US 3775053 A
A continuous process of recovering dirty non-flammable solvent after discharge from a remote applicator moving over a fabric being cleaned. Immediate vacuum extraction of the dirty solvent from the applicator with purification effected by boiling and condensation, condensate recirculated to applicator. Portable apparatus adapted for in-situ use includes an applicator to spray the solvent under pressure, vacuum pump structure for suction extraction and to provide some of the pressure which is augmented by a liquid pump, electric or combustible gas means to boil dirty extracted solvent, condensa to distil pure solvent introduced into a supply tank for recirculation through the applicator.
Description (OCR text may contain errors)
llnited States Patent 1191 Wisdom [451 Nov. 27, 1973 CONTINUOUS SOLVENT RECOVERY PROCESS  Inventor: Dorothea R. Wisdom, 23017 Kent St., Torrance, Calif. 90505  Filed: Nov. 12, 1971  Appl. No.: 198,111
 References Cited UNITED STATES PATENTS Brewer Dapprich Charreau 68/18 C Hays 15/321 Wisdom 15/322 X Primary Examiner-Mayer Weinblatt Attorney-Brian J. Wood [5 7] ABSTRACT A continuous process of recovering dirty nonfiammable solvent after discharge from a remote applicator moving over a fabric being cleaned. Immediate vacuum extraction of the dirty solvent from the applicator with purification effected by boiling and condensation, condensate recirculated to applicator. Portable apparatus adapted for in-situ use includes an applicator to spray the solvent under pressure, vacuum pump structure for suction extraction and to provide some of the pressure which is augmented by a liquid pump, electric or combustible gas means to boil dirty extracted solvent, condensa to distil pure solvent introduced into a supply tank for recirculation through the applicator.
9 Claims, 8 Drawing Figures PATENTED NOV 2 7 I975 SHEET 10F 3 Pmimwmm 1913 I 3; 775.053
SHEET 2 OF 3 7'0 VACUUM PUMP r0 mow/w PUMP /6 F76.
CONTINUOUS SOLVENT RECOVERY PROCESS FIELD OF THE INVENTION The invention relates to a continuous process of recovering soil laden solvent as it is being used with a remote applicator for cleaning drapes, upholstery, rugs,
and like fabrics, with the solvent being purified and re-' cycled to the applicator. The invention also provides apparatus expressing the process.
BACKGROUND OF THE INVENTION AND PRIOR ART The present invention is particularly, but not exclusively, directed to cleaning of drapes, rugs and carpets, upholstery, and like fabric, whilst the same are in place. That is to say for example light and, particularly, heavy drapes can be cleaned by the instant process without taking them down, and are dry in a few hours.
Fluorocarbon solvents are commonly used for such cleaning purposes, and are expensive; consequently they are often reclaimed and regenerated. A classical method of regenerating solvents is by boiling and subsequent distillation, with or without filtering. U.S. Pat. No. 3,177,126 issued to Charreau in 1965 teaches process and apparatus for purifying solvents by evaporation at a temperature substantially below boiling point in an atmosphere swept by a hot inert gas. A mixture of gas and vapors is cooled and the solvent recovered in a liquid state. This is a process adapted to operate continuously, the regenerated solvent being returned to a cleaning machine and reused. This ingenious process is well adapted for use with a stationary cleaning machine such as is commonly used in a dry cleaning establishment.
U.S. Pat. No. 2,924,557 of which De Furia is the inventor, is directed to a closed filter and distillation system particularly well adapted for use with a solvent having noxious fumes, the apparatus being directly connected to existing systems of a dry cleaning plant.
A process capable of expression in portable apparatus which can be taken, for instance, to the home of a customer for cleaning drapes and upholstery in-situ without taking down the drapes, and without removing the upholstery fabric, which apparatus is also capable of cleaning rugs and carpets and, at the same time of effecting a continuous withdrawal and cleaning of soil laden solvent with recycling for continuous use, is not known to the present inventor.
OUTLINE OF THE INVENTION In the contemplated uses the solvent is sprayed upon the fabric. While, in one expression of the invention, the spray is confined in an applicator, this is not a closed circuit since at least some of the sprayed solvent escapes into the atmosphere. Consequently, and because of heat later applied effects change of state, use
of a nonflammable solvent is required, and it is in a practical sence required that the solvent have little or no odor or, at least, have an odor which quickly disap pears.
Broadly the method withdraws soil laden solvent from the fabric as it is being cleaned, the withdrawn solvent being then in a liquid state with the soil in solution. A first change of state is effected changing the liquid solvent to a gas. In the first change of state the soil in solution does not pass over, and means are provided for collecting, and for disposing of, the soil. A second change of state follows wherein the gas, now without material soil content, is changed to clean liquid solvent. The clean solvent is collected and introduced into a tank for recirculation and spraying. This completes a continuous cycle.
An embodiment of the apparatus includes vacuum means for withdrawing the soil laden solvent from an applicator used to clean the fabric, means to effect the first change of state by adding heat to change the liquid to gas, means to effect the second change of state condensing the gas to clean solvent, the clean solvent then being introduced into a solvent tank supplying clean solvent under pressure to be sprayed on the fabric by the applicator.
A detail description following related to drawings, exemplifies apparatus by means of which the process is accomplished, the detail description also sets forth further particulars of the process. The invention can be expressed in process and in apparatus other than particularly described below.
DESCRIPTION OF THE DRAWINGS FIG. 1 shows means effecting recovery of soil laden solvent and removal of the soil therefrom by a continuous process according to the invention, recovery and removal being concurrent with cleaning, the means aforesaid being shown in side elevation with parts broken away to show interior construction, and an applicator being shown in perspective.
FIG. l-A is an alternative means for extracting heat to change state of the solvent from gas to liquid, being an elevation of an air cooled condenser.
FIG. l-B is a further alternative means for extracting heat, being an evaporation condenser with parts broken away to show interior construction.
FIG. 2 is an alternative means for changing state of the solvent from liquid to gas, heat being supplied by an electrical heating element, the said means being shown in vertical section with some parts not sectioned.
FIG. 3 is a change of state means alternative to FIG. 2, heat being supplied by a combustible gas.
FIG. 4 is a top plan of an intake pipe of the FIG. 3
FIG. 5 is a perspective detail of the applicator.
FIG. 6 is a side elevation of the applicator viewed from 66 FIG. 5, with parts broken away to show interior construction.
PREFERRED EMBODIMENT, MEANS DESCRIPTION OF FIG. 1
Apparatus means designated generally 10, has a solvent recovery tank 11 having a vacuum gauge 11.1, and a solvent tank 12 having a liquid gauge 12.1, a pressure gauge 12.2, and a pressure relief valve 12.3. The tanks are secured to a frame 13 having wheels 14 for movement on a floor 15.
A vacuum pump 16 is secured to lower members of the frame 13, and an intake pipe 17 extends vertically upwards through the tank 11 as shown. The pipe 17 has an upper open bell mount 18 spaced below a top wall 19 of the tank. A solvent recovery intake pipe 21 extends inwards through a side wall of the tank, the intake having a downturned inner discharge end 22.
The vacuum pump 16 has a discharge pipe 23 leading from a discharge port of the pump to an inlet port 24 of a condenser 25. A check valve 23.1 of the discharge pipe permits flow only in a direction shown by an arrow luouuu m,
23.2. The condenser has a helical coil 25.1, and a discharge pipe 25.2 extends centrally downwards within the solvent tank 12 as shown, with the condenser being disposed centrally above the solvent tank.
A solvent outlet pipe 26 leads downwards from an outlet port 27 of the tank 12 to an inlet port of a liquid pump 28 a discharge line 29. A pressure gauge 29.1 is provided in the discharge line 29 as shown, an outer end of the line being adapted for securing a flexible hose 31 thereto. The flexible hose 31 extends to a fluid inlet connection 32 of a remote applicator 33. The applicator shown is a known two chamber hand tool, later described. A fluid outlet, or vacuum, connection 34 of the applicator is adapted for securing a second flexible hose 35 thereto, the hose 35 being of a relatively large diameter extending to the recovery intake line 21 aforesaid, and being attached to an outer end thereof.
An electric motor 36 is secured to lower members of the frame 13 as shown, and is operatively connected by drive means 37 and 38 adapted to drive, respectively, the liquid pump 28 and the vacuum pump 16. A male receptacle 39 is provided on an end member of the frame, with a three conductor cable 41 extending from the motor to the receptacle.
A bottom wall of the recovery tank 11 is designated 42, closely spaced heating elements severally 43 being provided as shown spaced above the tank bottom wall 42. A second male receptacle 39.1 and a second three conductor cable 41.1 supply the heating elements, switches 39.2 and 39.3 are provided to control the motor and the heating elements respectively. MECHANICAL OPERATION Mechanical operation of the apparatus is as follows.
A solvent 44 is introduced into the solvent tank 12 through a filler spout 45 having a removable pressure cap 46. The solvent has particular properties exemplified later herein. With power lines (not shown) plugged into each of the receptacles 39 and 39.1, when the switches 39.2, 39.3 are on the motor drives the liquid pump 28 and the vacuum pump 16, and the heating elements 43 are energized.
Flow of fluid is indicated by unreferenced arrows. The solvent from the tank 12 passes down the line 26 and is driven by the liquid pump 28 outwards through the discharge line 29 as shown by the arrows, and enters the applicator 33. The discharge line 23 of the vacuum pump 16 is connected to the condenser, consequently there is a pressure urging the fluid out of the tank through the line 26 aforesaid, which pressure augments that of the liquid pump 28 so that pressure at the applicator is the sum of these less line drop.
The fluid outlet connection 34 of the applicator 33 is connected by the flexible hose 35, which is a suction line, to the recovery tank 11. FIG. 1 shows a hanging fabric 47, for instance a heavy drape, being cleaned in position. The applicator is moved downward by hand in a direction shown by an arrow 33.1, while being held against the fabric. Solvent under pressure discharges from the applicator as a spray impinging directly against the fabric 47 being cleaned as indicated by arrows 48, seen in FIG. 6 only. Because of suction from the vacuum pump 16, the solvent impinging the fabric 47 is in major part withdrawn to pass outwards of the fluid outlet connection 34 and, at this stage, the solvent is dirty being laden with soil in solution extracted from the fabric. The soil laden solution now passes through I the hose 35 and discharges from the inner end 22 of the pipe 21 in liquid form, as small droplets, or as a mist, discharging on the heating elements 43 and changes state from liquid to gas. Suction from the vacuum pump 16 maintains pressure within the tank 11 somewhat below atmospheric, thus depressing boiling point of the liquid solvent. This results in less energy required to vaporize the liquid and facilitates condensation back to liquid. The elements 43 are means to supply heat to the withdrawn solvent changing its state from liquid to gas, a first change of state. With this change of state, the soil in solution with the solvent is in part deposited on the tank bottom wall 42 as indicated at 49, with some adhering to the heating elements 43 as a crust. At least one cleanout port 51 is provided, opening into the tank side wall above the base in a position convenient for insertion of a cleaning tool to remove the deposited soil 49, and to clean the crust off the heating elements 43.
In the change state from liquid to gas, the soil does not pass over but is deposited as above. A proportion of the gas, depending upon conditions, may change state back to liquid. The liquid being of soil free gas is, as it forms, clean or free of soil. The solvent which has changed its state from liquid to gas, together with any liquid produced as above, are drawn upwards and enter the bell mouth 18 of the vacuum pump intake pipe 17, being drawn downward to and pass through the pump 16.
This gas and any liquid droplets or mist are now driven by the pump to pass as shown by the directional arrows upwards through the discharge pipe 23 and enter the condenser 25 through its inlet port 24, passing through the condenser coil 25.1. Liquid condensate discharges at 25.2, as shown; as recovered liquid. The recovered liquid, which as explained is soil free or substantially so, will thus be added to the unused solvent 44 in the tank. The condenser is a means to extract heat from the solvent gas, adapted to effect a second change of state viz from gas to liquid, the tank being a collecting means for the recovered or cleaned solvent.
Flurocarbon solvents which are non-flammable and are suitably odorless are well known being used in the trade for cleaning of this general kind. For instance an intermediate grade of trichlorotriflouroethane is suitable for use in the instant process and apparatus, or a mixture of such solvents can be used. These solvents are characterized by relatively low boiling points and latent heats, l 18 and 63 BTU/lb being the boiling point and latent heat at atmospheric pressure of a particular trichlorotrifluouroethene suitable for use herein, namely ISOTRON T produced by Pennusalt Cehmicals Corp. of Philadelphia. Solvents and mixtures of solvents required for optimun cleaning in particular cleaning operations are well known in the trade and, therefore, are not further discussed in that aspect herein.
ALTERNATIVE MEANS FOR EFFECTING THE FIRST CHANGE OF STATE DESCRIPTION OF FIG. 2
In FIG. 2 an alternative recovery tank 52 has a cylindrical side wall 53 through which a recovery pipe 54 extends, the pipe having a capped inner end 54.1. An outer end of the recovery pipe is adapted for attachment of the flexible hose 35, FIG. 1. The pipe 54 has perforations 55 adapted to discharge solvent as shown at 56 to impinge a saucer like member 57 supported above a heating element 58 on forked brackets 59. The heating element 58 shown is a common Calrod unit of suitable wattage.
' An electrical conduit pipe 61 containing a conductor cable is secured in a bracket 62 of the member 57, an outer end of the conduit having a male receptacle 63 as the receptacles 39 and 39.1 FIG. 1.
The soil laden solvent from the applicator enters the flexible hose 35, passes to discharge through the perforations 55 of the recovery intake pipe 54, and impinges the shallow saucer 57 heated by the heating element 58. Thus upon impingement the dirty solvent changes state from liquid to gas, with the soil being deposited in the saucer 57. An inspection plate 64 is secured over a clean out port 65 of the side wall 53 by bolts 66. The conduit 61 has an outer end secured in the plate 64, thus by removing the bolts 66, the heating elements, saucer, and conduit, can quickly be removed together as a unit. The bracket 62 is also forked so that the saucer 57 is readily removable, either for cleaning or for replacement with a clean saucer. The 'soil in the dirty solvent entering the flexible hose 35 collects in the saucer 57 as explained, and the solvent in the form of a gas passes downwards through an intake 67 to the pump 16 as before. Note that the boiling point of the exemplified solvent is under 120 F.
DESCRIPTION OF FIGS. 3 AND 4 In FIG. 3 tank 69 has a cylindrical side wall 71 and a concave upwards saucerlike base 72. An intake pipe 73 with an open upper bell mouth 74 (similar to the intake pipe 17 FIG. 1) leads to the vacuum pump 16 FIG. 1. The base 72 is spaced upwards from the frame 13 FIG. 1 by legs 75 to provide space for a burner 76 supported by the said frame. The legs are secured to the frame 13 and to the base 72. The burner 76 is adapted for attachment of a gas supply line 77, providing propane or other combustible gas. Discharge of the dirty solvent is as before, and the action of the FIG. 3 boiler is as described with reference to FIG. 2. A cleanout port 78, as the cleanout port 51 FIG. 1, is provided for cleaning of the soil accumulated in the concave bottom wall of the tank.
The recovery intake pipe 54 can have a generally circular shape as seen in FIG. 3. In FIG. 2 the intake pipe 54, which is there shown as a straight perforated pipe, can be an intake pipe as 54.1 FIG. 4. A straight pipe 54 FIG. 2 can be used in the FIG. 3 alternative with a suitable positioning with reference to the pump intake pipe 73 to avoid interference therewith.
MOTOR AND PUMPS fluid pump can be dispensed with. Obvious by-pass means (not shown) can be provided to isolate the pump in these circumstances.
HEAT EXTRACTIONS MEANS EFFECTING THE SECOND CHANGE OF STATE The condenser FIG. 1 is shown with an outer jacket 81 having an intake 82 and an outlet 83. A cold water supply hose (not shown) can be attached to the inlet 82, with a waste hose (not shown) attached to the outlet 83, the hose leading to a sink drain. Cooling of the condenser coil can thus be effected.
The motor 36 FIG. 1 draws not over 15 amps, so that it can be connected to one ordinary household circuit and, as later will be explained, an applicator can require further power. Thus three circuits might be required. Where these are not conveniently available, suitable connection is made to the distribution box. In the three conductor cables referred to above, the third conductor is a ground, wiring of the apparatus is according to code requirement, and is well grounded to the frame 13.
The vacuum pump 16 FIG. 1 is a positive feed blower as used in positive extraction systems. 1 to 1 V4 HP is adequate. The liquid pump can be an impeller type, 4 HP will suffice an automative-type water circulation liquid pump. being suitable. In some circumstances the Under some conditions, the jacket 82 can be dispensed with, leaving the coil 25.1 exposed to ambient air. Where this provides insufficient cooling, a common electric fan 85 FIG. l-A is used to cause a current of air 86 to flow over the coil 25.1 for cooling.
FIG. l-B shows a condenser 91 having a coil 92 with an outer lagging 93 of absorbent material, and means 94 for moistening the lagging. Evaporation of the moisture results in cooling so that the coil 92 connected as before described is also cooled extracting heat from the gas so as to condense it. Evaporation cooling as above is, as is well known, particularly effective in conditions of high ambient temperature and low humidity. Fan cooling means as FIG. l-A can be included to increase evaporization.
THE HAND APPLICATOR DESCRIPTION OF FIGS. 5 AND 6 The applicator 33 has fluid inlet and vacuum connections 32 and 34 aforesaid, and includes a transversely extending elongated head portion 96 having a hollow interior enclosed by front and rear walls 96.1 and 96.2 respectively, opposite end walls 98, and a top wall 100. The head has an open flat bottom provided with a large mouth 101. A baffle 102 is disposed within the mouth 101 extending transversely between the end walls 98, so as to partition the interior of the head into two chambers, a front vacuum chamber 104 and a rear spray chamber 106. A lower edge surface of the baffle 102 can have spaced notches 103 to minimize the gripping power of the vacuum when end walls of the mouth 101 are in contact with upholstery or other fabric.
At least one spray nozzle 108 is mounted in the rear wall 96.2 within the spray chamber so as to direct a liquid spray uniformly outwardly of the mouth 101. The spray nozzle 108 has a coupling 110 at an exterior face of the rear wall 96, to which coupling one end of a short length of flexible tubing 112 is attached. An opposite end of the tubing 112 is coupled to an outlet end of a shutoff valve 114 mounted on an upper portion of the head 96. A lever 115 is provided so that the valve can be controlled by hand.
The applicator above is a hand tool as described in US Pat. No. 3,562,844, issued 16 Feb. 1971 in which the present inventor is named as co-inventor. This is adapted for use on drapes and upholstery being processed according to the present invention.
In FIG. v6 the applicator is shown with end walls of the mouth in contact with an outer surface 47.1 of a fabric 47.2 having as here illustrated, a nap 47.3. The fabric is shown in section, with exaggerated depth. The hand tool is moved in a direction shown by an arrow 1 17, the solvent spray from the nozzle 108 passing as shown by the arrows 48 passing through the nap 47.3 and over the surface 47.1 to the vacuum chamber 104. In so doing the solvent picks up soil from the fabric. It is seen that there is an incremental strip 47.4 of fabric being sprayed, and a contiguous incremental strip 47.5 being subjected to vacuum. The applicator thus provides a confined vacuum space defined by the vacuum chamber 104 and the incremental strip 47.5, and a confined spray space defined by the spray chamber 106 and the strip 47.4
A rug or carpet, or floor, tool (not shown) differs from the hand applicator 33 in size, and in obvious provision of handle means to move it along the rug or carpet. Because of the increased size, a plurality of spray nozzles is provided.
DESCRIPTION OF THE CONTINUOUS PROCESS From the description of mechanical operation it is seen that the process therein expressed includes steps as follows.
The soil laden solvent is withdrawn from the fabric. The solvent as continuously withdrawn is in a liquid state although, having been discharged as a spray, it will be mainly small droplets with the soil being contained in the droplets.
The state of the solvent so withdrawn is then changed to gas. This is accomplished by adding heat, effected by the heating element 43, FIG. 1, or by one of the means illustrated in FIGS. 2 and 3, or for instance by electronic means not shown. I
It is now required to change the state of the soil free gas to liquid solvent. This is effected by extracting heat in a condenser according to FIG. 1, l-A, l-B, or by suitable heat exchange means.
The first change of state above requires heat to be added according to the latent heat of the solvent while the second change of state requires heat to be extracted in the like amount. The particular means used to effect the addition and extraction of heat are not relevant to the method.
Finally, the recovered cleaned solvent is collected. In the FIG. 1 apparatus it is introduced into the solvent supply tank 12 recirculated and reused tq have its soil removed as before. Thus there is a cycle in which the solvent is sprayed on the fabric, picks up soil, is removed, loses the soil in the first change of state, the second change of state results in clean solvent and the cycle repeats.
With the FIG. 1 apparatus, pressure of discharge of the solvent through the nozzle 108 FIG. 2 is (when the pump is not by-passed) limited as aforesaid to somewhat less than pump plus vacuum pressure.
With this limited pressure, in order that the spray do its work rather than escape in material quantity and be dissipated in the open air, it is confined in a splay space defined by the spray chamber FIG. 6 and the incremental strip being sprayed. The vacuum too is confined in a vacuum space defined by the vacuum chamber FIG. 6 and the contiguous incremental strip. With relative motion of the applicator to the carpet as shown by an arrow 117 FIG. 6 the incremental strip after being sprayed is exposed to the vacuum. The exposure commences immediately and, the incremental strip having a finite width in the direction of travel exposure of the incremental strip to vacuum is substantially immediate which term is used herein to describe the action above.
An applicator or head according to U.S. Pat. No. 3,436,787 or U.S. Pat. No. 3,439,374, both of which is issued to the present inventor, can be used upon rugs and carpets. As well as differing from the hand applicator in size, both heads have additional heating means.
The first patent above has a heated head, and in the second lips of the nozzle are also heated. Each requires additional electric power.
These heads do not confine the jet as in the applicator 33, but they provide means to increase the pressure of discharge. With the increased pressure confinement is not necessary. However, a lower limit of pressure for effective spray operation of the above heads is about 20 psi, and 30 to 40 psi is ordinarily used. This is higher than that required for satisfactory operation of the hand applicator 33 which in some circumstances can work without a pump at all. Hence when either patented head is used with the FIG. 1 apparatus, the liquid pump 28 is capable of delivering 30 or 40 psi, This indicates a positive displacement pump such as e.g. a Roote pump or a piston pump.
It will be observed that, while spraying and exposure to vacuum occur simultaneously in time, as seen by the incremental strip there are two discrete actions, first exposure to the spray then substantially immediately thereafter exposure to the vacuum. Using the process as most of the solvent sprayed is readily recovered both with the hand applicator 33 and with either heated head above.
The process can also be expressed in an apparatus (not shown) wherein the fabric is caused to move with respect to a stationary applicator. This part of the process is expressed in any apparatus providing relative motion between applicator and fabric, whether the applicator moves as in the described apparatus, or whether the carpet moves as in apparatus for use in a fixed position, e.g. a cleaning plant.
With the hand applicator 33, or using a heated head according to either patent above in lieu of the illustrated applicator, the process is restricted to use with a non-flammable solvent. While the process is operative with a solvent regardless of whether, or what, odor it have, for practical reasons the process is used with an odorless or nearly odorless non-toxic solvent, or at the lowest with a solvent having an odor which disappears rapidly after the fabric has been cleaned.
What I claim is:
1. A continuous process of recovering cleaned noninflammable dry cleaning solvent from soil laden solvent, the solvent being used in a remote applicator for cleaning drapes, upholstery, rugs and like fabric having an outer surface, the applicator receiving clean solvent and returning soil laden solvent, there being relative motion between the applicator and the surface being cleaned, the process including steps of:
a. discharging clean solvent liquid under pressure from the applicator as a spray directed to impinge an incremental strip of the outer surface of the fabric, the solvent extracting soil from the fabric to form soil laden solvent,
b. substantially immediately thereafter exposing the incremental strip to a vacuum to withdraw the soil laden solvent from the fabric, the solvent being substantially liquid as it is withdrawn,
c. vaporizing the withdrawn soil laden solvent liquid into a soil free solvent gas to separate the soil from the solvent,
d. condensing the soil free solvent gas into liquid re mote from the separated soil so as to obtain soil free solvent liquid,
e. collecting the recovered solvent liquid,
f. returning the recovered solvent liquid back to the applicator for recycling through the steps above.
2. A continuous process as claimed in claim 1 in which vaporization of the solvent is effected by heating.
3. A continuous process as claimed in claim 1 in which the exposure of the incremental strip to vacuum is effected by a vacuum produced in a confined space defined in part by the incremental strip.
4. A continuous process as claimed in claim 1 in which the discharge of solvent onto the incremental strip is effected from within a confined spray space defined in part by the incremental strip.
5. A continuous process as claimed in claim 1 in which the solvent has a relatively low boiling point and a relatively low latent heat.
6. A continuous process as claimed in claim 1 in which the condensation of the soil free solvent gas into liquid is effected by heat exchange between ambient air and the gas.
7. A continuous process as claimed in claim 1 in which the condensation of the soil free solvent gas into liquid is effected by heat exchange between a relatively colder liquid and the gas.
8. A continuous process as claimed in claim 1 in which the condensation of the soil free solvent gas into liquid is effected by heat exchange between evaporation of a second liquid and the soil free gas.
9. A continuous process as claimed in claim 2 in which the heating takes place under a pressure less than atmospheric.
UNITED STATES PATENT OFFICE CERTIFICATE CORRECTION Patent No. 3,775,053 Dated November 37, L973 Inventor(s) Dorothea R. Wisdom It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
The name of the inventor is incorrect and should read:
--  Inventor: William H. Wisdom, Deceased, by
' Dorothea R. Wisdom, Executrix,
23017 Kent Street, Torrence, Calif.
Signed and sealed this 29th day of October 1974.
McCOY M. GIBSON JR. 0. MARSHALL DANN v Attesting Officer Conunissioner of Patents FORM PO-105O (10-69) USCOMM-DC 6037 6-P69 uasr GOVERNMENT PRINTING ornc: was o-ass-au