Abstract: A control system for a hydrostatic transmission is disclosed of the type including an engine driven fluid pump and a fluid motor. The control system includes a main control operable in response to an electrical command signal to vary the displacement of the pump, and a command signal generator for generating the command signal. The anti-stall control includes means for comparing electrical signals representative of engine speed and a reference speed, and generating an electrical anti-stall signal representative of the maximum percentage of commanded pump displacement which is permissible without causing the engine to drop below the reference speed. The anti-stall control includes means for electrically multiplying the anti-stall signal and the command signal, downstream of the shaping and rate limiting circuits. The invention provides a simple, inexpensive anti-stall control which can be adjusted to have the maximum possible gain (responsiveness) without inducing circuit instability.

Abstract: An automatic control system for a hydrostatic transmission having a control circuit receiving a control flow from a control pump which represents a speed of a prime mover and valve components including a single adjustable valve which creates a delta pressure signal to control the transmission ratio which controls the speed of the prime mover.

Abstract: An electro-hydraulic control for a hydrostatic transmission including a variable displacement hydraulic pump, a fixed displacement hydraulic motor, and fluid operable strokers to vary the displacement of the pump. The electro-hydraulic control is in series between the charge pump and the standard manual controller and determines the pressure of the charge fluid ported to the standard controller. The electro-hydraulic control includes a spool biased toward a first position to port fluid from the charge pump to the standard controller, and biased toward a second position to relieve to tank the pressure of fluid ported to the manual controller. The biasing toward the second direction is accomplished, in part, by pressure in a fluid chamber exerting a biasing force on the spool, the fluid chamber being in communication with drain through a variable orifice which is variable in response to a pressure command signal.

Abstract: An underspeed actuator has a piston connected to a control means of a first pump driven by a prime mover and is movable between a first position at which the first pump is at minimum displacement and a second position at which the first pump is at maximum displacement. The underspeed actuator has first and second actuating chambers at opposite ends of the piston and a biasing device urging the piston towards the first position. The piston is movable between the first and second positions in response to pressure differential in said first and second chambers. A signal device controllably develops first and second control signals in response to the operating speed of the prime mover and delivers said first and second signals to respective first and second chambers. A first device controllably reduces the magnitude of fluid pressure in the first chamber in response to the rate of pressure rise of the output fluid of said first pump exceeding a preselected rate of pressure rise.

Abstract: A total fluid power system for an engine powered vehicle includes an engine driven, variable displacement pump, a pair of variable displacement wheel motors and auxiliary functions. Transducers sense engine speed, pump output pressure and motor speeds to supply signals to pump and motor controls which process the signals with operator input signals to maintain pump and motor displacements for optimum engine power usage and desired vehicle performance.

Abstract: An integrated transmission-engine control for a transmission, such as a hydrostatic transmission having a variable displacement unit connectable to an engine and a second displacement unit connected to an output shaft, including fluid pressure-operated ratio governor means for the transmission, fluid pressure-operated means for controlling the supply of fuel to an engine, a power demand valve for converting a particular power demand to a particular fluid pressure primary control signal. The primary control signal is applied to the ratio governor means in opposition to a signal representing engine speed to set the transmission ratio for a desired engine speed and also applied to the fuel supply controlling means to establish a fuel setting to match engine horsepower to engine speed for minimum fuel consumption.

Abstract: An underspeed actuator has a piston connected to a control means of a first pump driven by a prime mover and is movable between a first position at which the first pump is at minimum displacement and a second position at which the first pump is at maximum displacement. The underspeed actuator has first and second actuating chambers at opposite ends of the piston and a biasing device urging the piston toward the first position. The piston is movable between the first and second positions in response to pressure differential in said first and second chambers. A signal device controllably develops first and second control signals in response to the operating speed of the prime mover. First and second conduits deliver said first and second control signals to said first and second chambers, respectively. A shunt valve is connected to the first and second conduits for passing fluid expelled from the first chamber to the second chamber in response to said flow of fluid exceeding a preselected flow rate.

Abstract: A control arrangement for preventing overloading of a prime mover which drives a pump comprises a pair of hydraulically operating adjusting units operative for adjusting the volume of fluid discharged by the pump. The arrangement further comprises a negative-feedback stabilizing circuit connected to the adjusting units and to a multi-setting regulating valve. The stabilizing circuit is operative for causing the valve to regulate the operation of the pump by controlling the operation of the adjusting units in dependence upon the output pressure of the pump. In order to protect the prime mover when the loading thereof has reached a predetermined value, an overload signal is generated which actuates an over-ride device. The override device is operative in response to the overload signal to cause the valve to assume a setting such that the adjusting units decrease the quantity of fluid discharged by the pump so as to unload the prime mover.

Abstract: A combined summing and underspeed valve including a valve body having a bore, a spool within the bore, an outlet from the bore in the body intermediate the ends of the bore, a pair of spaced inlets in the bore for receiving fluid under pressure to apply force to opposite ends of the spool, at least two additional inlets in the body for receiving fluid under pressure to apply force to one of the ends of the spool, and pistons for isolating fluid from the inlet of the pair applying force to the spool one end from fluid from the additional inlets while applying force to the spool.

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.

Abstract: A hydraulic system for controlling the displacement of a plurality of variable displacement pumps driven by a single prime mover including a source of pilot fluid under pressure including a fixed displacement pump adapted to be driven by the prime mover proportional to the speed thereof, a double-piloted, underspeed valve having an inlet and an outlet, the outlet being adapted to be connected to the variable displacement pumps for controlling displacement thereof, a conduit connecting one of the pilots to the source, an additional conduit, including a flow restricting device, connecting the other of the pilots to the source, and a summing valve having ports adapted to be connected to respective ones of the pumps, a port connected to the second conduit and a port connected to the inlet of the underspeed valve.

Abstract: A hydraulic circuit for steering control in articulate vehicles which comprises an engine, a fixed displacement pump driven by the engine, a variable displacement pump driven by the engine, an exit port of the variable displacement pump being connected to a control valve of a steering actuator, an orifice provided at an outlet side of the fixed displacement pump and, a controlling cylinder connected to the variable displacement pump for controlling displacement of the variable displacement pump, the controlling cylinder being actuated by a spring disposed therein and a differential hydraulic pressure at the orifice.

Abstract: A hydraulic control device for protecting a drive from excess loading conditions includes at least one pump having adjustable members for controlling the quantity of fluid transported by the pump. A pressure-responsive control slide is mounted for movement relative to a housing and is moved towards respective positions, each of which corresponds to a normally loaded condition of the drive by a control pump which generates a pressure force which is indicative of the rpm of the drive at normally loaded conditions. The device further includes an arrangement for securing the control slide when the drive is subjected to loads in excess of the respective normally loaded conditions so that a valve member is permitted to move in response to excess loads relative to the control slide after the latter has been secured in said respective positions by the securing arrangement between switching positions in which the adjustable members are operative to adjust the quantity of fluid being transported by the pump.

Abstract: In a hydraulic system having a plurality of variable displacement pumps driven by a prime mover, each pump has a variable ratio input device connected to a load sensing means. Each variable ratio input device automatically reduces the displacement of its respective pump by the same proportion when the prime mover is overloaded irrespective of the displacement setting of the pump and automatically increases the displacement of its pump by the same proportion up to the set displacement when the prime mover is not overloaded.

Abstract: A load sensitive hydraulic circuit for material handling equipment is energized by a prime mover. The hydraulic circuit includes variable displacement pumps coupled to the prime mover and having pressure and flow compensating control means for varying the volumetric output. Each pump is connected to a valve bank which controls various hydraulic actuators of the material handling equipment. Load pressure feedback is provided to the pump compensators for establishing pump flows to operate the actuators at a fixed pressure differential in excess of load pressure. The valve banks contain pressure compensated valves for providing desired fluid flow rates and speeds in the hydraulic actuators. Means are provided to sense reductions in the prime mover speed resulting from excessive hydraulic loads.

Abstract: A vehicular powertrain includes a conventional gasoline internal combustion engine, a continuously variable ratio transmission, and a feedback control system and engine speed sensor for regulating the power produced by the engine to a value selected by the vehicle operator. The feedback control system operates the engine at wide open throttle and a lean burn air-fuel ratio over a wide range of operating conditions of the vehicle, with the control system adjusting the transmission ratio to regulate the engine speed to a value corresponding to the power selected by the operator. As a result of the extensive engine operation at wide open throttle and a lean burn air-fuel ratio, exhaust emissions are held to a low level while fuel economy is significantly increased.

Abstract: A hydraulic circuit for controlling actuators in a construction vehicle which comprises an engine, a fixed displacement pump driven by said engine, a variable displacement pump driven by said engine, a controlling cylinder connected to the variable displacement pump for controlling the displacement thereof, an orifice provided between the output of the fixed displacement pump and a tank and, an unloading valve connected to the fixed displacement pump and also to the variable displacement pump via a pilot line for selectively unloading an output fluid from the fixed displacement pump when it is open.

Abstract: In a hydraulic system having a plurality of variable displacement pumps driven by a prime mover, each pump has a variable ratio input device connected to a load sensing means. Each variable ratio input device automatically reduces the displacement of its respective pump by the same proportion when the prime mover is overloaded irrespective of the displacement setting of the pump and automatically increases the displacement of its pump by the same proportion up to the set displacement when the prime mover is not overloaded.

Abstract: In a hydraulic system having a plurality of variable displacement pumps driven by a prime mover, each pump has a variable ratio input device connected to a load sensing means. Each variable ratio input device automatically reduces the displacement of its respective pump by the same proportion when the prime mover is overloaded irrespective of the displacement setting of the pump and automatically increases the displacement of its pump by the same proportion up to the set displacement when the prime mover is not overloaded.

Abstract: A demand compensated hydraulic system includes a pump responsive to pressurized fluid in a demand feedback pilot line. The pilot line is connected to sense fluid demand between a hydraulic motor and its associated control valve which is closed by servo feedback from the motor. A flow sensitive device is interposed in an output line connecting the pump and the control valve to sense when the flow decreases until it is insufficient to operate the function. At a predetermined decreased flow rate, the flow sensitive device operates to momentarily connect the demand feedback pilot line to a reservoir to cause the pump to go into a stand-by condition.

Abstract: A hydraulic drive control system for driving a generator or alternator or the like at a constant RPM regardless of variations in the output load or the input load comprising a driven pump having a variable volume and variable pressure output connected in a closed system to a hydraulic motor which will maintain a constant RPM output, regardless of the RPM's of the driving means, which is coupled to the device to be driven. Connected between the pump and the motor is a volume control line having a volume control valve which insures that the volume of fluid to the hydraulic motor will be constant thus providing a constant line RPM output of the driving motor, and a pressure regulating line connected between said pump and said motor to regulate the pump pressure output to insure that the motor RPM is constant although the load on the motor may vary. The volume control valve regulates hydraulic fluid between the pump and motor regardless of the pressure and volume output of the pump.

Abstract: A hydrostatic vehicle transmission with a primary and/or secondary part adjustable as to its delivery and its absorption capacity respectively. The hydraulic adjusting elements of said primary and/or secondary part are automatically by spring force adjusted in the direction toward their starting position and are connected to a control circuit which is adapted to be connected to the pressure conduit of a constant delivery pump and is also adapted for controlling the control pressure to be connected to a return line by means of a control member. An adjustable orifice of a limit load control is arranged in the pressure line, which orifice is arranged ahead of the connection of the control member when looking in flow direction. The adjusting member of said limit load control may for instance be connected to the gas pedal or manually operable gas lever of an internal combustion engine for instance a Diesel engine while the hydrostatic vehicle transmission also serves as vehicle brake.

Abstract: A control device for a driving unit which comprises an internal combustion engine and a hydrostatic vehicle transmission. The hydraulic adjusting members of the control unit are in response to a relief of pressure automatically by spring force moved to their starting position and are connected to a control circuit which is connectable to the pressure line of a constant delivery pump and is also by a control member connectable to a fluid return line for purposes of setting a control pressure. An adjustable measuring orifice of a limit load control is arranged in the above mentioned pressure line and, when looking in flow direction, is located ahead of the connection of the control member. The control member of the adjustable orifice is connected, for instance, to the gas pedal of the internal combustion engine. A check valve is arranged in a conduit extending from the limit load control to the control circuit of the hydrostatic transmission.

Abstract: This disclosure relates to a fluid transmission for automatically varying the drive ratio in accordance with the load placed thereon and includes a pump unit and a motor unit and wherein the pump unit is of a variable displacement with the displacement thereof being automatically adjustable in accordance with the pressure of the fluid output thereof and the input speed of the pump unit. The pump unit is of the radial piston type and includes a race member engaged by the pistons for controlling the displacement thereof. The race member has a cylindrical race surface and is mounted for tilting movement wherein in a neutral position the pistons have zero displacement and wherein when the race member is tilted, the displacement of the pistons increases.

Abstract: An hydraulic drive supplies power to the rear wheels of a scraper at loading speeds providing a pushing assist to the tractor engine powering the tractor wheels at the front. The drive includes a piston type motor mounted on the stinger or pusher frame of the scraper and connected through a short torque shaft to a drive axle driving the scraper wheels. A signal generator senses ground speed to maintain the motor free-wheeling at speeds attainable by the tractor which would be destructive to the motor.

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 hydraulic power system having a plurality of variable displacement pumps for supplying pressurized fluid for manipulation of an implement includes control means operative to automatically adjust pump displacement to the output horsepower of a prime mover driving the pumps of a system. The control system includes underspeed valve means responsive to a deviation in the speed of the prime mover from a predetermined normal speed to transmit a fluid pressure signal to a servo control means for adjusting the displacement of the pumps. The underspeed valve means includes adjusting means for adjusting the underspeed valve to respond to a deviation from other engine speeds different from the normal operating speed.

Abstract: A servo mechanism for a prime mover interconnected to a hydrostatic transmission includes a source of pressurized fluid, a fluid reservoir, an actuator having a piston operatively connected to the hydrostatic transmission and being provided with large and small hydraulic receiving areas which are exposed to first and second hydraulic chambers, respectively within the actuator housing, a first passage for connecting the pressurized fluid source to the second chamber, a second passage for connecting the pressurized fluid source to the first chamber, a third passage for connecting the first chamber to the reservoir, and a pair of spool valve means disposed, respectively, within the second and third passages and responsive to a signal indicative of the power required of the prime mover and an actual speed or feedback signal of the prime mover.

Abstract: A hydraulic control system includes a generating circuit for providing power to a work function. A driving apparatus operates the generating circuit. A control circuit is connected to the generating circuit and the driving apparatus for permitting delivery of power to the work function when the driving apparatus is operating up to a predetermined speed. The control circuit also stops delivery of power to the work function when the driving apparatus runs above the predetermined speed. The control circuit further includes a cut-off apparatus for stopping delivery of power to the work function when the driving apparatus is running up to the predetermined speed.

Abstract: The application discloses a system which includes a prime mover driving a variable displacement type pump which in turn drives a variable displacement type motor all coordinated by a control system. Details of valves employed in the control system are disclosed as well as the overall interconnection of such valves with the engine, pump and motor. The control system controls the amount of fuel supplied to the engine, pump displacement, and motor displacement in such a manner as to achieve optimum performance.

Abstract: Apparatus for adjusting a hydraulic machine driven by an adjustable driving motor comprises an adjustment motor which adjusts the machine in one sense under one fluid control input dependent upon actual driving motor speed and in an opposite sense under an opposing such input supplied at a control outlet of a pressure control valve device in dependence upon the position of a valve slide thereof urged by the first input against a biasing force selectively adjustable in dependence upon desired driving motor speed. When the actual speed falls sufficiently relative to the desired speed, the slide travels from one position, blocking flow from a fluid inlet of the valve device to its control outlet, to another position allowing such flow and also allowing the second input thus produced to act on the slide, in the same direction as the first does, until the slide returns to its initial position.

Abstract: An apparatus and method for operating an auxiliary hydraulic load at low noise levels. A pump having a capacity which is sufficiently large to supply the load with the necessary volume of hydraulic fluid at relatively low pump speeds is driven by an engine operating at a speed near its idling speed. Throttle control means control the fuel supply to the engine at a level sufficient to drive the pump while maintaining the engine speed near its idling speed. When the engine speed is increased to a predetermined level in excess of its idling speed, means are provided to maintain the output from the pump at or below a predetermined flow rate to not overload the pump means or the auxiliary load. The pump may include a variable displacement pump or a plurality of fixed displacement pumps with means to vary the pump output in response to the pressure demand from the auxiliary load to maintain the torque input requirements for the pump below a predetermined level.