A hydraulic steering unit includes a pressure port connected to a main flow path and a tank port connected to a tank flow path, left and right working ports connected to left and right working flow paths, respectively, a bridge arrangement of variable orifices having a first left orifice connected to the main flow path and to the left working flow path, a first right orifice connected to the main flow path and to the right working flow path, a second left orifice connected to the left working flow path and to the tank flow path, and a second right orifice connected to the right working flow path and to the tank flow path. A variable diagonal orifice is connected to the main flow path and to the tank flow path. The bridge arrangement orifices being closed in neutral position and the diagonal orifice being open in neutral position.

A steering mechanism and guidance system for a milling attachment device provides steering capability without impeding cutting depth control. The steering mechanism has at least one wheel that is rotated by an actuating mechanism such as an extending cylinder, synchronized actuators, or the like. The steering mechanism may be integrated with depth control by using a parallelogrammic structure with pivot points to assist in the depth control or may operate independent of and without impeding depth control.

The invention relates to a steering assembly (12) for a vehicle (10). The steering assembly (12) comprises a first steering actuator (14) and a second steering actuator (16). The first steering actuator (14) is adapted to be actuated in accordance with at least one signal issued from a motion control system (18) to control a steering angle of at least one steerable ground engaging member (20, 22) of the vehicle (10) to thereby control the steering of the vehicle (10). The first steering actuator (14) is associated with a first nominal steering capability, defining at least one limitation of at least one of the following: steering angle, steering angle rate and steering torque, for the at least one steerable ground engaging member (20, 22). The second steering actuator (16) is adapted to be actuated in accordance with at least one signal issued from the motion control system (18) to control the steering angle of the at least one steerable ground engaging member (20, 22) of the vehicle (10) to thereby control the steering of the vehicle (10). The second steering actuator (16) is associated with a second nominal steering capability, defining at least one limitation of at least one of the following: steering angle, steering angle rate and steering torque, for the at least one steerale ground engaging member (20, 22). The motion control system (18) is adapted to, upon detection of a malfunction associated with the first steering actuator (14), associate the second steering actuator (17) with a second enhanced steering capability instead of the second nominal steering capability. The second enhanced steering capability is different from the second nominal steering capability.

The invention relates to a steering assembly (12) for a vehicle (10). The steering assembly (12) comprises a first steering actuator (14) and a second steering actuator (16). The first steering actuator (14) is adapted to be actuated in accordance with at least one signal issued from a motion control system (18) to control a steering angle of at least one steerable ground engaging member (20, 22) of the vehicle (10) to thereby control the steering of the vehicle (10). The first steering actuator (14) is associated with a first nominal steering capability, defining at least one limitation of at least one of the following: steering angle, steering angle rate and steering torque, for the at least one steerable ground engaging member (20, 22). The second steering actuator (16) is adapted to be actuated in accordance with at least one signal issued from the motion control system (18) to control the steering angle of the at least one steerable ground engaging member (20, 22) of the vehicle (10) to thereby control the steering of the vehicle (10). The second steering actuator (16) is associated with a second nominal steering capability, defining at least one limitation of at least one of the following: steering angle, steering angle rate and steering torque, for the at least one steerale ground engaging member (20, 22). The motion control system (18) is adapted to, upon detection of a malfunction associated with the first steering actuator (14), associate the second steering actuator (17) with a second enhanced steering capability instead of the second nominal steering capability. The second enhanced steering capability is different from the second nominal steering capability.

Each zero turning radius mower steering lever module includes a one-piece plastic housing independently mounted on a grass mowing machine frame member. A central passage extends through each housing, and a steering arm bracket may be positioned in the central passage and pivotably mounted on a horizontal pivot axis. A steering arm may be attached to an upper end of the steering arm bracket, and a hydrostatic transmission linkage and a damper linkage attached to a lower end of the bracket.

Each zero turning radius mower steering lever module includes a one-piece plastic housing independently mounted on a grass mowing machine frame member. A central passage extends through each housing, and a steering arm bracket may be positioned in the central passage and pivotably mounted on a horizontal pivot axis. A steering arm may be attached to an upper end of the steering arm bracket, and a hydrostatic transmission linkage and a damper linkage attached to a lower end of the bracket.

In a self-propelled construction machine (1), in particular road milling machine, comprising a machine frame (8), at least three travelling devices (12, 16), wherein at least one of the three travelling devices (12, 16) is realized as a pivotable travelling device (16) so that said travelling device (16) is pivotable about at least one vertical pivoting axis in relation to the machine frame (8) between a first pivoted-in and at least one second pivoted-out position, at least one working device (20), in particular a milling drum, for working the ground pavement (3), at least one hydraulic drive system (70) for driving at least two travelling devices (12, 16), wherein at least one of the at least two driven travelling devices is the pivotable travelling device (16), wherein the hydraulic drive system (70) comprises at least one hydraulic pump (78), it is provided for the following features to be achieved: the hydraulic drive system (70) comprises one each hydraulic variable displacement motor (72) for driving the driven travelling devices (12) with the exception of the at least one pivotable travelling device (16), wherein the hydraulic drive system (70) comprises a hydraulic fixed displacement motor (74) for driving the at least one pivotable travelling device (16).

In a self-propelled construction machine (1), in particular road milling machine, comprising a machine frame (8), at least three travelling devices (12, 16), wherein at least one of the three travelling devices (12, 16) is realized as a pivotable travelling device (16) so that said travelling device (16) is pivotable about at least one vertical pivoting axis in relation to the machine frame (8) between a first pivoted-in and at least one second pivoted-out position, at least one working device (20), in particular a milling drum, for working the ground pavement (3), at least one hydraulic drive system (70) for driving at least two travelling devices (12, 16), wherein at least one of the at least two driven travelling devices is the pivotable travelling device (16), wherein the hydraulic drive system (70) comprises at least one hydraulic pump (78), it is provided for the following features to be achieved: the hydraulic drive system (70) comprises one each hydraulic variable displacement motor (72) for driving the driven travelling devices (12) with the exception of the at least one pivotable travelling device (16), wherein the hydraulic drive system (70) comprises a hydraulic fixed displacement motor (74) for driving the at least one pivotable travelling device (16).

A hydraulic steering arrangement (1) is described comprising a supply port arrangement having a pressure port (P) and tank port (T), a working port arrangement having two working ports (L, R), a steering unit (2) arranged between the supply port arrangement and the working port arrangement and a steering valve (3) arranged between the supply port arrangement and the working port arrangement. Such a steering arrangement should have a safety means. To this end in a manual steering mode the steering valve (3) is connected to the working port arrangement through the steering unit (2).

A hydraulic steering arrangement (1) is described comprising a supply port arrangement having a pressure port (P) and tank port (T), a working port arrangement having two working ports (L, R), a steering unit (2) arranged between the supply port arrangement and the working port arrangement and a steering valve (3) arranged between the supply port arrangement and the working port arrangement. Such a steering arrangement should have a safety means. To this end in a manual steering mode the steering valve (3) is connected to the working port arrangement through the steering unit (2).