US 3110544 A
Description (OCR text may contain errors)
1963 LE ROY E. MOULTHROP 3,110,544
CLEANING METHOD Filed April 5, 1965 3 Sheets-Sheet 1 C} C, Fl 6. 6 U
Q INVENTOR LEROY E. MOULTHROP ROBERT J. PATCH ATTORNEY 1963 LE ROY E. ITIOULTHROP 3,110,544
' CLEANING METHOD Filed April 5, 1968 5 sheets-sheet 2 H08 TIME MINUTES TIMER MOTOR FILTER PUMP MOTOR 27 EDUCTOR PUMP MOTOR 89 WASH MOTOR l5 VAPOR REMOVAL VALVE 55 FAN I07 BY-PASS VALVE 39 FILL VALVE 3| DUMP VALVE 47 VACUUM BREAK VALVE 5i EXTRACT MOTOR l7 VAPOR RECYCLE VALVE H5 HEATER Ill WASH EXTRACT RECLAIM A TlME- MINUTES 0l23456789l0lll2l3l4l5 PRESSURE INCHES 0F MERCURY '6 INVENTOR. E. MOULTH ROP ROBERT J. PATCH ATTORNEY Nov. 12; 1963 LE ROY E. MOULTHROP v 5 CLEANING METHOD Filed April 5, 1963 5 Sheets-Sheet 3v us I05 v 35 V I0? 9 53 we 25 3L I3 1 I3 33 I I u 29 g V l27- l5 H n 43 INVENTOR. LEROY E. MOULTHROP ROBERT J. PATCH ATTORNEY United States PatentOfiice 3,110,544 Patented Nov. 12, 1963 3,110,544 CLEANING mirror) Le Roy E. Meulthrop, 220 S. Olive, Alhambra, Calif, I
assignor of twenty five percent to Robert J. Patch,
Chevy Chase, Md.
Filed Apr. 5, 1963, Ser. No. 27 0,832
17 Claims. (Cl. 8-137 fabrics thus treated are comprised of animal, vegetable or certain synthetic fibers or the like, and may for example be woven, knitted, felted, and so on. The principal field of application of this invention is in the cleaning of wearing apparel.
The invention will be particularly described and illustrated in connection with dry cleaning by the use of organic liquids of the type of perchloroethylene, 1,1,2-tri chloro-l,2,2-trifiuoroethane (Freon 113), Stoddard solvent and other petroleum fraction solvents, trichlorethylene, carbon tetrachloride, and the like. It is to be expressly understood, however, that invention in many of its aspects is not limited to dry cleaning but rather is applicable also to water Washing, and that the term cleaning includes wash-ing both with organic cleaning liquids and with inorganic cleaning liquids such as water. Similarly, the term cleaning liquid includes both organic and inorganic cleaning liquids and includes water.
The essence of a cleaning operation of the type contemplated by the present invention is the production of relative movement between the cleaning liquid and the fabric to be cleaned. In the usual commercial machines, this is done solely by bodily agitating the liquid and the immersed fabric. Ordinarily, the machines are provided with containers or drums rotatable about horizontal axes. The fabric to be cleaned is placed in the drum, a quantity of cleaning liquid is introduced, and the drum is rotated to tumble the fabric and the liquid to clean the fabric.
Then comes the draining cycle, in which most of the cleaning liquid is removed from the fabric. In cleaning methods employing rotary drums, provision is usually made for spinning the drum at relatively high speed during the draining cycle, so as to extract or remove centrifugally a great part of the liquid that would not drain from the fabric merely by gravity.
The fabric, only moist with cleaning liquid, is then subjected to drying, during which the remaining cleaning liquid is removed by evaporation. in water Washing, and in dry cleaning operations employing a relatively cheap solvent such as Stoddard solvent, the cleaning liquid removed during the drying cycle can be discarded in vapor phase; but in the case of dry cleaning operations employing relatively expensive solvents such as perchlorethylene and Freon 113, the cost of the solvent dictates that it be reclaimed as by condensing it for reuse. Also, in dry cleaning operations, in addition to reclaiming as much as possible of the solvent for reuse, it is a common practice to pass the dirt-laden solvent from time to time through porous bodies of solid material in the nature of filtering and/ or absorbing agents to remove suspended and/ or dissolved impurities from the solvent.
These prior art cleaning methods depend for their cleaning action on vigorous agitation of the fabric and the cleaning liquid relative to each other. in doing so, however, they are only moderately effective to clean the fabric. In addition, they suffer from the enormous disadvantage that in partially cleaning the fabric, they also inevitably damage the fabric.
The damage to the fabric caused by cleaning methods as heretofore practiced takes a number of forms. One of the principal forms of damage is shrinkage. For example, fabrics of the type ordinarily dry-cleaned are not usually adapted for pre-shrinking treatments. As a result, they shrink when agitated during dry cleaning. This shrinkage results largely from a consolidation of the fibers very similar to felting, thatis, upon agitation, the fibers entwine and entangle ever more completely with each other, so that the size of the fabric is correspondingly reduced. Dry cleaning solvents ordinarily contain some soap-like detergent; and the solvents, and especially the detergents in the solvents, lubricate the fibers and accelerate this consolidation or shrinkage. Even in the case of water washing, many fabrics are subjected to cleaning that have not been pre-shrunk or otherwise protected against shrinkage; and the inevitable result is that these fabrics shrink the same as in the case of dry cleaning, or worse.
Other forms of damage are suffered by the fabric and its attachments by virtue of excessive pounding or rubbing of the fabrics during tumbling or other agitation. Buttons become broken up or dislodged, buckles become marred or snag other materials, and so on. Also, the
abrasion during such excessive agitation tends to spoil the finish of the fabric and to wear out the fabric.
Another disadvantage of the prior art which is particularly recognizable in the case of dry cleaning is due to the particular nature of the cleaning liquids, and especially dry cleaning solvents. Dry cleaning solvents are non-aqueous and non-conductive of electricity. Agitation of fabric in dry cleaning solvents actually generates static electricity, and as the liquids are insulators, this static charge is not dissipated but builds up in the fabric during the operation. These static charges cause the dirt to adhere to the fabric. Particles of dirt dislodged from the fabric during agitation actually return to the fabric and cling to the fabric under the influence of these charges. Moreover, the clarification powders with which the solvents are treated are also picked up by the charged fabric, so that foreign material is actually added to the fabric by the prior art methods.
Accordingly, it is an object of the presentinvention to provide cleaning methods that will minimize shrinking of fabric:
Another object of the present invention is the provision of cleaning methods that will minimize damage to the fabric or its attachments.
A further object of the present invention is the provision of cleaning methods that minimize the accumulation of static charges in the fabric.
Still another object of the present invention is the provision of cleaning methods which greatly speed up the cleaning process.
The prior art cleaning methods are also deficient in that they provide no satisfactory methods for drying the fabric after cleaning, and in the case of dry cleaning, no satisfactory methods for reclaiming the dry cleaning solvent. In the first place, the dry-ing methods of the prior art are so slow that they must be practiced in separate dryers or tumblers so that the washing equipment will not be unduly tied up during the long and slow drying 7 process. As a result, it has been necessary to provide, in addition to the machines designed to wash and spin the fabric until it is damp dry, separate dryers or reclaimers so that an economically large quantity of fabric can be handled in the generally more expensive washing and extracting apparatus. But the multiplication of the numbers of pieces of equipment thus necessary not only increases the capital investment of the professional cleaner but also ties up expensive floor space and necessitates a larger plant. Also, in the case of highly odorous dry cleaning solvents, the transfer of the damp fabric from the'washer-extractor to the dryer or tumbler causes a great deal of malodorous vapor to be thrown out into the plant, and this in turn necessitates installation of larger capacity ventilating equipment for the plant.
.In addition to their inability to dry fabric quickly, the cleaning systems of the prior art have also suffered from the disadvantage that they damage fabric by overheating it during drying or reclamation. In the case of all types of cleaning, excessive temperature during drying of the fabric can damage the fabric by charring and in orther ways; and in particular, in the case of dry cleaning with organic solvents, excessive temperature can decompose and carbonize the solvent with resultant dam age not only to the fabric but also to the equipment, and in the case of halogenated hydrocarbon solvents, can give rise to the production of such poisonous gases as ph osgene and/or hydrogen fluoride.
Accordingly,still another object of the present invention is the provision of cleaning methods which will be so fast that they can be economically practiced in a single piece of equipment having a dry-to-dry cycle time that is shorter than any known heretofore under comparable circumstances. 7 The invention also contemplates the provision of cleaning methods characterized in that drying or reclamation can be carried out at a temperature low enough to avoid damage to the fabric, and in the case of dry cleaning, to avoid damage-to the equipment and the production of noxious decomposition products of the solvent.
In the particular field of dry cleaning, in which the cost of the solvent makes it necessary to reuse the solvent, it is necessary to purify the solvent from time to time by passing it through a porous body of solid material in the nature of filtration and/or adsorption means. Most commonly, these means for cleaning the solvent employ a finely divided solid material as a principal constituent of the porous body, in the nature of filter powder which may be supported on a foraminous support that permits the passage of liquid through the support but not the passage of the filter powder. Filter powder for example may be diatomaceous earth or silica or the like, or, depending on the nature of the impurity to be removed from the solvent, charcoal. In any event, the finely divided material of the porous body of solid material from time to time becomes so highly charged with removed impurity that it must be removed and discarded and a fresh quantityof finely divided material added to the system. However, the spent material, or muc as it is known in this art, contains a large quantity of solvent, which must be reclaimed if the cleaning operation is to be conducted economically. In the past, it has been the practice to clean out the muck and put in a cooker which heats the muck to the point that the solvent is distilled otf. The vapor phase solvent distilled off the muck is then condensed with refrigeration and reused. Such a procedure, however, has the disadvantages that it requires special equipment and consumes a substantial quantity of power. Also, the transfer of muck to the cooker is a messy and disagreeable job. Furthermore, recovery of the solvent by use of a'cooker is a long and time-consuming process.
Therefore, a further object of the present invention is the provision of dry cleaning methods characterized by simple, easy, rapid and economical reclamation of solvent from muck.
Finally, it is an object of the present invention to pro vide cleaning methods that will be relatively simple, fast and inexpensive to practice, and that are well-adapted to be practiced by apparatus that is desirably compact in size, inexpensive to manufacture, easy to operate, and rugged and durable in use.
Other objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:
FIGURE 1 is a schematic macroscopic view of a length of dirty fiber showing in broken lines the extent of solvent penetration according to the present invention;
FIGURES 2-5 are schematic macroscopic views taken transversely of fibers during various stages of treatment according to the present invention, showing respectively the untreated dirty fiber in FIGURE 2, the application of liquid under increased pressure in FIGURE 3, the removal of dirt upon pressure decrease and outward liquid movement in FIGURE 4, and the cleaned fiber in FIG- URE 5;
FIGURE 6 is a view similar to FIGURES 2-5, but showing the failure of cleaning methods according to the prior art in terms of liquid movement relative to a dirty fiber;
FIGURE 7 is a diagrammatic w'ew of a cleaning system according to the present invention;
FIGURE 8 is a time sequence chart showing one embodiment of a cycle of operation of the present invention; and
FIGURE 9 is a graph of pressure against time, showing the pressure variations to which the fabric under treatment is subjected during a cleaning cycle of the present invention according to the embodiment of FIG- URE 8.
Briefly, the improved cleaning method of the present invention has a number of novel aspects. It has been discovered that the speed and efiiciency of cleaning are greatly improved if at the beginning of the cleaning cycle, a vacuum is drawn on the dry'fabric to be cleaned, before the :fabric is wet with cleaning liquid. Prior to entry of liquid into the chamber, and during the time the vacuum is initially being drawn, the dry fabric is subjected to tumbling in the presence of rapidly moving vapor which is withdrawn from the chamber, and this removes a substantial proportion of the dirt even before the fabric is contacted by the cleaning liquid. Thereafter, as the cleaning liquid contacts the fabric under vacuum, the wetting of the fabric by the liquid and the penetration of the liquid into the individual fibers of the fabric are greatly improved. Also, the introduction of cleaning liquid into a cleaning chamber under vacuum is greatly hastened by the higher upstream pressure of the cleaning liquid, so that the vacuum in the cleaning chamber in effect sucks in the clean-ing liquid.
The washing action is also greatly augmented by pressure fluctuation during washing. The pressure on the fabric Wet with cleaning liquid is caused to fluctuate, and this performs the actual cleaning operation in a manner more effective and efficient than any known heretofore. Specifically, the pressure fluctuation is achieved by manipulation of the cleaning liquid in such a way as not only to cause the pressure in the chamber to fluctuate but also to cause the liquid in the cleaning chamber to be at least partly changed so as to rinse the fabric. Preferably, the highest pressures attained in the cleaning chamber are substantially no higher than atmospheric throughout the cycle.
The efiectiveness of the washing cycle of the present invention is related to the viscosity of the cleaning liquid. The viscosity of the liquid should be low, that is, its consistency should be Watery. When its viscosity in creases substantially above that of water, the cleaning elliciency of the present invention drops off. Considering water to have a viscosity of about 1 centipoise (cp.) at room temperature, the viscosity of the solvent should be no more than about 2 cps., and preferably no more than about 1 cp. Fortunately, water and the common commercial dry cleaning solvents fall in this preferred range. In addition to waters viscosity of 1 cp., perchl'orethylene at room temperature has a viscosity of 0.84 cp., Freon 113 a viscosity of 0.69 cp., carbon tetrachloride 0.91 cp., and trichlorethylene 0.55 cp. Stoddard solvent has a viscosity in the less preferred range of the invention, in that its principal ingredient, n-dodecane, has a viscosity of 1.344 cps. These liquids became popular as cleaning liquids because of their high penetrability and solvent power, and in the case of dry cleaning solvents, good volatility and high or non-existent fiash points. These same qualities, plus low viscosity, render them ideal also for the present invention.
Although the reason for the effectiveness of fluctuating pressure in the washing cycle of the present invention is not known with certainty, it is believed at the present time that this aspect of the invention operates by producing movement of the solvent radially of the fibers at the surfaces of the fibers. It is thought that this feature can best be understood by considering the fibers of the fabric not to be solid elongated members, but rather to be elongated tubular lattices of solid material are disbursed multiple voids or interstices. These voids or interstices are internal to each fiber; for example, in the case of a cylindrical fiber, the voids are within the cylindrical contour.
The present invention, during the periods of pressure increase, moves the solvent radially inwardly of the individual fibers, the increased pressure proportionately compressing the vapor which fills the interstices within the body of the fiber. The periods of sudden pressure drop, however, are believed to be the true cleaning portions of the cycle, for during these pressure drops the liquid which had penetrated the fiber in compressing the vapor within the fiber now is forced out of the fiber with a movement that is radially outward of the fiber. It is to be understood that the term radial is not to be limited to its strict sense as referring only to fibers of circular cross-section, for of course wool is a major fiber to be treated by the present invention, and the fibers of wool are rather more flat than circular in cross-section. Instead, the term radial as used herein with reference to the fibers means perpendicular to the surface of the fiber at the point of egress of the liquid from the fiber.
This radial movement of the liquid is not visible to the unaided eye, for it proceeds in all directions at once inasmuch as the fiber surfaces are of random orientation relative to each other. Moreover, the movement of this liquid normal to any fiber-liquid interface is of very small linear extent. Nevertheless, since the liquid immediately adjacent the fiber is moving radially outwardly of the fiber, and since a portion of the liquid is passing from just inside the contour of the fiber to just outside the contour of the fiber, the liquid is moving in the ideal direction and along the ideal path for dirt removal. Even if the fabric and the body of liquid in which it is immersed were to give the outward appearance of lying quiescent throughout the process, in actual fact a dry cleaning operation would be proceeding with greater efiiciency than if the fabric were sloshing around in a violently agitated body of liquid Without pressure change according to the present invention. Inasmuch as one of the principal cleaning actions of the present invention is pressure fluctuation, the necessary amount of agitation of the liquid and the fabric bodily relaive to each other is enormously reduced. Of course, the fabric damage associated with such violent agitation does not occur. At the same time, however, the rinsing action needed to take the removed dirt away from the fabric is greatly augmented by the method of handling the cleaning liquid while producing the pressure changes.
The need for some agitation has not been eliminated, however, and a further feature of the present invention is'the discovery that a relatively small amount of agitation is necessary, in addition to pressure change, in order to promote the rinsing of dirt from the fabric and in order to avoid the formation of drying marks or swales as they are called in this art.
The improved cleaning efficiency of the present invention also makes it possible greatly to reduce the washing time, which turn reduces the tendency to shrinkage and fabric damage and decreases the amount of static electricity that builds up in the fabric. Therefore, freedom from fabric damage and decreased static electricity through which 6 are not bought at a priceon the contrary, they bring with them a cleaning efficiency'previously unobtainable in this art.
The washing aspects of the present invention should not be confused with the many processes for impregnating materials with liquids by pressure fluctuation. In such processes, it is a common practice to immerse a solid and a liquid and then alternately to increase and decrease the pressure of the liquid in which the solid is immersed. Such processes differ fundamentally from the present invention in that they aim to drive an impregnating liquid beneath the surface of a clean Solid in order to impregnate the solid with the liquid; but by contrast, the present invention aims to move a liquid radially away from the surface of a dirty fiber thereby to remove and carry dirt away from the fiber by the action of a moving liquid applied to thedirt in effect from the underside or fiber side of the dirt.
Indeed, far from teaching the present invention, the well known application of variable pressure in the impregnating art further emphasizes the pioneering nature of the present invention. In the art of impregnating, the application of variable pressure merely did better what had already been done before, that is, it merely speeded up the inward penetration of the impregnant. But in sharp contrast, the present invention achieves a plurality of results that have never before been achieved in this art, in a manner having no counterpart in this art, by achieving liquid movements in all directions, substantially all of which directions are radial to an adjacent fiber surface, and by achieving liquid movement from points inside the contours of dirty fibers to points outside the contours, while at the same time assuring that there will be a change of liquid adjacent the fiber surface to carry off the dirt thus removed and also a removal and change of.dirt laden liquid during washing. Accordingly, the present invention is a pioneer invention and is a major milestone in the development of the art of cleaning.
Just as the present invention is not to be confused with impregnating, for reasons discussed above, it is also not to be confused with prior art methods of cleaning in which pressure change is applied to material immersed in a cleaning liquid in a chamber and wherein the pressure change is applied in such a way as to promote no bodily movement of the liquid past the fabric, with the result that dirt loosened by pressure change is not carried off from the fabric but is merely redeposited on the (fabric by the filter action of the fabric. Such methods merely redistribute on the fabric substantially the same quantity of dirt that was initially present in the fabric.
As mentioned above, the dry-to-dry cycle time of the present invention is so short that drying or reclamation can economically be carried out in the same machine as the washing and extracting operation. Accordingly, another feature of the invention is that preparation for reclamation is begun during extraction. Specifically, hot vapors, which may be either air or vapors of the cleaning liquid or both, are circulated through the cleaning chamber during extraction, and this is achieved by introducing hot vapors into the central portion of the chamber and withdrawing them from a peripheral por-' tion of the chamber, whereby the rapidly spinning container during the extraction portion of the cycle functions as a centrifugal fan to circulate the heated vapor and speed heating of the wet fabric even during extraction. Preferably, the hot vapors passing in contact with the fabric contain a substantial proportion of vapors of the cleaning iiquid, thereby to increase the heat content of the hot vapors and to speed the heating of the fabric.
Another very important feature of the invention is the drying portion of the cycle which is carried out first by heating the fabric and then by drawing a deep vacuum on it. The principal portion of the reclamation cycle follows immediately on the extraction cycle, and is characterized by a relatively slow tumbling of the fabric in the chamber. Hot vapors, preferably laden with'vapors of cleaning liquid, are circulated through the fabnic to raise the fabric to an elevated temperature. Thereafter, a deep vacuum is drawn on the heated wet fabric, and the remaining liquid in the fabric is quickly boiled off, leaving the fabric quite dry but not too hot to be comfortably removed from the machine by hand.
The drying or reclamation process of the present invention is not to be confused with drying processes in which vacuum is continuously pulled during drying and heat is continuously simultaneously appiied to fabric. In such prior art drying or reclamation processes, it is necessary to apply the heat directly to the fabric, as by heating elements in contact with the fabric, in order to supply the necessary heat to the fabric. By contrast, in the present invention, in which the fabric is heated by circuiation of hot vapors prior to drawing the deep vacuum, it it possible to apply as much heat as is desired to the fabric in the shortest possible time, by increasing the flow rate and/or heat content of the hot circulating vapors, thereby to heat the fabric in the minimum time. For this purpose, the heating elements are disposed outside the chamber. When it is attempted simultaneously to heat the fabric and draw vacuum, however, or alternately to heat the fabric and draw vacuum in a plurality of repeating cycles, it is found that the heating must be performed quite'slowly so as to avoid charring the fabric or carbonizing the cleaning liquid because the heat must be applied directly to the fabric by the heating elements.
Thus, an important feature of the drying or reclamation process of the present invention is that the heat content of the fabric and its contained liquid at the higher temperature and pressure is at least about as great as the heat content of the fabric at the lower temperature and pressure to which it falls upon drawing the deep vacuum, plus the total heat of vaporization of the contained solvent at that lower temperature and pressure.
As indicated above, the cleaning cycle of the present invention, from dry-to-dry, is preferably a vacuum cycle, characterized by varying degrees of vacuum throughout the cycle. Another very important feature of the present invention is the way in which this vacuum is achieved and maintained. The kinetic energy of a relatively high pressure stream of liquid is used to withdraw a relatively low pressure stream of vapor from the cleaning chamber. This liquid is the same cleaning liquid that is used in the wash cycle. A body of cleaning liquid is maintained, and the relatively high pressure stream of liquid, with its entrained relatively low pressure stream of vapor, is directed beneath the surface of this body of liquid. Preferably, the vacuum-producing device is in the form of an eductor with the high pressure stream of liquid supplied from the body of liquid and the outlet of the eductor directed to a point below the surface of the body of liquid. Preferably, at least the outlet of the eductor is su merged in the body of cleaning liquid. This method of vacuum production is especially desirable in connection with the recovery of dry cleaning solvent vapors, because the vapors are partially condensed as they enter the low pressure inlet of the eductor and contact the higher pressure liquid stream, and are still further condensed when they emerge from the eductor and bubble up through the body of dry cleaning solvent.
In the case of dry cleaning, a further feature of the invention in connection with the production of vacuum is that the vapors withdrawn from the cleaning chamber under vacuum are partially condensed to the extent necessary to condense substantially all the water in the vapors and a portion of the dry cleaning solvent. The remaining vapors, and the condensed water and the condensed solvent, are then gravity separated in a phase separator, with the uncondensed vapor going to the low pressure inlet of the eductor, the water being discarded and the dry cleaning solvent being returned to the collected body of solvent. It has been found that in this way, the formation of wrinkles in the fabric in the course of the dry cleaning process can be entirely avoided.
Still another feature of the present invention in connection with'dry cleaning is the provision of a closed circuit refrigeration cycle, characterized in that a refrigerant moves in a closed cycle alternately through compression and expansion, with the heated refrigerant following compression being used to heat vapors that are introduced into the cleaning chamber to heat the fabric, and the cooled refrigerant following expansion being used in the partial condensation of vapors from the cleaning chamber, referred to immediately above, and also to condense excess vapors vented from storage. The refrigerant following expansion is also used to refrigerate the collected body of dry cleaning solvent.
Finally, the invention is characterized by an easy method of recovering dry cleaning solvent from the muck, comprising backwashing the filter, that is, running liquid through the filter and/or adsorber units in the reverse of the normal direction so as to dislodge finely divided filter aid and/ or adsorbent from the solvent cleaning equipment, followed by a vacuum reclamation of the muck thus dislodged. Preferably, the muck from which the solvent is to be reclaimed is placed in vacuum communication with the low pressure inlet of the eductor, so that no application of large quantities of extraneous heat is necessary to remove and recover the solvent from the muck in a short period of time.
Referring now to the drawings in further detail, some of the essential operative characteristics of the cleaning cycle of the invention as they are understood at present are set forth in FIGURES 1 through 5. As is there shown somewhat fancifully, a section of fiber 1 is shown of great- 1y elongated cylindrical configuration. A multiplicity of particles of dirt 3 are indicated as clinging to the outside of fiber 1. Fiber 1 is immersed in a body of liquid, and as the pressure of the liquid is increased, the liquid moves radially inwardly from the position indicated in FIGURE 2 to the position indicated in FIGURE 3, in which the farthest inward advance of the liquid is indicated by a circular broken line 5, represented by parallel lines 5 in FIGURE 1. In FIGURE 3, the direction in which the liquid moves is indicated by the arrows.
FIGURE 4 shows what happens when the pressure is again reduced. The gas within the fiber, compressed within the line 5 as in FIGURE 3, expands again and moves out toward its original outer limit at the outer contour of fiber 1 as in FIGURE 2. In so doing, the liquid moves in the directions of the arrows shown in FIGURE 4, the outermost limit of the expanding vapor, that is, the innermost limit of the receding liquid being shown by the broken line '7 in FIGURE 4. This outward rush of liquid radially of the fiber out and through the surface of the fiber to which the dirt particles cling, removes the dirt particles as shown in FIGURE 4. The particles then separate from the fibers, leaving the clean fiber as in FIGURE 5, the fiber no longer containing more liquid than normally penetrates by capillarity or absorption.
The contrast between the cleaning cycle of the present invention and the prior art is emphasized in FIGURE 6, in which the flow of liquid relative to dirty fibers according to the prior art is set forth. As is obvious from an inspection of FIGURE 6, the direction of liquid movement relative to the surfaces of the fiber is essentially at random and dirt removal is only fortuitous. At no point does the liquid move radially outwardly of the fiber at the fiber surface so as to remove the dirt by the most direct possible liquid movement as shown in FIGURE 4.
One of the many embodiments'of apparatus by which the present invention may be practiced is shown schematically in FIGURE 7. The entire operation of the present invention, including washing, extracting and reclaiming, is conducted in a closed cleaning chamber 9' which is a pressure-type vessel having a closure comprising a door (not shown). Preferably, the vessel is cylindrical for added strength under pressure. Cleaning chamber 9 contains a rotatable basket or cylinder 11, the outer cylindrical periphery of which is multiperforate. Chamber 9 and cylinder 11 are coaxial about a horizontal axis. Cylinder 11 rotates on its axis relative to stationary chamber 9 and contains a plurality of inwardly extending baffles 13 on the inner side of its cylindrical periphery, for the purpose of agitating the fabric and the cleaning liquid as the cylinder turns.
Means are provided for turning the cylinder at variable speeds, comprising a wash motor 15 which rotates the cylinder at a relatively low speed of rotation, for example 40 r.p.m., and an extract motor 17 that rotates the cylinder at a relatively high speed of rotation, for example, 625 r.p.m. Motor 15 operates during washing and drying, while motor 17 operates during spin drying or extraction.
In the case of a dry cleaning operation, a closed and hermetically sealed tank 19 is provided that serves to store a body of dry cleaning solvent 21. As used herein, the term body may include several separate sub-bodies of solvent maintained under different temperatures and/ or pressures. Solvent 21 is 'Withdrawn from the bottom of the supply through a supply conduit 23 and passes through a filter and/ or adsorber unit indicated at 25, on its way to the cleaning chamber. The solvent cleaning means indicated generally at 25 can of course take the form of plural units containing different porous solids for cleaning the liquid and preferably includes finely divided solid material in the form of filter aids or adsorbents or the like, as discussed above. However, for the sake of brevity, the solvent cleaning system will hereafter be referred to as ter 25, it being understood that this term may refer to a plurality of different units including adsorption units.
A filter pump 27 in conduit 23 urges solvent toward be only a small fraction of the quantity of solvent in the vapor.
The partially condensed mixture enters a phase separator 61, from which uncondensed vapor phase material containing at least a substantial proportion of vapors of solvent is removed through an overhead conduit 63. The condensed water and solvent will accumulate in two layers in the bottom of the phase separator, because they have different densities and are immiscible. In the case of a solvent such as perchlorethylene, which is substantially heavier than water, there will be an upper layer 65 of water which may be removed through a conduit 67 and filter 25 under the control of a valve 29. Downstream of filter 25, a fill valve 3-1 regulates the flow of solvent into the cleaning chamber. A conduit 33 is provided, under control of a valve 35, that permits the flow of solvent past filter 25. A by-pass conduit 37 also permits the flow of solvent from filter 25 back to tank 19. Conduit 37 is controlled by by-pass valve 39. A conduit 41 controlled by a valve 43 permits the flow of solvent back to tank 19 without going through filter 25. Accordingly, liquid from tank 19 may be sent either through filter 25 and into chamber 9, or through filter 25 and back to tank 19, or past filter 25 into chamber 9, or past filter 25 and back to tank 19, or along several other paths, as will be apparent from FIGURE 7.
Liquid in chamber 9 can drain by gravity through a dump conduit 45 under control of a dump valve 47, back into tank 19. To permit the pressure in chamber 9 to rise toward atmospheric, a vacuum break conduit 49 is provided that lets air into chamber 9 undercontrol of vacuum break valve 5 1.
To remove vapor from the chamber so as to create a vacuum in chamber 9 and/or to dry the fabric, a vapor removal conduit 53 is provided that communicates with a peripheral portion of chamber 9 outside cylinder 11. A pair of vapor removal valves 55 and 57 are provided in conduit 53in parallel to each other. Valve 55 is operable between fully opened and fully closed positions, while valve 57 is more in the nature of a bleed valve that can be set for a continuous, rather restricted flow of vapor therethrough.
The vapor leaving chamber 9 through conduit 53 passes through a condenser 59 in which it is partially condensed to the extent needed to condense substantially all of the water and a substantial proportion of the solvent in the vapor. Even if the solvent .boils higher than water, as in the case of perchlorethylene, substantially all of the water can be condensed while only partially condensing the perchlo-rethylene, because the quantity of water in the vapor in conduit 53 from a dry cleaning operation will sewercd, and a lower layer 69 of solvent which can be removed through conduit 71 past check valve 73, past control valve 75 and returned to tank 19'. Phase separator 61 is of course shown only very schematically. It will be understood that it can take any of the usual forms for separating unmixed liquids by gravity, such as by means of a float that will sink in water and float in perchlorethylene and which regulates the operation of control valve 75, closing valve 75 at a lower position of the float and opening valve 75 at an upper position of the float, in combination with a liquid overflow for water into conduit 67.
Vapor is moved through the system by means of an eductor 77 submerged in tank 19. Eductor 77 has a high pressure inlet 79 and a low pressure inlet 81, a stream of liquid under relatively high pressure passing through the high pressure inlet serving to draw in a stream of relatively low pressure fluid through the low pressure inlet 81. The mixed stream then passes through a reduced throat 83 and emerges from an. outlet 85 beneath the surface of and in contact with solvent 21. An eductor pump 37 draws liquid from beneath the surface of solvent 21 in tank 19 and forces it through high pressure inlet 79 at elevated pressure and at a substantial velocity as the high pressure stream. A motor 89 is mounted on a removable cover 91 on tank 19 and has its drive shaft 93 extending vertically down to pump 37 to drive pump 87. Conduit 63 also passes downwardly through cover 91 to the low pressure inlet of eductor 77. A coupling 95 in conduit 63 permits the portion of conduit 63 secured to cover 91 to be detached from the rest of conduit '63, so that cover 91 with motor 89 and shaft 93 and pump 87 and eductor 77 can be removed as a unit from the top of the tank without the need for draining the solvent from the tank. Detachable fastenings 97 removably secure cover 91 in hermetically sealed relationship with tank 19. Tank 19 is thus entirely sealed except for the entrance and exit conduits for liquid and vapor and drive shaft 93.
A vent conduit 99 provides egress for vapors in tank 19 above body of solvent 21. The vapors pass through a condenser 101 in which substantially all of the solvent vapors jare condensed and fall backwardly into'tank 19 in liquid phase A check valve in the form of a butterfly valve 193 ensures that vapor can move only one way through conduit 99, and is especially useful in climates characterized by high humidity, so that the quantity of water added to the system will be kept to a minimum.
A vapor recycle conduit 105 is also provided, for removing vapors from chamber 9 from the outer side of cylinder 11, heating the vapors, and returning them to the interior of the chamber within cylinder 11. A filter 106 catches and removes solid particles of dirt and lint from the vapor circulating in conduit 165-. To facilitate circulation of the vapors, a fan 107 is provided in conduit 105. Heaters 109 and 111 are also traversed in series by the vapors in conduit 1G5. Heater 109 operates at a lower temperaturelevel and heater 1 11 operates at a higher temperature level. Heater 111 is heated by a heating coil 113, which preferably is'su-pp'lied with steam from a boiler. A vapor recycle valve 115 in a conduit 117 controllably connects conduit 105 with vent conduit 99 so that vapors free from water can be added to the 1 l vapor recycling in conduit 1115. Of course, instead of connecting conduit 117 to conduit 9a downstream of condenser 101 it is also possible to connect conduit 117 directly with the vapor space in tank 19.
A closed cycle refrigeration circuit 119 is also provided, comprising the usual compressor 121 and expansion valve 123. However, the refrigeration circuit of the present invention differs from those heretofore known in this art in that relatively warm vapor following compression in compressor 121 is utilized in a heating coil 125 that provides heat for heater 109. Heating coil 125 is thus downstream of compressor 121 and upstream of expansion valve 123. Cooling coils 127 and 129 are provided in condensers 59 and 101, respectively, and a further cooling coil 13 1 is submerged in the solvent 21 in tank 19 so as to maintain the solvent temperature at a desirably low level, e.g., not more than about 70 F. or lower depending on the nature of the solvent. Cooling coils 127, 129, and 131 are shown in parallel with each other; but of course it will be realized that they can be in series or in other arrangements, depending upon the desired refrigeration duty to be borne by them. In any event, cooling coils 127, 129, and 13 1 are downstream of expansion valve 123 and upstream of compressor 12 1 in circuit 119. Of course, the temperature level of refrigeration circuit 119 may be adjusted upwardly or downwardly as desired. For example, an air cooler (not shown) for the refrigerant can be provided downstream of heating coil 125 and upstream of expansion valve 123. The refrigerant itself may be any of the usual refrigerants, such as ammonia or the halogenated hydrocarbons, e.g., chlorodifiuor-omethane (Freon 22).
For reclaiming solvent from spent muck from filter 25, a filter backwash conduit 133 is provided under the control of a valve 135. Conduit 1133 delivers into a muck reclaimer 137 characterized by a tube sheet .13? provided with a plurality of openings in each of which is set a multiperforate tube or screen tube 14-1, so that backwashed muck can enter reclaimer 137 above tube sheet 139 and its liquid drain and be drawn through tubes 141 and out through a conduit 143 controlled by a valve 145, that communicates with conduit 63, so that the vacuum in conduit 63 induced by eductor 77 also pulls on muck reclaimer 137 when valve 135 is closed.
A dry cleaning cycle according to the present invention will now be described in connection with the cycle diagram and pressure diagram of FIGURES 8 and 9. It is of course to be understood that the following cycle is merely one of many that can be devised to carry out the principles of the present invention. It is also to be understood that the pressures indicated on FIGURE 9 are only generally representative of what goes on in the cleaning chamber. It should be noted, however, that FIGURES 8 and 9 are in vertical alignment with each other, so that the events depicted in FIGURE 8 correpond to the pressures indicated directly below them in FIGURE 9. It should further be noted at the outset that the total cycle time, dry-to-dry, is only 15 minutes, which is incredibly short for a commercial dry cleaning machine using a solvent such as perchlorethylene. This cycle time is not merely illustrative but is one of the actual very short cycle times that have been achieved by the practice of the present invention. In general, the short cycle time is achieved by the unique cleaning methods, by certain novel steps during extraction, by the unique reclamation process of the present invention, and by so arranging the cycle that a number of the events in the cycle overlap each other timewise. These various features of the invention coact together to permit an extremely short overall cycle time for the dry-to-dry process adapted to be carried out in a single machine.
Beginning at the left hand margin of FIGURE 8, therefore, it will be seen that as the cycle begins, the timer motor (not shown) is actuated which may for example turn a cam shaft (not shown) through one full revolution during the cycle. The cam shaft may carry a series of generally circular cams (not shown) each of which corresponds to one of the timed elements of the present invention. Although the cycle of the present invention is novel in many respects, the mechanical operation of the timer motor and cam shaft, and the concept of timing the various elements each by means of its individual cam on the cam shaft, are quite conventional and hence need not be illustrated in the drawings.
The filter pump motor 27 is shown as being in operation throughout the cycle. Of course, it will be understood that except when flow valve 31 is open and solvent is being introduced into chamber 9, filter pump motor 27 may be operated or not as desired and as necessary to keep the solvent clean. Thus, filter pump motor 27 may be operated during the entire cycle, or during only part of the cycle, and during periods of operation that fall between cycles.
The eductor pump motor 89 operates throughout the cycle and a vacuum is constantly being drawn on conduit 63 by eductor 77. Even when vapor removal valve 55 is closed, bleed valve 57 is open, so that vacuum is continuously being drawn on chamber 9, although at a greater or lesser rate depending on whether valve 55 is open or closed, respectively. It is thus assured that the pressure in chamber will never exceed atmospheric, with the result that there is a minimum opportunity for solvent vapors to escape from the system to the ambient atmosphere.
Wash motor 15 is also shown as operating throughout the cycle. Actually, wash motor 15 turns cylinder 11 at its characteristic slow speed only during the first few minutes of the cycle, generally corresponding to the wash cycle, and during the last half of the cycle generally cor responding to reclamation or drying. Extract motor 17 spins the cylinder at relatively high speed during the intervening extract cycle, but it is easier to leave Wash motor .15 running during extraction, disconnecting it by means of a clutch, than to turn it on and off, although of course wash motor 15 may, if desired, be shut off during the extract cycle corresponding to the time between the four and seven minute intervals.
As the cycle starts, therefore, vapor removal valve 55 is open, fan 167 is operating and by-pass valve 39 is open. 'Fill valve 31 is closed, as are also dump valve 47 and vacuum break valve 51. This means that no solvent is entering chamber 9, but that fan 107 is circulating air at high speed through conduit and filter 106 and through the chamber while cylinder 11 slowly turns and eductor 77 draws a fairly deep vacuum in chamber 9, as represented by the sharply descending line on FIGURE 9 during the first 45 seconds or so of the first minute.
It is important to notice that during these first 45 seconds, the fabric is being tumbled dry and is being thoroughly and forcefully ventilated by a rapid flow of a large volume of vapor at the same time that the vapor in the chamber is being withdrawn and recycled through conduit 105. A result of this agitation and forceful blowing of the fabric and vapor withdrawal is that a good bit of dirt and dust is dislodged from the fabric and is drawn off in the withdrawn vapor. A great deal of dirt has been observed to accumulate on filter 106 during the first 45 seconds before any dry cleaning solvent touches the fabric. In the case of dry cleaning, it is important to recycle the vapor through the chamber rather than merely expel it to the atmosphere, for the recycling vapor will ordinarily contain an appreciable quantity of solvent vapor. The recycling of the vapor, in turn, makes it de sirable to include filter v106 to prevent dirt from being carried back into the fabric.
It should also be noted that during the first 45 seconds two events have been occurring simultaneously: (1) dirt has been dislodged and removed from the fabric by vigorous blowing; and (2) a fairly deep vacuum has been drawn in the chamber in preparation for the subsequent to note that at this time, the fabric is under a fairly deep vacuum, and it has been observed that the wetting of the fabric by the solvent is enormously improved by contacting the fabric with the solvent after a fiairly deep vacuum has been drawn on th-e'fabric. Apparently, the drawing of the vacuum ion the fabric prior to attempting to wet the fabric with the solvent reduces the quantity of adsorbed air or other vapor at the surface of the fibers and thus decreases theinterfacial surface tension between the fibers and the solvent upon initial contact. This action of drawing the vacuum before the solvent contactsthe fibers is distinctly different in its result from the operation of drawing a vacuum after the solvent contacts the fibers,
for in that latter instance, the relatively high surface tension between the vapor at the surface of the fiber and the solvent has already been established and cannot be overcome to the same extent by the drawing of the vacuum as if the vacuum is drawn prior to contact between the fiber and the solvent.
Another important result of drawing the vacuum before the solvent is admitted is that the flow of solvent into chamber 9' is greatly augmented by the vacuum. There is much less need to displace a gas with the entering liquid than when the chamber is at or about ambient atmospheric pressure. Moreover, flow through filter 25 is facilitated by the pressure differential in conduit 23 upstream and downstream of filter 2'5. Bleed valve 57 remains open, despite the closing of vapor removal valve 55, so that the escape of what vapor remains in chamber 9 is abetted during solvent entry. The rapid solvent entry, of course, contributes to the shortness of the overall cycle time.
From 45 seconds to about a minute and three-quarters, the solvent continues to enter chamber 9 until solvent fills about half the chamber or somewhat less. Depending upon the rate of solvent entry and the setting of bleed valve 57, the pressure in the chamber may or may not rise from the fairly deep vacuum of 45 seconds. In the illustrated embodiment, FIGURE 9 indicates a pressure rise due to solvent entering chamber 9 faster than vapor is bled through valve 57. in any event, at a minute and three-quarters, dump valve '47 is opened to drain the solvent through dump conduit 45. The draining of the solvent would be very slow were it not for the fact that at the same time, vacuum break valve 51 opens to let air enter through conduit 49, so that the pressure in chamber 9' rises rapidly toward atmospheric and solvent dumps quickly through conduit 45 into tank '19. After about 10* seconds, vacuum break valve 51 closes, whereupon the draining through dump valve 47 is greatly reduced or stopped altogether. However,.fill valve 31 rebecause vapor is being withdrawn through bleed valve-57 faster than solvent is entering through fill valve 31, until a low pressure is reached at about 15 seconds after three minutes, as shown in FIGURE 9. During this portion of the cycle, dump valve 47 is closed for this final filling of the chamber. At the end of this final filling, fill valve 31 closes and by-pass valve 39 opens, so that thereafter throughout the cycle the solvent will simply be recycled to the tank 19. After this final fill, dump valve 47 and vacuum break valve 51 both open, atabout three minutes and 15 seconds, whereupon the pressure rapidly rises as is shown by the ascending line after the three minute interval and up to about the four minute interval, which is mains open, sothat solvent is moving backinto chamber 7 9 tending to replenishthat which was dumped when vacuum break valve 51 was briefly open. At the same time,
however, a vacuum is being drawn through bleed valve 57, and at this time, vapor is being withdrawn through bleed valve57 at a faster rate than solvent is entering the chamber through conduit 23. As a result, the pressure in the chamber falls oif somewhat, as is indicated by the descending line immediately following the two-. minute interval in FIGURE 9. Shortly after two minutes, the vacuum break valve 51 opens again, and dump valve 47 remains open, so that even though the solvent level rapidly falls, air rushes in still faster, which accounts for the rise in chamber pressure betweentwo minutesup until about three minutes in FIGURE 9. At almost three minutes, the vacuum break valve closes and the fill valve 31 remains open, which causes the pressure to again fall the end of the wash cycle. r
Throughout these various pressurefiuctuations during the wash cycle, a very important washing action has been going on quite independently of the fact that the fabric has been bodily agitated relative to the solvent. From about the 45 seconds mark, when fill valve 31 first opened and solvent began to enter the chamber, the solvent 7 was contacting the fibers of the fabric under increasing pressure. This assured that the solvent was penetrating the fibers with an action far more rapid and efficient than if the fibers had simply been left to soak up the solvent at ambient atmospheric pressure. As mentioned above, the reduced quantity of vapor adjacent the surface of the fibers greatly augmented this action, and the increasing pressure of the solvent on the fiber as the pressure rose from a fairly deep vacuum toward atmospheric pressure took advantage of this increased wettability of the fiber and in addition positively caused a penetration of the fiber independent of mere absorption of solvent by the fiber. T hits, the saturation of the fabric by the solvent was rapidly effected first by increasing the Wettability of the fibers by the solvent under greatly reduced pressure, and second by thereafter contacting the fibers with the solvent and increasing the pressure of the solvent on the fibers to cause an initial penetration of the fabricby the solvent. Following this initial penetration, the subsequent reductions in pressure, shown in FIGURE 9 immediately following the second and third minute intervals, caused the radial (2) The increased Wettability of the fabric when the fabric is under vacuum as initially contacted by the liquid;
(3) The penetration of the solvent into the newly-wet fabric upon increasing pressure, for example during the interval preceding the two-minute interval; and
(4) The radial outflow of solvent relative to the individual fibers for example immediately following either or both or" the two and three minute intervals.
At four minutes, the-extract motor 17 starts to operate and the cylinder 11 starts to spin at relatively high velocity. It should be noted that cylinder 11 is provided with baffies 13, and also that the tabric withincylinder 11 is never uniformly arranged about the periphery of the cylinder. As a result, cylinder .11 presents a somewhat ,unev en interior, and as the cylinder with its uneven interior peripheral portion spins at-high speed, it has the ability to act as the rotor of a centrifugal fan. .A very cylinder 11 during extraction. At the same time, refrigeration circuit 119 is in operation and coil 125 is serving to heat heater 109, so that the vapors circulating through conduit 105 are heated and tend to raise the temperature of the fabric during extraction.
After extraction is partly over, heater 11 1 with its steam coil 113 is actuated to impart additional heat to the vapor circulating in conduit 105. At the same time, fan 107 is actuated to increase the circulation and also increase the heat transfer to the fabric. As the fabric increases in temperature, the amount of solvent leaving it in vapor phase increases, so that vapor removal valve 55 is also opened, whereupon the withdrawal of vaporized solvent from chamber 9 through conduit 53 is greatly increased. These vapors withdrawn through conduit53 are, as mentioned above, partially condensed in condenser 59, then further condensed by contact with the relatively high pressure stream of liquid solvent as they enter eductor 77 through the low pressure inlet, still further condensed when the remainder of the vapor emerges from outlet 85 of eductor 77 and bubbles through the relatively cool solvent 21, and then finally substantially completely condensed as they pass out through vent conduit 99 through condenser 101.
Heating the fabric preparatory to reclamation of the solvent has thus begun at the very onset of extraction and is increased toward the end of extraction. The reclamation and extraction cycles thus overlap each other in the present invention, and this is another example of doubling up the events of the cycle of the present invention so as to reduce overall cycle time.
At the seven minute interval, extraction is over and cylinder 11 returns to its previous relatively slow speed of rotation so that the damp dried fabric is tumbled in the cylinder. However, fan 107 continues to operate, and hot solvent vapors continue to recycle at high velocity through conduit 1 05. The build-up of excessive solvent vapor in the cleaning chamber is prevented by continuous vapor removal through valve 55.- Heat continues to be added to the fabric by heat exchange, in heaters 169 and 11 1. The temperature and heat content of the wet fabric is rapidly rising during the first four and one-half minutes of reclamation, upto about the 11% minute interval.
At the 11% minute interval, vapor recycle valve 115 closes. This means that the only communication between the cleaning chamber and tank 19 is now through the inlet 81 of eductor 77. As a result, a deep vacuum is again very swiftly drawn in chamber 9, for the apparatus is now in the same condition as during the first 45 seconds of the cycle; however, the fabric is now damp dry and quite hot. As the pressure drops to a fairly deep vacuum, the boiling point of the solvent rapidly falls. The remaining solvent entirely boils off, leaving the fabric dry. The boil-off is quite napid, and this final drying need proceed only for a short time. It is important, however, that prior to drawing the vacuum, the temperature of the damp dry fabric be sufliciently high that its heat content will be at least about as great as the heat content of the dry fabric after drawing the vacuum plus the total heat of vaporization of the solvent-at the conditions of temperature andpressure under which vaporization occurred.
In this condition, it will be remembered that the temperature of the fabric and solvent will drop during boil-01f, and that the heat of vaporization of the solvent will in general vary inversely as the temperature. The temperature to which the fabric and solvent drop during boiloff should of course be sufficiently high that the solvent boils OE and the fabric is left dry.
When this specification and the claims speak of the heat content of the hot damp fabric at the higher temperature and pressure being about equal to at least the heat content of the fabric plus the total heat of vaporization at the lower temperature and pressure, it is to be rememe bered that heater 111 continues in operation for a short n3 time after the deep vacuum is drawn, so that heat is still added to the fabric for a short time after the deep vacuum begins to be drawn. Therefore, the term about is to be construed with this proviso in mind.
The precise temperature conditions at the higher and lower temperatures cannot be set forth with accuracy but must be determined having regard for the quantity of fabric, the nature of the dry cleaning solvent, the heating equipment, and other factors rwell known to persons skilled in this art. The temperature of the fabric cannot be measured with accuracy and therefore cannot be set forth in this specification. Sufiice it to say, however, that the necessary quantities'of heat to be addedto and removed from the fabric so as to arrive at a dry fabric at the lower temperature and pressure after drawing the deep vacuum can readily be ascertained by those having ordinary skill in this art, having regard for the vapor pressure and latent heat of vaporization curves of the particular solvent in question and the specific heats of the fabric undergoing cleaning.
In the cycle of the present invention, therefore, the rapid boil-off of the solvent depends upon adding substantially all of the heat necessary to achieve that boiloff to the damp dry fabric prior .to drawing the deep vacuum. This heat addition is effected by rapid circulation of hot solvent vapors through the tumbling fabric. The addition of solvent to what would otherwise be hot air increases the heat content of this rapidly recirculating vapor, and the quantity of heat to be added in this manner can be increased as much as desired by increasing the rate of recirculation of the hot vapors. Moreover, dam-age to the fabric is avoided because the heat exchange between the heating elements and the fabric is indirect: The heaters are outside the chamber and are not in direct contact with the fabric. In this connection, the use of steam heat'in heater 111 for the high temperature level heater is preferred, because the pressure of the steam can be so controlled that its temperature will never'rise high enough to cause an organic cleaning solvent to carbonlze or form toxic decomposition products.
At the end of vacuum reclamation, vacuum break valve 51 opens again to let in suflicient air to raise the pressure of the chamber to atmospheric. Fan 107 continues to operate and the cylinder continues to turn during these last 45 seconds or so of the cycle, and vapor removal valve 55 remains open with eductor 77 openating, so that solvent vapors within the chamber tend to be progressively displaced and-replaced by air entering the chamber through vacuum break conduit 49 at the very end of the cycle. At the same time, the fabric is aired out by the tumbling and the fan action in the presence of fresh air, so that solvent vapors and odors are to a large extent removed from the fabric before it is removed from the cleaning chamber.
With the return of the chamber to atmospheric pressure, the door can be opened and the dry fabric removed. The fabric will then be found to be at a temperature such that it can be handled comfortably, for the relatively high heat of the fabric just before the deep vacuum was drawn during reclamation was reduced by the boiling away of the solvent at the end of reclamation.
From time to time, the filter powder or other finely divided solid solvent cleaning agent on filter 25 will become spent and must be reclaimed to recover its solvent content. To do this, it is necessary only to open valves 35, 135, and 145 and close valves 29, 31, 39, and 43, with pump 27 operating, so that solvent enters filter 25 from the opposite direction and reverse Washes or backwashes filter 25, so that the muck is stripped from filter 25 and passes through conduit 133 in a slurry and enters muck reclaimer 137 where it surrounds screen tubes 14d. Eductor 77 is operating to draw vacuum through conduit 143 with valve 145 open, and the solvent is rapidly drained off through tubes 14-1 and conduit 143 and is returned to tank 19. Thereafter, valve is closed,
whereupon a relatively deep vacuum is drawn in reclaimer 137. After reclamation, the dry muck can be removed from reclaimer 137 through a door (not shown).
Although the solvent in the muck does not necessarily boil during reclamation in 137, nevertheless, the rate of evaporation of the solvent from the muck at ambient temperature is greatly increased. Moreover, with valve 135 closed, a vacuum can be drawn in reclaimer 137 with the rest of the system in operation. The evaporation of the solvent from the muck in reclaimer 137 under vacuum does not substantially affect the operation of any other portion of the system, so that muck can be transferred to reclaimer 137 and left there to be dried under vacuum while the system of the present invention is otherwise in normal operation. This is in sharp contrast to the usual muck reclairners, which in the first place have no such provision for convenient transfer to the reclaimer as in the present invention, and in the second place use steam or other heat to dry to boil off the solvent at elevated temperature. Such elevated temperature muck reclaimers or cookers, moreover, have the great disadvantage that they are slow, consume a great deal of power, and require a great deal of extra equipment. The reclamation method of the present invention, however, obviously requires only a minimum of additional equipment, and is fast and inexpensive to practice.
This application is a continuation-in-part of copending application Serial No. 44,978, filed July 25, 1960.
From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.
Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. In particular, there are many alternative ways of producing pressure change in the cleaning chamber during the washing cycle. In the illustrated embodiment, the pressure rises upon discharge of the solvent and falls upon reintroduction of rinse solvent; but the reverse arrangement can be effected, in which case the dump conduit and dump valve 47 are made sutliciently large that a substantial dumping flow rate of solvent can be achieved even with vacuum break valve 51 closed, so that the dumping of solvent would drop the pressure in the chamber and the refilling with solvent would again raise the pressure. These and many other modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.
What is claimed is:
1. A method of dry clean-ing soiled fabric, comprising passing dry cleaning solvent about a closed fluid circuit alternately through a chamber and through a solvent cleaning zone, wetting soiled fabric with the solvent in the chamber, causing the pressure in the chamber to fluctuate by introducing solvent into the chamber and discharging solvent from the chamber at flow rates that alternately exceed each other, the points of said introduction and of said discharge of the solvent being spaced a substantial distance apart so as to discharge a difierent portion of the solvent each time the rate of liquid discharge exceeds the rate of liquid introduction thereby progressively to rinse the fabric with clean solvent from the solvent cleaning zone.
2. A method of cleaning soiled fabric, comprising wetting soiled fabric with a cleaning liquid in a chamber, causing the pressure in the chamber to fluctuate by introducing cleaning liquid into the chamber and discharging cleaning liquid from the chamber at flow rates that alternately exceed each other, the points of said introduction and of said discharge of the liquid being spaced a substantial distance apart so as to discharge different portions of the cleaning liquid each time the rate of liquid 18 discharge exceeds the rate of liquid introduction thereby progressively to rinse the fabric.
3. A method of dry cleaning soiled fabric, comprising tumbling the soiled fabric in contact with a dry cleaning solvent, centrifugally extracting a substantial portion of the dry cleaning solvent from the fabric, heating the fabric after extraction to an elevated first temperature at a first pressure, and reducing the pressure on the wet fabric to a second pressure by withdrawing solvent vapor from the fabric by applying the kinetic energy of a relatively high pressure stream of liquid to thus-withdrawn vapor thereby to boil off the solvent and reduce the temperature of the fabric to a second temperature, said first and second pressures and said first and second temperatures being so related that the heat content of the fabric and solvent at the first temperature and pressure are at least about as great as the heat content of the fabric plus the total heat of vaporization of the solvent at the second temperature and pressure.
4. A method of dry cleaning soiled fabric in a chamber, comprising agitating soiled dry fabric in a chamber while passing vapor rapidly in contact with the fabric thereby to remove solid dirt from the fabrics, withdrawing the vapor from the chamber and removing solid dirt from the vapor and recycling the vapor into contact with the fabric in the chamber, and then wetting the fabric in the chamber with a dry cleaning solvent.
5. A method of cleaning soiled fabric in a chamber, comprising agitating soiled dry fabric in a chamber while passing vapor rapidly in contact with the fabric thereby to remove solid dirt from the fabric and withdrawing the vapor from the chamber, and then wetting the fabric in the chamber with a cleaning liquid.
6. A method of cleaning soiled fabric in a chamber, comprising establishing in a chamber a body of fabric saturated with cleaning liquid and also in contact with a body of cleaning liquid in the chamber in excess of the liquid that saturates the fabric, the liquid occupying only a portion of the container with a vapor space in the container above the liquid, alternately increasing and decreasing the pressure in the chamber by introducing cleaning liquid into the chamber and discharging cleaning liquid from the chamber at flow rates that alternately exceed each other thereby to cause dirt to leave the fabric and enter the liquid that saturates the fabric, withdraw ing from the chamber liquid from. said body of excess liquid, and agitating the fabric in the chamber at least as early as the withdrawing step by assembling the fabric in a container rotating in the chamber and extending above the liquid level in the chamber thereby repeatedly to drop the fabric through the vapor into the liquid to cause at least a portion of the dirt-laden saturating liquid to move into said body of excess liquid and be replaced by cleaner liquid from said body of excess liquid.
7. A method of dry cleaning soiled fabric in a chamber, comprising establishing in a chamber a body of fabric saturated with dry cleaning solvent and also in contact with a body of dry cleaning solvent in the chamber in excess of the solvent that saturates the fabric, the solvent occupying only a portion of the container with a vapor space in the container above the solvent, alternately increasing and decreasing the pressure of the solvent and the vapor in the chamber by introducing solvent into the chamber and discharging solvent from the chamber at iiow rates that alternately exceed each other thereby to cause dirt to leave the fabric and enter the solvent that saturates the fabric, withdrawing from the chamber solvent from said body of excess solvent, and agitating the fabric in the chamber at least as early as the withdrawing step by tumbling the fabric in a container rotating in the chamber and extending above the solvent level in the chamber thereby repeatedly to drop the fabric through the vapor into the solvent to cause at least a portion of the dirt-laden saturating solvent to move into 19 said body of excess solvent and be replaced by cleaner solvent from said body of excess solvent.
8. A method of dry cleaning soiled fabric in a chamber, comprising establishing a body of dry cleaning solvent outside of the chamber, passing a stream of said solvent in liquid phase through an eductor as the high pressure fluid, introducing vapor from the interior of the chamber into the eductor as the low pressure fluid thereby to produce a partial vacuum in the chamber, introducing the efflucnt from the eductor beneath the surface of and in contact with said body of solvent, and establishing fluid communication between the interior of the chamber and said body of solvent at a point below the surface of the body of solvent thereby to hasten passage of the solvent into contact with soiled fabric in the chamber.
9. A method of dry cleaning soiled fabric in a chamber, comprising agitating soiled dry fabric in a chamber While passing vapor rapidly in contact with the fabric thereby to remove solid dirt from the fabric, withdrawing the vapor from the chamber and removing solid dirt from the vapor and recycling the vapor into contact with the fabric in the chamber, progressively reducing the pressure within the chamber during the step of passing vapor rapidly in contact with the fabric, and then wetting the fabric in the chamber with a dry cleaning solvent.
10. A method of cleaning soiled fabric in a chamber, comprising agitating soiled dry fabric in a chamber while passing vapor rapidly in contact with the fabric thereby to remove solid dirt from the fabric and withdrawing the vapor trom the chamber, progressively reducing the pressure within the chamber during the step of passing vapor rapidly in contact with the fabric, and then wetting the fabric in the chamber with a cleaning liquid.
11. A method of dry cleaning soiled fabric, comprising passing dry cleaning solvent about a closed fluid circuit alternately through a chamber and through a solvent cleaning zone, wetting soiled fabric with the solvent in the chamber, causing the pressure in the chamber to fluctuate by introducing solvent into the chamber and discharging solvent from the chamber at flow rates that alternately exceed each other, said solvent to be introduced moving toward the chamber along the closed fluid circuit on the downstream side of the solvent cleaning zone and said discharged solvent moving away from the chamber along the closed fluid circuit on the upstream side of the solvent cleaning zone so as to introduce into the chamber a portion of the solvent other than the immediately previously discharged portion of the solvent each time the rate of solvent introduction exceeds the rate of solvent discharge thereby progressively to rinse the fabric with clean solvent from the solvent cleaning zone.
12. A method of dry cleaning soiled fabric comprising passing dry cleaning solvent about a closed fluid circuit alternately through a chamber and through a solvent cleaning zone, said closed fluid circuit including a collected body of dry cleaning solvent, Wetting soiled fabric with the solvent in the chamber, causing the pressure in the chamber to fluctuate by introducing solvent int-o the chamber and discharging solvent from the chamber at flow rates that alternately exceed each other, said solvent to be introduced moving toward the chamber along the closed fluid circuit on the downstream side of both the solvent cleaning zone and the collected body of solvent and said discharged solvent moving away from the chamber along the closed fluid circuit on the upstream side of both the solvent cleaning zone and the collected body of solvent so as to introduce into the chamber a portion ofthe solvent other than the immediately previously discharged portion of the solvent each time the rate of solvent introduction exceeds the rate of solvent discharge thereby progressively to rinse the fabric with clean solvent from the solvent cleaning zone.
13. A method of dry cleaning soiled fabric, comprising wetting soiled fabric with a dry cleaning solvent in a chamber, causing the pressure in the chamber to fluctuate by dischanging dry cleaning solvent from the chamber and introducing dry cleaning solvent other than the immediately previously discharged dry cleaning solvent into the cleaning chamber at flow rates that alternately exceed each other thereby progressively to rinse the fabric with dry cleaning solvent other than the immediately previously discharged dry cleaning solvent.
14. A method of cleaning soiled fabric, comprising Wetting soiled fabric with a cleaning liquid in a chamber, causing the pressure in the chamber to fluctuate by discharging cleaning liquid from the chamber and introducing cleaning liquid other than. the immediately previously discharged cleaning liquid into the cleaning chamber at flow rates that alternately exceed each other thereby progressively to rinse the fabric with cleaning liquid other than the immediately previously discharged cleaning liquid.
15. A method of cleaning soiled fabric, comprising tumbling the soiled fabric in contact with a cleaning liquid, centrifugally extracting a substantial portion of the cleaning liquid from the fabric, heating the fabric after extraction to an elevated first temperature at a first pressure, and thereafter reducing the pressure on the wet fabric to a second pressure by Withdrawing vapors of the cleaning liquid from the fabric by applying the kinetic energy of a relatively high pressure stream of liquid to thus-withdrawn vapors thereby to boil off the liquid and reduce the temperature of the fabric to a second temperature, said first and second pressures and said first and second temperatures being so related that the heat content of the fabric and liquid at the first temperature and pressure are at least about as great as the heat content of the fabric plus the total heat of vaporization of the liquid at the second temperature and pressure.
16. A method as claimed in claim 3, in which the liquid of said relatively high pressure stream is a further portion of said dry cleaning solvent.
17. A method as claimed in claim 15, in which the liquid of said relatively high pressure stream is a further portion of said cleaning liquid.
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