US2913893A

US2913893A - Conductivity measuring device for dry cleaning apparatus

Info

Publication number: US2913893A
Authority: US
Inventors: Martin B Mathews; Leander O Thunberg
Original assignee: RR Street and Co Inc
Current assignee: RR Street and Co Inc
Priority date: 1953-06-29
Filing date: 1958-12-15
Publication date: 1959-11-24
Anticipated expiration: 1976-11-24

Description

Ndm l, 1959 MQBLMATHIEWS ErAL CONDUCTIVITY MEASURING DEVICE FOR DRY CLEANING APPARATUS Original Filed June 29. 1953 /j 29 a0 27 a 5' D I 3/ Y m 8 86 J5 v 1 I v i 3 8557 War-- n 16 1 I 15 93 33 J? I Z4 a 36 J0 a5 a0 93 X I Ill 5? -11 1 2' 3 Sheets-Sheet 1 Jeaader' Q M. B. M ATHEWS ETAL 2,913,893 CONDUCTIVITY MEASURING DEVICE FOR DRY CLEANING APPARATUS Nov. 24;"1'959' 3 Sheets- Sheet 2 Original Filed June 29. 1953 I mmvroks Mr 0 My Nov. 24, 1959 M. B. MATHEWS EI'VAL v 2,913,893 CONDUCTIVITY MEASURING DEVICE FOR DRYCLEANING APPARATUS Original Filed Jun as. 1953.

' s Sheets-Sheet s wd m PM 0 CONDUCTIVITY MEASURING DEVICE FOR DRY CLEANING APPARATUS Martin B. Mathews, Chicago, and Leander O. Thnnberg, Riverdale, Ill., assignors to R. R. Street 8: Co., Inc., Chicago, 11]., a corporation of Illinois Original application 'June 29, 1953, Serial No. 364,844. Divided and this application December 15, 1958, Serial No. 780,330

26 Claims. (CI. 68--18) Our invention relates to the art ofdry cleaning of fabrics. It is particularly concerned with equipment to insure maintenance of high cleaning efficiency of the dry cleaning solvent in a simple and effective manner. 7

In the usual process ofdry cleaning fabrics, the soiled fabrics are subjected to the action of a volatile organic solvent which is immiscible with water as, for example,

naphtha, Stoddard solvent, carbon tetrachloride, gasoline, benzene, trichloroethylene, and the like. Such solvents are effective for the removal of grease or oil stains as Well as dust, dirt, lint and the like Which commonly adhere to the grease and oil It is conventional practice, in order to effect the removal of water-soluble stains, such as those caused by various foods and the like, to introduce into the volatile organic solvent in the washer a small proportion of water, usually of the order of 0.05%. This is commonly done by utilizing, in conjunction with the dry cleaning organic solvent, a small proportion of an oil-soluble dispersing agent which may, for example, be an oil-soluble higher fatty acid soap or other type of anionic, cationic or nonionic dispersing agent but is very commonly an oil-soluble synthetic organic detergent as, for example, long chain petroleum sulfonates such as the mahogany sulfonates; sulfate'd fatty alcohols, such as lauryl sulfate; long chain sulfoacetates, such as 'lauryl sulfoacetate; long chain alkyl sulfosuccinates such as dioctylsodiumsulfosuccinate; higher fatty acid monoglycerides such as mono-olein; higher fatty acid monoglyceride sulfates, such as m'ono-olein mono-sulfates; and the like, the sulfates and sulfonates being used in the form of salts. In the presence of such dispersing agents, the Water added to the dry cleaning volatile organic solvent is very finely orcolloidally dispersed throughout the solvent so as to form what is apparently, to the naked eye, a homogeneous solution or what may be characterized as a pseudo solution. While the advantages of the addition of water to a water-immiscible dry cleaning organic solvent and the solubilizing of the water by means of an oil-soluble dispersing agent have been, broadly speaking, heretofore known and used, the full potentialities of such existing knowledge have not been utilized in practice because of the failure founderstand certain aspects of the criteria which govern the conditions under which the dry cleaning operation is best practiced. Thus, for instance, as almost invariably practiced today, the amount of water added to the water-immiscible dry cleaning solvent is based upon the weight and nature or condition of the fabrics added to the washer, a situation which is affected, among other things, by the relative'humid-ity in the atmosphere and by other factors. The real key to the matter of insuring uniform superior dry cleaning inmodern reclamation systems lies in the discovery of the relationship and significance of electrical conductivity and the control and maintenance of the conditions which account for certain minimumelectricalconductivity essential for the-securing of the aforesaid results.

1n the dry cleaning operation proper, utilizing "such substantially clear homogeneous solutions," when the 2,913,893 h Patented Nov. 24, 1959 "ice soiled fabrics are contactedwith the dry cleaning solution" in the so-called washer for wheel, the fabrics absorb a certain amount of such Water from the dry cleaning solution, the amount of such absorbed water depending upon the nature and condition of the fabrics. The remaining moisture in the dry cleaning organic solvent solution remains more or less constant during the cleaning operation of that particular batch of clothes. How; ever, when a new batch of clothes or fabrics is introduced into the washer and is contacted with such dry cleaning organic solvent solution, an additional amount of the water dispersed therein is abstracted or absorbedby the clothes or fabrics. The result is that in the dry cleaning operations conducted by any plant the moisture content of the volatile organic solvent solution varies quite considerably from batch to batch of soiled fabrics and, at various stages of the use thereof for the cleaning of different batches of clothes or fabrics, the moisture content drops to a point where it is inadequate to serve its intended purposes, and the cleaning results are nonuniform.

In the dry cleaning step proper, as carried out in the so-called washer or wheel, it has been the practice to utilize various concentrations of oil-soluble soaps or de tergents as, for example, from a small fraction of one percent to as high as seven percent or even higher. During the cleaning of various batches of clothes, the concentration of the soap or detergent decreases and it has, therefore, been the practice to replenish the soap or detergent from time to time. 7

Despite all of such prior knowledge and practices, serious difiiculties and lack of significant knowledge have existed so that, from a practical standpoint, it has not been possible for the operator of a dry cleaning establishment to carryout the dry cleaning operations in such a manner as to obtain uniform, substantially optimum results from batch to batch of fabrics being cleaned.

It has been discovered that outstandingly satisfactory uniform cleaning results of high efiiciency can be obtained in a simple, safe and practical manner by procedure which may readily be understood and practiced by the average operator of a dry cleaning establishment. This invention is based, in part, on the discovery that, in dry cleaning with water-immiscible organic solvent solutions containing an oil-soluble dispersing agent or dry cleaning soap or detergent and water, as more particularly described below, the electrical conductivity of such solutions should be maintained at not less than about l0 l0 mhos to insure uniformly superior overall re sults with respect to removal of inert soil, water-soluble soil, prevention of soil redeposition, whiteness retention, avoidance of deleterious action On fabrics, economy of detergency consumption, and freedom from interference with proper operation of the filtration and distillation systems. The amount and type of dry cleaning dispersing agent or detergent and the amount of water influence the degree of electrical conductivity imparted to the dry cleaning water-immiscible organic solvent. However, the state of distribution of the water is also a very important factor. In all cases, for the effective practice of this invention, the water must be so finely or colloidally dispersed in the organic solvent as to produce a substantially clear homogeneous fsolutionj so far as the naked eye is concerned, or What may be characterized as a pseudo solution. tln this connection, it may be noted that it is entirelypossible to provide mixtures of water-immiscible organic solvents and oil-soluble dispersing agents and water, identical in proportions such as have been found to be especially effective as hereafter described, and still be unsatisfactory for purposes of this invention because their electrical conductivity falls appreciably below the aforesaid value of 10x10 mhos due to the fact that the water is not properly distributed through the organic solvent. Hence, it will be understood that when we speak herein of solutions containing oil-soluble dispersing agents or detergents and water, it will be understood that we meansuch solutions. wherein the water is so finely dispersed as to form a substantially clear homogeneous solution in the water-immiscible organic solvent, as viewed by the naked eye. It is also important, for the most effective practice of this invention, that the entire system be charged with water so that the solubilized water passes through the filter. I

This invention is based upon the utilization of equipment which, in practice, involves periodically determining the electrical conductivity of the aforesaid dry cleaning solutions and, if, during use of such solutions in the cleaning of a batch or successive batches of soiled fabrics, the electrical conductivity has dropped toappreciably below l 10- mhos, an amount of water is added to the solution so as to bring the electrical conductivity thereof to not less than the aforesaid minimum value thereof, this being coupled, if necessary, with the replenishing of the soil-soluble dispersing agent or dry cleaning detergent.

This invention is particularly advantageously practiced with the utilization, as the oil-soluble dispersing agent, of sulfate and sulfonate detergents containing an alkyl group of at least 8 carbon atoms and usually between 8 and 18 carbon atoms, in the form of salts thereof as, for instance, the alkali metal, ammonium and amine salts. In addition to the examples thereof described above, salts of higher alkyl aryl sulfonates such as dodecyl benzene -sulfonate, octyl benzene sulfonate, nonyl naphthalene sulfonate, keryl benzene sulfonates, and the like can be utilized. It is also particularly advantageous, in the especially preferred embodiments of this invention, to utilize proportions of oil-soluble dispersing agent or detergent, on the non-volatile basis, of not less than about 1.5%, based on the volume of the organic solvent, and desirably within the range of about 1.5% to about 3%, a good average being about 2%. In this connection, it will be understood that dry cleaning detergents are commonly marketed in the form of liquid or paste products and frequently contain diluents, volatile ingredients and the like over and above the nonvolatile dry cleaning detergents proper. When we speak of, for example, 1.5% to 3% of the dry cleaning detergent, said percentages are on the non-volatile active detergent basis. I

The amount of water added to the water-immiscible dry cleaning solvent should, in the particularly preferred embodiments of this invention, not be appreciably less than 0.2%, by volume, and most desirably ranges from about 0.2% to about 0.4%, it being relatively uncommon that this latter figure will be exceeded. So far as actual cleaning practice goes, these amounts of water are abnormally large but their use, under the conditions of the present invention, has been found to be most advantageous, cleaning of the fabrics being enhanced and subsequent spotting operations being reduced to a substantial minimum.

The optimum conditions under which the dry cleaning operation should be conducted, taking into account the over-all aspects, therefore, will, in general, involve the utilization of a water-immiscible dry cleaning organic solvent solution containing from about 1.5% to about 3%, with a good average of about 2%, of an oil-soluble sulfate or sulfonate detergent containing an alkyl group of at least 8 carbon atoms, and from about 0.2% to about 0.4%, with a good average of about 0.3%, of water, the electrical conductivity of said solution being not less than about 10 10' mhos.

In the light of the foregoing description, it will bev understood that, in the case of the foregoing dry cleaning organic solvent solutions, the electrical conductivity varies more or less uniformly as a function of the water and detergent content of such solutions, the greater the water and detergent content, at least within practical op- 4 erating ranges,- the greater the electrical conductivity. Within any given system utilizing a particular waterimmiscible dry cleaning organic solvent, a particular detergent and water, a substantially fixed relationship exists with respect to the variability of the electrical conductivity as a function of the qauntity of detergent and water, particularly the latter, dissolved or colloidally dispersed in the organic solvent in the form of the aforesaid solutions. Thus, with any given system, for example, one utilizing Stoddard solvent as the dry cleaning organic solvent, di-(Z-ethylhexyl) sodiumsulfosuccinate as the dispersing agent or detergent, and distilled water as the source of water, it is possible to plot curves showing the relationship of electrical conductivity to detergent and water content, particularly-the latter, within practical limits of the latter. Other curves can readily be prepared based upon electrical conductivity data utilizing any specific system of materials.

It will be understood that, through continued use of the dry cleaning solution on difierent'batches of soiled fabrics, said solution builds up a constantly varying amount of soluble impurities which afiect to a greater or lesser extent, depending upon the amount and nature of such impurities, the electrical conductivity. of said solution. In the usual case, this is not sufficient substantially to affect adversely the conductivity readings so far as their reflecting the condition of the solution with respect to the content of water and detergent therein. In the usual case, the electrical conductivity readings of a solution containing a relatively high proportion of soluble impurities resulting from long continued use of the solution prior to distillation thereof will show a somewhat lower conductivity than a similar pure organic solvent solution containing the same amounts of only the oil-soluble detergent and water. Suitable extrapolations can be resorted to, if desired, in situations of this kind, if deemed advisable, to take into account the effect of soluble impurities on the electrical conductivity of repeatedly used dry cleaning solutions. Extreme temperature variations in the solution also influence the electrical conductivity value of the solution, high temperature increasing and low temperatures decreasing the electrical conductivity. Suitable allowances may be made for such temperature variations and optimum results are enjoyed by maintaining the temperature of the solution between substantially 70 to F.

While satisfactory results are obtained with electrical conductivities maintained at notless than about 10 l0-' mhos, we prefer to operate at higher levels as, for example, from about 40 to about 120x l0- mhos or even higher, a particularly preferred range being from about 50 to about x 10- mhos.

In the preferred manner of carrying out the present invention, in the so-called two bath system, for example, in dry cleaning systems which include a washer-filter-trap assembly reserved for the detergent solution, and a separate rinse and filter system, and wherein said solution is continuously circulated through said washer-filter-trap assembly, the water-immiscible liquid organic solvent is activated with the requisite amount of oil-soluble non-volatile'dry cleaning dispersing agent or detergent and the resulting solution is circulated through said assembly to effect uniform distribution of said dispersing agent or detergentthroughout the entire body'of organic solvent in the assembly. The requisite amount of Water is then added and the resulting mixture 'is circulated through said assembly whereby to solubilize the water throughout the system, so that the solubilized water solution passes through the filter, and forms a substantially clear homogeneous solution having an electrical conductivity not less than about 10x10? mhos. The soiled fabrics to be dry cleaned are then subjected to the resulting dry cleaning solution in the usual way, successive batches of soiled fabrics being dry cleaned. The electrical conductivity of the solution" is measured and,

u) if the electrical conductivity has dropped to below the aforesaid value, an additional amount of water and, if necessary, detergent is added to bring the concentration of the water and detergent and the electrical conductivity of the solution to within the predetermined ranges. It will, of course, be understood that after the fabrics are cleaned they are rinsed and dried and fluffed in accordance with standard practices in the art.

It will be understood that the addition of oil soluble dispersing agent or detergent to the organic solvent solutions will occur far more infrequently than the additions of water. In this connection, it will be appreciated that the solubility and stability of the oil-soluble dispersing agent or detergent are such that the content thereof diminishes quite slowly so that replenishing thereof is necessary at only relatively sporadic intervals. Hence, when the electrical conductivity drops below about 1O 10' mhos it will, in most cases, be necessary to add only water in order to increase the electrical conductivity to a value above said minimum figure. The content of oilsoluble detergent in the dry cleaning solution can be determined from time to time by heretofore known procedures. It may be found, in certain instances, that when the electrical conductivity drops below the aforesaid minimum value there may be a deficiency of both detergent and water, and, in such cases, both detergent'and water will be added to bring the amounts thereof within the desired or predetermined ranges as well as restoring the electrical conductivity of the dry cleaning solution to a value not below said minimum figure. In the usual case, however, as stated, water additions alone will be sufiicient and the detergent content can be determined and maintained at desired proportions by procedures already known in the art.

An object of this invention is to provide an improved system of apparatus for measuring or determining the electrical conductivity of the solution circulating through the dry cleaning system for the purpose of maintaining high cleaning efficiency in a simple and effective manner. In this respect all of the circulating solution in the dry cleaning system is circulated in a continuous manner through the conductivity measuring apparatus in order to obtain accurate and continuous measurements and determinations of the electrical conductivity thereof, and said conductivity measuring apparatus offers substantially no impedance or restriction to the circulation of the solution. The apparatus is simple in construction and may be inexpensively manufactured and installed.

A further object of this invention is to provide an improved system of apparatus for automatically supplying water to the solution in the dry cleaning system for automatically maintaining the electrical conductivity of the solution at the desired values and to prevent an inadvertent and excessive supply of water thereto. The water is introduced into the system for the purpose of maintaining a certain minimum electrical conductivity value necessary for efiicient cleaning, compatible with avoidance of damage to the fabrics, such as excessive wrinkling and shrinkage, which may be brought about by excess water.

In this respect suitable water pipes, water reservoir and solenoid valves and signal lights controlled by the electrical conductivity measuring apparatus are utilized.

Further objects of this invention reside in the details of construction of the measuring and control apparatus and in the cooperative relationships between the com; ponent parts thereof.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawings in which; i

Figure 1 is an elevational view of a dry cleaning system embodying the features of this invention;

Figure 2 is a wiring diagram for the equipment illustrated in Figure 1;

estates Figure '3 is a vertical sectional view through the electrical conductivity responsive device and taken substantially along the line 3 3 of Figures 2 and 4;

Figure 4 is 'a horizontal sectional view taken substantially along the line 44 of Figure 3;

Figure 5, is a horizontal sectional view taken substantially along the line 55 of Figure 3;

Figure 6 is a sectional view of one of the spacer members illustrated in Figure 3;

Figure 7 is an enlarged partial sectional view showing the manner of making electrical contact with the electrodes as illustartedin Figure 3;

Figure 8 is a vertical sectional view similar to Figure 3 but illustrating a further formof the invention and taken substantially along the line 8-8 of Figure 9;

Figure 9 is a horizontal sectional view taken substantially along the line 9 9 of Figure 8;

Figure 10 is a horizontal sectional view taken substantially along the line 1010 of Figure 8;

Figure 11 is a sectional view through one of the spacer members illustrated in Figure 8.

Referring first to Figure 1, there is generally illustrated a conventional dry cleaning system or apparatus such as known in the trade as Prosperity 6A. It includes a dry cleaning washer 10 supported by feet 11 and having an access door 12 through which apparel to be dry cleaned is inserted. It also includes a filter 13 supported by feet 14 and having a removable cover 15. The filter 13 is provided with an inlet fitting 16 and an outlet fitting 17.

The dry cleaning solution is withdrawn from the washer 10 through a conduit 20, a button trap 21 and a conduit 22 bymeans of a pump 23 driven by an electric motonnot' shown. The pump discharges through a conduit 24 into the filter 13 through the fitting 16. The conduit 24 may be provided with a sight glass 25. The solution is discharged from the filter 13 through the discharge fitting 17, an upwardly extending conduit 26, a horizontally extending conduit 27 and a downwardly extending conduit 28 into the washer 10. Thus, the pump 23 operates to circulate the solution from the washer it) through the button trap 21, the filter 13 and back to the washer 10. A valve 29 and a sight glass 30 may be located in the horizontal conduit 27. The conductivity device 31 of this invention is preferably vertically arranged in the vertical conduit 26 adjacent the horizontal conduit 27 on the discharge side of the filter 13. In this connection the conductivity responsive device 31 is connected by a reducing fitting 32 to the conduit 26 and by a T-fitting 33 to the conduit 27. One through leg of the T-fitting 33 is secured to the conductivity responsive device 31 and the other through leg thereof is closed by a plug 34. The normal leg is connected to the horizontal conduit 27 The details of construction of the electrical conductivity responsive device are illustrated in Figures 3 to 7. It is shownto be constructed for use with a two inch conduit system, that is, where the vertical conduit 26 is formed from standard two inch pipe. Here, the electrical conductivity responsive device 31 includes a cylindrical housing 36 which may be formed from a three inch pipe or it may be formed from a casting, if so desired. The cylindrical housing 36 is threaded at its lower end as indicated at 37 and is secured to the reducing coupling 32 which in turn is secured to the conduit 26. The housing is also threaded at its upper end as indicated at 38 so that it may be secured to the T-fitting 33 which in this. instance is a three inch T-fitting wherein the through legs. of the T-fittingare three inch and the normal leg is of smaller size as, for example, a two inch leg for connection to the horizontal conduit 27 when it is a two inch conduit. Concentrically located within the housing, 36 are a pair of concentric tubular

metallic electrodes

39 and 40. These

electrodes

39 and 40 may be made of any suitable metal which will not be affected by the:

solution. For example, the inner electrode 39 may be formed of No. 16 gauge seamless steel tubing having an outside diameter of 2% inch and the outer electrode 40 may be formed of No. 16 gauge seamless steel tubing having an outside diameter of 2% inch. It will be noted here that the inside diameter of the inner tubular electrode 39 is substantially the same as the inside diameter of the two inch conduit 26 so that the

electrodes

39 and 40 will not restrict the flow of the solution through the dry cleaning system. The

electrodes

39 and 40 are held in concentric relation within the housing 36 by means of lower and

upper spacer members

41 and 42.

The lower and

upper spacer members

41 and 42 are each provided with a central opening 44 which corresponds to the inside diameter of the inner electrode 39. The

spacer members

41 and 42 are made of an electrical insulating material such as Lucite. Adjacent the opening 44 in the spacer member there is provided an annular seat 45 which receives the end of the inner electrode 39. It is also provided with an annular seat 46 of larger diameter for receiving the end of the outer electrode 40. Between the

seats

45 and 46 the spacer member is provided with a plurality of openings 47 so that the solution in addition to flowing through the inner tubular electrode 39 is also allowed to flow between the inner electrode 39 and the outer electrode 40. Substantially free flow of the solution is provided between the

electrodes

39 and 40 because of the relatively large number of these openings 47. The inner electrode 39 is secured to the lower spacer member 41 by means of a screw 49 received in a counterbored hole 50 in the spacer member, the screw 49 being screwed into a tapped hole in the lower end of the inner electrode 39.

The lower spacer member 41 is secured in place in the housing 36 by means of a pair of

screws

51 and 52 which are screwed into the spacer member 41. It is here noted that the

screws

51 and 52 do not touch either

electrode

39 and 40 so that there can be no electrical conduction between the

electrodes

39 and 40 and the housing 36 through these

screws

51 and 52. The screws 51 and -2 are sealed against leakage by washers or gaskets 53 which may be formed of Lucite. In this way the spacer member 41 is secured to the housing 36 which in turn concentrically mounts the lower ends of the

tubular electrodes

39 and 40. The upper spacer member 42 is secured to the housing 36 by means of a pair of

screws

54 and 58. The screw 54 is threaded into the upper end of the inner electrode 39 so as to make electrical contact therewith. The screw 54 is sealed against leakage and is electrically insulated from the housing 36 by means of an electrical insulator 55 which also may be made of Lucite. The screw 54 has a tapped hole therein for receiving a screw 56 to form an electrical connector for a conductor 57. The screw 58 is threaded into the upper end of the outer electrode 40 so as to make electrical contact therewith. It is also sealed against leakage and electrically insulated from the housing 36 by means of an insulator 55 and it is also provided with a tapped hole for receiving a screw 56 for forming an electrical connection to a conductor 59. Thus, the

screws

54 and 58 in addition to securing the upper spacer member 42 and the upper ends of the

electrodes

39 and 40 in place, also act as electrical connectors for making electrical connection to the

electrodes

39 and 40, respectively.

It is therefore seen that all of the solution being circulated through the dry cleaning system is circulated through the electrical conductivity responsive device 31, the solution passing through the inner electrode 39 and between the inner and

outer electrodes

39 and 40. Thus, the

electrodes

39 and 40 may operate continuously to measure or determine the electrical conductivity of the solution. At the same time the electrical conductivity responsive device 31 offers substantially no restriction or resistance to the flow of the solution therethrough. In this way accurate determinations may be made.

In the Figures 8 to 11 the electrical conductivity responsive device 31 is constructed for use with a three-inch conduit system, that is, where the vertical conduit 26 is formed from a pipe of three inch diameter. Here, the housing 36 is made larger as, for example, from a four inch pipe and likewise the T-fitting 33 is a four inch fitting. However, the

electrodes

39 and 40 may be of the same size as in Figures 3 to 7 so that they may be interchangeably used. Here, the spacer members are designated at 62 and 63; They correspond in all respects to the

spacer members

41 and 42 with the exception that they are provided with a plurality 'of outwardly extending ears 64 to form openings between the spacer members and the housing 36, these openings being designated at 65. The cars 64 may be integrally formed on the

spacer members

62 and 63 or they may be made from separate pieces such as Lucite which in turn are secured to the

spacer members

62 and 63 by a suitable cement such as ethylene dichloride. The solution flowing through the electrical conductivity responsive device 31 in Figure 8 in addition to flowing through the inner electrode 39 and between the inner electrode 39 and the outer electrode 40 also flows between the outer electrode 40 and the housing 36. In this way substantially no restriction or resistance to the flow of the solution is provided by the electrical conductivity responsive device and, yet, accurate measurements of the electrical conductivity of the solution may be obtained.

Referring now to Figures 1 and 2, the system of this invention includes an electrical resistance responsive device for measuring or determining the electrical conductivity of the solution" flowing through the dry cleaning system. This electrical resistance responsive device may comprise an adjustable Wheatstone bridge arrangement. It has a terminal strip 71 and a selector switch 72 cooperating with indicia 73 for determining the adjustment of the bridge. The bridge may be powered by any suitable source of electrical energy transmitted thereto through

line wires

74 and 75 connected to terminals "76 and 77, respectively. One of the legs of the bridge circuit may be connected to

terminals

73 and 79 which in turn are connected by the

conductors

57 and 59 to the

electrodes

39 and 40 in the electrical conductivity responsive device 31. In this way the electrical conductivity of the solution, as determined by the resistance to current flow therethrough, is utilized for balancing and unbalancing the bridge in the electrical resistance responsive device 70, the balancing point of which may be adjusted to any desired value by manipulating the knob 72. The bridge circuit in the electrical resistance responsive device 70 operates switching means for connecting the

line wires

74 and 75 across the terminals 80 and 81 and for connecting those line wires across the terminals 86 and 82. When the electrical conductivity of the solution is above a predetermined value as determined by the setting of the control knob 72, the

line wires

74 and 75 are connected across the terminals 80 and 81 by the switching mechanism. When the electrical conductivity of the solution is below the predetermined value, the

line wires

74 and 75 are connected across the terminals 80 and 82.

Water is supplied to the solution from a water reservoir which is suitably supported in an elevated position as by securing the same to the conduit 28 as indicated in Figure 1. Water is supplied to the reservoir 85 by means of a water supply pipe 86. A solenoid valve consisting of a valve 87 and a solenoid operator 88 is located in the pipe 86 for turning on and off the water. The pipe 86 also has a second valve 89 which is controlled by a float 90 responsive to the level of the water in the reservoir 85. When the solenoid 88 is energized to open the valve 87, water flows into the reservoir 85 up to a predetermined level therein whereupon the float 90 closes the valve 89 to shut off the supply of water to the reservoir. Water is fed from the reservoir 85 into the conduit 22 and, hence, into the circulating solution in the dry cleaning system through a' pipe WhlChis" connected by a petcock 933 into the conduit" 22: By

suitably'adjusting the petcock 92the rate ofwater feed into the water solution may be regulated; The pipe 91 is preferably provided with a strainer 93- for keeping foreign matter out of the solution. The flow of water through the pipe 91may' be-turned on-and' off by a valve operated by a solenoid 95L- When the solenoid 95 is energized, the valve 94 is openedto supply water to the solut on and, when the'solenoi'd 95 isdeenergized, the

valve 94 is closed. A signal light 96 having an indicating lamp 97 isconnected in paralled with the solenoid 95 so that the signal light is illuminatedwhile waterisbeing supplied to the solution in the dry cleaning system. To prevent opening of the valve 94 when the pump 23 is not running there is provided a relay having an operating coil 98 for operating a switch arm 99, the operating coil 98 being connected by

conductors

100 and 101 to the controlling switch for operating the motor which drives the pump 23. V

In starting the dry cleaning system the water reservoir 85 is first filled with water and then the pump 23 isturned on for circulating the solution through the washer and filter. The solution is checked for the amount of'oilsoluble non-volatile dry cleaning detergent to assure that a. proper amount of the detergent is present in the solution. The automatic control system is then activated; When the pump 23 is placed in operation, the switch 99 operated by the operating coil 98 is closed. If the electrical conductivity of the solution is below the desired value as determined by the control knob 72, a circuit is completed from the line wire 74 through terminal 76, terminal 82, conductor 105', switch 99, signal light 96 and solenoid 95 connected in parallel conductor 103, terminal 80 and terminal 77 back to the line wire 75. This energizes the'solenoid 95 for opening the valve 94 to supply water from the reservoir 85 to the conduit" 22 and, hence, to the solution in the dry cleaning system. The rate of application of the Water to the solution is regulated by the petcock 92. At the same time the indicating lamp 97 is illuminated. When the electrical conductivity of the solution'reach'es. the desired value, the aforementioned circuit isbroken and an-. other circuit is completed from the line wire 74 through terminal 76, terminal 81, conductor104, solenoid 89, conductor 103, terminal 80 and terminal 77 back to the line wire 75, this circuit being completed at the same time that the aforementioned circuit is broken. As a result, the indicating lamp 97 is extinguished, the solenoid 95 is deenergized to close the valve 94 to shut off the supply of water to the solution and the solenoid 88 is energized to open the value 87 to supply water to the reservoir running from ten: to twenty minutes depending upon the type; of garments being: cleaned; If water is introduced intermittently'during a cleaning cycle for shorter periods, this means that the water is being introduced at too great a rate and" to remedy this the petcock 92 is closed off somewhat in order to obtain the correct cycling. If water is admitted to the solution for longer periods than this two to five minute period, this indicates that something is wrong and: theoperator is advised of this by the signal light 96. The amount of water introduced into the solution. may be regulated by adjusting the control knob 72 on. the electrical resistance responsive device 70, the knob being turned in one direction for increasing the amount of water in solution" and in the other direction for decreasing the amount of such water.

While-for. purposes of illustration one main form of this invention has been disclosed, other forms thereof may become-apparent to those skilled in the art upon reference to this disclosure, and therefore, this invention is to be limited only by'the scope of the appended claims.

This application is a division of our application Serial No. 364,844, filed June 29, 1953.

We. claim as. our invention:

1; In a. dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting'the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile di'y cleaning detergent and water so finely dispersed as'to: form a; substantially clear homogeneous solution, the improvement which comprises a substantially cylindricalhousing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulatedfrom each other and the housing, the space between said concentrically arranged tubular metallic electrodes. being traversed by a portion of the circulating solution, and an electrical resistance responsive devicev electrically connected to said metallic elec-.

trodes for'responding to the electrical conductivity of the solution;

2. In, a dry cleaning system which includes a washer solution, the improvement which comprises a substanis being suppliedto the reservoir 85 forfilling the same.

If for some reason the control apparatus should not operate properly was to tend to supply water to the solution in excessive amounts, the amount of water so supplied is limited by the size of the reservoirl85. In this way it is impossible to add excessively large amounts of water to the solution. Also in this way the correct amount of water is maintained in the solution for providing maximum dry cleaning efliciency.

When garments are placed in the washer 10, they will absorb some of the water in the solution and, when this occurs, the control system of this invention automatically operates to replenish the water so absorbed so as to maintain at all times maximum cleaning efiiciency regardless of the character of the garments beingcleaned and the moisture content carried by such garments. The signal light 96 is illuminated during the time that the tially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a sole-. noid valve for supplying water to the solution in the ductivity of the solution for maintaining the water content of the solution at substantially a desired value.

3. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump 11 for circulating through the washer, filter and conduits a water-immiscible'organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, a water delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling said solenoid valves to supply water from the water reservoir to the solu-' tion and to shut off the supply of water to the water reservoir when the electrical conductivity of the solution falls below a desired value, and to shut off the supply of water from the water reservoir to the solution and to supply water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution.

4. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, con duits interconnecting the Washer and filter and'a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduitsvfor circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a solenoid valve for sup plying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value, and a signal light electrically connected to said controller and illuminated While water is being supplied to the solution.

5. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, a water delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to said solenoid valves to supply water from the water reservoir to the solution and to shut oh the supply of water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution, and a signal light electrically connected to said controller and illuminated while water is being supplied to the solution.

6. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a solenoid valve for supplying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value, and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply of water to the solution when the pump is not operating.

7. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a fioat valve for supplying water to a predetermined level in the water reservoir, a water delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling said solenoid valves to supply water from the water reservoir to the solution and to shut off the supply of water to the water reservoir when the electrical conductivity of the solution falls below a desired value, and to shut oh the supply of water from the water reservoir to the solution and to supply water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution, and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solutionfor preventing thesupply of waterto the solution when the pump is not operating.

8. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer'and filter and a pump for circulating through the washer, vfilter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a solenoid valve for supplying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value, and a signal light electrically connected to said controller and illuminated while water is being supplied to the solution, and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply of water to the solution when the pump is not operating.

9. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, con- 1 duits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the housing and electrically insulated from each other and the housing, the space between said concentrically arranged tubular metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, awater delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling, said solenoid valves to supply water from the water reservoir to the solution and to shut off the supply of water to the water reservoir when the electrical conductivity of the solution falls below a desired value, and to shut off the supply ofwater from the water reservoir to the solution and the supply water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution, and a signal light electrically connected to said controller and illuminated while water is being supplied to the solution, and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply of water to the solution when the pump is not operating.

10. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble non-volatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system and having a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a solenoid valve for supplying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution a substantially a desired value.

11. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through. the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and Water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system and having a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, a water delivery pipe forsupplying water from the reservoir into the solution in the, system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and 'an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling said solenoid valves to supply water from the water reservoir to the solution and to shut off the supply of water to the water reservoir when the electrical conductivity of the solution falls below a desired value, and to shut off the supply of water from the water reservoir to the solution and to supply water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution.

12. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and. filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble non volatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solu- 15 electrically connected to said metallic electrodes and said solenoid volve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value, and a signal light electrically connected to said controller and illuminated while water is being supplied to the solution.

13. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system and having a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, a water delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling said solenoid valves to supply water from the water reservoir to the solution and to shut oil the supply of water to the water reservoir when the electrical conductivity of the solution falls below a desired value, and to shut olf the supply of water from the water reservoir to the solution and to supply water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution, and a signal light electrically connected to said controller and illuminated while water is being supplied to the solution.

14. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system and having a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a solenoid valve for supplying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply of water to the solution when the pump is not operating.

15. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system aud'baving a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating-solution, a water reservoir,'means lncluding a'water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, a

water delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling said solenoid valves to supply water from the water reservoir to the solution and to shut off the supply of water to the water reservoir when the electrical conductivity of the solution falls below a desiredvalue, and to shut off the supply of water from the water reservoir to the solution and to supply water to the water reservoir when the electrical conductivity of the solution rises above the desired value, for maintaining the water content of the solution at substantially the desired value and for preventing an excess supply of water to the solution, and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply of water to the solution when the pump is not operating.

16. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system and having a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating solution, means including a pipe and a solenoid valve for supplying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value, and a signal light electrically connected to said controller and illuminated while water is being supplied to the solution, and switch means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply of water to the solution when the pump is not operating.

17. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dis persed as to form a substantially clear homogeneous solution, the improvement which comprises electrical conductivity means connected into the system and having a pair of spaced metallic electrodes, the space between said metallic electrodes being traversed by a portion of the circulating solution, a water reservoir, means including a water supply pipe and a float valve for supplying water to a predetermined level in the water reservoir, a water delivery pipe for supplying water from the reservoir into the solution in the system, a solenoid valve in the water supply pipe, a solenoid valve in the water delivery pipe, and an electrical resistance responsive controller electrically connected to said metallic electrodes and said solenoid valves and responsive to the electrical conductivity of the solution and controlling said solenoid valves to supply water from the water reservoir to the solution and to shut ageraieee off the supply ofiwaterto the water reservoir when the electrical conductivity of the solution falls below a water reservoir to the solutionand-to supply water to the to the solution, and switch-means operatively connected to the pump and electrically connected to the solenoid valve which controls the supply of water to the solution for preventing the supply-- of water to" the solution whenthe pump is not operating. 1

18. In a dry cleaning system which includes a washer adapted to liold' fabricsto be dry cleaned, a filter, conduits interconnecting the washer and filter and apump' for circulating through-the washer, filter and conduits a water-immiscible organic dry cleaning solvent which" is activated by small proportions of an oil-soluble nonvolatile drycleaning detergent and water so finely dispersedas to-forma substantially clear homogeneous solution, the improvement which comprises a substantially cylindrical housing connected into one of the" conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes concentrically mounted in the'housing and electrically insulated from each other and the housing, the

space between said concentrically arranged tubular metallic electrodes being-traversed by a portion of the circulating solution, the insidediameter of the conduits and themounting for" the tubular metallic electrodes heing suchvas to" provide substantially uninterrupted flow o'f'the'" solution through the system, and an electrical resistanceresponsive device electrically connected to said metallic' electrodes for responding to the electrical conductivity of the solution;

19. In a; dry cleaning system which includes a washer adapted. to hold fabrics to be dry cleaned, a filter, con duits interconnecting thewasher' and filter and apump-for circulating through the washer, filter and? conduits a water-immiscible organic. dry" cleaning? solvent which is activated. by small proportionsof an oil soluble non=- volatile dry cleaning" detergent and Water so finely dis persed' asitoi form a substantially clear homo'geneous so'lu tion, the conduit circulating the solution from the filter to the washer: having' a verticallportion adjacent the filter, the improvement which.- comprises a substantially cylindrical housing connected ihto said" vertical portion of said conduit for circulation ofthe solution therethrou'gh, a pair of spaced apart concentricallyarranged tubular metallic electrodes concentrically mounted. in the housing and electrically insulatedfi'o'm' each other and the housing, the space between. said. concentrically-arranged tubular metallic electrodes being traversed by a portion of the circulating solution and an electrical resistance responsive device electrically connected to said metallic electrodes for responding to the electrical conductivity of the solution.

20. An electrical conductivity device, adapted to be connected into a conduit for determining the electrical conductivity of a fluid flowing through the conduit, comprising a substantially cylindrical housing, fittings at the ends of the housing for connecting the housing into the conduit, a pair of spaced apart concentrically arranged tubular metallic electrodes, a pair of annular spacer members receiving the ends of the tubular metallic electrodes for concentrically supporting the same, means for removably securing the spacer members in the substantially cylindrical housing for concentrically mounting the tubular metallic electrodes in the housing, said annular spacer members allowing free flow of fluid through the inner tubular metallic electrode and having openings for allowing free flow of fluid between the inner and outer [ta 7 tubular" metallic electrodes; said annular spacer memb'ers being formed of electrical insulatinggmaterial for electrically insulating the tubular metallic electrodes from each other and from the housing, and means providing.

external' 'electrical connections to the tubular metallic electrodes.

21. An electrical conductivity device, adapted to be connected into a bend in a conduit for determining the electrical conductivity of a fluid flowing through the conduit, comprising a substantially cylindrical housing, a fitting connected at one end of the housing for connecting' the housing concentrically with one portion of the conduit; a T-fitting having one of its through legs connectedtoth'e other end of the conduit, its normal leg connecte'd to the other portion of the housing and its other through'leg closed bya removable plug, a pair'of spaced apart concentrically arranged tubular metallic electrodes, a pair of annular spacer members receiving the ends of the" tubular metallic electrodes for concentrically supporting the same, means for removably securing the spacer-members in the substantially cylindrical housing for concentrically mounting the tubular metallic electrodes: in the housing, said tubular metallic electrodes and spacer members being removablefrom the housing through" the T-fitting when the securing means for the spacer'members and the plug are removed, said annular spacer members allowing free flow of fluid through the inner tubular metallic electrode and having openings for allowingfree flow of fluid between the inner and outer tubular" metallic electrodes, said annular spacer memhers heing' formed of electrical insulating material for electrically insulating the tubular metallic electrodes from each other and from the housing, and means providing external electrical connections to the tubular metallic electrodes.

22-. An electrical conductivity device, adapted to be connected into. aconduit for determining the electrical conductivity of a fluid flowing through the conduit, comprising asubstantially cylindrical housing having an inside diameter larger than the inside diameter of the conduinfittings at the ends of the housing for connectingthe' housing into the conduit, apair of spaced apart concentrically arranged tubular metallic electrodes, a painof annular spacer members receiving the ends of the: tubular metallic electrodes for concentrically supporting the same,- means for removably securing the spacer members in the substantially cylindrical housing for concentrically mounting the tubular metallic electrodes in the housing, the diameters of said tubular metallic 'electr'o'desgthe inside diameters of said housing and the; construction of. said spacer members being such as torallow'free and'substantially unobstruct'edflow of fluid throughlthe-inner tubular metallic electrode, between the inner andouter tubular metallic electrodes and through theicondirit' said annular spacer members being formed of electrical insulating material for electrically insulating the tubular metallic electrodes from each other and from the housing, and means providing external electrical connections to the tubular metallic electrodes.

23. An electrical conductivity device, adapted to be connected into a conduit for determining the electrical conductivity of a fluid flowing through the conduit, comprising a substantially cylindrical housing, fittings at the ends of the housing for connecting the housing into the conduit, a pair of spaced apart concentrically arranged tubular metallic electrodes, a pair of spacer members each having a central opening, a seat adjacent the opening for receiving the inner tubular metallic electrode and a seat of larger diameter for receiving the outer tubular metallic electrode, for concentrically supporting the electrodes, means for removably securing the spacer members in the substantially cylindrical housing for concentrically mounting the tubular metallic electrodes in the housing, the central openings in the spacer members allowing free flow of fluid through the inner metallic electrode, said spacer members having openings therethrough between the seats thereof for allowing free flow of fluid between the inner and outer tubular metallic electrodes, said annular spacer members being formed of electrical insulating material for electrically insulating the tubular metallic electrodes from each other and from the housing, and means providing external electrical connections to the tubular metallic electrodes.

24. An electrical conductivity device, adapted to be connected into a conduit for determining the electrical conductivity of a fluid flowing through the conduit, comprising a substantially cylindrical housing, fittings at the ends of the housing for connecting the housing into the conduit, a pair of spaced apart concentrically arranged tubular metallic electrodes, a pair of spacer members each having a central opening, a seat adjacent the opening for receiving the inner tubular metallic electrode and a seat of larger diameter for receiving the outer tubular metallic electrode, for concentrically supporting the electrodes, means for removably securing the spacer members in the substantially cylindrical housing for concentrically mount-, ing the tubular metallic electrodes in the housing, the central openings in the spacer members allowing free flow of fluid through the inner metallic electrode, said spacer members having openings therethrough between the seats thereof for allowing free flow of fluid between the inner and outer tubular metallic electrodes, said spacer members having openings therethrough outwardly from the seat of larger diameter for allowing free flow of fluid between the outer tubular metallic electrode and the housing, said annular spacer members being formed' duits interconnecting the washer and filter and a pump,

for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises an electrical conductivity device including a substantially cylindrical housing, fittings at the ends of the housing for connecting the housing into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes, a pair of annular spacer members receiving the ends of the tubular metal-- lic electrodes for concentrically supporting the same,

means for removably securing the spacer members in the substantially cylindrical housing for concentrically mounting the tubular metallic electrodes in the housing, said annular spacer members allowing free flow of the solution through the inner tubular metallic electrode and having openings for allowing free flow of the solution between the inner and outer tubular metallic electrodes, said annular spacer members being formed of electrical insulating material for electrically insulating the tubular metallic electrodes from each other and from the housing, and means providing external electrical connections to the tubular metallic electrodes, and an electrical resistance responsive device electrically connected to said external electrical connections for responding to the electrical conductivity of the solution.

26. In a dry cleaning system which includes a washer adapted to hold fabrics to be dry cleaned, a filter, conduits interconnecting the washer and filter and a pump for circulating through the washer, filter and conduits a water-immiscible organic dry cleaning solvent which is activated by small proportions of an oil-soluble nonvolatile dry cleaning detergent and water so finely dispersed as to form a substantially clear homogeneous solution, the improvement which comprises an electrical conductivity device including a substantially cylindrical housing, fittings at the ends of the housing for connecting the housing into one of the conduits for circulation of the solution therethrough, a pair of spaced apart concentrically arranged tubular metallic electrodes, a pair of annu- 'lar spacer members receiving the .ends of the tubular metallic electrodes for concentrically supporting the same, means for removably securing the spacer members in the substantially cylindrical housing for concentrically mounting the tubular metallic electrodes in the housing, said annular spacer members allowing free flow of the solution through the inner tubular metallic electrode and having openings for allowing free flow of the solution between the inner and outer tubular metallic electrodes,

vsaid annular spacer members being formed of electrical insulating material for electrically insulating the tubular metallic electrodes from each other and from the housing, and means providing external electrical connections to the tubular metallic electrodes, means including a pipe and a solenoid valve for supplying water to the solution in the system, and an electrical resistance responsive controller electrically connected to said external electrical connections and said solenoid valve for controlling the supply of water to the solution in accordance with the electrical conductivity of the solution for maintaining the water content of the solution at substantially a desired value.

References Cited in the file of this patent 530,617 Canada Sept. 18, 1956