GB706406A - Improvements in and relating to pressure butt welding apparatus - Google Patents

Abstract

706,406. Welding. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Dec. 3, 1951 [Sept. 1, 1950], No. 21581/50. Class 83 (4) In a pressure butt welding apparatus comprising a hydraulic press wherein the application of pressure to the work is automatically controlled by the thermal expansion and subsequent shortening of the work, one set of elements attached to the work remote from the joint or to a part movable to follow dimensional change of the work and another set attached to a relatively fixed part of the apparatus control hydraulic means to apply after a low initial pressure, firstly a higher intermediate pressure to overcome thermal expansion and secondly a final high pressure to make the weld. In one embodiment two short tubes 4, 4 are placed between a fixed part of a frame and a hydraulic ram 3. An electric motor driven constant delivery pump 1 supplies oil to the ram 3. An adjustable relief valve 2 and normally open solenoid operated valves 6, 6A are supplied from the supply line to the ram 3, the discharge from the valves 6, 6A being controlled by bleed valves 8, 8A to a tank 9 which keeps the pump 1 free. A water cooled oxyacetylene burner 10 which may be oscillated about the tubes 4, 4 is moved with the ram 3 by means of a rack 20 attached to the ram 3 and acting on a pinion 19 secured to the burner 10 and the burner, 10 is supplied with fuel from a solenoid operated valve 11. Micro switches 7A, 7, 12 and 25 on a fixed part of the frame which operate the valves 6A, 6, 11 and the motor of the pump 1 respectively are actuated by contact with abutments 28A, 27, 27 and 28 attached to the ram 3. In operation with valves 6, 6A open and thus low pressure applied to the ram 3, heating of the tubes 4, 4 causes expansion thereof causing actuation of switch 7A and closing of valve 6A to apply intermediate pressure to the ram 3. On returning to the original position the switch 7 is actuated to close valve 6 and thus apply final high pressure determined by relief valve 2. Then operation of switches 12, 25 causes closing of oxyacetylene valve 11 and stopping of the pump 1. In a modification an apparatus for welding long pipes comprises three hydraulic pressure units comprising rams fixed to an end plate and cylinders attached to a further end plate slidable on the rams. The tubes are held in the end plates. Movement of the burner and operation of the controlling switches is in a manner similar to that in the first embodiment A solenoid operated gas valve and mixer for the oxygen and acetylene is described.