Patent Application
20230382119
The present invention claims priority under 35 U.S.C. § 119 to Japanese Application, 2022-087551, filed on May 30, 2022, the entire contents of which being incorporated herein by reference.
The present invention relates to an inkjet recorder.
An inkjet recorder is an apparatus that causes ink ejected by an inkjet head to adhere on a recording medium thereby forming an image on the recording medium. Not all the ink ejected by the inkjet head contributes to an image formation, and a part thereof floats as ink mist.
The ink mist is a microdroplet of ink and hence is easily flown by the surrounding airflow. If the ink mist flowed by the airflow goes out of its predetermined trajectory and adheres to the recording medium, a deterioration in image quality is resulted. Moreover, if the ink mist adheres to an area other than the recording medium, an ink contamination occurs in the inkjet recorder. Therefore, the inkjet recorder includes a mist collector that collects the ink mist.
Patent Literature 1 describes a technique in which ink mist moving with an airflow is separated from the air by a centrifugal force and then collected. In the technique described in Patent Literature 1, a spiral airflow is generated inside a cyclone housing, and the ink mist is caused to adhere on the inner wall of the cyclone housing by a centrifugal force generated at the time when the ink mist moves in circles with this airflow, so that the ink mist is separated from the air.
The ink mist is generated at the time when the ink is ejected from the inkjet head, but the particle size of the generated ink mist is uneven. In the technique described in Patent Literature 1, the ink mist not removed by the centrifugal cyclone is captured by a filter. In this case, the ink mist with a smaller particle size is required to be separated from the air before the ink mist arrives the filter in order to reduce the exchange frequency of filters.
The present invention has been made to solve the problem described above, and an object of the present invention is to provide an inkjet recorder with which the collection efficiency of ink mist by a cyclone can be enhanced.
The present invention is an inkjet recorder including a mist collector that collects ink mist, the mist collector includes: a nozzle through which air containing the ink mist is sucked from a suction port and discharged from a discharge port; and a cyclone that includes an outer cylinder to which the discharge port of the nozzle is connected and an inner cylinder disposed inside the outer cylinder, the cyclone forming a first airflow between the outer cylinder and the inner cylinder by the air taken into the outer cylinder through the discharge port thereby separating the ink mist from the air. The inner cylinder includes an intake hole through which air is taken into the inner cylinder and forms a second airflow inside the inner cylinder by the air taken thereinto through the intake hole, thereby separating the ink mist from the air.
According to embodiments of the present invention, the collection efficiency of the ink mist by the cyclone can be enhanced.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In the present specification and the attached drawings, elements having substantially the same function or configuration will be denoted by the same reference numerals, and redundant descriptions thereof will be omitted.
<Configuration of Inkjet Recorder>
As illustrated in
The image former 12 is a part that forms an image on a sheet of paper with use of ink. The paper exit 13 is a part that discharges a sheet of paper after an image has been formed thereon. The ink supply tank 14 is a tank that stores a predetermined amount of ink and supplies the ink to the image former 12.
As illustrated in
The image former 12 is provided with a conveyor drum 20, a plurality of inkjet heads 21Y, 21M, 21C, and 21K, a mist collector 22, an ultraviolet irradiator 23, an in-line sensor 24, a reverser 25, and a large and a small conveyor rollers 26a and 26b.
The conveyor drum 20 is provided rotatably in direction A. The conveyor drum 20 rotates with the sheet of paper 15 supplied from the paper feeder 11 being wound around the outer peripheral surface of the conveyor drum 20 thereby conveying the sheet of paper 15. The conveyor drum 20 causes the sheet of paper 15 to be sucked on the outer peripheral surface of the conveyor drum 20 by air suction, for example, and rotates in this state thereby conveying the sheet of paper 15 in the direction A. The direction A indicated by an arrow in
The plurality of inkjet heads 21Y, 21M, 21C, and 21K form an image on the sheet of paper 15 with inks of their corresponding colors. Specifically, the inkjet head 21Y forms an image with yellow (Y) ink, and the inkjet head 21M forms an image with magenta (M) ink. The inkjet head 21C forms an image with cyan (C) ink, and the inkjet head 21K forms an image with black (K) ink. In the present embodiment, ultraviolet curable inks are used.
The inkjet heads 21Y, 21M, 21C, and 21K each are arranged in a state of facing the outer peripheral surface on the upper side of the conveyor drum 20. Also, the inkjet heads 21Y, 21M, 21C, and 21K each are arranged with its position shifted in the circumferential direction of the conveyor drum 20. Note that, in the present embodiment, the four inkjet heads 21Y, 21M, 21C, and 21K are provided in the image former 12 so that a color image can be formed with four color inks, but the number of inkjet heads may be other than four.
The mist collector 22 is a device that collects ink mist generated at the time when each of the inkjet heads 21Y, 21M, 21C, and 21K ejects ink. Most of the ink mist is caused to flow in the direction A by an airflow generated at the time when the conveyor drum 20 rotates. For this reason, the mist collector 22 is disposed on the downstream side of the inkjet head 21K in the rotation direction A of the conveyor drum 20.
The ultraviolet irradiator 23 is disposed on the downstream side of the mist collector 22 in the rotation direction A of the conveyor drum 20. The ultraviolet irradiator 23 irradiates the sheet of paper 15 conveyed by the rotation of the conveyor drum 20 with ultraviolet light thereby curing the ink on the sheet of paper 15.
The in-line sensor 24 is disposed on the downstream side of the ultraviolet irradiator 23 in the rotation direction A of the conveyor drum 20. The in-line sensor 24 is a sensor that inspects the color density, the inclination, and the like of an image formed on the sheet of paper 15 during conveyance by the conveyor drum 20. The reverser 25 is a part that reverses the front and back of the sheet of paper 15 in order to form images on both sides of the sheet of paper 15. The conveyor rollers 26a and 26b are rollers that convey the sheet of paper 15 after an image has been formed thereon toward the paper exit 13.
The paper exit 13 is provided with an exit tray 13a. In the exit tray 13a, there are stacked one on top of the other the sheets of paper 15 after an image has been formed thereon.
<Operation of Inkjet Recorder>
Next, the operation of the inkjet recorder 10 according to the present embodiment will be described.
First, the sheets of paper 15 stacked on the paper feed tray 11a of the paper feeder 11 are taken separately one by one in order from the top and supplied to the image former 12. The sheet of paper 15 supplied to the image former 12 is gripped at the tip of the sheet of paper 15 by a conveyance claw (not illustrated). The conveyance claw feeds the sheet of paper 15 to the conveyor drum 20 at a predetermined timing. As a result, the sheet of paper 15 is sucked on the outer peripheral surface of the conveyor drum 20, and the sheet of paper 15 is conveyed by the rotation of the conveyor drum 20.
On the other hand, the inkjet heads 21Y, 21M, 21C, and 21K each eject ink at each predetermined timing to the sheet of paper 15 conveyed by the rotation of the conveyor drum 20 thereby causing the ink to adhere on the sheet of paper 15. As a result, an image is formed on the sheet of paper 15. Thereafter, the sheet of paper 15 is irradiated with ultraviolet light by the ultraviolet irradiator 23. As a result, the ink that forms an image on the sheet of paper 15 is cured.
The sheet of paper 15 after an image has been formed thereon is then conveyed by the conveyor rollers 26a and 26b, thereby being sent to the paper exit 13. The sheet of paper 15 sent to the paper exit 13 is discharged one on top of the other on the exit tray 13a. Through the above operation, the sheet of paper 15 on which an image has been formed is obtained.
<Configuration of Mist Collector>
Next, a configuration of a mist collector included in an inkjet recorder according to an embodiment of the present invention will be described in detail.
As illustrated in
The four nozzles 31 are arranged side by side in the paper width direction X. The nozzle 31 is a hollow member. The nozzle 31 is disposed in a state of being inclined with respect to the horizontal plane. The nozzle 31 includes a suction port 33. The suction port 33 is an opening through which air containing ink mist is sucked. The suction port 33 has a rectangular shape elongated in the paper width direction X, that is, it is open horizontally. The suction ports 33 of the four nozzles 31 are adjacent to each other in the paper width direction X.
Here, in the length direction of the nozzle 31, a nozzle end on a side where the suction port 33 is provided is defined as a tip of the nozzle 31, and a nozzle end on a side opposite to the suction port 33 is defined as a rear end of the nozzle 31. In such a case, the tip of the nozzle 31 is disposed at a position lower than the rear end of the nozzle 31, and the suction port 33 is open obliquely downward. The shape of the nozzle 31 is made to be a horizontally long shape at the tip of the nozzle 31 and a vertically long shape at the rear end of the nozzle 31. That is, the longitudinal sectional shape of the nozzle 31 changes gradually from a horizontally long shape to a vertically long shape from the tip toward the rear end of the nozzle 31. A discharge port 34 is provided at the rear end of the nozzle 31. The discharge port 34 is an opening through which the air sucked from the suction port 33 is discharged. The discharge port 34 is open vertically.
As with the nozzles 31, the four cyclones 32 are arranged side by side in the paper width direction X. The cyclone 32 is disposed in a state of standing vertically. The discharge port 34 of the nozzle 31 is connected to the top of the cyclone 32. The cyclone 32 centrifuges the ink mist from the air taken in through the nozzle 31.
Furthermore, the mist collector 22 includes four filter housings 35 and a fan cover 36. The filter housing 35 is disposed above the cyclone 32. A filter (not illustrated) is detachably attached to the filter housing 35. The fan cover 36 is a cover that covers four exhaust fans (not illustrated). The four filter housings 35 and the four exhaust fans each are provided corresponding to the four cyclones 32. The exhaust fan is provided as an example of an airflow generator. The airflow generator generates an airflow on a path from the nozzle 31 through the cyclone 32 to the filter. The fan cover 36 is provided with four exhaust ports 37 corresponding to the four exhaust fans. The exhaust port 37 is an opening through which air is discharged to the outside the device by rotational driving of the exhaust fan.
Hereinafter, the configurations of the nozzle 31, the cyclone 32, the filter housing 35, and the exhaust fan will be described in more detail.
As illustrated in
The cyclone 32 includes an outer cylinder 41 and an inner cylinder 42. The outer cylinder 41 is preferably formed of a resin. The outer cylinder 41 is formed in a cylindrical shape. A top end 41a of the outer cylinder 41 is open, and a bottom end 41b of the outer cylinder 41 is closed. That is, the outer cylinder 41 is formed in a bottomed cylindrical shape. The top end 41a of the outer cylinder 41 is connected to the bottom end of the filter housing 35. The bottom end of the filter housing 35 is open so that air can be taken into the filter housing 35 from the top end of the cyclone 32. The filter 40 is housed in the filter housing 35. In a case where the air taken into the filter housing 35 from the cyclone 32 contains ink mist, the filter 40 captures this ink mist.
As illustrated in
The discharge port 34 of the nozzle 31 is connected to the outer cylinder 41. In more detail, an air induction 43 is formed on top of the outer cylinder 41. The air induction 43 is formed integrally with the outer cylinder 41. The air induction 43 is a part through which the air discharged from the discharge port 34 of the nozzle 31 is introduced into a space (hereinafter, also referred to as a “first space”) 45 between the outer cylinder 41 and the inner cylinder 42. As illustrated in the transverse sectional view of
The inner cylinder 42 is preferably formed of a resin. The inner cylinder 42 is formed in a cylindrical shape. The inner cylinder 42 is disposed concentrically with the outer cylinder 41. That is, the central axis of the inner cylinder 42 and the central axis of the outer cylinder 41 are located on the same axis. The inside of the inner cylinder 42 is a space (hereinafter, also referred to as a “second space”) 46. The second space 46 is surrounded by the peripheral wall 48 of the inner cylinder 42. The top end 42a of the inner cylinder 42 is open, and the bottom end 42b of the inner cylinder 42 is closed. The inner cylinder 42 is formed integrally with the filter housing by integral molding of a resin, for example. In this regard, however, the inner cylinder 42 may also be made as a separate body from the filter housing 35. The top end 42a of the inner cylinder 42 is open upward, and through this opening, the inside of the inner cylinder 42 and the inside of the filter housing 35 communicate with each other. The term “communication” refers to a state of being spatially connected.
As illustrated in
As illustrated in
In
The inner sheet 56 is positioned between the outer peripheral surface of the peripheral wall 44 and the outer sheet 58 in the radial direction of the inner cylinder 42. Note that, in FIG. the illustration of the outer sheet 58 is omitted on the left side of the drawing in order to make it easier to understand the structure of the second tube 52 of the inner cylinder 42, but the inner sheet 56 and the outer sheet 58 are both disposed over the entire circumference of the peripheral wall 44.
As illustrated in
In
Each of the intake holes 57 is a slit-shaped long hole elongated in the central axis direction of the inner cylinder 42. The intake hole 57 is a hole through which air is taken into the inner cylinder 42. The intake hole 57 is also a hole through which air is taken from the first space 45 into the second space 46. The intake hole 57 is formed in a slit shape so as to intersect the rotating (circling) directions of the first airflow 61 and of the second airflow 62 as illustrated in
In
As also illustrated in
The upper side 59a is disposed closer to the discharge port 34 of the nozzle 31 than the lower side 59b. The length of the upper side 59a is shorter than the length of the lower side 59b. The upper side 59a is disposed so as to be parallel to the direction of the first airflow formed in the first space 45. The lower side 59b is disposed so as to be perpendicular to the direction of the first airflow. The vertical side 59c is disposed along the central axis direction of the inner cylinder 42. The oblique side 59d is inclined with respect to the central axis direction of the inner cylinder 42. The protrusion 59 is connected to the other part of the outer sheet 58 in the area of the oblique side 59d. The protrusion 59 is bent outward from the area of the oblique side 59d as a boundary, and the protrusion 59 protrudes radially outward by this bending.
A gap 60 is formed around the protrusion 59. The gap 60 is formed along three sides (59a, 59b, 59c) of the protrusion 59. Furthermore, the gap 60 communicates with the intake hole 57 of the inner sheet 56. The dimension of the gap 60 formed along the upper side 59a gradually increases from the oblique side 59d toward the vertical side 59c in accordance with the bending angle of the protrusion 59. The dimension of the gap 60 formed along the lower side 59b also gradually increases from the oblique side 59d toward the vertical side 59c in accordance with the bending angle of the protrusion 59. The dimension of the gap 60 formed along the vertical side 59c increases little by little from the upper side 59a toward the lower side 59b.
<Operation of Mist Collector>
Next, there will be described the operation of the mist collector including the above configuration.
The mist collector 22 operates by the rotation of the exhaust fan 47 at the time of forming an image when ink is ejected from the inkjet heads 21Y, 21M, 21C, and 21K onto the sheet of paper 15 conveyed by the conveyor drum 20.
By the rotation of the exhaust fan 47, the air containing the ink mist is sucked from the suction port 33 of the nozzle 31 into the nozzle 31. The air sucked into the nozzle 31 flows from the bottom end toward the top end of the nozzle 31, and then is discharged from the discharge port 34. The air discharged from the discharge port 34 is taken into the outer cylinder 41 through the air induction 43 of the cyclone 32.
As illustrated in
In the present embodiment, in order to force the first airflow 61 and the second airflow 62 to rotate in mutually opposite directions, the protrusion 59 is disposed on the upstream side of the first airflow 61 in the intake hole 57. The stream of air on the inner peripheral side (in the vicinity of the inner cylinder 42) forming the first airflow 61 is blocked by the presence of the protrusion 59. Furthermore, the air whose stream is blocked by the protrusion 59 turns around the protrusion 59 and is introduced into the intake hole 57, and then is taken into the inner cylinder 42 through the intake hole 57. The direction of the air thus taken into the inner cylinder 42 is reversed by the turnaround described above. Therefore, a second airflow 62 whose rotating direction is opposite to that of the first airflow 61 is formed inside the inner cylinder 42.
As described above, the first airflow 61 and the second airflow 62 are formed inside the cyclone 32, so that the ink mist is separated from the air that has been taken into the cyclone 32 from the nozzle 31. Specifically, a part of the ink mist among the ink mist contained in the air that flows through the first space 45 is subjected to the centrifugal force by the first airflow 61 and strikes the peripheral wall 44 of the outer cylinder 41, thereby being separated (centrifuged) from the air. The ink mist thus separated then moves downward and accumulates at the bottom end 41b of the outer cylinder 41.
On the other hand, a part of the ink mist among the ink mist contained in the air flowing from the first space 45 toward the second space 46 strikes the peripheral wall 48 of the inner cylinder 42 or the edge of the intake hole 57 at the time of turning around the protrusion 59, thereby being separated from the air. The ink mist thus separated then moves downward and accumulates at the bottom end 42b of the inner cylinder 42.
A part of the ink mist, out of the ink mist contained in the air taken into the inner cylinder 42, moves upward with the second airflow 62 and is captured by the filter 40. The other ink mist is subjected to the centrifugal force by the second airflow 62 and strikes the peripheral wall 48 of the inner cylinder 42, thereby being separated (centrifuged) from the air.
Here, the ink mist contained in the air that is taken into the outer cylinder 41 through the air induction 43 is roughly classified depending on particle size of the droplets into three groups: large droplets of ink mist; medium droplets of ink mist; and small droplets of ink mist. Given that the velocity of the airflow is constant, the centrifugal force applied to the ink mist is proportional to the mass of the ink mist and is inversely proportional to the rotational radius of the airflow. Therefore, a stronger centrifugal force is applied to the ink mist having a large particle size.
As illustrated in
In the present embodiment, the medium droplet of ink mist M2 and the small droplet of ink mist M3 move with a stream of air that turns around the protrusion 59 and is about to flow from the first space 45 into the second space 46. At this time, the rotational radius of the airflow turning around the protrusion 59 becomes extremely smaller than the rotational radius of the first airflow 61. For example, in a case where the rotational radius of the first airflow 61 is about 30 mm, the rotational radius of the airflow turning around the protrusion 59 is about 1/10 thereof, that is, about 3 mm.
For this reason, a very strong centrifugal force is applied to the medium droplet of ink mist M2 and the small droplet of ink mist M3 at the time of turning around the protrusion 59. Furthermore, the medium droplet of ink mist M2 is subjected to a centrifugal force stronger than that of the small droplet of ink mist M3. As a result, the medium droplet of ink mist M2 strikes the inner cylinder 42 (or the edge of the intake hole 57) at the time of turning around the protrusion 59. Therefore, the medium droplet of ink mist M2 can be separated from the air taken into the second space 46 from the first space 45. The small droplet of ink mist M3 enters the filter 40 together with the second airflow 62, thereby captured by the filter 40. Therefore, the air exhausted from the exhaust port 37 becomes clean air after the ink mist having been removed by the cyclone 32 and the filter 40. The air entering the filter 40 becomes air from which not only the large droplets of ink mist M1 but also the medium droplets of ink mist M2 have been removed.
As illustrated in
As described above, the inkjet recorder 10 according to the present embodiment separates the ink mist from the air by the first airflow 61 formed in the first space 45 and forms the second airflow 62 in the second space 46 by the air taken into the inner cylinder 42 from the intake hole 57 thereby separating the ink mist from the air. As a result, inside the cyclone 32, ink mist with a small particle size, which would not be separated only by the first airflow 61, can also be separated from the air. Therefore, as compared with a case where the ink mist is centrifuged only by the airflow of the first airflow 61, the collection efficiency of the ink mist by the cyclone 32 can be enhanced. As a result, the amount of mist captured by the filter 40 per unit time can be reduced, and the exchange frequency of the filter 40 can be lessened.
In the present embodiment, the intake hole 57 is formed in a slit shape so as to intersect the direction of the first airflow 61. As a result, a wide opening area of the intake hole 57 can be ensured while maintaining a small rotational radius of the airflow entering the second space 46 from the first space 45. Therefore, a strong centrifugal force can be applied to the ink mist with a small particle size thereby separating the ink mist from the air. In addition, the flow path resistance at the time when air passes through the intake hole 57 can be kept small.
In the present embodiment, the protrusion 59 is formed in a vane shape. As a result, an influx of air from the sides (the upper side 59a and the lower side 59b) of the protrusion 59 can be suppressed at the time when air is taken into the second space 46 from the first space 45. For this reason, a lot more ink mist is allowed to strike the peripheral wall 48 of the inner cylinder 42 or the edge of the intake hole 57, thereby enabling to enhance the effect of centrifugal separation.
Furthermore, in the present embodiment, the upper side 59a closer to the discharge port 34, out of the upper side 59a and the lower side 59b of the protrusion 59, has a length shorter than the length of the lower side 59b farther away from the discharge port 34. As a result, there can be suppressed an influx of air from the gap 60 of the upper side 59a into the inner cylinder 42.
In the present embodiment, the upper side 59a closer to the discharge port 34, out of the upper side 59a and the lower side 59b of the protrusion 59, has a smaller angle of inclination with respect to the first airflow 61 than that of the lower side 59b farther away from the discharge port 34. As a result, there can be suppressed an influx of air from the gap 60 of the upper side 59a into the inner cylinder 42.
In the present embodiment, the upper side 59a that is close to the discharge port 34 is disposed so as to be parallel to the direction of the first airflow 61 (see
In the present embodiment, the lower side 59b that is far from the discharge port 34 is disposed so as to be perpendicular to the direction of the first airflow 61 (see
In the present embodiment, the position of the intake hole 57 and the position of the discharge port 34 are shifted from each other so as not to overlap each other in the central axis direction of the outer cylinder 41. As a result, there can be provided a region where the ink mist is centrifuged by the first airflow 61 formed in the first space 45.
In the present embodiment, the inner cylinder 42 is provided with a plurality of intake holes 57. As a result, the flow path resistance can be kept small as compared with a case where single intake hole 57 is provided in the inner cylinder 42.
In the present embodiment, there is adopted a configuration in which the plurality of nozzles 31 and the plurality of cyclones 32 both are arranged side by side in the paper width direction X. As a result, the suction power of air can be made uniform in the paper width direction X.
Note that in the present embodiment, the inner sheet 56 and the outer sheet 58 are provided on the second tube 52 of the inner cylinder 42, but there may be adopted a configuration in which the inner sheet 56 and/or the outer sheet 58 is not provided.
For instance, a configuration in which the intake hole 57 is formed directly in the peripheral wall 48 forming the second tube 52 can be conceived as a configuration in which neither the inner sheet 56 nor the outer sheet 58 is provided in the second tube 52. In the case of adapting this configuration, the first airflow 61 formed in the first space 45 and the second airflow 62 formed in the second space 46 become airflows rotating in the same direction. A part of the ink mist among the ink mist contained in the air about to flow into the second space 46 from the first space 45 strikes the edge of the intake hole 57 of the peripheral wall 48 thereby separated from the air. In this respect, the situation is the same in a case where only the inner sheet 56 is disposed on the second tube 52 of the inner cylinder 42.
In a case of adapting a configuration in which the inner sheet 56 is provided on the second tube 52, the inner sheet 56 is extremely thin compared to the peripheral wall 48, and hence the ink mist is less likely to accumulate at the edge of the intake hole 57 in a case where the ink mist strikes the edge of the intake hole 57, and even if the ink mist accumulates, a mass of the ink mist can be peeled off by using the power of the air (wind pressure or the like) passing through the intake hole 57.
In the case of adapting the configuration in which the inner sheet 56 and the outer sheet 58 are provided on the second tube 52, the air is allowed to turn around by the protrusion 59, whereby the rotational radius of the airflow can be reduced, and a stronger centrifugal force can be applied to the ink mist. Therefore, the ink mist having a small particle size that would not be separated only by the first airflow 61 can be more reliably separated.
In the above-described embodiments, there has been described with an example of the inkjet recorder 10 that forms an image by ejecting ink from each of the inkjet heads 21Y, 21M, 21C, and 21K onto the sheet of paper 15 conveyed with being wound around the conveyor drum but the present invention is not limited thereto. For example, the present invention is also applicable to an inkjet recorder that forms an image by ejecting ink from each inkjet head onto a sheet of paper horizontally conveyed along a platen (not illustrated).
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-087551 | May 2022 | JP | national |
