GB1595254A

GB1595254A - Pumping unit for dishwashing machines

Info

Publication number: GB1595254A
Application number: GB2995/78A
Authority: GB
Original assignee: BERELSON R
Current assignee: BERELSON R
Priority date: 1978-01-25
Filing date: 1978-01-25
Publication date: 1981-08-12
Also published as: FR2415450A1; IT1094539B; SE427326B; IT7822748A0; SE7804774L; FR2415450B1; NL7804398A

Description

(54) PUMPING UNIT FOR DISHWASHING MACHINES (71) I, RUDOLPH BERELSON, a British subject, of 'Treelawns', 34 Fallowfield, Stanmore Hill, Stanmore, Middlesex, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to an additive pumping unit for dishwashing machines and to dishwashing machines incorporating such a unit.

Commercial dishwashers comprise a water tank of, say, 50 litre in which the dishes are washed at approximately 60"C and containing an overflow stand pipe through which excess water can drain off so as to maintain a constant volume of water when a flow of rinsing water at 820C or so is directed onto the dishes at a rate of roughly 1000 cc/10 sec. The washing water in the tank contains an additive of, say, 21% detergent to assist the cleaning operation.

The rinsing water desirably also contains an additive for reducing its surface tension from approximately 75 to 35 dyne/um. This rinsing additive helps the water to spread over the dishes so that it is less likely to leave spots and it also accelerates the drying step. The usual cycle of operations involves a washing step for 60 sec followed by a settling time of say 2 sec and rinsing for 10 sec.

At certain intervals (2 or 3 times daily) and particularly at the end of the day, the dirty washing water is emptied and fresh water is introduced to the tank when the machine is used again. The detergent for the washing water and the rinsing additive for the rinsing water are introduced through separate conduits by respective separately motor-driven pumps.

A grave problem that exists with conventional commercial dishwashers is that, although the 21% concentration of detergent in the freshly introduced washing water can be set by metering the appropriate amount of detergent as the washing water is being pumped into the tank, this concentration is very soon diluted after every 60 or so sec as the rinsing water flows in for 10 sec and is added to the washing water. Complicated electronic sensing systems have therefore been devised for automatically measuring the detergent concentration with a probe and, when necessary, pumping more detergent into the washing water. However, for small commercial dishwashers an elaborate detergent sensing and injection system is not viable in relation to the cost of the rest of the machine.

The invention aims to provide a more economical additive pumping unit for dishwashing machines that enables the detergent concentration to be automatically kept substantially constant without the use of sensing probes.

According to the invention, an additive pumping unit for dishwashing machines having a rinsing water supply comprises two diaphragm pumps for respective additives, a common electric motor for operating the pumps and a pressure responsive switch which is adapted to be connected in the rinsing water supply and is electrically connected to the motor so that the motor is energised whenever the pressure responsive switch is actuated by the rinsing water.

The invention also extends to a dishwashing machine comprising a tank for washing water, a supply for rinsing water controlled by a programme operated solenoid valve, a detergent supply containing a first motordriven diaphragm pump and leading to the tank, and a rinsing additive supply containing a second motor-driven diaphragm pump and communicating with the rinsing water supply, wherein a common electric motor is provided for driving both pumps and the rinsing water supply contams a pressureresponsive switch which is electrically connected to the motor so that the motor is energized whenever the pressure-responsive switch is actuated by the rinsing water.

By means of the invention, it becomes possible to inject a set amount of supplementary detergent into the tank whenever it is being diluted by rinsing water because the diaphragm pump for the detergent is driven by the motor as soon as rinsing water flows across the pressure responsive switch. At the same time, rinsing additive is fed in with the rinsing water because the diaphragm pump for this rinsing additives is driven by one and the same motor, thereby saving the cost of an additional motor. What is more once the pumping rate has been set in the factory for the rinsing water flow rate of a particular dishwashing machine, which can be done very accurately, no adjustment is required to be made by an unskilled user of the machine.

Preferably, a cam connected to the output shaft of the motor co-operates with two longitudinally reciprocatable thrust rods, one for operating each diaphragm pump. As each thrust rod is pushed through a forward stroke by the rotating cam, or by the outer race of a ball bearing which has its inner race connected to the cam, the associated diaphragm is displaced and injects additive into the tank and rinsing water supply, respectively. On the return stroke of each thrust rod, which may be effected by a spring, the associated diaphragm sucks the respective additive from a storage drum in readiness for injection during the next following forward stroke.

To permit factory adjustment of the stroke of each thrust rod, and hence of the amount of additive injected, each thrust rod is screw-threaded and its spacing from the cam is adjustable by turning a set nut engaged therewith, a lock nut being provided to fix the set position. It is also of advantage to provide a fixed pointer for co-operating with a graduated scale on the set nut, whereby the setting can be read off in terms of, say, percentage additive.

The aforementioned pressure responsive switch may comprise a diaphragm which is connected in the rinsing water supply and which, when deflected by water pressure, acts on a microswitch electrically connected to the motor. In a modification of the invention, the pressure responsive switch can be dispensed with if the electric motor is instead connected to the switch circuit of the existing programme operated solenoid valve of the dishwashing machine that controls the flow of rinsing water. In this case, the motor will be energised whenever the solenoid valve admits rinsing water to the machine, i.e. whenever the switch circuit of the solenoid valve is energised.

Accordingly, in a modification the invention provides a dishwashing machine comprising a tank for washing water, a supply for rinsing water controlled by a programme operated solenoid valve, a detergent supply containing a first motor driven diaphragm pump and leading to the tank, and rinsing additive supply containing a second motor driven diaphragm pump and communicating with the rinsing water supply, wherein a common electric motor is provided for driving both pumps and the motor is electrically connected to the solenoid valve so that the motor is energised whenever the solenoid valve is operated by the programme to feed rinsing water.

An example of the invention will now be described with reference to the accompanying drawing, in which the single figure diagrammatically illustrates a pumping unit installed on a commercial dishwashing machine.

A dishwashing machine comprises a tank 1 containing an overflow stand pipe 2 through which excess washing water 3 for dishes (not shown) can flow off to a waste pipe whenever the water exceeds a predetermined height, i.e. volume. Any scum on the washing water also flows off through the stand pipe, so it will be seen that the washing water need not be completely changed after every washing cycle. In fact, it is generally changed only about twice daily.

The washing water 3 contains a given quantity of liquid detergent, usually about %.

This detergent additive is required to enhance washing of the dishes.

The tank 3 is equipped with a rinse pipe 4 having rinse jets 5 which are directed onto the dishes. The pipe 4 is connected to a supply conduit 7 for hot rinsing water. After the dishes have been washed for, say 60 sec and after a settling time of a further 2 sec, the rinsing water supply is started by a solenoid valve 8 of the dishwashing machine. The rinsing water also contains an additive, namely one that reduces its surface tension so that it more readily spreads over the dishes, whereby subsequent drying of the dishes is accelerated and there is less likelihood of so-called water marks being left on the dishes. The rinsing water flows into the washing water 3 after leaving the dishes and, as already mentioned, excess water at the bottom of the tank 1 flows off through the stand pipe 2 which ensures that the volume of water in the tank remains constant.

Rinsing additive that has now entered the washing water for 10 sec has no detrimental effect on the efficiency of the next washing cycle but the fact that rinsing water has been added to the washing water and excess water has drained away means that the washing water is now diluted, i.e. it no longer contains the desired detergent concentration of, say, 2%, and this certainly detracts from efficient washing. To counteract this dilution of washing water, more liquid detergent has to be introduced through an inlet 9 and the present invention provides a pumping unit which, inter alia, enables this to be done accurately and automatically.

The pumping unit comprises two identical diaphragm pumps 11, 12, the respective diaphragms being indicated at 13 and 14 but the precise construction of the pumps being otherwise immaterial to the present invention. The pump 11 serves to inject a metered quantity of liquid detergent, governed by the amount o displacement of its diaphragm, into the washing water 3 by way of the inlet 9 of the dishwasher. Whenever a reciprocatable thrust rod 10 connected to the diaphragm 13 moves to the right in the drawing (return stroke), the diaphragm is also deflected to the right and detergent is sucked from a 25 litre supply drum 16 through a conduit 17 fitted with a nonreturn foot valve 18. On the forward stroke of the thrust rod 10, the latter displaces the diaphragm to the left to pump the liquid detergent through the aforementioned inlet 9 and into the washing water 3. Similarly, the diaphragm 14 of the pump 12 is operated by a thrust rod 19 to pump rinsing additive into the rinsing water supply conduit 7 on a forward stroke (to the right in the drawing) and to suck the rinsing additive from a supply drum 21 on the return stroke by way of a non-return foot valve 22 and a conduit 23. The connection of the outlet side of the pump 12 to the supply conduit 7 is preferably upstream of the solenoid valve 8 of the machine.

The two thrust rods 10, 19 are alternately reciprocated by means of a common electric motor 24 of which terminals 26 are constantly connected to an AC mains supply, possibly by way of an on-off switch, whenever the dishwashing machine is in use.

The output shaft of the motor is connected, possibly by way of step-down gearing 25, to a cam disc 27 eccentrically mounted on a shaft 30. The cam disc is secured to the inner race of a ball bearing 28, of which the outer race alternately acts on those ends of the thrust rods (the inner ends) remote from the ends connected to the diaphragms 13, 14 of the pumps 11, 12.

During each revolution of the shaft 30 and thus of the cam disc 27 and the inner race of the ball bearing 28, each thrust rod 10, 19 is caused to execute one forward stroke. The return stroke is implemented by a respective compression spring 29, 31 around each thrust rod. Each compression spring acts between a locating shoulder on the thrust rod, for example a circlip 32, 33 fixed to the thrust rod, and a bearing arm 34, 36 of a fixed bracket 37 for slidingly supporting the thrust rods. It should be emphasized that the compression springs do not necessarily keep the inner ends of the thrust rods in constant contact with the outer race of the ball bearing 28. On the contrary, in many cases the inner ends of the thrust rods 10, 19 will be spaced from the ball bearing 28 during part of each revolution of the cam disc, as will hereinafter be described. To facilitate assembly, the crossarm of bracket 37 is made separately from the bearing arms 34, 36 and only subsequently attached thereto.

It will be evident that the amount of respective additive delivered by each pump 11 or 12 is governed by the deflection of the respective diaphragm 13 or 14 and this deflection in turn depends on the length of the stroke executed by the respective reciprocatable thrust rod 10 or 19. The strokes of the thrust rods can be independently adjusted manually even though both rods are operated by one and the same motor acting through the single cam disc or ball race. Such independent adjustment is possible by means of a respective set nut 38 or 39 in screw-threaded engagement with the thrust rod 10 or 19 on the side of the respective bearing arm 34 or 36 opposite to the side on which the compression spring 29 or 31 acts.

Considering the thrust rod 10, the spring 29 can move it to the right only as far as the nut 38 will permit, i.e. until the nut 38, locked to the rod against rotation by a lock nut 41, abuts against the bearing arm 34 acting as an end stop. Accordingly, the position of the set nut 38 on the rod 10 limits the return stroke that the latter executes under the action of the spring 29 and, on termination of this return stroke, the inner end of the rod may well be spaced from the surface of the eccentrically rotating outer race of ball bearing 28. Consequently, the forward stroke of the rod 10 may likewise be limited to that fraction of one revolution of the cam disc 27 during which the ball bearing 28 is in contact with the rod. The maximum stroke, and hence maximum delivery of additive, is obtained when the set nut 38 is so positioned that it never abuts the arm 34 during reciprocation of the rod and so that the inner end of the thrust rod is always in contact with the ball bearing 28. Zero stroke and zero delivery of additive are obtained when the set nut is positioned to be in constant contact with the arm 34 and the inner end of the rod 10 makes no contact with the ball bearing 28 during a complete revolution of the disc 27. Of course the lock nut 41 is in practice positioned tightly adjacent the set nut 38 and not spaced from it as is shown in the drawing.

In the same way as described for the rod 10, the stroke of the thrust rod 19 is manually adjustable by selectively positioning the set nut 39 and then fixing its position by means of a lock nut 42.

By choosing a screwthread of appropriate lead on the respective thrust rod and by graduating the circumference of the associated set nut with a scale for co-operation with a respective fixed pointer, such as a line engraved on the bracket 37, it is possible to ensure that one turn of the set nut will move it along the rod from a position of maximum to one of zero additive delivery and that the actual setting of percentage additive can be read off with the aid of the pointer and graduated scale.

The pumping unit also comprises a pressure responsive electric switch 43 for connection in the rinsing water supply conduit 7 downstream of the solenoid valve 8 of the dishwasher and preferably also downstream of where the outlet from the pump 12 enters the conduit 7. The switch 43 is electrically connected to the motor 24 and, provided that the motor terminals 26 are alive, is effective to close and cause the motor to turn whenever rinsing water is flowing across the switch 43.

The operation of the pumping unit is as follows. At the beginning of the day the dishwashing machine will be empty. The operator ensures that electric power is applied to the motor terminals 26, loads the dishwashing machine with dishes and starts the machine. The programme of the machine is of course such that washing water 3 must first of all enter the tank 1.

This washing water is obtained from the supply of hot rinsing water through the conduit 7 and pipe 4. As soon as the flow of water is initiated through the conduit 7 by the solenoid valve 8, the water pressure closes the switch 43. The motor 24 and hence the shaft 30 and cam disc 27 therefore turn and, during each revolution of the cam disc, the thrust rods 10 and 19 are reciprocated once to and fro by the ball bearing 28 secured to the cam disc, the quantity of detergent additive entering the tank 1 from the diaphragm pump 11 through the inlet 9 and the quantity of rinsing additive entering the tank from the pump 12 through the pipe 4 being governed by the strokes of the respective thrust rods 10, 19 and hence by the positions of the nuts 38, 39. These positions are usually already set in the factory to be pro rata with the given hot water flow rate for which a particular dishwashing machine is designed and, once set, need not normally be changed by the user.

Although only detergent additive is actually required during this initial filling of the machine with washing water, rinsing additive is also injected by reason of the pump 12 being operative. However, this rinsing additive in the washing water is harmless and, since only a relatively small amount of rinsing additive is lost by this complete initial filling carried out some two or three times daily, it is not economical to provide a special bypass circuit for it. When the machine is full, a constant volume of washing water always being ensured by the stand pipe 2, the dishwashing machine programme is instrumental in shutting the solenoid valve 8, the switch 43 opens and the motor 24 stops. The dishwashing cycle now takes place. After a short settling period, the rinsing cycle commences by the valve 8 being opened, which also causes the switch 43 to close and the motor 24 and pumps 11, 12 to start operating. Consequently, rinsing water flows through the conduit 7, pipe 4 and rinse jets 5 and this water includes, as is required, a rinsing additive by reason of pump 12 being operative. Simultaneously, detergent is being injected by the pump 11 through the inlet 9 and flows direct to the washing water 3 to maintain its concentration and compensate for the dilution caused by the rinsing water. After the rinsing cycle, both pumps are again inoperative because the switch 43 will open when it is no longer activated by the pressure of hot rinsing water flowing through the conduit 7.

Some older types of dishwashing machines obtain their initial filling of washing water 3 not from the rinse pipe 4 but through a separate supply pipe 46 which is opened and closed by a manual stopcock 47.

To cater for these machines, i.e. to ensure that the pump 11 will inject the initial detergent even though no water is flowing through the conduit 7, the pump unit may be provided with a manually actuable override switch 48 which is electrically connected to override the pressure responsive switch 43 and start the motor 24. After a time corresponding to the filling cycle for an empty tank, the override switch 48 automatically becomes inoperative and thereafter the motor is actuated solely by the pressure responsive switch 43 in the manner already described.

There may also be a priming button 49 to allow the diaphragm pumps to be primed when their intakes from the supply drums are empty. The priming button is effective to short out the pressure responsive switch 43.

In a modification of the invention, the separately provided pressure responsive switch 43 is ommitted. Instead, the electric motor 24 is connected to the switch circuit of the solenoid valve 8 with which the dishwashing machine is already equipped and which is operated by the programme of the machine. Consequently, whenever the switch circuit of the valve 8 is energised to open the valve, the motor 24 is likewise energised to operate the diaphragm pumps 11 and 12. The disadvantage of this modification is that, for older types of machines receiving their initial supply of washing water 3 through a separate supply pipe 46, this initial washing water must, unless other special provisions are made, already contain a correct proportion of detergent because the solenoid valve 8 remains shut during initial filling.

WHAT I CLA1M IS: 1. An additive pumping unit for dis

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. it along the rod from a position of maximum to one of zero additive delivery and that the actual setting of percentage additive can be read off with the aid of the pointer and graduated scale. The pumping unit also comprises a pressure responsive electric switch 43 for connection in the rinsing water supply conduit 7 downstream of the solenoid valve 8 of the dishwasher and preferably also downstream of where the outlet from the pump 12 enters the conduit 7. The switch 43 is electrically connected to the motor 24 and, provided that the motor terminals 26 are alive, is effective to close and cause the motor to turn whenever rinsing water is flowing across the switch 43. The operation of the pumping unit is as follows. At the beginning of the day the dishwashing machine will be empty. The operator ensures that electric power is applied to the motor terminals 26, loads the dishwashing machine with dishes and starts the machine. The programme of the machine is of course such that washing water 3 must first of all enter the tank 1. This washing water is obtained from the supply of hot rinsing water through the conduit 7 and pipe 4. As soon as the flow of water is initiated through the conduit 7 by the solenoid valve 8, the water pressure closes the switch 43. The motor 24 and hence the shaft 30 and cam disc 27 therefore turn and, during each revolution of the cam disc, the thrust rods 10 and 19 are reciprocated once to and fro by the ball bearing 28 secured to the cam disc, the quantity of detergent additive entering the tank 1 from the diaphragm pump 11 through the inlet 9 and the quantity of rinsing additive entering the tank from the pump 12 through the pipe 4 being governed by the strokes of the respective thrust rods 10, 19 and hence by the positions of the nuts 38, 39. These positions are usually already set in the factory to be pro rata with the given hot water flow rate for which a particular dishwashing machine is designed and, once set, need not normally be changed by the user. Although only detergent additive is actually required during this initial filling of the machine with washing water, rinsing additive is also injected by reason of the pump 12 being operative. However, this rinsing additive in the washing water is harmless and, since only a relatively small amount of rinsing additive is lost by this complete initial filling carried out some two or three times daily, it is not economical to provide a special bypass circuit for it. When the machine is full, a constant volume of washing water always being ensured by the stand pipe 2, the dishwashing machine programme is instrumental in shutting the solenoid valve 8, the switch 43 opens and the motor 24 stops. The dishwashing cycle now takes place. After a short settling period, the rinsing cycle commences by the valve 8 being opened, which also causes the switch 43 to close and the motor 24 and pumps 11, 12 to start operating. Consequently, rinsing water flows through the conduit 7, pipe 4 and rinse jets 5 and this water includes, as is required, a rinsing additive by reason of pump 12 being operative. Simultaneously, detergent is being injected by the pump 11 through the inlet 9 and flows direct to the washing water 3 to maintain its concentration and compensate for the dilution caused by the rinsing water. After the rinsing cycle, both pumps are again inoperative because the switch 43 will open when it is no longer activated by the pressure of hot rinsing water flowing through the conduit 7. Some older types of dishwashing machines obtain their initial filling of washing water 3 not from the rinse pipe 4 but through a separate supply pipe 46 which is opened and closed by a manual stopcock 47. To cater for these machines, i.e. to ensure that the pump 11 will inject the initial detergent even though no water is flowing through the conduit 7, the pump unit may be provided with a manually actuable override switch 48 which is electrically connected to override the pressure responsive switch 43 and start the motor 24. After a time corresponding to the filling cycle for an empty tank, the override switch 48 automatically becomes inoperative and thereafter the motor is actuated solely by the pressure responsive switch 43 in the manner already described. There may also be a priming button 49 to allow the diaphragm pumps to be primed when their intakes from the supply drums are empty. The priming button is effective to short out the pressure responsive switch 43. In a modification of the invention, the separately provided pressure responsive switch 43 is ommitted. Instead, the electric motor 24 is connected to the switch circuit of the solenoid valve 8 with which the dishwashing machine is already equipped and which is operated by the programme of the machine. Consequently, whenever the switch circuit of the valve 8 is energised to open the valve, the motor 24 is likewise energised to operate the diaphragm pumps 11 and 12. The disadvantage of this modification is that, for older types of machines receiving their initial supply of washing water 3 through a separate supply pipe 46, this initial washing water must, unless other special provisions are made, already contain a correct proportion of detergent because the solenoid valve 8 remains shut during initial filling. WHAT I CLA1M IS:

1. An additive pumping unit for dis

hwashing machines having a rinsing water supply, comprising two diaphragm pumps for respective additives, a common electric motor for operating the pumps and a pressure responsive switch which is adapted to be connected in the rinsing water supply and is electrically connected to the motor so that the motor is energised whenever the pressure responsive switch is actuated by the rinsing water.

2. A unit according to claim, wherein a cam connected to the output shaft of the motor co-operates with two longitudinally reciprocable thrust rods, each connected to a pump diaphragm at one end, to move each thrust rod through a forward stroke.

3. A unit according to claim 2, wherein the cam is secured to the inner race of a ball bearing, the outer race of which acts on the other end of each thrust rod.

4. A unit according to claim 2 or claim 3, wherein each thrust rod is slidingly mounted in a respective bearing arm o a fixed bracket and its return stroke is implemented by a compression spring which is disposed around each thrust rod and acts between one side of the respective bearing arm and a shoulder on the thrust rod.

5. A unit according to any one of claims 2 to 4, wherein the return strokes of the thrust rods are independently adjustable.

6. A unit according to claims 4 and 5, wherein the return stroke of each thrust rod is limited by a set nut in screw-threaded engagement therewith and disposed to abut against the other side of the respective bearing arm which acts as an end stop.

7. A unit according to claim 6, wherein the circumference of each set nut is graduated with a scale for co-operation with a respective fixed pointer.

8. A unit according to any preceding claim, including a manually actuatable override switch electrically connected to the motor to energise same for a predetermined period when the pressure responsive switch is not being actuated by rinsing water.

9. A unit according to any preceding claim, including a priming button on the motor adapted to short out the pressure responsive switch to permit the pumps to be primed when no rinsing water flows in the supply.

10. A dishwashing machine comprising a tank for washing water, a supply for rinsing water controlled by a programme operated solenoid valve, a detergent supply containing a first motor driven diaphragm pump and leading to the tank, and a rinsing additive supply containing a second motor driven diaphragm pump and communicating with the rinsing water supply, wherein a common electric motor is provided for driving both pumps and the rinsing water supply contains a pressure responsive switch which is electrically connected to the motor so that the motor is energised whenever the pressure responsive switch is actuated by the rinsing water.

11. A dishwashing machine according to claim 10, wherein the rinsing additive supply is connected to the rinsing water supply downstream of the solenoid valve and upstream of the pressure responsive switch.

12. A dishwashing machine comprising a tank for washing water, a supply for rinsing water controlled by a programme operated solenoid valve, a detergent supply containing a first motor driven diaphragm pump and leading to the tank, and a rinsing additive supply containing a second motor driven diaphragm pump and communicating with the rinsing water supply, wherein a common electric motor is provided for driving both pumps and the motor is electrically connected to the solenoid valve so that the motor is energised whenever the solenoid valve is operated by the programme to feed rinsing water.

13. An additive pumping unit substantially as hereinbefore described with reference to the accompanying drawing.

14. A dishwashing machine substantially as hereinbefore described with reference to the accompanying drawing.