GB1306393A - - Google Patents

Abstract

1306393 Cams L P FLATLAND 14 Oct 1970 [17 Oct 1969] 48814/70 Heading F2K [Also in Divisions A5 and F1] A motor, such as a dental engine, comprises a shaft 83, Fig. 5, rotatable about the axis 72, Fig. 6, of a cylinder 71 but not axially displaceable, a piston 87 reciprocable along axis 72 but not rotatable thereabout, a cam surface 89 on the piston engaging a cam-follower 90 attached to shaft 83, means for admitting pressurized fluid from a source 78 into the cylinder adjacent one end thereof, a groove 97, Fig. 5, in the periphery of, or an axial bore in, the shaft 83 having ports 96, 98 for conducting fluid from one end of the piston to the other, and a valve wall 92 on piston 87 adapted to cover port 96 as shaft 83 rotates during at least part of a power stroke (right to left in Fig. 5) of piston 87 effected by the pressurized fluid, and to uncover port 96 during a return stroke of piston 87 effected by the action of cam-follower 90 on the piston. The shaft 83 may continue rotation during the piston return stroke owing to its own inertia, which may be augmented by a flywheel, or owing to the action of one or more additional piston/cam-follower assemblies, the movements of the pistons being out of phase. At or near the end of the piston power stroke pressurized fluid passes from a chamber 86 via port 96 to a chamber 101 to act on a further piston(s) or to pass directly to an exhaust port 107 via a bore in shaft 83. A needle valve 106 may be used to control the speed of shaft 83 from 0 to 10,000 r.p.m. A chuck 122 for mounting a tool 123 is attached to a shaft 119 driven by shaft 83 via a differential gear comprising bevel gears 126, 134 and a bush 131 carrying bevel gears 133. The differential gear normally rotates bodily but the bush may be held stationary by engagement with a movable pin 142 to reverse the drive of the tool. Alternatively, the tool may be rotated in a direction determined by the direction in which rotation is initiated, e.g. by hand, or, in an alternative embodiment, reversing is effected by reversing the flow of fluid through the engine.