Haulage apparatus for mining machines

A mining machine comprising a body movable along a track extending along a desired machine path, two hydraulically actuated piston and cylinder arrangements each of which is attachable at one end to the machine body and each of which has at its other end means for attaching to hydraulically actuated track-engaging means for releasably engaging the track under action of a hydraulic ram, and control means for simultaneously actuating the two piston and cylinder arrangements in an opposite sense with respect to each other, the control means comprising detector means for detecting when at least one of the piston and cylinder arrangements is approaching the end of one stroke and having operational modes indicative of the detected condition of said at least one of the piston and cylinder arrangements, a directional control valve which in use has different operational modes for controlling the supply of pressure fluid to the hydraulic rams of the track-engaging means and which is actuated between its operational modes in accordance with the operational mode of said detector means, and a further directional control valve which in use has different operational modes for controlling the supply of pressure fluid to the piston and cylinder arrangements and which is actuated between its operational modes in accordance with the operational modes of the first mentioned directional control valve.