Roll sheet conveyance device and image forming apparatus incorporating same

Abstract

An image forming apparatus includes an image forming device forming an image on a recording medium wound into a roll, and a roll sheet conveyance device unwinding and conveying the medium to the image forming device. The roll sheet conveyance device includes a roll sheet feed device, a torsion detector, and a control device. The roll sheet feed device includes a drive device including upstream and downstream shafts in a drive transmission direction to rotate the medium, and a feed device to feed the medium. The detection device includes a torsion coil spring provided between the upstream and downstream shafts, and a pair of an encoder and an encoder sensor detecting the torsion amount at the opposite ends of the torsion coil spring. The control device controls the torsion amount on the basis of a signal from the detection device, and applies a given back tension to the medium.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present patent application claims priority pursuant to 35 U.S.C. §119 from Japanese patent application No. 2007-295298, filed on Nov. 14, 2007 in the Japan Patent Office, the contents and disclosures of which are hereby incorporated by reference herein in their entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present patent application relates to a roll sheet conveyance device for unwinding and conveying a recording medium wound into a roll, and an image forming apparatus including the roll sheet conveyance device.[0004]2. Discussion of the Background Art[0005]Large-size electronic image forming apparatuses, such as copiers and printers that handle oversized documents such as drawings as well as other printing machines, perform an image forming operation by using a recording sheet (i.e., a recording medium) of a large size, e.g., the A0 size and the A1 size. To improve convenience in handling the large-size ...

AI Technical Summary

Benefits of technology

[0012]This patent specification describes a roll sheet conveyance device. In one example, a roll sheet conveyance device is configured to unwind and convey a recording medium wound into a roll to an image forming device configured to form an image on the recording medium. The roll sheet conveyance device includes a roll sheet feed device, a torsion detector, and a control device. The roll sheet feed device includes a drive device including an upstream shaft and a downstream shaft in a drive transmission direction to rotate the recording medium, and a feed device provided along a conveyance path of the recording medium to feed the recording medium. The torsion detector includes a torsion coil spring provided between the upstream shaft and the downstream shaft, and an encoder and an encoder sensor pair configured to detect the amount of torsion at the opposite ends of the torsion coil spring. The control device is configured to control the amount of torsion of the torsion coil spring on the basis of a signal output from the torsion detector, and to apply a given back tension to the recording medium.

[0013]This patent specification

Problems solved by technology

However, such a device uses a relatively large number of components including the plurality of friction torque plates, the unidirectional clutch, and the electromagnetic clutch.

Thus, the background device is complicated and costly.

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