Composite Material and Metal Canister

Field of the Invention

The present invention is directed to containers. More specifically, the present invention is directed to containers for withstanding high internal pressures and bending stresses at bulkhead joints.

An object of the present invention is to provide an improved canister for providing a lightweight structure capable of withstanding high internal pressures and bending stresses at bulkhead joints.

In accomplishing this and other objects, there has been provided, in accordance with the present invention a canister comprising a cylindrical shell, a bulkhead of a composite material arranged within the shell across one end of the shell and a compression ring of shape memory material for applying a compressive stress to the shell to join the shell to the bulkhead.

A better understanding of the present invention may be had when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is a cross-sectional illustration of a canister combining a first example of the present invention and

FIG. 2 is a cross-sectional illustration of a canister embodying a second example of the present invention.

Referring to FIG. 1 in more detail, there is shown a canister embodying an example of the present invention and having a cylindrical outer shell 2 of a corrosion resistant thin material, e.g., stainless steel. A first end of the shell 2 is closed by a composite bulkhead 4 which may be of a graphite/epoxy thermoset material or a graphite/PPS thermoplastic material. Such materials are well-known in the art as discussed in the article entitled "Fabricating the Future With Composite Materials" on pages 29 to 35 in the November, 1986 issue of "Materials Engineering". The other end of the shell 2 is also closed by a similar bulkhead 6 having a pair of openings 8 and 10 therein. The openings 8 and 10 are arranged to encircle respective electrical leads 12 and 14 and are filled with corresponding glass-to-composite seals 16,18 to provide a fluid-tight hermetic seal and electrical isolation for the leads 12,14. The electrical leads 12 and 14 are connected to respective terminals of a battery 20 located within the shell 2 when the shell 2 is used as a battery canister.

A pair of shape memory material rings 22 and 24 are located in respective grooves 26 and 28 on an outside surface of the shell 2. The grooves 26 and 28 are aligned with the circumferential edges of the bulkheads 4 and 6, respectively. The rings 22,24 may be of a nickel-titanium alloy such as that discussed in the article, "Sealing with Shape-Memory Rings" on pages 74 and 76 of "Machine Design" of Aug. 7, 1986. The effect of the shape memory rings 22,24 is to exert compressive stresses on the shell 2 and on adjacent bulkheads 4 and 6 when the rings 22,24 return to an original shape or dimension at room temperatures to provide a fluid-tight hermetic seal between the shell 2 and the bulkheads 4 and 6.

The shell 2 and the bulkheads 4,6 are formed from materials which provide corrosion resistance while exhibiting high structural strength particularly in highly stressed areas such as the bulkheads 4,6. Further, the use of the composite material for the bulkheads 4,6 is effective to produce a lightweight structure which is a significant factor in weight limited structures such as battery canisters to be used in electronic packages for projectiles, torpedoes, etc. In such applications, excessive weight of the battery canister would reduce battery energy density. On the other hand, corrosion resistance and the ability to withstand high internal pressures and bulkhead joint bending stresses must be maintained. The lightweight composite material is effective to provide both characteristics while exhibiting a lightweight characteristic. The shape memory rings 22,24 are effective to provide high compressive forces to join the dissimilar materials to provide a fluid-tight hermetic seal between materials not amenable to material fusion, e.g., welding.

In FIG. 2, there is shown another example of the present invention wherein a lining material, e.g., stainless steel is used within the shell 2 to provide additional corrosion resistance. The lining material is in the form of a shallow cup 30 holding the first bulkhead 4 and a second shallow cup 32 holding the second bulkhead 6. The leads 12 and 14 are arranged to pass through the bulkhead 6 and through openings 34 and 36 in the second liner cup 32. Glass-to-metal seals 38 and 40 are located around the wires 12,14, respectively and are arranged to electrically isolate the leads 12,14 from the second cup 32. The remainder of the structure shown in FIG. 2 is similar to that found in FIG. 1 and described above including the shape memory rings 22,24.

Accordingly, it may be seen that there has been provided, in accordance with the present invention an improved canister for withstanding high internal pressures and bending stresses at bulkhead joints while exhibiting a lightweight structure.