JPH02233451A - Sheet stacking device for image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent a sheet from being caught when sheets are stacked in a number exceeding a maximum allowable value, by incorporating sheet catch preventing members to members loosely fitted on the lower discharge rollers or members loosely fitted on the support shaft of the lower discharge rollers. CONSTITUTION:Each sheet catch preventing member 25 made of synthetic resin has a loosely fitting part 26 which is loosely and resiliently fitted radially outward onto a support shaft member between annular ribs C, C of a shaft 24, and a catch preventing part 27 which is brought into slidable contact with the rear end regulating surface S of a rear end regulating member 21. Further, the member 27 has dimensions such that its lower end is positioned below the bottom surface of a recess part (b) when the support shaft flexes to a maximum degree, in consideration with a deflection degree of the support shaft 24 accompanied with the rotation thereof. Accordingly, even though sheets are stacked being curled on a tray 20, or are stacked in a number exceeding a maximum allowable value, and even though a gap which possibly catch a sheet is formed between a lower discharge roller 17 and the upper edge part of the rear end regulating member, the members 27 close a part of the gap, thereby it is possible to prevent a sheet from being caught.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a paper stacking device installed in an image forming apparatus such as a laser printer or an electrostatographic copying machine. [Prior Art] As shown in FIGS. 8 and 9, a device for accumulating sheets of paper after image formation in a laser printer, for example, has an upper and lower ejector that discharges sheets of paper a after image formation onto a tray 41. A rear end defining member 44 is provided below the pair of paper rollers 42 and 43 and at the lower end of the obliquely installed tray 41 for aligning the rear ends of the sheets a accumulated on the tray 4l. be. In such a paper stacking device, generally, the number of sheets stacked until the top sheet a stacked on the tray 41 contacts the lower paper ejection roller 43 is the maximum number of sheets stacked in the paper stacking device. It is said that

By the way, in a laser printer configured to accommodate a large capacity of paper, image recording of a large number of sheets is performed continuously, and the number of sheets exceeding the maximum accumulated number is stored in the tray 41.
It is often accumulated in On the other hand, if the trailing end defining member 44 is simply provided on the lower side of the lower paper ejecting roller 43, a gap will be created between the upper peak of the trailing end defining member 44 and the lower paper ejecting roller 43. When more than the maximum number of sheets a are accumulated on the tray 4l, the uppermost sheet a in contact with the lower sheet ejecting roller 43 receives the conveying force of the lower sheet ejecting roller 43, and the sheet a This causes the inconvenience that the material gets caught in the gap. Therefore, a recess b is provided at the upper edge of the trailing end defining member 44, and the lower paper ejection roller 43 is inserted into the recess b to prevent the paper from being rolled into both sides of the recess of the trailing end defining member 44. We try to prevent this by [Problems to be Solved by the Invention] However, due to bending and rotation of the support shaft 45 of the lower paper ejection roller 43, the amount of insertion of the lower paper ejection roller 43 into the recessed portion b may become shallow. Especially in recent years, when the support shaft 45 is made of synthetic resin in order to make the lower paper ejection roller 43 lightweight and inexpensive, the above-mentioned deflection is noticeable. As the amount of insertion of the lower paper ejection roller 43 into the recessed portion b becomes shallower or the lower paper ejection roller 43 slips out, the upper edge portions on both sides of the recessed portion b and the lower paper ejection roller 43 become separated when viewed in the roller axis direction. A gap was created in between, and the yōgi a sometimes got caught in this gap. Preventing the paper a from being caught in the bending of the support shaft 45 can be achieved by increasing the amount of insertion of the lower paper ejection roller 43 into the recessed portion b; however, by increasing the depth of the recessed portion b. In addition, if the diameter of the lower paper ejection roller 43 is increased, the maximum number of sheets that can be stacked becomes extremely small, or the height of the lower paper ejection roller 43 with a larger diameter relative to the tray 41 is increased to meet the maximum number of sheets. Securing the number of stacked sheets of paper not only increases the bulk of the device, but also increases the
The paper ejection height of the pair of paper ejection rollers 42 and 43 against the tray 41 becomes too high, and the paper sheet a, which is slightly curled downward, is turned upside down before it is ejected to the tray 41. There is an inconvenience that the ejecting posture of paper a may be disturbed.

In addition, if paper a is accumulated in excess of the maximum number of sheets mentioned above, or if paper a is accumulated in a curled state, the paper a
There was also the problem that the trailing edge of the paper came into contact with the lower paper ejection roller 43 and the trailing edge of the paper became dirty or damaged. The paper stacking device of the first invention prevents paper from becoming entangled when stacking more than the maximum number of sheets, without sacrificing the maximum number of sheets that can be stacked or by increasing the diameter of the lower paper ejection roller. The aim is to enable effective prevention. In addition to achieving the first object, the paper stacking device of the second invention is capable of preventing dirt and damage on the trailing edge of the paper when stacking more paper than the maximum stacking number on the tray. The purpose is to [Means for Solving the Problems] In order to achieve the above first object, the present invention provides a method for stacking sheets on the lower side of the upper and lower discharge rollers and at the lower end side of the obliquely disposed tray. An image forming device equipped with a trailing edge regulating member for paper sheets! In the paper stacking device, a gap is formed between the upper edge of the trailing end defining member and the lower paper ejection roller between a member loosely fitted to the lower paper ejection roller or a member loosely fitted to the spindle of the lower paper ejection roller. It is characterized by the continuous installation of a paper entrapment prevention member that prevents paper from being entangled. In order to achieve the above-mentioned second object, the present invention provides, in addition to the paper stacking device of the image forming apparatus that has achieved the first invention, furthermore, The present invention is characterized in that a trailing edge defining portion of the sheet is provided in a range extending from the downstream side to at least the contact point of the lower sheet ejecting roller with a plane parallel to the tray surface, and protruding a little further than the outer circumferential surface of the lower sheet ejecting roller. [Operation] According to the paper stacking device of the first invention, in a situation where more than the maximum stacked number of sheets is stacked on the tray,
Even if a gap occurs between the upper edges on both sides of the recessed portion and the lower paper ejection roller when viewed in the roller axis direction due to the deflection of the lower paper ejection roller or the roller support shaft, the lower paper ejection roller or the roller support By making the entanglement prevention member that moves integrally with the shaft always close the gap,
Paper is reliably prevented from getting caught in the gap. According to the paper stacking device of the second aspect of the present invention, the function of the paper trailing edge defining section prevents the trailing edge of the sheets stacked in excess of the maximum number of sheets from coming into contact with the lower paper ejection roller. Prevents dirt and damage. [Example] Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 schematically shows a laser printer as an example of an image forming apparatus, in which a photoreceptor 2 is horizontally suspended inside a printer main body l, and around the photoreceptor 2, a charging device 3, a developing device 4, a transfer device 5. The cleaning devices 6 are arranged in this order in the rotational direction of the photoreceptor 2, and
An optical unit 7 is provided in the upper space of the cassette case 8, and a loading section 9 for the cassette case 8 is provided in the lower space of the cassette case 8. In addition, a paper discharge conveyance device l2 for conveying the paper after image transfer to the fixing device 1l, and a paper stacking device 13 for reversing the paper after image fixation and stacking it on the upper part of the printer are provided. ．． The paper stacking device 13 described above is configured as follows.
That is, the first paper ejection roller 14. feeds out the paper a after the fixed image has been formed. 15 pairs are provided immediately downstream of the fixing device 11, and the first paper ejection roller 14. A pair of upper and lower second paper ejection rollers 16, 17 are disposed above the 15 pairs of paper ejection rollers 14, 15, 16.
Seventeen pairs of path forming members 18 are rotatably provided around a horizontal axis 19 near the downstream side of the paper ejection roller pair 15. As shown by the imaginary line, by circulating the path forming member 18 to the outside of the apparatus around the horizontal axis l9, the path forming member 18 is used as a paper ejection tray, and the paper 1 after image formation is placed there. You can take it out without turning it inside out. On the other hand, said fixation! The upper face plate of the printer main body l corresponding to the upper part of the optical unit 7 and the upper part of the optical unit 7 is connected to the paper ejection rollers 16, 1? A tray 20 is formed by slanting the tray 20 such that it is positioned downward as the sides move downward, and the sheets stacked on the tray 20 are arranged at the lower end of the tray 20 and below the second paper discharge rollers 16, 17. A sheet trailing edge defining member 21 is provided for defining the trailing edge of the sheet. In addition, 22
is an auxiliary tray pivotably attached to the inclined upper side of the tray 20 so as to be freely foldable. As shown in FIGS. 2 to 4, the second paper discharge roller 16. 17 is a support shaft 23. made of synthetic resin, for example. 24 at a predetermined interval, and on the other hand, the upper edge of the rear end defining member 21 is formed with a recess b into which a part of the lower paper ejection roller l7 enters, and the paper ejection roller l7 and the support shaft 24 It has a shape that corresponds to the outline of. The lower support shaft 24 on the lateral side of the lower paper ejection roller 17 includes a lower paper ejection roller l7 and the rear end defining member 2, which are generated when the support shaft 24 is bent.
A paper entrainment prevention device 25 is provided to prevent the paper a from being entangled in the gap between the paper and the upper edge of the paper. The paper entrainment prevention device 25 is made of synthetic resin, for example, and has a C-shaped loose fitting member 26 that is loosely fitted into the support shaft portion between the annular ribs c and c formed on the support shaft 24. , a tapered paper entrainment prevention member 27 is provided in series, and the loose fitting member 26 is elastically loosely fitted from the outside in the radial direction to the support shaft portion between the annular ribs c, c. The entanglement prevention member 27 is slidably in contact with the rear end defining surface S of the rear end defining member 2l. Considering the amount of deflection of the support shaft 24 due to rotation, the lower end of the entanglement prevention member 27 is positioned below the bottom surface of the recessed portion b under the maximum deflection of the support shaft 24. It is arranged in dimensions.

According to the above configuration, when the sheets a are accumulated in the tray 20 in a curled state, or in a situation where more than the maximum number of sheets a are accumulated, the spindle 2
4, the lower paper ejection roller l is moved against the recessed portion b.
Even if the insertion amount of the support shaft 7 becomes shallow or it comes out, and a gap is created between the lower paper ejection roller l7 and the upper edge of the rear end defining member 2l, in which the support shaft a is caught, the support shaft 2
4, the entrainment prevention member 27 that moves together with the paper always faces the gap and functions to close a part of the gap. Even if the sheet a is received, the conveyance is prevented, and the uppermost sheet a is reliably prevented from being caught. Note that the lower end of the entrainment prevention member 27 may be formed as a flat surface, but as shown in FIG. As shown in Figure (B), when the support shaft 24 is bent and the #s @ entrapment prevention member 27 moves upward, and at this time, the handle a enters below the entrainment prevention member 27, the entrainment When the prevention member 27 returns to its original position, there is a risk that the paper a will be crushed by the entrainment prevention member 27. However, if the lower end of the entrainment prevention member 27 is made into a pointed shape, the original action of the entrainment prevention member 27 returning to its original position will cause the paper a that has entered the lower part of the entrainment prevention member 27 to be removed in the surface direction. can be moved to paper a
This has the advantage of preventing crushing. However, as shown in FIG. 5(C), the above-mentioned disadvantage can be avoided if a recess d is provided in the rear end defining member 21 and the entanglement prevention member 27 is inserted into the recess d. Next, a first alternative embodiment of the paper entrainment prevention device 25 is shown in FIG. In this case, a portion corresponding to the tray 20 of the loose fitting member 26 with the entanglement preventing member 27 provided therein protrudes slightly more than the outer circumferential surface S of the lower paper ejection roller L7 when viewed in the axial direction of the support shaft 24. Specifically, the paper trailing edge defining section 28 is provided in a state in which the paper trailing edge defining section 28 is set in such a state that the upper and lower paper ejection rollers 16.
An arbitrary point p on the downstream side of the 17 pairs of nip points P,
m (preferably two-ship point P,) to a contact point P of the lower paper ejection roller 17 with a surface S parallel to the tray surface St.
The paper trailing end defining portion 28 is provided in a range extending beyond the tip of the entrainment prevention member 27. According to the above configuration, it is possible to prevent the paper a from getting caught up in the paper a as described above, and when stacking the paper a more than the maximum stacked number one after another on the tray 20, the uppermost paper a is placed at the arbitrary point. Until P8 is reached, the trailing edge of the sheet a can be prevented from coming into contact with the lower sheet ejecting roller l7, and the trailing edge of the sheet a exceeding the maximum number of sheets can be removed by the lower sheet ejecting roller 17. It is reliably prevented from being soiled or damaged.

Note that the paper trailing edge defining section 28 is connected to the upper and lower paper ejection rollers 16, 1? It may be provided in a range extending from the downstream side of the pair of nip points P+ to at least the contact point P of the lower paper ejection roller 17 with respect to the surface S3 parallel to the tray surface S2. FIG. 7 shows a paper entrainment prevention device 25 according to a second alternative embodiment. In this device, members 29 having substantially the same shape as the sheet entrainment preventive device 25 shown in FIG. A paper trailing edge regulating section 28 made of a low friction material such as a resin sheet is attached, and the lower side of the paper trailing edge regulating section 28 is made to hang down below the plate-like member 30. The outer circumferential surface S of the roller 17 is covered with a plate-like member 30, and the member 29 is loosely fitted to the supporting shaft portions on both sides of the lower paper ejection roller 17. They are functionally the same. Although the entrainment prevention member 27 is arranged to correspond to the recessed part b, it may also be arranged at a location outside of the recessed part b, or the entrainment prevention member 27 may be narrowed so as to correspond to the recessed part b.
Although the configuration is such that two sheets are provided, it is also possible to have a wide-width shape and arrange one piece. In either case, it is important that the entanglement prevention member 27 exists at least within the width of the minimum size of paper to be stacked. be. In addition, the lower paper ejection roller 17 has a roller structure provided on the support shaft 24, but the lower paper ejection roller 17 is made into a single roller structure, and a large annular groove is provided in the same part, and the paper is rolled into this groove. It is also possible to adopt a structure in which the preventer 25 is loosely fitted. Furthermore, although the paper stacking device 13 is placed on the tray 20 of a laser printer, it can also be placed on the trays and sorters of electrostatic photocopiers, facsimile machines, etc., the trays of other automatic document feeders and ejectors, and the front and back sides of the interior of double-sided copying machines. It goes without saying that the paper stacking device 13 can be implemented on various objects, such as an intermediate tray for reversing.

〔Effect of the invention〕

As explained above, according to the paper stacking device 1 of the first invention, it is possible to reliably prevent paper from getting caught without increasing the diameter of the lower paper ejection roller or sacrificing the number of stacked sheets. According to the second invention, it is possible to effectively prevent dirt and damage caused by the lower paper ejection roller at the trailing edge of paper stacked in excess of the maximum number of stacked sheets, and as a whole, the conventional inconveniences can be overcome by a very simple improved technology. We were able to solve this problem rationally.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical side view of a laser printer as an example of an image forming device, Fig. 2 is a cross-sectional view of the main parts of the paper stacking device, and Fig. 3 is a diagram of the paper stacking device showing the removal state of the paper entrainment prevention device. FIG. 4 is a front view of the main parts of the sheet stacking device, and FIGS. 5 (Δ) to (C) are functional explanatory diagrams. 6 and 7 respectively show other embodiments of the paper entrainment prevention device, FIG. 6 is a sectional view of the main part of the paper stacking device, and FIG.
The figure is a perspective view of the paper entrapment prevention device. 8 and 9 show a conventional paper stacking device, with FIG. 8 being a perspective view and FIG. 9 being a sectional view. 16. 17... Paper ejection roller, 20... Tray, 2
DESCRIPTION OF SYMBOLS 1... Trailing edge defining member, 24... Support shaft, 26... Loose fitting member, 27... Entanglement prevention member 28... Paper trailing edge regulating portion, a... Paper, P, ... Nisob point, ps
. . . Contact point, S . . . Rear end defining surface, s1 . . . Outer peripheral surface of lower paper ejection roller, S. ... Tray surface, S, ... Surface parallel to the tray surface. Applicant: Sanda Kogyo Co., Ltd. Agent. Patent attorney Hideo Fujimoto

Claims (2)

[Claims] (1) In a paper stacking device of an image forming apparatus, a trailing edge defining member of the paper stacked on the tray is provided below the pair of upper and lower paper ejection rollers and at the lower end of the obliquely disposed tray. Prevents paper from being caught in the gap created by the upper edge of the trailing edge defining member and the lower paper ejection roller by a member loosely fitted to the lower paper ejection roller or a member loosely fitted to the support shaft of the lower paper ejection roller. 1. A paper stacking device for an image forming apparatus, characterized in that a paper stacking device for an image forming apparatus is provided with a member for preventing paper from being caught in the paper. (2) In a paper stacking device of an image forming apparatus, a trailing edge defining member of the paper stacked on the tray is provided below the pair of upper and lower paper ejection rollers and at the lower end of the obliquely disposed tray. Prevents paper from being caught in the gap created by the upper edge of the trailing edge defining member and the lower paper ejection roller by a member loosely fitted to the lower paper ejection roller or a member loosely fitted to the support shaft of the lower paper ejection roller. A sheet entrainment preventing member is provided in series to prevent paper from being caught in the sheet, and the sheet is provided in a range from downstream of the nip point of the paper ejection roller pair to at least the contact point of the lower paper ejection roller with respect to a plane parallel to the tray surface with respect to the loose fitting member. A paper stacking device for an image forming apparatus, characterized in that a paper trailing edge defining portion is provided that projects slightly beyond the outer peripheral surface of a lower paper ejection roller.