Abstract: A hydraulic mine prop comprises a cylindrical top ram portion and a bottom ram portion which is telescopically engageable in said top ram portion and has an upper piston portion in sliding sealing engagement with the interior of said top ram portion. A ram head closes the top of said ram portion and a valve seat body is disposed between the ram head at a spaced location therefrom adjacent the top of the top ram portion and defines a vent space therebetween. The valve seat body also encloses a pressure space between itself and the piston and a passage is defined through the valve body within a valve seat portion thereof which communicates the pressure space to the vent space. The passage is closed by a spring-biased valve which may open against the biasing force of the spring.

Abstract: A canopy and shield structure for supporting a shield adjacent a working face in a seam-like mine deposit, comprises a floor skid which is connected through an extensible and contractable prop at the working face end to the working face end of a canopy adapted to be positioned in parallel relation to the roof strata. The working space is covered at the waste removal end by a shield which includes a lower two-arm lever portion which is pivotally mounted on the skid and an upper portion which is pivotally connected to the longer arm of the two-arm lever adjacent the upper end thereof and is also pivotally connected to the canopy. The two-arm lever is driven by a hydraulic drive motor and a parallel linkage is connected between the upper shield part and the canopy in order to provide a guidance of the canopy in a direction substantially perpendicular to the strata.

Abstract: A canopy and shield structure for supporting a shield adjacent a working face in a seam-like mine deposit, comprises a floor skid which is connected through an extensible and retractable prop at the working face end to the working face, and of a canopy, which is adapted to be positioned in parallel relation to the roof strata. The working space is covered at the waste removal end by a shield which includes a lower portion pivotal on the floor skid, and an upper portion which is rigidly connected to the canopy at the opposite end of the canopy from the working face end. The shield is connectable to an extensible and retractable prop and a lemniscate guidance mechanism, so that the upper part of the shield may be moved upwardly and downwardly along its longitudinal axis. The upper part also carries an opening for the passage of a blast pipe which is supported on roller means carried by the canopy.

Abstract: A roof-support shield structure for use in an excavation to support and shield a roof above a floor of an excavation, such as a coal mine, comprises a sill beam adapted to be supported on the floor, and an inclined shield having one end pivoted to the sill beam and an opposite end pivoted to a roof cap lever. The roof cap lever includes an elongated roof cap arm which is adapted to be positioned against the roof and a crank arm which is connected to a fluid motor such as a piston and cylinder combination to pivot it and the associated roof cap arm for the purposes of positioning the roof cap arm in association with the roof. The roof is also supported by a prop in the form of a fluid piston and cylinder combination connected between the roof cap and the supporting sill. The sill is advantageously provided with a walking and aligning mechanism for coupling it to an adjacent shield which may be shifted along the mine floor therewith.

Abstract: A roof support structure for excavations comprises a supporting sill beam which is adapted to be anchored in a position below the roof in the shaft or excavation being worked. The sill beam includes a front curved working face forming a closed cover plate and a movable front structure is pivoted on the sill beam at the center of curvature of the cover plate and it has a closed front end plate which is telescopic over the cover plate during pivotal movement. A cave-in shield is pivotaly connected to the outer end of the front structure adjacent the front plate and its opposite end is directed toward the roof and a roof cap structure is pivotally mounted on this end and is positioned against the roof by adjustable hydraulic props which engage against the cave in shield and pivot it to a desired position.