JPH0133546Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field This invention relates to a friction separation roller paper feeding device used in copying machines and the like.

Prior Art A paper feed device for a copying machine, etc. consists of a pick-up roller that can come into contact with and separate from the top surface of a stack of sheets stacked on a paper feed tray and rotates in the paper feed direction, and a pick-up roller located downstream in the paper feed direction. A feed roller rotates in the same direction in synchronization with the paper path, and presses against the feed roller.
A constant torque is applied in the counter-feeding direction via a torque limiter, and a separation roller is rotatable in either the paper-feeding direction or the counter-feeding direction, and there is no paper between these rollers. If only one sheet of paper is sent between the two rollers from the paper feed table, the torque applied to the separation roller due to the frictional force between the rollers or between the paper and the rollers is applied by the above torque limiter. The separation roller follows the feed roller to overcome the applied torque and rotates in the paper feeding direction without slipping with the feed roller or the paper,
When two or more sheets of paper are fed between both rollers, the torque applied by the torque limiter overcomes the torque due to the frictional force between the sheets, and the second and subsequent sheets are transferred to the paper feed tray. A friction separation paper feeding device is known in which the paper is pushed back toward the paper to separate the paper, and only the one sheet in contact with the feed roller is fed toward the registration roller. Conventionally, in this type of paper feeding device, double-fed paper is separated and the paper fed by the pick-up roller is placed in the nip between the feed roller and the separation roller so as not to prevent the paper from being pushed back by the separation roller. Immediately after reaching the paper stack, the pick-up roller was controlled to be separated from the top surface of the paper stack. However, although the paper pushed back by the separation roller leaves the nip portion, it is not returned to its initial position on the paper feed tray. In addition, there is also a sheet of paper that is carried along with the sheet that is sent out by the pick-up roller and is sent halfway to the nip between the feed roller and the separation roller. Therefore, the position of the leading edge of the paper sent out by the paper feed signal is not necessarily aligned with the reference position on the paper feed table, and the position and the nip of the feed roller and separation roller Often the situation is somewhere in between. From this state, if the feed roller is driven for a certain period of time to transport the paper and it hits the registration rollers to form a buckling, there will be a difference in the amount of buckling depending on the initial position of the leading edge of the paper, and the difference between the leading edge of the paper and the photoconductor. There is a possibility that alignment of the leading edge of the upper image and skew correction may become uncertain.

In order to align the initial position of the leading edge of the paper to a fixed position, a feed roller and a separation roller separate the double feeding prior to feeding the paper to the registration roller, and the leading edge of the fed paper is kept at a fixed position until the leading edge of the paper reaches a fixed position. A method of prefeeding is known.

An example of the configuration of a friction separation roller paper feeding device that performs preliminary feeding is shown in the accompanying drawings.

A pick-up roller 1 is provided on the upper surface of the paper bundle S so as to be able to approach and separate from it, and a feed roller 2 is provided on the downstream side of the pick-up roller 1.
The nip between the feed roller 2 and the separation roller 3 is similar to a normal friction separation roller paper feeding device in that it is provided with a pair of rollers including a separation roller 3 and a separation roller 3 to which a constant torque is applied by a torque limiter. A paper leading edge detection sensor 4 is disposed at a certain position on the downstream side of the unit, and the leading edge of the paper that is fed out by the pick up roller 1, feed roller 2, and separation roller 3 in response to a paper feed signal is detected by this sensor. If detected by the sensor 4, the operations of the feed roller 2 and pick-up roller 1 are stopped. Therefore, the paper stops with its leading edge aligned with the position of the sensor 4. If paper is fed using this position as the second initial position, the path length up to the pair of registration rollers 5 provided at a certain position on the downstream side will always be constant, so the paper can be fed at a predetermined timing. I can do it.

A grip roller 6 is provided between the sensor 4 and the pair of registration rollers 5, and when the paper is conveyed by the feed roller 2 during paper refeeding and the leading edge of the paper reaches the grip roller 6, the paper is moved toward the registration roller 5 by the grip roller 6. The feed roller 2 is rotated via a one-way clutch.

Note that the pick-up roller 1 is moved toward and away from the sheet bundle S by a solenoid 7.

Now, in the friction separation roller paper feeding system, as mentioned above, normally, after the time required for the leading edge of the paper fed out by the pick-up roller to be held in the nip between the feed roller 2 and the separation roller 3, the solenoid 8 is activated, and the pick-up roller 1 is controlled to move away from the top surface of the paper stack. In addition, it is common to always apply torque to the separation roller in the opposite paper feeding direction via a torque limiter. Conventionally, the pick-up roller was controlled in this way even in a friction separation roller paper feeding device that feeds paper.

However, with a paper feeder that performs preliminary feeding,
After the paper has been pre-fed to a predetermined position, while waiting for the paper to be fed again, when the feed roller 2 is stopped, it is possible to check the type of paper and the settings for copying the back side of paper that has already been copied on one side in the case of double-sided copying. Depending on the state of the paper, such as when oil is attached to the paper during paper feeding, there is a risk that the paper may be returned due to the separation roller driving force or vibration. This return force is normally extremely small, but depending on the length of the waiting time and the condition of the paper, the paper may be returned to the paper feed tray, and its leading edge may move to the rear of the predetermined pre-feeding position. There was a drawback that the conveyance timing was not stable.

Purpose The purpose of this invention is to provide a paper feeding device with stable conveyance timing, which eliminates the above-mentioned drawbacks of the conventional friction separation roller paper feeding device that performs preliminary feeding.

Configuration Hereinafter, an embodiment in which the present invention is applied to a paper feeding device shown in the attached drawings will be described in detail.

In the paper feeding device according to the embodiment of the present invention, in the figure,
The paper stack S
The solenoid 8 is controlled so that the pick-up roller 1 is brought into contact with the upper surface with a predetermined pressing force and separated from the upper surface of the sheet bundle S at the same time as the paper refeeding starts.

By controlling as described above, when the feed roller is stopped while waiting until paper refeeding,
Even if a return force in the opposite paper feeding direction is applied to the paper due to the driving force or vibration of the separation roller, the return force is extremely small, so movement is suppressed by the stopped pick-up roller that is in pressure contact with the paper stack. , the paper is securely held in place in the pre-feed.

Next, the solenoid 8 is activated at the same time as the paper refeed signal, and if the pick up roller 1 is separated from the top surface of the paper stack S, double feeding separation using the normal friction separation roller paper feeding method is performed, and separated sheets are not fed. Since the pressing force exerted by the pick-up roller 1 has been removed from the paper, the paper is reliably returned from the nip portion, and only the one sheet of paper in contact with the feed roller 2 is fed.

Effects As described above, according to the present invention, when the variation in the paper leading edge position between the paper stack and the nip between the feed roller and the separation roller is corrected by preliminary feeding, the standby time that causes the variation remains. It is possible to prevent the sheet from moving backward, and to obtain stable sheet feeding performance without deteriorating the double feed separation performance.

[Brief explanation of drawings]

The accompanying drawing is a sectional view showing an example of the configuration of a friction separation roller paper feeding device to which the present invention is applied. 1... Pick up roller, 2... Feed roller, 3... Separation roller, 4... Paper leading edge detection sensor, 5... Registration roller, 6...
Grit roller, 7... Solenoid for pick-up roller contact/separation, S... Paper stack.

Claims (1)

[Scope of utility model registration request] A pick-up roller that can come into contact with and separate from the top surface of a stack of paper stacks and rotates in the paper feeding direction to feed out the paper, a feed roller that is located downstream in the paper feeding direction and rotates in synchronization with the pick-up roller in the same direction, and a paper path. It has a separation roller that pinches and presses against this, and is rotatable in either the forward or reverse direction by applying a constant torque in the counter-feeding direction via a torque limiter. The paper is separated from double feeding by a feed roller and a separation roller, and preliminary feeding is performed until the leading edge of the paper reaches a predetermined position on the downstream side of these rollers.
In a friction separation roller paper feeding device in which paper is re-fed by a feed roller and a separation roller at a predetermined timing after standby, the pick-up roller is pressed against the top surface of a stack of sheets with a predetermined pressing force during the preliminary feeding and when the feed roller is on standby. A paper feeding device characterized in that the pick-up roller is controlled so as to be in contact with the paper stack, and to separate the pick-up roller from the upper surface of the stack of paper simultaneously with the start of paper refeeding.