GB944038A - Epicyclic power transmission mechanisms - Google Patents

Abstract

944,038. Variable-speed gear; disc brakes. A. C. WICKMAN. May 18, 1960 [Jan. 1, 1960], No. 36/60. Addition to 831,661. Headings F2D and F2E. Planetary change-speed gearing for motor cars &c. comprises a friction clutch-brake by which a sun gear can be held stationary or can be coupled with another rotary part of the gearing, the clutch-brake consisting of an axially slidable disc frictionally engageable at its periphery with a stationary brake part and a second axially slidable disc adapted to engage its rim with the first disc, spring means actuating one of the discs and hydraulic means actuating the other disc. In one form, a direct and reduced-ratio gear comprises an input shaft 1, Fig. 2, fast with a ring gear 12 meshing planet pinions 11 in turn meshing a reaction sun gear 3 rotatable relatively to a driven shaft 2 fast upon which is the carrier 10 of the planet pinions, a brake disc 4 splined upon the sun gear normally being biased by springs 9 to engage a frusto-conical friction surface at its periphery against a stationary housing 5, so that the sun-gear is held against rotation and a stepdown ratio is imparted to the driven shaft. By admitting liquid under pressure to a ring- shaped cylinder containing a ring piston 15, a clutch disc 14 splined upon the driven shaft 2 is slidden leftwards to engage a frusto-conical friction surface at its periphery within a correspondingly shaped surface in the brake disc 4, further leftwards movement of the clutch disc 14 acting against the bias of the springs 9 to disengage the brake disc 4 from the stationary casing 5. Accordingly the sun gear 3 is clutched to the output shaft 2, and the planetary gearing is locked-up for direct drive. Springs 18 bias the brake and clutch discs 4, 14 apart. To obtain neutral in the gearing, liquid under pressure is admitted to a ring-shaped cylinder containing a ring piston 20 and thus acts through a thrust bearing 21 to draw the brake disc 4 leftwards of Fig. 2 against the bias of its spring 9, the clutch-engaging servomotor 15 remaining de-energized. In a modification, an overdrive planetary gear comprising an input shaft 1, Fig. 4, fast upon which is a planet carrier supporting planet pinions 11 meshing with a driven ring gear 12 fast with an output shaft 2, and with a sun gear 3 rotatable on the input shaft, has springs 9 normally biasing a clutch disc 14 splined upon the driving shaft to engage its frusto-conical periphery with a corresponding surface on a brake disc 4 splined upon the sun gear 3, so that the planetary gearing is locked-up for direct drive. By admitting liquid under pressure to a ring-shaped cylinder containing a piston 25, the clutch disc 14 and the brake disc 4 are together slidden leftwards of Fig. 4 to engage a frusto-conical friction surface on the brake disc with the stationary casing 5 of the gear, further leftwards movement of the piston 25 sliding the clutch disc 14 out of engagement with the brake disc 4. Accordingly the sun gear 3 is now held stationary and a step-up ratio is obtained between the driving and driven shafts 1, 2. To obtain a neutral position when the shafts 1, 2 are disconnected, liquid under pressure is admitted to a ring-shaped cylinder containing a ring piston 29 simultaneously with admission of liquid under pressure to the servomotor 25, the piston 25 acting to withdraw the brake disc 4 rightwards away from the clutch disc 14 and out of engagement with the casing 5.