A medium transport device includes a roller transporting a medium, such as recording paper; a first layer covering a surface of the roller facing the medium; a second layer laminated on the first layer; and convex portions provided between the first layer and the second layer, and the convex portions are formed from inorganic particles. The first layer binds the convex portions to the roller, and the second layer covers the convex portions for protection.

A roller includes a shaft, and an elastic body portion that is provided on an outer peripheral surface of the shaft, in which the elastic body portion includes an inner peripheral portion which becomes a shaft side, an outer peripheral portion which becomes an outer side with respect to the inner peripheral portion, a plurality of first connection portions which connect the inner peripheral portion and the outer peripheral portion, and a plurality of second connection portions which are provided in a space portion between the adjacent first connection portions and which partition the space portion into one side and the other side of the roller in the axial direction, and in which the first connection portion is inclined in the same direction in a peripheral direction with respect to a radial direction of the roller.

A nip roller includes a core material having a surface coated with rubber. The nip roller having a support length L.sub.1 of 5 m or longer. The rubber surface has a hardness H (deg) equal to or lower than 65 deg as measured by a JIS K6253 Type A durometer (A type). Mass W (kg) of the nip roller and second moment of area I.sub.1 (m.sup.4) and the Young's modulus E.sub.1 (Pa) of the core material satisfy E.sub.1I.sub.1/W80000.

A sheet feeder includes a stacker to stack sheets and a separation and conveyance device to separate one sheet from the sheets fed from the stacker and convey the sheets one by one. The separation and conveyance device includes a feed roller that rotates in a direction to feed the sheet and a separation roller to press against the feed roller via the sheet. The separation roller has an apparent hardness different from an apparent hardness of the feed roller and is configured to form an indentation in the feed roller.

A roller which has woven fabric at a surface thereof and which is employed in an apparatus permitting achievement of conservation of resources, conservation of energy. Roller 1 provided with covering 3 includes woven fabric at its surface is idler means or drive means for conveying, supply, of an object, means for air cooling or drying a moving object, rotating means making use of suction of an object, or is for cleaning a contact surface to which roller 1 is opposed, and has at the surface woven fabric 2 with variation or combination of weave pattern(s). The woven fabric 2 includes weaving in a linear pattern of bands or different patterns. It also has open holes including lattice-like gaps 8 or a rectangular pattern 6 for control of air permeability formed from weft yarn 25 and warp yarn 26.

An industrial roll includes: a substantially cylindrical metallic core; a rubber base layer that is adhered to and circumferentially overlies the core; a rubber top stock layer that circumferentially overlies the base layer; and a polyurethane coating that circumferentially overlies the top stock layer. In this configuration, the roll can provide improved abrasion-resistance, sheet release properties, and/or toughness compared to a roll with a rubber cover, but may provide these properties in a cover that is softer than a typical polyurethane cover.

A processing roll has a release layer that includes a porous rigid layer and polymer composite. The porous rigid layer may be a thermally sprayed metal that has discrete metal portions or a network of contiguous metal portions. Discrete metal from a flame sprayer may attached to each other on a contact surface to form the rigid layer. The polymer composite at least partially fills the spaces between the metal portions. The polymer composite may comprise a particulate filler, such as silica or glass beads. The release layer has good durability as the exposed surface contains both a portion that is the rigid material and a portion that is the polymer composite. This configuration enables very high release and long term durability even as the release layer wears.

A roller member includes a rotating shaft and a roller portion. The roller portion includes a first layer provided on at least a portion of an outer peripheral surface of the rotating shaft, and a second elastic layer provided on at least a portion of an outer peripheral surface of the first layer. The first layer is made of a material having a coefficient of linear expansion lower than a coefficient of linear expansion of a material of the second elastic layer.

A nip roller includes a core material having a surface coated with rubber. The nip roller having a support length L.sub.1 of 5 m or longer. The rubber surface has a hardness H (deg) equal to or lower than 65 deg as measured by a JIS K6253 Type A durometer (A type). Mass W (kg) of the nip roller and second moment of area I.sub.1 (m.sup.4) and the Young's modulus E.sub.1 (Pa) of the core material satisfy E.sub.1I.sub.1/W?80000.

There is provided a roller including: a shaft, and an elastic body portion that is provided on an outer peripheral surface of the shaft, in which the elastic body portion includes a plurality of first recessed portions which are provided on one side of the roller in a shaft mounting direction at intervals in a circumferential direction of the roller and each have a bottom portion, and a plurality of second recessed portions which are provided on the other side of the roller in the shaft mounting direction at intervals in the circumferential direction of the roller and each have a bottom portion, and in which each of the first recessed portions is positioned between the adjacent second recessed portions in the circumferential direction of the roller in the side view of the roller in the shaft mounting direction.