Abstract: A machining head carries at its end a sensor comprising a pressure-sensitive element (4) mounted on the parts (1, 2) holding the injector jet for the machining fluid, as well as the buffering pieces (5, 6, 12) forming a shield. The element (4) is an insulating and watertight tube, arranged to form a ring in the space left between the coaxial, truncated conical surfaces of the parts (1) and (2). It contains conducting parts which come into contact with one another when it is deformed by the action of a pressure whose value exceeds a given threshold. This results in the closing of an electrical circuit which transmits an appropriate signal to the controls of the EDM machine in order to interrupt the relative movement of the head. The device enables any shock or abnormal stress acting on the end of the machining head to be detected. By means of an O-ring seal (7) acting as a hinge, the part (1) and the piece (12) are returned to their original positions when the stress disappears.

Abstract: Machine for cutting by electrical discharge machining includes an electrode wire tensioned between and running betwee two guide heads each of which is mounted on an arm, one at least of the arms passing through a hole in one of the walls of a tank. The tank can move with respect to the arm and contains a machining liquid. A sealing plate 1 masks the hole in the tank and is linked by at least one seal 4 to the arm 5 through the wall. The wall 2 of the tank through which the arm passes slides along this plate. To prevent the forces due to friction and pressure arising between the plate 1 and the wall 2 and between the seal 4 and the arm 5 and acting asymmetrically on the arm through the wall being transmitted to the arm 5 and causing its deflection, a sheath 6 is mounted between the seal 4 and the arm 5 and encloses this arm without coming into contact with it.

Abstract: The device has a case (1) which has a wire guide (2) and a chamber (4) filled with machining liquid which is brought there under pressure by a pipe (7). A nozzle (5) in the shape of a truncated cone fits in the case and closes the chamber (4) in its normal working position by supporting its periphery on the flange (6) provided around the case (1), under the action of the pressure exerted by the dielectric liquid and if necessary by a return spring (8). The thrust exerted on the nozzle by an obstacle (10) during a lateral collision tilts the nozzle without damaging it and it causes at L an escape of liquid which causes the pressure to drop in the chamber (4). A transducer (13) signals the drop in pressure following the collision to the operator and/or to a control system of the erosion machine.

Abstract: A method and apparatus for automatically rethreading the electrode wire of a traveling wire EDM apparatus through a pair of close tolerance wire support and guide members, one disposed on one side of a workpiece and the other on the other side of the workpiece, and for threading the end of the wire through a starting aperture in the workpiece. Prior to threading or rethreading the wire, the wire is heated in a heating zone while a pull is exerted on the wire such as to elongate the heated portion of the wire to reduce its diameter. After cutting off the wire at the beginning of its reduced diameter portion, the reduced diameter portion of the wire is threaded through the wire guide members and the aperture in the workpiece. The threading of the wire is effected by a feed mechanism disposed upstream of the first wire guide member which preferably is the same mechanism as the brake mechanism effecting a pull on the wire during normal operation of the EDM apparatus.

Abstract: A method and apparatus for threading the electrode wire of a travelling wire EDM apparatus through an aperture in a workpiece. Prior to automatically threading the wire through the aperture in the workpiece, the wire is continuously straightened by pulling longitudinally on the wire, and the wire is passed through a guide tube and through a nozzle to which fluid under pressure is supplied for forming a jet stream at the outlet of the nozzle. Prior to a threading or rethreading operation the wire is cut off proximate to the outlet of the nozzle. The nozzle outlet is brought in close proximity to the aperture in the workpiece and the jet stream is aimed at the aperture in the workpiece for guiding the wire through the aperture, while being maintained coaxially by the jet stream.