Patent GB-1265915-A (GB)
IPC: F16L47/30
Filed: 1970-04-16
Abstract: 1,265,915. Seaming non-metallic sheet material. ROHREN-KELLER A.G. 16 April, 1970 [23 Oct., 1969], No. 18282/70. Heading B5K. [Also in Division F2]  A pipe branch joint of thermoplastic material, e.g. polyethylene, is made by heating a portion of a main pipe 3 sufficiently to soften the material in at least the annular zone in which a branch pipe 1 is to be attached to the pipe 3, heating an end portion of the pipe 1 sufficiently to soften the material thereof, urging the softened end portion of the pipe 1 towards and into the softened zone of the pipe 3 to cause a bead to form around the section of mutual contact and applying pressure to the pipe 1 substantially in the direction F of the longitudinal axis of the pipe 1 in such manner that the material of the beadis displaced in a direction perpendicular to the longitudinal axis and that material of the pipe 1 is displaced in a direction parallel to the longitudinal axis so that the curvature of the boundary line between the parts to be joined is increased, whereby the cross-sectional area of the weld is increased, Fig. 8. In one embodiment, the end of the pipe 1 is so shaped as to fit on the pipe 3 and is applied to a cylinder (4), Fig. 2 (not shown), of the same diameter as the pipe 3 and heated either electrically or by gas to 200‹ C. Simultaneously, the pipe 3, whilst laid on a support 6 and reinforced by an aluminium cylinder 7, is heated to 200‹ C. by an element (8), Fig. 4 (riot shown), having an end (9) corresponding in shape to the end of the pipe 1. A die P is used to apply pressure to the pipe 1 and comprises an outer aluminium sleeve 11 and an inner steel sleeve 12 non-rotatably connected by a screw 14 and a pin 15. The lower edges; of the sleeves 11, 12 are shaped as shown in Fig. 8. The die may be preheated to 50‹ C. by a heating element 16. The pressure applied to the die P is such as to cause the pressure in the weld zone to be between 10 and 100 kilograms per square centimetre and is maintained for 5-10 seconds. After removal of the die P, a cutter (20), Fig. 9 (not shown), is inserted into the pipe 1 to cut out a portion (21) of the pipe 3. In a modification, Fig. 12 (not shown), for use when the branch pipe is inclined relative to the main pipe the inner and outer sleeves of the die are inclined relative to the base thereof. In another embodiment, Fig. 13, a die which can be used for pressing the pipe 1<SP>1</SP> on to the heating element and on to the softened zone of the main pipe, comprises sleeves 27, 28 of aluminium and steel, respectively, the sleeve 28 having a closure 29 provided with a flange 30 through which a connecting ring 31 and the sleeve 27 are joined to the sleeve 28. A push rod 34 acts on a rod 41 which when pushed downwardly pivots detents 36 against the action of a spring 39 so that retaining lugs 36<SP>11</SP> are drawn inwardly. In operation, with the rod 34 retracted, the branch pipe 1<SP>1</SP> is introduced as far as the abutment 36<SP>11</SP>, hooks 36<SP>111</SP> being pushed in and then swinging out to hold the pipe 1<SP>1</SP>. The pipe 1<SP>1</SP> is then held against a cylindrical heating element so that the length of pipe projecting beyond the sleeves 27, 28 is heated to welding temperature and broadens laterally, Fig. 16 (not shown). The pipe 1<SP>1</SP> is pressed by the die on to the main pipe 3<SP>1</SP> which has been heated simultaneously with the pipe 1<SP>1</SP>. Pressure is exerted to displace the rod 34 to pivot the detents 36 and release the pipe 1<SP>1</SP> and to move the sleeves 27, 28 towards the pipe 3<SP>1</SP> to form a beaded weld, Fig. 20 (not shown).