US2180126A - Cleaning and degreasing system - Google Patents

Description

H. E. SOMES CLEANING AND DEGREASING SYSTEM Nov. 14, 1939.

Filed Feb. 8,- 1935 2 Sheets-Sheet l I N VEN TOR.

A TTORNEYS.

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Hon/dra 'yames,

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Nov. 14, 1939. 1+i-:7' soMr-:s

CLEANING AND DEGREASING SYSTEM 2 sheets-sheet 42 Filed Feb. 8, 1935 INVENTOR. Hon/ard' ZT 502722.05.

A TTORNEY.

Patentedv Nov. 14, 1939 UNITED STATES PATENT OFFICE 1 Claim.

The present invention relates to a cleaning and degreasing system, particularly adapted for the cleaning and degreasing of metallic articles. The most generally used cleaning and degreasing solvents are organic compounds such as benm'ne, gasoline, oleum spirits, tetrachlorethylene, and the like. The vapors of most of the solvents in commercial use are heavier than air and the vapors of practically all of these solvents are toxic or iniiammable. Consequently a cleaning system which permits the use of inexpensive solvents of the above nature and at the same time avoids the danger consequent upon the use of such materials possesses great utility. In many operations, particularly Where a surface coating is to be applied to a metallic article, it is impossible to secure satisfactory results unless the surface of the metallic article is thoroughly cleaned and freed from dirt and grease. Cleaning and degreasing prior to my invention was accomplished by dipping, spraying or otherwise bringing the surface of the lmetallic article in contact with the solvent to be employed. Some of the most effective solvents are organic solvents which have toxic vapors. Other of the organic solvents are relatively volatile and will be rapidly dissipated into the atmosphere, frequently causing res and explosions. Because of these characteristics, the methods heretofore employed have precluded, to a large. extent, a freedom oi choice among these classes of solvents.

The process and system herein proposed utilizes, in one embodiment, a solvent in its liquid phase to remove the greatest bulk of the objectionable dirt, grease and other adherent substances. In

addition, the system may utilize a spray, either alone or with a liquid, for removing any dirt or grease remaining after the liquid treatment. In order to remove thelast traces of dirt and grease remaining after the treatment with the solvent in the liquid phase, I utilize the solvents in their vapor phases. The work being cleaned has a temperature preferably below that of the vapors and below the condensation vpoint thereof. As a result, the vapors condense to liquid upon contact with the surface of the work, and this in effect permits only clean distilled solvent to come in contact withV the work during its iinal cleaning phase.

In systems heretofore used, the solvent when used in the liquid phase has performed more or less imperfectly since the bath "quickly becomes contaminated with grease and dirt, and since the solvent is much heavier than the grease which it removes, the grease oats to the surface and adheres to the part being cleaned when said part is withdrawn.

It is an importantv object of the present invention to provide a continuous cleaning and degreasing system in which solvents in their hot 6 liquid, cold liquid and in their vapor phases are employed successively to accomplish cleaning and degreasing of work passing therethrough.

It is a further object of the present invention to provide a cleaning and degreasing system hav' ing an enclosing shell sealed at its entrance end to preclude circulation of air or vapors of solvents therethrough.

It is a further object of the present invention to provide a cleaning and degreasing system in which definite control over the system is maintained at all times, both as to amounts of solvents used and as to time of contact of the metallic articles with such solvents.

It is an important object of the present in- '20 vention to provide a cleaning and degreasing system wherein the Work to be cleaned will pass successively through a hot agitated liquid solvent bath, a cold solvent spray, and thence through a solvent vapor bath, under such conditions that these successive treatments effect a thorough degreasing and cleaning of the work.

Further, it is an object to provide a cleaning and degreasing system in which the work, after the vapor bath, is raised to an elevated tempera- 30 ture substantially above the boiling point ofthe solvent, thereby to vaporize and drive off any adherent solvent imprisoned in the metal part, after which such solvent is reclaimed.

It is a further object of the present invention to provide a cleaning and degreasing system in which a novel construction is employed in fabrication of that portion of the enclosing shell where electrically operated induction coils are employed for heating purposes, which construction pre- 40 vents the flow of eddy currents from the inner to the outer shell.

Other objects of this invention will appear lin the following. description and appended claim, reference being had to the accompanying draw- 45 A ings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. 1 is a longitudinal section and side eleva.- tion of a portion of the apparatus utilized in a 50 cleaning and degreasing system of the present invention.

Fig. 2 is a view similar to Fig. 1 showing a continuation of the apparatus shown in Fig. 1.

Fig. v3 is a sectional view taken substantially on 55 theline 3-3 of Fig. 1 in the direction of the arrows.

Fig. 4 is a view similar to Fig. 1 but showing a modified apparatus' used in a vapor phase system.

Fig. 5 is a view similar to Fig. 2 but showing a modification thereof particularly adapted for use with the apparatus shown in Fig.. 4.

Fig. 6 is a section taken substantially on the line 6-6 of Fig. 1 in the direction of the arrows showing a preferred form of construction of the enclosing shell.

Fig. 'l is a section taken substantially on the line 1-1 of Fig. 1 in the direction of the arrows.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art.

An apparatus particularly adapted Afor use with a cleaning and degreasing system of the present invention is shown in Fig. 1 and comprises essentially a conveyor system of any conventional design, which includes a conveyor track I I which may be suspended from an enclosing shell I2 and extends longitudinally thereof. The track and shell are depressed at selected intervals to provide a downward and upward movement of the carrier I3ffas it follows the track I I.

As a part of my system I propose to locate, in the enclosure or oven, suitable depressed portions, shown as V-shaped enclosures IUII and IUI, the length of the risers being so chosen that any tendency for atmospheric air'to enter either end of the oven and thus sweep toxic and/or explosive vapors out of the other end of the oven is counteracted lby the weight of the column of vapor in these risers. Since most of the desirable solvents weigh, in vapor form. several times as much as an equal volume of air, the sealing of the enclosure or oven structure in this manner is facilitated. It is also possible, when the solvent is in .liquid form, to have the surface thereof close to the top of the depressed portion, whereby to reduce the size of the air passage through the oven.

This provision of risers effects an up and down dipping motion of the work I4 carried onthe carrier I3 in the tank portions I6 and I1 formed in the bottom of the V-'shaped enclosures. A power driven endless chain I5 is operatively connected with the carrier I3 and effects movement of the carrier I3 longitudinally of the track II.

Where the cleaning system is of the continuous type as just described, it is desirable to main- 'tain the temperature of the chain I5, and of the carrier I3 on which the chain may be supported. above that at which condensation of solvent vapors will occur. Accordingly I provide means |03, one form of which is shown in detail in Fig. "I, for heating the chain to such temperature.

' As here shown by way vof example, the heating .means may comprise an electrically actuated induction heating coil |05 which has a eld which is intersected by travel of the chain I5 and the carrier I3 longitudinally of the enclosure. This causes a heating of the chain I5 and the carrier I3. y Other types of heating means, such as rethrough the overflow 22.

sistance heating or the like, may be employed for this purpose and the construction here shown and described is by4 way of example only. Solvents of the type usually employed for cleaning and degreasing operations have substantially no effect except when in their liquid form, so the heating `of the chain I5 and the carrier I3 prevents conselected intervals the shell I2 is formed to provide the vats or tanks I6 and I'I which are adapted to hold cleaning or solvent materials either in their liquid or their vapor phase. The materials used in fabrication of the shell I2 depend upon the use to which the apparatus is to be put and the materials to be used therein. In each instance the shell and the vats or tanks are formed of non-corrodible material such as Salvanized sheet metal, concrete, glass-lined steel, porcelain, stainless steel, enameled sheet metal, tile or the like, the choice of material depending upon the solvents to be used at each point along the length of the shell structure.

In the installation shown in Fig. 1 I propose to utilize bothA the liquid and vapor phases of the cleaning and degreasing solvents. Accordingly I provide in a vat or tank I5 a bath of liquid solvent, preferably an organic compound chosen l from the list previously mentioned, the solvent being used either alone or in combination with other liquid materials having a substantially higher boiling point than the solvent. The solvent used should preferably have vapors which are heavier than air.

Heating means 20, such as steam coils or the like, are placed in the bottom of the vat or tank I6 and are heated and controlled to lmaintain the body of the liquid solvent at a temperature :lust below the boiling point thereof. to conserve the heat, the vat or tank I6 is preferably insulated or formed of materials through which there is a relatively small amount of heat transference.

When using the solvent in its liquid phase in the vat or tank I 6, it is advisable to maintain it at such a level that the conveyorv does not come in contact with the liquid. The vapors which emanate from ther liquid in the tank are heavier than air and the height of the risers is so chosen as to confine a vapor column of suiilcient height to constitute a barrier to prevent substantial circulation of air longitudinally through the enclosure I2. The necessary level of the liquid solvent is maintained by feeding the liquid solvent at a constant rate through the solvent feed pipe 2l and continually removing the excess 'I'he solvent flowing through the overflow 22 is then passed through a water separator 23 and a still 24 tothe clean solvent storage tank 25, from which it is then pumped to the clean solvent supply line 26.

In using solvent materials at ltemperatures closely approximating their boiling points, lt is inevitable that some vaporization will occur. In order to prevent loss of the solvent materials in In order the form 'of vapors I provide a series of condenser coils 21 within the shell I2 and surrounding the four sides thereof. The conveyor, carrier and work pass through' the interior of the coils 2'I before they pass into the liquid solvent in the vat or tank I6. The condenser `coils are cooled to a temperature sufficiently below the temperature of the vapors driven off the liquid solvent to liquefy any vapors which pass into this portion of the enclosure. The vapors upon condensation to the liquid phase may drop back into the vat or tank I6, or may be diverted into the overflow pipe 22, thus preventing wastage thereof.

As the solvent in the vat or tank I6 is required to remove the first and consequently the greatest bulk of dirt or grease, it is advisable to provide a skimming paddle 28 which constantly agitates the surface of the liquid, and tends to prevent the formation of a surface scum containing the removed dirt and grease. This skimming paddle 28 tends to keep the surface scum in circulation so that it flows with the liquid to the overflow pipe from whence it is removed from the tank. This results in keeping the surface of the liquid relatively cleaner than would otherwise be the case.

As the work I4 on the carrier I 3 is moved longitudinally of the enclosing shell I2, it is dipped into the hot liquid solvent in the vat or tank I6 and is then carried under and beneath the depending portion of the shell and conveyor which extend inwardly to a point adjacent the surface of the liquid solvent. The work then is carried upward along the riser and away from the vat or tank I6 and thereafter passes through the spray rinse 30 which in this instance consists of a series of connected pipes 3I having, small perforations therein from which cold solvent under pressure is sprayed as sharp needle-like sprays directly upon the surface of the Work I4. In the embodiment here shown and as shown in more detail in Fig. 3, the connected pipes 3| extend around the sides and bottom of the shell I2 as well as longitudinally thereof for any desired distance. Liquid solvent is supplied in predetermined amounts through the conduit 32 which communicates through a feed pipe 33 with the filling line 26. A valve 34 permits control of the amount of solvent drawn from the conduit 33. In order to prevent contact of the liquid solvent with the conveyor system, and consequent grease removal therefrom, baffles |06 are secured to the shell I2 and extend downwardly therefrom and converge inwardly at their ends to form an enclosure which shields the conveyor from direct contact with the liquid solvent of the spray rinse.

Directly beneath the spray rinse 30 I provide a catch basin 35 in which cooling coils 36 are placed. 'Ihe catch basin 35 receives solvent from the feed conduit 32 and from the spray rinse 30. As the work I4 retains some heat by reason of its passage through the heated solvent in the vat or tank IB, the solvent sprayed thereon becomes heated so that` subsequent cooling is required. Unless cooled, the solvent passing from the spray rinse would vaporize instantly upon contact with the heated work and would not effect the agitation, scrubbing and flushing action desired. As the liquid solvent accumulates in the catch basin 35 it is cooled and withdrawn from the bottom thereof through the conduit 31 and thereafter passes through the recirculating pump 38 and the conduit 39 connected with the pipes 3|. As the work I4 passes through this spray rinse, adhering dirt and grease particles which have been loosened by the heated solvent in the vat or tank I6 are flushed oi the surface of the work.

Where, after the spray rinse, it is found desirable'to provide a still further cleaning action, I propose to subject the work to a bath of solvent vapors, and the cooli'ng of the work upon passing through the cold spray serves the purpose of lowering the t mperature of the work to a point where the solvent vapors of the subsequent bath will collect thereon. By condensing distilled solvent vapors on the work, the cleaning action of the solvent may be obtained without, however, running 1any vdanger of additionally contaminating the surface of the work by dirt or grease carried by the solvent, as might perhaps occur in the cold spray or in the liquid tank.

When the vapor bath is to be used, the work passes from the spray rinse 30 to a vat or tank I 1, being carried downwardly thereto through a passage the length of which is sufficient to contain a heavy enough body of solvent vapor so that displacement thereof by any atmospheric air entering the ends of the oven is minimized. Here, as in the case of the vat or tank I6, I may employ insulating materials either in the formation of the vat or tank Il, or I may surround the vat or tank I'I with heat insulating materials which are effective to prevent substantial heat losses therethrough. There is this difference, however; here the purpose is to utilize the solvent in its vapor phase, so the walls of the enclosure H2 are also insulated against heat loss so that when they become heated by contact with the heated vapors of the solvent, they will retain suflicient of the heat to preclude chilling of the vapors and consequent condensation thereof. Suitable solvent material in the liquid phase is supplied to the vat or tank I7 through a supply pipe 40 fed from the feed pipe 26 and controlled by the valve 4I. The supply pipe 40 has its discharge end terminating at a point within the vat or tank 'II, which is adjacent the top of the electrically actuated heating device 42, which generates sufcient heat to convert the liquid solvent to its vapor phase. The heating of the solvent is controlled by high and low level thermocouples 43 and 44 and suitable electric switches or controls (not shown but indicated diagrammatically at 45). By the use of the high and low level thermocouples the level of the vapors in the olischarge end of the vat or tank I 6 is definitely controlled within predetermined xed limits; for example, this electric control system is so arranged that if the high level thermocouple d3 is heated by the vapor, the flow of current to the heating device 42 is decreased and the solvent is boiled less vigorously. When, however, the vapor drops below the low level thermocouple 4t2, indicating adecrease in temperature, the flow of current to the heating device 42'is increased and the temperature of the solvent is increased. 'I'his results in the formation ofan increased amount of hot vapors and the subsequent mixture of the vapors at a predetermined level, depending upon the placement of the thermocouples 43 and 45.

To prevent flow of vapors longitudinally of the tunnel, I provide a series of condenser coils 46 between the work exit end of the spray rinse and the work entrance end of the vat or tank I1. These coils are similar in construction and operation to the condenser coils 2'I, when the heated vapors contact with the cooled zone within the condenser coils, the vapors are liquefied and when so liquefied may drop back intov the tank from which they issued. I have found that the use of the solvent in its vapor phase in the tank or vat I1 is superior to its use in a liquid bath or spray because the vapors are pure distilled solvent and are free from impurities which are apt to be present in a body of the solvent as aliquid. By using the vapors only, the grease, dirt and the like remain in the liquid solvent and so do not contaminate the cleaned surface.

After passing through the solvent vapors in the vat or tank l1, the work I4 is carried upwardly through induction heating coils 50 where it is heated to a suicient temperature to vaporize any adhering solvent particlesand to dry the surface thereof. The use of induction heating `coils at this point is preferable to other forms of heating systems since the heat so applied raises the temperature of the metal parts only above the top of the surrounding vapors or air. The use of induction heating coils minimizes the danger of explosions occurring in the tunnel as by this means the number of heated parts inside the tunnel and in contact with the vapors is reduced. The use of radiant or conductive heating means requires placement of the heating means inside the tunnel and in contact with the vapors therein. Such heating means depends upon a circulation of air or heated vapors to carry the heat from the heating means to the object to be heated.. There is an unavoidable heat loss in this transfer which must beprovided for by maintaining the heating means at temperatures substantially higher than required temperatures for heating the article undergoing treatment.

By the use ofinduction heating at this stage of the process, the heat is generated only in the particular object requiring heating and only to a predetermined and controlled extent. The heating of the object is accomplished without requiring a circulation of air or the vapors, which is desirable since it does not affect adversely the process for reclamation of the vapors driven oi the object undergoing treatment.

After passing through the induction heating coils 5u, the work passes into a drying oven 5l (Fig. 2) Which is heated in any desired manner and to any desired' temperature. The shell l2 at the points adjacent the induction heating colis 50 and surrounding the oven portion 5i is insulated to out down the heat loss therethrough. ln this manner heat is conserved within the enclosure i2 at these points. .As shown, the oven is constructed with a sloping bottom portion inclined downwardly toward the'vat or tank l?. This directs any liquid solvent particles or the heavy vapors o the solvent downwardly toward the vat or tank il and so conserves solvent materials which otherwise would be wasted in carrying out the process.

As the work passes from the oven 5l it travels through a passageway oi more restricted crosssectional area to a tack ragging and inspection station 52. As the vworlrcools progressively after leaving the heating section 59, the reduction or'. the cross-sectional area of the passageway tendsto` minimize-the amount of air which otherwise wouid be introduced into the oven 5l. rihe workv then passes from the linspection station 52 to a paint spray booth, dip tank or other surface treating chamber 53, after which the work may then pass to othei treating chambers (not shown) such as ovens or the like. D

Various types of construction may be employed in the construction of the enclosure I4. Where, however, a metal shell type of oven is employed in which induction heating coils 50 are used, there In a preferred construction these shells are spaced apart and thermal insulating material 62 is interposed therebetween. When using induction heating means, it has been found that .the usual types of metallic connecting members employed to hold the inner shellA 60 in place act as conductors of eddy currents passing into the inner shell 60, these eddy currents flowing through the connections to the outer shell which becomes heated thereby. This results` in a considerable power loss which cuts down the efficiency of the oven. 'I'he use of the thermal insulating material 62 between the two-shells is of no assistance in reducing this loss. I have therefore provided a modified form of connecting member for use in ovens heated by induction heating means, which, when used to connect the inner shell 60 and theA outer shell 6|, prevents the ow of eddy currents from the shell 60 to the shell 6I. As here shown, the connector comprises end members 63 and 64 connected to flanges 65 and 66 secured respectively to the outer and inner shells 6I and 60. The members 63 and 64 may be formed of any desired material and are connected by a center member 61 formed of any preferred dielectric material, such as porcelain, mica or the like. The use of the dielectric center member 61 between the adjoining ends of the members 63 and 64 has been found to eliminate the flow of eddy currents from the inner shell 60 to the outer shell 6l and cuts down the loss heretofore mentioned.

I have found that the system of the present I' invention, in certain installations, may be used with the solvent maintained in its vapor phase at all stages except the spray rinse stage. Figs. 4 and 5 represent, therefore, a modified form of apparatus adapted particularly for use in a cleaning and degreasing system wherein the solvent is employed in its vapor phase in both of the treating vats or tanks 'lil and 'i I. In such modication, the tank 'i0 is similar in construction and operation to the tank ll heretofore described and provides columns of the heavy vapors which prevent any substantial circulation of air through the enclosure. In this construction I employ a solvent boiling heater '52 of the electrically actuated immersion type. The heater 'i2 is controlled by high and low level thermocouples i3 and "H acting through electrically 'operated control members shown diagrammatically at l5.

It is an important feature of my invention that in the present embodiment the temperature of the articles treated may be so controlled that the same is always below the temperature of superheated solvent vapor and consequently no evaporation of the liquid solvent in the spray may occur. Such control is achieved by the thermocouples 13 and ll, either by controlling the temperature of the vapor, or by controlling the level of vapor in the bath. For the last type of control,

in order to prevent overheating of the work orl acted ln said spray by the excess supply of liquid solvent from an independent source, the liquid ca- Pacity of which is not limited to the amount of condensate produced in the tank l0, as is the case lin some prior structures. A

aladino Flow of the vapor from the vat or tank 18 is prevented by condenser coils 18 similar in construction andcperation to the condenser coils 46 (Fig. 1) heretofore described in detail. Here, as in the case of the vat or tank |1, the tank is heat insulated or is formed of heat insulating materials. Work |4 on the conveyor is carried into and through the solvent vapors in the tank 20 and then passes through the spray rinse 30 heretofore described in detail. 'Thereafter the work passes into the vat or tank 1| in which there is supplied a quantity of superheated solvent vapors. The vat or tank 1| is of similar construction and operation as the vats or tanks heretofore de scribed and is so constructed that the vapors provide a column which prevents substantial circulation of air currents through the vat or tank 1|. The superheated vapors of the solvent may be supplied initially from the vapor boiler 80 (Fig. 5) and thereafter superheated in the superheater 8|, or they may pass through a pipe 82 of magnetic material through the shell of the oven and inside the induction heating coils 83. Both methods are here shown and may be used either conjointly or as alternate methods.

To prevent ilow of superheated vapors in counter-current to the direction of travel of the work, condenser coils 84 similar in construction and operation to the coils 46 are interposed between the exit end of the spray rinse 80 and the entrance end of the tank 1|. After passing throughthe induction heating coils 83, the work |4 passes through an oven 5|, tack ragging and inspection zone 52 and into a spray booth, dip tank, or other surface treating member 53, as has been previously described.

As the work leaves the last vapor phase treatment, there is a condensate of distilled solvent which adheres to the surface or is imprisoned in the pores of the metal. The cleaning and degreasing system of the present invention provides a method and means for reclaiming such solvent. 'I'he work is heated to an elevated temperature as it travels through the induction heating coils and is heated to such a temperature as may be required to vaporize all adherent or imprisonedsolvent. The vapors, being heavier than air, drop downwardly and iiow down the inclined bottom portion and are conducted back to the vapor tank.

As shown in Figs. 2 and 5. the enclosure is formed as a hood which is provided with a downward opening. The air in the enclosure and in the hood is heated in the oven and by contact with the heated work, and rises against the top of the enclosure and the hood. This combination eects a seal which prevents any substantial drawing of air inwardly into the tunnel from the discharge end thereof. There is, therefore, little if any air circulation which might impair the successful operation of the solvent reclamation process due to turbulence in the vapors and carrying the vapors forwardly into further contact with the work.

Thus,l considered from one of its broader aspects, my invention contemplates providing a novel degreasing and cleaning structure of a. continuous and multiple stage type, in which the surfaces of the articles treated are subjected in each of the several stages of treatment to the action of hot liquid solvent, said hot liquid solvent being applied iirst in the form of a hot liquid bath of solvent, and thereupon produced by contact of the cold liquid with the hot surface of the articles, and the hot vapor with the cold surface 'of the' articles, the resulting temperature oi the solvent at the surfaces of the articles being substan- Y tially equal in each of said stages and being at such a point to produce best dissolving action upon oil and impurities; and in which system the hot solvent produced at the surface of the articles treated increases in its purityin each of the succeeding stages of treatment.v

I claim: An apparatus for the surface treatment of 'metallic articles which comprises an enclosure having spaced inner and outer shells formed of magnetic material such as sheet metal or the like, thermal insulating material interposed between said spaced shells, induction heating coils adjacent the inner of said shells, a series of spacing connectors joining said inner shell and said outer shell in spaced relation, each of said connectors comprising a body portion formed of electrical insulating material secured at its terminal end portions to said inner and outer shells and eiective to prevent iicw of current from the said inner to the said outer shell.

HOWARD E. SOMES.

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