Patent GB-885942-A (GB)
Title: A self-shifting change speed gear
IPC: F16H61/02
Filed: 1959-02-02
Abstract: 885,942. Variable-speed epicyclic gear; positive clutches. ZAPLETAL, F. K. Feb. 2,1959 [Feb. 24, 1958], No. 3594/59. Class 80 (2). A three-element epicyclic gear is shifted automatically by the action of torque-responsive spring-loaded claw clutches to provide three ratios. In an embodiment incorporated in a three-speed bicycle hub (Fig. 1), a driving sprocket 25 is connected in known manner by a freewheel 24 to an input member 23 in permanent driving dog 23<SP>1</SP> connection with an axially movable shifting member 16. The member 16 is axially loaded by a prestressed spring 19 and carries a set of integral torqueresponsive dog teeth 18a and a roller freewheel 27 whose outer member 28 is formed with interlock teeth 29. The teeth 18a can engage corresponding teeth 18a<SP>1</SP> on a planet carrier 6, 7 of an epicyclic train having a sunwheel 2 rigid with a fixed axle 1, planets 10 and a ring gear 11 to which is secured a sleeve 14 having at one end teeth 29<SP>1</SP> to correspond with the teeth 29 on the freewheel. The other end of the sleeve 14 is formed with torque-responsive teeth 18b<SP>1</SP> engageable with complementary teeth 18b rigid with the hub shell 34. A set of interlock teeth 32, engaged with corresponding teeth 32<SP>1</SP> on the hub shell, is formed on the outer member of a roller freewheel 27<SP>1</SP> mounted on the planet carrier element 7. The teeth 18a and 18b are arranged to have differing release angles α and # such that the teeth 18a release at a lower torque than teeth 18b. The interlock teeth 29, 32 are arranged such that when the teeth 18a, 18b release they are held out of engagement as long as the torque does not fall below the release value set by the combination of tooth angle and loading of spring 19. For high-speed torque is transmitted through the input member 23, shifting member 16 and teeth 18a to the planet carrier 6, 7 which drives the ring gear 11 connected by teeth 18b to the hub shell 34, the freewheels 27, 27<SP>1</SP> over-running. At a first predetermined torque the teeth 18a disengage against the spring 19 and drive is transmitted through the freewheel 27, interlock teeth 29, sleeve 14 and teeth 18b to the hub shell. At a second higher torque, the teeth 18b disengage to move the epicyclic gear axially against spring 19 and the drive from the sleeve 14 passes through the ring gear 11, planets 10 to planet carrier 6, 7 and thence by freewheel 27<SP>1</SP> and interlock teeth 32 to the hub shell. On decreasing torques or back-pedalling, corresponding upward changes take place. In a second embodiment, Fig. 3, for use in a motor vehicle provision is made by a dog clutch 44, 44b, 47<SP>1</SP>, for forward, neutral and reverse drive, a brake 48 being applied to the sun-wheel 2, when the clutch 44b connects the driving- shaft 43 to the intermediate shaft 46 carrying the input member 23; and a brake 49 being applied to the planet carrier 6, 7 when the sunwheel 2 is driven through the clutch 47<SP>1</SP>. When in reverse the torque responsive teeth 18b, 18b<SP>1</SP> of ring-gear 11 are held engaged by a stop 88 axially moved by a lever 86. To allow continuation of torque during over-run conditions the interlock teeth are bevelled on each face and are supplemented by cone friction clutches 28<SP>1</SP>, 31<SP>1</SP>. The ratio shift is also made output-speed responsive by loading the spring 19 by fluid pressure acting on a piston 57, the pressure being generated by a gear pump 58 driven by output shaft 56. The pressure fluid is delivered to the rear of piston 57 and to an adjustable by-pass valve 84 under the control of the driver.