Patents Assigned to J-D Equipment Incorporated
  • Derrick counterweight assembly
    Patent number: 5161639
    Abstract: A telescoping derrick has a safety line which is attached to a harness which secures to a worker to be used while climbing the ladder of the derrick. Telescoping tube sections are mounted to the derrick for extension and contraction with the derrick sections. The line is trained over a pulley attached to the crown of a derrick, then passes into the telescoping tube. The line is connected to a counterweight located in the telescoping tube. The line and counterweight remain inside the telescoping tube during rig up and rig down of the derrick.
    Type: Grant
    Filed: December 20, 1991
    Date of Patent: November 10, 1992
    Assignee: J-D Equipment Incorporated
    Inventor: James H. Ice