US2253579A - Portable degreasing unit - Google Patents

Description

Patented Aug. 26., 1941 PORTABLE DEGREASIN G 'UNIT WillarrlD. Phillips and Ralph A. Van Fossen, Chicago, Ill., assignors, by direct and mesne assignments, to The Dow Chemical Company, Midland, Mich., a, corporation oi.' Michigan.

Application June 3, 1940, Serial No. 338,478

2 Claims.

This invention relates to degreasing apparatus and more particularly to a small, portable, vaportype degreasing unit adapted to be used in ma-y =matched by comparable economies in cleaning the finished product, with the result that the degreasing costs on small screw machine items or similar parts are often greatly disproportionate to the manufacturing costs and, therefore, assurne exaggerated economic importance.

One of the factors contributing to this disproportionate cleaning lcost has been the fact that the degreasing apparatus commonly used in the prior art has been large and bulky equipment, inconveniently located -with respect to the manufacturing machinery, and has been considered as not adapted to use in close proximity to factory rooms or other crowded localities be cause of the fumes developed by the degreasing apparatus.

It will be recognized that there are obvious advantages-in the provision of a small portable unit, since such a -unit may be positioned immediately'adjacent an automatic machine, so that the manufactured parts will drop directly from the cut-off of the machine through a chute into the degreasing chamber, thus eliminating the necessity of providing conveyor equipment or employing labor to handle the parts and convey ,them from the manufacturing machines to the degreasing equipment. It is also greatly advantageous to have a small, light-weight degreasing unit, which may be easily moved from place to place according to the requirements of the moment, and which may be readily lifted and inverted to discharge metal chips or other insoluble and foreign matter without the necessity fof dismantlingthe apparatus'for cleaning. It

in the prior art units and itations, however, of the prior artstructure has has been unsatisfactory for portable installations, since it has required extensive piping in the nature of gas or steam pipes for heating, cold water pipes for the condenser systems, or exhaust ducts or fans to carry oi excessk vapors.

A cursory survey of the prior art indicates that the deficiencies of the structures have arisen from a number of reasons: q

First: In the apparatus heretofore known, the complete units have usually been quite large and elaborate, even though the actual cubic area of the degreasing chamber itself has been comparatively small. This condition often arises from the provision of dual chambers for re'distillation of a hydrocarbon solvent, and while some provision for redistillation of the solvent must be incorporated in a successful apparatus, yet the disproportionate size of the entire apparatus with respect to the size of thefvactual treating chamber' is a distinct disadvantage. It is also a distinct disadvantage to require a large quantity of liquid l solvent to maintain a vapor in a comparatively small vapor chamber, since the solvents are relai tively expensive.

vportable unit for the reason that `it requires extensive piping, and also for the reason that any water jackets, condensers or steam. structures greatly add to the weight of the unit, and since these structures are customarily positioned near the top of the degreasing chamber, they tend to cause a unit to be top heavy, and thus unsafe or undesirable for use in a crowded factory room.

Third: The degreasing apparatus customarily A used has been ordinarily provided with a solvent having a boiling point somewhat lower than the boiling point of water, wherein the water vapors present in the solvent chamber are not neces-` sarily expelled, but may under certain conditions combine with the chlorinated hydrocarbon solvent to produce hydrochloric acid. 'Ihe corrosive action of this acid is well recognized, and it has heretofore been combatted only by the provision of unusually heavy wall surfaces in the degreasing cabinet, which are obviously undesirable in,

a portable unit by reason of the increased weight of the unit. 1 Fourth: Probably the most fundamental lim been the imperfect devices utilized to control the vapor level within the degreasing chamber. In this connection it is pointed out that in order to be satisfactory for use in a crowded factory building, it is essential that the hydrocarbon vapors utilized as the active element in degreasing equipment lbe properly and eectively confined within the degreasing apparatus, since the' presence of undue vapors in the air introduces an -unpleasant.atmosphere. and if the concentration vof vapors rises above a minimum, it may be Y actually harmful for persons working in the vicinity for long periods of time. This situation has been recognized by the public health authorities in practically every locality, and almost every community has in eiect public health regulations dening the maximum` concentration of hydrocarbon vapors legally allowable in indus-f trial locations. In. fact, 'in industrial centersinspections of -manufacturing premises are regularly conducted, and the degree of concentration of hydrocarbon vapors, in the atmosphere regularly tested by yinstruments designed for the purpose; for example, the halide lamp.

It is, therefore, a principal object of this in vention to provide a simpliiied degreasing apparatus particularly adaptedvto use as a portable unit and arranged to be of a low height, so that it may be positioned below the discharge chutes of automatic screw machines and similar machinery.

Another important object of the invention is to provide an improved mechanical design or a degreasing apparatus, such that the actual area within` the walls of the vapor chamber is substantially as large as the-entire area occupied by the apparatus.

Another essential object of the invention is the provision of a novel and improved mechanism to control the vapor level withinthe vapor chamber, this'mechanism being characterized by the fact that its operation interrupts the vaporization of i the liquid solvent, as contrasted with the prior art devices, which attempted to control the vaporv level by means to cond-ense vapors as rapidly as they were produced by the heated section of the apparatus.

A further object of the invention is to provide control devices to indicate the presence of undue quantities of oils in the liquid solvent and to interrupt the operation of the apparatus whenever a point of dangerous concentration of oils in the solvent is reached.

Another object of the invention isv to provide an improved mechanical design for a degreasing vention are accomplished by practicing the principles of this invention and by the use of a typical structure, such as illustrated in the drawing forming a part of this specification, in which:

Fig. l is a vertical sectional view through a typical portable degreasing unit; g f

Fig. 2 is a plan view of the unit illustrated in Fig. l, showing the cover removed;

F181 3 is a schematic electrical circuit diagram of the essential elements of the unit; and

Fig. 4 is a fragmental sectional view of the degreasing unit illustrating a slightly modiedv control arrangement.

The degreasing cabinet, or vapor chamber, illustrated in Figs. l and 2, comprises a thin sheet metal cylindrical body portion Il terminating at its upper extremity in a beaded reinforcing rim I2, and terminating at its lower extremity in a beaded rim I3 interconnecting with the annular bottom portion Il. The bottom portion I4 extends inwardly and is joined to the walls of a cylindrical chamber or vaporizing sump I 5 at a point somewhat below the upper extremity of the cylindrical wallsto provide an upstanding partition I6 to define a distillate receiver or sump 20 between the cylinder I5 and the outer cylinder II. The cylinder I5 is closed at the bottom by a bottom portion I1 to which a reinforcing flange I8 is secured, and an electrical heating element I9 is threaded into the ilange'fl in close proximity to the bottom of the' cylinder I5.

The heating element i9 is preferably arranged to provide a large screw threaded shank 2i having a hexagonal nut portion 22 at its upper end to facilitate threading into the flange I8, and the active element o the heater preferably consists of a tubular metal-covered resistor 23 of the socalled calrod type. The element 23 is fitted into drilled openings; in the shank 2l, and the apparatus,` whereby a small quantity of solvent may be satisfactorily utilized to provide vapor throughout a relatively large vapor chamber.

Another important object of the invention is to provide a degreasing apparatus of improved mechanical design varranged so that the entire wallarea of the vapor chamber may act as a. condenser surface during the redistillation of the solvent, to the end that a solvent within the unit may be redistilled and'puriiied quickly and conveniently. f

4A further object of the invention is -to provide a simple portable degreasing unit having a distribution of mass of the elements of the apparay tus so arranged as to provide a compact and efcient unit having a relatively low center o f migravityi-,oeimpart stability to the structure and resist tipping, thus providing a safer and more desirable apparatus for portable installations.

These and other important objects of the in. 'la

electrical connections, are carried through these openings and connected to feed wires 24 and 2l n housed within the connection box 26.

The entire unit is supported on three legs 3l preferably welded -to the cylindrical vapor chamber II and provided with casters 32 or other friction-reduction devices to facilitate easy and convenient movement of the entire unit.

A `cover 33 is provided with a beaded edge 34 adapted to ilt the upper beaded edge I2 of the vapor chamber and this cover 33 is preferably' also provided wi-th a lifting handleV (not shown) and an orifice 38 near one edge. It is not essential that the cover 33 be used in the operation of the Vmachine since the vapor level is actually.

controlled by mechanisms to be hereinafter described, but when the use of the cover is not otherwise objectionable, it may be desirable in order to prevent violent currents of air'from disturbing the proper level of the vapor. For ex-4 ample, if the unit is positioned adjacent an automatic screw machine, it is convenient to place the cover in position and to introduce the screw machine parts into the vapor chamber by a small chute, which may extend through the orifice 3l. It will be understood that when machine parts are chuted into the chamber, as thus described, a suitable basket (not shown) is provided in the degreasing chamber so that they may be quickly and easily removed whenever a lsudicient number The principal cleaning action ofthe unit is accomplished by ahydrocarbon vapor withinthc vapor chamber II, but it has also been .found desirable io provide flushing means adapted to sprayliquidsolventsoverthepartstoremon chamber.

42. A' motor-driven pump 43 is removablymounted in the top of the chamber 4| and is provided with a removable mesh screen 44 so that the entire pump and screen may be removed at will by loosening the machine screws `45 to provide convenient access to the inside of the chamber 4l in order to remove any accumulation of sediment within the bottom of the The pump 43 is arranged to draw solvent from the chamber 4l and discharge the solvent upwardly through the ilexible tube 46, and the hook-shaped metal discharge tube 41, which may be provided with a handle portion 4I. The hook-shaped ,ube 41 may be suspended over the upper beaded rim l2 of the chamber Il to extend downwardly through the orifice 3 6 into the inside of thechamber and spray liquid solvent into the chamber at all times, but preferably it is used only when particularly obstinate accumulations of insoluble matter have formed on the work, and it is then directed towards the surface of the work by the operator.

The importance of a proper vapor control mechanism has been pointed out hereinbefore,

but it will be appreciated that although the hydrooarbon vapors used are approximately five might tend to rise above the rim of the chamber and overflow into the atmosphere. So far as is known to the applicants, these devices have been highly unsuccessful with the result that'it has been regarded 'as a foregone conclusion in the vantage by apparatus heated by an open flame,

-but it will .be seen that this vdisadvantage has been overcome in the present construction by the provision of a heating unit entirely submerged in liquid solvent. Under these circumstances no portion` of the apparatus can ever reach a temperature higher than the boiling point of `the liquid in which the unit is submerged, with the result that even though a small amount of vapor should escape, there are no highly heated flash surfaces on the machine that might tend to convert the vapors into dangerous gases.

The improved vapor control mechanisms disclosed by this invention depend for their principle of operation on the fact that the body of vapor within the chamber will always be at an exactly uniform temperature, since the vapor chamber is unsealed, or open, and operates under atmospheric pressure only, and since any cooling of the vapor will re-convert v it into liquid, whereupon it will drop to the lower portion of the chamber.

This invention takes advantage ofthis characteristic'and provides a thermostat 5l positioned on the side wall of the vapor chamber il at a point substantially-above the bottom of the chamber, but somewhat below .the upper rim l2.

As hereinbefore pointed out, the hydrocarbon vapors are approximately five times heavier than air, thus as the liquid solvent is heated and vapor begins'to form, it will slowly rise to auniform level throughout the chamber until the upper level of the vapor reaches the thermostatv 5l. -It is-,understood of course, that the critical temperature of the thermostat 5I is adjusted to art that a considerable quantity oi' vapors will escape from any degreasing apparatus and that the apparatus is, therefore,' unsuitable and dangerous for use in any location in close prox' imity to other workers. 'I'his has -been particularly true of apparatus utilizing exposed flamev heaters or in any apparatus in close proximity to res or highly heated objects, since the chlorif nated hydrocarbon solvents may, if exposed to high temperatures, break down into chlorine or phosgene gases which are extremely dangerous in any appreciable degree of concentration.

The characteristics of the individual solvents vary considerably, but may be illustrated bythe characteristics of tetrachlorethylene, which is vapors are raised to a temperature in the nelgh borhood of 275 F., they may break down into gases which are extremely unpleasant and Aharm-- ful, and actuallydangerous if encountered in hsufficient concentration. Normally, these gases,

if not under pressure, will not reach this temperaturenbut it has been found that if theyl escape, they may be drawn into an open flame 5 by convection and a certain amount of gas will be below the boiling point of the solvent, so that l whenever the high temperature vapor contacts the thermostat, the thermostat may act through the temperature sensitive element 52 to open the electrical circuit through the heating element 2l and prevent the further production of vapor. vSimilarly, as the vapor condensesgby contact with the work; or the sidewalls, the vapor level will gradually fall until it is below the level of the thermostat 5I. As this occurs, the air from the atmosphere of the room will be drawn in through they open cover and will contact the thermostat 5I, and since this air is at a temperature far below the boiling point ofthe solvent, it will actuate the thermostat to again close the circuit'through the heating ele- Ament I9. .It is to be noted, however, that alis absolutely constant at all times.

'Ihe thermostat 5I may be` of any desirable form, as for example, a conventional, tubular,

temperature-sensitive thermostat bulb 5| a, illustrated in Fig. 4. It has been found, however,

lthatva. more accurate control of the vapor level may be accomplishedby providing a thermostat y having a temperature-sensitive element 52 including a multiplicity. of thin ns to effecta more instantaneous heat transfer. With vthis type of thermostat, it is desirable to provide a small thermostat pocket or chamber 53 outside of the vapor chamber Il and connected therewith and to mount the thermostat 52 on a vertical sleeve 54 welded or otherwise secured in the top of the chamber53. :By'providing this ther-V mostat chamber, the thermostat bulb is removed to a position outside :of the regular dimensional limits ofthe vapor chamberjso that the entire the thermostat bulbv saturation.

`area within the chamber will be clear and may be -utilized to containV objects undergoing degreasing treatment. Thus, the thermostat will not interfere with the introduction of large objects into the degreasing chamber and will not be in danger of becoming damaged as the articles are placed in or taken from the chamber.

l The vertical sleeve 54 is not necessarily an essential element of the invention, but it has been found that in practice this sleeve is quite important, since when such a sleeve is used, the temperature control of the thermostat functions more satisfactorily and controls the vapor level with a greater degree of accuracy.

'Ihe temperature-sensitive element of the thermostat i vis connected with a pressure switch 55 by an operating tube 56. The pressure switch 55 includes contactor members 51 and 55 arranged in circuit with the power supply lines :passe chamber ll, where it will pass from the outer annular sump 25, through the port 21 in the inner annular partition and come to rest in the vaporizing sump and submerge the heating element I5. The operator will then close themanually operated switch 55 to bring the heating l element to full heat and begin vaporizing of the solvent. It is understood, of course, that vat this time both of the thermostat bulbs 5| and 53 are relatively cool and thepressure switch contacts 51 and 55 will be closed.

As the solvent boils, the vapors will rise in the vapor chamber l I and since they are considerably more dense than the air, they will maintain a constantly level upper surface and will rise until this upper surface envelops the thermostat bulb 5I. The vapors, of course. are at a temperatlne of 249.5 F. and when they strike the thermostat bulb 5I will operate the pressure switch to element I9 is also provided with a tubular tem.-

perature-sensitive thermostat bulb 53 connected to the pressure switch 55 by an operating tube 64. The bulb 463 may be soldered or clamped in intimate engagement with the heating element i9 to establish an intimate heat transfer relationship between the heating element and rupt the circuit through the heating unit. However, it has been discovered that after a long period ofv operation of the degreasing unit without the desirable redlstillation. of the solvent considerable quantities of oil may mingle with the solvent in the vvaporizlng sump and under certain conditions this mixture may have a boiling point considerably higher than the boiling point of the pure solvent. In fact, it has been found that unless the degree of saturation of oil inthe solvent is controlled, it is possible for this boiling point of the mixture to rise sunlciently to cause a chemical breakdown of the solvent and generate dangerous gases directly from the liquid.

uIt is not believed that this characteristic has been fully appreciated in the prior art and it is one of the objects of this invention 'to provide means to control the degree of saturation of the solvent, or rather, toninterrupt the operation of the machine in the event that the solvent and oil mixture approaches a dangerous point of This is well accomplished bythe provision of the thermostat bulb 55, since whenever the mixture of oil and solvent becomes of suiiicient concentration to raise the boiling point appreciably, the pressure switch 55 will operate to break the contacts 51 and 55 and interrupt the electrical circuit to the heating element I5. The thermostat 53 also provides another incidental, desirable function, since lt will interruptl the circuit to the heating element I9 in the event that the solvent level falls below the upper level of the resistance unit and thus prevents any possibility of burning out these units.

The operation of the mechanism is 'as follows: The solvent is placed in the bottom of the vapor The thermostat bulb 53 side of the chamber.

temperature solvent employed, it has been found' break-the contacts 51 and 55 and interrupt the electrical circuit of the heating element I3. 'Ihe vapor level will then gradually fall, due to the fact that the vapors are constantly condensing on the thin outer walls of the vapor chamber Il,

r and when the vapor level moves below the theracting as condenser surfaces and are at all times being cooled by contact with the air on the out- By virtue of the highunnecessary to provide water Jackets or ,other auxiliary cooling mechanisms, since the thin metal of the chamber Il provides a good heatconducting medium and particularly since there the level at a point substantially below the upper surface of the chamber, so that the vapors can not escape even though they be agitated by introduction or vremoval of large materials being treated, or by swirling currents of air in the vicinity. It will be seen that the normal vapor level is several inches below the top'- of the vapor chamber and thus the vapors may be permitted to swirl or eddy considerably without danger of overflow.

Articles `to be treated by the degreasing process v.are suspended within the chamber I i in any convenient mannen'as, for example, by hooks. wires or baskets, so that the vapors may condense on the cold metal and flush any grease or foreigny through the pump motor 43 and may direct the stream of liquid solvent from the hook-shaped nozzle of the exlble solvent hose against the surface to assist in flushing heavy or insoluble oils removed from the work willhave to a certain extent adulterated the liquid solvent, although 21 in the annular upstanding partition between the vaporizing sump and the distillate sump and then close the switch 65 to the heating element, The vapors in the chamber will form in the usual way and rise to the regular control level. Since no Work-is in the machine at the time, however, the only condensation will be on the side walls of the vapor chamber Il and all of the solvent thus condensed ywill ow into the annular distillate sump,` It is to be particularly noted that this arrangement utilizes the entire area of the chamber walls and thus accomplishes the distillationwith extreme rapidity, so that it is entirely l unnecessary to interrupt the operation of the device for more than avery few minutes at any `time. AWhen the distillation process has contion of the thermostat bulb 63 and the pressure switchv 65. In fact, this is preferred, since by allowing this thermostat to operate all of the solvent may be reclaimed within the margin of safety carefully calculated and determined by the critical temperature of the thermostat B3.

The pure solvent in the distillate sump may then be removed from the unit by a syphon or through a drain petcock '61, and the oils and foreign matter removed from, the vaporizing sump either by .operating the flushing pump, or in any other manner. A

It is to be particularly noted, however, that any heavy chips, metal, sand, gravel, etc., that may have collected in the bottom surface of the sumps may be easily and quickly discharged from the machine by simply inverting the machine to allow 'the heavy materials to fall out and that the light and durable construction of the unit makes this procedure entirely feasible .and elim'- inates the necessity of dismantling the degreasing unit ,to remove these heavy materials.

The pure solvent is then placed in the sumps, the plug in the partition is removed, and the device is again ready to operate. f

From the foregoing description, it should be apparent that the portable unit disclosed herein accomplishes certain notable advances in the art not'heretofore accomplished, nor apparent, as

follows:

First: The present invention disclosesa mechanical design of extreme simplicity unequalled in the prior art.

Second: The present design provides a de-v greasing unit having a very large capacity as compared with the space occupied by the unit. In this connection it is pointed out that the enrapid operation.

tire diameter of the vapor chamber ll is available to treat the work and this diameter is substantially equivalent to the entire outside diam- Fourth: By practicing the principles of this invention, it is possible to eliminate the danger of production of dangerous gases, since this invention discloses means to indicate the degree of concentration of oils in the liquid solvent and, further, since the device is arranged so that no exposed flame or highly heated surface can possibly be contacted by the hydrocarbon vapors,

even in the event that a certain overflow should take place.

Fifth: I'he design of the present. disclosure permits a small volume of solvent to be satisfactorily used to produce a vapor throughout a comparatively large vapor chamber.

Sixth: The present invention discloses a novel mechanical design for a degreasing unit, such that redistillation of the solvent'.- may be accomplished in the same chamber in which work ls treated and provides means whereby the entire area of the chamber may be utilized as a condenser surface during this redistillaticn to eil'ect Seventh: All of the above features have been incorporated in a single small unit having a comparatively low height adapted to be placed under the discharge chute of modern, automatic production machinery and arranged in a convenient, portable assembly having a low center of gravity and an equalized distribution of mass, thus providing a unit of great stability.

While we have shown and described the present preferred embodiment of .this invention in compliance with the patent statutes, it is subject to numerous changes and modifications without departing from the invention spirit, and we, therefore, do not wish to vbe limited except as ,by the scope of the appended claims.

We claim:

1. In a portable degreasing apparatus, the combination of a vapor chamber having side walls of .thin heat' conducting material, a distillate sump in the' bottom of .said chamber, a vaporizing sump .below the distillate sump, said sumps being arranged to include means to direct all of the condensateon the side walls of said chamber into the distillate sump, mansr to direct the condensate from the distillate sump, either to the vaporizing sump or toa separate container at the A will of the operator, an electric heating element mounted in the vaporizing sump adjacent its bottom, a temperature-sensitive element in operative relationship with said heating element, a temperature control chamber adjacent the top of the vaporizing chamber and outsidey of the tillate to the vaporizing sump for continuous degreasing operation, and to separate the clear liquid solvent from contaminated solvent, incl'uding only the thin heat conducting side walls o f A tillate sump in the bottom oi' said chamber, a

vaporizing sump below the distillate sump, said ment inoperative relationship with said heating element, -a temperature-sensitive element mounted in the vaporizing. vchamber adjacent the sumps being arranged to include means to direct `all of the condensate on the side walls of said chamber into the distillate sump. means todilrect the condensate from the distillate sump,

either to the vaporizing sump or to a separate container at the will of the operator, an electric heating element mounted in the vaporizing sump adjacent its bottom. a temperature-sensitive eletop of said chamber, means responsive to the operation of said temperature-sensitive elements to control the aforesaid heating elements, and proportions, weight and structure of the chamber, sumps, the heating element providing means to operate the device practically continuously as a degreasing unit and to distill clear liquid solvent from contaminated solvent withthe thin heat-conducting side walls of the vapor chamber as the sole condensing means, the device as a unit permitting manual dumping of the refuse without disturbing any part or connections.

WULARD D. PHILLIPS. RALPH A. VAN FossEN.

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