GB544754A - Improvements in and relating to welding equipment - Google Patents

Abstract

544,754. Welding. BRIGGS MANUFACTURING CO. Jan. 8, 1941, No. 275. Convention date, Jan. 8, 1940. [Class 83 (iv)] An electric welding apparatus comprises a number of welders having fluid pressure operated electrodes sequentially connected to the source of fluid and a fluid operated welding control switch closed by opening a valve independently of the means for controlling fluid pressure to the electrodes each time fluid is admitted to a welder the switch being opened in timed relation to its closing. A number of groups of fluid-operated spring-returned spot welders, each group consisting of one or more welders 10, are connected by flexible pipes 23 to a number of radial passages 22 in a plate 20, the downwardly extending inner ends of the passages being normally in communication with the interior of an oil &c. tank 24 and successively registering with a passage 25 in the arm 21 of a distributing valve, which is mounted on a hollow shaft 26 rotated by worm gear 29, 30 from an electric motor. The shaft 26 is connected by gearing to an hydraulic pump 28 which constantly charges the passage 25 with fluid so as to operate the groups of welders in succession. The electric-circuit is closed after the electrodes engage the work and is open prior to movement of the electrodes away from the work. The welding contact switch 32 is controlled by a valve 43 opened by a plunger 53 operated by a pegged disc 78 on the shaft 26 either through a lever 81, Fig. 7, or through levers 80, 77 which close a switch in an electric circuit containing a solenoid 70. The valve piston 45 which is normally closed by a spring 51 is provided with a partition 49 engaged by the plunger 53 to open the valve so as to open the passage 47 to a supply of compressed air from the inlet 42 which passes through ports 46 in the bush 44 and a groove 50 in the valve piston. When the valve is opened fluid passes also through a restricted port 55 in the bush and a groove 54 and port 57 in the plunger so as to return the plunger. The fluid passes from the passage 47 through an adjustable needle valve 58 into the chamber 39 of the switch 32 so as to push forward the switch plunger against the action of a spring 40 so that the bridge member 37 engages the stationary contacts 33 to close the welding circuit. At the same time fluid passes through adjustable needle valve 60 into chamber 59 in communication with the switch chamber 35. The area of the switch plunger exposed to pressure in the chamber 35 is greater than that exposed in chamber 39 and when the pressure builds up in the chamber 35 the switch is opened. The chamber 59 also communicates through an adjustable needle valve 63 with a chamber 62 connected by a port 64 to the rear of the valve piston the area of which exposed to fluid pressure is greater than the area acted on by fluid passing through the bore 47. The pressure behind the valve piston builds up until the valve is pushed into its closed position and opens the passage 47 to exhaust port 65 through passages 66 in the bush 44 to exhaust the switch.