| 摘要 |
<p>A valve assembly is provided for use with a hydraulic mine roof support, the assembly having uni-directional control means 49 interconnecting first and second pressure sectors of the valve assembly, and further control means 20 embodied in the first pressure sector which further control means is arranged for activation by fluid pressure in the first pressure sector to allow pressure fluid to flow from the second pressure sector to the first pressure sector until the fluid in the first pressure sector is equal to or exceeds the fluid pressure in the second pressure sector.</p> |
