GB1338605A - Gearing - Google Patents

Abstract

1338605 Variable-ratio gearing; toothed gearing DAVID BROWN GEAR INDUSTRIES Ltd 27 May 1971 [5 June 1970] 27423/70 Headings F2D and F2Q In a change-speed gear in which a multispeed gear is housed in a front portion of a casing 11 and is in series with an auxiliary range shift two-speed gear housed in the rear portion of the casing 11 with a separating wall 12 therebetween, the multi-speed gear comprises two or more symmetrically disposed countershafts 23 carrying identical sets of spur pinions 36, 37, 38 in constant mesh with pinions 29, 30, 31 freely journalled on a mainshaft 20 and selectively clutchable thereto by synchronized dog clutches 34, 35, the countershafts 23 being driven from an input shaft 15 via meshing gears 19, 26 the latter of which each is drivably connected to its respective layshaft 23 by a permanently engaged torque limiting multiplate friction coupling 27 loaded by a Belleville spring 28 such that the transmitted torque is normally passed through one or other layshaft 23 up to the maximum torque limitation of its coupling 27 and only when this maximum transmitted torque is exceeded does the relevant operative coupling 27 slip so that the excess torque is transmitted by the other layshaft. The mainshaft 20 drives via meshing gears 39, 47 two further countershafts 44 of the range shift two-speed gear, each countershaft having an oppositely handed helical gear 52, 53 respectively meshing correspondingly oppositely handed helical gears 50, 51 splined together and freely slidably jounalled on an output shaft 40 which may be selectively clutchable thereto or direct to the mainshaft 20 by a synchronized dog clutch 55, the relatively axially slidable helical gears 50, 51 ensuring balanced torque loading between the countershafts 44 of the two-speed gear. A reverse gear (Fig. 2) is arranged to be operated by a dog clutch 66 when the mainshaft dog clutches 34, 35 are in their neutral central positions.