Mine roof supports
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United States of America Patent
Stats
-
Sep 25, 1984
Grant Date -
N/A
app pub date -
Feb 23, 1983
filing date -
Mar 6, 1982
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A mine roof support includes a first liquid supply means having a first control valve for connecting a source of liquid under pressure to the legs of the support. The support is also provided with a second control valve which is actuatable, when the pressure of the liquid being supplied to the legs attains a value below the setting pressure for the legs, to connect the legs to a source of liquid under pressure by way of a second liquid supply means. Time-delay means is operable on the second control valve to cause it to close when a predetermined time has elapsed after the pressure in the legs has reached the setting pressure.
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Cited Art Landscape
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