Sheet-conveying mechanism

Abstract

A sheet transport guide includes a torsion coil spring (X). The spring (X) has a first arm (B4) with an end (B5). Through the end (B5), the spring (X) supports a rotation shaft of driven roller (R32) and applies elastic force to the roller (R32). Through the arm (B4) that is curved, the spring (X) guides a sheet toward a rotation roller R31. The spring (X) has a coil portion (B1) and an end (B3) of a second arm (B3) both fixed to a frame of an apparatus body. A plurality of driven rollers (R32) are aligned approximately parallel to a shaft (R31a) of the roller (R31). The rollers (R32) are each provided with the springs (X). A largest elastic force is applied to the roller (R32) at a predetermined reference position, and smaller elastic forces are applied to the other rollers (R32) at positions distant from the reference position.

Description

TECHNICAL FIELD [0001] The present invention relates to a sheet transport mechanism such as provided in image forming apparatuses, that includes a rotation roller, a movable member elastically biased toward the roller, and a sheet transport guide for guiding a sheet to be transported between the rotation roller and the movable member. BACKGROUND ART [0002] Conventional image forming apparatuses include a rotation roller for transporting a sheet such as of record paper, and a movable member such as a driven roller or a separation roller. The movable member is elastically biased toward the rotation roller. The rotation roller is rotated, thereby transporting a sheet as fed between the rotation roller and the movable member. Also, a sheet transport guide is provided upstream and / or downstream of the rotation roller in a sheet transport direction. The sheet transport guide guides a sheet between the rotation roller and the movable member. Or, the sheet transport guide guides a sheet whi...

AI Technical Summary

Benefits of technology

[0014] A guiding portion such as the arm of the torsion coil spring extends to the movable member that faces the rotation roller, so as to bridge a gap between the arm and the movable member. A sheet is thus transported smoothly. When the elastic member (i.e., the sheet transport guide) is curved according to a radius of curvature of a sheet transport path, the sheet transport guide allows a sheet to be transported more smoothly.

Problems solved by technology

A resulting problem is that a sheet jam occurs with increased frequency because a sheet is more likely to collide with a movable member or with a rotation roller around a gap provided between the sheet transport guide and the movable member.

In FIG. 4, a sheet transport path has a particularly small radius of curvature around the gap 5 and, therefore, causes frequent occurrence of sheet jam.

However, the film member has difficulty in guiding a sheet along a sheet transport path which has a small radius of curvature.

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