US2487821A - Method of and apparatus for cooling and dispensing objects - Google Patents

Description

Nov. 15, 1949 E. L. M CANDLESS ETAL 2,487,821

METHOD OF AND APPARATUS FOR COOLING AND DISPENSING OBJECTS 2 Sheets- Sheet 1 Filed June 10, 1944 76 Fvhausiery Gas ffizlder or Compmsor EDWARD L. MC CANDLESS GEORGE w. PATCH JR. PHILLIP M. AHLST'RAND INVENTORS 'ATTORNEY Nov. 15, 1949 E. L. M CANDLESS ETAL 2,487,821 METHOD OF AND APPARATUS FOR COOLING AND DISPENSING OBJECTS 2 Sheets-Sheet 2 .Filed June 10, 1944 INVENTORS EDWARD L. Mc CANDLESS GEORG CH,JR.

STRAND E W. PAT PHILLIP M. AHL

ATTORNEY Patented N". 15,1949

Phillip M. Ahlstrand, Kenmore, N. Y., aslignors to The Linde Air Products Company, a corporation of Ohio Application June 10, 1944, Se'rialNo. 539.760

29 Claims. (Cl. 62-1) This invention relates to a method of and apparatus for cooling and dispensing objects, especially to condition and deliver metal parts for use in making shrink fits.

A shrink-fit joint between interfitting metal members or machine elements can be made either by heating the outer member or by cooling the inner member prior to assembly. Heating the outer member is often undesirable since excessive heating may cause warping or metallurgical damage in precision machine elements. In general, a strong shrink-fit joint may be made by cooling the inner member sufliciently without heating the outer member.

In order to cool metal parts, particularly those to be inserted in and joined by a shrink fit to a recessed part as a step in a mass production system', it is desirable that the cooling procedure and apparatus shall efficiently cool a succession of such parts to substantially the same low temperature and then deliver them to an assembling station in a dry cold condition ready for immediate insertion in the recesses of the parts to which they are to be united by a shrink fit. Moreover, to expedite the cooling operation and to increase the amount of shrinkage and thereby obtain the advantages of greater clearance for assembling, it is preferable to employ a vaporizable moisturefree cooling medium. A liquefied gas having a low boiling point, such as liquid oxygen, liquid nitrogen, or liquid air is particularly advantageous as the cooling medium. However, the efficient use of liquefied gases involves the need for preventing undue loss of refrigeration; and, with liquid air or liquid oxygen as the cooling medium, of eliminating possible hazard, both within the apparatus, as when the metal parts carry oil or other matter which may react with oxygen, and in the atmosphere around the apparatus where high oxygen concentration would be undesirable.

Accordingly, the principal objects of this invention are: to provide a method and an apparatus for expeditiouslyand efficiently cooling objects to condition the latter for a shrink fitting operation or for other purposes; to provide a method of and an apparatus for utilizing liquefied gas, such as liquid oxygen, as the coolant without, however, directly contacting the liquefied gas with the objects to be cooled; to provide a method of and apparatus for cooling a succession of metal objects and for delivering them in a cold and dry condition suitable for immediate assembly in the recessed members to which they are to be shrink fitted; to provide a method of and an apparatus for shrinking metal objects in which the liquefied gas (e. g., liquid oxygen, liquid air or liquid nitrogen) used as the cooling medium is so contained and insulated that undesirable evaporation, loss of refrigeration, and hazards of operation are greatly minimized; to provide a method and an apparatus for cooling an object by subjecting it to heat transfer relation with. but preferably not direct contact with, a body of vaporizable-cooling medium, and also subjecting said object to heat transfer relation with, preferably by direct contact with, a vaporized portion of said body of cooling medium; and to provide a method of and apparatus for cooling an object to substantially the temperature of a low-boiling point liquefied gas cooling agent while maintaining the object substantially free of moisture and frost until required for use.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings which illustrate apparatus by which the method of this invention may be performed. In the drawings:

Fig. 1 is a vertical sectional view of an apparatus embodying the invention and adapted to perform the improved method;

Fig. 2 is a sectional view of the apparatus taken on theline 2-2 of Fig. 1 and looking downward, portions being broken away to more clearly show certain elements of the apparatus;

Fig. 3 is a sectional view on an enlarged scale. taken alon g line 3-3 of Fig. 2;

Fig. 4is a fragmentary front view on an enlarged scale of the inlet ends of the cooling tubes, one of which is shown in section in Fig. 3;

.Fig. 5 is an enlarged plan view illustrating an alternative construction of the inlet end of the apparatus shown in Figs. 1 to 4, inclusive; and

Fig. 6 is a sectional view taken on the line 6-.-6 of Fig. 5.

In general, the method embodying this invention comprises cooling an object by subjecting it to the cooling effect of a body of vaporizable cooling medium while maintaining the object out of direct contact with the main body of cooling medium, and also subjecting the object to the cooling effect of a vaporized portion of the cooling medium. As disclosed herein, a refrigerating and dispensing apparatus embodying this invention may include a thermally insulated tank T for containing a refrigerant as cooling medium, such as a body of moisture-free low-boiling point liquefied gas and a moisture-free vaporized portion of such gas; one or more metal object guides tubes B extending through the tank T and the liquefied cooling medium therein but communieating with the vapor space of the tank. such tube or tubes thereby providing one .or more cooling chambers or heat transfer zones through which the objects to be cooled may be advanced whiie being indirectly, cooled by the liquefied cooling medium and directly cooled by a vaporized portion of such medium; and a delivery conduit. such as an inclined chute C, having its entrance adjacent thedischarge ends of the tubes 13 and arranged to receive the cold objects and keep them out of contactwith the outside air, so that 'the objects will be delivered in a cold dry condition at the delivery end of the chute below the inlets of the tubes B. Outside air, which normally contains moisture that would deposit as frost on the cold objects, is susbtantially excluded from the cooling tubes B and the chute C and is obstructed from'circulating therethrough, by closures E and F which normally close the inlet ends of the tubes B and the delivery end of the chute C, respectively; and a trap door D is located between the outlet ends of the tubes 13 and the entrance of the chute C to confine the vaporized cooling medium, .to assist in obstructing air circulation within the tubes and the chute, and to transfer the cold objects, in succession and without damage thereto, from the outlet ends of the tubes to the entrance of the chute. from which point the objects will slide down to the delivery end of the chute. Metal objects to be cooled for shrink fitting may be inserted one ata time through each closure E into the inlet end of the respective supporting shield or tube 13, pushing a succession of such objectsby the application of force .to a rear object and thereby advancing the objects in succession through the tube and thus pushing a forward cold object onto the trap door D which, when released, deposits the cold object into the 4 bined filling and drain line l5 terminating in a valve l8 through which vaporizable liquefied gas (e. g., liquid oxygen, liquid air or liquid nitrogenl is either charged into or drained from the tank over the safety disc to puncture it if thepressure in the tank T reaches a predetermined excessive value.

The discharge ends of the several tubes B open directly into a header or single chamber G normally closed at its bottom by the trap door D.

' One side wall of the chamber G is formed by a portion of the rear wall of the tank T, and.

the other side wall and the top wall of, the chamber G consist of two separate walls 24 and 25 to provide a space 26 between them which communicates through a passage'26' with the interior of the tank T, so that the space 26-may be filled with liquid cooling medium and thus aid in keeping the chamber G and the'vapor entrance or upper end of the chute, and when the object reacheisgthe delivery end of the chute it is in a cold dry'i'condition ready to be inserted into a recess in the metal member to which it istobeshrinkfltted.

Since the several tubes andassociated parts are similarly constructed, only one tube B and its associated elements will.need to be described in detail. Referringito land 2, the object is inserted into the inlet end of the thermallyconductive metal tube B'through the closure E which is shown in greater-detail in Figs. 3 and 4. The closure E may comprise a flexible diaphragm Ill having a. diametral slit H which is self-closing and of sufiicient size and flexibility to permit the insertion of an object therethrough into the tube B. The margin of the diaphragm I0 is clamped between a pair of mating annular flanges I2 and 13, so as to normally close and seal the entrance of the tube. The flange l2 may be welded to the inlet end of tube B, and clamping screws l4 secure the flange l3 to the flange 12 in such a; position that the diaphragm l0 and its slit I l are aligned with the passage of the tube. Part of the length of each tube B nearer its discharge end extends through the tank T, preferably close to but not contacting the bottom of the tank, so that this part of the tube will always be entirely submerged in the liquid cooling medium in the tank, whereby the object advancing through this part of the tube will be in heatand-cold exchange relation through the thermally-conductive metal tube wall with the body of cooling medium in the tank.

The tank T is provided with a suitable comtherein at a low temperature. A branch l5 of the combined filling and drain line I5 is connected to the bottom of the space 26 for the purpose of removing the liquid therefrom at the same time the tank Tis drained.

When the object leaves the outlet end of-the tu-be B it enters upon the normally horizontal trap door D mounted on door shaft 21. The shaft 21 is journalled in bearings 28 within shields 29 which maintain a gas-tight seal around each end of shaft 21. The front edge of the trap door D contacts the wall of the tank T, its rear edge contacts a strip 30 secured to the inside of wall 24, and the two end edges of the trap door are closely adjacent the end walls 3| and 32 of the chamber G, thus providing a seal efiective in obstructing circulation of gas between the chambers separated by the trap door.

Cold gas vapor from the gas space above the normal level of the body of-co1d liquid in the tank T is delivered by a conduit 33 and a perforated pipe 34 into the chamber G and from the latter into each tube B to further cool the objects in each tube by directly contacting them with such cold longitudinally of the chamber G, is closed at one end, and its opposite end opens into the conduit 33. The perforations 35 in-the pipe 34 are arranged above the outlet ends of the tubes B and distribute the cold vapor throughout the length of the chamber G and into each of the tubes B.

The trap door D may be swung downwardly about its pivot to an inclined position to deliver the object restingthereon into the chute C. The trap door may be operated by inwardly pressing a rod 36 pivoted to a link 31 secured to the shaft 21 keyed to the trap door D. The front end of the rod 36 is arranged adjacent the inlet ends of the tubes B, and the trap door may be restored to its normal horizontal position, either 'by pulling the rod 36 in an outward direction or of the chute until the object rests against the.

closure F which normally seals the discharge gas vapor. The pipe 34 extends asaaaai end of the chute. As shown in the drawing, the.

automatically-operating closure F may comprise a cover 31 carried by a rocker arm 33 pivoted at 39 and provided with a handle 43. A spring 4| resiliently joining the rocker arm 38 to a bracket 42 urges the cover 31 against the discharge end of the chute. Beneath the closure F is a tray 43 serving toreceive an object as it discharges from chute C.

With the exception of a short length of the inlet end of each tube B and the delivery end of the chute C, a housing H encloses the remainder of the herein-before described apparatus.- Legs 44 support the tank T substantially centrally within the housing H. The voids between the housing H and the elements therein are filled with thermal insulation 1, such as mineral wool, to minimize heat leakage to the tank T and its closely associated elements. The housing H desirably is substantially gas-tightly sealed in order to minimize the circulation of atmospheric air through the insulation therein with attendant wetting of the cold insulation. Excessive gas pressure accidentally occurring in the housing H may be relieved through a safety disc 45 which gas-tightly covers a hole 46 in the top wall of the housing and is arranged to be punctured at a predetermined pressure by a knife 41. The housing H may be supported at a convenient height from the floor as by posts P.

The vaporized portion of the cooling medium which has served to directly contact and cool the objects advancing through the tubes B desirably is removed from the region adjacent the inlets of the tubes B and may be collected for reuse, particularly if such vapor or gas is commercially pure oxygen or nitrogen; or such vapor may be collected and diluted with another gas, such as air, and then either stored or discharged into the atmosphere. As shown in Figs. 1 and 2, for example, a hood 48 may be arranged directly over and close to the row of closures E to collect and remove the gas (e. g., oxygen) leaking from the tubes B incidental to the insertion of the objects to be cooled. Air enters the open end of the hood to mix with and dilute the eilluent oxy-. gen, and this gas mixture is then conveyed through a duct 49 to a blower or exhauster 50 mounted on the housing H. The gas mixture may then be exhausted into the atmosphere or into a suitable gas holder for use where oxygen-, enriched air may be utilized. The mixture of the air at room temperature with the cold gas and the movement of the mixture through the hood 48, duct 49, and exhauster 50, serves to warm the ends of the tubes or guides B which project out of the housing H by the relatively warm air sweeping over'such ends. In doing so, there is a tendency to reduce the formation of frost on the ends of the tubes B.

As previously indicated, it often is desirable and more economical to recover and reuse the. vaporized cooling medium without diluting the same with a gas such as air, especially when liquid oxygen or liquid nitrogen is used as the cooling medium. To this end, the modified inlet) construction shown in Figs. and 6 may be used. Here each of the tubes B has one or more perforations 5| near its entrance, which perforasure for reuse, as for gas welding or cutting. Each of the closures E comprises a cover 54 adapted to seal the entrance of a tube B. The cover 54 is carried by a plate 55 hinged at 58 to a bracket 51 secured to the header 52, and a spring 58 is provided to normally hold the cover 54 in closed position. Otherwise, the construction and operation of an apparatus embodying the modification shown in Figs. 5 and 6 is similar in all respects to the apparatus disclosed in Figs.

1 and 2.

In using the apparatus, a liquefied gas, preferably liquid oxygen, may be forced through the filling line l5 into the tank T until the liquid has reached the level of the overflow line H, as indicated by the try-cock IS. The gauge K actuated by the float I9 indicates the progress of the filling operation. Heat from the objects being cooled is transmitted in part to the tubes B and convection currents of liquid refrigerant distribute such heat through the body of the refrigerant. The warm condition of the tank T or heat leaking into it from the tubes B and from other members connected to it, will cause a portion of the liquid oxygen to evaporate and expand in the gas space above the body of liquid in tank T and to flow through the conduit 33, pipe 34, and perforations into the chamber G. From the chamber G, the cold gaseous oxygen flows into each of the tubes B and forwardly in the direction Of the arrows while enveloping and directly contacting the objects to be cooled which are advanced in a counter direction through the tubes; and finally gaseous oxygen escapes either through the slits II in the rubber diaphragm H) as the objects are inserted into the tubes, or the gaseous oxygen escapes through the perforations 5| into the header 52. Thus, while advancing lengthwise of and in contact with the tube B, the metal parts are pro-cooled by direct contact with the cold gaseous oxygen in the tube and also give up their heat to the cold wall of the tube, to ultimately cool the parts to a temperature near the temperature of liquid oxygen. The gaseous oxygen enveloping the metal parts also sweeps away any moisture-laden air which might be carried along with them when they are inserted through the closure means at the entrance of the tube. In this manner, deposition of frost upon the metal parts is substantially prevented, because the parts reach a temperature equal to the dewpoint of air at a location where no moisture-laden air exists. When a tube B has been filled throughout its length with parts to be conditioned, any additional part that is inserted will advance a cold conditioned part onto the trap door D. When delivery of a cold part is desired, the plunger 36 is pressed, whereupon the trap door is lowered tions open into a common header 52 gas-tightly,

exhauster or a gas holder, or to a compressor f adapted to restore the oxygen to a suitable presbe cooled.

and the part slides therefrom into the chute C and to the front or delivery end of the latter. The cold part is retained within the chute by closure F, to be released at the operators will. The time required to assemble a cold part in a recessed member usually is short enough to prevent frosting of the part during the assembling operation. Gaseous oxygen which escapes through the closure is drawn through the hood 48 along with air from the room into the duct 49 and the blower 50. Alternatively, the suction through the perforations 5| into the duct 53 may be sufficient to prevent the escape of any substantial or hazardous amount of gaseous oxygen through tLe closure E' when the latter is opened to introduce a part to 7 While specific embodiments have been disclosed to illustrate the principles of this invention, it will be understood that numerous changes may be made in the constructions shown without departing from such principles. For example, although the herein-disclosed refrigerating apparatus and method is applied to one kind of object or machine element, it will be apparent that other types of objects may be similarly cooled or refrigerated, depending upon the sizes and cross-sectional shapes of the tubes or cooling chambers employed. Any desired number of chutes, trap doors and plungers, from one of each common to all of the tubes, as shown, to one for each tube may be employed. Thus, a single chamber G and a single chute C may be employed, as shown, with a row of cooling tubes B, but when the cooling tubes are designed to cool different kinds of parts, an individual chamber G and an individual chute C may be provided for each cooling tube, so that if there are eight tubes for example, it will be possible to cool and dispense eight difierent kinds of objects, each variety of object being inserted in its correspondingly sized and shaped tube. Furthermore, it will be evident that certain features of theinvention may be employed independently of others.

What is claimed is:

1. A method of cooling an object which comprises subjecting said object to the cooling eflect of a substantially moisture-free body of vaporizable cooling medium while maintaining such object in thermally-conductive relation to but out oi direct contact with said body of cooling medium; and subjecting said object to the cooling efiect of a vaporized portion of said body of cooling medium while substantially excluding atmospheric moisture from access to the object beingcooled.

2. A method of cooling an object as claimed in claim 1, wherein said object is subjected to direct contact with said vaporized portion while the latter is in a moisture-free condition.

3. A method of cooling an object as claimed in claim 1, wherein said object is simultaneously subjected to the cooling effect of said body of cooling medium and to the cooling efiect of said vaporized portion while excluding atmospheric air from said body of cooling medium and from said vaporized portion during the cooling of said object.

4. A method of cooling a metal object which comprises placing said object in a chamber having a thermally-conductive wall with which said body contacts; maintaining a body of vaporizable moisture-free cooling medium in contact with a surface of said wall which is opposite to and on the other side of said wall from said object, to cool said chamber and said object; and passing a moisture-free vaporized portion of said cooling medium into said chamber and into direct contact with said object, to provide a moisture-free atmosphere around said object and to cool the latter in addition to the cooling of the object by thermal conduction through said wall.

5. A method of cooling a metal object which comprises advancing said object through a chamber having a thermally-conductive wall; maintaining a body of vaporizable moisture-free liquid cooling medium in contact with an outside surface of said wall, to cool said chamber and said object therein; and flowing a vaporized portion of said body of cooling medium into said chamber and in a counter-current direction relative to the direction of advance of said object, to directly contact and cool said object and to envelop the same in a moisture-free atmosphere.

6. A method of cooling an object which comprises enclosing said object in a chamber adapted to exclude atmospheric air; and subjecting the interior of said chamber and the object therein to the cooling effect of.a moisture-free liquid cooling medium selected from the group consisting of. liquid oxygen, liquid air and liquid nitrogen, while maintaining said object in thermally-conductive relation to but free from direct contact with said liquid cooling medium.

7. A method of shrinking and conditioning a metal object to prepare it for assembly within a recess in a metal member, said method comprising placing said object in a chamber having a thermally-conductive wall; subjecting said chamber and said object therein to the cooling effect of a body of moisture-free vaporizable cooling agent maintained in contact with at least a portion of the exterior surface of said wall; and conducting a moisture-free vaporized portion of said body of cooling agent into said chamber and into direct contact with said object.

8. A method of shrinking and dispensing metal objects for assembly within recesses in metal members, said method comprising advancing said objects in succession lengthwise of a tubular chamber having a thermally-conductive wall; maintaining a body of vaporizable cooling medium in contact with an outside surface of said wall, to cool said chamber and the objects therein; flowing a vaporized portion of said body of cooling medium lengthwise of said chamber and in a counter-current direction relatively to the direction of advance of said objects, to envelop said objects in such vaporized cooling medium and to additionally c001 them; transferring such cooled objects in succession from said chamber into a delivery chamber; and removing the cooled objects from said delivery chamber for assembly in such recesses.

9. Apparatus for cooling an object comprising, in combination, means having a thermally-conductive wall and providing a chamber to enclose said object; and means, including a moisturefree body of liquid cooling medium in thermallyconductive relation to said wall but outside said chamber and selected from the group consisting of liquid oxygen, liquid air and liquid nitrogen. for cooling the interior of said chamber and said object therein.

10. Apparatus for cooling an object comprising, in combination, means providing a chamber to enclose said object; and means for cooling the interior of said chamber and said object therein, such cooling means including a body of vaporizable cooling medium outside said chamber, and conduit means for conducting a vaporized portion of said body of cooling medium into said chamber, at least a part of said chamber having a thermally-conductive wall disposed within and in thermally-conductive relation with said body of cooling medium.

11. Apparatus for cooling an object comprising, in combination, means providing a chamber to enclose said object; and means for cooling the interior of said chamber and said object therein, such cooling means including a body of vaporizable cooling medium outside said chamber, and conduit means for conducting a, vaporized portion of said body of cooling medium into said chamber, said chamber having an inlet adjacent one end thereof and an outlet adjacent the opposite end thereof; at least a part of said chamber having a thermally-conductive wall disposed within said body of cooling medium; and said conduit means communicating with the outlet end of said chamber.

12. Apparatus for cooling and dispensing objects comprising, in combination, av tank adapted to contain a cooling medium; an object guide extending through said tank and the cooling medium therein, said guide being constructed for the advance of objects along it for cooling; a delivery conduit adapted to receive cooled objects which have advanced through said guide; and means operable to impede admission of air into said guide and into said conduit.

13. Apparatus for cooling and dispensing objects, as claimed in claim 12, wherein said guide has an outlet at one end and has an inlet at its other end through which objects may be inserted into the guide; and said delivery conduit being inclined downwardly from the outlet end of said guide.

14. Apparatus for cooling and dispensing objects comprising, in combination, a tank adapted to contain a cooling medium; a tube having an' inlet end and an outlet end and extending through said tank and the cooling medium therein, said tube being constructed for the advance therethrough of the objects to be cooled; a delivery conduit having its entrance adjacent the outlet end of said tube; and means operable to transfer objects from said outlet end of said tube to said entrance and normally obstructing communication between said tube and said conduit.

15. Apparatus for cooling metal objects to condition them for shrink fitting, such apparatus comprising, in combination, a tank containing a vaporizable cooling medium; a plurality of tubes each having a thermally-conductive wall contacting the cooling medium in said tank, said tubes providing chambers adapted to receive such metal objects; and conduit means providing communication between said chambers and the vapor space in said tank, to conduct a vaporized portion of said cooling medium into said chambers and into direct contact with the metal objects in said chambers.

16. Apparatus for cooling metal objects, as claimed in claim 15, wherein each tube has a normally-closed inlet which is openable for the insertion of a metal object; and means, including a duct associated with said tubes, to remove vaporized cooling medium from the region adjacent such inlets.

17. Apparatus for cooling an object comprising, in combination, a tank for a vaporizable liquid refrigerant, means providing a cooling chamber for said object, a conduit leading from the upper portion of said tank above a normal liquid level therein into said chamber adjacent one end thereof for conveying vaporized refrigerant from the tank into contact with said object, a housing enclosing said tank and at least a major portion of said chamber, thermal insulation between the tank and housing extending around at least a portion of said chamber, and a closure outside the housing for an end of said chamber, said closure being adapted for opening to allow insertion of said object into the chamber and being normally closed against egress of vaporized refrigerant through the object input end of said chamber except when open.

18. Apparatus for cooling an object comprising, in combination, a tank for vaporizable liquid refrigerant, a housing around said tank, thermal insulation between the housing and tank, an

10 elongated object cooling chamber supplied with vaporized refrigerant from above a normal liquid level in said tank, said chamber being enclosed by thermal insulation at least to some extent and said chamber extending into said housing, and a discharge duct leading at substantially a right angle to the longitudinal axis of said chamber from near said elongated chamber and adjacent the junction of said chamber and housing for carrying oil? much of the vaporized refrigerant after it has moved longitudinally of said chamber. 19. Apparatus for cooling objects comprising, in combination, a tank for a vaporizablellquid refrigerant, a housing about said tank, thermal insulation between the tank and housing, a plurality of cooling chambers within the housing for receiving objects to be cooled, a header to which said chambers are connected, a conduit for supplying vaporized refrigerant from an upper portion of said tank above a normal liquid level therein to said header and chambers for cooling I objects in such chambers, and a closure for the object input end of each chamber.

20. A method which comprises subjecting an object to the cooling effect of a substantially moisture-free body of vaporizable refrigerant by maintaining said object in a zone in heat transfer relation to and traversing said body of refrigerant; also by subjecting said object to the cooling effect of a vaporized portion of said body of refrigerant discharged into said zone while substantially excluding access of atmospheric moisture to the object being cooled; and diluting with another gas at least a part of the vaporized portion escaping from said zone.

21. Amethod which comprises maintaining an object in a zone in heat transfer relation to and traversing a body of substantially moisture-free vaporizable refrigerant to cool said object; subjecting said object to the cooling effect of a vaporized portion of said body of refrigerant discharged into said zone while substantially excluding access of atmospheric air and moisture to the object being cooled; and, after such vaporized refrigerant has been used to cool said object, diluting with another gas at least a part of the vaporized portion escaping from said zone, thereby avoiding a localized high concentration of used vaporized refrigerant in the atmosphere.

.22. In an apparatus for cooling arr'object, in combination, means providing a chamber having a thermally-conductive wall and constructed to enclose said object and to exclude atmospheric air and moisture therefrom; means for cooling the interior of said chamber and said object therein, such cooling means including a body of vaporizable and substantially moisture-free liquid refrigerant contacting the outer surface of said wall of said chamber, said cooling means for the interior of said chamber including conduit means for conducting a vaporized portion of said body of refrigerant into said chamber to contact said object therein;- said chamber having an opening through which vaporized refrigerant discharges after contacting said object; and means for collecting vaporized refrigerant discharged from said chamber through said opening.

23. Apparatus for cooling an article comprising, in combination, an article chamber for enclosing an article to be cooled; means for subjecting an article in said chamber to the cooling effect of a gaseous cooling medium; a mixing chamber constructed and arranged to receive such cooling medium after the latter has been used to 0001 said article; and means for supplying air to 11 said mixing chamber to dilute the cooling medium therein.

24. Apparatus for cooling an article comprising, in combination, an article chamber to enclose said article; means for supplying a cooling gas to said article chamber to cool an article therein; a, mixing chamber constructed and arranged to receive such cooling gas after the latter has been used to cool said article; means for supplying air to said mixing chamber to dilute the cooling gas in the latter; and means for discharging diluted cooling gas from said mixing chamber into the atmosphere.

25. Apparataus for cooling a metal article comprising, in combination, a container adapted to hold a body of liquefied vaporizable gas and to provide a gas space above said body to confine the vaporized gas; an article chamber adapted to enclose the article to be cooled and having a thermally-conductive wall externally in contact with said body of liquefied gas; means for conducting vaporized gas from said gas space into said article chamber; amixing chamber constructed' and arranged to receive vaporized gas after the same has contacted said article; and means for supplying air to said mixing chamber to dilute the vaporized gas in the latter.

26. The combination with a tank for vaporizable liquid refrigerant, of a housing enclosing said tank, thermal insulation between said housing and tank, object guide means extending into said liquid refrigerant for effecting transfer of heat from an object in said guide means to said liquid refrigerant in said tank to cool said object and also to eifect at least some vaporization of the liquid refrigerant within said tank, and conduit means extending from above the liquid level in said tank to said guide means for leading vaporized refrigerant from said tank into said guide means and into direct contact with an object to be cooled in said guide means.

27. The combination with a tank for vaporizable liquid refrigerant, of a, housing enclosing said tank, thermal insulation between the housing and tank, an object guide extending from outside said housing through said tank of liquid refrigerant, a closure for each end portion of said guide whereby objects may be moved into one end portion and out the other end portion of said guide, and a conduit for transferring vaporized refrigerant from said tank into said guide, the free egress of vaporized refrigerant from said guide being impeded by the closure for each end portion of said guide.

28. A method of cooling an object which comprises supporting said object within a zone traversing a body of liquid refrigerant and spaced from the bottom of the. liquid while excluding access of moisture to said object and while shielding said object from direct contact with said body of liquid, transferring heat from said object to said body of liquid by heat conduction from said object through said zone, facilitating heat transfer from said zone to said body of liquid by establishing convection currents of liquid past said zone.

29. In an apparatus for extracting heat from an object to be cooled, said apparatus comprising a tank for vaporizable refrigerant, thermal insulation around said tank, and a cooling chamber within said apparatus for objects to be cooled and through which vaporized refrigerant may pass in contact with said objects, said chamber extending through said insulation from outside the apparatus, the combination therewith of the improvement for eliminating possible concentration of spent vaporized refrigerant around the object input end of said chamber, said improvement including a duct for leading at least a substantial part of said spent refrigerant from adjacent said object input end of said chamber, and a pump for moving said spent refrigerant through at least a portion of said duct.

EDWARD L. McCANDLESS. GEORGE W. PATCH, JR. PHILLIP M. AHLSTRAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 686,531 Ostergren Nov. 12, 1901 1,905,885 Bonnet Apr. 25, 1933 1,978,204 Hurt Oct. 23, 1934 2,038,592 Morris Apr. 28, 1936 2,356,779 Morrison Apr. 29, 1944

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