JPH05201557A - Paper feed device - Google Patents

Abstract

PURPOSE:To surely prevent overlapping feed of sheets, irrespective of a number of sheets stacked on a pressure plate. CONSTITUTION:A pressure plate 30 on which sheets S are stacked, is divided into a rotary part 30a adapted to be rotated about a fulcrum 30d, and a parallel moving part 30b which is urged by a compression spring 35 so as to be moved parallel, the parts 30a, 30b being rotatably coupled together by means of a coupling part 30c. Meanwhile, a receiving member 40 for receiving the uppermost one of the sheets S on the pressure plate 30 at a predetermined height, is disposed between the coupling part 30c and a paper feed roller 22. During feed of the sheets S, when the number of sheets S remaining on the pressure plate 30 becomes less, the parallel moving part 30b is moved upward parallel by means of the compression spring 35, and accordingly, the uppermost one of the sheets S is received by a receiving member 40 so as to maintain the feed-out direction of the sheets S at a predetermined angle alpha at which the sheets S may be easily loosened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to printing, transfer, copying,
It can be applied to a sheet processing apparatus that performs printing or the like. More specifically, the present invention relates to such a sheet processing apparatus, which separates stacked sheets one by one and sequentially feeds the uppermost sheet to the processing apparatus main body.

[0002]

2. Description of the Related Art Conventionally, in this type of sheet feeding device, as shown in FIG. 10, for example, sheets S are stacked on a pressure plate 2 in a sheet feeding cassette 1, and the pressure plate 2 is pressed by a pressure spring 3. It is urged to rotate about the fulcrum 2a, and the leading end of the uppermost sheet S is pressed against the sheet feeding roller 4. Further, the separation pad 6 is pressed against the paper feed roller 4 at a constant angle by being biased by the biasing spring 5.

Then, at the time of feeding the sheet, the sheet feeding roller 4
And the stacked sheet S is fed out in the direction of arrow a in the figure.
At this time, even if a plurality of sheets S are fed out in an overlapping manner, the leading ends of the sheets S are abutted against the pad surface 6a of the separation pad 6 to separate them one by one, and the sheets S are sequentially separated from the uppermost sheet S. I was sending it out.

[0004]

However, in the above-described conventional sheet feeding device, as shown in FIG. 9, when the number of sheets stacked on the pressure plate 2 is large, the front end of the sheet S is the pad surface 6.
However, as shown in FIG. 8, the rotation angle θ of the bottom plate 2 gradually increases as the sheet stacking amount decreases, and the angle α formed by the bottom plate 2 and the pad surface 6a is increased. It gets smaller and smaller. Therefore, when the number of stacked sheets is small, it is not possible to effectively separate the plurality of sheets S that are fed out in a stacked manner by the separation pad 6, and as a result, it is not possible to reliably prevent the double feeding of the sheets.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reliably prevent double feeding of sheets in the above-described sheet feeding device regardless of the amount of sheets stacked on the pressure plate.

[0006]

Therefore, what is stated in claim 1 is, for example, as shown in the following illustrated embodiment,
The sheet S is stacked on the pressure plate 30, and the pressure plate 30 is urged by an urging member such as a compression spring 35 to rotate about a fulcrum 30d, and the uppermost sheet S is fed. The paper feed roller 22 is pressed against the paper roller 22, and the paper feed roller 22 is rotated and pressed against it.
In the sheet feeding device 20 that sequentially feeds out the uppermost sheet S, the pressure plate 30 is moved in parallel with a rotating portion 30a that rotates around the fulcrum 30d, and a parallel movement that receives the biasing force of the biasing member. The moving part 30b is divided into two parts, which are rotatably connected to each other, and the connecting part 30c.
A receiving member 40 that receives the uppermost sheet S is provided between the sheet feeding roller 22 and the sheet feeding roller 22.

According to the second aspect, for example, FIG.
The sheet feeding device 2 according to claim 1, as in the embodiment shown in FIG.
0, the parallel displacement part 30 is used as the biasing member.
A first compression spring 50 for urging the tip side of b
And a second urging member such as the second compression springs 51, 51 for urging the connecting portion 30c side.

According to a third aspect of the present invention, for example, as in the embodiment shown in FIG. 7, in the sheet feeding device 20 according to the second aspect, the first urging member is connected to the second urging member. It is characterized by being stronger than the biasing force.

According to a fourth aspect of the present invention, for example, as shown in the illustrated embodiment, the sheet feeding device 20 according to the first aspect is provided with a rotatable roller 55 as the receiving member. And

[0010]

According to the first aspect of the present invention, when the stacking amount of the sheets S on the pressure plate 30 becomes small at the time of feeding the sheet, the rotating portion 30a is rotated accordingly, and the parallel moving portion is moved by the biasing member. 30b is moved in parallel to receive the uppermost sheet S by the receiving member 40, and the feeding direction of the uppermost sheet S is always set to the sheet S regardless of the amount of stacked sheets.
Hold at a constant angle for easy handling.

According to the second aspect of the present invention, the first biasing member and the second biasing member bias the tip end side of the parallel displacement portion 30b and the coupling portion 30c side without a large inclination.

According to the third aspect of the invention, the uppermost sheet S is strongly pressed against the sheet feeding roller 22 by the receiving member 40.

According to the fourth aspect, the roller 55 receives the uppermost sheet S on the pressure plate 30.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a laser printer provided with a sheet feeding device according to an embodiment of the present invention, and shows the overall schematic structure of the internal mechanism thereof. Reference numeral 10 in the figure denotes the apparatus main body. A belt-shaped photosensitive member 12 is provided in the main body 10 of the apparatus at substantially the center thereof. Around the photoconductor 12, a charging device 13, a developing device 14, a transfer device 15, and a transfer device 15 in this order in the driving direction shown by the arrow in FIG.
The cleaning device 16 is arranged. An optical writer 17 is arranged above the charger 13 and the cleaner 16.

Further, the paper feeder 20 of the present invention is provided below the apparatus main body 10. A paper feed cassette 21 accommodating sheets S is detachably attached to the paper feed device 20. Then, a paper feed roller 22 made of rubber is provided on the upper right side of the paper feed cassette 21 in FIG.

In the illustrated laser printer, however, the sheet S in the sheet feeding cassette 21 is fed in the direction of arrow A in FIG. Stop. Then, the sheet S is conveyed to the lower side of the photoconductor 12 by the registration roller pair 23 at a timing. The photoconductor 12 is driven in the clockwise direction indicated by the arrow, and at that time, the surface thereof is uniformly charged by the charger 13, and the laser beam L from the optical writing device 17 is irradiated to the photoconductor 12 to electrostatic latent. Form an image. This latent image is visualized by toner when passing through the position of the developing device 14. Then, this visible image is transferred by the transfer device 15 onto the upper surface of the sheet S conveyed to the lower side of the photoconductor 12. Then, after the image transfer, the sheet S is guided by the conveyance guide 24 and conveyed to the fixing device 25, and the transfer image is fixed by the fixing device 25. Then, the sheet S that has exited the fixing device 25 is further conveyed by the sheet ejection roller 26 and ejected in the direction of arrow B or C in FIG.

On the other hand, after the image transfer, the photoconductor 12 is cleaned by the cleaning device 16 to remove the residual toner, and then the static eliminator 2 is used.
Remove electricity at 7.

By the way, the sheet feeding device 20 will be described in detail in FIG.
As shown in, the pressure plate 30 on which the sheets S are stacked is arranged in the paper feed cassette 21. The pressure plate 30 is divided into a plate-shaped rotating portion 30a and a parallel moving portion 30b, and the connecting portions are rotatably connected to each other by a connecting portion 30c. Then, a fulcrum 30d is provided at the base end of the rotating portion 30a, and the rotating portion 30a is rotatably mounted in the paper feeding cassette 21 about the fulcrum 30d.

Further, in the paper feeding device 20, a compression spring (biasing member) 35 is provided below the parallel moving portion 30b of the pressure plate 30.
To provide. Then, the uppermost sheet S loaded with the parallel moving portion 30b is urged by the compression spring 35 and pressed against the sheet feeding roller 22.

On the other hand, on the upper side of the pressure plate 30, the connecting portion 30 is provided.
The receiving member 40 that receives the uppermost sheet S is fixed at a predetermined height position between c and the paper feed roller 22. Receiving member 40
Is a plate-shaped member having a small friction coefficient, such as metal or plastic, having a U-shaped cross section.

Further, the paper feeding device 20 includes the paper feeding cassette 2
A pad holder 44 having a T-shaped cross section is provided on the right side of 1. The pad holder 44 has a separation pad 45 attached to the upper part thereof. Then, the pad holder 44 is urged by the urging spring 46 to press the separation pad 45 against the paper feed roller 22. The separation pad 45 is provided so as to be inclined at a predetermined angle with respect to the feeding direction D so that the leading end of the separation pad 45 abuts the pad surface 45a when the sheet S is fed.

However, in the above-described paper feeding device 20, when a plurality of sheets S are temporarily fed by the paper feeding roller 22 during paper feeding, the sheets S are separated and separated by the separation pad 45 one by one. Meanwhile, the uppermost sheet S is sequentially sent out. After that, when the sheet stacking amount on the pressure plate 30 gradually decreases in accordance with the delivery amount of the sheet S, the parallel moving portion 30b is translated upward by the biasing force of the compression spring 35, as shown in FIG. The uppermost sheet S is received by the receiving member 40. Then, the pressure plate 3
The feed-out direction D of the sheet S is always kept at a constant angle α with which the sheet S can be easily separated with respect to the pad surface 45a, regardless of the amount of sheets stacked on the sheet 0.

In the illustrated embodiment described above, the compression spring 35 is provided at a lower position between the sheet feeding roller 22 and the receiving member 40 to urge the parallel moving portion 30b. However, in the paper feeding device 20 of the present invention, as shown in, for example, FIGS. 4 and 5, the first compression spring (first biasing member) 50 is provided below the paper feeding roller 22 and the parallel moving portion is provided. The second compression spring (second urging member) 51 is provided below the receiving member 40 while urging the distal end side of 30b, and urging the connecting portion 30c side of the parallel moving part 30b. You can also Then, the first compression spring 50 and the second compression spring 5
With 1, the parallel displacement part 30b is urged in a well-balanced manner.

In the sheet feeding device 20 of the present invention, the first compression spring 50 and the second compression spring 51 as described above are used.
In the case of biasing the translation unit 30b, as shown in FIG. 6, the biasing force of the first compression spring 50 and P _1, when the urging force of the second compression spring 51 and the P _2, P ₁ > P ₂ is preferable.

When the friction coefficient between the uppermost stacked sheet S and the paper feed roller 22 is μ ₁ and the friction coefficient between the sheet S and the receiving member 40 is μ ₂ , the paper feed roller 22
The conveying force F ₁ at the time of feeding the sheet due to is μ ₁ P ₁ ,
The resistance force F ₂ of the receiving member 40 at that time is μ ₂ P ₂ . Then, P ₁ > P ₂ and μ ₁ > μ _2, so F
₁ > F ₂ , and as a result, at the time of feeding the sheet, the influence of the resistance of the receiving member 40 can be reduced and the sheet S can be smoothly fed by the feed roller 22.

In the illustrated embodiment described above, a plate member is used as the receiving member 40, but as shown in FIG. 7, for example, a roller 55 rotatably provided around a shaft 55a.
Alternatively, the roller 55 may be used to receive the uppermost sheet S.

[0027]

Therefore, according to the first aspect of the present invention, when the sheets are sent out, the parallel moving portion is moved in parallel as the stacking amount of the sheets on the pressure plate decreases, and the uppermost sheet is received by the receiving member. Since the receiving and feeding direction of the sheets is always kept at a constant angle for effectively separating the sheets, it is possible to reliably prevent the double feeding of the sheets regardless of the amount of sheets stacked on the pressure plate.

According to the second aspect, the first urging member and the second urging member can urge the parallel displacement portion without a large inclination.

According to the third aspect of the present invention, since the front end side of the parallel moving portion is biased more strongly than the connecting portion side, it is possible to reduce the resistance of sheet feeding by the sheet feeding roller.

According to the fourth aspect, since the uppermost sheet is received by the roller, the resistance of the sheet feeding by the sheet feeding roller can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a sheet feeding device according to an embodiment of the present invention in a state where a large number of sheets are stacked on a pressure plate.

FIG. 2 is an explanatory configuration diagram of a state in which the amount of sheets stacked on the pressure plate is reduced.

FIG. 3 is an overall schematic configuration diagram of an internal mechanism of a laser printer including the paper feeding device.

FIG. 4 is a schematic configuration diagram showing an example of urging the leading end side and the connecting side of the parallel moving part of the pressure plate of the paper feeding device according to another embodiment of the present invention.

FIG. 5 is a perspective view thereof.

FIG. 6 is a state explanatory view of a paper feeding device which is still another embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a sheet feeding device according to still another embodiment of the present invention and using a roller as a receiving member.

FIG. 8 is a state explanatory view showing a conventional sheet feeding device in a state where a sheet stacking amount on a pressure plate is small.

FIG. 9 is a state explanatory view showing the conventional sheet feeding device with a large amount of sheets stacked on a pressure plate.

FIG. 10 is a configuration diagram of the conventional paper feeding device.

[Explanation of symbols]

 20 Paper Feeding Device 22 Paper Feeding Roller 30 Pressure Plate 30a Rotating Part 30b Parallel Moving Part 30c Connecting Part 30d Support Point 35 Compression Spring (Biasing Member) 40 Receiving Member 45 Separation Pad 50 First Compression Spring (First Biasing Spring) Member) 51 second compression spring (second biasing member) 55 roller (receiving member) S sheet

Claims (4)

[Claims] 1. A sheet is stacked on a pressure plate, and the pressure plate is biased by a biasing member to rotate about a fulcrum, and the uppermost one of the stacked sheets is pressed against a sheet feeding roller, 1 with a separation pad that rotates the paper feed roller and presses against it
In a sheet feeding device that separates the sheets one by one and sequentially feeds the uppermost sheet, a rotating unit that rotates the pressure plate about the fulcrum and a parallel unit that receives the biasing force of the biasing member and moves in parallel. A sheet feeding device, which is divided into a moving section, which is rotatably coupled to each other, and which is provided with a receiving member for receiving the uppermost sheet between the coupling section and the sheet feeding roller. 2. The urging member comprises a first urging member for urging the distal end side of the parallel displacement portion and a second urging member for urging the connecting portion side. 1. The paper feeding device according to 1. 3. The sheet feeding device according to claim 2, wherein the first biasing member is stronger than the biasing force of the second biasing member. 4. The sheet feeding device according to claim 1, wherein the receiving member includes a rotatable roller.