US2626620A

US2626620A - Regulator responsive to the electrical conductivity of a solution

Info

Publication number: US2626620A
Authority: US
Inventors: Smith Albert Woodall
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-08-30
Filing date: 1948-08-30
Publication date: 1953-01-27
Anticipated expiration: 1970-01-27

Description

Jan. 27, 1953 A. w. SMITH 2,626,620

REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUCTIVITY OF A SOLUTION Filed Aug. 30, 1948 4 Sheets-Sheet l z IN VEN TOR.

'daa; 60M 620% f @165;

AYTORNEYfi Jan. 27, 1953 A. w. SMITH 2,626,620

REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUCTIVITY OF A SOLUTION Filed Aug. 30, 1948 4 Sheets-Sheet 2 INVENTOR.

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Jan. 27, 1953 w. sMlTH 2,626.620

REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUCTIVITY OF A SOLUTION Filed Aug. 50, 1948 4 Sheets-Sheet 3 INVENTOR.

@PMQE Jall- 1953 A. w. SMITH 2,626.620

. REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUQTIVITY OF A SOLUTION Filed Aug. 50, 1948 4 Sheets-Sheet 4 7/8 fiE J I INVENTOR.

Mag-s.

Patented Jan. 27, 1953 REGULATOR RESPONSIVE TO THE ELEC- TRICAL CONDUCTIVITY OF A SOLUTION Albert Woodall Smith, Kenmore, N. Y. Application August 30, 1948, Serial No. 46,864

18 Claims.

This invention relates to a regulator responsive to the electrical conductivity of a solution and is more particularly described in conjunction with a detergent feeder wherein the concentration of a detergent solution being used is maintained by additions of the detergent under automatic control of a regulator responsive to the electrical conductivity of the solution.

In the type of milk or cream can washing machine used in a dairy it is common practice to pump a wash solution from a sump tank and deliver it under pressure through'spray jets to the inside and outside walls of a passing line of cans.

The wash solution usually contains a suitable detergent and is held between a minimum of 140 F. and a maximum of 150 F. generally by a thermostatic control set at some selected point within this range. It was found that detergents of a caustic nature such as sodium hydroxide would damage the tin coating on the cans and use of this as a detergent was discontinued in favor of milder alkalies such as sodium carbonate, trisodium phosphate, sodium metasilicate, sodium sesquisilicate or, a combination of these. Detergent powders ai'e' now commercially supplied to dairies and which in addition to the above milder alkalies contain a higher polyphosphate and a wetting agent or synthetic detergent for conditioning the water, preventing preciptation of water hardening ingredients, and enhancing the detergency of the wash solution. With such alkalinedetergent solutions as used in washing milk cans and the like, it is important that the strength of the detergent solu tion be maintained within relatively close limits. For example, the New York City Board of Health requires an alkaline detergent can wash solution to be held between 0.05% and 0.10% active alkalinity as sodium hydroxide to phenolphthalein.

In recent years an acid detergent has been used as an alternative to an alkali detergent. such acid detergents comprise an organic acid and a wetting agent or synthetic detergent. Such acid detergents have been found to give best results at a pH of from 6.7 to 6.8, the latter being, of course, quite close to the neutral point.

The present practice in bottle soakers is to use a wash solution around 2 of sodium hydroxide with trisodium phosphate to improve the rinsing properties of the solution, as sodium hydroxide is diflicult to wash ofi the walls of the bottles, and it is usual also to apply a wetting agent and synthetic detergent. It is importarit that the strength of the detergent solution be maintained within relatively close limitsi for washing milk cans and the like and also for washing milk bottles, and while the particular construction set forth in the accompanying drawings and description is suited more especially for use with machines for washing milk cans and the like, it is understood that the construction shown in the drawings may, with slight modifications and within a coverage of the here-- inafter claims, he used for maintaining the required detergent strength in machines for washing milk bottles and the like.

As a solution becomes more acid or more alkaline its specific conductance increases, and consequently an electric current passing between two electrodes placed in such asolution will vary in the same manner and can be used to control valves or equivalent feed devices to feed a concentrated detergent when the detergentjn the wash solution falls below a predetermined con-- centration and to stop the feed of such concentrated detergent when the strength of the wash;

solution has been restored to the desired level.

In precision instruments for measuring conductance, in order to avoid polarization of the electrodes, alternating current up to 1000 or more cycles per second can be employed, and in the present application cycles per second is preferred, the weak current passing through the to have been difficulties, such as fouling of the electrodes, which have prevented the practical use of such devices in dairies for controlling the alkalinity or acidity of wash solutions close enough to meet the above requirements of the New York City Board of Health. Thus, where a conductance cell has been employed it has been submerged in the solution tank and much trouble has been experienced due to depositsforming on the surfaces of the electrodes which were usually left in the tank until long after they ceased to perform their function correctly.

Moreover, the alkalinity or acidity of the solution is not the only factor which determines its electrical conductivity. cream can washing proceeds the washing solution picks up neutral or foreign salts, notablysodium lactate and sodiun acetate which progres'-- sively increase the electrical conductivity of the washing solution and hence act in the same man-t ner as if increases in the alkaline detergent hadv Thus, as the milk or.

been made. The present invention therefore also provides an approximately accurate compensation for these neutral or foreign salt additions so that a true detergent concentration is maintained at all times.

It is accordingly one of the principal objects of the invention to provide a sensitive control responsive to the electrical conductivity of a washing solution for overcoming the above disadvantages and for maintaining the conductivity of the wash solution within close limits, the control including an electronic circuit under control of a conductance cell and in" turn progressively incrementing additions ofconcen-- trated detergent for maintaining the active detergent strength of the washing solution within the required limits.

Another object is to provide such a control in which the electrodes are not subject to being- 20 invention" providing a moving stream. ofstrained; wash: solution pastthe electrodes and which areafouled by deposits forming thereon, the present readily removable. The electrodes have been found to function. properly for. very long periods with-1' alternating current ofnot less. than 69 cycles per second provided the electrodes are exposed to a moving stream of wash solution from whichparticles'i'n suspension have been previously strainediout and further provided they are. at alltimes preventedfrom drying bysubmersion-in a. vessel: of: clean. water: when: not inuse.

Another obiect 'is-ta provide such-:a control: in

which thezelectrodes can be readily removed from: the apparatus 'for the above mentioned purpose: and in which the strainer can also be readily removed for. removing: the particles in suspension.-

Another aim isto provide such a control'in which theoperator is constantly apprised of thecondition: ofoperationgof the control and also is warned and the washer rendered inoperativeunless the detergent solution is up to the required minimum limit of concentration.

Another object is to provide such a control which is free from critical attenton and supervision and which is automatically out into and outof service when the can washer is placed in use and shut down.

Another object is to provide such a control in which any failure, as the burning out of a thermionic tube, relay or transformer. will give awarningsignal and/or-shut down the washer.

Another aim is to provide such a controlwhich can'readily be set to suit any-of the-various de-v tergents-on the market and maintain thedesiredconcentration but which is free from other; adjustments-so that the apparatus can be readily serviced.

Another object isto provide such a control which is simplegandrugged inv construction and reliable in: operation so-that it will stand up un derrconditionsaof severe and. constant use without. requiringre-adjustment or repairs.

Another-object istoprovide a simple and effective-device for-compensating for the addition of salts other thanthe detergent, the addition of'such foreign salts taking place incident to the washingioperation.

Other: objects and advantages of the invention willlbe apparent fromthe following; description and drawings inwhich:

Fig; 1 is-adiagrammatic side elevational representationof a regulator responsive to the electrical conductivity of the wash solution of a milk can washer or the like and feeding a concentrated detergent solution to the wash solution to maintain its detergent strength within close limits.

Fig. 2 is an enlarged vertical section partly in elevation, of the conductance cell and its housing and forming part of the control shown in Fig. 1, this section being taken on line 2-2, Fig. 1.

Fig. 3 is a vertical transverse section through the compensator shown in Fig. 1.

Fig. 4 is a vertical fore and aft section through the;. compensator shown in Figs. 1 and 3, this sectiombeing taken generally on line 4-4, Fig, 3.

Fig; 5* is awiring diagram showing the electricalconnections. between the various components of the control andthe stop button circuit of the drive motorand how electrical energy is provided when the pump motor is switched: on.

The. regulator; forming; the. subject. of; the. present". invention. is. designed. to be: used. in. con:

from: the. sump or. tank :at-the. bottom-.of the washer through the usual. pressure'sprays and.

also supplies-a stream: of. thewashing solution for control purposes, andthe; washer. is' shown as having a stop button 8 for the drive motor (not-shown) which drive: motor-'activatesrthe movable parts of the-washer...

A part; of the spray water-orwashing" solution circulated; byrthepump motor: 5: is .admitedunder; pump. pressurezto; an. inlet pipe.- lflr'of' the.

housing a of; a; conductance cell; indicatedxgenorally at. H, this conductance cellzand: inletpipe. being carrisi-by. a. supporting plate. 12. through; which; the. inlet. pipe: l0; extends and to which it is. secured by-apair or 1111125113 onthe pipe I0 engaging oppositesides .of: the supporting plate l2-.. The inlet pipe lfl-is-shown as having acheck valve M which prevents reverse flow of the washing solution.

The'conductance cell housing 9 isshown-as including a vertical cylindrical-body [5 having an upper end head 16. brazed or; secured thereon in any. suitable manner and having a bottom or. lower'end head. It detachably securedto. itslower, endand; capable. ofready removal to. permit re-. moval. of; a. strainer screenztherein. Flor-this.- purpose the lower. endhead or bottom It is. PRO-5 vided onits upper; face. withaan. annular groove housing an annular'gasket 19 against which the lower: extremity-of the cylindrical body I5 seats and the lower end head or bottom. I8 is provided with opposite, radially extending bifurcated ears 20 adapted toreceivethe threaded'ends of swing bolts-.2] which are-hung-upon pins 22 carried by the cylindrical body I5 and carry wing nuts 23 which tighten against the undersides of the ears extension 25 of the upper end head l6 enterin the upper end of this cylindrical screen and by a cylindrical extension 26 rising from the lower head or bottom l8. The upper end head I9 is provided with a coaxial through bore 28 leading to the space within the cylindrical screen 24 and in this bore is slidably and removably fitted a cylindrical shell 29 of dielectric material, the lower open end of which is spaced from the bottom or lower end head |B of the body and the upper end of which extends through the upper end head Hi and has a cylindrical dielectric plug 39 fitted therein. The periphery of the cylindrical plug 39 is provided with one or more axial grooves 3| which establish communication between the chamber within the dielectric shell 29 and a chamber provided by a cylindrical body 32 brazed or otherwise secured to and extending coaxially upwardly from the upper end of the housing 9 for the conductance cell.

This cylindrical body 32 is provided with an upper readily removable end head 33, a gasket 34 being interposed between this cylindrical body and upper end head and this upper end head being removably clamped down by a pair of swing bolts 35 carried by pins 36 secured to the cylindrical body 32 and having their threaded ends arranged to enter bifurcated cars 38 projecting radially from the upper end head 33, these swing bolts being provided with wing nuts 39 adapted to bear downwardly on the bifurcated ears 38.

The upper part of the axially channeled plug 30 is of tapered form, as indicated at 40, and is fitted into a plug 4| which is in turn screwed into the upper end head 33. The axially channeled plug 30 is also provided above its tapering part 49, with a flexible two-wire cable 42 housing two

wires

43 and 44. To provide a watertight seal between the plug 4| and the tapered part 40 of the plug 30, the upper part of the plug 4| is shown as provided with a conical recess containing a conical follower 47 of soft, resilient, plastic material, this follower being expansively forced into its conical recess by a screw cap on the plug 4| or in any other suitable manner.

One of the wires 43 connects with an electrode or probe 45 extending downwardly from the axially channeled plug 39 and exposed to the stream of wash solution flowing upwardly through the dielectric sleeve 29 and the other of these wires connects with an electrode or probe 46 extending downwardly through a dielectric sheath 48 from the plug 36 and also having its lower end exposed to the stream of wash solution flowing upwardly through the dielectric sleeve 29. It will be seen that the conductance cell assembly comprising the

electrodes

45, 46, axially channeled plug 39, dielectric sleeve 29, flexible cable 42, plug 4| and upper end head 33 can be readily removed by the simple expedient of loosening the wing nuts 39 and swinging the swing bolts 35 outwardy. This permits the conductance cell unit, including its

electrodes

45 and 46 to be removed between washing periods and kept in clean water to prevent fouling of the same.

end 50 of a drain pipe 5|, the horizontal run of which extends through the supporting plate I 2 and is fastened thereto by a pair of nuts 52 embracing opposite sides of this supporting plate. The drain pipe 5| can drain back into the milk can washer in any suitable manner.

An outlet pipe 55 connects with the side of the upper cylindrical body 32 and extends downwardy into a solution feeder or generating tank 56, this pipe 55 terminating in a horizontal run 58 extending along the bottom of the solution feeder tank. The outlet pipe 55 is shown as having a hand valve 59 but essentially is provided with a normally closed solenoid valve 60, the leads to which are indicated at 6| and 62. The outlet pipe 55 extends through the supporting plate l2 and'is fastened thereto by a pair of nuts 63 tightening against opposite sides of the supporting plate. A green light 64 is arranged across the lines 6| and 62 of the solenoid valve 60 so as to be illuminated when this solenoid valve is operative.

The solution feed or generating tank 56 is shown as provided above the horizontal end 58 of the washing solution outlet pipe 55 with a horizontal foraminous partition 65 adapted to support a quantity of the detergent in solid form in the upper part of this tank. Above this bed of solid detergent the tank 56 is provided with an overflow 66 which can drain back into the milk can washer in any suitable manner. It will be seen that the depleted wash solution passing upwardly from'the pipe 58 through the bed of solid detergent supported on the foraminous partition 65 in the solution feed or generating tank 56 takes a portion of the solid detergent into solution and overflows at 66 back into the washing solution system of the can washer. The solid detergent in the tank 56 can be in the form of powder, lumps or briquets. The acid detergents used are in liquid form and for such acid detergents the form of the feeder is necessarily modified.

The electrode wire 43 from the electrode 45 connects directly with an electronic control circuit contained within a control casing 68 shown in Fig. 1. The electrode wire 44 connects with a compensator indicated generally at 69, this compensator being in turn connected through the Wire 19 with the electronic control circuit contained within the casing 68, Fig. 1. This compensator 69 is for the purpose of compensating for the neutral salts foreign to the detergent which are added to the solution as the can washing operation proceeds and will be later described in detail.

The electronic control circuit is essentially a balanced bridge responsive to changes in voltage drop across the wash solution between the elec trodes 45 and 46, an amplifier for the voltage changes of the bridge, and differential relays actuated by the amplifier output and in turn actuating the solenoid valve 60 to control the additions of concentrated detergent to the wash solution and also rendering the drive motorof the can washer inoperative so that the operator can only use the washer when the detergent is present in the wash solution in the minimum amount called for by the setting of the control. The control circuit also operates signals, such as light or sound signals, or both, to show the condition of operation of the control.

The input to the amplifier is a balanced bridge circuit comprising a variable resistor 10 adjusted by a calibrated knob and pointer II on the front face or panel of the casing 68 (Fig. 1) and having zonezendxconnect dit on ofthese ondarywindings 12 of a-transformer 13,-the primary windine ,14. of-which: isconnected across the load lines .15 and IS- of-the-threephase pump motort. This -transform er I3 supplies alternating current for the operation of thecontrol circuit, and hence it will be-seen that the-control circuit is only opera- .tive when the pump motor 6 is operative and that ion shut down of thispump motor-the control circuit is rendered completely inoperative, this insuring-that nopartof the-electronic or. control -circuit is left ener izedon shut down of the pump 'gmotor-fi.

,The cthertnd cftheisecondary winding I2 of -.the transformer1l3 is Qonnectedto the line 43 f ;the-.- electrode 45 r and :the other rounded nd ...the: calib ated variabl :resist r 10 connected lthroughga line 19 and compensator 69 with the lineMIof the other electrode, 46. Acenter tap of .th secondary ztransformerwind n 12 is nnected, by a wire 80 (with the control grid 8 I of a thermionic amplifier tube 82, this being shown .,as-being a pentode. It will therefore be seen that ;a bridge circuit is provided, two legs of which are provided by the two halves of the secondary winding-1270f the transformer T3, the third leg by ,,the variable resistor, and thefourth leg by the

electrodes

45,49. The power input to this bridge .isacross the secondary-winding l2'which forms v twoofits legs and the grid 8| of the amplifier ,tube is connected to the corner of the bridge between these legs, the opposite corner being grounded. Accordingly, any change in conductance of the leg containing the

electrodes

45, 46 upsets the balance of thebridge. and impresses a signalvoltageon the grid.8I of the amplifier tube 82.

Theplate 90 ofthis amplifier tube 82 is conv nectedtosa wire 9I which is connected through a resistor 95 with the control grid ,92 of a thermipnic vacuum tube 93for a relay 94 and directly, with the control grid- 96 of a thermionic-vacuum tube 98 for a relay 99. The plate circuit of the amplifier tube32 is completed through a resistor I00. connected with the grid end of the resistor 95 .and wire IOI connecting with the center tap of a secondary winding I02 of the transformer 13. A pair of resistors I03 and I94 are connected in series from this center tap wire to one end I09 ,of this secondary winding I02 of the transformer 73 and a wire I06 connects the midpoint of these {resistors I03, I04 to the grounded end of a variable .resistor I07. The movable contact I08 of this variable resistor I91 is connected by a wire I09 with the cathode I I0 of the amplifier tube 82 and also with its suppressor grid III, this variable resistor I01 thereby controlling the-grid bias of the amplifier tube 32. The screen grid II2 of the amplifier tube 82 is connected with the transformer-center tap wire IOI and a bypass condenser II3 is provided between the plate and .screen grid.

It will be seen that plate current of the ampli' fier tube 82 passes through the plate 90, wire SI, resistors 95 and I00, center tap wire IOI, lower ,half of the secondary transformer winding I02, ,resistor I04, wire I06, variable resistor I91 and wire I09 to the cathode H0. It will also be seen that a differential in potential impressed on the .control grids 92 and 9B of the

relay vacuum tubes

93 and 98, respectively, is obtained through the resistor 95.

The plate II5 of the relay tube 98 is connected by a .wire II6 with the winding II8 of its relay gg the otherl end' of;t hi s winding being connected .toawire I I9- leading to the end-of the secondary ,transformer winding I02 opposite its side I05.

mally closed solenoid valve 60 thereby to permit this .valve to-close and out off the fiow of wash solution'through the regenerating or feeder tank .56.

The plate I25 of the ;relay tube 93 is connected by awi e I26 withzthewinding I28 of its-relay 94, the other end of this winding being connected to the wire 'I I9 leading to the end of the second ary transformer winding I02 opposite its side I05.

This relay has two mechanically connected movablecontacts I29 and I30 insulated from each other, thecontact I29 being connected by a'wire I'3I with the load line I5 of the pump motor 6. The movablecontact I29 is normally closedor in engagement with the fixed contact I32 of a line I33 connecting with the load line 16 of the pump motor 6 and-containing a red warning light or signal I35 which can also be in the form of.an audible signal. 'Ihemovable contact I30-is normally open with-reference to its-fixed contact I36,-the. contacts being in circuit through wires I31 and I38- with the stop button 8 of the starter forithe drive motor (not shown), this drive motor actuating the mechanically moving parts of the washer. When the winding I28 of the relay'94 issufliciently energized the normally openmovable contact I30 is pulled up into enga ement with the fixed contact I36 tocomplete the stop .button'circuit 8 of the drive motor for the milk can washer and render it operative. At the same t me the movable contact'l29 is pulled away from its fixed contact I32 to de-energize the red warning light or signal I35. The reverse takes place when the conductivity of the wash solution falls tea-predetermined danger level, the coil I38 of the relay 94 being effectively tie-energized, the red warning signal I35 being energized and the can washer drive motor stopped by breaking the circuit through its starter 8.

As the washing of the cans proceeds, salts other than the detergent progressively build up in the washing solution. "These neutral or foreign salts, of course, increase the electrical conductivity of the washing solution-and-since the controlof-the detergent additions in the practice of the present invention is in response to the electrical conductivity of the washing solution, it is apparent that unless compensation is made for the building up of such foreign salts, inadequate additions of the detergent-would be made as the can or bottle washing proceeded, the control not distinguishing between the increased conductivity provided by the detergent additions and the increased conductivity provided by the gradual accumulation of foreign salts. To compensate for such gradual accumulation of foreign salts, the compensator I59 is provided across the solenoid valve 50 and which can be constructed as follows:

The numeral I45 represents a rectangularcas- -ing having a vertical back wall I45 and a removable front wall I48. Within this casing is suit- .ably secured a, vertical partition I49 arranged parallel with the front and-rear walls I46 and the

lines

44 and 19 for this purpose.

the moving parts of the compensator. A solenoid I50 is secured to the front face of this partition at one end thereof with its axially movable core II projecting toward the opposite end of the partition. This core I5I is normally retracted from the winding of the solenoid by a helical compression spring I52 anchored on a bracket I53 which can be adjustably secured to the front face of the partition I49 by screws I54; the axial movement of the core against the resistance of this spring I52 being effected by the energization of the solenoid. For this purpose one end of the winding of the solenoid I50 is connected with the load line 16 of the pump motor 6 and the other end of the winding of the solenoid I50 is connected by a line I55 with the other line 6| of this solenoid valve 60. It will therefore be seen that the solenoid I50 is connected in parallel across the solenoid valve 60 and that every time this solenoid valve 60 is actuated the solenoid I50 is energized.

Above themovable core I5I of the solenoid I50, a bushing I56 is mounted in the partition I49 to project axially forwardly therefrom, this bushing .being shown as having a reduced threaded neck extending through the partition I49 and secured by a lock nut -l58. In this bushing is journalled a shaft I59 which projects forwardly through an opening in the removable front wall I48 of the casing and is provided with a hand knob 160 by means of which the shaft I59 can be manually .tumed to zero, this hand knob being shown as having an arrow for this Purpose and which is adapted to be brought into register with a zero mark on the front wall I48 of the compensator casing. The rear end of this shaft I59 is con- .non-rotative relation to the partition I49 by a supporting pin I63 on which the rheostat casing is slidingly mounted and which is in turn fixed to the partition I49 by a screw I64. This rheostat is connected in one of the lines to the conductivity cel1 II, it being shown as connected to It functions progressively to cut resistance into the conductivity cell circuit to compensate for the increased conductivity occurring through the building up of neutral or foreign salts in the washing solution. A second rheostat I61 is shown (Fig. 5)

as connected in parallel with therheostat [SI for adjustment purposes.

A thrust washer I65 is arranged on the shaft I59 in advance of the bushing I56 and in advance of this thrust washer is arranged a bearing bushing I66 which is loose on the shaft I59 and which carries a ratchet wheel I68 which can also be loose thereon. On this bearing bushing I66 is also journalled the end of a depending arm I69, the free end of which is slotted as indicated at I and connected by a pin I1I to the core of the solenoid I50 so that the arm I69 is oscillated about the axis of the shaft I59 each time the solenoid I50 is energized.

As best shown in Fig. 3, this arm I69 has pivoted thereto a pawl I12, the tooth of which is urged into engagement with the teeth of the ratchet wheel I68 by a small spring I13 between the pawl and its arm I69. The teeth of this ratchet wheel are also engaged by a holding dog I14 pivoted on the partition I49 and having its tooth urged into engagement with the teeth of the ratchet wheel I68 by a small spring I between the holding dog and the partition I49. It will be seen that each time the solenoid I50 is energized to oscillate the arm I69 to the right, as viewed in Fig. 3, the pawl I12 is drawn along the teeth of the ratchet wheel I68 to engage a subsequent tooth thereof, retrograde movement of the ratchet wheel I88 being prevented by the holding dog I14. Each time the solenoid I50 is de-energized the spring I52 draws the solenoid core I5I and arm I69 to the left, as viewed in Fig. 3, thereby, through the pawl I12, to impart a partial clockwise rotation to the ratchet wheel I68. The ratchet wheel I68 is thereby advanced step-bystep as the solenoid I50 is energized and deenergized.

This step-by-step advance of the ratchet wheel I68 is transmitted to the rheostat I6I by a friction clutch which is shown as comprising a disk 518 on the shaft I59 in advance of the ratchet wheel I68 and as having its hub secured to this shaft by a set screw I19 or in any other suitable manner. A friction ring I of any suitable frictional material is shown as secured totherear face of this disk I18 by screws I8I and as engaging the forward face of the ratchet wheel I68. The frictional contact between this friction ring I80 and the ratchet wheel I68 is determined by a helical compression spring I83 surrounding the shaft I59 and interposed between the partition I49 and rheostat casing I62. It will be seen that this friction clutch permits the rheostat I 6 If to .be set to zero after each shutdown of thewashing machine. Thus the rheostat is advanced step-by-step by the solenoid I50 to cut resistance into the conductivity cell II circuit as the washing proceeds to compensate for neutral or'foreign salt additions. When the washer is shut down the operator turns the knob I60=and shaft I59 to reset the rheostat I6l to zero, this being permitted by the friction clutch engagement between the friction ring I80 and the ratchet wheel I68. I

Operation tion in its spray system has an activealk'alinity of 0.04%, this being below the range which-the control is set to maintain.

The operator places the spray jets of the washer in operation by starting the three-phase pump motor 6 (Fig. 5) through its starter 1. This, through the pump motor loadlines15 and 16 energizes the electronic control circuit and also pumps washing solution into the inlet pipe .I0 (Fig. 1) of the conductance cell housing II.

This washing solution from the inlet pipe I0 passes the check valve I4 into the lower cylindrical body I5 of the conductance cell housing. In this lower cylindrical body (Fi 2) this stream of washing solution passes through the-cylindrical screen 24 and through the lower open end of the dielectric sleeve 29 upwardly through this sleeve and past the exposed

electrodes

45 and 46, escaping through the axial grooves 3| in the dielectric plug 30 into the upper cylindrical body 32. From this upper cylindrical body this stream of washing solution spills from the nozzle 49 into the upstanding end 50 of the drain pipe 5| which returns the washing solution to the can or bottle washer.

Referring to Fig. 5, it will be-seen that the contacts of the relay 94 are normally in the position shown with its contact I29 closed and hence on so starting the pump motor 6 with a substandard detergent concentration, the red light I35 is illuminated, this red light being energized by cur rent supplied from the load line I5 of the pump motor 6, wire I 3|, closed contact I29 and fixed contact I32 of relay 94, wire I33 and red light I35 to the other load line I6 of the pump motor 6. This red light shows that the can washer is not yet in condition for full operation. It will also be seen that the relay 94 prevents the drive motor (not shown) from starting at this time. Thus, in this normal or effectively de-energized condition of this relay 94 its contacts I30 and I36 are open sothat the circuit through the stop button circuit 8 of the drive motor is open.

Referring again to Fig. 5, it will be seen that therelay 99 is normally closed and hence on so starting the pump motor 6 with a substandard detergent concentration, the normally closed solenoid valve 60 is opened, this normally closed solenoid valve being energized by current suppliedfrom the load line I5 of the pump motor, closed contact I20 of the effectively deenergized relay 99, fixed-contact I2I, wire 6|, solenoid valve 60 and wire 62 to the other load line I6 of the pump motor 6. At the same time the green light 64 in parallel with the solenoid valve 60 is illuminated to indicate that the solenoid valve 60- is open and operating.

With the solenoid valve 60 so open a part of the washing solution entering at the pipe I passes to the upper cylindrical body 32 (Fig. 2), escapes through the pipe 55 (Fig. 1) and past the open solenoid valve 60 and hand valve 59 into=the space inthe feeder tank 56 below its foraminous partition 65. This dilute solution flows upwardly through the bed of solid alkaline detergent, in briquet, granular or powder form, supported on the foraminous partition 65 and escapes through the overflow 66 and returns to the spray section of the can washer. In so flowing upwardly through the bed of solid alkaline detergent on the foraminous partition 65, the dilute washing solution dissolves a part of the solid detergent and hence is fortified or strengthened in its detergent component. This results, of course, in a steady increase in detergent strength and alkalinity of the washing solution beinglcirculated by the pump driven by the motor Gas just described.'

At the assumed start of operation, energization of the load lines I and 16 (Fig. 5) of the threephase pump motor 6 energizes the primary winding I4 of the transformer I3 and hence also energizes its secondary windings I2 and I02. This secondary winding 12 forms two legs of a bridge, the other two legs of which contain, respectively, the variable resistor I0 and the electrodes or probes 45 and 46. together with the compensator 69. The potential impressed upon the'bridge by the secondary winding I2 is thereby impressed across the variable resistor I0 and, through the WireIQ, rheostats ISI and I6! of the compensator 69 and wire 44 across the

electrodes

45 and 46 of the conductance cell II, the electrode 45 connecting with the winding I2. The variable resistor I0 has been assumed to have been set to maintain the desired operating point and as it is also assumed that the wash solution passing the

electrodes

45 and 46 is below strength, the bridge is unbalanced and hence a potential is impressed on the control grid '8I of'the amplifiertube'82-to' render this tube conductive.

Since the solfibi'd" valve 60 is open, concentrated detergent is being added to the washsolution and-its conductance is increasing, this tending to bring the bridge to the balance determined by the setting of the variable resistor I0. When the active alkalinity of the wash solution increases to 0.065%, 1. e. the setting of the variable resistor I0, the bridge is brought to balance and the potential on the control grid 8| of the amplifier tube 82 reduced to its cutoff point to render it nonconductive.

The plate potential for the amplifier tube 82 is supplied by the lower section of the secondary winding I 92 of the transformer I3, the plate current passing-from the plate through wire 9|, resistors and I89, wire IOI,' lower section of the secondary winding I02 and-resistors I04 and I03to wire I 06, bias resistor I0! and wire I09 to the cathode H0." The

relay tubes

93 and 98 have the same characteristics and since the control grid 92 of the relay tube 93 is connected through the resistor 95 withthe plate 90 of the amplifier tube 82 it is at a lower negative bias than the grid-96 of the relay tube 98 so that on rising values of plate current from the amplifier tube 82 the relay tube 98 becomes conductive before the relay tube 98. In practice, these

relay tubes

93 and 98 are conductive under all conditions of operation, their relays being selected to cutin and out at predetermined'platecurrent values.

The plate potential for the relay tubes 93-and 98- is supplied by the upper section of the secondary winding I02 of the transformer I3. When the relay tube 93 becomes eifctively operative its plate current passes through and effectively energizes the winding I28-of its relay 94. This opens its contacts I29 and I32and thereby extinguishes the red light I35 in circuit therewith, this informing the operator that'he can start the main motor '(not shown) of the washer. This condition is obtained through the-closing of the other two contacts I30; I36 ofthe relay 94 and which closes the circuit through the stop button circuit 8 ofthe drive motor starter.

The solenoid valve at this time is still open and hence detergent'is still being added to the wash solution. It is important that the alkalinity of the wash solution does-not exceed a predeterminedvalue, this being assumed to be 0.08% active-alkalinity. As the wash solution approaches this maximum active alkalinity value the plate current from the amplifier tube 82 also rises and when this value is reached, the potential impressed on the control grid 96 of the relay tube 98 is above the cut off point of this relay tube so that this relay tube is rendered effectively conductive. With this relay tube 98 effectively conductive its plate current flowing through the winding I I8 of its relay 99 elfectively energizes this relay. This pulls up its contact I28 so as to break the circuit through the normally closed solenoid valve 60 and green light 64 in parallel therewith. With the solenoid valve 60 closed the flow of wash solution'through' the feeder tank 56 is-cut 01f so that detergent additions to the washing solution are cut off.

As the washing of the cans or bottles proceeds the concentration of detergent in the washing solution diminishes both through the function of the detergent in cleaning the cans and also through a part of the washing solution clinging to the cans, make-up water being supplied. When the concentration of the washsolution drops to 0.065% active alkalinity, the increasing negative potential impressed on the control grid 8| of the amplifier tube 82 by the unbalancing of the bridge through the resistance provided by the washing solution passing the

electrodes

45 and 46 in one of its legs causes such decreased value of plate current from the amplifier tube 82 that the potential impressed on the control grid 95 of the relay tube 98 is reduced to a point where the plate current from this relay tube 98 is insufiicient to hold the relay 99 efiectively energized. The effective deenerglzation of this normally closed relay 99 causes its movable contact I20 to re-engage the fixed contact I2I and hence re-establish a circuit through the normally closed solenoid valve 60 and its green light 54. This opens the solenoid valve 60 so as to re-establish a flow of washing solution through the feeder tank 59 thereby to add to the detergent content of the washing solution'from the solid alkaline detergent contained in the feeder tank 59.

It will be seen that each time the active alkalinity of the wash solution reaches the assumed 0.08% the relay tube 98 and its relay 99 are rendered operative to de-energize the normally closed solenoid valve 60 and its green light '04 and cut ofi detergent addition to the wash water and that each time the active alkalinity of the washing solution drops to the assumed 0.065% the relay 99 is effectively deenergized to energize the normally closed solenoid valve 60 and its green light 64 and start the addition of detergent to the washing solution. Accordingly, the washing solution is maintained at an active alkalinity of from 0.065% to 0.08% by the successive opening and closing of the solenoid valve 60 in response to the changing conductivity of the wash solution.

' As the wash operation proceeds neutral or foreign salts form and accumulate in the washing solution. Where milk cans are being washed such neutral salts are principally in the form of sodium lactate and sodium acetate. The

electrodes

45, 46 are, of course, unable to distinguish between the increased conductivity provided by such neutral salts as compared with the alkaline detergent and hence, in the absence of compensation for the accumulation of such neutral salts the washing solution would progressively be fed less and less detergent and the detergent concentration would fall below the standards which the control is set to maintain.

In accordance with the present invention increments of resistance are progressively cut into series with the

electrodes

45, 46 so as to counterbalance the increased conductivity provided by the accumulation of neutral salts. In the practice of the present invention an increment of resistance is added in series with the electrodes each time the solenoid valve 60 operates so that the resistance added is in proportion to the use of the detergent. Thus (Fig. each time the solenoid valve 60 is energized, the solenoid I50 in parallel therewith is likewise energized. This solenoid I50 (Fig. 3) swings the lever I99 to the right, thereby drawing its pawl I12 along the teeth of the ratchet wheel I68, corresponding movement of this ratchet wheel being prevented by the holding dog I14. When the solenoid I50 is de-energized, its return spring I52 draws the core I5I and arm I69 to the left as viewed in Fig. 3, thereby to advance the ratchet wheel I58 one step. Therefore, each time the solenoid valve 00 and solenoid I50 are de-energized, the ratchet wheel I68 is advanced one step.

This ratchet wheel is connected through the frictionwhel I18 with the shaft I59 which is turn is connected with the movable contact of the.

rheostat I6I. The resistance of this rheostat is held stationary in its casing which in turn is prevented from rotating by its mounting on the pin I68 and the direction of movement of the movable contact is such as to add an increasing amount of resistance each time the ratchet wheel I68 is advanced one step. This rheostat IBI is in series with one of the leads from'the conductivity cell II and hence it will be seen that this resistance is added to the electrode circuit to compensate for the accumulation of neutral salts.

On shutdown, when the operator de-energizes the three-phase pump motor 6, he likewise deenergizes the entire electronic control circuit inasmuch as this electronic control circuit is across two of the load lines of this three-phase pump motor. It will therefore be seen that on shutdown of the washer there is no danger of leaving any part of the control circuit energized and no special switch is therefore required for the control circuit.

the operator restoresthe knob I00 (Fig. 1) to its zero position. Turning this knob, which is fast to the shaft I59, re-sets the rheostat I6I to the position in which it does not offer any resistance. I Such resetting of the knob does not affect the ratchet mechanism mounted on the shaft I59 because .of the presence of the friction clutch ring I between the friction wheel I18 fast to the shaft I59 (Fig. 4) and the ratchet wheel I58. The apparatus is now in the condition'assume'd at the start of the operation and ready for reuse as described.

From the foregoing it will be seen that the present invention provides a very simple and accurate control for maintainingthe detergent strength of a washing solution within close limits and which will stand up under conditions of severe and constant operation without getting out of order and requiring servicing. ,Fur-

ther, adequate compensation is made for the accumulation of neutral salts in the washing solution, particularly where cans are unusually dirty and the detergent is used up faster and the feeding periods are spaced at shorter intervals and more increments of resistance are added in a given time to compensate for the extra neutral salts being formed. It will also be seen that with the forced flow of a small screened stream of the washing solution through the conductivity cell II and with the form of this cell there is little danger of this cell fouling up and rendering the control inoperative. Further, the screen 24 can be readily removed for cleaning and the electrode assembly, including the removable head 33 and flexible cable 42, can likewise be readily removed so that the electrodes can be stored in clean water during shutdown periods of the washer.

By warning signal as used in the appended claims is meant to include the shutting down of the washer itself through the energization of this main drive motor, such automatic shutdown of the washer operating, of course, as a very pointed warning to the operator that conditions should be rectified.

I claim: 7

1. A regulator for restoring the specific electrical conductance of a solution maintained at a predetermined temperature, whenever a small reduction in conductivity occurs, which comprises a feeder arranged to add to said solution a concentrated'component thereof, 'means providing Also, on emptying wash tank.

assume an-electricalcurrent'in excess of a predetermined value and varying in response to changes :in conductivityof said solution, a'pair of parallelelectrical circuits energized by said electrical current slightly below said low value and inoperative when said conductivity is raised-to said low value, 'and means in circuit with'said switch opened 'in response to said high value of conductivity and arranged to render said feeder operative -when.

said-conductivity falls toa level slightly below said high "value and arranged to render said feeder inoperative when said conductivity is restored to said high value,--whereby the conductivity of said solution'is maintained substantially constant.

'2. A regulator for restoring the .specific electrical conductance -of-a solution'maintained at 'a predetermined temperature,- whenever a small reduction inconductivity-occursnvhichcomprises a "feeder arranged to add to "said solution a concentrated component thereon-means providing an'electrical current in-excess of a'predetermined value and varying in response-to changes in conductivity of said solution;a pairof-parallel electrical circuits energized by said electrical current varying means to respond to'the variations of said electrical current and one-actuatinga normally closed switch closed in response to a low value of conductivity of said solution-and the other actuating a switch opened in'response to a high value of conductivity of said solution, a warning signal in circuit with and rendered operative by the closing of said normally closed switch when said-conductivity falls slightly below said low value and inoperative when said conductivity is raised to said low -value, and means in circuit with said switch openedin response to a high value of conductivity and arranged to render said feeder operative when said conductivity falls to a level slightly below said high value and arranged to render said feeder inoperative when said conductivity is restored to said high value, whereby the conductivity of said solution is maintained substantially constant.

'3. A regulator for restoring the electrical conductivity of a solution maintained at a predetermined temperature, whenever alsmall reduction in conductivity occurs, which comprises-a feeder arranged to add to saidsolution :a con centrated component thereof, :a pair of electrodes immersed in said solution, means arranged to pass a current through said electrodes and through the solution therebetween, a pair of parallel electrical circuits energized in response to small changes in voltage dropin excess of a. predetermined value across the solution between said electrodes and one actuating-a firstrswitch rendered operative in response to a high level in said voltage drop and the other actuating :a second switch rendered operative in response to a low level of said voltage drop, a warning means, means in circuit with said first switch and arranged to render said feeder operative when said voltage .drops slightly -:below said :high .level and arranged to render :feeder inoperative when :said voltage is'restored to said high level whereby the conductivity of said solution is maintained substantially constant, and means'in circuit with said second switch and arranged to render said warning means operative when said voltage falls slightly below said low level and inoperative when said voltage is raised to low level.

4. A regulator for restoring the specific electrical conductance of a solution maintained at a predetermined temperature, whenever a small reduction inconductivity occurs, which comprises a feeder arranged to add to said solution a concentrated component thereof, a pair of parallel electrical circuits each including the cathode, grid and plate of a thermionic vacuum tube and the winding of a relay actuated in response to a predetermined level of the plate current thereof, means biasing said grids to provide different plate current levels in response to the same source :of grid potential, means providing an electrical current varying in voltage in excess of a predetermined .value in response to-changes inconductivity of said solution in excess of a predetermined valueand providing said source of grid potential, a warning means, means in circuit with the contactsof the relay having its winding in :the circuit maintained at a lower level of plate current, and arranged to render said feeder 0perative when the plate current in the circuit maintained at-alower level of plate current drops slightly below its said predetermined level and arranged-to-render said feeder inoperative when the plate current in the circuit maintained at a lower level of plate current is restored to its said predetermined ,level, and means in circuit .with the contacts of -,-the relay having its winding in circuit with-the-circuit maintained at a .higher level of plate current and arranged to render said warning means operative when the plate current in the circuit maintained at a higher level of plate current falls slightly below its said predetermined level and inoperative when the plate current in the circuit maintained at a higher level of plate current is raised to its said predeterminedlevel.

5. A regulator for restoring the specific electrical conductance of a solution maintained at a predetermined temperature, whenever a small reduction in conductivity occurs, which comprises a feeder arranged to add to said solution a concentrated component thereof, electrodes immersedin said solution, a pair of parallel electrical circuits each including the cathode, grid and plate of a thermionic vacuum tube and the winding of'a relay actuated in response to a predetermined-level of the plate current thereof, means biasing said grids to provide different plate-current levels inresponse to the same source of grid potential, an amplifier including a thermionic vacuum tube in circuit with said electrodes and responsive to small changes in voltage drop in-excess of a predetermined value across the solution therebetween and providing said source of gridpotential, a warning means, means in circuit-with the contacts of the relay having its winding in the circuit maintained at a lower level of plate current, and arranged to render said feeder operative when the plate current in the circuit maintained at a lower level of plate current drops slightly below its said predetermined level and arranged to render said feeder inoperative when the plate current in the circuit maintained at a lower level of plate current :is restored to its said predetermined level, and means in with the contacts of the :relay having its winding in circuit with the circuit maintainedat ahigher level of plate current and arranged to render said warning means operative when the plate current in the circuit maintained at a higher level of plate current falls slightly below its said predetermined level and inoperative when the plate current in the circuit maintained at a higher level of plate current is raised to its said predetermined level.

6. A regulator for maintaining the detergent strength of the washing solution in a washer having a warning means, which comprises means passing an electric current through the washing solution, an amplifier for said current, a resistor in the output line of said amplifier, a first control grid of a first thermionic relay tube connected with said output line between said amplifier and said resistor, a second control grid of a second thermionic relay tube connected with said output line on the side of said resistor remote from said amplifier, a first relay energized by the plate current controlled by said second control grid and arranged, when energized, to deactivate said warning'means, a detergent feeder adapted to feed a concentrated detergent to said washing solution, a second relay energized 'by the plate current controlled by said first control grid, and means in circuit with said second relay for rendering said detergent feeder operative when said second relay is deenergized and inoperative when said relay is energized.

7. A regulator for maintaining the alkaline detergent strength of the washing solution in a washer having a drive motor magnetic starter with a. stop button circuit,- which regulator comprises means passing an electric current through the washing solution, an amplifier for said current, a resistor in the output line of said amphfier, a first control grid of a thermionic relay tube connected with said output line between said amplifier and said resistor, a second control grid of a thermionic relay tube connected with said output line on the side of said resistor remote from said amplifier, a normally closed relay energized by the plate current controlled by said second control grid and arranged. when energized, to break said circuit through said drive motor starter, a detergent feeder adapted to feed a concentrated detergent to said washing solution, a second normally closed relay energized by the plate current controlled by said first control grid, and means in circuit with said second relay for rendering said detergent feeder operative when said second relay is deenergized and closed.

8. A regulator for maintaining the detergent strength of the washing solution in a washer having a drive motor magnetic starter with a stop button circuit and a warning device, which comprises means passing an electric current through the washing solution, an amplifier for said current and providing rising outputvoltage in response to rising electrical conductivity of said washing solution, a thermionic relay network responsive to a low value of said output voltage below a predetermined value and deenergizing said drive motor starter when said output voltage falls to said low value, a detergent feeder adapted to feed a concentrated detergent to said washing solution, a second thermionic relay network re sponsive to a higher value of said output voltage, means actuated by said second thermionic relay network 'for deenergizing said detergent feeder to render it inoperative 'when said output voltage rises to said high value, and means adjustably regulating the operating point '01 said amplifier.

9. In a regulator for maintaining the de rgentstrength of the washing solution in awasher wherein the solution continuously increases in useless conductive salt accumulations and having a pair of electrodes immersed in said solution, means passing an electric current through said electrodes and the solution therebetween, an amplifier for said current, a relay closed by the current, below a predetermined value, from said amplifier, a detergent feeder for feeding, when energized, a concentrated detergent to said washing solution and means responsive to the closing of said relay for energizing said detergent feeder when said current from said amplifier falls to a predetermined level above said predetermined value and deenergizing said detergent feeder when said current from said amplifier rises above said predetermined level whereby the conductivity of said solution is maintained substantially constant: the combination therewith of a com-' pensator for said useless conductive salts accu mulating in said washing solution, comprising a rheostat in circuit with said electrodes, and means synchronized with the operation of said relay and successively actuating said rheostat to successively increase the value of its resistance to compensate for the changing conductance of said washing solution caused by the accumulation of said salts, whereby the detergent strength of salid'solution is maintained substantially constant.

10. In a regulator for maintaining the detergent strength of the washing solution in a washer wherein the solution continuously increases in useless conductive salt accumulations and having a pair of electrodes immersed in said solution, means passing an electric current through said electrodes and the solution therebetween, an amplifier for said current, below a predetermined value, a relay closed by the current from said amplifier, a detergent feeder for feeding, when ener ized, a concentrated detergent to said washing solution and means responsive to the closing of said relay for energizing said detergentfeeder when said current from said amplifier falls to a predetermined level above saidv predetermined value and deenergizing said detergent feeder when said current from said amplifier rises above said predetermined level whereby the conductivity of said solution is maintained substantially constant; the combination therewith of a compensator for said useless conductive salts accumulating in said washing solution, comprising a rheostat in circuit with said electrodes, a solenoid energized by said relay, and means actuated by said solenoid, when energized, and progressively advancing said rheostat to progress ively increase the value of its resistance in circuit with said electrodes to compensate for the changing conductance of said washing solution caused by the accumulation of said salts, whereby the detergent strength of said solution is maintained substantially constant.

11. In a .regulator for maintaining the Ge tergent strength of the washing solution in a washer wherein the solution continuously increases in useless conductive salt accumulations and having a pair of electrodes immersed in said solution, means passing an electric current through said electrodes and the solution therebetween, an amplifier for said current, below a predetermined value, a relay closed by the current f om said amplifier, a detergent feeder for feeding, when energized, a concentrated detergent to said washing solution and means responsive to the closing of said relay for energizing said detergent feeder when said current from said amplifier falls to a predetermined level above said predetermined value and deenergizing said detergent feeder when said current from said amplifier rises above said predetermined level whereby the conductivity of said solution is maintained substantially constant; the combination therewith of a compensator for said useless conductive salts accumulating in said washing solution, comprising a rheostat in circuit with said electrodes, a solenoid energized by said relay, and a ratchet mechanism advancing said rheostat through motion derived from said solenoid, when energized, to progressively increase the value of its resistance in circuit with said electrodes to compensate for the changing conductance of said washing solution caused by the accumulation of said salts, whereby the detergent strength of said solution is maintained substantially constant.

12. A regulator for maintaining the strength of a body of a solution subject to depletion of a component which affects the electrical conductivity of said solution, which comprises a conductivity cell housing, a pair of removable electrodes projecting into said cell housing, means continuously passing a stream of solution withdrawn from said body through said cell housing,

in contact with said electrodes therein, aconduit returning said stream of solution from said cell housing to said body, a feeder for feeding, when energized, said component tosaid solution, a second conduit adapted to divert a part of the stream of solution from said cell housing to said feeder, a valve in said second conduit, means passing an electric current through said electrodes and the solution therebetweeen, an amplifier for said current, means responsive to changing values of said amplified current above a predetermined value for energizing said valve' when said current from said amplifier falls to a predetermined level above said predetermined value and deenergizing said value when said current from said amplifier rises above said predetermined level whereby the conductivity of said solution is maintained substantially constant, and means returning said solution from said feeder to said body.

13. In a regulator for maintaining the strength of a body of a solution subject to depletion of a component which affects the electrical conductivity of said solution, a tubular conductivity cell housing having end heads at its opposite ends and having and inlet adjacent its periphery and an outlet adjacent its axis, a tubular screen removably arranged coaxially in said housing and dividing said housing into an inner chamber communicating with said outlet and an outer chamber surrounding said inner chamber and communi-- cating with said inlet, and a pair of removably spaced electrodes projecting axially from one end head of said housing into said inner chamber and immersed in the screened solution passing therethrough.

14. In a regulator for maintaining the strength of a body of a solution subject to depletion of a. component which affects the, electrical conductivity of said solution, a tubular conductivity cell housing having an inlet adjacent its periphery and an outlet adjacent its axis, a tubular screen removably arranged coaxially in said housing and dividing said housing into an inner chamber communicating with said outlet and an outer chamber surrounding said inner chamber and communicating with said inlet, a dielectric sleeve fitted in said outlet and projecting axially into opposite end thereof, a dielectric lug fitted in said sleeve and partly closing the same, a pair of spaced electrodes projecting axially from said plug into said sleeve and immersed in the screened solution passing therethrough, and means removably securing said dielectric plug in said housing.

15. In a regulator for maintaining the strength of a body of a solution subject to depletion of a component which affects the electrical conductivity of said solution, a conductivity cell housing including a lower tubular body, a coaxial upper tubular body, an intermediate partition interposed between and secured to said tubular bodies, an upper end head detachably secured to said upper tubular body, a lower end head detachably secured to said lower tubular body, said intermediate partition being provided with an axial opening providing communication between said tubular bodies and said upper and lower tubular bodies being provided, respectively, with an outlet and an inlet, a dielectric sleeve fitted in said axialopening and projecting axially into said 'lower tubular body, atubular screen interposed between: said intermediate partition and said detachable lower end head and surrounding said sleeve,a tubular dielectric plug passing through and secured to said detachable upper end head-in line with-said sleeve and fitted in said sleeve and partly closingthe'same and a pair 7 of electrodes projecting-=axially from said second plug-intoisaid' sleeve and immersed in the solution passing therethrough.

. 'lfiaAregulator-for restoring the specific electrical conductance of a solution maintained at a predetermined -"temperature, whenever a small reductionin conductivity occurs, which comprises a feeder arranged to add to-said solution a concentrated component thereof, electrodes immersed in said-solution, a-pair of parallel electrical circuits, a first switch actuated in'response to a predetermined current level in one of said circuits, means in circuit with said electrodes responsive to small changes in voltage drop in excess of a predetermined value across the solution therebetween for adjusting the current level in said one of said circuits to a lower value, at a given voltage drop between said electrodes, than the current level in the other of said circuits, means in circuit with said first switch arranged to render said feeder operative,-when said current in said one of said circuits drops slightly below its said predetermined current level and arranged to render said feeder inoperative when said current in said one of said circuits is restored to its predetermined level, whereby the conductivity of said solution is maintained substantially'constant, a second switch actuated in response to current changes in said-other of said circuits, a warning means, and means in circuit with said second switch and warning means and arranged to render said warning means operative when said ciirrent level in said other of said circuits falls slightly below its predetermined level and inoperative when said current level in said other of said circuits is raised to its said pre determined level,'o'r whenever said feeder fails to maintain the conductivity of said solution substantially constant.

17..A regulator for periodically restoringthe detergent'strength of the .washing solution maintained at a predetermined temperature whenever a small reduction of the detergent strength occurs in a washerhaving an electric motor driven pump, said pump arranged torecirculate said washing solution from a sump containing the main body of said solution, and in addition to provide a small sample stream representative at all times of the electrical conductivity and of the detergent strength of the solution, a power source for said motor driving said pump, a motor starter arranged in series between said power source and said motor for controlling said motor, a circuit passing a current tapped from a point between said starter and said motor arranged to energize said regulator upon start of said motor and deenergize same upon shutdown of said motor, a conductivity cell housing, and said representative sample stream arranged to pass through said housing and return to said sump, a pair of spaced electrodes mounted and projecting into said housing and immersed in the representative sample passing through said housing, said sample stream being started upon starting of said electric motor driving said pump and stopped upon shutdown of said motor, a circuit from said regulator when energized passing a current through said electrodes and the solution therebetween, an amplifier for said current, a relay actuated by current above a predetermined value from said amplifier, and means controlled by said relay and actuated by current from said power tap to feed a concentrated detergent to said washing solution to maintain detergency of said solution substantially constant.

18. A regulator for restoring at intervals the hydroxyl ion or the hydrogen ion concentration level of a solution maintained at 'a given temperature, whenever a small reduction in the conductivity of said solution occurs, comprising a feeder arranged, when energized, to add to said solution a concentrated component thereof, electronic switching means, means responsive to small changes in the specific conductance of said solution, above a predetermined value, arranged to activate said switching means and energize and render operative said feeding means when said conductivity falls to a predetermined level above said predetermined value and to deenergize and render said feeding means inoperative when said conductivity rises above said predetermined level, whereby the conductivity of the solution is maintained substantially constant, and an incremental means energized by said switching means and arranged in said electronic switching means to successively increment the amount of said concentrated component of the solution by that predetermined value that will substantially compensate for extraneous additions, occurring through use, of useless conductive material to the solution and thus maintain the ionic concentration level of required useful material substantially constant.

ALBERT WOODALL SMITH.

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

UNITED STATES PATENTS Number Name Date 2,078,645 Swingle Apr. 27, 1937 2,203,251 Bonner June 4, 1940 2,243,436 Mumford May 27, 1941 2,263,847 Holven Nov. 25, 1941 2,299,529 Crampton Oct. 20, 1942 2,377,363 Noble June 5, 1945 2,490,634 Keene Dec. 6, 1949