| 摘要 |
940,319. Moulding sealing rings. THOMPSON RAMO WOOLDRIDGE Inc. Jan. 1, 1962, No. 60/62. Heading B5A. Articles such as sealing rings (see Figs. 5 and 6, not shown) are made by heating a sintered blank of heat-gelable plastics material, e.g. P.T.F.E., which has the characteristic of elastic memory, in a closed die cavity to a temperature above its gel temperature and subsequently cooling the blank and then removing it from the die. A hollow frusto-conical blank 11 of thickness 0.1-0.015 inches is skived from a tube of P.T.F.E. and subsequently shaped, by a punch 13, on the lower die half 12 to a shape illustrated in phantom at 11c. The top and bottom mould halves are then clamped together by clamp 17 and the whole placed in a furnace and heated to 700-1750‹ F. to expand the blank to conform with the cavity. The members are cooled quickly by quenching with a cold liquid after the above temperature range has been reached. The final article is then removed from the die. The die members are metal, preferably chromium plated steel. The die cavity is shaped to form a bead on the inner circumference of the sealing ring upon expansion of the P.T.F.E. when heated (Fig. 4, not shown).
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