Patent Application
20130027465
The present application claims priority from Japanese Patent Application No. 2011-167036, which was filed on Jul. 29, 2011, the disclosure of which is herein incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a liquid ejection apparatus having a liquid ejection head for ejecting a liquid.
2. Discussion of Related Art
There is known a liquid ejection apparatus in which mist produced by a liquid ejection is moved upward by sucking air between a plurality of heads for ejecting a liquid.
In a case where an airflow generating means is disposed near the heads, due to the airflow, it is possible that a recording medium rises from a support surface and comes into contact with the head. When the recording medium comes into contact with the head, it is possible that the head is damaged or an image recorded on the recording medium is defective.
It is therefore an object of the present invention to provide a liquid ejection apparatus to restrain a rising of the recording medium.
In order to achieve the above-mentioned object, according to the present invention, there is provided a liquid ejection apparatus comprising: a conveyor mechanism configured to convey a recording medium in a conveying direction; a plurality of liquid ejection heads each of which has an ejection face from which a liquid is ejected and which are arranged in the conveying direction; a support member opposed to the ejection face and configured to support the recording medium; a first suction mechanism having a first suction opening located between two of the plurality of liquid ejection heads adjacent to each other in the conveying direction, the first suction mechanism being configured to suck air via the first suction opening; and at least one first contact member located between the two liquid ejection heads adjacent to each other in the conveying direction and configured to be contactable with a recording face of the recording medium at a position closer to the support member than the first suction opening in a perpendicular direction perpendicular to the ejection face.
The above and optional objects, features, and advantages of the present invention will be better understood by reading the following detailed description of the embodiments of the invention when considered in conjunction with the accompanying drawings, in which:
Hereinafter, there will be described embodiments of the present invention with reference to the drawings. An overall structure of an inkjet printer 1 as one embodiment to which the present invention is applied will be described with reference to
The inkjet printer 1 includes a casing 1a having a rectangular parallelepiped shape. In an upper portion of a top panel of the casing 1a, there is provided a sheet-discharge portion 31. In a space defined by the casing 1a, there is formed a sheet conveying path through which a recording sheet P as an example of a recording medium is conveyed from a sheet-supply unit 1c (described later) to the sheet-discharge portion 31 along a thick arrow A in
The pre-coat head 10 is a line-type head having a generally rectangular parallelepiped shape extending in a main scanning direction. To the pre-coat head 10, an image-quality enhancing liquid is supplied from a liquid tank (not shown). A lower face of the pre-coat head 10 is an ejection face 10a in which a plurality of nozzles or ejection openings for ejecting the image-quality enhancing liquid are formed. As an example of the image-quality enhancing liquid, a clear and colorless liquid is used so as to coagulate pigment of ink. Materials of the liquid are suitably selected, e.g. a liquid including multivalent metal salt such as cationic polymer and magnesium salt and so forth. When ink lands on an area of the recording sheet P to which the image-quality enhancing liquid is applied in advance, the multivalent metal salt and the like affects on dye or pigment in the ink such that insoluble or hardly-soluble metal complex or the like is coagulated or precipitated. The image-quality enhancing liquid may be a liquid having a function to enhance a color optical density of the ink. The pre-coat head 10 is controlled by the controller 1p so as to eject a pre-coat liquid from the nozzles thereof.
The inkjet head 11 is a line-type head having the same shape as the pre-coat head 10. The inkjet head 11 is located side by side with the pre-coat head 10 on a downstream side of the pre-coat head 10 in a direction of the arrow A in
Platens 14, 15 (as an example of a support member) are located below the respective heads 10, 11. On respective upper faces of the platens 14, 15, there are formed flat support faces 14a, 15a for supporting the recording sheet P. The support faces 14a, 15a are located at the same position with each other in the vertical direction. The heads 10, 11 are supported by the casing 1 a via a head holder 3 such that small clearances suitable for an image recording made between the ejection face 10a and the support face 14a and between the ejection face 11a and the support face 15a, respectively. The clearance between the ejection face 10a and the support face 14a and/or the clearance between the ejection face 11a and the support face 15a form the conveying path. In other words, the conveying path, is a space defined by the ejection face 10a and the support face 14a and/or by the ejection face 11a and the support face 15a. The image-quality enhancing liquid is adhered to the recording sheet P by ejection of the image-quality enhancing liquid from the head 10 while the recording sheet is supported on the support face 14a. The ink is adhered to the recording sheet P by ejection of the ink from the head 11 while the recording sheet P is supported on the support face 15a. Further, a guide 29 is disposed between the platens 14, 15 in a sub-scanning direction. An upper face of the guide 29 is located at the same position as the support faces 14a, 15a in the vertical direction. A guide 29 is disposed between a spur roller 81 and a driven roller 82 in the sub-scanning direction. At a position opposite to a suction opening 111b in the guide 29, there is formed a penetrating hole 29a.
The conveyor mechanism 60 includes the sheet-supply unit 1c, the guide 29, pairs of feed rollers 22, 26 through 28, a pair of register rollers 23, and a pair of between-heads rollers 24. The conveyor mechanism 60 is controlled by the controller 1p to convey the recording sheet P from the sheet-supply unit 1c to the sheet-discharge portion 31 along the sheet conveying path.
The sheet-supply unit 1c includes a sheet-supply tray 20 and a sheet-supply roller 21. The sheet-supply tray 20 is detachably attached to the casing 1a in the sub-scanning direction. The sheet-supply tray 20 has a box-like structure opening upward and can accommodate a plurality of recording sheets P. The sheet-supply roller 21 is rotated by control of a sheet-supply motor 21M (shown in
The pair of register rollers 23 are rotated by control of a register motor 23M (shown in
The pair of between-heads rollers 24 are rotated by the control of the feed motor 22M by the controller 1p. The pair of between-heads rollers 24 are located between the heads 10, 11 in the sub-scanning direction and have two rollers of a drive roller 25 (as an example of a conveyor roller) and a driven roller 82. The drive roller 25 and the driven roller 82 will be described later. The pair of between-heads rollers 24 nip the recording sheet P fed from the pair of register rollers 23 between the heads 10, 11 and further feed the recording sheet P to the pair of feed rollers 26 along the arrow A in
In the present embodiment, the sub-scanning direction is a direction along the arrow A in
As shown in
In the present inkjet printer 1, there are disposed suction mechanisms 110, 120 (as examples of a first suction mechanism and a second suction mechanism) for sucking mists of the image-quality enhancing liquid and the ink produced in the printer 1. When the image-quality enhancing liquid and the ink are ejected from the heads 10, 11, it is possible that a part of those ejected liquid becomes a tiny droplet and floats in the air in an atomized state. In the present embodiment, in a case where the liquids are ejected from the heads 10, 11 toward the recording sheet P such that the image is recorded on the recording sheet P, the recording sheet P is conveyed in a direction of the arrow A. Therefore, in the vicinity of the heads 10, 11, there is produced airflow in the direction of the arrow A with conveying of the recording sheet P. In other words, the mists of the liquids ejected from the heads 10, 11 floating in the air without landing on the recording sheet P move in the direction of the arrow A due to the airflow.
Hereinafter, a construction of the suction mechanisms 110, 120 and the periphery thereof will be described with reference to
The opening 111c communicates with the outside of the printer 1. The pump 112 is disposed in a middle of the passage 113. The pump 112 is controlled by the controller 1p to suck air in the space 111a via the passage 113 and discharge it to the outside of the printer 1. When the pump 112 sucks the air in the space 111a, the air in the vicinity of the suction opening 111b is sucked into the space 111a with the mist, then moved upward in the vertical direction along an arrow B in
The suction mechanism 120 includes a duct 121, the pump 122 and a passage 123 similarly constructed to respective portions of the suction mechanism 110. The suction opening 121b (as an example of a second suction opening) disposed at a lower end of the duct 121 is located in the vicinity of a downstream portion of the head 11 in the sub-scanning direction. Further, the suction opening 121b is located at a position higher than the ejection face 11a of the head 11 in the vertical direction, i.e., at a position farther from the guide 29 than the ejection face 11a in the vertical direction. The pump 122 is controlled by the controller 1p to suck the air in a space 121a, in the duct 121 via the passage 123. Accordingly, the air in the vicinity of the suction opening 121b is sucked into the space 121a with the mist, then moved upward in the vertical direction along an arrow C in
The pump 112 of the suction mechanism 110 is greater in suction power than the pump 122 of the suction mechanism 120. More precisely, an amount of air per unit time sucked from the suction opening 111b by the pump 112 is adjusted to be greater than that sucked from the suction opening 121b by the pump 122. In other words, the amount of air that flows through the suction opening 111b in an airflow produced by the pump 112 (hereinafter, referred to as the amount of air of the suction mechanism 110) is greater than the amount of air that flows through the suction opening 121b in an airflow produced by the pump 122 (hereinafter, referred to as the amount of air of the suction mechanism 120). Therefore, the mist of the image-quality enhancing liquid is more effectively restrained from moving toward the head 11.
In a case where the suction mechanisms 110, 120 suck the air, it is possible that the recording sheet P positioned below the suction openings 111b, 121b rises from the support faces 14a, 15a and/or the guide 29. Especially a front end portion and a rear end portion (a downstream end portion and an upstream end portion in the sub-scanning direction) of the recording sheet P in the sub-scanning direction are easy to rise, compared to a middle portion of the recording sheet P in the sub-scanning direction. In a case where the recording sheet P rises and contacts the head 10 or the head 11, accuracy of conveying of the recording sheet P is reduced or the ink and the image-quality enhancing liquid adhered to the ejection faces 10a, 11a is transferred to the recording sheet P, so that a quality of image formed on the recording sheet may be decreased. It is also possible that the heads 10, 11 are damaged.
Accordingly, in the present embodiment, there are disposed three rollers in order to restrain rising of the recording sheet P. The three rollers are located between the suction openings 111b, 121b and the support faces 14a, 15a in the vertical direction.
The first roller is the spur roller 81 (as an example of a first rotary member) located between the head 10 and the duct 111 in the sub-scanning direction. The spur roller 81 has a rotary shaft 81a extending in the main scanning direction and a plurality of roller portions 81b fixed to the rotary shaft 81a. The rotary shaft 81a extends over the head 10 in the main scanning direction and is rotatably supported by the casing 1a. As shown in
The second roller of the three rollers is the driven roller 82 (as an example of the first rotary member) as one of two rollers forming the pair of between-heads rollers 24 which contacts the recording sheet P from upward. The driven roller 82 nips the recording sheet P together with the drive roller 25 as the other of the two rollers which contacts the recording sheet P from downward and is driven with the movement of the recording sheet P. The driven roller 25 has a rotary shaft 82a extending in the main scanning direction and a roller portion 82b fixed to the rotary shaft 82a. The rotary shaft 82a extends over the head 10 in the main scanning direction and is rotatably supported by the casing 1a. The roller portion 82b has a generally cylindrical shape having the substantially same length as the head 10 in the main scanning direction. The roller portion 82b has a smooth surface with no projections. A lowermost point of the driven roller 82 in the vertical direction is located at the generally same position as the conveying path of the recording sheet P in the vertical direction. A fluorine coating is made on an outer circumferential surface of the roller portion 82b. Therefore, when the driven roller 82 and the recording face of the recording sheet P come into contact with each other, the image-quality enhancing liquid ejected to the recording sheet P is restrained from being adhered to the roller portion 82b of the driven roller 82.
The drive roller 25 is located at a position opposite to the driven roller 82 in the vertical direction. The drive roller 25 is rotated by a drive of the feed motor 22M by the controller 1p. By a rotation of the drive roller 25, the recording sheet P nipped by the drive roller 25 and the driven roller 82 is fed in the direction of the arrow A in
The third roller of the three rollers is a spur roller 83 (as an example of a second rotary member) located in the vicinity of the downstream portion of the duct 121 in the sub-scanning direction. The spur roller 82 consists of a rotary shaft 83a and a plurality of roller portions 83b having the similar structure as the rotary shaft 81a and the roller portions 81b. As shown in
In the present embodiment, in a case where the recording sheet P is about to rise due to sucking of air by the suction mechanism 110, the spur roller 81 and the driven roller 82 prevents the rising of the recording sheet P. When the recording sheet P is fed in the direction of the arrow A, the front end of the recording sheet P first reaches below the spur roller 81 and then reaches below the suction opening 111b. Therefore, when the front end portion of the recording sheet P is about to rise due to the suction by the suction mechanism 110, the recording sheet P is restrained from rising by the spur roller 81, so that the rising of the recording sheet P is surely restrained. In other words, because the spur roller 81 is located on the upstream side of the suction opening 111b in the sub-scanning direction, the rising of the recording sheet P can be surely restrained. Further, on the downstream side of the suction opening 111b in the sub-scanning direction, the driven roller 82 restrains the rising of the recording sheet P. The rising of the recording sheet P is thus restrained both on the upstream side and the downstream side of the suction opening 111b in the sub-scanning direction, so that the recording sheet P is restrained from contacting the ejection faces 10a, 11a.
Further, the guide 29 is located between the platens 14, 15, and the pair of between-heads rollers 24 are located on the downstream side of the suction opening 111b in the sub-scanning direction. The pair of between-heads rollers 24 makes the conveying path of the recording sheet P narrow sharply. Thus, an airflow going to the downstream side along the conveying path collides with the pair of between-heads rollers 24 and tends to change its direction to the vertical direction. In other words, the airflow heading for the downstream side along the conveying path tends to become an airflow in the vertical direction via the penetrating hole 29a. Because the suction opening 111b is located above the penetrating hole 29a, the airflow going upward through the penetrating hole 29a is smoothly guided into the suction opening 111b. Accordingly, the suction mechanism 110 can effectively suck the air.
In a case where the recording sheet P is about to rise due to sucking of air by the suction mechanism 120, the spur roller 83 located on the downstream side of the suction mechanism 120 in the sub-scanning direction prevents the rising of the recording sheet P. Therefore, it is restrained that the recording sheet P rises to contact the head 11.
In a case where the mists produced from the heads 10, 11 are sucked by the suction mechanisms 110, 120 as in the present embodiment, it is preferable that the suction openings 111h, 121b are respectively located right on the downstream sides of the heads 10, 11 in the sub-scanning direction. Further, in order to suck the mists produced from the heads 10, 11, it is preferable that the amount of air of each of the suction mechanisms 110, 120 is large. However, if the amount of air of each of the suction mechanisms 110, 120 is large, it is possible that the recording sheet P easily rises so as to contact the ejection faces 10a, 11a.
In the present embodiment, the head 10 is a head which ejects the image-quality enhancing liquid. If the image-quality enhancing liquid is adhered to the ejection face 11a of the head 11, it is possible that the ink in the vicinity of the ejection openings is coagulated or precipitated so as to close the ejection openings. In a case where the ejection openings are closed, it is possible that the ejection failure occurs. Therefore, in order to suck the mist of the image-quality enhancing liquid ejected from the head 10, the amount of air of the suction mechanism 110 is determined to be relatively large. Further, since the spur roller 81 and the driven roller 82 are disposed on the upstream side and the downstream side of the suction opening 111b in the sub-scanning direction, the rising of the recording sheet P is restrained. Because the amount of air of the suction mechanism 110 is relatively large, it is possible that the recording sheet P rises and the image-quality enhancing liquid is adhered to the spur roller 81 and the driven roller 82 located near the suction opening 111b. However, because the image-quality enhancing liquid is clear and colorless, even if the image-quality enhancing liquid is adhered to the spur roller 81 and so on and further transferred to the recording sheet P, it hardly causes that the recording sheet P is directly contaminated. Therefore, as in the present embodiment, it is preferable to effectively restrain the rising of the recording sheet P by such structure that the suction mechanism 110 suck the mist with the large amount of air and also the spur roller 81 and the driven roller 82 are located on the upstream and the downstream sides of the suction opening 111b in the sub-scanning direction.
Furthermore, in the present embodiment, the head 11 is a head located on the most downstream side among the heads 10, 11 in the sub-scanning direction. The mist is moved in the direction of the arrow A in
Furthermore, as mentioned before, the respective lowest points of the spur roller 81, the driven roller 82 and the spur roller 83 in the vertical direction are located between the suction openings 111h, 121b and the support faces 14a, 15a in the vertical direction. In other words, those lowest points of the rollers 81, 82, 83 are closer to the conveying path of the recording sheet P in the vertical direction than the suction openings 111b, 121b. Accordingly, when the recording sheet P is about to rise, the rollers 81, 82, 83 surely contacts the recording sheet P so as to restrain the rising of the recording sheet P. In a case where the spur roller 81, the driven roller 82 and the spur roller 83 are not disposed, the guide opposite to the recording face of the recording sheet P and the recording sheet P come into contact with each other. In this case, the image-quality enhancing liquid and the ink adhered to the recording sheet P are adhered to the guide 29, so that it is possible that an image of the recording sheet P is defective and the following recording sheet P fed after the above-mentioned recording sheet P having contacted the guide 29 is contaminated. Since the spur rollers 81, 83 have the plurality of projections on the outer circumferences thereof so as to make a point contact with the recording face of the recording sheet P, it can be restrained that liquid is adhered to the spur rollers 81, 83. Moreover, since the fluorine coating is made on the outer circumferential surface of the driven roller 82, it can be restrained that liquid is adhered to the driven roller 82.
The present invention is not limited to the illustrated embodiment. It is to be understood that the present invention may be embodied with various changes and modifications that may occur to a person skilled in the art, without departing from the spirit and scope of the invention defined in the appended claims.
In the illustrated embodiment, rollers (the spur roller 81 and the driven roller 82) are respectively located on the upstream side and the downstream side of the suction opening 111b of the duct 111 in the sub-scanning direction. However, an arrangement different from that in the illustrated embodiment may be adopted, as long as at least one of the spur roller 81 and the driven roller 82 and the suction opening 111b are located between the heads 10, 11 in the sub-scanning direction. For example, as shown in
In the illustrated embodiment, the lowermost point of the spur roller 81 in the vertical direction is located at the approximately same position as the conveying path of the recording sheet P in the vertical direction. However, a position of the spur roller 81 in the vertical direction may be located higher than that in the illustrated embodiment, as long as the lowermost point of the spur roller 81 in the vertical direction is closer to the conveying path of the recording sheet P than the suction opening 111b. It is similar to a positional relation between the spur roller 83 and the suction opening 121b.
Further, in the illustrated embodiment, one pre-coat head 10 and one inkjet head 11 are arranged in the sub-scanning direction. However, one pre-coat head 10 and two or more inkjet heads may be arranged in the sub-scanning direction. In this case, it is preferable that the pre-coat head 10 (as an example of a second head) is located on a most upstream portion among the heads (on an upstream side of the inkjet heads) in the sub-scanning direction and the suction mechanism 110 and the spur roller 81 are located between the pre-coat head 10 and the inkjet head (as an example of a first head) adjacent to the pre-coat head 10, Furthermore, without the pre-coat head 10, only a plurality of inkjet heads may be disposed. Between the inkjet heads adjacent to each other, the suction mechanism 110 and the spur roller 81 may be located or the suction mechanism 120 and the spur roller 83 may be located. In the illustrated embodiment, the platen 14 is located at the position opposite to the ejection face 10a of the head 10, while the platen 15 is located at the position opposite to the ejection face 11a of the head 11. As a modified example, one platen may be located to be opposed to the ejection face 10a of the head 10 and the ejection face 11a of the head 11. Moreover, though, in the illustrated embodiment, the spur roller 81, the driven roller 82 and the spur roller 83 have rotary members (the roller portions 81b, the driven roller 82 and the roller portions 83b), at least one of the spur roller 81, the driven roller 82 and the spur roller 83 may be a contact member which does not rotate but contacts the recording face of the recording sheet P. The contact member has a relatively small frictional resistance with the recording face of the recording sheet P and restrains the rising of the recording sheet P. This contact member restrains the rising of the recording sheet P, so that the recording sheet P can be restrained from contacting the ejection faces 10a, 11a.
The present invention is not limited to a printer, and is applicable to various liquid ejection apparatus, e.g., a facsimile machine, a copier machine, and so forth. A head may eject liquid other than the ink and the image-quality enhancing liquid.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-167036 | Jul 2011 | JP | national |
