Patent GB-1240154-A (GB)
Title: Hydrostatic extrusion of compound material
Inventor: BURSTROM MARTIN
IPC: B21C23/00
Filed: 1968-09-26
Abstract: 1,240,154. Extruding; jointing by stamping; making wire; making bus-bars. ALLM€NNA SVENSKA ELEKTRISKA AB. 26 Sept., 1968 [27 Sept., 1967; 15 March, 1968], No. 45783/68. Headings B3A, B3P and B3Q. A billet for hydrostatic extrusion into a sheathed wire comprises a core 12 of one material and a casing 13 of another material which are combined so that axial forces arising from the different resistances of the materials are transferred between the core and casing. The core is preferably aluminium or an aluminium alloy and the casing copper or copper alloy. The core must be sealed to the casing to prevent hydrostatic fluid, e.g. castor oil, entering therebetween. In one embodiment, Fig. 3, an annular groove 14 with a sealing ring 15 is used. A second groove 16 is also provided and the casing forced into the groove by isostatic pressure either in the extrusion pressure chamber or in a separate chamber or by rolling. Alternatively, the end of the billet is sealed by an elastomeric plate (19), Fig. 4 (not shown), with a flange which tightly fits around the casing or a steel plate may be welded or soldered to the casing. In a further embodiment, Fig. 5 (not shown), the core is recessed relative to the casing and an elastomeric plate (21) resiliently held against the core. The plate 23 may be metal, Fig. 6, and welded or soldered to the casing. In a further embodiment, Fig. 7 (not shown), an L- cross-section sealing ring (26) of elastomeric materials seals the billet. In a further embodiment, Figs. 8 (not shown), a plug (31) with a sealing ring (29) is used. The plug or the core is recessed to define a groove for the casing to be pressed into. The rear face of the core may be recessed, Fig. 9, to receive a complementary projection 40 on the plug 36. All the cores of the above embodiments may have either annular locking grooves or one or more helical locking grooves. The casing is preferably tapered at the forward end, Fig. 4 (not shown), and preferably extends over the conical tip 60. After extrusion the portion of the billet left in the die can be used as the tip of the next billet. The casing 13a, Fig. 6, of the new billet is welded or soldered to the old casing 13b and the new core 12a pressed into its casing to contact the old core 12b. The mating surfaces of the cores may be shaped to co-operate, Fig. 9, or a peg 43 of core material is used. The peg may be threaded, Fig. 7 (not shown), or be double frusto-conical, Fig. 8 (not shown). The casing and the core must be cleaned, for example by pickling in hydrochloric acid, before assembly. The core and casing may also be sandblasted. It is preferable to anneal the remaining portion of the old billet before jointing to soften the copper casing. In an alternative form of billet, Figs. 10 and 11 (not shown), a rigid end plate (61, (62) is used to combine the core and casing and the joint between the plate and casing sealed by an elastomeric ring (64) or plate (66). Any of the billet end constructions of the earlier embodiments can be combined with this sealing. arrangement. A hydrostatic press for producing copper clad aluminium wire comprises an operating cylinder 50, Fig. 12, and a high pressure cylinder 3. The high pressure cylinder comprises a steel cylinder (4), Fig. 2 (not shown), with a sheath (5) of high tensile tape to pre-stress the cylinder. The billet 11 and die 10 are inserted into the press and the cylinder moved rightwards. Hydraulic fluid is pumped into the space 55 to move the billet supporting piston 54 to the right. The piston is freely movable in the cylinder 3 and has a built-in overflow valve through which the fluid flows with a pressure drop. After extrusion the wire may be drawn or rolled into flat bus-bars.