US1898977A - Vacuum insulation - Google Patents

Description

Feb. 21, 1933. I CQMSTOCK 1,898,977

- vApuuM INSULATION Filed Sept. T, 1928 3 Sheets-Sheet l Feb 211, 3933.

D. F. coMsTocK 1,898,977

VACUUM INSULATION Filed Sept. 7, 1928 3 Sheets-Sheet 2 Feb. 21, 1933. D. F. coMsTocK 'vAcuuu INSULATION Filed Sept. 7, 1928 s Sheets-Sheet s Egg j i pzaw/ferzki Jailed .E' ('02 @WMqMq Patented Feb. 21, less uurrs rear oFFic DANIE F. COMS' IOCK, O BOSTON, MASSACEUSETTS, A SSIGNOR, BY MESNE ASSIGN- IIHEITIS, 1'0 STATOB EEFRIGEEA'EIGN', INC., A CORPORATION OF DELAWARE VACUUM. INSULATIQN Application filed September 7, 1928.= Serial No. 304,589.

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.

VVhile it has heretofore been proposed to utilize vacuum chambers for insulating refrigerators or the like, the difiiculty of permanently maintaing a comparatively high vacuum in housings of this character has made the commercial provisionof 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 having minute interconnected voids in the vacuum chamber.

The elements of this filler material may be so disposed in indiiierent' particle-to-particle contact that they afiord 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 pro- I vides as good a heat insulating efiiciency as does a high vacuum in chambers that are free from the separated or foraminous fillers.

One of the deficiencies of vacuum insulat ing 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 walls 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, in vacuum 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 consequently 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 conducitv1ty between the face sheets or metal walls at opposite sides of the vacuum chamber. Thus, for example, T may provide nonmetallic supporting elements between the margins of the i er and outer walls, which are adapted to support the same against the external atmospheric pressure and l. may associate comparatively thin metal bridges with these non-metallic elements, the bridges preferably being formed of metal having comparatively high heat resistivity. Thus the thin metal is united with the opposite face sheets in order to provide a substantially gas-tight 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 supportin material which permits the use of the thin metal bridges obviously may be a comparatively poor heat conductor.

It is thus evident that a housing having walls formed in accordance with time invention ordinarily will be characterized by par allel metal sheets which normally may be at quite difi'erent 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 furtheradaptation of my invention,

I preferably provide similar bridges or conable SlZe 1n commercial quantities, especito provide abs'IO- 1,756,802, when this 'with sures,the

formed of metal sheets with soldered and/or welded joints or seams. It is feasible however to provide vacuum insulating chambers of this character which under orary conditions of use have only a low rate of gas leakage. I therefore propose to provide Pumping means to maintain a comparative yehlgh vacuum within the insulating cham r. Pumpi .means of this character may bearran to'be more or less continuously operab e, for example being associated or combined with the means for maintaining a low temperature within a refrigerator. .Thus, when utilized for a refri erator provided with mechanically operaile cooling means, the pumping means may be arranged to receive-its ener from the same source as that which provides refrigeration. Furthermore, when used in con unction with refrigerating apparatus characterized by comparatively low prespumping means may conveniently be multi-stage, the first stage of the same being arranged to exhaust from the vacuum chambered wall and to raise the pressure of the same to the the refrigerating apparatus stage being associated with that a paratus and adapted to recelve stage and to emit the same to, the atmosphere or any point of exhaustion. Thus, for exm its preferred embodiment the umping means may be associated with regerat apparatus of the character disclosed n e copending application ofEast- Kan A. Weaver, Serial No. 733,699, filed ugust 1,761,551 and the oogndinfi-application of Lyman F. Whitney, rial 0. 159,342, filed January 6, 1927, now issued as Patent No.

allfi when these vacuuin containers are par tia y and the second or inherent in apparatus is provided means for exhausting non-condensable gases ,suchasd1sclosedmm co ding ed i s 14,

tion Serial No.-198,71.5, is thus associated with refrige rat" apparatus of the-mechanlcal type, 1t 18 evident thata portion of the energy imparted to the refrigerating appae ratus 18 utilized to enhance the insulating 3]1811'2188 of the walls of the re ra amber, so that the total amount 0 energy manned to maintain a given temperature d 1 erence between the inside and the out fildceed of that chamber may be greatly rev v In accordance with a further aspect of this invention, the pumping means which is adapted to maintain the vacuum in the insulatlng wall may be arranged to be-automatically operable in response to a temperature difference existing at opposite sides of the insulating wall. Pum

When the invention premure within .terial to 23, 1924, now issued as Patent No;

' frigeratorprovl ping means of this,

cha'acter h re erred aspect ave ides of the insulating ing automatically operable whenever a temperature difference exists at opposite sides of the wall-.. For this urpose, for example pumping means may utilized which is o the same general type conveniently combined with the mechanical refrigerating apparatus, or the temperature difference existing at opposite sides of the insulating wall may be utilized in various. other ways to maintain a and thus greatly enhance example, thermal transpiration may be utilized for this purpose.

A specific pumping means provided by the present invention comprises a fluid circuit arranged so that a circulating fluid p from a region of high pressure to a region of low pressure, during this movement entraining a second the circuit for which is arranged to entrain from the insulating wall and to exhaust same to the low pressure refrigerating apparatus, to the atmosphere, or at any other suitable on. a,

en an'ins wall is filled with materials having minute interconnected voids, it may prove somewhat difiicult to cause a continuous gas flow from all portions of the chamber thus filled to a single 1 outlet. Therefore, in its preferred ement my invention provides the vacuum chamber with suitable air or gas assages arranged in conjunction with the permit the circulation or movement of gas from widely spaced re 'ons within the insulating wall to the sing 0 gas outlet. Thus, for example, I may preferably provide air pways which are substantial- 1 ve with a face of the wall itself. novel insulat' wall is disclosed and claimed in my co iinglapplication Serial No. 437,377 whim a 'v1s1on of this application.

In the accompanying drawings:

may be associated with, and in its Fig. 1 illustrates a vacuum walled re-' pumping means associated with a low pressure refri rating ap tus which in turn is prefera ly prov1 ed means for exhausting non-condensable to the atmosphere;

F sho a somewhat similar form of automat i fiy operable umping means arranged in combination wi a refrigerator adapted to utilize ice as the coo means, the pumping means illustrated in arto operate in response to tem tune difl'erences at op te sides of the 3am wall, to receive gases from the same and to exhaust them into the here;

Fig. 3 isa front view of a H g;

vacuum in the wall its efliciency. For

is a more'or less diagrammatic view i refrigerator rtions at op 'te her or wailf lie.

asthatwhichmaybe fluid, a portion of or particles.

' 1, the pumping means 8 is arrangedgto-em1t providing a comparatively high vacuum.

.. which maintains the cooler at a suitable low;

disclosed herein may conveniently utilize a comparatively heavy propellant having a high boiling oint, such as mercury or the like, and a refrigerant such as water or the like. A system ofthis character comprises a boiler 41 provided with a heating factor 42, such as an electrical resistance element. Mercury is vaporized in the boiler 41, rises in pipe 43, and flows outwardly through the aspirator jet 44, where there is a large in- Fig. 4 is a cross-sectional view through a rear corner of the same;

Fig. 5 is a similar view showing the construction, of the front corner adjoining the door hinges; V

Fig. 6,is an elevational detail of the nonconductive frame within the casing;

Fig. 7 is an elevational detail of the screen and fabric arrangement provided to maintain air-passages within the casing;

Fig. 8 is a perspective view of an optional bridge arrangement;

Fig. 9 is a section through a door embodying the same;

Fig. 10 is a section 6; and a Fig. 11 is a sectional detail of a factor for stabilizing vapor fiow.

Referring first to Fig. 1 of the accompanying-drawings, it may be seen that the refrigerator housing 1 is provided with inner and outer shells.2 and 3 which afiord a suitable space therebetween which may be exhausted of air, gases, and vapors, thus refrigerant is contained in 'the cooler 5, and refrigerant vapor is drawn from the surface of this liquid through the duct 20, being entrained in the mercury stream which gives up its kinetic energy in the pumping of the refrigerant vapor.

' The mixture of vapors passes into the inclined funnel 46 where the kinetic energy of the propellant is absorbed in compressing the vapor mixture. Funnel 46 is provided with cooling means 21 in order to cause conon line 1010 of Fig.

cury at a comparatively high temperature and the drainage of the same toward the lower end of the'funnel. It is evident'that the temperature of funnel 46 is normally below the condensation point of the mercury and above the condensation point of the refrigerant at the pressure conditions prevailing after compression within the'system, so that the refrigerant vapor flows upwardly through passage 22 to refrigerant condenser 47 where condensation of the refrigerant occurs.

The condenser 47 comprises a pipe having a general downward inclination, being ar ranged to drain condensed refrigerant to the separating chamber 23, into the mid-portion This space is preferably filled with closely spaced, finely divided or foraminous material which is a poor transmitter of heat, such as silocel powder, closely spaced sheets of paper, attenuated-fibrous material or the like, as well as silocel brick, 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 Suitable gas-collecting passageways may be arranged within the vacuum chamber in amanner which will be described below, these passageways being connected to the air exhaust pipe 7. The latter is adapted to direct gases from the refrigerator wall to the first stage pumping means -9 which is operable concomitantly with the refrigerating apparatus. the embodiment of the invention shown -in Fig.

frigerant flows to the bottom of chamber 23 and passes downwardly through pipe 48 to cooler 5, this pipe being provided with a suitable liquid trap 24 in order to permit different pressures in the cooler and the condenser. A drain 27 which comprises a liquid adapted to permit the flow of any heavier propellant which may have been'carried into the cooler 5 back to the duct 11 of the propellant circuit.

In apparatus of this character which nor- -mally is operated at a low pressure so that .the maximum pressure existing within the system may be of the order of atmospheric, and so that the lowest pressures within the the non-condensable gases into a portion of. the low pressure refrigerating, apparatus temperature. a; For purposes .of convenience in under standing a specific application of tliegiiive 7 tion, I will first describe a low-.pressuevre frigerating apparatus which has beenxin raction of the maximum pressure, it is de- Practical operation for t d ra le periodilrsirable to provide means to exhaust nonand which is described and 'gclfllilfleds "iiecondensable gases from the system and to the copending applications of EastmanaA mperihitcontinued maintenance of a low pres- Weaver and Lyman F. W hitneys, idlentified zsu-rei therein, since gas is likely to find its above. :5." "-wayislowly into the system from or through Refrigerating apparatus of'the haract'ermthe-metal' walls or the .joints of the same,

crease in velocity and decrease in the pressure of the mercury vapor stream. Liquid densation of the major portion of the mer-' of which the passage 22 vents. Liquid retrap 28 is connected to the trap 24, being i system are of the order of a fairly small avemel31intowhiht 'posedpi and thus cause the pressure within the system unduly to rise.

In to permit exhaustion of .nongases from the apparatus, a pipe 16 is to the upper end of the condownwardly to join par-- demer and extends tion of duct 19. This duct is arranged to drain propellant from the lower-end of the funnel 46 and from the lower end of the upstanding' 22 and com rises a U- shaped liquid trap 29, a continuation of which forms an upward bend 10' of inverted The other leg of tube 11 comprises an up. e

standing pi which forms an outlet for t propellant 0m 31 and holds a column 32 of pro t. The upper end of this leg of tube 11 terminates at ins connection with a downwardly inclined ipe 12 which joins a substantially vertical dis- 13, which is ada ted to ho d another co umn of the propel ant, designated by numeral 34 proportioned to balance the vapor presure in boiler 41, the juncture of P p 12 and issuin designated by the nu-' meral 14. The lower portion of pi 13 forms a liquid trap through whic the firt'opellant may return to the boiler, the outof the trap below the liquid level in the same, 'pe 13 is continued upwardly beyond point 14 to provide a bypa n 35 connect] with the drain 19 at point 6, which is ocated near the juncture of pipe 22 with the funnel outlet and at a tion designed to be always above the gziiid level in trap 29 during normal opera- In the operation of this system, propellantvliquid is vaporized in boiler 41 and'rises through upstanding pipe 43 to the as irator Jet 44 through which it passes, therea r entraining re rigerant vapor at reduced pressure coming from the cooler 5 through duct The vapor mixture-passes into the funnel 46 where condensation of practically all of the propellant may occur, while the refrigerant, which is now compressed and has Q ahigher temperature of condensation than rly, passes upwardly through pipe 22 and chamber 23 to the refrigerant condenser 47 where it condenses.' The liquid refrigerant flows down to the bottom of chamber 23 andthmughpipe48andtrap24tocooler'5,

the upper a i height of response to variations in thebarometric pres-- asses-:7

to the end of the system.

When liquid propellant piles up in the leg of tra 29 adjoin point I) to a suflicient heig t, it causes t e pro llant in the other leg of the trap to 0w inwardly through capillary section 10 past the a where pipe 16 joins tube 10. Since tu 10 is capillary, gases and vapor from pipe 16 will be entrained by the liquid as it flows by the point a towards the vessel 31, the liquid in trap 29 preventin flow of the fluid in the opposite direction. gas and vapor will tend to be compressed as it downwardly-to open vessel 31. The hter fluid then rises to the top of the liqui in vessel given up to the atmosphere. The the liquid in'vessel :31 varies in -sdre, it being obvious that the head due to the weight of the liquid in this leg of tube ".11, plus the atmospheric resure, will balance the pressure of liqui column 82 in the other le of tube 11 plus -thef pressure thereabove. [his height is determined by the position of point 15 which defines the u per end of the liquid cblumn, and will flow from the top of the column the drain 12 to the pipe 13 where it forms the liquid column 34 to balance the premure in boiler 41.

int

It is obvious that. instead of the vemel11 venting to the atmosphere as shown in the drawi it could vent into a closed v the o y condition being that said vemei must be large enough so that it will not 'becomefull of gas unduly soon or some meansmust be provided for the removal of the gas either continuously or intermittently.

It will be noted that point a is somewhat higher than point 15 and that the li uid head due to the weight ofv the pro ent column in'the capillary tube plus that in the adjoining portion of vessel 31 below the outlet of the tube must substantiall' balance the head due to the weight of the li uid column 32, the diflerence'in height of t can columns is eflective in determining the amount of fluid that is entrained in the propellant as it passes point a. The various parts of the system are so arranged that a proper amount'of fluid will be entrained at point a in order to exhaust the maximum quantity of 'non-condensable gas that may ordinarily appear in the system. However, even when no non-condensing w: appear in the system, the amount 0! refrigerant vapor ex 'austed willbe so small as to have a substantially negligible effect on the quantity of refrigerant liquid in the system even over long periods oftime. In practice, the point a is preferably arranged near a hot part of the system, such as riser 43, so that the refrigerant in pipe 16 will remain Vaporized and so that liquid refrigerant will not be pumped to vessel 31.

My 1 improved vacuum pumping means may conveniently be combined with refrigerating apparatus of the character described above, which has been in practical use for a considerable length of time. In accordance with the. present invention the vacuum pumping means 8 may be arranged to receive a portion of the compressed refrigerant vapor passing upwardly from the compression duct 46 to the condenser 47. For this purpose a pipe 9' is connected to the pipe 22 having a downward continuation 50 to which is connected an upwardly turned pipe '51. A suitable drain 52 is connected to the pipes 50 and 51 and is adapted to receive any stray mercury particles that may pass into this portion of the piping and return the same to the propellent column 32. Pipe 51 e}:- tends upwardly to a pressure stabilizing factor 53. The latter may be provided with a plurality of restricted passages or openings which tend to stabilize .the pressure conditions .of the vapor sweeping through the same; accordingly sudden irregularities or surges in the flow of fluid are substantially eliminated.- Fig. 11 illustrates more in detail one specific arrangement of this factor which, for example, may be a porous plug or which, as shown, may comprise a series of parallel disks 390 spaced by suitable rings or the like 394 and provided with compartively smallopenings 391 out of alignment with each other. Preferably the disks may 'be spaced from each other at distances substantially of the order of the diameter of the openings 391. It is accordingly evident that vapor passing through the factor 53 flows through a plurality of restricted and tortuous passages and accordingly sudden changes in the volume and/ or pressure of the flowing vapor stream are opposed. Preferably the factor 53 and the adjoining pip ing are arranged close to a hot portion of the system, such as the hot riser 43- As a result of this arrangement'condensation of the vapor passing to or through the stabilizing factor is prevented, and accordingly the pocketing of condensed fluid below the same is avoided. v

A pipe 58 connected to the upper end of factor 53 is continued in a downwardlv extending pipe portion 54, the lower end of which may be inclined diagonally to provide one leg of a mercury trap 57,. Extending upwardly from the UYYBI portion of this leg of the trap is a tube 59 of capillary size, i. e., of such a diameter that mercury globules m pressure in lifting mercury flowin through the tube may contact upon all si es with the internal surface of the same to form liquid pistons. At the top of tube 59 is a separating chamber 60 from which a pipe 61 extends upwardly to the vapor duct 20 of the refrigerating apparatus. The chamber 60 is partially filled with merinto the leg of mercury trap 57 which is opposite tube 59.

in the operation of pumping means 8 in conjunction with the refrigerating system, compressed refrigerant vapor such as water vapor is received in the pipe 9 and passes through the stabilizing factor 53 to the pipe 5412. Tube 59 joins the diagonal continuation of this pipe substantially at the top' of the mercury contained in that leg of the trap 57 so that the vapor pressure .in pipe 54 may cury andis at the top of one leg of a merdepress the mercury and intermittently push globules of the same upwardly into pipe 59. The vapor still under pressure bubbles upwardly. through the -mercury contained in chamber 60, being released to the low pressureexisting in pipes 61 and 20. Thus the vapor passing into the pipe 9 gives'up its globules from trap 57 to chamber 60 and is received at low pressure in pipe 20 where it rejoins the main refrigerant circuit. Due to the induced circulation of mercury globules through pipe 59, the mercury level in chamber 60 tends to be raised and mercury flows downwardly through trap 62 and upwardly past the juncture with pipe 7,

The mercury thus being lifted to the mouth of pipe 7 tends to form intermittent globules which pass over into the upper end tube 65, trapping bodies of of the smuous gas and vapor therebetween. It is evident 62 prevents refrigerant vapor from passing from chamber 60 to pipe 7 The sinuous arrangement of tube 65 and its average moderate downward inclination that the trap permits the passage of successive mercury I globules which are spaced at a considerable distance from each other, and accordingly a comparatively large volume of gas may be entrained between being desirable due to the extremely low pressure prevailing in'pipe 7 and accord ingly'the degree of compression which desirably occurs in pipe 65. As the mercury globules pass down through thelatter the successive globules, this.

- sure duct 20.

- able volume,

' system 8 into the duct 20 of the re .atedin pumping means 8 won oin the body of mercury which is contained .in chamber 66 which is located above the u per end of the corres nd' 1 of tra 5?, while the trapped vaigbrs ii d ases flo upwardly throu pipe 68 to the ow prese increase in the weight of the mercury in chamber 66 causes the liquid in the corresponding leg of trap 57 to move downwardly and the mercury to flow upwardly in the o posite leg of the trap, thus replenishin the supply of mercury at the lower end -0 pipe 59.

It is evident that the pressure head, due to the weight of mercury an the leg of trap 57 w ich adjoins the chamber 66 as well as in that chamber and the va r pressure thereabove substantially equa s mercury in the opposite leg of the trap, and the pressure of t e globules in pipe 59 plus the fpressure thereabove. Since the mercury sur ace in chamber 60 is above that in chamber. 66, the difierence in mercury levelsis effective in determining the volume of water vapor which passes upwardly through pipe 59 and causes the movement-of mercury in the mercury circuit.

Obviously above practically equalize each other. Since the pressure in va r duct 20 may, for exam- Dle, be of the ortlgi' of three or four millimeters of mercury, while the pressure within pipe 7 may bea fairly small fraction of one millimeter of mercury the liquid level in the le of tra 62 adjoining the pi 7 Wlll bes ightly igher than the leve in chamber 60. Since tlie'latter has considerslight variations in pressure at either side of the trap tend to be equalized glllld do not seriouslv affect the operation of Obviously fluid vented from the pumping fngerati System, after assing throughthe aspirator unnel46, wi gather at the top of the refrigerant condenser where it will join the non condensable gases to be exhausted through duct 10 and vessel 31. The tra 24 an the chamber 66 may be connected by a pipe 307 so that the mercurylevels in the same may remain substantially equalized; thus accidental straying of mercury particles from the refrigeratin not, even during a very long time, unduly increase the amount of mercury contained in the latter. In the accompanying drawings the size of the pumping ngans 8is considerably exaggerordeirto permit a clear showing of the same. 'The mercury levels in chambers 60 and at the juncture of pipes 7 and will normally diifer by only a few millimeters,

,generally the head of the th the weight of the liquid 001- d fumns m trap 62 plus the pressures there- 8 straight down ,to

trap 157 which is apparatus to the aaeaon this distance being determined by the difierence of pressures, within duct 20 and pipe 7. Inpractice, the quite compact an only needs to have a comparativel small pumping capacity to maintain the esired vacuum.

2 illustrates pumping means of the general character disclosed in Fig.1 as applied to a refrigerator utilizing a cake of ice,

which is designated bynumeral 80, as the cooling medium. The refrigerator housing itself may be of the same general character as described above. An arrangement of this character is more'particularly claimed in my copending application Serial N 0. 602,008, filed Marclf 30, 1932.

e pumpin means disclosed in Fi 2 is sun or to that shown in 1 1, the pipe 107 of F e gas passages wit in the vacuum chamber of the refrigerator housing. In this form of the invention a condenser 150 is located withinthe refrigerator adj oinin the cooling medium 80, the upper end of thisc enser being connected y the duct 15.. itthe separating chamber 160. The lowerportion :of the condenser is connected to a vaporizer 154 that in turn joins the lower end of a capilla tube 81. This tube is continued ownwar in an extension' 82, which may be non-capillary, if desired, while its upper end terminates in a separating chamber 160. The lower rtion of pipe 82 is continued in a U-shape extension or trap 157. To the opposite leg of this trap 18 connected a branch 168 which is protected by a cover 140, theliquid within the-pipe 168 being exposed to theatmosphere.

A trap 162 is located between the bottom of separating chamber 160 and a chamber 138 at the juncture of the pipe 107 and the sinuous or coiled pi 165 0 small diameter, i. e., of substantia y ca illary dimensions. The'latter is continued ownwardly first in a generally sinuous or helical form and then join the vertical leg of joinedby the pipe 168. In this embodiment of the invention, vapor is liquefied in condenser coil 150 due to the low temperature existing within the re- P frigerator. The liquid'thence asses downwardly tothe va r 154, w ere the temperature of the hquid is raised substantially to the tem ratui-e without the refrigerator. vaporization tends tocause the same to rise upwardly through tube 81, where globules ofmercury are entrained between bodies of vapor, the vapor passing through the mercury in chamher 160 and continuing upwardly in pipe 159 tothe condenser where thecircu t is com leted.' a Y e mercury overflows into trap 162, thence passes upwardly intov chamber 138 where entrainment of non-condensable g'ases (pumping means 8 may be 2 being connects to of the liquid at this pointfrom pipe 107 occurs. The pipe portion 165 successive mercury globules become greatly compressed, in fact, tending to consolidate with one another. Thus the gas, when it reaches the pipe 168, is compressed to a pressure slightly above atmospheric and rises in pipe 168, being exhausted through the open end of the same to the atmosphere.

It is evident that the pressure conditions within the closed system comprising the pumping means of Fig. 2 are so determined in relation to the vapor pressure of theliqaid in vaporizer 154, that the liquid will boil at ordinary room temperatures and will condense at temperatures ordinarily prevailing in a refrigerator. In this embodiment of the invention the distance from the junction of pipe 168 and the main mercury pipe to the other portions of the apparatus is sufficient to permit tbe'liquid columns to balance atmospheric pressure. It is thus evident that in general the pumping apparatus shown .in Fig. 2 resembles that disclosed in Fig. 1, but that the greater height of mercury columns permits the direct exhaustion to the atmosphere. It is further evident that apparatus of the type disclosed in Fig. 2 is particularly advantageous when a refrigerator using ice as a coolingvmedium is provided with vacuum insulated walls and further that apparatus of-this type may be provided in a mechanically cooled refrigerator, particularly when the cooling apparatus is not of the low pressure type, although either specifically or broadly the arrangement shown in Fig. 1 may be advantageous, especially when the refrigerating system is operating at a comparatively low pressure and when the source of energy forthe refrigerating apparatus is also conveniently usable for the pumping means to exhaust the refrigerator housing. 7

, Ubviously the pumping means disclosed in Fig. 2 may be utilized wherever a' temtion to pressure conditions within the sys.

. said regions.

perature difference exists between regions at opposite sides of a vacuum wall, the vapor pressure of the alternately vaporized and condensed liquid being determined in relatem and the temperature ranges of the afore- .Figs. 3, 4, 5, 6, 7 and 8 illustrate various structural details of one form of refrigerator housing provided with walls which include vacuum chambers. Fig. 3 shows a front view of a housing 1 of this character whichmay comprise inner and outer shells 2 and 3 which are nested in spaced relation .sion .of, meshed to each other to provide a vacuum space therebetween, the box thus formed being provided witha suitable door or swinging closure 170 which also contains a vacuum chamber, this chamber beingconnected by a suitable duct with a chamber in the housing proper.' The inner sheet metal casing 2 may carry a plurality of spacing elements or columns 171 ofhard, non-conducting material, such as bakelite, asbestos wood, hard rubber, wood, or other material, which preferably is rendered impervious .to moisture. Spacers'l7l may be held to the inner shell 2 by means-of metal clips 172 which are soldered,

175. This screening preferably may be substantially coextensive with the outer face of the shell wall, and similarscreening, similarly designated, may be arranged within the door 170. A suitable fabric 207, such for example as felt, may be arranged against the wire screen being suiiiciently 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 silocel, 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 171 engage the sheet 207, aiding in holding the same in place. The filling material-packed between thefabric and the inner shell and about each of the spacers also aids in supporting the walls against the external atmospheric pressure, and with, properly, rein-- forced walls the internal reinforcements or spacers 171 may be omitted and dependence placed upon the filling. material alone for this purpose, if desired. Y a

If, porous solid material such as siloc'el blocks is used for a filler, the internal reinforcements can ordinarily be omitted and the filler material itself be depended upon to- 1'74, this fabric preferably lad 8 macaw? support the outer walls against the external 191 and the corner trim 192 and the edge pressure; h 8111i vSpecial means are provided between the e door preferably is formed of mner edges of ,the inner and outer shell to prevent and outer metal sheets 200 and 201, the

6 heat conduction therebetween, thus materialscreen 174 ad'oining the in- 70 85 ridge elements preferably may enlarged 'ly raising the heat insulating eficiency of the ner face of the r. Sur la spacer: 171 hous' For this u 'pose, I p efer may be arranged between the mner and outrange e'edges of e mner and outer ells er sheets after the manner decnbed above in Spaced P81111181 mlfltionlnd provide with reference to the main vacuum chamber.

10 pecially. constructed non-cohductlve bridges The bridge elements 185, which are artherebetween. In the specific arrangement ran thi th d i correspond to illhstl'amd herewith, p h 8 of the s i inilar stripe similarly designated and he inner ing 2 may be turned outwardly L described above, and similarly may be amoto provide a perimetric flange 183 wh1le the ag dith m metdlkg fille 221 int! thin 16 edge of the outer casi is mturned to rot l Y l n 220. The inner metal so vide a flange 184. The orm of non-con uct- -ti f m g -id hi ithi the door ing bridge which is illustrated therewith may may b w ld d t h main h f flu i comprise strips 185 of heat ihglllhting ner sheet 200, while the outer metal element rial such, e a p as hhkellhe, asbestos may be secured to the rectangular frame 197,

20 wood, hard rubber, or various other, synfl f b in seem d by soldering, weldthetic compositions, or natural wood impregfl m d i by m eral 198 nated with suitable moisture-resistant mate t th h t 9%1, Th doo may be rialysuch forexample as high boiling p rovidmth suitable covering means and )araflin. The inner and outer ed of these a i my d i d manner, a l

%:bridge members may convenientlybe and ma receive sheet metal channels 186, the assembled t compose 011ml 8 0f the of which firmly before they are disposed between the innerflanged about the 8 "8 P011501?! the and outer shells or betwetm the face sheets non-metallic l m t as dwsnmd h of the door. .FOI' this purpose the strips humeml A suitable strip ml 185 and the channels 186 are provided with be a a between the mmrned m mitered joints, Fi o, and slots 20s are cut P01110118 187 toprovlhe f' wbmntl in the mitered en of the non-metallic the ahghed Wlth the h g n ments 185, these slots preferably cxten metal sting 186. A thin metal plate 220 the f ll depth f the elements,

86 may then securedby soldering or the like in Fi A comparatively 53' mm. to these ali edsurfaoes of the strips 186, has material, which my i this metal p ate bemg supported b; the tiller at d by e high melting point M or e 'P "g the1ike,maybefoldedtoprovi anangle gas-fight seal: tween h two 1 element 407 which is engaged in the slots The sealing strip refemhly is .omed at eends of strips 186 resphan or fishof metal having high eat resistivity such, pa or similar i for example, constantan, nichrome, or the h since in m 53 like, and preferably is of thin gage n order and sturdy and yet fi i t' d bil; to provide low heat conductivity. The noni unit is introduction into the 46 ellliegttllic elemenfttfih sup rtsnstheopposite en the bridge rtions o m we agalnst exmumer ternalg rgssure so that the; metal s-embled m an! the ad strip oes not need to ve great strucsecured 'ehh tural staging-(2h and accordingly may be made to each other by sold or 0 V a 4 I o one ofthe strips 186 v11 11 reach offlw eeriee m 7t$$bZ fiad i 31$? bridges haunted by so dering or weldw each to pmvidh mg to the fl whlle the 9P stantially' continuous metallic seal. It is tportion 1 is secured to a as 1;;- f 189 of sheet fi y evid nt that the ctangula bridge frame m flan 184 and frame l89 -lie in the-same* in the f to m V plflll and are spaced from each other. A 9 for the but ant g 7 'suitable cover frame which also igeferm 9! "bout ably is rectangular, than he gi frame 1n the former eaaerather than his 111 11g, designated by numeral 6.

60 or welded upon the outer faces of frame theemme shown in v 15' fee andflan 1 thereb chain the see e similar between d 3? rimy those utilised between mner and conventional outer sheathing or covering sh lls of the housing may also be I as metznssxlzliay beolirovided as, for example, the adjoining each of the openings for the ppm ou r eets veneer or decorative metal which are adapted to permit typical pipe circulate from the refrigerating apparatus at this point, suitable metal channels hav-' ing 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 186 may be soldered or welded to the face of sheet 3 adjoining the pipe opening therein, while the corresponding opening in the inner sheet may be somewhat larger so that the edge thereof registers with the face of the adj oining metal channel 186, thus permitting these parts to be joined by soldering or welding after the inner and outer housings are assembled.

Similarlyin this case 'a non-metallic filler element 221 may be arranged between the inturned portions of. the channels 186 inside of the annular bridge member, and a metallic sealing strip 220 may be soldered or otherwise secured to the aligned surfaces of the channels 186*, this strip being supporte by the filler 221".

A suitable ring of heat insulating material 211 is arranged within the annular member and is adapted to hold the pipe 110 in spaced relation thereto and spaced from the inner and outer walls of the vacuum chamber. If desired, this portion of the a single metal tube with an undulatory wallpipe may be made of material having low. heat conductivity, such as German silver or nichrome and/or may have thin walls.

In order to permit the flow of gas from the air passages provided by the meshed p screen in the door to the corresponding passages within the chamber, I provide a suitable flexible. duct 217 which is connected to the interior of the door and the interior of the chamber. This duct may be formed of of the type commonly utilized for metal bellows or the like, the ends ofthis tube being welded, brazed, soldered-or otherwise. secured to the outer walls 3 and 201 of the housing "and door respectively and the ends of this tube being arranged in somewhat spaced relation from the edges so that each local portion of the same is only moderately flexed when the door is opened.

Figs. 8 and 9 illustrate a modified form of bridge construction. As in thecase of the construction shown in Fi 5 these connecting bridges may be utilized both be tween the inner and outer shells of the casing and the inner and outer walls of the closure, Figs, 8 and 9 illustrating the latter specifically.

In order to minimize heat conduction between .the inner sheets 300 and the outer sheets 301, 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 iscutilized for this urpose I preferably provide a bridge s eet 302 which may be of a gauge conslderably thinner than that of the outer and inner sheets 300 and 301. This sheet preferably has portions welded or otherwise secured to the edges of the sheets 300 and 301 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 301. For this purpose I may arrange a plurality of filler. elements .3 0 t in channels formed in the sheet, the adjoining channels facing in opposite directions and being reinforced b that fit tightly wit ments may be of any sultable material having low heat conductivity, and may conveniently be formed of materlal adapted to withstand considerable heat so that they (1 may be heated when the chamber is initially evacuated. Asbestos wood is therefore suitable for this purpose.

Suitable non-conductive finishing material may be arranged about the bridge strip 302, as shown in Fig. 9.

Fig. 8 illustrates a typical corner construction in a door having a metallic bridge of the type shown in Fig. 9, it being understood that the channels may be built up and welded together at the corners 1n order to make the same substantially continuous about the rimeter of the .bridge frame. It is evident that the construction shown in Flgs. 8 and 9 permits the provis'on of a metallic bridge between an inner and outer wall of the vacuumcasingwhich may remaln at different temperatures. The heat res1st1v1ty 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 contam one or more vacuum chambers that preferably are filled with closely spaced, or foraminousnon-heat transmitting material and WhlCh are e hausted to a fairly high vacuum; that-this invention isparticularly intendedto prothe filler elements 304 'n the same. These elevide a commercially feasible type of wall that is 'not absolutely free from atmospheric leakage but which is adapted to receive a small amount of gas either from the atmosphere or from the metal of the walls, the vacuum chamber being combined with pumping means continuously to maintain the vacuum within the chamber.

According to this invention pumping means of this character would be in substantially continuous operation when the vacuum wall is in use as an insulating factor. Thus this pumping means may be operated from the same source of energy as the refrigerating apparatus, so that the refrigerator wall is being evacuated while the refrigcrating apparatus is operating, or it may be arranged to be partially or wholly responsive to a difference in temperature between opposite sides of the insulating wall so that once such a temperature difference is established, it will be maintained for a long period of time. 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 ortions are very effective 1n enhancing the lnsulating efficiency of the vacuum wall, since otherwise a comparatively large flow of heat would occur if the conventional metal sheets of the inner and outer walls were directly joined to each other.

hen insulating means of this character is utilized in conjunction with refrigerating apparatus characterized by comparatively low pressures and adapted to receive noncondensable gases and to exhaust the same to the atmosphere or to make use of them in any other suitable way, the first stage pumping means may'serve merely to raise the pressure of the gas drawn from the vacupm chamber to the minimum pressure existing within the refrigerating apparatus. On the other hand, pumping means of the same general type may be arranged as shown in Fig. 2 to raise the pressure of the gas directly to atmospheric pressure and to exhaust the same directly to the air.

From the foregoing it will be evident that an lmportant feature of the invention consets 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 minimlzed 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. 8 and 9.

- While I have disclosed this invention particularly as a plied to a refrigerator housing and specifically as combined with refrigerating apparatus, it is evidentthat 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 withheaters, ovens or boilers, while the walls of houses may simiilarly be provided with hollow evacuated panels that are provided with means arranged as disclosed and. herein. 7

I claim: a

1. In combination a refrigerator, an insulating housing associated therewith, the walls of said housing including a vacuum chamber, a cooler within the housing, pumping means to circulate refrigerant through a cycle to maintain the cooler at low temperature, a refrigerant duct connecting the cooler with the pumping means, said duct normally containing rarefied refrigerant, and a connection between the vacuum chamber and duct whereby the pressure within the former may be maintained at least substantially as low as that in the duct.

2. In combination a refrigerator, an insulating housing associated therewith, the walls of said housing including a vacuum chamber, a cooler within the housing, pumping means to circulate refrigerant through a cycle to maintain the cooler at low temperature, and pumping means to maintain a comparatively high vacuum in the chamber of the insulating wall, said last-named pumping means bein multi-stage, one of the stages thereof being associated with said refrigerant pumping means.

In combination a refrigerator, an insulating housing associated therewith, the walls of said housin including a vacuum chamber, a cooler wit in the housing, pumping means to circulate refrigerant through a cycle to maintain'the, cooler at low temperature, a refrigerant duct connecting the cooler with th normally contaming rarefied refrigerant, and pumpin means to maintain a vacuum in the cham r of the insulating wall, said last-named pumping means bein adapted to emit gas into the refrigerant uct.

4. In combination a refrigerator, an insulating housing associated therewith, the walls of said housing including a vacuum chamber, a cooler within the housin pumping means to circulate refrigerant through a umpin escrlbe e pumping means, said duct cycle to maintain the cooler at low temperature, a refrigerant duct connecting the cooler with the pumping means, said duct normally containing a rarefied refrigerant, and pumping means to maintain a vacuum in the, chamber of the insulating wall, said last-' na'med pumping means being adapted to emit gas into the refrigerant duct, and means to eliminate non-condensing gases from the refrigerant circuit.

5. The method of maintaining a vacuum in a chamber of an insulating wall and of compensating for leaks in the same, which comprises establishing a temperature differential at" opposite sides ofthe wall, circulating fluid from one side of the wall to the other, the pressure in the fluid circuit permitting vaporization of the fluid at one side of the walland condensation at the other, pumping a second fluid through a second circuit having a portion, in common with the first circuit by means of entrainment in the common part of the circuits, and entraining'gas from the chamber in a portion of the second circuit between bodies of the fluid circulating therein, there compressing said as and exhausting the gas from said circuit. 6. The method of maintaining a temperature diflerence at opposite sides of an insulating wall which comprises creating a temperature difference with a source of energy,

pressure portions with fluid flowing between saidportions during operation of the apparatus, the circulation of liquid in said pumping means occurring in response to the differences of pressure in said apparatus.

10. In combination, refrigerating apparatus including a cooler, an insulating wall impeding undesirable heat flow to the cooler, said wall providing a vacuum chamber, and multi-st-age pumping means to remove noncondensable gases from the chamber, said pumping means including a liquid circuit for the first stage pumping means, a capillary tube in said circuit, wherein circulating liquid entrains gases from the chamber, and a common source of energy forsaid refrigerating apparatus and at least two stages of the pumping means including said first stage pumping means.

11. In combination, a refrigerating apparatus including a cooler, an insulating wall impeding undesirable heat flow to the cooler, said Wall providing a vacuum chamber, and multi-stage pumping means to remove noncondensable gases from the chamber, said pumping means including a liquid circuit for the first stage pumping means, a capillary 'tube in said circuit,wherein the circuqlating liquid entrains gases from the chamcirculating fluid in response to the tempera ture difference at opposite sides of the wall to pump gases from the wall and maintain a vacuum in the Wall, whereby-heat leakage through the wall is reduced and the total effect of the energy supply in providing a temperature difference is enhanced.

7-.The method: herein described which comprises maintaining a' difference in temperature between two'regions separated by a vacuum and maintaining the vacuum by the energy of the difference in temperature between theregions.

8. In combination, refrigerating apparatus including a cooler, an insulating wall impeding undesirable heat flow to the cooler, said wall providing a vacuum chamber, and pumping means to remove non-condensable gases from the chamber, said pumping means including a liquid circuit, a capillary tube in said circuit, wherein circulating liquid entrains gases from the chamber, and a common source of energy for said refrigeratmg apparatus and pumping means.

9. In combination, refrigerating appara tus including a' cooler, an insulating wall impeding undesirable heat flow to the cooler,

said wall providing a vacuum chamber, and pumping means to remove'non-condensable gases from the -chamber, said pumping means mcluding a liquid circuit, a capillary tube 1n said circuit, wherein clrculating liquid entrains gases from the chamber, said rc-' frigeratmg apparatus having high and low multi-sta'ge pumping means to remove her, and a common source, of energy for said refrigerating apparatus. and at least two I stages of the pumping means, including said first stage pumping means, said refrigerating apparatus having high and low pressure portions and fluid flow between said portions during operation of the apparatus, the circulation of liquid in the first stage pumping means occurring in response to the differences of pressure in said apparatus.

12. In-combination, a refrigerating apparatus including a cooler, an insulating wall impeding undesirable heat flow to the cooler, said wall providing a vacuum chamber, and

noncondensable gases from the chamber, said pumping means including capillary tubes,

wherein the circulating liquid entrains gases from the chamber, said refrigerating apparatus having high and low pressure portions and fluid flow between said portions during operation of the apparatus, the circulation of liquid through said capillary tubes of said pumping means occurring in response to the differences of pressure in said apparatus.

13. In combination, refrigerating apparatus including a cooler, a heat insulating wall associated with: the cooler and including a vacuum chamber, pumping means for maintaining'a vacuum in the chamber, said means including a fluid circuitdiaving a portionwherein falling liquid globules entrain gases fromthe chamber, the apparatus. having high and low pressure portions between which fluid normally circulates, a

part of the liquid circuit receiving fluid flowing between the high and low pressure portions, the fluid being effective in this part in lifting slugs of the liquid to cause its circulation through the liquid circuit of the pumping means, whereby gases are automatically pumped from the vacuum chamber in response to normal operation of the refrigerating apparatus.

14. In combination, refrigerating apparatus including a cooler, a heat insulating wall associated with the cooler and including a vacuum chamber, pumping means for maintaining a vacuum in the chamber, said means including a fluid circuit having a portion wherein falling liquid globules entrain gases from the chamber, the apparatus having high and low pressure portions between which refrigerant vapor normally circulates, a part of the liquid circuit being connected to the apparatus and receiving the vapor flowing between the high and low portions, the vapor being effective in this part in lifting slugs of liquid to cause its circulation through the liquid circuit of the pumping means, whereby gases are automatically pumped from the vacuum chamber in response to normal operation of the refrigerating apparatus.

15. In combination, low pressure refrigeratingvapparatus including a cooler, an insulating wall including a vacuum chamber, means operable to maintain low pressure in pressure tending capillary tube wherein liquid globules entrain non-condensable gases, separating means at the lower end of the tube exhausting the gases to a region of higher pressure, pumping means connected to the chamber, said pumpingmeans comprising a fluid circuit, a duct between high and low pressure portions of the apparatus, said duct having a part in common with the fluid circuit wherein liquid globules are lifted by fluid flowing through the duct, thereby causing circulation of liquid through the circuit,

'the circuit also having a portion wherein falling liquid globules entrain and compress gases from the chamber, a connection directing the gases from said portion to the firstnamed tube, whereby both system and from the chamber may be ex; hausted.

I Si ned by me at 80 Federal Street, Boston, ass., this 1st da of Se tember, 1928.

, DANIEIZ F. C MSTOCK.

the apparatus comprising a downwardly extending capillary tube wherein liquid globules entrain non-condensable gases, separating means at the lower end of the tube exhausting the gases to a region of higher pressure, the capillary tube also receiving gases from the vacuum chamber, whereby low pressures are concomitantly maintained in the apparatusand the chamber.

6. n combination, low pressure refrigerating apparatus including a cooler, an insulating wall including a vacuum chamber,

means operable to maintain low pressure in the apparatus comprising a downwardly extending capillary tube wlierein liquid globules entrain non-condensable gases, separatmg means at the lower end of the tube exhausmg the gases to a region of higher pressure, pumping means connected to the cham ber, said pumping means comprising a portion wherein falling liquid globules entrain and compress gases from the chamber, and a connection directing the gases from said portion, to the first-named tube, whereby both gases from the are exhausted.

17. In combination, low pressure refrigcrating apparatus including a cooler, an insulating wall including a vacuum chamber means operable to maintain low pressure in the apparatus comprising a downwardly exsystem and from the chamber gases from the

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