Arrangement for stopping automatically an electric spark eroding machine having its work-performing electrode tool in the shape of a wire or band

Claim 1

In an electrical spark-eroding machine which performs erosion-machining on a workpiece by means of an electrode, of the type comprising: a conductive wire or band for the electrode; a motor means; a receiving reel rotated by the motor means and receiving a supply of the electrode wire or band thereon; and electrical power source supplying power for formation of sparks; means for mounting the workpiece; means for changing the disposition of the workpiece as required; and a device for stopping the machine by interrupting said power source and stopping the functioning of the means for changing the disposition of the workpiece, the improvement being that the device for stopping the machine comprises a supply reel carrying a supply of the wire or band, mounted on a shaft; a further motor means rotating the shaft; an arrangement guiding the electrode wire or band from said supply reel through a working stage, to the receiving reel in such a manner that the torques of said two motor means are in opposition; a mechanism on the shaft including a loose sleeve eccentrically disposed around the shaft and a clutch means on the shaft which couples the sleeve for angular movement with the shaft only in the direction of the torque of said further motor means and not the other; a radial projection on said projection to prevent the Completion of rotation of the sleeve when the latter is engaged by the clutch; and means actuated when said projection abuts said stationary abutment, to interrupt said power source and stop the functioning of the means for changing the disposition of the workpiece, whereby in the event of the wire or band snapping, the torque of said further motor means is not opposed and enables the clutch means to couple said sleeve and said shaft for angular movement to cause the machine to stop.