Sheet feeding apparatus and method of detecting double feed

Abstract

A sheet feeding apparatus includes a stacker for stacking a sheet; a feeding device for feeding the sheet on the stacker to a predetermined processing position; a drive device for driving the feeding device; a double feed detection device having a sending element and a receiving element arranged at a downstream side of the feeding device for detecting a double feed of the sheet; a sensitivity adjustment device for comparing a detected value of the receiving element with a predetermined reference value for adjusting an output of the sending element; and a control device for controlling a transport speed of the feeding device. The sensitivity adjustment device adjusts the output of the sending element when the control device controls the drive device to stop the sheet or to decelerate the sheet at a predetermined speed.

Description

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT [0001] The present invention relates to a sheet feeding apparatus for sequentially separating sheets such as originals on a stacker into a single sheet and feeding the sheet to a processing platen for reading in other processes. More particularly, the present invention relates to a sheet feeding apparatus provided with a double feed detection function for detecting a double feed of sheets in a path from the stacker to a processing platen. [0002] A conventional sheet feeding apparatus feeds sheets such as originals to a processing platen. A reading apparatus for reading images on the sheets at the processing platen is widely known as a scanner, copier, or a facsimile machine. An apparatus for printing at a processing platen is widely used as a printer. [0003] It is necessary to accurately separate the sheets into a single sheet and to feed the sheet to the processing platen with proper positioning. Particularly, when sequentially ...

AI Technical Summary

Benefits of technology

[0013] The sensitivity adjustment device adjusts the output of the wave sending element when the drive device is stopped or decelerated at a predetermined speed. The sensitivity adjustment device compares the output value of the wave receiving element with the predetermined reference value. According to a result of the comparison, the sensitivity adjustment device increases or decreases, for example, amplitude of high frequency power in a case of the ultrasonic sensor to change electrical energy supplied to the wave sending element. Accordingly, it is possible to obtain a predetermined output from the wave receiving element. It is possible to stably detect the double feed of the sheets even if detection sensitivity of the wave sending element and the wave receiving element is degraded due to a temperature change or aging.

[0017] Accordingly, even when the ultrasonic wave sensor has characteristics changing easily, a tolerable range of characteristics is widened, thereby reducing manufacturing cost. Further, the output of the wave sending side is adjusted when transport of the sheet such as a test sheet is stopped or the sheet is decelerated to a predetermined speed. Accordingly, it is possible to accurately obtain the output of the wave sending element without an influence of a variance in a sheet transport speed.

Problems solved by technology

Particularly, when sequentially reading a series of originals, it is possible that the sheet is not fed to the platen, i.e., a non-feed, or two or more sheets are fed to the platen, i.e., a double feed, thereby causing an improper process at the processing platen.

When printing a series of originals at the processing platen, an incorrect process may occur at the platen due to the non-feed or double feed.

It is difficult to accurately detect the double feed of the sheets, and a detection element and a judgment circuit are expensive.

In a system in which scanners or copiers are linked through a network, the double feed of the sheets can cause a serious system error.

The elements of the conventional ultrasonic wave sensor for detecting the double-feed of the sheets are measured in the manufacturing process as described above, thereby increasing cost of the elements.

When an ambient temperature fluctuates or the sensor is deformed upon receiving an impact, it is possible to cause an erroneous detection.

Accordingly, the apparatus tends to be expensive and durability may be compromised.

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