| 摘要 |
360,552. Annealing. HEVI - DUTY ELECTRIC CO., 4100, Highland Boulevard, Milwaukee, Wisconsin, U.S.A.-(Assignees of Smalley, E. L. ; Whitefish Bay, Wisconsin, U.S.A.) Sept. 2, 1930, No. 26196. Convention date, Sept. 3, 1929. [Class 72.] In furnaces for magnetizable metal through which the metal is positively and intermittently fed either by a flexible conveyer or by a pusher acting upon the rearmost of successive charges a magnetic flux is passed through the metal by a primary coil during the heat treatment and the loss of magnetic properties occurring at the critical temperature is utilized to bring about automatic movement of the metal from the heat treatment position, the progress of the heating being indicated by a galvanometer in circuit with a secondary coil. As shown the charges 1 are moved through the furnace chamber 3 on a conveyer 2 driven by an electric motor 4 and are adapted to be aligned with opposite pole members 6, 7 of a magnetic circuit 5. A primary winding 30 on the polepiece 7 energized from a line 31 establishes a field through the furnace chamber and until the critical temperature is reached the flux energizes a secondary coil 11 on the polepiece 6 connected to a solenoid 10 which opens the circuit of the motor 4 at 8. When the flux decreases due to change in the magnetic properties of the charge the switch 8 is closed starting the conveyer 2 to move the charge 1 out of the furnace or to a position for further heat treatment, the next charge 12 taking its place. The circuits are balanced preparatory to heating by a variable reactance 25 and a galvanometer 19, Fig. 3, having its moving coil 23 connected in series with the variable reactance, the secondary coil 24 and the solenoid 10 while its field winding 20 is connected across the supply line 21 for the primary coil 22. When the charge is introduced the reactance 25 is adjusted to obtain a predetermined balanced position of the galvanometer pointer and movement from this position advises the operator of the progress of the heating.
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