Patent GB-407548-A (GB)
Title: Improvements in or relating to change speed gearing
IPC: B62M9/1246
Filed: 1933-04-21
Abstract: 407,548. Variable speed gearing. NOVITAS FABRIK ELEKTRISCHER APPARATE AKT.-GES., 3, Zellerstrasse, Zurich, Switzerland. April 21, 1933, No. 11660. Convention date, April 21, 1932. [Classes 80 (ii) and 80 (iii).] In variable-speed chain gearing for cycles, of the kind in which a chain is deflected laterally from one to another of a set of differentsized sprockets 2, 3, 4 on the rear hub, by axial movement of a spring-loaded shaft 9 carrying a guide-sprocket 12, this axial movement is effected by turning a cam-sleeve 17 through a Bowden-wire 19, the sleeve 17 having a frontal cam face bearing on a similar face on a second sleeve 16 connected by a screw 15 with the guide-sprocket shaft 9. The cam-sleeve 17 is rotatable on a fixed sleeve 8 secured to a bracket 7 adjustably mounted on a fixed clip 6, and the guidesprocket shaft 9 is slidably urged within the sleeve 8 by a tensionspring 13. The screw 15 passes through an axial slot 8<1> in the sleeve 8. A cover-sleeve 18 and end-nut 21 are attached to the cam-sleeve 17. Rotatable on the shaft 9 is an arm 10 carrying a tension-sprocket 11 loaded by a spring 22. The arm 10 at its upper end carries a spring-loaded detent 23 which, by engaging stops 25<1>, 25<11>, 25<111> on an adjustably-fixed plate 25, ensures the correct chain-tension and also allows for play of the chain during transfer. By preventing forward movement of the arm 10, the stops permit the use of the gear on cycles with back-pedal brakes. On changing from the sprocket 2 to the sprocket 3, the detent 23 first moves from the face 25<1>, Fig. 10, of the plate 25, to the position 41 which is slightly forward of the next face 25<11>, such excess axial movement being effected by moving the Bowden control-lever, Fig. 3, from the position a beyond the final position b to a further position b<1>. The sprocket 3 being larger than the sprocket 2, the tensionarm 10 yields and allows the detent to move to an intermediate position in which the chain lies inclined over the tops of the teeth of the sprocket 3. When the chain drops into complete engagement the detent returns to the position 43 whereupon the control-lever is released by the operator and assumes the final position b, the detent 23 moving inwardly against the face 25". During upward changes, i.e. to smaller sprockets, the necessary play of the chain during transfer is permitted by the widened bases of the notches of the plate 25, and the forward face of the detent 23 is bevelled to allow it to pass under the steps of the plate in the downward direction. In the modification shown in Fig. 8, the steps 55<1> &c. of the plate 55 are plain and there is no overthrow of the control-lever. The play of the chain during transfer is permitted by providing the tensionarm 51 with an open slot 51<1> embracing the shaft 9 which is normally held against the bottom of the slot by a blade-spring 54. During a change the blade-spring yields and allows the entire tension-arm 51 to rock about the detent 52, such rocking movement being prevented in the highest speed by engagement of an angle piece 56 with the fixed bracket 7. The side of the detent 52 is bevelled to allow it to pass under the plate 55 during upward changes. The cable-engaging end-nut 21 is retained against loss by a fixed plate 20 which also guards against the device being used as a step. Bowden mechanism.-The control-lever shown in Figs. 3 and 4 comprises a lever integral with a plate 29 rotatable in a fixed base-plate 26 against which it is pressed by a coil-spring surrounding a central screw 34. The Bowdenwire 19 passes around a channel formed by an upstanding flange and an attached ring 30, the cable being secured to the plate by a nut 32. Within the flange is an annular space for the end of the cable. The lever is retained in the operative position by a pin 28 which engages slots 27 in the base-plate 26 to allow the overthrow, above-referred to, of the lever. Retaining tension-sprockets on shafts.-The spindle of the tension-sprocket 11, Fig. 9, is ball-faced to allow a limited tilting movement of the inner race of the sprocket thereon. The Specification as open to inspection under Sect. 91, shows also, in Fig. 7 (Cancelled) and not shown, a modification in which the double cam sleeves 16, 17 are replaced by a single sleeve having a helical slot engaged by a pin carried by the sprocket shaft 9 and passing through an axial slot in the fixed sleeve 8. This subject-matter does not appear in the Specification as accepted.