JP5562016B2 - Printing device - Google Patents

Description

  The present invention relates to an inkjet printing apparatus.

  When ink is ejected from an ink jet print head, fine mist-like ink particles (ink mist) are generated around the ink droplets. In addition, when ink droplets land on the sheet, not all ink droplets instantaneously land on the sheet, but some of the ink droplets bounce off the surface of the sheet due to impact of the landing, etc. Ink mist may be generated by scattering.

  The minute ink mist is scattered in the printing apparatus and adheres to and stains the components and members inside the printing apparatus. This contamination may cause a decrease in recording quality and a device failure. For example, dirt may adhere to the transport mechanism to cause the sheet to become dirty, dirt to the optical sensor may cause detection failure, and carriage drive resistance may increase to cause operation failure.

  In order to suppress scattering of ink mist, a configuration is known in which a gas containing ink mist is sucked with a fan and discharged to the outside of the apparatus through a duct. For example, in the apparatus disclosed in Patent Document 1, in order to increase the separation efficiency of ink mist mixed with the gas sucked by the fan, the gas is passed through a duct provided with a large number of ribs (projections) inside. ing. Part of the ink mist mixed with the gas adheres to the rib surface and liquefies. Fine particles in the gas that cannot be removed by the ribs are trapped by a filter provided at the duct outlet.

JP 2005-238784 A

  The device disclosed in Patent Document 1 is provided with a filter and a duct on the downstream side (exhaust side) of the fan. That is, air is fed from the upstream of the duct with a fan and pushed out from the outlet of the duct. Since there is nothing to trap ink mist upstream of the fan, a large amount of ink mist generated from the periphery of the print head enters the fan. For this reason, ink mist accumulates in the fan as it is used in the apparatus and is liable to be liquefied or fixed, and the performance of the fan deteriorates quickly. In other words, frequent maintenance work is required.

  In addition, the device disclosed in Patent Document 1 has a turbulent flow in the vicinity of the outlet of the fan in which the rib is formed, and the flow velocity distribution of the airflow is not uniform. If the rib is not arranged at a position where the flow velocity is as high as possible, the effect of trapping ink mist is small. For this reason, it is difficult to realize a highly efficient and small mist collecting mechanism with a small degree of freedom in arrangement of the ribs.

  The present invention has been made based on recognition of the above problems. An object of the present invention is to provide a printing apparatus having a small and highly efficient ink mist collecting mechanism that requires less maintenance.

A printing apparatus of the present invention that solves the above-described problem includes a printing unit having a print head that discharges ink, a duct and a fan, and the fan rotates and gas is passed from the space near the printing unit through the duct. A suction mechanism for suctioning, wherein the duct includes a non-linear flow path between the inlet and the outlet, the flow path at least partially surrounding one or both of the inlet and the outlet And a plurality of protrusions for trapping ink mist contained in the gas are formed on at least a part of the outer peripheral side of the non-linear flow path. .

  According to the present invention, the ink is included in the gas by the plurality of protrusions formed on at least a part of the inside of the duct, including the suction mechanism that sucks the gas from the space near the print unit through the duct as the fan rotates. Trap the mist. For this reason, the ink mist contained in the gas can be effectively trapped, and the probability of occurrence of a fan failure due to the ink mist can be reduced. Therefore, it is possible to provide a printing apparatus having a small and highly efficient ink mist collecting mechanism that requires less maintenance.

Perspective view of printing device Top view of printing device Side view of printing device Cross section of suction mechanism Airflow vector diagram by airflow analysis of duct Comparison of configurations with and without duct ribs List of results of determining the ink mist trap rate (%) Detailed view of the duct of the second embodiment Detailed view of the duct of the third embodiment

  Hereinafter, an embodiment of a printing apparatus using an inkjet method will be described. As the inkjet method, a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS element, or the like can be adopted. The printing apparatus of the present invention can be widely applied to apparatuses having a printing function, such as a printer, a multifunction printer, a copying machine, a facsimile machine, and various device manufacturing apparatuses.

  1 is a perspective view of the entire printing apparatus according to the first embodiment, FIG. 2 is a top view of FIG. 1, and FIG. 3 is a side view of FIG. The printing apparatus 1 includes a housing 2, and the housing 2 includes a printing unit, a suction mechanism including a duct, other mechanisms, and a control unit. The sheet supply unit 3 holds a plurality of sheets S and supplies them one by one to the printing unit.

  The print unit includes a print head 4, a carriage 5, a drive motor 6 for the carriage 5, and a platen 7. The print head 4 is integrally provided with a nozzle portion for ejecting ink and an ink tank. An ink tank may be installed at a position away from the printing apparatus 1 and ink may be supplied to the nozzle portion of the print head 4 via a tube. The carriage 5 carries the print head 4 and reciprocates in the main scanning direction. As a drive mechanism for the carriage 5, there are provided a drive motor 6 and a transmission mechanism including a pulley and a belt for converting the rotation of the drive motor 5 into a straight motion and moving the carriage straight.

  Recording is performed by ejecting ink from the print head 4 toward the sheet S. The apparatus of this embodiment forms a two-dimensional image on the sheet S by alternately carrying the sheet S in the sub-scanning direction (Y direction) and reciprocating the carriage 5 in the main scanning direction (X direction). A so-called serial printer. The present invention is not limited to a serial printer, and can also be applied to a line printer that forms a two-dimensional image while moving a sheet with respect to a fixed line print head.

  The suction mechanism includes a suction portion provided on the side surface of the housing 2 and a circulation duct 33. The suction part has a fan 30 and a main duct 31. The fan 30 rotates to generate an air current, and for example, a highly efficient sirocco fan is suitable. A main duct 31 is provided between the space of the print unit and the fan 30. An upper portion of the main duct 31 is covered with a duct cover 32 to form a sealed gas flow path. The gas (air) in the space A in the vicinity of the print unit contains a lot of ink mist (fine ink particles floating in the air) generated when ink is ejected because the print head 4 is close. The gas containing a large amount of ink mist is drawn from the duct inlet 31a1 of the main duct 31 by the rotation of the fan 30, and is sucked into the main duct 31 (arrow B). The gas that has passed through the flow path of the main duct 31 is sucked into the fan 30 from the duct outlet 31a2. And it is discharged | emitted from the discharge port 30b of the fan 30. FIG. A suction port 33a which is one end of the circulation duct 33 is connected to the discharge port 30b. The circulation duct 33 is covered with a duct cover and is a sealed gas flow path. The circulation duct 33 forms a single sealed gas path from the suction port 33a to the discharge port 33c via the intermediate portion 33b that wraps around the outside (front surface portion) of the housing 2. A discharge port 33 c that is the other end of the circulation duct 33 is connected to the opening of the other side surface of the housing 2. In the middle of the flow path of the circulation duct 33 (here, in the vicinity of the discharge port 33c), a filter 33d is provided for filtering foreign matter such as ink mist and dust remaining in the gas. The gas (arrow C) discharged from the duct outlet 31a2 passes through the circulation duct 33 (arrow D, arrow E) and is reintroduced in the vicinity of the print portion (arrow F).

  The controller 9 is a controller that performs various controls of the entire printing apparatus, and includes a CPU 9, a memory 9b, and various I / O interfaces. The control unit 9 may be built in the housing 2 or may be externally attached. In the case of external attachment, the control unit 9 may be a computer in which control software is incorporated in a computer connected to the printer.

  Next, a more detailed structure and operation of the suction mechanism will be described. FIG. 4 is a cross-sectional view showing the internal structure of the main duct 31 of the suction mechanism. For ease of explanation, the drawing shows the internal state with the duct cover 32 removed.

  The gas sucked from the duct inlet 31a1 of the main duct 31 (arrow B) is introduced into the flow path of the main duct 31 (arrow G). The introduced gas flows along the non-linear flow path (arrow H, arrow J, arrow K). And it is discharged | emitted from the duct exit 31a2 (arrow L), and is discharged | emitted to the circulation duct 33 through the fan 30. FIG. When viewed in cross section, most of the flow path of the main duct 31 is non-linear. The flow path from the duct inlet 31a1 to the duct outlet 31a2 has a cross-sectional shape of a non-linear curve (substantially arc) at least partially surrounding the duct outlet 31a2 around the duct outlet 31a2. When viewed in the cross section of FIG. 4, the arc-shaped portion of the flow path is composed of a duct outer peripheral wall 31 b on the outer peripheral side (long path distance side) and a duct inner peripheral wall 31 c on the inner peripheral side (short path distance side). The sandwiched space is a flow path. In the direction perpendicular to the paper surface of FIG. 4, the flow path is closed by a flat plate on the back side, and the front side is closed by a flat duct cover 32 (not shown in FIG. 4). The cross-sectional shape of the flow path along the direction is a rectangular shape. In this example, the rectangular cross-sectional shape is used for ease of manufacturing, but the flow path may have a cross-sectional shape of other shapes (circular, polygonal, or other arbitrary shapes).

  A plurality of protrusions for trapping ink mist contained in the gas are arranged at substantially equal pitches along the gas flow direction inside the main duct 31, here on the surface of the duct outer peripheral wall 31 b which is a part of the inner surface. It is formed with. That is, among the four sides of the rectangular cross-sectional shape of the flow path, a number of protrusions are provided on one side having the longest path length. The protrusions are duct ribs 31d made of straight walls having a predetermined height, and a large number of protrusions are provided along the flow path. A duct pocket 31e is formed between the adjacent duct ribs 31d. When the gas flows through the section indicated by the arrow J in the flow path, local vortices I1 to I9 are generated in the small spaces of the plurality of duct pockets 31e. Since the gas that has entered the small space of the duct pocket 31e remains swirled for a relatively long period of time, most of the ink mist contained in the gas has three surfaces of the duct pocket 31e (the surfaces of the front and rear duct ribs 31d and the surface of the duct outer peripheral wall 31b). And collide with the pocket surface 31f. The amount of ink mist in the gas decreases by the amount attached. By this action, the ink mist gradually decreases while the gas passes through the flow path. That is, the plurality of duct ribs 31 function to effectively trap ink mist contained in the flowing gas. The gas in which the ink mist has decreased in the region of arrow J flows in the directions of arrows K and L and is discharged from the duct outlet 31a2. The discharged clean gas passes through the circulation duct 33 and is supplied again to the printing unit inside the housing 2.

  The duct rib 31d has the highest ink mist trapping efficiency when provided on the outer peripheral wall 31b. This is because the arc-shaped outer periphery side duct pocket 31e is more likely to generate a local vortex because airflow is more likely to flow therethrough. Furthermore, the outer peripheral wall 31b can be provided with more duct ribs 31d as much as the distance is longer than others. The greater the number of duct ribs, the greater the chance of trapping ink mist. The duct rib 31d may be further formed on one or more of the other inner wall surfaces of the main duct 31, for example, the duct inner peripheral wall 31b, the back side flat plate, and the front side flat plate (duct cover 32). Further, a plurality of protrusions such as a plurality of ribs may be provided along the flow path at a position floating inside the main duct 31 from the inner side surface of the duct. Further, the duct rib 31d may be formed not only in the region indicated by the arrow J but also in the region indicated by the arrow H in the foreground or in the region indicated by the arrow G that is a linear path on the near side. With the above configuration, the main duct 31 can increase the trap efficiency of ink mist even if the flow path from the duct inlet 31a1 to the duct outlet 31a2 is short.

  The gas flow in the flow path of the main duct 31 is counterclockwise in FIG. The rotation direction (arrow M) of the blades of the fan 30 (sirocco fan) is also counterclockwise, and the rotation directions of both are the same. That is, the rotation direction of the fan and the rotation direction of the gas flow along the non-linear flow path coincide. The fan 30 is a high-efficiency sirocco fan, and a suction airflow swirling spirally is formed in the vicinity of the duct outlet 31a2. Since the swirl direction of the air flow coincides with the rotation direction of the air flow in the channel just before the air flow is introduced, a smooth gas flow can be obtained without generating turbulence or stagnation. Therefore, the ink mist is collected with higher efficiency. Since the duct outlet 31a2 (the outlet of the fan 30) and the fan 30 are arranged on the same axis, a smooth gas flow can be obtained without generating turbulence or stagnation.

  When a large number of ink mists adhere to the pocket surface 31f, the ink liquefies. The liquefied ink gradually accumulates and falls in the direction of gravity. In order to absorb the dropped ink, an ink absorber 34 (preferably a porous body capable of absorbing more liquid) is provided at the bottom of the main duct 31 to absorb ink.

  FIG. 5 is an airflow vector diagram by airflow analysis in the main duct 31. It is the result of the airflow analysis by simulation. FIG. 5A is a diagram showing the air flow in the main duct 31 by the suction of the fan 30 as a vector diagram, and FIG. 5B is an enlarged view of one duct pocket 31e in FIG. 5A. It is. It can be seen that the airflow is swirling in the small space of the duct pocket 31e. Since the plurality of duct ribs 31d are formed at substantially equal pitches, the state of vortices generated in each duct pocket is similar.

  With the above configuration, since the ink mist generated in the printing unit during printing is sucked by the suction mechanism provided near the mist generation source, the ink mist is effectively diffused into the housing 2 effectively. It is suppressed. The ink mist slightly diffused in the machine is gradually collected if the suction mechanism continues to operate even during non-printing, so that the dirt in the machine due to the ink mist is suppressed.

  In order to show the superiority of this embodiment, the trap efficiency of the ink mist is examined using a comparative example. FIG. 6A shows a main duct having duct ribs as described above. FIG. 6B shows a main duct having a configuration in which the duct rib is omitted as a comparative example. The other shape and configuration are the same as those in FIG.

The ink mist trap rate is determined by the following procedure for both of them that differ depending on the presence or absence of the duct rib. (1) The trap rate in the area where the fan and duct are combined is measured. In this method, the amount of ink mist is measured at each of the inlet (fan suction port) and the outlet (duct discharge port), and the trap rate is calculated using these measurement results. For measuring the ink mist amount, an APS (Aerodynamic Particle Sizer) measuring device is used to determine the ink mist amount contained in the gas. When the ink mist amount M1 at the inlet and the ink mist amount M2 at the outlet are set, the trap rate T of the ink mist between the inlet and the outlet is calculated from the following equation 1.
Trap rate T (%) = (1− (M2 / M1)) × 100 (Formula 1)
T = 100% when all the ink mist is captured, and T = 0% when the ink mist is not captured at all.

  For comparison, (2) the trap rate in the area of the duct alone and (3) the trap rate in the area of the fan alone are obtained in the same manner. A single duct measures the amount of ink mist at each of the inlet (duct inlet) and outlet (duct outlet). A single fan measures the amount of ink mist at each of the inlet (fan suction port) and the outlet (fan discharge port). Then, the trap rate is calculated from Equation 1 using these measurement results.

  FIG. 7 summarizes the results of obtaining the trap rate (%) under each condition. In FIG. 6A in which the duct rib is provided, the trap rate is about 68%, whereas in the configuration in FIG. 6B without the duct rib, the trap rate is about 53%. That is, 15% of the difference is the effect of the duct rib. Further, comparing the trap rates of the ducts alone, it can be seen that when the duct ribs are present, the trap rate is about 32%, whereas when there is no duct ribs, the trap rate is about 0%, and almost no traps are made. In addition, the trap rate measured by a single fan is about 53%. As described above, it can be seen that the provision of the duct ribs improves the ink mist trap rate. Moreover, it turns out that a trap rate increases further by a synergistic effect by combining with a fan.

  As described above, according to the first embodiment, the suction mechanism includes the main duct 31 and the fan 30, and the fan 30 rotates and sucks gas from the space near the print unit through the main duct 31. The main duct 31 includes a non-linear flow path, and a plurality of duct ribs for trapping ink mist contained in the gas are provided in the non-linear flow path in at least a part of the inside of the main duct. Are formed along. The flow path of the main duct 31 has a non-linear cross-sectional shape that at least partially surrounds the duct outlet (the duct outlet 31a2), and at least a part of the non-linear flow path on the outer peripheral side. Duct ribs are formed. For this reason, the ink mist floating in the gas can be efficiently captured and recovered, and the ink mist is prevented from adhering to the inside of the apparatus and becoming dirty. For example, it is possible to prevent the conveyance mechanism from being contaminated and causing the sheet to become contaminated, the optical sensor to be contaminated and causing a detection failure, and the carriage driving resistance to increase and cause an operation failure.

  In addition, since the fan is arranged downstream of the flow in the suction mechanism, the ink mist entering the suction mechanism is reduced by the amount trapped in the main duct. For this reason, it is possible to reduce the probability of occurrence of a failure such as the ink mist adhering to the suction mechanism and the working part being fixed. In other words, the maintenance frequency can be reduced. Furthermore, since the burden on the filter 33d provided in the circulation duct is reduced, the maintenance frequency of the filter 33d can also be reduced. Furthermore, since the suction mechanism has a fan disposed downstream of the main duct, the gas sucked into the main duct from the print unit is not disturbed by the fan in the vicinity of the duct inlet, and the flow velocity distribution is greatly uneven ( Disturbance does not occur. Therefore, the degree of freedom of arrangement of the duct ribs is high, and a highly efficient and compact device configuration is possible.

  When a sirocco fan is used, a swirling airflow is generated downstream of the fan. Since the rotation direction of the flow path of the main duct coincides with the rotation direction of the sirocco fan, a smooth gas flow can be achieved without generating turbulence or stagnation. Therefore, the ink mist is collected with higher efficiency. In addition, since the main duct and the fan are arranged on the same axis, a smooth gas flow can be obtained without generating turbulence or stagnation.

<Embodiment 2>
The second embodiment of the present invention will be specifically described. Except for the shape and structure of the main duct, the second embodiment is the same as the first embodiment, and thus the repeated description is omitted. FIG. 8 is a cross-sectional view showing the internal structure of the main duct 41 of the suction mechanism. For ease of explanation, the drawing shows the internal state with the duct cover removed.

  In FIG. 8, the gas sucked from the duct inlet 41 a 1 of the main duct 41 (arrow N) is introduced into the flow path of the main duct 41. The introduced gas flows along the non-linear flow path (arrow O, arrow P, arrow Q, arrow R, arrow S). Then, the air is sucked into the fan 40 from the duct outlet 41 a 2 of the main duct 41. Then, the air is discharged from the discharge port of the fan 40 to the circulation duct 44. When viewed in cross section, most of the flow path of the main duct 41 is non-linear. The first half of the flow path from the duct inlet 41a1 to the duct outlet 41a2 has a substantially circular cross-sectional shape surrounding the duct inlet 41a1 around the center. The latter half of the subsequent flow path has a substantially circular cross-sectional shape surrounding the duct outlet 41a2 around the center. When viewed in the cross section of FIG. 8, the arc-shaped portion of the flow path is a flow path that is sandwiched between the duct outer peripheral wall 41b on the outer peripheral side of the arc and the duct inner peripheral wall 41c on the inner peripheral side. As in the first embodiment, the flow path is closed with a flat plate on the back side, and the front side is closed with a flat duct cover (not shown). Although the cross-sectional shape of the flow path along the gas flow direction is a rectangular shape, it may be a flow path having a cross-sectional shape of other shapes (circular, polygonal, or any other shape).

  On the surface of the duct outer peripheral wall 41b, a plurality of duct ribs 41d, which are projections for trapping ink mist, are gas in the first half (section indicated by arrows O to P) and the second half (section indicated by arrows R) of the flow path. Are formed at substantially equal pitches along the flow direction. A duct pocket 41e is formed between the adjacent duct ribs 41d. When the gas flows through the sections indicated by arrows O and P in the flow path, local vortexes T1 to T15 of local airflow are generated in the small spaces of the plurality of duct pockets 41e. When the gas flows through the section indicated by the arrow R in the flow path, local vortices T16 to T21 are generated in the small spaces of the plurality of duct pockets 41g. As in the previous embodiment, the gas that has entered the small space of the duct pocket remains swirled for a relatively long time, so that most of the ink mist contained in the gas collides with and adheres to the wall surfaces 41f and 41h of the duct pocket. The amount of ink mist in the gas decreases by the amount attached. By this action, the ink mist gradually decreases while the gas passes through the flow path. The gas with reduced ink mist flows in the direction of arrow S and is discharged from the main duct 41 through the duct outlet 41a2. The discharged clean gas passes through the circulation duct 33 and is supplied again to the printing unit inside the housing 2.

  The gas flow in the flow path of the main duct 41 is counterclockwise in FIG. The rotation direction (arrow M) of the blades of the fan 40 (sirocco fan) is also counterclockwise, and the rotation directions of both are the same. That is, the rotation direction of the fan and the rotation direction of the gas flow along the non-linear flow path coincide. For this reason, as mentioned above, it becomes a smooth gas flow without generating turbulent flow or stagnation. Therefore, the ink mist is collected with higher efficiency. Since the duct outlet 41a2 and the fan 40 are arranged on the same axis, a smooth gas flow can be obtained without generating turbulence or stagnation.

  The ink mist adhering to the duct pocket wall surfaces 41f and 41h is liquefied and falls in the direction of gravity. In order to absorb the dropped ink, an ink absorber 44 that absorbs ink is provided at the bottom of the main duct 41 (the bottom of the section indicated by the arrow Q).

  Thus, in Embodiment 2, the flow path of the main duct 41 has a non-linear cross-sectional shape that at least partially surrounds both the inlet (duct inlet 41a1) and the outlet (duct outlet 41a2) of the duct. Yes. And the duct rib is formed in a part of at least outer peripheral side of a non-linear flow path. According to the second embodiment, it is possible to obtain the same effects as those of the above-described embodiment.

<Embodiment 3>
The second embodiment of the present invention will be specifically described. Except for the shape and structure of the main duct, this embodiment is the same as the first embodiment. FIG. 9 is a cross-sectional view showing the internal structure of the main duct 51 of the suction mechanism. For ease of explanation, the drawing shows the internal state with the duct cover removed.

  In FIG. 9, the gas (arrow V) sucked from the duct inlet 51 a 1 of the main duct 51 is introduced into the flow path of the main duct 51. The introduced gas flows along the non-linear flow path (arrow W, arrow Y). Then, the air is sucked into the fan 50 from the duct outlet 51 a 2 of the main duct 51 and discharged to the circulation duct 33. When viewed in cross section, most of the flow path of the main duct 51 is non-linear. The flow path from the duct inlet 51a1 to the duct outlet suction 51a2 has a substantially circular cross-sectional shape surrounding the duct inlet 51a1 of the main duct around the center. When viewed in the cross section of FIG. 9, the arc-shaped portion of the flow path is a flow path sandwiched between the outer peripheral duct outer peripheral wall 51 b and the inner peripheral duct inner peripheral wall 51 c.

  A plurality of duct ribs 51d, which are protrusions for trapping ink mist, are formed on the surface of the duct outer peripheral wall 51b at substantially equal pitches along the gas flow direction. Duct pockets 51e are formed between the adjacent duct ribs 51d, and local airflow vortices X1 to X7 are generated in the respective small spaces. As in the previous embodiment, the gas that has entered the small space of the duct pocket remains swirled for a relatively long time, so that most of the ink mist contained in the gas collides with and adheres to the wall surface 51f of the duct pocket. An ink absorber 54 that absorbs ink is provided at the bottom of the main duct 51 in order to absorb the ink that has fallen on the wall surface 51f.

  Thus, in Embodiment 3, the flow path of the main duct 51 has a non-linear cross-sectional shape that at least partially surrounds the duct inlet (duct inlet 51a1), and at least the non-linear flow path Duct ribs are formed on part of the outer peripheral side. According to the third embodiment, it is possible to obtain the same operational effects as the above-described embodiment.

30 Fan 31 Main duct 31a1 Duct inlet 31a2 Duct outlet 31b Duct outer wall 31c Duct inner wall 31d Duct rib (protrusion)
31e Duct pocket 31f Pocket surface 32 Duct cover 33 Circulating duct 34 Ink absorber

Claims (7)

A print unit having a print head for ejecting ink;
A suction mechanism having a duct and a fan, wherein the fan rotates and sucks gas from the space near the print unit through the duct;
With
The duct includes a non-linear channel between an inlet and an outlet, the channel having a non-linear cross-sectional shape at least partially surrounding one or both of the inlet and the outlet;
A printing apparatus, wherein a plurality of protrusions for trapping ink mist contained in a gas are formed on at least a part of the non-linear flow path on the outer peripheral side . And rotational direction of the fan, the the rotation direction of the non-linear flow path to the gas along the flow, characterized in that the matching, printing apparatus according to claim 1. The printing apparatus according to claim 2 , wherein the fan is a sirocco fan. Wherein the plurality of protrusions, characterized in that it has a plurality of ribs formed on the inner surface of the duct at substantially the same pitch along the gas flow direction, printing according to any one of claims 1 3 apparatus. Wherein the duct ink absorber is provided, characterized in that ink the trapped ink mist projections are produced by liquefaction was to be absorbed in the ink absorber 4 from claim 1 The printing apparatus according to any one of the above. The gas discharged by the fan from the duct, characterized by comprising a circulation duct for re-introduction into the vicinity of the printing unit, the printing apparatus according to any one of claims 1 to 5. The printing apparatus according to claim 6 , wherein the circulation duct is provided with a filter for filtering foreign substances in the gas.

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