Patent GB-424190-A (GB)
Title: Improvements in or relating to the heat treatment of metal strip
IPC: C21D11/00
Filed: 1933-05-13
Abstract: 424,190. Hardening, tempering, or annealing metal strip. GILLETTE SAFETY RAZOR CO., 15, West 1st Street, Boston, U.S.A. May 13, 1933, No. 14006. Convention date, May 13, 1932. [Class 72] [See also Group XXXVI] Ferrous metal strip fed at variable speed through heating, quenching, or cooling zones to harden, temper, or anneal it uniformly, is tested by a balanced circuit responsive to the relative magnetic permeabilities of the moving strip and of a standard, the current in the circuit being utilized through relays to increase or decrease the speed of the strip as required. The strip A, Figs. 1 and 3, is unwound from drum 3 on to drum 5 by rollers 6, 7 driven from the electromotor 24 through variable speed gearing consisting of opposed conical rollers 21, 22 connected by a belt 28 which is shifted as required by a fork 29 operated by a reversible electromotor 32. The fork 29 is traversed by a screwed shaft 31 connected to the motor 32 by a chain 34. The strip A passes through an electric induction furnace 1, water cooled quenching plates 10, 11 for hardening, and a second induction furnace 13 for tempering. When thus hardened and tempered, the strip passes through a solenoid 36 by which its magnetic permeability is compared with that of a standard B surrounded by a similar solenoid 37, any differences being utilized to regulate the speed. The primary windings of the solenoids are in series and are supplied with A.C. from the mains e through a switch d, the secondary windings 41, 42 being opposed and connected to an amplifier 43 whereby flow in either direction due to want of balance resulting from differences of permeability is utilized in conjunction with a rectifier 44 to operate the pointer 50 of a galvanometer 49. The pointer is in a central position when the secondary windings 41, 42 are balanced, but engages contacts 51 or 52 when current flows in one direction or the other, whereby the reversible motor 32 is rotated in a corresponding direction by current supplied from the mains 70<1> so as to increase or decrease the rate of feed. If the pointer 50 engages contact 51, a circuit from the mains 57, 58 is completed through coil 59 whereby switch 60<1> is moved against the pull of a spring to connect contacts 61, 62 and also contacts 69, 70. A circuit is thus completed from main 58 through contacts 61, 62 and coil 64 back to main 57 whereby switch 66 closes contacts 67, 68 which in turn complete a circuit from main 58, through contacts 69, 70 coil 55, and contacts 67, 68 to one of the leads 701. Switches 53 are thus closed and the motor 32 is rotated to vary the speed of the strip until balance is restored in the secondary circuit 41, 42 or until a switch a stop member 75, which moves with the fork 29 operating the belt, disengages the switch 66. When the pointer engages the contact 52, a similar series of relays closes the switches 79, 83<1>, 56 whereby the motor 32 is rotated in the opposite direction. In a modification shown in Fig. 4, the opposed secondary windings 41, 42 are connected to the moving coil 90 of an A.C. galvanometer having a field coil 92 connected with an A.C. supply line 94. The moving coil supports a mirror 95, Figs. 5 and 7, by which light from a source 96 may be directed through lenses j, k on to a light sensitive element 100 when the current in the opposed windings 41, 42 flows in one direction. The light is intercepted by the wall 97<1> when the mirror is swung oppositely by current flowing in the other direction. When light strikes the wall 97<1> so that the light cell 100 is inoperative, the switch 104 closes contacts 112, 113 so that current from the mains 108 flows through coil 114, closing switches 115, 120. A circuit is thus completed from mains 108 through switch 66 which in turn completes a circuit from mains L2 through contacts 67, 68, coil 55, contacts 118, 120 to main L<1>. Coil 55 closes switches 53 so that motor 32 is energized from the mains L<1>, L<2>, L<3>. When light strikes the element 100, the coil 109 is energized through an amplifying valve 102, and a transformer 105. The switch member 104 then leaves contacts 112, 113, so that the switches 115, 118 are opened, and also engages contacts 121, 122. The switch member 103 also engages contacts 110, 111. A circuit is thus completed from the mains 108 through coil 83, so as to close contacts 84, 85 whereby switches 54 are closed and the motor 32 is rotated from the mains L<1>, L<2>, L<3> in the opposite direction. The motor 32 is stopped when balance is restored in the secondary leads 41, 42 or when the stop member 75, which moves with the fork 29, operating the belt, disengages either of the switches 66, 83<1>.