GB1206460A - A percussive drill - Google Patents

Abstract

1,206,460. Percussion tools. Z. MORISHITA, and S. KAWATA. 12 Dec., 1967, No. 56504/67. Heading B4C. [Also in Divisions B3 and F2] A cam operated drop and spring type percursive tool comprises a hammer piston 8 with a laterally extending roller 29 which coacts with a cam 24 rotated via shaft 23 by a primemover, e.g. an electric, oil pressure or compressed air motor. The slot 26 through which the roller protrudes may be parallel or inclined with respect to the axis of the piston. The piston is mounted in a tubular housing 1 to which an oil tank 2 and a tool bit holder 15 are connected. In operation, vibration in the tool causes valve member 4 which is biased by a compression spring into aperture 3 to be displaced to permit oil to pass into the housing. Steel balls 11 carried by the piston are lubricated by the oil. The oil also lubricates the shank of the tool bit 13, and forms a film between washers 14 to assist in absorbing the force of the piston. Relative rotation between the housing and the holder and oil tank is prevented by springs 20. The shaft 36 of the motor has a tapered end which is in frictional engagement with a coupling plate 37. The plate 37 has pins received in rubber bushes in holes in coupling plate 38. The lower end of the cam shaft is supported by a steel ball 34 contacting a convex piece of stone. In an alternative embodiment (Fig. 8), the lower end of the cam-shaft 23 has a gearwheel 49 which engages with an annular gear 48 connected to the tool bit holder 43, 46 which is adapted to rotate relative to the housing. The tool bit has a hexagonal portion received in a corresponding aperture in the holder. The tool bit includes a detachable tip 50 frictionally engaged in a tapered recess. The tip can be released by inserting a tool through an aperture 51, and additionally or alternatively by aid of nut 52. The motor may be connected to the cam-shaft by a flexible shaft.