Patent GB-1009387-A (GB)
Title: Improvements in and relating to raise drilling methods and mechanism
IPC: E21B7/28
Filed: 1963-09-18
Abstract: 1,009,387. Boring earth, &c. JAMES S. ROBBINS & ASSOCIATES Inc. Sept. 18, 1963 [Sept. 19, 1962], No. 36776/63. Heading E1F. A raise RH extending between levels UL, LL is formed by fixing a drilling rig D in the level UL, drilling a pilot hole PH between the levels using a drill stem S and a cutter PC, substituting a larger cutter RC for the cutter PC at the level LL, and lifting and rotating the stem so that the cutter RC forms the raise. A U-shaped base member B is fixed in the level UL, and the rig, on a tractor C, is transported horizontally into position adjacent the base. The tractor carries portions of the hydraulic and electrical circuit associated with the rig, viz. an electric control panel 30, a motor 32 driving low and high pressure pumps 34, 36 and a reservoir 38. Valves 200, 266, (Fig. 11) are set to connect the pump 36 to supply the lower parts of cylinders 26 to pivot the rig about 78 into place on the base, fluid from the top of the cylinders being discharged to the reservoir through a valve 270 which is opened by the pump pressure. Pins 84, 86 are inserted to connect the rig to the base and the pins forming the pivot 78 are removed. The final angle of inclination of the rig to the level UL is obtained by installing and adjusting turnbuckles 88, 90 which connect base and rig. The valve 200 is set as shown and the valve 204 rotated to connect the lines 230, 234, and the lines 236, 232 so that the pump flows combine and pass through check valve 240 to extend cylinders 158, 160 which carry a gear reducer 122 having a rotatable drill stem connector pin 116, the flow from the top of the cylinders passing through the check valve 256 and combining with the flow from the pumps. When the gear reducer is in its uppermost position a length of drill stem S with cutter head PC is fitted to the pin 116, the cutter head being a rotary cone cutter or an air hammer drill. The pilot hole is drilled by rotating the pin and setting the valve 204. to connect the lines 23.0, 236 and the lines 234, 232, fluid from the pump 36 only passing through the check valve 246 to contract the cylinders 158, 160, the flow from the lower part of the cylinders discharging through valve 240 which is opened by the pressure in line 252 and the flow from the pump 34 being returned to the reservoir through valve 214 which is opened by the pressure in line 216. After the gear reducer has reached its lowest position it is raised and a further length is interposed in the stem, the process of drilling and adding lengths of stem then being repeated until the pilot hole breaks through into the level LL. Manual adjustment of the valve 242 may vary pressure difference across the pistons of the cylinders to compensate for increased length of drill string and give a constant bit pressure during drilling. At the level LL the cutter PC is replaced by the cutter RC which is rotated and forced upwardly by extension of the cylinders 158, 160. During this extension the fluid pressure in line 234 increases due to the cutting resistance and the pressure in the line 250 opens the valve 248 so that fluid is discharged from top of cylinders without back pressure to increase the force exerted by the cylinders. When the reducer reaches its uppermost position a length of the drill stem is removed and the reducer lowered preparatory to drilling a further section of the raise, the process of reciprocation of the reducer and removal of lengths of stem continuing until the raise is completed.