Abstract: A thin perforate, helically wound welded edge tubing is used as a filter core for a roving wound filter. The slightly roughened external edges of the spirally formed welded joint greatly adds to the ability of securing the fiber roving to the tube and prevents relative slippage therebetween. Also, the invention comprehends an apparatus for, and a method of making the helically seamed tube by first drawing a sheet metal from a supply and raising two lateral edges thereof to form flanges. The material can be guided in a helical path by engaging the inside of the flanges so that the trailing edge abuts the leading edge. The abutted edges are heated so that the flanges themselves provide the filler for a weld on the exterior surface thereof. Drive rollers are provided to move the welded tube from the welding area and to torque the tube to prevent edge separation prior to the cooling of the weld.

Abstract: A thin perforate, helically wound welded edge tubing is used as a filter core for a roving wound filter. The slightly roughened external edges of the spirally formed welded joint greatly adds to the ability of securing the fiber roving to the tube and prevents relative slippage therebetween. Also, the invention comprehends an apparatus for, and a method of making the helically seamed tube by first drawing a sheet metal from a supply and raising two lateral edges thereof to form flanges. The material can be guided in a helical path by engaging the inside of the flanges so that the trailing edge abuts the leading edge. The abutted edges are heated so that the flanges themselves provide the filler for a weld on the exterior surface thereof. Drive rollers are provided to move the welded tube from the welding area and to torque the tube to prevent edge separation prior to the cooling of the weld.