Abstract: A hydraulic shock-absorber and vibration damper comprising a cylinder (1), a damping piston (2) disposed so as to be axially movable inside the cylinder (1) and dividing off two working chambers (9, 10) filled with a hydraulic damping medium and connected by at least one throttle means (62), a piston rod (3) connected to the damping piston (2) and guided in sealing-tight manner out of the cylinder (1), and a compensating chamber (11) connected to one (9) of the working chambers (9, 10) for receiving a volume of damping medium displaced by the piston rod (3). A damping valve (26) driven by an electromagnet (24) and acted upon by a closing force is disposed at the transition between the working chamber (9) and the compensating chamber (11). The damping valve (26) is disposed in series with the throttle means (62), so that all the damping medium flowing between the working chamber (9) and the compensating chamber (11) flows through the damping valve (26).

Abstract: A hydropneumatic shock-absorber and vibration damper comprising a cylinder (1) a damping piston (2) disposed for axial movement inside the cylinder (1) and dividing off two working chambers filled with a hydraulic damping medium and connected by a connection which includes at least one throttle, a piston rod (3) mechanically connected to the damping piston and guided outwardly from the cylinder (1) in sealing-tight manner, a compensating chamber (11) connected to one (9) of the working chambers (9, 10) for receiving a volume of damping medium displaced by the piston rod (3), and a pneumatic spring chamber (13) filled with a compressible medium and separated in sealing-tight manner from the compensating chamber (11) by a freely movable floating piston (12). The piston rod (3) is a hollow cylinder and the damping piston (2) is annular.

Abstract: An electro-hydraulic control system for self-advancing mine-roof supports in a high-output longwall mine is used to form a sequence zone behind the mining machine whereby individual supports simultaneously operate in the sequence of prop drawing, advancing and setting so that, during the sequence, the roof in the sequence zone is supported by at least each second support with the length of the sequence phase so depending on the cutting speed of the mining machine that it increases with increasing speed to ensure that the roof exposed by the mining machine is supported without delay.

Abstract: The invention is concerned with apparatus for maintaining a set "between-centers" distance between the elements of self-advancing mine-roof supporting means for long-wall mining, the support means having at least two elements connected via connecting means so that they can pivot to a limited extent with respect to an abutment which, in use, extends substantially parallel to the long-wall face, the connecting means of at least one element being constructed as a drive means, in which the portions of the abutment connected to the respective connecting means are interconnected so that their length can be varied, and a guide lever is pivoted to the connecting means of at least one element and to an abutment portion connected to an adjacent element so that the two places at which the lever is pivoted and the place at which the connecting means of the first-mentioned element are connected to the abutment lie at the corners of a triangle.