JPH0632517A - Sheet inverting device - Google Patents

Abstract

PURPOSE:To provide a sheet inverting device which can surely switch back even a curled sheet, and to provide a printer incorporating the above-mentioned sheet inverting device. CONSTITUTION:A sheet inverting device for conveying sheets in a switch-back manner while crossing the sheets, is arranged such that an entrance guide A17 and an entrance guide B18 are provided in an entering and conveying path 15 while an outlet side guide A19 and an outlet side guide B19 are provided on the outlet side 16A, and the downstream end part P of the entrance guide A17 is curved so as to be convexly bulged while the entering and conveying path 15 is connected to the outlet side 16A with a convex bulge therebetween.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium (hereinafter referred to as a sheet) conveying device used in a printer, and more particularly to a mechanism suitable for switching back sheets conveyed one by one.

[0002]

2. Description of the Related Art Conventionally, a sheet switchback used in a printer or the like is disclosed in Japanese Utility Model Laid-Open No. 2-88945 and No. 2-88946. It is known to convey the material while sucking it. Further, Japanese Patent Application Laid-Open No. 64-69451 discloses a technique in which reversible conveyance control of a sheet can be easily performed by switchback by a reversible conveyance means using a conveyance roller.

[0003]

In the prior art, for example, when conveying while suctioning with a negative pressure suction portion, a gap is provided between the sheets at the time of switchback to reduce the contact resistance between the sheets. Also, when the sheet is conveyed in the forward direction, it can be dropped by free flight, so the sheet will not break. Therefore, a large number of sheets can be switched back at high speed and with high reliability in a short time. But,
It has the drawback that it is not suitable for downsizing and cost reduction. Further, since noise of negative pressure suction is generated, it is rarely used in a small-sized, low-noise non-impact electronic printer used in an office or the like.

On the other hand, in the system using the reversible conveying means, when the sheet enters from the entrance conveying path to the reversing conveying path having the reversible conveying means by the advancing conveying means rotating in one direction, the reversible conveying means reverses to cause the sheet. -The switch is conveyed back in the opposite direction to that of the entry and moves on the reversing conveyance path.
If the seat is straight without any out-of-plane deformation (hereinafter called curl), the seat that switches back and the seat that enters
They do not collide or break when they cross.
However, the sheet may curl in an arc shape. For example, when the sheet is moved from a high humidity environment to a low humidity environment and left as it is, or when a thick sheet is printed by heat fixing using a laser printer or the like, a large curl occurs. Further, since the curl is generated due to expansion and contraction due to the difference in water content between the front and back of the sheet, in the case of a double-sided printing printer, even after the curl having the shape formed by the first heat fixing is subjected to the second heat fixing. Often remains. For this reason, when the sheet on which one side has been printed is switched back and conveyed through a predetermined conveyance route and printing on the other side and then enters the reversing conveyance path again, the sheet and front and back sides of the sheet are conveyed. The direction of Le is reversed. Therefore, the sheets that have finished printing on one side or both sides alternately enter the reversing conveyance path and switch back, so that the sheet curled in the entering direction and the curl in the direction opposite to the entering direction. The intersected seat intersects. As a result, the sheet that switches back returns to the approaching conveyance path and causes a conveyance jam. The sheet that switches back enters the guide at a large angle (collision) and breaks at a corner of the sheet (corner). ) (3)
Dimensional shape: a combination of two curls) When the sheet enters the reversing transport path, the corners make small folds (ear folds) when the sheet rushes into the guide. Since the leading edge of the sheet that breaks inward rushes into the sheet that switches back at a large angle, there arises a problem that the sheet is bent by the conveying force in the opposite direction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet reversing device capable of reliably switching back even a curled sheet in order to solve the above problems. Another object of the present invention is to provide a sheet reversing device which can switch back even a sheet having a corner turned over without causing ear breakage. Further, another object of the present invention is to
It is an object of the present invention to provide a sheet reversing device in which the leading end of an incoming sheet is not bent due to the switchback sheet returning in the opposite direction. Still another object of the present invention is to provide a printer provided with the above-mentioned sheet reversing device.

[0006]

In order to solve the problem, (a) when the sheet enters the exit side of the reversing conveying path and the rear end passes through the entering conveying path, the rear end of the sheet is Make the sheet face the return side of the reversing conveyance path (b) When the sheet enters the exit side of the reversing conveyance path or switches back to the return side, the rush angle to the guide is reduced (c) A guide is provided at a position for covering the corners of sheets of various sizes to prevent the corners from being deformed such as curling (d) An outlet for the sheet that switches back to the return side It is necessary to satisfy the functions such as reducing the plunge angle of the sheet entering the side.

The above-mentioned problem is to provide a reversible conveying means on the exit side of the reversing conveying path, a unidirectional conveying means to the returning side on the returning side of the reversing conveying path, and a sheet in the middle of the reversing conveying path. Of the sheet that is conveyed to the outlet side and is connected to an entrance conveying path that guides the sheet to the exit side in the forward direction, and an entrance conveying means that conveys the sheet in one direction is provided on the entrance conveying path. In a sheet reversing device that conveys the sheet to the return side by reversing the reversible conveying means after the rear end has passed through the entrance conveying path, the entrance guide A forming the entrance conveying path is connected to the downstream end P. Is connected to the outlet side guide A so as to have a convex bulge on the side of the reversing conveyance path so that the sheet bends convexly when the sheet enters the exit side from the entrance conveyance path. , On the side facing the approach guide A, the approach guide B is in front of the downstream end Q. Provided by shifting the entrance conveying path than the downstream end P of the entry guide A, provided substantially parallel to are opposed to two on the outlet side guide on the exit side, on the return side,
The upstream end R of the return side guide A is continuously provided integrally with the downstream end Q of the approach guide B so as to be opposed to the return side guide A so that the upstream end S thereof is continuous with the outlet side guide B. This is achieved by providing a return side guide B by tilting the side T toward the return side guide A.

The above problem is also solved by the fact that the reversing conveyance path near the downstream end Q of the entrance guide B is closer than the sheet conveyance gap X _{1 of the} reversing conveyance path near the downstream end P of the entrance guide A. The sheet conveyance gap X ₂ is widened to allow the return side guide B.
Sheet conveyance gap X of the inversion conveyance path near the downstream side T of
_This can also be achieved by making the sheet conveying gap X ₂ wider than ₃ .

The above problem is also solved by integrally forming the entrance guide B and the return guide A in a range from the downstream vicinity C of the entrance conveying means to the downstream end Q in a substantially V shape. Is also achieved.

The above problem is also solved by the guide A on the outlet side.
Can also be achieved by placing at least the end faces of the sheets of various sizes to be transported.

The above problem is also solved in that the rear end of the sheet sent to the exit side of the reversing conveyance path by the rotation of the advancing conveyance means and the reversible conveyance means has a downstream end Q of the entrance guide B. When the sheet passes through the passage and is rotated from the entrance conveyance path to the reversal conveyance path with the downstream end P of the entrance guide A as a fulcrum so as to follow the direction of the exit side guide, the sheet is returned by the return side guide B. It is also achieved by allowing the rear end to stop short of the extension line on the exit side.

The above-mentioned problem is that the intersection angle between the entrance guide A and the exit side guide of the entrance conveyance path is 40 ° or more, and the intersection angle between the entrance guide A and the return side guide B is less than 40 °. It is also achieved by setting the intersecting angle between the return guide A and the return side guide B to be less than 40 °.

The above object can also be achieved by a printer using the above-mentioned technical means.

[0014]

The sheet is conveyed to the exit side of the reversing conveyance path which is bent and connected at an angle of 40 ° or more with respect to the extension line of the entrance conveyance path by the entrance conveyance means provided in the entrance conveyance path. Further, when the sheet is conveyed by the reversible conveying means provided on the outlet side and rotating in the forward direction and the advancing conveying means, and the rear end of the sheet passes through the advancing conveying guide B provided on the advancing conveying path, the sheet enters. With the downstream end P of the guide A as a fulcrum, the pendulum is swung swiftly so as to follow the posture of the sheet on the exit side.
However, before the rear end of the sheet returns to the posture of the sheet on the exit side, its rotation is stopped by the return side guide B provided on the side facing the downstream end P of the approach guide A and stopped. That is, the rear end of the sheet holds its position and posture so as to push the return side guide B by the bending rigidity force. For this reason, the sheet
Even if there is a line, its position and posture (direction) hardly change. At this time, in the direction of the extension line at the rear end of the sheet, there is provided a return side on which the sheet is switched back and moves. After that, the sheet is surely transported back to the return side of the reversing transport path by the reverse rotation of the reversible transport means. After that, at a predetermined timing, the next sheet enters the exit side of the reversing conveyance path by the advancing conveyance means, so that the two sheets moving in mutually opposite directions intersect while contacting each other. In this case, the sheet that is switch-back-transported passes through the reversible transport means, and after the reversible transport means rotates in the forward direction again, the tip of the next sheet that has entered the exit side reaches the reversible transport means. In addition, the sheets are conveyed at a predetermined timing by controlling the conveying intervals for sheets of various sizes. On the other hand, when entering the reversing conveyance path from the approaching conveyance path, the front end of the sheet enters the upstream side of the return guide B (the position facing the downstream end P of the entrance guide A) and then the reversing conveyance path. Enter the exit side. Entry angle of seat is 40
Since the return side guide B is formed so as to be less than °, the sheet enters the exit side so as to slide on the return side guide B.

In the case where the seat has a curl whose front end warps toward the outlet side (a shape in which the rear end also has a warp toward the same surface of the seat; hereinafter referred to as a concave curl). When entering the exit side, the seat enters the smooth. In addition, when switching back and entering the return side, as described above, the rear end of the seat (which becomes the tip at the time of switchback) that swiftly rotates with the downstream end P of the approach guide A as a fulcrum. The return side guide B is pushed by the bending rigidity force and the amount of deformation of the curl is substantially reduced.
Since it touches, it hardly changes its position and posture,
It surely enters the return side without causing backflow or breakage into the approaching conveyance path as in the past. The seat enters the exit side, the rear end passes through the downstream end Q of the entrance guide B, and the rear end of the seat turns toward the return guide B with the downstream end P of the entrance guide A as a fulcrum. (I) the certainty of its rotation, (ii)
High reliability can be secured by optimizing the stability of the position of the seat after the rotation, and (iii) the rush angle to the guide at the time of subsequent switchback. Among these,
It is important to secure (i) and (ii). If a thin sheet having a small rigidity is swung quickly, and a thick sheet having a large curl is pushed by the rigidity of the other end conveying guide 2 to stop. In order to stabilize the position, the above-mentioned points P, Q and return side guide B
The position and the posture of the return side guide A are determined. Therefore, the downstream end P of the approach guide A and the approach guide B
If the sheet conveyance gaps at the downstream end Q of the sheet, the downstream side T of the return side guide B, and the like are X ₁ , X ₂ , and X ₃ , respectively, X ₂ is wider than X ₁ and X is larger than X _{3. 2} is widely formed.

The four corners at the front end and the rear end are provided with two directions of a conveying direction and a 90 ° direction.
Depending on Le, there is "turning". In this case, when it rushes into the guide, it is likely to break. In particular, if the guide is formed near the inside of the corner (close to the center of the sheet), the corner that is turned up when the sheet rushes into the guide is wrapped around the edge of the guide. When transported while sticking, the corner "turning" gradually increases due to the transport resistance, and as a result, the contact angle increases and the transport resistance increases, causing the corner to bend in a vicious circle. .
For this reason, if the corner is caught in the transport path on the downstream side (at least the entire surface of the sheet is caught at the time of transfer and fixing), it will cause ear breakage. In order to prevent this, at least the return side guide A in which the sheet to switch back enters first
Is the corner for sheets of various sizes being transported.
Is formed at a position that can guide the. In the formation of the return side guide A, the approach guide B and the return side guide A in the range from the downstream vicinity C of the approach conveying means to the downstream end Q are integrally formed in a substantially V shape, and a sheet is formed. This can also be achieved by using one substantially V-shaped guide longer than the width of the gutter or by disposing a plurality of substantially V-shaped guides at predetermined positions.

When a curl whose tip is warped toward the return side (a shape in which the rear end also has a warp toward the same side of the sheet; hereinafter referred to as a convex curl) is present on the seat, it is concave. Contrary to the shape curl, the plunge angle increases when entering the exit side. However, the return side guide B where the sheet entering the exit side first rushes,
By forming the plunge angle to be less than 40 ° when there is no curl, the sheet enters the smooth side on the outlet side without breaking. The coefficient of friction between the sheet and the guide is 0.
It is 5 or less. Therefore, when the seat is straight without a curl, the seat can slide and move in the traveling direction when the guide has a plunge angle of about 60 ° or less. However, if the sheet has a convex curl, the sheet
The angle at which the tip of the gutter plunges into the guide increases. As a result of investigating the bending angle of the sheet tip by the curl, the maximum is 2
It was found to be 0 °. From this, it was found that the angle of entry of the sheet into the guide must be 40 ° or less. Moreover, it was confirmed that the sheet should be switched back at a sheet with curls and set to 40 ° or less.

Next, the case where the concave curl sheet and the convex curl sheet intersect at the time of switchback will be described. As described above, the rear end of the seat that has entered the exit side stops while pushing the return side guide B by the bending rigidity of the seat, but this is not limited to the rear end but moves by switchback. -It goes without saying that the same situation will occur in any part of the g. Therefore, it is necessary to switch back to the return side.
The rushing angle of the sheet entering the exit side toward the sheet is almost the same as when the first sheet directly rushes into the return side guide B. However, comparing the coefficient of friction between the sheet and the guide and the coefficient of friction between the sheets, the latter coefficient of friction is greater, so the transport resistance increases, but
By forming the guide B on the return side so that the plunge angle is less than 40 ° when there is no curl, the sheet can smoothly enter the exit side without breaking. 2 with the printer
When printing more than one sheet continuously, since the sheets cross each other, it is common that another sheet rushes into the sheet, but as described above, the sheet folds. It is possible to switch back without causing a conveyance jam.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a printer to which the present invention is applied, showing a main part of an apparatus according to the present invention, and a conventionally known apparatus such as a document handling device, a document reading device, and a toner coating device. Illustration of parts is omitted. The figure shows a sheet 1 housed in the bottom of the apparatus, a sheet feeding roller 2 arranged near one end of the sheet 1 and rotated to feed out the sheets one by one, and a sheet. Transport rollers 3A, 3B for transporting 1
And a transport roller 4 for transporting the sheet 1, and a transport roller 4
Registration roller (hereinafter referred to as "registration roller") 5 disposed on the downstream side (hereinafter referred to simply as "downstream side") in the sheet conveying direction, and arranged endlessly on the downstream side of the registration roller 5. And a transfer belt 6 on which the sheet 1 is placed and conveyed, a cylindrical photosensitive member 7 arranged so as to contact the sheet conveyance surface of the transfer belt 6 from above, and the transfer belt 6 downstream. The fixing device 8 arranged close to the end, the heater 8A and the backup roller forming the fixing device 8
8B, an advancing and conveying means 9 arranged downstream of the fixing device 8 for conveying the fixed sheet 1 in one direction, and a sheet 1 arranged downstream of the advancing and conveying means 9. And a discharge roller 1 for discharging the sheet 1 which is arranged on the downstream side of the reversible transfer means 10 and which is conveyed by the forward rotation of the reversible transfer means 10 onto the apparatus.
1 and a stacker 12 disposed on the downstream side of the discharge roller 11 for accumulating the sheet 1, and the sheet 1 switch-back-transported by the reverse rotation of the reversible transport means 10 to the discharge roller. A transport roller 13A that transports the sheet 1 in the opposite direction, and transport rollers 13B and 13C that are disposed downstream of the transport roller 13A and that transport the sheet 1 to the transport roller 4 again.
13D and 13E are shown.

In the apparatus having the above construction, when printing is instructed, the stored sheet 1 is sent to the transport roller 3A by the paper feed roller 2 and further transported to the transport rollers 3B and 3B.
Then, it is sent to the transport roller 4 and is transported toward the resist roller 5 by the transport roller 4. The sheet 1 conveyed toward the registration roller 5 is posture-controlled between the registration roller 5 and the conveyance roller 4, and then sent to the transfer belt 6 by the registration roller 5 and transferred to the transfer belt 6. 6 is seat 1
While the sheet is being conveyed, the sheet 1 is brought into contact with the photoconductor 7 carrying the developed image on the surface by the developing machine 14. Sheet 1 is photoconductor 7
While not in contact with the photosensitive member 7 by a transfer device (not shown)
The developed image carried on the surface is transferred. The sheet 1 on which the developed image is transferred is sent to the fixing device 8 by the transfer belt 6,
After passing through the fixing step, the entrance conveying means 9 sends the reversible conveying means 10 to the reversible conveying means 10. When the instructed printing is completed, the sheet is discharged by the reversible conveying means 10 to the discharge roller 1.
1 and further discharged to the stacker 12 on the apparatus by the discharging roller 11 and accumulated. When the instructed print is not completed and the other side of the print is required, the sheet is switched back by the reversible transport means 10 and sent to the transport roller 13A, and further the transport roller 13B,
After passing through 13C, 13D and 13E, it is again conveyed to the conveying roller 4. After this, when the instructed printing is completed through the series of steps described above, the sheet 1 is conveyed by the above-described path and deposited on the stacker 12.

Next, the sheet inverting device according to this embodiment shown in FIG. 1 will be described in detail with reference to FIGS. 2, 3 and 4. The sheet reversing device shown in FIG. 2 is a printer side plate (not shown), which has a pair of rollers 9A and 9B arranged so as to be in contact with each other and having their rotation axes parallel to each other, A pair of rollers 10A arranged on the printer side plate (not shown) on the downstream side of the entrance conveying means 9 so that the rotation axes thereof are parallel to each other and are in contact with each other.
10B, the reversible transport means 10, the approach transport means 9 and the approach transport path 15 through which the sheet 1 travels in one direction when the approach transport means 9 is driven by a drive motor (not shown). After passing through, the reversible conveying means 10 is driven in both forward and reverse directions by a driving motor (not shown) so that the sheet 1 enters in the forward direction or travels in the reverse direction by switchback. Exit side 16 of the reversing transport path
A, the return side 16B and the outlet side 16 of the reversing conveyance path in which the sheet 1 conveyed by switchback by the reverse rotation of the reversible conveyance means 10 travels in the direction opposite to the discharge roller 11.
A reversing conveyance path 16 composed of the return side 16B at A;
An approach guide A17 disposed on the approach transport path 15 for guiding the transport of the sheet 1, and an approach guide B18;
An outlet side guide 19 formed by 19A and 19B which forms the outlet side 16A and guides the conveyance of the sheet 1 in the forward and reverse directions, and the return side 1 for guiding the conveyance of the sheet 1.
6B, a return side guide A20, a return side guide B21, and a switchback for detecting that the sheet 1 which is switchback conveyed by the reverse rotation of the reversible conveying means 10 has passed through the reversible conveying means 10. And a sensor 22.

The downstream end Q of the approach guide B18 is disposed closer to the approach conveyance path 15 than the downstream end P of the approach guide A17, and the upstream end R of the return side guide A20 is continuous with the downstream end Q. Return side guide B formed integrally
The upstream end S of 21 is continuously close to the outlet side guide 19B, and the return side guide B21 is closer to the return side guide A20 as it is closer to the downstream side T thereof. Further, the sheet of entry guide A17 at the downstream end the reversing conveyance path 16 at P near - than DOO conveying gap X ₁ of the reversing conveyance path 16 at the downstream end Q vicinity of the entry guide B18 sheet - DOO The conveyance gap X ₂ becomes wider, and the sheet for the reversal in the vicinity of the downstream end Q of the approach guide B18 than the sheet conveyance gap X _{3 of the} reversal conveyance path 16 in the vicinity of the downstream side T of the return side guide B21. Sheet transport gap X _{2 on the} transport path 16
Are arranged to be wide. Further, the coefficient of friction between the sheet and the guide is 0.5 or less, which is 4 as described above.
If you arrange the guides so that they intersect at an angle of less than 0 °,
Even if there is a curl on the sheet, the sheet can slide smoothly on the guide to move smoothly, so that the sheet can be moved to the entry guide A17 of the entry conveyance path 15 and the exit side guide 19 of the exit side 16A. Intersection angle θ ₁ of 40 ° or more, the intersection angle θ ₂ of the approach guide A17 and the return side guide B21 of the approach conveyance path 15 is less than 40 °, and the return side guide A20 and the return side guide It is arranged so that the intersecting angle θ ₃ with B21 is less than 40 °. Further, the entrance transport means 9 and the reversible transport means 10 are arranged such that the distance between them is at least smaller than the minimum size of the sheet to be transported. For example, B5 size (1
82 × 257 mm) in the lateral direction and A5 size (148 × 210 mm) smaller than that in the lateral direction are conveyed in the longitudinal direction, the approaching conveying means 9 and the reversible conveying means 1
0 means that the interval is 182 mm or less (for example, 145 mm)
Will be placed.

In the sheet reversing device having the above structure, the sheet
The entrance 1 is carried toward the exit side 16A by the entrance carrying means 9, and the crossing angle θ ₂ is 40 ° at the return side guide B21.
It rushes in less than and enters the exit side 16A into the smooth. The sheet 1 is further conveyed by the reversible conveying means 10 and the advancing conveying means 9 which rotate in the forward direction, and the rear end is the admission guide B18.
When passing through the downstream end Q of the exit guide A17, it rotates about the downstream end P of the approach guide A17 that bulges in a convex shape as a fulcrum.
Try to imitate the posture within 9. However, the return guide B
Since the sheet 21 is arranged so as to be inclined so that the downstream side T thereof is closer to the approaching conveyance path 15 side, the sheet 1 is restricted from rotating and stops. As a result, the rear end of the sheet 1 pushes the return side guide B21 by the bending rigidity force to maintain its position and posture. For this reason, even if the seat 1 has a curl, the seat 1 follows the posture of the return side guide B21.
Stops and the posture of the seat does not change. After that, the reversible conveying means 10 is rotated in the opposite direction by a motor (not shown), so that the sheet 1 is surely moved in the direction of the return side guide A20 without flowing backward into the approach conveying path 15 and is returned. It is sent to 16B and is transported by switchback. After the sheet 1 that is switchback-transported has finished passing through the reversible transport means 10, at least after the reversible transport means 10 rotates in the forward direction again, the next sheet 1 transported by the incoming transport means 9 The conveyance interval is controlled so that the leading end reaches the reversible conveyance means 10 and the conveyance is performed. For example, when printing is instructed, the size of the sheet 1 set in the apparatus by a plurality of sensors (not shown) is known in advance. Approach conveyance path 1
By detecting the front end of the sheet 1 that has entered the exit side 16A from 5 with the sensor 22, the timing at which the sheet 1 switches back and finishes passing through the reversible transport means 10 can be known in advance. Therefore, the rotation and stop of the advancing and conveying means 9 are controlled so that the leading end of the next sheet 1 does not reach the reversible conveying means 10 at an earlier timing, or the trailing end of the sheet and the next sheet are controlled. It controls the conveyance interval with the tip of the tray.

By arranging the return side guide B21 so as to be inclined toward the entrance conveyance path 15 side with respect to the direction on the extension line of the exit side guide 19, the sheet 1 has a crossing angle θ ₂ of less than 40 ° with the return side guide B21. Rush in and enter the exit side 16A into the smooth. Therefore, whether the curl of the sheet 1 is concave or convex, the sheet can surely enter the outlet side 16A.
Further, since the intersection angle θ ₁ between the approach guide A17 and the exit side guide 19 on the exit side 16A is arranged to be 40 ° or more and the downstream end P of the approach guide A17 is formed by bulging in a convex shape,
When the rear end of the seat 1 passes the downstream end Q of the approach guide B18, the rear end of the seat 1 that has entered the outlet side 16A stops by pushing the return guide B21 by the bending rigidity of the seat. Therefore, the posture is almost constant, and even if there is a concave or convex curl, the return side 16B can be surely returned during switchback.
Enter. As a result, even when the sheets are continuously switched back while intersecting the sheets, the sheet 1 does not suffer from conveyance jams or breaks in the sheets.

FIG. 3 shows another sheet reversing device, which is a part of the downstream side of the approach guide B18 and the return side guide A.
It shows a guide 23 integrally formed with a part of 20 in a substantially V shape.

That is, the range from the downstream vicinity C of the approach conveying means 9 in the approach guide B18 to the downstream end Q and the range on the upstream side of the return side guide A20 are integrally molded with a member having a low friction coefficient. It was done. Also, seat 1
When the switch back is performed, the rush angle into the return side guide A20, that is, the intersecting angle θ ₃ between the upstream side of the return side guide B21 and the upstream side of the return side guide A20 is set to less than 40 °. Therefore, even if the sheet 1 is thin, it does not enter the return side 16B into the smooth and the jam does not occur.

Further, in the four corners of the sheet 1,
The curl in the carrying direction and the curl in the direction perpendicular to the carrying direction are combined, resulting in "turning". In this case, when the end surface of the guide is near the inside of the end surface of the sheet 1 (close to the center of the sheet), the sheet 1 wraps around the edge of the guide and plunges into the guide so as to cling. If the sheet 1 has the concave curl, the above phenomenon may occur when the corner at the tip of the sheet 1 rushes into the return side guide A20 during switchback. In this case, the sheet 1 comes into contact with the end face of the return side guide A20 near the inner side of the end face of the guide A20, and the sheet 1 moves when the "flipping" gradually increases due to the conveyance friction resistance. , The contact angle between the end of the return side guide A20 is further increased, and the frictional resistance of conveyance is increased. Finally, the corner of the sheet 1 is bent or broken. . Therefore, the arrangement of the guide 23 integrally formed in the substantially V shape shown in FIG.
Shown in. By arranging at least the end faces of the sheets of various sizes to be transported so that they can be guided, the sheet 1
It is possible to prevent the corner from bending and the ear being broken.
The guide shown in FIG. 4 is arranged in the case where the reference position of the seat is at the left end in the traveling direction, but also in the case of the center reference, the guide 23 may be similarly arranged on the end face of the seat. In addition,
Regarding the shape of the guide, as shown in FIG.
The portion of the downstream end P of the protrusion 17 that bulges in a convex shape is formed by bending a single plate material, or as shown in FIG.
A portion of the downstream end P that bulges into a convex shape may be integrally formed. In either case, it is important to bulge the downstream end P of the approach guide A17 into a convex shape.
In this case, when the convex portion is formed into a smooth circular arc, the radius of the circular arc may be reduced to form the sheet 1 in the approach conveyance path 1.
Needless to say, it is important to prevent the backflow to the 5th. Further, the portion of the downstream end P of the approach guide A17 may be simply bent to bulge into a convex shape. Further, various methods may be used to inflate the portion of the downstream end P of the entry guide A17 into a convex shape as long as it meets the purpose of the present invention to prevent the sheet 1 from flowing back into the entry conveyance path 15. . Therefore, it goes without saying that the transport gap X ₁ of the sheet 1 at the portion where the downstream end P of the approach guide A17 bulges in a convex shape is made small.

[0029]

According to the present invention, even when the sheet has a curl, when the sheet is switched back while being crossed with the sheet, the posture of the sheet at the time of inrush is stably maintained. At the same time, the plunge angle between the sheets and the plunge angle of the sheet into the guide can be kept small. Further, since the end faces of the sheets of various sizes are received by the guide, out-of-plane deformation can be suppressed even for the sheet with the corners turned up. For this reason, it is possible to provide a sheet reversing device that can switch back without causing breakage of the sheet, jamming of the conveyance, breaking of ears, and the like.

[Brief description of drawings]

FIG. 1 is a side view of a printer showing an embodiment of the present invention.

FIG. 2 is a detailed side view of the sheet reversing device.

FIG. 3 is a detailed side view of the sheet reversing device.

FIG. 4 is a plan view showing a position of a guide.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sheet, 2 ... Paper feed roller, 3, 3A, 3B ... Conveyor roller, 4 ... Conveyor roller, 5 ... Regist roller, 6 ... Transfer belt, 7 ... Photoconductor, 8 ... Fixer, 8A ... HEATRO
La, 8B ... Backup roller, 9 ... Incoming transport means, 1
0 ... Reversible conveying means, 11 ... Ejecting roller, 12 ... Stacker, 13A, 13B, 13C, 13D, 13E ... Conveying roller, 14 ... Developing device, 15 ... Entry conveying path, 16 ... Inversion conveying path, 16A ... Exit side, 16B ... Return side, 17 ... Entry guide A, 18 ... Entry guide B, 19, 19A, 19B
... exit side guide, 20 ... return side guide A, 21 ... return side guide B, 22 ... sensor, 23 ... guide, P ... downstream end of approach guide A, Q ... downstream end of approach guide B, R ... return side Upstream end of guide A, S ... Upstream end of return side guide B, T
… Downstream of the return guide B, θ ₁ … Intersection angle of the approach guide A and exit guide, θ ₂ … Intersection angle of the approach guide A and return guide B, θ ₃ … Upstream of the return guide A Crossing angle between the upstream side of the return guide B and X _1, ... Sheet conveyance gap of the reversing conveyance path near the downstream end P of the approach guide A, X ₂ ... Near the downstream end Q of the approach guide B. the reversing conveyance path sheet - DOO conveying gap, downstream T of X ₃ ... return side guide B
Sheet conveyance gap in the inversion conveyance path in the vicinity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Hashimoto 2-6-2 Otemachi, Chiyoda-ku, Tokyo Nitate Koki Co., Ltd.

Claims (7)

[Claims] 1. An approach conveying means provided on an approach conveying path for guiding a sheet in a forward direction; a reversible conveying means provided on an exit side of a reversing conveying path for guiding a sheet from the approach conveying path; A sheet provided with a one-way conveying means provided on the return side of the reversing conveying path for conveying the sheet in the reverse direction by the reverse rotation of the reversible conveying means.
In the reversing device, an entrance guide A17 and an entrance guide B18 are provided substantially parallel to the entrance conveyance path 15, and an exit side guide A19A and an exit side guide B19B are provided parallel to the exit side 16A of the reversal conveyance path 16. Approach guide A1
The downstream end P of 7 is bent in a convex shape and connected to the outlet side guide A19A to connect the entrance conveyance path 15 and the exit side 16A of the reversal conveyance path with a convex bulge. The approach guide B provided facing A17
A downstream end Q of the entry guide A17 is provided on the upstream side of the entry conveyance path 15 with respect to the downstream end P of the entry guide A17, and a return side guide A20 is provided on the return side 16B of the reversing conveyance path with the upstream end R of the entry guide A20. A sheet reversing device, which is integrally provided at a downstream end Q of the guide B18 and is provided with a return side guide B21 facing the return side guide A20. 2. The return guide B21 is provided so as to be inclined so as to approach the return guide A20 from the upstream end S side toward the downstream side T, and the approach guide A21 is provided.
Wherein the reversing conveyance path 16 at the downstream end near P of 17 - DOO conveying gap the reversing conveyance path of the downstream end Q vicinity of the entry guide B18 than X ₁ sheet - widening the preparative conveying gap X _2, sheet of claim 1, characterized in that the wider the door conveying gap X ₂ - sheet downstream T the reversing conveyance path 16 in the vicinity of the return-side guide B18 - than DOO conveying gap X ₃ the sheet −
Reversing device. 3. The approach guide B18 and the return side guide A20 in the range from the downstream vicinity C of the approach conveying means 9 to the downstream end Q are integrally formed in a substantially V shape. The sheet reversing device according to claim 1. 4. The sheet according to claim 1 or 3, wherein the return side guide A20 is arranged at a position where at least an end surface of a sheet having various sizes to be conveyed can be guided. Inversion device. 5. The approach guide A17 and the approach guide B
18 according to the gap between the downstream end Q to claim 1 or claim 2, characterized in that narrower than the gap X _1, X _2, X ₃ of sheet - DOO conveying device. 6. A crossing angle between the outlet side guide 19 of the entry guide A17 of the entrance conveying path 15 the outlet 16A theta ₁
Is 40 ° or more, and the intersection angle θ ₂ between the approach guide A17 and the return side guide B21 of the return side 16B is 40 °.
And the return side guide A20 of the return side 16B
The sheet conveying device according to any one of claims 1 to 5, wherein an intersecting angle θ ₃ between the return guide B21 and the return side guide B21 is less than 40 °. 7. A cassette for accommodating a sheet, a developing / transferring unit for forming an image on the sheet carried out from the cassette, and a fixing unit for fixing the image transferred on the sheet at the developing / transferring unit. , A sheet conveying system having a sheet reversing device for reversing the sheet so that it can be recorded on the front and back of the sheet, and a sheet having an image fixed thereon. 7. A printer including a stacker for accumulating sheets, wherein the sheet reversing device according to any one of claims 1 to 6 is used as the sheet reversing device.