A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (5) and a tank port (T) connected to a tank flow path (6), a working port arrangement having a left working port (L) connected to a left working flow path (7) and a right working port (R) connected to a right working flow path (8), a bridge arrangement (14) of variable neutral open orifices, said bridge arrangement (14) comprising a first left orifice (A2L) connected to a main flow path (5) and to the left working flow path (7), a first right orifice (A2R) connected to a main flow path (5) and to the right working flow path (8), a second left orifice (A3L) connected to the left working flow path (7) and to the tank flow path (6), and a second right orifice (A3R) connected to the right working flow path (8) and to the tank flow path (6). Such a steering unit has a good steering behavior but can function as a closed-center solution. To this end a further variable orifice arrangement is arranged between the supply port (P) arrangement and the working port arrangement (T), which further orifice arrangement is closed in neutral position.

A fluid controller includes a valve housing having an inlet port, a return port, first and second control ports and a load sense port. The fluid controller further includes a fluid meter in selective fluid communication with the valve housing and a valve assembly adapted to provide selective fluid communication between the valve housing and the fluid meter. The valve housing includes a main flow path and a load sense flow path. The main flow path is adapted to provide selective fluid communication between the inlet port and the first control port. Fluid in the main flow path passes through the fluid meter. The load sense path is adapted to provide selective fluid communication between the load sense port and the main flow path. The load sense flow path includes a variable load sense orifice that substantially closes prior to a maximum rotational displacement of the valve assembly.

A fluid controller includes a valve housing having an inlet port, a return port, first and second control ports and a load sense port. The fluid controller further includes a fluid meter in selective fluid communication with the valve housing and a valve assembly adapted to provide selective fluid communication between the valve housing and the fluid meter. The valve housing includes a main flow path and a load sense flow path. The main flow path is adapted to provide selective fluid communication between the inlet port and the first control port. Fluid in the main flow path passes through the fluid meter. The load sense path is adapted to provide selective fluid communication between the load sense port and the main flow path. The load sense flow path includes a variable load sense orifice that substantially closes prior to a maximum rotational displacement of the valve assembly.

A hydraulic steering device is provided comprising a supply port arrangement having a supply port (P) and a return port (T), a working port arrangement having two working ports (L, R), direction valve means (2) arranged between said supply port arrangement and said working port arrangement, at least two fluid meters (3, 4), each of said fluid meters (3, 4) having a movable metering element (12, 15), said metering elements (12, 15) being connected by a shaft (5), said shaft (5) having an axis, selector valve means (6) being provided, said selector valve means (6) in a first position arranging said fluid meters (3, 4) hydraulically in parallel and in a second position shutting off one of said fluid meters (3, 4), said selector valve means (6) having a valve element (20) shiftable in an direction parallel to said axis. It is an object to reduce wear in said hydraulic steering device in a simple manner. To this end said selector valve means (6) are arranged between said two fluid meters (3, 4), said shaft (5) extending through said valve element (20).

A hydraulic steering device is provided comprising a supply port arrangement having a supply port (P) and a return port (T), a working port arrangement having two working ports (L, R), direction valve means (2) arranged between said supply port arrangement and said working port arrangement, at least two fluid meters (3, 4), each of said fluid meters (3, 4) having a movable metering element (12, 15), said metering elements (12, 15) being connected by a shaft (5), said shaft (5) having an axis, selector valve means (6) being provided, said selector valve means (6) in a first position arranging said fluid meters (3, 4) hydraulically in parallel and in a second position shutting off one of said fluid meters (3, 4), said selector valve means (6) having a valve element (20) shiftable in an direction parallel to said axis. It is an object to reduce wear in said hydraulic steering device in a simple manner. To this end said selector valve means (6) are arranged between said two fluid meters (3, 4), said shaft (5) extending through said valve element (20).

The invention relates to a power steering system for a working machine, said power steering system comprising at least one steering cylinder comprising two compartments separated by a piston, a tank, a steering unit comprising a steering valve and a metering device, for supplying one compartment of the steering cylinder with a metered liquid flow, a hydraulic pump for pumping liquid from the tank to the steering unit through a supply line (SL), a return line (RL) through which the liquid flows back to the tank, a recirculation line connecting the RL to the SL, a check valve being arranged on said recirculation line to prevent liquid from flowing from the SL to the RL, two control lines, respectively connecting the steering unit to the two compartments and a liquid accumulator connected through a branch to the RL. A relief valve is arranged on the RL between the tank and an accumulator connection point.

The invention relates to a power steering system for a working machine, said power steering system comprising at least one steering cylinder comprising two compartments separated by a piston, a tank, a steering unit comprising a steering valve and a metering device, for supplying one compartment of the steering cylinder with a metered liquid flow, a hydraulic pump for pumping liquid from the tank to the steering unit through a supply line (SL), a return line (RL) through which the liquid flows back to the tank, a recirculation line connecting the RL to the SL, a check valve being arranged on said recirculation line to prevent liquid from flowing from the SL to the RL, two control lines, respectively connecting the steering unit to the two compartments and a liquid accumulator connected through a branch to the RL. A relief valve is arranged on the RL between the tank and an accumulator connection point.