GB842435A - A drawworks for well drilling - Google Patents

Abstract

842,435. Boring earth; cutting pressure control. CALIFORNIA RESEARCH CORPORATION Oct. 14, 1958 [Oct. 24, 1957], No. 32810/58. Class 85. [Also in Group XXIV] A rotary well drilling draw-works tor use in an off-shore drilling rig has means to maintain constant pressure of the drill bit on the well bottom regardless of movement of the drilling, barge with the surface of the water. The apparatus comprises a power unit 10 driving through a clutch 12 a sprocket assembly 18 which is free to rotate on the shaft 20 of a variable ratio gear box 22 which also includes a fluid coupling which can be set to provide a given torque output for a constant engine speed. The sprocket assembly 18 can be coupled to the shaft by a clutch 24. The shaft 26 drives a sprocket 30, which can be coupled to the sand line drum 32 by a clutch 34, and also drives a sprocket 38 which can be coupled to the casing line drum 60 by a clutch 84. The sprocket assembly 18 also drives a catshaft 54. The casing line drum is free to rotate on the shaft 66 and carries a second shaft 40 coaxial with the first. Free to rotate on the shaft 40 is the sprocket wheel 38 which carries a clutch member 76 with splines 78 which drive friction discs 80 and 82. The hub 86 of the clutch is keyed to the shaft 40 and has splines 90 which drive plates 92 and 94. The portion 96 of the clutch has a chamber 98 one wall of which is formed by a diaphragm 100. Pressurized air can be admitted to the chamber through duct 101 to flex the diaphragm and force the friction components 80, 82, 92 and 94 against the flange 88. At the opposite end of the casing line drum is a main brake assembly 104, secured to the shaft 66, which can be coupled to the drum by a clutch of similar construction to that already described and operated by air admitted through the duct 131. A brake band 140 is applied to the brake drum by a manually operated lever which also actuates the clutch air valve so that the clutch is engaged as the lever is displaced. Similarly the clutch is disengaged as the brake is released. An over-riding control permits the clutch to be permanently engaged regardless of the position of the brake lever. If the air supply should fail an emergency brake band 158 is applied by a spring to a brake drum 156 which is secured to the casing line drum. The emergency brake can also be operated manually. In operation the drive is set to rotate the casing line drum in a direction to wind in the casing line at a tension determined by the setting of the fluid coupling and hence support the bit with a predetermined weight on the bottom. If the drilling barge lifts with the water, the fluid coupling is over-loaded and the line is paid off the drum at the pre-selected tension, whereas if the barge drops the drum is driven to wind in the line until the tension is correct.