JPH0592859A - Sheet reversing method in image forming device and device therefor - Google Patents

Abstract

(57) [Summary] [Object] To provide a reversing method and a reversing device of an image forming apparatus capable of reversing in a small space. [Structure] When a sheet is guided by a guide 1a and its leading end is clamped by a clamp claw 6, a take-up drum 5 starts rotating counterclockwise and is taken up by the drum 5. After winding the paper, if the winding drum 5 is rotated in the opposite direction,
The sheet is unwound and the rear end thereof is spread outward by centrifugal force, and the rear end serves as the front end and is delivered to the carry-out path 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet reversing method and apparatus for an image forming apparatus having a double-sided function, such as a copying machine and a printer, for reversing a sheet having an image formed on one side and conveying it to a double-sided sheet feeding section. Regarding

[0002]

2. Description of the Related Art When an image is formed on both sides of a sheet, an image forming unit is required to use an electrophotographic process.
Since there is only one, the image is formed on one side and then conveyed again to the image forming unit. However, at this time, if the sheet is not reversed by the reversing device, an image will be formed twice on the same surface, so various reversing devices have been proposed, and FIG. 7 is an example of the reversing device.

In FIG. 7A, first, when a sheet having an image formed on one side exits a fixing unit (not shown) and is conveyed in the direction of arrow a, as shown in FIG. 7B, the sheet is conveyed. The sheet P is nipped and conveyed by the roller pair 20, and the reversing claw 21 opens the inversion path 23 at this time, so that the sheet P is nipped and conveyed by the conveyance roller pair 20 and the reversing roller 22. When the trailing edge of the sheet P passes over the reversing claw 21, the reversing roller 22 stops the rotational drive in the clockwise direction. At the same time, as shown in FIG.
Switch to release 4. Then, the reversing roller 22
Rotates in the reverse direction, that is, rotates counterclockwise, and the rear end of the paper P serves as the leading end and is conveyed to the conveyance path 24.

[0004]

Although the reversing device has a simple structure, the paper P must be temporarily stored in the reversing path 23. Therefore, the reversing path 23 needs to have a length equal to or larger than the length in the conveyance direction which is the maximum size capable of forming double-sided images on a sheet. Therefore, there is a problem that a very large space is required when the length in the conveyance direction of the maximum size capable of forming a double-sided image on the sheet is the vertical direction of A3 size. Therefore, it has been proposed to eject a part of the paper that has entered the reversing path 23 to the outside of the machine, but there is a risk that the user may accidentally pull out the paper.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above conventional problems and provide a reversing method and a reversing device for an image forming apparatus capable of reversing in a small space.

[0006]

The constitution of the present invention for achieving the above object is as follows.

(1) In a paper reversing method of an image forming apparatus for reversing a sheet having an image formed on one side and conveying the sheet to a double-sided paper feeding section, one end of the sheet having an image formed on one side conveyed from a carry-in path is rotated. A method of reversing a sheet, comprising: clamping the sheet on a body; then rotating a rotating body to wind a sheet around the rotating body; and, after winding, rotating the rotating body in a direction opposite to a winding direction and sending the sheet to a carry-out path.

(2) In a sheet reversing device of an image forming apparatus for reversing a sheet on which an image is formed on one side and conveying the sheet to a double-sided sheet feeding section, a sheet having an image formed on one side is conveyed and a conveyance path. A clamp means for clamping a sheet of paper, a clamp means provided on the surface, a rotating body that rotates in one direction and then rotates in the opposite direction, and a discharge path for discharging the sheet unwound from the rotating body. Characteristic paper reversing device.

(3) The sheet reversing device according to the above (2), wherein the rotating body is a drum capable of rotating in the forward and reverse directions.

(4) In the above (2), the rotating body is a belt which is wound around a plurality of belt rollers including a belt roller which can be driven in forward and reverse directions and which can run in two directions. The sheet reversing device described.

[0011]

According to the above construction, one end of the paper is clamped and wound around the rotating body, and after winding, the rotating body is rotated in the direction opposite to the winding direction and sent out to the carry-out path. Since it does not require the maximum length in the transport direction, it can be made extremely compact.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall schematic view showing an embodiment of a reversing device according to the present invention.

In FIG. 1, a sheet conveyed from a fixing device (not shown) in the direction of arrow a is sandwiched by a pair of carry-in rollers 1 from a carry-in path 1 and sent to a reversing unit 3.
In the reversing unit 3, a winding drum 5 as a rotating body is arranged in a casing 4 thereof, and the winding drum 5 is driven to rotate normally and reversely by a driving device (not shown). The surface of the take-up drum 5 is provided with a clamp claw 6 for clamping one end of the paper, and the take-up drum 5 is on standby in the position of FIG. 1 until the clamp claw 6 clamps the paper. A guide 1a for guiding the sheet to the clamp is provided at the leading end of the carry-in path 1.

The clamp claw 6 is, as shown in FIG.
It is composed of a fixed portion 8 fixed to the winding drum 5 and a movable portion 9 which is openably and closably mounted via the fixed portion 8 and a pin 7, and the fixed portion 8 and the movable portion 9 are provided on opposite surfaces thereof. A member 10 having a high coefficient of friction, such as a rubber material, is attached so that the clamped sheet can be securely held.

The reversing unit 3 is connected to a carry-out path 12 for sending out a sheet, and a sheet reverse-feeding prevention guide 11 is provided on the front side thereof. The reverse feed prevention guide 11 and the guide 1a are formed of a film sheet so as not to interfere with winding. A pair of carry-out rollers 13 is provided in the carry-out path 12 so that the paper is carried in the direction of the arrow b and sent to a double-sided paper feeding unit (not shown).

The sheet reversing method of the reversing device having the above construction will be described. In FIG. 3, the sheet P having an image formed on one surface and conveyed from the fixing device is nipped by the pair of carry-in rollers 1 from the carry-in path 1 and sent to the reversing unit 3.
At this time, the movable portion of the clamp claw 6 opens its mouth, and the winding drum 5 is stopped so that the clamp claw 6 is held at the standby position shown in FIG. Here, as shown in FIG. 4, when the paper P is guided by the guide 1a and its leading end is clamped by the clamp claw 6, a sensor (not shown) detects this and the take-up drum 5 moves counterclockwise. To start rotating. Then, when the trailing edge of the paper P passes through the guide 1a, the counterclockwise rotation of the take-up drum 5 is stopped, whereby the paper P is taken up by the take-up drum 5 as shown in FIG.

After the paper P is taken up by the take-up drum 5, the take-up drum 5 starts rotating in the reverse direction, that is, in the clockwise direction as shown in FIG. With this rotation, the paper P is unwound and the rear end of the paper P tries to expand outward due to centrifugal force. By utilizing this phenomenon,
The sheet P is not returned to the carry-in path 1 by the reverse feed prevention guide 11, but is fed to the carry-out path 12 with its rear end as the leading end. Then, when the inverted paper P is sandwiched by the carry-out roller pair 13, the paper P is conveyed to the double-sided paper feeding unit.

Thus, the paper P is reversed, but since the paper P is wound around the take-up drum 5 at the time of reversal, the reversing device does not need the maximum size in the conveying direction capable of forming a double-sided image and is extremely compact. Become.

FIG. 6 shows another embodiment of the present invention. In this embodiment, the rotating body of the reversing unit 3 is composed of a belt 14. The belt 14 includes belt rollers 15 and 16
Since one of the belt rollers 15 and 16 is wound around the drive roller and is driven by the drive device to rotate in the forward direction and the reverse direction, and the other is driven roller, the belt rollers 15 and 16 travel in two directions.

By operating the reversing device having such a structure as in the above embodiment, the paper can be reversed, and the same effect as that of the above embodiment can be obtained.

[0022]

[Effect] According to the above configuration, one end of the paper can be clamped and wound around the rotating body, and after winding, the rotating body can be rotated in the direction opposite to the winding direction and sent out to the carry-out path.
The reversing device only needs to have a space for installing the rotating body, and the entire device can be made extremely compact.

[Brief description of drawings]

FIG. 1 is an overall schematic view showing an embodiment of a reversing device according to the present invention.

FIG. 2 is an explanatory diagram of a clamp claw.

FIG. 3 is an overall schematic view showing a sheet carrying-in state of the reversing device.

FIG. 4 is an explanatory diagram showing a paper winding state.

FIG. 5 is an overall schematic view showing a sheet unloading state of the reversing device.

FIG. 6 is an overall schematic view showing another embodiment of the reversing device according to the present invention.

7 (a), (b) and (c) are explanatory views showing the operation of a conventional reversing device over time.

[Explanation of symbols]

 3 Reversing unit 5 Take-up roller 6 Clamp claw 14 Take-up belt 15 and 16 Belt roller P Paper

Claims (4)

[Claims] 1. A sheet reversal method of an image forming apparatus for reversing a sheet having an image formed on one side and conveying the sheet to a double-sided sheet feeding section, wherein one end of the sheet having an image formed on the one side conveyed from a carry-in path is rotated by a rotary member. A method for reversing a sheet, comprising: clamping the sheet to a sheet, winding the sheet around the rotating body by rotating the rotating body, rotating the rotating body in a direction opposite to the winding direction, and sending the sheet to a carry-out path. 2. In a sheet reversing device of an image forming apparatus for reversing a sheet on which an image is formed on one side and conveying the sheet to a double-sided sheet feeding section, a carry-in path through which the sheet on which an image is formed on one side is conveyed, and a conveyance path for conveying the sheet. It is characterized in that it has a clamping means for clamping a sheet, a rotating body which is provided on the surface and rotates in one direction and then rotates in the opposite direction, and a carry-out path for discharging the sheet unwound from the rotating body. Paper reversing device. 3. The sheet reversing device according to claim 2, wherein the rotating body is a drum that can rotate in the normal and reverse directions. 4. The rotating body is wound around a plurality of belt rollers including a belt roller capable of normal rotation and reverse rotation drive,
The sheet reversing device according to claim 2, wherein the belt is a belt that can travel in two directions.