JPH0625460Y2 - Paper feeder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an automatic sheet feeding device suitable for various image forming apparatuses such as a copying machine and a printer. The present invention relates to a paper feeding apparatus of a type in which stacked sheets are separated one by one while being fed, and then the conveyance direction of the sheets is reversed by 180 ° to feed the sheets.

[Prior art and its problems]

As a method of automatically feeding the stacked sheets one by one,
The method of using the separating claw as shown in FIG. 4 has been frequently used. FIG. 4 is a cross-sectional view of a sheet feeding device using a sheet feeding cassette, in which sheets P are stacked and stored in the sheet feeding cassette 41. The sheet P is placed on a bottom plate 42 that is rotatably mounted, and the bottom plate 42 is pressed upward by a pressing member 43. The two corners on the leading end side of the stacked sheets P have separation claws 44,
It is locked by 44. Therefore, the paper feed rollers 45, 4
Even if the sheet 5 starts to rotate and comes into contact with the uppermost sheet P ₁ of the stacked sheets P and tries to send it out, the uppermost sheet P ₁ cannot move forward because it is locked at both corners, and other sheets P ₁ rise. And separated. Since the separating claw 44 presses the sheet P by its own weight, the uppermost sheet P ₁ is eventually released from the regulation by the separating claw 44 and is fed in a predetermined direction.

In the case of the separation method by the above-mentioned double-angle regulation, the uppermost paper P ₁ is forcibly deformed and separated, and after the separation, the elasticity of the paper itself,
That is, it is expected that the original flat shape will be restored by the "strength of the waist". However, if the separation claw 44 does not swing smoothly and is pressed and locked excessively strongly, a "ear break" phenomenon occurs in which the two corners of the leading end of the separated sheet are bent.
Further, since label paper and moisture-absorbed plain paper have a weak stiffness, the bent bends at both corners are not recovered immediately after separation, but are fed as they are.

As described above, when both the leading edges of the sheet separated and fed from the sheet stacking portion are bent, the leading edges of the sheet do not smoothly ride on the sheet guide surface of the transport guide member arranged in the next order, and the sheet is skewed or the like. May cause improper transport or jam. In particular,
In the case where the transport guide member is a so-called turn guide that reverses the transport guide direction of the delivered sheet by 180 ° in order to reduce the size of the apparatus, the guide surface is composed of a plurality of ribs and the sheet and the guide surface are separated from each other. The method of reducing the friction between the two is usually adopted, but when a sheet with bent front corners is fed to such a turn guide, both corners enter between the ribs and cause conveyance failure or jam. Easier to do. Further, in the area of the turn guide where the conveying force of the paper feed roller directly acts, there is a problem similar to the above that the paper is easily deformed or the paper easily enters between the ribs.

[Purpose of device]

The present invention has been made in view of the above-mentioned problems of the prior art, and regardless of the "strength of the paper" or the like, all types of paper are always stabilized after being separated one by one by the double-angle regulation method. An object of the present invention is to provide a sheet feeding device that can reversely feed sheets.

[Key points of device]

According to the present invention, the above object is to provide a sheet stacking unit for stacking sheets to be fed, a regulating member for locking both corners on the leading end side with respect to the feeding direction of the stacked sheets, and sequentially sending the loaded sheets. And a turn guide in which a plurality of ribs each having a curved sheet guide surface are provided upright and which guides the sheets separated from the sheet stacking unit one by one in a direction to be reversed. The turn guide is formed such that the heights of the plurality of ribs at the receiving portion, at which at least the leading end of the fed-out sheet comes into contact, are gradually lowered only at both side portions corresponding to the regulating member, and the turn guide is provided on the sheet feeding member. This is achieved by providing a sheet feeding device characterized in that the standing intervals of the ribs in the corresponding areas are made narrower than the standing intervals in the other areas.

[Example of device]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a schematic cross-sectional view showing a main part of an optical writing printer to which a paper feeding device as an embodiment of the present invention is applied.
The figure is a perspective view showing the turn guide in the sheet feeding device.
Further, FIG. 2 is an explanatory view showing the correspondence between the turn guide and the sheet feeding cassette.

In FIG. 3, the photosensitive drum 1 is rotatably supported and is driven and rotated in the arrow direction. In the vicinity of the peripheral surface of the photoconductor drum 1, along the rotation direction thereof, the photoconductor drum 1
A charger 2 for uniformly charging the surface to a predetermined polarity, and a photosensitive drum 1 for uniformly charging an optical signal corresponding to image information.
An optical writing unit 3 that irradiates the surface to form an electrostatic latent image, a developing unit 4 that applies toner to the electrostatic latent image to visualize the toner image, and a sheet feeding mechanism including a sheet feeding device described below for the toner image. An image forming unit is formed by sequentially arranging a transfer device 5 for corona-transferring onto a sheet fed through the sheet, a cleaner 6 for removing the toner remaining without being transferred from the surface of the photosensitive drum 1, and the like.

Next, the paper feeding mechanism will be described. Below the image forming unit (bottom of the machine body), a paper feed cassette 7 for accommodating and storing paper P is inserted, and the paper feed cassette 7 is freely inserted and removed along an insertion table 8. A bottom portion 9 is rotatably mounted inside the paper feed cassette 7, and paper sheets P are stacked on the bottom plate 9. A spring 10 is interposed between the bottom plate 9 and the bottom surface of the paper feed cassette, and the stacked sheets P are inserted via the bottom plate 9.
Is urged upward. Further, on both sides (see FIG. 2) in the paper feed cassette 7, there are provided a pair of separation claws 11 as restriction members for locking both corners of the stacked paper P on the leading end side with respect to the paper feed direction B. It is rotatably provided. The separation claw 11 of the present example is rotatably supported by engaging one end of the L-shape into the slit 7b formed in the cassette bottom 7a, and has a U-shaped free end side claw part. 11a and the bottom plate 9 are configured to hold and clamp the leading edge of the stacked sheets P. Above the paper feeding side of the paper feeding cassette 7, a pair of paper feeding rollers 12 having a shape in which a part of the circumference is cut out.
Are respectively arranged at predetermined positions in the paper width direction, and are driven and rotated in the arrow direction. Therefore, the paper feed roller 12 starts to rotate in response to the print start signal, and the circumferential portion of the paper feed roller 12 contacts the upper surface (top paper) of the stacked paper P and pushes down against the elastic force of the spring 10 and the top paper. Is to be sent in the paper feeding direction B. At this time, the separation claw 11 moves down by its own weight following the stacked sheets P, presses and locks both corners of the uppermost sheet to be sent out by its own weight pressure, and prevents its advance. As a result, the uppermost sheet floats up and is separated from the other sheets in the same manner as in the example shown in FIG. 4, and eventually both corners are released from the constraint of the separating claws 11 and the entire uppermost sheet is fed in the sheet feeding direction B. In this case, since both corners of the sheet are constrained by the separating claws 11, the portions are fed while being bent.

A turn guide 13 that reverses the traveling direction of the paper P by 180 ° is disposed downstream of the paper feeding cassette 7 in the paper feeding direction. In the turn guide 13 of this example, as shown in FIG. 1, 20 ribs 14a to 14t are provided along the sheet advancing direction.
Is erected. The roof portion of each of the ribs 14a to 14t that comes into contact with the paper has a circular cross section and is curved in a concave shape to form a smooth paper guide surface.

As shown in FIG. 2, the heights of the ribs 14a to 14t and the standing gaps in the intermediate portion ZM (which serves as a sheet receiving portion) of the turn guide 13 with which the leading edge of the delivered sheet comes into contact with each other are as shown in FIG. 11 and the paper feed roller 12 are set in correspondence with each other. That is, the ribs 14a, 14b and 1 located on both sides Ws of the paper transport path W, in which the separation claw 11 is disposed and the "ear edge" of the paper tends to occur due to the restraining effect.
The heights of 4s and 14t are lower than those of the other ribs 14c to 14r located in the central portion Wc, and are gradually lower toward the side ends. Therefore, the rib 14 located at the outermost end
The height of a and 14t is the lowest. Also, the rib 1 of the central portion Wc
The heights of 4c to 14r are set to be constant in order to smoothly advance the paper.

Therefore, the leading edge of the sheet, which is fed from the sheet cassette 7 by the separation claw 11 in a state where both corners are bent, comes into contact with the intermediate portion ZM of the turn guide 13 and includes the roof of each rib 14. It is guided upward along the curved guide surface. At this time, if the paper with weak stiffness such as label paper is
The both corners of the tip contact the guide surface while being bent downward, but ribs 14a, 14b and 14s, 14t of that portion
As described above, since it is formed to be gradually lower toward the side edge as described above, it is possible to reliably prevent the inconvenience that the bent sheet corner portion enters between the ribs and causes a paper feeding failure such as a jam. Thus, the entire area W of the leading edge of the sheet has 20 ribs 14a.
After being reliably supported on 14 to 14t, it is smoothly reversed and conveyed along the smooth curved guide surface at the tip of each rib 14 as the paper feed roller 12 rotates.

Further, as is apparent from FIG. 2, the area Wc1 corresponding to the position where the sheet feeding roller 12 of the turn guide 13 is arranged.
The standing interval of the ribs of Wc2 is set narrower than that of the other portions. This is intended to suppress the deformation of the paper as much as possible by narrowing the support interval by the ribs in the areas Wc1 and Wc2 where the carrying force of the paper feed roller 12 directly exerts a strong force. In, the ribs 14c to 14r are substantially flatly supported and smoothly guided along the curved guide surface.

In FIG. 3, a vertical wall surface 13a is formed in the lower part of the turn guide 13 facing the front portion 7c of the paper feeding cassette 7, and the wall surface 13a has a central portion as shown in FIG. The projecting degree is set so as to be close to the portion 7c and gradually separate toward both sides. Further, the wall surface 13a is formed only in the central region Wc of the sheet passing width. Then, the ribs 14c to 14 located in the central region Wc
r extends in a curved shape starting from the upper portion of the wall surface 13a. Therefore, the degree of protrusion of the ribs 14c to 14r toward the sheet cassette 7 at the starting point is also largest in the center and gradually decreases toward both sides. Also, on the wall surface 13a,
The sponge band 15 is attached.

By forming the lower portion of the turn guide 13 as described above, it is possible to remarkably suppress the generation of abnormal noise that occurs when the trailing edge of the paper is fed from the paper feed cassette 7. When the trailing edge of the paper leaves the front portion 7c of the cassette, it comes into contact with the lower portion of the turn guide 13 so that it is repelled by the "strength of the paper". Since they come into contact with each other and gradually abut toward both sides, the abutting sounds of the respective parts are deviated with time to be weakened. Further, since the contact is buffered by the sponge band 15, the above-mentioned contact noise is substantially eliminated.

Returning to FIG. 3, in front of the exit side of the turn guide 13,
A slip roll pair 16 is provided, and further in front of it,
A resist plate 17 is swingably arranged. Therefore,
The paper whose direction of travel has been reversed by the turn guide 13
The resist sheet 17 is sandwiched between the slip rolls 16 and conveyed, and the resist plate 17 that has advanced into the conveyance path prevents the progress thereof. At this time, the sheet is applied to the resist plate 17 while being slipped by the slip roll pair 16 to correct skew or the like. Eventually, a re-feeding signal is issued in synchronism with the image formed on the photosensitive drum 1, and in response to this, the resist plate 17 descends to allow the sheet to advance, and at a predetermined timing to the transfer position. Feed the paper.

It should be noted that the present invention should not be limited to the above-described preferred embodiments, and it is needless to say that various modifications can be made within the technical scope of the present invention. For example, the present invention can be applied to a paper feeding device that stacks paper on a paper feeding table that automatically moves up and down instead of a paper feeding cassette as the configuration of the feeding unit.

[Effect of device]

As described above in detail, according to the present invention, the height of the ribs of at least the paper receiving portion of the turn guide connected to the paper feeding portion is formed to be gradually lowered only at the both sides,
In addition, by narrowing the standing intervals of the ribs in the area corresponding to the sheet feeding member as compared with other areas, even for "weak" paper such as label paper, the direction of conveyance is set to 180 after separation by regulation of both leading edge angles.
A sheet feeding device of the type that reverses and feeds, one by one, and always stable and smooth feeding can be performed without conveyance defects such as skew and jam.

[Brief description of drawings]

FIG. 1 is a perspective view showing a turn guide 13 in a sheet feeding device as an embodiment of the present invention, and FIG. 2 is a sectional view of a sheet receiving portion of the turn guide 13 and a plan view of a sheet feeding cassette showing the correspondence between them. Explanatory drawing, FIG. 3 is a schematic sectional view showing an essential part of an optical writing printer to which a paper feeding device as an embodiment of the present invention is applied, and FIG. FIG. 6 is an explanatory diagram showing a sheet separating operation in FIG. 1 ... Photosensitive drum, 7, 41 ... Paper feed cassette, 9,
42 ... Bottom plate, 11,44 ... Separation claw, 12, 45 ...
Paper feed roller, 13 ... Turn guide, 14a-14t ...
Ribs, 16 ... slip roll pair, 17 ... resist plate.

Claims (1)

[Scope of utility model registration request] 1. A sheet stacking unit for stacking sheets to be fed,
A regulating member that locks both corners on the front end side with respect to the feeding direction of the stacked sheets; and a sheet feeding member that sequentially feeds the stacked sheets,
A plurality of ribs each having a curved sheet guide surface are provided upright, and a turn guide for guiding the sheets separated from the sheet stacking unit one by one in a direction to be inverted is provided, and at least the turn guide is delivered. The heights of the plurality of ribs in the receiving portion with which the leading edge of the coming sheet comes into contact are formed so as to be gradually lowered only in both side portions corresponding to the regulating member, and the ribs in the region corresponding to the sheet feeding member are formed. A sheet feeding device characterized in that the standing interval is made narrower than the standing intervals in other areas.