Patent GB-1396495-A (GB)
Title: Method of joining the ends of thermoplastic members
Inventor: ANSCHUTZ O
IPC: B29C53/00
Filed: 1973-02-09
Abstract: 1396495 Seaming non-metallic sheet material O ANSCHUTZ 9 Feb 1973 [10 March 1972] 6447/73 Heading B5K The ends of thermoplastic members 14 are welded together by placing the whole faces of the ends of the members 14 completely into contact with a heated element 10, Fig. 2, so as to soften the whole thermoplastic material in the region of the ends, preventing outward displacement of the thermoplastic material during softening thereof, removing the ends from contact with the element 10 after occurrence of the desired softening, moving the ends into abutment with one another, Fig. 3, and preventing outward displacement of the softened material while it hardens. In one embodiment, Fig. 2, two hollow thermoplastic members 14 of rectangular crosssection are mounted in holders 25 and are moved into recesses 12 to contact an electrically heated plate 10. The recesses 12 prevent outward displacement of the material of the members 14 during softening. The circumferential surfaces 20 of the recesses 12 are bevelled and opposite sides of the plate 10 are provided with a polytetrafluoroethylend coating 22. The members 14 are retracted and the plate 10 is replaced by a jig 28, Fig. 3, having a passage 30 extending therethrough and having a polytetrafluoroethylene, coating 32. The softened ends 27 of the members 14 pressed into contact in the passage 30 until they harden. The passage 30 prevents an outer bead forming but allows the formation of an inner bead 26. In another embodiment, Fig. 4, of the heated plate, the recesses 12<SP>1</SP> are formed only in part in the plate 10<SP>1</SP> itself. Oute prortions 44 are applied to the plate 10<SP>1</SP> but are separated therefrom by thermally insulating material 46. The bottom walls of the recesses 12<SP>1</SP> have a coating 22<SP>1</SP> of a thermally insulating and non-stick material. In a modification, the portions 44 are made from polytetrafluoroethylene and the material 46 is omitted. In a further embodiment, Fig. 5, the recesses of the heated plate are provided with projections 50 to determine the configuration of the internal beads 2611. In a still further embodiment, Figs. 6 and 7, the heated element comprises an electrically heated plate 10<SP>111</SP> has outer plate elemts 10a hinged thereto at 62 or slidable into and out of engagement therewith. The elements 10a comprise polytetrafluoroethylene portions 60 supported by metal carriers 61. The plate 10<SP>111</SP> has projections 50a which enter into recesses 12<SP>111</SP> in the elements 10a and have circumferentially inclined surfaces 57 to form a groove for shaping the internal bead formed during welding. After welding, the elements 10a are moved out of contact with the plate 10<SP>111</SP> to allow the operator to remove any plastics material adhering to the surfaces 57. In yet another embodiment, Fig. 10, for welding two members 14 whose longitudinal axes are inclined to each other, the heated plate 10<SP>1111</SP> is formed with recesses 12<SP>1111</SP> shaped to receive the inclined ends of the members 14 and is yieldably mounted by a spring 54 urging it to its normal rest position.