Welding method and tubular member and gear pump made using the welding method

Abstract

A gear pump having an inner rotor and an outer rotor is covered by a cylindrical outer casing and side casings. The cylindrical outer casing has two outer circumferential edges which are welded over the entire circumference thereof to the outer edges of the side casings, respectively. The outer casing has two angularly spaced recesses in its inner periphery for receiving slide seals therein. Welding is started at a welding start point which is 90 degrees spaced from the middle point between two recesses. During welding, welding energies are applied to the welding start point and the middle point between two recesses. Those energies tend to deform the casing into oval shapes that are 90 degrees out of phase from each other. Thus, these energies cancel each other, thereby preventing the casing from being deformed.

Dependencies are inferred from the claim text.