GB845302A - Improvements relating to mine roof supporting frames - Google Patents

Abstract

845,302. Mine roof supports. DOWTY MINING EQUIPMENT Ltd. May 29, 1958 [May 29, 1957], No. 17091/57. Class 20(2) A mine roof support comprises three telescopic props 12 pivotally mounted on a common base 10 and carrying a roof bar comprising a rear section 22 and a cantilever section 21 joined by a hinge pin 24 with a spring 39 to maintain them substantially in line when not engaged with the mine roof. A third section 20 is hinged at 23 to the section 22. The props 12 are each joined to the roof bar by a conically headed bolt 29 which passes through a bearing plate 28 to extend with clearance into a conical recess in the head of the prop. A bolt 32 securing the section 21 has a longer shank extending through a bearing box 33. The bases of the props are convex with a central spigot which engages a hole in a mounting plate within the base which also contains resilient means to urge the props upright (Fig. 1b not shown, refers). A moving jack 76 is provided below the cantilever section 21. The spring 39 may be located by a stud instead of the socket 38 shown or may be replaced by a torsion spring around the hinge 24, the ends of the spring bearing on the undersides of the sections 21, 22. (Figs. 6 and 7, not shown, refer). Where the roof bar comprises only two sections the rear section 22 is weighted to assist in the contraction of the prop in compensation for the weight of the cantilever. Where the props are hydraulic, pressure fluid is supplied from a channel 81, Fig. 11 through radial bores 84 in a removable plug 83 to a channel 85 leading to the front prop. To contract the prop a valve (not shown) is operated to give access through a valve 86 to the return pipe via a bore 87 which is small enough to retard the contraction. The bore 85 of the rear prop will be smaller and the bore 87 larger than that of the cantilever prop to compensate for the unequal loading.