Patent GB-191409766-A (GB)
Title: Improvements in and relating to Rock-cutting Mechanism for Tunneling & Shaft Sinking.
IPC: E21D9/10
Filed: 1914-04-20
Granted: 1915-04-20
Abstract: 9766. Marks, E. C. R., [Imperial Tunneling Machine Co.]. April 20. Percussive channelling-drills. - In rock-cutting mechanism for tunnelling and shaft sinking comprising a number of sets of reciprocating cutters mounted in a head revoluble about an axis transverse to the direction of advance of the mechanism, the reciprocation of each set being automatically suspended during its motion through substantially a semicircular zone, all the cutters are operated independently in the manner shown in Figs. 6 and 7. High-pressure fluid passes through a port 22 into the valvechest 167, passing thence mainly through a throttle-valve bushing 180 and ports into the hollow small end of a differential distributing- valve 50 and partly through a port 3, adjustable by a needle valve, to a chamber 175 to act on the large end of the valve 50. With the valve 50 in the position shown, low-pressure air passes from a chamber 9<d> through a passage 237 and past a check valve 239 to move the cutter piston 140 rearward while the exhaust passes through ports 6, a space 174 around the valve 50, passages 6<e>, the cutter guide 142, and a passage 6<g> in the cutter-bit holder 145 to blow away the cuttings. When the piston 140 engages a tappet valve 213. the fluid in the chamber 175 is exhausted through ports 3<d>, 3<i>, 189, and the valve 50 moves to the left, closing the exhaust and admitting fluid through ports 1 to move the cutter piston forward. The throttle valve 182 is connected to a piston 183, opposite sides of which communicate through a circumferential leak or a bleed port, the movement of the piston being limited by an adjustable screw 250. Fluid normally passes to each side of the piston 183 from the cylinder 141 through a port 4<w> and past a check valve 247. When the cutter encounters soft rock, the piston 140 takes a longer stroke and, passing ports 237, 4<w>, cushions fluid which passes the check valve, 247 and moves the piston 183 to the right, thus partly closing the throttle valve and reducing the amount of air admitted in the next working stroke. The lower passage in the throttle-valve bushing has a reduced end portion 241, Fig. 22, terminating in a substantially circular portion 242 which is always clear of the valve. The exhaust passage 189 of the valve chest chamber 175 terminates in a tapered plug cock on which a spring-pressed vertically-hanging weighted casing 191 is arranged so as to close the exhaust passage 189 during the half-revolution of the head 113 in which the corresponding cutters are away from the rock face, thus holding the said cutters stationary and at the inner ends of their stroke. During this period, however, any cutter may be reciprocated by manipulating a hand-valve 205 in the exhaust duct 3d leading from the valve chest chamber 175 so as to close the duct and open it to atmosphere alternately. The cutter-bits 143 are preferably triangular prisms, the edges of which may be used in turn, and are fixed by wedges 147. Any cutter-bit holder 145 may be removed from its piston-rod 144 by inserting a bar through an opening 155 and then causing a rearward movement of the piston 140.