JPH0330360Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a paper feeding device that feeds paper in image forming devices such as copying machines and printers, and in particular works with a paper feeding roller to feed paper into one sheet. This invention relates to an improvement of a retard pad for feeding sheets one by one.

[Prior Art] Image forming apparatuses such as copying machines and printers feed sheets of paper one by one and form images on the paper. In this case, various measures are taken to prevent multiple sheets of paper from being fed at once, so-called double feeding. That is, by providing a retard roller for the paper feed roller or by providing a retard pad and setting the frictional force between the paper and the retard pad or retard roller to be larger than the frictional force between the sheets, the sheets are separated and double feeding is prevented. That's what I do. In such a paper feeding device, as shown in Japanese Patent Publication No. 55-21696, for example, the paper introduction side portion of the retard pad is covered and held by a low friction member such as a metal plate or ABS resin. In addition to functioning as a holder to hold the retard pad, this holder also prevents paper being fed from stopping or folding the edges of the paper due to direct contact with the retard pad, which has a high coefficient of friction, and nipping the paper. It functions as a paper guide member to feed the paper smoothly.

[Problems to be solved by the invention] However, when this retard pad was used for a long period of time, the following problems occurred. That is, when a metal plate as described above is used as a paper guide member, as shown in FIG. 3, the retard pad is worn and scraped due to friction with the paper feed roller and paper, but it still covers the paper introduction part. Since the metal plate does not wear out, the contact pressure of the paper feed roller is mainly applied to the contact area between the metal plate and the paper feed roller, and the contact pressure at the nip between the paper feed roller and the retard pad is reduced. As a result, as the retard pad wears out and the pressure decreases, the sheets that have been separated at the nip cannot be separated properly, resulting in double feeding of the sheets. In addition, when ABS resin is used as a paper guide member, ABS resin is soft and easily abraded, so when paper is introduced, the ABS resin will wear out faster than the retard pad wears out due to collisions caused by the edges of the paper. As shown, it is scraped and the paper introduction side of the retard pad is no longer sufficiently covered. As a result, when the paper is introduced, the leading edge of the paper may be folded or jammed, making it difficult to feed the paper properly.

This invention was made in view of the above-mentioned problems and aims to provide a paper feeding device that can feed paper stably over long periods of use.

[Means and operations for solving the problems] In order to solve the above problems, the paper feed device of the present invention includes a paper feed roller and a paper feed roller that feeds sheets one sheet at a time in pressure contact with the paper feed roller. The retard pad is provided with a retard pad for feeding the retard pad, and a paper guide member that is attached to the paper entry side surface of the retard pad and has approximately the same abrasion resistance as the retard pad due to contact with the paper feed roller.

More preferably, the retard pad is made of isoprene rubber with a rubber hardness of 70°±6°, and the paper guide member is made of any one of polyester, polyvinyl fluoride, polyimide, polyvinyl chloride, and polyacetate. Thickness 0.02~0.2
Constructed of mm plastic film.

With this configuration, the paper to be fed is introduced into the nip between the paper feed roller and the retard pad by the paper guide member with almost no friction. In addition, if the retard pad wears out during long-term use and the paper feed roller comes into direct contact with the paper guide member, the paper guide member itself will wear to the same extent as the retard pad.
The contact pressure between the paper feed roller and the retard pad does not decrease significantly.

Furthermore, when the retard pad and the paper guide member are made of the above-mentioned isoprene rubber and the above-mentioned plastic film, respectively, the retard pad and the paper guide member wear to the same extent due to contact with the paper feed roller, so the paper feed roller and the retard pad The pressure of contact with the paper does not decrease significantly, and the plastic film is hard enough not to be scraped by collision with the edge of the paper, so the plastic film will not be worn out by collision with the paper. There's nothing to do.

[Example] An example of this invention will be described with reference to FIGS. 1 and 2.

The paper mounting table 1 is pushed up by a biasing means (not shown) so that the paper 2 placed thereon comes into contact with the paper feed roller 3 with a predetermined pressing force. A retard pad 4 is disposed in pressure contact with the paper feed roller 3 downstream of the location where the paper feed roller 3 and the paper 2 are in contact with each other. The surface of the retard pad 4 that comes into pressure contact with the paper feed roller 3 is formed into a gentle arc, and the paper introduction side is also formed into an arc-shaped curved surface so that the paper 2 is smoothly fed into the nip section, and the bottom surface is formed by a holder. 5 with adhesive or the like. The surface of the paper introduction side of the retard pad 4 has a paper guide member 6 with a thickness of 0.02 to 0.2 mm, preferably 0.05 to 0.1 mm.
A plastic film (for example, polyester film) is attached. This plastic film 6 as a paper guide member is attached to the paper feed roller 3.
4 on the upstream side of the nip between the retard pad 4 and the retard pad 4.
It is attached so as to cover the upstream end from the mm position. The paper feed device configured in this way is
Support frame 7 fixed to the main body of the paper feeder (not shown)
The locking piece 5 of the holder 5 is inserted into the support hole 7a provided in the
a has been inserted. Further, a support stand 8 fixedly installed on the paper introduction side of the bottom surface of the support frame 7 and the top of a spring 9 fixedly installed downstream thereof are in contact with a holder 5 fixed to the retard pad 4. That is, the retard pad 4 is biased in the direction of arrow A in the figure by the spring 9 using the support base 8 that is in contact with the holder 5 as a fulcrum so that it comes into pressure contact with the paper feed roller 3, and the locking piece 5a of the holder 5 is pressed against the paper feed roller 3. By being inserted into the support hole 6a and locked, it is supported so as to be detachable and swingable up and down. The feeding paper roller 3 is made of isoprene rubber having a rubber hardness of 40°±5°, and the retard pad 4 is made of isoprene rubber having a rubber hardness of 70°±6°.

The operation based on the above configuration will be explained. The paper 2 placed on the paper loading table 1 and in contact with the paper feed roller 3 slides smoothly over the plastic film affixed to the retard pad 4 as a paper guide member 6 by the rotation of the paper feed roller 3 in the direction of the arrow. The paper is fed to the nip between the retard pad 4 and paper feed roller 3. The paper 2 fed to the nip section is sent downstream of the nip section by the rotation of the paper feed roller 3 in such a manner that the retard pad 4 pressed against the paper feed roller 3 is pushed down by a spring 9. At this time, if two or more sheets of paper fed to the nip overlap, the frictional force between the sheets will increase in the order of paper 2 and retard pad 4, and paper 2 and paper feed roller 3. Since the pressure and materials of the paper feed roller 3 and the retard pad 4 are set, the paper 2 that is double fed when passing through this nip portion is separated and the paper is fed one by one with certainty. When this device is used for a long period of time, the retard pad 4 rubs against the paper feed roller 3 in an arcuate manner.
Then, the paper feed roller 3 feeds the plastic film 6.
When it comes into contact with the retard pad, this plastic film 6 is also worn to the same extent as the retard pad, and is therefore deformed by wear as shown in FIG. Here, the thickness of the plastic film attached as the paper guide member 6 is
It is thin, preferably 0.02 to 0.2 mm, preferably 0.05 to 0.1 mm, wears to the same extent as the rubber used for retard pad 4, and is hard enough not to be scraped by the edge of the paper when paper is inserted. A plastic film was selected that would not allow the ends of the plastic film to stretch due to friction when the film is pressed or comes into contact with the paper feed roller 3. Therefore, it is possible to prevent a change in the contact pressure at the nip portion due to the paper guide member 6 coming into contact with the paper feed roller 3 and pushing up the paper feed roller 3. Furthermore, since the edge portion of the paper is less likely to be scraped when the paper enters, folding or jamming of the leading edge of the paper is less likely to occur. Furthermore, since it is difficult to stretch, there is no possibility that the end of the plastic film will be stretched to the nip, resulting in poor paper separation and double feeding.

When feeding paper using a polyester film (Scotch tape #850, thickness 0.05 mm, manufactured by 3M Co., Ltd.) as a plastic film attached as the paper guide member 6, double feeding of paper occurred when more than 300,000 sheets were fed. Paper is fed reliably without paper folding, paper folding, jamming, etc., and approximately
Polyvinyl fluoride, polyimide, vinylidene chloride, hard vinyl chloride, and acetate films exhibit significantly better durability than the approximately 100,000 sheets produced using polytetrafluoroethylene (Teflon). Almost the same reliable paper feeding was achieved when using .

[Effects of the invention] According to the paper feeding device of this invention, a thin plastic film having appropriate characteristics is pasted on the surface of the paper introduction side of the retard pad, so that the pressure contact between the paper feeding roller and the retard pad is maintained even after long-term use. There is little pressure change, paper folding or jamming at the leading edge of the paper is less likely to occur, and it is possible to always perform stable paper separation and paper feeding without double feeding over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view for explaining an embodiment of the paper feeding device according to this invention, Fig. 2 is a sectional view of main parts showing a worn state of the retard pad of the paper feeding device according to this invention, and Fig. 3 is a conventional one. In the example, a sectional view showing the state of wear of the retard pad when a metal cover is used as the paper guide member, and Figure 4 shows the state of wear of the paper guide member when ABS resin is used for the paper guide member in the conventional example. FIG. 3... Paper feed roller, 4... Retard pad, 6
...Paper guide member.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A paper feed roller 3; a retard pad 4 that feeds paper one sheet at a time in pressure contact with the paper feed roller 3; A paper feeding device characterized by having a paper guide member 6 which has approximately the same abrasion resistance as the retard pad 4 due to contact with the paper feeding roller 3. 2 The retard pad 4 is made of isoprene rubber with a rubber hardness of 70°±6°, and the paper guide member 6 is made of polyester, polyvinyl fluoride, polyimide, polyvinyl chloride,
The paper feeding device according to claim 1, which is a plastic film made of any one of polyacetate and having a thickness of 0.02 to 0.2 mm.