KR100465327B1 - Paper feeding apparatus having a unit for priventing pick-up error - Google Patents

Abstract

The present invention relates to a paper sheet feeding apparatus having a function of preventing heavy feeding of two or more sheets of paper simultaneously fed to an electrophotographic image forming apparatus. The paper feeding device with a feed prevention function according to the present invention is provided with a cassette on which a plurality of sheets are stacked, a paper separating member installed at the front end of the cassette and preventing the tip of the sheets being conveyed, and installed at the top of the cassette. And a pickup roller which rotates while pressing the upper surface of the upper paper and transfers the papers, and an anti-feeding means installed on the rear end of the cassette and pressing the rear ends of the papers loaded under the top paper to be conveyed. . Here, the feeding prevention means is characterized in that it comprises a pressing member for pressing the rear end of the paper, and an elastic member for pressing the pressing member.

Description

Paper feeding apparatus having a unit for priventing pick-up error}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a paper feed apparatus for use in an electrophotographic image forming machine and the like, and more particularly, to a paper feed apparatus having a feeding function for preventing feeding during feeding.

An electrophotographic image forming machine forms an electrostatic latent image on a photosensitive member by using a laser beam or the like, and then develops it with a developer and transfers it onto a paper to print. Such an electrophotographic image forming machine is generally provided with a sheet feeding apparatus capable of continuously feeding the sheet so as to enable continuous printing.

Such a paper feeder stacks a plurality of sheets in a cassette and separates the stacked sheets one by one from the top sheet and transfers them to the printing unit. Various apparatuses capable of doing such work have been devised, but generally, a dam type or a finger or claw type paper feeder having a low manufacturing cost is used.

1 shows a front portion of the paper feeder to explain the principle that the paper is separated and fed one by one in the finger-type paper feeder.

Referring to Fig. 1, the force acting on the paper 5 loaded in the cassette includes the pressing force P by the pickup roller 1 and the repulsive force R by the finger portion 3 as the paper separating member.

Here, in order to generate the pressing force P, the following two methods are usually used. One is to rotate the pick-up roller downward to the height of the paper centered on one point of the image forming machine body, and the pick-up roller presses the paper. The plate is elastically supported upward so that the paper presses the pickup roller.

In this state, the following conditions must be satisfied in order for the sheets loaded in the cassette to be separated and fed one by one.

Here, P is the pressing force by the pickup roller 1, R is the repulsive force in the finger portion (3), Is the coefficient of friction between the paper 5 and the pickup roller 1, Is the coefficient of friction between the sheets 5,6.

therefore, Is a frictional force generated between the pick-up roller 1 and the uppermost sheet 5 by the pressing force, and is a conveying force of the sheet, Is the friction force generated between the top sheet 5 and the second sheet 6 below by the pressing force. Therefore, the feed force by the pickup roller 1 Repulsive force R by this finger portion 3 and frictional force generated between the top sheet 5 and the bottom sheet 6 If the sum is larger than the sum, the top sheet 5 is separated and conveyed in the feeding direction. At this time, the friction force between the uppermost sheet of paper 5 and the lower sheet of paper 6 It must be smaller than the repulsive force R by this finger part 3.

If friction coefficient between media To increase the friction between the top sheet (5) and the bottom sheet (6) When larger than the repulsive force R by this finger part 3, the heavy feed in which the uppermost sheet | seat 5 and the immediately lower sheet | seat 6 are fed together arises.

That is, in the conventional dam-type or finger-type paper feeder, when the paper has a different friction coefficient or a large electrostatic force, there is a problem in that multiple feeds occur without feeding the sheets one by one.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a paper feeding device having a feed prevention function to prevent heavy feedings during feeding while maintaining a dam method or a finger method at low cost. Its purpose is to.

1 is a conceptual diagram showing a state in which the paper is separated from the paper feeder according to the prior art,

Figure 2 is a cross-sectional view showing a sheet feeding apparatus with a heavy feed prevention function according to the present invention.

3 is a view showing an embodiment of the pressing member of FIG.

4 is a view showing another embodiment of the pressing member of FIG.

* Description of the symbols for the main parts of the drawings *

10; Cassette 11; Paper separation member

13; Paper 20; Pick up roller

21; Picking arm 30; Medium Congestion Prevention

31,31 '; Pressing member 33; Elastic member

In order to achieve the above object, a paper feeding device having a non-feed function according to the present invention includes a cassette on which a plurality of sheets are stacked, and a paper separating member installed at a front end of the cassette and blocking the tip of the sheets to be conveyed. And a pickup roller which is installed on the upper side of the cassette and rotates while pressing the upper surface of the top sheet to convey the sheets, and a middle feed that presses the rear end of the sheets loaded below the top sheet to be conveyed and installed at the rear of the cassette. It characterized in that it comprises a prevention means.

Here, the feeding prevention means is characterized in that it comprises a pressing member for pressing the rear end of the paper, and an elastic member for pressing the pressing member. At this time, the pressing member is preferably formed with an inclined surface corresponding to the inclination of the step shape formed by the rear ends of the sheets when the sheets are conveyed by the pickup roller. In particular, the inclined surface is preferably shaped into a step shape corresponding to the steps formed by the rear ends of the sheets. In addition, it is preferable that the elastic member uses a compression coil spring.

In addition, the feeding prevention means is characterized in that the pressing force for pressing the rear end of the paper is larger than the electrostatic force generated between the top sheet and the bottom sheet.

Hereinafter, with reference to the accompanying drawings will be described in more detail with respect to a preferred embodiment of a paper sheet feeding apparatus having a feed prevention function according to the present invention.

Referring to FIG. 2, the paper sheet feeding apparatus according to the present invention includes a cassette 10, a paper separating member 11, a pickup roller 20, and a feeding prevention means 30.

The cassette 10 loads a plurality of sheets 13 and supports the sheet separating member 11 and the conveyance preventing means 30.

The paper separating member 11 is installed at the front end of the cassette 10 and exerts a repulsive force on the conveyed paper so that the loaded paper is separated one by one. The paper separating member 11 has a dam method as shown in FIG. 2 and a finger method as shown in FIG. 1. This finger is also called claw.

The pickup roller 20 is installed at one end of the picking arm 21 hinged to the main body (not shown) of the electrophotographic image forming machine, and rotates while pressing the upper surface of the loaded paper 13. Therefore, even if the conveyance of the paper is continued and the stacking height of the paper 13 is lowered, the pickup roller 20 pivots downward about the other end of the picking arm 21 to continue to press the top sheet.

The anti-feeding means 30 is to prevent the lower sheet of paper from being conveyed together when the upper sheet of paper is conveyed by the pickup roller 20, and includes a pressing member 31 and an elastic member 33.

The pressing member 31 is installed at the rear end of the cassette 10 and presses the rear end of the paper 13 so that the lower second paper is not conveyed together when the uppermost paper is transferred. As for the pressing member 31, it is preferable to form the contact surface with the paper 13 as the inclined surface 31a like FIG. The reason is that when the uppermost sheet is transported by the pickup roller 20, a certain number of sheets of paper pressurized by the pressing force are transferred by a certain amount in the paper feeding direction, so that the rear end of the predetermined number of sheets is inclined. Because it is achieved. Therefore, it is most preferable to set the inclined surface of the pressing member to the step shape 31b corresponding to the step shape of the paper as shown in FIG.

The elastic member 33 elastically supports the pressing member 31, so that the pressing member 31 can press the rear end of the paper. Therefore, the elastic member 33 may be used a spring or the like to apply a pressing force. At this time, the elastic member 33 may be a compression spring may be used, depending on the arrangement of the elastic member 33 and the pressing member 31, a tension spring may be used.

At this time, when the inclined surface 31a of the pressing member presses only the rear end portion of the lower sheet of paper without pressing the rear end portion of the top sheet of paper, the pressing force applied to the rear end portion of the sheet by the anti-feeding means 30 is between the sheets. The lower sheet is set to be larger than the force to be conveyed with the upper sheet by the electrostatic force. In addition, when the inclined surface 31a of the pressing member presses the rear end of the top sheet at the same time, the pressing force applied to the rear end of the sheet by the anti-feeding means 30 should be set within a range satisfying the above expression (1). do.

Hereinafter, with reference to the accompanying drawings will be described the operation of the sheet feeding apparatus having a feed prevention function configured as described above.

When the pickup roller 20 rotates, the sheet moves toward the sheet separating member 11 by the friction force between the pickup roller 20 and the top sheet. At this time, due to the friction force between the sheet and the sheet, a certain number of sheets below the sheet from the top sheet are conveyed toward the sheet separating wall 11 together with the sheet at the top. That is, the top sheet is moved the most and the bottom sheet is moved less than the sheet on it. Therefore, the rear end of the paper forms a stepped shape in which the height of each end corresponds to the paper thickness as shown in FIGS. 3 and 4.

When the sheet 13 is conveyed by the pickup roller 20, the inclined surface 31a of the pressing member 31 presses the rear end of the inclined sheet by the elastic force of the elastic member 33. Therefore, since the rear end portion is pressed by the pressing member 31, the second lower sheets can be prevented from being conveyed directly by the uppermost sheet.

As described above, according to the sheet feeding apparatus with the feed preventing function according to the present invention, the second sheet is placed at the bottom because the rear end portions of the sheets stacked below the top sheet are pressed by the pressing member of the feed preventing means. No heavy feeds that are transported with the paper above will occur.

The present invention is not limited to the above-described specific embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the invention as claimed in the claims. Such changes are intended to fall within the scope of the claims.

Claims (9)

A cassette in which a plurality of sheets of paper are stacked; A paper separating member installed at a front end of the cassette and blocking a front end of the sheets to be conveyed; A pickup roller which is installed on the upper side of the cassette and rotates while pressing the upper surface of the top sheet to transfer the sheets; and, It is installed on the rear end of the cassette, and the non-feeding means for pressing the rear end of the paper loaded under the top paper to be transported; The conveyance preventing means, A pressing member for pressing the rear ends of the sheets; And, And an elastic member for applying a pressing force to the pressing member. delete The method of claim 1, wherein the pressing member, And a sheet feeding device having a feed preventing function when the sheets are conveyed by a pick-up roller. The method of claim 3, wherein the inclined surface, And a paper feed prevention function, characterized in that it is molded in a step shape corresponding to the steps formed by the rear ends of the paper sheets. The method of claim 1, wherein the elastic member, Paper feeding device having a feed prevention function, characterized in that the coil spring. The method of claim 1, wherein the conveyance preventing means, And a pressing force for pressing the rear ends of the sheets is greater than the electrostatic force generated between the top sheet and the bottom sheet. A cassette in which a plurality of sheets of paper are stacked; A paper separating member installed at a front end of the cassette and blocking a front end of the sheets to be conveyed; A pickup roller which is installed on an upper side of the cassette and rotates while pressing an upper surface of a top sheet to transfer the sheets; A pressing member which is installed at a rear end of the cassette and presses rear ends of the sheets under the top sheet to be conveyed; And An electrophotographic image forming apparatus comprising a sheet feeding apparatus having an anti-feed function, including an elastic member for applying a pressing force to the pressing member. The method of claim 7, wherein the pressing member, And an inclined surface corresponding to a stepped inclination formed by a rear end of the sheets when the sheets are transferred by a pickup roller. The method of claim 7, wherein the elastic member, Electrophotographic image forming apparatus, characterized in that the coil spring.