Abstract: A working vehicle includes a first hydraulic pump (e.g., a variable displacement pump) with a delivery flow rate controlled by load sensing control, a second hydraulic pump (e.g., a fixed displacement pump), at least one working-machine-related control valve to control at least one working-machine-related hydraulic actuator, a power shift valve to control at least one traveling-power-transmission-related hydraulic actuator, and a power steering controller to control a steering-related hydraulic actuator. The at least one working-machine-related control valve is provided in a first hydraulic system supplied with hydraulic fluid by the first hydraulic pump, and at least one of the power shift valve or the power steering controller is provided in a second hydraulic system supplied with hydraulic fluid by the second hydraulic pump.

Abstract: Disclosed embodiments of power machines, implements and hydraulic systems utilize a hydraulic flow control circuit and method to implement multiple modes of operation while optimizing hydraulic fluid flow to either or both of primary and secondary function devices.

Abstract: On a work appliance, an extension arm is held rotatably, and a scoop is held rotatably on the extension arm. Actuation of the extension arm and of the scoop is by means of hydraulic cylinders. Each cylinder is assigned a valve which controls the flow of pressure medium from a pump to the cylinder and from the latter to the tank. A rotational movement of the extension arm is accomplished with the top edge of the scoop maintaining its angular position when the extension arm is being raised or lowered. Valves which control the flow of pressure medium to the cylinders are activated with the ratio of the pressure medium quantities supplied to the cylinders being kept at a constant value independently of the size of the control signal controlling the flow of pressure medium to a cylinder for the actuation of the extension arm.

Abstract: The present invention generally pertains to hydro-mechanical transmission using fixed displacement motors and pumps in conjunction with two or more mechanical differentials to accomplish continuously variable transfer ratio change and a means to seek the operating point of peak efficiency. In addition a hydraulic transmission is described that uses only one differential. In addition, an all-mechanical by-pass feature is included to allow the operation of road vehicles at high speed for extended periods at high efficiency. A means is described to provide for mechanical stability under all operating conditions. One intended application is a hydraulic transmission system for vehicles using hydraulic regenerative braking. The all mechanical by-pass allows operation in an “overdrive” and “free-wheeling” mode.

Abstract: A hydraulic control device of construction machinery having a main merging/diverging valve interposed in a connecting oil path connecting discharge oil paths of first and second hydraulic pumps in a merging position, operating levers for corresponding works operated to actuate plural actuators, an operating condition judging section judging a lever operating condition of each operation lever, a pattern collating section selecting an operating pattern matching an actual operation pattern from set and stored various operation patterns corresponding the operating conditions in a controller. When a load pressure of each actuator is high, a discharge pressure of each discharge oil path is also high, and when a total of the discharge pressures exceeds a predetermined set pressure, the main merging/diverging valve is switched to a diverging position, and when the total of the discharge pressures drops to below the set pressure, the main merging/diverging valve is switched to the merging position.

Abstract: A hydraulic system for utility vehicles, in particular agricultural tractors, with a regulated hydraulic pump (1) is disclosed for prioritised pressure medium supply to internal and external pressure medium consumers (6, 11, 12), which are fed via load sensing spool valves (20, 26), the external pressure medium consumers (11, 12) being supplied with pressure medium via a priority valve (17). In the case of known utility vehicles the lowest priority is assigned to the internal pressure medium consumers. Situations are known however, when operating an air seeder for example, in which it is not expedient with the pressure medium supply to give preference to the internal pressure medium consumers over the external because the power capacity of the hydraulic system is not then exploited to an optimum. Short supply to such implements leads to a negative influencing of the work pattern.

Abstract: A divider combiner valve using only one spool without any springs. The correct holes open and close by ball and seat type check valves although these could be a poppet or disk as well and these valves may be located in the valve body, the spool, or both. These are simple and reliable. There is no chance of the holes not being in the correct location. Since there is only one spool, contamination cannot keep the spools from shifting into their correct relationship with each other. The extra pressure drops, needed to overcome the spring forces in the earlier designs, have been eliminated all together. Also, the number of spools has been reduced from two or three down to a single spool, thus reducing the cost to manufacture the finished valve. Because there is only one spool, clearances are closer. There is less internal leakage, more accuracy while the cylinders are in motion. This closer clearance tends to lock the loads rather than transfer oil from one cylinder to the other.

Abstract: Method of sharing hydraulic fluid, includes: inputting first signal from a first manual control and second signal from a second manual control; sending a first control signal controlling a first valve in response to first signal; sending a second control signal controlling a second valve in response to second signal, wherein the first valve and second valve direct flow through a first sub-circuit and a second sub-circuit, respectively, wherein the first sub-circuit moves a boom arm and the second sub-circuit moves an implement; determining whether the boom arm and implement are in a first, second, third, or fourth condition; modifying at least one of the first and second control signals when the boom arm and implement are in first or second conditions; and controlling the first valve using the unmodified or modified first control signal and controlling the second valve using unmodified or modified second control signal.

Abstract: An automotive hydraulic system having a power steering unit of a vehicle connected in parallel with an externally mounted, hydraulic-cylinder-powered accessory, such as a liftgate, snow plow or dump bed. The vehicle's power steering pump supplies the required hydraulic fluid to the power steering unit and to a cylinder in the accessory, simultaneously in the preferred embodiment and alternately in another. A preferred valve assembly is disclosed which includes a priority flow control valve and a three-position, four-way accessory control valve mounted together in a manifold designed for connection to the vehicle's power steering pump, power steering unit, and hydraulic fluid reservoir, and to a double-acting hydraulic cylinder in the accessory.

Abstract: A fluid control system for powering vehicle accessories includes a pump for generating a supply flow of hydraulic fluid. The system also includes a fluid valve assembly having a housing which includes an inlet, a first outlet, a second outlet, and a third outlet defined therein. The inlet is in fluid communication with the supply flow of fluid. The fluid valve assembly provides (1) a first fluid path between the inlet and the first outlet, (2) a second fluid path between the inlet and the second outlet, and (3) a third fluid path between the inlet and the third outlet. The system also includes a fan motor for rotating an engine cooling fan. The fan motor is in fluid communication with the first outlet. Moreover, the system includes a steering control circuit which is in fluid communication with the second outlet. The system further includes a reservoir which is in fluid communication with the third outlet. A method of controlling fluid flow between a plurality of vehicle components is also disclosed.

Abstract: An unloader valve is connected to a pump and has first and second ends, a priority flow port communicating with the first end and being connected to a first conduit connected to a first hydraulic circuit, an excess flow port communicating with a tank, and a spring disposed at the second end biasing the unloader valve to a priority flow position with a force sufficient to maintain the pressure in the priority flow port above a predetermined minimum level. The unloader valve is biased toward an unloading position in opposition to the spring force by pressure generated force acting on the second end. A check valve is disposed between the first conduit and a second conduit connected to a second hydraulic circuit. A valve device controls the pressure at the second end of the unloader valve in response to pressure in the second conduit so that pressure in the second conduit is maintained above a second higher predetermined level.

Abstract: A self-leveling system controlling a boom (13) and a bucket (15) by double acting cylinders (17, 19). The system includes a self leveling valve assembly (27) including a first valve section (27a) including a flow divider spool (41) whereby flow from the rod end of the boom cylinder (17) is divided, one portion flowing to the head end of the bucket cylinder (19). The valve assembly also includes a second valve section (27b) including a flow dividing spool (61), whereby flow from the head end of the boom cylinder (17) is divided, a portion flowing to the rod end of the bucket cylinder, as the boom (13) is lowered. The self leveling valve assembly (27) includes capability whereby, even when the bucket cylinder (19) is fully extended or fully retracted, it is still possible to operate the boom cylinder (17).

Abstract: An hydraulic line and valve assembly for supplying hydraulic pressure to an hydraulic auxiliary implement, the implement being adapted for attachment to a construction vehicle having an hydraulic power system, the implement having an hydraulic motor driven workpiece, and the implement having a plurality of hydraulic positioning means; the hydraulic line and valve assembly comprising an on demand priority flow control valve, a branched primary pressure line an end of which being fixedly attached to the on demand priority flow control valve, a plurality of position control valves, the position control valves being fixedly attached to the opposing branched ends of the primary pressure line, and a branched hydraulic load signaling line extending from the position control valves to the on demand priority flow control valve, the hydraulic load signaling line being capable of sending pressure signals to the on demand priority flow control valve causing said valve to divert hydraulic pressure to the position control

Abstract: A control system is typically used for controlling the implements of a machine. The control system includes a lift circuit and a tilt circuit. The control system includes a module which receives a signal from the lift circuit and the tilt circuit and selects a signal for controlling a valve to meter pump-to-cylinder fluid flow.

Abstract: A valve for controlling the flow of hydraulic fluid from a hydraulic pump to and back from a pair of hydraulic motors. The valve includes a selector spool for selectively energizing and de-energizing the motors. A pair of flow dividers each include a pair of flow divider spools which are slidingly longitudinally arranged. A pair of poppets, also longitudinally slidingly arranged, are located between the spools are selectively shifted in response to the hydraulic fluid flow and pressures within the motors. The spools and poppets longitudinally shift to equalize the pressure of the hydraulic fluid delivered to each motor and minimize loses. An override spool is selectively shiftable for bypassing the flow dividers and directly connecting the pump to the motors.

Abstract: A one-piece terminal block (73) is provided as a hydraulic linking element as well as a mechanical carrier for control valves (68 to 72) of a boom control unit, for an operating mode selector valve (74), and for switching elements of a pressure supply device (77). A pressure line (119), return line (132), control line (166), and a further return line (167,168) are designed as bores extending in an axial direction of the terminal block, from which connection channels originate which terminate within terminal arrays (163, 163.sup.I to 163.sup.IV) in a bore layout for the valves. Sections (102') of a load feedback line (102), which are serially connectable to each other by comparative valves (114) are formed by individual longitudinal bores (188,188.sup.I to 188.sup.

Abstract: A priority control valve used in a hydraulic apparatus for supplying fluid delivered from a single pump to at least two actuators respectively via parallel fluid lines, the actuators operating independently or in combination with each other. The variable priority device includes a priority control valve installed in the parallel fluid line associated with one of the actuators and adapted to be switched between an orifice state and an orifice release state, the priority control valve being initially maintained at the orifice release state by resilience means while being switched from the orifice release state to the orifice state against a resilience of the resilience means in response to a pilot pressure for moving the spool of a control valve for the other actuator.

Abstract: A hydraulic circuit is disclosed for a tractor in which a steering circuit and an implement circuit are utilized to provide a high flow capability to the implement valve stack. A series of priority valves are operable to divert hydraulic flow from the steering circuit to the implement circuit under conditions where the steering mechanism is not being operated and the implement circuit pump is operating at full capacity. The first priority valve diverts the hydraulic flow from the steering circuit to a second priority valve that is controlled by a pressure differential valve that senses the implement circuit pump working at full displacement, whereupon the second priority valve directs the diverted hydraulic flow into the implement circuit. The first priority valve retains hydraulic flow within the steering circuit whenever the steering mechanism is being operated.

Abstract: A compensation system for a hydraulic circuit of a hydraulically driven vehicle for straight traveling, with left and right traveling valves having load detection ports; left and right pressure compensation valves arranged in respective pressurized fluid supply passages between a fluid pressure source and the traveling valves; and a by-pass passage for connecting together the load pressure detecting ports of the left and right traveling valves. There may be an on-off valve in the by-pass passage.

Abstract: A control device for hydraulically operated machines for carrying out control to move a working unit with priority over other working units. A weight is added to each of the same manipulated amount of a plurality of operation levers 3, 4 in association with work type of M1 to M5 and the weights are stored in a memory of a controller 5 in association with the type of the operation levers 3, 4 and the work type. The work type M1 to M5 are selected by a switch 2. When the operation lever 3, 4 is manipulated and a work type is selected by the switch 2, the weight associated with the type of the manipulated operation lever 3, 4 and the selected work type M1 to M2 is read from the memory, and the read weight is added to a manipulated amount S1, S2 of the manipulated operation lever 3, 4. Then, not signals indicative of the manipulated amount S1, S2 of the operation lever 3, 4 but signals E, E' added with the weight which are indicative of the manipulated amount are outputted to control valves 7.

Abstract: Cylinder head (81) of a hydraulic lift cylinder (39) includes a fluid input port (74) and first fluid output port (75) to be connected respectively to a pump (46) and to a power steering mechanism (40). These ports preferably open at one and the other side surfaces of the head. The head further includes a second fluid output port (83) and fluid inlet port (84) which open at a front surface of the head. These ports are connected through an inside of a cover member (49a, 50a; 201; 250a) detachably mounted on the front surface of head. The head includes therein a flow divider (47) which divides inflow of the input port into first and second flows directed respectively to the first and second output ports. Fluid returned into the inlet port is directed towards a first control valve assembly (48) for the lift cylinder.

Abstract: Disclosed is a hydraulic system for a machine having a pump, a steering circuit and first and second hydraulic implements, e.g., a hydraulic loader and a backhoe, powered by first and second valve sections, respectively. In the improvement, the system includes a priority valve receiving fluid from the pump and configured for movement between a first position and a second position. In the first position, the priority valve flows fluid to the steering circuit and to the second valve section and in the second position, the priority valve flows fluid to the both valve sections which are connected in series.

Abstract: A fluid pressure driving system for a vehicle includes a reservoir tank in which an amount of fluid is stored, a variable capacity oil pump sucking the fluid from the reservoir tank and discharging the resultant fluid, a control device for adjusting a quantity of the fluid discharged from the variable oil pump, and a distributor valve having an inlet port for receiving the fluid from the variable capacity oil pump. The distributor valve discharges a fixed amount of the fluid and the remaining amount of the fluid from a first outlet port thereof and a second outlet port thereof, respectively. A first passage connects the first outlet port of the distributor valve and the reservoir tank. A second passage connects the second outlet port of the distributor valve and the reservoir tank. A power steering device is associated with a steering wheel and disposed in the first passage. A hydraulic motor is disposed in the second passage, and a cooling fan is mounted rotatably on the hydraulic motor.

Abstract: In a driving mechanism of a circuit breaker having first and second hydraulic operation apparatuses respectively driving a main contact and a resistor contact, a sequential control valve is provided between the first and second hydraulic operation apparatuses. The sequential control valve detects the operation of a differential piston for opening the main contact and switching the differential piston for sequentially opening the resistor contact after the opening of the main contact.

Abstract: A power sensing regenerator includes a pair of displacers (24 and 26) connected in tandem for dividing a flow of fluid from a pump (12) into predetermined proportions for servicing one or more loads (42). Flow control valves (32 and 34) regulate respective flows from the displacers (24 and 26) to the one or more loads (42). A control system, which includes differential pressure regulators of the flow control valves (32 and 34), responds to a difference between discharge pressures of the displacers (24 and 26) for reducing discharge pressure of the pump (12).

Abstract: The present invention relates to a valve assembly for the supply of users in hydraulic control systems with pressurized fluid for the load pressure (LS) independent control of several simultaneously actuated hydraulic users wherein the ratio of the partial flows once set is maintained at undersupply of the system with the pressurized fluid. When the demand of the users exceeds the maximum output flow of the variable displacement pump, the (high) priority users receive the demanded quantity whereas the low priority users receive a reduced quantity by switching the control pressure for the low (i.e. no) priority users via a directional control valve and a pressure relief valve to a lower pressure level. Only when undersupply of the entire system occurs, i.e. when the maximum output flow of the variable displacement pump is no more sufficient despite the limitation of the control pressure for the low priority users, then the presently flowing partial flows of all users are reduced proportionally.

Abstract: A plurality of directional control valves (5, 6) respectively disposed between a hydraulic pump (50) and a plurality of actuators (3, 4) each comprises a pump port (9), a pressure chamber (10), a feeder passage (11), actuator ports (12a, 12b), a reservoir port (13), first meter-in variable restrictors (15a, 15b) disposed between the pump port and the pressure chamber, and a pressure compensating valve (16) disposed between the pressure chamber and the feeder passage and having a pair of opposite ends, one of which is subjected to a pressure in the pressure chamber and the other of which is subjected to a maximum load pressure among the plurality of actuators. The hydraulic pump (1) includes a pump flow control device (2) for controlling a delivery rate of the hydraulic pump so that a delivery pressure of the hydraulic pump is held higher by a predetermined value than the maximum pressure obtained, as a load sensing pressure, from load pressures of the plurality of actuators.

Abstract: A control device for hydraulic operating cylinders of a combined lifting platform and closing wall of a vehicle, having a hydraulic fluid pump (1), driven by a motor (2), which pump can be made to communicate with a fluid supply (4) and, via pump branch lines (8', 8") beginning at a pump line (8), with a chamber of at least one lifting cylinder (11) and of at least one closing cylinder (14) of the lifting platform and closing wall, respectively, via associated control valves (9, 10; 12, 13), wherein a pressure transformer and piston cylinder unit (15) is connected parallel to the pump branch lines (8', 8").

Abstract: In a pressure-control device for affecting the closing behavior of powershift clutches (K.sub.1 -K.sub.X) in a powershift transmission, a regulating valve (1) cooperates with a damping device (2) as pressure-control valve. Chokes (4, 40, 400) for a more or less smooth connection are arranged in combination with pressure lines (P.sub.S, P.sub.R) over the pressure cycle when the clutch concerned (K.sub.1 -K.sub.X) is engaged. The travel of the damper piston (21) in a direction toward the regulating valve (1) is shortened by a pressurizing piston device (3) cooperating with the piston (21) of the damping device (2). Thus the time for the slipping phase in the engaged clutch concerned is shortened and, together with a higher initial pressure after the clutch is filled, the friction is limited.The limitation of the friction can also be obtained by adding a second choke in parallel in the control pressure line (Pr) by which the choked cross section is increased.

Abstract: The invention relates to a hydraulic circuit for supplying at least one motor incorporating "disengageable" pistons, comprising a fluid distributor valve obturating, in one of its positions, the supply and exhaust conduits of said motor.According to the invention, the fluid distributor valve comprises a shuttle valve presenting two inlet connections and one outlet connection, and, in said position, establishes communications of the supply conduit with one of the inlet connections, of the exhaust conduit with the other inlet connection, and of a conduit evacuating fluid towards a reservoir with said outlet connection of the shuttle valve.One application of the invention is the production of a vehicle translation circuit comprising a "disengageable" assistant motor.

Abstract: A hydraulic drive system consists of a first partial system I and a second partial system II. Each partial system has a pump regulated by the stream required (1,9) and a hydraulic energy consumer connected to its output line (2,10). Load pressure lines (7,13) that sense the maximum load pressure are also provided in each partial system I and II; they are connected with the required flow regulators (8,14) of the pumps (1,9). A coupling device III is provided for connecting the feed lines (2,10) and the load pressure lines (7,13) of the two partial systems I and II. The coupling device III can be switched as a function of a consumer designed for driving and is connected with a circuit logic IV that supervises the driving of this consumer. The circuit logic consists of a NAND (not-and-) element (19) and an UND (and-) element (22).

Abstract: A Hydraulic control circuit and a hydraulic control apparatus therefor are disclosed to preferentially feed fluid in a controlled amount or below to a first circuit system and feed fluid in an excessive amount exceeding the controlled amount to a second circuit system, and change over a pressure generated to a pilot pressure. Changing-over of control valves which are provided in the second circuit system permits a pilot pressure to be generated in the circuit. When any trouble occurs in the control valves, fluid fed to the second circuit system is unloaded, to thereby eliminate a possibility that an actuator is unexpectedly actuated.

Abstract: An apparatus controls a fluid system of a work vehicle. The work vehicle has an engine and at least one fluid circuit which has a pump driven by the engine. A plurality of control valves controllably pass fluid from the pump to a plurality of respective work elements. The control valves have movable valve stems. A work attachment which has a respective control valve is added to the fluid system. A plurality of operator control elements provide demand signals in response to selected settings. Each demand signal is indicative of a requested fluid flow to a respective work element or work attachment. A memory device stores select parameters of the fluid system. One of the select parameters is a predetermined priority value representing the precedence in which fluid is delivered from the pump to the control valve of the work attachment. A controller receives the predetermined priority value of the work attachment and the demand signals.

Abstract: A brake valve (45) is disclosed of the type which permits communication from a source (11) of pressurized fluid to a brake actuator (47) in response to manual movement of a valve spool (57) from a neutral position (FIG. 2) to a power brake position (FIG. 5). In the power brake position, the valve spool permits fluid communication between a work port (53), which communicates with a brake actuator, and a brake load signal chamber (87), the brake load signal controlling the fluid output of the source. As the valve spool moves toward a manual brake position (FIG. 6) communication between the work port and the brake load signal chamber is blocked. In the manual brake position, movement of the valve spool causes a large piston (63) to displace fluid from its piston bore (73) into a piston bore (75) in which is disposed a small piston (61), the small piston being operable in response to movement of the valve spool to build brake pressure in the work port (53).

Abstract: Disclosed is a hydraulic control valve system, for driving a plurality of hydraulic actuators by a single pump, including pressure compensation valves and a shuttle valve disposed in a vertical bore orthogonal to a lateral bore of a valve body, into which a spool of a direction switching valve is fitted. A load sensing chamber for introducing a load pressure of an actuator is formed at an intersection between the lateral bore and the vertical bore. An opening-side first pressure receiving surface of the pressure compensation valve confronts the load sensing chamber. The pressure compensation valve has an opening-side second pressure receiving surface contacting a pilot pressure in the vicinity of the opening-side first pressure receiving surface. Formed on the upper side of the pressure compensation valve are a closing-side first pressure receiving surface on which a bridge pressure acts and a closing-side first pressure receiving surface on which an external control pressure acts.

Abstract: A service valve circuit of a hydraulic excavator connected beforehand for use in controlling a special attachment in addition to a prescribed actuator control valve. The service valve circuit comprises a confluence valve 17 for performing electromagnetic proportional flow rate control, disposed in a confluence circuit 16 in communication with the section between inflow circuits 3F and 3R of two variable pumps 2F and 2R, an electrical switch 21 for switching the confluence valve 17 on or off according to a required flow rate and a volume 22 for adjusting the quantity of flow after passing through a confluence valve 17 in a range of flow for a maximum of one to two pumps. Since the requirement of confluence with respect to a required quantity of flow for a special attachment e and the quantity of confluence are set in advance, there will be no excess or shortage of the quantity of confluence.

Abstract: A hydraulic apparatus for an industrial vehicle adapted for enabling to carry out a pump capacity control whenever necessary, and including a variable capacity type hydraulic pump driven by an engine, a flow dividing valve disposed in an outlet pipe line of the pump and adapted for dividing a flow of a pressurized hydraulic oil into a flow required for a power steering hydraulic circuit and a balance flow for a cargo handling hydraulic circuit, a switching valve pilot-operated by a pressure of the cargo handling hydraulic circuit and adapted for selecting a supply pilot pressure between a pressure of the power steering hydraulic circuit downstream with respect to the flow dividing valve and a pressure of the outlet pipe line upstream with respect to the flow dividing valve, and a capacity control valve pilot-operated by a differential pressure between the supply pilot pressure and the pressure of the outlet pipe line and adapted for controlling a capacity varying mechanism of the pump.

Abstract: An industrial truck has a hydraulic fluid supply and at least one double-acting hydraulic cylinder assembly for moving a movable element of the vehicle. The cylinder assembly includes a cylinder having a fluid chamber therein, and a piston movable axially in the cylinder. An actuator rod extends from the piston for connection to the movable element. The piston divides the fluid chamber into a rod end chamber and a piston end chamber each having hydraulic fluid therein. A pair of two-way two-position poppet valves are selectively actuatable between a first joint state in which both of the valves are in a normally closed position in which the piston does not move; a second joint state in which a first one of the valves is closed and a second one of the valves is open to move the piston in a first direction; and a third joint state in which the first one of the valves is open and the second one of the valves is closed to move the piston in a second direction opposite to the first direction.

Abstract: An oil hydraulic circuit for a hydraulic shovel with which a composite operation can be performed readily and smoothly without special skill in operation of the hydraulic shovel. The oil hydraulic circuit comprises a first actuator which can operate with pressure oil from a predetermined one or both of a pair of hydraulic directional control valve sets, a second actuator which operates only with pressure oil from the other hydraulic directional control valve set, a proportional changing over device interposed intermediately in a pipe line communicating the other hydraulic directional control valve set with a first actuator for adjusting the maximum meter-in opening value to the first actuator in response to a magnitude of a signal received at a signal receiving portion of the proportional changing over device, and a controller for arbitrarily adjusting the signal to be supplied to the signal receiving portion of the proportional changing over device.

Abstract: A hydraulic pressure-control device, specially for powershift transmissions of motor vehicles, comprises a fluid pump (1) and a main valve for regulating the pressure in at least one high-pressure consumer device (6), which is attached to a pressure pipe (3) between the fluid pump (1) and the main pressure valve. The main pressure valve is designed as pressure-relief valve. In the main pressure valve is integrated the operation of a second pressure-relief valve. Two different pressure limits can be adjusted in the pressure pipe (3) by a valve piston (21) through two compression springs (17, 18) connected in parallel of which one compression spring (18) is bound.

Abstract: A hydrostatic steering device is provided with a pump connected with a reservoir, a steering valve, a controlled-volume pump that is capable of being activated by a steering wheel and with a steering cylinder. The steering mechanism has a variable working flow and a constant pilot flow, with the pilot stream flowing through a constant throttle and the pressure drop through the constant throttle serving as a control signal for the conveying flow in a pressure delivery line. The controlled-volume pump is coupled mechanically with an adjustment throttle through which the pilot flows. Between the constant throttle and the adjustment throttle lies a pressure compensator that is controlled by the adjustment throttle's differential pressure. To receive the load signal, a control line branches off between the constant throttle and the pressure compensator and leads to the pump or, in the case of a fixed displacement pump with a rear-position flow-dividing valve, to the flow-dividing valve.

Abstract: A control system for the hydraulic operating circuit associated with a vehicle lifting device in which the circuit is provided with pressure fluid control valves and flow sensors which are operative on the vehicle lowering cycle to establish substantial evenness of the lowering mechanism and protection against malfunction of an operating component to arrest the travel of the vehicle lifting device in its lowering cycle.

Abstract: The negative pressure booster equipment according to the present invention is provided with a variable orifice, by which the area of the air passage in the pathways other than one pathway, of two or more pathways communicating two or more variable pressure chambers with atmospheric air, is gradually decreased as the valve plunger moves forward, and it is gradually increased as the valve plunger moves backward in relation to the valve body. Consequently, the pathways other than one pathway are throttled by the variable orifice as the valve plunger moves forward. As the result, most of the air flowing through the control valve is intensively introduced into the variable pressure chamber communicating with the pathway, which is not throttled by the variable orifice, and the pressure in this variable pressure chamber is rapidly increased.

Abstract: A vacuum supply system for a brake power assist unit of a motor vehicle with at least one additional vacuum consuming device is achieved by the installation of a valve, which can be switched as a function of existing vacuum level in a pipe leading from the vacuum generating device to the at least one additional consuming device. Switching of the valve causes a throttling of this pipe to be more extensive when the existing vacuum level is above a certain absolute pressure value.

Abstract: A hydraulic system is provided for powering a steering unit, a trailer brake and an auxiliary power unit from a single pump. A control circuit ensures that the hydraulic trailer brake and/or the power steering unit on the vehicle will operate on a preferential basis over the auxiliary power unit. The hydraulic control circuit has two priority valves connected in series. The upstream priority valve has a priority position in which it makes the pump fluid available to a supply line for the common priority flow for the steering and braking apparatus and a non-priority position for powering the auxiliary power unit. The common priority flow is passed through the second or downstream priority valve for priority powering of the power steering circuit.

Abstract: A vacuum supply system for a brake power assist unit of a motor vehicle and at least one additional vacuum consuming device, is achieved by a parallel arrangement of two pipes leading from a vacuum generating device one to the brake power assist unit and one to the additional consuming device. Both pipes are equipped with flow control devices one of which is blockable by means of a check valve with an increased restoring or closing force for securing a vacuum supply priority for the brake power assist unit.

Abstract: A hydraulic system having multiple actuators is provided with positive pressure flow equalization for both advancing and retracting movements of the system by means of first and second flow divider elements for each actuator. The flow divider elements are cross-coupled between the actuators, a controllable source of pressurized fluid and a reservoir. The flow divider elements are positive-displacement gear or vane pump units that are connected by a common shaft for coordinating fluid flow to the various actuators. Two or more of the actuators can be connected for lifting a load such as an automobile, the system being provided with safety latches at each actuator, the flow dividers not only coordinating the actuator movements during normal raising and lowering operation, but also preventing loss of synchronization of the actuators in case of engagement of a subset only of the latches.

Abstract: The variable speed hydraulic unit has the peculiarity of comprising a fixed body and a rotatable body with hydraulic actuation and fixed displacement, which are operatively interconnected. The output shaft of the fixed body is rigidly associated with the input of the rotatable body in turn operatively associated with a terminal output shaft. A flow divider is furthermore provided for dividing the flow of working fluid fed at a constant flow-rate, having its deliveries connected respectively to the fixed body and to the rotatable body, the percentual distribution between the deliveries determining the direction and speed of rotation of the terminal output shaft.

Abstract: A hydrostatic drive assembly with an adjustable pump driven by a primary power source, which acts on several consumers of hydrostatic energy, is disclosed which has a control and regulating device with nominal speed value pickups and adjustable restrictors for each consumer. In order to obtain a control and regulating device at a low production cost, one that operates with a low power loss, it is proposed that the nominal speed value pickup send an electric signal to an electronic control device, that each consumer be provided with an actual speed value pickup, which the control device, and the restrictors assigned to each of the consumers in their connection lines are designed as electromagnetic throttle valves controlled by the electronic control device.

Abstract: A hydraulic valve is adapted to be connected between a pressurized supply line and first and second lines feeding respective first and second circuits with different functions, such as the steering and braking functions of an automobile vehicle. It comprises a first control member adapted to connect the supply line to the first feed line, a two-way distributor device for the second feed line and a second control member adapted to apply to the second feed line a pressure proportional to the force exerted by the user damped by virtue of a dashpot effect.