Ring forming machine

Apparatus for the production of annular articles from elongated workpieces of thermoplastic material, the elongated workpieces having a first and a second end, comprising:

• a. a base,
• b. a first clamp moveably attached to the base and adapted to grasp the first end of the workpiece,
• c. a second clamp moveably attached to the base and adapted to grasp the second end of the piece, the elongated workpieces having a longitudinally-directed concave groove and each of the clamps including a protuberance of shape corresponding to the groove and positioned to engage the groove when the ends of the workpiece are held by the clamps,
• d. a heating plate moveably mounted on the base and having first and second opposed, parallel surfaces,
• e. positioning means for presenting the first end of the workpiece to the first surface of the plate,
• f. a manipulator which causes the second clamp to present the second end to the second surface of the plate,
• g. means moving the plate from between the ends when they have been heated, and
• h. a gaping means for moving the second clamp away from the heating plate a short time before the plate is moved from between the ends, the second clamp being pressed toward the plate by a cylinder and the gaping means momentarily introducing into the cylinder pressure medium of a substantially different value.