| 摘要 |
774,929. Joint-making packing. WILLS, P., and WILLS PRESSURE FILLED JOINT RING, Ltd. Jan. 12, 1956 [Jan. 12, 1955], No. 1013/55. Class 122 (3). A gas-filled joint-ring 23 is made from thermoplastic synthetic material, such as polytetrafluoroethylene, by introducing a gas producing substance into a split ring of the material, clamping the ring in a mould with its ends 24 abutting, heating the mould until the ends fuse together and further heating to decompose the contents of the ring and produce gas under pressure therein. The mould is formed by metal discs 11, 12 and steel rings 17, 18 each having quadrantal grooves co-operating to form an annular groove in which the ring is clamped as shown and the mould is heated in an oven to a temperature of from 360‹ to 400‹ C., sufficient sodium azide having been inserted in the ring to produce an internal pressure of about 350 pounds per square inch when decomposed. Specification 696,684 is referred to. |
