Patent Application
20120187624
1. Field of the Invention
Embodiments of the present invention relate to a recording device which forms an image on a sheet. Specifically, the embodiments of the present invention relate to a conveyance device having a suction conveyance unit that suctions and conveys various sizes of sheets of materials, which are recording media, using airflows.
2. Description of the Related Art
In a conveyance device used for an image forming device, such as a conventional inkjet printer, when an image is formed, it may be necessary to maintain a constant spacing between a recording unit and a recording medium. Thus, it is not possible to convey the recording medium while holding the recording medium. Therefore, when the recording medium is conveyed, it may be necessary that a deformation or a lifting of the recording medium is regulated. Further, during an image forming process, when a deformation of the recording medium itself occurs, for example, when stretching of the recording medium associated with adhesion of ink (hereinafter, referred to as stretching) or deformation of the recording medium associated with application of heat occurs, it may be necessary to provide a groove portion so that the deformation of the recording medium is released to the opposite side of the recording unit. As described above, the following conveyance device is known. Namely, as shown in
In the above described conveyance device, when the recording medium is conveyed to a position where the recording medium covers all the suction ports 22 of orifices 14, which are arranged on the conveyance surface, since inside of each orifice 14 is sealed, a negative pressure increases and the suction force increases. In this manner, a deformation of the recording medium which exists prior to forming an image or a deformation of a recording medium caused by adhered ink when forming the image is suppressed, and the recording medium can be stably conveyed. Further, since the orifice 14 has a constant length, when a deformation, such as the stretching, occurs on the recording medium, an amount of the deformation can be released to the reverse side of the recording unit by the suction force.
However, at a position shown in
Patent Document 1 discloses a technique such that, when a sheet covers suction ports, an output of a pump is reduced so as to prevent a suction force from becoming rapidly large. However, in this configuration, the air is always suctioned through suction ports other than the suction ports conveying the sheet. In such a case, it may be necessary to adjust the suction force of the pump, so that the sheet is surely conveyed, even if the sheet does not cover all the suction ports. Thus a large pump tends to be used. Therefore, the configuration disclosed in Patent Document 1 has problems that the device becomes large, and noise and cost increase.
Patent Document 2 discloses a technique for avoiding unnecessary suctioning. In the technique, for the suction ports other than the suction ports conveying the sheet, a driving means for opening and closing a valve system and a sensor are used, so as to selectively avoid unnecessary suctioning. With this configuration, the size of the pump can be reduced. However, for example, when a surface for suctioning the sheet is large, in order to selectively avoid unnecessary suctioning at finer areas so as to prevent tips of the sheet from lifting, it may be necessary to place plural driving units for opening and closing the valve system. This leads to complication of the device and growth in size of the device. Further it can be a cause of a cost increase.
Patent Document 3 discloses a technique using a pressure adjustment valve. Namely, when a sheet covers a suction port, the pressure adjustment valve causes a suction force to be generated, and when the sheet does not cover the suction port, the pressure adjustment valve does not allow unnecessary suctioning to be performed. However, in this technique, a suction force is not obtained until the sheet completely covers an orifice (a suction port). Thus, the suction force at the tip of the sheet is always weaker than the suction force at the center of the sheet. Therefore, there is a problem that the technique does not handle the lifting of the tips of the sheet. Further, in this technique, the pressure adjustment valve is closed by fluid flow (wind). However, when the pressure adjustment valve is closed, the fluid does not flow, and the pressure adjustment valve is opened. Patent Document 3 does not disclose a technique to overcome this problem. However, as a technique to overcome this problem, a method in which the valve unit is not completely closed and the valve unit partially leaks the fluid, or a method of completely closing the pressure adjustment valve by a pressure difference between a suction side and an orifice side, the pressure adjustment valve being pinched between the suction side and the orifice side, can be considered. However, when the pressure adjustment valve is not completely closed, since not all the unnecessary suctioning is stopped, inefficiency of the suctioning remains. Further, in the method of completely closing the pressure adjustment valve by the pressure difference between the suction side and the orifice side, at an instant when the recording medium covers the orifice, the pressure difference for closing the pressure adjustment valve is not released, and the pressure adjustment valve is not opened. When the pressure inside the orifice is increased by leakage through a gap between the orifice and the recording medium, the pressure adjustment valve is opened. Therefore, the problem that the technique does not handle the lifting of the tips of the sheet remains. Further, in order to cause the pressure adjustment valve to be opened when a sheet covers a portion of an orifice, a valve may be opened and closed in response to a very small pressure difference or a very small flow difference of a fluid. Therefore, a highly precise valve system may be required, and a suction force from a suction mechanism may be very precise. Such a technique is not realistic, and it leads to problems, such as a cost increase, degradation of proccessability, and growth in size of the device.
In one aspect, there is provided a sheet conveyance device including a support unit that supports a sheet; plural suction ports placed on the support unit; a suction unit that suctions the sheet toward the support unit, the suction unit being connected to the plural suction ports; plural valve systems, each valve system being placed between the corresponding suction port and the suction unit, each valve system being openable and closeable; plural valve interlocked suction ports that are to be covered by the sheet when the sheet is conveyed, the plural valve interlocked suction ports being arranged separately from the plural suction ports; and plural opening and closing units that open and close the plural valve systems, each opening and closing unit being placed between one of the valve interlocked suction ports and one of the valve systems.
In another aspect, there is provided an image forming device including a sheet conveyance device. The sheet conveyance device includes a support unit that supports a sheet; plural suction ports placed on the support unit; a suction unit that suctions the sheet toward the support unit, the suction unit being connected to the plural suction ports; plural valve systems, each valve system being placed between the corresponding suction port and the suction unit, each valve system being openable and closeable; plural valve interlocked suction ports that are to be covered by the sheet when the sheet is conveyed, the plural valve interlocked suction ports being arranged separately from the plural suction ports; and plural opening and closing units that open and close the plural valve systems, each opening and closing unit being placed between one of the valve interlocked suction ports and one of the valve systems.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
It is an objective of embodiments of the present invention to solve the above described problems. Further, it is an objective of the embodiments of the present invention to provide a conveyance device that can suction a sheet immediately before the sheet covers a suction port, that can keep suctioning the sheet until the sheet is completely separated from the suction port, that can surely prevent the sheet from lifting, and that can perform efficient and stable sheet conveyance, without additionally arranging a sensor or an actuator.
A valve interlocked suction port 27 is placed at upstream side of the corresponding suction port 25 on the guide plate 23 in the conveyance direction of the sheet 1. The valve interlocked suction port 27 is connected to the suction unit 20. In the channel connecting the valve interlocked suction port 27 and the suction unit 20, an opening and closing unit 28 for opening and closing the valve system 26 is placed. As shown in
With the above described configuration, in a state shown in
In the above described embodiment 1, the air is suctioned prior to the front tip of the sheet 1 reaching the orifice 24. When the front tip of the sheet 1 reaches the orifice 24, a sufficient suction force from the suction unit 20 is acting. Therefore, by using a lower cost configuration in which sensors or electrical driving mechanisms are not used, the sheet 1 can be stably conveyed while the lifting of the front tip of the sheet 1 is prevented. Further, plural of the suction ports 25 and plural of the valve interlocked suction ports 27 are arranged in the width direction of the sheet 1. Therefore, when a sheet having a different width is conveyed, an unnecessary suction is not performed, and the sheet can be stably conveyed while the lifting of the sheet is prevented. Further, since the valve interlocked suction port 27 is placed at upstream side of the suction port 25 in the sheet conveyance direction, it is ensured that the front tip of the sheet 1 is suctioned first. Therefore, the sheet 1 can be stably conveyed while the lifting of the tip of the sheet 1 is surely prevented. Further, since the plural suction ports 25 are also arranged in the sheet conveyance direction, an unnecessary suction is not performed when an image is formed over a long distance in the sheet conveyance direction. Therefore, the sheet 1 can be stably conveyed while the lifting of the tip of the sheet 1 is prevented. Further, when a pressure difference between the atmospheric pressure and the pressure inside the valve interlocked suction port 27 is greater than a predetermined value, the opening and closing unit 28 opens the on-off valve 31. Therefore, the valve system 26 can be opened and closed more reliably.
In the embodiment, the valve interlocked suction port 27 is arranged at downstream side of the pair of conveyance rollers 32 in the sheet conveyance direction. However, the position of the valve interlocked suction port 27 is not limited to this. It is preferable that the valve interlocked suction port 27 be arranged at a suitable position depending on a conveyance speed of the sheet 1, or a layout of the inkjet recording device 10. Further, in the configuration of the embodiment, the flexible member 30 is used in the opening and closing unit 28. However, a piston mechanism can be used instead of the flexible member 30.
With the above described configuration, in addition to the effect of the first embodiment, the following effects can be obtained. Namely, in the state shown in
With the above described configuration, when plural orifices are densely arranged, a valve system arranged in a first orifice can be opened and closed by a pressure difference between the atmospheric pressure and the pressure in a second orifice, which is neighboring to the first orifice, without introducing a new valve interlocked suction port. Therefore, a stable conveyance can be realized without cost increase. Further, since check valves are provided, even if the suction ports 25 neighboring to each other are opened, the valve mechanisms 26, 35 can be surely operated.
In the above configuration, when types of the sheet 1 are limited to several types, and, for example, when the sheet 1 is conveyed while the sheet 1 is aligned to the central portion, the width of the area A may be adjusted to be a width of the smallest type of the sheet 1 to be conveyed. Further, it is not necessary that a valve interlocked suction port 27 be placed for each suction port 25. With the above configuration, cost reduction may be achieved. Additionally, the above configuration is advantageous as a layout of the inkjet recording device 10.
With the configurations shown in the embodiments, when plural sheets 1 are conveyed while the sheets 1 are evenly spaced apart in the conveyance direction or in the width direction, it is possible to cause the suction ports 25, above which the sheets 1 do not exist, not to suction, and cause the only suction ports 25, to which the sheets 1 are to be conveyed immediately after, to suction. Therefore, recording papers are efficiently suctioned, and the recording papers can be stably conveyed. Further, when an image is formed by a single scanning across the spacing of the sheets (for example, when the sheets are conveyed while the sheets are evenly spaced apart in the conveyance direction, a case in which an image is formed by a single scanning of a rear end portion of the front sheet and a front end portion of the successive sheet), an occurrence of an air current caused by the suction can be minimized by eliminating redundant suction operations, which are the suction operations between the sheets. In this case, adverse effects on ink discharge caused by the occurrence of the air current can be reduced.
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
The present application is based on Japanese Priority Application No. 2011-011092, filed on Jan. 21, 2011, the entire contents of which are hereby incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-011092 | Jan 2011 | JP | national |
