GB157487A - Improvements in hammer drills - Google Patents

Abstract

157,487. Potter, H. S. July 3, 1919. Percussive drills.-In a hammer drill of the type comprising a hammer piston with helical devices co-operating with a rifled nut and ratchet mechanism to effect rotation of a toolholder, the piston having hammer portions on each end and being thus reversible, the hammer portions are identical, each being provided with a number of helical grooves, projections, or the like, and a number of straight grooves, projections, or the like. The piston 17 has two extensions 18, 19, either of which may be used as the hammer member; each extension has straight grooves or ribs for engagement with straight ribs or grooves in the chuck 24, and also has helical grooves or ribs for engagement with helical ribs or grooves in the ratchet wheel 39 of the twist mechanism. The chuck is rotatably held in the front head 4 by a pin 25 engaging an annular groove 27. The ratchet-wheel 39 is duplex so as to be reversible when one end is worn by engagement with the pawls; two sets of recesses for the pawls are formed in the cylinder. Bushes 49, 38 support the piston extensions, the rear bush 49 being formed to allow passage of motive fluid to act on the end of the rear extension. A further bush 77 extends into the rear cover to shut off an annular chamber which is divided by partitions into a lower lubricant chamber 71a and an upper fluid chamber 71, the latter having ports leading to the throttle valve 79 and distributing- valve chest 2. The throttle valve 79 has a cam 88 thereon adapted, simultaneously with the opening of the motive-fluid supply ports 82, 83, to depress a valve 86, Fig. 3, and so admit water from a supply pipe 106 through ports 103, 90, 91 to a central pipe 99 leading to the hollow drill 35. When in another position, the throttle valve admits motive fluid through ports 111, 110, the central tube and the hollow drill to the bore-hole. The tool may be provided with a handle and the motive-fluid supply-pipe connected directly to the valve chest. If desired, the central tube 99 may pass through a gland 114, Fig. 8, in the rear cover and be directly connected to a water-pipe 116. Specification 156,475 is referred to.