Abstract: A high pressure water control device comprising a water inlet, a high pressure water outlet, a low pressure water outlet and a valve for selectively communicating the inlet with one or other of the outlets. The valve is a spool valve comprising a sleeve and a spool slidable in the sleeve. The spool has two axially spaced apart annular seals and the sleeve includes an annular groove in its outer surface and one or more dump ports which communicate between the groove and the inside of the sleeve so that when the dump ports are disposed between the spaced apart seals of the spool high pressure water will be delivered to the high pressure water outlet. The control device is in the form of a water gun having an elongate nozzle terminating in the high pressure outlet and a barrel surrounding the nozzle and terminating in the low pressure outlet.

Abstract: A high pressure water control device comprising a water inlet, a high pressure water outlet, a low pressure water outlet and a valve for selectively communicating the inlet with one or other of the outlets. The valve is a spool valve comprising a sleeve and a spool slidable in the sleeve. The spool has two axially spaced apart annular seals and the sleeve includes an annular groove in its outer surface and one or more dump ports which communicate between the groove and the inside of the sleeve so that when the dump ports are disposed between the spaced apart seals of the spool high pressure water will he delivered to the high pressure water outlet. The control device is in the form of a water gun having an elongate nozzle terminating in the high pressure outlet and a barrel surrounding the nozzle and terminating in the low pressure outlet.

Abstract: An energy recovery device includes at least one cylinder, a piston slidable in the cylinder, a first valve for selectively connecting one end of the cylinder to waste liquid at a first relatively high pressure and to drain and a second valve for allowing feed liquid to enter the other end of the cylinder at a second lower pressure via a feed liquid entry port and to be discharged via a feed liquid discharge port from the other end of the cylinder in response to movement of the piston caused by waste liquid entering the one end of the cylinder. A rod which extends from the other end of the cylinder and into but not through the piston, ensures that the area of the piston acting on the feed liquid is less than the area of the piston acted upon by the waste liquid so that the piston acts as a pressure intensifier to discharge feed liquid through the feed liquid discharge port at a higher pressure than the pressure of waste liquid entering the one end of the cylinder.

Abstract: An energy recovery device comprises at least one cylinder, a piston slidable in the cylinder, first valve means for selectively connecting one end of the cylinder to waste liquid at a first relatively high pressure and to drain and second valve means for allowing feed liquid to enter the other end of the cylinder at a second lower pressure via a feed liquid entry port and to be discharged via a feed liquid discharge port from said other end of the cylinder in response to movement of the piston caused by waste liquid entering said one end of the cylinder. Also, means, such as a rod which extends from the other end of the cylinder and into but not through the piston, ensures that the area of the piston acting on the feed liquid is less than the area of the piston acted upon by the waste liquid so that the piston acts as a pressure intensifier to discharge feed liquid through the feed liquid discharge port at a higher pressure than the pressure of waste liquid entering said one end of the cylinder.

Abstract: A pilot operated check valve is provided for use in controlling the hydraulic leg 14 of a hydraulic mine roof support, the valve having means 23 to connect a leg extension port 18 to a return port 17 within the valve, when the valve is used to lower the leg 14. This provides more rapid operation than with prior art arrangements in which released pressure from the leg has to return from an extension port back to a remote spool valve controlling leg extension before reaching a return line.

Abstract: A swivel coupler for releasably and fluid tightly connecting two parts together so that fluid can pass between the two parts and the two parts can rotate relative to one another, comprises a body having an outer surface which, at least in part, is right cylindrical and a collar mounted on the right cylindrical outer body surface for rotation relative thereto. The collar projects beyond one end of the body for connection to one of the two parts and the body is connectable to the other of the two parts. Rotary sealing elements are provided between the collar and the right cylindrical outer body surface. There is a first ball or roller bearing race in the right cylindrical outer body surface and at least one radially extending bearing assembly aperture in the collar for inserting ball or roller bearings into said race when the race and aperture are radially aligned.

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 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 system including a relief valve communicable with the props of each roof support through respective control valve means, and a main return pipe for receiving liquid discharged, by way of the relief valve, from the props when liquid at high pressure is no longer supplied thereto and the roof support is being advanced. A movable element of the relief valve comprises at least two relatively-movable and connected parts and is so co-operable with its seating as to ensure that when the support is so advancing a substantially constant predetermined back-pressure is maintained in the props sufficient to maintain the support in contact with the mine roof. If the pressure in the main return pipe exceeds the pressure then subsisting in the control valve means, one of the parts of said element is caused automatically to close onto the seating.