lance 6 for supplying the chambers 57 of the rotary piston pivot motor 5 with hydraulic oil is introduced into the axial bore 511 of the pivot motor shaft 51 the lance 6 is configured essentially cylindrically at the end side the lance 6 has a head piece 61 followed by a shaft 62 which makes a transition into a slide bearing section 63 that is enlarged in diameter two channels 64 for supplying the chambers 57 of the rotary piston pivot motor 5 are introduced into the lance 6 coaxial to its center axis 11 the channels 64 open into a ring groove 65 disposed within the slide bearing section 63 in each instance which is disposed so that one of the radial bores 512 of the pivot motor 5 is disposed orthogonal to this groove which axial bore 511 represents the connection with the chamber 57 in each instance of the rotary piston motor 5 sealing of the ring grooves 65 relative to the pivot motor shaft 51 takes place by way of a very narrow gap between the slide bearing section 63 and the inner wall of the axial bore 511 of the pivot motor shaft 51 whereby the slide bearing section is.