US3308839A

US3308839A - Method and apparatus for cleaning objects with solvent

Info

Publication number: US3308839A
Application number: US403142A
Authority: US
Inventors: Donald J Barday
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-10-12
Filing date: 1964-10-12
Publication date: 1967-03-14
Anticipated expiration: 1984-03-14

Description

3 Sheets-Sheet l INVENTOR ATTORNEYS D. J. BARDAY METHOD AND APPARATUS FOR CLEANING OBJECTS WITH SOLVENT March 14, 1967 Filed oct. 12, 1964 March 14, 1967 D.J. BARDAY METHOD AND APPARATUS FOR CLEANING OBJECTS WITH SOLVENT 5 Sheets-Sheet E Filed Oct. 12, 1964 INVNTUR ,Doi/ald Jard@ March 14, 1967 D. J. BARDAY 3,308,839

METHOD AND APPARATUS FOR CLEANLNG OBJECTS WITH SOLVENT Filed OC'C. 12, 1964 5 SheetS-Sheet I5 1I/l C 7 INVENTOR Donald Jbardafy ATTORNEYS United States Patent O 3,308,839 METHOD AND APPARATUS FOR CLEANING B] ECTS WITH SOLVENT Donald J. Bai-day, 721 16th St., Boulder, Colo. 80302 Filed Oct. 12, 1964, Ser. No. 403,142 11 Claims. (Cl. 134-76) This invention relates to an apparatus for cleaning objects by contacting them with a fluid solvent and, it more particularly relates to a vapor degreasing type of such apparatus.

Pre-existing vapor degreasers drastically heat the liquid solvent in the wash tank to generate a vapor zone above it. This introduces contaminants into Ithe vapor zone and promotes vapor losses, which become significant when more expensive solvents are utilized. This solvent loss is particularly serious with respect to the fluorinated hydrocarbons and the more volatile chlorinated hydrocarbons, which have quite advantageous cleaning properties. They leave little or no residue on cleaned parts upon evaporation and are not injurious to plastics, code markings, electrical insulating materials and the like, but they are relatively expensive. This makes it uneconomical to tolcrate the normal losses occurring in industrial cleaning from vapor losses and solvent contamination. Such fluorinated hydrocarbon solvents are trichloromonouoromethane, trichlorotriuoroethane, tetrachlorodifluoroethane, or any mixture of them. Such chlorinated hydrocarbon solvents are methyl chloroform, methylene chloride, carbon tetrachloride, or any mixture of them and the lluorinated hydrocarbon solvents. Other advantageous mixtures may contain alcohol or a relatively non-volatile chlorinated hydrocarbon such as trichloroethylene..

An object of this invention is to provide an efficient, simple and economical apparatus for cleaning objects by contacting them with a uid solvent.

Another object is to provide such apparatus of the vapor degreasing type. Y

A further object is to provide such apparatus that minimizes solvent losses and makes it possible to economically utilize the efficient, more volatile and expensive cleaning solvents.

In accordance with this invention, vapor zone in a vapor cgreaser is maintained by ash evaporating the solvent liquid from a fine spray at temperatures below the normal boiling temperature of a `body of the liquid. This minimizes the carryover of contaminants from liquid into the vapor, facilitates dense saturation of the vapor zone and makes it possible to selectively evaporate the more volatile from a mixture of solvents. A more volatile and expensive solvent can thus be mixed with a less volatile and more economical wash solvent and be selectively utilized in the vapor zone and for rinsing in a single chamber unit.

The vapor zone may be effectively maintained by continuously flooding and withdrawing the generated vapor from the area above the liquid. This may be eiliciently performed by evaporating a spray of wash solvent `upon the heat emitting section of a heat pumping system, and by directing the withdrawn vapor over the heat absorbing section of the same system to condense the liquid from it. This productively utilizes all of the energy in the heat pumping system and provides a supply of pure solvent for rinsing purposes. The heat pumping type of vapor generating, solvent recovering and purifying system is of the type described and claimed in U.S. Patent 3,070,463 by this same inventor.

When a mixture of solvents of differing volatility is utilized, the more volatile component can be selectively evaporated into the vapor. This provides maximum cleaning and rinsing efficiency in the vapor zone with a relatively small amount of more volatile and expensive solvent. Rnsing with relatively cool solvent also cools the 3,308,839 Patented Mar. 14, 1967 lCC objects below the temperature of the saturated vapor zone to condense solvent liquid upon the objects which supplements the rinsing spray.

A vapor barrier or blanket of unsaturated air may be maintained directly over the warm saturated vapor zone to isolate it from the ambient atmosphere and to abstract any drops of solvent clinging to the objects. This air blanket may be maintained by continuously withdrawing air and any absorbed vapor from above the warm saturated vapor zone, cooling it to condense any solvent vapor in it and returning the dry air above the vapor zone. In an apparatus open to atmosphere the dry air is returned over it at a temperature cooler than atmosphere to form a dense blanket. The rinsed objects from the vapor zone are thus completely dried in the unsaturated vapor air barrier or blanket before leaving the apparatus and all solvent is retained within the apparatus. Since 4the temperature of the warm vapor zone is higher than that of the vapor barrier or blanket, the heat absorbed from the vapor zone into the vapor barrier further unsaturates it and improves its drying efficiency. The air withdrawn from above the warm vapor zone may also be advantageously cooled by the heat absorbing section of a heat pumping system and the abstracted condensate utilized for rinsing. The unsaturated vapor barrier may be condensed separately or in conjunction with the saturated vapor zone.

The heat balance of the heat pumping system may be maintained by an auxiliary cooling section for helping condense the vapor because more heat is emitted by a heat pump than is absorbed. The efficiency of condensation of more volatile liquids can be improved by channeling the vapor through a cooled packed redux column saturated with solvent liquid before contacting the vapor upon the heat absorbing element. The reflux column is maintained saturated by an extra cooling coil mounted above it that drips liquid solvent through it.

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

FIG. 1 is a diagrammatic cross-sectional view in elevation of a vapor degreasing apparatus that is one embodiment of this invention;

FIG. 1A is a diagrammatic cross-sectional view in elevation of a modification of the vapor condensing portion of the apparatus shown in FIG. 1;

FIG. 2 is a perspective view partially broken away of a vapor degreasing apparatus that is another embodiment of this invention;

FIG. 3 is a top plan view partially broken away in cross section of the apparatus shown in FIG. 2;

FIG. 4 is a cross-sectional View taken through FIG. 3 along the line 4 4; and

FIG. 5 is a diagrammatic cross-sectional view in elevation of a separately contained solvent purifying and recovering apparatus.

As shown in FIG. l, pump 16 draws dirty wash solvent 10 from the bottom of tank 12 of vapor degreasing cleaning apparatus 14 through lter 18. Pump 16 discharges into solvent heating and evaporating chamber 20 by spraying solvent through perforated pipe 22. Solvent evaporating chamber 20 contains the heat emitting element 24 of a heat pumping system 27 which includes a refrigerant compressor 28 and a heat absorbing element 30. These elements together with an expansion valve 32 and a refrigerant receiver 34 are connected in a closed heat pumping system by piping 36. Heat emitting or rejection section 24 is, for example, the refrigerant condensing coil of a heat pumping system 27; and heat absorbing section 30 is, for example, the refrigerant evaporating coil.

Heat absorbing element 30 is enclosed within a solvent condensing chamber 38, and a vapor conduit 40 connects solvent condensing chamber 38 to cleaning machine tank 12. Solvent evaporating chamber 20, on the opposite side of cleaning machine tank 12, is connected to tank 12 by conduit 41. The outlet from conduit 41 and the inlet to conduit 40 are at about the same elevation. This elevation controls the height of the saturated vapor zone 66 in tank l2.

Vapor produced in solvent evaporating chamber 20 is conducted by conduit 41 into cleaning machine tank 12 by distribution header 45 (laterally extended but not so shown). As saturated vapor in cleaning machine tank 12 rises to the level of vapor collecting header 47 (also laterally extended but not so shown), it spills into collecting header 47 and is conducted by conduit 40 into solvent condensing chamber 38.

Blower fan 48 induces a flow of saturated vapor into collecting header 47 and, at the same time, induces flow of a vapor-air mixture 64 from above saturated vapor zone 66. The resultant mixture of saturated vapor and vapor-air mixture is conducted by conduit 40 into solvent condensing chamber 38. Heat absorbing element 3|) converts most of the vapor entering solvent condensing chamber 38 to pure liquid solvent by cooling the vapor to about 35 F. Blower fan 48 draws air, unsaturated with vapor into conduit 49 and discharges a relatively cool mixture thereof into cleaning machine tank 12 through distribution header 50 (also laterally extended but not so shown) at an elevation higher than the saturated vapor zone. A damper 51 in conduit 49 provides a means for fine adjustment of air flow `back into tank 12.

The mixture is cooler than the ambient atmosphere. Thus a relatively cool and relatively dense layer of air and vapor forms a blanket 64 over the saturated vapor 66 in the machine. Blower fan 48 and distribution header S0 are designed to provide a relatively slow exit velocity of air and vapor mixture. This assures its stratification and substantially prevents the intermixing of outside air and the resultant escape of solvent vapor from the top of tank 12.

Although the air returned to tank 12 through conduit 49 and distribution header 50 is saturated with solvent vapor at about 35 F., the air vapor blanket 64 itself is somewhat above 35 F. or approximately 50 F. to 60 F. Therefore, blanket 64 is not saturated with vapor but is only 60 to 70% saturated. Heat conducted into blanket 64 from the relatively warm vapor zone 66 below, the relatively warm air above and the sides of the cleaning machine account for some temperature increase and a corresponding reduction in saturation value or relative humidity. Since blanket 64 is not saturated with solvent vapor, warm parts emerging from the machine and passing through it dry promptly by evaporation of liquid from their surface.

Three factors contribute to rapid drying of parts in the air-vapor barrier zone 64. (l) Parts passing through the saturated vapor zone 66, below, are warmed by vapor condensing on the part in final rinse operation; (2) the air-vapor blanket is not saturated with solvent vapor and has the capacity to absorb additional vapor; and (3) the vapor rinse solvent is relatively volatile and has a characteristically high evaporation rate.

Solvent system cycle of operation of FIG. l

Compressor 28 and pumps 16 and 46 are started. Blower fan 48 is started. Pump 46 withdraws pure reclaimed solvent from storage tank 62 and forces the liquid through rinse spray nozzles 53. Cleaning machine tank 12 may either be empty or may contain an operating charge of relatively non-volatile wash solvent. In the first case, where a homogeneous precision solvent is used alone, liquid discharged from spray nozzles 53 enters the inlet to pump 16 as this liquid falls to the bottom of tank 12.

In the second case, liquid is immediately available to pump 16.

Pump 16 supplies both the wash spray nozzles 52 and perforated pipe 22 within solvent evaporating chamber 20.

As pumps 46 and 16 force liquid solvent through spray nozzles 53 and 52 respectively, some of the liquid evaporates in chamber 20 and fills cleaning machine tank 12 with vapor up to the saturated vapor line 68. Thereafter, vapor enters collecting header 47 and is conducted by conduit 40 to heat absorbing element 30.

Heat taken up by heat absorbing element 30 in the process of condensing this vapor to liquid, is promptly transferred to heat emitting element 24 by the refrigerant pumped by compressor 28. As discharge pressure of compressor 28 increases, a pressure-operated, modulating solvent control valve 54 admits liquid solvent to perforated pipe 22.

The liquid solvent is distributed uniformly over heat rejecting element 24 and it cascades downward in a thin film to wet the entire surface of the heat rejecting element 24. The more volatile precision solvent component such as trichlorotriuo-roethane, easily liash evaporates from a mixture containing it, and thevresultant vapor enters cleaning machine tank l2 through conduit 4l and distribution header 45. Less volatile solvent com ponents, such as trichloroethylene, and soluble contat'nxnants, such as oil, grease, ux, resins and the like, are returned to tank 12 as liquid through drain line 55.

Solvent control valve 54 admits liquid solvent to distribution header 22 and heat emitting element 24 in precisely the proper amount to maintain a constant surface temperature of heat rejecting element 24. Flow valve 54 can be adjusted to maintain any heat rejecting temperature within the range of 75 F. to 150 F. and possibly higher. Therefore, the heat emitting temperature can be precisely controlled to cause evaporation of a precision solvent component while less volatile components and contaminants are returned to cleaning machine tank 12 as liquid. Consequently, vapor in the machine tank 12 and vapor entering solvent condensing chamber 38 is substantially pure, homogeneous solvent of the precision cleaning type. Flash evaporation without liquid boiling eliminates entrainment of contaminated liquid droplets in the vapor.

Since a heat pumping system rejects more heat than it absorbs (in the amount of heat equivalent of electrical energy supplied to the compressor drive motor) it is in herently thermally unbalanced. Heat dissipated through conduction, convection and radiation from machine tank 12 tends to rebalance it thermally. An auxiliary watercooled heat absorbing element 56 is also located in the upper part of solvent condensing chamber 38 to intercept and condense some of the solvent vapor entering chamber 38. Heat absorbed by element 56 is transferred to the cooling water and is removed from the system to positively maintain its thermal equilibrium. Furthermore, energy supplied to the compressor motor is utilized to evaporate more solvent than otherwise would be produced by transferral of heat from heat absorbing element 30 to heat rejecting element 24.

A pressure-operated, modulating ow control valve 57 admits precisely the proper amount of water to auxiliary heat absorbing element 56 to maintain thermal equilibrium conditions at all times. Flow control valve 57 senses discharge pressure of compressor 28 and admits cooling water to auxiliary heat absorbing element 56 only when the temperature of heat rejecting element 24 tends to rise above the predetermined operating temperature and the discharge pressure of compressor 28 tends to rise above the predetermined operating pressure.

A third auxiliary or supplemental heat absorbing element S8 is in a heat transfer relationship with refrigerant piping 36. Supplemental heat absorbing element S8 subcools liquid refrigerant before it is expanded within heat absorbing element 30. Heat absorbing element 58 may also function as an auxiliary refrigerant condenser during periods when precision solvent is being recovered for storage in reservoir 62, particularly toward the end of the recovery cycle. Heat absorbing element 58 may also function as an auxiliary refrigerant condenser during periods when the cleaning machine is not in use and full recovery of precision solvent is not desired. Water flow control valve 59 admits water to heat absorbing element 58 only when auxiliary cooling of refrigerant is necessary. While cleaning operation is suspended, precision solvent remains in tank 12 and the heat pumping system operates periodicaly to maintain the cool air blanket and prevent the loss of solvent vapor. Automatic operation is easily attained by the use of temperature operated and pressure operated controls of conventional type.

The selective vapor generating aspects of this provide a simple and economical method of using a mixture of a relatively expensive precision cleaning solvent, such as trichlorotrifluoroethane, and a relatively inexpensive solvent, such as trichloroethylene. Stich selective flash evaporation also makes it possible to utilize an azeotropic mixture for wash purpose and a substantially homogeneous precision solvent for rinse purpose. For example, an excess of trichlorotrifluoroethane can be added to an azeotropic mixture of trichlorotrifluoroethane and methylene chloride or to an azeotropic mixture of trichlorotrifluoroethane and ethyl alcohol. Vapor in the machine and Vapor condensed to liquid is substantially pure trichlorotriiluoroethane while wash liquid in the machine has the composition of the azeotrope. The parts are rapidly dried in the unsaturated air-vapor zone be fore they leave the machine thus eliminating solvent loss by evaporation of solvent from parts outside the machine. All of the volatile solvent is thus purified and reclaimed for repeated use. Heat-sensitive solvents, such as methyl chloroform, may also be efiiciently used in a vapor degreasing operation without the danger of solvent decomposition. The low temperature vapor zone also contributes to the overall efficiency of operation, purity of vapor and avoidance of undue solvent losses.

Cleaning cycle of operation of FIG. 1

The cleaning cycle with respect to parts or assemblies moving through the apparatus shown in FIG. l is as follows:

A conveyor or other means, not shown, lowers parts into cleaning machine tank 12 along the right-hand side of the tank along path 63 as shown in FIG. l. Parts pass through the cool air-vapor blanket 64 then into the saturated vapor zone 66 and between the wash spray nozzles 52.

The parts or objects then enter the immersion wash bath at the bottom of tank 12 near the ultrasonic transducers 26 and are exposed to ultrasonically agitated liquid solvent to remove adherent soils. The parts continue through the immersion wash solvent 10 to the left-hand side of the tank shown in FIG. 1 where they emerge from wash solvent 10 and pass through a pure liquid spray rinse from spray nozzles 53 in saturated vapor zone 66. The rinse solvent discharged through nozzles 53 is relatively cool and, consequently, the parts being cleaned are cooled to a temperature well below the temperature of the vapor in the saturated vapor zone 66. The cooled parts are then within the saturated vapor zone and pure vapor promptly condenses on them to help rinse them with precision cleaning solvent.

As the parts leave saturated vapor zone 66, they are warmed up to approximately its temperature and wet with liquid solvent. As these parts pass through the relatively cooler and unsaturated air-vapor blanket zone, a combination of effects causes all liquid to evaporate from them. The vapor so evolved is retained in the cleaning apparatus system as condensed rinsing solvent as the dry, clean parts pass out of the apparatus.

In FIG. 2 is shown a modified version 14A of vapor degreaser 14. lt includes tank 12A similar to tank 12 which is enclosed on sides and bottom by casing 70A shown in phantom but open on the top. The near side of tank 12A is removed to facilitate illustration of its interior. Wash and rinse sprays 52A and 53A are disposed in

wall

92A and 78A (removed in FIG. 2). All portions not specifically mentioned herein are similar to those in apparatus 14.

The principal difference in apparatus 14A from 14 is separate vapor condensing system 72A for unsaturated air-vapor zone 64A. Zones 64A and 66A are not shown and are similar to 64 and 66. As shown in FIGS. 2-4, vapor condensing system 72A includes a cooling chamber 74A through which the air-vapor mixture from unsaturated barrier zone 64A is passed. The air-vapor mixture is withdrawn through a set of slots 76A (shown in FIG. 3) in the side of wall 78A (removed in FIG. 2). The mixture accordingly enters abstracting header 47A and is conducted therefrom into condensing chamber 72A through duct 80A. The mixture is cooled by contact with cooling coils 82A and then passed through pump or fan 84A driven by motor 86A into return header 45A. Slots A in wall 92A feed the dried and cool air-vapor mixture in an unsaturated condition to unsaturated vapor barrier or blanket zone 64A. The heat from saturated vapor zone 66A below it and the ambient heat raises the temperature of barrier zone 64A to further unsaturate it and improve its drying ability. The air blanket is accordingly maintained through a separate abstracting. cooling and return system over the saturated vapor zone 66A the same as shown in FIG. 1. Cooling coils 82A may be part of a heating pumping system similar to that described in conjunction with FIG. 1, but it also might be a separately cooled system such as by water circulation. The condensate from condensing chamber 72A passes through pipe 94A into liquid solvent storage tank 62A.

Ultrasonic generator

65A powers transducers 26A in the sloped bottom wall 67A of tank 12A that sheds solid soil. Bypass duct 69A around blanket zone condenser 72A controls the temperature of the air-vapor mixture returned to zone 64A above saturated vapor upper limit 68A in conjunction with butterfly valve 71A and control handles 73A. Apparatus 14A is controlled from panel 75A in conjunction with instrument panel 77A. Sattlrated vapor is fed into tank 12A through header 45A as shown by arrows 79A, and the overflow is withdrawn through header 47A as shown by arrows 81A. The liquid solvent level is shown by the line 11A.

In FIG. 1A is shown a modification of solvent condensing chamber 38B in which a reflux column 96B is interposed in the path of vapor collected by header 47B and conducted through duct 40B. Reflux column 96B includes a series of baffles 98B between which packing 100B having extended surface such as wool is packed. Bati'les 98B are effectively made of stainless steel. Column 95B is maintained saturated with solvent liquid by dripping it down upon it from an extra cooling coil 102B mounted above it. This cooling coil may be cooled by water circulation or by `heat absorbing section of a heal pump. Reflux column 96B enriches the vapor before it contacts condensing coil 30B to improve the overall cfiicicncy of condensation. This is particularly true where a more volatile cleaning solvent is utilized.

FIG. 5 shows a separately contained solvent purifying and recovering apparatus C of the type described and claimed in U.S. Patent 3,070,463 by this same inventor. It includes a solvent evaporating chamber 20C and a solvent condensing chamber 38C between which reflux column 96C is mounted. Unit 110C can be used to purify the main body of wash solvent 10 of apparatus 14 when it becomes loaded with contaminants. Solvent 1I) is sprayed through pipe 22C of heat emitting coils 24C and vapor is fiash evaporated to pass in the direction of arrow 112 C toward reflux column 96C. Excess solvent not evaporated is returned to tank l2 through drain connection 114C. The vapor is enriched in reflux column 96C in the manner previously described and ultimately condensed by heat absorbing coil 30C which is advantageously part of a heat pumping system that also includes heat emitting coil 20C. The purified solvent is returned to tank l0 through outlet 116C.

What is claimed is:

l. An apparatus for cleaning objects by contacting them with a solvent liquid comprising a tank for containing said liquid and its vapor, vapor generating means connected to said tank for establishing and maintaining a warm saturated vapor zone above the level of said liquid, first vapor abstracting means connected to said tank a distance above said liquid level for limiting the upper level of said warm saturated vapor zone, second means for abstracting the mixture of air and solvent vapor disposed within said tank above said saturated vapor zone and said first vapor abstracting means, means for drying said abstracted mixture and returning it above said warm saturated vapor zone to provide a cool unsaturated air blanket above it to shield said warm saturated vapor zone from the ambient atmosphere, the portion of said tank between said warm saturated vapor zone and said blanket being free of any means preventing said blanket from directly contacting said warm saturated vapor zone, and conveyor means for moving said objects from said liquid where they are washed through said warm saturated vapor zone where they are rinsed and through said blanket where they are dried.

2. An apparatus as set forth in claim 1 wherein rinse spray means is disposed within said tank within said warm saturated vapor zone in the path of movement of said object.

3. An apparatus as set forth in claim 1 wherein said drying means comprises cooling means for condensing said vapor and cooling said air below the temperature of the ambient atmosphere to blanket said warm saturated vapor zone from said ambient atmosphere.

4. An apparatus as set forth in claim 1 wherein said vapor generating and first vapor abstracting means are respectively comprised by the heat emitting and heat absorbing sections of a heat pumping system whereby the energy in said system is completely utilized, and said heat absorbing action being adjusted to condense said vapor.

5. An apparatus as set forth in claim 4 wherein said vapor generating means comprises spray means for discharging a fine spray of said solvent liquid upon said heat emitting section of said heat pump whereby said vapor is flash evaporated from said liquid at a relatively low temperature.

6. An apparatus as set forth in claim S wherein an auxiliary cooling section is mounted adjacent said heat absorbing section of said heat pumping system for maintaining said system thermally balanced.

7. An apparatus as set forth in claim 4 wherein a pure liquid solvent reservoir is provided, a connection from said first vapor abstracting means to said reservoir for draining said liquid condensed in said rst vapor abstracting means to said reservoir, pumping means connected to draw from said reservoir, rinse spray means mounted in said tank Within said Warm saturated vapor zone, said pump being connected to supply said rinse spray means with relatively cool solvent whereby the temperature of said objects in said rinse spray is lowered whereby additional vapor is condensed upon said objects from said warm saturated vapor zone for helping rinse them.

8. An apparatus as set forth in claim 7, wherein a wash solvent pumping means is connected to said tank for drawing said liquid solvent from it, wash spray means in said warm saturated vapor zone, piping connecting said wash solvent pumping means to said wash spray means and to evaporating spray means for discharging it in heat exchange relationship with said heat emitting section of said heat pumping system, and drain means from said heat emitting section to said tank for returning excess unevaporated solvent to it.

9. An apparatus as set forth in claim 7 wherein a reflux column is disposed in front of said heat absorbing section of said heat pump, solvent liquid supplying means being disposed at the top of said column for dripping liquid solvent through said column, vapor conducting means for passing said vapor through said column into said heat absorbing section, and packing means in said column for collecting and holding said liquid dripped through it from said auxiliary cooling means to enrich said vapor directed into said heat absorbing section and to improve liquid recovery from said vapor.

10. An apparatus as set forth in claim l wherein said rst and second abstracting means for said warm saturated vapor and cool unsaturated mixture of air and vapor above said warm saturated vapor zone comprise a single abstracting means disposed at said upper level of said warm saturated vapor zone.

11. An apparatus as set forth in claim 1 wherein said first abstracting means for said warm saturated vapor zone is disposed adjacent the upper level of said warm saturated vapor zone and said second abstracting means for said cool mixture of air and vapor above said saturated vapor zone is disposed a substantial distance above said upper level of said warm saturated vapor zone for effectively defining the upper level of said air blanket.

References Cited by the Examiner UNITED STATES PATENTS 1,892,652 12/1932 Heath 203-87 X 2,220,125 11/1940 Seaton 134-11 2,265,762 12/1941 McKittriCk et al. 203-10() X 2,755,208 7/1956 Kearney 134-11 2,896,640 7/1959 Randall et al. 134-11 X 2,949,119 8/1960 Smith 134-76 X 3,030,913 4/1962 Arnold et al. 134-11 X 3,070,463 12/1962 Barday 134-11 3,074,417 1/1963 Lisowski et al 134-76 3,106,927 10/1963 Madwed 134-76 3,106,928 10/1963 Rand 134-79 CHARLES A. WILLMUTH, Prl'mray Examiner.

R. L. BLEUTGE, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION Patent Nou 3,308,839 March 14, 1967 Donald Jo Barday It is hereb;r Certified that error appears in the above numbered patent requiring Correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, lines 2 and 3, and in the drawings, sheets l to 3, for "METHOD AND APPARATUS FOR CLEANING OBJECTS WITH SOLI/ENT" read APPARATUS FOR CLEAN ING OBJECTS WITH SOLVENT column l, line 39, after "Such" in- Signed and sealed this 7th day of November 1967.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting fficer

Claims

1. AN APPARATUS FOR CLEANING OBJECTS BY CONTACTING THEM WITH A SOLVENT LIQUID COMPRISING A TANK FOR CONTAINING SAID LIQUID AND ITS VAPOR, VAPOR GENERATING MEANS CONNECTED TO SAID TANK FOR ESTABLISHING AND MAINTAINING A WARM SATURATED VAPOR ZONE ABOVE THE LEVEL OF SAID LIQUID, FIRST VAPOR ABSTRACTING MEANS CONNECTED TO SAID TANK A DISTANCE ABOVE SAID LIQUID LEVEL FOR LIMITING THE UPPER LEVEL OF SAID WARM SATURATED VAPOR ZONE, SECOND MEANS FOR ABSTRACTING THE MIXTURE OF AIR AND SOLVENT VAPOR DISPOSED WITHIN SAID TANK ABOVE SAID SATURATED VAPOR ZONE AND SAID FIRST VAPOR ABSTRACTING MEANS, MEANS FOR DRYING SAID ABSTRACTED MIXTURE AND RETURNING IT ABOVE SAID WARM SATURATED VAPOR ZONE TO PROVIDE A COOL UNSATU-