Process and apparatus for making helical coils from thermoplastic material

Claim 1

APPARATUS FOR MAKING HELICAL COILS OF THERMOPLASTIC ROD, WHICH COMPRISES A MANDREL ROTATABLY MOUNTED AT ONE END AND HAVING IN THE AXIAL DIRECTION AWAY FROM SAID END A SHARPLY TAPERING PORTION FOLLOWED IMMEDIATELY BY A PART OF CONSTANT CROSS-SECTIONAL AREA AND A SECOND PART OF CONSTANT CROSS-SECTIONAL AREA WHICH IS LESS THAN THE CROSS-SECTIONAL AREA OF SAID PART, A HOLLOW MEMBER PARTLY ENCLOSING SAID PART OF CONSTANT CROSS-SECTION AND PROVIDING THE OUTER WALL OF AN ANNULAR SPACE FOR THE PASSAGE OF THE HELIX, SAID WALL SERVING TO LIMIT TRANSVERSE EXPANSION OF THE HELIX, THE INNER WALL OF SAID SPACE BEING THE OUTER SURFACE OF SAID PART OF CONSTANT CROSS-SECTION, THE INTERNAL CROSSSECTION OF SAID HOLLOW MEMBER BEING OF THE SAME SHAPE AS THE CROSS-SECTION OF SAID PART, MEANS FOR ROTATING THE MANDREL AND THE HOLLOW MEMBER AT THE SAME ANNULAR SPEED IN THE SAME DIRECTION, MEANS FOR RECIPROCATING THE HOLLOW MEMBER AXIALLY DURING ITS ROTATION, AND MEANS ACTUATED BY THE RECIPROCATION ROD FROM THE PART OF THE MANDREL TURNS OF THERMOPLASTIC ROD FROM THE PART OF THE MANDREL IN WHICH THE CROSS-SECTION IS SHARPLY DECREASING ON TO AND ALONG THE PART OVER WHICH THE CROSS-SECTION IS CONSTANT, AND THROUGH SAID ANNULAR SPACE.