Patent Application
20080308989
1. Field of the Invention
The present invention relates to a sheet processing apparatus which carried out skew correction and punching processing to a sheet discharged from an image forming unit of MFP (multi-function peripheral), which is a digital multi-function machine, a copy machine, a printer or the like.
2. Description of the Related Art
In an image forming apparatus such as MFP, copy machine or printer, a post-processing device (finisher) is provided next to a paper discharge unit in the image forming apparatus body in order to carry out post-processing such as punching processing and staple processing to a sheet on which an image has been formed.
In such a post-processing apparatus, a sheet discharged from the image forming apparatus body may become slant (hereinafter referred to skew) with respect to the conveying direction. If punching processing (hole punching) is carried out to the skewed sheet, the hole punching position is deviated, causing a trouble at the time of filing. Therefore, a skew correcting unit is provided to correct the skew of the sheet and then punching processing is carried out.
JP-A-2000-153953 discloses a sheet processing apparatus in which a punching unit is movable in a direction that intersects the sheet conveying direction. In this example, the punching unit is moved from the home position (HP) into the direction that intersects the sheet conveying direction and carries out punching. During the operation to move the punching unit to HP after punching is finished, the punching unit is moved to the standby position.
JP-A-2006-16129 discloses a sheet processing apparatus having a pair of rollers for skew correction and a hole punching unit. In this example, the pair of roller for skew correction carries a sheet, and plural edge detection sensors are provided in order to detect the lateral edge of the conveyed sheet.
JP-A-10-194557 discloses a sheet hole punching apparatus having a detection unit which detects the lateral edge of a conveyed sheet. In this example, a hole punching unit is made movable in a direction orthogonal to the sheet conveying direction, and the moving position of the hole punching unit is decided in accordance with the result of detection by the detection unit.
JP-A-2005-31877 discloses a control apparatus for a motor used for conveying a sheet or the like. In this example, the apparatus has a first control system which moves a sheet at a constant speed up to a halfway position before reaching a target stop position, and a second control system which moves the sheet at a low speed from the halfway position to the target stop position. A motor is rotationally driven in two stages.
Moreover, JP-A-9-249348 discloses a punching processing apparatus in which a punching mechanism is movable in a direction orthogonal to the sheet conveying direction. In this example, prior to punching processing, the punching mechanism is moved to a predetermined standby position and caused to wait there. The standby position is preset according to the sheet size.
Meanwhile, high-speed processing and power saving are required of the recent image forming apparatus. As the image forming apparatus operates at a higher speed, the sheet conveying speed becomes higher. Therefore, at the time of punching processing, it is difficult to stop a sheet at a regular position and the position of the punch hole may be deviated. Also, skew correction may take time and measures must be taken to deal with high-speed processing. Moreover, measures for power saving are necessary.
According to an aspect of the invention, a sheet processing apparatus is provided in which position control of a punching unit can be performed at a higher speed in accordance with high-speed operation of the image forming apparatus.
According to an embodiment of the invention, a sheet processing apparatus includes: a hole punching section arranged, in order to perform punching processing to a sheet conveyed thereto, orthogonally to a conveying path of the sheet; a moving mechanism configured to move the hole punching section along a direction orthogonal to the conveying path and move the hole punching section in a direction toward a retreat position and a punching processing position; a detection unit arranged upstream from the hole punching section and configured to move by being interlocked with the hole punching section and detect a lateral edge of the sheet conveyed thereto; and a control unit configured to control the moving mechanism in accordance with a result of detection by the detection unit and vary the position of the hole punching section, thus controlling the punching processing position with respect to the sheet. The control unit causes the hole punching section to be moved in the direction to the retreat position along with the conveying of the sheet, causes the hole punching section to retreat by a prescribed quantity with reference to the result of detection by the detection unit, then causes the hole punching section to be moved in the opposite direction, and controls movement to the punching processing position in accordance with the result of detection by the detection unit.
Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus of the present invention.
Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings. In the drawings, the same parts and components are denoted by the same reference numerals.
In
In the following description, an MFP (multi-function peripheral), which is a multi-function machine, is employed as an example of the image forming apparatus. However, the invention can also be applied to other image forming apparatuses such as a printer or copy machine.
A document table (not shown) is provided at the top of the body 11 of the image forming apparatus 10. An automatic document feeder (ADF) 12 is provided on the document table in such a manner that it can freely open and close. Moreover, an operation panel 13 is provided at the top of the body 11. The operation panel 13 has an operation unit 14 including various keys, and a touch-panel display unit 15.
The operation unit 14 has, for example, ten keys, a reset key, a stop key, a start key and so on. With the touch-panel display unit 15, the user can designate sheet size, the number of copy sheets, punching processing and the like.
In the body 11, a scanner unit 16 and a printer unit 17 are provided. At the bottom of the body 11, plural cassettes 18 are provided in which sheets of various sizes are housed. The scanner unit 16 reads a document fed by the ADF 12 or an original set on the document table.
The printer unit 17 includes a photoconductive drum and a laser. A laser beam from the laser scans and exposes light to the surface of the photoconductive drum, and thus forms an electrostatic latent image on the photoconductive drum. A charger, a developing device, a transfer device are arranged around the photoconductive drum. The electrostatic latent image on the photoconductive drum is developed by the developing device, and a toner image is formed on the photoconductive drum. The toner image is transferred to a sheet by the transfer unit.
The configuration of the printer unit 17 is not limited to the above example and various systems can be employed. The sheet processing apparatus 20 is arranged to the paper discharge side of the body 11. The sheet processing apparatus 20 is generally called a finisher. In the following description, it is referred to as finisher 20.
A sheet on which an image has been formed by the body 11 (image forming unit) is conveyed to the finisher 20. The finisher 20 carries out post-processing of the sheet supplied from the body 11, for example, punching processing, sorting processing, staple processing and so on.
The finisher 20 shown in
The paper storage tray 27 is movable and receives the bundle of sheet to which punching processing or staple processing has been performed. The staple mechanism 21 has an alignment device which aligns the sheets conveyed thereto in the direction of width. This alignment device can be used to sort and discharge sheets. In the case where post-processing is not carried out, the sheet conveyed from the body 11 is directly discharged to the paper storage tray 27 or the fixed tray 28, without being processed in any way.
The staple mechanism 21 of the finisher 20 will now be briefly described. A sheet supplied from the body 11 via the punching mechanism 30 is received by entrance rollers 22 provided near a carry-in port of the finisher 20. Paper feed rollers 23 are provided downstream of the entrance rollers 22. The sheet received by the entrance rollers 22 is stacked on a processing tray 24 via the paper feed rollers 23.
The sheet stacked on the processing tray 24 is guided to a stapler 25 and staple processing is performed. Also, a conveying belt 26 is provided which carries the sorted or stapled sheet to the paper storage tray 27.
The sheet conveyed by the conveying belt 26 is discharged to the paper storage tray 27. The paper storage tray 27 is moved up and down by a driving unit (not shown) and receives the sheet.
There is a case where a sheet is discharged to the paper storage tray 27 without being stapled. In this case, the sheet is discharged without being dropped on the processing tray 24. The sheet which requires no post-processing can also be discharged to the fixed tray 28. A conveying path to guide the sheet to the fixed tray 28 is provided, though not shown.
Next, the punching mechanism 30 will be described. The punching mechanism 30 is arranged between the body 11 and the staple mechanism 21, and has a punching unit 31 and a dust box 32.
The punching unit 31 is provided with a hole punching cutter (not shown) which conveyed out punching processing to a sheet. As this hole punching cutter moves down, a punch hole is opened in the sheet. The part of the sheet that is punched out by punching processing falls into the dust box 32.
In the route from the body 11 to the entrance rollers 22 of the staple mechanism 21, plural rollers 33 and 34 for conveying a sheet are provided. The rollers 33 are provided in the body. The rollers 34 are provided at the final exit of the punching mechanism 30. A sheet discharged from the body 11 is conveyed to the punching mechanism 30 by the rollers 33 and is then conveyed to the staple mechanism 21 by the rollers 34.
The punching processing by the punching unit 31 is executed when the punch mode has been set by the user's operation of the operation panel 13.
Hereinafter, the configuration of the punching mechanism 30 of the sheet processing apparatus according to one embodiment of the invention will be described in detail with reference to
The punching unit 31 has a hole punching section 35 which punches a punch hole in the sheet S conveyed therein from the body 11, and a skew detection unit 60 to detect a skew. The hole punching section 35 is provided downstream of the skew detection unit 60.
The skew detection unit 60 and the hole punching section 35 are arranged substantially parallel to each other and orthogonally to the sheet conveying direction Z. The hole punching section 35 is provided with plural (in
The hole punching cutters 36 are driven to rise and fall by rotation of a punch motor 58 (
The hole punching section 35 is movable in the direction of the arrow A (lateral direction) orthogonal to the conveying direction Z of the sheet S. One end (lower end in
A moving mechanism to move the hole punching section 35 in the lateral direction (the direction of the arrow A) is shown in an enlarged view of
As shown in
In order to move the hole punching section 35 in the lateral direction (direction A), a gear group 43 is provided which meshes with the rack 41 and thus rotates. To rotate this gear group 43, a lateral registration motor 44 is provided.
Moreover, a sensor 45 is arranged at a position at a predetermined distance from the protruding flap 37. The sensor 45 is to detect that the hole punching section 35 has moved in the direction of the arrow A and has reached its home position (hereinafter, it may also be called HP). The protruding flap 37 is provided with a shutter 46 which is formed to extend in the direction to the sensor 45. As the shutter 46 traverses the sensor 45, the sensor detects that the hole punching section 35 has moved to the home position in the direction A.
Meanwhile, a sectorial cam 47 to rotate the hole punching section 35 in the direction of the arrow B is connected to the protruding flap 38 of the hole punching section 35. The cam 47 turns about a shaft 48 as a fulcrum which is provided on the body side of the finisher 20. The cam 47 has a lever 49 at its one end and has a gear 50 formed at its other end. The lever 49 is provided with a shaft 51. This shaft 51 is fitted in the elongated hole 40 in the protruding flap 38.
Moreover, to rotate the hole punching section 35 in the longitudinal direction (direction B), a gear group 52 is provided which meshes with the gear 50 and thus rotates. A longitudinal registration motor 53 is provided to rotate this gear group 52. As the longitudinal registration motor 53 rotates, the cam 47 rotates and thus the lever 49 turns. The hole punching section 35 turns in the longitudinal direction (direction B) about the fixed shaft 42 as its fulcrum.
Also, a sensor 54 is arranged at a position at a predetermined distance from the cam 47. The sensor 54 is to detect that the hole punching section 35 has turned in the direction of the arrow B and has turned to the home position, as shown in
In this way, the hole punching section 35 can be moved in the lateral direction (direction A) by the rotation of the lateral registration motor 44 and can be turned in the longitudinal direction (direction B) by the longitudinal registration motor 53. The above-described moving mechanism in the lateral direction (direction A) and the rotation mechanism in the longitudinal direction (direction B) form a moving mechanism for the hole punching section 35.
The moving distance of the hole punching section 35 is managed by the number of pulses when driving the lateral registration motor 44. Similarly, the rotation control of the hole punching section 35, that is, its angle, is managed by the number of pulses when driving the longitudinal registration motor 53.
On the sheet S carry-in side of the hole punching section 35, a sensor group 56 to detect the edge in the lateral direction (lateral edge) of the sheet S is provided, and also a sensor 57 is provided which detects the edges in the longitudinal direction (forward edge and rear edge) when the sheet S is conveyed. The sensor 57 forms a first detection unit. The sensor group 56 forms a second detection unit.
In the sensor group 56 and the sensor 57, for example, a light emitting device and a light receiving device are arranged to face each other, and when the sheet is conveyed and passes between the light emitting device and the light receiving device, the lateral edge, forward edge and rear edge of the sheet S are detected.
Meanwhile, sensors 61 and 62 for skew detection are provided in the skew detection unit 60. Also in these sensors 61 and 62, for example, a light emitting device and a light receiving device are arranged to face other, and when the sheet S is conveyed out and passes between the light emitting device and the light receiving device, the skew of the sheet is detected.
That is, the sensors 61 and 62 are arranged on the upstream side in the punching unit 31 and detect the passage of the forward edge and the rear edge of the sheet S conveyed thereto. The sensor 61 and the sensor 62 are provided in parallel orthogonally to the sheet conveying direction, at positions at a predetermined distance L1 from each other on the inner side than the minimum width dimension of the sheet S having the minimum sheet width that enables punching processing, as shown in
Detection signals from the sensors 61 and 62 are sent to a control unit, which will be described later. The control unit is provided with timer counters. The timer counters start counting time when the sensors 61 and 62 has detected the passage of the forward edge of the sheet S. For example, in the case where the sheet S is not tilted at all with respect to the conveying direction, the sensors 61 and 62 simultaneously detect the passage of the forward edge of the sheet S. Therefore, the timer counters simultaneously start counting and no time difference occurs.
On the other hand, in the case where the sheet S is tilted because of a skew as it is conveyed, since the first sensor 61 and the second sensor 62 are fixed at a predetermined distance from each other, a time difference occurs in the passage of the sheet S detected by the sensors 61 and 62. Thus, it can be known that the sheet S is skewed.
In the case where the sheet S is inserted in a skewed state and, for example, the sensor 61 first detects the sheet S and then the sensor 62 detects the sheet S, a skew error distance (a) is calculated from the time difference in the detection and the conveying speed V. If the distance between the first sensor 61 and the second sensor 62 is L1 and the skew angle is (θ), the following equation (1) holds.
a=L1×tan θ (1)
As the skew angle θ is calculated from this equation (1), the longitudinal registration motor 53 is driven at the number of pulses enough to rotate the hole punching section 35 by the angle θ. Thus, the hole punching section 35 is tilted and skew correction is carried out in accordance with the quantity of skew of the sheet.
As the lateral registration motor 44 and the longitudinal registration motor 53, stepping motors are suitable in which the number of rotations can be controlled by the number of pulses or frequency. The conveying rollers 34 are driven at a predetermined number of rotations by a conveying motor 59 and carry the sheet S conveyed thereto from upstream (the entrance of the punching unit 31), to downstream (the exit of the punching unit 31) at the conveying speed V.
Next, the control system to drive the punching unit 31 will be described with reference to
In
Also, the lateral registration motor 44, the longitudinal registration motor 53, the punch motor 58 and the conveying motor 59 for conveying the sheet are connected to the control unit 70. The control unit 70 controls the rotation of each motor in response to the result of detection from the above various sensors.
The home position sensor 45 is to detect a home position when the hole punching section 35 has been moved in the lateral direction (direction A) by the lateral registration motor 44. The home position in the lateral direction is the center part of the conveying path for the sheet S.
The home position sensor 54 is to detect a home position when the hole punching section 35 has been turned in the longitudinal direction (direction B) by the longitudinal registration motor 53. The home position in the longitudinal direction is the position where the hole punching section 35 is tilted most.
The home position sensor 73 is to detect a home position when the hole punching cutters 36 have been moved up and down by the punch motor 58. The home position of the hole punching cutters 36 is the position in the state where the hole punching cutters 36 have been pulled out of the sheet S, that is, the position away from the sheet face of the sheet S.
Moreover, a control unit 80 for controlling the body (MFP) 11 is connected to the control unit 70. The various parts of the body 11, for example, the operation panel 13, the printer unit 17, the ADF 12 and so on are connected to the control unit 80.
The control unit 70 and the control unit 80 operate in an interlocked manner to designate punching processing, designate a sheet size, and so on in accordance with the operation on the operation panel 13. In response to this, the punching unit 31 executes conveying of the sheet S, skew correction, punching processing and so on.
Next, the basic operation of the punching unit 31 of the invention will be described with reference to
After that, when the sheet S is conveyed in, the skew detection unit 60 detects skew at the forward edge of the sheet S. As the quantity of skew is detected by the skew detection unit 60, the control unit 70 drives the longitudinal registration motor 53 and the hole punching section 35 is turned and tilted in the direction of the arrow B2 in accordance with the quantity of skew of the sheet S conveyed therein, as shown in
The thin dotted line in
Next, when the forward edge of the sheet S is detected by the sensor 57 and it is detected that the sheet has been conveyed by a prescribed quantity, the lateral registration motor 44 is driven and the hole punching section 35 is moved in the direction of the arrow A2 from the retreat position toward the center of the conveying path. In this stage of movement, the sensor group 56 detects the lateral edge of the sheet S along the conveying direction.
In the detection of the lateral edge, a sensor of the sensor group 56 is designated in accordance with the sheet size designated through the operation panel 13, and the lateral edge is detected by the designated sensor. For example, the lateral edge of an A4 sheet is detected by an outer sensor 561. For a small sheet size, the lateral edge is detected by an inner sensor 564. As the lateral edge is detected by a sensor of the sensor group 56, the lateral registration motor 44 stops and also the hole punching section 35 stops moving.
After that, when the sheet S is further conveyed, as shown in
Then, after the rear edge of the sheet S is detected by the sensor 57, the sheet S is conveyed by a predetermined quantity from that position to a prescribed position where punching processing is to be carried out, as shown in
Driving of the punch motor 58 may be started in timing before the conveying motor 59 stops, in consideration of the time taken for the hole punching cutters 36 to be butted against the sheet. In this case, driving of the punch motor 58 may be started after the lapse of a predetermined period from when the rear edge of the sheet S is detected by the sensor 57.
As the hole punching processing ends, the control unit 70 drives the conveying motor 59 again to discharge the punched sheet. If there is a subsequent sheet, the processing of
In
In step S3, the skew detection unit 60 detects the skew at the forward edge of the sheet S conveyed therein. As the quantity of skew is detected by the skew detection unit 60, the longitudinal registration motor 53 is driven and the hole punching section 35 is turned and tilted in accordance with the quantity of skew of the sheet S conveyed therein, in step S4.
Next, when the forward edge of the sheet S is detected by the sensor 57, the lateral registration motor 44 is driven and the hole punching section 35 is moved from the retreat position toward the center of the conveying path. In step S5, the sensor group 56 detects the lateral edge of the sheet S. As the lateral edge is detected, the lateral registration motor 44 is stopped and also the hole punching section 35 stops moving. After that, as the sheet S is conveyed further, the skew detection unit 60 detects the quantity of skew at the rear edge of the sheet S, in step S6.
In step S71 of step S7, it is determined whether there is a difference between the quantity of skew at the forward edge and the quantity of skew at the rear edge. If there is a difference, the longitudinal registration motor 53 is driven to make fine adjustment of the tilt of the hole punching section 35 by the amount of the difference, in step S72. In this case, if there is a shift of the lateral edge of the sheet S, the lateral registration motor 44 is driven to make fine adjustment of the hole punching section 35 in the lateral direction as well.
After skew correction is done, the sheet S is conveyed by the predetermined quantity to the prescribed position where punching processing is to be carried out, and driving of the conveying motor 59 is stopped. In step S8, the punch motor 58 is driven to lower the hole punching cutters 36, thus punching punch holes in the sheet S. As the hole punching processing ends, the conveying motor 59 is driven again to discharge the punched sheet. If there is a subsequent sheet, the processing of steps S1 to S8 is repeated. If there is not subsequent sheet, each device is set at the home position (HP) and punching processing ends in step S9.
S1 to S8 shown in
As can be seen from
Meanwhile, the punching unit 31, which carries out the above-described basic operations, may be improved in the following manner.
Specifically, as the conveying speed of the sheet S becomes higher because of higher-speed operation of the image forming apparatus 10, also the conveying motor 59 needs to be rotated at a higher speed. When the conveying motor 59 is to be stopped, the rotation speed is decelerated to stop the conveying motor.
In the example of
If the time period (t1) from the detection of the rear edge of the sheet S until the conveying motor 59 stops is made longer, the sheet can be stopped at the accurate position even in the case where the conveying motor 59 is rotating at a high speed. However, in this case, the distance between the sensor 57 for detecting the rear edge of the sheet and the hole punching section 35 needs to be expanded, and therefore the apparatus increases in size.
Meanwhile, a technique of starting deceleration of the conveying motor 59 at the time when a predetermined time period has passed after the forward edge of the sheet S is detected, and then stopping the conveying motor 59, may be considered. However, in this case, the deceleration is carried out while the rear edge skew of the sheet S is being detected. Therefore, it becomes impossible to detect the skew at the rear edge. That is, since skew detection is based on calculation from the time difference between the detections by the sensor 61 and the sensor 62 and the conveying speed of the sheet S, the quantity of skew cannot be correctly calculated unless the speed is constant.
Thus, the punching mechanism 30 of the invention is characterized in that the conveying motor 59 is driven according to the control shown in the flowchart of
In
After that, as the sensor 57 detects the forward edge of the sheet S in step S13, the processing shifts to step S14. In step S14, the conveying motor 59 is pulse-driven until a predetermined number of pulses are counted after the time point when the forward edge is detected. The conveying motor 59 is then rotated at the same speed. The number of pulses counted in step S14 is prescribed by the sheet size of the conveyed sheet. For a longer sheet size, the prescribed number of pulses is set at a greater value.
As the prescribed number of pulses are counted in step S14, the conveying motor 59 is decelerated to a second speed that is lower than the first speed, in step S15. The deceleration to the second speed is completed before the rear edge of the sheet S reaches the skew detection unit 60. While the sheet S is being conveyed at the second speed, the rear edge skew of the sheet S is detected in step S16.
After that, as the rear edge of the sheet S is detected by the sensor 57 in step S17, the second-stage deceleration of the conveying motor 59 is carried out to stop the sheet S at a predetermined position, in step S18.
When the conveying motor 59 is stopped, the punch motor 58 is driven in step S19. Punching processing to the sheet S is carried out by the hole punching section 35 and punch holes are punched in the sheet S. When the hole punching processing has ended, the conveying motor 59 rotates again at the first speed to discharge the sheet S. If there is a subsequent sheet, the processing of steps S11 to S19 is repeated. If there is no subsequent sheet, the sheet conveying processing ends in step S20.
In this case, the conveying speed of the sheet S at the time of detecting the forward edge skew is the first speed, and the conveying speed of the sheet S at the time of detecting the rear edge skew is the second speed. Therefore, the control unit 70 detects the quantity of skew at the forward edge and the rear edge in consideration of the difference in the conveying speed.
S11 to S19 in
As can be seen from
Also, while the conveying motor 59 is conveying the sheet S at the first speed, the sensors 61 and 62 detect the forward edge skew. The conveying motor 59, triggered by the detection of the forward edge of the sheet S by the sensor 57, starts deceleration at the point when a prescribed number of pulses have been counted (after the lapse of a time period t2), and thus decelerates to the second speed.
The timing of decelerating the conveying speed of the sheet S from the first speed to the second speed is set closely to (slightly before) the timing of detecting the rear edge of the sheet by the sensor 57. Thus, as the period during which the sheet is conveyed at the first speed is made long and the period during which the sheet is conveyed at the second speed is made short, the overall processing speed is made faster.
While the sheet S is conveyed at the second speed, the sensors 61 and 62 detect the rear edge skew. After that, the conveying motor 59 stops rotating. Then, when the conveying motor 59 is stopped, the punch motor 58 is driven to perform hole punching processing.
Therefore, since the skew detection is carried out when the conveying motor 59 is rotating at a constant speed, the quantity of skew can be accurately detected.
The conveying motor 59 temporarily decelerated to the second speed and then shifts to the stop operation. Therefore, braking can be sufficiently effective at the time of stop and the sheet S can be stopped at the accurate hole punching position. Thus, the position of the punch holes to be formed by the hole punching section 35 is not deviated.
Moreover, since the distance between the forward edge and rear edge detection sensor 57 and the hole punching section 35 need not be expanded, the apparatus can be miniaturized. As the conveying motor 59 rotates fast at the first speed most of the time, it can sufficiently deal with the high-speed operation of the image forming apparatus 10.
In this way, according to the one embodiment of the invention, the sheet can be stopped at the regular position and hole punching processing can be accurately carried out without affecting skew detection and the like and without increasing the size of the apparatus.
Meanwhile, in the basic operations of the punching unit 31 described above, the hole punching section 35 is moved in the direction of the arrow A1 by driving of the lateral registration motor 44 and is situated at the retreat position before the sheet S is conveyed therein, as shown in
However, when the image forming cycle in the image forming apparatus 10 reaches a certain speed or more, punch holes are punched in the sheet S that has already been conveyed in, and the next sheet is conveyed in before the hole punching section 35 retreats. As the image forming cycle becomes shorter, this phenomenon emerges more conspicuously.
In a certain case, a sheet is conveyed in the state of being shifted in the direction of width from the center of the conveying path, for a reason such that the user sets sheets at a wrong position in the sheet cassette 18 of the image forming apparatus 10. The shift of the sheet can be several millimeters in the positive direction and in the negative direction from the center.
Therefore, it is necessary to set the hole punching section 35 at the retreat position, considering the quantity of shift of the sheet to be conveyed therein. This causes the moving distance to the retreat position to be longer.
Thus, it takes time for the hole punching section 35 to go through the process of reciprocating movement to the retreat position and from the retreat position to the position where the lateral edge of the sheet is to be detected. The time loss in this reciprocating movement causes obstacle to higher-speed operation of the image forming apparatus 10.
Even when plural retreat positions are provided according to different sheet sizes, as in the example disclosed in JP-A-9-249348, the problem in the case where the conveyed sheet is shifted from the center cannot be solved. If the configuration having separate driving sources for the hole punching section and the lateral edge detection unit is employed, as in JP-A-2006-16129, the cost increases significantly.
Thus, the second embodiment of the invention is characterized in that the time required for the reciprocating movement of the hole punching section 35 is reduced. The movement control of the hole punching section 35 is carried out by the control unit 70.
In the state shown in
When the lateral edge of the sheet S is detected by the sensor 561 halfway through the movement in the direction of the arrow A1, as shown in
After that, the hole punching section 35 is moved again in the opposite direction (the direction of the arrow A2), as shown in
By such operations, the quantity of movement of the hole punching section 35 can be reduced and the time required for its reciprocating movement can be reduced.
In the case where the size of the conveyed sheet S is changed, a sensor for lateral edge detection is selected form the sensor group 56 accordingly. Therefore, in this case, in moving the hole punching section 35 in the retreat direction, the hole punching section 35 can be moved by a prescribed quantity (L2) after the newly selected sensor detects the lateral edge of the sheet.
For example, if the sheet size is changed to a smaller size and the sensor 562 for lateral edge detection is selected, in moving the hole punching section 35 in the retreat direction, the hole punching section 35 is moved by a prescribed quantity (L2) after the sensor 562 detects the lateral edge of the sheet S, and then the hole punching section 35 waits at the standby position.
In
In this case, the hole punching section 35 is moved while the lateral edge is detected by the sensor group 56. As the lateral edge of the sheet S is detected in step S24, the hole punching section 35 is moved by a prescribed quantity (L2) after the time point of detecting the lateral edge, in step S25. Then, when it is detected in the next step S26 that the hole punching section 35 is moved by the prescribed quantity, driving of the lateral registration motor 44 is stopped and movement of the hole punching section 35 is stopped in step S27.
After that, in step S28, the lateral registration motor 44 is driven to move the hole punching section 35 in the opposite direction (direction A2). The hole punching section 35 is moved again to the hole punching position in accordance with the result of detection by the sensor 56 and is then stopped. If there is a subsequent sheet, the processing of steps S22 to S28 is repeated. If there is no subsequent sheet, the hole punching section is moved to the home position and the processing ends in step S29.
The original retreat position of the hole punching section 35 is the position shown in
On the assumption that a sheet is shifted as it is conveyed, the sheet can be shifted by several millimeters in the positive direction and in the negative direction from the center of the conveying path. Therefore, considering the quantity of shift, it is necessary to set the original quantity of retreat at about 10 mm or more. On the other hand, the prescribed quantity of retreat L2 of the hole punching section 35 in
Thus, in the second embodiment of the invention shown in
In the case where a stepping motor is used as the lateral registration motor 44, the number of rotations of the lateral registration motor 44, that is, the moving distance of the hole punching section 35, can be controlled according to the setting of the number of pulses. Therefore, the number of pulses for movement of the hole punching section 35 can be significantly reduced.
Next, a modification of the second embodiment of the invention will be described with reference to
In this modification, movement control of the hole punching section 35 is carried out, using the detection results of a sensor used for detection of the sheet size and the other sensors, of the sensor group 56. The movement control is carried out by the control unit 70.
For example, it is assumed that the interval between the sensors of the sensor group 56 is 3 mm each, as shown in
When the sheet S is conveyed with a downward shift, as shown in
Thus, the hole punching section 35 is controlled to retreat by 2 mm from there at the time point when the sensor 562 detects the lateral edge. That is, in this case, since the sheet S is already shifted by 3 mm in the opposite direction to the retreat direction of the hole punching section 35, the hole punching section 35 can retreat to the position which is shifted by 5 mm relatively to the sheet S, simply by retreating by 2 mm. Thus, the hole punching section 35 only needs to move 2 mm, instead of the original distance of 5 mm.
In the state of
Thus, the hole punching section 35 is controlled to keep its position without moving in the retreat direction when the sensor 563 has detected the lateral edge. That is, in this case, since the sheet S is already shifted by 5 mm in the opposite direction to the retreat direction of the hole punching section 35, the hole punching section 35 does not have to retreat. Thus, the hole punching section 35 does not have to move, instead of moving by the prescribed distance of 5 mm.
In this way, in the above-described modifications, the program is set to control the movement of the hole punching section 35, using the detection results not only of the original lateral edge detection sensor but also of the other sensors linked to the former sensor. Thus, in moving the hole punching section 35 in the retreat direction, as the quantity of movement is controlled in accordance with the number of sensors that have already detected light, of the sensor group 56, the quantity of reciprocating movement can be reduced further. Moreover, the time for punching processing, power consumption and the like can be reduced as well.
In this way, according to the second embodiment of the invention, the quantity of movement of the hole punching section 35 in the lateral direction at the time of punching processing can be reduced to realize high-speed processing. Also, even when a sheet is shifted in the lateral direction as it is conveyed, punch holes can be formed at prescribed positions.
Next, a sheet processing apparatus according to the third embodiment of the invention will be described. In the third embodiment, the technique of skew correction is improved, which will be described with reference to
Skew correction is carried out by rotation control of the hole punching section 35. As shown in
As shown in
In the case of carrying out skew correction based on the detection of the forward edge skew, the longitudinal registration motor 53 can be driven, for example, by 12 pulses in the positive direction and 12 pulses in the negative direction from the center position (indicated by the chain-dotted line y). That is, the longitudinal registration motor 53 can be driven by 24 pulses at the maximum.
Meanwhile, as a skew correction range based on the detection of the rear edge skew, the longitudinal registration motor 53 can be driven, for example, by six pulses in the positive direction and six pulses in the negative direction in consideration of the processing time. That is, the longitudinal registration motor 53 can be driven by 12 pulses at the maximum. Therefore, the cam 47 turns within a predetermined angular range that is symmetrical about the position (y) where the hole punching section 35 is orthogonal to the conveying path. If the skew correction range at the forward edge is expressed by w1 and the skew correction range at the rear edge is expressed by w2, the following relation is set.
w1>w2≧w1/2
Meanwhile, in such driving setting, it may be impossible to deal with a large quantity of skew correction. For example, a case will now be described in which the quantity of skew detected at the forward edge of the sheet is equivalent to +10 pulses as indicated by the dotted line f1 and the quantity of skew detected at the rear edge of the sheet is equivalent to +2 pulses as indicated by the dotted line b1, as shown in
On the other hand, for skew correction at the rear edge, correction by ±6 pulses is possible. However, since the longitudinal registration motor 53 is driven by 10 pulses in the positive direction by skew correction at the forward edge, the range in which the longitudinal registration motor 53 can be driven at the time of rear edge skew detection is two pulses, that is, from 10 pulses to 12 pulses in the positive direction. In the negative direction, the longitudinal registration motor 53 can only be driven by six pulses (up to the position of +4 pulses) from 10 pulses. Therefore, the driving range according to the rear edge skew is a total of eight pulses and the operation range is narrowed by four pulses. If the quantity of skew b1 at the rear edge is equivalent to +2 pulses, correction is insufficient.
Thus, in the third embodiment of the invention, another measure is taken in the technique of skew correction. Specifically, the invention is characterized in that, in the case where the quantity of skew at the forward edge exceeds the skew correction range w2 (±6 pulses) at the rear edge, skew correction at the forward edge is carried out by the amount equivalent to the skew correction range w2 (±6 pulses) at the rear edge, and the insufficient correction is compensated for by skew correction at the rear edge.
For example, when the quantity of skew correction at the forward edge is equivalent to a prescribed number of pulses (for example, ±6 pulses) or less, the hole punching section 35 is turned in proportion to the quantity of skew at the forward edge. On the other hand, when the quantity of skew correction at the forward edge exceeds the prescribed number of pulses (for example, ±6 pulses) the way of controlling the turning varies.
The operation in the case where the quantity of skew at the forward edge is larger than the prescribed value will be described with reference to
Then, if the quantity of skew correction at the forward edge (indicated by the dotted line f1) exceeds the prescribed number of pulses (for example, if it is equivalent to +10 pulses), the longitudinal registration motor 53 is driven by the prescribed number of pulses (six pulses) in the positive direction. After that, skew correction at the rear edge is carried out.
In the skew correction at the rear edge, correction is made by the difference between the quantity of skew at the forward edge after correction and the quantity of skew at the rear edge. For example, if the quantity of skew at the rear edge (indicated by the dotted line b1) is equivalent to +2 pulses, the longitudinal registration motor 53 is situated at the position of +6 pulses after the skew correction at the forward edge. Therefore, the longitudinal registration motor 53 is driven in the negative direction by four pulses equivalent to the difference. Thus, it is possible to correct the position to the regular position of +2 pulses.
In the example shown in
Also, in the example of
In
For example, if the quantity of skew correction is 10 pulses, the processing shifts to step S331. To correct the forward edge skew, the longitudinal registration motor 53 is driven by six pulses and the hole punching section 35 is thus turned. After that, in step S341, the quantity of skew at the rear edge of the sheet S is detected.
If the result of skew detection at the rear edge shows, for example, the position of +2 pulses, the longitudinal registration motor 53 is driven by four pulses in the negative direction corresponding to the difference from the current position in consideration of the quantity of skew at the rear edge, in step S351. Thus, the hole punching section 35 can be turned to the regular position of +2 pulses.
Meanwhile, if the quantity of skew correction is less than six pulses in step S32, the processing shifts to step S332. To carry out skew correction at the forward edge, the longitudinal registration motor 53 is driven by the number of pulses equivalent to the quantity of skew and the hole punching section 35 is thus turned and tilted.
After that, in step S342, the quantity of skew at the rear edge of the sheet S is detected. If the result of skew detection at the rear edge shows, for example, the position of +2 pulses, the longitudinal registration motor 53 is rotated by +2 pulses, which are equivalent to the quantity of skew at the rear edge, in step S352. Thus, the hole punching section 35 can be turned to the regular position of +2 pulses. Step S36 is the step of ending skew correction.
In this way, in the third embodiment of the invention, since the hole punching section 35 can be rotationally controlled within the prescribed range in the positive direction and in the negative direction at the time of skew correction at the rear edge, the driving range according to the rear edge skew correction is not narrowed. Therefore, skew correction can be accurately made. Moreover, the time for skew correction can be reduced.
In this modification, the quantity of skew detected at the forward edge of the sheet and the quantity of skew detected at the rear edge of the sheet are measured for each sheet size, at each sheet conveying speed, and so on. Then, statistics of the difference in the quantity of skew between the forward edge and the rear edge are taken and the technique of skew correction is automatically or manually switched.
For example, in the case where the quantity of skew at the rear edge tends to be two pulses or more in the positive direction with respect to the quantity of skew at the forward edge, as shown in
That is, in the characteristics shown in
On the other hand, in the case where correction by +2 pulses is made in advance, the skew-correctable range is from +8 pulses to −4 pulses with the point of +2 located at its center, as shown in
According to such a modification, even when the quantity of skew differs largely between the forward edge and the rear edge of the sheet, the hole punching section 35 can be effectively turned within the allowable range by skew correction at the rear edge, and accurate skew correction can be made. Also, the time for skew correction can be reduced.
In the above-described example, the state of the sheet is detected by various sensors. For example, plural sensors are used to detect the state of skew of the sheet S, the position of the edge in the direction of width (lateral edge), the positions of the forward and rear edges and so on.
However, if a greater number of sensors are used, the space for attacking these sensors is required and the punching unit itself becomes larger. Moreover, if the number of sensors increases, the possibility of detection errors increases accordingly and power consumption increases as well.
Thus, in the fourth embodiment of the invention, an improvement is made so that the forward and rear edges of the sheet S are detected by using the sensors 61 and 62 of the skew detection unit 60, and the forward edge and rear edge detection sensor 57 of
Hereinafter, a sheet processing apparatus according to the fourth embodiment of the invention will be described with reference to
In
The configuration of the hole punching section 35 is the same as the configuration shown in
Moreover, to turn the hole punching section 35 in the longitudinal direction (direction B), a cam 47, a gear group 52, and a longitudinal registration motor 53 for rotating the gear group 52 are provided.
On the side of the hole punching section 35 where the sheet S is conveyed in, a sensor group 56 for detecting the edge in the lateral direction (lateral edge) of the sheet S is provided. Meanwhile, sensors 61 and 62 which detect skew and also detect the forward and rear edges of the sheet S are provided in the skew detection unit 60. In these sensors 61 and 62, for example, a light emitting device and a light receiving device are arranged to face each other, and when the sheet S is conveyed and travels between the light emitting device and the light receiving device, these sensors detect the passage of the sheet.
The sensor 61 and the sensor 62 are situated on the inner side than the minimum width dimension of the sheet S, as shown in
Detection signals from the sensors 61 and 62 are sent to a control unit 70 shown in
That is, the sensors 61 and 62 form a first detection unit, which is used for skew detection and detection of the forward and rear edges of the sheet S. Therefore, the forward edge and rear edge sensor 57 shown in
Next, the operation of the punching unit 31 of
It is assumed that the skewed sheet S is conveyed in, as shown in
In the case of
If the intermediate point between the sensors 61 and 62 is P, the time after the lapse of X/2 hours from the detection of the forward edge of the sheet by the skew detection sensor 62 is the timing when the center of the forward edge of the sheet S passes the intermediate point P.
Thus, if the distance between the skew detection unit 60 and the hole punching section 35 (lateral edge detection sensor group 56) is expressed by L3 and the conveying speed of the sheet S is expressed by V, the time after the lapse of a period expressed by (L3/V+X/2) from the timing when the skew detection sensor 62 detects the forward edge of the sheet is the timing when the center of the forward edge of the sheet S is conveyed into the hole punching section 35. This timing is equivalent to the timing of detecting the forward edge of the sheet by the forward and rear edge detection sensor 57 of
The rear edge of the sheet S is similarly detected. That is, the time after the lapse of a period expressed by (L3/V+X/2) from the detection of the passage of the rear edge of the sheet by the skew detection sensor 62 is the timing when the center of the rear edge of the sheet S passes the hole punching section 35.
This timing is equivalent to the timing of detecting the rear edge of the sheet by the forward and rear edge detection sensor 57 of
Thus, as the control unit 70 having the arithmetic operation function is employed, the skew detection sensors 61 and 62 can also be used as the sheet forward and rear edge detection sensor and the number of components can be reduced.
The control unit 70 also controls the longitudinal registration motor 53 in accordance with the result of skew detection, controls the tilt angle of the hole punching section 35 to perform skew correction, and controls movement of the hole punching section 35 in accordance with the result of lateral edge detection by the sensor group 56. The control unit 70 also controls operations such as deceleration and stop of the conveying motor 59 in accordance with the result of calculation of the forward edge and the rear edge of the sheet S. Moreover, the control unit 70 controls the punch motor 58 of the hole punching section 35 in accordance with the position information of the sheet S and thus controls the operation of punching processing.
In this way, according to the above embodiment of the invention, reduction in the number of sensors, saving of space, reduction in cost, and saving of power can be realized.
Although the punching mechanism 30 and the body 11 are configured as separate units in the above description, the punching mechanism 30 may be formed within the body 11. Also, though the punching mechanism 30 forms punch holes in a sheet outputted from the body 11 in the above examples, sheets may be sequentially conveyed into the punching mechanism 30 by using an inserter and punch holes may be formed in the sheets conveyed from the inserter.
Various modifications can be made without departing from the scope of the attached claims.
Although exemplary embodiments of the present invention have been shown and described, it will be apparent to those having ordinary skill in the art that a number of changes, modifications, or alterations to the invention as described herein may be made, none of which depart from the spirit of the present invention. All such changes, modifications, and alterations should therefore be seen as within the scope of the present invention.
This application is based upon and claims the priority of U.S. Provisional Application No. 60/943,596, filed on Jun. 13, 2007, U.S. Provisional Application No. 60/944,935, filed on Jun. 19, 2007, U.S. Provisional Application No. 60/944,936, filed on Jun. 19, 2007, and U.S. Provisional Application No. 60/944,943, filed on Jun. 19, 2007, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60943596 | Jun 2007 | US | |
| 60944935 | Jun 2007 | US | |
| 60944936 | Jun 2007 | US | |
| 60944943 | Jun 2007 | US |
