US Patent 7669496 Driving force transmission apparatus and sheet conveyance apparatus

A driving force transmission apparatus has a driving gear; a driven gear; a toothed clutch transferring the driving force from driving gear to driven gear and which includes driving-side and driven-side ratchets that are movable in the axial direction of the clutch; and a compression spring biasing driven-side ratchet toward driving-side ratchet. When the tip end of the pawl of the driven-side ratchet is at the same position as the tip end of the pawl of the driving-side ratchet in the axial direction of the toothed clutch, the compression spring biasing force acts on the driven-side ratchet. And when the driven-side ratchet fully engages the driving-side ratchet, the biasing force does not act on the driven side ratchet.