the central axis 23 thereof the valve housing 41 is formed as a lining sleeve which is connected by an adhesive to or sealingly fitted in an outer housing 38 the slide 40 is maintained axially by a cross pin 42 in the valve housing 41 which engages a ring groove 43 in the slide 40 an end flange 44 forms the outer termination of the slide 40 while its opposite end forms or is connected to a positioning axle 13 extending through the hollow axle 19 fig2 a plate 46 connects the outer housing 38 to the carrier 18 with the valve axis 23 in coaxial relation to the pivot axle 19 the slide 40 has two control lands 51 52 and adjacent thereto and therebetween three balancing lands 53 all said lands are terminated by annular graooves 47 carrying o rings 48 which seal against the valve housing 41 the control lands 51 52 are provided with mutually opposed peripheral passages 49 50 fig5 which for purposes of to certain extent balancing pressures preferably are disposed in mirror symmetry with respect to a common central plane 45 and extend each to a pair of opposed narrow slits 54 55 and 56 57 each of said slits extends to its respective groove 58 in the outer periphery of the valve housing 41 the slits 55 57 via the grooves 58 at one side of the outer housing 38 are both in communication with a conduit o which is connected to one end in fig1 the upper end of the control cylinder 26 at the opposite side of the outer housing 38 the respective.