over the crockery the heat losses are high and the overall cycle time consequent ly longer.

In this known machine regeneration ofthe resins in the water softener takes place during the main wash stage of the washing cycle.

It is an object of the present invention to reduce overalltimeforthewash and rinse cycles ofa dishwashing machine.

According to one aspect ofthe present invention a dishwashing machine of the kind which operates automatically to a pre-determined programme, comprises an arrangement in which thewarm orhotwater requirements for at least one phase ofthe programme are met by means of at least one watertank provided in addition to but separate from the wash-chamber of the machine, and in which water is pre-heated to a predetermined temperature prior to commencement of that phase and is mixed with water at a lower temperature level to achieve the required quantity at the desired temperature for that phase of the programme.

Preferably, the water at the higher and lower temperature levels is mixed in the wash-chamber.

The wash-chamber may also incorporate a thermo statically controlled heaterto compensate for temper- ature losses andiorto compensate for any variation of the water inputtemperature of the water fed directly from the supply to the wash chamber.

For space saving reasons and compactness the, or each,tankforthe pre-heated water is preferably incorporated in the machine. Alternatively, the, or each, tank may be remote from the machine.

Preferably, the water in the, or each, tank is heated by a thermostatically controlled electrical immersion heater which is connected into the control circuit ofthe machine and is switched on automatically according to the selected programme and input temperature of the water.

The, or each, heater is preferably controlled so that water in the, or each, tank reaches the required temperature prior to commencement ofthe relevant phase ofthe programme, and without delaying commencement of that phase.

In the case of multiple tanks, each provided with a heater, preferably only one heater is energised at any time and preferably there is a priority switching system between thethermostats of each tank and the wash-chamberto maintain the desired temperatures.

Alternatively, where a multiple tank system for pre-heated water is used it may be possible and advantageous to provide electric heaters for these tanks which can be used contemporaneously, for example by having several heaters of lower wattage for a 13 amp electric supply, or by having a higher input electric supply so avoiding the possibility of an overloaded circuit when two or more heaters are in circu it together.

Theflow of waterto and from the tank ortanks, is preferably controlled by flow control valves connected to the programme timer and which provide for constant or varied flows (i.e. volumes) of heated water to the wash-chamber. Similarly,theflow ofunheated waterto the wash-chamber is preferably controlled by a flow control valve connected to the programme timerto provide constant or varied flows (volumes) to said wash-chamber.

The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

The claims were filed later than the filing date within the period prescribed by Rule 25(1) of the Patents Rules 1982.

Where the dishwasher incorporates awatersoften- erthewaterdeliverysystem to the wash-chamber comprises a two-pipe arrangement on the exit side of the water softener, one pipe leading to the, oreach, hotwatertankandtheotherby-passingthe,oreach tank, to convey unheated waterto the wash-chamber.

Preferably, impregnation ofthe resins in the water softener resin chamberis programmed to occuratthe end of a wash programme, with regeneration taking place while the machine is idle i.e. between washes.

Evacuation of the resin chamber into the washchamber and thence to waste is then preferably programmed to occur at the beginning of the next wash.

The means for mixing the heated and unheated waterto the required temperature may be achieved in several ways, for example: (a) the final temperature ofthe pre-heated water may be varied by manual selection, or automatically, according to the chosen wash programme and timed constant flows (volumes) of pre-heated and unheated water, also at a predetermined temperature, flow into the wash-chamber until the required quantity at the required temperature is available; (b) the temperature of the pre-heated water may be fixed and time varied flows i.e. varied volumes accordingtothetemperatureofthe pre-heated and unheated water respectively, are passed to the washchamber; and (c) combinations of (a) and (b) above may be used, for example, mixing atimed constantflow(volume) of pre-heated water at a predetermined temperature with a varied flow (volume) of unheated water varied according to its temperature, or varying the flow (volume) of pre-heated water according to its predetermined temperature with a constant flow of unheated according to its inputtemperature, in each case achieving the desired quantity at the desired temperature for each task.

According to a second aspect ofthe invention a dishwashing machine ofthe kind which operates automatically to a pre-determined programme, com prisesawatersoftenerassemblyconnected between a water inletto the machine and a chamber in which wash waterand/or rinse water is heated, and the arrangementofthe programme is such that regeneration ofthewatersoftening material takes place substantially after completion of all the wash and rinse cycles of the machine.

Embodiments of the invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a diagrammatic arrangement of a dishwashing machine according to one embodiment ofthis invention; Figure 2shows graphically the time periods required bythe wash programme of a typical conventional dishwasher; Figure 3 shows graphically the time periods required by the wash programme of a dishwasher according to Figure 1 ofthe present invention; and Figure 4 sho Jvs graphically the time periods required by the wash programme of a dishwasher according to another embodiment ofthe present invention.

The dishwasher diagrammatically depicted in Figure 1 is largely conventional in that it comprises: a water softener 1 ,a wash-chamber 2 mounting a pressure pump 3 wh ich feeds upper4 and lower 5 spray bars, depressurisation valve 6 and overflow valve 7 for the wash-chamber and a suction pump 8 for draining the wash-chamber 2 via a non-return valve 9 and drain pipe 23. An airtrap 10 is connected to a pair of pressure switches 11 for sensing water levels within the gas-chamber 2. The airtrap 10 senses the water levels in the wash-chamber and one switch 11 is linked to the water inlet valve and senses the correct level, whilst the other sense excess water level and energisesthewaste pump.

As already stated hotwaterfrom a domestic supply.

12 has a deleterious effect on the resins 13 in the water softener 1 if a bove 38"C and in order to overcome this problem whilst obtaining a reduced overall cycle time for operation ofthe machine the conventional sequential heating times for water supplied to the washchamber2 are reduced or eliminated and a preheating arrangement is substituted. That is to say cold domestic supply water, or heated domestic supply water which is below 38 C, may be passed through the water softener 1 as before but downstream of the water softener it is treated in a novel manner.

In this embodiment of the invention the pre-heating arrangement is achieved by means of a single tank 14 which is additional to but separate from the washchamber 2 and in which 'cold' water is pre-heated priorto the commencement ofthe wash programme.

As will be seen from Figure 1,the separate tank 14, hereinafter referred to as the hot-tank, for heating water above the inputtemperature ofthe domestic supply is incorporated in the machine and although shown diagrammatically above the wash-chamber2 may be in any suitable space within the machine. This tank 14 is of 1 3/8 gallons capacity and comprises an electrical immersion heater 15 which is controlled by a multi-temperature thermostat and capable of heating waterfrom the domestic supply 12,which may be 'cold' (approximately 100C) or'hot' maximum 38"C,to a much highertemperature, 900C, for example.

On the exit side of the water softener 1 the water supply pipe 16 is divided into a two-pipe arrangement, one pipe 17 leads directly to the wash-chamber 2 via the wash-chamber depressurisation and overflow valves 6,7 and the other pipe 18 leads to the hot-tank 14. Each ofthetwo pipes 17,18 is provided with a flow/no flow control valve 19 connected to the programme timer 20 and which caters for constant or varied flows, as required, in orderto supply a controlled amount of water at the input temperature of the domestic supply system 12, either directly to the wash-chamber2, ortothe hot-tank l4forheatingto a predetermined temperature. Subsequently, a controlled amount of water at the predetermined temperature leavesthe hot-tankl4via delivery pipe 21 and flow control valve 22 and is mixed with a controlled amount of water fed directly into the wash-chamber 2.

Thus, it is possible for the flow of waterto the wash-chamber2 to bewhollyunheatedforcold rinsing for example, orwholly heated to a predetermined temperature, or supplied in appropriate quantities of heated and unheated water for mixing in the wash-chamber.

The conventional components of the machine previously mentioned and their operation need not be described in detail as they do notform partofthe invention and it is sufficient for a clear understanding of the invention to state that by providing the hot-tank 14 and a two-pipe arrangement feeding the hot-tank and wash-chamber2 respectively, each fitted with suitable flow control valves, it is possible to mix appropriate quantities of 'softened' water atthe required temperature to meet the demands ofthefull wash and rinse cycle in a much shorter time than hitherto achieved in conventional dishwashers.

Because of the shortened wash and rinse cycles in a dishwasher according to this invention impregnation of the resins 13 in the resin chamber of the water softener 1 takes place at the end of the wash cycle and regeneration of the resin 13 takes place while the machine is idle, i.e. between washes. Evacuation of the resin chamber into the wash-chamber and thence to waste is programmed to occuratthe beginning of the next wash.

Figure 2 shows a time chartforan operational example of conventional dishwasher and it will be apparent from this chart and from the data given on pages 1 and 2 that the total heating time for the water is 37 mins. and the total running time, including heating time, is 591/2 mins. for the full programme. In this case the water is heated in the wash-chamber.

Figure 3 shows a similartime chart for a dishwasher embodying the present invention which can be directly related to Figure 2 in respect of the time scale and programmetasksperformed. In this case a smaller quantity of water (1 3/8 gals) at the input temperature of 1 00C for a water softener system is heated to a much highertemperature for the main wash and hot rinse stages and then mixed with an appropriate quantity of water at 10 C in the washchamber 2, to meet the same programmed temperature levels, resulting in a running time of 341/2 mins, giving a saving of 25 mins.

Apart from achieving significant reductions in programme times there will be further savings in energy consumption due to reductions in heat loss.

In afurtherembodimentofthe invention (not shown) the arrangement of the dishwasher shown in Figure 1 is modified to give an even greatertime saving in the washlrinse programme.

In the modified dishwasherthree separate hot-tanks 14 are provided in addition to the wash-chamber 2, each of which has a similar plumbing system and valve control arrangements to that shown in Figure 1.

All three hot-tanks 14 incorporate thermostatically controlled immersion heaters programmed to provide hot water at the required temperature prior to commencing the wash programme. As a result of this modified arrangement it is possible to have an immersion heater in the wash chamber also, to compensate fortemperature losses during the wash or rinse cycles as well as to correct any variation of actual inputtemperature. Preferably, only one heater would be energised atanytime and therewould be priority switching by the control circuit between thermostats to maintain the desired temperatures in the hot-tanks and the wash-chamber.Alternatively, each ofthe hot-tanks 1 4 may be provided with an electric heater of comparatively low wattage to permit contemporaneous use with the other heaters in a 13 amp electricity supply circuit, or with a heater of comparatively high wattage for contemporaneous use in a supply circuit of much higher input.

The working cycle of a dish-washer provided with three hot-tanks A, B & C, is illustrated graphically in Figure 4from which it can be deduced that tank A heats cold domestic supply waterfrom 1 00C to 50 C prior to commencement ofthe working cycle and is then mixed with cold water (1 0'C) in the wash chamber for the pre-wash phase at 38"C. Similarly, tank B heats cold domestic supply water from 1 00C to 75 C prior to commencement of the main wash phase at 55 C, and tank C heats cold (1 0"C) domestic supply water from 1 00C to 90 C prior to the hot rinse phase at 65 C.The three heating phases of tanks A, B & C do not overlap unless the above-mentioned alternative arrangement is used. The wash-chamber heater is energised during the heated water cycles to compensate for temperature losses due to heat absorption by the wash chamber 2 and its contents. Its use would not extend the wash and rinse cycle times.

The overall running time forthe dishwasher according to this second embodiment is 25 minutes as compared with 341/2 minutes for that ofthe first embodiment and 591/2 minutes for the conventional dishwasher, which figures, although theoretical, demonstrate a very considerable saving in running time.

It will be appreciated from the foregoing description the water capacity of the, or each, hot-tank, the power ofthe, or each, immersion heater and the maximum temperature to which water in the, or each, hot-tank is elevated may be varied to meet different requirements and even where the dishwasher does not incorporate a water softener a running time reduction by preheating waterfrom the domestic supply to an elevated temperature may provide advantages.

Claims

1. A dishwashing machine of the kind whhich operates automatically to a pre-determined programme, comprising an arrangement in which the warm or hot water requirements for at least one phase of the programme are met by means of at least one water tank provided in addition to but separate from the wash-chamber of the machine, and in which water is pre-heated to a predetermined temperature prior to commencement of that phase and is mixed with water at a lower temperature level to achieve the required quantity at the desired temperatureforthat phase of the programme.

2. A dishwashing machine as claimed in claim 1, whereinthewateratthehigherandlowertempera- ture levels is mixed in the wash-chamber.

3. A dishwashing machine as claimed in claim 2, wherein the wash-chamber incorporates a thermostatically controlled heater to compensate for temperature losses and/orto compensate for any variation of thewaterinputtemperaure of the water fed directly from the supply to the wash chamber.

4. A dishwashing machine as claimed in any of claims 1 to 3, wherein the, or each, tank forthe pre-heated water is incorporated in the machine.

5. A dishwashing machine as claimed in any one of the preceding claims, wherein the water in the, or each, tank is heated by a thermostatically controlled electrical immersion heaterwhich is connected into the control circuit ofthe machine and is switched on automatically according to the selected programme and inputtemperature of the water.

6. A dishwashing machine as claimed in claim 5, wherein the, or each, heater is controlled so that water in the, or each, tank reaches the required temperature priorto commencement ofthe relevant phase ofthe programme, and without delaying commencement of that phase.

7. A dishwashing machine as claimed in claim 5 or claim 6, wherein the machine is provided with a plurality of pre-heating tanks each provided with a heater and wherein there is a priority switching system between the thermostats of each tank and the wash-chamberto maintain the desired temperature.

8. A dishwashing machine as claimed in any one of the preceding claims, wherein the dishwasher incorporates a water softener and the water delivery system to the wash-chamber comprises a two-pipe arrangement on the exit side of the water softener, one pipe leading to the, oreach, hotwatertank andthe other by-passing the, or each tank, to convey unhe- ated water to the wash-chamber.

9. A dishwashing machine as claimed in any one of the preceding claims, wherein the flow ofwaterto and from the tank or tanks, is controlled by flow control valves connected to the programme timer and which provide for constant orvaried flows of heated water to the wash-chamber, and wherein the flow of unheated waterto the wash-chamber is controlled by a flow control valve connected to the programme timerto provide constant orvariedflowsto said wash-chamber.

10. A dishwashing machine as claimed in claim 1 and substantially as hereinbefore described with reference to Figures 1,3 and 4 of the accompanying drawings.

11. A dishwashing machine of the kind which operates automaticallyto a pre-determined programme, comprising a water softener assembly connected between a water inlet to the machine and a chamber in which wash water and/or rinse water is heated, and the arrangement of the programme is such that regeneration ofthewatersoftening material takes place substantially after completion of all the wash and rinse cycles ofthe machine.

12. A dishwashing machine as claimed in claim 11, wherein the chamber in which the wash and/or rinse water is heated is separate from a wash chamber and evacuation of the resin in the water softener resin chamber into the wash-chamber and thence to waste is programmed to occur atthe beginning of the next wash.

13. A dishwashing machine as claimed in claim 11 and substantially as hereinbefore described with reference to Figures 1,3 and 4 of the accompanying drawings.