Microwave Drying Equipment

Abstract

To provide a microwave dryer which enables reduction of a possibility that a web is placed into contact with a wave guide by a gas blown to the web to be damaged.SOLUTION: A microwave dryer includes: a wave guide 21 which radiates microwaves to a web W transported therein; and a gas supply part 16 which supplies a gas to be blown to the web W. Further, the wave guide 21 has: first through holes which supply the gas from the gas supply part 16 to one surface of the web W; and second through holes which supply the gas to the other surface of the web W.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a microwave drying device. [Background technology]

[0002] Conventionally, a microwave drying device that irradiates microwaves has been used to dry ink on a web printed by a printing machine. Also, a microwave drying device has been developed that evaporates water on a web by irradiating microwaves and promotes evaporation of water on the web by feeding gas into a waveguide (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-222134 A Summary of the Invention [Problem to be solved by the invention]

[0004] The microwave drying device according to Patent Document 1 includes a gas supply unit and a gas suction unit, and circulates air in the waveguide by supplying gas from the gas supply unit and suctioning gas from the gas suction unit, thereby suppressing an increase in humidity due to steam generated by microwave irradiation and promoting evaporation of moisture on the web.

[0005] However, since the supplied gas is only sprayed onto the printing surface on which the ink is attached, there is a risk that the sprayed gas will cause the web to flutter and come into contact with the waveguide. Therefore, there is a limit to the amount of gas that can be supplied, making it difficult to improve the drying efficiency.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a microwave drying device that can reduce the risk of the web coming into contact with the waveguide due to the blown gas, resulting in damage to the web. [Means for solving the problem]

[0007] In order to achieve the above object, a microwave drying apparatus according to the present invention comprises: It is connected to a microwave generator and irradiates microwaves onto the web being transported inside. Multiple A waveguide; a gas supply unit that supplies a gas to be blown onto the web; A measurement unit that measures the reflected power of the microwave in the waveguide; a control unit that controls an incident power of the microwave oscillated by the microwave oscillator based on the reflected power measured by the measurement unit; Equipped with The waveguide is The gas supplying section has a first through hole for supplying the gas from the gas supplying section to one side of the web and a second through hole for supplying the gas from the gas supplying section to the other side of the web. death, Microwave oscillators connected to one end of the web are arranged alternately on both sides in the transport direction of the web, The control unit is The incident power of the other waveguides is controlled so that the difference between the incident power and the reflected power of the waveguide disposed most downstream in the transport direction of the web is equal to or less than a predetermined threshold value.

[0010] Moreover, the waveguide is a U-shaped waveguide arranged so that the web passes through two straight portions. This may also be the case.

[0011] Further, the opening diameters of the first through hole and the second through hole are equal to or smaller than the wavelength of the microwave oscillated by the microwave oscillator. This may also be the case. Effect of the Invention

[0012] According to the microwave drying device of the present invention, the web is dried by blowing gas onto both sides of the web inside the waveguide, which makes it possible to suppress flapping of the web and reduce contact between the web and the waveguide. [Brief description of the drawings]

[0013] [Figure 1] 1 is a front view of a microwave drying device according to an embodiment of the present invention. [Diagram 2]FIG. 1 is a side view of a microwave drying device according to an embodiment. [Diagram 3] 3 is a cross-sectional view taken along the line AA' of FIG. [Figure 4] 1 is a plan view showing an internal structure of a microwave drying device according to an embodiment. FIG. [Diagram 5] 1A is a partial perspective view of a waveguide, and FIG. 1B is a partial cross-sectional view of the waveguide. [Figure 6] FIG. 2 is a functional block diagram of a control unit according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The microwave drying device 1 according to the present embodiment is a drying device that dries the ink on the web W printed in a printing unit by irradiating microwaves and blowing gas. Hereinafter, the microwave drying device 1 according to the embodiment of the present invention will be described with reference to the drawings.

[0015] As shown in the front view of Fig. 1, the side view of Fig. 2, and the cross-sectional view of Fig. 3, the microwave drying apparatus 1 includes a lower housing 11, an upper housing 12, an air cylinder 13, a trap 14, a web roll 15, a gas supply unit 16, and a waveguide 21. The microwave drying apparatus 1 also includes a control unit 40 (not shown).

[0016] In addition, in the drawings explaining each part of the microwave drying apparatus 1, an orthogonal coordinate system is set in which the left-right direction in a front view of the microwave drying apparatus 1 shown in FIG. 1 is the X-axis direction, the depth direction of the microwave drying apparatus 1 is the Y-axis direction, and the up-down direction of the microwave drying apparatus 1 is the Z-axis direction, and these will be referred to as appropriate.

[0017] The lower housing 11 is a housing with an open top, and houses the web roll 15, the waveguide 21, etc. An insertion opening 11a through which the web W is inserted is provided on one (-X side) surface (hereinafter also referred to as the insertion side surface) of the surfaces of the lower housing 11 perpendicular to the X axis. Also, a discharge opening 11b through which the web W is discharged is provided on the other (+X side) surface (hereinafter also referred to as the discharge side surface) of the surfaces of the lower housing 11 perpendicular to the X axis.

[0018] An air intake port 11c for supplying gas into the housing is formed on one side surface (-Y side) perpendicular to the Y axis of the lower housing 11 (hereinafter also referred to as the front side surface), and a duct hose for supplying gas is connected to the air intake port 11c. An exhaust port 11d for discharging gas from inside the housing is formed on the front side surface of the lower housing 11, and a duct hose for discharging gas is connected to the exhaust port 11d.

[0019] Upper housing 12 is a housing with an open bottom, and is disposed so as to cover the top of lower housing 11. An air inlet 12a for supplying gas into the housing is formed on the front side surface of upper housing 12, and a duct hose for supplying gas is connected to air inlet 12a. An exhaust port 12b for discharging gas from within the housing is formed on the front side surface of upper housing 12, and a duct hose for discharging gas is connected to exhaust port 12b.

[0020] 2, air cylinder 13 connects upper housing 12 and lower housing 11 at one side surface (+Y side) perpendicular to the Y axis (hereinafter also referred to as the rear side surface). Air cylinder 13 has a piston, and by moving the piston in the +Z direction, the connection part with upper housing 12 rises and upper housing 12 opens. Also, by moving the piston in the -Z direction, the connection part with upper housing 12 falls and upper housing 12 closes.

[0021] The trap 14 has a through hole 14a through which the web W is inserted. The trap 14 is connected to the insertion side surface of the lower housing 11 so that the through hole 14a communicates with the insertion port 11a of the lower housing 11. In addition, another trap 14 is connected to the discharge side surface of the lower housing 11 so that the through hole 14a communicates with the discharge port 11b of the lower housing 11. The trap 14 prevents microwaves from leaking from the microwave drying device 1 and also prevents steam generated by drying the ink on the web W from leaking out of the microwave drying device 1.

[0022] The web roll 15 is housed in the lower housing 11 and supports the web W transported within the lower housing 11. As shown in Fig. 1 and Fig. 4, the web roll 15 according to the present embodiment is disposed on the upstream side, the central portion, and the downstream side in the transport direction of the web W.

[0023] 3, the gas supply unit 16 arranged inside the lower housing 11 guides the gas supplied from the air supply port 11c of the lower housing 11 to the lower surface of the waveguide 21. The gas supply unit 16 arranged inside the upper housing 12 guides the gas supplied from the air supply port 12a of the upper housing 12 to the upper surface of the waveguide 21. The material, shape, etc. of the gas supply unit 16 are not particularly limited.

[0024] As shown in the plan view of FIG. 4, the waveguide 21 is a U-shaped waveguide having two straight portions and a bent portion. A microwave oscillator 22 that generates microwaves is connected to one end of the waveguide 21. As shown in FIGS. 5(A) and 5(B), a slit 21a through which the web W is inserted is formed on the side of the straight portion of the waveguide 21, and the waveguide 21 is arranged so that the web W transported in the X-axis direction passes through the two straight portions of the waveguide 21. In this embodiment, as shown in FIG. 4, four waveguides 21 are attached to the lower housing 11. Hereinafter, one side (-X side) of the waveguide 21 perpendicular to the X-axis is also referred to as an upstream side, and the other side (+X side) is also referred to as a downstream side. In addition, the slit 21a is preferably at a height that can transport the web W and does not leak microwaves out of the waveguide 21, and is, for example, about 10 mm high.

[0025] In general, the projected area of ​​the microwave oscillator 22 on the XZ plane is larger than the cross-sectional area (XZ cross section) of the waveguide 21 to which it is connected. Therefore, if the waveguides 21 are arranged with a sufficient clearance secured so that the microwave oscillators 22 do not come into contact with each other between adjacent waveguides 21, the length of the arrangement in the transport direction of the web W becomes large. Therefore, in this embodiment, the waveguides 21 are arranged so that the microwave oscillators 22 connected to their ends are alternately positioned on both sides in the transport direction of the web W. This allows the installation interval between the waveguides 21 to be reduced, and therefore the microwave drying device 1 can be made more compact.

[0026] As shown in Figs. 5A and 5B, a plurality of first through holes 21b are formed in one surface (+Z side) perpendicular to the Z axis of the waveguide 21 (hereinafter also referred to as the upper surface). A plurality of second through holes 21c are formed in the other surface (-Z side) perpendicular to the Z axis of the waveguide 21 (hereinafter also referred to as the lower surface). The first through holes 21b and the second through holes 21c are holes for introducing gas supplied to the inside of the lower housing 11 and the upper housing 12 into the inside of the waveguide 21. The size, shape, etc. of the first through holes 21b and the second through holes 21c are not particularly limited, but in order to prevent the microwaves oscillated by the microwave oscillator 22 from leaking out of the waveguide 21, it is preferable that the opening diameters of the first through holes 21b and the second through holes 21c are equal to or smaller than the wavelength of the oscillated microwaves. Here, the opening diameter according to this embodiment refers to the maximum length of the opening, regardless of the shapes of first through hole 21b and second through hole 21c.

[0027] Further, a power monitor M, which is a measurement unit (not shown), is installed near the microwave oscillator 22 of each waveguide 21. The power monitor M measures the reflected power of the microwave that is incident from the microwave oscillator 22 and reflected at the opposite end of the waveguide 21. The power monitor M transmits data of the measured reflected power to the control unit 40.

[0028] The control unit 40 is, for example, a computer device, and includes a control unit 41, a storage unit 42, a display unit 43, and an input unit 44, as shown in FIG.

[0029] The control unit 41 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and controls the operation of the microwave drying device 1, and also controls the microwave oscillator 22 to adjust the incident power of the microwaves to be oscillated, based on the reflected power measured by the power monitor M, etc.

[0030] The control unit 41 loads various operation programs and data stored in the ROM, storage unit 42, etc. of the control unit 41 into the RAM and operates the CPU, thereby realizing each function of the control unit 41 shown in Fig. 6. In this way, the control unit 41 operates as a reflected power acquisition unit 411, a calculation unit 412, and an oscillator control unit 413.

[0031] The reflected power acquiring unit 411 controls the power monitor M to acquire measurement data indicating the magnitude of the reflected power of the microwave in the waveguide 21. In addition, the reflected power acquiring unit 411 transmits the acquired measurement data of the reflected power to the calculation unit 412.

[0032] The calculation unit 412 calculates the microwave attenuation in each waveguide 21, i.e., the microwave energy absorbed by the moisture contained in the ink on the web W passing through the waveguide 21, based on the reflected power acquired by the reflected power acquisition unit 411, and estimates the degree of drying of the ink. The calculation unit 412 transmits data relating to the estimated degree of drying of the ink on the web W to the oscillator control unit 413.

[0033] The oscillator control unit 413 adjusts the incident power by controlling the microwave oscillator 22 connected to each waveguide 21, based on the degree of dryness of the ink estimated by the calculation unit 412. The control of the incident power will be described later in detail.

[0034] The storage unit 42 is a non-volatile memory such as a hard disk or a flash memory, and stores the measured values ​​of the power monitor M, the estimated degree of dryness of the ink, a control program for the incident power of the microwaves, and the like.

[0035] The display unit 43 is a display device, such as a liquid crystal display, provided in the control unit 40, which is a computer device. The display unit 43 displays the incident power of the microwave, the reflected power measured by the power monitor M, the estimated degree of drying of the ink, etc.

[0036] The input unit 44 is an input device for inputting instructions to start and end the operation of the microwave drying apparatus 1, parameters related to the control of the microwave oscillator 22, etc. The input unit 44 is a keyboard, a touch panel, a mouse, etc. provided in the control unit 40.

[0037] Hereinafter, a method for drying ink on a web W using a microwave drying device 1 according to the present embodiment will be described with reference to the drawings.

[0038] The web W that has been printed by a printing machine (not shown) and transported to the microwave drying device 1 is inserted into the lower housing 11 through the through hole 14a of the upstream trap 14, as shown in the cross-sectional view of Fig. 3 and the plan view of Fig. 4. The web W inserted into the lower housing 11 is supported by the web roll 15, and is inserted into the waveguide 21 through the slit 21a on the upstream side surface of the waveguide 21.

[0039] Inside the waveguide 21, the ink on the web W is dried by microwaves generated by the microwave oscillator 22. More specifically, the microwaves generated by the microwave oscillator 22 propagate through the waveguide 21 from the end of the waveguide 21 to which the microwave oscillator 22 is connected. The microwaves propagated from one end of the waveguide 21 to which the microwave oscillator 22 is connected are reflected at the bent part of the U-shaped waveguide 21 and propagate to the end to which the microwave oscillator 22 is not connected. Furthermore, the microwaves reflected at the end propagate to the end on the microwave oscillator 22 side.

[0040] When the microwaves are irradiated onto the web W, they vibrate the water molecules contained in the ink on the web W, causing the water molecules to generate heat and evaporate, thereby drying the ink.

[0041] The microwaves oscillated by microwave oscillator 22 are absorbed by the moisture contained in the ink and gradually attenuate. Therefore, the energy of the microwaves reflected at the end of waveguide 21 to which microwave oscillator 22 is not connected (reflected power) is smaller than the energy of the microwaves oscillated by microwave oscillator 22 (incident power).

[0042] In this embodiment, the waveguides 21 are arranged so that the microwave oscillators 22 connected to one end are alternately positioned on both sides in the transport direction of the web W. This prevents the microwaves irradiated to the web W from being biased in the width direction (Y-axis direction) of the web W, and suppresses the occurrence of uneven drying. Furthermore, by alternately arranging the microwave oscillators 22 on the sides of the microwave drying device 1, the width of the device in the X-axis direction is reduced, making the device more compact.

[0043] The control unit 41 also estimates the drying state of the ink on the web W based on the measurement value of the power monitor M. The reflected power acquisition unit 411 of the control unit 41 measures the incident power of the microwaves oscillated from the microwave oscillator 22 by the power monitor M and the reflected power of the microwaves absorbed and attenuated by the moisture in the ink. The calculation unit 412 estimates the degree of drying of the ink on the web W based on the difference between the incident power and the reflected power. As described above, the microwaves in the waveguide 21 are absorbed and attenuated by the moisture in the ink, so that the attenuation of the microwaves is large in the waveguide 21 on the upstream side in the transport direction of the web W and is small in the waveguide 21 on the downstream side where drying has progressed.

[0044] The oscillator control unit 413 controls the microwave oscillator 22 based on the degree of dryness in each waveguide 21 estimated by the calculation unit 412, and adjusts the incident power so that the difference between the incident power and the reflected power in the most downstream waveguide 21 is equal to or less than a preset threshold. For example, when it is determined that the difference between the incident power and the reflected power in the second most downstream waveguide 21 is equal to or less than a predetermined threshold and is sufficiently dried, the oscillator control unit 413 reduces the incident power of each microwave oscillator 22. This makes it possible to prevent the web W from being over-dried.

[0045] Furthermore, gas supplied from the air inlet 12a of the upper housing 12 is blown onto the web W in the waveguide 21 through the first through hole 21b in the upper surface of the waveguide 21. Moreover, gas supplied from the air inlet 11c of the lower housing 11 is blown onto the web W in the waveguide 21 through the second through hole 21c in the lower surface of the waveguide 21. By blowing the gas onto the printing surface of the web W, the boundary film on the ink can be reduced and the drying efficiency can be improved.

[0046] In this embodiment, as described above, gas is blown onto both sides of the web W. This makes it possible to prevent the web W from coming into contact with devices such as the waveguide 21 due to the blown gas, and thus to prevent the web W from being damaged. Furthermore, gas flows out from both sides (upper and lower sides) of the web W of the slits 21a of the waveguide 21, thereby improving the effect of preventing the web W from coming into contact with the waveguide 21. Furthermore, since it is possible to prevent the web W from coming into contact with the waveguide 21, it is possible to increase the amount of gas blown onto the web W. This makes it possible to further improve the drying efficiency.

[0047] The type and temperature of the gas blown onto the web W are not particularly limited, but from the viewpoint of promoting evaporation of moisture on the web, it is desirable that the temperature of the gas be room temperature or higher.

[0048] The gas blown onto the web W is exhausted to the outside of the housing through the exhaust port 12b of the upper housing 12 and the exhaust port 11d of the lower housing 11. This replaces the air in the waveguide 21 and removes the steam in the waveguide 21, thereby preventing condensation in the microwave drying device 1.

[0049] As described above, according to the microwave drying device 1 of this embodiment, gas is blown onto both sides of the web W inside the waveguide 21, thereby reducing the risk of the web W flapping and coming into contact with the waveguide 21. This allows the amount of gas blown onto the web W to be increased, making it possible to improve the drying efficiency of the ink printed on the web W.

[0050] In the present embodiment, the incident power of each waveguide 21 is controlled so that the difference between the incident power and the reflected power of the waveguide 21 arranged on the most downstream side is equal to or less than a predetermined threshold value that has been set in advance, but this is not limited to this. For example, when there is a waveguide 21 in which the difference between the incident power and the reflected power is equal to or less than a predetermined threshold value, the oscillator control unit 413 may stop the oscillation of the microwave oscillator 22 of the waveguide 21 downstream of this waveguide 21. This makes it possible to more easily prevent the web W from being overdried. [Explanation of symbols]

[0051] 1 microwave drying device, 11 lower housing, 11a insertion port, 11b exhaust port, 11c air inlet, 11d exhaust port, 12 upper housing, 12a air inlet, 12b exhaust port, 13 air cylinder, 14 trap, 14a through hole, 15 web roll, 16 gas supply section, 21 waveguide, 21a slit, 21b first through hole, 21c second through hole, 22 microwave oscillator, 40 control unit, 41 control section, 411 reflected power acquisition section, 412 calculation section, 413 oscillator control section, 42 memory section, 43 display section, 44 input section, W web

Claims

1. a plurality of waveguides connected to a microwave generator for irradiating microwaves onto the web conveyed therethrough; a gas supply unit that supplies a gas to be blown onto the web; A measurement unit that measures the reflected power of the microwave in the waveguide; a control unit that controls an incident power of the microwave oscillated by the microwave oscillator based on the reflected power measured by the measurement unit, The waveguide is a first through hole for supplying gas from the gas supply unit to one surface of the web and a second through hole for supplying gas to the other surface of the web, Microwave oscillators connected to one end of the web are arranged alternately on both sides in the transport direction of the web, The control unit is controlling the incident power of the other waveguides so that a difference between the incident power and the reflected power of the waveguide disposed at the most downstream side in the transport direction of the web becomes equal to or less than a predetermined threshold value; A microwave drying apparatus characterized by the above.

2. The waveguide is a U-shaped waveguide arranged so that the web passes through two straight sections.

2. The microwave drying device according to claim 1 .

3. The opening diameters of the first through hole and the second through hole are equal to or smaller than the wavelength of the microwave oscillated by the microwave oscillator.

3. The microwave drying device according to claim 1 or 2.

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