US2490634A

US2490634A - Apparatus for controlling the concentration of solutions which tend to foam

Info

Publication number: US2490634A
Application number: US653675A
Authority: US
Inventors: Paul A Keene
Original assignee: Allied Chemical and Dye Corp
Current assignee: Allied Corp
Priority date: 1946-03-11
Filing date: 1946-03-11
Publication date: 1949-12-06
Anticipated expiration: 1966-12-06

Description

6; 1949 P A. KEENE 2,490,634

APPARATUS FOR COliTROLLING THE CONCENTRATION OF SOLUTIONS WHICH TEND T0 FOAM Filed March 11, 1946 "1Cyl.

INVENTOR Paul/"141190120 BY Q 14/ ATTORNEY 4 Patented Dec. 6, 1949 APPARATUS FOR CONTROLLING THE GON- CENTRATION F SOLUTIONS WHICH TEND TO FOAM Paul A. Keene, Syracuse, N. Y., assignor to Allied Chemical & Dye Corporation, a corporation of New York Application March ll, 1946, Serial No. 653,675

a Claims.

This invention relates to control apparatus for controlling the concentration of solutions which tend to form foam or suds; for example, alkaline solutions containing organic detergents. In the specifications hereinafter, and claims, the term "foam" is used in a broad sense and is intended to include suds.

In dish washing machines, for example, it is common practice to spray a detergent solution from a body thereof on the dishes, after which the dishes are rinsed by spraying them with hot rinse water. The rinse water usually collects in the body of wash solution where it causes some dilution, with consequent change in the concentratlon of this solution. A portion of the wash solution from the body thereof flows through an overflow pipe during operation, thus maintaining the level of the body of solution substantially constant. As successive racks of dishes are washed, the washing and rinsing cyces are repeated. During the course of the washing, detergent should be added to the wash solution to maintain, as nearly as practicable, a uniform concentration of detergent therein, i. e. to replace the detergent which is wasted in the overflow, and also that which reacts in each cycle to effect removal of dirt and other constitutents washed from the dishes. For best results, the concentration of detergent in the wash solution should be maintained within fairly narrow limits. Concentrations below the predetermined limit produce ineflicient washing and concentrations above this limit result in unnecessarily large losses of detergent.

It has been proposed to control the concentration of such washing solutions within relatively narrow limits by means of a controller involving an electrode disposed in the solution and responsive to changes in concentration, which electrode controls the feed of detergent solution to the wash solution.

When such controllers are employed in washing machines employing detergent solutions, such as are commonly used, which solutions in use tend to foam, certain difiiculties are encountered. For example, when the foam contacts the control electrode, due to the fact that the foam has a very much higher resistance than the solution from which it arose, the electrode registers the resistance of the foam, and causes the controller to remain in the operating position, so that detergent continues to be fed even though the concentration of the solution is above the desired predetermined value. This continuance of feed of detergent solution results in the production ill of, more foam and may eventually lead to the solution overflowing the washer.

Among the objects of this invention is to protailed description thereof.

In the preferred embodiment illustrated on the drawing, the invention is shown incorporated in a dish washing machine and the present description will be confined to the present illustrated embodiment of the invention. It will be understood, however, that the novel features and improvements are susceptible to other applications such, for example, as can washing machines or other machines in which it is desired to maintain within narrow limits the concentration of a solution which tends to foam in use. Hence, the scope of this invention is not confined to the embodiment herein described. The invention is broadly applicable to the control of concentrations of any solute in-a solution the conductivity of which varies with the concentration of the solute; for example, aqueous solutions of electrolytes.

In the accompanying drawings,

Fig. 1 is a diagrammatic vertical sectional view partially in elevation illustrating a dish washing machine embodying this invention;

Fig. 2 is a wiring diagram showing a bridge type of electrical control embodying this invention; and

Fig. 3 a fragmentary vertical section on an enlarged scale, as compared with Fig; 1, showing one form of detergent dispenser which may be associated with the washing machine.

Referring to Fig. 1, the dish washing machine comprises a housing ill in which racks of dishes ii are placed on perforated supports [2. Top and bottom wash sprays I3, I! are arranged to be supplied with wash solution under pressure through branch pipes l5, I6 from a motor driven pump l'l, the suction intake I8 of which is in communication with a body of detergent solution l9 disposed in a tank 20 positioned near the-bottom of the washing machine. Hot rinse water is supplied from a pipe 2| having branches 22,

3 23 extending to the top and

bottom rinse sprays

24, 25. It will be understood that the washer shown in the drawing represents one well-known type of washer and the present invention may be applied not only to this washer but to other s also.

I esirably the detergent solution may be a caustic soda, soda ash, modified soda or other alkaline solution, containing an organic detergent such, for example, as that sold under the trade-mark Nacconol, (salts of alkyl benzene sulfonates, the alkyl group of which has an average carbon content of from 12 to 18 carbon atoms), or that sold under the trade-mark Nytron," (organic nitrosation-sulfitation products disclosed in United States Patent No. 2,265,993 granted December 16, 1941) or other solutions, the conductivities of which vary with the concentrations of the solute, solutions with higher concen trations having higher conductivities.

In the operation of the dish washing machine, the dishes H are washed by operating pump IT for a predetermined period of time, and then this pump is stopped and the dishes are rinsed by supplying relatively hot rinse water from the

sprays

24, 25. Each rack of rinsed dishes, after rinsing, is removed and replaced by another rack of dishes to be washed, and the cycle of operation repeated. Rinse water from each cycle of operation dilutes the body of solution l9 and causes some of the latter to flow through the overflow pipe 26, the top of which is disposed at such elevation within tank 20 as to maintain the solution therein at the desired level. Thus the concentration of detergent in the body of solution i9 is progressively reduced by the reaction of the detergent with food and other material on the dishes, by the dilution of the solution with the rinse water,

and due to the overflow through pipe 26.

Detergent solution is supplied to the washing machine from a dispenser 21 mounted on a bracket support 28 fastened to the side of the washer. The dispenser 21 is desirably in the form of a cylindrical container 29 having a base 33, a discharge outlet 33 leading from the dispenser into a discharge conduit 34, which in turn leads into the washer, a downwardly sloping plate 3| disposed just above the base 30 and extending completely across the container 29, and a concavo convex vertically extending member 32 having its ends welded or otherwise fastened to the inner walls of the container 29, and extending from near the top of container 29 to the plate 3 I. Thus, there is produced a channel 35, semi-circular in crosssection, extending vertically along the inner wall of container 29, and occupying a minor portion of the volume thereof, and a compartment 36 occupying a major portion of the volume of container 23, which compartment receives solid detergent to be dispensed. The concavo convex portion of member 32 defining a sidewall of compartment 36, as shown in Fig. 3, is perforated to place the compartment 38 in. communication with channel 35; for. example, the intermediate portion of member 32 maybe a screen desirably-of 30-mesh. A perforated distributor plate 31 is disposed across the top of compartment 36. A. cover 38 may be provided for the container 29 to prevent steam and vapor escaping when the cover reservoir 40 is also provided with a valve opening or seat 42, flow through which is controlled by valve plug 43. Opening 42 communicates with a spout 44, the discharge outlet of which ls'disposed above distributor plate 31. Water, preferably hot water at a temperature of F., is supplied to reservoir 40 through water inlet line 45 which may be a branch line from the main rinse line 2|. Valve plug 43 is fastened to one end of valve stem 46, the other end of which is secured by a valve hinge pin 41 to the armature 45'. Stem 45 passes through a flexible sleeve 43' which is fastened to the base wall of housing 38 and is secured to stem 46, thereby preventing moisture from entering the solenoid housing 33.

On activation, the solenoid armature 48' is raised, pulling the valve plug 43 from its seat against the action of a spring 49. Water already present in reservoir 40, along with fresh water from line 45, passes through opening 42 to the spout 44, and thence to distributor plate 31 where it passes over or through the detergent in the compartment 35. The resulting concentrated detergent solution flows through channel 35, discharge outlet 33 and conduit 34 into the washer, where it mixes with the body of wash solution l3. As the quantity of water required to dispense the required amount of detergent is small, of the order of 8 to 10 gallons per hour, the dilution of the wash solution is by the minor portion of this water flowing through overflow pipe 4| and channel 35 and not passing through the solid detergent-is negligible.

The controller, as shown in Fig. 2, involves a control circuit 50 and a main circuit 5|. The latter is energized from an alternating current source which is connected to the input terminals of the primary 52 of a multi-coil transformer 53. Disposed in the main circuit 5| is the operating solenoid 48, a switch 54 which is normally open but which is adapted to be closed, as hereinafter described, by the control circuit to cause current to flow through the main circuit to energize solenoid 48, and a signal lamp 55 shunted across the solenoid 48 and showing when current is flowing in the main circuit, and the dispenser is, therefore, operative to dispense detergent solution to the washer.

The control circuit comprises variable resistors 56, 51 in a Wheatstone bridge arrangement, to one arm 58 of which are connected

conductors

59, 60, leading to a control electrode 5|. This electrode may be of any well-known type for measuring conductivities of solutions, and desirably consists of a pair of closely spaced platlnized rods in a common casing. It is disposed in the washer within the body of solution i9 as shown in Fig. 1. In parallel with the control electrode St is an auxiliary electrode 62. This electrode desirably may consist of two metallic plates 63, 54, say each approximately 2" long and 2 wide and closely spaced, sa one-half inch apart, so that the electrode has a lower resistance when foam fills the space between the plates than the resistance of electrode 6| when submerged in a solution of the desired concentration. The presence of foam between plates 63, 64 in effect short circuits the control electrode 6|, i. e. materially decreases the resistance in the arm 58 of the Wheatstone bridge. As shown in Fig. l, electrode 62 is located at a point above the normal level of body of solution I!) where the foam will reach it quickly. Consequently, in operation the dispensing of detergent solution will be stopped when foam reaches the electrode 62, which will edea take place before enough detergent is added to cause the solution to overflow the machine. As soon as the foam dies down due, for example, to the presence of soil in the wash water, the electrode 62 is left free and clear, becoming an infinite resistance, and consequently exerting no further effect on the control electrode ll.

Secondary coils 85, 88 of transformer 43 are connected by conductors with points 48,." of the Wheatstone bridge. Secondary coil 88 supplies current to the

filaments

69, 10 of electronic tubes ll, I2. Tube 1| desirably is a conventional triode or pliotron, and tube I2 desirably is of a type to produce a higher emission of electrons, such into the washer where is collects in tank 20.

As the concentration of the solution in tank 20 increases, the resistance across the electrode as the well-known thyratron. Tube II, as con ventlonal, comprises a cathode 12, a grid I3 and an anode 14. The tube 12 comprises a cathode II, a grid 16, a screen electrode I1 and an anode I8.

Secondary coil 19 of the transformer 53 is in circuit with points 80, 8| of the Wheatstone bridge. Located in this circuit is the grid circuit of the tube H as shown in Fig. 2. The output anode circuit of the tube Ii includes a resistor 14 across which the input circuit of the tube 12 is shunted. In the output anode circuit of tube 12 is disposed relay 82 for operating switch 54 in the main circuit 5|. Resistor I4 is such that when the current flowing through the output anode circuit of tube H reaches a certain value, the potential drop across the resistor 14' causes the tube I2 to pass sufllcient current through its anode circuit to operate the relay 82, to close switch 54.

The control circuit hereinabove described, except for the electrodes GI, 62 and the lead wires connected thereto, and the parts of the main circuit except for the solenoid 48 and signal lamp 45, are all preferably disposed in a control box 83 which may be positioned on support 28 next to dispenser 21. The control is, therefore, readily applicable to existing washers not equipped with controls, particularly in cases where it is desired to supply such washers with dispense rs of the type hereindescribed. When modifying a washer to embody this invention, it is only necessary to install the dispenser and control box on the side of the washer, connect the discharge of the dispenser with the washer, and place the electrodes GI, 64 within the washer in the relative 50 positions shown.

In operation, resistance 51 is set at a point previously determined by calibration, which point is dependent upon the desired concentration of 8! decreases, and a gradual decrease in the instantaneous voltages between the grid I3 and cathode 12' of tube ll occurs, which causes an increase in the current flowing through resistor 14'. The resultant increase in voltage appearing across the control grid 18 and cathode I5 of tube 12 finally reaches a point where the control grid 16 resumescontrol and extinguishes the tube, stopping the current flow through the relay 82, deenergizing it, and opening the switch 54, whereupon, under the influence of spring 49, valve stem 48 returns valve plug 43 to its seat 42. Water thereafter supplied through line 45 flows from reservoir 40 through overflow pipe 4| into and through passage 35 and not to the body of detergent maintained in compartment 36 of the dispenser 21.

When foam is produced,'as is frequently the case when employing a solution containing an organic detergent, and the foam rises to a point such that it enters between'the plates 63, 64 of the auxiliary electrode 62, the resistance in the arm 58 of the Wheatstone bridge is thereby reduced so that, as hereinabove described, valve plug 43 is seated in seat 42 and the water flows through channel 35 and not through the body of detergent. Hence, as long as foam is present at a level such that it contacts the auxiliary elec-' trode 62, no detergent is fed to the washer. When the foam dies down, the auxiliary electrode 62 is left free and clear, exerting no further effect on the control electrode 8| and permitting this electrode to maintain the concentration of the deter- 18121125111 the washer within the desired narrow Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be inthe detergent used. Resistance 56 is likewise set reted at a point previously determined by calibration, p as illustrative and not In a limiting which point is dependent upon the temperature of the body of wash solution it. Since the grid I3 and plate 14 of tube Ii are approximately 180 out of phase, an increase in the resistance of the solution, due to a decrease in concentration, causes a gradual increase in the instantaneous voltages between the grid 18 and cathode i2 00 which tends to foam, which which in turn causes a decrease in the current flow through the resistor 74'. The control voltage developed across resistor M', applied across the control grid 16 and cathode of tube 12, is sufllcient to prevent tube 12 from firing before the concentration of the solution starts to decrease. When the decrease in voltage drop across resistor 14', resulting from the increase in resistance across the electrode 5!, reaches a critical value, depending upon the tube employed, the control grid 16 loses control andthe tube 12 fires which causes current to flow through the 76 sense.

What is claimed is:

l. A control for maintaining within narrow limits the concentration of a body of solution comprises in combination, a control electrode responsive to changes in concentration in said body of solution, a control circuit in which said electrode is disposed, said control circuit effecting feed of material to said body of solution responsive to changes in concentration to maintain said concentration within said narrow limits and an auxiliary electrode in said control circuit and disposed above the normal level of said body of solution, said auxiliary electrode being adapted to be contacted by foam rising above the normal level of said body of solution, and while thus contacted rendering the control circuit inoperative and preventing the feed of further material to said body of solution.

2. A control for maintaining within narrow limits the concentration of a body of solution which tends to foam, which comprises in com-.

bination, a control electrode responsive to changes in concentration in said body of solution, a control circuit in which said electrode is disposed, said control circuit efiecting feed of material to said solution responsive to changes in concentration to maintain said concentration within said narrow limits, and an auxiliary electrode disposed above the normal level of said body of solution and arranged to be contacted by foam produced in said body of solution, said auxiliary electrode being connected in parallel with the control electrode and when contacted by said foam rendering the control electrode inoperative.

3. A control for maintaining within narrow limits the concentration of a body of alkaline solution which tends to foam, which comprises in combination, a dispenser for feeding alkaline solution to said body of solution, a control electrode disposed in said body of solution, means operated by said electrode for causing said dispenser to feed alkaline solution to said body of solution when the concentration thereof falls below a predetermined value, means for interrupting the feed of said alkaline solution to said body of solution when the concentration thereof is restored to said predetermined value, an auxiliary electrode disposed above the normal level of said body of solution and arranged to be contacted by foam produced in said body of solution, said auxiliary electrode being connected in parallel with the control electrode, and when contacted by said foam functioning to short circuit said control electrode to render it inoperative and prevent feed of further solution to said body of solution.

4. A control for maintaining within narrow limits the concentration of a body of solution which tends to foam, which comprises in combination, a Wheatstone bridge, a control electrode responsive to changes in concentration of said solution connected to one arm of said bridge, an auxiliary electrode connected in parallel in the circuit containing said control electrode, said auxiliary electrode being arranged above the normal level of said body of solution and, when contacted by foam, decreasing the resistance in said arm of said Wheatstone bridge, a control circuit in which said bridge is located, a relay operated by said control circuit, a main circuit, a switch in said main circuit operated by said relay, and means operated by said main circuit for dispensing detergent to said body of solution to maintain the concentration thereof within said narrow limits.

5. A control for controlling the concentration of a body of detergent solution which tends to foam, in combination, a dispenser for dispensing detergent solution to said body of solution, a control electrode disposed within said body of solution, an auxiliary electrode disposed above the normal level of said body of solution, a Wheatstone bridge, said control electrode and said auxiliary electrode being connected in parallel in a circuit connected with one arm of said bridge, a control circuit in which said Wheatstone bridge is disposed, a relay operated by said control circuit, a main circuit, a switch in said main circuit operated by said relay and a solenoid in said-main circuit for efiecting operation of said dispenser responsive to changes in concentration of said body of solution as indicated by said control electrode.

PAUL A. KEENE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,231,211 Halsey et a1. Feb. 11, 1941 2,370,609 Wilson et al Feb. 27, 1945