Abstract: A working fluid supply system for a hydraulic power booster and a power steering system includes first and second fluid supply pumps, a hydraulic power boosting apparatus, a power steering unit, various fluid passages connecting thereto and a control apparatus. The first pump supplies pressurized working fluid to a first inlet port of the hydraulic power boosting apparatus. The second pump, controlled by the control apparatus, selectively supplies pressurized working fluid to a second inlet port of the power boosting apparatus to render the fluid supply flow rate applied to the power boosting apparatus substantially constant at a predetermined level when the fluid discharge rate of the first pump is less than the predetermined level. By this, a sufficient amount of pressurized working fluid is supplied to the hydraulic power boosting apparatus to fully operate it under all actual engine speeds.

Abstract: A drive control circuit for a dental treatment table with a hydraulic cylinder for elevating and lowering a seat comprising a hydraulic drive circuit equipped with a hydraulic pump, a first hydraulic valve for elevating said cylinder, and a second hydraulic valve for lowering said cylinder, and a hydraulic pump operation circuit equipped with an air switch, a first air valve for controlling said air switch and said hydraulic valve for elevating said cylinder, and a second valve for controlling said hydraulic valve for lowering said cylinder. The drive control circuit may further comprise a second cylinder for tilting a backrest which can be controlled by the hydraulic drive circuit and the hydraulic pump operation circuit.

Abstract: A substantially horizontal rotating drum mounted on roller pairs which drum is driven via some of the rollers, drive rollers, by means of a hydrostatic motor on each drive roller. In order to avoid problems, e.g., stoppage if the contact between the drum and one or more drive rollers ceases, each hydrostatic motor is part of a separate power circuit further comprising a hydrostatic pump and a squirrel-cage motor constantly ensuring essentially the same peripheral speed for drum and drive roller irrespective of the torque size.

Abstract: An engine speed control for a variable speed engine wherein the engine can have a set speed to operate at a relatively low working speed or at an idle speed and which is adjustable to increase engine speed. The engine drives plural pumps and a control circuit is responsive to a certain flow rate from either of said pumps to increase the speed of the engine to provide for additional flow from the pumps. In a hydrostatic transmission as usable in the drive of a vehicle, there are a pair of fluid translating devices, in the form of a pump and a motor, with at least one of the devices being of variable displacement and having a displacement control responsive to a speed control signal. In such a system, the engine which powers the hydrostatic transmission is set at a desired speed of operation below maximum speed and is adjusted in response to the speed control signal for increase in said engine speed when the speed control signal exceeds a predetermined level.

Abstract: A drive unit is provided consisting of an internal combustion engine, a continuously variable transmission unit and a fluid operated regulating assembly interconnecting said internal combustion engine and transmission and operated by a single manual control. A second manual control may be provided for interconnecting the engine and a stroke mechanism drive independently of the transmission for operating an auxiliary hydraulic or like circuit.

Abstract: A hydraulic power brake system has a pump driven through a variable torque magnetic clutch by an engine-drive pulley. A rheostat controlled by movement of the brake booster push rod varies the amount of current to the clutch to control the torque transmitted to the pump. The pump pressure output varies directly with clutch torque. Pump pressure is delivered to a closed center hydraulic booster. The pump does not operate when no braking effort is required.

Abstract: A gearless transmission providing pressurized hydraulic fluid to torque motors for driving a vehicle. A hydraulic pump is driven by a turbine engine shaft to provide fluid to accumulators and then to the transmission device. Fluid is selectively admitted into the transmission by the vehicle accelerator pedal. Thereafter the fluid flow may be restricted through fluid circuitry having orifices which provide variable torque output. The circuitry is controlled by a shifter selector with pilot lines to actuate fluid control valves between two control positions. Especially important for turbine-powered vehicles, the transmission provides a braking function when the accelerator pedal is released in either the low or second control range of operation. Means for providing a reverse mode of operation is also disclosed.A hydraulic differential is also provided and is controlled by the steering mechanism to restrict flow to one of the torque motors during a turn.

Abstract: A system for automatically regulating the fuel supplied to the engine of a mobile construction machine which has a hydraulic pump driven by the engine. A tool is carried by the machine for performing work functions and hydraulic cylinders are provided for manipulating the tool responsive to pressurized fluid being supplied to the hydraulic cylinders. A manually operated valve mechanism is provided for controlling the flow of hydraulic fluid between the hydraulic pump and the hydraulic cylinders. A lever arm regulates the flow of fuel to the engine. The lever arm can be manually manipulated or it can be manipulated automatically by means of a double action cylinder. A piston rod extending from the double action cylinder is connected to the lever arm so that the fuel supplied to the engine is regulated responsive to changes in pressure in the hydraulic system.

Abstract: An apparatus and method of controlling the input power to a drill feed or other hydraulic system in which the hydraulic power source is obtained from a compressed air supply. Wherein, the flow of air is varied in response to a hydraulic signal controlled by the load demand of the hydraulic system. Low and high mode controls are provided to operate hydraulically actuated mechanisms; and a hydraulic absorbing load is imposed to prevent stall or overspeed of the pump and motor during low load conditions.

Abstract: An engine for operating a hydraulic motor. Opposed pistons, joined by a common connecting rod operating between two cylinders and between internal combustion valving and ignition components, are used to drive fluid under pressure through a series of cross-over valves to and from a hydraulic motor. Hydraulic fluid is stored and maintained under pressure within the engine cylinders on the other side of the pistons forming an internal combustion engine. A series of embediments within the common connecting rod actuate a matched set of proximity detectors. The proximity detectors, in turn, time the operation of the engines and the operation of the cross-over valves without mechanical linkages. A hydraulic pump is used to start the engine. A blower is used to mix the fuel and air within the engine and to exhaust combustion gasses. The hydraulic motor drives a flywheel to store energy and to dampen the pulsations resulting from the shifting of the cross-over valves and the reciprocating action of the pistons.

Abstract: A control system is disclosed for a hydrostatic transmission of the type including a prime mover driven variable displacement pump, the displacement of which is controlled by a pair of strokers (28, 30). Flow of pressurized control fluid from the charge pump to one of the strokers, and from the other stroker to tank, is controlled by a main control valve (34). The control system includes an auxiliary control valve (44) defining passages (98, 100, 102) communicating between the lines connecting the main control valve and the strokers. The auxiliary control valve includes an on-off, electro-hydraulic valve (46) which prevents flow through the auxiliary valve in response to an electrical signal in one condition, and permits flow in response to an electrical signal in another condition.

Abstract: An engine-transmission control system having an engine associated with a variable hydrostatic transmission with a ratio governor valve to set the transmission ratio and, thus, control engine speed, a horsepower demand signal valve and an engine speed signal valve with the signals derived from these valves being applied in opposition to the ratio governor valve for control thereof, and an engine fuel governor for the engine providing an operating curve for the engine which relates engine speed to engine horsepower to cause operation along the locus of minimum fuel consumption for the engine whereby operation of the transmission to set the engine speed determines engine horsepower by operation of the engine along the operating curve.

Abstract: Flow from a pressure source is bidirectionally conducted to a prime-mover driven, bidirectional, positive displacement pump and in-series flow restrictions; the pressure source and flow restrictions functioning to provide the reference flow rate; the pressure gradient across said pump bidirectionally signaling the error in prime-mover speed. Means responsive to said pressure gradient provide proportional plus integral control of the prime-mover speed.

Abstract: There is shown a safety control system for a self-propelled road roller having hydrostatic transmission, which includes a prime mover, an hydraulic pump driven by the prime mover and included in a main hydraulic circuit incorporating a motor with a power-off brake device, a check valve bridge with a ventable relief valve and a main control valve, and means for selecting automatically the speed and a predetermined operating speed, the speed selecting means comprise a secondary hydraulic circuit including means operatively connectible with the prime mover speed control means and controllable by the ventable relief valve in accordance with the operation of the main control valve.

Abstract: Three embodiments of a hydraulic safety mechanism are adapted to adjust the speed setting for an engine upon a reduction of pressure in a chamber, due for example, to loss of lubricating pressure, overspeeding of the engine or overheating, for example. In each embodiment, a speed control element for the engine is maintained in a normal operating position by a piston and cylinder combination which hydraulically blocks the chamber from the fluid drain in a normal operating position, the piston responding to reduced pressure in the chamber by communicating the chamber with the drain the piston thereby being hydraulically unlatched and permitting the speed control element to be repositioned to a reduced speed setting. A restrictive orifice, preferably of variable size and self-cleaning construction, regulates communication between the hydraulic circuit and the chamber. In another embodiment the safety mechanism includes a solenoid and accumulator chamber to adapt it for remote operation.

Abstract: The control system has an adjustable flow-rate pump and a fixed flow-rate pump which is supplied with hydraulic fluid via a supply conduit. A first throttle is interposed in this conduit and produces first signals in form of pressure differentials in dependence upon variations in the rotational speed of an ungoverned combustion engine which powers the hydraulic drive, which signals trigger flow-rate adjustments of the main pump. A second throttle is also interposed in the supply conduit and produces second signals in form of pressure differentials in dependence upon variations in the load upon the hydraulic motor of the hydraulic drive, which signals trigger movements of the throttle flap of the internal combustion engine towards the open or closed position thereof.

Abstract: A hydrostatic transmission has an input connected to a prime mover and an output connected through a speed-change transmission to a load. A control element of this transmission is urged in a direction tending to increase the transmission ratio by a control cylinder pressurized from a hydraulic tachometer operated by the transmission input, and is urged in the opposite direction to decrease the ratio by a regulating cylinder connected via a feed line to the hydraulic network interconnecting the pump and motor of the transmission. During speed change the two cylinders are depressurized and the regulating cylinder is isolated from the network.

Abstract: A control circuit (10) for the variable displacement pump (18) of a hydrostatic transmission (16) or the like comprises an underspeed actuator (31) connected to the servo system (19) of the pump (18), a venturi (15) interconnected between a source of pressurized working fluid (11) and the pump (18) and a pressure regulating valve (36) interconnected between a downstream side of the venturi (15) and the pump (18). A throat (29) and upstream side of the venturi (15) are connected to the underspeed actuator (31) for communicating a differential fluid pressure signal thereto to automatically control the displacement of the pump (18) under certain operating conditions of an engine of a vehicle.

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: The present invention relates to a control device for a combustion engine and particularly to a combustion engine for use with hydrostatic transmissions particularly as used in a fork lift truck.

Abstract: A control system and method for loading an engine driven apparatus such as an engine driven tractor having a plough the depth of which can be regulated by a suitable control system. The engine has a fuel injection pump which includes a maximum fuel feed limiting structure, a stop, and a structure for urging the maximum fuel feed limiting structure against the stop when an overload is imposed on the engine. Under the latter overload conditions the force with which the maximum fuel feed limiting structure is urged against the stop is detected by way of a force transducer such as a strain gauge or hydraulic pressure transducer, so that a signal indicative of the overload is produced and can be utilized for reducing the load on the engine. Thus, in the case of an engine-driven tractor which operates a plough, the latter signal can be utilized to raise the plough so as to reduce the load on the engine.

Abstract: The carriage of a fork lift truck is actuated by the action of hydraulic fluid controllably supplied through a manually operated control system from a pump driven by an internal combustion engine having a carburetor. The throttle valve of the carburetor is partially opened in response to the operation of the control system in order to increase the discharge amount of the hydraulic fluid of the pump during idling of the engine.

Abstract: Apparatus for regulating the output of a system feed with a fluid medium irrespective of the instantaneous pressure in the system comprising a regulating device including an adjustable throttling connected in the inlet line of the system. A preset non-return valve is connected downstream of the throttling and a spring loaded non-return valve is connected in series with the preset non-return valve and is fitted with a leakage connection extending to a reservoir tank. A control line is connected between the pre-set non-return valve and the spring loaded non-return valve and it senses pressure drop at the throttling so that when the pressure drop reaches a predetermined value the non-return valve opens so that fluid medium is transferred and pressure in the control line increases. A central device is connected in the control line for regulating a quantity of flow to the primary line and the control device comprises a spring loaded piston actuated by increased pressure in the control line.

Abstract: A vehicular gas turbine engine power system includes an engine, an automatic clutch, a service clutch and an infinitely variable transmission coupled successively along a power train. A vehicle control system controls engine speed, transmission ratio and automatic clutch engagement in response to operator selected ground speed and engine speed commands as well as other vehicle conditions. The vehicle control system operates in a manual mode to maintain engine speed as commanded by an operator or in an automatic mode to maintain an engine speed which will minimize fuel consumption. The transmission ratio is controlled for fixed rate vehicle acceleration toward a commanded speed if sufficient power is available. Otherwise ground speed is cut back to match required power with available power. However, ground speed cut back is limited as a safety feature and disengagement of the automatic clutch prevents engine stall when the engine becomes overloaded.

Abstract: A combined control system for simultaneously control-line a vehicle throttle and transmission from a single pedal wherein the control pedal is mounted for fore and aft rocking movement with transmission linkage means connected thereto for movement therewith for controlling forward and reverse of the transmission. Linkage means for the throttle includes a pair of bell cranks mounted fore and aft of the pivot axis of the control pedal whereby one bell crank is engaged by the pedal when rocked in one direction and the other bell crank is engaged by the pedal when rocked in the opposite direction with the bell cranks connected together and to the throttle linkage means so that either direction of rocking of the control pedal imparts a movement in the same direction through one or the other of the bell cranks to the throttle control linkage.

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: A hydraulic fluid supply system for providing pressurized fluid to fluid actuated components on a refuse collection vehicle, generally including a fluid tank, a pump operatively connected to the crankshaft of the refuse vehicle engine for continuous operation and having an inlet communicating with the tank, a diversion valve having an inlet communicating with the outlet of the pump and having an outlet selectively communicating with the tank and the fluid actuated components on the refuse collection vehicle, means for increasing the idle speed of the engine to a predetermined actuation idle speed when the diversion valve outlet is communicating with the fluid actuated components, and means for preventing the engine from exceeding a predetermined override speed when the outlet of the diversion valve is communicating with the fluid actuated components thereby preventing damage to the pump if an operator accidentally depresses the accelerator pedal in the vehicle.

Abstract: A foot pedal is connected to a first link which is also connected to the first arm of a bellcrank. The bellcrank is secured to an input shaft of a hydrostatic transmission. The first link is adapted to reciprocate in opposite directions upon pivoting of the foot pedal in opposite directions. A second link, interconnected between a second arm of the bellcrank and an engine throttle control lever, is adapted to pivot the throttle control lever in the same direction in response to reciprocation of the first link in either direction thereof. Thus, depression of the pedal in either direction will actuate the transmission to place it in its forward or reverse mode of operation whereas the throttle control lever will be actuated in the same direction in response thereto.

Abstract: A hydrostatic transmission comprising a closed loop system incorporating a hydraulic pump and a hydraulic motor driven by the pump has an accelerator for the motor drive shaft which sets the maximum delivery pressure of the pump, and control means which acts to vary the relative volume displacement of the pump and the motor to maintain the pump delivery pressure at the maximum value determined by the setting of the accelerator. Thus, the closed loop system maintains a substantially constant maximum pressure throughout the flow range, and since the output torque of the motor drive shaft is proportional to this system pressure a true acceleration control is achieved. The relative value displacement of the pump and the motor may be influenced by the low pressure of delivery of the pump on overrun of the motor shaft and by a spring loaded braking valve adjustable by a pedal control to provide for braking of the motor drive shaft.

Abstract: A hydraulic priority circuit for a fork lift truck or the like includes a variable output pump controlled by a motor. The speed of the motor is controlled by feedback from a demand indicator in a primary work system, such as a hydraulic steering system, and from a demand indicator in a secondary work system, including, for example, tilt and lift hydraulic circuits. A valve means, including a priority control valve, a sequence valve, and pressure compensated flow control orifices, is provided to regulate the fluid flow requirements of the primary work system on a priority demand basis, with the excess fluid flow being coupled to the secondary work system.

Abstract: An electrically powered vehicle, e.g. a forklift truck or other utility-type battery-powered vehicle, is provided with a hydraulic power-steering system with a pump driven by an electric motor. A circuit is provided to cut out the power-steering pump motor when the vehicle attains an elevated speed, thereby reducing battery drain during period in which power-steering is not normally required.

Abstract: A fluid drive vehicle has an engine speed control, a fluid drive transmission having a fluid actuator device for moving a control element from its neutral position progressively to increase the drive ratio, and a control system which includes a first fluid circuit which has a control valve movable from a neutral fluid blocking position progressively to increase the flow of pressurized fluid from an auxiliary pump to the fluid actuator device. A fluid responsive servo mechanism moves the control valve from the neutral position while a fluid motor is operative to move the engine speed control from an idling position to increase the engine speed.

Abstract: The present invention relates to an apparatus providing for the co-ordinated driving of a towing vehicle and a towed vehicle equipped with a hydrostatic driving system of its own. The respective driving wheels of the towed vehicle are each driven by a separate hydrostatic transmission and a variable output hydraulic pump coupled to a hydraulic motor which can be driven by output of said hydraulic pump and can be engaged with a driving wheel. The apparatus includes for each respective transmission control circuits having a control device mounted on the towing vehicle. The invention is particularly useful for a cross-country towing vehicle and a towed vehicle in the form of a heavy field artillery gun which for purposes of operating the hydrostatic transmissions is equipped with a reciprocating engine, for instance a gasoline engine, which actuates said transmissions via a dividing gear box.

Abstract: The throttle of an engine is controlled to maintain its speed substantially constant in spite of variations of load upon it. The illustrated load comprises hydraulically operated equipment in a hydraulic system powered by a pump driven by the engine. Throttle control mechanism comprises a pair of cylinders supplied from fluid pressure in the hydraulic system. Pistons in the respective cylinders are connected by pivots with a control arm linked to the throttle control. When equipment is hydraulically operated from the hydraulic system, the fluid back pressure against the pump increases, this back pressure being greater the greater the hydraulic load. The increased load on the engine from the pump would slow the engine down if its throttle opening were to remain at its original setting.

Abstract: A fluid power system comprising a steam generator connected to a hydraulic pumping device for delivering steam under pressure to the device for driving the same, while steam is returned to the steam generator via a condenser. The hydraulic pumping device is connected by means of suitable conduits to a plurality of hydraulic motors for driving the same and the conduits include valving means for controlling the direction of fluid between the hydraulic pumping device and the hydraulic motors and returning fluid to a reservoir from which fluid is initially drawn by the hydraulic pumping device. The hydraulic motors provide a rotary output for driving the wheels of a vehicle on which the fluid power system is used. The system further comprises valve means for controlling the pressure at which the system operates.

Abstract: A vehicle drive system utilizing an engine controlled to operate at a substantially constant speed during vehicle operation. Means are provided to vary that engine speed in accordance with different types of operation. The engine powers an hydraulic pump, the output flow from which is varied to determine the vehicle speed. An hydraulic motor receiving fluid from the pump is driven thereby and is coupled to the drive shaft of the vehicle.

Abstract: The novel arrangement of prime movers and associated driven pumps in cooperation with a hydraulic summating system disclosed in this application consists of a plurality of prime movers, each of which is connected to drive a group of interconnected fixed displacement pumps. Separate sets of pumps are formed with one pump of each driven group connected in parallel to supply fluid under pressure to separate systems containing various hydraulically operated functions. The summating system includes a valve arrangement whereby the total engine power generated by the prime mover of each group of pumps is available for one or all pumps in the group and thus any one or all of the hydraulically operated functions in each system has available all or a portion of the prime movers' total engine power up to the maximum available.

Abstract: An overspeed protection control for an engine which drives at least one pump and having valve means selectively operable to cause an increase in pressure in a circuit supplied by said pump and a resulting increase in load torque on the engine. Means responsive to the engine speed exceeding a predetermined value causes operation of the valve means, and includes a control valve positionable either in response to a pressure differential across an orifice in the circuit supplied by the pump with the pressure differential being an indication of flow rate and, therefore, engine speed, or operable by a control circuit including means for detecting engine speed.

Abstract: A hydrostatic unit of the type contemplated by the present invention includes one or more pump and motor combinations interconnected by means of a conventional closed loop. Controls for the hydrostatic unit include a speed control and vent valve assembly as well as a venturi manifold which functions to normally establish a selected pressure differential in a pair of supply conduits for determining instant operating conditions for the transmission. In order to automatically regulate displacement of each pump unit in response to prime mover speed, an underspeed actuator valve unit includes a piston which is hydraulically responsive to the differential pressure in order to adjust operation of a lever which controls displacement of the pump unit. A part throttle control valve prevents the underspeed actuator from reducing displacement of the pump unit when speed of the prime mover is reduced by a manual throttle control.

Abstract: Two adjustable-stroke pumps are driven off a common drive shaft and supply fluid to respective consumers via respective control valves settable by the user of the system. Each pump is provided with its own pressure regulator operative for regulating the output pressure of the respective pump by automatically adjusting the setting of the stroke-adjustment member of the pump. Transducers generate first signals indicative of the settings of the stroke adjustment members and second signals indicative of the settings of the control valves. A control arrangement maintains the settings of the volume-adjustment members in correspondence with the settings of the control valves by automatically altering the operation of the pressure regulators in response to discrepancies between the settings indicated by the first and second signals.

Abstract: The combined sensor and control comprises a flow sensor through which passes working hydraulic fluid delivered by a pump through a hydraulic power circuit to a hydraulically operated power mechanism which is subjected to variations in load. The sensor senses incipient changes in a preselected rate of flow of the working hydraulic fluid by detection of very slight changes in the differentials in the pressure of the working fluid at opposite sides of a restricting orifice through which the working fluid is constrained to pass. These differentials in pressure, or pressure drops, operate a pneumatic pressure control device by which pneumatic pressure supplied to an actuator through a circuit, isolated from the working hydraulic circuit, is controlled. The pressure control device causes the applied pneumatic pressure to be varied almost instantly in a manner analogous to the slight variations in the normal preselected differential in pressure across the orifice.

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: The disclosure relates to plural, motor driven hydraulic pump circuits, including circuits having the pumps in at least one circuit operated in pairs with all pumps being driven by a single prime mover. A speed responsive control device unloads one pump in one circuit when engine speed drops below a predetermined value without regard to the source of the condition causing the slowdown. Also included is a crossover means for sensing the pressure in aother circuit for preventing reloading of the unloaded pump when speed rises above the predetermined value unless and until the pressure including the pressure sensed in the other circuit is below a predetermined pressure.

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: Coordinated control of engine speed, transmission drive ratio and drive direction is provided for with a single foot pedal and a compact economical linkage arrangement for coupling the pedal to a vehicle engine and hydrostatic transmission. Forward rocking of the pedal from a neutral position progressively increases transmission drive ratio in the forward direction while backward rocking of the pedal from the neutral position progressively increases the drive ratio in the reverse direction. The pedal linkage further produces a unidirectional progressive motion of the engine speed control upon being rocked in either the forward or backward direction and this engine speed control motion may be continued by additional pedal movement after the transmission control member has reached the maximum possible movement in either direction.

Abstract: A stepless, preferably hydrostatic, transmission is provided for an internal-combustion engine and the system is controlled by an operating member. A mechanism connects the members to the transmission and the engine so that both the engine and the transmission controls respond to this member. Means is provided for affecting the linkage in response to the torque on the transmission shaft, preferably in dependence upon the pressure in a transmission-fluid line.

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.