GB812305A - Method and apparatus for heating metal work, particularly non-ferrous metal work - Google Patents

Abstract

812,305. Continuous metal heating furnaces; gas-fired combustion apparatus. BRITISH FURNACES Ltd. Dec. 4, 1956 [Jan. 23, 1956], No. 37060/56. Classes 51 (1) and 51 (2). A continuous furnace for heat treating brass billets comprises a rotary hearth 22 sloping towards a discharge shoot 41 and formed with Spaced grooves supporting the billets 40, radial pipes 64 extending from a manifold 63 over each groove except at a charging station 70 and formed with nozzles directing hot gases downwardly at high velocity over the billets, a cylindrical combustion chamber 50, and a flue opening 66. Air is supplied to the combustion chamber from a jacket 56 through tangential ports 54 in which are disposed gas burners 52. A pipe 58 supplies steam which passes with the burnt gases through the manifold 63 and pipes 64 and which prevents scaling of the billets. The hearth 22 is rotated step-by-step to bring each groove in turn up to the charging station 70 by a pawl 95, Fig. 8, engaging spaced lugs 68 and actuated by a pneumatic cylinder 91 through a piston rod 92 and a sliding plate 94 to which the pawl is pivoted at 96. Each time the hearth stops, a latch 113 operated by a pneumatic cylinder 111 and piston rod 116 engages a lug 68 to lock said hearth. The charging mechanism 25 comprises a pneumatic cylinder 71, Fig. 5, a piston rod 72 to which is attached a tray 73 supported on rollers, and a stripper bar 77 pivotally supported by a member 78 and actuated by another pneumatic cylinder 80. In operation, one or more billets 40 are placed on the tray 73 which is pushed into the furnace displacing treated billet or billets from a groove into the discharge shoot 41, the stripper bar is lowered, and the tray 73 is retracted leaving its load in the vacant groove. The hearth is then rotated to bring the next loaded groove opposite the charging opening 70, and the latch 113 actuated to lock it in position. Automatic operation.-The various operations are performed automatically and in sequence by a pneumatic control system, Fig. 12, comprising an air supply line 130 connected to fourway valves 133, 146, 153 and 161 which respectively control the pusher cylinder 71, the stripper cylinder 80, the index cylinder 91 and the lock cylinder 111. Solenoid-operated valve 131 is momentarily opened by timer 132 supplying air through line 134 to operate valve 133 forcing pusher rod 72 forward on a charging stroke. As the rod moves, a tang 143 closes a relief valve 140 and, at the end of its stroke, opens valve 141, admitting air to valves 146 and 153 through line 144. It also opens valve 142 bleeding off air through the line 134 and causing valve 133 to reverse and retract the rod 72. Air admitted to valve 146 through line 145 rapidly operates said valve causing stripper cylinder 80 through pusher bar 87 to rotate stripper bar 77 into position, where it stays until tang 143 again opens bleeder valve 140 at the end of the outward stroke of the pusher rod 72. Air admitted to valve 153 through line 152 causes index cylinder 91 to retract the rod 92 closing bleeder valve 170 and, at the end of its stroke, opening valve 171 admitting air to valve 161 through lines 158 and 160. Valve 161 causes locking rod 116 to retract, operating limit switch 166 and causing solenoid-operated bleeder valve 167 to open, thus releasing air from line 152 and causing the rod 92 to extend again. As said rod moves forward, it shuts off air from line 158 by valve 171 and, having moved the hearth, in its forward position, it opens bleeder valve 170. Air being thus released from line 160, valve 161 operates, restoring rod 116 to lock the furnace hearth and actuate limit switch 166 again. Bleeder valve 167 is thus closed, preventing forward movement of rod 92 while the hearth is locked, and completing the cycle of events. A check valve 172 in line 152 prevents air from bleeding through valve 140 when the rod 72 is retracting, movements of the hearth being thus made dependent on the lock cylinder only.