GB557021A - Improvements in electric seam welding machines - Google Patents

Abstract

557,021. Electric welding. BRITISH INSULATED CABLES, Ltd., and BROUGHTON, R. B. July 15, 1942, No. 9817. [Class 83 (iv)] In a resistance seam welding machine of the kind having upper and lower roller electrodes between which the work is traversed by positively rotating the upper electrode, a cycle of operations effected automatically after initiation by pressing a pedal &c., comprises the application of pressure to the work by the upper electrode, and when the pressure reaches a predetermined value, a pressure controlled device sets in operation the drive to the upper electrode and effects the switching-in of the welding current and when the work has travelled forward the desired amount it activates a device which stops the travel, cuts off the welding current, relieves the welding pressure and lifts the upper electrode to permit the work to be removed. Arms 3, 4 extending from a pillar 1 carry respectively the electrodes 12, 7. The arm 4 is in the form of a U-shaped trough supplied with water to keep the electrode 7 cool and connected to one of the terminals of a transformer secondary 6. The electrode 12 is supported in the forked lower end 13 of a vertical slide 14, is coupled by a flexible conductor 15 to the other transformer terminal and is positively rotated by bevel gear 23, 21, through cordon joints 22 and through spur gear 19, 20, clutch 18, and speed reduction gear 17 from a motor 16. The slide 14 is connected to a pneumatic piston 25 controlled by a solenoid-operated valve 27 connected to a reducing valve 49 associated with a lubricator 50 and adjusted by a hand wheel 49 as to a pressure as indicated on a gauge. The work such as a metal drum 9 is placed over a pair of guide bars 10 of insulating material secured to the arm 4 by adjustable brackets 11 and separated by bridge pieces 31 in which is connected a spring-controlled rod 32 provided with an adjustable stop 34. The control circuit 37 contains a switch 38 which is onened by the end of the rod 32 when the end of the work pushes forward the stop 34. The circuit 37 contains a push-button switch 42 located in the front of the arm 3 so that the machine mav be stopped at will In operation the circuit 37 is closed by a pedal operated switch 36 so as to energize solenoid 39 and so close contactor 40, A locking circuit 41 independent of the switch 36 is thus completed and a solenoid 28 is energized to operate the air valve 27 to admit air to the upper end of the cylinder 26. When the air pressure reaches a predetermined value a spring-loaded switch 29 adjustable by a knob 30, is closed by the air pressure so as to energize a coil 44 to close contactor 45. A circuit containing a solenoid 47 is thus energized to operate the clutch 18 and so start rotation of the electrodes and at the same-time the primary circuit of the welding transformer is closed direct or through a relay circuit 48 actuating a timing device. When welding is completed the limit switch 35 is opened by the rod 32 to open contactor 40 and thus de-energize the solenoid 28 to operate the valve 27 so as to lift the electrode 12. The switch 29 is thus opened to cause the contactor 45 to be returned to throw out the clutch 18 and open the circuit 48. When the work is removed the switch 35 again closes. The position of the piston 25 relatively to the slide 14 is adjusted by a screw 52 so as to give the smallest gap for insertion of the work. The electrodes may be rotated continuously or intermittently within the latter case reduction of the flow of current between the electrodes during rotation. The motor 16 may be controlled by the solenoid 47 instead of using a clutch. The piston 25 may be returned by a spring instead of by air pressure.