Patent GB-1445618-A (GB)
Title: Shiftable power transmission
IPC: F16H3/097
Filed: 1973-08-21
Abstract: 1445618 Change-speed gearing EATON CORP 21 Aug 1973 [28 Aug 1972] 39656/73 Heading F2D A variable-ratio transmission, especially for heavy vehicles, has means for by-passing at least a part of the transmission to effect a substantially continuous connection between input and output during a ratio shift. The transmissions described have a six-speed main unit followed by a two-speed range unit, sixth speed with low range providing the same overall ratio as first speed with high range, and the by-passing means is automatically engaged to provide positive drive between input and output at substantially that ratio during the double shift between sixth and first in the main unit and low and high in the range unit. In the embodiment shown diagrammatically, Fig. 2 is a sectional view in a plane substantially perpendicular to that of Fig. 1. Lowest ratio is established when a movable clutch member 72, Fig. 2, of the main unit couples a gear wheel 63 to a shaft 76 and a movable clutch member 58 of the range unit couples a gear wheel 56, Fig. 1, to the output shaft 61. Power flow is then from the input shaft 1 and gear wheel 2 to the wheel 63, thence through shaft 76, meshing wheels 77, 44 to a shaft 43, and through a wheel 45 fixed to the shaft 43 and meshing with wheels 41, 48 to shafts 51, 52 having wheels 53, 54 meshing with the wheel 56. Second ratio is established by declutching the wheel 63 from the shaft 76 and engaging a wheel 7, Fig. 1, with a shaft 32 by a clutch member 17. The shaft 43 is then driven by meshing wheels 33, 42. Release of wheel 7 from the shaft 32 and clutching of a wheel 6 with a shaft 31 engages third ratio through engaged clutch members 34, 39, wheels 41, 45, 48 and shafts 51, 52 &c. A wheel 38 meshing with an idler (not shown) in mesh with the wheel 42 enables reverse to be selected by engagement of the clutch member 34 with a member 36. Fourth, fifth and sixth ratios are established by engagement of clutch members 72, 17, 16 respectively with wheels 68, 22, 21 so that the input to the shafts 76, 32, 31 is via a wheel 3. Further upshifts necessitate a double shift involving disengagement of the clutch member 16, switching of clutch member 58 from 57 to 46, and re-engagement of clutch member 72 with 63 to establish drive at the same overall ratio. Thereafter higher ratios are established by engagement of clutch members 17, 16, 72 in the sequence previously described. Drive to the output shaft 61 is maintained during the double shift by automatic engagement, e.g. pneumatically, of a clutch 89. The gearing 2, 81, 93, 62 through which this drive is established has a slightly lower ratio than sixth ratio through the main and range units so that a slight overrun of the clutch member 91 relatively to the member 88 takes place both during engagement of the clutch 89 and as the drive is resumed through the main and range units after the double shift. This overrun is permitted by the shape of the teeth or dogs on the members 88, 91. Modifications are described in which the clutch 89 is mounted coaxially with the shaft 61, and in which the clutch 89 is a friction clutch. Also, it is stated that, in place of the friction clutches 10, 15, 67, eddy current or magnetic clutches or dog clutches with synchronizers may be used.