Abstract: A displacement control device for a hydraulic unit includes: an actuator for applying operator input force to a movable member for varying displacement of the unit; a control valve having a spool and a sleeve displaceable with respect to each other, one of these being coupled with the movable member and the other being coupled with the actuator, the control valve being capable of generating a control signal based upon the relative displacement of the spool and sleeve; a servo which is operatively connected to the movable member and receives the control signal so as to move the movable member and change the fluid displacement of the unit in response to the control signal; and a bias coupling connecting the spool and the sleeve of the control valve. Thus, a preload force is interposed between and the spool and the sleeve such that relative displacement between the spool and the sleeve takes place when the feedback force exceeds the preload force.

Abstract: An integrated hydrostatic transmission has a housing comprised of two separable elements detachably joined together along a substantially horizontal parting plane. A hydrostatic transmission including a hydrostatic pump, a hydrostatic motor, and a center section is separately mounted within the housing. The center section comprises a generally L-shaped member having a hydrostatic pump and motor mounting surfaces thereon disposed at right angles to each other. A pair of fluid ports is on each of the mounting surfaces, and internal passageways are in the L-shaped member connecting each of the fluid ports on one of the mounting surfaces with one of said fluid ports being on the other of the mounting surfaces. The L-shaped member comprises first and second legs integrally joined and extending at right angles to each other, with the first leg normally extending in a horizontal direction, and the second leg normally extending in a vertical direction.

Abstract: An integrated hydrostatic transmission has a housing comprised of two separable elements detachably joined together along a substantially horizontal parting plane. A hydrostatic transmission including a hydrostatic pump, a hydrostatic motor, and a center section is separately mounted within the housing. The center section comprises a generally L-shaped member having a hydrostatic pump and motor mounting surfaces thereon disposed at right angles to each other. A pair of fluid ports is on each of the mounting surfaces, and internal passageways are in the L-shaped member connecting each of the fluid ports on one of the mounting surfaces with one of said fluid ports being on the other of the mounting surfaces. The L-shaped member comprises first and second legs integrally joined and extending at right angles to each other, with the first leg normally extending in a horizontal direction, and the second leg normally extending in a vertical direction.

Abstract: An axle driving apparatus having a common housing of at least two separable pieces for a hydrostatic transmission comletely contained within the housing. A pair of oppositely-extending differentially-connected axles extend from the housing. The housing pieces are separable at a horizontal parting plane.

Abstract: An integrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely-extending differentially-connected axles to have the common housing provide a common sump therefor and with a specifically-shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission. The center section is a unitary member separate from the common housing, with the exterior thereof exposed to the common sump. The center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section. Such casting can result in a porous center section with possible leakage from a passage having high pressure fluid.

Abstract: An integrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely-extending differentially-connected axles to have the common housing provide a common sump therefor and with a specifically-shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission. The center section is a unitary member separate from the common housing, with the exterior thereof exposed to the common sump. The center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section. Such casting can result in a porous center section with possible leakage from a passage having high pressure fluid.

Abstract: An integrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely-extending differentially-connected axles to have the common housing provide a common sump therefor and with a specifically-shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission. The center section is a unitary member separate from the common housing, with the exterior thereof exposed to the common sump. The center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section. Such casting can result in a porous center section with possible leakage from a passage having high pressure fluid.

Abstract: An integrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely-extending differentially-connected axles to have the common housing provide a common sump therefor and with a specifically-shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission. The center section is a unitary member separate from the common housing, with the exterior thereof exposed to the common sump. The center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section. Such casting can result in a porous center section with possible leakage from a passage having high pressure fluid.

Abstract: An intergrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely-extending differentially-connected axles to have the common housing provide a common sump therefor and with a specifically-shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission. The center section is a unitary member separate from the common housing, with the exterior therefor exposed to the common sump. The center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section. Such casting can result in a porous center section with possible leakage from a passage having high pressure fluid.

Abstract: An integrated hydrostatic transaxle having a common housing for a hydrostatic transmission and a pair of oppositely-extending differentially-connected axles to have the common housing provide a common sump therefor and with a specifically-shaped center section interconnecting the pair of hydraulic displacement units constituting the hydrostatic transmission. The center section is a unitary member separate from the common housing, with the exterior thereof exposed to the common sump. The center section has passages and arcuate ports which are interconnected by certain of said passages and which are located whereby the center section may be cast to minimize any machining required to finish the center section. Such casting can result in a porous center section with possible leakage from a passage having high pressure fluid.

Abstract: A dual pressure source, or selectively alternative high pressure source, control system for a variable displacement hydraulic unit servo mechanism wherein normal control of the unit is provided by the low pressure source, such as a transmission charge pump, and wherein a high pressure source of control fluid with a restrictive orifice is provided to initiate servo movement, especially under conditions generating high internal friction. The flow restrictive orifice generates a pressure drop in a high pressure control line once the servo mechanism starts to move, inducing flow through such line. Thus, the control system provides a momentary source of high pressure fluid but permits control rate changes which are substantially independent of the hydraulic unit working pressure. Preferably, the high pressure source is a shuttle selected highest pressure of a transmission main loop incorporating the hydraulic unit.

Abstract: The invention relates to a swashplate leveling and holddown mechanism wherein an axially sliding leveling mechanism is biased into engagement with a swashplate of an axial piston variable displacement hydraulic unit to position the swashplate in a zero displacement position when there is no control input to the hydraulic unit. The leveling mechanism has a pair of contact points, one positioned on each side of the swashplate tilt axis in a manner that both contact points positively engage the swashplate when it is centered to its zero displacement position. Such mechanism requires no spring adjustment and has no backlash. Furthermore, the axial bias on the leveling mechanism helps seat the swashplate in its support bearings. Utilized in conjunction with the leveling mechanism is an axially biased control input which operates on the opposite side of the swashplate to further hold the swashplate in its support bearings.

Abstract: An engine speed control for a variable speed engine wherein the engine can have a set speed to operate at a relatively low working speed or at an idle speed and which is adjustable to increase engine speed. The engine drives plural pumps and a control circuit is responsive to a certain flow rate from either of said pumps to increase the speed of the engine to provide for additional flow from the pumps. In a hydrostatic transmission as usable in the drive of a vehicle, there are a pair of fluid translating devices, in the form of a pump and a motor, with at least one of the devices being of variable displacement and having a displacement control responsive to a speed control signal. In such a system, the engine which powers the hydrostatic transmission is set at a desired speed of operation below maximum speed and is adjusted in response to the speed control signal for increase in said engine speed when the speed control signal exceeds a predetermined level.

Abstract: A transmission ratio control system including an engine having fuel supply means for controlling engine power, a hydrostatic transmission driven by the engine including means for varying transmission ratio, a ratio control valve for controlling the ratio varying means, means for applying a bias to the ratio control valve proportional to engine speed, and means responsive to system pressure in the hydrostatic transmission for applying an opposing bias to the ratio control valve proportional to engine torque. In operation, the fuel supply means calls for a predetermined amount of power to be delivered by the engine and the system pressure in the hydrostatic transmission is utilized and as modified by the transmission ratio to provide an indication of engine torque, with the ratio control valve being responsive to the engine speed and the engine torque to vary the transmission ratio to obtain a desired power/speed curve for operation of the engine.

Abstract: A torque limiting control for a pair of variable displacement hydraulic pumps having displacement varying means and servo means including springs urging each of the displacement varying means to a position for maximum pump displacement and fluid operated means acting in opposition to the springs to shift said displacement varying means for reduction in pump displacement, said control including means for summing the fluid pressures generated by both pumps and controlling the servo means for the two pumps to progressively move the displacement varying means for reduction of pump displacement as the sum of the fluid pressures rises above a predetermined value at a certain pump displacement and thereby limit the sum of the torques required by said pumps.

Abstract: A torque limiting control for a pair of variable displacement hydraulic pumps having displacement varying means and servo means including springs urging each of the displacement varying means to a position for maximum pump displacement and fluid operated means acting in opposition to the springs to shift said displacement varying means for reduction in pump displacement, said control including means for summing the fluid pressures generated by both pumps and controlling the servo means for the two pumps to progressively move the displacement varying means for reduction of pump displacement as the sum of the fluid pressures rises above a predetermined value at a certain pump displacement and thereby limit the sum of the torques required by said pumps.