GB759418A - Improvements in or relating to a cable tool drill for drilling earth formations - Google Patents

Abstract

759,418. Earth-boring apparatus. RUSTON-BUCYRUS, Ltd.. May 21, 1954, No. 15047/54. Class 85 In a cable-tool drill the means, a motor 36, to cause, as drilling proceeds, unspooling of a bit-supporting cable 25 from a winch 27 is actuated under control of means, a valve 83, responsive to any abnormally high back pressure being set up in the fluid-actuated means, a piston-cylinder motor 53, that causes deflection of the cable 25, the back pressure being due to the bit 26 continuing to fall after the fluidactuated means is reversed to deflect the cable to raise the bit. The bit 26 is allowed to fall freely from a position to which it is raised by a pulley 28 mounted on a piston rod 64 of the single-acting, hydraulically-actuated motor 53 to which hydraulic fluid is supplied and exhausted through a two-way valve 81. On an abnormally high back pressure being set up in the motor 53, the valve 83, connected in the same pipe line 82, 69 to the motor 53 as the valve 81, opens and pressurized hydraulic fluid passes from the pipe line 82, 69 through said valve to actuate the winch motor 36 to cause unspooling of the cable 25 until the drilling conditions are restored to normal with no high back pressure being set up so that the valve 83 may close. The means controlling the setting of the valve 81 forms the subject matter of Specification 759,467, which'is referred to.