Tapered helically reinforced hose and its manufacture

A method of making a length of helically externally ribbed plastic tubing with at least a portion of the tubing length changing progressively in diametrical size, including the steps of:

• a) providing a plurality of elongate rods that are canted relative to an imaginary central axis and that converge as the rods approach a wrapping station defined by the rods at a location along the central axis, with each of the rods having a centerline about which the rod is individually turned at a same speed of rotation and in a same direction of rotation;
• b) continuously extruding a hot, tape-like web of thermoplastic material generally toward the wrapping station, with the extruded thermoplastic material also having a longitudinally extending rib;
• c) continuously helically winding the web of the hot, extruded thermoplastic material circumferentially around the plurality of turning rods at the wrapping station to form a continuous tubular wall that advances away from the wrapping station along the central axis, with one edge region of each newly wound convolution of the web overlapping and bonding to an adjacent previously wound convolution of the web to thereby form the continuous tubular wall, and with the rib being integrally connected to and helically wound externally about the tubular wall to provide reinforcement thereto;
• and,
• d) progressively concurrently radially moving the turning rods transversely relative to the central axis during winding of the thermoplastic material at the wrapping station to progressively alter the diametrical size of at least a continuous portion of the length of tubing formed at the wrapping station.