GB1292290A - Forming hollow workpieces - Google Patents

Abstract

1292290 Electrohydraulic forming SIEMENS AG 29 Oct 1969 [15 Nov 1968] 53048/69 Heading B3Q [Also in Division H1] Electro-hydraulic apparatus for forming tubular work 18, Fig. 1, comprises a spark-gap formed between an electrode 15 and a pressure permeable housing 11 which provides a return path for the current to a capacitor battery 111 and fits within the workpiece 18. An ignition wire 17 may be used between the electrodes and may have a non-vaporizable core as described in Specification 1,241,313, to which reference is made. The housing-electrode has an insulating base 14 connected to the top 12 by metal bars 13, between which the shock waves, transmitted through water, strike the brass, aluminium or steel workpiece 18. The housing may shield parts of the workpiece where no forming is required, and a surrounding restricting cylinder may be used. Non-circular workpieces may be formed. Water may be supplied through the electrode 15. The ignition wire 17 may be fed from the electrode 15 to the top 12, or in the opposite sense if a supply roller is provided on or in the plate 12. In another construction, Fig. 2, the wire is supplied from a reel 21 on the base 26 and passes through a passage 29 in one of the bars 23, water being supplied through a passage 230. For shorter workpieces, Fig. 3 (not shown), adjustable electrodes (35, 35<SP>1</SP>) are used without a bridging wire. A housing-electrode (41), Fig. 4 (not shown), may be used for workpieces (48) of different lengths if a clamping collar (411) is used. As applied to forming curved tubes 58, Fig. 5, perforated, insulating guides 512 are used having metal bushes 513 re-receiving the wire 57. A plastics or rubber envelope may separate the housing and workpiece, and it is stated that the housing may be used if the forming pressure is generated by an explosive.