Manufacturing process for making tube with thickened wall in central portion has two annular pistons with profiled ends forced toward each other while fluid flows in through holes in outer tube

摘要

The profiled tube (15,16) is made from a tube of constant wall thickness (1) with chamfered ends (13). It is compressed longitudinally during manufacture so that it has a thickened wall in its central portion. The finished tube has a stepped inside diameter formed by the profiled ends (11,12) of two annular pistons (3) forced toward each other (F A). Fluid under pressure (P u) flows in through channels (8) and holes (9) in the outer tube (2) containing the two pistons. The fluid lubricates the outer wall of the tube which remains cylindrical. A rod (5), defining the minimum inside diameter of the tube, fits in the central bores (4) of the two pistons.