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Method for drawing seamless metal tubing particularly copper tubing under inclusion of a floating mandrel and a diameter reducing die

  • US 4,856,703 A
  • Filed: 11/23/1988
  • Issued: 08/15/1989
  • Est. Priority Date: 11/24/1987
  • Status: Expired due to Term
First Claim
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1. Method for drawing seamless metal tubing particularly copper tubing under inclusion of a floating mandrel and a diameter reducing die wherein the wall thickness is reduced under cooperation of the mandrel and of the die in an action zone defined by a drawing gap between the mandrel and the die, there being means to apply a drawing force to the drawn tube downstream from the die, comprising the steps of:

  • connecting a plurality of tubings end-to-end to each other thereby providing a joint in each instance of connection;

    normally and regularly drawing the tubing in portions not having any joint;

    shifting the mandrel away from the action zone of the die as a joint between two of said tubings approaches the mandrel and keeping the mandrel out of the action zone in relation to the die as the joint passes through the die;

    hollow drawing the tubing so that as a consequence of the shifting step, only a portion of the combined tubing including the joint is deformed, for a diameter reduction without concurring wall thickness reduction;

    returning the mandrel to the action zone of the die following passage of the joint through the die; and

    applying a pulling force to resume drawing to be effective downstream from the die but upstream from the joint that just passed through the die.

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