Control apparatus

Details Control apparatus Control apparatus

1981-12-30

1984-04-17

Taylor, Dennis L.

Hydraulic and earth engineering

Earth treatment or control

Ground stabilization or reinforcement

405291, E21D 1546

Patent

active

044431350

ABSTRACT:
A mine roof support unit has a floor sill, a roof cap supported above the floor sill by a pair of inclined hydraulic props, and control apparatus for controlling load-bearing capacity of the props. The inclination of the props relative to the vertical increases as the props are retracted. The control apparatus comprises a pressure-relief valve for limiting the pressure of the hydraulic fluid supplied to the hydraulic props. The pressure-relief valve has a closure member which is biased towards its closed position by a spring. The spring is backed by an abutment member which constitutes a setting device for adjusting the biasing force of the spring, thereby controlling the operating pressure of the pressure-relief valve, and hence the load-bearing capacity of the props. The setting device is operatively associated with a movable part of the roof support unit in such a manner that the operating pressure of the pressure-relief valve is reduced in response to movement of said movable part of the roof support unit which results from extension of the hydraulic props.

REFERENCES:
patent: 2752757 (1956-07-01), Joy
patent: 2859022 (1958-11-01), Frye
patent: 3478522 (1969-11-01), Rieschel
patent: 3832856 (1974-09-01), Sigott et al.
patent: 4325659 (1982-04-01), Plevak et al.

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