GB740692A - Improvements in or relating to automatic change speed gears - Google Patents

Abstract

740,692. Change speed gearing; friction clutches. SELF-CHANGING GEARS, Ltd. Aug. 12, 1953 [May 28, 1952], No. 13555/52. Class 80(2) An automatic change - speed gear for motor vehicles comprises a speed and torque responsive clutch-and-link device in which clutch shoes act as drive transmitting links for a relatively low speed ratio and are engaged with a complementary clutch element for a comparatively high ratio, one-way means being provided to allow the high ratio to be engaged. In one form, a shaft 1, Fig. 3, drives a clutch drum 2 and annulus 3 engaged by friction shoes 9, biased radially outwardly both by springs and by centrifugal force, and by planet gears 5 on a carrier 6, the planets also meshing a sun gear 4 held from reverse rotation by a one-way detent 7. The shoes 9 are mounted on a driving plate 8 of the carrier connected to a driven plate 10 on a driven shaft 11. The connection between the parts 8 ... 10 is such that increase torque transmitted to the driven shaft tends to cause the clutch shoes 9 to slip relatively to the drum 2 and be drawn out of engagement therewith, to give a reduced drive through the planets 5 and carrier 6, the one-way detent 7 holding the sun gear 4 stationary to act as the reaction member. On increasing speed and/or reducing the torque transmitted, the clutch shoes 9 are engaged with the drum 2 for direct drive. The single train thus described may be combined with additional similar trains in series to give more than two speeds, the four speed gear of Fig 5 having clutch shoes 9a, 9b, 9c of three trains engageable with the drum 2, the driven plate 10a of the first train forming the internally toothed annulus 3b of the second train and the driven plate 10b of the second train forming the internally toothed annulus 3c of the third train. In a preferred embodiment of this type of gear, the flywheel 20, Fig. 6 of an engine drives the drum 2 through a centrifugal clutch 21, or according to the Provisional Specification, through a fluid coupling. The sun gears 4a, 4b, 4c are mounted by one-way detents 7 on a sleeve 24 fast with the fixed outer casing 25. The connections between each of the sets of shoes 9 and its driving and driven plates 8, 10 are similar, that between the shoes 9b and plates 8b, 10b being shown in Fig. 7. The driving plate 8b is provided with sloped slots 28 receiving rollers 29 on pins joining the inwardly and radially directed arms of the U forming each shoe 9b. The driven plate 10b has radial slots 31 receiving driving blocks 32 fast on the clutch shoes. As shown, springs 33 urge the shoes into engagement with the drum 2, but the springs may be omitted or be replaced by hydraulic or electromagnetic means or by springs urging the shoes to the disengaged position. The pin and slot connection 28, 29 between the clutch shoes and the driving plate 8b are such that transmission of torque through these parts urges the clutch shoes radially inwards, against the force of the springs 33 and the centrifugal force acting on the shoes 9, to give a low speed transmission through the train. When the shoes 9b engage the drum 2, for direct drive therefrom at a comparatively light load, torque does not pass through the pin and slot connections 28, 29 but through the driving blocks 32 and slots 31 to the driven plate 10b. There is therefore no tendency for torque to disengage the clutch shoes from the drum in this condition. If the driven load increases sufficiently, the shoes 9b slip relatively to the drum 2 and some torque accordingly passes from the driving plate 8b through the pin and slot connection 28, 29 to the shoes 9b blocks 32, slots 31 and the driven plate 10b. The shoes are accordingly drawn out of engagement from the drum. When the shoes are thus disengaged, they act merely as torque transmitting links. With the 'three trains in series shown in Fig. 6, first speed is obtained with all three sets of shoes 9a, 9b, 9c disengaged from the drum 2, second is obtained with the shoes 9a engaging the drum, third with shoes 9a, 9b engaged and direct drive with all the shoes engaged. Alternatively, the clutch shoes may be arranged as described in Specification 679,473. The driven plate 10c of the third train drives a sleeve 11 connected through a planetary forward-or-reverse gear to a final driven shaft 40. The end of the sleeve 11 is formed as a sun gear 41 meshing planet gears 42 in a carrier 44 held stationary by a brake band 46 to drive reversely an annulus 43 rigid with a drum 39 fast on the driven shaft 40. The drum 39 forms one element of a hydraulically operated clutch 38 engaged, when the brake band 46 is disengaged, to couple the sleeve 11 direct to shaft 40. In a modified form of planetary two-speed gearing, Figs. 2, 9, 10 (not shown), the planet carrier is connected for rotation with the driving shaft, the sun gear is fixed and a freewheel is located between the planet carrier and the driving plate of the torque-responsive clutch disengaging means. In further modifications of planetary gearing, Figs. 1, 8 (not shown), the sun gear 4 of Fig. 3 is fixed and a freewheel is located between the planet carrier and driving plate 8. In a form of countershaft gearing, the driving shaft 1, Fig. 4, carries a gear 14 driving, through a countershaft 16, a gear 15 integral with a drum 2 engaged by friction shoes 9 carried on driving and driven plates 8, 10 with a torque responsive connection therebetween. The driven plate 10 is fast on the driven shaft 11 and the driving plate 8 is connected to driving shaft through a freewheel 7. An overdrive speed is obtained through the gear train when the clutch 9, 2 is engaged, the freewheel 7 overrunning, and direct drive is obtained through the freewheel with the clutch disengaged. Specification 679,523 also is referred to.