Patent ID: 11946372
Assignee: VERMEER MANUFACTURING COMPANY
Field: Civil engineering (Other fields)
Classification: CPC E | IPC E

Claim 18:
19. A horizontal directional drilling machine comprising:
a cam-lobe radial piston hydraulic motor having an output member configured to connect with and selectively drive rotation of a drill string;
a hydraulic circuit having a first configuration that puts the hydraulic motor in a drive mode to apply torque to the drill string through the output member, the hydraulic circuit having a second configuration that puts the hydraulic motor in a freewheel mode disabled from applying torque to the drill string, the hydraulic circuit including
a first fluid flow path including a first rotary ball valve configured to selectively connect the hydraulic motor to one of an inlet side and an outlet side of a drive pump, and
a second fluid flow path including a second rotary ball valve configured to selectively connect the hydraulic motor to the other of the inlet side and the outlet side of the drive pump, wherein, when the hydraulic circuit is in the freewheel mode, the first and second fluid flow paths are blocked;

one or more accumulators in fluid communication with the first and/or second fluid flow paths between the hydraulic motor and the first and second rotary ball valves; and
an accumulator cut-off valve positioned between the one or more accumulators and a source of pressurized fluid, the accumulator cut-off valve controlled to a closed position concurrent with the freewheel mode to inhibit fluid flow from the source of pressurized fluid to the one or more accumulators,
wherein, when the hydraulic circuit is in the drive mode, there is no reduction in cross-sectional area along the first fluid flow path and there is no reduction in cross-sectional area along the second fluid flow path.