US 2573966 A
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Description (OCR text may contain errors)
Nov. 6, 1951 COOLING WATER TO ATMOSPHERE SOLVENT H. F. HAMLIN METHOD OF DRY CLEANING Filed Feb. 19, 1947 To l SEWER SOLVENT RECOVERY 3 TORAGE INVENTOR HENRY FREDERICK HAMLIN BY EM, MMMW ATTORNEYS.
Patented Nov. 6, 1 951 UNITED STATES asgaa'ee METHOD OF DRYonEANI-NG Henry Frederick Hamlin, to United States 'Hofim tion, New York, N. 1., se ration ornia ware Application February 19, 194i, serial Rama-500 8 Claims.
This invention relates to dry cleaning and more particularly to a low temperature dry cleaning process whereby the various steps of the cleaning operation can be .carried out efficiently in a single piece of equipment to produce cleaned u goods that are in a desirable condition Conventional bulk .dry cleaning processes commonly comprise three principal steps, namely, washing the goods in a non-aqueous Solvent and draining excess solvent from the goods, centrifuging the goods to remove solvent therefrom by centrifugal force; and drying the goods with hot air to remove residual solvent therefrom. These three steps are usually carried out in three different pieces of equipment, the goods being transferred from onelpiece of equipment to another when each step is'completed, The washing step is ordinarily carried out by introducing the goods into a Washer, i. 'e.', a horizontal cylindrical rotatable drum having" perforated walls and mounted in a casing in such manner that the non-aqueous solvent canbe'introduced into the casing and drum and the drum rotated to agitate the goods, thereby promoting effective contact between the goods and the solvent. Uponcompletion of the washing operation the solvent is drained from the goods and they are transferred to a centrifuge which comprises a 'foraminous basket usually rotatabl'e about a vertical axis. The basket containing the solvent-laden clothes is rotated at a relatively high rate of speed to remove additional solvent from the goods. At the end of the centrifuging step the goods are transferred to a drier, which may be atumbler generally similar in construction to the washer referred to above, and wherein the goods are exposed to a heated drying medium, usually a stream of hot air, which removes the residual solvent from the goods.
It is evident that if these principal steps of the dry cleaning operation can be carried out in a single piece of equipment, substantial advantages result. Thus a saving in labor can be effected since it is unnecessary to handle the goods between the successive steps of the dry cleaning operation. .Moreover, spillage and evaporation of the solvent that normally occurs durthe transfer of the goods from one piece of ing out the process in a single machine. Hence less solvent is lost to the atmosphere, employees are not exposed to the solvent during transfer of the goods, and, inthe case of flammable solvents,
a serious fire hazard iseliminated.
-.. i ,cl enieee eretie e wi le e oiette sis ha e ee m a p s hat s lld be sed 1 5.61
ie mehi w dry ean m a but so fa e is here a on 9. ssfu ethereeen y h a pec a ire. 9
., e .SllQh igsl rum a ses ou o the dis .eu y smi in .step and the centrifuging 99; EILQQEQB? 1 19 tive washing of the goods, the w H Should be ea ed Qlifif admin test r ata at a h ize iiel x s b t f. h @ent fiisin as a ed 1 f d e he isp dru asymme y 9f he 9 a d the e t of i i F 919 l iiz 9 Em i"? 79 799. 9? ibreti nse .hies sec e-and hem es e efs ri ee .ebgtraction that may be used is limited. on the ot hand if the speed is maintained low enough to ave-id undesirable vibration, the extraction o'f the solvent is poor, i. e., quantitatively inferior to that obtainable with conventional centrifuge s, and considerable quantitiesfof solventare left in the goods. When fg'oods containing such a'relatively large quantity'of solvent are dried, for example, by exposure to hot air, there is aserious loss of solvent and the case of flammable solvents, if the temperature of the heated air is above the flash point of solvent, there isa danger of explosion. Moreover an unduly long periodof time is required to removethe relatively large quantities of solvent left in the 'goods'a'nd the final condition of the goods leaves considerable to be desired.
It is accordingly an Object of the present invention to provide an improved dry cleaning process whereby the various steps of the dry cleaning operationmjay be carried out in a single piece of equipment. 'Ifh'ave found that this may be accomplished, in 'generah'by washing 'thegoo'ds in the horizontal 'rotatabledrum of a tumbler; draining off the solvent; increasing the speed of rotation of the drum to an extent vsufficient Ito removesolvent from the goods by centrifugal force, but sufficiently low to avoid excessive vibration, then reducing the drum speed to 'a value which will produce uniform distribution :01 "the goods with t e d um and exposi the good to steam under a high vacuum and at a relatively iow temperature, preferably less than about 120 to remove residual solvent there- 55 from. 'The' he'at of the steam is used to vaporize 3 the solvent, and solvent vapors and steam are removed continuously during the drying step and condensed.
I have found that by using steam at a low temperature and pressure underthe conditions set forth hereafter, the difficulties previously encountered in attempting to carry out the dry cleaning process in a single machine are substantially eliminated. Although. as pointed out above, centrifuging at a speed sufficiently low to prevent excessive vibration results in relatively poor extraction and leaves a relatively large quantity of solvent in the goods, the present process provides for substantially complete recovery of the residual solvent left in the goods and hence the process can be used economically with an extraction of low efiiciency. Furthermore since steam is used as a drying medium and replaces the air in the tumbler, the atmos-' phere within the drier is free from uncombined oxygen and hence there is no danger of explosion. In fact, the present process provides a double safeguard against explosion hazards since not only is the atmosphere within the drier largely composed of water vapor but also the i drying step is carried out at a temperature that is below the flash point of most of the commonly used flammable solvents. In addition it has been found that vacuum steam drying in accordance with the present process is an unusually rapid washing and centrifuging steps are normally carried out at temperatures approximating room temperature, but the drying step has commonly been carried out at temperatures well above room temperature. In the present process all three steps are carried out at relativel low temperatures and there are numerous advantages that flow from the use of such a low temperature throughout the cleaning process.
For example, the use of low temperatures in the drying step as Well as in the other steps of the process facilitates the spotting operation that commonly follows the bulk cleaning operation. The spotting operation involves the removal of stains from the articles being dry cleaned. Some of these stains, such as albumen and lipstick, are set by high temperatures. Other stains are caused by chemical compounds which increase in activity with increasing temperature and may cause fabric damage at high temperatures. Most stains are more difiicult to remove after they have been heated. Hence when the present low temperature process is used for bulk dry cleaning, the subsequent removal of stains may be more readily accomplished. Moreover, the water vapor used in the drying step moistens the goods to an extent sufficient to facilitate removal of stains during subsequent spotting.
High temperatures may also damage certain types of goods. Thus it is well known that certain of the newer synthetic plastics, for example, Vinyon, are unusually temperature sensitive. Likewise, furs that have been tanned with certain tanning agents tend to be heat sensitive and for this reason it is desirable to carry out the cleaning of fur-trimmed garments at low temperatures. In particular cases excessive heating may cause felting of fabrics, distortion of overpa e rice and damage to plastic ornaments. Also heat tends to set wrinkles in garments and makes subsequent finishing of the garment more difficult. With the present low temperature process these various disadvantages of high temperatures are avoided and it becomes unnecessary to sort out the goods prior to cleaning and segregate for special handling those articles that are particularly heat sensitive.
It is another object of the present invention to provide a dry cleaning process wherein the moisture content of the goods being dry cleaned can be brought to a desired value. In the present process the goods are dried by bringing subatmospheric pressure live steam into direct contact with the goods at low temperatures. It has been found that by utilizing steam instead of hot air under the conditions described hereafter it is possible not only to retain in the goods the natural moisture associated with the fibers thereof but also to increase the moisture content of the goods somewhat and bring it to a value that is particularly desirable for effective pressing of the goods after they have been dry cleaned.
The use of steam under the conditions set forth herein as a medium for removing residual solvent possesses numerous advantages in addition to its advantage in adjusting the moisture content of the goods. Thus when air is used as a drying medium, i. e'., solvent removal medium, the air because of its oxygen content tends to form with the vaporized solvent an explosive mixture. This tendency can be overcome by using a relatively non-volatile solvent and maintaining the relative proportions of air and solvent vapor outside the explosive range. However such modifications constitute an operating limitation which can be completely eliminated by substituting steam for air. When steam is used there is no explosion hazard irrespective of the volatility of the solvent used and the relative proportions of solvent vapor and drying medium.
When air is used as a drying medium recovery of the solvent from the mixture of air and solvent vapor is expensive and in most cases uneconomical. Also failure to recover the solvent involves an economic loss that may be serious, particularly where valuable solvents are used. Furthermore, in cases where the dry cleaning plant is located in a thickly settled area, it becomes something of a problem to dispose of the lint and solvent vapors present in the air after it passes through the drier in such manner that they do not constitute a nuisance. When steam is used as a solvent removal medium the mixture of steam and solvent vapor may be easily condensed and the solvent thereby effectively recovered. Any lint that may be present is removed with the condensate. By using steam as an operating medium it becomes practicable from an economic standpoint to utilize relatively expensive solvents which could not be used in a process Where there was a substantial loss of solvent. Hence a wider variety of solvents is made economically available by the present process.
It has been found that hot air drying tends to produce static electrical charges on the goods particularly where the goods are tumbled during the drying process. These static charges tend to cause lint to adhere to certain of the materials being treated. When steam is used, static electrical charges are largely eliminated, and adherence of lint to the goods is reduced to a negligible aura-see of the solvent and are: particularlynoticeable :wherethe. solvent comprises amixtureof .co'mpounds rather than a single chemicalcompound. when steam is substituted fort-air there is-nofree .o xygenpresent in the mixture .of solvent vapor and carrier medium and therefore no oxidation of the solvent is likely to occur. Inpointof. fact it hasbeen found that byutil-izingsteam instead of. hot air under the conditions described below the residual odor with a .givensolventcan be substantially reduced.
A further advantage of using steam in place of air. is that much more effective heat transfer is obtained between steam and the goods than is obtained betweenrhot air and. the goods. Because of thi improved heat transfer thetime required for removing solvent, to a given extent is substantially reduced. Also there is more effi .cien-t utilization of the heat supplied to the solvent-laden goods.
When air isused a blower or fan is necessary to move the air through the goods and such fansare frequently objectionably noisy. When steam used, the noise of the fan or blower canbe eliminated. Because of this. noise elimination and also because of the reduction inv explosion hazard and solvent vapor discharge that may be achieved by utilizing. the present process, this process makes it possible to locate adry cleaning plant in many neighborhoods where such aplant could not otherwise be located.
' Other objects and advantages of the present process will be in-part obvious and in part will appear from the following description ,of my process. 1
In one of its broaderaspects the method ofthe present inventionrcomprises the steps of washing with a suitable nomaqueous solvent articles that are to be dry cleaned to remove dirt, grease and the like therefrom; draining off such portions of .the solvent as can be drained from the goods; centrifuging the goods to remove additional solvent therefrom; and removing the remainder of the solvent fromthe goods by bringing subatmos- .pheric pressure live steam into intimate con-tact with the goods under such conditions that the solvent is vaporized while maintaining the goods a a temperature that is sufiiciently low to prevent setting of stains that may be present on the goods and to prevent damage to any heatsensitiye materials that may be, present in the batch of goods being cleaned. In a somewhat narrower aspect the method; of the invention comprises introducing into the rotatable drum of ,a tumbler a batch of goods to :be dry cleaned; introducing a Suitable noneaqueous solvent into the tumbler; rotating the drum of the tumbler to cause the goods to be washedby the solvent; draining solvent fromthe goods; increasing the speed of rota on of the tumbler drum to a yalue sufliciently .hight remove solvent from the goods. by. centrifugal force but su fhciently low to avoid. unde sires r on. ee red ess-the .siru s ed t lower than the boiling point of water.
.alvaiuesufilcient to produce approximately uni:- form distribution ofthe goods within the tumbler drum andiiexposingthe goods tosubeatmospheric pressure live steam at. a temperature of less than about 12.0? F. for arperiod .ofv time sufficient to remove residual solvent from the goods; removing amixtureof steam andsolvent vapors from the drum and condensing the mixture to recover the solvent; and removing the solvent free goods from the tumbler. .It has. been found that if the dryingi step of. the process is carried out at a temperature. nohigherethanabout 120? F. and pref- .erably'in the neighborhood of 1.00 F. setting of .stainsis avoided and even unusually heat sensitive materialsmay be processed without loss of strength or other desirable characteristics. Furthermore attemperatures of thisorder of magnitude'the water. content of textile fibers may be increased to provide a moisturecondition which is highly desirable where the article being cleaned i subsequently to be pressed.
The lower temperature limit of the drying step .oftthe. process does not appear to be critical and is". determined primarily by practical and economic considerations. By using a refrigerated .condenser the operating temperature may be carried down to room temperature or below. However in mostcases the cost of refrigeration outweighs any advantages that might be gained by the use of very low temperatures and hence in most cases it is desirable to use ordinary coolingwater as a cooling medium and operate at temperatures not lower than about F. As the temperature is raised'the amount of water vapor condensed on. the goods increases and vice versa.
7 It has. been found that a particularly desirable moisture condition of the goods canbeachieved whenioperating in the neighborhood of F. to F.
i As pointed out above a wide variety of solvents may beused, since the formation of an explosive mixture during the drying step is precluded .by'the presence of the steam. The boil- ;ing point of'thesolvent may be either higher or As an example, I may use the well-known Stoddard solvent, which is relatively non-volatile, that is,
it "has a'boilin'g point higher than the boiling --.point of Water.
It is a matter of some importance to provide :intimate contact between the live steam and goods :during the solvent removal step of the proc.8655 and to'tha't end it is desirable to maintain the; goods in a substantially continuous state of -agitationzand in loosely packed condition during thesolventremoval step and to cause the steam gztolflow. throughthe goods while they are in this :loosely packedcondition so that the steam-may penetrate to all portions of the goods and vaporize; the solvent therefrom. 'By suitably agitating .the goods as the. steam flows therethrough the .efliciency and economy of the process may be substantially improved. The desired distribution .of goods during the drying step may be obtained by suitably regulating the speed of r'otationof'the tumbler drum. It has been found that effective 15 .eflective operation of the present process in respect to all three ofthe principal operations, namely, washing, centrifuging and drying is the loading of the tumbler drum. It has been found that good results may be obtained by using a drum load between 2 and 5 pounds per cubic foot of drum volume and that optimum results are obtained with a load of about 3 pounds per cubic foot of drum volume.
In order to operate at the low temperatures that are desirable in the present process it is.
necessary that the steam pressure be maintained well below atmospheric pressure, that is to say, it is necessary that a relatively high vacuum be used. The heat required to vaporize the solvent is supplied by the steam which condenses on the goods and thereby gives up its latent heat. The condensing steam supplies the heat required to heat up the goods to the operating temperature of the drier and also to vaporize the solvent. The heatsupplied to the goods by the steam for vaporizing the solvent can be transferred to the goods at either a high or a low temperature depending upon the steam pressure used. However, 7
because of the fixed relationship between the temperature and pressure of saturated steam, the low temperatures utilized in the present process can be achieved in practice only by maintaining the steam pressure at a relatively low value.
It has been found, in general, that the steam pressure should desirably be maintained in the neighborhood of 0.5 to 2.0 pounds per square inch absolute. Since the system is substantially completely filled with condensible vapors these low pressures may be conveniently attained by providing a condenser in which the vapors are condensed and using a vacuum pump after the condenser to remove from the system any small quantities of noncondensible gas that may be present.
As indicated above, my processis preferably carried out with the goods contained in a single piece of apparatus and with certain ancillary equipment provided to supply steam to the goods, maintain the desired low pressure in contact with the goods, condense the steam-solvent vapor mixture leaving the goods and provide for recovery pfthe condensed solvent. Apparatus capable of carrying out the process of the invention is shown in the accompanying drawing. The apparatus .there shown comprises, in general, a tumbler for introducing steam and solvent into the drum,
a condenser for condensing the mixture of steam and solvent vapor, a vacuum pump for removing non-condensible gases from the system, and a separator for recovering the condensed solvent.
Referrin to the drawing, the tumbler, which is designated by the numeral [0, may be general- .ly similar to conventional tumblers used in the dry cleaning art, but is modified in certain re- .spects described hereafter. It comprises an out- .er stationary casing l2 and an inner rotatable drum l lwithin which the goods are placed for cleaning. The casing I2 is provided with a door It which is adapted to register with a door [8 of the rotatable drum I4 to permit introduction of the goods into the drum. The casing 12 and door I 6 are made air tight to permit the interior of the casing to be evacuated, andthe casing I2 is made strong enough to withstand external atmospheric pressure when the interior ,Of the casing is highly evacuated.
;The drum I4 comprises a perforated cylindrinal ribs 25 which extend radially inward toward the center of the drum and serve to lift and tumble the goods as the drum is rotated;
To rotate the drum I4 amotor 28 is provided which is connected through pulley 30, belt 32 and pulley 34 with a shaft 36 by which the drum I4 is rotated. The shaft 36 is mounted in a suitable bearing 38 and is provided withia conventional seal 40 which permits rotation of shaft 3'6 and at the same time prevents any substantial amount of leakage of air into the casing l2 when the casing is evacuated. The other end of drum I4 is mounted by means of the narrow portion of the flared inlet 24 in the bearings 42 anda vacuum-tight seal is provided by housing 44.
Steam and solvent may be introduced into the casing l2 and drum I4 through a pipe 46 that extends through the housing 44 and the initial portion of the flared inlet 24 to substantially the point at which the wall of the flared inlet begins to diverge. Solvent is supplied to pipe 46 through a branch pipe 48 provided with a valve 50 and steam is supplied to pipe 46 through a branch pipe 52 provided with a shut off valve 54 and steam flow control valve 56. To remove solvent from the apparatus there is connected to the bottom of casing l2 a drain pipe 58 provided with a shut off Valve 60 and pump 62 by means of which solvent may be pumped from the casing to a solvent storage tank (not shown).
Steam and solvent vapor flow out of casing l2 through a pipe 64 which is preferably connected to the casing at several spaced points as indicated in the drawing. The pipe 64 is connected to a direct contact condenser 66 at a point near the bottom thereof. The condenser 66 is provided with a number of staggered horizontal plates 66. Cooling water is supplied to the top of condenser 66 through a pipe 10 provided with a control valve 12, the construction being such that cooling Water may flow down over the plates 68 and-condense the upwardly flowing vapor mixture.
The resulting mixture of water and liquid solvent is withdrawn at the bottom of the condenser through pipe 14 by means of a pump 16 and flows through pipe T8 to a separator 8*), where it separates into a lower water layer and an upper solvent layer. The water layer is continuously withdrawn through an overflow pipe 82 and passes to a sewer or other suitable point of disposal. At the end of a dry cleaning operation solvent may be withdrawn from the separator through pipe 84 which is provided with a I control valve 86.
In order to evacuate the interior of casing [2 the top of spray condenser 66 is connected by a pipe to the suction of vacuum pump 88 which may be a conventional reciprocating pump or other pump capable of producing a high vacuum in the drier system. The pipe 90 is provided with a shut off valve 92. The discharge of the pump 88 is open to the atmosphere through a pipe 94. The system, including the tumbler l0 and condenser =66, may be vented through a branch pipe SE-Whi'ch connected to the pipe 90 .and provided witha shutoff valve 98; '1
The apparatus just described may be used in to leave ample spacefor movement of the goods as the drum is rotated. In this way effective contact between the goods and solvent during the washing step and effective contact of the steam and goods during the drying step may be achieved.
After the drum has been charged valve is opened to cause solvent to'flow through pipe 48 to the casing I2. During'the early stages of the process, vacuumvalve 92 is closed and vent valve 98 open, sothat the system operates under atmospheric pressure. When a-suflicient quantity of solvent has been admitted to fill the casing l2 and drum le'to a level of about one-third their diameters, valve '50 is closed and motor 28 is started to rotate the drum. The motor is preferably provided with conventional electrical controls which cause it to rotate the drum M for several revolutions inone direction and then reverse the direction of rotation of the drum for an equal number of revolutions. As the drum M rotates the ribs" 26 operate to carry clothing up along the periphery of the drum and drop it into the center of the drum. In this manner the goods are agitated in the solvent, and dirt, grease and thelike are removed therefrom. The speed of rotation of the drum I4 is not critical but may be of the order of 30 R. P. M. Reversal of the direction of rotationof. the drummay ocour every 20 seconds.
When the washing step has been completed valve 60 is opened and pump 52 started to-cause the solvent to be withdrawn through pipe 58 and -pumped to a suitable storage receptacle. When the casing l2 has been emptied of solvent the speed of rotation of drum I4 is increased to, for example, a speed of 500 R. P. M. when the drum is 30 inches in diameteniat which speed the centrifugal force created is suflicient to remove additional quantities of solvent from the goods. During centrifugal extraction the drum is rotated in one direction only. As previously pointed out, the eccentricity of the load in the drum l4 and the efiect of gravity are such that the drum tends to vibrate when rotated at high speed and hence,
with existing types of horizontal extractors, it
some centrifugal extractors'presently used in the art, i. e., vertical extractors'the lesser degree of extraction can be tolerated in the present, process because of the greatly improved efiiciency ofthe. "drying step and the substantially complete .re-
covery of the solvent. Upon completion of the extraction step vent valve 98 and drain valve are closed, vacuum valve 92 is opened and the vacuum pump 88 is started to evacuate the system. At thesame' time valve 12 is; opened to admit water to the-con-' denser 66 and transfer pump 16' is started to pum low temperature during drying.
found thatinthe case of a drum 30 inches in cooling water and condensate through pipes 14 and l8 to the separator'BlL The system is initially evacuated'to a pressure of the order of 1" of mercury absolute and valves 54 and 56 are then opened to admit steam to the interior of easing 2. The flow of steam is regulated by the valve 56' and the pressure within casing 52 is maintained at about 2" of mercury absolute by regulating the flow of cooling water to condenser 66 by means'of valve F2. The corresponding temperature within the casing i 2 is about 100 F.-
The order. in-which. the steps just described are carriedout is'a matter "of some importance. The flash point of many organic solvents decreases with a decrease in pressure. Also there is air within the drum M at 'thetime evacuation is initiated, andhenc'e there is'a slight possibility of the formation .of an: explosive mixture within the drum during evacuation, notwithstanding the fact that the temperature of the drum is below the atmospheric pressure flash point of the solvent. Accordingly, it is desirable that rotation of the drum be stopped at'the end of the extraction step and the initial evacuation of the apparatus carried outwith the drum stationary. When: the pressure has been reducedto the desiredpoint, steam is admitted to sweep out any remaining air, and thereafter the drum is rotated as described below to secure a desired'distribution of the goods.
I The steam enters drum [4 through the flared inlet 'z iand expands and is distributed thereby across the cross-sectional area of the drum. The steam then flows through the perforated end plate 22','through the'goods Within the drum, and out through the. opposite perforated end plate 23 of drum l4 and also through the cylindrical wall of the drum. During the drying step'the drum is rotated to induce effective contactbetween the goods and the steam flowing through the drum. The speed of rotation of the drum is preferably so adjusted as to produce a centrifugal force at the drum periphery of about one pound per pound of goods. In this way the goods may be caused to float within the drum and unusually effective distribution of the goods and contact between the steam and goods as well as the goods prevails than it would be if the steanr were forced through tightly packed goods. This isan important factor where, as in the present case, it is desirableto keep the steam pressure low in order to maintain the goods at a desired diameter this optimum condition wherein the goods are substantially uniformly distributed throughout theinterior of the drum may be obtained by using a speed of the order of 50 R. P. 'M.
The heat of the steam vaporizes the solvent from thegoods and a mixture of steam and solvent vapor flows from casing I2 through pipe 64 to the condenser 65 wherein it is condensed by direct contact with cooling water. The cooling water and condensate as previously described are transferredto the separator so that the sol vent can be recovered.
It is of course to be understood that the foregoing description is illustrative only. The math I 0d of the invention may be modified in various ways and may be carried out in apparatus'othe'r than that disclosed in the drawing. For example, i
the condensation of the steam-solvent vapor mix- It has been ture may be effected ina surface-type condenser wherein the cooling medium does not come in contact with the vapors, or, as indicated in the drawing, the cooling water may be brought into direct contact with the vapors. Steam for vaporizing the solvent during the solvent removal step may be fed to one end of the tumbler drum or to both ends thereof. The end wall 23 of the drum may be made partially perforate as shown or may be made imperforate to cause all of the steam-vapor mixture to leave the drum through the periphery thereof. Other modifications will occur to those skilled in the art.
= As previously pointed out it is important that the conditions within the drum [4 during the drying step be carefully controlled in order to prevent injury to delicate fabrics that may be contained therein; The temperature within the drum may be controlled by controlling the flow of cooling water to the condenser which in turn determines the pressure within the casing l2. This pressure is desirably maintained between 0.5 and 2.0 pounds per square inch absolute in order to make sure that the temperature of the goods doesnot exceed about 120 F. The steam flow in atypical case, for example, in a 30" drum loaded as indicated above, may be of theorder of 2 pounds per minute. When the temperature of the goods is maintained on the order of 100 F. to 110 F. and steam flow, loading and speed of rotation of the drum are within the indicated ranges, the final moisture content of the goods attains a value that is favorable for subsequent pressing of the goods.
It has been found that under the'conditions set forth substantially complete removal of the residual solvent can be efiected in a period of about 20 minutes. The'goods when removed from the drum [4 are dry to the touch and completely free from objectionable odors. Because of the low temperature used throughout the process the strength of fabrics is undiminished and heat sensitive articles such as plastic ornaments and the like are unaffected by the dry cleaning process. Furthermore, any stains on the goods may be readily removed in the subsequent spotting operation. I
It should be particularly noted that the entire-bulk cleaning process, including the washing,. draining, extracting and drying steps, is carried out within the drum [4 and thus the transfer of goods between separate washers, extractors and driers that is characteristic of most conventional dry cleaning processes is eliminated in the present process. This is an important advantage vof the present process since the cost of handling the goods is reduced and substantial overall economies are thereby effected. The process may be characterized as a dry-to-dry process since the goods. are dry both when charged into the tumbler and also when removed therefrom. Thus there is no point in the process where solvent-laden goods are exposed to the atmosphere and hence the loss of solvent entailed in such an exposure to the atmosphere is precluded.
Since many embodiments might be made of the present invention and since many changes might be made in the embodiment disclosed herein, it is to be understood that the foregoing description is to be interpreted as illustrative only and not in a limiting sense.
l. 'A method of dry cleaning goods in the rotary drum of a tumbler .which comprises intros ducing. into said drum said goods and a; quantity of a flammable organic dry cleaning solvent adapted to remove dirt, grease andthe like therefrom, rotating said drum at a relatively 'low speed to agitate said goods and cause said solvent to wash said goods, then draining from said drum such portions of said'solvent as can be drained therefrom, then centrifuging said goods by rotating said drum at a speed sumcient to re-. move considerable additional solvent from said goods but insufficient to cause undesired vibra-' tion of said drum, thenreducing the speed of rotationof said drum to the point where the centrifugal force at the drum periphery is between 0.4 and 2.0 pounds per pound of goods to produce desired distribution of: the goods'within said drum, introducing live steam into said drum at a pressure between 0.5 and 2.0 p. s. i. a. without preheating said goods to vaporize the remainder of said solvent from said goods, to deposit a desired quantityof water in said goods and continuously removing a mixture of steam and solvent vapor from said drum.
[2. A method of dry cleaning goods in the rotary drum of a tumbler which comprises loading said drum with between 2 and 5 pounds of said goods per cubic foot of drum volume, charging said tumbler with a quantity of a flammable organic dry cleaning solvent adapted to remove dirt, grease and the like from said goods, rotating said drum at a relatively low speed to agitate said goods and cause said solvent to wash said goods, then draining from said drum such portions of said solvent as can be drained there from, then centrifuging said goods by rotating saiddrum at a speed sufficient to reduce the solvent content of said goods to about 20% by weight but insufiicient to cause undesired vibration of said drum, then reducing thespeed of rotation of said drumto reduce the centrifugal force exerted at the periphery of said drum to between 0.4 and 2.0 pounds per pound of goods to produce desired uniformity of distribution of said goods within the interior of the. drum, in-- troducing sub-atmospheric pressure live steam into said drum without preheating said goods to vaporize the remainderof said solvent from said drum and to deposit a 'desired quantity of water in said goods, maintaining the steam pressure within said drum between 0.5. and 2.0 p. s. i. a.-
to maintain the temperature of said goods sufficiently low to prevent setting of stains on said goods and damage to any heat sensitive portions of said goods, and removing a mixture of steam and solvent vapor from said drum.
3. The method of removing residual organic dry cleaning solvent from goodsthat have been dry cleaned with said solvent which comprises confining said goods in a foraminous rotary drum in an air-tightchamber, continuously rotating said drum during removal of said solvent from said goods at a speed sufficient to produce a centrifugal, force on-said goods at the periphery of said drum of between .04 and 2.0 pounds per pound of goods to produce desired uniformity of distribution of said goods within said drum, continuously introducing sub-atmospheric pressure live steam into said chamber to vaporize saidsolvent from said goods and continuously removing from said chamber the resulting mixture of steam and solvent .Vapor.
A. The method of removing residual organic.
dry cleaning solventfrom goods that have been dry cleaned with said solvent which comprises. confining said goods in a foraminous rotary drum.
in an air-tight chamber, continuously rotating said drum during removal of said solvent from said goods at a speed suflicient to produce a centrifugal force on said goods at the periphery of said drum approximately equal to the force of gravity to produce an essentially unpacked condition of said goods within said drum, continuously introducing sub-atmospheric pressure live steam into said chamber to vaporize said solvent from said goods and continuously removing from said chamber the resulting mixture of steam and solvent vapor.
5. The method of removing residual flammable organic dry cleaning solvent from goods that have ben dry cleaned with said solvent which comprises confining said goods in a foraminous rotary drum in an air-tight chamber, continuously rotating said drum during removal of said solvent from said goods at a speed sufficient to produce a centrifugal force on said goods at the periphery of said drum between 0.4 and 2.0 pounds per pound of goods to produce a desired uniformity of distribution of said goods within said drum, continuously introducing sub-atmospheric pressure live steam into said chamber without preheating said goods to vaporize said solvent from said goods and to deposit a desired quantity of water in said goods, continuously removing from said chamber the resulting mixture of steam and solvent vapor and maintaining the steam pressure within said chamber between 0.5 and 2.0 p. s. i. a. to maintain the temperature of said goods below that value at which stains on said goods are set and heat sensitive portions of said gooods are damaged.
6. The method of removing residual flammable organic dry cleaning solvent from goods that have been dry cleaned with said solvent which comprises confining said goods in a foraminous rotary drum in an air-tight chamber, continuously ro- L tating said drum during removal of said solvent from said goods at a speed suflicient to produce a centrifugal force on said goods approximately equal to the force of gravity to produce substantially uniform distribution of said goods within said drum, continuously introducing sub-atmospheric pressure live steam into said chamber without preheating said goods to vaporize said solvent from said goods and to deposit a desired quantity of water in said goods, continuously removing from said chamber the resulting mixture of steam and solvent vapor and maintaining the steam pressure within said chamber between 0.5 and 2.0 p. s. i. a. to maintain the temperature of said goods below that value at which stains on said goods are set and heat sensitive portions of said goods are damaged.
7. A method of dry cleaning goods in the rotary drum of a tumbler which comprises introducing into said drum said goods and a quantity of a flammable organic dry cleaning solvent adapted to remove dirt, grease and the like therefrom, rotating said drum at a relative low speed to agitate said goods and to cause said solvent to wash said goods, then draining from said drum such portions of said solvent as can be drained therefrom, then centrifuging said goods by rotating said drum at a speed suificient to reduce the solvent content of the goods to about 20% by weight but insufficient to cause undesired vibration of said drum, then stopping said drum and evacuating air therefrom, then introducing into said drum substantially saturated sub-atmospheric pressure live steam without preheating said goods and to vaporize the remainder of said solvent from said goods and to deposit a desired quantity of water in said goods, resuming rotation of said drum after steam has started to enter said drum, maintaining the speed of rotation of said drum at such a value as to produce a centrifugal force of the periphery of said drum between 0.4 and 2.0 lbs. per lb. of goods to produce a desired uniformity of distribution of said goods within the interior of the drum, maintaining the steam pressure within the drum between 0.5 and 2.0 p. s. i. a. to maintain the temperature of said goods sufiiciently low to prevent setting of stain on said goods and damage to any heat sensitive portions of said goods, and removing a mixture of steam and solvent vapor from said drum.
8. The method of removing residual organic solvent from goods that have been dry cleaned with said solvent which comprises confining said goods in a rotary drum in an air-tight chamber, rotating said drum at a speed sufiicient to produce a centrifugal force on said goods at the periphery of said drum between 0.4 and 2.0 lbs. per lb. of goods to produce a desired uniformity of distribution of said goods within said drum, continuously introducing substantially saturated sub-atmospheric pressure live steam into said chamber without preheating said goods to vaporize said solvent from said goods and to deposit a desired quantity of moisture in said goods, continuously removing from said chamber the resulting mixture of steam and solvent vapor, and maintaining the steam pressure within said chamber between 0.5 and 2.0 p. s. i. a. to maintain the temperature of said goods below that value at which stains on said goods are set and heat sensitive portions of said goods are damaged.
HENRY FREDERICK HAMLIN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date Re. 22,375 Chamberlin et al. Sept. 14, 1943 509,589 Watel Nov. 28, 1893 1,426,053 Endicott Aug. 15, 1922 1,567,443 Jenkins Dec. 29, 1925 1,799,649 Schenck Apr. '1, 1931 2,011,083 Sando Aug. 13, 1935 2,198,412 McDonald Apr. 23, 1940 2,328,256 Breckenbridge Aug. 31, 1943 2,357,909 Ridge .'l Sept. 12, 1944 2,406,187 Bayless Aug. 20, 1946