Improvements in and relating to apparatus for cutting or working electrically conductive materials

摘要

768,230. Cutting by spark discharge. SPARCATRON, Ltd. Jan. 27, 1955 [June 3, 1953], No. 15354/53. Class 83 (4). Apparatus for the electro erosion of metals, particularly metal carbides, tool steel and stainless steel by electric spark discharges from a capacitance 3 across a gap between an electrode 1 and workpiece 2, has at least two spark gaps in series in the discharge circuit. One or more additional spark gaps 6, 7 may be provided in a direct current supply circuit, Fig. 5. In an alternating current supply circuit, Fig. 4, an electrode 1 is connected through an additional spark gap 6 with one side of the capacitance 3 and another electrode 10 is connected to the other side. The workpiece 2 is earthed. An inductance 11 may be provided in the discharge circuit and/or in the charging circuit to render the circuit resonant. The additional spark gaps may be air gaps or they may be immersed in a liquid dielectric or electrolyte contained in receptacles 12, 13. Preferably the additional spark gaps consist of tungsten electrodes immersed in paraffin whose dielectric strength has been decreased by a colloidal suspension of graphite, the paraffin being circulated through the gap by a stirring device. Alternatively one or more of the additional gaps may be formed by_rotary interrupter electrodes, Fig. 6 (not shown). Rectifiers may also be included in the discharge circuit. The additional gap or gaps may-have means for automatically maintaining the gap or gaps constant or at predetermined different widths and automatic means may be provided for cleaning the electrodes. In rotary interrupter type gaps the speed of the interruptions may be varied. A protective casing may be provided for the workpiece and/or its electrode and/or the additional gaps and a safety device thereon renders the apparatus inoperative when the casing is out of position. Specifications 637,872 and 756,727 are referred to.