Patent GB-1484728-A (GB)
Title: Electroerosion machining
IPC: B23H7/10
Filed: 1974-08-13
Abstract: 1484728 Electrolytic machining FUR INDUSTRIELLE ELEKTRONIK AGIE LOSONE BEI LOCARNO AG 13 Aug 1974 [15 Aug 1973] 35670/74 Heading C7B [Also in Division B3] For electroerosion or electrolytic machining of a hole in a workpiece having a starting bore 9, a  drive and guide assembly dispenses a filamentary electrode from a supply on one side of a workpiece, feeds it automatically to and through the bore and into a take up device of the assembly. Wire or tape electrode from a supply reel 73 is driven by a roller 75 through guides 76, 77 and a flushing nozzle 771 to a bore 9 in the workpiece 5. Guides 77a, 741, flushing nozzle 772 and take-up rollers 79 are disposed on the take up side of the workpiece. The electrode may be stiff enough to be fed into the take-up rollers 79 by the roller 75. If not, a gripping device 13 is lowered to bring pivotable arms (132, 133), close to the workpiece and the arms execute a sweeping movement to grip the electrode between them, Figs. 9a, b (not shown), and the device is raised to introduce the electrode into the roller 79. Between the dispensing and take up rollers there may be a holding and cutting device 10, holder 11, a device 12 for connecting electrode lengths between the cutting of successive holes in the workpiece or a device 15 combining 10 and 12. In the Fig. 3 arrangement, when a hole (8) Figs. 2a or b (not shown), has been machined, devices 10 and 11 are moved into the solid line working position and actuated. The device 10, Fig. 14b, comprises gripping pliers 143a, b and a pivotable blade 151 actuated by a wedge 145 with fluid cylinder, rack and pinion 171, 172 or electromagnetic drive. The device 11 comprises two pairs of gripper jaws 185 on an adjustable shaft 187, Fig. 17a, actuated by an electromagnet 181 via a lever 183 with a return spring 186. After the electrode has been cut by knife 151, the jaws 185 are opened and the 'old' electrode is raised by the rollers 79 until the trailing end has passed the lower pair of jaws 185. A sensor (189) Fig. 17 (not shown), which was pressed against the electrode between the jaws now opens a contact (189c) which stops the rollers 79. The workpiece and electrode are relatively repositioned for machining a new hole. The leading end of the 'new' electrode is pulled through the new bore by the gripping device 13 until the electrodes overlap. As jaws 300, 301, Fig. 18c, of connection device 12 are moved towards the electrodes a wheel 302 is moved towards them from the opposite direction, a spike 303 which it carries going between the electrodes. The wheel 302 is then rotated to twist the wires which are now clamped by the jaws. Alternative connection devices comprise soldering means (Figs. 19a-d) and cam-actuated pliers (503) which clamp a metal clip 518a about the wires, Figs. 20a-c. In the Fig. 4 arrangement, an elongated portion of a gripping device 13 passes through the bore 9 and enters a bore (152) in a holder and cutting device (10), Figs. 15a-c. The electrode is inserted between spring arms (139a) of the device 13, Fig. 10 (not shown), and is clamped when the arms are drawn up into a sheath (139b). The combined holding cutting and joining device 15 of the Fig. 5 arrangement comprises pliers and a knife similar to the device 10 of Fig. 14b but having a bore (163), Fig. 21, into which is inserted a still further form of gripper device 13, that of Fig. 12 or Fig. 13 (not shown), to position the 'old' electrode adjacent the 'new' which is held by the pliers 143a, b. A further bore 168 extending longitudinally of the pliers houses another such gripper which is advanced to grip both wires, retracted somewhat, and rotated to twist the electrodes together. In the Fig. 6 arrangement, the holding and cutting device 10 and connection device 12 are on the take-up side, and no gripper 13 is needed as the electrode is fed through a threading nozzle 81-83 by a fluid jet (84) as far as the rollers 79. When the electrode is cut, the old end is held by device 10 and a roller 91 mounted on a piston 92 deflects the electrode below the nozzle to remove it from the old bore. To prevent the core being cut out by the electrode from tilting or falling out of the workpiece, an adhesive, e.g. a metal alloy or a cement including electrically conductive additives, is injected at intervals along the path followed by the electrodes. A control system 1 fed by punch cards, magnetic tape &c. controls drive motors 3 for positioning  the electrode relative to the workpiece so as to form holes of the desired contour during machining and motors 3a for actuating the devices 10-15 &c. It also supplies a machining voltage to leads 121, 121a. Using a lesser voltage, the electrode may be used as a probe to initially position the workpiece and locate the bores 9.