VALVE DEVICES

A valve device is provided for use in a pressurized hydraulic fluid path, for example the hydraulic path of a hydraulic leg of a mine roof support which is required to yield under two different sets of conditions. The valve device has a port 15 for connection to the pressurized hydraulic fluid path, a bleed valve 25 being arranged to permit hydraulic fluid to bleed from the path at a first rate when the pressure in the path exceeds the first limit, for example to permit the hydraulic leg to collapse at a very slow rate, for example as a mine roof converges. There is also a dump valve 20 arranged to permit hydraulic fluid to flow from the path at a second greater rate, for example if a rock burst occurs. Although the dump valve 20 reacts to high pressure surges of fluid, it does not react to low pressure surges because a non-return valve device 30 traps on one side of the dump valve hydraulic fluid which is at a pressure in the region of the first limit. Thus the dump valve only operates if the pressure on the other side of the dump valve exceeds the first limit.