JP2004075201A - Pneumatic sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic sheet feeder capable of coping with a paper sheet of arbitrary length with a simple absorption belt operation pattern. <P>SOLUTION: Driving timing of the absorption belt is variably controlled based on information of length on the paper sheet in a conveying direction to keep time for absorbing and carrying the paper sheet by the absorption belt constant regardless of length of the paper sheet in the conveying direction, to cover an opening part of a vacuum chamber by a no suction hole part of the absorption belt after completion of conveyance of the paper sheet by absorption to the absorption belt. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic paper feeder for an electrophotographic apparatus.
[0002]
[Prior art]
FIG. 1 shows the structure of a sheet feeding device using air pressure, that is, a sheet feeding device generally called an air sheet feeding system in a conventional electrophotographic apparatus. In FIG. 1, a sheet 2 loaded on a sheet elevating table 1 is always kept at a constant height by a sheet upper surface detecting sensor 3 and a control means 4 for controlling the driving of the sheet elevating table 1 based on information of the sheet upper surface detecting sensor 3. Is controlled to be located at Above the paper 2, a suction belt 6 which is a belt member having a vacuum charging chamber 5 and a suction hole, and a driving device 7 for driving the suction belt 6 are provided. In the vicinity of the upper end of the sheet 2, an air jetting mechanism 8 for separating the sheet 2 by an air flow is provided, and plays a role of separating the sheet 2 so as not to cause multiple feeding in the process of sucking and conveying the sheet 2. Downstream in the paper transport direction, a transport roller 9 that is a paper transport unit that receives the paper 2 transported from the suction belt 6 and transports the paper 2 to an image forming unit (not shown) is provided. In this conventional air feeding method, in order to transport the paper 2 to the paper transport roller 9 at a constant interval by the suction belt 6, the suction belt 6 is driven after the first paper 2 is transported. After stopping and after the paper 2 reaches the transport roller 9, it is necessary to release the suction of the paper 2 to the suction belt 6 so as not to hinder the transport of the paper. Therefore, the suction belt 6 needs to be intermittently driven in accordance with the sheet feeding timing of the paper 2, and the suction of the vacuum charging chamber 5 needs to be intermittently operated in accordance with this. To switch the intake air in the vacuum charging chamber 5, an intake switching valve is provided, or a suction hole is provided partially on the suction belt 6 instead of the entire surface, and the position of the suction belt 6 is switched to a portion having no suction hole. As a result, a method of switching intake air by substituting an intake valve has been common.
[0003]
[Problems to be solved by the invention]
In the pneumatic paper feeder described above, first, in the method employing the suction switching valve, there is a time lag from the valve switching to the actual change of the suction pressure, so that it is difficult to increase the paper feeding speed, and the valve switching mechanism is used. The structure itself is complicated and disadvantageous in terms of cost. On the other hand, when the suction belt is partially provided with a suction hole and the intake valve is substituted by a method by switching to a portion having no suction hole, a means for detecting the position information of the suction hole, If there is no control device that controls the drive pattern of the suction belt based on the information obtained, the suction belt that has finished transporting the paper rotates and returns the paper that has been being fed until it returns to the initial position again. This causes a conveyance failure due to the suction, or a problem that the next sheet is suctioned and taken out. Therefore, it is possible to properly feed only one type of paper length synchronized with the timing of returning to the initial position, and to handle a plurality of types of paper, that is, papers having a plurality of paper lengths, It has not been possible to always perform appropriate paper feeding. On the other hand, a method of detecting and controlling the position information of the suction belt is described in Japanese Patent No. 2934442. This is to control the driving speed of the suction belt and the driving speed of the transport roller based on information from the detecting means for detecting the position of the suction hole of the suction belt. In this method, the position of the suction hole is detected by a sensor, and in a portion where there is no suction hole unrelated to the conveyance of the sheet, the driving speed is increased to rotate the suction belt to feed the sheet appropriately. According to this method, the return time of the suction belt to the initial position can be shortened, so that there is an advantage that the paper feeding speed can be easily increased. However, even in the case of this method, since the retracting time of the suction hole for a plurality of paper lengths, that is, the time for shielding the opening of the vacuum charging chamber in a portion having no suction hole is not controlled, it is not controlled. It is necessary to prepare a specific suction belt drive pattern to adapt to the length of paper to be printed. For example, this method is used in an electrophotographic apparatus in which the paper size is defined only as the maximum and minimum sizes, and the paper width and length can be freely selected within the range. In such a case, control must be performed so that an appropriate drive pattern of the suction belt can always be changed based on the information on the length of the sheet, and a disadvantage that the control becomes complicated remains.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic paper feeder which can solve the above-mentioned problem and can cope with a paper having an arbitrary paper length with a simple suction belt driving pattern.
[0005]
[Means for Solving the Problems]
The object of the present invention is to variably control the drive timing of the belt member based on information on the length of the sheet in the conveyance direction, and to eliminate the suction hole of the suction belt after the conveyance of the sheet by the suction to the belt member is completed. This is achieved by controlling the section to block the opening of the vacuum plenum.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 2 to 5 show an embodiment according to the present invention, and show how paper is fed according to the present invention with respect to time. FIG. 6 is a diagram showing a driving pattern of the suction belt in the series of sheet feeding operations shown in FIGS.
[0007]
First, FIG. 2 is a diagram showing the suction belt and the initial position of the sheet. In FIG. 1, the sheet 2 is set at a sheet feeding position by a sheet lifting table (not shown), and is separated by a separation mechanism 8 that separates the sheet 2 by jetting air. , In a state where the upper layer portion is being loosened. The suction belt 6 located at the upper part of the sheet 2 is provided with portions P1 and P2 having suction holes and P3 and P4, and the lengths of P1 and P2 are equal to those of P3 and P4. Further, the lengths of the portions P2 and P3 having no suction holes and the portions of P4 and P1 are set to be equal. Inside the suction belt 6, a vacuum charging chamber 5 having an opening in a downward direction is installed. The vacuum charging chamber 5 is connected to an air supply / discharge device (not shown), which is generally called a blower. During operation of the apparatus, the inside of the apparatus is constantly sucked and a negative pressure is applied. The suction belt 6 rotates while being in contact with the opening of the vacuum charging chamber 5, so that the sheet 2 having a suction hole is rotated. It is a mechanism to adsorb. On the other hand, when a portion having no suction hole is positioned at the opening of the vacuum charging chamber 5 due to the rotation of the suction belt 6, the opening is blocked and the sheet 2 is not sucked. A transport roller 9 is provided downstream in the paper traveling direction, and plays a role of receiving the paper 2 sent out by the suction belt 6 and transporting the paper 2 to an image forming unit (not shown). Further, a light reflection type sensor 10 for detecting the tip of the suction hole is provided in the vicinity of the suction belt 6, and a control device (not shown) detects the tip of the suction hole of the suction belt 6 based on the information of this sensor. The opening of the vacuum charging chamber 5 is controlled to stop at a fixed position (point A).
[0008]
Here, the operation of the sheet 2 and the suction belt 6 in FIGS. 2 to 5 will be described in comparison with the driving patterns of the suction belt and the transport roller in FIG. First, the leading end P1 of the suction hole of the suction belt 6 at the initial position in FIG. 2 starts rotating in response to a sheet feed start signal from a central control device (not shown), and is driven according to the drive pattern shown in FIG. The point B shown in FIG. Point B is a sheet suction position, at which point the suction belt 6 stops from time t3 to time t4, during which the sheet 2 is sucked by the suction belt 6.
[0009]
Next, the suction belt 6 is driven from time t4 to time t6, during which the sheet 2 is also transported together with the suction belt 6, and reaches the transport roller 9 shown in FIG. Thereafter, the suction belt 6 continues to be driven until time t8, and the sheet 2 that has reached the conveyance roller 9 is conveyed at a speed v2 higher than the conveyance speed v1 of the suction belt 6. Here, a speed difference occurs between the suction belt 6 and the paper 2. However, the paper holding force of the conveyance roller 9 is larger than the paper holding force of the suction belt 6. 6, since the suction area of the sheet 2 with respect to the sheet 2 is small, the suction force is reduced, and slippage occurs between the sheet 2 and the suction belt 6, so that troubles such as poor conveyance do not occur.
[0010]
When the suction belt passes at time t6, the other end portions P3 of the suction holes P3 to P4 have already been detected by the light reflection type sensor 10, and the signal of the light reflection type sensor 10 indicates that the suction hole The leading end P3 stops at the point A shown in FIG. 5, that is, at the same position as the initial position in FIG. 1, and the feeding operation of one sheet is completed. On the other hand, at this initial position, the opening of the vacuum charging chamber 5 is blocked by the suction-hole-less portion of the suction belt 6, so that the rear end of the paper 2 being conveyed is not sucked, and the conveyance failure is not achieved. No problem is caused. When the continuous printing is further performed, the sheet feeding operation is started again at time t9 by a sheet feeding signal from the central control device (not shown). By repeating the cycle from time 0 to t9 as one cycle, continuous paper feeding is possible.
[0011]
Times 0 to t9 are determined by the sheet length based on the sheet length and the sheet interval. That is, according to the present invention, the drive pattern of the suction belt at time 0 to t8 in FIG. 6 is kept constant, and the time from t8 to t9, that is, the shielding time of the opening of the vacuum charging chamber by the suction holeless portion is variable. By doing so, it is possible to feed paper of an arbitrary length.
[0012]
Furthermore, in the present invention, one sheet is fed by rotating the suction belt 6 half a turn, so that two sheets can be fed in one rotation, which is advantageous for increasing the feeding speed. . In the embodiment of the present invention, the maximum sheet length that can be fed is Lp, the length of the sheet in the transport direction, L1 is the distance from the leading edge of the sheet to the transport roller, and suction is from the leading edge of the sheet at the initial position. L2 is the distance to the leading end position of the hole, S1 is the distance of the paper conveyed by the suction belt (corresponding to the area S1 shown in FIG. 7), and S1 is the distance of the paper conveyed by the conveyance rollers (the area shown in FIG. 7). (Corresponding to the portion of S2) is S2, which is determined by the conditions of L1 <S1 <Lp and Lp <S1 + S2 + L2, and the positional relationship between the suction belt 6 and the transport roller 9 and the sheet 2 and the driving speed of the suction belt 6 are It must be selected to meet the conditions.
[0013]
【The invention's effect】
As described above, according to the present invention, a plurality of drive patterns for the suction belt are not required, and only the control for changing the drive timing in accordance with the paper feed interval is performed. However, it is possible to always perform appropriate paper feeding.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the structure of a pneumatic paper feeder according to the related art.
FIG. 2 is a cross-sectional view showing an initial position of the suction belt according to the embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a state in which a sheet is suctioned and conveyed by a suction belt according to the embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating a state in which a sheet is conveyed by a suction belt and reaches a conveyance roller according to the embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating a state in which the suction belt according to the embodiment of the present invention has returned to an initial position.
FIG. 6 is a diagram illustrating a driving pattern of a suction belt and a conveyance roller according to the embodiment of the present invention.
FIG. 7 is a diagram illustrating a conveyance distance in which the suction belt and the conveyance roller convey a sheet according to the embodiment of the present invention.
[Explanation of symbols]
1 is a sheet lifting table, 2 is a sheet, 3 is a sheet upper surface detection sensor, 4 is a control means, 5 is a vacuum charging chamber, 6 is a suction belt, 7 is a driving device, 8 is an air ejection mechanism, 9 is a transport roller, Reference numeral 10 denotes a light reflection type sensor, P1 and P3 denote front ends of the suction holes, P2 and P4 denote the ends of the suction holes, A denotes an initial position of the suction holes, and B denotes a sheet suction position of the suction holes.

Claims (2)

A storage member capable of storing a plurality of sheets of paper, a separation mechanism located at the top of the storage member for separating the paper using air pressure, and suctioning the separated paper using air pressure And a suction hole portion for contacting the opening of the vacuum charging chamber for sucking and transporting the sheet and a portion without a suction hole for shielding the opening. A pneumatic sheet feeder comprising: a belt; a detection unit configured to detect a position of a suction hole of the suction belt; and a control unit configured to control a driving timing of the suction belt based on a signal from the detection unit. A pneumatic paper feeder, wherein the drive timing of the suction belt is variably controlled based on information on the length of the sheet in the conveying direction. The drive timing of the suction belt is controlled such that the time during which the sheet is suctioned and conveyed by the suction belt is constant regardless of the length of the sheet in the conveyance direction, and the suction of the sheet is performed. 2. The pneumatic paper feeder according to claim 1, wherein after the transfer by suction to the belt is completed, a control is performed such that the suction holeless portion of the suction belt shields the opening of the vacuum charging chamber. apparatus.

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