Improvements in the means controlling the tensioning of the chain in bicycle and thelike chain shifting change speed gears

摘要

684,211. Chain-shift change-speed gearing. JUY, L. C. H. Feb. 7, 1951 [July 11, 1950], No. 3023/51. Class 80 (ii). In chain shift change-speed gearing of the type in which a driving chain 6, Fig. 1, is alternatively engaged with either of two sprockets 7, 8 by the usual transverse reciprocating means, a pivotable spring urged arm 2 carries a first guide sprocket and a spring urged pivotable tensioning arm 5 on which is mounted a further guide sprocket, the spring means acting upon the tensioning arm 5 being controlled in such a way that alteration in the relative angular position of the arms 2, 5 occasioned by a change of speed does not affect the tension in the driving chain. The spring means acting on the tensioning arm 5 comprises a coil spring 4, Fig. 6, one end 4' of which is engaged in one or other of several notches in a cup shaped member 9 attached to the tensioning arm, while the other end 4SP2/SP has secured to it a cable 13. The cable 13 lies in a groove in a rotatable pulley 10 and at 14 enters a sheath 15 through which passes also a cable 16, controlling the transverse reciprocating movement of the arm 5 in the normal way to change speed, the two cables being joined to a single control cable 17. When the chain shift mechanism is actuated, the cable 13 is simultaneously moved so that the variation of the tension in the spring 4 is automatically compensated, despite the alteration in the relaytive angular positions of the several parts. A stop 18, Fig. 1, is provided to limit the rearward travel of the carrier arm 2. Specifications 662,003 and 665,167 are referred to.