Surface coating device of core body

Claim 1

Apparatus for providing a synthetic resin coating on an elongate cylindrical article comprising an extrusion body having an extrusion chamber and an extrusion opening, said extrusion opening and chamber being adapted to receive an elongate article to permit passage thereof through said chamber and out through said opening, said chamber being provided with synthetic resin inlet means for feeding extrudable synthetic resin to said chamber; a fixed die mounted outside said chamber opening in fixed position relative thereto and having a fixed die orifice axially aligned with said chamber opening for permitting passage of said elongate article therethrough, said die orifice being sized to provide an extruded resin coating on said elongate article and being provided along its length with a plurality of grooves in its surface extending from one end to the other of said die orifice; and a moveable die mounted between said chamber opening and said fixed die, and having a moveable die orifice axially aligned with said chamber opening and said fixed die orifice permitting passage of said elongate article therethrough, said moveable die orifice being sized to provide an extruded resin coating on said elongate article and being provided along its length with a plurality of grooves in its surface extending from one end to the other of said moveable die orifice and which, upon rotation of said moveable die, can be brought into and out of alignment with the grooves in said fixed die; said grooves in said moveable die orifice surface being in flow communication with said extrusion chamber whereby resin in said extrusion chamber flow thereinto; whereby, when said grooves in said moveable die orifice surface are in alignment with said grooves in said fixed die orifice surface, said resin will flow into the grooves in said fixed die orifice surface and thus form a plurality of projections of resin spaced circumferentially about the resin coating extruded onto an elongate article passing through said die orifices; and whereby, when said grooves in said moveable die orifice surface are out of alignment with said grooves on said fixed die orifice surfaces, said resin will not flow into the grooves in said fixed die orifice surface thus interrupting the formation of said resin projections.