Patent GB-1250901-A (GB)
IPC: B21D26/12
Filed: 1968-06-19
Abstract: 1,250,901. Making electrodes; hydroelectric forming; drawing. K. INOUE. 19 June, 1968 [28 June, 1967; 28 Aug., 1967; 2 Sept., 1967; 9 Nov., 1967; 10 Nov., 1967], No. 29175/68. Headings B3A, B3P and B3Q. [Also in Division B5] A method of forming a metallic or other plastically deformable workpiece by means of a shock wave produced by an electrical discharge comprises superimposing the shock wave on a column of liquid propelled across a gas-filled space into force-transmitting relationship with the workpiece. Apparatus for carrying out the method and forming an electrode for electrochemical or electro-erosion machining which may be protected by an elastomeric membrane (not shown), comprises a chamber 11c, Fig. 1, against which the die 13 is held by hydraulic clamps 14C, 14C<SP>1</SP>. Dielectric fluid, e.g. transformer oil, is supplied from a tank 15 to the clamps and also to a tubular electrode 11 which is adjustable angularly for training against different parts of the workpiece. A jet of liquid is forced by a pump 15b against the workpiece at a velocity of 100-10,000 m/sec. and spark-induced shock waves superimposed thereon. The jet may be pulsed by a timer T synchronizing the sparkswitch 16C and a valve 15i connecting an accumulator 15j with the liquid input line to the electrode 11. A pair of plates may be formed simultaneously, one to be used as a sampleforming electrode and the other a finishing electrode. In a modification, Fig. 2, a shock wave generated in a lower chamber 21b by adjusting an electrode 22b to reduce the gap 22c is transmitted to the workpiece 20 through a flexible or flangible diaphragm 21e, a secondary body of liquid, e.g. water, and a rubber &c. membrane 20a. A succession of shock waves may be applied to the workpiece. The secondary liquid may be contained in a cup-shaped flexible member (30b), Fig. 3 (not shown), within a tubular workpiece (30) which it expands into a plurality of surrounding die-cavities 33(a). A modified container for secondary liquid of the type shown in Fig. 2 comprises a concave metalfoil diaphragm (41e), Fig. 4 (not shown). Modified secondary liquid containers of the type shown in Fig. 3 are disclosed in Figs. 5 and 6 (not shown). In another apparatus, Fig. 7, utilizing an air-gap 57g, a jet of dielectric liquid may be pumped from the central, hollow electrode 72b, which is adjustable by rack-andpinion gearing, or the column of liquid may be propelled only by spark discharge. A housing 71 for this assembly may be pivotal to direct the forming effect, and a rubber membrane may overlay the workpiece 70. It is stated that the annular electrode produces a magnetic field which increases the energy of the shock wave, and that at least one such electrode and at least one central electrode are desirable. Another example, Fig. 8 (not shown), uses a ring electrode (82a) and a die with chambers (83a) for a tubular workpiece (80). The electrodes may be made of silver-tungsten alloy, and the discharge is triggered by the introduction of an electrolyte, a metal powder or a wire through ports (86c) into the gap between the electrodes. A further form, Fig. 9, uses a metal wire, screen or (as shown) a foil-electrode 92a, which may be used as a partition between two liquids, the fail being perforated by the spark and producing particles of relatively high mass for increasing the transferred energy. Extruding and drawing.-A ring of shockforming guns 101a, Fig. 10, each supplied with a high-velocity stream of liquid through a pipe 105a and with spark-discharge electrodes, direct jets against a tubular workpiece 100 to reduce its diameter. The workpiece is filled with sand &c. and advanced by rollers 107a- 107c. A two-stage arrangement may be used, Fig. 11 (not shown), in which the guns are contained in a housing (111) for collecting the jetliquid.