GB892621A - Improvements in or relating to gear box units - Google Patents

Abstract

892,621. Variable-speed gears; toothed gearing. CLARK, A. N. April 14, 1958 [April 12, 1957], No. 12037/57. Classes 80 (1) and 80 (2). [Also in Group XXII] Countershaft gearing for use with a portable high-speed tool such as an electric or air-operated drill comprises an output shaft 15 having a squared end 16 on which a double dog clutch member 17 is mounted and slidable to the right to clutch the output shaft directly to an input shaft 12, or to the left to clutch a loose wheel 20 to the shaft 15 so that shaft 15 is driven at the reduced ratio from a gear 13 on the input shaft, gears 25, 26 on a lay shaft and the wheel 20. Shaft 12 is internally screw-threaded for connection to the chuck driving spindle of a power drill, and the casing of the unit has a split aperture 40 which fits over the nose of the drill and is fixed in position by a clamping screw. A handle 51 is provided on the casing to enable the unit to be steadied when in position on the drill and to prevent rotation of the casing. The clutch is actuated by a crank-pin engaging a groove 30 in the member 17 and carried by a shaft 31 fast with an operating lever 33. A spring 37 is secured to the casing and cooperates with stops 35, 36 and flats 39 formed on a boss of the lever to limit its movement and retain it in its end positions. In a modification the gear unit consists of a simple countershaft reduction gear, the double dog clutch being replaced by a thrust bearing interposed between gear 13 and the wheel 20 which is fast with the output shaft.