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US 3,991,578 AGranted
Self-advancing mine roof supports
AssigneeGullick Dobson Limited
InventorsJohn Cooke, Derek Alker
Life of this patent
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AssigneeGullick Dobson Limited
InventorsJohn Cooke, Derek Alker
Estimating the term…
A control means, for a mine roof support having hydraulically extensible prop means and some other pressure-fluid-operated component (e.g. a hydraulic ram for advancing the support), comprises a control valve having selectable positions in one of which (the prop extend position) it will select for a supply of hydraulic pressure-fluid to said prop means. The control means also include a valve device having a position in which it will provide for a supply of pressure-fluid to the prop means and having means adapted to cause it to move to that position, when the control valve is operated to the prop extend position, and to keep it in that position even position. the control valve is operated from the prop extend positon. By this arrangement a pressure-fluid supply to the prop means will still be maintained so as to ensure proper setting thereof and to make up any leakage of fluid. The operation of the control valve from the prop extend position may be, for example, to bring it into a neutral position or to a position in which pressure-fluid is supplied to the advancing ram of the support. In one preferred embodiment of the invention the valve device has a pressure-fluid responsive movable member and is adapted to be connected, for its operation, to a pressure-fluid supply via the control valve.
Control means for a mine roof support comprising a control valve having selectable positions including a prop extend position in which a supply of pressure-fluid is selected to operate extensible prop means of the support and a prop release position in which the extended prop means are selected for release, and a valve device intercoupled with the control valve by pressure-fluid lines and including means movable to a first position in response to selection of said prop extend position by said control valve and, when in said first position, for providing a supply of pressure-fluid to said prop means of the support, said valve device also including pressure-fluid connection means connected to the pressure-fluid supply of said prop means for keeping said valve device in said first position when the control valve is moved from said prop extend position for maintaining pressure-fluid supply to said prop means until said control valve is moved to said prop release position to release said pressure-fluid connection means for permitting said valve device to move to a second position for release of said prop means.
Dependencies are inferred from the claim text.