Patent GB-191226452-A (GB)
Title: Improvements in Drills and Drill Holders.
Inventor: SCOTT JOHN
IPC: E21B17/04
Filed: 1912-11-18
Granted: 1914-01-19
Abstract: 26,452. Scott, J. Nov. 18. Percussive drills.-A detachable bit for a percussive rock-drill, or a drill for a percussive drilling machine are respectively secured in their socket and chuck by providing on the holder a radially-acting cam, curved wedgeshaped recess, or eccentric surface against which the bit or jaws in which the drill is carried are secured by rotating either part, means being provided for positively preventing longitudinal movement between the parts. In the form shown in Figs. 1, 3, and 4, the bit 4, which may have grooves 8, 9 communicating with a hole 2 in the socket for conveying water to the cutting- point, has a tang 6 provided with two eccentric projections 10, 11 engaging similar recesses 14, 15 in the socket against the end of which the shoulder 7<a> on the bit rests. The socket has longitudinal grooves 16, 17 to engage lugs 12, 13 on the end of the tang, the grooves terminating in an enlarged recess 18 having a shoulder 18<a> against which the lugs rest when in operative position to prevent displacement of the bit due to an axial force such as that arising from the sticking of the bit in a hole. In a modification, the tang and the socket may taper rearwards and be provided with either one or two eccentric surfaces, the portion of the tang between the lugs and shoulder being longer than the bore 7 in the socket so that a further tightening of the bit is effected when it strikes the rock. In a further form, the socket may be forwardly tapered with a bore shaped as shown in Fig. 15 and the tang of the bit provided with flattened sides 20, 21 and eccentric projections 10, 11, Fig. 17, or with concentric ends as shown in Fig. 19, longitudinal displacement being prevented by the taper of the bore. In a further modification, a parallel tang, Fig. 22, may have a conical end 26, the opposite sides of which are flattened as at 27 so that it may pass into the socket and, on being rotated, pass beneath the lugs 24, 25 in the socket, Fig. 21. In securing drills in their chucks as shown in Figs. 24 and 25, in which an axial bore for water is provided. the drill is clamped in a two-part bush 31 having eccentric projections engaging similar recesses in the chuck body 30. Longitudinal displacement may be prevented by the use of lugs as previously described or by pins 39 engaging grooves in the bush sections. The flanged ends 37, 38 of the bush are flattened at the sides as also is the body 30, so as to facilitate relative rotation for fixing purposes. In the form shown in Figs. 27 and 28, the bush portions 51, 52 are provided with projections 53, 54 which pass through grooves 55, 56 into a ring 47 in an enlarged part 44 of the chuck body. The ring is rotated bv striking the part 48 with a hammer. Instead of having an enlarged part on the chuck body, the ring may be mounted at the end thereof and the ends of the bush jaws flanged. The slot in the ring may be square to engage a squared part on the bush and the inner ends of the jaws may have lugs to prevent axial motion similar to the forms previously described. In a further modification, a final tightening is effected by providing part of the eccentric recess on a flanged cylindrical piece 73, Fig. 31, rotatably mounted in the counterbored front end of the chuck, which is kept in position by square flanged heads on the bush jaws. In a further form, Fig. 33, the initial clamping is effected by forcing the drill against a projection 86 on the end of the bush jaw 85, the upper jaw being retained in position by a flange 92 engaging an annular recess 94 in the chuck body or being fixed by a pin 95. In a further form, the chuck body, which is formed with eccentric recesses to engage the eccentric projections on a pair of flanged bush jaws as in the other forms, is split longitudinally the parts being drawn together by a bolt to give the final clamping operation.