GB713018A - Tool rotator for reciprocating hammer - Google Patents

Abstract

713,018. Ratchet gearing. SYNTRON CO. Oct. 15, 1951, No. 24003/51. Class 80 (3) [Also in Group XXIII] A reciprocating member, such as the tool holder 37 of an electromagnetic percussive drill, is rotated step-by-step as it reciprocates by a frictional ratchet device comprising two oppositely-acting annular pawl members 50, 51 of rubber or the like held within non-rotatable cups 44, 45 so as to be alternately compressed and released against the faces of a flange 41 on the tool holder, the compression flexing the levers 62, Fig. 5, of the pawl members and imparting a rotation to the tool holder. The cups 44, 45 are secured together to give the pawls an initial compression determined by one or more spacing washers which may be removed when the rubber has acquired a permanent deformation. The cups are connected by two tie rods (not shown) to a plate 32 supporting a rubber member 30 slidable in a sleeve 34 and forming the upper stop for a magnetic piston 6 which is reciprocated by alternately energized coils 3, 4. A spring 33 urges to its uppermost position the movable frame comprising the plate 32, the tie rods and the cups 44, 45. When the piston 6 strikes the holder 37 the pawl 51 is compressed and is released by its own resilience, thereby compressing the pawl 50. Similarly, as the piston strikes the stop 30 the impact on the frame compresses the lower pawl 51 which is again released by its own resilience. The pawl 51 thus constitutes the main driving member of the ratchet gear and is formed with a heavier flange than the oppositely-acting pawl 50, which is operated by the reactions of the pawl 51 and serves principally to prevent back-running or oscillation of the flange 41. In a modification, Fig. 9 (not shown), the movable frame is dispensed with and a single rubber pawl member acts between the casing and the upper side of a flange on the tool holder, the under side of the flange being urged upwards by a spring whose lower end engages a thrust bearing in an extension of the casing. The levers 62 of each pawl member may have metallic inserts, and there may be eight levers each tapering towards the centre of the annulus so as to be triangular in plan view. The drill is powered by an alternating current supply which passes from input terminal 28 through a switch 14 in the handle to the centre 23 of a metal disc rectifier. The end plates of the rectifier are connected respectively to the coils 3, 4 which are thus alternately energized, the common return 26 being taken through the switch 14 to the second input terminal 27. In a modification, the piston 6 is replaced by a hammer piston reciprocated by a crank driven by an electric motor. It is stated that each pawl member may comprise flexible metal spring elements extending from a ring and engaging a knurled or shallow-toothed surface to constitute a positive ratchet gear.