Patent GB-1265223-A (GB)
IPC: F16H47/04
Filed: 1969-10-20
Abstract: 1,265,223. Change-speed gear. URS SYSTEMS CORP. 20 Oct., 1969 [21 Oct., 1968], No. 51295/69. Heading F2D. A torque-splitting five-element planet gear for a motor-vehicle, bulldozer &c., has two reaction elements, e.g. suns 22, 24, drivably connected through a steplessly variable hydrostatic gear 32, 35, or electric or mechanical friction gear; a single input element, e.g. planet carrier 13, on an input shaft 11; and two output elements, e.g. rings 21, 23, selectively clutchable to a main output shaft 50 through different ratio gear-pairs 40, 44; 41, 45 and 42, 46; 43, 47 respectively introduced by dog clutches 51 ... 54, which are engaged, synchronously and sequentially, alternatively with cycling of the stepless gear 32, 35 through its full range in both directions, to produce a wide continuous range of stepless ratios at the final output 50. The planet carrier 13 carries intermeshed planets 17, 18 meshing the respective suns and rings. Other combinations of connections of the five elements are specified, and one embodiment, Figs. 10A and 10B, not shown, has an additional torque-splitting three-element train to reduce the power peaks in the stepless gear, whilst another, Fig. 14, not shown, has an inputconnected stepless gear which may take all the starting torque. Timed cams (75 &c.), Fig. 1A, not shown, on a common manually or automatically turned shaft, effect the sequential control of the clutches 55 &c. through snap-action togglevalves (81 &c.) and double-acting fluid servos 71 &c., and of the hydrostatic gear 32, 35 through a follow-up servo, Fig. 7, not shown, actuating the linked swash-plates of the gear. The automatic control may operate in response to input and output speed, pressure in the hydraulic system, vehicle acceleration or wheel slip. Fig. 1 shows the setting giving lowest output speed, the first ring 21 driving the output 50 through the gear-pair 40, 41 and clutch 51, whilst the second ring 23 spins freely. The sun 24 is held by the hydrostatic unit 35, which is at full stroke, whilst the zeroized unit 32 frees the sun 22. With an input speed of 2000 r.p.m., taking the hydrostatic gear through a full single cycle to the dotted position causes the first ring 21 to accelerate the output 50 from 800 to 1600 r.p.m., at which time the second ring 23 has decelerated to synchronism and is clutched to the output through the gear-pair 42, 46 and clutch 53, the clutch 51 being released. A complete reverse cycle of the hydrostatic gear back to Fig. 1 setting now causes the second ring 23 to accelerate the output 50 from 1600 to 2400 r.p.m. whilst the first ring 21 decelerates to synchronism. The cycle is then repeated for each of the gear pairs 41, 45 and 43, 47, resulting in a final output speed of 7200 r.p.m. Fig. 8, not shown, modifies the above arrangement to provide a decreasing range of output speeds down to zero, for clutchless starting, and a small (or equal) reverse range. In both ranges the sun 22 is clutched alone to the output 50 through a gear pair 30 (154) for the decreasing forward range, and through a similar train (157) but including an idler (159) for the reverse range. Sequential operation by timed cams on a common shaft provides for reverse, through zero, to full forward speed in one continuous movement of the cam-shaft. In these lower stages the hydrostatic units are operated independently by separate cams and servos to provide full stroke of both units at starting. In Figs. 10A and 10B, not shown, an additional three-element planet train (204) is arranged between the two main reaction suns (222, 224), and clutches (209, 257, 262, 267, 270) connect the hydrostatic units (232, 235) selectively to the reaction suns through gear trains and the additional planet train (204), which acts as a further torque-splitter and serves to reduce the power peaks in the hydrostatic gear, but to increase their number, in its various modes of action. Fig. 14, not shown, differs from the above in that the hydrostatic gear (432, 435) connects the main input (411) to the two reactions suns (422, 424) of the planet gear through selector clutches (503, 520) and gear-pairs (431, 521). In this case the hydrostatic units may be clutched alone directly between input and output (450) for starting. The hydrostatic unit (432) is not variable, only the unit (435) being varied.  The Specification includes curves showing speeds and torques of the various elements as well as the power transmitted by and pressure in the hydrostatic system.