Patent Application
20070284803
a) is a sectional view of an essential part of the driving transmitting mechanism for the registration roller in
With reference to the drawings, description will be given below for a sheet feeding device and an image reading apparatus comprising the sheet feeding device.
In
The ADF 10 includes a placement tray 15 on which a plurality of sheets are placed, a sheet feeding section 11 that separably feeds each of the sheets on the placement tray 15 toward the first platen 2, a conveying section 12 that passes the sheet along the top surface of the first platen 2 at a predetermined speed, a sheet discharging section 13 that receives and discharges the sheet having passed over the top surface of the first platen 2, and a sheet discharging tray 16 that houses the sheet from the sheet discharging section 13. The ADF 10 further includes a switchback section 14 that allows the sheet discharging section 13 to switch back the sheet carried out from the first platen 2 to return the sheet to the sheet feeding section 11 so that the first platen 2 can read a back surface of the sheet. The ADF 10 further includes a circulating path 30.
The sheet feeding section 11 is composed of the above placement tray 15, a pickup roller 18, sheet feeding rotating means 19, a registration roller 21, and a sheet feeding path 25. The placement tray 15 is composed of a tray member shaped so that sheets with a size preset in accordance with apparatus specifications are placed. Side guides 17 are located on the placement tray 15 so that the side edges of a sheet can be aligned with the side guides 17. A gate stopper 38 is located at a leading end of the placement tray 15 so that the leading end of a sheet can be abutted against and aligned with the gate stopper 38; the gate stopper 38 can be projected from and retracted onto the placement tray 15. The illustrated placement tray 15 is attached to a device frame so as to incline at a predetermined angle. The placement tray 15 can pivot around a supporting point at its leading end, shown at 15a in the figure.
The pickup roller 18 is located so as to be able to elevate and lower between a standby position (corresponding to the state shown in
The sheet feeding rotating means 19 is composed of rotating members such as a belt and a roller in order to separably feed each sheet downstream; the illustrated sheet feeding rotating means 19 is composed of a sheet feeding roller supported by the rotating support shaft 19b. In the description below, the sheet feeding rotating means is the sheet feeding roller 19. Separating means 20 such as a separating pad (not shown) or a separating roller is brought into pressure contact with the sheet feeding roller 19 to separably feed each sheet delivered by the pickup roller 18, to the interior of the apparatus. The arrangement of the sheet feeding roller 19 will be described below. Since sheets are set in the placement tray 15 by centering, the sheet feeding roller 19 is located at a position corresponding to the center of the sheets.
The sheet feeding path 25 is curved like the letter U to guide a sheet from the placement tray 15 to a processing position (first platen 2 described above). The registration roller 21 is located on the sheet feeding path 25 and composed of a pair of rollers 21a and 21b that are in pressure contact with each other. One of the rollers 21a and 21b is coupled to a second driving motor M2 described below. The conveying section 12 is composed of a carry-in roller 22 located upstream of the first platen 2 and a carry-out roller 23 located downstream of the first platen 2. Each of these rollers 22 and 23 is composed of a pair of rollers that conveys a sheet nipped between them. A backup guide 26a is located above the first platen 2, and a scooping guide 6 is located downstream of the first platen 2. Reference numeral 26 in the figure denotes a conveying path along which a sheet from the first platen 2 is carried out and guided to a sheet discharging path described below 27.
The sheet discharging section 13 is composed of a sheet discharging path 27, a path switching flapper 29 located on the sheet discharging path 27, and a sheet discharging roller 24. A rear end of the sheet discharging path 27 constitutes a switchback path 28. The switchback path 28 continues into a circulating path 30. The sheet discharging roller 24 rotates reversely with the trailing end of a sheet nipped between the rollers to switch back and feed the sheet to the circulating path 30. Thus, a sheet discharging roller 24b is separated from a sheet discharging roller 24a when the end of a sheet passes by the rollers; the sheet discharging rollers 24a and 24b constitute the sheet discharging roller 24. Further, the path switching flapper 29 is always urged downward by an urging spring to switch the path by means of an electromagnetic solenoid.
The circulating path 30 is composed of an upper guide 28a and a lower guide 28b so as to guide the sheet having its conveying direction reversed by the switchback path 28. Reference numeral 28 in the figure denotes a Myler guide that guides the sheet from the circulating path 30 to a nip point of the registration roller 21. A plurality of sensors S1, S2, and S3 (
In the present invention, the pickup roller 18, sheet feeding roller 19, registration roller 21, carry-in roller 22, carry-out roller 23, and sheet discharging roller 24 are coupled to the first and second driving motors. Driving mechanisms for the conveying rollers will be described with reference to
On the other hand, a base end of the elevating and lowering arm 18a is fitted around the rotating support shaft 19b via spring clutches A and B. The spring clutches are set so as to be loosened when the rotating support shaft 19b rotates forward and so to be compressed when the rotating support shaft 19b rotates backward. Consequently, forward rotation of the rotating support shaft 19b loosens the spring clutches to swing the elevating and lowering arm 18a from the standby position, located above, to the operative position, located below, under its own weight. In contrast, backward rotation of the rotating support shaft 19b compresses the spring clutches to raise the elevating and lowering arm 18a from the operative position to the standby position under a rotating torque from the shaft. Although not shown, the elevating and lowering arm 18a has a stopper at its standby position. While being restricted by the stopper, the elevating and lowering arm 18a is held at the standby position through the action of a spring clutch C (torque limiter) located between the pulley P36 and the gear Z17.
Even after the sheet feeding motor M1 is stopped, the spring clutches A and B remain compressed to hold the elevating and lowering arm 18a at the standby position under the load of the driving system. Thus, forward rotation of the sheet feeding motor M1 lowers the pickup roller 18 from the standby position to the operative position. The pickup roller 18 then rotates in the sheet feeding direction to deliver the sheets on the placement tray 15 in conjunction with the sheet feeding roller 19. After all the sheets on the placement tray 15 are delivered, the sheet feeding motor M1 rotates backward to swing the elevating and lowering arm 18a to raise the pickup roller 18 from the operative position to the standby position. In
Now, description will be given to a driving mechanism for the second driving motor (hereinafter referred to as the conveying motor) M2, which drivingly rotates the registration roller 21, carry-in roller 22, carry-out roller 23, and sheet discharging roller 24; the driving mechanism is shown in
On the other hand, the driving force of the conveying motor M2 is transmitted to the sheet discharging roller 24 through a pulley 42, a timing belt T5, and a pulley P48 shown in
Thus, rotation of the conveying motor M2 is transmitted to a timing belt T3 through the timing belt T5 via a pulley 63 and a pulley 67 that is coaxial with the pulley 63. The rotation is further transmitted to a driving roller 21a of the registration roller 21 via a one-way clutch OW1 provided on the pulley 28a. This transmission system has a sliding friction clutch means 60 described below. The sliding friction clutch means 60 is configured as shown in
As shown in
On the other hand, a driven sleeve-side end of the spring 65 is bent and fixed to the gear 66. The gear 66 is loosely fitted on and supported by flanges formed on the driving sleeve 63a and driven sleeve 64 so as to rotate freely regardless of rotation of the pulley 63 and rotating shaft 62. The gear 61, connected to the sheet feeding motor M1, meshes with the gear 66. The gear 61 is attached to the rotating shaft 61a (see
Now, the operation of the driving mechanism will be described with reference to the timing chart shown in
The apparatus is powered on to turn on the empty sensor S4 on the placement tray 15 to rotate the sheet feeding motor M1 forward (sheet feeding direction). At this time, the conveying motor M2 is stopped. The forward rotation of the sheet feeding motor M1 rotates the pickup roller 18 and the sheet feeding roller 19 in the sheet feeding direction (rightward in the figure). At the same time, the spring clutches A and B between the rotating support shaft 19b and the elevating and lowering arm 18a holding the pickup roller 18 are compressed to swing the elevating and lowering arm 18a in conjunction with rotation of the rotating support shaft 19b to lower the elevating and lowering arm 18a from the standby position to the operative position. The rotation of the rotating support shaft 19b is similarly transmitted, via the timing belt T2, to the pickup roller 18 supported at a swinging end of the elevating and lowering arm 18a. The rotating operation of the pickup roller 18 delivers each of the sheets on the placement tray 15 to the sheet feeding roller 19. The separating means 20 then separably feeds the delivered sheet. The elevating and lowering arm 18a stops swinging when the pickup roller 18 moves to the operative position to press the leading sheet to loosen the spring clutches A and B to stop rotating the rotating support shaft 19b. Further, the elevating and lowering arm 18a moves to the standby position to abut against a stopper (not shown) to loosen the spring clutch C. This turns off the sheet feeding driving system.
This operation allows the leading end of the sheet carried out to the sheet feeding path 25 to be sensed by the registration sensor S5. Subsequently, the sheet abuts against the registration roller 21. At this time, the conveying motor M2 coupled to the registration roller 21 is at a stop, so that the leading end of the sheet abuts against the nip point of the registration roller 21 and is thus bent. The bending of the sheet allows the leading end of the sheet to be registered. At a predetermined delay time (registration time) after the issuance of a sensing signal from the registration sensor S5, the sheet feeding motor M1 is stopped. During this process, in the sliding friction clutch means 60, the gear 66 rotates in conjunction with the gear 61 coupled to the sheet feeding motor M1. However, since the spring 65 is set in an opening direction (loosening direction), the spring 65 and the driven sleeve 64 slip against each other to keep the rotating shaft 62 at a stop; the rotating shaft 62 is not driven by the sheet feeding motor M1. The registration roller is at a stop without being rotated.
Then, a predetermined time after a processing operation such as image reading, a sheet feeding instruction signal is issued, and in response to the signal, the conveying motor M2 is rotated forward (sheet feeding direction). At this time, the sheet feeding motor M1 is at a stop as previously described. The forward rotation of the conveying motor M2 rotates the pulley 63 clockwise in
The rotation of the registration roller 21 transfers the sheet downstream along the sheet feeding path 25. Simultaneously with the operation of the registration roller 21, the forward rotation of the conveying motor M2 is transmitted to the carry-in roller 22 and carry-out roller 23 via the pulley P33 and timing belts T6 and T7 as previously described. These rollers are thus rotated in the sheet feeding direction. The motor M2 also transmits rotation in a sheet discharging direction to the sheet discharging roller 24 via the timing belt T5 and pulley P48. During this process, the clockwise rotation (in
The lead sensor S6, located upstream of the carry-in roller 22, senses the leading end of the sheet conveyed as described above to issue a cue signal in accordance with which the first platen 2 reads an image. Then, the registration sensor S5 senses the trailing end of the sheet, and after the time when the trailing end of the sheet is expected to pass through the registration sensor 21, the sheet feeding motor M1 at a stop is actuated to rotate forward (sheet feeding direction). At this time, the conveying motor M2 continuously rotates forward (sheet feeding direction). Rotating the sheet feeding motor M1 and the conveying motor M2 at the same time subjects the coil spring 65 around the rotating shaft 62 to both the rotating force of the conveying motor in a compressing direction (shown by arrow a in
Thus, for the sliding friction clutch means 60, the relationship between the rotation speed V2 (angular speed) of the conveying motor M2 transmitted to the rotating shaft 62 by the pulley 63 and the rotation speed V1 (angular speed) of the sheet feeding motor M1 transmitted by the gear 66 is set to be V1>V2. That is, the rotation speed of the sheet feeding motor M1 in the loosening direction acts more significantly on the coil spring 65 than the rotation speed of the conveying motor M2 in the compressing direction.
Consequently, the driving sleeve 63a and the coil spring 65 slip against each other, preventing the driving force of the sheet feeding motor M1 from being transmitted to the rotating shaft 61a. This stops the registration roller 21. On the other hand, rotation of the conveying motor M2 is transmitted to the carry-in roller 22, carry-out roller 23, and sheet discharging roller 24, coupled to the conveying motor M2. These rollers continue to rotate in the above directions. Accordingly, the sheet conveyed by the registration roller has its trailing end carried out from the roller 21 and is then conveyed to the first platen 2 by the carry-in roller 22. The platen then executes a reading process. The sheet from the platen 2 is carried out to the sheet discharging tray 16 by the carry-out roller 23 and sheet discharging roller 24.
The simultaneous rotation of the sheet feeding motor M1 (forward rotating CW direction) and conveying motor M2 (forward rotating CCW direction) stop the registration roller 21 as described above. At the same time, the pickup roller 18 and sheet feeding roller 19, coupled to the sheet feeding motor M1, rotate in the sheet feeding direction to deliver the next sheet from the placement tray 15 for registration. On the basis of the timing when the next sheet is fed to the registration roller 21, for example, on the basis of a leading end sensing signal from the registration sensor S5, the sheet feeding motor M1 is stopped. The conveying motor M2 finishes carrying the sheet out to the sheet discharging tray 16 and stops before the sheet feeding motor M1 stops. Further, stopping and rotating the registration roller 21 does not necessarily require the stoppage of the conveying motor M2; the registration-roller 21 can be stopped and rotated with the conveying motor M2 rotating, by rotating and stopping the sheet feeding motor M1. Then, in this state, the sheet fed to the registration roller 21 waits for the next sheet feeding instruction signal. Subsequently, the process returns to the second operation, which is then repeated as described above.
On the other hand, the sheet from which the image has been read is fed to the carry-out path 26 and carry-out path 27. At this time, in a double-side reading mode in which the back surface of the sheet is also read, the carry-out sensor S7 detects the trailing end of the sheet during above second operation. A predetermined time later, the carry-out sensor S7 switches the rotation of the conveying motor M2 to the backward direction (CW direction). At this time, the sheet feeding motor M1 is kept at a stop. The backward rotation of the conveying motor M2 reverses the direction in which the sheet nipped by the sheet discharging roller 24 is conveyed. The sheet is then fed to the circulation circuit 30. When the sheet is fed along the circulating path 30 and the trailing end of the sheet reaches the registration roller 21, the registration roller 21 at a stop registers the leading end of the sheet. That is, the backward rotation (CW direction) of the conveying motor M2 is transmitted to the pulley 63. However, a rotating force in the loosening direction acts on the coil spring 65 to prevent the backward rotation from being transmitted to the rotating shaft 62, coupled to the registration roller 21. After the circulated sheet is registered by the registration roller 21, the conveying motor receives a sheet feeding instruction signal at a predetermined timing and is thus rotated forward (CCW direction). The process returns to the second operation, which is then sequentially repeated.
Once all the sheets on the placement tray 15 are delivered, the empty sensor S4 is turned off to issue the corresponding signal. Then, when the final sheet is carried out to the sheet discharging tray 16, for example, after a predetermined delay time since the sheet discharging sensor S8 issues a sheet trailing end detection signal, the sheet feeding motor M1 is rotated backward (CCW rotation). The rotation compresses the spring clutches A and B, provided on the elevating and lowering arm 18a as described above, to raise the elevating and lowering arm 18a from the operative position to the standby position under the rotating torque from the support shaft. Even after the sheet feeding motor M1 is stopped, the spring clutches A and B remain compressed to hold the elevating and lowering arm 18a in its standby position under the load of the driving system.
As described above, according to the present invention, the first driving motor drivingly rotates the pickup roller and sheet feeding rotating means, which separates and feeds each of the sheets on the placement tray. The second driving motor drivingly rotates the registration roller and carry-in roller, located downstream of the pickup roller and sheet feeding rotating means. Further, the sliding friction clutch means is provided between the second driving motor and the registration roller. The transmission of a driving force through the sliding friction clutch means is blocked by the corresponding rotation of the first driving motor. Consequently, even while a sheet delivered from the tray is being conveyed by the downstream carry-in roller, the rotation of the first driving motor for delivering the following sheet blocks the transmission of a driving force to the registration roller. This enables the pickup roller and sheet feeding rotating member to deliver the next sheet to the registration roller at a stop, allowing the sheet with its leading end registered to stand by. Thus, sheets can be consecutively fed at a high speed.
Therefore, compared to the conventional technique with which a motor rotates forward to perform a pickup operation and backward to perform a registered feeding operation, the present invention can control the motor so that the pickup roller is lowered from the standby position before starting the operation and raised from the operative position after finishing the operation. This eliminates the need to elevate and lower the pickup roller between the standby position and the operative position whenever a sheet is to be delivered. A precise process can be executed at the downstream processing position without any noise or vibration. Moreover, the required configuration is such that, for example, the coil spring is wound around the rotating shaft, connected to the registration roller, so that the registration roller being rotated by the second driving motor can be stopped by appropriately rotating the first driving motor to loosen the coil spring. Thus, the required structure is simple and can be easily controlled. Therefore, the present invention exerts significant effects.
Therefore, the automatic sheet feeding device set forth in the present invention can controllably stop and rotate the registration roller by rotating the sheet feeding motor forward and stopping it. The device enables the sheet to be separated from the pickup roller to stand by by reversely rotating the sheet feeding motor. This allows the provision of an automatic sheet feeding device and an image processing apparatus which eliminate the need for an expensive electromagnetic clutch otherwise required to stop and rotate the registration roller, the device and apparatus also enabling the pickup roller to always abut against the sheet during the sequential separation and feeding of sheets, reducing the possibility of vibration or noise.
Further, the sheet feeding motor M1 can be driven at a low speed while the registration roller 21 is being driven. By rotating the motor at a driving speed appropriate to prevent a plurality of overlapping sheets from being simultaneously fed, it is possible to feed the sheet being conveyed by the conveyance driving system, in a trailing end-first position. This enables smooth conveyance with a reduced conveying load.
The disclosure of Japanese Patent Application No. 2006-103668 filed on Apr. 4, 2006, is incorporated as a reference.
While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-103668 | Apr 2006 | JP | national |
