Hydrostatic transmission displacement control

Claim 2

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid to said fluid operable means movable to a first position porting fluid to said fluid operable means and a second position porting fluid from said fluid operable means, manual control means, linkage means interconnecting said manual control means And said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, and means for reducing backlash in linkage means resulting from a torque reversal in said units including means continuously biasing said servo valve means in one direction regardless of the servo valve being in the first or second position.

Claim 3

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servovalve for controlling fluid to said fluid operable means, manual control means, linkage means interconnecting said manual control means and said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, and means for reducing backlash in said linkage means including means for continuously biasing said valve means in only one direction.

Claim 4

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servovalve for controlling fluid to said fluid operable means, manual control means, linkage means interconnecting said manual control means and said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, and means for reducing backlash in said linkage means including means for continuously biasing said valve means in only one direction.

Claim 5

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid to said fluid operable means, manual control means, linkage means interconnecting said manual control means and said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, means for reducing backlash in said linkage means and said manual control means resulting from a reversal of torque in said units including spring means biasing said servo valve means in one direction and means biasing said manual control means away from said linkage means.

Claim 6

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid to said fluid operable means, manual control means, linkage means interconnecting said manual control means and said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, means for reducing backlash in said linkage means and said manual control means resulting from a reversal of torque in said units including spring means biasing said servo valve means in one direction and means biasing said manual control means away from said linkage means.

Claim 7

A hydrostatic transmission comprising: an axial piston hydraulic pump, a hydraulic motor, conduit means interconnecting the pump and motor, pivotal cam means for varying the displacement of the pump, fluid operable means for positioning the cam means, servo valve means for porting fluid relative to said fluid operable means, a manual control handle to position said servo valve means, a three-pivot-point link for pivoting said servo valve means, control linkage interconnecting said control handle and said link at one of the points, means interconnecting the servo valve means and the link at a second of said points, means interconnecting said cam means and said link at a third of said points to provide position feedback, and means for reducing backlash in said link caused by the pump acting as a motor including spring means for biasing said servo valve means continuously in a direction tending to reduce the displacement of the pump.

Claim 8

A hydrostatic transmission comprising: an axial piston hydraulic pump, a hydraulic motor, conduit means interconnecting the pump and motor, pivotal cam means for varying the displacement of the pump, fluid operable means for positioning the cam means, servo valve means for porting fluid relative to said fluid operable means, a manual control handle to position said servo valve means, a three-pivot-point link for pivoting said servo valve means, control linkage interconnecting said control handle and said link at one of the points, means interconnecting the servo valve means and the link at a second of said points, means interconnecting said cam means and said link at a third of said points to provide position feedback, and means for reducing backlash in said link caused by the pump acting as a motor including spring means for biasing said servo valve means continuously in a direction tending to reduce the displacement of the pump.

Claim 9

A hydrostatic transmission as defined in claim 4, including means for eliminating backlash in said control linkage including means biasing said control linkage toward said control handle.

Claim 10

A hydrostatic transmission as defined in claim 5, wherein said servo valve includes a first port when pressurized tending to increase pump displacement and a second port when pressurized tending to decrease pump displacement, said cam means being connected to said link at a position so that in response to stroke-reducing movements on the cam means the link will tend to move the servo valve to a position pressurizing the first port and in response to stroke-increasing moments on the cam means will tend to move the servo valve means to a position pressurizing said second port.

Claim 11

A hydrostatic transmission as defined in claim 6, wherein said means biasing said control linkage includes a centering spring.

Claim 12

A hydrostatic transmission as defined in claim 7, wherein said first point is intermediate with respect to said second and third points.

Claim 13

A hydrostatic transmission as defined in claim 7, including a yieldable linkage in said control linkage means.

Claim 14

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said hydraulic pump and motor units, fluid operable meanS for varying the displacement of one of said units, servo valve means for controlling fluid relative to said fluid operable means, manual control means, link means interconnecting said manual control means with said servo valve means, feedback means connected to said servo valve means, feedback means connected to said fluid operable means and said link means, said link means having three pivotal interconnections respectively with said valve means, said control means and said feedback means, and means for biasing said pivotal interconnections in the same direction regardless of the direction of movement of the fluid operable means.

Claim 15

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said hydraulic pump and motor units, fluid operable meanS for varying the displacement of one of said units, servo valve means for controlling fluid relative to said fluid operable means, manual control means, link means interconnecting said manual control means with said servo valve means, feedback means connected to said servo valve means, feedback means connected to said fluid operable means and said link means, said link means having three pivotal interconnections respectively with said valve means, said control means and said feedback means, and means for biasing said pivotal interconnections in the same direction regardless of the direction of movement of the fluid operable means.

Claim 16

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid to said fluid operable means, manual control means, linkage means interconnecting said manual control means and said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, means for reducing backlash in said manual control means including a link in said manual control means and means for biasing the link away from said link means.

Claim 17

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid to said fluid operable means, manual control means, linkage means interconnecting said manual control means and said servo valve means, means connecting said fluid operable means to said linkage means to provide position feedback, means for reducing backlash in said manual control means including a link in said manual control means and means for biasing the link away from said link means.

Claim 18

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid relative to said fluid to said fluid operable means and a second position porting fluid from said fluid operable means, a rigid link interconnecting said fluid operable means and said servo valve to effect feedback, a manually controlled link interconnecting said fluid operable means and said servo valve to effect feedback, a manually controlled link connected to said rigid link to position the same in accordance with the desired displacement of the hydraulic unit, and means for reducing backlash in the connection with the rigid link including means continuously biasing said servo valve in one direction regardless of the servo valve being in the first or second position and means continuously biasing said manual link in one direction with respect to the rigid link regardless of whether the servo valve is in the first position or the second position.

Claim 19

A hydrostatic transmission, comprising: a hydraulic pump unit, a hydraulic motor unit, conduit means interconnecting said units, fluid operable means for varying the displacement of one of said units, a servo valve for controlling fluid relative to said fluid to said fluid operable means and a second position porting fluid from said fluid operable means, a rigid link interconnecting said fluid operable means and said servo valve to effect feedback, a manually controlled link interconnecting said fluid operable means and said servo valve to effect feedback, a manually controlled link connected to said rigid link to position the same in accordance with the desired displacement of the hydraulic unit, and means for reducing backlash in the connection with the rigid link including means continuously biasing said servo valve in one direction regardless of the servo valve being in the first or second position and means continuously biasing said manual link in one direction with respect to the rigid link regardless of whether the servo valve is in the first position or the second position.