GB544322A - Improvements in and relating to electric resistance welding apparatus - Google Patents

Abstract

544,322. Welding. MALLORY METALLURGICAL PRODUCTS, Ltd. (Mallory & Co., Inc., P.R.). Jan. 29, 1941, No. 1191. [Class 83 (iv)] In an electric resistance welding machine the welding electrodes are cooled by a fluid expansion type refrigerating system the fluid expansion passages of which are within the electrodes. The necessity for thermal insulation of parts of the machine is avoided since the electrodes are cooled below room temperature as is also the tendency for the electrodes to stick to metals such as aluminium. The machine may be provided with reciprocating or wheel electrodes of copper, silver or alloys thereof. The electrodes 52, 28 are respectively carried in holders 13, 14 in a fixed arm 11 and in a spring retained pedal operated pivoted arm 12. The holders are connected to but electrically insulated from metal hoses 30 which are connected to the header 22 through which the expanded refrigerant fluid such as ammonia returns to the compressor 24 via a normally open valve 23. The compressor is connected by pipes 25 cooled by a water spray 26 to a storage tank 27 which is connected by a valve 55 with hoses 33 centred by coil springs within the hoses 30. The other ends of the hoses 33 are connected by couplings 34 to pipes 36 which are normally pressed into contact with the bottom of the recess 37 in the electrodes by plungers 40 fixed to spring-pressed sealing diaphragms 43 and having rods 44 connected to adjustable rocker arms 46 which are pivoted to the part 42 and connected by cables 47, 53 to the pedal lever 16. When the pedal is pressing the electrode 28 is forced against the work, the welding switch 21 is closed and the plungers 40 raised so that the compressed liquid refrigerant raises the pipes 36 and expands within the recesses in the electrodes so as to cool the tips thereof. The recesses have helical or longitudinal ribs 38 to increase the surface of the electrode in heat exchange relation with the refrigerant. The electrode holders and hoses 30 may be provided with a layer of heat insulation. The expansion valves may be disposed at the top of the pipes 36 or at an intermediate point instead of at the bottom. Valves may be provided for connecting circulating water to the hoses 30, 33 in place of refrigerating liquid. The refrigerating system may be located at a distance from the machine if desired and a single system may be connected to a number of welding machines. The compression type refrigerator may be replaced by-one of the absorption type.