Indexed drive system
View Patent ↗An indexed drive system ( 10 ) for mechanised tools, in particular an electric toothbrush, for selectively imparting various drive modes to a pair of concentrically-arranged drive shafts ( 12, 14 ) thereby imparting various brushing modes to the head (H) of the mechanised tool, in particular an electric toothbrush.
1. A drive system for an electric toothbrush comprising concentric inner and outer rotatable shafts, the inner shaft extending beyond the outer shaft; an indexing assembly comprising a carriage located about the inner shaft and reciprocally displaceable longitudinally of the inner shaft; and a first coupling selectively operable to transmit drive from the inner shaft to the carriage, wherein the drive system further comprises a pair of converters for translating linear displacement of the carriage in one direction into a first limited angular displacement of the carriage and linear displacement of the carriage in a second direction opposite to a first direction into a limited second angular displacement of the carriage.
2. A drive system according to claim 1 wherein at least a first converter of the pair of converters comprises a cam and follower.
3. A drive system according to claim 2 wherein the cam is fixed relative to the shafts and the follower is provided on the carriage.
4. A drive system according to claim 2 wherein the cam defines a helical cam surface concentric with the shafts.
5. A drive system according to claim 2 wherein the follower extends longitudinally from an end of the carriage.
6. A drive system according to claim 2 wherein the follower comprises a pair of diametrically opposed follower elements.
7. A drive system according to claim 1 wherein one of the converters extends longitudinally from each of the opposed ends of the carriage.
8. A drive system according to claim 1 wherein the drive system comprises an actuator operable to effect the linear displacement of the carriage.
9. A drive system according to claim 8 wherein the actuator comprises a forked yoke received in an annular channel circumscribing the carriage.
10. A drive system according to claim 1 wherein the first coupling is selectively operable in response to linear displacement of the carriage.
11. A drive system according to claim 10 wherein the first coupling comprises a 1st tab on the inner shaft and a corresponding 2.sup.nd tab on the carriage.
12. A drive system according to claim 1 wherein a second coupling is provided to transmit drive from the carriage to the second shaft which comprises a key and keyway provided between the carriage and the outer shaft.
13. An electric toothbrush comprising a drive system according to claim 1 .