Abstract: A through flow coupler comprises two parts having intercommunicating passages therein so that fluid can flow through the two parts. A sealing member provides a fluid tight seal between the two parts when the two parts are held together in a sealed condition. A pressure sensitive device, which may comprise a frangible ring, holds the two parts in the sealed condition when the fluid pressure within the passages is below a certain value and allows the two parts to move relative to one another to a pressure relief condition so that fluid can escape from the passages when the fluid pressure within the passages exceeds said certain value. Also, mutually co-operable members, e.g. flanges, are provided to prevent total separation of the two parts when the pressure sensitive device allows the two parts to move relative to one another.

Abstract: A mine roof support includes a ground engaging base section, a roof engageable canopy, and hydraulic props for raising and lowering the canopy relative to the base section. An advancing mechanism is provided for advancing the roof support towards the mine face, and a base lifting mechanism is provided for raising one end of the roof support prior to advancing the support towards the mine face. The base lifting mechanism includes a lifting ram mounted with respect to the base section for slidable movement between an upper operative position in which the ram can be extended to lift the one end of the roof support clear of the ground and a lower position in which the canopy can assume a position relative to the base section lower than would be possible with the lifting ram in its upper operative position.

Abstract: A mine roof support comprises a canopy, a base section, hydraulic props for raising and lowering the canopy relative to the base section, a hydraulic valve for supplying hydraulic fluid under pressure to the props via a check valve, and a yield valve connected across the check valve. The yield valve has a valve member movable between a first position in which it co-operates with a valve seat to prevent the release of fluid from the props via the yield valve and a second position in which fluid can be released from the props via the yield valve. One side of the valve member is subjected to fluid pressure downstream of the check valve to urge the valve member towards its second position and the other side of the valve member is acted upon by a spring device to urge the valve member towards its first position.

Abstract: A mine roof support comprises a ground engageable base section, a canopy, a shield section pivotally connected at one end to one end of the canopy and at the other end to one or more members connected to the base section, and hydraulic props for raising and lowering the canopy relative to the base section. An opening is provided in the canopy and a door is mounted with respect to the canopy for pivotable movement between a first position in which it closes or substantially closes the opening in the canopy and a second position in which it is inclined downwards away from said one end and towards the other end of the canopy for guiding material which in use falls through the opening towards a conveyor located adjacent to a mine face being worked.

Abstract: A mine roof support assembly comprises a mine roof support having a first end adjacent to the mine face and a second end remote from the mine face, an advancing mechanism for advancing the roof support towards the mine face, and a base lifting mechanism. The base lifting mechanism includes two substantially parallel arm members pivotally connected to a base section of the mine roof support, and two lifting rams each of which acts between a respective arm member and the roof support. The lifting rams act on the roof support at a position which is nearer than the center of gravity of the roof support assembly to the second end of the roof support to pivot the roof support relative to a respective arm member and thereby lift the first end of the roof support clear of the ground. Also, an advancing ram of the advancing mechanism is connected to the arm members by an arrangement which provides some movement of the ram relative to the arm members in two mutually transverse directions.