GB682235A - Improvements in or relating to gear change mechanisms for cycles and the like - Google Patents

Abstract

682,235. Change-speed chain gearing. STURWEY-ARCHER GEARS, Ltd. Nov. 23, 1949 [Nov. 23, 1948], No. 30399/48. Class 80 (ii). [Also in Group XXXI] In a change-speed gearing for bicycles and like vehicles, in which speed changes are effected by shifting the driving chain 5 from one to another of a group of rear hub sprockets 2-4 through lateral movement of a shifter element 8 in an operative path wherein it is too close to the sprockets to allow rear wheel removal, the element 8 can be moved, on the release of positive locating means, out of said path into an inoperative position, shown chained, allowing such removal. In one form, an arm 11, pivotable about a depending lug 14 on a rear hub locating: member 13, carries a spindle 10 on which the element 8 in the form of a fork is slidably but non-rotatably mounted through a pin 17 engaging a slot in the spindle. Movement of the fork 3 along the spindle to control the gear ratio is effected in the usual manner through a leveractuated Bowden control 9, 19 acting against a spring 20, an adjustable limit stop 22 being provided. The arm 11 pivots about a shouldered bolt 24 to carry the fork 8 into the inoperative position, and is located with the fork in operative position either by the spring-pressed ball detent 23 shown, by a manually retractable spring-loaded pin detent or, according to the Provisional Specification, by a set screw. The ferk 8 may be replaced by a pulley or sprocket, when, in order to resist the chain thrust, a pin detent is always used. The locating member 13 comprises a plate secured to one fork end blade 1 by a screw 40 passing loosely through the blade slot and finally engaging in a portion of the plate doubled over round the blade. The member 13 has a slot corresponding to that of the fork end blade but which is countersunk at the inner end to receive and locate the rear hub spindle wing nut 26. Tensioning of the driving chain is effected by adjusting a bolt 27 screwing through the member 13 and abutting the rear of the fork end blade. A similar locating member, but without the lug 14, is mounted on the other fork end blade. In another form of the invention, the arm 11 is dispensed with, the shifter fork being rotatably but non-slidably mounted on a rod sliding non-rotatably in a fixed tubular support under a similar Bowden control to that above acting against a coil compression spring within the support and which may also extend into a hollow in the rod. The shifter fork is yieldably retained at its operative angular position on the rod and is rotated to an inoperative position to allow rear wheel removal. The Provisional Specification further describes an embodiment in which a spindle analogous to the spindle 10 but having a completely slotted and enlarged free end is similarly mounted directly on a frame bracket above the lower run of the driving chain. The spindle carries a slidable but non-rotatable bush, operatively controlled for speed-changing in the same general manner as the fork 8, and on which is rotatable a fork assembly comprising arms journalled on reduced end portions of the bush and secured together by screws or rivets, on one of which may be mounted a spring clip for retaining the fork in an operative position from which it can be swivelled forwardly to allow rear wheel removal.