A gear pump or motor includes a main pump or motor connected to a drive source, and an auxiliary pump or motor. The main pump or motor includes helical main drive and driven gears, and a main drive shaft. A main connection part is formed at a leading end surface of the main drive shaft. The auxiliary pump or motor includes an auxiliary drive shaft extending toward the main drive shaft, an auxiliary connection part formed at a leading end face of the auxiliary drive shaft. A connecting member connects the main and auxiliary connection parts, and is in contact with an outer edge portion of the leading end face of the main drive shaft. A space opposes a receiving surface of the connecting member. The receiving surface opposes the auxiliary pump or motor. High-pressure operating fluid is supplied to the space.

A gear pump or motor includes a main pump or motor connected to a drive source, and an auxiliary pump or motor. The main pump or motor includes helical main drive and driven gears, and a main drive shaft. A main connection part is formed at a leading end surface of the main drive shaft. The auxiliary pump or motor includes an auxiliary drive shaft extending toward the main drive shaft, an auxiliary connection part formed at a leading end face of the auxiliary drive shaft. A connecting member connects the main and auxiliary connection parts, and is in contact with an outer edge portion of the leading end face of the main drive shaft. A space opposes a receiving surface of the connecting member. The receiving surface opposes the auxiliary pump or motor. High-pressure operating fluid is supplied to the space.

A hydraulic motor brake for providing load holding torque to a hydraulic motor and comprising a housing, a plate fixedly mounted within the housing, a piston mounted for bi-directional translation relative to the plate along a longitudinal axis, and a plurality of friction-producing members arranged such that the piston and plate at least partially define a brake release chamber and the piston, normally biased in engagement with the friction-producing members to produce load holding torque, translates away from the plate and disengages from the friction-producing members to stop producing load holding torque in response to pressurized hydraulic fluid being received by the brake release chamber. The hydraulic motor brake further comprises a wear plate with the brake housing and wear plate defining bores arranged in coaxial alignment with threaded bores of the hydraulic motor for detachably attaching the hydraulic motor brake to the hydraulic motor as a self-contained unit.

A hydraulic motor brake for providing load holding torque to a hydraulic motor and comprising a housing, a plate fixedly mounted within the housing, a piston mounted for bi-directional translation relative to the plate along a longitudinal axis, and a plurality of friction-producing members arranged such that the piston and plate at least partially define a brake release chamber and the piston, normally biased in engagement with the friction-producing members to produce load holding torque, translates away from the plate and disengages from the friction-producing members to stop producing load holding torque in response to pressurized hydraulic fluid being received by the brake release chamber. The hydraulic motor brake further comprises a wear plate with the brake housing and wear plate defining bores arranged in coaxial alignment with threaded bores of the hydraulic motor for detachably attaching the hydraulic motor brake to the hydraulic motor as a self-contained unit.

A rotary fluid pressure device, such as a low-speed, high-torque gerotor motor, is provided with a valve drive shaft that is partially inserted into and engaged with a main drive shaft as the main drive shaft engages a rotating output shaft and engages a rotating and orbiting star member of a positive displacement device. The device is also provided with a drive retainer configured to retain the engagement of the main drive shaft and the valve drive shaft.

A rotary fluid pressure device, such as a low-speed, high-torque gerotor motor, is provided with a valve drive shaft that is partially inserted into and engaged with a main drive shaft as the main drive shaft engages a rotating output shaft and engages a rotating and orbiting star member of a positive displacement device. The device is also provided with a drive retainer configured to retain the engagement of the main drive shaft and the valve drive shaft.

A progressing cavity device operates as a motor to impart torque to a bit. A stator of the device defines an internal profile having uphole stages with a first dimension being less than a second dimension of downhole stage. A rotor has an external profile with a constant outer dimension along its length. Disposed in the stator, the rotor defines cavities with the stator and is rotatable with pumped fluid progressing in the cavities from the uphole to downhole to transfer torque to the drive toward the downhole end. Although the rotor is subjected at the downhole end to a reactive torque from the bit, the interference fit of the rotor's constant dimension with the stator's downhole stages is less than with the uphole stages, which can mitigate issues with heat buildup in the downhole stages. The device can also operates as a progressing cavity pump.

A progressing cavity device operates as a motor to impart torque to a bit. A stator of the device defines an internal profile having uphole stages with a first dimension being less than a second dimension of downhole stage. A rotor has an external profile with a constant outer dimension along its length. Disposed in the stator, the rotor defines cavities with the stator and is rotatable with pumped fluid progressing in the cavities from the uphole to downhole to transfer torque to the drive toward the downhole end. Although the rotor is subjected at the downhole end to a reactive torque from the bit, the interference fit of the rotor's constant dimension with the stator's downhole stages is less than with the uphole stages, which can mitigate issues with heat buildup in the downhole stages. The device can also operates as a progressing cavity pump.

Provided is a gear pump or a motor provided with: a casing internally provided with a gear housing compartment in which a pair of gears are housed; a side plate interposed between the casing and the gears; and a gasket which is disposed on a non-slide surface, and which divides a space between the non-slide surface and the casing into a high pressure side and a low pressure side. The gear pump or the motor is configured such that, in order to discover early the mounting of the side plate in a wrong attitude, such as the upper and lower sides thereof being reversed or the high pressure portion side and the low pressure portion side being reversed, flow rate efficiency is decreased when the side plate is in an attitude other than a predetermined attitude, compared to when the side plate is in the predetermined attitude.

A hydrostatic transmission system includes a hydraulic motor and at least one proportional control valve and at least one pump connected to the hydraulic motor to provide fluid to operate the hydraulic motor. The at least one pump includes at least one fluid driver having a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from the pump inlet to the pump outlet. The hydrostatic transmission system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover and concurrently establishes an opening of the at least one proportional control valve to adjust at least one of a flow and a pressure in the hydrostatic transmission system to an operational set point.