GB951287A - Drilling apparatus - Google Patents

Abstract

951,287. Boring earth &c. JERSEY PRODUCTION RESEARCH CO. April 25, 1962, No. 15761/62. Heading E1F. Apparatus for applying drilling pressure to a bit 12 comprises a hollow shaft 10, loading units 14, 16 rotatable and axially slidable on the shaft and having shoes 36, 66 engageable with the wall of the hole 18, and means 24 or 68 on at least one of the units to exert an axial thrust to the shaft and bit. The units have housings 20, 52 which are splined together to have a non-rotatable but axially slidable relationship. The shoes comprise metal elements 38 mounted in rubber 40 in the walls of pressure chambers 28, 60 in the housings, and the means 24, 68 comprise pistons 46, 78 on the shaft 10 moving within cylinders 42, 70 in the housings. Mounted in a chamber 110 in the housing 52 is a slide valve 118 controlling fluid supply to the chambers and cylinders. The apparatus is run into the hole on drill pipe after oil has been injected through the plugs 50 or 84 to fill the conduit 86, and the cylinders beneath the pistons. During drilling the pipe, shaft and bit are rotated, and drilling fluid is pumped down the pipe and shaft to the bit. A small amount of the fluid is by-passed through the ports 140 into the interior of the valve. In the position of the valve shown some of the by-passed fluid passes through a port 94, a conduit 92 and a port 98 into the chamber 60 to force the shoes 66 to engage the wall whilst the rest of the by-passed fluid passes from the conduit 92 through a port 96 into the cylinder 70 to force the piston 78, shaft and bit downwardly. During movement of the piston 78 oil from beneath the piston passes through the conduit 86 to the cylinder 42 beneath the piston 46 to reset the housing 20 by driving it downwardly, the shoes 36 remaining retracted. As drilling proceeds the shaft moves the valve downwardly until the valve fingers 130 are released from the shaft shoulder 134 by a projection 146 on a valve cage 114 so that the valve is moved upwardly by spring means 124 to engage the valve fingers 128 with the shaft shoulder 132. Movement of the valve diverts the by-passed fluid through a port 106, a conduit 100, and ports 102, 104 to engage the shoes 36 with the wall, and to apply downward pressure to the piston 46 and shaft, the oil from beneath the piston 46 passing through the conduit 86 to lower the housing 52 to reset it. As drilling progresses a projection 127 on the cage forces the fingers 128 from the projection 132, and the valve and other parts of the apparatus return to the positions shown. In a modification (Figs. 8-10, not shown) the oil is dispensed with, the housings being reset by some of the by-passed fluid which is directed to the cylinders by the valve. A star-shaped projection immediately above the bit facilitates the drilling of straight holes. In a further modification the piston and cylinder are eliminated from the upper unit, the upper shoes preventing rotation of the housings whilst the lower housing is reset. In yet another modification (Figs. 11, 12, not shown) the upper and lower units are operative to exert a force on the bit at all times except for brief resetting times, two valves being provided to reset the units at different times.