Vermeer Manufacturing Company, Inc.

Zach Buckley

Robert D Franz

Jacob Rewerts

Jason Morgan

A horizontal directional drilling machine includes a drill string rotational drive unit having an output member configured to connect with and selectively drive rotation of a drill string, the rotational drive unit including a hydraulic motor. A hydraulic circuit has a configuration that puts the motor in a drive mode to apply torque and a second configuration that puts the motor in a freewheel mode disabled from applying torque. The hydraulic circuit includes a first fluid flow path for connecting the hydraulic motor through a first rotary ball valve to one of an inlet side and an outlet side of a drive pump, and a second fluid flow path for selectively connecting the hydraulic motor through a second rotary ball valve to the other side of the drive pump. In the first configuration, there is no pressure drop across the first and second rotary ball valves.

Horizontal directional drill with freewheel mode

A method of controlling a horizontal directional drill having a rotary drive system. The rotary drive system includes a variable displacement pump providing pressurized fluid to a motor, a displacement control that adjusts motor displacement, a torque limiter valve that opens at a torque limit to provide pressurized fluid to the displacement control to allow the system to limit torque, and cross-port relief valves that open at a cross-port relief pressure to limit pressure applied across a motor inlet and a motor outlet. The method includes adjusting the torque limiter pressure to vary the maximum torque applied to a drill string based on operating parameters of the horizontal direction drill, and adjusting the cross-port relief pressure to be higher than the torque limiter pressure each time that the torque limiter pressure is adjusted.

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Ankeny, IA, United States of America

Zach Buckley