GB726279A - Improvements in or relating to devices for testing the security of roof bolts and the like - Google Patents

Abstract

726,279. Testing the security of roof bolts. GULLICK, Ltd., and SEAMAN, T. July 3, 1963, No. 18440/53. Class 106(2). A device for testing the security of roof bolts, as used for example in coal mines, comprises an abutment member adapted to be secured to the lower end or head of a roof bolt protruding from the roof, an extensible device between the roof and the abutment member to urge the latter away from the roof and a tell-tale device for indicating any movement of the abutment member away from the roof under the action of the extensible device. In Fig. I the abutmeiit member 15 is screwed onto the protruding end 13 of a roof bolt 12. A hydraulicallyactuated extensible member 18 is placed between a flange 14 on the member 15 and a roof plate 11. A washer 21 is held firmly between the upper part of the member 15 and the roof plate 11. In use, pressure fluid is pumped into the extensible member 18 and at a certain pressure the load on the roof bolt 12 will be'such that the washer 21 has become slack. Access for testing the tightness of the washer and noting immediately it becomes slack is provided by an opening 18a in the sleeve 18. If, when the washer becomes slack, the load as indicated by a pressure gauge is below a predetermined level, then this is an indication that the roof bolt has not been properly anchored in the roof. The modification shown in Fig. 4 is applicable to cases where instead of the screw-threaded end of the bolt protruding from the roof only the head of the bolt is accessible. For this, the apparatus described with reference to Fig. 1 is used together with (a) an adaptor extension 22 screwed into the member 15 and having a clawed end 23 for gripping the bolt head, and (b) an extension piece 25 for disposal between the extensible member 18 and the roof. The mode of operation is identical with that already described.