Control system for hydrostatic transmission
First Claim
1. In a hydrostatic transmission including an engine-driven hydrostatic pump, a hydrostatic motor coupled with a load and fluidically linked with said hydrostatic pump, and setting means on said pump for varying the magnitude and sign of a torque fluidically transmitted to said hydrostatic motor, the combination therewith of:
- a switchover member mechanically linked with said setting means, said switchover member having a normal position coinciding with zero torque and being shiftable to either side of said normal position for transmitting a torque of a corresponding sign to said hydrostatic motor;
biasing means urging said switchover member into said normal position;
normally de-energized first actuating means operatively coupled with said switchover member for exerting thereon a directive force displacing said switchover member to one side from said normal position with resulting rotation of said hydrostatic motor in a first direction;
normally de-energized second actuating means operatively coupled with said switchover member for exerting thereon a directive force displacing said switchover member to the opposite side from said normal position with resulting rotation of said hydrostatic motor in a second direction;
selector means with a neutral position and with two working positions for respectively connecting said first and second actuating means to an energy source; and
inhibiting means effective upon displacement of said switchover member by a predetermined minimum distance from said normal position by one of said actuating means for preventing energization of the other of said actuating means whereby a change in sign of said torque upon a subsequent changeover of said selector means from one working position to the other can occur only after a reverse displacement of said switchover member by said biasing means.
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Accused Products
Abstract
A system for controlling the operation of a reversible hydrostatic transmission including an engine-driven pump, particularly for a self-propelled utility vehicle such as a forklift truck, comprises a switchover member coupled with a setting lever of the hydrostatic pump which is biased by a pair of counteracting springs into a normal centered position. A shift lever, upon being moved from "neutral" to "forward" or "reverse", causes a displacement of the switchover member into a corresponding off-normal position by a fluidic or electromagnetic directive force generally proportional to engine speed. At a speed exceeding a certain limit in either direction, the switchover member deactivates the fluidic or electric operating circuit for the opposite direction whereby a shift from "forward" to "reverse", or vice versa, will let a change in direction take place only after the switchover member has been restored to near-normal exclusively by its biasing springs against the gradually decaying directive force previously applied. A pedal-operated linkage, coupled with the switchover member, serves for a rapid restoration of that member to normal or for fine speed control at near-zero velocities.
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Citations
12 Claims
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1. In a hydrostatic transmission including an engine-driven hydrostatic pump, a hydrostatic motor coupled with a load and fluidically linked with said hydrostatic pump, and setting means on said pump for varying the magnitude and sign of a torque fluidically transmitted to said hydrostatic motor, the combination therewith of:
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a switchover member mechanically linked with said setting means, said switchover member having a normal position coinciding with zero torque and being shiftable to either side of said normal position for transmitting a torque of a corresponding sign to said hydrostatic motor; biasing means urging said switchover member into said normal position; normally de-energized first actuating means operatively coupled with said switchover member for exerting thereon a directive force displacing said switchover member to one side from said normal position with resulting rotation of said hydrostatic motor in a first direction; normally de-energized second actuating means operatively coupled with said switchover member for exerting thereon a directive force displacing said switchover member to the opposite side from said normal position with resulting rotation of said hydrostatic motor in a second direction; selector means with a neutral position and with two working positions for respectively connecting said first and second actuating means to an energy source; and inhibiting means effective upon displacement of said switchover member by a predetermined minimum distance from said normal position by one of said actuating means for preventing energization of the other of said actuating means whereby a change in sign of said torque upon a subsequent changeover of said selector means from one working position to the other can occur only after a reverse displacement of said switchover member by said biasing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification