US 3167933 A
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Description (OCR text may contain errors)
United States Patent Ofifice York Filed Oct. 24, 1962, Ser. No. 232,685 14 Claims. (Cl. 62-371) This invention relates to cryogenic storage containers and particularly to double-walled, vacuum insulated containers for storing materials at low temperatures wherein a cryogenic liquid is used as the source of refrigeration.
Low boiling liquefied gases are being increasingly used for the storage and preservation of perishable products such asfoodstuifs and biologicals. The materials are for the most part stored in double-walled vacuum-insulated cylindrical containers. Although these containers are able to withstand the forces imposed upon the vacuum insulated walls more readily than a container of rectangular construction, they are relatively unsatisfactory for pro viding maximum use of available storage space.
Specifically, in order to achieve the same amount of storage space as is available in a given size rectangular container, a cylindrically-shaped container would have to be substantially larger or bulkier. The use of a box-like construction, however, presents the serious problem of making the walls of the box, forming the. evacuable insulation space, strong enough to carry the forces imposed by the combination of the internal atmospheric pressure of the inner box and the external atmospheric pressure and yet thin enough so that the heat leak into the box is kept to a minimum and, further, thin enough so that the weight is kept to a minimum. Also, in order to effectively utilize the storage area available in a rectangular type construction, the opening for the box should be substantially equal to the cross-sectional area of the inner storage area. This tends to materially increase the heat leak to thecontainer.
There have been many solutions proposed for the problem of forming high strength double-walled vacuum box-like containers with a minimum of heat leak. One solution utilizes a foam plastic that is strong enough to act not only as an insulating material but also as a load bearing material. The diificulty with this solution is that the heat leak through the material by conduction will be excessive. Another solution utilizes spacers between the two walls. Thisobviously would increase the heatleak by conduction.
It is an object of this invention to provide a doublewalled vacuum-insulated storage container of substantially uniform rectangular cross-section. Another object is to provide a rectangular double-walled container having flat walls capable of withstanding pressure forces without the use of intermediate Wall supports. A further object is to provide such a container with unique features that minimize its weight. Another object is to provide a container which is suitable for storing material at low temperatures forprolonged periods. Another object is to provide a container having greater accessibility to its storage area. Still another object is to provide an insulated cover for such a container that will aid in reducing heat transmission through the container. These and other objects and advantages of this invention will become Patented Feb. 2, 1965 apparent from the following description and the accompanying drawings, in which:
FIGURE 1 is a vertical cross-section through a doublewalled container illustrating the features of the present invention;
FIGURE 2 is a vertical cross-section through a cover for the container of FIGURE 1.
The present invention comprises a unique double-walled and vacuum-insulated storage container for storing ma terial at low temperatures by refrigerating the same by use of a cryogenic liquid. The container more efficiently utilizes available storage space in that it has a substantially uniform rectangularcross-section and a rectangular opening of substantially the same size as the cross-sec tional area of the inner storage vessel. The inner vessel is suspended from, and solely supported by, a neck tube which joins the top portions of the inner vessel and the container outer jacket. The space between the inner vessel and the outer jacket forms an evacuable insulation space.
The outer jacket is a composite structure comprising a core which is substantially completely covered with metallic sheeting. The inner vessel structure comprises a relatively flexible metallic material that is reinforced by crossbridging the inner vessel walls so as to prevent excessive inner vessel wall deformation resulting from the pressure differential between the inner vessel interior and the surrounding evacuable insulation space. Inasmuch as the inner vessel is preferably constructed of relatively thin material to reduce the weight of the container, such pressure differential could cause the walls of the inner vessel to excessively deform if cross-bridging were not employed.
The container is closed by a cover constructed to fit within the neck tube and designed to close the inner vessel opening such that refrigerant vapors escaping from the inner vessel will pass along the inner surface of the neck tube to cool the same and thereby recover the sensible refrigeration of the escaping vapor.
Referring now to the drawings and specifically to FIG- URE 1, numeral 10 designates the preferred form of the container of the present invention. Container 10 com prises an outer jacket 12, an inner vessel 14, a neck tube 16 which defines an inner vessel opening 18 and which, in combination with inner vessel 14 and outer jacket 12, defines an evacuable insulation space 20.
The composite outer jacket 12 is constructed of a core material 21 that is substantially completely covered with metallic sheeting 22. Core 21 is preferably constructed of laminated material such as plywood or Masonite, unlaminated plain wood such as maple or a suitable metallic honeycomb structure. Flexible supporting metallic sheeting 22 is preferably constructed of stainless steel and bonded to the inner and outer surfaces of core 21 by means of a suitable adhesive.
Outer jacket 12 is preferably constructed of separate sheets of core material, each -of which constitutes a wall of the outer jacket. When outer jacket 12 is constructed of separate sheets, it is preferable that each outer jacket wall be beveled about its periphery as shown in FIG. 1 so that load bearing surfaces such as 24a and 24b may be provided between adjacent walls to increase the structural rigidity of container 10. It is also preferable that each outer jacket wall be encased in separate pairs of metal sheeting such as 22a and 22b which substantially completely enclose a corresponding outer jacket wall. Adjacent interior metal sheets 22b are preferably welded together to provide a gas-tight outer wall for evacuable insulation space 20. Spaces 26 are preferably provided along the edges of the outer jacket wall peripheries so that such welding may be accomplished without damaging the core structure of outer jacket 12. The corners and top rim of outer jacket 12 are preferably protected by metallic strips 28.
Inner vessel 14 is constructed of relatively flexible thinwalled metallic sheeting and reinforced against excessive wall deformation .due to the pressure differential across the inner vessel walls, by cross-bridging the inner vessel walls. Such cross-bridging is preferably provided by intersecting metallic sheets 30 each of which have one end rigidly connected to the inner surface of an inner vessel wall and an opposite end rigidly connected to the other metal sheets through a vertical support member 32. The choice of the number and the-positioning of these metal sheets 30 depends on the reinforcing requirements of inner vessel 14 and on the number of vertically-divided compartments formed by the intersecting metal sheets 30 that are desired. 7 I
The pressure differential between the ambient atmosphere and the low pressure in evacuable insulation space 20 is'compensated by the rigidity of the composite Wall of core 21 and the metallic sheeting 22 and the suspension of inner vessel 14 therefrom. Thus, the forces imposed on outer jacket 12 from such pressure differential are car-l ried Without the aid of intermediate spacers bridging evacuable insulation space 20; The use of intermediate spacers would result in greater heat ,leak into inner vessel 14 and is therefore not desirable. Further, because of the inner vessel wall cross-bridging, the innerxvessel walls work together to resist the tendency to deform excessively as a result of the evacuation of insulation space 20. This materially aids in minimizing the Weight of container 10 in that the inner vessel walls maybe constructed of thinner material.
Thecompartments of inner vessel 14 are preferably closed by covers such as sliding covers 34 and 36, al. though a single cover could be used. These covers permit access to a desired compartment without exposing other compartments to the atmosphere when container '10 is opened on removal of the containercover. Sliding covers 34 and 36 arepreferably supported and guided by channel members such as 38, 40, and .42 which areconnected to the upper portion of inner vessel 14' above metal sheets 30.
It is preferred that sliding covers 34 and 36 be constructed of aluminum in order to reduce thermal radiation into inner vessel 14.
Neck tube 16 may be constructed of a thin metallicmaterial, or a substantially gas impervious reinforced fibrous laminate impregnated with a thermosetting resin, examples of which are reinforced phenolic and epoxy resins. Neck :tube 16 is preferably connected to outer jacket 12 by reinforcing angle 44 having a downwardlypositioned apex. Angle member 44 is welded to the upper load bearing surfaces as shown at 24c: and 24d and to an upper neck tube reinforcing strip 46. It has been found to be preferable to employ anangle member in an inverted position as shown at 44 rather than achannel member of a member of some other configuration. Angle 44 is easier to fit into place and in addition provides. a convenient and protected space for the vacuum pinch-off tube 48 and also provides greater strength at'less weight.
Neck tube '16 maybe additionally reinforced by lower neck tube reinforcing strip 50 and by neck tube corner reinforcements such as angles 52 and 54, the legs of such anglesbeing preferably welded to the inner surface of neck tube 16. Inasmuch as it is preferable to construct neck tube 16 of relatively thin material so as to reduce heat leak therethrough, the above-mentioned reinforcements may be insufficient in which case it would bepreferable 'to fasten a low-thermally conductive material (not 4 shown) such as polyurethane foam plastic to the exterior surface of neck tube- 16. Such plastic would be bonded to the outer surface. of neck tube 16 by a suitable adhesive and would preferably extend across the width of evacuable insulation space 20.
In its preferred form, container 10 employs thermal insulation 56 in evacuable insulation space 20 to reduce heat leak therethrough. Preferably, opacified insulation of the alternate layer type described in' US. Patent 3,007,596 issued to L. C. Matsch is employed. This insulation comprises alternate layers of a low heat conductive material and thermal radiation impervious barriers. Examples of the low heat conductive material, which may be produced in sheet, form, include filamentary glass material such as glass-wood and fiber, glass. The spaced radiation barriers may comprise eithera metal, metal oxide, or metal coated material, such as aluminum coatedplastic film, or other radiation adsorptive material. Radiation reflective material comprising thin metal foils are particularly suited in the construction of the present invention. When fiber sheets .areemployed as the low conductive material, they may additionally serve .as a support means for the relatively fragile radiation impervious sheets.
Notwithstanding the employment. of inner vessel wall cross-bridging, there will be some outward deformation of the inner. vessel walls. Therefore, opacified insulation 56 must be so arranged withinxevacuable insulation-space 20 so that such deformation will not unduly compress the insulation. To provide against such undue compression, it is preferred that a space he leftfbfitWCEn the insulation material and the outer wall of evacuable insulation space 20 as shown at 5-8 and 60 to allow for such deformation.
' tion thereof asshown inFIG. 1 so that =anexcessive amount of the conductive radiation impervious barriers will not be in close proximity to the top of container 10 which is at substantially ambient-temperature.
In fabricating container 10, inner'vessel14 and neck tube 16 are first completely fabricated with the alternate layer opacified insulation 56 preferably tightly installed about the outer surface of inner vessel 14 by taping or other suitable means. 7 Inner vessel 14' is suspended in I container 10-fromthe top portion of outer jacket 12 through neck tube 16 by welding the latter to outer jacket 12 as shown in FIG. -1. Evacuableinsulation space 20 is then evacuated resulting in some unavoidable outward deformation of the inner vessel walls. Because of the inner vessel wall cross-bridging, the deformation will not be' excessive. Thus, although insulation 56 may now substantially fill evacuable insulation space .20 because .of this inner vessel wall deformation, it will not be unduly compressed. Such undue compression would deleteriously increase theheat leakage into inner vessel '14 through the insulationmaterial and is highly undesirable.
To achieve maximum utilization .of the storage space in inner vessel '14,: the'opening thereto through neck tube 16 should have substantially the same cross-section as that of inner vessel 14. An opening of this relative size creates the problem of properly. insulating by means of a suitable cover, what is otherwise a largev uninsulated area comprising about Ms of the container surface. The cover used with container "10 is particularly adaptable for insulating such areas. This cover is shown in FIG. 2.
Referring to FIG..2, cover 62 preferably comprises a top metal sheet 64'bonded to layers of insulation material 66 which are separated by-thin metallic sheets .68. A suitable insulation material, "is a unicellular foam plastic such as polyurethane. Metallic sheets 68,'-pref erably constructed of aluminum, act asthermal radiation barriers to reduce the passage of infrared rays without significantly increasing :the thermal conductivity of cover-62." A more important function of metallic-sheets 68 is to act as lateral thermal conductors such that heat will be conducted through the sheets 68 and absorbed by escaping refrigerant vapors passing between cover 62 and neck tube 16 when the cover is installed in neck tube 16. Since the metallic sheets 68 conduct heat radially out of the cover 62, the greater the number of such sheets 68, the more effective will cover 62 be in reducing heat leak. However, an excessive number of metallic sheets 68 will cause the insulation material 66 to lose its effectiveness. Use of plastic as the insulation material 66 permits sectionalizing cover 62 if desired to correspond to the number and size of the inner vessel storage compartments. Alternatively, cover 62 could be of the vacuum-insulated type to provide even greater protection against heat leak, or constructed entirely of the aforementioned plastic.
If the length of container is sufliciently great, it may be necessary to reinforce the top of the outer jacket walls against deformation because of the beam length of the longer panels. Such reinforcing may be accomplished by positioning suitable support members across the top of container 10 between outer jacket walls. Where this is done, sectionalization of cover 62 is particularly useful.
To aid in the maintenance of the vacuum in insulation space 20, a molecular sieve adsorbent 70 is preferably employed in the manner described in US. Patent 2,900,- 800 issued to P. E. Loveday. The bottom wall of inner vessel 14 may be constructed in the form of an inverted pan for covering the adsorbent 70 which may be held in place by a glass cloth (not shown) providing gas communication between adsorbent 70 and evacuable insulation space 20.
When only a portion of the storage space is utilized, or where the material stored is to be kept away from the refrigerant in inner vessel 14, an inverted pan (not shown) may be placed on the bottom wall of inner vessel 14 for such material.
As an illustration of the manner in which the embodiment of this invention shown in FIGURES 1 and 2 might be utilized, consider the following. Liquid nitrogen may be transferred from a storage vessel into the container storage space defined by inner vessel 14. On sliding cover 36 beneath cover 34, to expose the inner vessel storage space, the material to be stored, such as biologicals, are then inserted into the inner vessel and immersed in the liquid nitrogen. Sliding cover 36 is now returned to position and the container cover 62 is inserted into the container opening 18. Whenever it is desired to remove any of the stored material, cover 62 is removed and one of the sliding covers 34 or 36 is positioned to expose the inner vessel storage space and the material removed through the opening to the inner vessel so provided.
Although preferred embodiments of the invention have been described in detail, it is contemplated that modifications thereof may be made and that some features may be employed without others, all within the spirit and scope of the invention.
What is claimed is:
l. A low temperature storage container having spaced outer jacket and inner vessel walls with an evacuable insulation space therebetween comprising in combination: composite outer jacket bottom and side walls constructed of a core material and metallic sheeting substantially completely covering the exterior and interior surfaces of said core material and bonded thereto to form an outer jacket of substantially uniform rectangular cross-section for the container, the metallic sheeting being constructed to form a gas-tight outer wall of said evacuable insulation space; an inner vessel of substantially uniform cross-section within said container comprising bottom and side walls constructed of relatively flexible metallic sheeting and adapted to contain a vaporizable refrigerant; a neck tube of substantially the same cross-section as said inner vessel gas-tightly constructed and joined to the top portions of said outer jacket and said inner vessel to suspend the latter from the former; the inner vessel side and bottom walls and said neck tube being constructed to form a gas-tight inner wall of said evacuable insulation space; inner vessel wall cross-bridging means within said inner vessel constructed to prevent excessive inner vessel wall deformation resulting from the pressure differential between the inner vessel interior and the surrounding evacuable insulation space; cover means comprising top and bottom walls of substantially rectangular cross-section and insulation means disposed therebetween, said cover means being constructed to loosely fit within said neck tube and close the container opening defined by said neck tube such that refrigerant vapors escaping from said inner vessel pass along the inner surface of said neck tube and cool said inner surface thereby recovering the refrigerating effects of such vapor.
2. A low temperature storage container according to claim 1 wherein the bottom and side walls of said outer jacket comprise separate sheets of material and the outer jacket metal sheeting comprises separate pairs of metal sheets, each of such pairs substantially completely enclosing a corresponding outer jacket wall.
3. A low temperature storage container according to claim 1 wherein the inner vessel wall cross-bridging means comprise metal sheets, each having one end rigidly connected to the inner surface of an inner vessel wall and being constructed to vertically subdivide the interior of said inner vessel into compartments.
4. A low temperature storage container according to claim 1 wherein the container cover insulating means disposed between the top and bottom walls of said cover means comprises layers of low thermally conductive material, and thin high thermally conductive radiation impervious sheets separating the low thermally conductive layers.
5. A low temperature storage container according to claim 2 wherein the separate sheets which comprise the outer jacket bottom and side walls have beveled peripheries constructed to provide load bearing surfaces between separate sections of said outer jacket.
6. A low temperature storage container according to claim 1 wherein said evacuable insulation space is substantially filled with thermal insulation.
7. A low temperature storage container according to claim 1 wherein said evacuable insulation space is substantially filled with thermal insulation comprising alternate layer opacified insulation material.
8. A low temperature storage container according to claim 1 wherein the cover means is constructed in sections and the container cover insulating means disposed between the top and bottom walls of said cover means comprises layers of low thermally conductive material, and thin high thermally conductive radiation impervious sheets separating the low thermally conductive layers.
9. A low temperature storage container according to claim 1 wherein the cover means is vacuum insulated.
10. A low temperature storage container according to claim 1 including outer jacket support member positioned across the top of the container to resist beam deformation of the outer jacket walls.
11. A low temperature storage container according to claim 1 wherein said evacuable insulation space is substantially filled with thermal insulation comprising alternate layer opacified insulation material, such opacified insulation material being arranged in said evacuable insulation space to prevent undue compression thereof due to outward deformation of the inner vessel walls by providing a space between such insulation and said outer jacket.
12. A low temperature storage container according to claim 1 wherein said evacuable insulation space is substantially filled With thermal insulation comprising alternate layer opecified insulation material, such opacified insula- '2' tion being tapered'at the top portion of said insulation space.
13. A low temperature storage container accordingto claim-1 wherein said neck tube isconnected to said outer jacket by means of an angle member having a downwardly positioned apex. 1
14. A low temperature storage container according to claim 1 wherein said neck tube is constructed from a gas impervious reinforced fibrous laminate impregnated with a thermoset synthetic resin.
References Cited in the file of this patent UNITED STATES PATENTS 1,256,162 Patee Feb. 12, 1918 8 Glennan Aug. 30, Richmond Nov. 15, Owens Sept. 12, Williamsonet a1. Jam 2, Freedman June 23, Rupp Aug. 4, Morrison July 14, Morrison,. Jan. 24, Telks June'27, Brown 1 Dec. 25,
Morrison Aug. 20,