GB1473938A - Earth boring bits - Google Patents

Abstract

1473938 Boring earth &c DRESSER INDUSTRIES INC 28 Aug 1974 [12 Sept 1973] 37569/74 Heading E1F In an earth boring bit 30 of the type having a rotatable cutter 34 mounted on a bearing pin 32 by bearing means including ball bearings 36, substantially the entire out-thrust load on the cutter 34 (i.e. the load parallel to the axis 39 of cutter rotation) is transmitted to the bearing pin 32 through the ball bearings 36. As described the bit 30 includes an arm 31, the lower end of which forms the bearing pin 32, and the cutter is a rotary cone cutter 34 having inserts 38. The bearing pin 32 and cutter 34 are formed with ball bearing raceways 40, 41 respectively, and both bearing surfaces of the raceways 40, 41 extend a substantial distance to either side of axes 42 which pass through the centres of the ball bearings 36 and are parallel to the axis 39 of cutter rotation so that the out-thrust load on cutter 34 is transmitted to the bearing pin 32 through the ball bearings 36. Preferably the raceways 40, 41 extend at least 5‹ on either side of the axes 42. The bit also includes roller bearings 35 and a friction bearing 37, the radial load on the cutter 34 being transmitted to the bearing pin 32 through the bearings 35, 36, 37. A gap is left between the end face 45 of bearing pin 32 and the inner end face 44 of cutter 34.