GB877646A - Toothed gears - Google Patents

Abstract

877,646. Toothed gearing. IMPERIAL CHEMICAL INDUSTRIES Ltd. Nov. 30, 1959 [Jan. 13, 1959 (4)], Nos. 1284/59, 1285/59, 1286/59 and 1287/59. Class 80 (1). Where at least one nylon gear is used in a toothed gear train, the nylon gear or a mating gear is arranged to take up back lash, caused by changes in ambient humidity and consequent changes in dimensions of the nylon gear, by forming it into parts 1, 2, Figs. 1-3, of the first Provisional Specification, one being attached to a shaft and the other being rotatable relatively thereto under the control of an arcuate element 3 accommodated in cut out portions of the gear parts and having a projection 6 engaging the part 1 and a projection 5 engaging the part 2 and being of a material dimensionally stable to change in humidity, for example, steel, if the gear is nylon, and vice versa. Thus as the two nylon wheels 1, 2 expand on moisture absorption, the arcuate element 3 causes relative rotation between the wheels 1, 2 thus reducing their combined tooth gap. In Figs. 1-4 of the second Provisional Specification, not shown, a control arm is journalled about a gear-shaft axis and accommodated in recesses between the gear parts and at its other end has a projection extending in both axial directions for engaging complementary inclined cross-slots in the gear parts, so that if the gear parts are of nylon and the arm of dimensionally stable material and vice versa, relative expansion and contraction causes relative rotation of the gear parts by the projection sliding in the slots to take up back-lash. The control arm may be accommodated outside the gear parts and a pair of control members may be used. Details of design considerations are given.