Patent Application
20080150221
The present application claims priority from Japanese Patent Application No. 2006-350680, which was filed in the Japanese Patent Office on Dec. 26, 2006, the disclosure of which is herein incorporated by reference in its entirety.
Apparatuses and devices consistent with the present invention relate to sheet feeders and, in particular, to sheet feeders for conveying sheets by using a plurality of rotating bodies.
A related art sheet feeder is provided in an image-recording device such as a printer. The related art sheet feeder includes a sheet tray and feed rollers. Sheets placed on the related art sheet tray are separated one by one by the feed rollers, and the separated sheets are fed in the conveying direction.
The above-described related art sheet feeder includes a device which comprises two feed rollers apart in the conveying direction of sheets, as, for example, disclosed in Patent Document 1.
[Patent Document 1] Japanese Published Unexamined Patent Application No. 2003-146455
Moreover, in related art sheet feeders, a greater conveyance resistance (conveyance friction) is applied to a sheet on conveyance of a wide sheet than on conveyance of a narrow sheet. As a result, there are concerns in the related art that a feed roller may slip on a sheet. Thus, in an attempt to address this problem, Patent Document 1 proposes providing two feed rollers. However, this approach has a disadvantage in that in a mechanism for conveying sheets with two feed rollers, it is impossible to completely synchronize the rotating speed of the two feed rollers. This causes a problem in the case where a sheet is deflected between the two feed rollers or pulled by them. In such a case, the deflected sheet may suffer damage such as creases or cuts.
Exemplary embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. However, the present invention is not required to overcome the disadvantages described above, and thus, an exemplary embodiment of the present invention may not overcome any of the problems described above. Accordingly, it is an aspect of the present invention to provide a sheet feeder capable of conveying a sheet reliably without causing damage where a conveyance resistance is imparted to the sheet.
A sheet feeder according to first aspect of the present invention is a sheet feeder comprising: a sheet tray which retains a sheet; at least one driving source; a first conveying mechanism including a first rotating body which is in contact with a sheet on the sheet tray and a first driving-force transfer mechanism which transfers a driving force of the driving source to the first rotating body; and a second conveying mechanism including a second rotating body which is in contact with the sheet on the sheet tray and a second driving-force transfer mechanism which transfers the driving force of the driving source to the second rotating body; wherein the first rotating body is rotated in a conveying direction of the sheet by the driving force transferred by the first driving-force transfer mechanism, so that the sheet positioned on the sheet tray is conveyed in a predetermined direction at a first speed; the second rotating body is rotated by a friction force between the sheet and the second rotating body, when a conveying speed of the sheet on the sheet tray is greater than a second speed which is smaller than the first speed; and the second rotating body is rotated in the conveying direction of the sheet by the driving force transferred by the second driving-force transfer mechanism, when the conveying speed of the sheet on the sheet tray is smaller than the second speed.
Also, a sheet feeder of second aspect of the present invention is a sheet feeder according to first aspect, wherein the second driving-force transfer mechanism includes a one-way clutch.
Also, a sheet feeder of third aspect of the present invention is a sheet feeder according to second aspect, wherein a peripheral speed of the first rotating body which is driven by the driving source is greater than a peripheral speed of the second rotating body which is driven by the driving source.
Also, a sheet feeder of fourth aspect of the present invention is a sheet feeder according to first aspect, wherein the first conveying mechanism further comprises a first arm member on which the first rotating body is provided so that the first rotating body may rotate; the second conveying mechanism further comprises a second arm member on which the second rotating body is provided so that the second rotating body may rotate.
Also, a sheet feeder of fifth aspect of the present invention is a sheet feeder according to fourth aspect, wherein an angle of an extending direction of the second arm member with respect to a surface of the sheet positioned on the sheet tray is greater than an angle of an extending direction of the first arm member with respect to the surface of the sheet positioned on the sheet tray.
Also, a sheet feeder of sixth aspect of the present invention is a sheet feeder according to first aspect, wherein the second rotating body is disposed separate from and upstream of the first rotating body in the conveying direction of the sheet.
Also, a sheet feeder of seventh aspect of the present invention is a sheet feeder according to first aspect, wherein the second conveying mechanism further comprises a speed detecting mechanism which detects a conveying speed of the sheet positioned on the sheet tray.
Also, a sheet feeder of eighth aspect of the present invention is a sheet feeder according to seventh aspect, wherein the second conveying mechanism further comprises a solenoid which switches whether the driving force of the driving source is transferred to the second rotating body.
Also, a sheet feeder of ninth aspect of the present invention is a sheet feeder according to seventh aspect, wherein the speed detecting mechanism detects a rotation speed of the second rotating body.
Also, a sheet feeder of tenth aspect of the present invention is a sheet feeder according to ninth aspect, wherein the speed detecting mechanism detects a rotation speed of the first rotating body and compares the rotation speed of the first rotating body with the rotation speed of the second rotating body.
According to an exemplary embodiment of the present invention, a sheet feeder is provided wherein if the first rotating body slips on a sheet, a conveying force is imparted to the sheet from the second rotating body and where the first rotating body does not slip on a sheet, a conveying force is imparted to the sheet only by the first rotating body.
The above and other aspects of the present invention will become more apparent and more readily appreciated from the following description of exemplary embodiments of the present invention taken in conjunction with the attached drawings, in which:
Hereinafter, a description will be given of exemplary embodiments of the present invention with reference to the drawings. It is noted that the embodiments to be described below are only an example of embodiments of the present invention and, as a matter of course, these exemplary embodiments can be modified whenever necessary, within a scope not departing from the spirit of the present invention as defined in the following claims.
The multi function device 1 has a substantially rectangular shape which is greater in width and depth than height, with an upper part of the multi function device 1 being a scanner portion 3. The scanner portion 3 is constituted as a so-called flat bed scanner. As shown in
The lower part of the multi function device 1 is a printer portion 2. The printer portion 2 records images and text on recording sheets on the basis of print data including image data and/or text data input externally. An opening 10 is formed on the front face of the printer portion 2. An upper sheet feed tray 12, a lower sheet feed tray 13 and a sheet discharging tray 14 are vertically provided in a stage-like manner inside the opening 10. In this exemplary embodiment, the upper sheet feed tray 12, the lower sheet feed tray 13 and the sheet discharging tray 14 are respectively assembled into an integrated sheet feed cassette.
Recording sheets are stacked and accommodated in the upper sheet feed tray 12 and the lower sheet feed tray 13. The respective trays may accommodate recording sheets with different dimensions. For example, A4 size sheets may be accommodated in one of the trays and sheets smaller than A4 size such as B5 size or postcard size can be accommodated in the lower sheet feed tray 13. As an alternative example, recording sheets with small dimensions such as postcard size or photo L size can be accommodated in the upper sheet feed tray 12. The tray face of the lower sheet feed tray 13 may be extended by pulling out a slide tray 15, thereby making it possible to accommodate, for example, legal-size recording sheets. Recording sheets accommodated in the upper sheet feed tray 12 and the lower sheet feed tray 13 are fed inside the printer portion 2 to record desired images, and sheets are discharged to the sheet discharging tray 14. It is noted that the printer portion 2 and the scanner portion 3 are activated on the basis of operational instructions given from an operation panel 4 provided on an upper part of the front face of the multi function device 1 and/or instructions sent from a computer via a printer driver or a scanner driver.
Hereinafter, with reference to
The printer portion 2 comprises the sheet feeding device 6. The sheet feeding device 6 comprises the upper sheet feed tray 12, the lower sheet feed tray 13 and a sheet feeding mechanism 33. As seen best in
Returning to
As shown in
As shown in
The sheet conveying path 23 is formed by an outer guide face and an inner guide face opposing each other at an interval at portions other than those where the image recording unit 24 and others are disposed. The interval may be predetermined. For example, a curved portion 17 of the sheet conveying path 23 at the back of the multi function device 1 is constituted with an outer guide member 18 and an inner guide member 19 fixed to a frame of the multi-function device 1. When the recording sheet is conveyed to the curved portion 17, the recording sheet is bent in a curved form by the curved portion 17. Therefore, when the recording sheet passes over the curved portion 17, the recording sheet moves in contact with the guide face of the outer guide member 18, thereby receiving a conveyance friction (i.e., a frictional resistance force) from the guide face in a direction reverse to the conveying direction. There is a tendency that the conveyance friction is greater particularly in a case where the recording sheet to be conveyed is thick paper which is elastically strong or glossy paper the recording surface of which is processed with a coating processing.
As shown in
As shown in
Hereinafter, with reference to
The sheet feeding mechanism 33 comprises the first feed roller 25, the second feed roller 26, the first driving-force transfer mechanism 30, the second driving-force transfer mechanism 31, the first swing arm 27 and the second swing arm 28. The first driving-force transfer mechanism 30 further comprises a plurality of gears and the second driving-force transfer mechanism 31 also comprises a plurality of gears. The first feed roller 25 and the plurality of gears constituting the first driving-force transfer mechanism 30 are connected to the first swing arm 27, and the second feed roller 26 and the plurality of gears constituting the second driving-force transfer mechanism 31 are connected to the second swing arm 28.
A driving shaft 29 is provided above the upper sheet feed tray 12. The driving shaft 29 runs the width of the multi-function device 1. A main body frame of the multi function device 1 supports the driving shaft 29 so that the driving shaft 29 may rotate freely. As shown in
The first swing arm 27 is formed by two plate members 75. The plate members 75 are made of synthetic-resin. However, any material that provides adequate structural support may be used. The two plate members 75 are disposed facing each other at an interval, which may be predetermined, and are connected together at each end by a rib 76 between both ends of the respective long plate members 75. As shown in
The first feed roller 25 is connected to the other end of the first swing arm 27. Specifically, two first feed rollers 25 are connected respectively to each end of a first supporting shaft 78 connected to the other end (i.e., the leading end) of the first swing arm 27 so that the first swing arm 27 may move rotationally. For example, as shown in
As shown in
The first swing arm 27 is supported by the driving shaft 29 so as to move rotationally. Therefore, the first swing arm 27 is allowed to move rotationally downward by the weight of the first swing arm 27, the first feed roller 25 and the first driving-force transfer mechanism 30 as well as a spring force resulting from a spring and halted at a position at which the face of the first feed roller 25 is in contact with the recording sheets. As shown in
As shown in
The second feed roller 26 is provided at a second end (i.e., the leading end) of the second swing arm 28. Specifically, the second feed roller 26 is connected to a second supporting shaft 88 provided at the leading end of the second swing arm 28 so that the second swing arm 28 may move rotationally. In this exemplary embodiment, the second feed roller 26 is connected inside of the two plate members 85, as shown in
The second driving-force transfer mechanism 31 comprises a plurality of gears. The plurality of gears comprises a first transfer gear 87, first and second intermediate gears 90, 91 and a second transfer gear 89. The first transfer gear 87 of the second driving-force transfer mechanism 31 has a same diameter as the first transfer gear 77 of the first driving-force transfer mechanism 30. The first transfer gear 87 of the second driving-force transfer mechanism 31 has a same number of teeth as the first transfer gear 87 of the second driving-force transfer mechanism 31. The first transfer gear 87 is connected to the driving shaft 29 inside the two plate members 85. The first transfer gear 87 is firmly fixed to the driving shaft 29 and rotates in a same direction as a rotation of the driving shaft 29. The second transfer gear 89 is connected to the second supporting shaft 88 inside the two plate members 75. The second transfer gear 89 is firmly fixed to the second supporting shaft 88 and rotates in a same direction as the rotation of the second supporting shaft 88. The first and second intermediate gears 90, 91 are provided serially between the first transfer gear 87 and the second transfer gear 89. Thereby, a rotational driving force input into the driving shaft 29 is transferred to the second feed roller 26 via the first transfer gear 87, the first and second intermediate gears 90, 91 and the second transfer gear 89 of the second driving-force transfer mechanism 31.
The second driving-force transfer mechanism 31 also comprises a one-way clutch 92. As shown in
The second swing arm 28 is connected to the driving shaft 29 so that the second swing arm 28 may move rotationally. Therefore, the second swing arm 28 is allowed to move rotationally downward by the weight of the second swing arm 28, the second feed roller 26 and the second driving-force transfer mechanism 31 as well as a spring force resulting from a spring (not shown) and halts at a position at which the face of the second feed roller 26 is in contact with the recording sheets. The second swing arm 28 is shorter in the direction extended from the driving shaft 29 than the first swing arm 27. Therefore, as shown in
In this exemplary embodiment, the transfer gears of the respective first and second driving-force transfer mechanisms 30, 31 are appropriately designed in diameter and number of teeth, or the first feed roller 25 and the second feed roller 26 are appropriately designed in outer peripheral length, in order to produce a peripheral speed V1 of the first feed roller 25 that is greater than a peripheral speed V2 of the second feed roller 26. For example, where each of the transfer gears comprising the first and second driving-force transfer mechanisms 30 and 31 is the same in structure, an outer diameter of the first feed roller 25 is made greater than an outer diameter of the second feed roller 26, thus making it possible to set the peripheral speed V1 greater than peripheral speed V2. Alternatively, where the outer diameter of the first feed roller 25 is the same as the outer diameter of the second feed roller 26, the diameter and number of gears of the transfer gears of the first driving-force transfer mechanism 30 may be increased relative to the diameter and number of gears of the second driving-force transfer mechanism 31 in order to set the peripheral speed V1 greater than the peripheral speed V2.
Since the sheet feeding mechanism 33 is constituted as described above, a rotational driving force is transferred from the driving shaft 29 via the first driving-force transfer mechanism 30 to the first feed roller 25. Thereby, the first feed roller 25 is rotated at a peripheral speed V1. Further, a rotational driving force which rotates the second feed roller 26 at the peripheral speed V2 slower than the peripheral speed V1 is transferred to the second supporting shaft 88 via the second driving-force transfer mechanism 31. In this instance, a recording sheet is conveyed in the conveying direction indicated by the arrow 68 (refer to
Moreover, upon conveyance of a recording sheet which may be wide or thick, there is a case where a conveyance resistance (i.e., a conveyance friction) applied to the recording sheet at the curved portion 17 is greater than a conveying force of the first feed roller 25. In this instance, the conveying force of the first feed roller 25 is insufficient and the first feed roller 25 slips on the surface of the recording sheet. In this instance, a conveying speed of the recording sheet decreases from V1 to less than V2. Then, the second supporting shaft 88 of the second feed roller 26 is rotated in a direction which rotates the second feed roller 26 in the conveying direction indicated by the arrow 68 (refer to
Hereinafter, a description will be given for another exemplary embodiment of the present invention with reference to
As shown in
The ROM 102 accommodates programs and other information for controlling various motions of the multi function device 1. The RAM 103 is used as a storage area and a work area which temporarily stores various data used for execution of the programs by the CPU 101. Further, the EEPROM 104 accommodates various settings and flags to be retained after a power source is turned off.
The ASIC 106 generates a phase excitation signal for energizing a motor 71 according to a command from the CPU 101, and provides the signal to a driving circuit 110 of the motor 71, energizing a driving signal via the driving circuit 110 to the motor 71, thereby performing the rotation control of the motor 71.
The driving circuit 110 drives the motor 71 which is connected to the first feed roller 25 and the second feed roller 26. The drive circuit 110 generates an electric signal for rotating the motor 71 upon receipt of an output signal from the ASIC 106. The motor 71 rotates upon receipt of the electric signal, and a rotational driving force of the motor 71 is transferred to the first feed roller 25 and the second feed roller 26 via the driving shaft 29, the first driving-force transfer mechanism 30 and a driving-force transfer mechanism 121. The motor 71 is also connected to a conveying roller 60 and a discharge roller 62 (refer to
The ASIC 106 is coupled to a first rotary encoder 115 and a second rotary encoder 116. The first rotary encoder 115 detects a rotational quantity of the first feed roller 25 and the second rotary encoder 116 detects a rotational quantity of the second feed roller 26. The CPU 101 calculates a rotating speed V1, of the first feed roller 25 and a rotating speed V2, of the second feed roller 26 on the basis of the rotational quantity of each of the first and second rotary encoders 115, 116, respectively.
The ASIC 106 is coupled to the solenoid 113. The CPU 101 controls the ASIC 106 to output an output signal at a timing on the basis of control programs accommodated in the ROM 102, thereby activating the solenoid 113. The timing may be predetermined. The solenoid 113 is assembled into the driving-force transfer mechanism 121. The solenoid 113 connects or separates an intermediate gear 90 and a transfer gear 89 connected to the second feed roller 26 or detaches the intermediate gear 90 therefrom, and a solenoid shaft is connected via a known link mechanism either to the transfer gear 89 or the intermediate gear 90. When a signal is input into the solenoid 113, the solenoid 113 moves in a direction at which the transfer gear 89 is meshed with the intermediate gear 90. Thereby, a rotational driving force is transferred to the second feed roller 26. Further, in a state that no signal is output to the solenoid 113, the transfer gear 79 is disengaged from the intermediate gear 90. Therefore, in this state, no rotational driving force is transferred to the second feed roller 26.
Turning now to
In operation S1, a rotating speed V1 of the first feed roller 25 and a rotating speed V2 of the second feed roller 26 are detected. These rotating speeds V1 and V2 are detected on the basis of rotational quantities of the rotary encoders 115 and 116.
In operation S2, it is determined whether the rotating speed V1 is greater than the rotating speed V2. Where the first feed roller 25 does not slip, the second feed roller 26 is also rotated together with the recording sheet at a speed V1 which is the same as the speed of the first feed roller 25. Therefore, the rotating speed V1 will not exceed the rotating speed V2. On the contrary, where the first feed roller 25 slips, recording sheet is conveyed at a speed slower than the rotating speed V1. Alternatively, the recording sheet is not conveyed but stopped, by which the second feed roller 26 is decreased in rotating speed or the recording sheet is stopped. On the other hand, the first feed roller 25 is rotated at the rotating speed V1 in the midst of slippage. Therefore, in this instance, the rotating speed V1 is greater than the rotating speed V2. In other words, in operation S2, the rotating speed V1 is compared with the rotating speed V2, thereby making it possible to determine whether the first feed roller 25 slips.
In operation S2, if it is determined that the rotating speed V1 is greater than the rotating speed V2, the CPU 101 of the controller 100 turns the solenoid 113 on (operation S3). Thereby, the transfer gear 89 is meshed with the intermediate gear 90, and a rotational driving force of the motor 71 is transferred to the second feed roller 26 via the second driving-force transfer mechanism 121. As described above, even if the first feed roller 25 slips, a rotational driving force is instantly transferred to the second feed roller 26, thereby the recording sheet is always conveyed smoothly and stably. It is noted that where the rotating speed V1 is judged to be less than or equal to the rotating speed V2 in operation S2, the solenoid 113 is kept off, and the recording sheet is continuously conveyed only by the first feed roller 25 (operation S4).
In operation S5, it is determined whether the leading end of the recording sheet has arrived at a threshold position. The threshold position may be predetermined. This determination is made based on detection results of sheet sensors including an optical sensor installed in the sheet conveying path 23. In this instance, the threshold position is, for example, such a position that the recording sheet can be conveyed from the first feed roller 25 by a conveying roller 60 installed downstream in the conveying direction. When the leading end of the recording sheet has arrived at this threshold position, the recording sheet is conveyed by the conveying roller 60, and no switching of the transfer of a driving force by the solenoid 113 is performed. Therefore, if it is determined that the leading end of the recording sheet has arrived at the threshold position in operation S5, the process is complete and processing ends. If it is determined that the leading end of the recording sheet has not arrived at the threshold position (“No” in operation S5), processing returns to operation S2.
It is noted that in this exemplary embodiment, the rotating speed V1 is compared with the rotating speed V2, and it is determined whether the first feed roller 25 slips. However, whether the first feed roller 25 is slipping may also be determined based on whether the rotating speed V2, which is calculated on the basis of a detection signal of the rotary encoder 116, is lower than a threshold
(1) The embodiment is a sheet feeder for conveying sheets in the conveying direction. The sheet feeder is provided with a sheet tray, a first rotating body, a second rotating body and a conveying-force transfer means. The first rotating body and the second rotating body both impart a conveying force to sheets retained on the sheet tray. The conveying-force transfer means imparts a conveying force from the second rotating body to a sheet where the first rotating body slips on the sheet but does not impart a conveying force from the second rotating body to the sheet where the first rotating body does not slip on the sheet.
(2) The conveying-force transfer means is provided with a one-way clutch which transfers a rotational driving force in the conveying direction to the second rotating body and does not transfer a rotational driving force in a direction reverse to the conveying direction to the second rotating body but slips on a sheet.
Thereby, it is possible to mechanically constitute a mechanism which imparts a conveying force from the second rotating body to a sheet upon slippage of the first rotating body.
(3) A peripheral speed on driving the first rotating body is set to be greater than a peripheral speed on driving the second rotating body.
Thereby, where the first rotating body does not slip on a sheet, no rotational driving force is transferred to the second rotating body by the one-way clutch. Therefore, no deflection or pulling of the sheet between the first rotating body and the second rotating body is caused.
(4) The sheet feeder of the present invention is provided with a first arm member for supporting the first rotating body so as to rotate and additionally provided with a second arm member for supporting the second rotating body so as to rotate.
Thereby, it is possible to realize favorably the support of the first rotating body and the second rotating body.
(5) In the sheet feeder, a conveying force imparted from the second rotating body to a sheet is greater than a conveying force imparted from the first rotating body to a sheet.
Thereby, the sheet feeder is able to convey even a sheet, which cannot be conveyed by the first rotating body alone, by the second rotating body alone without a conveying force of the first rotating body. For example, where the first rotating body slips completely on a sheet, the second rotating body is able to convey the sheet reliably.
(6) A second angle of the second arm member in an extended direction with respect to the surface of a sheet retained on the sheet tray is greater than a first angle of the first arm member in an extended direction with respect to the surface of a sheet retained on the sheet tray.
Thereby, it is possible to concretely realize a mechanism in which a conveying force imparted to a sheet from the second rotating body is set to be greater than a conveying force imparted to a sheet from the first rotating body.
(7) It is preferable in realizing the present invention that the second rotating body is disposed apart upstream of the first rotating body in the conveying direction.
(8) The sheet feeder is additionally provided with a curved sheet conveying path through which sheets conveyed from the sheet tray are allowed to pass.
Where a sheet is conveyed by a device provided with the above-described sheet conveying path, a relatively great conveyance resistance is applied to the sheet. Therefore, the present invention is favorably applicable to such a sheet feeder.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-350680 | Dec 2006 | JP | national |
