초록 ▼

A vehicle has a pair of opposite drive wheels driven by a dual path hydrostatic transmission. Steering and speed/direction controls are effected by changing the displacement and/or direction of fluid flow through the pair of reversible, variable displacement pumps that are respectively coupled to fi

A vehicle has a pair of opposite drive wheels driven by a dual path hydrostatic transmission. Steering and speed/direction controls are effected by changing the displacement and/or direction of fluid flow through the pair of reversible, variable displacement pumps that are respectively coupled to fixed displacement ground wheel drive motors. The control mechanism for accomplishing steering and/or speed/direction control includes a steering rack that is caused to pivot about a fixed post in response to steering wheel movement. A first crank arm is coupled for pivoting in concert with the rack and a second crank arm is coupled for pivoting in concert with a pivot plate about a second axis, the pivot plate having a pair of connection points respectively coupled to control arms of the pair of pumps by a pair of pump control rods. The pivotal motion of the steering rack is transmitted to the pivot plate by a tie-rod coupled between the first and second crank arms. This tie-rod is parallel to a pivot support bar that swings about the fixed post in response to fore-and-aft movement of a speed/direction control lever, the pivot plate being pivotally mounted to the free end of the pivot support bar. Thus, the pivot support bar, first and second crank arms and the tie-rod cooperate to define a four-bar linkage that causes the pivot plate to retain its pivoted position about the second axis during speed/direction control so that such control is made independently of steering, and vice-versa.

대표청구항 ▼

A vehicle has a pair of opposite drive wheels driven by a dual path hydrostatic transmission. Steering and speed/direction controls are effected by changing the displacement and/or direction of fluid flow through the pair of reversible, variable displacement pumps that are respectively coupled to fi

A vehicle has a pair of opposite drive wheels driven by a dual path hydrostatic transmission. Steering and speed/direction controls are effected by changing the displacement and/or direction of fluid flow through the pair of reversible, variable displacement pumps that are respectively coupled to fixed displacement ground wheel drive motors. The control mechanism for accomplishing steering and/or speed/direction control includes a steering rack that is caused to pivot about a fixed post in response to steering wheel movement. A first crank arm is coupled for pivoting in concert with the rack and a second crank arm is coupled for pivoting in concert with a pivot plate about a second axis, the pivot plate having a pair of connection points respectively coupled to control arms of the pair of pumps by a pair of pump control rods. The pivotal motion of the steering rack is transmitted to the pivot plate by a tie-rod coupled between the first and second crank arms. This tie-rod is parallel to a pivot support bar that swings about the fixed post in response to fore-and-aft movement of a speed/direction control lever, the pivot plate being pivotally mounted to the free end of the pivot support bar. Thus, the pivot support bar, first and second crank arms and the tie-rod cooperate to define a four-bar linkage that causes the pivot plate to retain its pivoted position about the second axis during speed/direction control so that such control is made independently of steering, and vice-versa. valve spool being movable by said actuating drive against the force of said spring to place one of said control openings into communication with said pressurized fluid supply chamber for supplying pressurized fluid to said camshaft drive through said one control opening and the other of said control openings in communication with one of said pressure release chambers for releasing fluid from said camshaft drive to said drain passage and said valve spool being movable by said spring in the opposite direction to place the other of said control openings into communication with said pressurized fluid supply chamber for supplying pressurized fluid to said camshaft drive through said other control opening and to place said one control opening in communication with other pressure release chamber for discharging fluid from said camshaft drive through said one control opening for controlling operation of said camshaft drive. 2. A camshaft timing device according to claim 1, wherein the connection of the annular passage to the fluid drain passage is made via a transverse bore. 3. A camshaft timing device according to claim 1, wherein the connecting passage extending centrally through said valve spool is closed at the camshaft-side end of the valve spool. 4. A camshaft timing device according to claim 1, wherein the camshaft-side end of the valve control spool is formed by the annular web delimiting an end region of said housing, the end region of the housing of the control spool which is delimited via said annular web having a drain connection. 5. A camshaft timing device according to claim 1, wherein said clamping screw has, in its camshaft-side end region, a central connecting bore forming a pressure-side supply connection which leads to a central oil supply bore of said camshaft. 6. A camshaft timing device according to claim 5, wherein the central connecting bore is connected to the pressurized fluid supply chamber by means of bores formed in said clamping screw . 7. A camshaft timing device according to claim 6, wherein some of the bores extending in said clamping screw have a bore opening terminating at the outer surface of the clamping screw and that the respective bore openings are in communication by way of a connecting space formed in said central opening of the camshaft. 8. A camshaft timing device according to claim 7, wherein said clamping screw is tightly fitted at least into the end region of said central openings and seals off said central opening.