Abstract: A hydraulic steering unit (1) is described, said hydraulic steering unit (1) comprising a supply port arrangement having a pressure port (P) connected to a main flow path (3) and a tank port (T) connected to a tank flow path (4), a working port arrangement having a left working port (L) connected to a left working flow path (5) and a right working port (R) connected to a right working flow path (6), a bridge arrangement (14) of variable orifices having a first left orifice (A2L) connected to the main flow path (3) and to the left working flow path (5), a first right orifice (A2R) connected to the main flow path (3) and to the right working flow path (6), a second left orifice (A3L) connected to the left working flow path (5) and to the tank flow path (4), and a second right orifice (A3R) connected to the right working flow path (6) and to the tank flow path (4). Such a hydraulic steering unit should be operated together with a pressure source of fixed displacements.

Abstract: A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (8) connected to a main flow path (6) and a tank port (T) connected to a tank flow path (7), a working port arrangement having a left working port (L) connected to a left working flow path (9) and a right working port (R) connected to a right working flow path (10), a bridge arrangement (14) of variable orifices having a first left orifice (A2L) connected to the main flow path (6) and to the left working flow path (9), a first right orifice (A2R) connected to the main flow path (6) and to the right working flow path (10), a second left orifice (A3L) connected to the left working flow path (9) and to the tank flow path (7), and a second right orifice (A3R) connected to the right working flow path (10) and to the tank flow path (7). Such a hydraulic steering unit should allow comfortable steering.

Abstract: A hydraulic steering unit (3) is disclosed comprising a working port arrangement (L, R) having two working ports (L, R), a supply port arrangement having a high pressure port (P) and a low pressure port (T), a main flow path (7) having a main bleed (A1) and a metering device (8) and being arranged between said high pressure port (P) and said working port arrangement (L, R), an amplification flow path (9) having an amplification bleed (Au) and being arranged between said high pressure port (P) and said working port arrangement (L, R), said main bleed (A1) and said amplification bleed (Au) being controlled together by means of a steering handle (6) and being closed in neutral position of said steering handle (6), and a drain bleed (Ad) which is open in neutral position of said steering handle (6), said drain bleed (Ad) connecting a point (11) upstream said main bleed (A1) and said amplification bleed (Au) to said low pressure port (T).

Abstract: A hydraulic fluid supply portion of a hydraulic steering control system may include an accumulator holding a quantity of pressurized steering fluid, and a priority valve. The priority valve may have a priority supply inlet port fluidly connected to the accumulator for receiving pressurized steering fluid from the accumulator, and a priority supply outlet port fluidly connected to a steering flow amplifier circuit. The priority valve may have a normally open position with a minimal pressure drop between the priority supply inlet port and the priority supply outlet port, and a flow restriction position where fluid flow between the ports is restricted. A load signal line from a steering control circuit to the priority valve may bias the priority valve toward the normally open position in response to an operator steering command to provide pressurized steering fluid to the steering flow amplifier circuit.

Abstract: A hydraulic steering system 1 is described comprising a steering unit and a priority valve, said steering unit comprising a working port arrangement having two working ports, a supply port arrangement having a high pressure port and a low pressure port, a load sensing port, a main flow path having a main bleed and a metering device and being arranged between said high pressure port and said working port arrangement, an amplification flow path having an amplification bleed and being arranged between said high pressure port and said working port arrangement, said main bleed and said amplification bleed being controlled together by means of a steering handle and being closed in neutral position of said steering handle, wherein said priority valve comprises a priority outlet connected to said high pressure port of said steering unit, a valve element moveable in a priority direction to connect an inlet of said priority valve to said priority outlet, and a load sensing connection connected to said load sensing port

Abstract: A steering system includes a fluid motor and a steering unit. The steering unit is in fluid communication with the fluid motor. The steering unit includes a fluid meter adapted to meter fluid to the fluid motor in response to actuation of the steering unit. A valve housing is in fluid communication with the fluid meter. The valve housing defines a valve bore. A valve assembly is disposed in the valve bore. The valve assembly defines a primary fluid path to the fluid meter and to the fluid motor from the fluid meter. The valve assembly further defines a secondary fluid path to the fluid motor that bypasses the fluid meter. An amount of fluid through the secondary fluid path is based on volumetric efficiency of the fluid motor.

Abstract: An aspect of the present disclosure relates to a steering system having first and second steering circuits in fluid communication with a fluid actuator wherein the steering circuits are disposed in parallel to each other. The second steering circuit includes a proportional valve having a load-sense feature in selective fluid communication with a load-sense connection and the first steering circuit. The load-sense feature is open to the first steering circuit when the proportional valve is in a neutral position and closed to the first steering circuit when the proportional valve is moved to a first or second steering position. When the proportional valve is actuated from the neutral position to the first or second steering position the movement of the proportional valve closes the load sense feature from the first steering circuit and operates to deactivate the first steering circuit.

Abstract: An exhaust gas treatment system for an internal combustion engine is provided. The exhaust gas system includes an exhaust gas conduit, a generator, a vehicle electrical system, a primary energy storage device, a rechargeable secondary energy storage device, an electrically heated catalyst (“EHC”) device, and a control module. The primary energy storage device is selectively connected to the generator. The primary energy storage device has a threshold state of charge (“SOC”). The rechargeable secondary energy storage device is selectively connected to the generator and the vehicle electrical system. The EHC device is in fluid communication with the exhaust gas conduit. The EHC device has an electric heater that is selectively connected the generator for receiving energy and a selectively activated catalyst that is heated to a respective light-off temperature.

Abstract: The brake or coupling system (1) comprises a first piston (2) arranged in a first piston cylinder (3) thereby forming a first piston chamber (5) and a second piston (8) arranged in a second piston cylinder (9) thereby forming a second piston chamber (10). The first piston (2) is adapted to be displaced between a braking position and a rest position. The first piston (2) is spring biased in the direction of its rest position, and the second piston (8) is adapted to adjust a distance (X) provided between a friction element (6) and a rotatable element (7) in the rest position of the first piston (2) by means of adjustment of a volume of hydraulic fluid trapped in the second piston chamber (10). At least one spring element is arranged to act between the first and second pistons (2, 8).

Abstract: A hydrostatic drive, especially a hydrostatic fan drive, includes a hydraulic constant-displacement pump configured to drive a hydraulic motor for a fan. The drive further includes a hydraulic machine configured to supply a second hydraulic circuit with a pressure medium. The constant-displacement pump is configured to be hydraulically combined with the hydraulic machine.

Abstract: A control device (1) for a hydrostatic steering motor comprises supply and return pump and tank connections (P, T), a slide valve arrangement in which inner and outer slide element sleeves are rotatable relative to each other to both sides of a neutral position through a limited small angle, said sleeves mutually forming controlled supply and return passages connected to said motor having supply and return throttles which are closed when said sleeves are in a neutral position, bypass throttle means (7) between said pump and tank connections (P, T) being open when said sleeves are in a neutral position, said bypass throttle means (7) having a set of at least two variable orifices connected in series. In such a device the noise should be reduced when a higher supply pressure of hydraulic fluid is used.

Abstract: A wind turbine generator (100), or other energy extraction device, has a hydraulic circuit comprising a hydraulic pump (129) driven by a rotating shaft (125) and a hydraulic motor (131) driving an electricity generator (157), or other load. A high pressure manifold (133) extending between the pump and motor is in communication with an accumulator (145, 147, 149). A controller receives a control signal and regulates the displacement of working fluid by the hydraulic pump and the hydraulic motor relative to each other. Thus, power input through the rotating shaft and output to the load can be decoupled for at least a period of time and the energy output of energy extraction device can be varied, for example to smooth the total power output to an electricity grid (101), without compromising power input. A group of energy extraction devices can be controlled in concert to maximise power input while providing smooth power output.

Abstract: A hydraulic drive device with energy recovery function, includes a pressure medium pump for supplying a consumer with pressure medium and a return line for removing the pressure medium from the consumer. The discharged pressure medium is returned under pressure to the suction side of the pressure medium pump.

Abstract: The present invention pertains to a hydraulic pressure control device of a variable displacement type hydraulic pump for construction equipment, wherein operable sections of operation systems are formed in a wide manner while the hydraulic pump discharges a relatively small flow rate compared with the operation amount of the respective operation systems in the case of complex operations, so as to improve the pressure loss and the fuel ratio of the hydraulic pump. The device includes a flow rate controller, which is preferably connected to an operation amount detecting means and a swash plate control device, and receives operation signals from the operation system of a control device that are detected by the operation amount detecting means so as to control the discharge flow rate of the hydraulic pump.

Abstract: A method of controlling a hydraulic system, the hydraulic system including a ram cylinder unit having a cylinder and a ram, and a hydraulic pump and a reservoir used to supply hydraulic fluid to the cylinder, and hydraulically driving the ram using the hydraulic fluid so as to move against a specific load, the method includes determining what a present state is one of an initial state, a proportional steady state, and a later state, controlling the pumping rate, which is obtained by adding the flow rate corresponding to the volume loss due to the compression of the hydraulic fluid thereto, to control the ram in the initial state, and controlling the pumping rate, which is obtained by subtracting the flow rate corresponding to volume recovery of the hydraulic fluid due to the relief of compression of the hydraulic fluid therefrom, to control the ram in the later state.

Abstract: The invention concerns a hydraulic steering arrangement (1) with a supply connection arrangement (P, T), a working connection arrangement (A, B) connectable to a steering motor (5), a steering unit (6) located between the supply connection arrangement (P, T) and the working connection arrangement (A, B), and a steering valve (14) whose outlet is connected to the working connection arrangement (A, B). It is endeavored to keep the load of such a steering arrangement small. For this purpose, the steering unit (6) is made as an open-center steering unit, an inlet (20) of the steering valve (14) being connected to a pressure supply arrangement (22) that can be activated by an activation of the steering valve (14).

Abstract: The invention provides a fluid controller, e.g. for a hydrostatic power steering. The controller comprises a cylindrical valve member cooperating with a housing to define at least one fluid path from a pressure source to a steering cylinder. The valve member is rotatable in the housing and comprises a sleeve and a spool, wherein the spool is rotatable within the sleeve. The fluid flow is metered by a flow meter, and the valve member comprises a plurality of meter ports communicating the fluid between the valve member and the flow meter. To obtain less friction between the sleeve and the housing and between the sleeve and the spool, the meter ports are grouped in two groups in which groups the ports are in mutually fluid communication.

Abstract: A fluid controller (15a) in a multiple-input hydrostatic power steering system includes a check valve assembly (101), having a first fluid passage (111), defining a check valve seat (105) and a check valve (103) operably associated therewith, in fluid communication with a second fluid passage (109), with the second fluid passage (109) being in fluid communication with a return port (25a). In the left (L) and right (R) operating positions, return flow can flow from the interior region (114) of the valve (27), through the first fluid passage (111), past the check valve (103), and through the second fluid passage (109) to the return port (25a). In the neutral position (N), pressurized fluid can flow from an inlet port (19a) to the return port (25a), with the check valve (103) preventing fluid from flowing through the first fluid passage (111) and into the interior region (114) of the valve (27).

Abstract: A fluid controller (17) controls a main fluid path (18) from a pump (11) to a primary steering cylinder (19) and a second fluid path (26) from a fluid meter (37) to a second cylinder (31). A mechanical or electrical linkage (149) couples the primary steering cylinder (19) to the second cylinder (31) such that displacement of the primary cylinder (19) results in proportional corresponding displacement of the second cylinder (31). The main fluid path (18) and the second fluid path (26) are maintained separate from each other. As such, the main fluid path (18) provides pressurized fluid from the pump to the primary steering cylinder (19) without communicating main fluid flow to the secondary cylinder (31). Due to the separate fluid paths, the present invention can be used to provide a substantial amount of fluid through a fluid controller (17) with a relatively small displacement fluid meter (37).

Abstract: An anti-saturation valve assembly (51) for use in a hydraulic system having priority (17) and auxiliary (25) load circuits, the priority circuit providing a priority load signal (19). The anti-saturation valve assembly includes a pressure sensor portion (61) which senses a decrease between pump pressure (23) and the priority load signal (19), and generates a force on a pressure reducing portion (63) to reduce, correspondingly, a pilot pressure (59): The reduced pilot pressure to a pilot valve (35) results in reduced flow to a pilot-operated main control valve (27) in the auxiliary load circuit (25), thus providing anti-saturation protection for the circuit, without throttling a main flow path and wasting substantial hydraulic power.

Abstract: A control valves for a servo steering system, having an inlet for supplying a hydraulic liquid at a first pressures and an outlet for discharging the hydraulic liquid into a region having a smaller, second pressure, especially into a pressureless reservoir. The control valve has a guide and a valve slide accommodated in the guide so as to be movable therein along an axis. The valve slide is acted upon on one side by the hydraulic liquid with the first pressure and on the opposite side by a defined supporting force. An opening structure is provided on at least one of the valve slide and guide. A cover corresponding to the opening structure is provided on the other of the guide and valve slide. A movement of the valve slide relative to the guide effects a change of a free passage area of the opening structure that is not closed off by the cover, whereby the hydraulic liquid is able to flow from the inlet, through the free passage area, to the outlet.

Abstract: According to one embodiment of the invention, a gerotor apparatus includes an outer gerotor having an outer gerotor chamber, an inner gerotor, at least a portion of which is disposed within the outer gerotor chamber, and a synchronizing apparatus operable to control the rotation of the inner gerotor relative to the outer gerotor. The inner gerotor includes one or more entrance passages operable to communicate a lubricant into the outer gerotor chamber.

Abstract: A power steering apparatus includes a hydraulic power cylinder, and a reversible pump driven by a motor. A steering assist sensor senses a steering assist force provided to a steering wheel. A controller ascertains a pump discharge quantity of the reversible pump, and a cylinder volume variation of the pressure chambers of the hydraulic power cylinder; and calculates a leak quantity of the reversible pump from a difference between the pump discharge quantity and the cylinder volume variation. The controller controls the motor to cause the motor to produce a desired fluid pressure in accordance with the steering assist force and the leak quantity.

Abstract: A leakage compensation system in a control device (S) has a fully hydraulic steering system (1) with a supply connection arrangement having a high-pressure connection (P) and a low-pressure connection (T). A working connection arrangement has two working connections (CL, CR), a control section between the supply connection arrangement (P, T) and the working connection arrangement (CL, CR). A control element (2) for activating the control section, a steering member (3) and an auxiliary fluid path (12) has a valve arrangement (A6, A7), through which hydraulic fluid can be supplied or drained off.

Abstract: Hydrostatic power steering device comprising a source of pressurized fluid, a cylindrical barrel-type distributor the elements of which are connected elastically together, and of which the inner element, the so called spindle, is connected to the steering wheel; the distributor being arranged to assume a central position, the so-called neutral position, in which it directly short-circuits, to discharge, the fluid originating from the source of pressurized fluid, and two positions, symmetrical about the central position, in which the distributor, via a dispenser of orbital type the rotor of which is rigidly connected to the steering wheel shaft and to the spindle, feeds the fluid to one and respectively to the other of the chambers of a hydraulic actuator connected to the steering wheel; the device also comprises an auxiliary conduit for feeding the pressurized fluid to the cylindrical distributor; a slide valve operable by the driver to feed said auxiliary feed conduit when desired; a barrel locking system op

Abstract: A hydraulic steering arrangement includes a steering valve, a steering motor, connected with a high-pressure connection and a low-pressure connection via the steering valve, and with a steering unit, connected via the steering valve with a pilot pressure valve, whose outlet is connected with the low-pressure connection. It is endeavoured to improve the steering behaviour. For this purpose, the pilot pressure valve is opened, before the steering valve creates a connection between the high-pressure connection and the steering motor.

Abstract: A hydraulic steering system (1) with a supply connection arrangement, having a high-pressure connection (P) and a low-pressure connection (T), and with a working connection arrangement (L, R), a directional valve (2) and a metering pump unit (3, 4) being arranged between the supply connection arrangement and the working connection arrangement, the metering pump arrangement having at least two hydraulically parallel-connected and mechanically parallel-operated metering pumps (3, 4) with a shut-off valve (6) in a hydraulic connection between the two metering pumps (3, 4), said shut-off valve (6) having a return spring (16) and a first control inlet (15) that is connected with the high-pressure connection (P).

Abstract: A fluid controller (27) for use with a fluid pressure operated device (45) having an inlet (47) and an outlet (49) and defining a fluid leakage path therebetween. The controller (27) includes valving (61) defining a main fluid path and further defines a fluid bleed passage including a variable bleed orifice (AB), having a substantially zero flow area when the controller valving (61) is in its neutral position (N) and in the normal operating position (R), but beginning to open as the valving approaches its maximum displacement position (R-M).

Abstract: An open center fluid controller (15) controls the flow from a pump (11) to a steering cylinder (17) and to a downstream auxiliary device (99) requiring a predetermined minimum flow availability. The open center fluid controller (15) includes controller valving (19) having a neutral position (N) a normal operating position (R) and a maximum displacement position (R-M). The controller defines an auxiliary fluid path providing communication between an inlet port (31) and an auxiliary or power beyond port (87), which is in communication with the auxiliary device (99). The auxiliary fluid path includes a neutral variable orifice (AN) having a decreasing flow area as the valving (19) is displaced toward the maximum displacement position (R-M). The valving defines an auxiliary flow control orifice (AA) providing communication from the inlet port to the auxiliary port (87) when the valving approaches the maximum displacement position.

Abstract: Hydrostatic power steering device comprising a source of pressurized fluid, a cylindrical barrel-type distributor the elements of which are connected elastically together, and of which the inner element, the so called spindle, is connected to the steering wheel; the distributor being arranged to assume a central position, the solo called neutral position, in which it directly short-circuits, to discharge, the fluid originating from the source of pressurized fluid, and two positions, symmetrical about the central position, in which the distributor, via a dispenser of orbital type the rotor of which is rigidly connected to the steering wheel shaft and to the spindle, feeds the fluid to one and respectively to the other of the chambers of a hydraulic actuator connected to the steering wheel; the device also comprises an auxiliary conduit for feeding the pressurized fluid to the cylindrical distributor; a slide valve operable by the driver to feed said auxiliary feed conduit when desired; a barrel locking system

Abstract: A hydraulic steering system (1) with a supply connection arrangement, having a high-pressure connection (P) and a low-pressure connection (T), and with a working connection arrangement (L, R), a directional valve (2) and a metering pump unit (3, 4) being arranged between the supply connection arrangement and the working connection arrangement, the metering pump arrangement having at least two hydraulically parallel-connected and mechanically parallel-operated metering pumps (3, 4) with a shut-off valve (6) in a hydraulic connection between the two metering pumps (3, 4), said shut-off valve (6) having a return spring (16) and a first control inlet (15) that is connected with the high-pressure connection (P).

Abstract: Disclosed herein is a method for hydraulic steering. The method includes supplying a steering unit with a controlled working pressure from a load signal line dependent upon a load signal. The load signal being generated via a load signal fluid having a fluid flow. Also disclosed herein is a hydraulic steering arrangement for carrying out the method. A load signal adjustment device is provided through which the fluid flow can be adjusted to an at least approximately constant value.

Abstract: A full fluid-linked steering system includes a fluid pump (11), a fluid controller (19), a steering actuator (17), an electro-hydraulic compensation valve (21), and a vehicle microprocessor (23). Downstream of the fluid pump (11) is a load sensing priority flow control valve (15) having both a controlled flow outlet port (CF) and an excess flow outlet port (EF). The excess flow outlet port (EF) communicates with an inlet port (35) of the fluid controller (19), while the controlled flow outlet port (CF) communicates with a fluid inlet (63) of the compensation valve (21). As a result, when the steering actuator (17) is at the end of its travel, pressure will be communicated only through the compensation valve (21), and the operator will be unable to turn the steering wheel further in the same direction.

Abstract: A hydrostatic steering system of the type including a fluid controller (21) for controlling the flow of fluid from a source (11) to a steering actuator (19) in response to movement of a steering wheel (W). The controller (21) is of the type having a fluid meter (65) including a moveable star member (95), the movement of which corresponds to the flow of fluid to the actuator (19). The controller includes a sensor assembly (125) which senses the movement of the star member (95) and generates an electrical signal (127) representative of the fluid flow through the fluid meter (65).

Abstract: A full fluid-linked steering system includes a fluid pump (11), a fluid controller (19), a steering actuator (17), an electro-hydraulic compensation valve (21), and a vehicle microprocessor (23). Downstream of the fluid pump (11) is a load sensing priority flow control valve (15) having both a controlled flow outlet port (CF) and an excess flow outlet port (EF). The excess flow outlet port (EF) communicates with an inlet port (35) of the fluid controller (19), while the controlled flow outlet port (CF) communicates with a fluid inlet (63) of the compensation valve (21). As a result, when the steering actuator (17) is at the end of its travel, pressure will be communicated only through the compensation valve (21), and the operator will be unable to turn the steering wheel further in the same direction.

Abstract: A hydraulic steering system for a tractor is provided which can be operated in a conventional steering mode or in a fast steering mode. In conventional steering mode, a conventional steering wheel and steering motor direct pressurized oil to the steerable wheels for selecting the turning direction, the turning angle, and the speed with which the turning angle is achieved. In fast steering mode, a fast-turning valve is controlled by the operator to direct oil directly to the steerable wheels, thereby by-passing the steering motor. The conventional steering wheel and steering motor continue however to control the steering operation.

Abstract: A hydraulic steering arrangement with a directional valve and a metering pump unit having two hydraulically parallel connected and mechanically parallel operable metering pumps, each having a toothed ring with inner toothing and a gear wheel with outer toothing being able to perform rotary and orbiting movements in the toothed ring. It is desired to extend the life of the metering pumps. For this purpose, a through-going driving part is provided for both gear wheels.

Abstract: The invention concerns a rotary slide set for a hydraulic steering arrangement with an outer rotary slide and an inner rotary slide arranged in the outer rotary slide, and having in its surface tank grooves, which are, at least in predetermined rotary positions, connected with a low pressure connection, and at least one through-opening in its wall, each overlapping, at least partly, a tank groove. In a rotary slide set of this kind it is desired to avoid jamming between the inner and the outer rotary slides. For this purpose, surface recesses have been made at the remaining tank grooves to serve as balancing areas.

Abstract: A fluid controller (17) to control flow to a steering cylinder (19) is modified to include a selector valve assembly (41,73) having two operating positions. In a first position (“R” in FIG. 1), the selector valve (73) permits fluid flow though the main fluid path (53) in the normal manner, as would be used when the vehicle is in a “roading” mode. In a second position (“W” in FIG. 1 and in FIG. 3), the selector valve (73) blocks flow through the fluid meter (43) which normally provides the follow-up movement (51) to the controller valving (31,33), and bypasses the fluid meter in a “working” mode. Thus, the normal flow rate can be achieved by merely rotating the steering wheel (27) an amount which corresponds to the desired deflection of the controller valving (31,33), without the need for the continuous rotation of the steering wheel, as required during normal steering.

Abstract: A hydraulic steering system for a tractor is provided which can be operated in a conventional steering mode or in a fast steering mode. In conventional steering mode, a conventional steering wheel and steering motor direct pressurized oil to the steerable wheels for selecting the turning direction, the turning angle, and the speed with which the turning angle is achieved. In fast steering mode, a fast-turning valve is controlled by the operator to direct oil directly to the steerable wheels, thereby by-passing the steering motor. The conventional steering wheel and steering motor continue however to control the steering operation.

Abstract: The invention relates to a hydraulic steering arrangement (1) with a housing (4), in which an inner control slide (7) and an outer control slide (6) are arranged to be mutually rotational, forming together a variable flow path device between a supply connection device (P, T) and a working connection device (L,R), at least one pressure chamber (17) being arranged between two working slides (15, 16), connected with both control slides (6, 7), the volume change of said pressure chamber (17) causing the relative displacement, and with a measuring motor (10). In such steering arrangements a simple an inexpensive way of realizing a remote control principle is desired. For this purpose, an intermediary plate (14) is arranged between the measuring motor (10) and the control slides (6, 7), in which plate at least one fluid channel (18, 19) is arranged to form at least one part of a connection from the pressure chamber (17) to the outside.

Abstract: A hydraulic steering device, in particular for vehicles, is disclosed, having a housing in which two sliders are arranged to move relative to one another and together form at least one adjustable throttle, a restoring device for restoring the two sliders to their neutral position being provided, one of the two sliders being driveable and the other of the two sliders being in operative connection with a measuring device. In such a steering device it is desirable to improve the correlation between steering torque and flow amplification; in particular it is desirable to linearize the relationship better. For that purpose the measuring device is arranged in a flow path closed in itself, and operates as a pump, while an open flow path runs past the closed flow path from an inlet connection arrangement to an outlet connection arrangement.

Abstract: A hydrostatic steering device having substantially identical first and second steering systems, each including a pump connected to a steering unit, which is connected to a steering motor by two motor hoses. A steering wheel is common to both steering units. The device includes a change-over valve which has an operation position hydraulically coupling together the two motor hoses of the second steering system, while hydraulically isolating from each other the two motor hoses of the first steering system, and an emergency position hydraulically coupling together the two motor hoses of the first steering system, while hydraulically isolating from each other the two motor hoses of the second steering system. A switching device switches the change-over valve from the operation position to the emergency position, when a fault occurs in the first steering system.

Abstract: A full fluid-linked steering system, especially for use in on-highway steering, in which the system includes a fluid controller (21) including a fluid meter (65) operable to provide follow-up movement to controller valving (87,89), in response to the flow of fluid through the meter. The controller (21) includes a centering or biasing spring assembly (75) which provides sufficient torque that, upon rotation of the steering wheel (W), fluid is communicated to the steering actuator (19) without relative displacement of the valving, thus providing driver with the desired road feel. The system includes an EHC valve assembly (23) which controls flow to or from the actuator (19) in response to appropriate input signals (113,115) to maintain steered wheel to steering wheel registry.

Abstract: A hydraulic control device is disclosed, having a pressure connection and a tank connection and having a metering pump unit (4) that comprises at least two metering pumps (5, 6) connected hydraulically in parallel and operable mechanically in parallel and also a cut-off valve (8) in hydraulic connection between the two metering pumps (5, 6), the cut-off valve (8) being flange-mounted on a metering pump (6) and having in a housing (13) a slider member (12) which, under pressure form the pressure connection (P), is movable axially towards the metering pump (6). It is desirable to keep wear and tear to a low level such a control device. For that purpose, a displacement-limiting device (26, 28) for the slider member (12) is provided, which prevents the slider member from bearing on the metering pump (6).

Abstract: A fluid controller (15) of the type which controls the flow of fluid to an unequal area steering cylinder (25), wherein the controller is of the load reaction type. The controller (15) includes valving (27) which, when it is in neutral (FIGS. 1 and 5), defines a load reaction fluid path (LR) permitting fluid communication between the control fluid ports (21, and 23) through the fluid meter (29) in response to an external load imposed on the cylinder (25). In accordance with the invention, the valving (27) includes a fluid path (97,95,99,71,75) between the load reaction fluid path (LR) and the return port (19), when the valving is in neutral. When the rod end chamber (A) is contracting, fluid is drawn from the return port into the load reaction fluid path (LR), preventing cavitation, and when the head end chamber (B) is contracting, fluid flows from the load reaction fluid path (LR) to the return port (19), preventing pressure intensification.

Abstract: A fluid controller (15) of the type having a primary, spool valve (43) and a followup, sleeve valve (45) which define a relative neutral position (FIG. 1) and first and second maximum, opposite operating positions (L and R). The controller includes a fluid meter (29) having a member (51) which orbits and rotates. To impart the rotational movement of the member (51) to the follow-up valve (45), the present invention provides a shaft member (53) having a forward end (57) defining a diametral bore (67) with a pin member (69) in close fit relationship in the bore (67) and having ends (71) extending radially into axially elongated slots (75) defined by the sleeve valve (45). The axial length of the slots (75) is sufficient to permit the ends (71) of the pin member (69) to move to and fro as the metering member (51) orbits and rotates.

Abstract: In order to continuously change the transmission ratio between power-assisted steering mode and emergency steering mode and to maximize the flow of hydraulic oil in the power-assisted steering mode when the steering wheel is rapidly turned, a steering assembly is proposed which uses a common line which bypasses the metering pump, as a supply line for flow amplification during power-assisted operation and as a return line for changing the transmission ratio during emergency operation. This common line is connected to selected supply lines by way of throttles and with corresponding cylinder lines or with all cylinder lines by way of throttles. Steering devices of this type are employed in mobile equipment, in particular in slowly moving vehicles.

Abstract: A hydrostatic power steering system comprising a fluid motor (19) which receives pressurized fluid from a controller (17) in response to the rotation of a vehicle steering wheel (W). As the motor (19) or the steered wheels reach the stops, control logic (31) receives signals (37,77) representing steered wheel and steering wheel position, respectively, and generates appropriate command signals (33,27) to a pressure reducing/relieving valve (15) and to a proportional electromagnetic valve (23), respectively, closing the valve (15) somewhat, and opening the valve (23). A pressure differential is built between an additional fluid path (21) and the high pressure conduit (15c) between the controller (17) and the fluid motor (19). Pressure is communicated through the valve (23) into the conduit (51c), and back into the fluid meter (43) of the controller, preventing any further rotation thereof in response to an attempt to turn the steering wheel, thus eliminating travel limit slip.

Abstract: A hydraulic power steering system for a vehicle comprising a hydraulic fluid displacement pump, operated by a thermal engine of the vehicle and provided with a suction port and a delivery port, a reservoir for collecting said fluid, connected to suction port, a double-acting hydraulic cylinder, capable of controlling direction of front wheels of the vehicle, and a distribution unit fitted with an inlet port, connected to delivery port, a vent port, connected to reservoir and two service ports, connected to respective chambers of hydraulic cylinder; distribution unit comprising a first and a second distributor, respectively controlled by hydraulic cylinder and by a steering wheel of the vehicle and movable with respect to each other; pump being of the variable displacement type and system further comprising a flow request sensor from and to chambers of cylinder and a device for adjusting displacement of pump, controlled by sensor.