GB686640A - Improvements in or relating to lagging members for shoring operations - Google Patents

Abstract

686,640. Mine roof supports. MULLER, M., and BORGGRAFE, K., (trading as MULLER & BORGGRAFE KOMMANDIT-GES.). Feb. 2, 1951, No. 2664/51. Class 20(ii) Mine roof supporting bars, e.g. of I-section, are coupled end-to-end by means of two slidable elements c, Fig. 1, 1A, arranged at both sides and adapted to project from one end of one bar a, the elements @ having tapered end portions c<SP>11</SP> between which is inserted the end of a similar bar b to be supported temporarily by the bar a, the bar b having undulating inclined faces adapted to engage the tapered portions c<SP>11</SP> and lock the two bars together. The main body portions of the elements c fit closely between the upper and lower flanges of the I-section bar a and are retained in this position by side plates d each having a longitudinal slot e provided at one end with a stop h. Each element c, Fig 2, is provided with a handle f and a lateral lug g engaging the stop h when the element c is fully advanced. On the inside surface of each of the side plates d there is mounted a pawl ico-operating with a rack k in the element c which is outwardly biased by a spring q. The bar b is also provided with side plates m formed with longitudinal slots l, the wedges o having handles n projecting through the slots. The top surface of each wedge o bears against the lower surface of the upper flange of the bar b, whilst the lower undulating inclined surface bears against the tapering upper surface of the slidable element c. Chains are attached to the handles n of the wedges o and, after the unshored bar b is propped up and the wedges o loosened, the chains are hooked on to the lugs g of the elements c which are then retracted until the chains tighten, the elements c being retained in this position by the pawls i engaging the racks k and the two bars being thus interconnected only by the chains in the final stage of the shoring operation.