SHEET PROCESSING APPARATUS AND IMAGE FORMING APPARATUS

Abstract

A sheet processing apparatus including: a conveying unit, which conveys a sheet; a stacking unit on which the conveyed sheet is stacked; a processing unit, which processes the stacked sheet; a buffering unit, which allows the sheet conveyed to the stacking unit by the conveying unit to pass, and buffers a predetermined number of sheets to be passed during an operation of the processing unit; a transferring unit, which receives the buffer sheets and transfers the predetermined number of buffer sheets from the buffering unit to the stacking unit; and a controlling unit, which controls a sheet conveying speed to make a speed when the transferring unit transfers the buffer sheet lower than a speed when the transferring unit receives the buffer sheets to prevent the sheet conveyed by the conveying unit from interfering the transferring unit during an operation of transferring the sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional front view schematically illustrating a copying machine serving as an image forming apparatus including a sheet processing apparatus according to an embodiment of the present invention in an apparatus main body.

FIG. 2 is a control block diagram of the copying machine of FIG. 1.

FIG. 3 is a cross-sectional front view schematically illustrating a sheet processing apparatus according to an embodiment of the present invention in an apparatus main body.

FIG. 4 is a cross-sectional front view schematically illustrating drive systems of the sheet processing apparatus according to an embodiment of the present invention in an apparatus main body.

FIG. 5 is an enlarged view illustrating a main part of the sheet processing apparatus according to an embodiment of the present invention.

FIG. 6 is a control block diagram illustrating the sheet processing apparatus of FIG. 3.

FIG. 7A is a diagram illustrating an operation of the sheet processing apparatus in a case where a sheet is not required to be buffered during sheet processing, and in a state where a first sheet is fed into the sheet processing apparatus.

FIG. 7B is a diagram illustrating an operation of the sheet processing apparatus in a case where a sheet is not required to be buffered during sheet processing, and in a state where a first sheet is received by the sheet processing apparatus.

FIG. 8A is a diagram illustrating an operation of the sheet processing apparatus, which follows the operation of FIG. 7B, in a case where a sheet is not required to be buffered during sheet processing, and in a state where the first sheet is further fed to a sheet processing tray.

FIG. 8B is a diagram illustrating an operation of the sheet processing apparatus in a case where a sheet is not required to be buffered during sheet processing, and in a state where the first sheet is brought into abutment against a stopper.

FIG. 9 is a diagram illustrating an operation of the sheet processing apparatus in a case where a sheet is not required to be buffered during sheet processing, and in a state where three sheets are stacked on a tray;

FIG. 10A is a diagram illustrating an operation of the sheet processing apparatus in a case where a sheet is to be buffered during sheet processing, and in a state where the first sheet is fed to a switchback point.

FIG. 10B is a diagram illustrating an operation of the sheet processing apparatus in a case where a sheet is to be buffered during sheet processing, and in a state where the first sheet is received by a trailing-edge receiving portion.

FIG. 11A is a diagram illustrating an operation of the sheet processing apparatus, which follows the operation of FIG. 10B, in a case where a sheet is to be buffered during sheet processing, and in a state where a second sheet is fed into the sheet processing apparatus.

FIG. 11B is a diagram illustrating an operation of the sheet processing apparatus, in a case where a sheet is to be buffered during sheet processing, and in a state where a third sheet is fed into the sheet processing apparatus.

FIG. 12A is a diagram illustrating an operation of the sheet processing apparatus, which follows the operation of FIG. 11B, in a case where a sheet is to be buffered during sheet processing, and in a state where a sheet bundle is started to be delivered from the processing tray to a stack tray.

FIG. 12B is a diagram illustrating an operation of the sheet processing apparatus, in a case where a sheet is to be buffered during sheet processing, and in a state where the sheet bundle and a buffer sheet are conveyed in a discharge direction.

FIG. 13A is a diagram illustrating an operation of the sheet processing apparatus, which follows the operation of FIG. 12B, in a case where a sheet is to be buffered during sheet processing, and in a state where the sheet bundle is delivered from the processing tray to the stack tray.

FIG. 13B is a diagram illustrating an operation of the sheet processing apparatus, in a case where a sheet is to be buffered during sheet processing, and in a state where the buffer sheet is fed to the processing tray.

FIG. 14A is a diagram illustrating an operation of the sheet processing apparatus, which follows the operation of FIG. 13B, in a case where a sheet is to be buffered during sheet processing, and in a state where the buffer sheet is fed to the processing tray.

FIG. 14B is a diagram illustrating an operation of the sheet processing apparatus, in a case where a sheet is to be buffered during sheet processing, and in a state where the buffer sheet is further fed to the processing tray.

FIG. 15 is a flowchart illustrating an operation of the sheet processing apparatus of FIG. 3 when a sheet bundle is delivered.

FIG. 16 which is composed of FIGS. 16A and 16B are flowcharts of a halfway sheet operation of FIG. 15.

FIGS. 17A and 17B are diagrams illustrating that the subsequent sheet does not interfere with a rocking roller pair.

FIG. 18 is a timing chart illustrating where a leading edge and a trailing edge of the sheet are positioned with an elapse of time.

FIG. 19 which is composed of FIGS. 19A and 19B are flowcharts illustrating an operation when the numbers of sheets, which are less than those a buffering unit can buffer, are buffered.

FIG. 20 is a flowchart illustrating an operation different from that of FIGS. 19A and 19B.

FIG. 21 is a cross-sectional view taken along a sheet conveyance direction of a sheet processing apparatus according to another embodiment of the present invention.

FIGS. 22A and 22B are diagrams illustrating an operation of a conventional sheet processing apparatus.

FIGS. 23A and 23B are diagrams illustrating an operation of the conventional sheet processing apparatus which follows the operations of FIGS. 17A and 17B.

FIGS. 24A and 24B are diagrams illustrating an operation of the conventional sheet processing apparatus which follows the operation of FIG. 18.

FIG. 25 is a diagram illustrating a problem caused in the conventional sheet processing apparatus.

Claims

1. A sheet processing apparatus, comprising: a conveying unit, which conveys a sheet;a stacking unit on which the sheet conveyed by the conveying unit is stacked;a processing unit, which processes the sheet stacked on the stacking unit;a buffering unit, which allows the sheet conveyed to the stacking unit by the conveying unit to pass, and buffers a predetermined number of sheets to be passed during an operation of the processing unit;a transferring unit arranged in a region for the buffer sheet buffered to the buffering unit, for receiving the buffer sheets and transferring the predetermined number of buffer sheets from the buffering unit to the stacking unit after the predetermined number of buffer sheets are buffered; anda controlling unit, which controls a sheet conveying speed of the conveying unit,wherein the controlling unit lowers a sheet conveying speed. obtained when the transferring unit transfers the buffer sheet than a sheet conveying speed obtained when the transferring unit receives the buffer sheets so that the sheet conveyed by the conveying unit is prevented from interfering the transferring unit during an operation of transferring the sheet.

2. A sheet processing apparatus according to claim 1, wherein the transferring unit includes a pair of rotary members, and the pair of rotary members are spaced apart from each other when receiving the buffer sheets, and nip the buffer sheets when conveying the buffer sheets to rotationally convey the buffer sheets.

3. An image forming apparatus, comprising: an image forming portion, which forms an image on a sheet; anda sheet processing apparatus, which processes the sheet on which the image is formed by the image forming portion,wherein the sheet processing apparatus is a sheet processing apparatus according to claim 1.

4. An image forming apparatus, comprising: an image forming portion, which forms an image on a sheet; anda sheet processing apparatus, which processes the sheet on which the image is formed by the image forming portion,wherein the sheet processing apparatus is a sheet processing apparatus according to claim 2.

5. A sheet processing apparatus, comprising: a conveying unit, which conveys a sheet;a stacking unit on which the sheet conveyed by the conveying unit is stacked;a processing unit, which processes the sheet stacked on the stacking unit; anda buffering unit, which buffers a predetermined number of sheets to be conveyed to the stacking unit by the conveying unit during an operation of the processing unit; anda controlling unit, which controls conveyance of the sheet by the conveying unit,wherein the controlling unit controls the conveyance of the sheet when a number of job sheets to be processed by the processing unit is less than the predetermined number of buffer sheets to buffer only sheets corresponding to the number of job sheets to the buffering unit so that the processing unit can process the sheets for each one job.

6. An image forming apparatus, comprising: an image forming portion, which forms an image on a sheet; anda sheet processing apparatus, which processes the sheet on which an image is formed by the image forming portion,wherein the sheet processing apparatus is a sheet processing apparatus according to claim 5.

7. An image forming apparatus, comprising: a conveying unit, which conveys a sheet;an image forming portion, which forms an image on a sheet;a stacking unit on which the sheet conveyed by the conveying unit is stacked;a processing unit, which processes the sheet stacked on the stacking unit;a buffering unit, which allows the sheet conveyed to the stacking unit by the conveying unit to pass, and buffers a predetermined number of sheets to be passed during an operation of the processing unit;a transferring unit arranged in a region for the buffer sheet buffered to the buffering unit, for receiving the buffer sheets and transferring the predetermined number of buffer sheets from the buffering unit to the stacking unit after the predetermined number of buffer sheets are buffered; anda controlling unit, which controls a sheet conveying speed of the conveying unit,wherein the controlling unit lowers a sheet conveying speed obtained when the transferring unit transfers the buffer sheet than the sheet conveying speed obtained when the transferring unit receives the buffer sheets so that the sheet conveyed by the conveying unit is prevented from interfering the transferring unit during an operation of transferring the sheet.

8. An image forming apparatus according to claim 7, wherein the transferring unit comprises a pair of rotary members, and the pair of rotary members are spaced apart from each other when receiving the buffer sheets, and nip the buffer sheets when transferring the buffer sheets to rotationally convey the buffer sheets.

9. An image forming apparatus according to claim 7, wherein the conveying unit comprises a roller pair arranged on an upstream side of the image forming portion.

10. An image forming apparatus, comprising: a conveying unit, which conveys a sheet;an image forming portion, which forms an image on a sheet;a stacking unit on which the sheet conveyed by the conveying unit is stacked;a processing unit, which processes the sheet stacked on the stacking unit; anda buffering unit, which buffers a predetermined number of sheets to be conveyed to the stacking unit by the conveying unit during an operation of the processing unit; anda controlling unit, which controls conveyance of the sheet by the conveying unit,wherein the controlling unit controls the conveyance of the sheet when a number of job sheets to be processed by the processing unit is less than the predetermined number of buffer sheets to buffer only sheets corresponding to the number of job sheets to the buffering unit so that the processing unit can process the sheets for each one job.

11. An image forming apparatus according to claim 10, wherein the conveying unit comprises a roller pair arranged on an upstream side of the image forming portion.