GB286587A - Improvements in and relating to earth boring drills - Google Patents

Abstract

286,587. Reed, C. E. March 5, 1927, [Convention date]. Borehole apparatus.-An earth-boring bit of the roller cutter type has the cutter mounted on a bushing attached to a spindle, the joint between the cutter and the bushing, or that between the bushing and the spindle, being of the bayonet type. In Figs. 1, 4 and 5, an integral head 1 has an inverted V-shaped recess 2 in which opposed roller cutters are supported. Each cutter has internal flanges 3b and gates 3c, Fig. 5, cooperating with wings 8w, 9w, Fig. 4. on a stepped or conical bushing 30 for mounting the cutter, and the bushing has internal flanges 31 and gates 32 co-operating with wings on the spindle 5y for mounting the bushing; a locking member 33a is then inserted to hold the spindle, bushing and cutter together while permitting rotation of the cutter. After assembly, the shank 6y of the spindle is inserted in a socket in the head 1 parallel with the axis of the latter, and is secured by wedges, or by caps with bayonet joints and cotter pins locking the caps, the head 1 then holding the locking member 33a in position. Separate locking pieces may be provided for the two joints. In a modification, the bushing is axially divided and provided with a wing or wings co-operating with a flange and a gate or gates in the cutter, the bushing-halves being inserted in turn into the cutter. In Figs. 9 and 10, the bushing is axially divided, each half having external wings 8w, 9w co-operating with gates as 3c, Fig. 5, whereby the halves may be inserted in the cutter in turn. The bushing also has interior flanges 31x, one half also having gates 32x, and the spindle is axially divided, each half having wings co-operating with the gates 32x whereby the halves of the spindle may be inserted in turn into the bushing. Locking members 31y are then inserted in the gates 32x to hold the parts together and the spindle shank is inserted in the drill head which then holds the locking members in place. If desired, the cutter may be merely slipped on the bushing, being then retained in position by the opposing cutter. Further, the divided spindle and shank may be employed with an integral bushing.