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Drilling rig

  • US 4,478,291 A
  • Filed: 03/01/1982
  • Issued: 10/23/1984
  • Est. Priority Date: 01/08/1982
  • Status: Expired due to Term
First Claim
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1. A drilling rig comprising:

  • a mast,(b) a top drive adapted to be moved vertically along the mast,(c) a hydraulic cylinder having one end linked to the bottom of the mast, and having its other end extending toward the top of the mast parallel to the axis of the mast,(d) a lifting pulley rotatably fixed to the other end of the hydraulic cylinder,(e) lifting chain means having one end fixed to the top drive passing over the lifting pulley and having its other end linked to the bottom of the mast,whereby upon extension of the hydraulic cylinder, the lifting pulley rises, causing the chain to lift the top drive, said other end of the chain exerting tension against the bottom of the mast and said one end of the hydraulic cylinder exerting pressure against the bottom of the mast, the lifting force thus being exerted against the bottom of the mast, andfurther comprising;

    (f) a first pulley rotatably fixed to said other end of the hydraulic cylinder,(g) a second pulley rotatably fixed to the top of the mast,(h) a third pulley rotatably fixed to the bottom of the mast,(i) a cable having one end fixed to the top of the mast, passing under the first pulley, passing over the second pulley, passing under the third pulley, and having its other end fixed to the top drive, whereby upon contraction of the hydraulic cylinder, the cable is pulled downward by the first pulley, the cable pulling the top drive downward, the hydraulic cylinder further drawing down the lifting pulley, allowing the top drive to draw down the lifting chain means.

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