| 摘要 |
<p>A ring is made from a length of thermoplastic material by gripping its ends by clamps, pushing the ends onto a heating plate reciprocable to a position between the clamps, withdrawing the clamps, withdrawing the heating plate, and maring the clamps together to bond the heated ends together. The ring is provided with a ridge on its inner surface which ridge is engaged by a corresp. recess in each clamp, this sensing to align the ends of the length accurately.</p> |
