US 2000882 A
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I May 7, 1935.. F CQMSTOK' 2,000,882
INSULATING HOUSING Original Filed Sept. 7, 1928 2 Sheets-Sheet l 26/ i ifz fla 2.
Daniel F Comsloc y 9 r o. F..coMsTocK' 2,000,882
INSULATING HOUSING Original Filed Sept. 7, 1928 2 Sheets-Sheet 2 Patented May 7, 1935 INSULATING HOUSING Daniel F. Comstock, Boston, Mass., assignor, by mesne assignments, to Stator Refrigeration, Inc., a corporation of Delaware Original application September 7, 1928, Serial No. 304,589. Divided and this application March 20, 1930, Serial No. 437,377
This invention relates to insulation as applied to or incorporated in refrigerators, refrigerator cars, refrigerant ducts, hot or cold fluid pipes or tanks, heaters, boilers, houses, or other installations, and more particularly as associated with the former. This application is a division of my copending application No. 304,589, filed September 7, 1928, and all of the specification and disclosure of that application are included by reference in the present application.
While it has heretofore been proposed to utilize vacuum chambers for insulating refrigerators or the like, the diificulty of permanently maintaining a comparatively high vacuum in housings of this character has made the commercial provislon of such insulating means impractical. The present invention provides vacuum insulation for purposes of this character, preferably utilizing a fairly high vacuum in conjunction with powdered or closely spaced filling material or other material Iiaving minute interconnected voids in the vacuum chamber.
The elements of this filler material may be so disposed in indifferent particle-to-particle contact that they afford a very poor path for direct heat conduction between opposite sides of the vacuum chamber, while preventing direct heat radiation between the same and providing only a low rate of reradiation. The voids in the filler material preferably have dimensions substantially less than the mean free path of the gas molecules. The filler is also preferably non-hygroscopic and not highly gas absorptive. When material of this character is located within a vacuum chamber, a considerably lower vacuum provides as good a heat insulating efficiency as does a high vacuum in chambers that are free from the separated or foraminous filler.
One of the deficiencies of vacuum insulating walls or casings of the character heretofore proposed has been the freedom with which heat could pass from one wall of the vacuum chamber to the other by paths other than through the vacuum space'itself; for example, the wall connecting hot and cold sides of the chamber have usually provided such a low resistance to the flow of heat that the effect of the vacuum insulation was substantially nullified. Thus, for example, invacuum insulating walls of the character heretofore built or proposed it has been common to provide continuous metal connections between the opposite hot and cold Walls of the chamber, the metal of these connections being of substantially the same thickness as the opposite hot and cold walls or face sheets of the vacuum chambers and conse quently providing paths of high heat conductivity between the hot and cold sides of the insulating wall. The present invention preferably obviates these deficiencies by providing bridges or connections of low heat conductivity between the face sheets or metal walls at opposite sides of the vacuum chamber. Thus, for example, I may provide non-metallic supporting elements between the margins of the inner and outer walls, which are adapted to support the same against the external atmospheric pressure and I may associate comparatively thin metal bridges with these nonmetallic elements, the bridges preferably being formed of metal having high heat resistivity Thus the thin metal is united with the opposite face sheets in order to provide a substantially gastight seal, while the thinness of the metal as well as its natural heat resistivity causes it to-afford a comparatively poor heat conductive path. The non-metallic supporting material which permits the use of the thin metal bridges preferably may be a comparatively poor heat conductor. It is thus evident that a housing having walls formed in accordance with this invention ordinarily will be characterized by parallel metal sheets which normally may be at quite different temperatures, having their edges connected by bridges of low conductivity whereby there is only a slight leakage from the high temperature to the low temperature sheet.
As a further adaptation of my invention, I preferably provide similar bridges or connective means not only betweenthe edges or margins of the sheets, but at openings which are provided for the necessary pipes or the like that may pass through the wall to provide connections for refrigerant flow or the like and at other locations.
When an insulating wall is filled with material having minute interconnected voids, it may prove somewhat difficult to cause a continuous gas flow from all portions of the chamber thus filled to a single gas outlet. Therefore, in its preferred embodiment my invention provides the vacuum chamber with suitable air or gas passages arranged in conjunction with the filling material to permit the circulation or movement of gas from widely spaced regions within the insulating wall to the single gas outlet. Thus, for example, I may preferably provide air passageways which are substantially coextensive with a face of the wall itself. These passageways communicate with a duct that may be connected to any suitable evacuating means such as that, for example, dis-. closed .in my copending application referred to above, so .that the pumping means may be continuously operable to maintain a fairly high vacuum in the insulating wall to compensate for leakage into the chamber, or, if desired, this duct may be connected to means arranged to evacuate the chamber.
In the accompanying drawings:
Fig. 1 is a front elevation of a refrigerator in which my invention may be incorporated;
Fig. 2 is a broken horizontal -section indicated by line 2-2 of Fig. 1;
Fig. 3 is an elevational detail of the screen and fabric arrangement provided to permit the ready evacuation of the vacuum wall or casing;
Fig. 4 is an elevational detail of the vacuum casing;
Fig. 5 is a section on line 5-5 of Fig. 4;
Fig. 6 is a perspective detail of a corner portion of an optional form of frame for a casing of this character;
Fig. 7 is a vertical section through a portion of a door showing an optional construction of the same; and
Fig. 8 is a section through a door having a heat non-conductive bridge of the type shown in Fig. 6.
Referring first to Figs. 1 and 2 of the accompanying drawings, it may be seen that the refrigerator housing is provided with inner and outer walls which afford a suitable space therebetween which may be exhausted of air, gases, and vapors, thus providing a comparatively high vacuum; This space is preferably filled with closely spaced, finely divided or foraminous material which is a poor transmitter of heat, such as comminuted diatomaceous earth, which may be pressed into bricks, closely spaced sheets of paper, attenuated fibrous material or the like, cork or similar porous material, which not only prevents direct radiation from one wall of the vacuum chamber to the other, but which minimizes the effect of reradiation and which affords small voids which at a proper vacuum are substantially smaller than the mean free path of the gas molecules. Radiation is also minimized, because each particle can ordinarily radiate only to a juxtaposed particle or particles. Suitable gas-collecting passageways may be arranged within the vacuum chamber in a manner which will be described below, these passageways being connected to the air exhaust pipe 1. The latter may be connected to any suitable evacuating means, such as the first stage of the multi-stage pumping means illustrated in my above identified application, or to any desired type of vacuum pump.
As shown more particularly in Fig. 2 the refrigerator housing I is provided with the inner and outer shells 2 and 3 which may conveniently be formed of sheet metal and which are nested in spaced relation to each other to provide a vacuum chamber therebetween. The box is preferably provided with a suitable swinging door or closure I10 which also comprises a vacuum chamber that is connected by a suitable duct with the chamber in the housing proper. The inner sheet metal casing 2 may carry a plurality of spacing elements or struts l1l of hard non-conducting material, such as bakelite, asbestos wood, hard rubber, or other material which preferably is rendered impervious to moisture. Spacers I'll may be secured to the inner shell 2 by means of metal clips I12 which are soldered, welded, or otherwise joined to the shell.
Located along the inner face of the outer shell 3 are suitable means to provide fluid passages which may connect with the pipe 1. These passages preferably are arranged to permit the exhaustion of gas and vapor from widely spaced and distributed portions of the vacuum chamber. One mode of attaining this result consists of the provision of meshed wire screening I14 held against the face of the metal shell by clips I15. This screening preferably may be substantially coextensive with the outer face of the shell wall, and similar screening, similarly designated, may be arranged within the door I10. A suitable fabric 201, such for example as felt, may be arranged against the wire screen l14, this fabric preferably being sufliciently impervious to prevent the finely divided filling material from penetrating into the air spaces between the wires of the meshed screen, while readily permitting the flow of gas.
As previously stated, the finely divided or foraminous filler material preferably is packed between the inner and outer walls of the vacuum chamber. Such material, for example, may be diatomaceous earth, closely spaced sheets of paper, closely packed fibrous material, or similar substances, which are adapted to prevent the movement of heat by radiation between opposite walls of the vacuum chamber and which may provide interconnected voids having dimensions substantially less than the mean free path of the gas molecules.
The outer ends of spacers or struts l1| engage the sheet 201, aiding in holding the same in place. The filling material packed between the fabric and the inner shell and about each of the spacers also aids in supporting the walls against the external atmospheric pressure, and with properly reinforced walls of the internal reinforcements or spacers l1| may be omitted and dependence placed upon the filling material alone for this purpose, if desired. Fig. '7 illustrates a door having a substantially solid filler which may conveniently be diatomaceous earth in the form of bricks or blocks 40 which forms suitable reinforcements for the opposite sheet metal walls of the chamber, so that the internal reinforcements or struts "I are ordinarily not required when this 'form of the invention is employed, the screen I14 and fabric 201, however, may be employed as in conjunction with'the finely divided filler material, or the brick may be scored or roughed to provide air passages between the brick and the metal sheets and between the bricks themselves.
Special means are provided between the edges of the inner and outer shell to prevent heat conduction therebetween, thus materially raising the heat insulating efficiency of the housing. For this purpose, I preferably arrange the edges of the inner and outer shells in spaced parallel relation and provide especially constructed non-conductive bridges therebetween. In the specific arrangement illustrated herewith, for example, the edge of the inner casing 2 may be turned outwardly to provide a. perimetric flange I83 while the edge of the outer casing is inturned to provide a flange I84. The form of non-conducting bridge which is illlustrated therewith may comprise strips I05 of heat insulating material such, for example, as bakelite, asbestos wood, hard rubber, or various other synthetic compositions, or natural wood impregnated with suitable moisture-resistant material, such for example as high boiling point paraffin. The inner and outer edges '01 these bridge elements preferably may be enlarged and may receive sheet metal channels I86, the outer edges of the legs of which are firmly flanged about the enlarged portions of the nonmetallic elements as designated by the numeral I8I. A suitable filler strip 22I maybe arranged between the inturned metal portions I81 to provide a surface substantially aligned with the aligned surfaces of metal strips I88. A thin metal plate 220 may then be secured by soldering or the like to these aligned surfaces of the strips I88, this metal plate being supported by the filler 22I and serving to provide a substantially gas-tight seal between the two strips I88. The sealing strip 220-preferably is formed of metal having high heat resistivity such as, for example, constantan, nichrome, invar, or the like, and preferably is of thin gage in order to provide low heat conductivity. The non-metallic element I85 supports the opposite edge portions of the metal walls against external pressure so that the metal sealing strip 220 does not need to have great structural strength and accordingly may be made quite thin.
One of the strips I88 upon each of the bridges I85 is secured by soldering or welding to the flange I83, while the opposite metal portion I88 is secured to a rectangular frame I89 of sheet metal. Preferably flange-I84 and frame I89 lie in the same plane and are spaced from eachother. A suitable cover frame I90, which also preferably is rectangular, may then be soldered or welded upon the outer faces of frame I89 and flange I84, thereby closing the space between casings 2 and 3. Thereafter any conventional outer sheathing or covering means may be provided as, for example, the outer sheets of veneer or decorative metal IBI and the comer trim I92 and the edge strips I93.
The door preferably is formed of inner and outer metal sheets 280 and 28I, the screen Ill being arranged adjoining the inner face of' the latter. Suitable spacers III may be arranged between the inner and outer sheets after the manner described above with reference to the main vacuum chamber. The bridge elements I85, which are arranged within the door, may correspond to the similar strips similarly designated and described above, and similarly may be associated with non-metallic fillers HI and thin metal sealing plates 228. The inner metal portion of the bridge strip within the door may be welded to a marginal face of the inner sheet 208, while the outer metal element may be secured to the rectangular frame I91, this frame being secured by soldering, welding or the like to the edge of sheet 2M. The door may be provided with suitable covering means and flanges in any desired manner, as shown.
The bridge members may conveniently be assembled to compose rectangular frames before they are disposed between the inner and outer sheets or between the face sheets of the door.
For this purpose the strips I and the channels I88 are provided with mitered joints, Fig. 4, and slots 208 are cut in the mitered ends of the nonmetallic elements I85, these slots preferably extending the full depth-of these elements, as indicated in Fig. 5. A comparatively stiff, impervious sheet material, which may be impregnated by a high melting point paraflin or the like, may be folded to provide an angle element 881 which is engaged in the slots at the ends of the strips I88; pressphan or fish-pam'r or similar material is suitable for this purpose, since it is comparative- -ly stiff and sturdy and yet has sufficient yieldability to permit its introduction into the slots 208. When the bridge strips are thus assembled in this manner, the adjoining portions of' the metallic channels I88 may be secured to each other by soldering or welding, as designated by numeral 205, Fig. 4. The sealing strips 220 which meet at the corners may then also be welded or otherwise secured to each other to provide a substantially continuous metallic seal. It is evident that the rectangular bridge frame utilized in the door is similar to that provided for the casing, but that the sealing strips 228 are located about the bridge frame in the former case rather than inside the same as shown in Fig. 6.
Bridges similar in general construction to those flow between opposite sides of a wall of the hous ing- Thus, as shown in Fig. 2, a cooler 8| may be connected by a pipe 82 extending through the back of the refrigerator housing to any suitable exterior refrigerating means. With a pipe of this character which necessarily passes through the vacuum wall, suitable circular openings may be cut in the inner and outer sheets with a diameter somewhat larger than that of the pipe. An annular or spool-like bridge of any desired composition, such as hard rubber, wood, bakelite, asbestos wood, or the like is arranged between the inner and outer sheets at this point, suitable metal channels having their legs clinched about enlarged portions of the annular member in the same general manner, as described in reference to the bridges at the edges of the box with the exception that these members are curved rather than straight. Thus the outer metal member I85 may be soldered or welded to the face of sheet 3 adjoining the pipe opening therein, while the corresponding opening in theinner sheet may portions of the channels I85 and I88 inside of the annular bridge member, and a metallic seal-. ing strip 220* may be soldered or otherwise secured to the aligned surfaces of the channels I88, this strip being supported by the flller 22h.
A suitable ring of heat insulating material 28I is arranged within the annular member and is adapted to hold the pipe 82 in spaced relation thereto and spaced from the inner and outer walls of the vacuum chamber. If desired. this portion of the pipe may be made of material having low heat conductivity, such as constantan, nickel-chromium, or invar, and/ or may have thin walls.
In order to permit the flow of gas from the air passages provided, by the meshed screen in the door to the corresponding passages within the chamber, I provide a suitable flexible duct 2II which is connected to the interior of the door and the interior of the chamber. This duct-may be formed of a single metal tube with an undulatory wall of the type commonly utilized for metal bellows or the like, the ends of this tube being welded, brazed, soldered, or otherwise secured to the outer walls 8 and NI of the housing and door respectively and the ends of this tube being arranged in somewhat spaced relation from the bridge construction. As in the case of the construction shown in Fig. '5 these connecting bridges may be utilized both between the inner and outer shells of the casing and the inner and outer walls of the closure, Figs. 6 and 8 illustrating the latter specifically.
In order to minimize heat conduction between the inner sheets 300 and the outer sheets 30!, it is desirable to use material having low heat conductivity, to make the path to be traversed by the heat comparatively long, and to minimize the cross-sectional area of the conductive path. Accordingly when metal is utilized for this purpose I preferably provide a bridge sheet 302 which may be of a gage considerably thinner than that of the outer and inner sheets 300 and 30L This sheet preferably has portions welded or otherwise secured to the edges of the sheets 300 and 30! and is preferably formed of metal having low heat conductivity, such for example as constantan or nichrome. Furthermore this metallic bridge may be arranged to follow an indirect course between the inner and outer sheets 300 and (MI. For this purpose I may arrange a plurality of filler elements 304 in channels formed in the sheet, the adjoining channels facing in opposite directions and being reinforced by the filler elements 304 that fit tightly wi hin the same. These elements may be of any suitable material having low heat conductivity, and may conveniently be formed of material adapted to withstand considerable heat so that they may be heated when the chamber is initially evacuated. Asbestos wood is therefore suitable for this purpose.
Suitable non-conductive finishing material 308 may be arranged about the bridge strip 302, as shown in Fig. 8.
Fig. 6 illustrates a typical corner construction in a door having a metallic bridge of the type shown in Fig. 8, it being understood that the channels may be built up and welded together at the corners in order to make the same substantially continuous about the perimeter of the bridge frame. It is evident that the construction shown in Figs. 6 and 8 permits the provision of a metallic bridge between an inner and outer wall of the vacuum casing which may remain at different temperatures. The heat resistivity of the bridge metal as well as the length of the same, and the thinness thereof thus may cooperate in permitting only a slight heat flow between the inner and outer sheets.
From the foregoing it will be evident that this invention provides an insulating wall or housing which may contain one or more vacuum chambers that preferably are filled with closely spaced, or foraminous non-heat transmitting material and which are exhausted to a fairly high vacuum; that this invention is suited to the provision of a commercially feasible type of wall that need not be absolutely free from atmospheric leakage, but which may receive a small amount of gas either from the atmosphere or from the metal of the vacuum chamber walls, suitable pumping means such as disclosed in my above identified copending application then being connected to the duct 1 continuously to maintain the vacuum within the chamber. It is further evident that my invention permits the ready removal of gas from all portions of the evacuated chamber despite the packing of the same with a filler providing minute voids, since air passages are provided which are substantially coextensive with the wall and are adapted to remove gas which might otherwise tend to become trapped in local portions of the filler. The bridges between the inner and outer metal wall portions are very effective in enhancing the insulating efliciency of the vacuum wall, since otherwise a comparatively large flow of heat would occur if the metal sheets of the inner and outer walls were joined to each other in the conventional manner.
From the foregoing it will be evident that an important feature of the invention consists in the unique construction of the bridges which interconnect the inner and outer walls around the boundary of the vacuum spaces, whereby heat conduction is minimized not only through the insulation walls but also along the boundary bridges; that'low bridge conduction may be attained by making the bridges of low conductivity, thin, or long, or with any two of these three characteristics, or with all three characteristics; and that a long bridge may be provided without increasing the spacing. between the walls by turning the bridge back and forth in suitable contour as illustrated in Figs. 6 and 8.
While I have disclosed this invention particularly as applied to a refrigerating housing, it is evident that the principles thereof are widely applicable to various installations where a heat insulating wall or jacket has proven or may prove desirable. Thus, for example, a vacuum chambered housing of this general type may be utilized in conjunction with heaters, ovens or boilers, while the walls of muses may similarly be provided with hollow evacuated panels that are provided with pumping means arranged as disclosed and described herein.
1. In combination, a heat insulating housing, said housing having a swinging closure, the walls of the housing including the closure being hollow and containing a gas pervious filler, a flexible gas duct connecting the closure with one of the fixed walls of the housing, and air passageways extending along the filler and being substantially coextensive with the wall area of the housing, said passageways communicating with the flexible gas duct and a second gas duct communicating with said passageways for connection to exterior evacuating means.
2. A heat insulating housing having a hollow wall providing a vacuum chamber, a duct extending through the chamber, opposite face sheets having openings with their edges spaced from the duct, compression-receiving material of low heat conductivity surrounding the duct and extending between the face sheets, a thin metal sealing strip of low conductivity integrally connected to the face sheets to provide a substantially air-tight seal, and a layer of non-conductive material between said strip and the duct, whereby heat flow between the sheets and the duct as well as between the sheets themselves is impeded.
3. An insulating wall providing a vacuum chamber and opposite metal face sheets, struts of material having low heat conductivity extending between the sheets and bracing them against exterior pressure, metallic elements secured to the sheets and engaging end portions of the struts to hold the latter in place, the intermediate part and one end of each strut being free from metal, whereby heat flow between the sheets is impeded, and finely divided material packed between the sheets and about the struts, said material aifording numerous small voids communicating with one another, the metallic elements being connected to one of said sheets, a sheet of gas-pervious material adjoining the other sheet and cooperating therewith in defining gas passages, a duct communicating with said passages for connection to an evacuating pump.
4. A housing with an enclosure in the form of inner and outer shells having their margins connected to afford a hollow vacuum chamber, filler means comprising finely comminuted material between the shells opposing exterior pressure thereon, said material providing numerous minute irregular, interconnecting voids, a duct connected to the interior of the chamber for connection to a vacuum pump, said filler means cooperating with the-inner surface of one of said shells in defining regular, continuous air passages substantially coextensive with that surface of the shell, said passages being substantially larger than the interconnected voids, the passages permitting the ready flow of gas to the duct, whereby the resistance to gas flow from any part of the chamber to the duct is substantially determined by the resistance afiorded by said voids to the flow of gas to the nearest of said passages.
DANIEL F. CQMSTOCK.