. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. utting head n, so that the coal is [removed in washers or ring. The breaking downapparatus is shown in Figs. 903 to 906; o are the expanding pieces, formed with taper grooves intheir interior; p is the wedge ; Fig. 903 is a section through the expanding pieces, showing the wedgeinserted; Fig. 904 the wedge driven home and the block of coal breaking away from the faceby the expansion of the pieces o ; Figs. 905 and 906 are end views, before and after driving inthe wedge. 2 D 2 404 COAL MINING. Fig, 907 is H
. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. utting head n, so that the coal is [removed in washers or ring. The breaking downapparatus is shown in Figs. 903 to 906; o are the expanding pieces, formed with taper grooves intheir interior; p is the wedge ; Fig. 903 is a section through the expanding pieces, showing the wedgeinserted; Fig. 904 the wedge driven home and the block of coal breaking away from the faceby the expansion of the pieces o ; Figs. 905 and 906 are end views, before and after driving inthe wedge. 2 D 2 404 COAL MINING. Fig, 907 is Hurd and-Simpsons apparatus for breaking down the block of coal cut out by theheading machine, and for removing the thin layers of coal left by the machine between the roof andfloor of the heading and the hole cut out. This apparatus consists of a cast-steel wedge or shovel X,which is forced forward by the screw Y; this screw is turned round by the lever Z and catch Zacting on the toothed wheel V, being in fact an adaptation of the ordinary ratchet brace. The catch iSfei^^^^feassMM^M^. is reversible, the end of the screw Y working in a socket which abuts against one of the cast-ironprops B; the adjustable stay C serving to increase the resistance to the screw Y. The wedgeshovel X is 14 in. wide, and is partly double wedged in cross section to prevent it slipping sidewayswhen the power is applied; the full length of the wedge is 24 in., with a taper of 6 in. and a screwtraverse of 20 in. ; all the working parts being made of steel. Fig. 908 is a longitudinal section of J. Grafton Jones hydraulic wedge for getting coal, andFig. 909 a cross section on the line E E ; T are tension bars which enclose the inclined steel
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectenginee, bookyear1879
