Switchback device and image forming apparatus including it

To suppress generation of scratches and dirt on a printed face and to intend to reduce in size, a switchback device (1) provided in a conveyance path (12) for a printed medium (3), for reversing the direction of movement of the medium (3) sent from an upstream part (4) of the conveyance path (12) and then delivering the medium (3) to a downstream part (5) of the conveyance path (12), comprises a pair of operation rollers (15) including a drive roller (13) for conveying the medium (3) and a slave roller (14) cooperating with the drive roller (13) to pinch the medium (3); and a changeover mechanism (16) for changing a direction of the pair of operation rollers (15) including the drive roller (13) and the slave roller (14). The medium (3) sent from the upstream part (4) of the conveyance path (12) which is pinched by the pair of operation rollers (15) is, in this state, changed in direction as a result of a change of the direction of the pair of operation rollers (15) by the changeover mechanism (16), and then is delivered to the downstream part (5) of the conveyance path (12) by reversing rotation of the drive roller (13). Thus, generation of scratches and dirt on the printed face (3a) of the medium (3) can be suppressed and the space for taking the medium (3) in upon switchback can be reduced in size.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a switchback device, provided in a conveyance path for a printed medium, for reversing the direction of movement of the medium and then delivering the medium from an upstream part to a downstream part of the conveyance path.

2. Description of the Related Art

In an inkjet printer, a photo printing/developing machine, or the like, a printed medium such as a printed paper is discharged from the machine preferably in a state wherein the printed face of the medium faces upward, in order that the user can easily check the printed condition. For this purpose, some such machines are provided with switchback devices in their media conveyance paths.

JP-A-2001-142190 discloses a photo printing/developing machine including a switchback device. As shown inFIGS. 7 and 8, the switchback device102is provided between an upstream part100of a conveyance path and a downstream part101of the conveyance path. The switchback device102includes a pair of operation rollers105including a drive roller103and a slave roller104; plate-like fixed guides107for guiding a medium108along both faces of the medium108from a pair of rollers106in the upstream part100of the conveyance path to the pair of operation rollers105; and a rotatable switchback guide109for changing the direction of the medium108being pinched by the pair of operation rollers105, and then guiding the medium108to the downstream part101of the conveyance path. The switchback guide109does not rotate relative to the medium108.

FIG. 7is a side view showing a state wherein the medium108is being taken in the switchback device102. The medium108being conveyed from the pair of rollers106in the upstream part100of the conveyance path is guided to the pair of operation rollers105by the fixed guides107. The medium108comes into contact with the switchback guide109and the direction of the movement of the medium108is changed downward at a nearly right angle by the switchback guide109. The medium108is then pinched by the pair of operation rollers105. In this process, the leading edge and the printed face108aof the medium108come into contact with the switchback guide109and they are rubbed by the switchback guide109.

FIG. 8is a side view showing a state wherein the medium108has been completely taken in the switchback device102. When the rear end portion of the medium108is pinched by the pair of operation rollers105, the switchback guide109rotates by its own weight in the direction indicated by an arrow inFIG. 8. The pair of operation rollers105is then reversed in rotation. Because the switchback guide109has rotated, the medium108is guided by the switchback guide109to a pair of rollers110in the downstream part101of the conveyance path, as shown by an alternate long and two short dashes line inFIG. 8. Thus, the medium108is, after switchback, guided to the downstream part101of the conveyance path.

JP-A-2001-142190 further discloses another switchback device in which the slave roller104is disposed at a position somewhat lower than the drive roller103and the switched guide109is fixed.

In JP-A-2001-142190, the printed face108aof the medium108comes into contact with the switchback guide109, which does not rotate relative to the medium108. In this state, the medium108is forcibly bent and guided by the switchback guide109. This may cause scratches and dirt on the printed face108a. In addition, because one fixed guide107is provided between the pair of rollers106in the upstream part100of the conveyance path and the pair of operation rollers105so as to face the printed face108aof the medium108, the fixed guide107may cause scratches and dirt on the printed face108aif the medium108is curved.

Further, the drive roller103can not be reversed until the rear end portion of the medium108is pinched by the pair of operation rollers105. Thus, a large space is required so that the whole medium108can be taken in for switchback. This makes it difficult to reduce the size of the device.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a switchback device that can suppress generation of scratches and dirt on the printed face of a medium and can realize a reduction in size of the device.

According to an aspect of the present invention, a switchback device provided in a conveyance path for a printed medium, for reversing the direction of movement of the medium sent from an upstream part of the conveyance path and then delivering the medium to a downstream part of the conveyance path, comprises a pair of rollers including a drive roller that conveys the medium and a slave roller that cooperates with the drive roller to pinch the medium; and a changeover mechanism that changes a direction of the pair of rollers including the drive roller and the slave roller. The medium sent from the upstream part of the conveyance path which is pinched by the pair of rollers is, in this state, changed in direction as a result of a change of the direction of the pair of rollers by the changeover mechanism, and then is delivered to the downstream part of the conveyance path by reversing rotation of the drive roller.

According to this aspect, switchback of the medium can be realized without using a switchback guide that does not rotate relative to the medium, as in the prior art. Therefore, generation of scratches and dirt on the printed face of the medium can be suppressed. Further, because a change of direction of the medium can be performed even in a state wherein the entire medium has not been taken in by the pair of rollers, the space for taking the medium in upon switchback can be reduced in size.

According to another aspect of the present invention, the drive roller is fixed in a predetermined position, the slave roller revolves around the drive roller, and the changeover mechanism revolves the slave roller to change the direction of the pair of rollers. According to this aspect, the direction of the pair of rollers can be changed by moving only the slave roller.

According to still another aspect of the present invention, the switchback device preferably further comprises a guide member that is disposed in the vicinity of the pair of rollers and guides the medium, the guide member being able to change the direction in which the medium is guided, in accordance with the change of direction of the pair of rollers. According to this aspect, because the medium is always guided by the guide member in the vicinity of the pair of rollers, the medium can surely be conveyed.

According to still another aspect of the present invention, it is preferable that the guide member does not rotate relative to the medium and is provided only on the back side of the medium. According to this aspect, because no guide member that does not rotate relatively to the medium is provided on the printed face side of the medium, the printed face of the medium is prevented from coming into contact with such a guide member and thereby generation of scratches and dirt on the printed face can be suppressed.

According to still another aspect of the present invention, the guide member is preferably a freely rotatable guide roller. According to this aspect, because the guide member rotates while it is in contact with the printed face, the medium can be guided by the guide member with suppressing generation of scratches and dirt on the printed face.

According to still another aspect of the present invention, the switchback device preferably further comprises a contact member that is provided on the back side of the medium sent from the upstream part of the conveyance path and being pinched by the drive roller and the slave roller, the contact member coming into contact with a back face of the medium when the changeover mechanism changes the direction of the pair of rollers.

According to this aspect, when the changeover mechanism changes the direction of the pair of rollers including the drive roller and the slave roller, the back face of the medium that has passed between the drive roller and the slave roller and is being pinched by them comes into contact with the contact member. At this time, the medium is curved by either of the drive roller and the slave roller which is in contact with the record face of the medium. When the medium is conveyed in that state toward the downstream part of the conveyance path and passes between the drive roller and the slave roller, the medium is curved in reverse to curl. Thus, curl of the medium is relieved.

According to still another aspect of the present invention, the contact member is preferably a freely rotatable roller. According to this aspect, because the contact member rotates while it is in contact with the back face of the medium, generation of scratches and dirt on the back face of the medium can be suppressed.

According to still another aspect of the present invention, it is preferable that, after the changeover mechanism changes the direction of the pair of rollers, the medium having passed between the drive roller and the slave roller is pinched by the contact member and either of the drive roller and the slave roller which is located on the record face side of the medium relative to the common tangent of the drive roller and the slave roller.

According to this aspect, the medium having passed between the drive roller and the slave roller is conveyed toward the downstream part of the conveyance path while the medium is pressed onto the roller locating on the record face side of the medium relative to the common tangent of the drive roller and the slave roller. Therefore, because the medium having passed between the drive roller and the slave roller is surely conveyed in a state wherein the medium is curved in reverse to curl. Thus, the curl of the medium conveyed to the downstream part of the conveyance path is relieved at a high probability.

According to still another aspect of the present invention, the switchback device preferably further comprises a pressing member that, after the changeover mechanism changes the direction of the pair of rollers, presses the medium onto the contact member while being in contact with a record face of the medium having passed between the drive roller and the slave roller. According to this aspect, because the pressing member presses the medium onto the contact member, a case can be prevented wherein an edge of the curved medium rebounds and collides with another member and as a result, the medium is bent or scratched and dirt is generated on the record face of the medium.

According to still another aspect of the present invention, an image forming apparatus comprises the switchback device according to any of the above-described aspects. According to this aspect, because generation of scratches and dirt on the printed face of the medium in the switchback device is suppressed, the finish print quality is improved. In addition, a reduction in size of the image forming apparatus can be intended.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2is a side view of a medium conveyance path12of an inkjet printer2including a switchback device1of the present invention. As shown inFIG. 2, the switchback device1is provided in the conveyance path12for a printed medium3. The conveyance path12includes an upstream part4, as a part of the conveyance path12upstream of a pair of upstream rollers9as will be described later, and a downstream part5, as a part of the conveyance path12downstream of a pair of downstream rollers10as will be described later. The switchback device1reverses the direction of movement of the medium3sent from the upstream part4of the conveyance path12, and then delivers the medium3to the downstream part5of the conveyance path12. The conveyance path12of the inkjet printer2includes therein a paper roll6on which a continuum of media3for printing is rolled so that the faces of the media3to be printed face outward; a printing head7for printing on each medium3; a cutter8for cutting the continuum of media3into each medium3; a pair of upstream rollers9for sending each medium3into the switchback device1; the switchback device1; a pair of downstream rollers10for sending the medium3out of the switchback device1; and a tray11for stocking discharged media3. Media3forms a continuum upstream of the cutter8.

FIG. 1is a side view of the switchback device1of the present invention before operation. The switchback device1comprises: a pair of operation rollers15including a drive roller13for conveying a medium3and a slave roller14cooperating with the drive roller13to pinch the medium3; a changeover mechanism16for changing the direction of the pair of operation rollers15including the drive roller13and the slave roller14; and a receiving roller27used for relieving curl of the medium3. In the switchback device1, the medium3sent from the upstream part4of the conveyance path12is pinched by the drive roller13and the slave roller14. In this state, the direction of the pair of operation rollers15including the drive roller13and the slave roller14is changed by the changeover mechanism16, and then the drive roller13is reversed in rotation, to send the medium3to the downstream part5of the conveyance path12.

The changeover mechanism16includes a supporting frame17for rotatably supporting the drive roller13and the slave roller14; a slave member19fixed to the supporting frame17and having a cam groove18; a cam21having a cam follower20being engaged with the cam groove18; and a notshown rotation mechanism for rotating the cam21by an electric motor. The drive roller13is fixed at a predetermined position relative to the inkjet printer2. Thus, the supporting frame17rotates around the drive roller13. The slave roller14revolves around the drive roller13. Attendant upon the revolution of the slave roller14, the direction of the pair of operation rollers15is changed.

FIG. 3is a plan view showing a relation between the cam21and the slave member19. The slave member19is C-shaped in cross section and the cam groove18is formed inside the slave member19. The cam21is rotatably supported by a shaft22. When the cam21is rotated by an operation of the rotation mechanism, the cam follower20is guided in the cam groove18to rotate the supporting frame17, as shown inFIGS. 1,4, and5.

The changeover mechanism16is provided with a guide member23for guiding the medium3between the pair of operation rollers15and the upstream part4of the conveyance path12and between the pair of operation rollers15and the downstream part5of the conveyance path12. The guide member23can change the direction in which the medium3is guided, in accordance with the change of direction of the pair of operation rollers15. The guide member23includes a guide plate24provided only on the back side of the medium3; and a freely rotatable guide roller25provided on the printed face3a side of the medium3. The guide plate24does not rotate relative to the medium3. A sensor26for detecting the medium3is provided between the pair of operation rollers15and the upstream part4of the conveyance path12.

A receiving roller27is provided in the rear of the drive roller13. The receiving roller27is rotatable around a shaft fixed to the body of the printer2. Before the changeover mechanism16changes the direction of the pair of operation rollers15, that is, before switchback, the receiving roller27is on the back side of the medium3relative to the common tangent L1of the drive roller13and the slave roller14, shown by an alternate long and short dash line inFIG. 1, that is, on the same side as the drive roller13. Contrastingly, after the changeover mechanism16changes the direction of the pair of operation rollers15, that is, after switchback, the receiving roller27is on the printed face side of the medium3relative to the common tangent L2of the drive roller13and the slave roller14, shown by an alternate long and short dash line inFIG. 5, that is, on the same side as the slave roller14. In any case, the receiving roller27is disposed so as to be able to come into contact with the back face of the medium3that has passed the pair of operation rollers15.

The changeover mechanism16is further provided with a pressing member28for pressing the medium3during a switchback operation. The pressing member28includes a frame29rotatably attached to the supporting frame17; and a pressing roller30rotatably supported in the frame29. The pressing member28presses, by its own weight, the medium3being pinched by the drive roller13and the slave roller14, onto the receiving roller27.

An operation of the above-described switchback device1will be described below.

A continuum of media3is drawn out from the paper roll6and printing is performed by the printing head7. A printed medium3is cut off from the continuum of media3by the cutter8. The cut-off medium3is sent by the pair of upstream rollers9into the switchback device1, as shown by a solid line inFIG. 1. The medium3is guided by the guide plate24and the guide roller25. At this time, the printed face3aof the medium3is in contact only with the guide roller25, which can rotate attendant upon the movement of the medium3. Thus, generation of scratches and dirt on the printed face3acan be suppressed.

Afterward, the medium3is pinched by the pair of operation rollers15including the drive roller13and the slave roller14. In this state, the drive roller13is driven to take the medium3within the switchback device1, as shown by an alternate long and two short dashes line inFIG. 1. When the sensor26detects the tail edge3bof the medium3, the drive roller13is stopped. Thus, a change of direction of the medium3can be performed even in a state wherein the entire medium3has not been taken in by the pair of operation rollers15. This makes it possible to reduce the size of the space for taking the medium3in upon switchback, and thus a reduction in size of the switchback device1can be realized. Afterward, the rotation mechanism for the cam21is operated to rotate the cam21. Thereby, the supporting frame17is rotated.

FIG. 4is a side view showing a state wherein the supporting frame17has somewhat rotated. Attendant upon the rotation of the supporting frame17, the slave roller14revolves around the drive roller13to change the direction of the pair of operation rollers15. Attendant upon this, the direction of the medium3being pinched by the pair of operation rollers15is also changed. Further, the pressing member28moves down attendant upon the rotation of the supporting frame17so that the pressing roller30presses the medium3onto the receiving roller27. This can prevent a case wherein the leading edge of the curved medium3rebounds and collides with another member and as a result, the medium3is bent or scratched and dirt is generated on the printed face3a.

FIG. 5is a side view showing a state wherein the supporting frame17has completely rotated. The tail edge3bof the medium3faces the pair of downstream rollers10. At this time, the slave roller14is pressed onto the receiving roller27to pinch the medium3. Thus, the medium3having passed the pair of operation rollers15is wrapped on the slave roller14and pinched by the slave roller14and the receiving roller27.

Afterward, the drive roller13is reversed in rotation so that medium3is conveyed in a state wherein its tail edge3bhas turned into the leading edge. At this time, the medium3is curved in reverse to curl. In this state, the medium3is conveyed with its printed face being pressed onto the slave roller14. Thus, the medium3is decurled. Afterward, as shown by an alternate long and two short dashes line inFIG. 5, the medium3is sent to the pair of downstream rollers10in the downstream part5of the conveyance path12. Thus, a switchback operation is completed. After the completion of the switchback operation, the rotation mechanism for the cam21operates in reverse to return the supporting frame17to its original position. The medium3is then discharged and stocked on the tray11. Because the medium3was decurled in the switchback device1, curl of the discharged medium3has been relieved.

Although a preferred embodiment of the present invention has been described, the present invention is not limited to the embodiment and various modifications, changes, and alternations can be made within the scope of the invention. For example, although the guide member23is constituted by the guide plate24and the guide roller25in the above-described embodiment, the present invention is not limited to that. The guide member23may be constituted by one of the guide plate24and the guide roller25. For example, both faces of the medium3may be guided by guide rollers or guide plates. Further, no guide member may be used.

In the above-described embodiment, the drive roller13is fixed in a predetermined position and the slave roller14revolves around the drive roller13. However, the present invention is not limited to that. In a modification, the slave roller14may be fixed at a predetermined position and the drive roller13may revolve around the slave roller14. In another modification, both of the drive roller13and the slave roller14may be movable.

In the above-described embodiment, the changeover mechanism16is rotated by a cam mechanism. However, the present invention is not limited to that. For this purpose, another known rotation mechanism can be used, for example, the changeover mechanism16may be rotated by directly using the rotational force of an electric motor.

In the above-described embodiment, the receiving roller27is provided as a contact member for relieving curl of the medium3when the medium3having passed the pair of operation rollers15is being sent to the downstream part5of the conveyance path12. In a modification, however, no such contact member may be used. Further, the contact member is not limited to the form of a roller. It may be a member in another form. For example, as shown inFIG. 6, the contact member may be in the form of a nearly U-shaped fixed receiving guide57. Even in case that the contact member is in the form of a fixed receiving guide, the shape of the guide may be arbitrarily changed.

In the above-described embodiment, after the changeover mechanism16changes the direction of the pair of operation rollers15, the medium3having passed the pair of operation rollers15is pinched by the slave roller14and the receiving roller27. In a modification, however, the medium3may not be pinched by the slave roller14and the receiving roller27. For example, the receiving roller27may be disposed at a distance from the slave roller14after the direction of the pair of operation rollers15is changed, as long as the back face of the medium3having passed the pair of operation rollers15can come into contact with the receiving roller27. Even in case that the receiving roller27is at a distance from the slave roller14, the distance between them is preferably as small as possible.

In the above-described embodiment, the pressing member28presses the medium3, which has passed the pair of operation rollers15, onto the receiving roller27. In a modification, however, no such pressing member is used.

In the above-described embodiment, the switchback device1is used in the inkjet printer2. However, the present invention is not limited to that. A switchback device of the present invention may be used in an image forming apparatus of another type, for example, a photo printing/developing machine.