JPS59128144A - Paper feeder - Google Patents

Abstract

PURPOSE:To accurately convey copying paper, by putting a separator out of pressure contact with a feed roller after pinching the front edge of the copying paper betweena pair of conveying rollers, to apply no resistance to their conveying force. CONSTITUTION:When a sheet pass sensor 10 has detected that the front edge of copying paper 2 is pinched between a pair of conveying rollers 8, a solenoid 11 is excited according to a detection signal from the sensor to pull a separation roller 5 out of pressure contact with a feed roller 4 through the action of an arm 12 against the elastic force of a spring to apply no resistance to the conveying force of the conveying rollers 8. As a result, the copying paper 2 is accurately conveyed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a paper feeding device for a copying machine, and more particularly to a double-feed prevention control method therefor.

(Prior art) Paper fed from a paper feed section consisting of a cassette or paper feed table? As a double-feed prevention mechanism for separating only one sheet and conveying it downstream, in addition to the so-called corner claw separation method, a friction separation method has recently become mainstream.

Although it is called a friction separation method, it is more detailed (in other words, the so-called friction pad method, fixed separation roller pair method (feed roller rotation, separation roller stopped), rotating separation roller pair method (feed roller and separation roller both at the contact point). In short, it consists of a feeding roller that feeds the transfer paper and a separation member that is in pressure contact with the feeding roller and has a coefficient of friction lower than that of the feeding roller.

The separation member that presses against the feed roller to prevent double feeding of two or more sheets of transfer paper is required to have a lower friction coefficient than the feed roller. It needs to be larger than that.

Further, the pressure applied to the feed roller must be strong enough to prevent the sheets from escaping when a large number of sheets are fed at once from the sheet feed section.

Due to these circumstances, the resistance between the feeding roller and the separating member is quite large.

Therefore, when the leading edge of the paper is caught in a pair of conveying rollers such as registration rollers downstream of this feeding roller and the paper is about to be conveyed further, the trailing edge of the paper is still between the feeding roller and the separating member. If you were to get caught between the two, this would be a big load.

Therefore, especially when conveying a large-sized paper based on the edge surface, the load before and after the conveyance roller is large (different, causing skew (diagonal feeding)).Also, the conveyance force on the pair of conveyance rollers is small. In this case, slipping may occur, leading to paper jams or registration defects.In order to prevent this, the pressure applied to the pair of transport rollers has been increased, but this increases the load torque of the entire device.
This will affect the life of bearings, drive parts, etc.

(Purpose) The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and its purpose is to prevent skew and non-feeding at the conveyance roller portion without increasing the torque of the entire device. Paper feed device flF controlled by 5? It is about providing.

(composition) The configuration of the present invention will be explained below based on an illustrated embodiment.

FIG. 1 is a simplified mechanical diagram of a paper feeding device according to an embodiment of the present invention.

(In the figure)! The transfer paper 2 stored therein is fed by the pickup roller 3 in order from the top paper. Normally, only one sheet is fed, but sometimes two or more sheets may be fed. 4 is a feeding roller installed near and downstream of this cassette 1, and the paper is fed from the paper feeding section. The transfer paper 2'%' that has arrived at ℃ is further conveyed downstream. At this time, it works together with a separation roller (separation member) 5 to separate the electrotransfer paper, and only one sheet is separated and conveyed. Separation roller 5
is controlled so that the pressure is released from the feeding roller 4 by a solenoid IIK, which will be described later. Reference numeral 8 denotes a conveyance roller pair consisting of a drive roller 6 and a driven roller 7, which generally constitute a registration roller pair. The transfer paper 2 is conveyed by the pair of conveyance rollers 8, then turned at right angles in the direction of the arrow, and conveyed to the next station by the driving roller 6 and the driven roller 9.

Reference numeral 10 denotes a paper passing sensor provided on the upstream side near the pair of conveying rollers 8, and when this paper presence signal, that is, the presence of the transfer paper 2 at the pair of conveying rollers 8, the conveying system is temporarily stopped, and the temperature rises to a temperature of 0.degree. C. as shown in the figure.
After alignment with both images on the photoreceptor, conveyance is restarted.

The separation roller 5 is usually held in a spring member (not shown) and pressed against the feed roller 4, but as will be described later, the separation roller 5 is connected to a solenoid IC arm 12 which is turned on in response to a paper presence signal from a paper sensor 100. It is designed to relieve pressure by being pulled through it. The arm 12 is rotatable about a fulcrum 13 and rotates clockwise when the solenoid 11 is on.

That is, once the leading edge of the transfer paper 2 is nipped by the pair of transport rollers 8, the transfer paper 2 is thereafter transported by the transport force of the pair of transport rollers 81C. , the feeding p-ra 4 and the separation member 5vc that are added to the section.
As mentioned above, this load has a negative effect.

Therefore, in the present invention, the paper passing roller 10 detects that the leading edge of the transfer paper 2 is nipped by the pair of conveying rollers 8, and based on this signal, the separating roller 5 is depressurized from the feeding roller 4. It is something.

FIG. 2 shows an embodiment of the control circuit according to the present invention.

In the figure, the paper passing sensor 10 consists of an LEDI Oa and a seven-dimensional transistor 10b, and 12 indicates a paper passing detection circuit. Reference numeral 13 denotes a CPU which takes in the paper presence signal S1m and the paper size signal Si from the paper passage detection circuit 12 and outputs a drive signal to the solenoid.

tv, knee R, ~R5 are resistors, C1 and C2 are capacitors, IC1 is a comparator, and a threshold level for detecting paper is set.

The paper presence signal 82w turns on the solenoid 11,
The separation roller 5 is in a depressurized state, but when the separation roller 5 is depressurized, the paper fed in the next paper feeding operation will not be separated. There is no way to release pressure from the separation roller 5. Therefore, the paper size signal 81v is input to the CPU 13 to prevent the solenoid 11 from being turned on only by the paper presence signal S2.

(Effects) As described above, in the present invention, after the leading edge of the transfer paper is nipped by the pair of conveyance reelers, the separating member is depressurized by the feed roller by °C, so that the conveyance force by the pair of conveyance reelers is This allows accurate paper conveyance without applying any load.

[Brief explanation of the drawing]

FIG. 1 is a simplified configuration diagram according to an embodiment of the present invention, and FIG. 2 is a control circuit diagram thereof. 4... Feeding roller, 5... Separation member,
8... Conveyance reeler pair, 10... Paper passing sensor.

Claims (1)

[Claims] a feeding roller provided on the downstream side near the paper feeding section; and a separation member that separates the multi-fed transfer paper by contacting and applying pressure to the feeding roller;
Furthermore, it consists of a pair of conveying rollers provided downstream from the feeding roller, and a sheet passing sensor located upstream near the pair of conveying rollers, and a paper presence signal from this sheet passing sensor causes the separation member to be moved against the feeding roller. A paper feeding device characterized in that it is controlled to a depressurized state.