Abstract: Single and dual hydraulic piston pump units comprising at least one pump unit including a variable displacement axial piston main pump rotatably journalled within an at least one pump housing, and operatively interconnected for dual pump units, the pump housing(s) being of a size having an integral fluid reservoir for the at least one pump unit, the reservoir including a drain port and plug and the housing including an air venting device. A block portion includes at least one pair of reversible fluid inlet and outlet ports and a fluid filter connecting portion. At least one center through shaft drives the main pump(s), the charge pump, and a cooling fan. A single pump unit in combination with a rotatable electric motor comprises a portable hydraulic power-producing unit. A dual pump unit in combination with a vehicle, having independently hydraulic motor-driven left and right wheels, permits independent wheel propulsion thereof.

Abstract: Improvement in a hydrostatic valve assembly for use in a hydrostatic transmission, for controlling fluid transfer between a first, second and third line, wherein two of the lines define first and second pressure lines within a closed loop circuit. The valve assembly comprises a valve body having ports in communication with the three lines; a spool bore and valve spool reciprocating therewithin, having first and second end portions joined by a connecting portion, and first and second bypass orifices within the valve spool; and dampers for centering the valve spool in a neutral position. The bypass orifices utilize increased cross-sectional areas that permit the passage of substantially the full flow of the charge pump, without using a charge pump relief valve, at a low pressure drop. A hydraulic system utilizing this valve assembly and a method for increasing the transmission efficiency, in the neutral mode, are also set forth.

Abstract: A compact, integrated hydrostatic transmission without reduction gearing wherein the pump and motor are contained within a single housing, and an output shaft extends from the housing inline with a shaft of the motor. The output shaft is directly connectable to a wheel of a vehicle. The pump and motor share a common sump within the housing in which pump and/or motor leakage is collected.

Abstract: A speed adjusting mechanism that includes a return to neutral feature for returning a control member of a pump to neutral after the control member has been moved to a forward or reverse position. The speed adjusting mechanism is characterized by the use of a torsion spring that enables the mechanism to be composed of just a few parts.

Abstract: A hydrostatic transmission system having a pump and a motor, and a manually controlled bypass valve for creating a short circuit that includes the motor and not the pump, the bypass valve being located closer to the motor than the pump. In a preferred embodiment the bypass passage is located within a housing of a motor of a hydrostatic transmission system and includes a manually controlled valve member that when open and closed respectively permits and blocks flow of fluid between the supply and return line. More particularly, the bypass valve may be integral with the motor of the hydrostatic transmission, and the motor may be a gerotor motor.

Abstract: A rotary fluid pressure device having a housing member, a manifold assembly, an internally generated rotor type gerotor set, an end plate, and a rotatably journaled torque transfer shaft interconnected with the gerotor set and extending within the housing member and manifold assembly. The gerotor set having at least an internally toothed stator member and a rotating rotor member disposed within the stator member. The rotor member having a first and second axial end surface and external teeth which interengage with the internal teeth of the stator to define a plurality of expanding and contracting volume chambers. The rotor member also having a plurality of circumferentially spaced laterally directed fluid paths fluidly connecting the manifold assembly with a plurality of circumferentially spaced radiating fluid paths which directly connect with the volume chambers. The fluid pressure device further including a plurality of coupling members for interconnecting the components.

Abstract: A housing for a motor having fluid passages integrated within. The passages include a first passage for receiving a fluid from outside the motor, a second passage for directing the fluid away from the motor, and at least one other passage from conveying the fluid to a set of components attached to the motor housing. The housing has at least one relief valve positioned within the fluid passages for diverting a portion of the fluid directly from the first passage to the second passage.

Abstract: A hydraulic valve assembly, for use in a hydrostatic transmission, for controlling fluid transfer between a first, a second and a third line, wherein two of the lines define first and second pressure lines, within a closed-loop circuit. The valve assembly comprises: a valve body having ports in communication with the three lines; a spool bore; a valve spool, adapted for sealing reciprocation within the spool bore, having a first and second end portion, a connecting portion, and a first and second bypass orifice within the valve spool; and dampers for centering the valve spool. This spool is movable from a neutral position occurring when the fluid pressure forces in the first and second pressure lines are substantially similar, to a first or a second position occurring when the fluid pressure force in the first pressure line is greater or less than that in the second pressure line, respectively.

Abstract: A hydraulic pump for a closed-loop hydrostatic transmission circuit having an integrated shuttle valve for diverting hot fluid from the hydrostatic transmission circuit to a reservoir. The circuit operatively interconnects the hydraulic pump and a motor and includes a first line connecting a first port within the hydraulic pump to a first port within the motor and a second line connecting a second port within the hydraulic pump to a second port within the motor.

Abstract: In a variable displacement hydraulic pump having a housing with a multiplicity of interconnected surfaces, including opposed end surfaces and intermediate side surfaces, the improvement comprising the location of at least one case drain orifice in each of a plurality of differing ones of the surfaces in a manner such that at least one of the orifices is located in the vicinity of the top surface of the housing in any spatial orientation of the housing.

Abstract: A hydraulic device for one of a motor and pump, having a manifold assembly positioned between a gerotor set and a housing for the device, the manifold assembly adapted for conducting pressurized fluid to the gerotor set and conducting exhaust fluid from the gerotor set. The manifold assembly having a first axial end, a second axial end, a central internal bore extending freely from the first axial end to the second axial end and adapted for conducting at least a portion of one of the fluids, a first fluid passage extending directly from the central internal bore to a location radially outward from the central internal bore and therefrom to the second axial end, and a second fluid passage extending substantially laterally from the second axial end to the first axial end.

Abstract: A rotary fluid pressure device having a housing member, a manifold assembly, a gerotor set, a channeling plate and an end plate. The gerotor set having a stator member with at least one axial fluid path extending therethrough and a rotor member, disposed within said stator member, having an axial end surface with a recess, and a plurality of axially extending through holes for fluid flow therethrough adapted for hydraulically axially balancing its axial ends relative to the stator. The channeling plate having a first and second fluid passage extending therethrough, and a plurality of through holes. Means for routing the high pressure fluid from the housing member through the gerotor set, through the channeling plate first and second fluid passages, into and subsequently out of a cavity between the channeling plate and the end plate and into the rotor recess to overbalance the rotor towards the manifold assembly.

Abstract: A rotary fluid pressure device having a housing member, a manifold assembly, a gerotor set, an end plate, and a rotatably journaled torque transfer shaft interconnected with the gerotor set and extending within the housing member and manifold assembly. The gerotor set having an internally toothed stator member and a rotating rotor member disposed within the stator member. The rotor member having a first and second axial end surface and external teeth which interengage with the internal teeth of the stator to define a plurality of expanding and contracting volume chambers. The rotor member also having a first plurality of circumferentially spaced laterally directed fluid paths which extend through the rotor for fluid connection between the manifold assembly and the volume chambers, and a second plurality of circumferentially spaced, laterally directed fluid paths interposed between the first plurality of fluid paths for sequentially channeling fluid between both axial end surfaces.

Abstract: A rotary fluid pressure device having a housing member, a manifold assembly, a gerotor set, a channeling plate and an end plate. The gerotor set having a stator member with at least one axial fluid path extending therethrough and a rotor member, disposed within said stator member, having an axial end surface with a recess, and a plurality of axially extending through holes for fluid flow therethrough adapted for hydraulically axially balancing its axial ends relative to the stator. The channeling plate having a first and second fluid passage extending therethrough, and a plurality of through holes. Means for routing the high pressure fluid from the housing member through the gerotor set, through the channeling plate first and second fluid passages, into and subsequently out of a cavity between the channeling plate and the end plate and into the rotor recess to overbalance the rotor towards the manifold assembly.

Abstract: A hydraulic device for one of a motor and pump, having a manifold assembly positioned between a gerotor set and a housing for the device, the manifold assembly adapted for conducting pressurized fluid to the gerotor set and conducting exhaust fluid from the gerotor set. The manifold assembly having a first axial end, a second axial end, a central internal bore extending freely from the first axial end to the second axial end and adapted for conducting at least a portion of one of the fluids, a first fluid passage extending directly from the central internal bore to a location radially outward from the central internal bore and therefrom to the second axial end, and a second fluid passage extending substantially laterally from the second axial end to the first axial end.

Abstract: A rotary fluid pressure device having a housing member, a manifold assembly, an internally generated rotor type gerotor set, an end plate, and a rotatably journaled torque transfer shaft interconnected with the gerotor set and extending within the housing member and manifold assembly. The gerotor set having at least an internally toothed stator member and a rotating rotor member disposed within the stator member. The rotor member having a first and second axial end surface and external teeth which interengage with the internal teeth of the stator to define a plurality of expanding and contracting volume chambers. The rotor member also having a plurality of circumferentially spaced laterally directed fluid paths fluidly connecting the manifold assembly with a plurality of circumferentially spaced radiating fluid paths which directly connect with the volume chambers. The fluid pressure device further including a plurality of coupling members for interconnecting the components.

Abstract: A rotary fluid pressure device having a housing member, a manifold assembly, a gerotor set, an end plate, and a rotatably journaled torque transfer shaft interconnected with the gerotor set and extending within the housing member and manifold assembly. The gerotor set having an internally toothed stator member and a rotating rotor member disposed within the stator member. The rotor member having a first and second axial end surface and external teeth which interengage with the internal teeth of the stator to define a plurality of expanding and contracting volume chambers. The rotor member also having a first plurality of circumferentially spaced laterally directed fluid paths which extend through the rotor for fluid connection between the manifold assembly and the volume chambers, and a second plurality of circumferentially spaced, laterally directed fluid paths interposed between the first plurality of fluid paths for sequentially channeling fluid between both axial end surfaces.

Abstract: A hydraulic motor 10/110/210 has an end cover 12/112/212 including a first port 14/114/214 and a second port 16/116/216, and a gerotor drive assembly 18/118/218 which hypocycloidally moves a drive link 22/122/222. The motor's flow circuit comprises a working path (e.g., for providing rotational motion) from the end cover 12/112/212, through the drive assembly 18/118/218 and back to the end cover 12/112/212. Bolts 26/126/226 extend through registered openings in the end cover 12/112/212, the drive assembly 18/118/218 and a housing 20/120/220 and the bolts 26/126/226 are positioned in a circular array outside the motor's pressure vessel whereby the motor 10/110/210 has a “dry bolt” design. The motor's flow circuit can also comprises a non-working path (for cooling, lubrication and/or sealing purposes) which circulates fluid through chambers surrounding the drive train components.

Abstract: A hydraulic valve assembly, for use in a hydrostatic transmission, for controlling fluid transfer between a first, a second and a third line, wherein two of the lines define first and second pressure lines, within a closed-loop circuit. The valve assembly comprises: a valve body having ports in communication with the three lines; a spool bore; a valve spool, adapted for sealing reciprocation within the spool bore, having a first and second end portion, a connecting portion, and a first and second bypass orifice within the valve spool; and dampers for centering the valve spool. This spool is movable from a neutral position occurring when the fluid pressure forces in the first and second pressure lines are substantially similar, to a first or a second position occurring when the fluid pressure force in the first pressure line is greater or less than that in the second pressure line, respectively.

Abstract: A hydraulic motor 10/110/210 has an end cover 12/112/212 including a first port 14/114/214 and a second port 16/116/216, and a gerotor drive assembly 18/118/218 which hypocycloidally moves a drive link 22/122/222. The motor's flow circuit comprises a working path (e.g., for providing rotational motion) from the end cover 12/112/212, through the drive assembly 18/118/218 and back to the end cover 12/112/212. Bolts 26/126/226 extend through registered openings in the end cover 12/112/212, the drive assembly 18/118/218 and a housing 20/120/220 and the bolts 26/126/226 are positioned in a circular array outside the motor's pressure vessel whereby the motor 10/110/210 has a “dry bolt” design. The motor's flow circuit can also comprises a non-working path (for cooling, lubrication and/or sealing purposes) which circulates fluid through chambers surrounding the drive train components.