US3323335A

US3323335A - Dry cleaning machine

Info

Publication number: US3323335A
Application number: US435525A
Authority: US
Inventors: Irving N Schneider
Original assignee: Engelhard Hanovia Inc
Current assignee: Engelhard Hanovia Inc
Priority date: 1965-02-26
Filing date: 1965-02-26
Publication date: 1967-06-06
Anticipated expiration: 1984-06-06
Also published as: AT274721B; DE1610939A1; GB1101430A

Description

l. N. SCHNEIDER DRY CLEANING MACHINE `ulne 6, 1967 2 Sheets-Sheet l Filed Feb. 26, 1965 `Fune 6, 1967 N. SCHNEIDER 3,323,335

DRY CLEANING MACHINE Filed Feb. 26, 1965 2 Sheets-Sheet 2 Fmg - l l# Flc-5.3

117 p7 f Trap A TTO/P/VEV nited States Patent Ofi ice Patente, ,ufi

3,323,335 DRY CLEANING MACHINE Irving N. Schneider, Livingston, NJ., assignor to Engelijiard Hanovia, Inc., Newark, N J., a corporation of New ersey Filed Feb. 26, 1965, Ser. No. 435,525 5 Claims. (Cl. 68-18) This invention relates to dry cleaning machines and has particular utility in the eflicient and economical application of dry cleaning solvents.

In dry cleaning machines, the length of time required for a cleaning cycle is of great significance :as it determines the output capacity of the machine. A short operating cycle is particularly desirable -in coin-operated dry cleaning machines, where it means not only greater earning power, but also greater consumer appeal. In recent years, considerable progress has been made in reducing the duration of the dry cleaning cycle by the introduction of new, low boiling point solvents. For instance, the fluorocarbon based solvent, commercially known as Valclene has reduced the time of the solvent removal to 7 minutes from the customary 3() minutes required for the removal of the perchloroethylene solvents generally employed in the dry cleaning industry. The utilization of these low boiling point solvents, however, has -a serious obstacle; their cost is several times higher than that of the customary perchloroethylene solvents. For this reason, these new solvents cannot be used economically in existing dry cleaning machines due to their high solvent loss.

In my copending application U.S. Ser. No. 301,240, filed Aug. 12, 1963, now Patent No. 3,222,896, a novel dry cleaning machine is disclosed having as one principal feature the utilization of a pump capable of handling mixtures of liquid solvent, solvent vapor and air, and-provided with means to introduce cold solvent to the intake of the pump in order to more effectively condense solvent vapors and reduce the loss thereof during operation of the machine. The present application provides further improvements in dry cleaning machines of the type described in the aforesaid patent application.

The principal object of the present invention is to provide a dry cleaning machine in which solvent l-oss is reduced to such a low value as to make the util-ization of these expensive, low-boiling point solvents commercially practicable, and thereby attain the advantages of a considerably shortened dry cleaning cycle.

Another important object of my invention is to provide a dry cleaning machine which utilizes -a novel drying technique for reducing the solvent loss, characterized by the employment of vacuum :and controlled heat-creating pressure and temperature conditions in which the solvent will boil out of the wash load, combined with a novel solvent purication and recovery system which causes rapid and complete condensation of dry cleaning solvent and separation thereof from entrained air.

A further important object of my invention is to provide an automatically lubricated du-al pump system for drawing vacuum on the dry cleaning machine herein described, in order to further reduce solvent losses encountered in cyclical operation of such machines.

Other objects .and advantages of my invention will be apparent during the course of the following description, taken in consideration with the accompanying drawing forming a part of this application, wherein:

FIGURE 1 depicts .a schematic view of the preferred form of my dry cleaning machine;

FIGURE 2 is a diagrammatic view of the heater and temperature control equipment;

FIGURE 3 is a schematic view of an automatic safety lubrication system for the vacuum pumps employed in my dry cleaning machine, and

FIGURE 4 is a diagrammatic View of the sequence timing motor and vacuum controlled switches.

Referring to the drawing, the numeral 11 designates the wash chamber, which is cylindrical, and is designed to withstand vacuum. It is provided with :a seal-tight frontal door. Mounted within this wash chamber 11 is the wash basket 12, having perforated cylindrical wall and being rotatably supported by a sh-aft 13 passing through the back wall of the wash chamber 11. A driving mechanism including motor 14 and conventional drive means indicated by dotted line 16, is provided to rotate the -wash basket 12 selectively at pre-determined speeds. In the preferred form of my invention, three selective speeds are; tumbling speed, at which the centrifugal force acting as the wash load is less than the gravitational force; distributing speed, at which the centrifugal force measured at somewhat smaller radius than that of the wash basket is equal to the gravitational force; and extracting speed, at which the centrifugal force is considerably greater than the gravitation-al force acting on the wash load. As the seal-tight frontal door of the wash chamber 11 and the driving mechanism of the wash basket 12 are of conventional construction, known in the art, they are not illustrated in detail in the drawing.

Secured to the cylindrical wall of the wash basket 12 is the electrical heater 18 which, in the preferred form, consists of a metallic strip wound on the exterior surface of the wash basket and electrically insulated therefrom. lMounted on the wash basket is a thermostat 19, the function of which is to control the drying temperature in the wash chamber. The electrical connections of the heater 18 and the thermostat 19 are shown in FIGURE 2 of the drawing, The shaft 13 supporting and rotating the wash basket 12 is partially hollow and its outside end portion is provided with four insulated electric slip rings, of which 21 and 22 are connected to the

heater

18 and 23` and 24 are connected to the 'thermostat 19, by means of insulated and sealed wires passing through the interior of the hollow shaft. These slip rings receive electrical energy `from the supply terminals 26 as controlled by the relay 27 which is so constructed that, when the thermostat closes the circuit, due to low temperature, between

rings

23 and 24, the relay 27 will be energized assuming the full line position of its contacts and thereby causing the energization of the heater 18. When the maximum desired temperature is reached on the surface of the wash basket, the pre-set thermostat 19 will open the circuit between the

slip rings

23 and 24, deenergizing the l relay 27 and causing the relay contacts to assume the dotted line position, as a result of which, the heater 18 will be deenergized and the cooling period of the wash chamber started. The thermostat thus serves to maintain the temperature of the wash basket within predetermined limits during the period when power is supplied to terminals 26.

Solvent which is employed in the dry-cleaning cycle is initially stored in storage tank 31 which in its preferred form consists of two

compartments

34 and 35 separated by the partition or Weir 36, which permits overflow of solvent from compartment 34 to compartment 35 to separate supernatant water from the heavier solvent in compartment 34. Solvent passes from the storage tank 31 to wash chamber 11 by line 32, controlled by solenoid valve 33 which is normally in closed position.

A further element of my invention is a still 41 which is provided with hot water coil 42 through which hot water flow is controlled by solenoid valve 43. Solvent is dumped from the wash chamber 11 into the still by line 37 provided with valve 38. Valve 38 may be a conventional electrically-controlled solenoid valve, but in a preferred embodiment is hydraulically activated by water under pressure introduced -by line 39 as controlled by threefway solenoid valve 40. Utilization of water line pressure of about V20 p.s.i., normally available in drycleaning machine installation, to activate dump valve 38, facilitates more positive closing of this valve than could be achieved unless an expensive solenoid valve were employed, and is especially necessary to ensure positive closing should bits of lint or dirt settle on the valve facing.

A vapor outlet from the still is provided to pass vaporized solvent by line 44 to the cold water condenser 45 provided with cold water coils 47. Vaporized solvent which condenses in the cold -water condenser 4S is returned by line 46 to storage tank 31. In order to conserve utilities, the cold water ow in coils 47 is controlled by valve 48 responsive to temperature sensor 49 in line 46 so that cold water is passed to the unit only at such times as required by a vapor load in the condensor.

As shown in FIGURE l, line 51 provided with solenoid valve 52 is provided to introduce solvent containing supernatant impurities from compartment 35 of storage tank 31 to still 41. Line 53 controlled by valve 54 is a pressure equalization line between wash chamber 11 and still 41, the function of which is more fully described hereinafter.

In order to `facilitate the cleaning operation, there may be introduced into the wash chamber, along with solvent, minor amounts of liquid detergent. Referring to FIGURE l, a detergent dispenser 50 is provided having ll line 55 provided with solenoid valve 56 and dispensing line 57 provided with solenoid valve 58 leading to the wash chamber 11. A pressure equalization line S9 controlled by solenoid valve 60 connects the vapor space of the wash chamber 11 and of the detergent dispenser 50. Line 55 may be attached to a flexible hose dipping into a container of liquid detergent. In operation with wash chamber 11 under va-cuum, valve 60 is opened, creating vacuum in detergent dispenser 50 which is then lled with a charge of detergent drawn up by vacuum upon opening of valve 56. Valve 56 is then closed, and all or a portion of the detergent charge in detergent dispenser 501 introduced into the wash chamber by line 57, upon opening of valve 58.

An important element of the present invention is recovery chamber 61 which is so constructed as to enable operation at somewhat elevated pressure, for example up to about p.s.i.g. Chamber 61 is provided with inlet vapor line 62 and exit vapor relief valve 63 which can be adjusted to any desired pressure, for example from about 2 to about l0 p.s.i.g. Recovery chamber 61 is `further provided with internal refrigerated coils 64 and baffles 66, the baffles being so arranged as to direct solvent vapor entering by line 62 into contact with coils 64 which are supplied with refrigerant preferably flowing in counter current direction to solvent vapor ow and introduced by line 67 from conventional refrigeration system 68, shown in dotted box, returning thereto by line 69. Recovery chamber 61 is designed to have sucient volume so that the vapor velocity in the recovery chamber is less than about 50 linear feet/ minute in order to fully recover solvent from entering vapors and to avoid entrainment of droplets of condensed solvent in the air which exits by valve 63.

Solvent vapor which condenses in recovery chamber 61 returns by line 71 and line 51 to compartment 35 of storage tank 31. During the major part of the solvent recovery cycle, sufficient heat is provided by solvent vapors to prevent freezing of the solvent on coils 64, but when the solvent vapor ow is reduced, as at the end of a cycle, solvent freezes and accumulates on the coils 64. By-pass line 72 provided with solenoid valve 73 is provided to permit a defrost cycle which is advantageously employed for a short period of time prior to start of each 4 drying cycle to remove any frozen solvent or water which has accumulated on the coils 64.

Another important element of my invention is the vacuurn pumping system, consisting of two

vacuum pumps

81 and 82 which are employed to draw a vacuum on wash chamber 11 by line 83 and to assist in ecient recovery of solvent.

Pumps

81 and 82 are conventional oil lubricated piston pumps, and are cascaded in tandem in order to enable the attainment of a vacuum in the wash chamber of at least about 28 inches of mercury, and preferably as low as 291/2 inches of mercury. By employing a dual pump system, the pressure in wash chamber 11 at the end of the cycle is so low that there is substantially no solvent loss due to retention of liquid solvent 1n the clothes charge.

As shown in FIGURE l, line 84, connecting

pumps

81 and 82 is provided with bypass line 85 provided with solenoid valve 86, and bypass safety relief valve 90. Line 87 provided with check valve 88 is provided to conduct vapor exhaust from pump 82 to still 41. In order to protect the pumps from entrained matter, filter 89 is provided in line 83.

In a preferred embodiment of my invention,

vacuum pumps

81 and 82 are provided with automatic oil level control means in order to protect the pumps from bearing failure due to a lack of proper lubrication. Referring to FIGURE 3, pump casing 101 is shown having an inlet chamber 102 and outlet chamber 103 and piston means 104. The pump casing is partially filled with oil providing splash lubrication of piston driving means 106. Exit line 107 of the pump is provided with trap 108 in which exhaust gases are directed in a circular path resulting in Separation of oil droplets entrained in the exhaust gases. Separated oil drains by capillary line 109 to inlet chamber 102, An oil reservoir 111 is provided with inlet line 112 and connected by bottom entering pipe 113 to oil feed chamber 114. Line 116 provided with check valve 117 permits introduction of oil from feed chamber 114 to pump casing 101.

The operation of the automatic oil level control means is as follows: In normal operation of the vacuum pump, entrained droplets of oil are continuously separated from the pump exhaust in trap 108 and returned by capillary line 109 to the inlet chamber 102 of the pump, thence passing by drain back to casing 101. Oil feed chamber 114 is under the same vacuum as pump casing 101. When the pump operation is stopped, and atmospheric air admitted to chamber 102, pump casing 101 reaches latmospheric pressure, but operation of check valve 117 prevents loss of vacuum in oil feed chamber 114. Consequently, the pressure in casing 101 applied by line 112 to oil reservoir 111 results in transfer of oil from oil reservoir 111 by line 113 to oil feed chamber 114. When the pump is again started, the oil thus transferred to oil feed chamber 114 is `automatically drawn through line 116 by operation of valve 117 into pum-p casing 101. Line 112 is so positioned that excess oil above the desired level in casing 101 returns by gravity to oil reservoir 111. By this means, provided ,the oil level in oil reservoir 111 is occasionally checked, the pump is protected against failure due to lack of proper lubrication.

The operation of the motor drive and various solenoid valves employed in my dry cleaning machine is controlled by a sequence timing motor which operates a conventional cam-type switching arrangement for starting, maintaining `and stopping timed steps in the dry cleaning operation. While such sequence timing mechanisms are well known in the art, and need not be further described here, reference is made to FIGURE 4 which is a diagrammatic view of the sequence timing switches and electrical connections which are employed in controlling two important steps in the sequence operation of the dry cleaning machine.

Referring to FIGURE 4, sequence timing motor 121 receives electrical energy from supply terminals 122 as controlled by

switches

123, 124, 125 and 126. Switch 125 is responsive to pre-set vacuum in wash chamber 11 and is herein referred to as the leak sensor switch. Switch 123 is likewise responsive to pre-set vacuum in chamber 11 and is herein referred to as the dry sensor switch. 'Ihe function of these switches will be described hereinafter.

The operation of my dry cleaning machine is as follows. The wash load is deposited in the Wash basket 12, the door of the wash chamber is closed and vacuum pump 81 is started to create a vacuum in the wash chamber. Air initially present in the wash chamber is exhausted by pump 81 through line 85 to the atmosphere. Referring to FIGURE 4, switch 124 is closed when the machine is started, but sequence timing motor is not activated since

switches

123, 125 and 126 remain open. At predetermined pressure in the wash chamber, e.g. a pressure of 4 p.s.i.a. or less, pre-set leak sensor switch 125 closes, permitting activation of sequence timing motor 121 and initiation of the iill period. It will be appreciated, therefore, that switch 125 acts as a safety switch in preventing sequential operations of the machine, including filling of the wash chamber 11 with solvent, unless a proper vacuum is drawn on the Wash chamber, indicating absence of any appreciable leaks, improper sealing of the frontal door, etc.

Upon initiation of the sequence timing motor 121, valve 86 is closed and solenoid valve 33 opened for a predetermined period of time, admitting wash solvent from compartment 34 of storage tank 31 into the wash chamber 11 by line 32, and starting the wash period. Detergent contained in detergent dispenser 50 is introduced to wash chamber 11 by opening of valve 58. Upon introduction of solvent into wash chamber 11, switch 125 opens because of the reduced vacuum in the wash chamber. At this time, however, switch 126 is closed, permitting continued operation of the sequence timing motor. During the wash period, the wash basket is rotated at tumbling speed for a predetermined period of time.

Prior to completion of the wash cycle, solenoid valve 54 in line 53 connecting Wash chamber 11 and still 41 is opened in order to equalize the pressure in the system, and valve 52 is also opening permittingWater-contaminated solvent to drain from compartment 35 of storage tank 31 to the still by line 51. The addition of cold solvent to the still at this time serves the purpose of cooling hot Water coils 42 which may still be hot from previous wash cycles, and thus prevents flashing of solvent and vapor locking of line 37 when solvent is dumped from the wash chamber to the still.

Following the wash period, dump valve 38 in line 37 connecting the wash chamber and still is opened, permitting solvent to drain from the wash chamber, and the wash basket is rotated first at the distribution speed to cause distribution of the load, and then at the extraction speed to mechanically extract solvent from the wash load. At the termination of the extraction, spinning of the wash basket is stopped for a brief period, e.g. 20 to 30 seconds, to complete draining of solvent from the wash chamber.

The next period is the drying period, during which the wash basket is rotated at tumbling speed, which may be interrupted for short interv-als by distribution speed. At the beginning of the period, all valves on lines leading to the wash chamber are closed and vacuum is applied to the wash chamber by line 83 by operation of

vacuum pumps

81 and 82. At the beginning of the drying period, valve 52 is also closed and hot water enters coils 42 by opening of valve 43 permitting distillation of solvent in still 41 to begin. Check valve 8S prevents passage of vapor from the still to the pressure side of

pumps

81 and 82.

During the drying period, heat is applied to the wash basket by energization of strip heaters 18, and so long as appreciable amounts of solvent are being vaporized from the wash load, the upper temperature limit of thermostat 19 is not reached and heat is supplied continuously. During the initial portion of this period, the vacuum in the wash chamber is not appreciably reduced due to the` high vapor pressure of solvent, but as the solvent evaporates and is removed by line 83, the vacuum gradually increases to the maximum provided |by

pumps

81 and 82, for example to below 28 inches, and preferably below 29 inches of mercury. As the residual solvent in the wash load decreases, the cooling effect due to solvent vaporization decreases, until heat translation conditions are nally reached at Which the thermostat is no longer cooled by solvent vaporization to the lower limit 4at which it is set to energize the heater strips 18. During the drying cycle, switch 126 opens thus preventing energization of the sequence timing motor 121 until such time as sulcient vacuum is attained in chamber 11 to activate dry sensor switch 123. Ordinarily switch 123 is set to close at a vacuum somewhat less than the best vacuum attainable with the vacuum pump system. Activation of switch 123 thus will not occur until substantially all solvent lvapor has been removed from wash chamber 11.

Upon closing of switch 123, e.g. upon reaching a vacuum of 28 inches of mercury in Wash chamber 11 sequence timing motor 121 is activated and solenoid valve 91 is opened, providing a controlled stream of air into the Wash chamber. The air coming in through valve 91 displaces solvent vapor remaining in the wash chamber and thus removes final traces of solvent vapor by evacuation through the pumping system.

It should further be noted that during the drying period, the utilization of dual pumps in tandem provides a further meritoriousv function in solvent recovery. Pump 82 fully removes all liquid solvent from pump 81, and line 84, any residual solvent remaining being trapped in pump 82. Upon shut-down, solenoid valve 92 is closed, land any solvent remaining in pump 82 is conserved until the next drying cycle, pump 81 being used alone for initial evacuation of the wash chamber. Thus even the smallest loss of solvent from the vacuum pump itself is avoided when large amounts of air are evacuatedfrom the system.

Returning now to the solvent recovery system, solvent distills from still 41 during the drying cycle and is condensed in tank 31, filling compartment 34 and overflowing entrained moisture into compartment 35. Uncondensed solvent vapor, together with any entrained air passes by line 62 to recovery chamber 61 where the refrigeration coils 64, coupled with the ba'le arrangement, result in substantially complete condensation of all solvent vapors. Valve 63 set to open at slightly superatmospheric pressure permits venting of air at about 3 p.s.i.g., and it has been found that, if the vapor velocity in chamber 61 is below about 50 linear feet/minute, little or no solvent droplets will escape with the vented air. Typically, in a dry cleaning machine employing 13 gallons Valclene solvent, having a nominal value of $9.00 per gallon, solvent losses using the described m-achine can be held to less than 25 cents per wash load.

Condensed solvent, during the drying cycle, is returned continuously from recovery chamber 61 to chamber 35 by

lines

71 and 51. Upon completion of the drying cycle final traces of solvent and water vapor evaporate from the still 41 to provide the cold solvent reserve in compartment 35 which is employed in the first stage of the subsequent cycle, whereupon valve 43 closes to cut off the hot water supply to coils 42.

Finally, operation of pumps S1 and 82 is terminated and solenoid valve 91 is used to break the vacuum before opening the frontal door of the wash chamber.

It will be apparent to those skilled in the art that the dry cleaning machine described herein is particularly suited for the recovery of maximum amounts of expensive dry cleaning solvent, while avoiding all conditions of vapor and/or liquid blockage in the vapor and liquid transfer lines which could interfere with smooth operation of the machine. The condensation of exhaust vapors from the vapor space of a solvent recovery chamber is particularly advantageous in this respect, since the passage 7 of refrigerated (possibly frozen) solvent through'narrow lines or orices is avoided. The utilization of a dual pump system to provide vacuum and to avoid loss of solvent by blowing vapors into the ai-r is particularly useful in reducing solvent losses to a minimum. Finally, the simplicity of operation and ease of control of necessary hot and cold water utilities makes the machine eminently suitable for coin-operation with minimum attention by an attendant.

It is to be understood that the form of my invention herein described and illustrated is only an example of the same= and that various changes in the size, shape and arrangement of parts may be resorted to, without thereby departing from the spirit of my invention, or the scope of the adjoined claims.

What is claimed is:

1. A dry cleaning machine comprising a storage tank containing cleaning solvent; a wash chamber communieating with said storage tank by means of a pipe connection and a valve which is closed and is operated in response to pressure in said chamber; a wash basket having perforated Wall rotatably mounted within said wash chamber; driving means adapted to rotate said Wash basket at preselecfedspeed; electric heating means mounted on said wash basket; an electric supply for energizing said heating means as controlled by a thermostat creating alternating heating and cooling periods so as to maintain the temperature in said wash chamber between predetermined limits; a still communicating with said wash chamber and having an outlet for vaporized solvent; condensing means adapted to return condensed solvent vaporized from the still to the storage tank; said storage tank having a vapor outlet communicating with a vapor recovery chamber provided with refrigerating means and an exhaust port opening into the atmosphere; means for returning liquid solvent from the recovery chamber to the storage tank, vacuum pump means for evacuating the wash chamber, said vacuum pump means being adapted to conduct solvent vapor from the wash chamber to the still, the vacuum pump means comprises a pump having an inlet chamber, an outlet chamber and a casing with oil-lubricated piston means for drawing gases into said inlet chamber and expelling said gases through the outlet chamber, said casing having an opening at a desired oil level in the casing, an oil reservoir positioned to receive excess oil from said casing by gravitational force and having a first pipe connection to said opening and a second pipe connection to an oil feed chamber having Ia pipe connection to said casing, the pipe connection between the oil feed chamber and casing having valve means to prevent ow of gases from the casing to said oil feed chamber.

2. Apparatus of claim l wherein a valved pipe connection is provided between the wash chamber and the still for equalizing the pressure in the system.

3. Apparatus of claim ll wherein a valved pipe connection is provided between the storage chamber and the still.

4. Apparatus of claim 1 wherein the vacuum pump means consists of dual vacuum pumps interconnected in series arrangement.

5. A dry cleaning machine comprising a storage tank containing cleaning solvent; a wash chamber communicating with said storage tank by means of a pipe connection and ya valve which is closed and is operated in response to pressure in said chamber; a wash basket having perforated wall rotatably mounted within said wash chamber; driving means adapted to rotate said wash basket at pre-selected speed; electric heating means mounted on said Wash basket; and electric supply for energizing said heating means as controlled by a thermostat creating alternating heating and cooling periods so as to maintain the temperature in said wash chamber between predetermined limits; a still communicating with said wash chamber and having an outlet for vaporized solvent; condensing means adapted to return condensed solvent vaporized from the still to the storage tank; said storage tank having a vapor outlet communicating with a vapor recovery chamber provided with refrigerating means and an exhaust port opening into the atmosphere; means for returning liquid solvent from the recovery chamber to the storage tank, vacuum pump means for evacuating the Wash chamber, said vacuum pump means being adapted to conduct solvent vapor from the wash chamber to the still, the vapor recovery chamber containing refrigerated coils and a plurality of spaced baies, the baies being arranged adjacent to and along the coils to provide a sinuous gas ow path adjacent the coils.

References Cited UNITED STATES PATENTS 2,198,412 4/l94() McDonald 68-18 X 2,633,646 4/1953 Smith 68-20 X 3,238,750 3/1966 Candor et al 68-20 FOREIGN PATENTS 383,794 1/1908 France.

WILLIAM I. PRICE, Primary Examiner.

Claims

5. A DRY CLEANING MACHINE COMPRISING A STORAGE TANK CONTAINING CLEANING SOLVENT; A WASH CHAMBER COMMUNICATING WITH SAID STORAGE TANK BY MEANS OF A PIPE CONNECTION AND A VALVE WHICH IS CLOSED AND IS OPERATED IN RESPONSE TO PRESSURE IN SAID CHAMBER; A WASH BASKET HAVING PERFORATED WALL ROTATABLY MOUNTED WITHIN SAID WASH CHAMBER; DRIVING MEANS ADAPTED TO ROTATE SAID WASH BASKET AT PRE-SELECTED SPEED; ELECTRIC HEATING MEANS MOUNTED ON SAID WASH BASKET; AND ELECTRIC SUPPLY FOR ENERGIZING SAID HEATING MEANS AS CONTROLLED BY A THERMOSTAT CREATING ALTERNATING HEATING AND COOLING PERIODS SO AS TO MAINTAIN THE TEMPERATURE IN SAID WASH CHAMBER BETWEEN PREDETERMINED LIMITS; A STILL COMMUNICATING WITH SAID WASH CHAMBER AND HAVING AN OUTLET FOR VAPORIZED SOLVENT; CONDEING MEANS ADAPTED TO RETURN CONDENSED SOLVENT VAPORIZED FROM THE STILL TO THE STORAGE TANK; SAID STORAGE TANK HAVING A VAPOR OUTLET COMMUNICATING WITH A VAPOR RECOVERY CHAMBER PROVIDED WITH REFRIGERATING MEANS AND AN EXHAUST PORT OPENING INTO THE ATMOSPHERE; MEANS FOR RETURNING LIQUID SOLVENT FROM THE RECOVERY CHAMBER TO THE STORAGE TANK, VACUUM PUMP MEANS FOR EVACUATING THE WASH CHAMBER, SAID VACUUM PUMP MEANS BEING ADAPTED TO CONDUCT SOLVENT VAPOR FROM THE WASH CHAMBER TO THE STILL, THE VAPOR RECOVERY CHAMBER CONTAINING REFRIGERATED COILS AND A PLURALITY OF SPACED BAFFLES, THE BAFFLES BEING ARRANGED ADJACENT TO AND ALONG THE COILS TO PROVIDE A SINUOUS GAS FLOW PATH ADJACENT THE COILS.