Patent GB-910741-A (GB)
Title: Improvements relating to batch-type controlled-atmosphere heat-treatment furnaces
Inventor: WATSON ERNEST FRANCIS
IPC: F27B9/04
Filed: 1957-10-02
Abstract: 910,741. Heat-treatment furnaces. EFCO FURNACES Ltd. Jan. 2, 1959 [Oct. 2, 1957], No. 30896/57. Class 51 (2). A gas or electrically fired radiant-tube horizontal batch-type furnace for the heat-treatment e.g. carburizing of metal workpieces in a suitable gaseous atmosphere of controlled composition and temperature comprises a purge chamber 1, Fig. 1, a main heating chamber 2 and a heated storage compartment 4 of L-shape which forms a holding chamber 22 and a lock chamber 24, Fig. 2, at right angles thereto having metal heatconducting walls. Pneumatically operated vertically sliding doors 3, 5, 13, 25, 26 maintain an endothermic gas mixture within the chambers which is introduced therein through pipes 30, 34 and circulated by fans 31, 35. The door 5 is gas tight to allow heating of the chamber 2 without effecting conditions in the compartment 4, and the exit doors 13, 26 have bleeder holes which allow the gas to escape to the outside air to ensure a continuous supply of fresh gas. A flame curtain of burning gas is formed over each exit on opening the doors 13, 26 to inhibit the entry of outside air into the furnace. The chamber 2 and compartment 4 are heated by vertical radiant tubes 40, 41, 42 supplied with gas from points 43, 44 which are controlled by valves (not shown) operated by temperature controllers (not shown) whose sensitive elements are thermocouples 47, 48 mounted in the roofs of the chambers. Each batch of workpieces 12 is divided into portions and loaded on to separate charge carriers 15 which are supported on a common supporting grid 16 which rests on and can be moved along a two-track roller conveyer 14 which extends longitudinally through the furnace. Each carrier 15 is slid off the grid 16 transversely to the length of the conveyer 14 along an auxiliary roller conveyer 64 which transports the individual loaded charge carriers 15 one at a time from the grid 16 through the lock chamber 24 to the exit door 26, while the carrier 16 continues along the conveyer 14 and is discharged through an aperture 50 and tube 51 with a trap door 52 and associated flame curtain on to a trolley 67. A tube 54 lies between the tracks of the conveyer 14 and has a continuous slot in its top surface for a chain 55 driven by a motor 58 and a mechanism 56, 57 at the front and rear of the furnace respectively so that a dog 59 engages a projection 60 on the grid 16 to pull the grid from the chamber 2 along the conveyer 14 into the chamber 22 and through trap door 52. Drawbars (not shown) are used to push the grid 16 into the heating chamber 2 and the individual carriers 15 into the lock chamber from the storage compartment 22. A batch may be removed after purging in chamber 1 for treatment in an upper part 69 with water-jacketed steel walls which acts as a slow-cooling chamber, or for treatment in a lower part 70 which contains an oil bath for quenching by means of a two-deck elevator 71, which is pneumatically raised or lowered so that a portion of roller conveyer 14 and a section of the tube 54 or that deck which lies in the normal position lies flush with the remainder of the conveyer 14 and tube 54.