Hydraulic rear axle steering

A hydraulic rear axle steering for multi-axle vehicles, comprising:

• a steering cylinder (30), which comprises a cylinder chamber, a piston (33a) mounted in a sealing manner in the cylinder chamber, which divides the cylinder chamber into two working chambers (39, 40), and at least one piston rod (33) carried by the piston (33a);
• the steering cylinder (30) includes a mechanical blocking device (34, 35, 36, 36′), which blocks the piston (33a) once the piston reaches a central position within the steering chamber (30);
• the blocking device (34, 35, 36, 36′) comprises at least one blocking member (36, 36′), which in the blocked state is retained by a locking element (34, 35) in an engaged position (42);
• an actuator (37, 38, 45) by which the locking element (34, 35) is adjustable, the actuator (37, 38, 45) is actuated hydraulically separate from the piston (33a) and piston rod (33) and moves between a blocking position, in which the locking element (34, 35) holds the blocking member (36, 36′) in the engaged position (42), and at least one first unblocking position, in which the locking element (34, 35) releases the blocking member (36, 36′);
• a return line from each of the two working chambers (39, 40) leads to a tank (7);
• a hydraulically unblockable valve (15, 17) is arranged in each of the return lines;
• the hydraulically unblockable valves (15, 17) comprise admission-pressure controlled valves and each include a control connection that is connected in each case to a pressure line (11, 12) leading (34, 35, 36, 36′) from a pump (3) to the respective other working chamber (39, 40);
• and
• the hydraulically actuated actuator (37, 38, 45) is adjustable such that, when a first pressure value is applied, the locking element (34, 35) moves into the unblocking position and the admission-pressure controlled valves (15, 17) are adjusted such that, when a second pressure value is applied, the admission-pressure controlled valves (15, 17) open at the respective control connection, and the second pressure value is higher than the first pressure value.