GB887139A - Improvements in or relating to apparatus for the manufacture of electric resistance welded tubing - Google Patents

Abstract

887,139. Welding by pressure. STEWARTS & LLOYDS Ltd. July 4, 1960 [July 17, 1959], No. 23286/60. Class 83 (4). An impeder assembly in or for apparatus for pregressively forming tubing by high-frequency electric resistance welding, comprises an elongated rod 20, a tube 30 of material of high magnetic permeability and not subject to high eddy currents or hysteresis losses telescoped on the rod, a sleeve 35 of dielectric material telescoped over the tube, means for directing coolant over at least a portion of the surface of the tube inside the sleeve and guide means 40, 45 secured to the rod to maintain the rod aligned within the tubing. The assembly is positioned within gapped tubing whose edges 11 are heated by current of the order of 450 kc. per second and pressure welded together at point 15 by rollers 37. A stainless steel pipe 16 is threaded into a socket 22 on one end of the rod 20, of bronze, connected at its other end to an inside bead trimmer (not shown). The tube 30 of bonded powdered iron with longitudinal grooves in its outer surface is telescoped over rod 20 and the sleeve 35 of fibreglass or silicone rubber is held on the rod by a ring 36. A guiding nylon sleeve 40 is secured to the pipe 16 and a guiding sleeve 45 with longitudinal grooves 47 is secured to the rod 20 at the end of the tube 30. In operation, water or oil is supplied to pipe 16 to flow through ports 25 in the socket 22 and between the tube and sleeve. In a modification the bronze socket is separate from but screwed to the bronze rod and the tube of bonded powdered iron is spaced radially from the sleeve of fibreglass or silicone rubber so that the coolant flows in an annular space between the tube and sleeve.