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 first bridge arrangement (15a, 15b) of variable orifices having a first left orifice (A2L) connected to the main flow path (2) and to a first 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 first right connecting point (17) at the right working flow path (10), a second left orifice (A3L) connected to the first 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 first right connecting point (17) at the right working flow path (10) and to the tank flow path (3). It should be possible to change the steering characteristics of such a steering unit. This is achieved by at least a second bridge arrangement (20a, 20b) of variable orifices having a third left orifice (A2L) connected to the main flow path (2) and to a second left connecting point (21) at the left working flow path (9), a third right orifice (A2R) connected to the main flow path (2) and to a second right connecting point (22) at the right working flow path (10), a fourth left orifice (A3L) connected to the second left connecting point (21) at the left working flow path (9) and to the tank flow path (3), and a fourth right orifice (A3R) connected to the second right connecting point (22) at the right working flow path (10) and to the tank flow path (3), wherein the first bridge arrangement (15a, 15b) and the second bridge arrangement (20a, 20b) have different steering characteristics, and by selection means (23) connecting at least one of the bridge arrangements (15a, 15b; 20a, 20b) between the pressure port (P) and the working port arrangement.

The invention relates to a hydraulic steering device that hydraulically connects a steering cylinder to a supply system, whereby the supply system is hydraulically operatively connectable to the steering cylinder via a steering valve to form a main flow connection and the supply system is hydraulically operatively connectable to the steering cylinder via a flow regulation valve arrangement to form a branch flow connection that circumvents the main flow connection, whereby the flow regulation valve arrangement is triggerable by an electric control unit and the flow regulation valve arrangement comprises valve groups that are triggerable individually, which are respectively connected in the forward flow and return flow of the branch flow connection and a release-shutoff valve is assigned to the flow regulation valve arrangement. It is provided that the release-shutoff valve is connected between the flow regulation valve arrangement and the steering cylinder.

The invention relates to a hydraulic steering device that hydraulically connects a steering cylinder to a supply system, whereby the supply system is hydraulically operatively connectable to the steering cylinder via a steering valve to form a main flow connection and the supply system is hydraulically operatively connectable to the steering cylinder via a flow regulation valve arrangement to form a branch flow connection that circumvents the main flow connection, whereby the flow regulation valve arrangement is triggerable by an electric control unit and the flow regulation valve arrangement comprises valve groups that are triggerable individually, which are respectively connected in the forward flow and return flow of the branch flow connection and a release-shutoff valve is assigned to the flow regulation valve arrangement. It is provided that the release-shutoff valve is connected between the flow regulation valve arrangement and the steering cylinder.

A valve for hydraulic parallel work systems is provided. The valve includes a first pair of ports, a second pair of ports, a first connection, and a second connection. The first connection is between the first pair of ports when the valve is in a load reaction-enabling state. The first connection transmits a load reaction from a load at a steering actuator to a steering device of a hydrostatic steering circuit. The second connection is between the second pair of ports when the valve is in an electro-hydraulic steering enabling state. The second connection fluidly connects a fluid source to an electro-hydraulic steering circuit.

A valve for hydraulic parallel work systems is provided. The valve includes a first pair of ports, a second pair of ports, a first connection, and a second connection. The first connection is between the first pair of ports when the valve is in a load reaction-enabling state. The first connection transmits a load reaction from a load at a steering actuator to a steering device of a hydrostatic steering circuit. The second connection is between the second pair of ports when the valve is in an electro-hydraulic steering enabling state. The second connection fluidly connects a fluid source to an electro-hydraulic steering circuit.

A steering arrangement for a vehicle includes: a hydrostatic steering unit provided with two work ports, a high-pressure port, a low-pressure port, a main branch of the flow arranged between the work ports and the high-pressure port and comprising a dosing device, and an amplification branch arranged between the work ports and the high-pressure port, in parallel with the dosing device, and comprising a flow-rate regulating device of the electrically actuated type, a steering shaft provided with a first end adapted for being connected to a steering member and a second end adapted for being connected to the hydrostatic steering unit, an electric motor configured to set the steering shaft in rotation, and an electronic control unit configured to actuate the flow-rate regulating device as a function of a parameter indicative of an operating condition of the vehicle.

A hydraulic steering system for vehicles includes a steering control member; a hydraulic pump provided with a rotatable driving shaft on which the control member is fitted; a hydraulic actuating cylinder connected with two ports of the pump alternately operating as delivery side and return side of the pump and mechanically connected with a direction changing member, which determines a change in the direction by modifying orientation via an actuating cylinder as a function of the supply of hydraulic fluid to the cylinder from the pump by the steering control member. The driving shaft is dynamically connected with an electric motor/transmission assembly, which is activated alternatively by generating a rotational force auxiliary to the movement manually exerted on the steering control member or opposing the manually exerted movement, or by driving to rotate the driving shaft of the pump in place of the manual action driving the steering control member.

A hydraulic steering system for vehicles includes a steering control member; a hydraulic pump provided with a rotatable driving shaft on which the control member is fitted; a hydraulic actuating cylinder connected with two ports of the pump alternately operating as delivery side and return side of the pump and mechanically connected with a direction changing member, which determines a change in the direction by modifying orientation via an actuating cylinder as a function of the supply of hydraulic fluid to the cylinder from the pump by the steering control member. The driving shaft is dynamically connected with an electric motor/transmission assembly, which is activated alternatively by generating a rotational force auxiliary to the movement manually exerted on the steering control member or opposing the manually exerted movement, or by driving to rotate the driving shaft of the pump in place of the manual action driving the steering control member.

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 first working port arrangement having a first left working port (L1) connected to a first left working flow path (4) and a first right working port (R1) connected to a first right working flow path (5), a variable first left orifice (A2L) connected to the main flow path (2) and to the first left working flow path (4), a variable first right orifice (A2R) connected to the main flow path (2) and to the first right working flow path (5), a variable second left orifice (A3L) connected to the first left working flow path (4) and to the tank flow path (3), a variable second right orifice (A3R) connected to the first right working flow path (5) and to the tank flow path (3), and a second working port arrangement having a second left working port (12) connected to a second left working flow path (9) and a second right working port (R2) connected to a second right working flow path (10), wherein the variable first left orifice (A2L) is connected to the second left working flow path (9) and the variable first right orifice (A2R) is connected to the second 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 first working port arrangement having a first left working port (L1) connected to a first left working flow path (4) and a first right working port (R1) connected to a first right working flow path (5), a variable first left orifice (A2L) connected to the main flow path (2) and to the first left working flow path (4), a variable first right orifice (A2R) connected to the main flow path (2) and to the first right working flow path (5), a variable second left orifice (A3L) connected to the first left working flow path (4) and to the tank flow path (3), a variable second right orifice (A3R) connected to the first right working flow path (5) and to the tank flow path (3), and a second working port arrangement having a second left working port (12) connected to a second left working flow path (9) and a second right working port (R2) connected to a second right working flow path (10), wherein the variable first left orifice (A2L) is connected to the second left working flow path (9) and the variable first right orifice (A2R) is connected to the second right working flow path (10).