A hydraulic steering arrangement is shown having a steering unit and two working ports each of which being connected to the steering unit by a working line (3), wherein an anti jerk valve (9) is arranged in each working line (3), the anti jerk valve (9) having a valve element (12) being loaded in opening direction by the pressure in the working line (3) and in closing direction by restoring means (17). A vehicle equipped with such a steering arrangement should have a good comfort. To this end the valve element (12) is loaded in closing direction by the pressure in the working line (3) via delay means (21).

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (2) and a tank port (T) connected to a tank flow path (3), 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 (15) of variable orifices having a first left orifice (A2L) connected to the main flow path (2) and to a left connecting point (16) at the left working flow path (9), a first right orifice (A2R) connected to the main flow path (2) and to a right connecting point (17) at the right working flow path (10), a second left orifice (A3L) connected to the left connecting point (16) at the left working flow path (9) and to the tank flow path (3), and a second right orifice (A3R) connected to the right connecting point (17) at the right working flow path (10) and to the tank flow path (3). Such a steering unit should allow for a comfortable steering. To this end reverse flow prevention means (20, 21) are arranged in at least one of the left working flow path (9) and the right working flow path (10).

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (2) and a tank port (T) connected to a tank flow path (3), 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 (15) of variable orifices having a first left orifice (A2L) connected to the main flow path (2) and to a left connecting point (16) at the left working flow path (9), a first right orifice (A2R) connected to the main flow path (2) and to a right connecting point (17) at the right working flow path (10), a second left orifice (A3L) connected to the left connecting point (16) at the left working flow path (9) and to the tank flow path (3), and a second right orifice (A3R) connected to the right connecting point (17) at the right working flow path (10) and to the tank flow path (3). Such a steering unit should allow for a comfortable steering. To this end reverse flow prevention means (20, 21) are arranged in at least one of the left working flow path (9) and the right working flow path (10).

A fluid controller (1), in particular as part of a hydraulic steering unit, is described said controller (1) comprising a housing (2) having a supply port arrangement, a sleeve (4) arranged rotatably in a bore of the housing (2), a spool (3) arranged rotatably in the sleeve (4), and a measuring motor, wherein the measuring motor comprises a plurality of working chambers, each working chamber being connected to the bore, wherein the sleeve (4) comprises a commutation geometry (7) having a first partition and controlling together with a housing geometry (5) of the housing (2) a flow of hydraulic fluid into and out of the working chambers and the spool (3) comprises a spool geometry (14) controlling together with a valve geometry (10, 11) of the sleeve (4) a flow of hydraulic fluid between the supply port arrangement and the commutation geometry. Such a fluid controller should have a stable control behavior. To this end the valve geometry (10,11) comprises a second partition different from the first partition.

A steering gear includes a housing defining a chamber. A piston divides the chamber into first and second chamber portions. The piston is moveable along a linear axis relative to the housing upon pressurization of fluid in one of the first and second chamber portions. A pressure relief vents pressurized fluid from one of the first and second chamber portions to one other of the first and second chamber portions upon movement of the piston to a predetermined position. The pressure relief assembly includes a first valve at a first end of the pressure relief assembly and a second valve at a second end of the pressure relief assembly. The pressure relief assembly is axially movable relative to the piston to adjust the position of the first valve and the second valve relative to the piston.

A vehicle includes a vehicle frame, a steering swivel unit supported on a head pipe of the vehicle frame and angularly movable about a steering axis, a front wheel angularly movable in unison with the steering swivel unit, and an automatic steering mechanism for angularly moving the steering swivel unit, wherein the vehicle frame includes a main frame extending rearwardly from the head pipe, and the steering mechanism includes a steering motor for angularly moving the steering swivel unit, the steering motor being supported on the main frame.

A steering system and method for a vehicle having steerable front and rear wheels has rear hydraulic steering device that may be coupled to one or more of the rear wheels. A rear valve assembly may hydraulically control the rear hydraulic steering device to steer the rear wheels based upon a rear steering command from a controller. In a manual steering mode, the controller does not determine a rear steering command for the rear valve assembly such that the rear wheels are freely rotatable. In a rear steering assist mode, the controller determines the rear steering command based upon, at least in part, the manual steering input.

A steering system and method for a vehicle having steerable front and rear wheels has rear hydraulic steering device that may be coupled to one or more of the rear wheels. A rear valve assembly may hydraulically control the rear hydraulic steering device to steer the rear wheels based upon a rear steering command from a controller. In a manual steering mode, the controller does not determine a rear steering command for the rear valve assembly such that the rear wheels are freely rotatable. In a rear steering assist mode, the controller determines the rear steering command based upon, at least in part, the manual steering input.

A system and method for detecting the functional state of a piloted or direct-operated isolation valve in a hydraulic circuit is presented. In some examples the hydraulic circuit is a steering circuit and the isolation valve provides selective isolation between a hydraulic actuator and one or more metering valves. In some examples, the isolation valve assembly is movable between a first position, in which fluid flow between the metering valve and the actuator is enabled, and a second position, in which fluid flow between the metering valve and the actuator is blocked. When the isolation valve assembly is moved to one of the first and second positions, an inlet port and a pressure sensing port of the isolation valve assembly are placed in fluid communication with each other. When the isolation valve assembly is moved to the other of the first or second position, a second inlet port and the pressure sensing port are placed in fluid communication.

A system and method for detecting the functional state of a piloted or direct-operated isolation valve in a hydraulic circuit is presented. In some examples the hydraulic circuit is a steering circuit and the isolation valve provides selective isolation between a hydraulic actuator and one or more metering valves. In some examples, the isolation valve assembly is movable between a first position, in which fluid flow between the metering valve and the actuator is enabled, and a second position, in which fluid flow between the metering valve and the actuator is blocked. When the isolation valve assembly is moved to one of the first and second positions, an inlet port and a pressure sensing port of the isolation valve assembly are placed in fluid communication with each other. When the isolation valve assembly is moved to the other of the first or second position, a second inlet port and the pressure sensing port are placed in fluid communication.