US2108212A - Metal-walled vacuum chamber or container - Google Patents

Description

Feb-l5, 1938. E. L. scHELLi-:Ns

Y METAL WALLED VACUUM CHAMBER OR CONTAINER Filed Aug, l, 1954 {lly TOR

BY uw Sgm Kiwi-001 rCaM-ykl( Patented Feb. 15, 1938 UNITED STATES PATENT oFFicE METAL-WALLED VACUUM CHAIWBER OR CONTAINER Application August 1, 1934, Serial No. 737,863

'7 Claims.

This invention relates to metal-walled vacuum chambers or containers of the class wherein the walls constitute a chamber enclosing a space from which air and gases are to be or have been evacuated for heat-insulating purposes; and the improvement includes the construction of the chamber and as well its mode of production.

The invention is adapted to a wide range of practical utility; for example it may be employed in the construction of double walled or hollow panels, either fiat or of other shape, adapted to be embodied. as enclosing panels of refrigerators or various other products; or it may be employed in the construction of containers or vessels of l5 various kinds and shapes, such as vacuum bottles, boxes or jugs, cooking or cooling apparatuses, and the like.

Examples of metal walled vacuum chambers or containers of the class referred to are shown in my prior application Serial No. 626,384, filed July 30, 1932, Patent No. 2,024,065, issued December 10, 1935, disclosing features which may be usefully employed in connection with the present invention, and which patent may be referred to for various details thereof not herein fullyr disclosed, including a mode of surface sealing the metal Walls to render gas-tight the chamber or container. Said patent discloses evacuated chambers or spaces which are empty, but which might be occupied by various known filling materials of mineral or other matter in brous or other form.

In the art of vacuum heat-insulated containers or chambers it has long been known to construct the walls thereof of sheet metal rather than glass, but these were impractical, for one reason because of the metal walls having given off occluded gases in such quantity as materially to impair the insulating effect. In the expired Patent of' Stanley No. 1,071,817 of September 2, 1913 this diiculty was reduced by lling or partly filling the chamber or space, before evacuation, with a finely divided material, such as carbon, so treated by heating and reh-eating that it would not only not give olf gas but would absorb and hold gas given off by the metal Walls; and such filling material was very iinely powdered to minimize heat conduction. The powdered carbon however was found to absorb moisture to the impairment of the insulating property, and it was thereafter suggested to apply heat during evacuation so as simultaneously to drive off the moisture. The plan was thereafter tried of compressing the powdered carbon to pack it between the metal walls so that the material would be able to lend some mechanical support to maintain the spacing of the Walls; the container in that case having been a cylindrical bottle and the nlling and compressing having to be performed before the circular bottom wall was applied. However, the mechanical compressing of the finely powdered carbon was found to cake it and impair its insulating properties; and to minimize this it was later suggested to mix carbon in the form of soft wood charcoal powder with seven times its volume of diatomaceous earth, both in finely divided and heattreated condition. Prior to my said patent the art of metal-walled vacuum chambers has been unsatisfactory and not a complete practical success.

The objects of the present invention are the provision of a metal-walled vacuum chamber wherein the enclosed space is filled with a certain class of lling material aifording some or preferably al1 of the following functions. The material is a special and activated form of carbon as will be described, meaning that it has been treated to afford high capacity for absorbing and retaining gas molecules at ordinary temperatures. The lling material is what may be described as granular in structure, as distinguished from powdered; this minimizes heat conductivity by reason of the minuteness of the contacts between granules; and in the preferred form the granules may be perforated, or have passages giving it capillary character, further improving the gasabsorption properties. The filling material hereof by its distinctively granular character is adapted to give ready passage to flow through the body of material of air and gases outgoing from the chamber during the process of evacuation under heat. Such lling material by reason of its hard, dense granular character, is packed in place by working or shaking without the need of mechanically compressing it, and constitutes a highly efcient internal bracing means between the metal walls, holding them in their spaced ap-art relation against the external pressure and resisting deflection or collapse, whether the chamber be in the form of a iiat or curved panel or other chamber or container forms. The lling material is in such hard and smooth granular form as to be fluent and capable of being poured into the chamber through a small lling opening, after the chamber walls have been assembled and united, and without the need of forcible compressing operations to compactly fill the chamber. It is believed to be new to provide a chamber lled with a filling answering most or all of these advantages.

Further objects and advantages of the present invention will be pointed out in the hereinafter following description of illustrative embodiments thereof or will be apparent to those conversant with the subject. To the attainment of such objects and advantages the present invention consists in the novel metal-walled vacuum chamber or container and the novel features of combination and construction herein illustrated or described, and as well the novel method of manufacture thereof.

In the accompanying drawing Figure 1 is a transverse vertical section of a metal-walled vacuum chamber, in the form of a flat panel, embodying the present invention.

Fig. 2 is a bottom plan view of the panel of Fig. 1.

Fig. 3 is a transverse vertical section taken through the connection or fitting by which the interior space is filled and evacuated.

Fig. 4 is a side elevation of part of the panel of Figs. l to 3 shown mounted between exterior casing or frame parts.

Fig. 5 is a vertical section of a shaped panel or container comprising several unitary walls and adapted for such uses as the lining of a refrigerator.

Fig. 6 is a vertical central section of a vacuum container in the form of a jug or bottle of a design corresponding generally With that shown in my said prior application.

Fig. 7 is a horizontal section taken on the line I--T of Fig. 6.

Fig. 8 shows a body of granular activated carbon adapted for the purposes of this invention, and Fig. 9 shows enlarged a single granule of preferred form, with interior capillary passages or pipes.

Referring rst to Figs. 1 to 3 there is shown a complete metal-walled vacuum chamber in the form of a panel I4, constructed of a first wall I5, for example of sheet steel, having its margin I6 dished in corrugated manner, and with an outer flange I'l parallel to the body of the sheet. Facing the wall I5 is a fiat second wall I8 having its margin welded to the fiange I'I of the first wall by aline weld at I9, so that the two walls are integrally united to form a flat chamber enclosing a space 20, which may be for example one half inch thick and as wide and long as circumstances require. One of the walls, I8, is provided with a fitting or connection 2| for filling and exhausting purposes, this being shown in Figs. 1 and 5 applied at the interior side of the wall, but in Figs. 3 and 6 the wall being dished and the fitting mounted in the recess thereof at the exterior side of the wall, in line with a corresponding opening 22 in the wall itself. The fitting 2| is shown as comprising a bushing 23 welded to the wall and interiorly adapted, as by threads, to receive a screw plug 25 which in turn is centrally apertured to receive a taper plug 26. The bushing has an outward extension 24 for attachment of evacuating connections.

In accordance with my prior patent, metallic copper may be applied upon the interior or exterior or both surfaces of the two walls, also adjacent to the weld line I9 and the joint between wall I8 and bushing 24, prior to the welding together of the two walls. After the parts are welded together the entire structure may be raised to a temperature to melt the copper, in a hydrogen atmosphere, as described in said Patent No. 2,024,065, the copper thus being caused to flow and spread over the interior surfaces of the walls to render them gas-tight, and into the welded joints to seal them against leakage.

Merely as an instance of a practical use of the panel I4 it is shown in Fig. 4 as confined between two plates or boards 2l of ply-wood, serving to stiffen the panel and protect the metal walls thereof, with a surrounding frame 28 which may also be of wood. 'Ihe final structure may constitute a door or other product wherein heat transfer is minimized.

As partly indicated in Figs. l and 3 the space 20 within the panel I4 is filled with the special granular activated carbon 30 of this invention, as will be later more fully described. The material in suitable condition is poured in through the bushing 23 and merely shaken cr worked into place until the chamber is packed full. The screw plug 25 is then inserted and sealed by welding or soldering. IIhe gases are then exhausted in usual manner under heat through the aperture in the screw plug, and the taper plug 26 is then driven home and sealed by solder.

In the modification of Fig. 5 a container or liner IlIIa is shown extending around a plurality of sides, in this case five sides, the product being adapted for use as a liner for refrigerators or other products. Shaped inner and outer walls I 5a and Iila face each other in parallelism, the wall I5a having a rim ange IEa overlapping and welded to the edge of the wall I8a along the weld line I9a. Between the walls is the space 2|)a to be lled with filling material 30 and evacuated. At the wall I8a is shown a connection or fitting 2|a for filling and evacuating purposes, which may be similar to that shown in Fig. 3.

In the vacuum container or bottle I4b of Figs. 6 and '7 the first or inner wall I5lo and the second or outer Wall I3ID are assembled in spaced relation and welded in the manner described in said Patent No. 2,024,065, enclosing a space 2|!b to be evacuated after filling with material 30. The lower part of the outer wall I8b is provided with a dished opening in which is mounted the connection or fitting 2 Ilo for lling and exhausting the enclosed space, comprising a bushing 23b welded to the wall and having a relatively large port, and a first plug 25b occupying the bushing after the chamber has been filled, such plug having a relatively small port opening into the large port, and a second plug 26h to occupy and close permanently the relatively small port in the first plug. The walls are shaped to enclose a container space 34 within which liquids or various other commodities may be stored at hot or cold temperatures.

As in said Patent No. 2,024,065, the structure of the container I4b may comprise substantially the following details. The top rim of the Wall I8b is outwardly flanged at 35. Between the two walls near their top rims. is a spacing channel 36 welded to both walls. The cross sectional shape of the container and walls may be substantially square as shown in Fig. 7, with flat sides more likely to defiect under external pressure than cylindrical ones. Surrounding the connected walls. is shown an enclosing and protecting shell comprising a circumferential casing or enclosure 31, and below the container a bottom enclosure 38, these preferably composed of a non-metallic insulating material, such as bakelite, giving protection and reenforcing the structure, the shell 3l, 38 being preferably cemented or otherwise united to the outer wall IIBIJ to stiffen the latter against deflection. Overlying the flange 35 and channel 35 is shown a ring 39 of insulating material, and resting on the inside rim of the ring is shown an apertured ring 4i) which may be a hollow metalwalled evacuated ring, its central aperture serving for access to the container space 34. Surrounding the parts 35 and 39 is shown an upward extension 4I of bakelite attached to the shell 31 and having screw threads to receive a cap piece 42, which may also constitute the mouth of the container and is interiorly shaped to receive a stopper.

The special active or absorbent (adsorptive) carbon filler of this invention is distinguished from an ordinary carbon or charcoal powder in that it is in a granular form, consisting of dense, hard granules, preferably containing capillary recesses or passages some of which may be of almost molecular dimension. Fig. 8 shows the character of the contacts between the granules, in a diagrammatic manner; and Fig. 9 shows with some exaggeration the capillary character of the surface of each granule, the fine stipplings representing innumerable passages or recesses, and there sometimes being also a smaller number of larger recesses as, also indicated on this figure.

This filling material after proper activation is highly absorbent of residual gases left after evacuation and of occluded gases escaping from the metal walls during and for a long period after evacuation and sealing. By absorption or adsorption the filling material actively captures gas molecules by condensation, or capillary attraction, or both, and has high capacity for retaining and holding the same fixed indefinitely, so that heat transfer by convection or conduction is practically zero.

The granular carbo-n of this invention is obtainable from certain dense vegetable products, notably fruit pits, as plum, peach and apricot, or even cocoanut shells, for example, by the following procedure. The raw material should first be carbonized at moderate temperatures, as. 400 to 500 C., after which it may be reduced or broken up into granules of appreciable size, as to -s inch diameter, powdered particles being eliminated by screening. The material is activated, as by heating for several hours in retorts or by superheated steam, at 800 to 900 C., to remove or drive off all hydrocarbons. Before filling the carbon should preferably be reheated in vacuum to nearly the same temperatures, or at least to a fairly high temperature for supplemental activation and elimination of moisture; when it may be poured into the chamber, the smooth hard granular form readily permitting this.

The step of activating carbonized vegetable matter is not herein claimed to be new per se, and reference may be made to disclosures such as the Chaney Patents 1,497,543 and 1,497,544 of June 10, 1924 for details of an activation process.

Such material however in mobile granular form as a filler is believed to be novel,

The filling material hereof is itself a good nonconductor of heat, and its insulating property is enhanced by the hard granular form, avoiding extensive surface contact between granules and providing innumerable voids throughout the mass.

The mass of hard, firm granules in mutual contact additionally constitutes a practically rigid packing, eiectively resisting inward bending of the flat or other walls of the chamber, a function not obtainable with ordinary powdered charcoal, certainly without mechanical compressing and consequent caking with loss of insulating quality. Yet the mass is sufficiently loose and pervious to allow gas ow through it during exhausting, making it possible to withdraw gas thoroughly from all parts of the chamber. After the lling, evacuating and the sealing of the chamber the structure is cooled down, rendering more active the absorbing property of the filler, which thus gets, fixes and retains substantially all residual gas, including molecules later escaping from the metal walls. Thus the various advantages rst above set forth are attained to a high degree. The wall bracing function is believed to be novel irrespective of the use of carbon or activated material, and is afforded by other granular filling material, as glass, gravel etc.

The metal-walled vacuum chamber or container hereof may be summed up generally as follows. Occupying the vacuum space is the described loosely massed and packed filling composed of hard granules with interconnecting interstices or voids between them; on a small scale the mass resembles broken coal in a bin, the granules being classified to exclude particles below or above a predetermined range of size, as between 0.05 and 0.20 inch. Of this granular filling at least a substantial part consists of hard dense granules of activated carbon. Preferably the principal part or entirety consists of such carbon granules, but to lower the cost such carbon granules may be mixed or diluted with granules of other materials such as glass, clean gravel or the like, since a relatively small quantity of the highly activated carbon granules will Sulce for absorbing and retaining to. an adequate degree residual gases existing within or entering the space after exhaustion and sealing. While the original source of the carbon has been stated preferably to be such a dense vegetable material as fruit pit, yet other sources are available, such as anthracite coal, properly granulated and classied, and possessing after activation substantially the properties recited. While the lling mass is preferably composed entirely of hard granules it is not intended to exclude the mixing therewith of a light quantity of more finely divided material, as pulverized diatomaceous earth or silocel, itself an effective insulating material, and of possible advantage in certain cases, if the proportion thereof is so. small as not to block gas flow through the mass. Each of the described llings embodying this invention will be seen to` have the properties of (a) absorbing and-retaining to a substantial degree gases existing within the space, (b) preventing to a substantial degree heat conduction through its own mass, (c) allowing substantially free gas flow through its mass for evacuation of the space, (d) constituting a substantially rigid bracing support between the chamber walls, like coal in a bin, to resist susbtantial deflection thereof by external pressure, and (e) mobility of the loose mass of hard granules for pouring it fluently into the vacuum space.

Having thus disclosed several embodiments of the principles of this invention it is desired to be understood that the invention is not to be limited to specic features of combination, construction and method except to the extent set forth in the appended claims.

I claim:

1. A metal-walled vacuum chamber or container comprising the metal walls enclosing gastightly the vacuum space, and, occupying such space, a rigidly packed filling composed of a mass of hard discrete granules having negligible surface contact with each other and the mass rendered pervious by ample interconnecting interstices or voids between the granules, of which granular filling at least a substantial part consists of hard, dense granules of activated carbon; and such lling having the properties of (a) absorbing and retaining to a substantial degree gases existing within the space, (b) preventing to a substantial degree heat conduction through its own mass, (c) allowing substantially free gas flow through its mass for evacuation of the space, (d) constituting a substantially rigid interior bracing structure between the chamber walls to resist substantialv deection thereof by external pressure, and (e) mobility of the loose mass of hard granules for pouring it into place in the vacuum space.

2. A metal-walled vacuum chamber or container comprising the metal walls enclosing gas tightly the vacuum space, and, occupying such space, a rigidly packed lling composed of a mass of hard discrete granules of substantial size having negligible surface contact with each other and the mass rendered pervious by ample interconnecting interstices or voids between the granules, of which granular filling at least the principal part consists of hard, dense granules of activated carbon having capillary pores or passages; such filling affording the functions of absorbing and retaining to a substantial degree gases existing within the space, allowing substantially free gas iiow through its mass for evacuation, and constituting a substantially rigid bracing support between the chamber walls to resist substantial inward deflection.

3. An article of manufacture as in claim 2 and wherein the hard lling granules are of size between about 0.05 and 0.20 inch.

4. A Vacuum chamber comprising sheet metal walls enclosing gas-tightly the vacuum space, and of such character as to be subject to collapse or inward deflection in practical use, and, occupying such vacuum space, a rigidly packed lling cornposed of a mass of hard granules of appreciable size and relatively small contacts between them, and forming interconnected interstices throughout the mass; such filling by reason of such character having the properties of preventing to a substantial degree heat conduction through its own mass, and allowing susbtantially free gas flow through its mass for evacuation of the space, and constituting a substantially rigid internal bracing support from chamber wall to wall, thereby to resist effectively a substantial deflection thereof by external pressure.

5. An article as in claim 4 and wherein one or more of the vacuum chamber walls is substantially flat and therefore liable to bending by eX- ternal air pressure but mechanically braced internally by such lling to oppose. substantial bending.

5. A chamber as in claim 4 and wherein the lilling granules are non-metallic, hard, and of diameters between .05 and .20 inch more or less, and touch each other substantially by point contacts.

'7. A vacuum chamber as in claim 4 and wherein the filling mass of hard granules is loose and pourable and comprises in substantial part hard granules of adsorptive material.

EUGENE L. SCHELLENS.

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