JPH05319591A - Paper feeder - Google Patents

Abstract

PURPOSE:To ensure separation of paper sheets from each other by pressing paper sheets situated no higher than the first by a pressing means after the rear end part of the uppermost paper sheet is lifted upward by a vacuum means and is thus sucked thereby. CONSTITUTION:Driving of a roller 1 and a vacuum member 2 is stopped while a paper sheet retaining member 3 is separated from an uppermost paper sheet P1, at the time of stand-by. When a feed-starting command is issued in this condition, the driving of the vacuum member 2 is started, while a fan 2a is started to be rotated, and rear end of the uppermost paper sheet P1 is lifted and is sucked by the vacuum member. The paper sheet retaining member 3 is lowered at the same time or slightly later, and is abutted on a second paper sheet, and a bundle of paper sheets P of no higher than the first one is retained thereby. Although the roller 1 which is called at the same time, is started to be rotated at the same time, since the paper sheets P of no higher than the first one are retained by the paper sheet retaining member 3, only the uppermost paper sheet P1 is fed, and double feeding is securely prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device applied to an image forming apparatus.

[0002]

2. Description of the Related Art In a sheet feeding device for feeding a stack of sheets stacked on a sheet stacking table in order from the topmost sheet, various sheets are fed in order to feed the sheets one by one without double feeding. Although a paper separating mechanism has been proposed, a so-called friction separating method has recently become mainstream. In this friction separation system, a paper feed roller and a friction pad, or a paper feed roller and a separation roller with a built-in torque limiter are brought into pressure contact with each other, and the double feed is stopped at the pressure contact position or returned to the original position.

[0003]

However, in the paper feed device adopting the friction separation method, if there is a surface having a different inter-paper friction coefficient in the sheet bundle, a large number of sheets are fed across the surface. There is a danger, and in that case, we may not be able to deal with it.

The present invention has been made based on such a background, and an object of the present invention is to provide a sheet feeding device excellent in double feed prevention performance.

[0005]

SUMMARY OF THE INVENTION The above-mentioned object is to provide a sheet feeding roller for pressing the leading end side of the stacked uppermost sheet of sheets with a proper sheet feeding pressure, and a rear end portion of the uppermost sheet of the sheet bundle. A vacuum means for lifting up and sucking the side by air suction, and a pressing means for pressing the rear end of the second and subsequent sheets of paper following the topmost sheet, driven by the air suction operation and timing of this vacuum means. This is achieved by the first means provided.

The above object is also achieved by the second means, which is the first means in which the paper feed roller and the pressing means are mechanically drive-connected.

Further, the above-mentioned object is achieved by the third means, in which the first means is provided with a sensor for detecting the drive of the paper feed roller, and the pressing means is driven by a signal from this sensor. ..

[0008]

In the first means, after the rear end of the uppermost paper is lifted up and sucked by the vacuum means, the second and subsequent sheets are pressed by the pressing means, so only the uppermost paper is pressed. Paper can be fed by the paper feed roller, and the paper can be reliably separated.

In the second means, since the pressing means is mechanically connected to the paper feed roller, the driving mechanism of the pressing means can be constructed at low cost.

In the third means, drive control of the pressing means is performed by turning on / off a signal from the sensor (solenoid,
Since it is carried out (via a motor or the like), the reliability of the operation of the pressing means can be improved and it can be applied to a model having a high linear velocity.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a standby state of a sheet feeding device according to an embodiment, and FIG. 2 is a configuration diagram showing a state of sheet feeding.

In these figures, P is a sheet bundle stacked on a sheet stack (not shown), 1 is an upper side of the leading edge of the sheet bundle P, and the uppermost sheet P ₁ is appropriately fed. A calling roller (feeding roller) 2 which comes into contact with pressure is located above the rear end portion of the sheet bundle P and sucks the uppermost sheet P ₁ upward by air suction by the rotation of the fan 2a (vacuum means). 3 is disposed above the rear end of the sheet bundle P, and is located at a position away from the surface of the uppermost sheet P ₁ as shown in FIG. 1 and at a position at which the uppermost sheet P ₁ is pressed as shown in FIG. It is a paper pressing member (pressing means) that is displaced between the two.

Next, the operation will be described. At the standby time shown in FIG. 1, the calling roller 1 and the vacuum member 2 are not driven, and the paper pressing member 3 is the top paper P _1.
It is in a position away from. When a paper feed start command is issued in this state, the vacuum member 2 starts driving, that is, the fan 2a starts to rotate, and the rear end side of the uppermost paper P ₁ is lifted and adsorbed. At the same time or with a slight delay in timing, the sheet pressing member 3 is driven by a drive mechanism described later.
Moves down and comes into contact with the second sheet, and presses the second and subsequent sheet bundle P (state in FIG. 2). At the same time, the calling roller 1 starts to rotate, but since the second and subsequent sheet bundles P are held by the sheet holding member 3, only the uppermost sheet P ₁ is fed, and double feeding is accurate. Well prevented.

FIG. 3 is a structural view showing a mechanical drive connecting mechanism of the calling roller and the paper pressing member.
Of the timing belt 5 between the pulley (not shown) and the pulley (not shown) of the pressing cam 4 on the paper pressing member 3 side.
The driving force is transmitted to the pressing cam 4 by the timing belt 5.
The pressing cam 4 has a fulcrum 3 by a compression coil spring 6.
The pressing arm 3a, which rotates counterclockwise around b and is biased upward, is in contact. The state shown in FIG.
A state in which the tip of the pressing arm 3a is pressing the second or lower sheet bundle P, and the pressing cam 4 moves from this state to 1
In the state of being rotated by 80 degrees, the pressing arm 3a rotates clockwise around the fulcrum 3b against the elastic force of the compression coil spring 6, so that the tip end thereof is separated from the second sheet. ing.

FIG. 4 is a block diagram showing an electrically driven connecting mechanism of the calling roller and the paper pressing member.
7 for detecting the rotation of the CPU, and a CPU for outputting a drive command for the pressing arm 3a based on ON / OFF signals of the sensor 7.
8 and a solenoid (or motor) 9 driven by a command from the CPU 8. The plunger of the solenoid 9 is locked to one end of the pressing arm 3a, and one end of the tension coil spring 10 is locked to the opposite side of the pressing arm 3a.

Normally, as shown in FIG. 4, the pressing arm 3a is urged to rotate clockwise around the fulcrum 3b by the tensile force of the tension coil spring 10 and its tip is separated from the sheet bundle P. When the calling roller 1 starts to rotate and the sensor 7 is turned on, the solenoid 9 is turned on in response to a command from the CPU 8, and the pressing arm 3 is pushed through the plasticizer.
A is counterclockwise urged against the tensile force of the tension coil spring 10. Thereby, the pressing arm 3a
The sheet bundle P of the second sheet or less is pressed at the tip of the sheet (as described above, the uppermost sheet P ₁ is attracted by the vacuum member 2 at this point).

[0017]

According to the first aspect of the invention, after the rear end of the uppermost paper is lifted up and sucked by the vacuum means, the second and subsequent sheets are pressed by the pressing means. Only the topmost paper can be fed by the paper feed roller, and the paper can be reliably separated.

According to the second aspect of the present invention, since the pressing means is mechanically connected to the paper feed roller, the driving mechanism of the pressing means can be constructed at low cost.

According to the third aspect of the invention, since the drive control of the pressing means is performed by turning on and off the signal from the sensor (via the solenoid, the motor, etc.), the reliability of the operation of the pressing means is improved. It is also possible to support high-speed models with high linear speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a standby state of a sheet feeding device according to an exemplary embodiment of the present invention.

FIG. 2 is a configuration diagram showing a state at the time of sheet feeding of the sheet feeding device according to the embodiment of the present invention.

FIG. 3 is a configuration diagram showing a mechanical drive connection mechanism of a calling roller and a paper pressing member.

FIG. 4 is a configuration diagram showing an electric drive connection mechanism of a calling roller and a paper pressing member.

[Explanation of symbols]

 1 Calling Roller (Paper Feeding Roller) 2 Bacumiume Device (Vacuum Means) 3 Paper Holding Member (Holding Means) 3a Holding Arm 3b Support Point

Claims (3)

[Claims] 1. A paper feed roller that presses the leading end side of the uppermost sheet of the stacked sheet bundle with an appropriate sheet feeding pressure, and a rear end side of the uppermost sheet of the sheet bundle is lifted upward by air suction. A sheet feeding device provided with a vacuum means for adsorbing the sheet and a pressing means that is driven at a timing with the air suction operation of the vacuum means and holds the trailing edge of the second and subsequent sheets of paper following the topmost sheet. 2. The paper feeding apparatus according to claim 1, wherein the paper feeding roller and the pressing unit are mechanically connected to each other. 3. The paper feeding device according to claim 1, further comprising a sensor for detecting the driving of the paper feeding roller, wherein the pressing unit is driven by a signal from the sensor.