Drying apparatus and printing apparatus

Abstract

In a drying apparatus and a printing apparatus that heats and dries a printed medium after printing, a protective function is provided that operates effectively even when there are two modes with different amounts of heat. [Solution] The drying apparatus and printing apparatus according to the present invention include a first mode in which the output light amount from the light source is large and the shielding rate for light directed from the light source to the printing medium is low, and a second mode in which the output light amount from the light source is smaller and the shielding rate for light directed from the light source to the printing medium is high. The two modes can be made to coexist by changing the way in which the light emitted from the light source is incident on the current blocking section and by making the sensitivity characteristics that represent the correlation between the output light amount of the light source and the temperature of the current blocking element different.

Description

Technical Field

[0001] The present invention relates to a drying device for thermally drying a printed medium after printing and a printing device including the same.

Background Art

[0002] In a printing technique for printing on a printing medium using a recording material such as ink, it is necessary to quickly dry the printing medium to which the recording material adheres. For this reason, a printing device or a printing system that performs such printing is provided with a drying device for heating and drying the printing medium. For example, in Patent Document 1 previously disclosed by the applicant of the present application, corresponding to the fact that the conveyance speed of continuous paper as a printing medium can be changed, a mode of applying a large amount of heat to the printing medium and a mode of applying a smaller amount of heat than this are executable. A printing device is disclosed.

[0003] In this technique, a shutter that can be opened and closed is provided between a light source that emits light including infrared rays and the printing medium. Then, by increasing the output light amount from the light source and opening the shutter, high-intensity light emitted from the light source is directly incident on the surface of the printing medium, and thus it becomes possible to apply a large amount of heat to the printing medium in a short time. On the other hand, by making the output light amount from the light source smaller and closing the shutter, instead of directly incident light, the printing medium can be gently heated through the heated air.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Such printing apparatuses are naturally equipped with control means to appropriately control the amount of light output from the light source according to the purpose. In addition, it is desirable to provide a protective mechanism to prevent excessive heat generation in the event of a control malfunction. For example, a current interruption element can be inserted into the power supply path to the light source, and the power supply path can be shut off when the temperature rise exceeds expectations.

[0006] A thermostat is a suitable example of such a current interruption element. A thermostat has the function of forcibly interrupting the current path autonomously, without control, when the temperature exceeds its inherent interruption temperature. Therefore, it is expected to be an effective measure to prepare for such abnormalities.

[0007] However, in a configuration having two modes with different light output levels as described above, there are issues to consider regarding the use of the current interruption element. Specifically, if the placement and interruption temperature of the current interruption element are set so that the protection mechanism operates effectively even in the mode with low light output, there is a risk that the current interruption element will over-operate in the other mode where the light output is higher and the temperature rises more. Conversely, if the settings are made according to the mode with higher light output, the element may not operate properly in the mode with lower light output. The most problematic of these is that the protection function may not work when needed.

[0008] Patent Document 1 makes no mention of such protection functions in the event of an abnormality, and therefore does not describe the installation of current interruption elements corresponding to the two modes described above. Thus, in printing apparatuses and drying apparatuses for which there are two modes with different output light quantities from a light source, there is a need to establish a technology that can effectively operate the protection function while maintaining compatibility between these modes.

[0009] This invention has been made in view of the above problems, and aims to provide a protective function that works effectively even when there are two modes with different amounts of heat in a drying apparatus and a printing apparatus that heat and dry a printing medium after printing. [Means for solving the problem]

[0010] One aspect of this invention is a drying apparatus for drying a printing medium after printing, comprising: a light source that receives an electric current supply and emits light toward the printing medium; a current interruption unit including a current interruption element that interrupts the current supplied to the light source when the temperature rises above a predetermined interruption temperature; a sensitivity changing unit that changes the sensitivity characteristics showing the correlation between the amount of output light from the light source and the amount of temperature rise of the current interruption element by changing the way in which light is incident from the light source toward the current interruption unit; a light shielding unit disposed between the light source and the printing medium and capable of changing the shielding rate for the light from the light source toward the printing medium; and a control unit that selectively executes a first mode and a second mode in which the output light amount and the shielding rate are different from each other.

[0011] In the first mode, the output light intensity is greater and the shielding ratio is smaller than in the second mode. Furthermore, the sensitivity changing unit makes the sensitivity characteristics different between the first mode and the second mode, so that in both the first and second modes, the temperature of the current interruption element is below the interruption temperature.

[0012] In the invention configured in this way, by executing the first mode, light emitted from the light source is directly incident on the printing medium, and the rapid drying of the printing medium can be promoted by high-intensity radiant heat. In contrast, in the second mode, the amount of light output from the light source is smaller, but the light shielding rate is higher, so the amount of heat supplied to the printing medium is less than in the first mode.

[0013] As described above, a protection mechanism is needed that can balance a first mode in which the temperature rise is large and a second mode in which the temperature rise is smaller, while avoiding abnormal temperature increases due to excessive current, for example. In this invention, protection against excessive heat generation is achieved by using a current interruption element that forcibly interrupts the current supplied to the light source when the temperature rises to a predetermined cutoff temperature.

[0014] Specifically, the sensitivity changing unit alters the way light is incident on the current interruption unit, thereby changing the sensitivity characteristics of the current interruption element to the output light intensity of the light source, that is, the correlation between the output light intensity of the light source and the temperature rise of the current interruption element. Different sensitivity characteristics are then applied between the first mode and the second mode. For this reason, even if the output light intensity of the light source is the same in the first mode and the second mode, the temperature of the current interruption element heated by that light will not be the same.

[0015] By utilizing this principle, if the temperature of the current-cutting element does not reach the cutoff temperature when there is no malfunction in either the first or second mode, the problem of excessive protection function activation can be avoided in either mode. On the other hand, in either mode, if there is excessive heat generation, the temperature of the current-cutting element will rise further, and when it eventually reaches the cutoff temperature, the current supplied to the light source will be forcibly cut off. This stops the emission of light from the light source, and an abnormal temperature rise is avoided.

[0016] In this way, in both the first and second modes, where the amount of heat generated from the light source differs from that of the first mode, it becomes possible to suppress excessive intervention by the protective function during normal operation while still providing appropriate protection against excessive temperature rises.

[0017] Another aspect of the present invention is a printing apparatus including a conveyance unit that conveys a printing medium, a printing unit that performs printing on the printing medium to be conveyed, and a drying unit provided downstream of the printing unit in the conveyance path of the printing medium and having the same configuration as the above-described drying device. In the invention configured as described above, since the excellent effects described above can be obtained in the drying unit that dries the printed printing medium, it is possible to satisfactorily dry the printing medium while avoiding troubles due to abnormal heat generation.

Advantages of the Invention

[0018] As described above, according to the present invention, for each of two modes with different heat generation amounts from the light source, by varying the sensitivity characteristics of the temperature rise with respect to the output light amount of the light source, it is possible to provide a protection function capable of suppressing excessive operation and avoiding abnormal temperature rise.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic configuration diagram showing the whole printing apparatus according to the present invention. [Figure 2] It is a diagram showing a drying mechanism included in this printing apparatus. [Figure 3] It is a diagram showing a main part of this drying mechanism. [Figure 4] It is a diagram showing an internal structure of a heating unit. [Figure 5] It is a diagram for explaining two modes realized by a drying mechanism. [Figure 6] It is a block diagram showing a configuration of a control unit related to control of a drying mechanism. [Figure 7] It is a diagram showing a concept of a protection mechanism by a thermostat. [Figure 8] It is a diagram showing a relationship between an open / closed state of a shutter and a temperature distribution. [Figure 9] It is a diagram showing a case where preferable regions in two modes do not overlap. [Figure 10] It is a diagram showing an attachment state of a thermostat to a movable plate. [Figure 11] It is a diagram showing a mechanism for interlocking a plurality of movable plates. [Figure 12] It is a diagram showing an example in which a movable plate is used as a light-shielding plate for a thermostat section. [Figure 13] It is a diagram showing another modification example. [Figure 14] It is a diagram showing another modification example.

Embodiment for Carrying Out the Invention

[0020] Hereinafter, an embodiment of a printing apparatus according to this invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the whole of the printing apparatus according to this invention. Further, FIG. 2 is a diagram showing a drying mechanism provided in this printing apparatus, and FIG. 3 is a diagram showing a main part of this drying mechanism. <Explanation of the Whole Configuration> First, referring to FIG. 1, the whole configuration of the printing apparatus 1 will be described. The printing apparatus 1 of this embodiment is an inkjet type printing apparatus. The printing apparatus 1 includes a paper feeding section 3, a printing apparatus main body 5, and a paper discharging section 7. In order to uniformly show the directions in the following respective figures, an XYZ orthogonal coordinate axis is set as shown in FIG. 1. Here, the XY plane represents a horizontal plane, and the Z direction represents a vertical direction. More specifically, the (-Z) direction represents a vertically downward direction. FIG. 1 is a front view of the printing apparatus 1, and the front side of the paper surface, that is, the (-Y) side corresponds to the front of the printing apparatus 1.

[0021] The paper feeding section 3 rotatably holds a roll of continuous paper (continuous accounting paper) WP around a horizontal axis. The paper feeding section 3 supplies the continuous paper WP from the roll of the continuous paper WP to the printing apparatus main body 5. The printing apparatus main body 5 performs printing on the long continuous paper WP. Then, the paper discharging section 7 winds up the continuous paper WP printed by the printing apparatus main body 5 around a horizontal axis. The paper discharging section 7 includes an electric motor for winding up the continuous paper WP. Assuming the supply side of the continuous paper WP as the upstream and the discharging side of the continuous paper WP as the downstream, the paper feeding section 3 is arranged upstream of the printing apparatus main body 5.

[0022] The printing device body 5 includes a drive roller 9, a drive roller 11, a plurality of transport rollers 13, and a nip roller 15. The drive roller 9 is located on the inlet side of the printing device body 5. The drive roller 11 is located on the outlet side of the printing device body 5. Each of the drive rollers 9 and 11 is rotatably supported and driven by an electric motor. The drive roller 9 takes in continuous paper WP from the paper feed section 3. The drive roller 11 feeds the continuous paper WP to the paper discharge section 7. Each of the drive rollers 9 and 11 provides power for transporting the continuous paper WP. The plurality of transport rollers 13 are rotatably supported rollers that guide the continuous paper WP and are driven rollers that rotate passively by contacting the moving continuous paper WP. Unlike the drive roller 11, the plurality of transport rollers 13 do not have an electric motor and do not provide power for transporting the continuous paper WP.

[0023] Furthermore, the printing apparatus body 5 is equipped with a printing unit 19, a drying mechanism 21, a cooling unit 23, and an inspection unit 25, arranged in order from the upstream side along the transport path of the continuous paper WP.

[0024] The printing unit 19 applies ink (ink droplets) to the printing surface FF of the continuous paper WP being transported. The printing unit 19 is equipped with, for example, four inkjet heads 19A to 19D. The four inkjet heads 19A to 19D eject ink droplets using, for example, a piezoelectric element method or a thermal (bubble) method. The upstream inkjet head 19A ejects black (K) ink droplets. The next inkjet head 19B ejects cyan (C) ink droplets. The next inkjet head 19C ejects magenta (M) ink droplets. The next inkjet head 19D ejects yellow (Y) ink droplets.

[0025] In this example, the printing unit 19 is equipped with four inkjet heads 19A to 19D, but it is not limited to this. For example, the printing unit 19 may be equipped with one, two, or six inkjet heads.

[0026] The drying mechanism 21 heats the continuous paper WP discharged (conveyed) from the printing unit 19 to dry the ink. The detailed configuration of the drying mechanism 21 will be described later. The cooling unit 23 cools the continuous paper WP heated by the drying mechanism 21. The cooling unit 23 is equipped with, for example, a water-cooled roller with a built-in channel for passing cooling water. The inspection unit 25 is equipped with, for example, a CCD sensor or a CIS (contact image sensor). The inspection unit 25 inspects the image printed on the continuous paper WP.

[0027] The printing apparatus 1 includes a control unit 27. The control unit 27 controls each component of the printing apparatus 1 (for example, the printing unit 19 and the drying mechanism 21). To enable this, the control unit 27 includes a memory for storing the program necessary for the operation of the printing apparatus 1 and a central processing unit (CPU) for executing this program. <Configuration of the drying mechanism> Next, the drying mechanism 21, which is a characteristic feature of the present invention, will be explained using Figures 2 and 3. Figure 3 shows the details of the transport path of the continuous paper WP in the drying mechanism 21.

[0028] (A) Configuration of multiple rollers The drying mechanism 21 includes a guide roller R, a print surface contact roller 29, a transport roller 31, and a path changing roller 33. The transport roller and the print surface contact roller may be referred to simply as "rollers" as appropriate. In continuous paper WP, the print surface FF is the surface to which ink has been applied by the printing unit 19. The reverse side BF is the surface opposite the print surface FF, and is the surface to which ink from the printing unit 19 has not been applied.

[0029] These guide rollers R, print surface contact roller 29, transport roller 31, and path changing roller 33 are driven rollers similar to the transport roller 13 described above. Specifically, each of the guide roller R, print surface contact roller 29, transport roller 31, and path changing roller 33 is rotatably supported and guides the continuous paper WP. Since the guide roller R, print surface contact roller 29, transport roller 31, and path changing roller 33 do not have electric motors, they do not provide power for transporting the continuous paper WP, and rotate passively by contacting the moving continuous paper WP.

[0030] In this embodiment, seven guide rollers R are provided. As shown in Figures 2 and 3, each guide roller R is distinguished by assigning the designations R1 to R7 to them in order from the upstream side in the conveying direction of the continuous paper WP. That is, among the multiple guide rollers R, guide roller R1 is located at the upstream side, and guide roller R7 is located at the downstream side.

[0031] Each of the guide rollers R contacts the back surface BF of the continuous paper WP discharged from the printing unit 19, changing the transport direction of the continuous paper WP. The printing surface contact roller 29 is located downstream of the seven guide rollers R1 to R7. The printing surface contact roller 29 is the first roller to contact the printing surface FF of the continuous paper WP among the multiple rollers provided by the drying mechanism 21 (printing device 1). The printing surface contact roller 29 also has the function of changing the transport direction of the continuous paper WP. The continuous paper WP discharged from the printing unit 19 and transported into the inlet of the drying mechanism 21 is transported in a swirling motion by the guide rollers R1 to R7.

[0032] Here, we will describe the path by which the continuous paper WP is transported by the guide rollers R1 to R7. First, the continuous paper WP discharged from the printing unit 19 is transported in the order of transport roller 13A, guide roller R1, guide roller R2, and guide roller R3. These transport rollers 13A and guide rollers R1 to R3 are located downstream of the printing unit 19 and in front of the printing unit 19 in a plan view.

[0033] The transport roller 13A is positioned downstream of the printing unit 19 (i.e., the downstream inkjet head 19D) and upstream of the guide roller R3. The transport roller 13A is positioned close to the inkjet head 19D. The transport roller 13A is in contact with the back surface BF of the continuous paper WP. Each of the transport roller 13A, guide roller R1, and guide roller R2 guides the continuous paper WP diagonally downward so that the printing surface FF of the continuous paper WP faces upward. The inclination angle (absolute value) of the continuous paper WP increases as it approaches the guide roller R3. The continuous paper WP, whose direction has been changed by rollers 13A, R1, and R2, is then changed vertically downward by the guide roller R3.

[0034] After the continuous paper WP is transported to guide roller R3, it is transported in the order of guide rollers R4, R5, R6, and R7. Guide roller R4 changes the direction of the continuous paper WP, which has been changed direction by guide roller R3, diagonally downward so that the printed surface FF of the continuous paper WP faces downward.

[0035] Guide roller R5 is positioned lower than guide roller R4. Guide roller R5 changes the direction of the continuous paper WP diagonally upward so that the printing surface FF of the continuous paper WP faces downward.

[0036] Guide roller R6 is positioned higher than guide roller R5. Also, guide roller R6 is positioned at approximately the same height as guide roller R4. Guide roller R6 redirects the continuous paper WP, which has been redirected by guide roller R5, vertically upward.

[0037] Guide roller R7 is positioned higher than guide roller R6. Guide roller R7 is positioned at approximately the same height as guide roller R3. Guide roller R7 is also positioned between the continuous paper WP, which is transported between transport roller 13A and guide roller R3, and guide roller R6. Guide roller R7 changes the direction of the continuous paper WP, which has been changed direction by guide roller R6, diagonally downward so that the printing surface FF faces upward.

[0038] As shown in Figure 2, the four guide rollers R3, R4, R6, and R7 are arranged to form a roughly rectangular shape when viewed in the width direction perpendicular to the transport direction TD of the continuous paper WP. The width direction of the continuous paper WP corresponds to the Y direction in Figure 1, etc.

[0039] The printing surface contact roller 29 is positioned within the area enclosed by the four guide rollers R3, R4, R6, and R7, as shown in Figure 2. In other words, the printing surface contact roller 29 is positioned within the area enclosed by the continuous paper WP being transported between guide rollers R3 and R7.

[0040] The printing surface contact roller 29 is the roller that first contacts the printing surface FF of the continuous paper WP after ink has been applied. The printing surface contact roller 29 guides the continuous paper WP toward the exit of the drying mechanism 21 by folding the ink-dried continuous paper WP back. Specifically, this guidance toward the exit of the drying mechanism 21 is performed by the printing surface contact roller 29 and the transport roller 31.

[0041] The transport roller 31 is positioned downstream of the printing surface contact roller 29. In this embodiment, nine transport rollers 31 are provided in the drying mechanism 21. The nine transport rollers 31 guide the continuous paper WP, which has been folded back by the printing surface contact roller 29, to the outlet of the drying mechanism 21, passing through the gap CL1 between the continuous paper WP being transported between the transport roller 13A and the guide roller R3 and the continuous paper WP being transported between the guide roller R7 and the printing surface contact roller 29.

[0042] Furthermore, the section in which the continuous paper WP is transported, where the heating units H1 to H4 (described later) are located, will be referred to as the "first section" below. As shown in Figure 3, the continuous paper WP in the portion corresponding to the first section will be referred to as the continuous paper WPa. Guide rollers R1 to R6 transport the continuous paper WPa in the first section. Guide roller R7 is the guide roller R located downstream of the first section and closest to the first section.

[0043] Furthermore, the section in which the continuous paper WP is transported, from the guide roller R7 to the printing surface contact roller 29, will be referred to as the "second section" below. Specifically, as shown in Figure 3, the section from the contact point P2 between the continuous paper WP and the guide roller R7 to the contact point P3 between the continuous paper WP and the printing surface contact roller 29 corresponds to the second section. And as shown in Figure 3, the portion of the continuous paper WP corresponding to the second section will be referred to as continuous paper WPb.

[0044] Furthermore, the section in which the continuous paper WP is transported, specifically the section transported by the transport roller 31, will be referred to as the "third section" below. Specifically, as shown in Figure 3, the section downstream from the contact point P3 between the continuous paper WP and the printing surface contact roller 29 corresponds to the third section. And as shown in Figure 3, the portion of the continuous paper WP corresponding to the third section will be referred to as continuous paper WPc.

[0045] Each of the route changing rollers 33 is positioned downstream of each of the guide rollers R in the transport direction TD of the continuous paper WP, and upstream of the print surface contact roller 29. In other words, the route changing rollers 33 are positioned downstream of the guide rollers R7. In this embodiment, four route changing rollers 33 are provided. As shown in Figure 3, each of the route changing rollers 33 is distinguished by assigning the reference numerals 33A to 33D in order from the upstream side in the transport direction of the continuous paper WP. That is, among the multiple route changing rollers 33, route changing roller 33A is positioned furthest upstream, and route changing roller 33D is positioned furthest downstream.

[0046] Each of the route-changing rollers 33 contacts the back side BF of the continuous paper WPb in the second section, thereby changing the transport path of the continuous paper WPb in the second section. That is, as the continuous paper WPb in the second section is wound around each of the route-changing rollers 33, the transport path of the continuous paper WP is changed from the straight path Wv shown by the dotted line in Figure 3 to a path that bypasses the straight path Wv. The path that bypasses the straight path Wv, shown by the symbol WPb and the solid line in Figure 3, is longer than the straight path Wv. In other words, each of the route-changing rollers 33 lengthens the path of the continuous paper WPb in the second section. Details of the transport path of the continuous paper WPb in the second section will be described later. (B) Configuration of the heating unit Furthermore, the drying mechanism 21 is equipped with four heating units H1 to H4. The four heating units H1 to H4 heat the continuous paper WP that is guided into the interior of the drying mechanism 21. Heating units H1, H2, H3, and H4 are arranged in this order along the transport path of the continuous paper WP. That is, of the four heating units H1 to H4, heating unit H1 is located furthest upstream. The four heating units H1 to H4 heat the continuous paper WP in a non-contact manner.

[0047] The heating unit H1 is positioned between guide rollers R1 and R2, facing the printing surface FF of the continuous paper WP. In other words, the heating unit H1 is positioned on the printing surface FF side of the continuous paper WP being transported between guide rollers R1 and R2.

[0048] The heating unit H2 is positioned between guide rollers R2 and R3, facing the printing surface FF of the continuous paper WP. The heating unit H3 is positioned between guide rollers R3 and R4, facing the printing surface FF of the continuous paper WP. The heating unit H4 is positioned between guide rollers R6 and R7, facing the printing surface FF of the continuous paper WP. In other words, the four heating units H1 to H4 of this embodiment are not positioned to face the back surface BF of the continuous paper WP.

[0049] Furthermore, between guide roller R4 and guide roller R6, the continuous paper WP is transported without being heated by the heating unit. The reason for this is explained below. Between guide roller R4 and guide roller R6, the printing surface FF faces downwards. Therefore, if the front of the heating unit (the heating side) is facing the printing surface FF, the front of the heating unit will face upwards. As a result, when the continuous paper WP slackens, the continuous paper WP will come into contact with the front of the heating unit and be excessively heated. Therefore, to avoid excessive heating of the continuous paper WP, the continuous paper WP is transported between guide roller R4 and guide roller R6 without being heated by the heating unit.

[0050] Thus, each of the heating units H1 to H4 is positioned in the first section so as to face the printing surface FF of the continuous paper WP. By directly heating the continuous paper WP in the first section that is positioned opposite each other, the ink on the printing surface FF is dried.

[0051] As an example, each of the heating units H1 to H4 heats the printed surface FF of the continuous paper WP with light (electromagnetic waves) including infrared rays. When heating the continuous paper WP with light, it is preferable that each of the heating units H1 to H4 be arranged to heat the printed surface FF of the continuous paper WP being conveyed between two adjacent guide rollers R. As an example, heating unit H1 heats the continuous paper WP being conveyed between adjacent guide rollers R1 and R2 with light. Here, the arrangement is such that guide rollers R1 and R2 do not enter the light irradiation area (heating area) of heating unit H1. By arranging the units so that the guide rollers R do not enter the heating area, it is possible to prevent the guide rollers R from being overheated. The same applies to the other heating units H2 to H4.

[0052] The following describes the structure of heating units H1 to H4 in more detail. The functions required of these heating units H1 to H4 are basically the same, and therefore, for example, units with the same structure can be used for each other. Here, we will describe the structure of one heating unit, H1, as a representative example, with reference to Figure 4.

[0053] Figure 4 shows the internal structure of the heating unit. More specifically, Figure 4(a) is a longitudinal cross-sectional view of the heating unit H1 along the width direction WD of the continuous paper WP. Figure 4(b) is a longitudinal cross-sectional view of the heating unit H1 along the transport direction TD of the continuous paper WP. The width direction WD is perpendicular to the transport direction TD. Figure 4(c) is a perspective view showing a part of the internal structure of the heating unit H1.

[0054] The heating unit H1 is equipped with multiple heaters 41 that irradiate the continuous paper WP with light including infrared rays. The heaters 41 are, for example, carbon (graphite) heaters. The multiple heaters 41 are arranged flat along the width direction WD. Each heater 41 is formed in a rod shape and is arranged longitudinally along the transport direction TD. The multiple heaters 41 are arranged two-dimensionally at regular intervals in a direction intersecting their longitudinal direction. The number of heaters is not limited to that shown in the figure and is arbitrary. For example, a single heater bent along one plane may be provided. In addition, heating elements other than carbon heaters may be used.

[0055] By irradiating the printing surface FF with light from the heater 41, the printing surface FF (ink and continuous paper WP) can be directly heated. Using the heater 41, it is possible to irradiate light with a wavelength that is optimal for heating (drying) the ink. In other words, the heater 41 can irradiate light with a wavelength that is well absorbed by water.

[0056] Multiple heaters 41 are housed in a housing 40. The housing 40 is formed in the shape of a rectangular parallelepiped with one side open. A grid fence may be provided on the open side 40A of the housing 40 to prevent contact between the continuous paper WP and the heaters 41. The circumferential surface of the heaters 41 is surrounded by a reflective cover 42, except for the direction facing the open side 40A. This allows the light generated by the heaters 41 to be efficiently guided toward the open side 40A and emitted to the outside.

[0057] A shutter 43 is provided between the heaters 41 arranged in this manner and the opening surface 40A. The shutter 43 has multiple movable plates 431 and fixed plates 432 arranged at regular intervals, which partially block the light emitted from the heaters 41. The movable plates 431 are positioned closer to the heaters 41 than the fixed plates 432, and are spaced apart from the fixed plates 432. The movable plates 431 are movable in the width direction WD and, as will be described later, have the function of opening and closing the light path from the heaters 41 to the continuous paper WP. This adjusts the amount of light irradiated onto the continuous paper WP.

[0058] As shown in Figure 4(c), the movable plate 431 and the fixed plate 432 are plate-shaped members that have an M-shaped cross-section stretched laterally and extend along the transport direction TD. Here, cost reduction is achieved by making the movable plate 431 and the fixed plate 432 the same shape, but they may be made into different shapes depending on the purpose.

[0059] By making the movable plate 431 and the fixed plate 432 roughly M-shaped in this way, higher mechanical strength can be obtained than if they were simply flat plates. Also, compared to a so-called channel shape, both ends of the surface facing the heater 41 protrude toward the heater 41, so that the light radiating from the heater 41 can be shielded more effectively.

[0060] The heating unit H1 further includes a blower fan 49 and a guide plate 48. The blower fan 49 is located on the side of the housing 40 and is driven by an electric motor (not shown). The blower fan 49 blows gas into the housing 40. This allows the gas surrounding the heater 41, which has been heated by the heater 41, to be sent to the printing surface FF. The guide plate 48 is located inside the housing 40 and guides the airflow formed by the blower fan 49 towards the heater 41. Rectifier plates 47 are placed between a plurality of reflective covers 42 surrounding each heater 41, and the airflow from the blower fan 49 flows out to the outside through the gaps between them. The rectifier plates 47 and the guide plate 48 are configured so that the air flows evenly from the front surface 40A of the housing 40.

[0061] Furthermore, the rectifier plate 47 also has the function of suppressing the dissipation of gas heated by the heater 41 into the internal space of the housing 40 on the opposite side of the opening surface 40A. This improves thermal energy efficiency.

[0062] The heating unit H1 is equipped with two exhaust sections 46. The two exhaust sections 46 are provided on the upstream and downstream sides of the housing 40, which houses the heater 41 and the like, so as to sandwich the housing 40 in the transport direction TD of the continuous paper WP. The openings of the two exhaust sections 46 face the printing surface FF. This allows the hot air blown from the opening surface 40A by the blower fan 49 to be collected and exhausted on the upstream and downstream sides of the housing 40. The number of exhaust sections 46 in the heating unit H1 may be changed as appropriate.

[0063] Furthermore, as shown in Figure 2, the printing apparatus 1 is equipped with four reflectors RF1 to RF4. Of these, reflector RF1 is positioned on the opposite side of the heating unit H1, sandwiching the continuous paper WP being transported between guide rollers R1 and R2. Similarly, reflector RF2 is positioned on the opposite side of the heating unit H2, sandwiching the continuous paper WP being transported between guide rollers R2 and R3. Reflector RF3 is positioned on the opposite side of the heating unit H3, sandwiching the continuous paper WP being transported between guide rollers R3 and R4. Reflector RF4 is positioned on the opposite side of the heating unit H4, sandwiching the continuous paper WP being transported between guide rollers R6 and R7.

[0064] Each of the four reflectors RF1 to RF4 is made of a glossy metal. Each of the four reflectors RF1 to RF4 reflects the light that is irradiated from the heater 41 and passes through the continuous paper WP. The reflected light can be re-irradiated onto the continuous paper WP. This makes effective use of the light irradiated from the heater 41.

[0065] Furthermore, as shown in Figure 2 and other figures, the openings 40A of the heating units H1 to H4 are arranged to surround the continuous paper WPa in the first section and the continuous paper WPb in the second section, respectively. This arrangement makes it easier for the temperature of the space in which the continuous paper WPa and continuous paper WPb are transported to rise due to the heating units H1 to H4, thus making it easier for the ink printed on the continuous paper WPa and continuous paper WPb to dry.

[0066] The drying mechanism 21 is equipped with an exhaust concentrator (not shown). The exhaust concentrator is located above the rollers 13A, R1~R8, 31, 33 and the four heating units H1~H4. The exhaust concentrator is connected to the exhaust section 46 of each of the four heating units H1~H4. The exhaust concentrator collects the gas drawn in by each of the exhaust sections 46 and sends the collected gas to the outside of the printing apparatus 1, more specifically to the exhaust duct of the building in which the printing apparatus 1 is installed.

[0067] Figure 5 illustrates two modes realized by the drying mechanism. Figure 5(a) corresponds to the first mode, in which a large amount of heat is supplied to the continuous paper WP by directly irradiating it with powerful light emitted from the heater 41. In the first mode, the movable plate 431 is positioned so as to almost overlap with the fixed plate 432 in the width direction WD. As a result, a path of light is formed that directly irradiates the continuous paper WP from the heater 41, as shown by the dotted arrow in Figure 5(a). In this specification, the position of the movable plate 431 at this time will be referred to as the "open position" because it opens the path of light from the heater 41 to the continuous paper WP.

[0068] At this time, a relatively large current is supplied to the heater 41, which increases the amount of light output from the heater 41. Therefore, a large amount of heat is supplied to the continuous paper WP by thermal radiation from the heater 41, allowing the ink adhering to the continuous paper WP to dry rapidly. The first mode is suitable, for example, when the continuous paper WP is transported at high speed.

[0069] On the other hand, Figure 5(b) corresponds to a second mode in which the continuous paper WP is heated indirectly by blowing heated gas onto it, rather than directly injecting light emitted from the heater 41 into it. The second mode is suitable, for example, when the continuous paper WP is transported at a low speed.

[0070] In the second mode, the movable plate 431 is positioned to close the gap between adjacent fixed plates 432. As a result, the light emitted from the heater 41 is shielded by the movable plate 431 and the fixed plates 432 and does not directly enter the continuous paper WP. For this reason, the position of the movable plate 431 at this time will be referred to as the "shielding position" in this specification.

[0071] In this mode, a smaller current is supplied to the heater 41 than in the first mode. Therefore, the amount of light output from the heater 41 is also smaller than in the first mode. As shown by the dotted arrow in Figure 5(b), the light emitted from the heater 41 at this time irradiates the movable plate 431, the fixed plate 432 and the surrounding components, raising the temperature of these components. This heats the surrounding gas, which is then blown onto the continuous paper WP as warm air by the operation of the blower fan 49, as shown by the dashed arrow in Figure 5(b). In this way, in the second mode, the continuous paper WP is slowly heated by the warm air.

[0072] In the first mode, the blower fan 49 is also operating, but heating by radiation is dominant, and the contribution of warm air is relatively small. For this reason, the airflow diagram is omitted in Figure 5(a) to avoid making the diagram too complex.

[0073] Figure 6 is a block diagram showing the configuration of the control unit involved in the control of the drying mechanism. In the control unit 27, various functional blocks necessary for operating each part of the device are realized by the CPU executing a predetermined program. As shown in Figure 6(a), functional blocks involved in the operation control of the drying mechanism 21 include the mode selection unit 271, the fan control unit 272, the shutter control unit 273, and the heater control unit 274. In addition to these, the control unit 27 also realizes functional blocks for controlling each part of the printing device 1, such as the printing unit 19 and the transport system, to perform printing operations.

[0074] The mode selection unit 271 selects whether to execute the first mode or the second mode depending on the content of the printing operation to be performed. The fan control unit 272 operates the blower fan 49 as needed.

[0075] Furthermore, the shutter control unit 273 controls the shutter drive mechanism 433 provided on the shutter 43 to control its open and closed state. Specifically, when the first mode is selected, the shutter control unit 273 operates the shutter drive mechanism 433 to position the movable plate 431 in the "open position". On the other hand, when the second mode is selected, the shutter control unit 273 operates the shutter drive mechanism 433 to position the movable plate 431 in the "closed position".

[0076] The heater control unit 274 controls the driver 44 that supplies current to the heater 41, thereby causing the heater 41 to emit a predetermined amount of heat. Specifically, the output from the heater 41 is controlled by adjusting the amount of current supplied to the heater 41 by the driver 44 in accordance with the control commands given by the heater control unit 274.

[0077] Furthermore, the heating unit H1 is equipped with a protection mechanism to prevent abnormal overheating of the heater 41. Specifically, the driver 44 is equipped with a current interruption element, such as a thermostat 450, which senses heat and interrupts the current. The thermostat 450 is positioned where it is heated by the heater 41. The thermostat 450 is inserted into the current path and interrupts the current path when it reaches its specific interruption temperature. This interruption is forced and not controlled by external forces, so even if abnormal overheating is caused by a problem in the control system, the current can be quickly interrupted and the heat generation stopped. Therefore, a highly reliable protection mechanism can be realized.

[0078] The thermostat 450 can be installed on the current supply path to the heater 41. However, since a large current flows through the heater 41, a thermostat with a large current capacity is required for installation in that current path. Alternatively, as shown in Figure 6(b), for example, the thermostat 450 can be installed on the control current path for turning on and off a switch (more specifically, a relay 411) inserted in the current supply path to the heater 41.

[0079] When the heater 41 overheats and the thermostat 450 reaches its shut-off temperature, the control current of the relay 411 is interrupted, causing its normally open contacts to open, thereby interrupting the current supply path to the heater 41. In this way, a large current cannot be prevented from flowing through the thermostat 450.

[0080] For the purpose of explaining the principle, a relay with mechanical contacts was used as an example here. However, in actual devices, devices that can switch the current path on and off without mechanical contacts, such as solid-state relays or thyristors, can be used.

[0081] The protection mechanism using the thermostat 450 will be explained in more detail. As explained earlier, in this embodiment, two modes with different output light amounts from the heater 41 are selectively executed. The protection mechanism is required to achieve compatibility between these two modes. This can be achieved by applying the following approach. In the following explanation, using Figures 7 to 9, we will use the premise that the light emitted from the heater 41 is incident on the thermostat 450 itself to raise its temperature. However, it is not essential that the emitted light is incident on the thermostat 450 itself. That is, the thermostat 450 may be thermally integrated with some light-receiving member, and the light emitted from the heater 41 may be received by this light-receiving member, thereby raising the temperature of the thermostat 450 due to the temperature rise of the light-receiving member.

[0082] Figure 7 illustrates the concept of the protection mechanism using a thermostat. In the graph, the horizontal axis represents the magnitude of the output light intensity from the heater 41, and the vertical axis represents the temperature of the thermostat 450. The symbol Ta represents the cutoff temperature of the thermostat 450. The correlation between the output light intensity of the heater 41 and the temperature of the thermostat 450 shown here will be referred to as the "sensitivity characteristic" of the thermostat 450.

[0083] First, let's consider the case where the thermostat 450 is fixedly installed at an appropriate position, referring to Figure 7(a). When the thermostat 450 is installed in a position where it is heated by radiation from the heater 41, as shown by the solid and dotted lines in Figure 7(a), the greater the output light from the heater 41, the higher the temperature of the thermostat 450. When that temperature reaches the cutoff temperature Ta, the thermostat 450 activates and the current path is cut off.

[0084] Here, the output light intensity of the heater 41 in the first mode and the second mode are denoted by the symbols I1 and I2, respectively. To obtain an appropriate protective function in the first mode, as shown by the solid line in Figure 7(a), the temperature of the thermostat 450 should be slightly lower than the cutoff temperature Ta when the output light intensity is I1, and when the output light intensity increases beyond the allowable value, the thermostat 450 should reach a temperature equal to or higher than the cutoff temperature Ta. Such conditions can be met by selecting a product with an appropriate cutoff temperature Ta as the thermostat 450 and installing it in an appropriate location.

[0085] On the other hand, since the output light intensity I2 in the second mode is smaller, the temperature of the thermostat 450 is also lower at that time. Therefore, when the thermostat 450 reaches the cutoff temperature Ta, the output light intensity is considerably larger than the original value I2, and it cannot be said that the protection function corresponding to the second mode is working effectively.

[0086] Conversely, as shown by the dotted line in Figure 7(a), if the settings are configured so that the protection function is effective in the second mode, then in the first mode, even with an appropriate output light intensity I1, the temperature of the thermostat 450 will exceed the cutoff temperature Ta, and the current cutoff function will activate, making it impossible to execute the first mode.

[0087] Thus, when the relative positions of the heater 41 and the thermostat 450 are fixed, it becomes difficult to enable both the first mode and the second mode to be executed simultaneously, while also ensuring that the protective functions operate effectively in each mode.

[0088] Therefore, as shown in Figures 7(b) and 7(c), if the sensitivity characteristics of the thermostat 450 are made to change between the first mode and the second mode, it becomes possible to accommodate both modes. In Figures 7(b) and 7(c), "Sensitivity Characteristic 1" is an example of the sensitivity characteristic corresponding to the first mode, and "Sensitivity Characteristic 2" is an example of the sensitivity characteristic corresponding to the second mode. Figure 7(b) shows an example where the gradients are different between the two sensitivity characteristics, and Figure 7(c) shows an example where the intercepts are different.

[0089] In order to utilize these different sensitivity characteristics, it is necessary to create conditions in which the temperature rise of the thermostat 450 differs even if the output light intensity from the heater 41 is the same. For example, by changing the way in which the light emitted from the heater 41 enters the thermostat 450, it is possible to make the amount of light entering the thermostat 450 different even if the output light intensity from the heater 41 is the same, thereby making the temperature rise of the thermostat 450 different.

[0090] For example, by changing the distance between the heater 41 and the thermostat 450, or the angle at which the heater 41 is viewed from the thermostat 450, the way in which the light emitted from the heater 41 enters the thermostat 450 can be altered, thereby changing the sensitivity characteristics. Furthermore, by shielding a portion of the light entering the thermostat 450 from the heater 41, the way in which the light enters the thermostat 450 can be altered, thereby changing the sensitivity characteristics. The following describes specific examples based on this concept.

[0091] Figure 8 shows the relationship between the open / closed state of the shutter and the temperature distribution. In the following, the movable plate 431 and fixed plate 432 of the shutter 43 will be simplified to flat plates. Here, for example, we consider placing the thermostat 450 at one of the positions corresponding to the upper surface of the movable plate 431 in the height direction (dashed line), and consider which position can be used to achieve both modes simultaneously.

[0092] The upper part of Figure 8 schematically shows the temperature distribution measured at each position corresponding to the height of the upper surface of the movable plate 431, indicated by the dashed line, in the second mode, for both the case where the heater 41 is operating normally and the case where abnormal heat generation occurs. In the second mode, the shutter 43 is in the "closed" state, that is, the movable plate 431 is in the "shielding position" where it blocks the output light from the heater 41. Also, the amount of output light from the heater 41 is smaller than in the first mode, which will be described later. Note that what we are considering here is the temperature at the height of the upper surface of the movable plate 431, indicated by the dashed line, so the influence of radiant heat from the heater 41 is dominant, regardless of the open / closed state of the shutter 43.

[0093] As shown by the solid line in the figure, if the heater 41 is operating normally, the temperature is highest directly below the heater 41 and decreases as you move away from the heater 41. Also, as shown by the dotted line, when the heater 41 is overheating, the tendency for the temperature to be highest directly below the heater 41 is the same as in normal operation, but the temperature value itself is higher than in normal operation. Therefore, if a thermostat 450 with a cutoff temperature Ta that is higher than the highest temperature in the temperature distribution under normal conditions and lower than the highest temperature during abnormal overheating is placed in the region Ra where the temperature exceeds the cutoff temperature Ta during abnormal overheating, the protection function in the second mode can be realized. This is because, under normal conditions, the temperature of the thermostat 450 does not exceed the cutoff temperature Ta and no current interruption occurs, while during abnormal overheating, the thermostat 450 becomes hotter than the cutoff temperature Ta and the current is interrupted.

[0094] The lower diagram in Figure 8 schematically shows the temperature distribution in the first mode. In this mode, the shutter 43 is in the "open" position, meaning the movable plate 431 is in the "open position" that allows the output light from the heater 41 to pass through, and the output light intensity of the heater 41 is greater than in the second mode. Therefore, the temperature at the height of the upper surface of the movable plate 431, shown by the dashed line, is higher than in the second mode. The temperature will be even higher in the event of abnormal heat generation.

[0095] Here, the region Rb in which the normal temperature does not exceed the cutoff temperature Ta, and the temperature during abnormal heat generation exceeds the cutoff temperature Ta, is the region in which the thermostat 450 should be placed to ensure that the protective function works properly in the first mode. In other words, by placing the thermostat 450 within this region Rb, the appropriate protective function in the first mode is achieved.

[0096] Therefore, the thermostat 450 must be located within region Rb in the first mode and within region Ra in the second mode. At least two methods can be considered to achieve this.

[0097] Firstly, if the preferred region Rb in the first mode and the preferred region Ra in the second mode spatially overlap, the thermostat 450 should be placed within that overlapping region. In the example in Figure 8, such an overlap exists, and point P1 within the overlapping region satisfies the requirements.

[0098] Secondly, there is a method of changing the position of the thermostat 450 to satisfy the requirements in each of the two modes. For example, since the position of the variable plate 431 of the shutter 43 changes between modes, it may be possible to satisfy the requirements in each of the two modes by moving the thermostat 450 in conjunction with this change. For example, point P2 on the variable plate 431 is within region Ra in the second mode shown in the figure above, and is therefore a suitable installation position for the thermostat 450 in the second mode.

[0099] On the other hand, the position of point P2 is outside the preferred region Rb in the first mode. However, if the thermostat 450 is placed at point P2 on the movable plate 431, point P2 will move into region Rb as the variable plate 43 moves in the first mode shown in the figure below, so the protective function will work properly even in the first mode.

[0100] Therefore, point P2, which is on the movable plate 431 and moves integrally with the movable plate 431, can be said to satisfy the requirements for the protection function to be effective in both modes. In the upper diagram of Figure 8 (second mode), the light emitted from the heater 41 is incident on point P2 (the installation position of the thermostat 450) almost perpendicularly. In contrast, in the lower diagram of Figure 8 (first mode), the light emitted from the heater 41 is incident on point P2 at an angle. Thus, between the second mode shown in the upper diagram of Figure 8 and the first mode shown in the lower diagram of Figure 8, the light emitted from the heater 41 is incident on point P2, which is the installation position of the thermostat 450 or the thermostat unit 45 described later, in different incident patterns. This ability to achieve both modes of protection by changing the incident pattern of light is also possible even when there is no overlap between the "preferred regions" in the two modes, as will be explained next.

[0101] Figure 9 shows a case where the preferred regions in the two modes do not overlap. Due to differences in the output of the heater 41 and the dimensions of each component, the temperature distribution exhibits various patterns, and as described above, cases where the preferred regions in the two modes do not overlap occur. In the example in Figure 9, there is no overlap between the preferred region Ra in the second mode and the preferred region Rb in the first mode.

[0102] However, by positioning the thermostat 450 at point P3 on the movable plate 431 of the shutter 43, the thermostat 450 can be positioned in a preferred region in each mode. In Figure 9, the positions of the movable plate 431 and the thermostat 450 in the second mode are shown by solid lines, and the positions of the movable plate 431 and the thermostat 450 in the first mode are shown by dotted lines. As can be seen from this, the requirements that the thermostat 450 is in region Ra in the second mode and in region Rb in the first mode are met.

[0103] Therefore, in both the first and second modes, the protection function against abnormal heat generation is effectively activated. More specifically, in the second mode, since the thermostat 450 is within region Ra, the current cutoff function of the thermostat 450 does not work during normal heat generation, and the heat generated by the heater 41 can be supplied to the continuous paper WP as warm air to promote its drying. On the other hand, in the event of abnormal heat generation, the current cutoff function of the thermostat 450 stops the heating of the heater 41, thus preventing the continuous paper WP from becoming abnormally hot.

[0104] Similarly, in the first mode, since the thermostat 450 is within region Rb, the current cutoff function of the thermostat 450 does not work during normal heat generation, allowing the light emitted from the heater 41 to directly enter the continuous paper WP, thereby promoting its drying. On the other hand, in the event of abnormal heat generation, the current cutoff function of the thermostat 450 stops the heating of the heater 41, preventing the continuous paper WP from becoming abnormally hot.

[0105] In the second mode, the thermostat 450 is located close to directly below the heater 41, whereas in the first mode, the distance between the thermostat 450 and the heater 41 is greater. Therefore, even in the first mode, which has a high output light intensity, the temperature rise of the thermostat 450 is suppressed, and the shut-off function is prevented from activating at times when it is not needed.

[0106] In this embodiment, the thermostat 450 is positioned on the movable plate 431 at a location corresponding to point P2 in Figure 8 or point P3 in Figure 9. Therefore, the thermostat 450 does not intervene under normal conditions, but in the event of abnormal overheating, the thermostat 450 cuts off the current to stop heater heating, protecting the continuous paper WP and the device itself. This function is effective in both the first and second modes.

[0107] Furthermore, in this embodiment, the following measures are taken regarding the placement of the thermostat 450 on the movable plate 431 in order to make the protective function more effective.

[0108] Figure 10 shows the state in which the thermostat is attached to the movable plate. More specifically, a thermostat unit 45, which includes at least a thermostat 450, is attached to the movable plate 431. The thermostat unit 45 includes the thermostat 450, a light receiving plate 451, and an insulating plate 452. Figure 10(a) is a partial perspective view showing the thermostat unit 45 attached to the movable plate 431, and Figure 10(b) is a side view thereof. As shown in Figure 10(a), the thermostat unit 45 is provided such that the light receiving plate 451 and the insulating plate 452 are interposed between the thermostat 450 and the upper surface 431a of the movable plate 431. More specifically, the insulating plate 452 is attached to the flat portion of a recess provided on the upper surface 431a of the movable plate 431. The light receiving plate 451 is attached to the upper surface of the insulating plate 452 and does not come into contact with the movable plate 431. Then, a thermostat 450 is attached to the upper surface of the light receiving plate 451. In this way, the thermostat unit 45 is constructed.

[0109] As shown in Figure 10(b), the thermostat 450 is positioned outside the end of the heater 41 in the transport direction TD, while the light receiving plate 451 extends from directly below the thermostat 450 to inside the end of the heater 41. A light shielding plate 53 is positioned above the thermostat 450 between it and the heater 41. Therefore, as indicated by the dashed arrow, light from the heater 41 enters the light receiving plate 451 but does not enter the thermostat 450 directly.

[0110] Therefore, the thermostat 450 does not heat up by directly receiving light from the heater 41, but rather by conductive heat from the heated light receiving plate 451. As a result, even when the output of the heater 41 is high, as in the first mode, the radiant heat from which the thermostat 450 becomes abnormally hot, preventing malfunction or deterioration, is avoided. Therefore, the protection function against abnormal heat generation can be stably performed over a long period of time.

[0111] Furthermore, in order to promptly detect abnormal heat generation from the heater 41, it is necessary that the thermostat 450 has a high temperature rise response to the heat generated by the heater 41. If the movable plate 431 is made of stainless steel, for example, its temperature response to the heat generated by the heater 41 is not high, so it is desirable to avoid the thermostat 450 being affected by the temperature of the movable plate 431. In this embodiment, the light receiving plate 451 is made of a material with higher thermal conductivity, such as copper or aluminum, and the thermostat 450 is attached to it, and an insulating plate 452 is provided between the light receiving plate 451 and the movable plate 431. This suppresses the influence of the temperature of the movable plate 431 and ensures excellent temperature response to the heat generated by the heater 41.

[0112] Each of these measures has a certain effect on its own. And when they are used in combination, as described above, a protective function that can respond to abnormal heat generation of the heater 41 with excellent temperature response can be stably maintained over a long period of time.

[0113] Furthermore, the thermostat section 45 may be provided only at one end of the movable plate 431, or it may be provided at both ends.

[0114] Furthermore, the operation after the thermostat 450 stops supplying power to the heater 41 and the temperature drops is not particularly limited. That is, when power is restored due to the temperature drop of the thermostat 450, heating by the heater 41 may continue, or heating may not be resumed until, for example, a predetermined recovery procedure is performed.

[0115] If heating is automatically restarted after a temperature drop, the abnormal overheating may recur if the event that caused the abnormal overheating has not been resolved. To address this problem, for example, the restart of heating can be prohibited if the thermostat 450 shuts off the system a predetermined number of times.

[0116] Furthermore, in the heating unit H1 of this embodiment, multiple heaters 41 are arranged in parallel, and multiple thermostats 450 are provided corresponding to each of them. How the individually operating protection functions of these thermostats are combined is arbitrary. For example, the protection function may be set to operate independently for each heater 41, or if the current cutoff function of any of the thermostats 450 is activated, power supply to all heaters 41 may be stopped. This can be achieved by electrically connecting multiple thermostats 450 in series.

[0117] Figure 11 shows a mechanism for linking multiple movable plates. In this drying mechanism 21, in the first mode all of the multiple movable plates 431 are positioned in the open position, and in the second mode all of them are positioned in the shielded position. Therefore, a mechanism for moving the multiple movable plates 431 independently is unnecessary; it is sufficient if they can be moved as a single unit.

[0118] Therefore, as shown in Figure 11, for example, the movable plates 431 can be integrally connected by attaching both ends of each movable plate 431 to a pair of frame members 434 outside the ends of the heater 41 in the transport direction TD, and the resulting combined body can be moved in the width direction WD by a shutter drive mechanism 433. Suitable shutter drive mechanisms 433 include, for example, an air cylinder or a rack and pinion mechanism that moves linearly by the drive of a motor.

[0119] In this case, the wiring extending from each thermostat 450 can be fixed to the frame member 434, thereby stabilizing the electrical connection. In addition, by routing the wiring outside the heater 41, it is possible to avoid the wiring becoming hot.

[0120] Furthermore, since the relative positions of the multiple movable plates 431 do not change, especially when connecting each thermostat 450 in series, it is possible to avoid complicated wiring and obtain the best results in terms of electrical stability.

[0121] The following describes some modifications of the above embodiment. In the following modifications, components that have substantially the same structure and function as those in the above embodiment and can be denoted by the same reference numerals will be denoted by the same reference numerals as in the above embodiment, and redundant descriptions will be omitted.

[0122] In the above embodiment, the thermostat unit 45 is attached to the movable plate 431 of the shutter 43 and moves integrally with it, thereby differentiating the position of the thermostat unit 45 between the first mode and the second mode, so that the protective function works appropriately in each mode. This has the advantage that the opening and closing of the shutter and the positioning of the thermostat unit 45 to the optimal position can be performed simultaneously with the same drive mechanism.

[0123] However, it is conceivable that the position of the thermostat unit 45, which can accommodate both modes, may not be achievable within the range of movement of the movable plate 431. In such cases, a separate mechanism can be provided to move the thermostat unit 45 independently of the movable plate 431, so that the thermostat unit 45 is positioned at the optimal location for each of the two modes.

[0124] Furthermore, in the above embodiment, the position of the thermostat unit 45 relative to the heater 41 is changed in order to change the way in which light is incident from the heater 41 to the thermostat unit 45 between the two modes. It should be noted that the term "incidence of light to the thermostat unit" here encompasses not only the case where light is directly incident on the thermostat 450, which is a current-blocking element included in the thermostat unit 45, but also the case where light is incident on the light-receiving plate 451, which transmits heat to the thermostat 450, as an "indirect" incident.

[0125] Essentially, the goal is to change the way in which the light emitted from the heater 41 enters the thermostat section 45, thereby changing the proportion of the light emitted from the heater 41 that contributes to the heating of the thermostat 450. In other words, in the first mode, the proportion of light emitted from the heater 41 that contributes to the heating of the thermostat 450 should be smaller than in the second mode.

[0126] Therefore, instead of changing the position of the thermostat unit 45, it is also possible to achieve this by using some optical means provided between the heater 41 and the thermostat unit 45. Specifically, it would be sufficient if the temperature rise could be suppressed in the first mode, where the amount of light is large and the temperature of the thermostat unit 45 tends to rise. For example, a light-shielding plate can be placed between the heater 41 and the thermostat unit 45, and its effect can be changed between the first mode and the second mode.

[0127] For example, if the light-shielding plate, which is positioned between the heater 41 and the thermostat unit 45 in the first mode, is retracted in the second mode, the sensitivity to the output of the heater 41 can be changed without changing the position of the thermostat unit 45. Therefore, by appropriately designing the light-shielding plate, it is possible to obtain the same effect as in the above embodiment. Furthermore, as will be described below, a movable plate 431 can be used as such a light-shielding plate.

[0128] Figure 12 shows an example in which the movable plate is used as a light shield for the thermostat unit. In this modified example, the thermostat unit 45 is attached to the upper surface of the fixed plate 432 of the shutter 43. Figure 12(a) shows the second mode, in which case the movable plate 431 is in the shielding position and therefore does not function as a light shield for the thermostat unit 45. Therefore, if abnormal heat generation occurs in the heater 41, it can be quickly detected and the current can be cut off.

[0129] On the other hand, in the first mode shown in Figure 12(b), the movable plate 431, which has moved to the open position, functions as a light shield for the thermostat unit 45. This suppresses the temperature rise of the thermostat unit 45, and avoids the problem of the protective function overreacting even during normal operation by exceeding the cutoff temperature Ta of the thermostat 450.

[0130] To achieve both protective functions in these two modes, as in the embodiment described above, the temperature distribution on the fixed plate 432 in each mode should be understood, and the cutoff temperature Ta and installation position of the thermostat 450 should be appropriately set accordingly. In this case as well, it is possible to incorporate the positional relationship with the heater 41 shown in Figure 10, as well as the concepts of the light receiving plate 451, the heat insulating plate 452, etc.

[0131] Figure 13 shows another modified example. In the embodiments and modifications described above, the thermostat unit 45 is positioned within or near the range of light irradiation from the heater 41. However, as shown in Figure 13(a), for example, a reflector 435 may be placed on the movable plate 431, and the thermostat unit 45 may be positioned on the optical path of the light emitted from the heater 41 and reflected by the reflector 435. Here, the surface shape, inclination, mounting position, etc. of the reflector 435 should be set such that when the movable plate 431 is in the shielding position as shown in Figure 13(a), more reflected light enters the thermostat unit 45 than when the movable plate 431 is in the open position as shown in Figure 13(b).

[0132] Figure 14 shows another modified example. In the shutter 43 of the above embodiment, the shielding position and the open position are switched by the sliding movement of the movable plate 431, but there are also shutters of this type that are opened and closed by the rotation of a flap. The modified example shown here has a shutter 43a having such a flap. In the example shown in Figure 14(a), when the main surface of the flap 436 faces the heater 41 (solid line), light from the heater 41 toward the continuous paper WP is shielded, and the position of the flap 436 at this time corresponds to the "shielding position". On the other hand, when the flap 436 rotates 90 degrees from this state and the main surface becomes parallel to the direction of light propagation (dotted line), the shielding effect on light is limited, and direct incidence to the continuous paper WP is allowed. The position of the flap 436 at this time corresponds to the "open position".

[0133] Even in this configuration, by placing the thermostat unit 45 on the flap 436 and changing the pattern of infrared radiation incident from the heater 41 between the shielded position and the open position, the sensitivity characteristics of the thermostat 450 can be changed. By utilizing this, and by using a light receiving plate or light shielding plate as needed, it is possible to achieve both protection functions in two modes, similar to the embodiment described above.

[0134] Figure 14(b) shows a modified example in which a reflector 437 is provided on the flap 436. By utilizing the fact that the amount of reflected light reaching the thermostat section 45 changes depending on the position of the flap 436, a similar effect can be obtained.

[0135] As described above, in each of the above embodiments, the continuous paper WP, which is the printing medium, corresponds to the "printing medium" of the present invention. Furthermore, the paper feeding section 3 and the paper discharge section 7, and each of the rollers provided on the transport path, function as the "transport section" of the present invention. Furthermore, the drying mechanism 21 functions as the "drying section" and "drying device" of the present invention. Furthermore, the heater 41 and the control unit 27 function as the "light source" and "control unit," respectively, of the present invention.

[0136] Furthermore, in the above embodiment, the shutter 43 functions as the "light-shielding part" of the present invention, and in particular, the movable plate 431 corresponds to the "movable shutter" of the present invention. In addition, the light-receiving plate 451, the heat-insulating plate 452, and the light-shielding plate 53 function as the "light-receiving member," "heat-insulating member," and "shielding member" of the present invention, respectively.

[0137] Furthermore, the thermostat 450 corresponds to the "current interruption element" in the present invention, and the thermostat section 45 including it corresponds to the "current interruption section" in the present invention. The shutter drive mechanism 433 in the above embodiment also functions as the "sensitivity changing section" in the present invention by moving the thermostat section 45 together with the movable plate 431. Moreover, in the above embodiment, the rectifier plate 47, guide plate 48, and blower fan 49 function together as the "airflow generation section" in the present invention.

[0138] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, the protection function against abnormal heat generation is appropriately activated in both the first mode, in which the output light intensity from the heater 41 is high, and the second mode, in which the output light intensity is lower.

[0139] However, when there are two modes with different output light levels, the minimum requirement is to satisfy two conflicting conditions: that the protection function works reliably in the second mode, which is at a relatively lower temperature, and that the protection function does not overreact in the first mode, which is at a higher temperature (i.e., the protection function works even when it is not necessary).

[0140] In this sense, the protective function against abnormal heat generation in the first mode can be considered an additional effect, and an invention can still be established even if this requirement is omitted. Therefore, the installation position of the thermostat and the setting of its shut-off temperature may be determined without considering the protective function in the first mode.

[0141] Furthermore, in the above embodiment, the thermostat section 45 includes a thermostat 450, a light receiving plate 451, and a heat insulating plate 452. However, the thermostat section corresponding to the "current interruption section" of the present invention only needs to include a thermostat, and it is not essential to include a light receiving plate and a heat insulating plate.

[0142] Furthermore, although a thermostat is used as the current interruption element in the above embodiment, other elements with similar functions may be used. For example, if automatic recovery after interruption is not required, a thermal fuse can be used as the current interruption element.

[0143] Furthermore, in the above embodiment, the continuous paper WP (printing medium) is heated in the second mode. However, in the second mode, it is sufficient for less heat (including virtually zero) to be supplied to the printing medium than in the first mode, and heating the printing medium in the second mode is not essential.

[0144] Furthermore, although the above embodiment applies the present invention to a printing apparatus 1 that incorporates a drying mechanism 21, it is also possible to apply the present invention not only to drying mechanisms that are pre-built into a printing apparatus, but also to devices that are manufactured as independent drying devices.

[0145] Furthermore, the "printing medium" of the present invention is not limited to the long printing paper (continuous paper) of the above embodiment, but may also be a short printing medium (for example, single sheets of paper). The material of the printing medium is not limited to paper, but may also be plastic film, corrugated cardboard, metal foil, or glass.

[0146] As described above with examples of specific embodiments, in the printing apparatus according to this invention, for example, the sensitivity changing unit may be configured to change the position of the current interruption unit between the first mode and the second mode.

[0147] In this case, the light-shielding section has a movable shutter that moves between a shielding position that blocks light from the light source toward the printing medium and an open position that retracts from the shielding position to allow direct incidence of light from the light source toward the printing medium. The movable shutter is configured to be in the open position in the first mode and in the shielding position in the second mode, and the current-cutting section moves integrally with the movable shutter, and the distance between the light source and the current-cutting section may be greater in the first mode than in the second mode. By increasing the distance between the light source and the current-cutting section, the temperature rise of the current-cutting section is suppressed even in the first mode when the output light amount from the light source is large, and the action of excessive protection can be avoided.

[0148] For example, the current interruption unit may be attached to a movable shutter. This allows for the simultaneous movement of the movable shutter and the repositioning of the current interruption unit.

[0149] In this case, the current interruption unit may further include a heat insulating member interposed between the current interruption element and the movable shutter, thereby preventing the operation of the current interruption unit from being affected by the temperature of the movable shutter.

[0150] Alternatively, for example, the current-blocking element may be provided outside the edge of the light source in a direction perpendicular to the direction of movement of the current-blocking section. By positioning the current-blocking element outside the edge of the light source, direct incidence of light can be suppressed, and the lifespan of the current-blocking element can be extended. In this case, the responsiveness of the temperature change of the current-blocking element to changes in output light intensity may decrease. For example, if a light-receiving member is provided in the current-blocking section to which light from the light source is directly incident, and the current-blocking element is attached to the light-receiving member, the temperature of the current-blocking element will also rise due to conductive heat from the light-receiving member, thereby improving responsiveness.

[0151] For the same reason, a light-shielding member may also be provided between the current-cutting element and the light source when the movable shutter is in the open position, to block light from entering the current-cutting element from the light source.

[0152] For example, the sensitivity changing unit may be configured to shield at least a portion of the light incident on the current blocking unit from the light source in the first mode, while not shielding in the second mode.

[0153] In particular, if the light-shielding portion has a movable shutter that moves between a shielding position that shields light from the light source toward the printing medium and an open position that retracts from the shielding position to allow direct incidence of light from the light source toward the printing medium, the movable shutter may be positioned in the open position in the first mode and in the shielding position in the second mode, and the current-cutting element may be shielded by the movable shutter when the movable shutter is in the open position, as viewed from the light source, but not shielded by the movable shutter when the movable shutter is in the shielding position.

[0154] Furthermore, the system may be further equipped with an airflow generation unit that generates an airflow from the light source toward the printing medium. With such a configuration, the heated gas generated around the light source can be used to heat the printing medium. This can improve energy efficiency.

[0155] Furthermore, for example, a thermostat can be suitably applied as the current interruption element in the present invention. [Industrial applicability]

[0156] This invention is suitable for a printing apparatus that dries a printing medium printed with ink or the like by heating. [Explanation of Symbols]

[0157] 1 Printing device 3. Paper feeding section (conveying section) 7. Paper output section (conveyor section) 21 Drying mechanism (drying section, drying device) 27 Control Unit 41 Heater (light source) 43. Shutter (light-shielding part) 45 Thermostat section (current interruption section) 47. Rectifier plate (airflow generation section) 48. Information board (airflow generation section) 49. Blower fan (airflow generation unit) 53 Light-shielding plate (light-shielding component) 431 Movable plate (movable shutter) 433 Shutter drive mechanism (sensitivity change section) 450 Thermostat (current interruption element) 451 Light-receiving plate (light-receiving component) 452 Insulation board (insulation material) WP continuous paper (printing medium)

Claims

1. A drying apparatus for drying printed media after printing, A light source that receives an electric current and emits light toward the printing medium, A current interruption unit including a current interruption element that interrupts the current supplied to the light source when the temperature rises above a predetermined interruption temperature, A sensitivity changing unit that changes the sensitivity characteristics showing the correlation between the output light amount from the light source and the temperature rise amount of the current interruption element by changing the incident pattern of the light incident on the current interruption unit, A light-shielding section is disposed between the light source and the printing medium, and the shielding ratio for the light directed from the light source toward the printing medium can be changed. A control unit that selectively executes a first mode and a second mode in which the output light quantity and the shielding ratio are different from each other. Equipped with, In the first mode, the output light quantity is greater and the shielding ratio is smaller than in the second mode. The drying apparatus wherein the sensitivity changing unit makes the sensitivity characteristics different between the first mode and the second mode, thereby keeping the temperature of the current interruption element below the interruption temperature in both the first mode and the second mode.

2. The drying apparatus according to claim 1, wherein the sensitivity changing unit changes the position of the current interruption unit between the first mode and the second mode.

3. The light-shielding portion is The system includes a movable shutter that moves between a shielding position that blocks the light from the light source toward the printing medium and an open position that retracts from the shielding position to allow the light from the light source to directly enter the printing medium. The movable shutter is positioned in the open position in the first mode and in the shielded position in the second mode. The drying apparatus according to claim 2, wherein the current interruption unit moves integrally with the movable shutter, and in the first mode, the distance between the light source and the current interruption unit is greater than in the second mode.

4. The drying apparatus according to claim 3, wherein the current interruption unit is attached to the movable shutter.

5. The drying apparatus according to claim 4, wherein the current interruption section has a heat insulating member interposed between the current interruption element and the movable shutter.

6. The drying apparatus according to claim 3, wherein the current interruption element is provided outside the end of the light source in a direction perpendicular to the direction of movement of the current interruption section.

7. The drying apparatus according to claim 6, wherein the current interruption unit has a light receiving member to which the light from the light source is directly incident, and the current interruption element is attached to the light receiving member.

8. The drying apparatus according to claim 3, wherein a light-shielding member is provided between the current-cutting element and the light source when the movable shutter is in the open position, to block the light that enters the current-cutting element from the light source.

9. The drying apparatus according to claim 1, wherein the sensitivity changing unit shields at least a portion of the light incident on the current interruption unit from the light source in the first mode, and reduces the amount of shielding in the second mode.

10. The light-shielding portion is The system includes a movable shutter that moves between a shielding position that blocks the light from the light source toward the printing medium and an open position that retracts from the shielding position to allow the light from the light source to directly enter the printing medium. The movable shutter is positioned in the open position in the first mode and in the shielded position in the second mode. The drying apparatus according to claim 9, wherein the current interruption element is shielded by the movable shutter when the movable shutter is in the open position, as viewed from the light source, and is not shielded by the movable shutter when the movable shutter is in the shielded position.

11. A drying apparatus according to any one of claims 1 to 10, comprising an airflow generating unit that generates an airflow from the light source toward the printing medium.

12. The drying apparatus according to any one of claims 1 to 10, wherein the current interruption element is a thermostat.

13. A transport unit that transports the printing medium, A printing unit that performs printing on the transported printing medium, A drying unit provided downstream of the printing unit in the transport path of the printing medium, having the same configuration as the drying apparatus described in claim 1, A printing device equipped with the following features.

14. The light-shielding portion is The printing apparatus according to claim 13, comprising a movable shutter that moves between a shielding position that shields the light from the light source toward the printing medium and an open position that retracts from the shielding position to allow direct incidence of the light from the light source toward the printing medium.

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