JP2000198600A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent impact noises and rebound-based paper sheet irregular stacking when printed paper sheets are output from printing means to an output paper stand. SOLUTION: A first output paper sensor 10 detects the trailing edge of paper sheets P after printing by a printing means 1. Upon the detection result of the first output paper sensor 10, a control means 12 lowers the paper output speed of a paper output roller 9 below the printing speed. The speed of the paper sheets P the paper output roller 9 discharges into an output paper stand 2 becomes slower such that the paper sheets P make less impact noise when butting against an output paper fence 7 and make fewer rebounds on the output paper fence 7 or pile up desirably. When a second output paper sensor 11 detects the trailing edge of the paper sheets P, the control means 12 returns the paper output speed of the paper output roller 9 to the original printing speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus provided with a mechanism for transporting a printed medium to a paper discharge tray.

[0002]

2. Description of the Related Art Stencil making means for making a stencil stencil sheet by punching a desired image on a stencil sheet serving as a stencil, and stencil stencil sheet wrapped around the outer peripheral surface of an ink-permeable cylindrical plate cylinder. 2. Description of the Related Art A stencil printing apparatus in which a stencil making unit and a printing unit are integrated, which comprises printing means for transferring ink to printing paper via a stencil sheet which has been made, is widely used. In such a stencil printing apparatus, a printed printing medium is conveyed to a paper discharge table by a paper discharge roller or suction type paper discharge means. A paper output fence is provided downstream of the paper output tray, where the front end of the print medium conveyed to the paper output table abuts. The sheets are aligned and stored in the paper discharge tray.

Here, as shown in FIG. 5, in a printing means 21, a printing medium P is sandwiched between a plate cylinder 24 and a paper cylinder 25 to perform printing, and the printed printing medium P is printed. The sheet is nipped by the sheet discharge rollers 29 and transported to the sheet discharge table 22. At this time, the peripheral speed of the plate cylinder 24 and the peripheral speed of the paper discharge roller 29 are substantially the same or the peripheral speed of the paper discharge roller 29 so that the printing medium P does not slack between the plate cylinder 24 and the paper discharge roller 29. The peripheral speed is set to be slightly faster. This is the same when using the suction type sheet discharging means 30 as shown in FIG. FIG. 5 shows an inner press type printing means, and FIG. 6 shows an outer press type printing means.

[0004]

In the printing apparatus as described above, printing is performed at a printing speed of 60 sheets / min to 120 sheets / min, that is, a rotation speed of the plate cylinder of about 60 to 120 rpm. Here, as the printing speed increases, the peripheral speed of the paper discharge rollers and the like increases in accordance with the peripheral speed of the plate cylinder, and the paper discharge speed of the printing medium carried into the paper discharge table also increases. As described above, when the discharge speed of the printing medium increases, the impact sound generated when the printing medium collides with the discharge fence increases, thereby causing a problem of apparatus noise. In addition, the printing medium may be rebounded by the paper discharge fence and returned to the upstream side, and the printing medium may not be properly aligned by the paper discharge table.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus which does not have a problem of noise and which can satisfactorily align a printing medium on a discharge tray. is there.

[0006]

According to the present invention, there is provided an image forming apparatus comprising: a printing unit having a plate cylinder for forming an image on a printing medium; a paper discharge table for storing a printed printing medium; And a paper discharge means for conveying the printed material printed by the printer to the paper discharge tray, the discharge speed of the paper discharge device when the print material is discharged from the printing device. And a paper discharge control means for returning the paper discharge speed of the paper discharge means when the paper discharge operation of the printing medium by the paper discharge means is completed.

In the image forming apparatus according to the present invention, the paper discharge control means includes a first detection means for detecting that the printing medium has been discharged from the printing means, and A second method for detecting the end of the discharge operation of the printed material
And a discharge speed of the paper discharge unit is reduced based on a detection result by the first detection unit, and a paper discharge speed of the paper discharge unit is reduced based on a detection result by the second detection unit. It is preferable to provide control means for restoring the speed.

Further, in the image forming apparatus of the present invention, the paper discharge control means includes a length detecting means for detecting a length of the printing medium, and an encoder for counting the rotation amount of the plate cylinder by the number of pulses. When the number of pulses counted by the encoder after the printing medium has been conveyed to the printing means coincides with the length of the printing medium, reducing the paper discharging speed of the paper discharging means; Control means for returning the discharge speed of the paper discharging means to the original when the number of pulses counted by the encoder after the reduction matches the moving distance until the printing medium is discharged from the paper discharging means. Preferably, it is provided.

Further, it is preferable that the paper discharge control means is means for reducing the paper discharge speed based on the peripheral speed of the plate cylinder.

[0010]

According to the present invention, when the printing medium is discharged from the printing means, the paper discharging speed of the paper discharging means is reduced. The speed will be reduced. For this reason, the impact when the print medium conveyed to the paper discharge tray collides with the paper discharge fence is reduced, thereby making it possible to reduce the impact sound and to reduce the rebound of the print medium by the paper discharge fence. be able to. Therefore, the problem of apparatus noise can be eliminated, and the printing medium can be properly aligned by the paper discharge tray.

[0011]

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

FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus according to a first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus according to the first embodiment includes a printing unit 1
And a paper discharge tray 2 for storing the paper P printed by the printing means 1, and a paper discharge means 3 for transporting the printed paper P from the printing means 1 to the paper discharge board 2.

The printing means 1 has an ink-permeable plate cylinder 4 having a porous structure, on which a stencil sheet is wound and mounted, and which is driven to rotate around its own rotation center in a counterclockwise direction in FIG. 4 includes a paper cylinder 5 for pressing the paper P against the paper P, and a pinch roller 6 for guiding the paper P from the paper cylinder 5 to the paper discharging means 3.

The paper discharge tray 2 is a tray on which the printed papers P are stacked and mounted. The paper discharge fence 7 for aligning the front ends of the papers P when the front ends of the papers P abut, and a side surface of the papers P And an alignment plate 8 for aligning them.

The paper discharging means 3 has a pair of paper discharging rollers 9 for holding the printed paper P discharged from the printing means 1 and transporting the paper P to the paper discharging table 2.

In the first embodiment, a first paper discharge sensor 10 for detecting the leading end of the paper P discharged from the printing means 1 and a paper discharge roller 9 provided upstream of the paper discharge table 2 are provided. Based on the detection results of the second paper discharge sensor 11 for detecting the trailing end of the paper P to be discharged, and the first and second paper discharge sensors 10 and 11, the paper P is discharged by the paper discharge roller 9 as described later. It has a control device 13 provided with a control means 12 for controlling the paper discharge speed.

Here, during normal printing, the plate cylinder 4
And the peripheral speed of the discharge roller 9 are set to be substantially the same, or the peripheral speed of the discharge roller 9 is set to be slightly faster than the peripheral speed of the plate cylinder 4. The control means 12 controls the peripheral speed of the paper discharge roller 9, that is, the paper discharge speed of the paper P, as described below. FIG. 2 is a diagram showing a control state of the paper discharge speed of the paper P by the paper discharge roller 9. First, when the leading edge of the sheet P printed by the printing unit 1 is detected by the first sheet ejection sensor 10 when the sheet P is conveyed to the sheet ejection roller 9, a signal from the first sheet ejection sensor 10 is controlled. Input to the means 12. Further, when the rear end of the sheet P is conveyed and the rear end of the sheet P passes through the detection position of the first sheet ejection sensor 10, the signal from the first sheet ejection sensor 10 is output. It is no longer input to the control means 12. At this time, the control means 12 makes the discharge speed of the discharge roller 9 lower than the printing speed of the plate cylinder 4.

Here, assuming that the printing speed is V1 (the rotation speed of the plate cylinder 4 rpm) and the discharge speed is V2 (the rotation speed of the discharge roller 9), the discharge speed V2 is determined by the following equation (1). Is done.

V2 = V1 × α × β (1) where α = 0.9 (V1 = 60 to 80 rpm) α = 0.8 (V1 = 80 to 100 rpm) α = 0.7 (V1 = 100 to 120 rpm) Β: a coefficient for matching the peripheral speed of the plate cylinder 4 with the peripheral speed of the paper discharge roller 9 Note that the paper discharge speed V2 is not limited to that obtained by the above equation (1), but is a predetermined value. It may be set to a value.

On the other hand, the second sheet ejection sensor 11 is provided immediately before the sheet ejection table 2 and detects the leading edge of the sheet P to be the first sheet ejection sensor 11.
And outputs a signal to the control means 12 in the same manner as the paper ejection sensor 10. When the paper P is conveyed and the rear end of the paper P passes through the detection position of the second paper discharge sensor 11, the rear end is detected and stored in the paper discharge table 2. The signal from the sensor 11 is not input to the control means 12. At this time, the control means 12 returns the discharge speed of the discharge roller 9 to the original printing speed.

Next, the operation of the first embodiment will be described. First, printing is performed on the paper P by the printing unit 1. At this time, the plate cylinder 4 sends out the paper P while rotating in the counterclockwise direction in FIG. 1 and the paper cylinder 5 rotates in the clockwise direction in FIG. 1, thereby displaying the stencil sheet wound around the plate cylinder 4. The image to be printed is printed on paper P. The paper P is conveyed to the paper discharge roller 9 of the paper discharge means 3 by the pinch roller 6 while being printed. At this time, after the leading edge of the sheet P is detected by the first sheet ejection sensor 10, the sheet P is ejected by the sheet ejection roller 9. When the paper P is conveyed by the paper discharge rollers 9, the leading edge of the paper P is detected by a second paper discharge sensor 11 provided immediately before the paper discharge table 2.

Further, when the sheet P is discharged, the first
The trailing edge of the sheet P is detected by the sheet ejection sensor 10. In response to this, the control means 12 sets the paper discharge speed by the paper discharge roller 9 to be lower than the printing speed. As a result, the sheet P is conveyed to the sheet discharge table 2 at a low speed, so that the impact when the sheet P strikes the sheet discharge fence 7 is reduced, and the impact sound is reduced. In addition, since rebound by the paper discharge fence 7 is reduced, the paper P can be properly aligned by the paper discharge table 2.

When the sheet P is carried into the sheet discharge tray 2 and the trailing end of the sheet P is detected by the second sheet discharge sensor 11, the control means 12 sets the sheet discharge speed of the sheet discharge roller 9 to the original print speed. Return to Thus, during printing, the paper P does not sag between the printing unit 1 and the paper discharge roller 9.

Next, a second embodiment of the present invention will be described. FIG. 3 is a schematic diagram illustrating a configuration of an image forming apparatus according to a second embodiment of the present invention. The printing unit 1, the paper discharge tray 2, and the paper discharge unit 3 of the image forming apparatus according to the second embodiment are the same as those in the first embodiment, and thus detailed description is omitted. In the second embodiment, an encoder 15 that detects the rotation amount of the plate cylinder 4 by the number of pulses, and a discharge speed of the sheet P by the discharge rollers 9 based on the rotation amount of the plate cylinder 4 detected by the encoder 15 Control means 16 for controlling
This is different from the first embodiment in that a control device 17 comprising: Note that in the second embodiment,
FIG. 2 illustrates a sheet supply table 18 that supplies a sheet P to the printing unit 1. Further, a length sensor 19 for detecting the length of the sheet P is provided on the sheet supply table 18, and the length sensor 19 is connected to the control unit 16. Further, the plate cylinder 4 is provided with a sensor (not shown) for detecting the start of sheet feeding to the printing unit 1.

The control means 16 controls the discharge speed of the discharge roller 9 as described below. First, the length of the sheet P detected by the length sensor 19 is input to the control unit 16. When the paper supply from the paper supply table 18 to the printing means 1 is started, a paper supply start signal indicating the paper supply start is input to the control means 16 from a sensor provided on the plate cylinder 4. When this sheet feed start signal is input, the control means 16 controls the plate cylinder 4 by the encoder 15.
The detection of the pulse generated by the rotation of is started. Here, since the printing speed by the plate cylinder 4 and the length of the sheet P are constant, the rotation amount of the plate cylinder 4 from the start of sheet feeding until the sheet P is discharged from the printing unit 1 is constant, As a result, the number of pulses (referred to as the first pulse number) generated by the rotation of the plate cylinder 4 during this period is constant. Accordingly, the encoder 15 detects the first number of pulses from the start of sheet feeding until the sheet P is ejected from the printing unit 1, and at the point of time when the first number of pulses is detected, the control unit 16 The discharge speed of the roller 9 is set lower than the printing speed. On the other hand, since the number of pulses (hereinafter referred to as a second pulse number) from when the paper P is discharged from the printing means 1 to when the paper P is discharged from the paper discharge roller 9 is also constant, the paper P is discharged from the printing means 1. The second pulse number from encoder 1
5, the control means 16 returns the discharge speed of the discharge roller 9 to the original print speed at the time when the second pulse number is detected.

Next, the operation of the second embodiment will be described. First, prior to printing, the length of the paper P set on the paper feed table 18 is detected by the length sensor 19 and input to the control means 16. Then, the sheet P
Is supplied to the printing means 1 and the printing means 1 prints on the paper P. A paper feed start signal indicating the start of paper feed is input to the control means 16 by a sensor provided on the plate cylinder 4. The paper P is conveyed to the paper discharge roller 9 of the paper discharge means 3 by the pinch roller 6 while being printed. Then, the fact that the paper P is discharged from the printing means 1 is notified by the encoder 15.
Is detected by counting the first pulse number from the start of sheet feeding, the control means 16 sets the sheet feeding speed of the sheet discharging roller 9 to be lower than the printing speed. As a result, the sheet P is conveyed to the sheet discharge table 2 at a low speed, so that the impact when the sheet P hits the sheet discharge fence 7 is reduced, and the impact sound is reduced. In addition, since rebound by the paper discharge fence 7 is reduced, the paper P can be properly aligned by the paper discharge table 2.

Further, the sheet P is discharged, and the sheet P
When the encoder 15 detects that is discharged from the paper discharge roller 9 by counting the second pulse number, the control means 16 returns the paper discharge speed of the paper discharge roller 9 to the original printing speed. Thus, during printing, the paper P does not sag between the printing unit 1 and the paper discharge roller 9.

In the above-described embodiment, the printed paper P is transported to the paper output tray 2 by the paper output roller 9, but the present invention is not limited to this. P may be conveyed to the paper discharge tray 2.

In the above embodiment, printing is performed by the inner press method, but printing may be performed by the outer press method.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention;

FIG. 2 is a diagram illustrating a control state of a discharge speed of a discharge roller according to the first embodiment.

FIG. 3 is a schematic diagram illustrating a configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a control state of a discharge speed of a discharge roller according to a second embodiment.

FIG. 5 is a view for explaining a paper discharge state by a conventional printing apparatus.

FIG. 6 is a view for explaining a paper discharge state by a conventional printing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 printing means 2 paper discharge table 3 paper discharge means 4 plate cylinder 5 paper cylinder 6 pinch roller 7 paper discharge fence 8 alignment plate 9 paper discharge roller 10 first paper discharge sensor 11 second paper discharge sensor 12 control means 15 encoder 16 control means 18 paper feed table 19 length sensor

Continued on the front page (72) Inventor Masakazu Miyata 2-20-15 Shimbashi, Minato-ku, Tokyo R-Science Industry Co., Ltd. F-term (reference) 3F049 AA02 AA08 DA12 EA14 EA28 EA29 LA06 LA07 LB03

Claims (4)

[Claims] 1. A printing means having a plate cylinder for forming an image on a printing medium, a paper discharge table for storing a printed printing medium, and a paper discharging means for printing the printing medium printed by the printing means. An image forming apparatus comprising: a discharge unit that conveys the print medium to the table; and a discharge speed of the discharge unit when the print medium is discharged from the print unit, the printing unit configured to perform the printing by the discharge unit. An image forming apparatus, comprising: paper discharge control means for returning the paper discharge speed of the paper discharge means when the paper discharge operation of the body is completed. 2. The sheet discharge control means includes: first detection means for detecting that the printing medium has been discharged from the printing means; and ending the discharge operation of the printing medium by the discharge means. And a discharge speed of the paper discharge unit based on a detection result of the first detection unit, and a discharge speed of the discharge unit based on a detection result of the second detection unit. 2. The image forming apparatus according to claim 1, further comprising control means for returning the paper discharge speed of the paper means to the original speed. 3. The printing apparatus according to claim 2, wherein the discharge control unit includes a length detection unit configured to detect a length of the printing medium; an encoder configured to count a rotation amount of the plate cylinder by a pulse number; When the number of pulses counted by the encoder after being conveyed to the unit coincides with the length of the printing medium, the paper discharging speed of the paper discharging means is reduced, and the pulse is counted by the encoder after the paper discharging speed is reduced. Control means for returning the discharge speed of the paper discharging means to the original when the number of pulses coincides with the moving distance until the printing medium is discharged from the paper discharging means. Item 2. The image forming apparatus according to Item 1. 4. The image forming apparatus according to claim 1, wherein said paper discharge control means is means for reducing said paper discharge speed based on a peripheral speed of said plate cylinder. apparatus.