JP2007031026A - Sheet double-feeding prevention device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet double-feeding prevention device capable of suppressing vibration at paper feeding without impairing motion and attachment/detachment property of a roller holder. <P>SOLUTION: The sheet double-feeding prevention device has a feed roller 3; a retard roller 1 pressure-contacted with the feed roller 3 and constituted such that it is rotated when a torque more than a certain value is received by a torque limiter; a roller holder 2 for retaining a shaft 23 of the retard roller 1 so as not to be rotated; a bearing part 34 provided on the roller holder 2 and having a circular inner surface; a fulcrum shaft 37 separately provided on an attachment part of the roller holder 2 and turnably supporting the roller holder 2 by being connected to the bearing part 34; and an urging means 6 for urging the roller holder 2 so as to pressure-contact the retard roller 2 with the feed roller 1. The fulcrum shafts 36, 37 have notched shapes 36a, 37a at a portion where it is contacted by force in a paper conveying direction acting on the roller holder 2 at paper feeding and own weight of the roller holder 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for preventing double feeding of sheet materials such as originals and recording paper, and an image forming apparatus provided with the same used in a paper feed cassette and an automatic document feeder in an image forming apparatus such as a copying machine, a printer, and a fax machine. It is about.

  First, a conventional sheet double feed prevention device described in Patent Document 1 will be described.

  4 is a schematic perspective view of a recording paper feeding portion of the paper feed cassette, FIG. 5 is a plan view showing a configuration of a retard roller, and FIG. 6 is a diagram showing a configuration of a roller holder that holds the retard roller. 7 is a perspective view in which a roller holder is mounted on the paper feed cassette, FIG. 8 is a perspective view of a roller holder mounting portion of the paper feed cassette, and FIG. 9 is a schematic side view showing a configuration around the roller holder. FIG. 10 is an enlarged view of the main part of FIG. 9 and shows the movement of the roller holder during paper feeding.

  In the figure, 1 is a retard roller, 2 is a roller holder for holding the retard roller 1, and 3 is a sheet of recording paper or the like (hereinafter simply referred to as recording paper) provided on the main body side of a copying machine, printer, FAX or the like. The feed roller 4 constituting the transport unit 4 also constitutes a part of the transport unit, and the pick-up roller 5 for feeding the recording paper 5 placed on the recording paper placing table 8 of the paper feed cassette 7 to the feed roller 3 side. Recording paper, 6 is a spring for pressing the roller holder 2 toward the feed roller 3, 7 is a paper feed cassette, and 8 is a recording paper placing table.

  In the sheet double feed prevention device configured as described above, the retard roller 1 is a fixed portion having notches 21 and 22 for snap-fitting the roller holder 2 on the left and right sides of the shaft 20 as shown in FIG. 23 and 24 are provided. The shaft 20 is configured to be fitted with a torque limiter 25 and a rubber roller portion 26 into which rubber made of EPDM or the like is press-fitted into an extension portion of the torque limiter 25. And when the torque more than the torque value which the torque limiter 25 generate | occur | produces is applied to the rubber roller part 26, it can be rotated in the arrow 27 direction.

  As shown in FIG. 6, the roller holder 2 includes snap-fit portions 30 and 31 that receive and fix the fixing portions indicated by 23 and 24 in FIG. 5 of the retard roller 1, and the roller holder 2 presses the spring 6. Conveying guide portions having bearing portions 33 and 34 that serve as pivots when receiving pressure on both sides and connecting the snap-fit portions 30 and 31 and the bearing portions 33 and 34 and guiding the recording paper 5. 32 and a spring receiver 35 for receiving the pressing force of the spring 6 shown in FIG.

  Further, as shown in FIG. 8, a pair of opposed upper and lower surfaces are formed in a horizontal plane in the recess 41 provided near the center of the recording paper conveyance path 40 of the paper feed cassette 7 indicated by 41 in FIG. In addition, fulcrum shafts 36 and 37 having a pair of opposite left and right side surfaces formed into arcuate surfaces are projected. The fulcrum shafts 36 and 37 are connected to the bearing portions 33 and 34 of the roller holder 2.

  In the sheet double feed preventing apparatus configured as described above, the roller holder 2 connects the bearing portions 33 and 34 to the fulcrum shafts 36 and 37 as described with reference to FIGS. 7 and 8, and further, as shown in FIG. In addition, the spring 6 is brought into contact with the spring receiver 35 and accommodated in the recess 41 of the paper feed cassette 7. The retard roller 1 is inserted into the snap fit portions 30 and 31 of the roller holder 2 by inserting the fixing portions indicated by 23 and 24 in FIG. Then, when the recording paper is placed on the recording paper placing table 8 in FIG. 4 and this paper feeding cassette 7 is inserted into the main body of a copying machine, printer, FAX or the like, a transport unit having a feed roller 3 and a pickup roller 4 is obtained. As shown in FIG. 4, the roller holder 2 presses the retard roller 1 accommodated with the bearing portions 33 and 34 as fulcrums against the feed roller 3 by the pressing force of the spring 6. Then, when the recording paper placing table 8 of the paper feeding cassette 7 is raised and the recording paper 5 on the recording paper placing table 8 comes to a position where it comes into contact with the pickup roller 4, preparation for recording paper conveyance is completed.

  When an instruction to convey the recording paper is received in this state, the pickup roller 4 in FIG. 4 first picks up the recording paper 5 at the top of the recording paper placing table 8 and sends it out in the nip direction of the feed roller 3 and the retard roller 1. At this time, even if the leading edge of the recording paper 5 hangs down, the recording paper 5 is fed in the nip direction between the feed roller 3 and the retard roller 1 by hitting the leading edge of the recording paper 5 against the conveyance guide portion 32 of the roller holder 2.

  When the recording paper does not reach the nip portion between the feed roller 3 and the retard roller 1, the retard roller 1 has a driving force transmitted from the feed roller 3 that is in pressure contact with the torque of the torque limiter 25 in FIG. It follows the feed roller 3 and rotates. When the recording paper 5 is fed into the nip portion of the feed roller 3 and the retard roller 1, the recording paper 5 advances as it is under the driving force from the feed roller 3 at the nip portion. In this case, the retard roller 1 also receives the driving force of the feed roller 3 through the recording paper 5, and the driving force exceeds the torque of the torque limiter 25 as described above. Therefore, the recording paper 5 is sent out in the image transfer position direction (not shown).

  Now, when a plurality of recording papers 5 are picked up by the pickup roller 4 and are fed to the nip portion between the feed roller 3 and the retard roller 1, the friction resistance between the recording papers 5 is relatively low. The paper 5 is fed by the feed roller 3, but a driving force that resists the torque of the torque limiter 25 is not transmitted to the retard roller 1 due to slippage between the recording papers 5 that have been fed double. The rotation stops. For this reason, the fed recording paper 5 other than the uppermost recording paper 5 is stopped from being conveyed at the nip portion of the retard roller 1 and is prevented from sending an image (not shown) in the transfer position direction.

  Therefore, only one sheet of recording paper 5 fed to the nip portion between the feed roller 3 and the retard roller 1 is fed in the direction of the image transfer position (not shown), and the other recording paper 5 is separated here. Stop at. That is, it is possible to stop the multifeed of the recording paper 5 that has been multifed without applying a reverse driving force to the retard roller 1 as in the prior art, so that a drive force transmission mechanism to the retard roller 1 is not required. Become.

Further, as described above, the retard roller 1 is only inserted and fixed in the snap-fit portions 30 and 31 of the roller holder 2, and the feed cassette 3 and the pickup roller 4 are pulled out from the body. In the state as shown in FIG. 7 in which there is no transport unit having, there is nothing that obstructs the removal of the driving force transmission mechanism and the like, so that it can be easily removed by hand, and the maintainability becomes very good.
JP 2002-167067 A

  However, in the above configuration, the roller holder 2 is rotatable around the fulcrum shafts 36 and 37 and can be easily removed by hand. Therefore, the bearing portions 33 and 34 and the fulcrum shaft 36 are provided. , 37 are required to be connected in a loosely fitted state, and as a result, a slight backlash (see d in FIG. 9) occurs.

  By the way, since the roller holder 2 is provided so as to face the feed roller 3, a force in the sheet conveying direction always acts on the roller holder 2 at the time of paper feeding. Then, as indicated by A in FIG. 10, the arc-shaped inner surfaces of the bearing portions 33 and 34 come into contact with the curved surfaces at the upper left of the fulcrum shafts 36 and 37, and the roller holder 2 moves in the sheet conveying direction within the range of the play. Are moved along the shape of the fulcrum shafts 36 and 37. The roller holder 2 is vibrated due to repetition of the sheet conveying force and the force of returning to the original position due to the weight of the retard roller 1 when the retard roller 1 slips, causing abnormal noise.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet double feed prevention device capable of suppressing vibration during paper feeding without impairing the movement and detachability of a roller holder, and an image forming apparatus including the same.

  In order to achieve the above object, the present invention provides a feed roller, a retard roller that is pressed against the feed roller, and is configured to rotate when a torque limiter provided on a shaft receives a certain level of torque, and the retard roller. A roller holder that holds the shaft of the roller holder so as not to rotate, a bearing portion that is provided on the roller holder and has an arc-shaped inner surface, and a roller holder that is separately provided on the mounting portion of the roller holder and is connected to the bearing portion. The sheet fulcrum shaft includes a fulcrum shaft that rotatably supports the sheet roller and a biasing unit that biases the roller holder so that the retard roller is pressed against the feed roller. Sometimes the notch shape is formed on the part that comes into contact with the force in the paper transport direction acting on the roller holder and the weight of the roller holder. It is characterized in.

  In addition, the shaft shape of the fulcrum shaft has a circular arc shape with a circular cylinder or an oval cross section.

  According to the present invention, the force in the paper transport direction acts on the roller holder during paper feeding, and even if the roller holder moves within the range of play, the notch is present in the upper left part of the fulcrum shaft. It is possible to reach the position where the movement is restricted at the shortest distance without receiving.

  Therefore, even if the retard roller slips due to the double feeding of the recording paper, the vibration of the roller holder is suppressed and the generation of abnormal noise can be prevented. In addition, since the connecting portion remains loose, it does not impair the rotatable movement and detachability of the roller holder.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. This is just an example.

  FIG. 1 is a perspective view of a roller holder mounting portion of a paper feed cassette according to an embodiment of the present invention, and FIG. 2 is a schematic side view showing the periphery of the roller holder of the paper feed cassette according to the embodiment of the present invention. FIG. 3 is an enlarged view of the main part of FIG. 2, and shows the movement of the roller holder during paper feeding. These drawings correspond respectively to the conventional examples of FIGS. 8, 9 and 10 described above, and the same parts as those in the conventional paper feeding cassette are denoted by the same reference numerals, and detailed description thereof will be given. Omitted.

  In the present invention, as shown in FIG. 1, the fulcrum shafts 36, 37 are in contact with the portion (A portion in FIG. 10) that is in contact with the force in the paper transport direction acting on the roller holder 2 during paper feeding due to the weight of the roller holder 2. , A shape having cutout portions 36a and 36b cut out at right angles. The shape of the fulcrum shafts 36 and 37 is not limited to the columnar shape of the oval cross section as shown in the figure, and may be a cylinder. The shape of the notch is not limited to a right angle, and may be an arc. Good.

  Then, as shown in FIG. 3, even if the roller holder 2 moves in the range of play due to the force in the paper transport direction during feeding, the notch 36a, Since 37a exists, it is possible to reach the position where the movement is restricted at the shortest distance (edge portions of the notches 36a and 37a in the drawing) without being affected by the shapes of the fulcrum shafts 36 and 37.

  Therefore, even if the retard roller 1 slips due to the double feeding of the recording paper 5, the vibration of the roller holder 2 is suppressed and the generation of abnormal noise can be prevented. In addition, since the connecting portion remains loose, the roller holder 2 does not lose its rotational movement and detachability.

  In the above description, the case where the present invention is applied to the feeding portion of the recording paper feed cassette has been described. However, such a retard roller is also provided in the feeding portion for sequentially feeding a plurality of stacked documents to the document table. It is clear that the double feed prevention device used is used, and in this case, it can be constructed in exactly the same way.

  The present invention can be used for a paper feed cassette or an automatic document feeder in an image forming apparatus such as a copying machine, a printer, or a FAX.

These are the perspective views of the roller holder mounting part of the paper feed cassette which concerns on embodiment of this invention. These are the schematic side views which show the roller holder periphery of the paper feed cassette which concerns on the said embodiment of this invention. FIG. 3 is an enlarged view of the main part of FIG. 2 and shows the movement of the roller holder during paper feeding. These are the schematic diagrams which show the principal part structure of a paper feed cassette. These are the figures which showed the structure of the retard roller. These are the figures which showed the structure of the roller holder of this invention holding a retard roller. FIG. 4 is a perspective view in which a roller holder is mounted on a paper feed cassette. FIG. 9 is a perspective view of a roller holder mounting portion of a conventional paper feed cassette. FIG. 6 is a schematic side view showing the periphery of a roller holder of the conventional paper feeding cassette. FIG. 10 is an enlarged view of the main part of FIG. 9 and shows the movement of the roller holder during paper feeding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Retarder roller 2 Roller holder 3 Feed roller 5 Recording paper 6 Spring 7 Paper feed cassette 25 Torque limiter 33, 34 Bearing part 36, 37 Supporting shaft 36a, 37a Edge part 40 Recording paper conveyance path 41 Recessed part (Roller holder mounting part)

Claims (3)

  A feed roller; a retard roller that is pressed against the feed roller and configured to rotate when a torque limiter provided on the shaft receives a certain level of torque; and a roller holder that holds the retard roller shaft so as not to rotate. A bearing portion provided on the roller holder and having an arcuate inner surface; and a fulcrum shaft that is provided separately on the mounting portion of the roller holder and is connected to the bearing portion to rotatably support the roller holder; In the sheet multi-feed preventing device having an urging means for urging the roller holder so that the retard roller is pressed against the feed roller, the fulcrum shaft has a force in the sheet conveying direction that acts on the roller holder during sheet feeding. A sheet double feed prevention device characterized by having a notch shape in the part that comes into contact with the roller holder due to its own weight .   The sheet double feed prevention device according to claim 1, wherein the shaft shape of the fulcrum shaft has a circular arc shape with a cylindrical or oval cross section.   An image forming apparatus comprising the sheet double feed prevention device according to claim 1.

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