Abstract: A roof support has a pair of floor sills carrying hydraulic props supporting a roof-engaging structure. The floor sills have guide rails on their adjacent sides which mate with a slidable guide block which connects to a shifting ram and thrust mechanism between the sills. The shifting ram has one of its displaceable parts, i.e. its cylinder or piston rod articulated to a thrust beam or a pair of thrust rods which link with a conveyor in front of the support. The sills are interconnected for relative vertical movement and are coupled to the other displaceable part of the ram. The guide is linked to the thrust beam or thrust rods remote from the conveyor by way of a pivot joint which resists traction but permits pivoting about an axis generally parallel to the ram and which is easily assembled and dismounted.

Abstract: A support assembly for a mine working has a floor-sill structure for engaging on the floor of the working and a roof-engaging member or members braced by one or more props against the roof of the working. The floor-sill structure employs one or more slidable skids which can be selectively extended in length at the forward end by fitting an extension component of the same width thereto. The or each skid is recessed to receive rear projections of the associated extension component and securing means, such as spindles or shaped locking elements, are used to secure the extension component to the skid. When the extension component is removed, inserts are located in the recesses of the skid to fill the latter and these inserts can be likewise secured with the same securing means.

Abstract: A releasable pivot joint for use in underground mining installations comprises first and second connecting members. The first connection member has a width which is greater than its thickness and a reduced portion that reduces its width to a core width. The second connection member is formed with a slot into which is inserted the reduced portion of the first connection member. The width of the slot is greater than the thickness and the core width of the first connection member. The length of the slot is greater than the width of the first connection member. The thickness of the second connection member is smaller than the core width of the first connection member. The width of the first connection member extends transversely of the length of the slot when the connection members are in the connected position.

Abstract: The invention relates to an advance mechanism for a roof support assembly constituted by a plurality of roof support units positioned side-by-side along, for example, a longwall face of a mineral mining working. The advance mechanism comprises a pair of hydraulic advance rams and a pair of resilient, generally parallel guide rods. The guide rods are interconnected at one end by means of a head-piece which is attachable to a conveyor extending along the longwall face. The other end of each guide rod is attached to a respective slide piece which is slidably guided on a respective guide rail which is attached to a floor girder of a roof support unit. The hydraulic advance rams are each pivotally attached to one of the slide pieces and to one of said floor girders. The guide rods are provided, adjacent said one end, with outwardly projecting alignment members each of which co-operates with one of said floor girders to align an associated roof support unit during its advance.

Abstract: The invention relates to an advance mechanism for a roof support unit to be used in a longwall face of a mineral mining working. The advance mechanism comprises a hydraulic advance ram and guide means constituted by a guide rod means and a guide rail. One end of the guide rod means is attached to a conveyor extending along the longwall face, the other end of the guide rod means being attached to a guide element. The guide rail extends slidably through a guide aperture in the guide element and is pivotally attached to the floor sill of the roof support unit for pivotal movement in a vertical plane perpendicular to the longwall face. The hydraulic advance ram is attached to the guide element and acts on a member fixed to the floor sill.

Abstract: A three-stage hydraulically-operated telescopic prop is disclosed having working chambers which can be charged with hydraulic pressure fluid to extend a central prop member relative to an outer prop member and an inner prop member relative to the central member. A pressure-operated spring biased non-return valve is operated by pressure to open communication between the working chambers to extend the inner member once the central member has been fully extended. The valve is also operated mechanically to open communication between the working chambers to allow retraction of the inner member when the central member has been retracted to a certain extent. Further chambers are provided between the central and outer member, and between the central and inner member, and these chambers can be charged with hydraulic pressure fluid to retract the central member relative to the outer member and the inner member relative to the central member.

Abstract: The invention relates to an advance mechanism for a roof support assembly constituted by a plurality of roof support units positioned side-by-side along, for example, a longwall face of a mineral mining working. The advance mechanism comprises a pair of hydraulic advance rams and a pair of resilient, generally parallel guide rods. The guide rods are interconnected at one end by means of a head-piece which is attachable to a conveyor extending along the longwall face. The other end of each guide rod is attached to a respective slide piece which is slidably guided on a respective guide rail which is attached to a floor girder of a roof support unit. The hydraulic advance rams are each pivotally attached to one of the slide pieces and to one of said floor girders. The guide rods are provided, adjacent said one end, with outwardly projecting alignment members each of which co-operates with one of said floor girders to align an associated roof support unit during its advance.