JPH023453Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a paper feeding device such as an automatic feeding device for copy paper in a copying machine or a sheet-like original document.

(Prior Art) In a copying machine that automatically obtains a copy of a stack of papers, especially miscellaneous papers such as sheet-shaped originals, by feeding them one by one onto a contact glass, two originals are printed. It is necessary to prevent them from being fed out in a state where more than one sheet is piled up. As a means to prevent this double feeding, there is a method in which the fed document is passed between two rollers that are in contact with each other and have a large coefficient of friction. That is, one of the rollers is rotated in the direction in which the document is delivered, while the other roller is kept stationary. When two or more originals try to pass while overlapped, the one that contacts the rotating roller receives frictional force in the transport direction from the roller, while the one that contacts the stopping roller receives frictional force from the roller. The document is prevented from moving by the frictional force between the document and the roller. As a result, both documents are separated by slippage between them, and only the document that comes into contact with the rotating roller is fed out.

By the way, the double feed prevention device has one
There is a problem when only one original is sent.
In other words, one side of the document contacts a rotating roller and receives a conveying force, and the other side contacts a stop roller and receives a braking force, so the difference between these two forces causes However, since the balance of this force is delicate, uneven force acts on the document, which tends to cause wrinkles and tears. This influence cannot be ignored, especially in the case of thin originals.

The above-mentioned problem occurs not only when only one document is fed, but also when the last sheet of a stack of documents is fed out.

(Purpose) The object of the present invention is to solve the above-mentioned problems, that is, to provide a double-feed prevention device that does not cause problems even when only one sheet of a thin original is fed. The purpose is to

(Structure) The structure of the present invention will be described below based on one embodiment.

In order to achieve the above-mentioned object, the present invention passes a sheet of paper between a rotationally driven friction roller and a stopped friction member opposing the roller, and separates and feeds out the paper one by one. In the paper double-feed prevention device, the friction member is composed of friction pieces having two types of high and low friction coefficients, so that they selectively occupy operating positions, and the paper to be fed is The friction member is configured to switch from a high friction coefficient to a low friction coefficient based on the output of a sensor that detects that there is only one sheet of paper.

Next, the present invention will be explained in detail based on illustrated embodiments. Reference numeral 15 denotes a copying machine body equipped with a contact glass 16 on the top surface, and the contact glass 1
6. Copies the original supplied on the screen. Reference numeral 14 generally shows an automatic document feeding device additionally set on the main body 15 of the copying machine. Reference numeral 1 denotes a document placement table, on which documents are stacked and placed. A calling belt 2 is arranged so as to be able to protrude and retract from the surface of the document placement table 1. The calling belt 2 protrudes from the surface of the document placement table 1 as shown by the chain line while traveling in the direction of the arrow.
Place the original placed there on the contact glass 1.
Send it out in the direction of 6. Reference numeral 17 denotes a pulley for pushing up the calling belt 2, and is driven by the intermittent rotation of a cam (not shown) by the action of a one-turn electromagnetic clutch to perform the above-mentioned operation. Reference numeral 3 denotes a guide made of a plastic sheet, which lightly presses down the stacked documents. Following the exit side of the calling belt 2, separation rollers 20 and 30 are disposed as a double feed prevention device, which will be described later. 4 is a separation roller 20, 3
This is a guide plate that projects diagonally from above on the entrance side of the paper, and the leading edge of the original comes into contact with this guide plate, so that the originals are shifted from each other. That is,
It has an effect similar to judgment. Separation rollers 20, 3
The document that has passed through the contact portion 0 is moved to pull-out rollers 8 and 9 that are applied with driving force while rolling into contact with each other.
The contact glass 16 is conveyed through the guide plate 10 and then onto the contact glass 16. A wide conveyor belt 13 is disposed on the contact glass 16. The conveyor belt 13 is stretched between the pulleys 11 and 12 and runs in the direction of the arrow along the contact glass 16 to transport the document onto the contact glass 1.
6 and transport it to a predetermined position. When the original reaches the fixed position on the contact glass 16, the conveyor belt 13 stops and the original image is transferred to the copying machine main body 1.
The image is projected onto a photoreceptor (not shown) in 5 and copied. When the projection of the original image is completed, the conveyor belt 13 is driven again to eject the original and feed the next original onto the contact glass 16.

FIG. 2 and FIG. 3 show the separation rollers 20, 3.
0 details. Lower separation roller 20
is coupled via a one-way clutch 23 to a shaft 21 supported by a bearing 22, and receives rotational force in the direction of arrow A. The lower separation roller 20 has a boss 20b
The entire circumference of the tire 20a is wrapped with a rubber tire 20a. The upper separation roller 30 covers each half of the boss 30c with rubber tires 3 having different coefficients of friction.
It has a configuration wrapped by 0a and 30b. The upper separation roller 30 is fixed to a shaft 31 supported by a bearing 33, and is pressed against the lower separation roller 20 by a spring 34. 32 is a disk fixed to the shaft 31, and is provided with two notches 39a and 39b spaced apart by 180 degrees. Numeral 35 is a stopper that engages with the notches 39a and 39b to prevent rotation of the disk 32, and is guided by a guide pin 36 implanted in the fixed portion to advance and retreat in the direction of arrow C. stopper 35
The rear end is connected to the plunger 41 of the electromagnet 40, and the stopper 35, which normally projects toward the periphery of the disc 32, is moved back by the force of the spring 38 when the electromagnet 40 is energized.

Rubber tires 20a of the lower separation roller 20
The coefficient of friction between the document and the document is μ _p2 , the coefficient of friction between the rubber tires 30a, 30b of the upper separation roller 30 and the document is μ _p3a , μ _p3b, respectively, and the coefficient of friction between the documents is μ _pp . Then, the rubber tires 20a, 3 are arranged so that the following relationship holds between them.
0a and 30b are selected in advance.

μ _pp < μ _p2 , μ _p3a ; μ _p3b ≒ μ _pp For example, μ _pp ≒0.4, μ _p2 ≒1.0, μ _p3a ≒1.4,
μ _p3b =0.4 to 0.8.

Next, the operation of the double feed prevention device will be explained.

Two or more originals S ₁ to S _o on the original table 1
If there is, sensor 7 detects it and
It is in ADF mode. In this state,
Since the notch 39a of the disk 32 is engaged with the stopper 35, the upper separation roller 30 is able to move the rubber tire 30a, which has a large coefficient of friction, to the lower separation roller despite the rotation of the lower separation roller 20 in the direction of arrow A. It is stopped facing 20. Figure 4 shows the document between the separation rollers 20 and 30 in the above state.
This shows the state of S ₁ to S _o . Bottom layer manuscript S ₁
is the frictional force between it and the lower separation roller 20
The difference between the frictional force F ₂ between F ₁ and the document S ₂ above it
Driven by F ₀ in the feeding direction, the original S ₂ is
It is braked by the difference F ₄ between the frictional force F ₃ between it and the rubber tire 30a of the upper separation roller 30 and the frictional force F ₂ between it and the original S ₁ . Both separation rollers 2
If the contact force between 0 and 30 is N, each of the above forces F ₀
~ _F4 is as follows.

F ₀ = F ₁ − F ₂ = Nμ _p2 − Nμ _pp = N (μ _p2 − μ _pp ) Since μ _pp < μ _p2 , F ₀ > 0 F ₄ = F ₂ − F ₃ = N μ _pp − N μ _p3a = N(μ _pp - μ _p3a ) Since μ _pp < μ _p3a , F ₄ <0 Therefore, the second document S ₂ from the bottom and the documents S ₃ to _{S o} in the upper layer are separated by the upper separation roller. 30 with a force F ₄ , and only the lowest document S ₁ is fed out with a force F ₀ by the lower separation roller 20 to perform separation. In this case, the braking force acting on the document S ₁ is F ₂ and is caused by the friction between the documents, so the operation is smooth.

As described above, the documents S ₁ to _{S o-1} are fed out one after another, and when the last document S _o comes to its turn, the sensor 7 detects it and switches from the ADF mode to the manual feeding mode. At this time, the electromagnet 40 is temporarily energized and the stopper 35 is removed from the notch 39a.
As a result, the upper separation roller 30 rotates by 180 degrees as shown by arrow B, and the stopper 35 returns to its original position.
is stopped at that position by engaging with the notch 39b. In this state, the rubber tire 30b with a low coefficient of friction faces the lower separation roller 20. Therefore, the lower separation roller 20 contacts the lower surface of the document S _o and applies a frictional force F ₁ =Nμ _p2 to drive it in the transport direction.
The rubber tire 30b is in contact with the upper surface and braking force _F5
give. Since this braking force F ₅ is F ₅ =Nμ _p3b , the original S _o is affected by the difference force F ₀ ′, that is, F ₀ ′=F ₁ −F ₅ =Nμ _p2 −Nμ _p3b =N(μ _p2 −μ _p3b ).

By the way, if the upper separation roller 30 is equipped with only tires with a high friction coefficient like the conventional one, the braking force F ₅ ' applied to the document S _o is F ₅ '=
Since μ _p3a and μ _p3b < μ _p3a , this is much larger than the braking force F ₅ due to the rubber tire 30b. Since this large braking force F ₅ ' opposes the driving force F ₁ applied to the lower surface of the document _So , the document _So becomes distorted, torn, or wrinkled. Also, since the driving force F ₁ and the braking force F ₅ ' are almost equal,
The force that is useful for conveyance is F ₀ ″=F ₁ −F ₅ ′≒0, and smooth conveyance cannot be achieved.

On the other hand, in the present invention, since the rubber tire 30b with a low coefficient of friction is used, the resulting braking force F ₅ is not much different from the friction force F ₂ between the originals, and is applied to the last original S _o . However, it is possible to draw out the manuscript without much difference from previous manuscripts. In other words, the force F ₀ '=F ₁ −F ₅ =N(μ _p2 −μ _p3b ) useful for conveyance at that time
Since μ _p3b ≒ μ _pp , F ₂ = N ( μ _p2 − μ _pp ) ≒ F ₀ ′
This shows that you can play the same way up to the last card.

The electromagnet 40 remains deenergized until the sensor 7 detects a plurality of documents, and the rubber tire 30b maintains the state facing the lower separation roller 20.

(Effects) As described above, the present invention makes it possible to switch the friction coefficient of the friction member in the stopped state, which is placed opposite to the rotationally driven friction roller, and when operating as a double feed prevention device, it is possible to change the friction coefficient of the friction member in the stopped state. Since the friction coefficient is set in a state with a low coefficient of friction, reliable operation can be expected, and when only one sheet is being passed, the friction coefficient is in a state with a low coefficient, so unnecessary braking force is not applied to the paper being passed. There is no. Therefore, even if the paper is thin, it can be smoothly passed through without tearing or wrinkling it. Further, even if the friction roller directly contacts the friction member, wear can be reduced because the friction roller has a low coefficient of friction.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention.
A front view of the automatic document feeder, FIG. 2 is an enlarged front view of the main parts, and FIG.
The chisel has been moved to a position rotated 90 degrees around the shaft 31. ), FIG. 4 is an enlarged front view showing the operating state. 7...Sensor, 20...Lower separation roller, 3
0...Top separation roller, 30a...Rubber tire (with high friction coefficient), 30b...Rubber tire (with low friction coefficient), 32...Disc, 35...Stopper,
39a, 39b...notsuchi, 40...electromagnet.

Claims (1)

[Scope of utility model registration request] Paper is passed between a rotationally driven friction roller and a stopped friction member opposing it,
In the paper double-feed prevention device, which separates and feeds the paper one by one, the friction member:
Consisting of friction pieces with two types of high and low friction coefficients,
They selectively occupy the operating position, and the output of the sensor detecting that only one sheet is to be passed causes the friction members to change from a high coefficient of friction to a low coefficient of friction. A device for preventing double feeding of paper, characterized in that it can be switched.