GB418171A - Improvements in and relating to furnaces - Google Patents

Abstract

418,171. Metal - heating furnaces. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Jennings, J. H. ; 2905, Brooklyn Avenue, Fort Wayne, Indiana, U.S.A.) Feb. 26, 1934, No. 6198. Convention date, Feb. 28, 1933. [Class 51 (ii).] In a furnace for heating metals in a selected atmosphere, the gas constituting the atmosphere, e.g. hydrogen, is supplied continuously during the heating process and means are provided for admitting an additional quantity of gas while the furnace chamber is opened for charging or discharging and for a, predetermined time after the furnace has been again closed. The invention is described as applied to an electricallyheated furnace having a heating chamber 13, with restricted end passages 13<a>, 13b and a cooling chamber surrounded by a water jacket having supply and discharge connections 23, 24. The charges 27, supported on trays 28, are inserted and removed by elevators 30, 31, a ram 41 being provided at the charging end to push the trays through the furnace on roller tracks 26. The elevators 30, 31 are actuated by fluid pressure motors 32, 32<a> which are interconnected with a motor for the ram 41 to provide a predetermined cycle of operation. The main supply of hydrogen or other gas to constitute the furnace atmosphere is admitted at the end of the cooling chamber through pipe 43, a hand-operated valve 44 in which is adjusted to provide, when the furnace is closed, a continuous current from the inlet 43 to a " burn-off " 45 at the charging end. The additional supply of gas is admitted at the junction of the heating and cooling chambers through a pipe 46<a> having a hand-operated valve 47 and an automatic valve 48 which is normally maintained closed and is fitted with an electric control responsive to the operation of the elevators 30, 31 and of a timing device 70. When either of the elevators is lowered by retraction of the piston rod 40 or 40<a>, the switch 55 or 56 is opened to break the energizing circuit for an electromagnet 54 and allow the valve 48 to open under the action of spring 52. On movement of the elevator to its closed position, the abutment 66 or 67 on the piston rod 40 or 40<a> closes a switch 62 or 63 which initiates the operation of the timing device 70 by energizing electromagnets 71, 72 and establishing holding circuits therefor. The magnet 72, together with a disc 80, constitutes the motor of the timing device and the worm 81 operated by this motor is moved into engagement with a worm wheel 82 when energization of the magnet 71 attracts the armature 73. The movement of this armature, in addition to establishing holding circuits for the magnets 71, 72, also moves a resilient member 74 to break the contacts 75 and to engage a switch arm 76 which is rigidly held in the open position by a latch 78. This latch is released, after the predetermined time interval, by a pin 83 on the wheel 82 and the arm 76 moves to close the contacts 77 thus de-energizing the magnets 71, 72 and returning the parts to initial position. Closing of the contacts 75 by the member 74 re-establishes the energizing circuit for the magnet 54 and thus the valve 48 closes. Specifications 241,883, [Class 38 (v)], and 353,062 are referred to.