Patent GB-796634-A (GB)
Title: Improvements in or relating to the extrusion of metal
IPC: B21C23/00
Filed: 1955-11-09
Abstract: 796,634. Extruding; forging. STERNBERG, J. DE. Nov. 9, 1955 [Nov. 16, 1954], No. 32090/55. Class 83 (4). A method of extruding metal comprises inserting a cold metal billet 6, Fig. 7, into a container 2 having at one end an extrusion die 27 and at the other end a closure member 13, forcing a pressure medium, such as powdered graphite, at high pressure through a duct 30 into the container bore to exert feed pressure on the billet, and subjecting the billet in an annular zone adjacent the die 27 to radial impact pressures produced by the same kind of pressure medium, but at a higher pressure, forced from cylinders 58, 59 to an annular groove 29, whereby the metal at the forward end of the billet is made plastic and extruded through the die to form an extruded product 26<SP>1</SP>. The rear end of the container is closed by a plunger 13 actuated by an hydraulic piston 14 working in a cylinder block 15 and backed up by a wedge 8. Upon withdrawal of the wedge by an hydraulic piston 9, the plunger is withdrawn and the cylinder block 15 is then raised by an hydraulic piston 20 to permit the insertion of a fresh billet, Fig. 8 (not shown). Pressure medium such as powdered graphite which acts as a lubricant during extrusion is admitted through a non-return valve 46 and pipe 45 into a feed cylinder 42 and is forced therefrom by means of a piston 43 subjected to pressure through pipe 44, into a duct 41. The graphite then passes through non-return valves 39, 40, Fig. 9, into pressure cylinders 33, 34 containing plungers 35, 36 which are operated alternately by hydraulic pistons 47, 48 controlled by change-over valves 55. Plungers 35, 36 force the graphite at high pressure past non-return valves and ducts 31, 32 into pipe 30 leading into the container 2. The position of piston 43 in feed cylinder 42 indicates the feed of the billet. Powdered graphite at higher pressure is forced into the groove 29, Fig. 7, from four radial cylinders such as 58, 59 by plungers 67<SP>1</SP>, 681 which are operated alternately in pairs by hydraulic pistons 661. The graphite is fed into the radial cylinders by an hydraulic accumulator. In this embodiment a second annular groove 78 is also pressurized with powdered graphite from cylinders 79, 80 by means of pistons 81, 82. The latter may lag behind the pistons 67<SP>1</SP>, 68<SP>1</SP> or may operate in advance, Fig. 8 (not shown), in order to provide a seal for the rear end of the nearly expended billet during insertion of a fresh billet. In another embodiment, Fig. 10, for forming a tube 26<SP>11</SP>, a mandrel 84 is secured to the closure plunger 13<SP>1</SP> which is held in position by a screw plug 83. The mandrel has a bore 86 through which a pressure medium, such as powdered graphite, is forced into an annular groove 85 by means of a piston 87 which works in sequence with the pistons 671, 681. The die 27 is held in a dieholder 72 which are removed, to permit insertion of a tubular billet 6 from the front. The die-holder may be removed and returned by hydraulic means. In another embodiment, Fig. 2, the extruded product issuing from'the die 27 passes into a closed two-part die 24, 24<SP>1</SP> where it is pressed into an article 26. The die part 24 is then withdrawn, Fig. 3 (not shown), carrying with it, by adhesion, the article 26 which is fractured off from the extruded bar and is subsequently removed from the die part 24 by an ejector 25. In this embodiment only two forcing pistons 67, 68, Fig. 5 (not shown), feed the annular groove 29. The container 2 is reinforced by shrunk-on sleeves 3 and the various pistons and piston rods are made from sintered material or from " Stellite " (Registered Trade Mark).