Valve devices
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United States of America Patent
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Apr 8, 1986
Grant Date -
N/A
app pub date -
Dec 17, 1984
filing date -
Jan 5, 1984
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
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.
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