| 摘要 |
The extruded plastic-aluminium compound pipe (1) for installations has a reinforcing layer of aluminium foil (4) between a plastic inner tube (2) and a plastic outer layer (3), which both consist of the same plastic, for example of a PP random copolymer according to type 3 DIN 8078. The inner tube (2), the aluminium foil (4) and the outer layer (3) have an overall wall thickness which is less than that of a tube of the same plastic without aluminium foil, the wall thickness of the plastic outer layer (3) accounting for approximately one quarter of the overall wall thickness. Before the polyfusion welding of the plastic-aluminium compound pipe (1) with fittings or moulded parts (8), the plastic-aluminium compound pipe (1) is peeled off in diameter to below the aluminium foil (4) from the end over a length of only about 5 mm, a frustoconical transitional face (7) being formed up to the outside diameter of the outer layer (3). The electrically heatable tool for welding comprises a heating bush (9, 9') for heating the peeled-off end of the compound pipe (1) and a heating spigot (10, 10') for heating the fitting or moulded part (8). In this case, the bore of the heating bush is inwardly reduced (13, 15) in diameter, and the heating spigot is reduced (14, 16) in a corresponding way in the outside diameter towards the end. The reduction may in each case be conical (13, 14) or graduatedly cylindrical (15, 16). <IMAGE> |
