Patent GB-605777-A (GB)
Title: Improvements in or relating to apparatus for heat-treating metallic strip material, particularly tin-coated steel strip
IPC: H05B6/02
Filed: 1943-10-20
Abstract: 605,777. Automatic control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Oct. 20, 1943, No. 17291. Convention date, Jan. 20. [Classes 38 (iv)] [Also in Groups II and XXXVI] In apparatus for heat-treating metal strip and specially tin-coated steel strip by means of inductive heating coil means, energized by high-frequency current, at least part of the coil means is immersed in a liquid bath through which the downwardly-moving strip passes, and upward circulation of the liquid being maintained in that portion of the bath through which the strip moves. The relation between the rate of electrical energy input into the strip and the speed of the strip is varied by regulating means, such as a light sensitive scanning means, a wattmeter and relay circuit or a thermostat. A metal strip 4 is fed through roller 12 and passes into a container 14 holding a quenching liquid 15, e.g. palm oil and provided with legs 16, 17, the leg 16 being restricted as at 18. The strip passes through induction heating coils 21, 22, 23, 24, to which power is supplied by an oscillation generator 27, such as described in Specification 568,463, [Group XL], the coil 21 being disposed above the level of the liquid 15, and each coil being provided with its own insulating shield or liner 25. The liquid is circulated in the container 14 by a pump 35 which supplies liquid to the bottom part 13 of the bath from a tank 36, the liquid returning from the container 14 by any one of the pipes. 37, 38, 39, 40 provided with electrically-operated valves 41, 42, 43, 44, and passing through a heat exchanger 47, where it is cooled before returning to the tank 36. The quantity of the liquid in the tank 36 is controlled by a float switch 51 connected to an electrically-operated valve 50 in a pipe leading from a tank 49 into the exchanger 47. To maintain a substantially quiescent body of heated liquid in the upper part of the leg 17; some of the oil in the upper part of the vessel 19 passes, into the upturned end 61 of a pipe 53 and is driven by a pump 54 operated by a motor 57 controlled by a thermometer vane 59 or other detecting means for the flow of liquid in the leg 17 past a heater 65 into the latter. If palm oil is used as the quenching liquid, its temperature must be kept at over 100‹ F. preferably at 130-150‹ F. A wattmeter W is responsive to the input of a transformer 31 deriving its power from a threephase supply line 32 through a breaker &c. 33, the supply being controlled by a regulator 34. The wattmeter is provided with a regulating solenoid 63 energized from a pilot generator PG mechanically connected to a motor M responsive to the speed of the strip and has a make contact 65 and a break contact 66 for energizing, respectively, a breaking winding 67 or a boosting winding 68 of a regulating motor which obtains its power from a relaying bus 71. A second or alternative regulator in the form of a reflecting light scanning device is provided by a light source 73, Fig.. 3, which sends through a pipe 77 a beam of light at approximately' right angles to the strip 4, the dispersed light from the matte surface of the coated strip reaching a photo-electric cell through a pipe 78 arranged at an angle to the pipe 77, both pipes being provided with electrically-operated valves 79, 80. The cell 73:controls a relay 82 having a make-contact 83 and a break-contact 84 both energizing, respectively the boosting winding 68 and the. breaking winding 67 of the motor 69. By means of a switch 82 either the conductor 86 connected to the contacts 65, 66 of the wattmeter circuit or a conductor 88 connected to the contacts 83, 84 of the relay 82 are energized. The rate of electrical energy input into the strip 4 and the speed of the strip are regulated by the induction regulator which thus controls the temperature of the strip. This temperature control can be accomplished either by changing the rate of heating or the speed of the strip or both simultaneously. In. a modification, the induction heating means is formed as a single coil having a single insulating shield and the regulating means is formed by a thermostat encircling the strip below the induction coil in the place of the photo-electric cell. Specification 605,776 also is referred to.