Method for fabricating a lead screw made of synthetic resin material and having a core tube therein

Abstract From the Canadian patent

To reduce the need for manual work, improve productivity and reduce the fabrication cost in the method for molding a lead screw for converting a rotational movement into a linear movement there are, provided a method and a die assembly which may involve the steps of forming a plurality of holes in a wall of a tube in a spiral arrangement, preparing a metallic die assembly provided with a cavity defining a thread groove adapted to form the thread crest matching in position with an array of the holes, placing the tube in the cavity, and injecting synthetic resin material into the cavity so that the synthetic resin material may flow in two separate flows, one flowing inside the core tube, and …