GB709184A - Improvements relating to the extrusion of metal - Google Patents

Abstract

709,184. Extruding. BRITISH INSULATED CALLENDER'S CABLES, Ltd. July 4, 1951 [July 5, 1950], No. 16817/50. Class 831 (4) In the extrusion of aluminium or aluminium alloy or other metal through a die from a hot billet, part of each billet which contains defective material is diverted from the die and discarded during the whole or part of the extrusion stroke. As applied to a press for producing tube, the container 10, Figs. 1 and 2, for a billet 2 is mounted within a liner 11 heated by tubular electric heaters 14 and the liner is located in a shell 12 secured by bolts 13 to a table 5 carried by the ram 6 of a hydraulic cylinder 7. The billet is extruded through an annular passage 18 in the die 19 when the container is raised against a stationary plunger 4. The die 19 ;s mounted in a holder 15 forming a continuation of the container 10 and having an annular step 24 provided with holes 25 through which the defective material is discarded. A bolster 16 which supports the die 19 has enlarged holes 26 normally m line with the holes 25 but may be rotated by a hand or power-operated worm 28 to bring the holes 25, 26 out of line. To allow rotation of the bolster 16 hydraulic pressure is admitted to a piston 31, causing pins 33 passing through arcuate slots in the bolster to raise the holder 15 slightly against the tension of bolts 13. Rotation of the bolster during extrusion allows defective material to be discarded at the beginning and end only of each stroke and closing of the holes 25 by the bolster severs the discard. The area of holes 25 and the time during which they are open are arranged so that the amount of discard is from 5 per cent to 25 per cent of the billet. The extruded metal enters the passage 19 through three ports 23 and an annular recess 22 which surrounds the mandrel 20. For extruding a sheath on a cable, the mandrel is hollow and may have cavities for circulation of coolant, the plunger 4 being annular. In a modified press the bolster 65, Fig. 6, is locked by a wedge 68 movable transversely to the axis of the die 64 by a hydraulic plunger 70 and is rotatable by a hydraulic plunger 77 to bring the holes 73 into or out of line with holes 72 in the die. The bolster 16 of Fig. 1 may be operated hydraulically and that 65 of Fig. 6 by a worm gear. The shell 55 for the billet-container 52 is mounted with freedom for radial expansion in a stationary casing 55b, and the ram 63 is carried by a crosshead 60 operated by a hydraulic plunger 59. The press of Fig. 6 may also be adapted for sheathing cables. The step.24, Fig. 2, limits the extruding stroke by engaging the ram and also assists in working the metal during extrusion ; this working may also be assisted by placing an apertured plate in front of the die. To assist in expelling defective metal and prevent trapping of air or gases, the ends of the extruding ram and the billet are made convex and concave with different radii of curvature so that contact commences at the centre and moves progressively outwards, and the forward end of each billet is also made concave or convex to act similarly with the residue in the container. In operation, with the outlet from the holes 25, Fig. 2, closed, a hot billet is acted upon by the ram so as first to fill the holes 25 and then be extruded through the die 19. The ram is stopped before completing its stroke, withdrawn to allow insertion of a new billet, and the outlet from holes 25 is opened so that the next stroke of the ram will eject the discard from the first billet and also if necessary, the forward end of the new billet. The ram is then withdrawn slightly to relieve pressure on the metal, the bolster 16 is rotated to close holes 25 and sever the discard which has already been ejected, and the ram again advanced to extrude most of the billet through the die. The ram is then withdrawn, the bolster rotated to open holes 25 and a new billet inserted for the next stroke.