# US 5,346,570 A · Cryogenic dewar and method of fabrication

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- Number: US 5,346,570 A
- Document ID: US5346570A
- Status: Granted
- Kind: A
- Application number: 07/922,677
- Filed: 1992-07-30
- Granted: 1994-09-13
- Earliest claimed: 1992-07-30
- Assignees: Biomagnetic Technologies, Inc.
- Inventors: Laurence Warden; Keith Esser
- Web page: https://patentgrep.com/patent/US5346570A

## CPC

- B29C 70/30: Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
- B29C 70/088: {and with one or more layers of non-plastics material or non-specified material, e.g. supports}
- B32B 1/00: Layered products having a non-planar shape
- B32B 1/08: Tubular products
- B32B 5/26: another layer {next to it} also being fibrous or filamentary {(relative arrangement of fibres or filaments of different layers B32B5/12)}
- B32B 7/12: using interposed adhesives or interposed materials with bonding properties
- B32B 15/02: {Layer formed of wires, e.g. mesh}
- B32B 15/14: next to a fibrous or filamentary layer
- F17C 3/08: by vacuum spaces, e.g. Dewar flask (for household use A47J41/02)
- B32B 2307/304: Insulating
- B32B 2315/085: Glass fiber cloth or fabric
- B32B 2439/00: Containers; Receptacles
- B32B 2597/00: Tubular articles, e.g. hoses, pipes
- F17C 2203/032: Multi-sheet layers
- F17C 2203/0345: Fibres
- F17C 2203/0391: by vacuum
- F17C 2203/0629: Two walls
- F17C 2209/227: by adhesive means
- F17C 2270/0509: "Dewar" vessels
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- F17C: VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES (storing fluids in natural or artificial cavities or chambers in the earth B65G5/00; construction or assembling of bulk storage containers employing civil-engineering techniques E04H7/00; variable-capacity gas-holders F17B; liquefaction or refrigeration machines, plants, or systems F25)

## Abstract

A dewar includes an inner dewar and a dewar thermal shield. The dewar thermal shield has a thermal shield body formed of a layer of radiative insulation, an inner layer of fiberglass cloth overlying the layer of radiative insulation, a metallic screen overlying the inner layer, and an outer layer of fiberglass cloth overlying the metallic screen. The dewar thermal shield also has a thermal shield tail cap attached to the thermal shield body. The tail cap is formed of a layer of radiative insulation, a layer of fiberglass cloth overlying the layer of radiative insulation, a layer of thermal foil overlying the layer of fiberglass cloth, the thermal foil being formed of thermal conductors embedded in a film adhesive matrix with the thermal conductors extending to the body, and a top layer of fiberglass cloth overlying the layer of thermal foil.

## Claims

### Claim 1

A method for preparing a dewar, comprising the steps of:
preparing a thermal shield tail cap by
furnishing a tail cap mandrel,
applying a layer of radiative insulation over the tail cap mandrel,
applying a layer of fiberglass cloth over the layer of radiative insulation,
applying a layer of thermal foil overlying the layer of fiberglass cloth, the thermal foil being formed of thermal conductors embedded in a B-staged film adhesive matrix,
applying a layer of fiberglass cloth overlying the layer of thermal foil, and
consolidating the layer of radiative insulation, layer of thermal foil and layer of fiberglass cloth, and partially curing the B-staged film adhesive;
preparing a thermal shield body by
furnishing a body mandrel,
applying a layer of radiative insulation overlying the body mandrel,
applying an inner layer of fiberglass cloth overlying the layer of radiative insulation,
applying a metallic screen overlying the inner layer, and
applying an outer layer of fiberglass cloth overlying the metallic screen;
joining the thermal shield cap to the thermal shield body; and
consolidating the joined thermal shield cap and thermal shield body, to form a dewar heat shield.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of joining is accomplished concurrently with the step of preparing a thermal shield body, and the step of joining includes the step of
interleaving at least some of the layers of the thermal shield tail cap and the thermal shield body.

### Claim 3 (depends on 1)

The method of claim 1, wherein the step of joining includes the step of
reinforcing the joined region with an annular piece.

### Claim 4 (depends on 1)

The method of claim 1, including the additional step of
joining the dewar heat shield to an inner dewar.

### Claim 5 (depends on 4)

The method of claim 4, wherein the step of joining the dewar heat shield to an inner dewar includes the step of
furnishing an inner dewar made of fiberglass.

### Claim 6 (depends on 4)

The method of claim 4, including the additional step, after the step of joining the dewar heat shield to an inner dewar, of
joining an outer dewar to the assembly of the inner dewar and the dewar heat shield.

### Claim 7 (depends on 1)

The method of claim 1, wherein the thermal shield tail cap and the thermal shield body are cylindrically symmetric.

### Claim 8 (depends on 1)

The method of claim 1, wherein the step of applying a metallic screen includes the step of
applying a unidirectional metallic screen with metallic wires running parallel to each other.

### Claim 9 (depends on 1)

The method of claim 1, wherein the step of applying a layer of thermal foil includes the step of
supplying metallic thermal conductors arranged substantially parallel to each other.

### Claim 10

A method for preparing a dewar, comprising the steps of:
preparing a cylindrically symmetric thermal shield tail cap by
furnishing a cylindrically symmetric tail cap mandrel,
applying a layer of radiative insulation over the tail cap mandrel,
applying a layer of fiberglass cloth over the layer of radiative insulation,
applying a layer of thermal foil overlying the layer of fiberglass cloth, the thermal foil being formed of metallic thermal conductors embedded in a B-staged film adhesive matrix, the thermal conductors lying parallel to a cylindrical axis of the tail cap mandrel,
applying a layer of fiberglass cloth overlying the layer of thermal foil, and
consolidating the layer of radiative insulation, layer of thermal foil and layer of fiberglass cloth, and partially curing the B-staged film adhesive;
preparing a cylindrically symmetric thermal shield body by
furnishing a cylindrically symmetric body mandrel,
applying a layer of radiative insulation overlying the body mandrel,
applying an inner layer of fiberglass cloth overlying the layer of radiative insulation,
applying a metallic screen overlying the inner layer, the metallic screen comprising unidirectional metallic wires extending parallel to a cylindrical axis of the body mandrel, and
applying an outer layer of fiberglass cloth overlying the metallic screen;
joining the thermal shield cap to the thermal shield body by interleaving layers of the thermal shield body and the thermal shield cap, wherein the step of joining is accomplished concurrently with the step of preparing the thermal shield body; and
consolidating the joined thermal shield cap and thermal shield body, to form a dewar heat shield.

### Claim 11 (depends on 10)

The method of claim 10, wherein the cylindrical diameter of the body mandrel is larger than the cylindrical diameter of the tail cap mandrel, and wherein the step of joining includes the step of
forming a radially extending interleaved joint between the layers of the thermal shield body and the layers of the thermal shield cap.

### Claim 12

A method for preparing a dewar, comprising the steps of:
preparing an unconsolidated thermal shield tail cap having a layer of thermal foil formed to a preselected shape, the thermal foil being formed of thermal conductors embedded in a B-staged film adhesive matrix, and a layer of insulation adjacent to the layer of thermal foil;
consolidating the thermal shield tail cap;
preparing a thermal shield body having a layer of a metallic heat conductor, and a second layer of insulation adjacent to the metallic heat conductor;
joining the thermal shield cap to the thermal shield body; and
consolidating the joined thermal shield cap and thermal shield body, to form a dewar heat shield.

### Claim 13 (depends on 12)

The method of claim 12, wherein the step of joining is accomplished concurrently with the step of preparing a thermal shield body, and the step of joining includes the step of
interleaving at least some of the layers of the thermal shield tail cap and the thermal shield body.