Patent Application
20110134200
1. Technical Field
The present invention relates to an apparatus for transporting a transportation target medium and an image formation apparatus. In particular, the invention relates to an apparatus for transporting a sheet-type transportation target medium while applying a force of suction to it. In addition, the invention relates to an image formation apparatus to which such a transportation-target-medium transportation apparatus is applied.
2. Related Art
An apparatus disclosed in JP-A-2009-137141 is known as an example of an image formation apparatus to which the above type of a transportation-target-medium transportation apparatus is applied. The transportation-target-medium transportation apparatus is provided with, at least, a rotatable drum and an endless belt that is partially wound around the drum. The entire area of the outer circumferential surface of the drum is dotted with a plurality of drum-side suction holes. These holes are formed through the outer circumferential surface portion of the drum. The entire area of the belt is dotted with a plurality of belt-side suction holes formed therethrough.
Even when the belt is displaced relative to the drum to some degree at the part where the belt is wound around the drum, the belt-side suction holes overlap, that is, are located partially over, the drum-side suction holes to remain in communication. Therefore, it is still possible to suck a transportation target medium on the belt through these suction holes. However, because of the displacement of the belt relative to the drum, the area of each opening where the belt-side suction hole overlaps the drum-side suction hole (i.e., opening ratio) changes. Therefore, it is not possible to ensure that a constant force of suction (vacuuming force) is applied to the transportation target medium on the belt.
An advantage of some aspects of the invention is to provide an apparatus for transporting a transportation target medium that makes it possible to suck a recording target medium on a belt with a constant force of suction even when the belt is displaced. In addition, as an advantage of some aspects thereof, the invention provides an image formation apparatus to which such a transportation-target-medium transportation apparatus is applied.
To overcome the above disadvantage without any limitation thereto, the following features of some aspects of the invention are disclosed in this specification. An apparatus for transporting a transportation target medium according to a first aspect of the invention includes an endless belt and a supporting section. The endless belt has a plurality of belt-side suction holes that is formed therethrough. The supporting section has a plurality of supporting-section-side suction holes that is in communication with a depressurizing source. The supporting section supports a part of the endless belt that is driven to run. The supporting section guides the endless belt. A force of suction acts at areas where the belt-side suction holes substantially overlap the supporting-section-side suction holes for transporting the transportation target medium on the front surface of the endless belt in a predetermined direction while sucking the target medium. The belt-side suction holes are arranged at a first pitch in a first direction, which is either a direction of the length of the endless belt or a direction that is orthogonal to the direction of the length of the endless belt, to form each of a plurality of lines. The plurality of lines of the belt-side suction holes is formed adjacent to one another at a second pitch in a direction that is orthogonal to the first direction. One line of the belt-side suction holes and another line of the belt-side suction holes that is formed adjacent to the one line of the belt-side suction holes are staggered by one half of the first pitch. The supporting-section-side suction holes are arranged at the first pitch in a second direction, which is orthogonal to the first direction, to form each of a plurality of lines. The plurality of lines of the supporting-section-side suction holes is formed adjacent to one another at the second pitch in a direction that is orthogonal to the second direction. One line of the supporting-section-side suction holes and another line of the supporting-section-side suction holes that is formed adjacent to the one line of the supporting-section-side suction holes are staggered by one half of the first pitch. Either of the belt-side suction holes and the supporting-section-side suction holes, or both the belt-side suction holes and the supporting-section-side suction holes, are quadrangular holes. The open width of each of the quadrangular holes is one half of the first pitch. With such a structure, even when the relative position of the endless belt shifts on the supporting section, the total of the open areas of the overlapping parts is always constant. Therefore, it is possible to apply a constant sucking force to the transportation target medium on the endless belt.
In the structure of an apparatus for transporting a transportation target medium according to the first aspect of the invention, preferably, the belt-side suction holes should be round holes, whereas the supporting-section-side suction holes should be the quadrangular holes. With such a preferred structure, the shape of the belt-side suction holes and the shape of the supporting-section-side suction holes are optimized for the material of the endless belt and the material of the supporting section, respectively. In the structure of an apparatus for transporting a transportation target medium according to the first aspect of the invention, preferably, the supporting section should include a rotatable drum that causes the endless belt to run. With such a preferred structure, when the supporting section includes the rotatable drum, it is possible to produce the same advantageous effect as above.
An image formation apparatus according to a second aspect of the invention includes a liquid ejecting head, an endless belt, and a supporting section. The liquid ejecting head ejects liquid. The endless belt has a plurality of belt-side suction holes that is formed therethrough. The endless belt runs in a direction of transportation through a position opposite to the liquid ejecting head. The supporting section has a plurality of supporting-section-side suction holes that is in communication with a depressurizing source. The supporting section supports a part of the endless belt that is driven to run. The supporting section guides the endless belt. A force of suction acts at areas where the belt-side suction holes substantially overlap the supporting-section-side suction holes for transporting a transportation target medium on the front surface of the endless belt in a predetermined direction while sucking the target medium. The belt-side suction holes are arranged at a first pitch in a first direction, which is either a direction of the length of the endless belt or a direction that is orthogonal to the direction of the length of the endless belt, to form each of a plurality of lines. The plurality of lines of the belt-side suction holes is formed adjacent to one another at a second pitch in a direction that is orthogonal to the first direction. One line of the belt-side suction holes and another line of the belt-side suction holes that is formed adjacent to the one line of the belt-side suction holes are staggered by one half of the first pitch. The supporting-section-side suction holes are arranged at the first pitch in a second direction, which is orthogonal to the first direction, to form each of a plurality of lines. The plurality of lines of the supporting-section-side suction holes is formed adjacent to one another at the second pitch in a direction that is orthogonal to the second direction. One line of the supporting-section-side suction holes and another line of the supporting-section-side suction holes that is formed adjacent to the one line of the supporting-section-side suction holes are staggered by one half of the first pitch. Either of the belt-side suction holes and the supporting-section-side suction holes, or both the belt-side suction holes and the supporting-section-side suction holes, are quadrangular holes. The open width of each of the quadrangular holes is one half of the first pitch. With such a structure, even when the relative position of the endless belt shifts on the supporting section, the total of the open areas of the overlapping parts is always constant. Therefore, it is possible to apply a constant sucking force to the transportation target medium on the endless belt during the formation of an image.
In the structure of an image formation apparatus according to the second aspect of the invention, preferably, the belt-side suction holes should be round holes, whereas the supporting-section-side suction holes should be the quadrangular holes. With such a preferred structure, the shape of the belt-side suction holes and the shape of the supporting-section-side suction holes are optimized for the material of the endless belt and the material of the supporting section, respectively. In the structure of an image formation apparatus according to the second aspect of the invention, preferably, the supporting section should include a rotatable drum that causes the endless belt to run. With such a preferred structure, when the supporting section includes the rotatable drum, it is possible to produce the same advantageous effect as above.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
With reference to the accompanying drawings, exemplary embodiments of the present invention will now be explained in detail. In the drawings referred to in the following description, the same reference numerals are used for components having the same structure to avoid repeated explanation.
A duplex image formation apparatus 100 includes a front-side image formation apparatus 1 and a reverse-side image formation apparatus 2. As illustrate in
The drum 13 and the rollers 14 and 15 have respective rotating shafts 13a, 14a, and 15a. The rotating shafts 13a, 14a, and 15a extend through the cross-sectional centers of the drum 13 and the rollers 14 and 15, respectively. Bearings support each of the rotating shafts 13a, 14a, and 15a rotatably. The bearings are not illustrated in the drawing. The drum 13, the roller 14, and the roller 15 function as an example of a supporting section according to an aspect of the invention. The supporting section supports a part of the belt 16 and guides the belt 16 downstream in the direction of transportation. The three rotating shafts 13a, 14a, and 15a rotate in the same direction, for example, clockwise. As these rotating shafts 13a, 14a, and 15a rotate, the belt 16 runs in one direction while being stretched between the drum 13 and the rollers 14 and 15.
For example, the output shaft of a driving source such as an electric motor or the like is connected to the rotating shaft 13a of the drum 13 either directly or through a speed reduction mechanism. The power of the electric motor is transmitted to the rotating shaft 13a. When the electric motor, which is the driving source, rotates in its normal direction, the drum 13 is driven to rotate around the rotating shaft 13a. As will be explained later, a plurality of suction holes 13b is formed in the outer circumferential surface of the drum 13. An example of the material of the belt 16 is rubber. As will be explained later, a plurality of suction holes 16a is formed in the surface of the belt 16. A negative pressure suction method is used to hold the recording paper P on the surface of the belt 16. That is, negative pressure is applied to the suction holes 16a of the belt 16 through the suction holes 13b of the drum 13 so as to suck (e.g., vacuum chuck) the recording paper P therethrough. For example, a depressurizing source, which is not illustrated in the drawing, reduces inner pressure to suck air toward the inner space of the drum 13. That is, the force of suction generated by the depressurizing source acts through the suction holes 13b and the suction holes 16a.
The partition wall member 63 is provided in a space 47 inside the belt 16 and outside the drum 13. The function of the partition wall member 63 is to demarcate a region to which negative pressure is applied in the space 47. Since the partition wall member 63 is provided in the space 47, the region surrounded by the partition wall member 63, the reverse face of the belt 16, and the outer circumferential surface of the drum 13 is substantially hermetically closed. Therefore, negative pressure is kept thereat. For this reason, at the surface of the belt 16, a force of suction due to the application of negative pressure thereto acts not only at the part of the belt 16 that is curved along the drum 13 but also at the part of the belt 16 that is not curved along the drum 13 near the curved part. That is, the force of suction acts also at the part of the belt 16 immediately upstream of the curved part and the part of the belt 16 immediately downstream of the curved part.
As a means for feeding the recording paper P onto the belt 16, for example, the front-side image formation apparatus 1 is provided with a pair of gate rollers 17. The gate rollers 17 mechanically correct the skew of the recording paper P by bringing their roller surfaces into contact with the recording paper P. In addition, the gate rollers 17 are configured to feed the recording paper P to a target position on the belt 16 in synchronization with drive-start timing.
As a means for performing recording operation on the recording paper P, for example, the front-side image formation apparatus 1 is provided with a line-recording type head (hereinafter referred to as line head) 19. The line head 19 is provided at a position opposite to a part of the outer circumferential surface of the drum 13 with a part of the belt 16 therebetween. The line head 19, which is an example of a liquid ejecting head according to an aspect of the invention, is made up of, for example, four line heads 19Y, 19M, 19C, and 19K. The line heads 19Y, 19M, 19C, and 19K discharge ink droplets of four colors, which are yellow (Y), magenta (M), cyan (C), and black (K), respectively. Ink of the corresponding color is supplied from an ink tank (not shown) in which it is contained to each of the line heads 19Y, 19M, 19C, and 19K through an ink supply tube. That is, the ink of the above four colors is supplied from the ink tanks through the tubes separately. The line heads 19Y, 19M, 19C, and 19K are arranged at predetermined spaces in the circumferential direction along the outer circumferential surface of the drum 13.
Each of the line heads 19Y, 19M, 19C, and 19K has a plurality of nozzles aligned in the direction that is orthogonal to the direction of transportation of the recording paper P in a plan view (i.e., in the direction of the width of the recording paper P). The line of the nozzles is long enough so that it is possible to perform recording throughout the entire width of a sheet of paper having the maximum size available for printing. Each of the line heads 19Y, 19M, 19C, and 19K ejects a required amount of ink in the form of droplets from the nozzles to positions on the recording paper P where it is necessary to form dots. By this means, the line head 19 forms very small ink dots on the recording paper P. The formation of ink dots is carried out for each of the above four colors. In this way, the front-side image formation apparatus 1 can perform printing on the front of the recording paper P held on the belt 16.
As a means for drying the discharged ink droplets on the recording paper P, for example, the front-side image formation apparatus 1 is provided with a drying device 61 such as a halogen lamp, a warm air blower, or the like. As illustrated in
As a means for performing recording operation on the recording paper P, for example, the reverse-side image formation apparatus 2 is provided with line heads 119Y, 119M, 119C, and 119K, which are collectively denoted as line head 119. The line head 119 is provided at a position opposite to a part of the outer circumferential surface of the drum 113 with a part of the belt 116 therebetween. Besides the above components, the reverse-side image formation apparatus 2 is provided with a drying device 161 such as a halogen lamp, a warm air blower, or the like as a means for drying ink droplets on the recording paper P. The structure and function of each of the transporting means, the recording means, the drying means, and a detecting means of the reverse-side image formation apparatus 2 is the same as that of the counterpart of the front-side image formation apparatus 1.
The duplex image formation apparatus 100 includes a relaying portion 4 that passes a sheet of the recording paper P from the front-side image formation apparatus 1 to the reverse-side image formation apparatus 2. The sheet is turned over before it is passed to the reverse-side image formation apparatus 2. The surface of the belt 16 of the front-side image formation apparatus 1 and the surface of the belt 116 of the reverse-side image formation apparatus 2 are in contact with each other at a prescribed overlapping region in the direction of transportation of the recording paper P. The relaying portion 4 is formed as the surface contact portion of the belts 16 and 116. The roller 14 of the front-side image formation apparatus 1 serves as a portion for releasing the outgoing recording paper P. The portion is hereinafter referred to as releasing portion 6. The roller 115 of the reverse-side image formation apparatus 2 serves as a portion for receiving the incoming recording paper P. The portion is hereinafter referred to as receiving portion 8. The angle of the part of the belt 16 that is curved along the roller 14 functioning as the releasing portion 6, which is denoted as θ1, is an acute angle. The angle of the part of the belt 116 that is curved along the roller 115 functioning as the receiving portion 8, which is denoted as θ2, is an obtuse angle.
The line head 19 performs printing on the front of a sheet of the recording paper P. After the printing, the recording paper P is transported on the belt 16 to the position of the roller 14, which is a downstream position in the transportation direction. The recording paper P is self-stripped (“curvature released”) at the curved surface of the belt 16 of which curvature is changed substantially depending on the diameter of the roller 14. The recording paper P is passed from the front-side image formation apparatus 1 to the reverse-side image formation apparatus 2. After having been passed to the reverse-side image formation apparatus 2, the recording paper P is transported downstream on the belt 116. The line head 119 performs printing on the back of the sheet of the recording paper P. After the printing, the recording paper P is transported on the belt 116 to the position of the roller 114, which is a downstream position in the transportation direction. The recording paper P is self-stripped at the curved surface of the belt 116 of which curvature is changed substantially depending on the diameter of the roller 114. The released recording paper P is ejected to the outside.
In the setting of the duplex image formation apparatus 100, the transportation velocity of the belt 116 of the reverse-side image formation apparatus 2, which is denoted as V2, is slightly higher than that of the belt 16 of the front-side image formation apparatus 1, which is denoted as V1. A paper edge detector 65 is provided immediately downstream of the relaying portion 4 in the transportation direction. The paper edge detector 65 detects the leading edge of the recording paper P on the front of which an image or the like has been printed. The paper edge detector 65 sends the detected edge to the storage area of the reverse-side image formation apparatus 2. By this means, it is possible to perform printing on the back of the sheet of the recording paper P while ensuring high precision in the reverse-side recording position.
Next, with reference to
The suction hole 13b is a hole that is formed through the outer circumferential surface portion of the drum 13. The suction hole 13b is a quadrangular hole. Therefore, as illustrated in
As illustrated in
Next, with reference to
For the purpose of explanation, attention is focused on another group of four suction holes 16a that are located adjacent to the four suction holes 16a explained above, specifically, four top-of-the-drawing-side adjacent suction holes 16a. Each of these four suction holes 16a overlaps the corresponding one of the suction holes 13b due to displacement in
For the purpose of explanation, attention is focused on another group of four suction holes 16a that are located adjacent to the four suction holes 16a explained above, specifically, four right adjacent suction holes 16a (though staggered). Each of these four suction holes 16a overlaps the corresponding one of the suction holes 13b due to displacement in
An advantageous effect of the present embodiment of the invention is explained above under an assumption that the belt 16 is displaced relative to the drum 13 either in the direction of the length of the belt 16 or in the direction of the width of the belt 16. However, the above advantageous effect can be produced even in a case where the belt 16 is displaced relative to the drum 13 in an oblique direction. In the present embodiment of the invention, as explained while referring to
As will be understood from the above explanation, a means for transporting the recording paper P according to the present embodiment of the invention offers the following advantage. When the belt 16 is displaced relative to the drum 13, the overlapping pattern of the suction holes 16a of the belt 16 and the suction holes 13b of the drum 13 changes. However, despite such a change in the overlapping pattern, the total of the open areas of the overlapping parts, that is, the total of the open areas of the suction holes in a communicated state, remains the same as that of a state without any displacement. In other words, irrespective of whether the belt 16 is displaced relative to the drum 13 or not, it is possible to keep the same effective opening ratio of suction holes. Thus, irrespective of whether the belt 16 is displaced relative to the drum 13 or not, a means for transporting the recording paper P according to the present embodiment of the invention makes it possible to apply a constant force of suction to the recording paper P on the belt 16.
Next, variation examples of the structure of the drum 13 and the belt 16 will now be explained. In the illustrated example of
In the illustrated example of
In the illustrated example of
For example, in some cases, in a structure that includes a combination of quadrangular suction holes and round suction holes, metal is used as the material of the drum 13, whereas rubber is used as the material of the belt 16. In such a case, from the viewpoint of material characteristics, machinability, and the like, it is preferable to form the suction holes 13b of the drum 13, which is made of metal, as quadrangular holes and the suction holes 16a of the belt 16, which is made of rubber, as round holes.
(1) In the structure of an image formation apparatus illustrated in
In such a structure, a plurality of suction holes that is the same as or similar to the suction holes 16a of the belt 16 illustrated in
The entire disclosure of Japanese Patent Application No. 2009-279811, filed Dec. 9, 2009 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-279811 | Dec 2009 | JP | national |
