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Top drive well drilling apparatus

  • US 4,421,179 A
  • Filed: 01/23/1981
  • Issued: 12/20/1983
  • Est. Priority Date: 01/23/1981
  • Status: Expired due to Term
First Claim
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1. Well drilling apparatus comprising:

  • a mast or derrick;

    a drilling unit including an element adapted to be connected to the end of a drill string for rotation therewith about the axis of the string, and a motor operable to drive said element and the connected string rotatively about said axis;

    a pair of elongated first guide rails;

    a pair of shorter second guide rails forming lower extensions of said first rails;

    a carriage by which said drilling unit is carried and engaging said rails for movement therealong between an upper position of guided engagement with said first rails and a lower position of guided engagement with said second rails;

    pivotal connection means mounting said first rails near their upper ends for swinging movement of said first rails and said second rails and said carriage and carried drilling unit relative to said mast or derrick between drilling positions in which said carriage and drilling unit are guided by said first and second rails for movement along said axis of the drill string and inclined positions in which the first and second rails extend at an angle to said axis and guide the carriage and drilling unit for movement along an inclined path at an angle to the axis for access to a mousehole; and

    a connection mounting at least one of said second rails to a corresponding one of said first rails for movement therewith between said drilling and inclined positions, and for swinging movement relative thereto with said carriage and drilling unit to move the drilling unit from an active position of alignment with said axis to a retracted position at a side of the axis.

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