JPH04286558A - Paper feeding device - Google Patents

Abstract

PURPOSE:To prevent the lower sheet of double-fed sheets from being over- returned in a paper feeding device used for a copying or printing machine. CONSTITUTION:A paper feeding device is provided with a pickup roller 12 for constantly pressing sheets S laminated in a sheets stocker 10, a feed roller 14 rotated in such a way as to convey the sheet fed from the pickup roller into the feed direction A, and a torque limiter provided separator roller 16 formed into a pair with the feed roller 14 but rotated in the reverse direction to the feed direction A.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device used in machines such as copiers and printers.

0002

[Prior Art] Paper fed from a paper stocker by a pick-up roller sometimes has a plurality of sheets stacked on top of each other. A method is adopted in which the second and subsequent sheets are returned to their original positions using a separator roller that rotates in the opposite direction.

[0003] In this case, the pickup roller does not always press the stacked paper in the stocker, but in order to reduce the load on the separator roller, after the fed paper reaches the feed roller, it retreats to an upper retraction position. method is adopted.

0004

[Problems to be Solved by the Invention] However, when the pickup roller is not pressing the paper, the paper pushed back by the separator roller does not necessarily stay at the correct position in the stocker, and may return too far to the rear. be. In this case, the pickup roller does not feed the paper at the top position in the stocker, but the paper below it first, followed by the paper at the top position. When these two sheets of paper are fed overlappingly between the feed roller and the separator roller, the lower paper that has advanced furthest forward will be pushed back by the separator roller. Therefore, the sensor that detects paper feeding may detect the lower paper that should be returned, which may also cause a jam.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to prevent the lower sheet from being returned too much when sheets are fed in duplicate.

[0006]

[Means for Solving the Problems] In view of the above objects, the present invention provides a pickup roller that constantly presses the sheets stacked in a paper stocker, and a pickup roller that constantly presses the sheets stacked in a paper stocker, and a pickup roller that moves the sheets fed from the pickup roller in the feeding direction. Provided is a paper feeding device comprising: a feed roller that rotates to convey paper; and a separator roller with a torque limiter that is paired with the feed roller and rotates in a direction opposite to the feeding direction. do.

[0007]

[Operation] Since the paper stacked in the paper stocker is constantly pressed by the pickup roller, when the multi-fed paper is pushed back by the separator roller that pairs with the feed roller, the paper is returned too much into the stocker. Things will go away.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below based on embodiments shown in the accompanying drawings. First, referring to FIGS. 1 and 2, in front of the stocker 10 in which sheets S are stacked, there is a pair of feed rollers 14 that rotate in the A direction for transporting the sheets and a separator roller 16 that rotates in the direction that returns the sheets. It is arranged as follows. Further, in the present invention, a pickup roller 12 for feeding the sheets S stacked in the stocker 10 from above between the pair of rollers is provided so as to constantly press the stacked sheets P.

A torque limiter 18 is attached to the lower separator roller 16 of this pair of rollers, and acts to return the double-fed sheets within a predetermined torque.

Next, the action of the above pair of rollers is shown in FIGS. 3 and 4.
Explain using. First, referring to FIG. 3, a normally fed sheet of paper S receives a conveying force F1 in the conveying direction from the feed roller 14, and also receives a conveying force F1 in the conveying direction from the separator roller 16.
A force F2 that pushes back the paper S acts from there. When the friction coefficient between the feed roller 14 and the paper S is μ2, the rotational torque of the separator roller 16 is T, the pressing force between the rollers is P1, and the radius of the roller 16 is R, the following equations hold true. F1=P1・μ2…(1) F2=T/R
...(2) In order for the paper P to be conveyed normally, the following relationship should be established. F1>F2...(3)

001
1] Next, referring to FIG. 4, it is a case where sheets S1 and S2 are fed double, the coefficient of friction between the sheets is μ1, the force acting between the sheets is F3, and the conveyance received by the sheet S1 from the feed roller 14 is μ1. Apply force F1' to the paper P from the separator roller 16.
The push back force received by roller 2 is F2', and the pressing force between both rollers is P2.
Then, the following formulas hold true. F1'=P2・μ2...(4) F2'=T/R...(5) F3=P2・
μ1...(6) Paper S1 is transported normally,
In addition, in order for the paper S2 to be pushed back, the relationship of the following equation should be established. F1'>F3...(7) F2'>F
3...(8)

However, in the present invention, since the pickup roller 12 constantly presses the paper and does not retreat, two sheets of paper S1 and S2
In the initial stage when the material is fed between the pair of rollers 14 and 16, it is affected by the feeding force F4 of the pickup roller 12, and for example, formula 8 becomes F2'>F3+F4, and the torque T needs to be set larger accordingly. There is. Although this is a drawback of the present invention, it is quite possible to design a paper feeding device that satisfies the relationships shown in each of the above equations. As shown in , the double-fed sheets S2 are not pushed back further than the pickup roller 12, but instead come into contact with the side wall of the stocker 10 and remain in that position while being bent. It is immediately conveyed by the pair of rollers 14 and 16 according to the force relationship expressed by Equation 3. Therefore, as in the past, the separator roller 1
6, problems such as detection errors and jams do not occur.

[0013]

As is clear from the above description, according to the present invention, when sheets are fed double from the stocker, the stacked sheets in the stocker are constantly pressed to prevent the lower sheet from being returned too much. This can be prevented by the presence of the pickup roller, which eliminates detection errors and jams caused by the sensor.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a paper feeding device according to the present invention during operation.

FIG. 2 is a diagram of a pair of rollers in FIG. 1 viewed from the direction of arrow line II.

FIG. 3 is an explanatory diagram of conveyance of one sheet of paper by a pair of rollers in FIG. 1;

FIG. 4 is a diagram illustrating the processing action of multi-fed sheets by the pair of rollers in FIG. 1;

[Explanation of symbols]

10...Paper stocker 12...Pickup roller 14...Feed roller 16...Separator roller

Claims (1)

[Claims] Claim 1: A pickup roller (10) that constantly presses the sheets (S) stacked in the paper stocker (10).
12), a feed roller (14) that rotates to convey the paper fed from the pickup roller in the feeding direction (A), and a feed roller (14) that is paired with the feed roller and rotates in the opposite direction to the feeding direction. A paper feeding device characterized by comprising a separator roller (16) with a torque limiter that rotates in the direction.