Abstract: The invention relates to a pressure limiting valve, mainly for hydraulic mine props, which has a working space with an inlet opening connected to a high-pressure space and an outlet opening connected to low-pressure space in the operative position of the valve, a displaceable first valve member engageable with a valve seat within this working space in the shut-off position of the valve, a spring pressing the first valve member to the valve seat and in a given case, a spring sustaining the valve seat, suitably a gas spring and in which according to the invention the first valve member has transfer passages ensuring communication between the inlet opening and the outlet opening in the open position of the valve, as well as second valve member provided with a frustoconical head facing the cover plate and having a stem loosely fitted in a guide bore formed in the first valve member which is formed with an annular axial flange surrounding the head of the second valve member which is concentrically arranged within

Abstract: A process for measuring the tightness of endless driving members, particularly straps, belts, chains, ropes etc. during operation, in the course of which a signal is displayed. First and second spaced markings are applied onto the driving member. Along the path of the driving member at least one sensing element is arranged and at a constant speed of the driving device the time elapsing between the passing of the first and the second markings before the sensing element is measured.

Abstract: End fitting or armature for multi-channel hoses having a positioning plate and a guiding plate extending perpendicularly to the longitudinal axis of the hose and apertured to receive hose coupling elements. Means are provided for varying the axial spacing of the plates. A resilient element is disposed between the plates, a part of which seats in a groove formed in the internal surface of the end fitting when the plates are pulled towards each other under load.

Abstract: The invention concerns an advanceable shield support assembly for longwall mining. The assembly has a pivotable main roof cap housing a retractable and extensible auxiliary roof cap. Normally the main roof cap supports the roof and the auxiliary one is retracted. However, before the assembly is advanced, the auxiliary roof cap is extended to support the roof section between the working face and the front edge of the main roof cap. The movement of the auxiliary roof cap, and the force with which it engages the roof section, are controlled by cooperating guide tracks and track-engaging elements capable of exerting a wedging action.