BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of this invention will become apparent in the following detailed description of a preferred embodiment of this invention, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic view of a conventional duplex document feeder disclosed in U.S. Pat. No. 5,784,680;
FIG. 2 is a schematic view of the preferred embodiment of a duplex document feeder according to this invention when a switching unit is disposed in a first position;
FIG. 3 is a sectional view taken along Line 3-3 in FIG. 2;
FIG. 4 is a schematic view of the preferred embodiment when the switching unit is disposed in a second position;
FIG. 5 is a schematic view of the preferred embodiment when the switching unit is disposed in a third position; and
FIG. 6 is a schematic view of the preferred embodiment, illustrating how a document is ejected.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 2, the preferred embodiment of a duplex document feeder according to this invention is mounted on an image forming apparatus 200 (such as a copier or scanner) for automatic feeding and two-sided scanning of documents 300 each having a first surface 310 and a second surface 320. The image forming apparatus 200 includes a scanning unit 210. The duplex document feeder includes a housing unit 10, a feeding roller unit 20 disposed in the housing unit 10, a conveying roller unit 30, an ejecting roller unit 40, a switchback roller unit 50, a switching unit 60, and a sensing unit 70.
The housing unit 10 has a generally C-shaped document-conveying path 11, an inverting path 12 in spatial communication with an intermediate portion of the document-conveying path 11, a switchback path 13 external to an assembly of the document-conveying path 11 and the inverting path 12, an ejecting tray 14 external to the document-conveying path 11, a switchback space 15 disposed directly above the ejecting tray 14, and a document-setting tray 16 disposed directly above the switchback space 15 and aligned with the document-conveying path 11. The document-conveying path 11 has a document-feeding end 111 and a document-discharging end 112 disposed below the document-feeding end 111. The inverting path 12 has an inlet end 121 aligned with the document-discharging end 112, and an outlet end 122 in spatial communication with the document-conveying path 11. The switchback path 13 is in spatial communication with the document-discharging end 112 and the inlet end 121. The housing unit 10 further has a triangular guiding member 17 disposed between and in proximity to the inlet end 121 and the document-discharging end 112. The guiding member 17 extends into the switchback path 13, and has a plurality of spaced-apart guiding paws 171 interconnected fixedly, a top surface 172 disposed in proximity to the inlet end 121, and a bottom surface 173 disposed in proximity to the document-discharging end 112. The scanning unit 210 is disposed between the outlet end 122 and the document-discharging end 112, and is disposed in a bottom end of the housing unit 10.
The feeding roller unit 20 is disposed at the document-feeding end 111.
The conveying roller unit 30 is disposed between the outlet end 122 and the scanning unit 210.
The ejecting roller unit 40 is disposed in the switchback path 13, and includes a first driving roller 41 and two first follower rollers 42 located respectively to two opposite sides of the first driving roller 41. When the first driving roller 41 is rotated in a direction, the first follower rollers 42 rotate in an opposite direction.
The switchback roller unit 50 is disposed in the switchback path 13 and in proximity to the switching unit 60, and includes a second driving roller 51 and a pair of upper and lower follower rollers 52, 53 disposed respectively above and under the second driving roller 51. When the second driving roller 51 is rotated in a direction, the upper and lower follower rollers 52 rotate in an opposite direction.
The switching unit 60 is disposed in the switchback path 13, and includes a first switching gate 61 coaxial with the upper follower roller 52, a second switching gate 62 connected fixedly to and disposed under the first switching gate 61 and coaxial with the lower follower roller 53, and a guiding path 63 disposed between the first and second switching gates 61, 62. The first switching gate 61 has a first pivot portion 611 and a plurality of first paw plates 612 connected integrally to the first pivot portion 611. The first paw plates 612 and the guiding paws 171 are alternatively arranged, as shown in FIG. 3. Each of the first paw plates 612 has a first guiding surface 613 at a top portion thereof. The second switching gate 62 has a second pivot portion 621 and a second paw plate 622 having an area corresponding to the total area of the first paw plates 612. The second paw plate 622 has a lower guiding surface or bottom surface 623 distal from the guiding path 63, and a second guiding surface 624 disposed between the guiding path 63 and the lower guiding surface 623. The guiding path 63 is aligned with a nip defined between the second driving roller 51 and the lower follower roller 53. The switching unit 60 is pivotable in the switchback path 13 among a first position shown in FIG. 2, a second position shown in FIG. 4, and a third position shown in FIG. 5.
The sensing unit 70 is disposed in the document-conveying path 11 between the conveying roller unit 30 and the scanning unit 210.
The operation of the preferred embodiment will now be described.
With reference to FIG. 2, when it is desired to perform a two-sided scanning operation, the documents are placed on the document-setting tray 16 such that the first surfaces 310 face upwardly, and the second surfaces 320 face downwardly. The feeding roller unit 20 is driven by a power source (not shown) to move the uppermost document 300 into the document-conveying path 11. In the document-conveying path 11, the uppermost document 300 is moved toward the scanning unit 210 by the conveying roller unit 30. When the sensing unit 70 detects the presence of the uppermost document 300 (i.e., alignment of a leading end of the uppermost document 300 therewith at this time), the controller activates the scanning unit 210, and pivots the switching unit 60 to the first position. In the first position, a free end of the first switching gate 61 is disposed under the document-discharging end 112 such that the first guiding surfaces 613 of the first switching gate 61 are in spatial communication with both the document-discharging end 112 and the inlet end 121. At this time, under the control of the controller, the first driving roller 41 rotates counterclockwise, and the second driving roller 51 rotates clockwise. Hence, after the first surface 310 of the uppermost document 300 is scanned, it is moved from the document-discharging end 112 into the switchback path 13. Thereafter, the uppermost document 300 is passed partially through a nip defined between the second driving roller 51 and the upper follower roller 52 such that the first surface 310 faces downwardly, and the second surface 320 faces upwardly.
With further reference to FIG. 4, when the sensing unit 70 detects the absence of the uppermost document 300 for a predetermined time following the above detection of the presence of the uppermost document 300, which indicates that a trailing end of the uppermost document 300 has passed through the guiding member 17 for a predetermined time period, under the control of the controller, the rotational direction of the second driving roller 51 is reversed (i.e., rotated counterclockwise), and the switching unit 60 is pivoted to the second position. In the second position, the free end of the first switching gate 61 is disposed in proximity to the inlet end 121 such that the inlet end 121 is in spatial communication with the first guiding surfaces 613 of the first switching gate 61. Also in the second position, the second guiding surface 624 is spaced apart from, and adjacent and parallel to the bottom surface 173 of the guiding member 17 so as to define therebetween a document path in spatial communication with the document-discharging end 112 and the guiding path 63. In other words, the document-discharging end 112 and the guiding path 63 are in spatial communication with each other via the second guiding surface 624. As such, the uppermost document 300 is moved from the switchback path 13 into the documents-conveying path 11 via the inverting path 12.
Thereafter, the uppermost document 300 is passed again through the scanning unit 210 so as to scan the second surface 320, and is moved by the ejecting roller unit 40 and the switchback roller unit 50 into the switchback space 15 via the guiding path 63 such that the uppermost document 300 is passed partially through the nip defined between the second driving roller 51 and the upper follower roller 52. At this time, the second surface 320 faces downwardly, and the first surface 310 faces upwardly.
With additional reference to FIG. 5, when the sensing unit 70 detects that absence of the uppermost document 300 for a predetermined time following a detection thereof during the above second pass, which indicates that the trailing end of the uppermost document 300 has passed through the guiding member 17 for the predetermined time period, under control of the controller, the switching unit 60 is pivoted to the third position, and the rotational direction of the second driving roller 51 is reversed again (i.e., rotated clockwise). In the third position, the guiding path 63 is aligned with the inlet end 121 such that the inlet end 121 is in spatial communication with the guiding path 63 via the top surface 172 of the guiding member 17, and the second guiding surface 624 of the second switching gate 62 abuts against the bottom surface 173 of the guiding member 17 such that the document-discharging end 112 is in spatial communication with the ejecting tray 14 via the lower guiding surface 623 of the second switching gate 62. As such, the uppermost document 300 is moved again into the inverting path 12 via the guiding path 63.
With additional reference to FIG. 6, the uppermost document 300 is subsequently moved from the inverting path 12 into the document-conveying path 11, and drops from the document-discharging end 112 onto the ejecting tray 14 such that the first surface 310 faces downwardly, and the second surface 320 faces upwardly. As such, when all of the documents 300 are ejected, they are arranged orderly.
In view of the above, the duplex document feeder of this invention has the following advantages:
- (1) Since the switching unit 60 is pivotable among the first, second, and third positions, the documents 300 can be arranged orderly when ejected. Furthermore, the switching unit 60 has a simple structure, and is able to be assembled with ease, thereby reducing the manufacturing costs of the duplex document feeder.
- (2) The documents 300 can be moved smoothly along the document-conveying path 11, the inverting path 12, the switchback path 13, and the guiding path 63. Thus, the documents 300 do not experience paper jam and curling problems when ejected.
- (3) With particular reference to FIGS. 5 and 6, after completion of scanning of the second surface 320 of the document 300, the leading end of the document 300 is ejected along the lower guiding surface 623 of the second switching gate 62. Thus, even if the trailing end of the document 300 remains in the guiding path 63 at the time the leading end of the document 300 is ejected, a paper jam resulting from overlapping of the leading and trailing ends of the document 300 can be prevented. Furthermore, since the duplex document feeder of this invention does not have the annular document path occurring in the duplex document feeder disclosed in U.S. Pat. No. 5,784,680, each of the document-conveying path 11 and the inverting path 12 is allowed to be short. Thus, the whole length and volume of the duplex document feeder can be reduced.
With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.
Patent Application
20080085141
