JP2513670B2 - Sheet feeding device - Google Patents

Description

The present invention relates to a sheet feeding device of an image forming apparatus such as a copying machine and a laser beam printer, and, for example, an image having a screen and a multiple image forming function. The present invention relates to a sheet feeding device that re-feeds a sheet on an intermediate tray portion in a forming device.

(B) Conventional Technology Conventionally, an image forming apparatus having a double-sided or multi-image forming function is provided with a sheet re-feeding unit such as an intermediate tray, and the sheets after the first image formation are temporarily accumulated and re-formed. It is common to ship. Then, in the image forming apparatus, it is important to properly re-feed the sheets accumulated in the sheet re-feeding unit one by one toward the image forming unit without causing double feeding or jam. As an example of the image forming apparatus thus configured, there is a copying machine M having a double-sided copying function as shown in FIG.

The copying apparatus M has a copying section (image forming section) 2 including a photosensitive drum 3 and the like at approximately the center of the machine body 1.
A document placing table 4, a light source 5 and a lens system 6 are provided above the machine body 1. Further, two sheet feeding cassettes 7a and 7b are arranged on the right side of the machine body 1 in the figure. Around the photosensitive drum 3, two developing devices 9a and 9b each containing a toner of a different color are provided so that they can be set / reset by moving in the arrow direction so that a desired color can be copied. , Transfer charger 10 and separation charger 11, and cleaner
12 and the primary charger 13 are wired. Further, paper feed rollers 14a, 14b are arranged above the paper feed cassettes 7a, 7b,
The sheet S is guided to the registration roller pair 17 via the conveyance roller pairs 15a and 15b and the paths 16a and 16b, respectively. Further, a sheet re-feeding unit 19 'is arranged below the machine body 1, and a sheet S to be multi-copyed or double-sided copied from the sheet re-feeding unit 19' is copied through the registration roller pair 17 to the copying unit. It will be re-delivered to the second. Further, a fixing device 20 is provided downstream of the conveying device 18 following the separation charging device 11, and further, a first discharge roller pair is provided downstream of the fixing device 20.
A sheet 21 is arranged to discharge the sheet S to a tray or the like outside the machine usually via the second pair of discharging rollers 22. A flapper 23 and an auxiliary flapper 24 are provided between the first discharge roller pair 21 and the second discharge roller pair 22.
Further, a paper inspection sensor including a detection arm 25a and an optical sensor 25b is provided, and when the sheet S normally discharged from the first discharge roller pair 21 is conveyed along the upper side of the flapper 23 in the solid line position, The conveyance force causes the auxiliary flapper 24 to swing in the direction of the arrow, and the detection arm 25 that moves based on it.
The optical sensor 25b is operated by a to detect the passage of the sheet S. Then, the sheet S is discharged to the outside of the machine by the second pair of discharge rollers 22 that rotate in the normal direction.

On the other hand, in double-sided copying, the sheet S is partially discharged to the outside of the machine by the forward rotation of the second discharge roller pair 22 as in the normal state, but the rear end of the sheet S is At the time of leaving the auxiliary flapper 24, the second discharge roller pair 22 is reversely driven by the detection of the discharge section paper detection sensors 25a and 25b, and the sheet S is guided by the left side portions of the auxiliary flapper 24 and the flapper 23 to be conveyed to the path 27. Will be introduced to.

Further, during multiple copying, the flapper 23 is switched to the dotted line position, and the sheet S discharged from the first discharge roller pair 21 is directly introduced into the path 27 by the guide action of the right side portion of the flapper 23. There is.

Then, the sheet S introduced into the path 27 is conveyed to the sheet re-feed unit 19 'and re-fed from the sheet re-feed unit 19' toward the registration roller pair 11.

Then, in the sheet re-feed unit 19 ', as shown in detail in FIG.
9. A pair of step rollers 30 and a pair of downstream rollers 31 are arranged at the substantially central portion, and an upstream vertical guide 32 is provided between the upstream conveying roller pair 29 and the step roller pair 30.
a, 32b, step roller pair 30 and downstream conveying roller pair 3
Downstream side upper and lower guides 33a and 33b are respectively arranged between them and 1. The step roller pair 30 can be rotated forward and backward, and is independently driven by a stepping motor so as to accurately control the transport distance of the sheet S. Then, the sheet S introduced into the path 27 is paired with the upstream side transport roller pair.
When the leading edge of the sheet S is conveyed through 29 and the upstream-side upper and lower guides 32a and 32b and reaches the step roller pair 30, the step roller pair 30 starts forward rotation, and the trailing end of the sheet S is on the upstream side lower guide 32b. Carry the distance B until it falls to
Then, the sheet S is reversed, and the sheet S is returned backward and stopped until a predetermined stacking shift amount l is reached. And the next sheet S
When the sheet roller reaches the step roller pair 30, the step roller pair 30 operates in the forward and reverse directions in the same manner as described above, and the sheet S is stacked on the previous sheet S in the state shifted by the stacking shift amount l backward. The succeeding sheets S are stacked in the state of being set back by the stacking shift amount 1 as described above (see FIG. 8). When the stacking of the sheets S is completed, the sheets S ... Are sent to the downstream side transport roller pair 31 by the step roller pair 30 at a constant timing, and further, the lowermost sheet is fed by the downstream side transport roller pair 31. The sheets S are sequentially fed one by one, and the sheets S are fed to the copying section 2 without being double fed.

(C) Problems to be Solved by the Invention By the way, the sheet S conveyed to the above-mentioned downstream side conveying roller pair 31 is conveyed for a long distance or is piled up and conveyed, so that the sheet S is conveyed in the conveying direction. A tilt (skew) occurs. Therefore, as is generally practiced by the registration roller pair 17, the leading end of the sheet is guided to the nip portion of the stopped roller pair, and the sheet is pushed by a predetermined amount, so that the sheet is transferred before the roller pair. It is conceivable to correct the inclination (tilt) of the sheet by forming a loop in a part so that the tip of the sheet surely hits the nip portion. However, conventionally, the loop A of the sheet S, including the case of the registration roller pair 17, is usually formed above as shown in FIG.

When the ... plurality of sheets S are stacked as described above, as shown in FIG. 10, what lowermost sheet S ₁ is being stacked on to form a predetermined loop It is very difficult to form a loop due to the weight of the stacked sheets and the resistance due to the strength of the hips, because it is necessary to lift several sheets S .. If the conveying force for pushing the sheet into the pair of rollers that is stopped is insufficient, an appropriate loop may not be formed and skew correction may not be possible.

Further, when forming the loop of the lowest sheet S ₁ , the stacked sheets S may be lifted and the leading end of the sheets S may be caught by the end portion of the guide 33a or the like to prevent reliable conveyance.

(D) Means for Solving the Problem The present invention aims to solve the above-mentioned problems, and guides the stacked sheets by sequentially shifting the leading end in the conveying direction by a predetermined amount, and aligns the moving sheets at a stop. The guide means is provided with a loop guide portion that guides the sheet to form a downward loop when it abuts against the means.

(E) Action Based on the above-mentioned means, when the stacked sheets are sequentially displaced by the predetermined amount in the conveying direction and guided and moved by the guide means, the lowermost sheet among these sheets stops the leading edge. It abuts against the aligning means and is pressed by the aligning means. Then, a downward loop is formed on the sheet along the loop guide portion of the guide means, and the leading end of the sheet is surely pressed by the aligning means to correct skew. Then, the sheet is separated from other sheets and fed by the aligning means that has started to rotate.

(F) Example An example in which the present invention is applied to a sheet re-feed unit of a copying machine will be described below with reference to the drawings.

The sheet refeed unit 19 according to the present embodiment is a partial modification of the previously described conventional sheet refeed unit 19 ', and therefore the same portion as the previously described sheet refeed unit 19'. Are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIGS. 1 and 2, the sheet re-feeding unit 19 that constitutes the sheet feeding device according to the present embodiment has a step roller pair 30 and is the same as the above-mentioned downstream side that constitutes the aligning means. The transport roller pair 31 is provided. Then, between the step roller pair 30 and the downstream side transport roller pair 31,
The upper side transport guide 35 and the lower side transport guide 36 constituting the guiding means are arranged so as to face each other, and a fixed guide 37 is fixedly provided facing the downstream side transport roller pair 31, and further above the fixed guide 37. An opening / closing guide 39 is provided in the door so that it can be opened / closed during jam handling. A swing guide 36 ', which constitutes a loop guiding portion, is arranged on the lower transport guide 36 so as to be swingable about a support pin 41 as a swing center.
A spring 42 is arranged at the cut-and-raised portion 36'a of the swing guide 36 ', and urges the tip end portion 36'b of the swing guide to the extent that it slightly contacts the lower conveyance guide 36. . The swing guide 36 'forms a smooth sheet conveying surface with the lower conveyance guide 36 when the leading end portion 36'b is in contact with the lower conveyance guide 36.

Since the present embodiment is configured as described above, the sheets S ... Stacked on the lower conveyance guide 36 in the state of being set back by the stacking shift amount l by the step roller pair 30 are downstream by the step roller pair 30. If the lowermost sheet S ₁ is fed toward the conveying roller pair 31 and is still fed even if the leading edge of the lowermost sheet S ₁ comes into contact with the stopped downstream conveying roller pair 31, the lowermost sheet S ₁ will form a loop A. And At this time, the rocking guide 36 'is moved by a slight force to its tip.
36'b The only is biased so as to contact the lower conveying guide 36, and further the loop formation of the sheet S ₁ of the lowest they also overlapping of the sheet S ... What Like upward resistance Therefore, the lowermost sheet S ₁ forms a loop A downward while pushing down the swing guide 36 ′. Then, the lowermost sheet S ₁ forming the loop A is surely pushed at its leading end into the nip portion of the lower conveying roller pair 31 to correct the skew, and starts rotating.
The sheet is sandwiched between the sheets and separated from the other sheets S ...
When the loop A of the sheet S ₁ disappears as the lowermost sheet S ₁ is fed, the swing guide 36 ′ is returned to the position where its tip end 36 ′ b abuts the lower conveyance guide 36. To do.

It should be noted that, as shown in FIG. 3, when the swing guide 36 'is not present, the sheet S moves downward from the gap between the lower conveyance guide 36 and the fixed guide 37 as shown in FIG. It is an amount that forms a space that can at least absorb the loop A that is naturally formed.

Further, in the above-described embodiment, when the sheet S forms the loop A, the swing guide 36 'is moved by the waist of the sheet to create the space for storing the loop A, but the present invention is not limited to this. , The swing guide 3 as shown in FIG.
A solenoid 43 is attached to the cut-and-raised portion 36'a of 6 ', and a sensor for detecting the leading edge of the sheet is provided in the vicinity of the upstream side of the downstream conveying roller pair 31, so that the leading edge of the sheet is located in the downstream conveying roller pair 31. The solenoid 43 may be activated at the timing of entering the nip portion, and the swing guide 36 'may be moved downward to make a space for storing the loop A therein.
With this structure, the sheet S itself does not need to move the swing guide 36 ', and the loop A can be formed more easily.

Further, as shown in FIG. 5, the lower transfer guide 36 of the above-described embodiment is partially changed in shape, and instead of the swing guide 36 ', the tip end 45a of the lower transfer guide 45 accommodates a loop. The shape may be such that there is a space for in this case,
The shape of the front end portion 45a is set in consideration of the type and size of the sheet so that the sheet can be guided and the loop can be stored without trouble.

Although the sheet feeding means 31 is shown as the aligning means in the above-described embodiment, a stopper member that can be moved in and out immediately before the means 31 may be provided and used as the aligning means.

Further, the present invention is not limited to the intermediate tray, and can be applied to sheet conveyance in a normal conveyance path. As a result, the speed of sheet conveyance can be increased.

(G) Effect of the Invention As described above, according to the present invention, the sheet is guided to the sheet feeding means on the upstream side of the sheet feeding means, and the moving sheet is stopped by the sheet feeding means. Since the guide means having the loop guiding portion for guiding the sheet to form a downward loop when abutting is provided, the sheets stacked with the front end in the transport direction shifted by a predetermined amount in order to feed the sheets one by one are provided. When feeding from the lowest sheet in order,
Loops can be properly formed without the influence of other stacked sheets to reliably correct skewing of these sheets.

[Brief description of drawings]

FIG. 1 is a side sectional view of a sheet re-conveying section according to an embodiment of the present invention, FIG. 2 is a perspective view thereof, FIG. 3 is a diagram showing a sheet loop formed in its natural state, and FIG. FIG. 5 is a side cross-sectional view showing a partially changed swing guide of the sheet re-conveying unit in the embodiment of the present invention, and FIG. Cross section,
FIG. 6 is a side sectional view of a copying machine equipped with a conventional sheet re-conveying section, and FIG. 7 is a side sectional view of a conventional sheet re-conveying section.
The figure is a side view showing the sheet stacking state, FIG. 9 is a side sectional view showing the conventional loop forming state, and FIG. 10 is a side sectional view showing the loop forming state when there are stacked sheets. It is a figure. A ... Loop, S ... Sheet, 19 ... Sheet feeding device (sheet refeeding unit), 31 ... Aligning means (downstream conveying roller pair), 36,45 ... Guide means (lower conveying guide) ), 36 ′,
45a …… Loop guide (swing guide, tip).

Claims (1)

(57) [Claims] 1. A sheet feeding device in which sheets are stacked with their front ends in the conveying direction being sequentially shifted by a predetermined amount, and these sheets are sequentially fed one by one, while guiding the sheets and stopping the moving sheets. A sheet feeding device comprising guide means having a loop guiding portion for guiding the sheet to form a downward loop when the sheet comes into contact with the aligning means.