US2795020A

US2795020A - Methods of making insulated cabinets

Info

Publication number: US2795020A
Application number: US328637A
Authority: US
Inventors: Robert M Kintz
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1952-12-30
Filing date: 1952-12-30
Publication date: 1957-06-11
Anticipated expiration: 1974-06-11

Description

June 11, 1957 R. M. KlNTz 2,795,020

METHODS OF MAKING'INSULATED CABINETS Fi led Dec. 50. 1952 I5 Sheets-Sheet 1 a n an Inventor* 'Rober-t M. Kim-2,

bg l

His Atnoreg June ll, 1957 R. M. KlNTz I 2,795,020

METHODS OF MAKING INSULATED CABINETS Filed DSC. 30, 1952 I 3 Shee-'l'fS-Shee't 2 Inventor: Robert, M.Kir1tz,

HiS Attorneg.

vJune 11, 1957 R M, KlNTZ 2,795,020

METHODS 0F' MAKING INSULATED CABINETS med nec. so, 1952 ssheets-sneet 5 Inventor: Rober-t, M.Kint.z, bg Q His Attorney.

nited States Patent O M' 2,795,00 METHODS oF MAKING INSULATED CABiNErs Robert M. Kintz, Millcreek Township, Pa., assignor t General Electric Company, a corporation of New York Application December 30, 1952, Serial No. 328,637

2 Claims. (Cl. 20-101) My invention relates to vacuum insulated cabinets and more particularly to methods of making vacuum insulated cabinets.

Vacuum insulated Istructures may be of the type described and claimed in the copending application of Herbert M. Strong and Francis P. Bundy, Serial No. 236,788 tiled July 14, 1951. It is to be understood that my invention is an improvement over the invention of the Strong and'Bundy application and therefore, I do not claim as my invention anything shown or described in said Strong and Bundy application which is to be regarded as prior art Vwith respect to the present application. The Strong and Bundy empl-oy a compressible iiller material for supporting the walls thereof. If, in the making of vacuum insulated cabinets, a compressible ller material of a thickness corresponding to the difference between the dimensions of the inner liner and the outer case were employed, this compressible filler material would be considerably compressed by the external pressure upon evacuation of the space between the walls, and the walls would therefore be Iconsiderably distorted because of the compression of the insulating material. In accordance with my invention however, a compressible insulating material of a thickness `substantially greater than the distance between the inner and outer walls of the cabinet is employed, so that after evacuation -and resultant compression of the iiller material, it supports the walls with the proper final spacing and with the walls substantially llat and undistorted. In accordance with my invention a convenient method is provided for effecting the compression of the ller material during assembly of parts of the cabinet.

It is an object of my invention to provide improved methods for making a cabinet of the vacuum insulated type including improved methods for facilitating the assembly lof the parts of such cabinets.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

` In carrying out the objects of my invention, the inner liner is formed with inclined side walls providing a tapering plug structure and the insulation placed within the outer case includes similarly inclined side walls providing a tapering receptacle for receiving the inner liner. Flexible strips are provided adjacent at least the lower portion of the side walls of the insulation so that these strips are engaged by the inner liner as the liner is inserted and compresses the insulation, whereby any tendency to force the insulation downwardly toward the bottom of the case and thereby to leave voids in the upper portion is minimized. A solid plug or an inflatable bag may be employed for supporting the walls of the inner liner during this assembly. Alternatively, the insulation may be compressed substantially to size by a plug before insertion of the inner liner to minimize the compression Patented June 1l, 1957 ice 2 elected by the installation of the inner liner. As an additional alternative the insulation may be placed around the exterior of the liner, compressed substantially to size, and the liner with the surrounding insulation then inserted within the outer case.

For a better understanding of my invention, reference may be had to the accompanying drawings in which Fig. 1 is a sectional elevation view of an insulated cabinet made in accordance with my invention.

Fig. 2 is an exploded view lshowing the cabinet of Fig. 1 just prior to assembly.

lFig. 3 is an exploded view similar to Fig. 2 showing a modified form of my invention.

Fig. 4 shows one stage of the construction of a cabinet being manufactured in accordance with another form of my invention.

Fig. 5 shows the structure of Fig. 4 in another stage of manufacture. n

Fig. 6 shows another modified form of my invention.

Fig. 7 yshows one stage lof a method of manufacture applicable to the form of invention shown in Fig. 6.

Referring to Fig. l, `there is shown an insulating cabinet which includes an outer case or wall 1 and an inner liner or wall 2. The outer caseincludes sidewalls and a bottom wall 3 welded to the side walls at 4 to complete the outer case. The space between the outer case and the inne-r liner is lled with a compressible heat-insulating material 5, which may be, for example, a glass liber heat-insulating material. In the form `s-hown the inner liner 2, like the outer case 1 includes a side wall structure 6 and a bottom wall 7 welded to the side wall structure at-8 to complete the inner liner. The top edges of the outer case and the inner liner are Welded at 9 to seal the space between the outer case and the inner liner. The space is evacuated in 'any conventional manner to provide a very low pressure therein. The side walls 6 'of the inner liner 2 are inclined inwardly toward the bottom to provide a liner having a tapering plug structure. The heat-insulating material 5 has similarly inclined side walls providing a tapering receptacle structure. The significance of these shapes `of the inner liner and of the heat-insulating material is explained in detail below.

The inner liner and the outer case are shown in the process of assembly in the exploded view of Fig. 2. As there shown the outer case 1 is received within a fixture generally represented by 10 for supporting the walls of the outer case against distortion or outward bulging during assembly. The fixture or form 10 has internal dimensions corresponding to the external dimensions of the outer case. Although the walls of the outer case may be yallowed to bulge outwardly as a result of the pressure exerted during assembly, reliance being had upon the evacuation of the space between the outer case and the inner liner for restoring the shape of the outer case, I refer to mount the outer case in a suitable wall supporting fixture It@ during assembly. The heat-insulating material 5, which is a compressible material suchV as glass ber, is then placed .within the outer case 1 adjacent the side walls and the bottom thereof. While illustrated as a single mass, this heat-insulating material may most convenientlybe assembled by providing it in the form of batts. One of these batts is placed adjacent the bottom and one batt adjacent each of the four side walls. The batts adjacent the side walls of the outer case are formed with inner surfaces 11 inclined inwardly toward the bottorn ends thereof. This provides a tapering receptacle for receiving the inner liner 2 which, as described above, includes similarly inclined side walls providing a tapering plug structure.

Since a compressible heat-insulating material is ernploy'ed as a filler material for supporting the walls of the outer case and the inner liner after evacuation of the space therebetween, it is necessary that this material be subjected to a substantial pressure and substantially compressed during assembly; otherwise, the, large external pressure exerted against the walls after evacuation would result in a substantial inward bowing and distortion thereof, detracting from the appearance of the tinished cabinet. In order to accomplish this result the thickness of the heat-insulating material, as illustrated in Fig. 2, is substantially greater than `the final thickness after assembly of the innerliner, as illustrated in Fig; 1. yin other words the inner. dimensions of the tapering receptacle Aare substantially smaller than the corresponding outer dimensions of the liner. It is necessary that the reduction in thickness of `the heat-insulating material, that is the compression of `the heat-insulating material, -be effected as the inner liner 2 is assembled and further that this be effected without `significantly forcing the heat-insulating material downwardly along the sidewalls which would tend to leave voids at the top portion of the cabinet. The aforementioned tapering structure of the inner liner and ofthe side walls of the heat-insulating `material is provided to assist in accomplishing this objective. It will be seen that this structure provides a mouth at 12 which is greater than the size of the bottom 7 of the inner liner so that the bottom of the inner liner may enter freely within the mouth 12.

In order to further minimize any tendency to force the heat-insulating material along the side walls downwardly toward the bottom of the cabinet one or more guide elements 13 are provided adjacent at least the lower portion of the inner surfaces 11 of the side walls of the heatinsulating material. In the form shown, a plurality of spaced strips 13 are provided around the entire perimeter of the lower portion of the heat-insulating material, these strips extending inwardly along a portion of the bottom of the heat-insulating material. t It will be apparent, however, that the guide element structure could be provided in the form of a single pan-like receptacle having slits at the corners to allow for outward movement during assembly of the inner liner. Alternatively, it could also consist of two sheets in overlapping cruciform structure each sheet v extending the full width or length of the bottom of the heat-insulating material and including ends extending upwardly-.along the side walls in the` same manner` as the strip guide elements illustrated in Fig. 2. The guide elements 13 may be made of any suitable material so long as it is sufficiently flexible to permit the necessary distortion and outward movement thereof as the inner liner is assembled. The upper ends 14 are extended upwardly along the side walls of the heat-insulating material a sufficient distance so that the dimensions of a `horizontal plane extending through the top edges 14 of the guide elements 13 exceed the corresponding dimensions of the bottom of the inner liner. For example, the dimension illustrated at d in Fig. 2 is slightly greater than the corresponding dimension d of the bottom of the inner liner 2. Because of this dimension relationship the bottom lof the inner liner 2 passes within the contines of the guide elements 13 before engaging the side walls of the heat-insulating material. Hence, any tendency to force the side wall portion of heat-insulating material downwardly toward the bottom during assembly, which might be significant if `the inner liner were allowed to engage the side wall portion of the heat-insulating material directly, is minimized. The inner liner engages the guide elements 13 and rides therealong, and the guide elements in turn contine the heat-insulating material and direct it toward the corresponding side walls of the outer case, minimizing the downward force exerted against the heatinsulating material. By this arrangement, therefore, the heat-insulating material is compressed to the shape and size shown in Fig. 1 while still retaining heat-insulating material in the space between the outer-case and the inner liner throughout the full height of the side Walls of the cabinet.

in order to minimize distortion of the inner liner 2 during assembly a solid, preferably wooden, plug 15, shaped to conform exactly to the interior surface of the inner `liner 2, is provided within the inner liner 2. During assembly a downward force is exerted on the top of the plug 15, as indicated by the arrows in Fig. 2, for urging the inner liner 2 into the receptacle provided by the heat-insulating material 5. As mentioned above, this downward force first brings the bottom of the inner liner into engagement with the guide elements 13 below the top edges 14 of these guide elements. Continued pressure exerted on the top of the plug 15 then forces the inner liner 2 downwardly to its iinal assembled posi tion relative to the outer case 1, compressing both the side walls and the bottom wall of the heat-insulating material 5. The force chosen is such as to exert a pressure of approximately 15 pounds per square inch throughout thcVheat-insulating material, since this will then balance the external force exerted on the walls of the outer case and the inner liner after the evacuation of the space therebetween. During this assembly, in the form shown, bulging of the walls of the outer case is prevented by the supporting fixture itl and bulging of the walls of the inner liner is prevented by the supporting plug 15. After the inner liner 2 has been urged downwardly to its assembled position the top edges of the outer case and the inner liner are welded, as indicated at 9 in Fig. l. This welding may be accomplished in several ways, al1 well-known in the art. For example, the inner liner may be spot welded to the outer ease in the area indicated at 9, while the outer case is retained Within the supporting fixture 10 and while the load remains on the plug 15. The assembled 'structure may then be removed from the fixture and the :load removed from the plug 15 and the sealing completed by line welding the top edges together. Aln ternatively,.the top edges may be line Welded at 9 while the outer case is retained in the supporting fixture 10 and while the load remains on the plug 15, completing the sealing of the outer case to the inner liner at that time. Similarly, the evacuation of the space between the outer case and the inner liner may be effected after the elements have been removed from the supporting fixture, as when initial spot welding is employed, or while the elements are still within the supporting iixture, as when the line welding technique is employed. Where the elements are removed before evacuation there will be some bulging of the walls of the outer case, but since the spot welding has established the proper relationship of the outer case and the inner liner while within the tixture the walls of the outer case will return to their flat shape after evacuation with n minimum of stress in the resulting structure. The evacuation of the space between the outer case and inner liner may be accomplished in any conventional manner well-,known in the art.

A modified form of my invention is shown in exploded lform in Fig. The same numerals have been employed to designate corresponding parts in Figs. l and 2 and in Fig. 3. Referring to Fig. 3, the structure includes an outer case or wall '1, an inner liner or wall 2 and heatn insulatingmaterial S. The side walls of the heat-insulat ing material are inclined as indicated at 11 and the side walls of the inner liner are similarly inclined as indicated 'at 6 as inthe previous form of invention. The form of invention shown in Fig. 3 differs from that illustrated in Figs. 1 and 2 in 'that an inflatable hollow plug 16 is substituted for the wooden plug 1S. The plug 16, which may be formed of rubber, plastic or other suitable intiatable flexible rmaterial, is placed within the confines of the innerrliner 2. The plug 16 is then inliated to a pressure-sud'icient to resist deformation while a compressive force of'app'roxiinately 15 pounds per square inch is exerted on the compressibleheat-insulating material` 5 during assembly. In other words, the plug 16 is preferably inatados() flated to a pressure' somewhat exceedinglS pounds per square inch. In order to confine the plug within the inner liner 2, a suitable block or closure member 17 is employed along the top thereof. A passage for inflating and dellating the envelopeof the plug 16 is provided at 18 extending through an opening in the block 17. The block 17 may be clamped or otherwise pressed into engagement with a shoulder 19 formed on the inner liner 2. After the plug 16 has been suitably inflated a downward force is exerted on the block 17, asindicated by the arrows, urging the inner liner first into engagement with guide elements 13, andthen further downwardly to compress the heat-insulating material, as in the formV of invention previously described. The assembly is cornpleted in the same manner as described in connection with Figs. l and 2.

Another alternative form of my invention is illustrated'in Figs. 4 and 5. Again, corresponding parts have been identified with the same numerals as in the previous figures.Y ln the form of invention shown in Figs. 4 and 5 an inflatable plug 16 corresponding to `that illustrated in Fig. 3, is also employed. This form of invention differs from that shown in Fig. 3, however, in that the inllatable plugY 16 is utilized for precompressing the heat-insulating material 5 before-the insertion` of the inner liner or wall 2. j Thus, as shown in Fig. 4, the inflatable plug 16 is first inserted within the tapcringreceptacle provided by the heat-.insulating material 5. Guide elements or strips'20, corresponding generally to the guilde elements 13, are employed.. ln this form of invention the strips have been made to extend the full height of the side walls of the heat-insulating material. 5, slightly overlapping -the top edge thereof and extending also slightly inwardly adjacent the bottom wall thereof. A block 21 corresponding somewhat to the block 17 in the form of invention shown in kFig.V 3 Vbut shaped to lit within the top portion of the outercase or wall 1 is employed adjacent `the top of the inflatable plug 16. The block 21 includes an otpening for receiving the inflating passagelt ofthe plug 16. The plug '16. is inserted within the receptacleprovided by the heat-insulating material 5 at least before inflation thereof has been completed. The block 21 is then-placed adjacent the top surface of the inflatable plug 16, the block 21 being positioned by engagement of the shoulder 22 thereof with the top edge 23 of the outer case. The block 21 may be clamped` in any suitable manner to the outer case or itmay be held in position merely by exerting a force in the direction of the Aarrows exceeding the upward pressure exerted by the inflatable plug :at its ultimate inllated pressure. After the plug 16 has been assembled within the receptacle provided by the heatinsulating material 5 and the block21 superimposed in the manner described above, the plu-g is inflated through the passage `18 to a pressure of at least approxiamtely l5 pounds per square inchto effect compression of the heatinsulating material to approximately its final dimensions. While the compressible heat-insulating material 5 tends toy return somewhat toward its original size after the pressure exerted by the inflatable plug is removed, this tendencyrnay be minimized by applying a suitable binder to thekmaterial 5 or by heat treating the mass in accordance with the invention described and claimed in the cepending application of Alfred G. Janes, Serial No. 303,324, tiled August 8, 1952 and assigned to the General Electric Company, the assignee of the present invention. I have found that the tendency of the compressible heat-insulating materialto reexpand after this precompression can also be minimized by subjecting the heat-insulatingA material to the pressure of the inflated plug for several successive times. That is, the plug may be inflated as described above to a pressure of at least approximately l5V pounds per square inch torcompress the heat-insulating material toapproxirnately its final dimensions. The plugmay be deflated and then reinated to the above pressure to again compress the heat-insulating material. I have found that subjecting the heat-insulating material to several such pressure applications, that is carrying the operation through several cycles as described above, results in a smaller reexpansion of the heat-insulating material after final removal of the pressure than is the case where' only a single compression of the heat-insulating material is effected.

After the compression of the heat-insulating material has been effected in the manner described above, the plug 16 is dellated and is removed from within the receptacle provided by the heat-insulating material. The precompression technique has the advantage that the heatinsulating material may be inspected before insertion of the inner liner and any deficiencies or voids corrected at that time.` The inner liner 2 is then inserted in the same manner as in the previous forms of my invention, a plug corresponding to the plug 15 in Fig. 2 or tothe inatable plug 16 bein-g preferably employed within the inner liner for supporting the Walls thereof. The guide elements 20 areretained during this assembly of the inner liner since the heat-insulating material may be expected to reexpand to a size somewhat exceeding the final size and it must therefore be recompressed as the inner liner is inserted into its assembled position. However, this recompression is substantially less than the compression necessitated where the heat-insulating material, as in the form of invention shown in Figs. l, 2 and 3 is not precompressed before assembly of the inner liner. The completion of the assembly by welding the top edges of the outer case and inner liner together and evacuation of the space therebetween is accomplished in the same manner as in the previous forms of my invention. While an inflatable plug 16 has been employed in the forms illustrated in Figs. 4 and 5, it will be apparent that this method could equally well be carried out using a solid plug similar to plug 15 in lieu of the inflatable plug 16 and block 21.

Intheforms of invention previously described the heatinsulating material has been placed within the outer case toprovide a tapering receptacle land the tapering inner liner has then been inserted within the receptacle. While this is the preferred form of my invention, my invention may also be carried out by providing the heat-insulating material adjacent the exterior walls of the tapering inner liner and by forming the outer case to provide :a tapering receptacle structure. Such a modified form of my vinvention is shown in Figs. 6 and 7. Thus, in Fig. 6 an outer case or wall 24 has been provided including downwardly and inwardly inclined side walls forming :a tapering receptacle. An inner liner or wall 2 corresponding to that employed in the previous forms of rny invention is also utilized in the form shown in Fig. 6. In the form of my invention shown in Fig. 6 heat-insulating material 25 is provided adjacent the exterior surfaces of the inner liner ,2. This heat-insulating material is of constant thickness throughout its area thereby providing exterior walls 26 which are downwardly and inwardly inclined in the same manner as the side walls of the inner liner 2. ,The inner liner and its surrounding heat-insulating material therefore provides a tapering plug structure.

*In order to facilitate introduction of the tapering plug structure into the receptacle provided by the outer oase 24 with .a minimum of voids resulting from shifting of the heat-insulating material, one or more guide elements 27, corresponding to the

guide elements

13 or 20 previously employed, are positioned `adjacent the lower portion of the exposed surfaces of the heat-insulating material 25. In this form of my invention the tapering plug formed by the inner liner and its surrounding heat-insulating material Vis then forced inwardly into the tapering receptacle provided by the outer case 24. The outer dimensions of the tapering plug are substantially greater than the corresponding inner dimensions of the tapering receptacle provided by outer case 24 so that a substantial compression of the heat-insulating material 25 is effected during the assembly ofthe liner within the outer c'as e p7 p As the taperingplug structure is forced into'the outer ease the guide elements 27 first engage the outer case. These guide elements then ride along the outer case during the completion of the inward movement of the tapering plug structure into `assembled position within the outer case 24, thereby minimizing shifting of the heat-insulating material particularly at the bottom corners of the inner liner 2.

In order to minimize outward bulging of the outer case during this assembly the outer case is preferably supported within a fixture 28providing a supporting structure conforming to the shape of the outer case. While for convenience `the assembly has been shown as being `accomplished 'bydownward movement of the inner liner in `the same manner `as in the previous forms of-rny invention, it will be apparent that this could be accomplished `in the present form, if desired, by inverting the outer case and effecting the assembly by an upward movement of the inner liner and its surrounding heatinsulating material into the tapering receptacle provided by `the outer case. In order to provide a finished appearance a` skirt, corresponding to the generally vertical side walls of the outer case 1 employed for example in the form shown in Fig. l, may be added to the assem bly, enclosing the tapering side walls of the outer case 24.

As in the form of invention shown in Figs. 4 and 5 the type of structure shown in Fig. 6 may also have the heat-insulating material precompressed before actual assembly within the outer case. An arrangement for accomplishingthis precompression is shown `in Fig. 7. As there illustrated a supporting fixture 29 having tapering 'walls corresponding to the shape of the outer case 24 is employed. Within this supporting fixture is placed a cup-shaped inatable diaphragm 30. The diaphragm 30 has a tube 31 extending therefrom for inflation and deflation of the diaphragm. The diaphragm is shown in Fig. 7 in its inated condition where, as in the form of invention shown in Figs. 4 and 5, it is inflated to a pressure of at least approximately l pounds per square inch to effect compressionof the heat-insulating material. However, it will be appreciated that this diaphragm is first inserted within the supporting fixture 29 in a de ated condition. The inner liner 2 with surrounding heat-insulating material 25 in an uncompressed condition is then placedwithin the deflated diaphragm 30. The top of this structure is then closed by a block 32 which engages the top 33 of the supporting fixture 29. An opening 34 is provided in this block 32 for the tube 31.

After the parts have been assembled in this manner, the

diaphragm 30 iis inflated through the tube 31 to a presn sure of at least approximately pounds per square inch, thereby effecting compression of the heat-insulating material to the dimensions showin in Fig. 7. As in the case of `the block 21, the block 32 may be clamped in place or held in position by a force exerted in the direction of the arrows in Fig. 7 and exceeding the ultimate iniiated `pressure of the diaphragm 30. Further the block 32 may extend into and till up the space within liner 2 so as to prevent any buckling of the liner walls during the compressing of insulation 25. As in the case of the invention shown in Figs. 4 and 5, when the diaphragm is deflated the heat-insulating material `will tend to reexpand to some extent but not to the original dimensions. Moreover the precompression may be accomplished `under the conditions described and claimed in the aforementioned Janos application in the same manner as suggested in connection with the form of invention` shown in Figs. 4 and 5 for minimizing such reexpansion. Also the amount of reexpansion may be reduced by applying the pressure of the inflated diaphragm to the heat-insulating material 25 several times in succession. That is, after the initial compression of the heat-insulating material the diaphragm vmay be deflated and then reinflated to again apply the same compressing pressure to the heat-insulating material. This process may be repeated several times as suggested above in connection with the form of invention shown in Figs. 4 and 5. I have found that by such repeated application of pressure the amount of reexpansion of the heat-insulating material after final removal of the pressure may be vsubstantially reduced. After the heatf insulating material has been precompressed in the manner described above the tapering plug structure formed by the inner liner 2 and the surrounding heat-insulating material is then inserted within the `outer case 24 and the assembly completed in the manner previously described. The guide elements 27 mayalso be employed in completing the assembly.

While I have shown and described specific embodiments of my invention, I do not desire my invention to be limited to the particular constructions lshown and described, and l intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of making a vacuum insulated cabinet which comprises providing an inner liner and an outer case, shaping said inner liner to provide side walls inclined inwardly toward the bottom thereby forming a tapering plug structure, placing compressible heat-insulating material within said outer case adjacent the side walls and bottom thereof with the inner surface of the side walls of said heat-insulating material being inclined inwardly toward the bottom to provide a tapering receptacle for receiving said inner liner, the inner dimensions of said tapering receptacle being substantially less than the outer dimensions of said liner, placing a iiexible guide element adjacent at least the lower portion of the inner surfaces of said side walls of said insulating material, placing within said inner liner an inatable hollow plug, inflating said hollow plug to conform to and to support said inner liner, exerting a downward force to move said tapering liner downwardly into engagement with said guide element and continuing ythe exerting of said force to urge said inner liner downwardly for compressing said insulating material along both the bottom and the side walls, securing the top edges of said inner liner and said outer case in sealing engagement, and evacuating the space between said inner liner and said outer case.

2. The method of making a vacuum insulated cabinet which comprises providing an inner liner and an outer case, shaping said inner liner to provide side walls inclined inwardly toward the bottom thereby forming a tapering plug structure, placing compressible heat-insulating material within said outer case adjacent the side walls and bottom thereof with the inner surface of the side walls of said heat-insulating material being inclined inwardly toward the bottom to provide a tapering receptacle for receiving said inner liner, the inner dimensions of said tapering receptacle being substantially less than the outer dimensions of said liner, placing a flexible guide element adjacent at least the lower portion of the inner surfaces of said side walls of said insulating material, placing within said inner liner an inflatable hollow plug, inflating said hollow plug to conform to and to support said inner liner, placing a block on the top of said inflatable hollow plug and in engagement with the top edge of said inner liner, exerting a downward force on said block to move said tapering liner downwardly into engagement with said guide element and continuing the exerting of said force to urge said inner liner downwardly for compressing said insulating material along both the `bottom and the side walls, securing the top edges of said inner liner and said outer case in sealing engagement, and evacuating the space between said inner liner and said outer case.

(References on following page) References Cited in the le of this, patent 2,375,182

UNITED STATES PATENTS 850,143 Donnelly Apr. 16, 1907 699,583 2,067,015 Munters Ian. 5, 1937 5 2,108,212 Schellens Feb. 15, 1938 2,164,143 Munters June 27, 1939 532,289

10 Y Anway May 8, 1945 Freeman June 29, 1949 Hedges July 3, 1951 Kurtz Ian. 18, 1955 FOREIGN PATENTS Great Britain Jan. 21, 1941