Patent GB-471152-A (GB)
Title: Improvements in or relating to variable speed friction transmission gearing
IPC: F16H15/38
Filed: 1936-02-26
Abstract: 471,152. Variable - speed friction gearing. HAYES, F. A. Feb. 26, 1936, No. 5759. [Class 80 (ii)] Variable-speed friction gearing with discs and rollers; and in which the speed is varied precessionally or otherwise by adjustment of the rollers, is combined with a toothed transmission train which takes the drive when the ratio of the friction gearing falls below that of the toothed train. This eliminates heavy curtailment of the fatigue life of the friction elements due to jolts when on the lowest speed. A one-way clutch 20, Fig. 1, allows the friction gearing to pick up the drive as its ratio rises above that of the toothed train. The friction variable-speed drive shown in Fig. 1 transmits from a shaft 8 through toric discs 4, 4a and rollers 9 with reversal of direction to a double disc 10 and through a drum 11 to a dog clutch 12 which must be engaged by a like clutch face 21a on a splined gear 19 in order that the variable friction drive may reach a tail shaft 22. When the gear 19 is in this position, it is being driven at a low speed through a countershaft 15 so that the one-way clutch 20 is or may be overrunning. To this end, when the gear 19 is moved left from the neutral position shown, it comes into mesh with an idle gear 18, Fig. 2, which is in line with and rigid with a gear 17 constantly meshing with a gear 16 fast on the countershaft 15. This idler arrangement is shown in Fig. 6. With the gear 19, Fig. 1, at left, therefore, as the speed ratio is reduced more and more, the one-way clutch 20 picks up the drive through the toothed train 13, 14, 16, 17, 18, 19 as the friction gearing passes to unloaded position. Since the friction gearing is not disconnected, so long as the main clutch of a vehicle is engaged, the clutch 20 does not allow freewheeling of the vehicle. When the gear 19 is moved right from the nodrive position of Fig. 1, it is driven in the opposite direction directly from the gear 16, and the one-way clutch 20 is locked out by a gear clutch 30, so that the vehicle is driven reversely and positively through the toothed gearing. An arrangement is described with reference to Fig. 5 (not shown) in which the toothed train is planetary. In an arrangement shown in Fig. 6, the one-way clutch 20 of Fig. 1, is replaced by an automatic shift. In forward drive, the gear 19 is at left so as to clutch the drum 11 to the tail shaft 22 and so as to engage the idler 18. As a vehicle starts up, the drive is through the toothed train 16, 17, 18, 19, 30, 22 from the countershaft 15. The friction-gear control is like that described in Specification 344,066 in which the engine pumps oil, and the higher the oil pressure, the higher the driven-shaft speed. The pressure builds up and the speed of the drum 11 tends to rise, and just before the friction gearing takes the whole load, the oil pressure, which also acts behind a piston 77, overcomes a spring 75 and thrusts the idlers 17, 18 to the left far enough to break the drive to the gear 19. As the vehicle slows down, the spring 75 asserts itself, and the teeth of the rotary gear 19 keep repelling the teeth of the idler 18 so that re-engagement of the toothed drive does not take place until the friction gearing has reduced speed to synchronism. A latch 79 may be provided to hold the idlers 17, 18 at left out of mesh. This may be tripped through a link 81 to allow engagement when the rollers 9 swing to extreme low gear position and strike a trip lever 75<1>. The latch 79 may alternatively be tripped by th e act of depressing the engine clutch pedal 80 to break the drive, which pedal acts through a spring 83, so that engagement of the toothed gears is not noisy. Specifications 254,341, [Class 80 (ii)], 343,988, 344,062, 382,321, 392,570, 392,586, and 392,589 also are referred to.