US3191795A

US3191795A - Vacuum insulated vessels

Info

Publication number: US3191795A
Application number: US303380A
Authority: US
Inventors: Molnar William
Original assignee: British Oxigen Ltd
Current assignee: BOC Group Ltd
Priority date: 1962-08-31
Filing date: 1963-08-20
Publication date: 1965-06-29
Anticipated expiration: 1982-06-29
Also published as: NL296903A; GB969821A; DE1230048B

Description

June 29, 1965 w. MOLNAR vacuum INSULATED VESSELS 2 Sheets-Sheet 1 Filed Aug- 20, 1953 1|. I I I l I I K Illllllllllll Luau/4M Mun AR ATTORNEY June 29, 1965 w. MOLNAR 3,191,795

VACUUM INSULATED VESSELS Filed Aug. 20, 1963 2 Sheets-Sheet 2 FIG. 3

INVENTOR WWW ATTORNEY United States Patent 3,191,795 VACUUM INSULATED VESSELS William Molnar, London, England, assignor to The ritish Oxygen Company Limited, a British company Filed Aug. 20, 1W3, Ser. No. 303,380 Claims priority, application Great Britain, Aug. 31, 1962, 33,608/ 62 3 Claims. (Cl. 2249-14) This invention relates to vacuum insulated vessels, usually termed Dewar flasks, such as are used for example for the storage and transport of low boiling point liquefied gases.

As is well known, vacuum insulated vessels comprise an inner container for the liquid and an outer shell mounted in spaced relationship with respect to the inner container, the space between the container and the shell being evacuated.

The vacuum space serves as a barrier against access of heat from the exterior to the container and in order further to reduce the ingress of heat it has been proposed to mount one or more radiation shields within the vacuum space. By the term radiation shield as used herein is meant an element of thin sheet material, the surface of which has a high reflectivity for heat radiation, the sheet being spaced from but shaped to follow the contour of the inner container and substantially to surround it. The radiation shield, like the outer shell, is usually suspended from the neck of the inner container.

The material of the radiation shield must itself be of low heat capacity and have a highly reflective surface. It may consist f metal foil, such as aluminium or copper or it may consist of a non-metallic film or fabric coated with a highly reflecting metal. All such materials lack rigidity and, when used as a radiation shield in a vacuum insulated vessel, there is risk of damage and of the shield becoming displaced or distorted and moving into contact with the wall of the inner container or outer shell or with another shield if, as is usual, more than one such shield is provided in the vacuum space. Such damage or displacement impairs the heat insulating properties of the vessel and the impairment is of particular disadvantage in cases where the vessel is used for the storage of very low boiling point gases such as liquid helium or liquid hydrogen.

It is an object of this invention to provide an improved mounting for a radiation shield in the vacuum space of a vacuum insulated vessel, oliering support for the material of the shield and restraining movement of the shield.

According to the invention, a vacuum insulated vessel for the storage and transport of low temperature materials such as very low boiling point liquefied gases comprises an inner container provided with a neck portion, an outer shell surrounding and spaced from the inner container to define therewith a vacuum space, and at least one radiation shield as hereinbefore defined mounted within the vacuum space, said radiation shield being suspended from the neck portion of the inner container and resting on a spider member of low thermal conductivity which supports and restrains the radiation shield against displacement, s that the radiation shield is maintained spaced from the body of the inner container and from the outer shell or from an adjacent radiation shield. The supporting spider member may be formed from thread, cord or wire, of plastics or metallic material of low heat conductivity, such as polyethylene terephthalate or nylon, stainless or titanium.

The invention is illustrated by way of example in the accompanying drawings, in Which- FIG. 1 is a view in diagrammatic sectional side elevation of the complete vacuum insulated vessel.

ice

FIG. 2 is a sectional view on a larger scale showing the lower end of the vessel of FIG. 1 and FIG. 3 is a sectional plan view showing a ring for use in attachment of the supporting and restraining spider.

The vessel shown in FIG. 1 comprises an inner container 1 usually of general cylindrical form having an elongated neck portion 2 extending from its upper region, and an outer shell 3 surrounding and spaced from the body of the inner container 1.

The shell 3 is formed with a neck at its upper end the extremity of which is sealed as at 3a in FIG. 1 to the exterior of the neck 2 of the container 1.

The walls of the container 1 and shell 3 define a vacuum space 4 between them.

Within the vacuum space 4 are mounted, in this embodiment, two radiation shields 5 and 6 of such a form as to surround the container 1 and a large and preferably major portion of the neck 2 of the container 1.

The shields 5 and 6 are spaced from both the container 1 and the shell 3 and also from one another, and as shown in this example they may be formed with

necks

7 and 8, the extremities of which are attached as at 7a and 8a in FIG. 1 directly to the exterior of the neck 2 of the container 1. Any convenient method of attaching the ends of the necks of the radiation shields 5 and 6 to the neck 2 of the container 1 may be employed, but it is desirable to employ a connection which provides good heat conduction, and soldering or brazing are at present preferred.

The shields 5 and 6 may be formed of a variety of materials having a high thermal conductivity and a surface of high reflectivity for heat radiation, and as examples may be mentioned polished metal foil such as aluminium or copper foil.

The radiation shields 5 and 6 at their lower ends are supported upon and located by spider members 9 (FIG. 1) formed by loops 1!) of polyethylene terephthalate thread extending radially between the centre of the bottom wall of a shield and the adjacent wall of the inner container 1, or of the shell 3, or of an adjacent radiation shield.

In the example shown a locating stud 11 is afiixed to the centre of the underside of the bottom wall of the container 1, e.g. by soft soldering, and a cup 12 is arranged to receive the stud 11.

A ring 13, f the form shown in FIG. 3, having three uniformly distributed indentations 14, is aflixed in a concentric position to the upper surface of the bottom wall of the innermost radiation shield 5, e.g. by soldering. The spider member 9 is completed by looping the thread about the cup 12 and through the indentations 14 of the ring 13 (FIG. 2).

A similar stud 11 and cup 12 are provided centrally at the underside of the bottom wall of the inner radiation shield 5, for use in conjunction with a similar ring 13 soldered to the upper surface of the bottom wall of the outer radiation shield 6, to permit a similar supporting and locating spider member 9 to be completed, with thread, between the inner and outer shields 5 and 6.

Again a similar stud 11 and cup 12 are provided centrally at the underside of the bottom wall of the outer radiation shield 6 for use in conjunction with a similar ring 13 soldered to the inner surface of the bottom Wall of the shell 3, to permit a similar supporting and locating spider member 9 to be formed between the outer shield 6 and the shell 3.

The improved construction otters the advantage that the thickness of the neck 2 may be made smaller than hitherto deemed necessary, since the maintenance of correct location of the radiation shields is no longer dependent exclusively upon the rigidity of the neck 2. This reduction in thickness also results in a reduction in loss of refrigeration by conduction along and radiation at amass It will be understood that the radiation shields are not required to be and indeed cannot be vacuum tight, in view of the need to be able to evacuate the vacuum space.

In some cases therefore the radiation shields themselves may be apertured for the passage and anchoring of the spider-forming threads and provided the total area of such holes does not exceed more than about 0.1% of the total area of the shield, the holes are without appreciable effect upon the refrigeration performance of the vessel.

The spaces within the vacuum space surrounding and between the radiation shields may if desired be filled with material of a kind adapted to impede the flow of heat by conduction and such material may assist the spider members in supporting and locating the radiation shields.

I claim:

1. In a vacuum insulated storage and transport vessel having an inner container provided with a neck portion for filling with low boiling point liquefied gases, an outer-shell surounding and spaced from said container and connected therewith at said neck portion in fluid-tight manner to define therewith a vacuum space between the container and the outer shell, and at least one radiation shield suspended from said neck portion Within said vacuum space surrounding and spaced from said container: means for preventing side-sway of the radiation shield within the vacuum space; said means comprising a stud fixed on the bottom external face of the shield extending axially therefrom at its center and spaced axially above the bottom of the outer shell, a cup seated on and housing the stud, a rigid ring concentric with said stud and fixedly attached to the inner face of the outer shell bottom, and at least three flexible threads of low heat conductivity and material other than elastic extending radially in equidistant circumferential spaced relation oetween the ring and the cup in connection with each and operative to hold said cup and stud against radial displacement.

2. In a vacuum insulated storage and transport vessel having an inner container provided with a neck portion for filling with low boiling point liquefied gases, an outer shell surrounding and spaced from said container and connected therewith at said neck portion in fluid-tight manner to define therewith a vacuum space between the container and the outer shell, and at least one radiation shield suspended from said neck portion within said vacuum space surrounding and spaced from said container: means for preventing relative side-sway between said inner container and the radiation shield; said means comprising a stud fixed on the bottom external face of the inner container extending axially therefrom at its center and spaced axially above the shield bottom, a cup seated on and housing the stud, a rigid ring concentric with said stud and fixedly attached to the inner face of the shield bottom, and atrleast three flexible threads of low heat conductivity and material other than elastic extending radially in equidistant circumferential spaced relation between the ring and the cup in connection with each and operative to hold said cup and stud against radial displacement.

3. In a vacuum insulated storage and transport vessel having an inner container provided with a neck portion for filling with low boiling point liquefied gases, an outer shell surrounding and spaced from said container and connected therewith at said neck portion in fluid-tight manner to define therewith a vacuum space between the container and the outer shell, and a plurality of spaced apart concentric radiation shields suspended from said neck portion within said vacuum space surrounding and spaced from said container: means for preventing sidesway of all said radiation shields and the container; said means comprising a stud fixed on the bottom external face of the container and a similar stud fixed on the bottom external fiace on each radiation shield, a cup seated on each stud and housing the same, all said studs extending axially on the center axis of the vessel and each cup being spaced axially above the bottom of the next outer one of the radiation shields and outer shell, the inner bottom faces of the Outer shell and the radiation shields each having fixedly attached thereto a rigid ring concentric with said studs, and at least three flexible threads of low heat conductivity and material other than elastic extending radially in equidistant circumferential spaced relation between each ring and the adjacent cup in connection with both and operative to hold the cups and studs against radial displacement.

References Iited by the Examiner UNITED STATES PATENTS 1,607,071 11/26 Gleason 220-l5 2,643,022 6/53 Cornell 220-15 2,863,297 12/58 Johnston 220-9 2,925,934 2/60 Hampton et al. 220-l5 FOREIGN PATE TS 492,508 9/38 Great Britain.

F THERON E. CGNDGN, Primary Examiner.

Claims

1. IN A VACCUM INSULATED STORAGE AND TRANSPORT VESSEL HAVING AN INNER CONTAINER PROVIDED WITH A NECK PORTION FOR FILLING WITH LOW BOILING POINT LIQUEFIED GASES, AN OUTER SHELL SURROUNDING AND SPACED FROM SAID CONTAINER AND CONNECTED THEREWITH A VACCUM SPACE BETWEEN THE MANNER TO DEFINE THEREWITH A VACUUM SPACE BETWEEN THE CONTAINER AND THE OUTER SHELL, AND AT LEAST ONE RADIATON SHIELD SUSPENDED FROM SAID NECK PORTION WITHIN SAID VACUUM SPACE SURROUNDING AND SPACED FROM SAID CONTAINER: MEANS FOR PREVENTING SIDE-SWAY OF THE RADIATION SHIELD WITHIN THE VACUUM SPACE; SAID MEANS COMPRISING A STUD FIXED ON THE BOTTOM EXTERNAL FACE OF THE SHIELD EXTENDING AXIALLY THEREFROM AT ITS CENTER AND SPACED AXIALLY ABOVE THE BOTTOM OF THE OUTER SHELL, A CUP SEATED ON AND HOUSING THE STUD, A RIGID RING CONCENTRIC WITH SAID STUD AND FIXEDLY ATTACHED AT THE INNER FACE OF THE OUTER SHELL BOTTOM, AND AT LEAST THREE FLEXIBLE THREADS OF LOW HEAT CONDUCTIVITY AND MATERIAL OTHER THAN ELASTIC EXTENDING RADIALLY IN EQUIDISTANT CIRCUMFERENTIAL SPACED RELATION BETWEEN THE RING AND THE CUP IN CONNECTION WITH EACH AND OPERATIVE TO HOLD SAID CUP AND STUD AGAINST RADIAL DISPLACEMENT.