摘要 |
653,211. Pipe joints. UNITED STATES RUBBER CO. Oct. 18, 1948, No. 26981. Convention date, Jan. 14. [Class 99(i)] [Also in Group VIII] A sheet of polyethylene is formed into a cylinder and a longitudinal lap joint formed therein. Two such cylinders may be joined together by lapping them telescopically and uniting the circumferentially lapped edges. Both the longitudinal and the circumferential joints are made by heating the material at the interface to a temperature of not less than 5‹ C. below and not more than 15‹C. above the melting point of the polyethylene while subjecting the lap joint to mechanical pressure, preferably such that the material flows so that the thickness of the joint is less than the sum of the thicknesses of the sheets being joined and is at least equal to the thickness of either of said sheets. The melting point is defined as the temperature at which the crystalline phase disappears as determined by the disappearance of the X-ray diffraction pattern. The time of heating may be controlled according to the thickness of the material, and the joint may be subjected to controlled cooling (see Group VIII). |