| 摘要 |
1,149,716. Seaming non-metallic sheet material. ATLANTIC RESEARCH CORP. 3 March, 1967 [18 March, 1966], No. 10091/67. Heading B5K. [Also in Division H5] A welding coil comprises a plurality of turns of insulated, electrical resistance wire 21 which comprises a sheath 26 of thermoplastic material having a cross-section wherein a first pair of opposed sides 27, 28 is longer than a second pair of opposed sides 30, 31 and a resistance element 22 embedded in sheath 26 such that the distance from element 22 to the first pair of opposed sides 27, 28 is less than the distance from element 22 to the second pair of opposed sides 30, 31. In the coil the wire is oriented with the first pair of opposed sides 27, 28 parallel to the direction along which the turns are serially added, each side of the second pair of opposed sides 30, 31 of each turn abutting against and being fused throughout its length to one side of the second pair of opposed sides 30, 31 of the turn contiguous thereto to provide an integral, self-sustaining coil. Element 22 is of iron, insulation 24 is of enamel such as inorganic ceramics or organic resins such as polytetrafluoroethylene and sheath 26 is of a thermoplastic aliphatic hydrocarbon polymer such as polypropylene. A cylindrical welding sleeve 34 for welding thermoplastic tubing is made by winding wire 21 on a mandrel and simultaneously fusing together adjacent turns by a pointed heating electrode or a heating shoe or by heating the mandrel, to form an integral coil and crossing one end lead 42 over the coil and fusing it to the coil 34, making a smooth outer surface 51 of the coil, insulation 24 preventing the crossed elements 22 from shorting. The coil 34 is placed in the annular gap between a thermoplastic pipe and a larger diameter thermoplastic fitting and an electric current applied to generate heat and weld the pipe, fitting and coil 34 together to form a solid joint. Alternatively, a flat planar pancake welding coil 70 may be made to weld together equal diameter pipes abutting end-on. The shape of sheath 26 is said to make for greater flexibility in the design of welding coils. |
