Patent ID: 7380782

Claim:
An automatic document feeder, comprising: a housing having a back plate which may be raised and a base pivotably connected to the back plate; a supporting element disposed on the housing and having a shaft hole; a first engaging structure disposed on the housing; and a friction roller assembly, which comprises: a rotating shaft, which has a first end disposed in the shaft hole; a friction roller, which is disposed onto the rotating shaft and fixed, wherein the rotating shaft drives the friction roller to rotate in order for the automatic document feeder to transport a sheet; and a first sleeve, which is rotatably mounted on the rotating shaft and has a second engaging structure which is engaged with the first engaging structure in order to rotatably and firmly mount the rotating shaft on the housing, wherein the friction roller assembly may be replaced when the second engaging structure and the first engaging structure are disengaged, wherein; the first engaging structure is engaged with the second engaging structure through relative rotation therebetween; the first engaging structure has an arced slot and an elastic rib; the second engaging structure has a projection and a radial part, both of which are connected to an external circumferential surface of the first sleeve, and an arced part, which is substantially parallel to the external circumferential surface and connected to the radial part; the arced part is fit into the arced slot; and the elastic rib is engaged with the projection.