JP2005225643A - Sheet feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of paper feeding failure due to overload of sheets inside a sheet housing cassette by an operator, and to stably feed paper sheets. <P>SOLUTION: An overload preventing lever 53 is turnably provided over a sheet loading part of a device main body. The overload preventing lever 5 in the home position hinders approach of the excessively loaded sheets. When feeding the sheets, the over-load preventing lever 53 is turned downstream to escape to a position not hindering feeding of the sheets. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus including the sheet feeding apparatus, and more particularly to a configuration of a prevention unit that prevents overloading of sheets.

  2. Description of the Related Art In recent years, image forming apparatuses such as printers, copiers, and facsimiles are provided with a sheet feeding device for separating sheets one by one and feeding them to an image forming unit. As such a sheet feeding device, for example, the pickup roller can be moved up and down, the sheet is fed by lowering the pickup roller to the sheet side when feeding, and the pickup roller is raised at times other than feeding. Some lift-up systems are designed to be separated from the seat.

  Here, in such a conventional sheet feeding apparatus of the lift-up method, when the sheet storage cassette is mounted, the intermediate plate incorporated in the sheet feeding cassette is lifted from the lowest position by driving the apparatus main body side. When the intermediate plate rises as described above, the pickup roller comes into contact with the uppermost sheet eventually, and when the intermediate plate further rises, the pickup roller also rises.

  Thereafter, when the pickup roller is raised to a predetermined position, the intermediate plate is stopped. The position where the middle plate stops is a position where an appropriate sheet feeding pressure is applied to the upper surface of the sheet by the pickup roller during feeding, and the sheet is reliably fed out by stopping the middle plate at such a position. Will be able to.

  By the way, such a conventional sheet feeding apparatus is provided with a detecting means for detecting the presence or absence of the sheets stored in the sheet storage cassette, and the sheets are sequentially fed to the sheet storage cassette. When the sheet no longer exists, the detection means detects this and informs the operator that there is no longer any sheet in the sheet storage cassette.

  6 and 7 are diagrams showing the configuration of such a conventional sheet feeding apparatus. In FIG. 6, reference numeral 41 denotes an intermediate plate provided in the sheet storage cassette 4, and reference numeral 50 denotes an actuator 51 and a sensor (not shown). Is a sheet presence / absence detection device. Reference numeral 41 a denotes a slit formed in the intermediate plate 41, and the slit 41 a is formed at a position facing the actuator 51. The actuator 51 is rotatably held by a holder 52 that is a fixed member.

  Here, when a small amount of sheets are present on the middle plate 41 of the sheet storage cassette 4, the actuator 51 comes into contact with the sheet and stops at the position shown in FIG.

  On the other hand, when the sheet on the intermediate plate 41 runs out, the actuator 51 passes through the slit 41a of the intermediate plate 41 and descends to a position indicating that there is no sheet on the intermediate plate 41 shown in FIG. 6B. It has become. Here, when the actuator 51 is lowered to such a position, a sensor (not shown) is turned on. When the sensor is turned on in this way, the control unit (not shown) determines that there is no sheet in the sheet storage cassette 4. The operator is notified of the absence of a sheet by a buzzer or a display.

  Further, when the operator completely fills the sheet with no sheets, the operator operates by using the mark 56 provided on the rib in the cassette or the sheet side restricting plate 57 as a guide. This prescribed full load state is shown in FIG. FIG. 7B shows a case where the operator has set the sheet in an overloaded state in which sheets are filled more than a specified amount.

  On the other hand, in a paper feed deck having an elevator platform paper bundle tray, when an operator tries to overload a stack of sheets, an overload sheet is loaded by a stopper that can swing the front end of the paper. There are some that cannot be stacked (see, for example, Patent Document 1).

  Further, there is a type in which a rotatable stopper is provided in the paper feed deck to prevent an excessively stacked sheet bundle from entering the image forming apparatus main body (see, for example, Patent Document 2).

In addition, there is a structure in which a sheet bundle for overloading cannot be set in the apparatus by a stopper which is a fixing member (see, for example, Patent Document 3).
Japanese Patent Publication No. 61-50858 JP 2003-221134 A Japanese Patent Laid-Open No. 11-43231

  However, in the above-described conventional example, as shown in FIG. 7B, when the operator sets the sheet in an overloaded state in which sheets are filled more than a specified amount, the following problems occur. When the operator mounts the cassette in the image forming apparatus main body from right to left, the sheet bundle forcibly pushes up the pickup roller 6 and the actuator 51, and the leading edge of the uppermost sheet in the sheet bundle is against the conveyance roller nip N. If the sheet is conveyed in a state where it is difficult to enter, jamming may occur, or the uppermost sheet of the sheet bundle contacts the lower surface 52a of the holder 52 and receives conveyance resistance in the direction of arrow B. It may cause skewing.

  Further, in the sheet feeding apparatus of the type disclosed in Patent Document 1, the leading edge of the sheet is damaged by a stopper when an overloaded sheet bundle is discharged out of the main body of the image forming apparatus in conjunction with the movement operation of the sheet feeding table. When the sheet is subsequently conveyed, there is a risk that the leading edge of the sheet may cause a jam that is caught by a part in the path. Further, there is a possibility that the sensor may be broken when the paper feed table is moved with a strong force.

  Furthermore, in the example of Patent Document 2, since the sheet bundle is inserted by the operator's hand, when the maximum amount of the sheet bundle is set in the machine, the operator finally puts a small number of sheets by trial and error. With fine adjustment work to set.

  And in patent document 3, since the stopper is a fixing member, when the sheet bundle swells in a fully loaded state and the net sheet bundle height becomes high, the re-upper sheet of the sheet bundle is fixed. It is conceivable that a conveyance resistance is received in the direction of arrow B from the stopper, and the sheet is jammed without being conveyed by the pickup roller.

  An object of the present invention is to provide a sheet feeding apparatus and an image forming apparatus that can solve these problems and prevent overloading.

  In order to achieve the above object, the present invention provides a sheet feeding apparatus including a sheet storage cassette for storing sheets and an apparatus main body that allows the sheet storage cassette to be detachably mounted. The sheet storage cassette is attached to the apparatus main body. A sheet overload prevention member that abuts against the amount of sheets exceeding the predetermined amount and prevents entry when the stored sheets are loaded in a state of being stacked in excess of the predetermined amount, The sheet overload prevention member is rotatably supported so as not to interfere with sheet feeding when the sheet is fed from the sheet storage cassette.

  As described above, according to the present invention, in the sheet feeding apparatus, even if a sheet storage cassette is mounted by an operator in a state where the sheet bundle is overloaded, the sheet feeding apparatus can be rotated on the apparatus main body side. The sheet overload prevention member serves as a stopper that pushes out the overloaded sheet bundle to the outside of the machine, and the sheet overload prevention member rotates and escapes so as not to cause conveyance resistance during normal conveyance of the sheet. As a result, it is possible to prevent sheets from being overloaded without causing adverse effects such as jamming or poor printing accuracy.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a laser beam printer which is an example of an image forming apparatus provided with a sheet feeding apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a laser beam printer. The laser beam printer 1 includes an image forming unit 2 that forms an image, a sheet feeding device 5 that separates and feeds sheets P one by one to the image forming unit 2, and the like. It has.

  Here, the image forming unit 2 includes a process cartridge 7 that can be attached to and detached from a laser beam printer main body (hereinafter referred to as an apparatus main body) 1A, a transfer roller 9, and the like. A sheet separating and feeding unit including a sheet storage cassette 4 as a means, a pickup roller 6 as a sheet feeding means, a feed roller 14 and a retard roller 15 is provided. The process cartridge 7 includes a photosensitive drum 8, a charging roller 20, a developing unit 22, a cleaning unit (not shown), and the like.

  The charging roller 20 is provided in contact with the photosensitive drum 8 so as to be driven to rotate by the photosensitive drum 8, and is used to uniformly charge the surface of the photosensitive drum when the photosensitive drum 8 rotates. The developing means 22 supplies toner to the developing area of the photosensitive drum 8 to develop the latent image formed on the photosensitive drum 7.

  In the figure, reference numeral 12 denotes a laser scanner unit, 10 denotes a fixing unit, 13 denotes a paper discharge roller for discharging the sheet P to the sheet discharge image stacking table 16, 1B denotes a cassette storage portion provided in the apparatus main body 1A, and 11 denotes It is a control unit.

  Next, an image forming operation of the laser beam printer 1 configured as described above will be described.

  When image information is sent from a personal computer (not shown) and a controller board (not shown) that performs image formation processing of this image information issues a print signal, it is loaded on a sheet storage cassette 4 that is detachably attached to the apparatus body 1A. The sheets P are fed one by one by the pickup roller 6 and the sheet separating and feeding unit, and sent to the nip between the photosensitive drum 8 and the transfer roller 9 in the process cartridge 7.

  On the other hand, based on the image information together with this print command, the laser scanner unit 12 irradiates the photosensitive drum with a bit image of the image information (laser light), and a latent image is formed on the surface of the photosensitive drum 8 according to the bit image. It is formed. Further, by developing this latent image, a toner image is formed on the photosensitive drum.

  The toner image thus formed on the photosensitive drum is then transferred to the sheet P fed into the nip between the photosensitive drum 8 and the transfer roller 9. Further, the sheet P on which the toner image is transferred is sent to the fixing unit 10 and is heated and pressed by the fixing unit 10, whereby the toner image is fixed semipermanently. Further, thereafter, the sheet P on which the toner image is fixed is discharged to the sheet discharge stack 16 by the discharge roller 13.

  In the figure, reference numeral 41 denotes a middle plate of the sheet storage cassette 4. The middle plate 41 is provided on the sheet storage cassette 4 so as to be rotatable (movable) in the vertical direction with the locking portion 41a as a fulcrum. Reference numeral 42 denotes a side plate that is suspended from one end of a push-up plate 43 provided below the intermediate plate 41 and has a rack 42a formed at the upper end. 44 is a motor (not shown) provided in the apparatus main body. It is a pinion that rotates.

  When the sheet storage cassette 4 is attached to a cassette storage portion 1B (see FIG. 1) provided in the apparatus main body 1A, the rack 42a of the side plate 42 meshes with the pinion 42. After that, the control unit 11 drives the motor to rotate the push-up plate 43 upward, thereby pushing up the intermediate plate 41 so that the upper surface of the sheet P has a substantially constant height at which appropriate pressure is applied when feeding. I try to raise it.

  2 shows the configuration of the sheet feeding apparatus 5. In FIG. 2, reference numeral 53 denotes an overload prevention lever which is a sheet overload prevention member according to the present invention. When the sheet storage cassette 4 is mounted on the apparatus main body 1A in a state where more sheets P are stacked, it serves as a stopper for discharging the excessively stacked sheets P out of the apparatus main body 1A. The overload prevention lever 53 has a structure in which a moment to rotate in the direction of arrow A due to its own weight acts at the home position, but the overload prevention lever 53 is stationary by the stopper portion 52a of the holder 52. Further, since the overload prevention lever 53 can be freely rotated when attempting to rotate in the direction opposite to the direction of the arrow A, the overload prevention lever 53 is used when a sheet is fed and when the cassette 4 is pulled out from the apparatus main body 1A. There is no resistance. Reference numeral 45 denotes a sheet presence / absence detection device which is detection means for detecting the presence / absence of sheets in the sheet storage cassette 4. FIGS. 3A to 3C are a side view, a front view, and a perspective view of the sheet presence / absence detection device 45 and the overload prevention lever 53, respectively.

  Here, the sheet presence / absence detection device 45 and the overload prevention lever 53 are arranged above the sheet storage cassette 4 (the middle plate 41) as shown in FIG. 2, and the sheet presence / absence detection device as shown in FIG. Reference numeral 45 includes an actuator 46 which is a lever member, and a sensor 47 which detects the position of the actuator 46 by being turned on and off by a flag 46b provided on a shaft 46a of the actuator 46. By the way, in this embodiment, the torsion coil spring 48 is compressed between the actuator 46 and the frame 45a of the sheet presence / absence detecting device 45 as shown in FIG. Is attached. The overload prevention lever 53 is provided at a position overlapping the minimum stackable paper set in the cassette 4 in the paper width direction.

  FIG. 4A shows a state in which the operator mounts the sheet storage cassette 4 on the apparatus main body in the direction of arrow C with the sheets P being overloaded. The rear end portion of the sheet bundle of the overloaded sheets P ′ is prevented from entering the apparatus main body by the overload prevention lever 53 and discharged in the direction of arrow D. As a result, it is possible to prevent the stacking of more than a prescribed amount of sheets. Here, even when the operator inserts the sheet storage cassette in the direction of arrow C with a strong force when the sheets are overloaded, the force applied to the overload prevention lever 53 by the overloaded sheets P ′ Since it is received by the receiving portion 52b, there is no fear of lever breakage. Note that the sheet P ′ for the excessive stacking is smoothly discharged out of the apparatus by the inclined surface 4a of the sheet cassette.

  Further, as shown in FIG. 4B, when the sheet P is transported in the direction of arrow E particularly in the full load state, the overload prevention lever 53 rotates in the direction of arrow F to pass the transport resistance to the sheet P. It is possible to hold down to a level that does not affect the paper.

(Embodiment 2)
FIG. 5 shows a second embodiment of the present invention. As shown here, the overload prevention lever 53 reliably biases the overload prevention lever 53 in the direction of the arrow G by the torsion coil spring 54, thereby ensuring the home position. However, by providing a roller 55 that can rotate with respect to the lower end portion of the overload prevention lever 53, the overload prevention lever 53 does not become a resistance when the sheet is fed and when the cassette 4 is pulled out of the apparatus main body 1A. It has become.

  In the first embodiment, a torsion coil spring 54 may be used instead of its own weight. In this case, a weak elastic force is set so as not to cause a large resistance to the fed sheet. As a result, the overload prevention lever 53 can surely return to the home position.

1 is a diagram illustrating a schematic configuration of a laser beam printer which is an example of an image forming apparatus including a sheet feeding device according to an embodiment of the present invention. FIG. 3 is a perspective view of a main part for explaining a configuration of a sheet feeding device of the laser beam printer. The figure explaining the structure of the overloading prevention lever and sheet presence detection apparatus which were provided in the said sheet feeding apparatus. FIG. 6 is a partial cross-sectional side view of the sheet feeding device for explaining the function of the sheet overload prevention lever. The figure which shows the structure of the sheet presence detection apparatus which is a detection means which detects the presence or absence of the conventional sheet | seat. The figure which shows the structure of the sheet presence detection apparatus which is a detection means which detects the presence or absence of the conventional sheet | seat. The figure which shows the structure of the sheet presence detection apparatus which is a detection means which detects the presence or absence of the conventional sheet | seat.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser beam printer 2 Image formation part 4 Sheet storage cassette 5 Sheet feeding apparatus 52 Lever holder 53 Overload prevention lever 54 Torsion coil spring 55 Roll

Claims (4)

In a sheet feeding apparatus comprising a sheet storage cassette for storing sheets, and an apparatus main body that allows the sheet storage cassette to be detachable,
When mounting the sheet storage cassette on the apparatus main body, if the stored sheets are to be mounted in a state where the sheets are stacked in excess of a predetermined amount, the sheet storage cassette comes into contact with the amount exceeding the predetermined amount. A sheet overload prevention member for preventing the sheet from being fed, and the sheet overload prevention member is rotatably supported so as not to disturb the sheet feeding when the sheet is fed from the sheet storage cassette. Sheet feeding device.   2. The sheet feeding apparatus according to claim 1, wherein a rotatable roller is provided at a position in sliding contact with the sheet of the sheet overload prevention member.   The sheet overload prevention member has a spring that is urged to rotate to a position that prevents entry of a sheet that exceeds a predetermined amount, and the elastic force of the spring is when the sheet is fed. The sheet feeding device according to claim 1, wherein the sheet feeding device is set to a size that does not hinder the rotation of the sheet. The sheet feeding apparatus according to any one of claims 1 to 3,
Image forming means for forming an image on a sheet fed from the sheet feeding device;
An image forming apparatus comprising:

Images