GB1399321A - Induction heating - Google Patents

Abstract

1399321 Induction heating PARK-OHIO INDUSTRIES Inc 19 Jan 1973 [27 March 1972] 2977/73 Heading H5H In induction heating apparatus for conical valve seats of the type disclosed in copending Specification 1,387,751 a detector is provided to ensure that when the carrier supporting the heating inductors 20, 22 is moved towards the engine blocks, the inductors engage their respective valve seats B, C and when the carrier has been retracted to set the desired air gap between the inductors and the valve seats, the inductors are all disengaged from their valve seats. Identical detector circuits 70, 72 are provided for the inductors. Each detector circuit comprises a transformer primary winding, e.g. 210 series connected to a relay coil 232 and a supply 230, and a secondary winding 214, one side of which is earthed, and the other side of which is connected to the inductor 20. When the inductor 20 physically engages the valve seat B which is earthed, the impedance of the secondary circuit is reduced thereby reducing the imped ance of the primary circuit sufficiently to energize relay 323. This energization of relay 232 causes illumination of indicator lamp 240, and energization of a clamp circuit 244 which locks the inductor 20 to the carrier. When all the inductors contact their respective valve seats the retract control 250 is energized to space the inductors a desired distance from their valve seats. During the retracting movement of the carrier the detectors are de-energized. When the carrier is in its retracted position the detectors 70, 72 are again energized and should one of the inductors still be in contact with its valve seat, due for example to a faulty clamp, one of the inductor lamps is illuminated and the commencement of the heating cycle is prevented.