GB854967A - Improved mine roof supports - Google Patents

Abstract

854,967. Mine roof supports. DOBSON Ltd., W. E. & F. Feb. 12, 1957 [Feb. 28, 1956], No. 6108/56. Class 20(2) An advancing mine roof support comprises two hydraulic pit props 2, 3 on a skid base 19 and connected to a third prop 1 by a hydraulic advancing ram 21 and cylinder 22, a cantilever roof beam 28 being joined to the props 2, 3 by ball joints 28 and projecting between two parallel box section arms 32, 33 on the head 27 of the prop 1. The ram 21, which is pivoted to the base 19 at 21a and to the base of the prop 1 at 22a, carries a guide 15. The cantilever beam 28 comprises two box section beams 28 and 29 joined end to end by a bolt 30. In operation, the beams 28, 29 support the roof while prop 1 is lowered by a pump P operated by a handle 53 and then advanced by the ram 21 manually operated by a valve 63. Handle 53 is then operated to raise the prop 1 and the arms 32, 33 to support the roof while lowering props 2 and 3 and beams 28, 29 preparatory to their advance up to the prop 1. Alternatively a two-armed beam 28 may entrain a single arm 32, 33. The beam 29 may be braced against the roof by wedges (not shown) driven between it and the prop head 27 or by a hydraulic cylinder and ram indicated in broken line at 47. The props are centralised by resilient means in their bases. The pump P comprises a cylinder 49, Fig. 5, in which a piston 52 is operated by the handle 53. The fitting to which the handle is attached (Fig. 6, not shown, refers) comprises a control knob incorporating an air release valve operated by the fastening of the handle. Fluid is pumped from a reservoir in the base via an inlet 50 and a valve 57 to prop 1 and, through an outlet 51, to props 2 and 3. Excessive movement of handle 53 raises a pressure relief valve 60. A spring 62 cushions normal pumping movements to prevent inadvertent release of valve 60. Specification 785,470 is referred to.