US2859760A - Automatic detergent feeding control - Google Patents

Description

Filed March 30,. 1955 Nov. 11, 1958 TLQ 2,859,760

AUTOMATIC DETERGENT FEEDING CONTROL 2 Sheets-Sheet i I I //VVE/V7'0E A rive/V Y Nov. 11, 1958 G. L. BORELL 5 AUTOMATIC DETERGENT FEEDING CONTROL Filed March 30, 1955 2 Sheets-Sheet 2 AUTOMATIC DETERGENT FEEDKNG CONTROL 7 George L. Borell, Glen Rock, N. J.

Application March 30, 1955, Serial No. 497,897

8 Claims. (Cl. 137--93) This invention relates to the art of automatically replenishing a constituent of aliquid which is progressively consumed as the liquid is employed in the performance of a process and the depletion of which beyond a certain point will impair the efiicacy of the process. The invention has utility in many processes which involve the electrical conductivity of an electrolyte, such as plating by electrolysis, but it has been principally devised and commercially employed in dispensing detergent into the wash water of dish washing machines in response to signals denoting depletion of the detergent. The invention will therefore be described in connection with the dispensing of detergents to dish washing machines. Such automatic dispensing of detergents is particularly desirable for large dish washing machines such as are employed in restaurants, hotels, clubs and the like Such machines commonlyhave dis-hes on trays moved progressively through wash sections and rinse sections, the wash operation being a continuous process. Hot water is pumped over the dishes in the rinse section and runs down onto a drain board and into the wash. tank. which contains soapy water. and from which the soapy. water is forcibly delivered upon the dishesin thewash section from. above and below. There is an overflow pipe in the wash tank and due to thercontinual delivery of water from the. rinse section'the waterbecomes diluted. It is therefore necessary to add detergent from time to time.

Machines operating upon this principle are Well known. The present invention aims to improve upon known machines and produce an automatic dispensing attachment whichis simpler, more dependable, more economical in .useandcheaper. to produce and maintain than those heretoforeused.

All automatic dispensersv of this character must work upon-the principle, of employinga mechanism which will in some manner sense-the depletion of the detergent in the. wash water. and send out a signal for replenishment, which signalwill cause a fresh quantity of detergent to bedelivered to the wash tank.

Obviously between the. delivery of the fresh charge to the wash tankandthe thorough distribution of the charge there is a lag which is reflected in the signal. Consequently there is apt to be an oversupply. To avoid this it is customary to anticipate the cut ofl signal, as, for eitample, providing a time responsive'd'r'ain" upon the ener gizing'current for a controlling relay. Su'chanticipation is of "course empirical'andis in no'wise dictated byconditions: Furthermore" as a rule it involves the used electronic tubes'zortimers-whichare expensive andvulnerable inusei Thefpresent'invention works upon a dilferent'principle fromprevious dispensers inthat it-utilizes the conditions in the container from'which theconcentrated detergent solution is dispensed-jointlywith theconditions in the wash tank tocontrol the replenishing. action. Inresponse to a. signal-.from the wash tank a valve is opened and water is;admitted.to thedispensing container. This raises the leveL-in thecontainer and at a proper height which rite States atent 2 determines the amount that is going to be 'dispensedthe valve is closed and the detergent solution in the amount admitted then runs out into the wash tank. If this "is not enough the valve again opens and the operation isr'epeated until the condition of the wash wate'r'is corrected. There is no continuous running until the signal from the wash tank signifies sufiiciency. Instead there is a succes sion of small quantities of detergent added until conditions are corrected. In this way overfeedin'g to any ma terial extent is impossible.

Specifically there is provided ata selected height in the dispenser container a pair of sensing elecfrodes'similafto those commonly used in the washtarik, and the two pairs are connected in parallel in a voltage divider network which operates the control relay. Hence both control the voltage to the relay winding to open and close the valve repeatedly until the signal voltage to the relay reaches a threshold valve which causes the control actionto cease.

The electrodes in the container are also sensitive to the detergent concentration and if the detergent gives out through inadvertentfailure of the operator to maintain a supply in the container, the container electrodes will be ineffective to close the valve. Under such condition the water will continue to run from the container into the wash: tank and proper control cannot be maintained. 1

To avoid this undesirable event signal means, both audible and visual are provided to announc'e when" the relay is energized and the valve is open. Ordinarily the signals are just momentary. If they become continuous the operator is thereby sufiiciently warned that more detergent material to the container in order to restore the desired control isrequired.

A feature of the invention is the'w'ay such signals'aie produced. There are various" other features of the invention which will appear from the following description of the embodiment illustrated iii the drawings.

Fig. 1 is a sectional elevation of thewash section and wash tank and dispensing container of a dish washing machine embodying the invention, together with a diagram of the electrical control system;

Fig. 2 isa plan partially in section of the dispenser container and of the electrical parts carried thereby;

FigL 3 is a fragmentary section of the container and associated parts on line3 3 of Fig. 2; and

Fig; 4 is a diagram of the electrical system;

A tray' of dishesl is shown in the wash section of a dish washing machine, on a conveyor which carries'the tray to therinse'section'o'n the right" (no-t sh0wn)i Water is pumped from the washtank 2 and delivered forcibly upon the dishes through the sp'raymeans 3. An'ove rfiow pipe 4' determines the level of' the water in tank2; A drain board 5leads the water which is' delivered to the rinse section by pipe 6 from the rinse section intotank 2, or, asoften is' the case, into'another tank which over flows into the wash tank. in large machines there are more than one tankreceivi'ng the rinse water'andpro'g'ressively overfiow'ing'orie into another and eventually into the wash tank; The rinse water is of course hotter than the wash water and assumes the proper temperature by the time it reachesthe washtank'.

This constant addition of clean water to the wash tank dilutes the detergent concentration and periodically more detergent-has to be added to the washwater. This is done automatically from ai'container 7 disposed above the wash tank and delivers through a discharge standpipe 8 into the wash tank.

To detect or sense the conditions both in the wash tank 2. and in the container 7, each has a pair of'closely spaced electrodes which are adapted to contact the contents and will be conductively bridged by the liquid which will afiord a resistance which willvary inversely with the alkaline or detergent content of the liquid.

The electrodes 9 in the tank 2 are suitably insulated and supported in the wall well below the top of overflow pipe 4 so as alway to be immersed in the wash water. The e ectrodes for the detergent container 7 are also suitably insulated and secured in the wall of the container ii -horizontal alinement at a height relative to the standplpe 8 which is important as will now be explained.

i Wheneventhe conductivity of the wash water reaches a certain minimum degree, it causes a valve to open as we shall see, to admit water to container 7. More S O1l(l detergent in the bottom of the con ainer is dissolved and the level of the detergent solution rises in the container until it reaches the electrodes 10 whereupon the resistance across the electrodes is reduced and the waterls shut off. This of course depends upon the detergent concentration in the container, and if the operator has allowed the detergent to become exhausted, the conductivlty will not be sufiicient to close the valve. In such case We shall see that a continuous signal is given.

The construction is such that the discharge from the contamer 7 does not begin until the inflow of water has ceased due to the closing of the valve. Then if the valve is not again immediately opened an amount of detergent solutlon exactly equal to the amount of water admitted wlll run out into the wash tank. Thus the efiluence is llmited to a definite amount which, as we shall see is determined by the height of the electrodes 10.

In addition to the open top end of standpipe 8 it has a side opening a certain distance below the end in which is secured the leg of a T-shape tubular member 11 the head of which is disposed vertically. Both the head and leg are tubular and they communicate, the head being open at both ends. Therefore liquid in the container can use in the head and escape through the leg into the standpipe. The water inlet pipe 12 has its nozzle entered lntO the top end of the head of the T-member 11 and the entering stream will therefore be confined by the head and directed past the entrance to the tubular leg and out the other end of the head. It is obvious therefore that 11' unopposed, the bottom of the leg will determine the level of the contents. If however a stream of sufiicient force is directed through the head of the T-member it W111 impinge upon the surface of the liquid and force it down into the head below the bottom of the leg and even to the very bottom of the head. Meanwhile of course the level outside the head is rising and will contlnue to do so until the water is shut off, whereupon the liquid will again rise in the head and run out of the tubular leg and side orifice into the standpipe until the natural level is again reached. The top opening of the stand ipe 8 provides a safety discharge whenever the solution level exceeds the height of the electrodes 10.

It is the electrodes 10 which determine when the water is shut off. As shown, they are located in a plane between the bottom of the leg and the top of the stand i e, and when the solution rises to that plane it condnctively bridges the electrodes and the valve is closed. Then the efiluence begins and thus its amount is determined.

The electrical circuit by which this joint control by the wash water and the detergent solution in the container is effected is diagrammatically shown in Fig. 4 and also in Fig. 1.

It is a low voltage system fed by a low voltage transformer 15, the output volta e being, for example, twenty one volts comparable to that of an ordinary domestic bell-current transformer. This of course makes for a safe and economical installation.

Wires 16 and 17 constitute the two sides of the supply line and electrodes 9 and 10 are connected in parallel across the line in series with resistances 18 and 19 which determine the distribution of the voltage drop in the connection across the line including the electrodes. The resistance 18 is variable and will be adjusted so that the drop across the measuring electrodes when the detergent need of the wash water is satisfied will be slightly less 4 than that required to energize the controlling relay to open the valve. Hence under that condition no water is being admitted into container 7.

The water pipe 12 has in it a valve 20 which is controlled by a solenoid 21. The valve has a solenoid controlled plunger 22 which is withdrawn by the solenoid to open the valve against the tension of coil spring 23. The solenoid Winding 21 surrounds a hollow core 24 which is closed at the end remote from the valve to form a seal and stop for the plunger to strike when the solenoid is energized. This is for the purpose of a signal, as will later be described.

The solenoid winding is connected across the wires 16 and 17 by wires 25 and 26, the latter including relay contact 28. Also shading coils 28 are provided to adapt the solenoid valve for A.-C. operation.

The control relay 30 includes the electro-magnet29 and the contact 28. It is connected across the electrodes 9 and 10 through a full wave rectifier 31. wire 32 connecting the rectifier to one side of electrodes 9 and 10 and wire 33 connecting the rectifier to the other s1de of the electrodes. Wires 34 and 35 connect the output of the rectifier to the opposite ends of the coil of electromagnet 29. A ca acitor 36 is connected in shunt w1th the electro-magnet to smooth out the pulsating recttfied voltage.

It will now be clear how the two pairs of sensing electrodes jointly control the energization of the relay 30 and hence the energization of the soleno1d 21 and the opening and closing of the valve 20.

Let it be assumed that the detergent requirement of the wash water is satisfied. The voltage drop across electrodes 9 is comparatively low, the ma or portion of the drop between wires 16 and 17 being across the resistors 18 and 19. Under such condition electrodes 10 are above the level of the solution in contamer 7 and consequentlv have no shunting effect. When the wash solution is diluted, voltage drop between wires 32 and 33 becomes sufi'lcient to activate the relay and close contact 28. Solenoid 21 is thereby energized, the plunger 22 1s retracted and the valve 20 is opened and water starts to flow into the head of the T-member 11. The level in the container rises with no efiluence into standpipe 8 untll the solution bridges electrodes 10, whereupon the drop between the connections of wires 32 and 33 falls and the relay allows contact 28 to open by the usual spring action. Spring 23 moves the plun er 22 to valve closing position and the water is shut off. Thereu on there is an effiuence from container 7 through the lateral orifice until the natural level at the bottom of the leg is a ain reached.

It will be seen. therefore, that in operation. there is a Succession of shots of a small quantity of deter ent delivered in o the wash water until an alkaline condition is r ached where the drop across electrodes 9 is no longer sufficient to ener ize the relay and open the valve. Where a succession of shots are required the drop across the electrodes 9 continues within the relay energizing range and as soon as the level in container 7 falls so as to uncover electrodes 10. the electrodes 9 immediately become eifective to reo en the valve and start the water flowing again before the level in the container reaches its natural level. Therefore the successive shots will be less than the ouantity represented bv the difference between the natural level in container 7 and the level of electrodes 10. Not until electrodes 9 cease causing a signal for more detergent will the valve stay closed and the solution in container 7 run out until its natural level is reached.

As above stated and as is obvious, if the detergent concentration of the solution in the container 7 is too low, the bridging of the electrodes 10 will not reduce the drop sufiiciently to open contact 28 and close valve 20.

In that event the liquid level will rise until it flows into the top of standpipe 8 and the wash tank will be getting clear water instead of detergent. The operator should, of

course, be apprised of such untoward condition, and signals for that purpose are provided.

An audible signal is of the buzzer type and comprises a vibratory reed 40 which is within the influence of the alternating flux in core 24. Also the solenoid is designed to be noisy. For example, the tension of spring 23 may be so related to the attraction of the solenoid that the plunger will chatter, that is, it will strike against the bottom of the core at the maximum flux and be slightly withdrawn by the spring as the flux decays and reverses. The easiest method of accomplishing this is to reduce the shading eifect of coils 28.

In addition a red light 41 is connected in shunt with the solenoid through a suitable limiting resistance, thereby providing a visual signal.

The circuit is closed by switch 42 when it is desired to start the automatic dispensing action, which condition is also visually indicated by a lamp 45 connected across the line through a current limiting resistance.

As shown, the electrodes are protected by a removable shield and suitable protecting means may also be provided for electrodes 9.

While the particular embodiment which has been above described and is shown in the drawings has proven satisfactory, the invention may be otherwise embodied without departing from its scope as defined in the following claims.

What is claimed is:

1. Means for controlling the delivery of a replenishing solution to a processing tank, said means comprising, in combination with a processing tank, a container for replenishing solution, an inlet pipe for the container, a control valve for the pipe, a solenoid in control of the valve,

an electric supply line, means including a relay winding for connecting the solenoid across the supply line, a set of sensing electrodes adapted to contact the solution in the container, a second set of sensing electrodes adapted to contact the solution in the processing tank, and means controlled jointly by the two sets of electrodes for delivering voltage from the supply line to the relay winding.

2. Means for controlling the delivery of a replenishing solution to a processing tank, said means comprising, in combination with a processing tank, a container for replenishing solution, an inlet pipe for the container, a control valve for the pipe, a solenoid in control of the valve, an electric supply line, means including a relay winding for connecting the solenoid across the supply line, a set of sensing electrodes in the side wall of the container, and a second set of sensing electrodes adapted to contact the solution in the processing tank, a resistor, the two sets of electrodes being connected in parallel and in series with said resistor across the supply line to form a voltage divider network and the relay winding being connected into said network.

3. Means for controlling the delivery of a replenishing solution to a processing tank, said means comprising in combination with a processing tank, a container for replenishing solution, an inlet pipe for the container, a control valve for the pipe, a solenoid in control of the valve, an electric supply line, means including a relay winding for connecting the solenoid across the supply line, means responsive to the height of the solution in the container for modifying the voltage delivered from the supply line to the relay winding, and separate means responsive to the concentration of a solution in the processing tank for delivering voltage from the supply line to the relay windmg.

4. Means for controlling the delivery of a replenishing solution to a processing tank as defined in claim 3 in which the said separate means comprise a set of sensing electrodes adapted to be disposed in the processing tank being connected to the suppiy line in shunt with the relay winding.

5. Means for controlling the delivery of a replenishing solution to a processing tank as defined in claim 4 in which the electric'energy in the supply line is alternating current, together with a full wave rectifier in the shunt connection of the relay winding arranged to deliver direct current to the relay winding.

6. Means for controlling the delivery of a'replenishing solution to a processing tank, said means comprising, in combination with a processing tank, a container for replenishing solution, an inlet pipe for the container, a control valve for the pipe, a solenoid in control of the valve, an electric supply line, means including a relay winding for connecting the solenoid across the supply line, means including a set of sensing electrodes in the container connected to the supply line in shunt with the relay winding for modifying the voltage delivered from the supply line to the relay winding, and a second set of sensing electrodes disposed in the processing tank and connected to the supply line in shunt with the relay winding.

7. Means for controlling the delivery of a replenishing solution to a processing tank as defined in claim 6 in which the two sets of electrodes are connected in parallel, together with a voltage distributing resistance in series with the pairs of electrodes in their connection across the line.

8. Means for controlling the delivery of a replenishing solution to a processing tank comprising, in combination with a processing tank, a container for replenishing solution, a standpipe in the container discharging into the processing tank and having a lateral orifice, an inlet pipe for the container directed across said lateral orifice adjacent thereto, a central valve for the pipe, a solenoid in control of the valve, an electric supply line, means including a relay winding for connecting the solenoid across the supply line, means including a pair of sensing electrodes in the container disposed above the bottom of said lateral orifice and connected to the supply line in shunt with the relay Winding for modifying the voltage delivered from the supply line to the relay winding, and a second set of sensing electrodes disposed in the processing tank and connected to the supply line in shunt with the relay windmg.

References Cited in the file of this patent UNITED STATES PATENTS 1,953,491 Sainte-Martine Apr. 3, 1934 1,981,530 Thomas Nov. 20, 1934 2,377,363 Noble et al June 5, 1945 2,483,450 Wolfner II Oct. 4, 1949 2,490,634 Keene Dec. 6, 1949 2,498,232 Andrews Feb. 11, 1950 2,576,253 Farrell et a1. Nov. 27, 1951 2,621,673 Hodgens Jr. Dec. 16, 1952

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