US3227629A

US3227629A - Metal degreasing apparatus

Info

Publication number: US3227629A
Application number: US230834A
Authority: US
Inventors: Thomas J Kearney; John M Cashman
Original assignee: Detrex Corp
Current assignee: Detrex Corp
Priority date: 1962-10-16
Filing date: 1962-10-16
Publication date: 1966-01-04
Anticipated expiration: 1983-01-04

Description

Jan. 4, 1966 T. J. KEARNEY ET AL METAL DEGREASING APPARATUS Filed 061;. 1e, 1962 www Km- ITI www.

INVENTORS Thomas I Keur/ve w S numana. mhh. NN

tml v @hmmm NNN |N NWNI United States Patent O 3,227,629 METAL DEGREASING APPARATUS Thomas J. Kearney, Detroit, Mich., and .lohn M. Cashman, Bowling Green, Ky., assignors to Deir-ex Chemical industries, Inc., etroit, Mich., a corporation of Michigan Filed Det. 16, 1962, Ser. No. 236,834 14 Claims. (Cl. 202--1'7tl) This invention relates to improvements in metal degreasing apparatus, and more particularly to such improved apparatus utilizing volatile solvent means for effecting the desired degreasing.

Heretofore, the degreasing of metals and similar nonabsorbent materials has been effected by the use of volatile solvents such as trichlorethylene, perchlorethylene, and the like. Conventionally, the solvent is maintained in the sump of a tank-type vessel having solid side walls, and having one or more openings in the top thereof for the purpose of admitting and discharging the articles to be degreased. In the known manner, heating means disposed adjacent the bottom of the vessel is utilized to vaporize the volatile solvent which then rises to the upper part of the vessel forming a vapor zone therein. To prevent the vaporized solvent from inordinately escaping from the open topped vessel, cooling means for condensing the solvent vapors are located medially of the top and bottom of the vessel, whereupon the `solvent vapors reaching the space adjacent said cooling means are condensed, thereby dropping back into the liquid solvent sump. Additional means are normally provided for continuously or intermittently introducing the metallic or other non-absorbent work objects through the open top of the vessel and into the vapor zone thereof whereby the hot solvent vapors are condensed on the surface of the articles, thereby effecting the desired degreasing, the condensed solvent and degreasing waste dropping from the surface of the objects into the liquid solvent snmp. The cleaning action of the degreasing vapors may iriclude any of the known forms of degreasing, including spraying the work with recirculated solvent, spraying with a distillate solvent spray, wiping with felt or brush wipers, and passing the work objects through a chamber containing liquid solvent so as to actually immerse the work in a stream of liquid solvent. In certain applications, the work objects are then allowed to completely dry of condensed solvent on their surfaces before being discharged from the vessel, in order to reduce the loss of volatile solvent. In all of these known applications vof volatile solvent degreasing principles, the loss of solvent vapors is inherent in view of the openings existent in the top of the vessel utilized for the introduction and discharge of Work to be degreased. Numerous attempts have been made to reduce the loss of solvent vapors through such top openings for reasons of economy and safety, however each such attempt has not been completely successful in reducing all loss of solvent, and additionally such attempts have placed restrictions upon the size and shape of the objects cleaned inthe degreasing apparatus, whereupon such apparatus generally is limited to 4the cleaning of a pre-determined shaped object. Additionally, for these reasons, it is irnpracticable in accordance with these conventional forms of apparatus -to introduce an object into the vessel which has an overall dimension greater than that of the largest dimension of the opening in the top of the vessel. This limitation would therefore exclude the treatment of such articles as continuous lengths of substantially rigid articles, and bulky articles which may not be accommodated to the space requirements imposed by the necessity of introducing the object through a top opening in the vessel,

and then withdrawing the same object from the vessel at the `same or another top opening. It is apparent therefore that such disadvantages of the former systems could be eliminated by the passage of the articles to be cleaned through the vapor zone within the vessel in a straight lirle proceeding from one side of the vessel to the other side thereof, thereby accommodating rigid objects of indefinite length which need not be diverted from a rectilinear path through the vessel. Similarly bulky objects could be accommodated by being limited to passage through a single spatial locus of a constant configuration from one side or the vessel to the other.

it is therefore an object of this invention to provide an improved degreasing apparatus having a sealed top Wherein the articles to be degreased enter the apparatus through a side opening of the vessel adjacent the vapor zone thereof, and are discharged from the vessel at a side opening adjacent the vapor zone thereof.

It is another object of this invention to provide such an improved apparatus embodying improved vapor sealing means adjacent the inlet and discharge openings of the degreasing vessel.

t is another object of this invention to provide such improved degreasing apparatus embodying a novel solvent recovery system.

Other objects and advantages of the apparatus of this invention will readily become apparent from a reading of the following description and drawings wherein:

FIG. l is a schematic side elevational view of the novel degreasing apparatus of this invention;

FIG. 2 is a schematic end view or" the apparatus of this invention taken along the lines and in the direction of the arrows lI-II of FIG. l;

FIG. 3 is a view similar to FIG. 2 showing a modied embodiment of a portion of the apparatus of this invention; and

FIG. 4 is a view similar to FIG. 2 showing a second modiiied embodiment of the apparatus of this invention.

As shown in FIG. l, the apparatus of this invention comprises a degreasing vessel 11 including sidewalls l2, top closure 13, bottom wall 14, and a false bottom 15. The sidewalls 12 and the false bottom 1S form a sump for a volatile liquid degreasing solvent 16 which may be any conventional degreasing solvent such as trichlorethylene, perchlorethylene, and the like. Communicating into the vessel l1 through a iitting 17 is a heating element 13 which may be conventionally a steam line or an electric heater or the like. Heating element 18 extends into the space occupied by the liquid solvent contained in the vessel 11. A cooling jacket 19 is affixed to the sidewalls 12 of the vessel l1 near the top closure 13 thereof, said cooling jacket extending perimetrically of the vessel ll. A slit-like entrance opening 20 is formed in a sidewall 12, and a similar discharge opening 21 is formed in an opposing sidewall l2. By virtue of this opposition of the entrance opening 20 and the discharge opening 21, it is apparent that it is therefore possible to pass an indefinite length of a strip-like article 22 through the vessel 11 along a substantially rectilinear path. Additionally, a boot or lip type seal providing sliding contact on the article 22 may also be positioned adjacent the openings 29, 21 to provide additional sealing means against the escape of vaporized solvent.

An entrance housing 26 is supported on the vessel 11, and entends laterally of the entrance opening 20. This entrance housing 26 comprises a plurality of

separate compartments

27, 28, 29, 30. The compartment 27 is defined by sidewall 12, top wall 31, bottom wall 32, backwall 33, bulkhead 34 and a front wall (not shown). The bulkhead 34- has formed therein an opening 35 similar in conguration to opening 2li.

Compartment 2S, a condensing housing, is defined by the top wall 3l, bulkhead 34, bottom walls 32, 36, bulkhead 37, backwall 38 and a iront wall (not shown). Bulkhead 37 has formed therein opening 39 similar to opening 35 and 2i?, while bottom walls 32 and 36 slope downwardly and terminate in a drain leg 4Q. The lower end of drain leg it? communicates through a litting il into the vessel 1i. A helical coil condenser t2 is supported within compartment 2S by any conventional means (not shown) at a position below the level of the

openings

35, 39. Coolant is lconventionally supplied to the helical coil condenser 42 by means (not shown) external to compartment 23 and communicating thereinto.

Compartment 29 is der'ined by top wall 3l, bulkhead 37, bottom walls 4e, 47, bulkhead bacirwall It? and a front wall (not shown). Bullihead has formed therein an opening 50 similar to the openings 39, 35', 2). The bottom walls 45, 47, of compartment 29 slope downwardly and terminate in a drain-leg 51, the other end of which communicates through a iitting 52. into the vessel 1l.

Compartment 3d is defined by top wall 3l, bulkhead 48, exhaust duct 53, bulkhead 5d, backwall 55, and a front wall (not shown) Bulkhead 54 has formed therein an opening 55 (also shown in FIG. 2) similar to

openings

561, 39, 35, 20, said opening appearing in detail in FG. 2.

An exit housing /a (identical to, and correspondingly numbered with subscripts as housing 26) is supported by vessel il extending laterally from the opening 2l, the compartments 21751, 28a, 22a, and 3tlg thereof being formed or elements corresponding to the elements torming compartments 27, 2S, 2.9, and 39. It will be seen from FIG. 2 that the relative coniigurations of the

similar openings

56, 55a, Si), 56a, 39, 39a, 35, 35u, 2li, 2l, and the cross-sectional area of strip 22 are such that a minimum clearance is provided therebetween for the purpose of limiting the amount of vaporized solvent i5 which may escape from the openings 20, 2l.

In operation, the vessel 11 is iirst charged with the desired solvent 16, and the article 22 is threaded or otherwise disposed, as shown in FIGS. l and 2, with respect to the apparatus, whereby continuous travel of article 22 is permitted in the direction of the single horizontal arrows in FlG. l. The conveying means for article 22 is not shown since it is of conventional structure. Cooling is instituted in the condensers 42, 42a, by admitting coolant thereto from conventional means (not shown). Heat is then applied to the heating element l to the extent necessary to achieve the desired vaporization rate of the solvent 16, whereby the vessel 1l is substantially filled with solvent vapors. As soon as solvent vaporization has reached the desired level, the conveying means for article ZZ is actuated and the rate of speed thereof controlled to insure complete cleaning of the article. As thus actuated, the vapor generated from the solvent 16 surrounds and condenses upon the article 22 between the entrance opening 21% and the exit opening 2l, thereby degreasing the article. The dissolved dirt entrained with the condensed solvent falls back into the body of liquid solvent 16 for revaporization and any purification or liltration necessary in accordance with conventional procedures. Condensation of vaporizcd solvent 16 is aided in the apparatus shown in FIG. l by the cooling jacket i9 within which coolant is circulated as desired, with the result of substantial limitation of the height or" completely vaporized solvent within the vessel ll -to the broken line V shown in FlG. 1. Alternatively, positive exhaust and external condensation means may be utilized to provide recirculation of the vaporized solvent 16 in the upper portion of the Vessel 11, to insure positive distillate return to the sump formed by bottom wall 1S and side walls l2. Additionally, while the portion of the apparatus portrayed in FIG. 1 between opening 2@ and opening 21 is depicted as a vapor-only degreaser, the

cleaning action actually taking place on the work in this area may additionally include spray systems with recirculated solvents, spray systems utilizing distillate spray, gravity distillate rinses, wiping with felt or brush wipers, brushing with either fixed brushes or power driven brushes, and passing through liooded chambers to actually immerse the article 22 in a stream of liqueiied solvent. Accordingly, the number and type of Sumps or liquid chambers in the vessel 11 may vary from the number and form shown by having as few or as many chambers as are required to supply the various types of solvents to be used in the desired cleaning cycle.

It will be clear from the description made thus far that the article 22 enters the vessel 11 below the solvent vapor level rather than entering from above said level and through the open top of the machine as is now conventional in degreasing apparatus.

it will be apparent that the solvent vapors contained within the vessel il, in order to leave the vessel must tirst pass through openings 2li, 21, as shown in FIGS. l and 2. The nature of said openings 20, 21 is such that they constitute the minimum clear area, i.e., only Suthcient clearance for the article 22 to pass through. Additionally, it the ar cle 22 is of such a nature that a boot or lip type seal would be compatible with sliding contact on article 22, either of such seals might be additionally employed to decrease solvent loss. The resultant etrect at the openings Z6, 21 is therefore to hold to an absolute minimum the escape of solvent vapors to the atmosphere surrounding the apparatus.

The reason for the sealing provisions just described are those of safety and economy. In the tirst place, it is undesirable to release into the atmosphere of a room or plant area a high concentration of solvent vapors viewed from the standpoint of personnel safety, since such high solvent concentration in the atmosphere constitutes a health hazard. The American Industrial Hygiene Association recommends a maximum allowable trichlorethylene vapor concentration of approximately l0() parts per million of vapors in room air surrounding apparatus of this type. Additionally, since the cost of solvent lost by vaporation in the operation of degreasing apparatus is a primary factor in the economics of such operations, it is desirable to have an apparatus design such that vapor loss it held to a minimum during normal operations. It is by reason of these necessary limitations on degreasing practice that prior designs of solvent vapor degreasers have necessarily utilized apparatus which contained the solvent and vapors in a confined area with no openings therefrom to the room atmosphere except in a vertical direction, since the solvent vapors being heavier than air are thereby trapped within the apparatus. This limitation obviously has contributed to the conventional requirements that work must normally enter degreasing apparatus at the top of the machine, be lowered into the vapors, and after cleaning be lifted in a vertical direction to leave the top of the machine for removal. It is therefore seen that the below vapor level entrance design of the apparatus of this invention is a distinct departure from the conventional practice. Therefore, although the concentration of the vapors at the points adjacent the interior side of openings 20, 21 may be on the order of Vten times that openings of the degreasing vessel 11, to the corresponding degreasing apparatus, the leakage area at openings 20, 21 is extremely small, i.e., on the order 1/100 or less of the normal degreasing apparatus top opening. In this respect, the maximum amount of solvent per unit time which may leak through the openings 20, 21 is extremely small as compared to the amount which would normally be lost at the open top of a conventional degreasing apparatus.

Vapors which do escape from the openings 20, 21 enter either of the coresponding compartments 28, 28a through openings 3S, 35a, respectively, compartments 28, a condensing housing, 28a, being open to the atmosphere through

openings

39, 39a, 50, 50a and 56, 56a. The Walls of compartments 28, 28a, a condensing housing, are exposed to the atmosphere and cooled by the ambient temperature thereof, whereby a certain amount of condensation occurs on the walls of compartments 28, 28a. Additionally, vapors which have escaped into the compartments 28, 28a, being heavier than air, fall by gravity to the lower portion of said compartments whereupon contact is made with the cooling surfaces of the condensers 42, 42a. This results in additional solvent vapor condensation, the total condensed solvent within cornpartments 2S, 23a, draining into the respective drain legs 40, 46a, from whence by gravity the condensate returns through fittings 41, 41a, into the vessel 11 to replenish solvent 16. Thus, a first recovery of escaped solvent vapors has been accomplished.

Those solvent vapors, which are not condensed Within the compartments 28, 23a, and which escape therefrom through

openings

39, 39a, are trapped within

compartments

29, 29a, which function similarly to the preceding compartments 28, 28a as air condensers, without auxilliary condensing means, the condensate from said compartments returning to the vessel 11 through the drain legs 51, 51a. Therefore, a second stage of recovery of escaped solvent is thus effected.

Finally, those vapors which escape from

compartments

29, 29a through

openings

56, 50a, are trapped within compartments 30, a, wherein a suction is maintained in

exhaust ducts

53, 53a, by exhausting means 53h thereby causing outside air to enter

openings

56, 56a, sweeping the final increment of escaped solvent vapors out of the apparatus. These vapors may be exhausted to the atmosphere outside of the building in which the apparatus is housed, or solvent recovery means can be utilized to recover liquid solvent. It is thus seen that a three stage recovery of escaped solvent vapors is efficiently carried out, said recovery being made possible by the straight through design of the degreasing apparatus, and the eii'icient utilization of ambient atmospheric temperature to provide condensing surfaces for the escaped solvent vapors.

Although the condensers shown in compartments 28, 28a, are of the conventional water cooled helical tube type, the type and number of condensers utilized within the primary vapor recovery chambers 28, 28a may take varied forms depending upon the speed of travel of the article 11, the cross-sectional area of the openings 20, 21, and the allowable solvent loss rate. Equivalent forms of such condensing apparatus would consist of water jacket condensers, finned tubes, air cooled condensers and the like. In any event, the eiective resulting atmosphere within the condensing chambers 28, 28a, at the

exit openings

39, 39a thereof will have a vapor concentration approximately in the order of 1/10 of the concentration found at the openings 20, 21.

If necessary, similar internal condensing means may be provided in

chambers

29, 29a although this is not normally anticipated with the design of the apparatus of this invention. In practice therefore, the leakage of solvent vapors which may eventually pass the

openings

56, 56a will be at suiciently low vapor concentration to be safely accepted by the room atmosphere.

It will be apparent from FIGS. 3 and 4, that the design of the apparatus lof this invention, :may be modified to accommodate work articles having configurations different from that of article 22. In making such modifications, it is apparent that the vapor leakage through the modified openings, will vary from one configuration to another, and therefore obvious that the extent of auxiliary condensing means and recovery means utilized within the

compartments

28, 23a, 29, 29a, 39, 36a, will vary accordingly. It is only necessary to adjust the parameters of the condensing means positioned adjacent the below vapor level openings of the degreasing vessel 11, to the correspondb ing parameters of the shapes to be accommodated, and the corresponding openings therefor.

It will further be readily appreciated that instead of maintaining liquid solvent within the vessel 11, and generating vaporized solvent by means of the heating element 18, means for generating a supply of solvent vapor outside of said vessel 11, and for conducting said vapor thereinto, could be provided. This alternative embodiment of the apparatus of this invention would function equivalently with the above-described embodiment except for the function of the means for providing a vaporous solvent atmosphere within the enclosed vessel 11.

Having thus described our invention, we claim:

1. In an apparatus for degreasing solid work objects, the combination of an enclosed vessel having a top wall, bottom wall and a pair of opposed side walls formed therein, each of said side walls having a substantially identically configured work opening formed therein mediate the top and bottom walls, an enclosed condensing housing amxed to each of said side walls and covering said work opening, said condensing housings being sealed from the atmosphere except for a work opening formed therein substantially identically configured to that formed in said side walls, said condensing housing extending laterally of said vessel, vapor condensing means disposed within each of said condensing housings, means for providing a supply of degreasing solvent vapor to said enclosed vessel, and means communicating from said condensing housings into said vapor providing means and adapted to contain condensed degreasing solvent, and means for circulating coolant from without said condensing housing through and out of said condensing means.

2. In an apparatus for degreasing solid Work objects, the combination of an enclosed vessel, a sump formed adjacent the bottom of said vessel, said sump being adapted to contain liquid degreasing solvent, heating means communicating into said sump and adapted to vaporize solvent contained therein, a pair of opposing side walls formed in said vessel, each of said side walls having a substantially identically configured work opening formed therein mediate said sump and the top of said vessel, an enclosed condensing housing affixed to each of said side walls and covering said work opening, said condensing housings being sealed from the atmosphere except for a work opening formed therein substantially identically configured to that formed in said side walls, said condensing housings extending laterally of said vessel, vapor condensing means disposed within each of said condensing housings, means for circulating coolant from without said condensing housing through and out of said condensing means, and means communicating from said condensing housing into said vessel at points above said sump and adapted to receive the condensate of said condensing housings.

3. The apparatus in accordance with claim 2, including cooling means aliixed to said vessel perimetrically thereof at an area thereof above said work openings and said condensing housings.

4. The apparatus in accordance with claim 2, wherein said condensing housings include bulkhead means disposed interiorly thereof substantially parallel to said side walls, thereby dividing said housings into a plurality of condensing compartments, said bulkhead means having formed therein a work opening substantially identically configured to that formed in said side walls and said condensing housings.

5. The apparatus in accordance with claim 4, wherein each of said plural condensing compartments contains means for collecting condensate and transmitting said condensate to said means communicating from said condensing housings into said vessel.

6. The apparatus in accordance with claim 5, wherein said vapor condensing means is disposed Within that plural compartment next adjacent to said opening in said side walls.

7. The apparatus in accordance with claim 6, wherein all of said work openings are in substantially rectilinear spatial alignment.

8. The apparatus in accordance with claim 7, including vapor exhaust means afxed to said condensing housing and partially enclosing said work opening in said condensing housing, said exhaust means including a work opening formed therein and congured substantially identically to that formed in said side walls, said condensing housings, and said bulkhead means.

9. The apparatus in accordance with claim l, including cooling means alixed to said vessel perimetricaliy thereof at an area thereof above said work openings and said condensing housings.

10. The apparatus in accordance with claim 1, wherein said condensing housings include bulkhead means disposed interiorly thereof substantially parallel to said side walls, thereby dividing said housings into a piurality of condensing compartments, said bulkhead means having formed therein a work opening substantially identically configured to that formed in said side walls and said condensing housings.

11. The apparatus in accordance with claim 10 wherein each of said plural condensing compartments contains means for collecting condensate and transmitting said condensate to said means communicating from said condensing housings into said vessel.

i2. The apparatus in accordance with claim 11, wherein said vapor condensing means is disposed within that CII plural compartment next adjacent to said opening in said side walls.

13. The apparatus in accordance with claim 12, wherein ail of said work openings are in substantially rectilinear spatial alignment.

14. The apparatus in accordance with claim 13, including vapor exhaust means affixed to said condensing housing and partially enclosing said work opening in said condensing housing, said exhaust means including a work opening formed therein and configured substantially identically to that formed in said side walls, said condensing housings, and said bulkhead means.

Reerences Cited by the Examiner UNITED STATES PATENTS NORMAN YUDKOFF, Primary Examiner.

GEORGE D. MITCHELL, Examiner.

Claims

1. IN AN APPARATUS FOR DEGREASING SOLID WORK OBJECTS, THE COMBINATION OF AN ENCLOSED VESSEL HAVING A TOP WALL, BOTTOM WALL AND A PAIR OF OPPOSED SIDE WALLS FORMED THEREIN, EACH OF SAID SIDE WALLS HAVING A SUBSTANTIALLY IDENTICALLY CONFIGURED WORK OPENING FORMED THEREIN MEDIATE THE TOP AND BOTTOM WALLS, AN ENCLOSED CONDENSING HOUSING AFFIXED TO EACH OF SAID WALLS AND COVERING SAID WORK OPENING, SAID CONDENSING HOUSINGS BEING SEALED FROM THE ATMOSPHERE EXCEPT FOR A WORK OPENING FORMED THEREIN SUBSTANTIALLY IDENTICALLY CONFIGURED TO THAT FORMED IN SAID SIDE WALLS, SAID CONDENSING HOUSING EXTENDING LATERALLY OF SAID VESSEL, VAPOR CONDENSING MEANS DISPOSED WITHIN EACH OF SAID CONDENSING HOUSINGS, MEANS FOR PROVIDING A SUPPLY OF DEGREASING SOLVENT VAPOR TO SAID ENCLOSED VESSEL, AND MEANS COMMUNICATING FROM SAID CONDENSING HOUSINGS INTO SAID VAPOR PROVIDING MEANS AND ADAPTED TO CONTAIN CONDENSED DEGREASING SOLVENT, AND MEANS FOR CIRCULATING COOLANT FROM WITHOUT SAID CONSENSING HOUSING THROUGH AND OUT OF SAID CONDENSING MEANS.