GB625112A - Improvements in expansible wheels for changes of speed, especially for bicycles and the like - Google Patents

Abstract

625,112. Expanding - wheel chain - gear. REMAND, F. May 30, 1946, Nos. 16469 and 16470. Convention dates, Jan. 5, 1939 and April 15, 1939. [Class 80 (ii)] Relates to an expanding driving sprocket on a pedal-cycle comprising toothed segments 1, moved radially on guide-arms 7, secured to the driving pedal-crank spindle 9, by pedalling in the appropriate direction whilst a cam-plate 11, normally rotating with the sprocket, is released therefrom and locked stationary so that pins 14, projecting from the segments 7, move along a continuous groove 12 in the cam-plate. The cam-groove 12 consists mainly of concentric circular portions joined by inclines 13 which latter lie on a radius so disposed that, when the cam-plate 11 is stationed for a change, the segment pins 14 pass successively through. the inclined parts 13 to reach the circular part of next smaller or larger radius whilst the segments are out of engagement with the chain 3. According to this invention the outermost groove of the cam-plate 11 is connected back' to the innermost groove by a return groove 12a so that the sprocket reverts directly back to its smallest diameter after reaching its largest without changing the direction of rotation of the pedals. Movement of the segment-pins 14 across the grooves 13 intersecting the return groove may be facilitated by making the pins 14 of elongated section or by providing projections in the adjacent parts of the grooves 13 for engagement with a groove in the end of the pins 14. The toothed segments 1 may, as shown, slide between paired guides 7 or may overhang from guides dovetailed in a single plate, and to prevent lateral distortion alternate ends of the segments may carry guide-bars 6a embracing the ends of adjacent segments. As shown in Fig. 2, the camplate 11 is caused to rotate with the sprocket by pins 17 on the plate embracing the guide-arms 7 of the sprocket. To make a change, the cam-plate 11 is slid axially to the left of Fig. 2 against the resistance of a return spring 15 so that the pins 17 leave the guide-arms 7 and a tooth 19 on the plate engages a fixed tooth 20 to lock the plate against rotation, whilst the pedals are turned in the appropriate direction to vary the diameter of the sprocket. In Fig. 10, not shown, the camplate 11 is locked to the sprocket by a spring- loaded pawl pivoted on its periphery and, for a change, rocked out of engagement with a notch in the sprocket and into engagement with a fixed locking projection by depressing a stationary lever into the path of the tail of the pawl. The chain 3 is tensioned by a spring-loaded jockey 4. The Specification as open to inspection under Sect. 91 shows also a form without the return cam-track. This subject-matter does not appear in the Specification as accepted.