An implementation of an assembly of the present teachings includes a transport roll having a shaft with a tapered surface and an encoder having a coupler that defines a recess and has a tapered surface. During use of the assembly, the tapered surface of the shaft physically contacts the tapered surface of the coupler, and the encoder can be urged toward the transport roll using a spring such as a leaf spring.

A sheet conveyance apparatus includes a conveyance unit, a conveyance guide, a driven rotary member, and a support portion. The support portion supports a shaft portion of the rotary member driven to rotate by a sheet conveyed by the conveyance unit and guided by the conveyance guide. The support portion includes first and second contact portions that support the shaft portion of the driven rotary member while being in contact with the shaft portion. With respect to a cross section of the shaft portion perpendicular to an axial direction of the shaft portion, the driven rotary member is disposed so that a portion, of the driven rotary member, that is on a lower side in a vertical direction relative to a horizontal line and is on one side in a horizontal direction relative to a vertical line comes into contact with the sheet.

A sheet conveyance guide includes a guide portion, a first thrust direction retainer, and a second thrust direction retainer. The guide portion is configured to guide a sheet. The first thrust direction retainer includes a first engagement portion configured to engage with a shaft of a sheet conveying roller configured to convey the sheet, and a guide releaser configured to be operated by a user to release engagement of the first engagement portion with the shaft of the sheet conveying roller. The second thrust direction retainer includes a second engagement portion configured to engage with the shaft of the sheet conveying roller.

A rotating device includes a shaft member, a counterpart member, a bearing, and a retaining member. The counterpart member includes a shaft insertion portion into which the shaft member is inserted. The bearing is disposed in the shaft insertion portion and interposed between the counterpart member and the shaft member. The bearing causes the counterpart member and the shaft member to be rotatable relative to each other. The retaining member is disposed on an end portion of the shaft member on one side in an axial direction of the shaft member. The counterpart member includes an opposing portion closer to the end portion of the shaft member on the one side in the axial direction than the bearing. The opposing portion faces the retaining member in the axial direction.

A sheet feeder includes a frame, a roller holder, and a holder stopper. The roller holder includes a feed roller for feeding a sheet. The roller holder is detachably attachable to the frame. The holder stopper is configured to move between a restricting position and a non-restricting position. In a case where the holder stopper is located at the restricting position, the holder stopper restricts the roller holder from moving from an attached position at which the roller holder is fixed to the frame. In a case where the holder stopper is located at the non-restricting position, the holder stopper allows the roller holder to move relative to the frame.

Examples of a paper-clearance apparatus for removing jammed paper from a printer are described herein. The paper-clearance apparatus includes an outer shaft mounted transversely above a printing medium path of a printer; an inner shaft movably disposed inside the outer shaft; a roller assembly including a sliding bush mounted over the outer shaft; and a handle connected inside the inner shaft from outside a printer housing. The handle is being rotatable so that the roller connected with the inner shaft touches the jammed paper and rotates along with the jammed paper to grip the jammed paper. Further, the handle is being pullable away from the printer housing so as to pull out the jammed paper beneath the printer housing.

Examples of a paper-clearance apparatus for removing jammed paper from a printer are described herein. The paper-clearance apparatus includes an outer shaft mounted transversely above a printing medium path of a printer; an inner shaft movably disposed inside the outer shaft; a roller assembly including a sliding bush mounted over the outer shaft; and a handle connected inside the inner shaft from outside a printer housing. The handle is being rotatable so that the roller connected with the inner shaft touches the jammed paper and rotates along with the jammed paper to grip the jammed paper. Further, the handle is being pullable away from the printer housing so as to pull out the jammed paper beneath the printer housing.

A bearing includes a body that defines a first arcuate support surface and a second arcuate support surface. The first and second arcuate support surfaces are to cradle a rotatable circular shaft against a net radial load that is to act on the shaft. The first arcuate support surface has a radius of curvature larger than a radius of the shaft. The second arcuate support surface has a radius of curvature larger than the radius of the shaft. The first and second arcuate support surfaces are positioned on opposite sides of a direction of action of the net radial load.

A medium transport apparatus includes a transport roller configured to transport a medium and a roller support portion configured to support the transport roller. The roller support portion includes a support member contacting an outer circumferential surface of the transport roller at two positions thereof in a circumferential direction to support the transport roller, a base member defining a position of the support member, and an intermediary member mediating the support member and the base member. The intermediary member is configured to cause separation between the support member and the base member without moving the support member and the base member.

A retaining ring 1 for a shaft 2a usable with a bearing 3 having an outer ring 3a and an inner ring 3b fixed on the shaft, wherein the inner ring 3b and the outer ring 3a are rotatable relative to each other, and the retaining ring 1 is provided on the shaft 2a adjacent to the bearing 3 in a thrust direction to restrict a position of the bearing 3 in the thrust direction, the retaining ring 1 includes a protrusion 1a protruding in the thrust direction from a surface opposing the inner ring 3b in the thrust direction to contact the inner ring 3b so that the retaining ring 1 is out of contact from the outer ring 3a.