JPH06211369A - Paper feed mechanism for image forming device - Google Patents

Abstract

PURPOSE:To release pressure force against paper of a paper feed mechanism by a double feed preventing mechanism while preventing a double feed of each paper, carried out from a plurality of cassettes, by a double feed preventing mechanism by separating paired relay rollers from each other when paired paper feed rollers with a double feed preventing function are rotated. CONSTITUTION:A paper feed roller 3 is driven, and when paper is discharged from the first paper feed cassette and detected by a switch 15, paired relay rollers 8a, 8b are driven to feed the paper to double feed preventing function- provided paired paper feed rollers 5a, 5b through the first conveying path 6. When detected the paper by a switch 16, the rollers 5a, 5b are driven to convey the paper to paired register rollers 11a, 11b. Now when two sheets of the paper are conveyed to be doubled, a sheet in an upper side is fed to the paired register rollers 11a, 11b by the roller 5a, and a sheet in a lower side is returned by the roller 5b, to hold the paper between the first conveying path and the paired rollers 8a, 8b till a feed is necessary for the next paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding mechanism for an image forming apparatus having a function of preventing double feeding of sheets, and is mainly used in copying machines, laser printers and the like.

[0002]

2. Description of the Related Art As a conventional paper feed mechanism of this type, there is known a paper feed mechanism for a plurality of paper feed cassettes.

[0003]

However, if the double feed preventing mechanism is provided for each of the plurality of sheet feeding cassettes, there is a problem that the structure of the entire sheet feeding mechanism becomes complicated. The present invention has been made in consideration of such circumstances, and prevents the double feeding of the respective sheets carried out from the plurality of cassettes by one double feeding preventing mechanism and the double feeding preventing mechanism with respect to the sheets of the paper feeding mechanism. It is intended to provide a sheet feeding mechanism for an image forming apparatus that releases a pressing force.

[0004]

SUMMARY OF THE INVENTION According to the present invention, an image configured to feed a sheet carried out by a sheet feeding roller from a sheet feeding cassette to a registration roller pair via a sheet feeding roller pair with a double feed prevention function. In the sheet feeding mechanism for the forming apparatus, a plurality of sheet feeding cassettes, one sheet feeding roller pair with a double feeding prevention function, and a plurality of conveyance paths for guiding a plurality of sheets to the sheet feeding roller pair with a double feeding prevention function, respectively. And a relay roller pair provided in the conveyance path in which the conveyance distance from the sheet feed roller to the pair of feed rollers with the double feed prevention function is longer than the length of the sheet in the sheet feed direction. A sheet feeding mechanism for an image forming apparatus, wherein the relay roller pair is separated from each other when the pair rotates.

A known feed roller pair with a double feed prevention function can be used. When two sheets are sandwiched, one roller (roller with torque limiter) rotates in the direction opposite to the feed direction. It is preferable to use one. The paper feed roller of the paper feed cassette is a so-called pickup roller (which is separated from the paper when not feeding) or a half-moon roller (the outer circumference of the roller consists of a circular portion and a straight portion, and is linear when not feeding. It is also possible to use a roller whose part faces the sheet and the roller separates from the sheet.

[0006]

When two sheets of paper are unloaded from the paper feed cassette in an overlapped manner, the sheet of paper is unloaded to the roller pair with the double feed prevention function via the relay roller pair if the transportation path includes the interruption roller. . When the paper feed roller pair with double feed prevention function is driven,
One sheet is conveyed downstream, and the other sheet is held in the conveying path without being fed by the relay roller pair because the relay roller pair separates from each other.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. This does not limit the invention. FIG. 1 is a block diagram of the essential parts of a copying machine, where 1 is the first
Paper feed cassettes 2, 2 is a second paper feed cassette, 3 is a paper feed roller that carries out paper from the first paper feed cassette 1, 4 is a half-moon type paper feed roller that carries out paper from the second paper feed cassette 2, 5
Reference numerals a and 5b are a pair of paper feed rollers with a double feed prevention function. In addition,
The roller 5b has a torque limiter function as described later.

Reference numerals 6 and 7 are first and second conveying paths for guiding the sheets in the first and second sheet feeding cassettes 1 and 2 to the roller pairs 5a and 5b, respectively, and 8a and 8b are for the first conveying path 6. A relay roller pair, which is provided on the way and feeds the sheet from the first sheet cassette to the roller pair 5a and 5b, and 9 is a photosensitive drum on which an electrostatic latent image is formed by an exposure device (not shown) which rotates in the direction of arrow A. Is. The roller 8a is a roller driven by a drive source (not shown), and the roller 8b
Is a driven roller for pressing the sheet against the roller 8a.

Reference numeral 10 designates a developing unit for developing the electrostatic latent image on the photosensitive drum 9 with toner, and 11a and 11b make the paper fed from the roller pairs 5a and 5b stand by to set the timing to the rotational position of the photosensitive drum. A pair of registration rollers for sending sheets together, a pair of registration rollers 11a,
11b is a transfer charger that transfers the toner image on the photoconductor drum 9 to the paper sent from 11b.

Reference numeral 12a designates the transferred paper as a photosensitive drum 9
A main charger for uniformly charging the surface of the photoconductor drum 9, a cleaning unit 14 for cleaning the photoconductor drum 9 after transfer, and a front part of the relay roller pair 8a, 8b (15). Switch for detecting whether or not there is paper in (upstream), 16 with roller 5
This is a switch for detecting whether or not there is a sheet from the sheet feeding cassette 1 or 2 in front of (upstream of) a or 5b.

FIG. 2 shows a pair of paper feed rollers 5a having a double feed prevention function.
5b is a perspective view of an essential part of 5b, and 17 and 18 are shafts which are simultaneously rotated in the directions of arrows B and C by a drive source (not shown). In this case, the arrow P indicates the paper feeding direction, and the roller 5a rotates together with the shaft 17.

FIG. 3 is an exploded perspective view of the roller 5b having a torque limiter function, and 19 is a limiter spring and 20 is a limiter spring.
Is a limiter color, and 21 is a limiter boss. The limiter boss 21 is fixed to the shaft 18 (FIG. 2), and the limiter boss 21 and the roller 5b are connected by a limiter spring 19.

Therefore, when the shaft 18 (FIG. 2) is rotated in the direction of arrow C while the roller 5b is fixed, the inner diameter of the limiter spring 19 becomes larger than the outer diameter of the limiter boss 21, so that the roller 5b slips. The rotational force from the shaft 18 is not transmitted to the roller 5b.

At this time, the roller 5a (FIG. 2) is indicated by the arrow B.
When rotated in the direction, the roller 5b receives the rotational force and rotates in the direction opposite to the arrow C. That is, the roller 5b rotates in the direction of arrow C when the load applied to the outer periphery of the roller 5b is equal to or less than the predetermined value, stops when the load is equal to or more than the predetermined value, and reverses when the rotational force in the reverse direction of the predetermined value or more is received.

Now, when feeding a sheet of paper in the direction of arrow P in the paper feed roller pair 5a, 5b with double feed prevention paper feed shown in FIG. 2, the roller 5a and the front surface of the paper, the back surface of the paper and the roller 5b. Since the friction coefficient of each is sufficiently large, the roller 5a
The roller 5b is rotated in the direction of arrow D by the rotational force in the direction of arrow B, and the sheet is conveyed in the forward direction (direction of arrow P).

However, when two sheets of paper are fed in the direction of arrow P, the coefficient of friction between the sheets is sufficiently smaller than the coefficient of friction between the rollers 5a and 5b and the sheets are slipped. As a result, the roller 5b rotates in the direction of arrow C, the paper in contact with the roller 5b is returned in the direction opposite to the arrow P, and only the paper in contact with the roller 5a is fed in the direction of arrow P. As a result, double feeding of paper is prevented.

4 to 6 show the pair of relay rollers 8a and 8b when the pair of feed rollers 5a and 5b with the double feed prevention function are driven.
This is a mechanism for preventing the feeding of the double-fed sheets (the sheet that should not be fed) by releasing the pressure of the relay roller pair 8a, 8b against the sheets by separating the sheet.

As shown in FIG. 4, the shaft 17 of the roller 5a and the shaft 23 of the roller 8b are gears 24 to 29.
Are joined by. The shafts 17 and 23 and the shafts of the gears 25 to 28 are rotatably supported by the frame 30, respectively.

As shown in FIG. 5, the shaft 17 and the gear 24 are connected via a one-way clutch 24a,
When the gear 29 rotates in the arrow J direction, the gear 24 idles in the arrow E direction even when the shaft 17 is stopped.

Further, the shaft 23 of the roller 8b is shown in FIG.
As shown in, the pin 29 and the snap ring 33 are coupled to the gear 29 through the bearing 31 slidably installed in the elongated hole 30a of the panel 30. The bearing 31 is a spring 3 that is coupled to the holes 30b and 30c of the panel 30.
4 by which the shaft 23 is always biased in the direction of arrow K (FIG. 5) and the roller 8b is
Press a. Therefore, when the roller 8a is driven, the roller 8b also rotates in the arrow J direction at the same time to feed the sheet.

At this time, the rotational force of the gear 29 is the gear 24.
Although the gear 24 is transmitted to the shaft 24, the gear 24 is rotated by the action of the one-way clutch 24a interposed between the gear 24 and the shaft 17 as described above.
Is not transmitted to.

Next, when the roller 5a is driven to feed the sheet, the gear 24 rotates in the direction of arrow E (FIG. 5). As a result, the gears 25 to 29 are respectively indicated by arrows F to
Rotate in the J direction. At this time, the rotational force of the gear 24 is transmitted to the gear J via the gears F to I. Then, the gear 28 rotates in the direction of the arrow I, and the rotational force causes a force in the direction opposite to the arrow K to act on the shaft 23, causing the spring 34 to rotate.
(FIG. 6) is stretched. As a result, the roller 8b is separated from the roller 8a, and the pressing force acting between the rollers 8a and 8b is removed. That is, when the sheet is started to be fed by the roller pair 5a and 5b, the roller pair 8a and 8b are separated and the sheet feeding operation is stopped.

Therefore, in the configuration of FIG. 1, when the paper feed roller 3 is driven, the paper is unloaded from the first paper feed cassette 1, and when the switch 15 detects the paper, the relay roller pair 8
The a and 8b are driven to feed the paper to the pair of paper feed rollers 5a and 5b with the double feed prevention function through the first feeding path 6.

When the switch 16 detects the sheet, the roller pairs 5a and 5b are driven to move the sheet to the registration roller pair 11
a, 11b. At this time, when the two sheets are conveyed in an overlapping manner, the upper one is fed to the registration roller pair 11a and 11b by the roller 5a, while the lower one is returned by the roller 5b. , The first conveying path 6 and the roller pairs 8a, 8 until the next sheet needs to be fed.
held during b.

When the half-moon type paper feed roller 4 is driven, the paper is unloaded from the second paper feed cassette 2. When the switch 16 detects the paper, the roller pair 5a, 5b is driven to move the paper to the registration roller pair. It is conveyed to 11a and 11b.

At this time, when two sheets are conveyed in an overlapping manner, the upper one is fed to the registration roller pair 11a, 11b by the roller 5a, while the lower one is fed by the roller 5b. Be pulled back. At this time, the paper feed roller 4
Since the flat portion faces the sheet in the cassette, the sheet is held in the second sheet feeding cassette 2 and the second transport path 7 until the next sheet needs to be fed.

FIG. 7 shows another embodiment of the present invention, which is shown in FIG.
It is a correspondence diagram, and this copying machine shows the third paper feed cassette 100.
A paper feed roller 101 for discharging the paper from the third paper feed cassette 100, a third conveyance path 102, and a pair of feed rollers 103a and 103b provided in the middle of the third conveyance path.
And a switch 104 for detecting whether or not the paper is in front (upstream) of the pair of feeding rollers 103a and 103b, but otherwise has the same configuration as that of the embodiment shown in FIG.

In the configuration shown in FIG. 7, the paper feed roller 10
When 1 is driven, the paper is unloaded from the third paper feed cassette 100, and when the switch 104 detects the paper, the feed roller pairs 103a and 103b are driven, and the paper is relayed via the third transport path 102 to the relay roller pair 8a. , 8b.

When the switch 15 detects the sheet, the relay roller pair 8a, 8b is driven to feed the sheet to the sheet feed roller pair 5a, 5b with the double feed prevention function through the first conveying path 6.
When the switch 16 detects the paper, the roller pair 5a, 5b
Is driven to convey the sheet to the pair of registration rollers 11a and 11b.

At this time, when the two sheets are conveyed in an overlapping manner, the lower one sheet is pulled back by the roller 5b (at this time, the roller pairs 8a and 8b are separated as described above). The paper is held on the roller pairs 8a and 8b and the first transport path 6 until the paper needs to be fed next time. The operation when the paper is unloaded from the first and second paper feed cassettes 1 and 2 is the same as that in the embodiment of FIG.

[0031]

According to the present invention, it is possible to prevent sheets fed from a plurality of cassettes from being fed by a single feeding mechanism.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is a detailed perspective view of a main part of FIG.

FIG. 3 is an exploded perspective view of a main part of FIG.

FIG. 4 is a detailed plan view of a main part of FIG.

5 is an explanatory diagram showing the operation of FIG. 4. FIG.

FIG. 6 is an exploded perspective view of a main part of FIG.

FIG. 7 is a view corresponding to FIG. 1 showing another embodiment of the present invention.

[Explanation of symbols]

 1 1st paper feed cassette 2 2nd paper feed cassette 3 Paper feed roller 4 Paper feed roller 5a, 5b Roller pair with double feed prevention function 6 1st conveyance path 7 2nd conveyance path 8a, 8b Relay roller pair 9 Photoreceptor drum 11a, 11b Registration roller

Claims (1)

[Claims] 1. A sheet feeding mechanism for an image forming apparatus, configured to feed a sheet discharged from a sheet feeding cassette by a sheet feeding roller to a registration roller pair via a sheet feeding roller pair with a double feed prevention function, A plurality of paper feed cassettes, a pair of paper feed rollers with a double feed prevention function, a plurality of conveyance paths for guiding a plurality of sheets to the paper feed roller pair with a double feed prevention function, and a double feed from the paper feed rollers A relay roller pair is provided in a transport path in which the transport distance to the paper feed roller pair with the prevention function is longer than the length in the paper feed direction, and the relay roller is provided when the paper feed roller pair with the double feed prevention function rotates. A sheet feeding mechanism for an image forming apparatus, characterized in that pairs are separated from each other.