A hydrostatic drive for reciprocating the transfer bar of a multi-station transfer mechanism wherein the motive power is supplied by a swashplate type pump, the control arm of which is pivoted to accelerate and decelerate the transfer bar by means of a yoke connected to the end of the control arm and adapted to be displaced by a control cylinder supplied with pressure fluid from an auxiliary pump through a four-way solenoid operated, spring centered valve. When the valve is in the centered position the yoke is spring biased toward a centered position, thus shifting the control arm of the swashplate pump to the neutral position so that the transfer bar can at any point between the ends of its stroke be stopped with a controlled rate of deceleration and again started with a controlled rate of acceleration.
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.
A system is provided for maintaining a permanent reciprocatory movement of a mechanical arrangement, particularly a pump unit. A main driving wheel is coupled to the mechanical arrangement and fastened on the shaft of a hydraulic motor which is supplied by a variable delivery pump provided with control means. The control means is coupled to the wheel by a drive mechanism which comprises a rocking lever coupled to the control means and a cam carrier wheel rotationally fixed to the wheel. As the mechanical arrangement moves in one direction, the rotation of the driving wheel causes the cam wheel to change the position of the rocking lever thus permitting the control means to direct the flow of fluid from the variable delivery pump to the hydraulic motor to reverse the direction of travel of the mechanical arrangement.
A speed control system for a working vehicle comprises a hydrostatic transmission for propelling the vehicle, a hydraulic cylinder and a control valve. The hydraulic cylinder includes a cylinder case operatively connected to a control shaft for varying a swash plate angle of the hydrostatic transmission, and a piston rod fixed to a case containing the hydrostatic transmission. The control valve is fixed to the cylinder case and includes a spool extending parallel to the hydraulic cylinder and operatively connected to a foot pedal for manually controlling the hydrostatic transmission. The cylinder case is shiftable following a shift of the valve spool.
A control system for a variable displacement compressor uses a mechanical valve to minimize energy consumption in an air conditioning system. The control system can also provide instantaneous indications to the vehicle controller of air conditioning power consumption to avoid engine loading. Controls are also used to contain oil within the compressor and to minimize its presence downstream of the compressor into the gas cooler and evaporator parts of the system.
