Patent GB-560837-A (GB)
Title: Improvements in or relating to induction heating apparatus
IPC: H05B6/06
Filed: 1942-03-23
Abstract: 560,837. Cooling systems. BUDD INDUCTION HEATING, INC. March 23, 1942, No. 12589 /43. Convention date, March 21, 1941. Divided out of, 560,630. [Class 64 (iii)] [Also in Groups XI and XII] The machine for heating workpieces by electromagnetic induction described in Specification 560,630 is controlled by the system shown in Fig. 8 which provides that power is applied to the heating coil only when a workpiece has been moved into the coil to engage an abutment operating a switch. When water is admitted to the cooling circuit, water pressure switch 235, thermal switch 230a controlling a heater 232 which heats the water-cooling system of the work-supporting rails to a temperature preventing condensation, thermal and flow switches 230, 231 associated with the, remaining cooling-water circuits are all closed and indicating lamps 247 illuminated. The relays 239, 242a are thereby energized and their contacts 240, 243 closed, which completes the circuit of the preliminary control line 241 governing the heat control relay 250. Contacts 251 of switch 174 remain closed while a workpiece is not placed in the machine. Relay 250 closes contacts 253, 254 and control line 242 is ready to be energized through contacts 244 when these are closed by relay 243a which is energized by the workpiece-actuated switch 174. Simultaneously, relay 243a opens its contacts 251, so that if heat-control relay 250 becomes de-energized and its now-closed locking contacts 253 opened, the relay cannot again be energized till the workpiece has been removed. The closing of the furnace door closes three micro-switches 203, 204, 205, switch 203 only momentarily. Pilot relay 255 is energized through circuit 257, 259 and - normally closed contact 260 of relay 275, and pulls up its contacts 261, 256, locking itself by the latter through contact 204. When the sequence-controlling switch 262 closes contact 263, current passes through 264, 267 to the starting relays 266 of a pair of timers 265 which operate through a predetermined heating cycle. Relays 266 pulling up, transfer potential from 267 through contacts 274 so that motors 269 of the timers and relays 271 are energized. The latter through contacts 277 in series close the circuit to contactor relay 275 which is energized through closed contacts 205. It pulls up its contacts, opening 260 and releasing pilot relay 255 which cannot be operated till another cycle is started, thereby releasing the sequence controller from connection with the timers till the machine has been reloaded. Relay 275 simultaneously closes contacts 282, 285, to rectifier 280 which supplies direct current to magnet 283 and closes contacts 286 to energize the heating coil 40, which continues till motors 269 complete their cycle..At this point contacts 274 move from points 270 to 273, relays 266 remaining locked. The timer motors stop, relays 271 are de-energized, and contacts 277 opened to de-energize relay 275 and open contacts 282, .285. Power is cut-off from heating coil 40 at switch points 286. Contacts. 279 are closed by relays 272, completing circuit to the door-latch solenoid 200 and releasing the furnace door which opens under its spring pressure and opens contacts 204, 205. The heated workpiece may then be removed by pedal-operated mechanism, opening the switch 174, de-energizing relay 243a, opening points 244, and unlocking timer relays 266 at contacts 268. The timers cannot be re-started till relays 266 are unlocked. The signal lamps 247 indicate . the correct functioning of the various operations. If the heating circuit be interrupted by any cause, relay 250 comes into operation and ensures that the machine must be unloaded and re-loaded before it can be re-started. Timers 265 may be operated chronometrically or thermometrically.