A method, an apparatus and an extrusion die of producing by extrusion electroweldable pipe sockets and electroweldable fittings of thermoplastic materials thereby using a first pipe part formed in a first extruder

摘要

Electroweldable pipe sockets and fittings by forming a first tube (1) being internally sized and cooled and on the outer side provided with a groove (2), having preferably a raised edge part (2a), winding an electrical conductor (3) in the groove, and the outer side of the first tube with electrical conductor (3) is coated with plastics (4) thereby maintaining the internal size of the first tube (1) by internal cooling and sizing. In this continuous process the speeds of the first tube (1) and of the continuous tube (1, 3) leaving the coating extrusion stage are equal. In the coating extrusion stage a negative pressure is maintained between the first tube (1) and the coating (4) to be applied. An apparatus for producing the electroweldable sockets or fittings comprises a first extruder (5) for forming a first tube (1), a grooving roller (29) for forming a groove (2) with raised edge (2'), cooling means (1') for internally cooling and sizing tube (1), a first drawing device (7) for feeding the first tube (1) to a coating extruder (6), means for generating a vacuum (24) in the head of the coating extruder (6), and a cooled drag piston (13) for maintaining the size of the first tube in the coating extruder, a cooling station (17), another drawing device (8), a measuring and controlling system (18) for controlling the speeds of the first tube (1) and completed tube (1, 3, 4), and a station (19) for dividing the shaped tube (1, 3, 4) into sockets or fittings. An extrusion die of the coating extruder (6) is provided with a mandrel (20) being disposed in a guide bush (21) with a vacuum connection (24), said guide bush being surrounded by a cooling jacket (22), and the guide bush (21) is fastened in the mandrel (20) by the thermal insulating rings (23, 26).