REDUCTION GEAR OF ELECTRONIC WRISTWATCH WITH STEPPING MOTOR AND SWEEP SECOND HAND

摘要

The reductions gear of an electronic wristwatch having a stopping motor and a sweep second, comprises three concentric output shafts adapted to be rotated at different speeds and oporatively connected with each other and with the shaft of a stopping motor through gear wheels. The shaft making one revolution per hour has mounted thereon a friction wheel and a bearing means including a bush press fitted in a bore of a plate of the wristwatch. The bush is mounted so that a portion thereof projects from the plate toward a bridge of the wristwatch, coordinated with respect to the plate and attached thereto by threaded means. The shaft making one revolution per hour passes freely through a bore in the bearing bush and is restricted from an unlimited axial displacement in one direction by an end face of the bearing bush, and in the other direction by an end face of that pinion which is mounted on this shaft with interference fit. This enables to arrange the entire toothed gearing between the shaft making one revolution per hour and the shaft making one revolution per minute to one side of the plate, facing the bridge, and to do without several complicated counterbores and milled areas in the plate, i.e. to simplify the manufacture of the plate and its structure. The structure of the output shaft assembly enables to significantly reduce the overall height of the reduction gear.