Patent GB-770548-A (GB)
Title: Improvements relating to apparatus for electrical induction heating
Inventor: TIBBS CHRISTOPHER EVAN MUNDELL
IPC: H05B6/02
Filed: 1954-07-30
Abstract: 770,548. Induction heating. RADIO HEATERS, Ltd. Oct. 25, 1955 [July 30, 1954], No. 22321/54. Class 39(3)  High frequency heating apparatus for hardening the journals and crankpins of crankshafts comprises a number of split-inductor heating coils arranged in parallel rows to receive two crankshafts, As shown, each heating coil consists of a lower half 7 fixed to an insulating base 9, and an upper half 8 hinged at 10 to supports 11, 12 also fixed to the base 9, each half including two semiannular plates 13, 14 or 16. 17 insulated from each other.. A channel 36 for quenching water extends round the major portion of the coil and is open round its inner periphery for the escape of water, the amount of water escaping being limited, however, by splash guards 38. When the top half of the coil is lowered and pressure applied to overcome the effect of a compression spring, a circuit is completed through the coil via contacts 26, 27 and 28, 29, current being supplied froin a generator unit to'copper bars 23, 24 which are cooled by passage of water through copper pipes 53, 55 soldered to them and which are positioned between two rows of coils contained within a housing 49; each coil is connected to the bars by means of conductors 25, 34. In using the apparatus, two crankshafts are placed in the lower halves of the coils, the upper halves then being  lowered and a timing unit set in motion. The timing unit includes for each coil a programme unit containing a number of cams driven by an electric motor, the first cam, i.e. the first to operate in a heating and quenching cycle, causing operation of an air ram 44 to press together, by a roller 39 on a bell-crank lever 40, the halves of the coil, and to connect the coil across the copper bars 23, 24. The second cam then switches the output of the generator unit to the bars 23, 24 and the journal or crankpin within the coil is heated. After a predetermined period, when the journal or crankpin has reached the Curie point, causing a modification of its electrical properties, a third camoperates to rematch the output circuit of the generator by shorting out a series coil. When the heating is completed, a fourth cam switches off the generator and switches on the quench water supply. After a further period, a fifth cam turns off the water supply and operates the air ram to withdraw pressure from the upper half of the coil, thus allowing it to be open-circuited; the cam also starts the next programme unit in operation. When the cycles of operation are completed for all the coils the crankshafts are changed over, so that the remaining journals and crankpins can be treated. In a modified form, one pair of current supply bars is provided for each row of coils, the timing unit being modified such that the coil to be closed is chosen from the two rows alternately and current is passed through one coil while quench water is supplied to the coil surrounding the journal or crankin which has just been heated. The air ram 44 and bell-crank lever 40 may be connected to the upper half of the coil such that when the latter is lifted to the position shown in Fig. 1 when the lever 40 is withdrawn. Single-turn coils of the split-inductor kind may be used in place of the two-turn coils. In a further modification, Figs. 7-9 (not shown), ejector arms operated by an air ram facilitate insertion and removal of the crankshafts.