Patent ID: 8534151

Claim:
A gear switching mechanism comprising: an axle defining a longitudinal axis; a gear supported by said axle for rotation about said longitudinal axis; a rotational coupling supported by said axle for rotation about said longitudinal axis; said gear and said rotational coupling supported for axial movement relative to each other along said longitudinal axis between a first position in which said rotational coupling is in engagement with said gear to transmit a rotary force thereto and a second position in which said rotational coupling is disengaged from said gear, said rotational coupling having a cam follower; a shuttle defining at least one cam surface slidably engaged with said cam follower and configured to move said rotational coupling axially between said first and second positions as said cam surface and said cam follower move relative to each other; and a drive mechanism for imparting relative movement between said shuttle and said cam follower in a plane substantially perpendicular to said axis, wherein said rotational coupling includes; a driven gear separate from said gear for transmitting rotation outside said switching mechanism a bias spring between said gear and said driven gear; and an engagement spring disposed between said cam follower and said driven gear, wherein said bias spring is configured to bias said rotational coupling to said second position, and said engagement spring is configured to overcome said bias spring when said cam follower moves relative to said cam surface.