JPH11334938A - Sheet double feed detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet double feed detecting device capable of certainly detecting sheet double feeding. SOLUTION: This sheet double feed detecting device comprises a first and second driving rollers 11, 21 which are rotated synchronously each other by a motor 31, a first driven roller 12 driven by abutting on the first driving roller 11, a second driven roller 22 driven by abutting on the second driving roller 21, a torque motor 32 which gives the first driven roller 12 a smaller torque than a torque of the motor 31 in a rotational direction opposite to the driven direction caused by the first driving roller 11, a rotational velocity detector 16 detecting a rotational velocity of the first driving roller 11, a rotational velocity detector 26 detecting a rotational velocity of the second driven roller 22, and a comparing means 41 detecting sheet double feeding by comparing between output values of both the rotational velocity detector 16 and the rotational velocity detector 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet for detecting two-sheet feed of a sheet-like material (hereinafter, simply referred to as "sheet") such as a film or paper conveyed by rollers.
The present invention relates to a sheet feed detecting device.

[0002]

2. Description of the Related Art Conventionally, as such a two-sheet feed detecting apparatus for a sheet, a sensor capable of detecting a leading end and a trailing end of a sheet is arranged in a conveying path of a sheet conveyed by a roller. Is used. In such a conventional two-sheet feed detecting device, a pulse generated in synchronization with the rotation of a motor for driving a roller is counted by a counter, and the sensor detects the leading edge of the sheet and then detects the trailing edge of the sheet. By measuring the number of pulses counted by this counter during the time before, the length of the sheet passing through the sensor is measured, and when the measured value of the length of the sheet becomes larger than the preset sheet length Then, it is determined that two sheets have been fed.

[0003]

In such a conventional two-sheet feed detecting apparatus for a sheet, when two sheets are conveyed in a state of being completely overlapped without being shifted from each other, the two sheets are detected. There is a problem that feeding cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide a sheet-feed detecting apparatus capable of reliably detecting sheet feeding.

[0005]

According to a first aspect of the present invention, there is provided a sheet feed detecting apparatus for detecting a sheet feed of a sheet conveyed by a roller, wherein the apparatus is driven by a driving means. A first drive roller, a second drive roller disposed downstream of the first drive roller and rotating in synchronization with the first drive roller, and abutting on the first drive roller. A first driven roller that is driven to rotate at the same speed as the first driving roller, and a second driven roller that is driven to rotate at the same speed as the second driving roller by contacting the second driving roller. A roller, a reverse rotation driving unit that applies a rotation force in a direction opposite to the driven rotation direction to the first driven roller with a driving force smaller than the driving force of the driving unit, and the first driving roller or The second drive row Detection means for detecting the rotation speed of the second driven roller, second detection means for detecting the rotation speed of the second driven roller, an output value of the first detection means and an output of the second detection means. A comparing unit that detects two-sheet feeding by comparing the values.

According to a second aspect of the present invention, in the first aspect, both the first driven roller and the second driven roller have a length less than a width of a sheet to be conveyed. have.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a two-sheet feed detecting apparatus according to the present invention.

The apparatus for detecting the two-sheet feed of a sheet includes a first driving roller 11 that rotates by driving a motor 31 and an endlessly disposed first driving roller 11 that is disposed downstream of the first driving roller 11. The second drive roller 21 that rotates in synchronization with the first drive roller 11 by being connected via the synchronous belt 33 of the first drive roller 11 and the first drive roller 11 that comes into contact with the first drive roller 11 A first driven roller 12 driven and rotated at the same speed, and a second driving roller 21
And a second driven roller 22 that is driven and rotated at the same speed as the second driving roller 21 by contact with the second driving roller 21, between the first driving roller 11 and the first driven roller 12, and
The sheet S is nipped and conveyed between the second drive roller 21 and the second driven roller 22.

The first drive roller 11 is connected via a shaft 13 to a rotation speed detector 16 composed of a slit plate 14 and a detection unit 15. The rotation speed of the first drive roller 11 is detected by the rotation speed detector 16 and sent to the comparing means 41 described later.

The second driven roller 22 is connected via a shaft 27 to a rotation speed detector 26 comprising a slit plate 24 and a detection unit 25. The rotation speed of the second driven roller 22 is also detected by the rotation speed detector 26 and sent to the comparing means 41 described later. The length L2 of the second driven roller 22 is equal to the width W of the sheet S to be conveyed.
It is much smaller.

The first driven roller 12 is connected to a torque motor 32 via a shaft 17. The torque motor 32 applies a rotational force to the first driven roller 12 in a direction opposite to the above-described driven rotation direction with a driving force smaller than the driving force of the first driving roller 11 by the motor 31. It is. The length L1 of the first driven roller 12
Is also sufficiently smaller than the width W of the sheet S to be conveyed.

Next, a description will be given of a detection operation for detecting the double feed of the sheet S by the double sheet feed detecting device.

In a normal state, the sheet S conveyed from the supply section of the preceding sheet S is the first drive roller 1
1 and the first driven roller 12 and the second driving roller 2
Each of which is nipped by the first and second driven rollers 22,
Conveyed.

At this time, the first driven roller 12 is provided with a driving force directed from the torque motor 32 in a direction opposite to the driven rotation direction of the first driving roller 11.
Since this driving force is smaller than the driving force of the first driving roller 11 by the motor 31, the first driven roller 12 rotates in the driven rotation direction with respect to the first driving roller 11 as the sheet S moves.

On the other hand, when the sheet S is sandwiched between the first driving roller 11 and the first driven roller 12 in a state of being superimposed, the first driven roller 11 is driven by a torque motor 32. By the force, it rotates in the opposite direction to the driven rotation direction. That is, the first driven roller 12 is provided with a driving force greater than the frictional force between the two sheets S superimposed on each other by the torque motor 32. A slip occurs between the sheets S, and the first driven roller 12 rotates in a direction opposite to the driven rotation direction with the slip.

In this state, if the frictional force between the two sheets S is sufficiently small, the sheet S located on the side of the first driven roller 12 among the sheets S overlapping each other is located at the position of the first driven roller 12. To prevent the sheet S from being fed twice. However, when the frictional force between the two sheets S is relatively large, these two sheets S
While passing through the first drive roller 11 and the first driven roller 12 while maintaining the speed difference due to the slippage, the second
And the second driven roller 22.

In a state where these two sheets S are conveyed while being nipped by the second driving roller 21 and the second driven roller 22, as described above, the distance between these two sheets S is increased. Has a speed difference due to slippage.
Also, the second driven roller 22 does not receive any driving,
Further, the length L2 is smaller than the width W of the sheet S. Therefore, the second driven roller 22 is driven not by the second drive roller 21 but by the sheet S located on the second driven roller 22 side among the sheets S overlapping each other.

In such a state, there is a speed difference between the rotation speed of the second driving roller 21 and the rotation speed of the second driven roller 22. At this time, the rotation speed of the second drive roller 21, that is, the first drive roller 1
The rotation speed of the first driven roller 22 is detected by the rotation speed detector 26, and the rotation speed of the second driven roller 22 is detected by the rotation speed detector 26. Then, the second drive roller 21 by the rotation speed detectors 16 and 26 is used.
The detected value of the rotation speed of the second driven roller 22 and the rotation speed of the second driven roller 22 are input to the comparing means 41.

The comparing means 41 includes the rotational speed detectors 16, 2
If there is a difference between the rotational speed of the second drive roller 21 and the detected value of the rotational speed of the second driven roller 22 due to No. 6, it is determined that two sheets of the sheet S have occurred. Then, the comparing means 41 sends a signal to the display means 42 to display the occurrence of the two-sheet feed, and stops the first and second driving rollers 11 and 21 and the first driven roller 12 to convey the sheet S. To stop.

The length L1 of the first driven roller 12 and the length L2 of the second driven roller 22 are preferably smaller than the width W of the sheet S to be conveyed. First
Length L1 of second driven roller 2 and second driven roller 2
When the length L2 of the sheet 2 is larger than the width W of the sheet S to be conveyed, the first driven roller 12, the first driving roller 11, and the second driven roller 22 are disposed on both sides of the sheet S. And the second drive roller 21 are in direct contact with each other. In this case, depending on the frictional force between the first driven roller 12 and the first driving roller 11 or the frictional force between the second driven roller 22 and the second driving roller 21, 1, the second driven rollers 12, 22 are the first,
Following the second drive rollers 11 and 21, it is impossible to cause slippage between the sheets S superimposed on each other, so that there is no speed difference required to detect the two-sheet feeding of the sheets S. That's why.

In the above-described embodiment, the first drive roller 11 is directly driven by the motor 31 and the second drive roller 21 is driven via the synchronous belt 33. 11 may be directly driven by a motor, and the first drive roller 21 may be driven via a synchronous belt. Further, each of the first drive roller 11 and the second drive roller 12 may be driven by a motor.

In the above-described embodiment, the rotation speed of the first drive roller that rotates in synchronization with the second drive roller 21 is detected by the rotation speed detector 16 so that the second drive roller is detected. Although the rotation speed of the second drive roller 21 is detected, the rotation speed of the second drive roller 21 may be directly detected.

Further, the first driving roller 11 or the second driving roller 11
When the driving roller 21 is driven by a motor such as a pulse motor capable of detecting its rotation speed, the rotation speed detecting means 26 may be omitted. In short, it is only necessary that the rotation speed of the first drive roller 11 or the second drive roller 21 rotating in synchronization with each other can be detected by some means.

[0024]

According to the first aspect of the present invention, the first driven roller applies a driving force in the opposite direction to the sheet, and then the first driving roller or the second driving roller is connected to the second driving roller. Since the two-sheet feed is detected by comparing the difference in rotational speed between the driven roller and the driven roller, even if the two sheets are conveyed in a state of being completely superimposed without being shifted from each other, the two sheets are conveyed. Feeding can be reliably detected.

According to the second aspect of the present invention, the first driven roller and the second driven roller have a length equal to or less than the width of the sheet to be conveyed.
The first and second frictional forces between the second driven roller and the second driven roller, or the frictional force between the second driven roller and the second driven roller.
Is not driven by the first and second driving rollers to prevent the occurrence of a speed difference required for detecting the two-sheet feeding of the sheet S, and the two-sheet feeding of the sheet S can be reliably detected. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a two-sheet feed detecting apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st drive roller 12 1st driven roller 16 Rotation speed detector 21 2nd drive roller 22 2nd driven roller 26 Rotation speed detector 31 Motor 32 Torque motor 33 Synchronous belt 41 Comparison means 42 Display means S sheet

Claims (2)

[Claims] 1. A two-sheet feed detecting device for detecting a two-sheet feed of a sheet conveyed by a roller, comprising: a first driving roller rotated by driving of driving means; The first stage is disposed on a subsequent stage side.
A second driving roller that rotates in synchronization with the first driving roller; and a first driving roller that contacts the first driving roller to rotate the first driving roller.
A first driven roller that is driven and rotated at the same speed as the second driving roller; and a second driven roller that makes contact with the second driving roller.
A second driven roller that is driven to rotate at the same speed as the driving roller, and a driving force that is smaller than the driving force of the driving means and that rotates in a direction opposite to the driven rotation direction with respect to the first driven roller. Reverse rotation driving means for applying; first detection means for detecting the rotation speed of the first driving roller or the second driving roller; second detection means for detecting the rotation speed of the second driven roller. And a comparing means for detecting the feed of two sheets by comparing the output value of the first detecting means with the output value of the second detecting means. Sheet feed detection device. 2. The sheet feed detecting device according to claim 1, wherein each of the first driven roller and the second driven roller has a length equal to or less than a width of a sheet to be conveyed. A two-sheet feed detection device for a sheet.