Microwave UV curing and drying system for printing

Abstract

A microwave UV curing and drying system for printing, comprising a magnetron (1), a waveguide (2), a resonant cavity (3), and a shielding cover (4). The magnetron is communicated with the waveguide by means of a cylindrical head (11) at the lower part of the magnetron; the waveguide is communicated with the resonant cavity; and the magnetron, the waveguide and the resonant cavity are sequentially and longitudinally connected from top to bottom. The resonant cavity comprises a cavity shell (31), and a reflector (32) and a microwave lamp tube (33) which are arranged in the cavity shell; and elongated through holes (321) allowing electromagnetic waves to pass through and elliptical through holes (322) for heat dissipation are formed in the reflector. The shielding cover is arranged outside an opening in the front wall of the cavity shell. The system further comprises a sealing cover; and the sealing cover is fastened to the front surface of the shielding cover and the front surface of the magnetron. According to the system, the arrangement direction of the magnetron, the waveguide and the resonant cavity changes; the resonant cavity is improved, so that the reflector and the shielding cover are well fixed and the electromagnetic waves are completely shielded; and the magnetron can use an independent fan outlet for heat dissipation, thereby prolonging the service life of the magnetron.

Description

A microwave UV curing and drying system for printing Technical Field

[0001] The invention belongs to the technical field of printing machinery manufacturing, and in particular relates to a microwave UV curing and drying system for printing. Background Art

[0002] Currently, most sheet-fed offset presses still use traditional UV lamp systems. For example, a multi-color, folio offset press typically uses six traditional UV lamps, each rated at 16 kW. Each lamp is equipped with a 1 kW cooling fan and a 25 kW chiller, for a total power rating of 127 kW. During normal production, the average power usage is around 70 kW. Since 2017, with the continued development of LED UV curing, some sheet-fed UV presses have gradually been equipped with LED UV lamps. However, LED UV curing is a cold light source, and its performance with UV-specific inks has been suboptimal. First, the photoinitiator wavelength of some ink coating solutions is less than 365 nm, while LED UV systems cannot initiate curing due to their wavelength of 365-410 nm. Second, printing and coating compatibility necessitates the addition of additives to improve their suitability. Some additives require high heat to evaporate and dry during the UV curing process. LED UV cold light sources rely on a portion of violet light, and the conversion of violet light into heat makes it difficult to achieve thorough drying. Therefore, the current single-sheet UV printing machine either continues to use traditional UV lamp groups, or uses a hybrid UV system of traditional UV lamp groups and LED UV lamp groups. Because the installation position of the traditional lamp group is a long-term lighting position, the power saving effect is not obvious, and the average practical power is about 55 kilowatts. The defects of mercury lamps such as high energy consumption, fire hazards, ozone pollution, poor stability, and short life have not been significantly improved.

[0003] Microwave UV curing systems have been developed in recent years. They are high-tech products developed by integrating the latest scientific and technological achievements in optics, power electronics, plasma science, and magnetic materials science. Microwave UV's spectral energy is concentrated, sharing the ultraviolet spectrum characteristics of traditional UV systems. Its infrared radiation is minimal compared to traditional lamps, resulting in a luminous efficiency of approximately 75%. It produces no ozone, and lamps with different spectra can be used depending on the target being cured. This allows for excellent curing and drying of traditional UV inks and coatings, while also offering a relatively long lifespan. Furthermore, it boasts high power density, high radiation efficiency, and adjustable spectrum and intensity. However, due to the complexity of its structure, the lamps are relatively large, making them unsuitable for smaller UV printing and coating equipment, such as sheet-fed offset presses, satellite rotary presses, and digital printers. Due to the limited availability of accessories in its early stages of development, its ease of use, maintenance, and luminous efficiency need to be improved. The electromagnetic shielding components used in its early stages also require testing to minimize electromagnetic wave leakage.

[0004] The current microwave UV still has the following shortcomings:

[0005] 1. Currently, the UV curing area in the delivery section of all sheet-fed offset printing presses is designed with a reserved curing space based on a traditional lamp system. Generally, the space available is large enough to accommodate a three-finger traditional lamp system, approximately 50 cm wide, 18 cm high, and 135 cm long, running between the two wall panels of the printing press. Currently available microwave UV lamp systems are 30 cm high and 20 cm wide, emitting downward light, and are significantly higher than the reserved space. Therefore, microwave UV lamps cannot be placed in printing presses for ink drying and curing. Currently, microwave UV systems are not suitable for offset UV curing.

[0006] 2. Resonant Cavity: a. The waveguide resonant cavity has circular and beveled holes on all four sides for heat dissipation. The beveled holes are at a 45-degree angle to the wall, and their diameter, measured from the wall, is greater than 6.5 mm, which is larger than one-twentieth of the wavelength of the electromagnetic waves emitted by the magnetron. This causes electromagnetic wave leakage, and the beveled holes cause more severe leakage. b. The resonant cavity reflector is 110 mm wide across the width of the UV lamp assembly. To meet electromagnetic wave shielding requirements, the reflector requires a wide contact surface for fixation, and electromagnetic induction heat also requires a large volume for heat storage and dissipation. Therefore, the resonant cavity is widened by 45 mm on both sides to fix the reflector and dissipate heat, resulting in a total lamp assembly width of 200 mm. A lamp assembly this wide would be difficult to install in a typical printing press, or would cause certain difficulties in operating the printing press.

[0007] 3. Reflector: The reflector's fixed edge is too wide and thick. While this prevents deformation and facilitates electromagnetic wave shielding, it makes the device too wide overall, making it difficult to install in the small spaces reserved for some printers. The reflector's openings are also imperfectly positioned and sized, making it difficult to start the lamp, forcing it to only start at high power. The magnetron, reflector, and lamp need to be aligned to achieve the optimal position to enable low-power startup.

[0008] 4. Shielding cover: a. Stainless steel clips, tungsten wire welding, and bending can easily cause deformation; b. The metal shielding strip is made of brass silver-plated filaments woven into a round strip. Due to its lack of elasticity, each disassembly and assembly can easily cause inconsistent tightness, resulting in induction sparks, inability to start or slow startup, and reduced lighting efficiency; the edge of the shielding cover is bent to increase rigidity and reduce deformation, but this makes processing more difficult, and is prone to radio wave leakage and induction arcing, resulting in problems such as difficulty in starting and low lighting efficiency.

[0009] 5. Heat dissipation: A fan first dissipates heat to the magnetron, and then dissipates the heat through the small holes on the waveguide and is discharged through the shielding cover; because the diameter of the heat dissipation holes on the waveguide in the wall is too large, electromagnetic waves may leak. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a microwave UV curing and drying system for printing.

[0011] The technical solution adopted by the present invention to solve the technical problem is: a microwave UV curing and drying system for printing, comprising a magnetron, a waveguide, a resonant cavity, and a shielding cover, wherein the magnetron is connected to the waveguide through a cylindrical head at its lower portion, and the waveguide is connected to the resonant cavity, and is characterized in that the magnetron, the waveguide, and the resonant cavity are longitudinally connected in sequence from top to bottom;

[0012] The resonant cavity comprises: a cavity shell, a reflector, and a microwave lamp. The front wall of the cavity shell is set to be open, and a first through hole is set in the middle of the upper wall of the cavity shell. The waveguide is connected to the resonant cavity through the first through hole. The reflector and the microwave lamp are both arranged in the cavity shell.

[0013] The reflector is rectangular, and has two longitudinal long through holes arranged horizontally thereon, and a plurality of regularly arranged elliptical through holes are provided on both sides of the two long through holes, the long through holes and the elliptical through holes are both provided on the upper half of the reflector, and the lower half of the reflector is a non-hole reflective mirror panel;

[0014] The left and right side walls of the cavity shell are symmetrically provided with a "C"-shaped semicircular step, the lower end of the step is located at the front end of the left and right side walls of the cavity shell; the left and right sides of the reflector are respectively closely connected to the left and right side walls of the cavity shell at the intersection of the height of the "C"-shaped semicircular step. After the close connection, the reflector also presents a "C"-shaped semicircular arc, its "C"-shaped bottom faces the rear wall of the resonant cavity, and its "C"-shaped opening faces the open opening of the front wall of the cavity shell; the elongated through hole and the elliptical through hole are located at the upper part of the "C"-shaped semicircular arc top of the reflector, and the lower part of the "C"-shaped semicircular arc top is a non-perforated reflector panel; the microwave lamp is transversely arranged in the middle part of the cavity shell, the "C"-shaped opening of the reflector faces the microwave lamp, and the two ends of the microwave lamp are respectively connected to the lower end of the "C"-shaped semicircular step on the left and right side walls of the cavity shell;

[0015] A semicircular flat plate is inserted at the lower end of the "C"-shaped semicircular step on the left and right side walls of the cavity shell, respectively. The arc edges of the two semicircular flat plates are connected to the two side edges of the reflector, and the straight edges are pressed onto the left and right side walls of the cavity shell by the shielding cover;

[0016] The upper and lower edges of the reflector are both provided with skirts bent 90 degrees, and a sealing strip is provided inside the skirts; the skirts are pressed onto the left and right side walls of the cavity shell by the shielding cover;

[0017] The shielding cover is arranged outside the open opening of the front wall of the cavity shell; the shielding cover includes a square frame, a woven mesh, a conductive silicone sealing strip, and a pressure strip. The four edges of the square frame are each provided with an embedding groove, and the four edges of the woven mesh are all embedded in the embedding groove; the conductive silicone sealing strip is arranged in the embedding groove and above the woven mesh, and the pressure strip is arranged in the embedding groove and above the conductive silicone sealing strip;

[0018] It also includes a sealing cover, which is buckled on the front surface of the shielding cover and the magnetron; a light-transmitting square hole is set at the lower part of the sealing cover, and the position of the light-transmitting square hole corresponds to the position of the open mouth; and a small square hole is set at the upper part of the sealing cover.

[0019] Preferably, it further includes a first and a second cooling fan, the magnetron is connected to the first cooling fan through an air duct; a second through hole is provided on the rear wall of the resonant cavity, and the second cooling fan is connected to the resonant cavity through the second through hole.

[0020] Preferably, an annular heat sink is sleeved on the outer surface of the magnetron body.

[0021] Preferably, the braided mesh is cross-woven and made of tungsten wire.

[0022] Compared with the existing technology, the beneficial effects of the present invention are: 1) The volume of the lamp body is reduced and its structure is changed, which can adapt to the curing and drying requirements of a specific space printing press; the electromagnetic wave leakage value is further reduced, and its maintainability is improved; the matching of the resonant cavity, reflector, lamp tube, etc. is improved to achieve the optimal effect, thereby improving the performance of the present invention. 2) The arrangement direction of the magnetron, waveguide, and resonant cavity is changed. The height of the lamp group in this arrangement is 16 cm, which is smaller than the spatial height of the printing press of 18 cm, and the width is 26 cm, which is smaller than the width of the printing press of 50 cm. The present invention can be smoothly placed in the curing and drying of a single-sheet UV printing and paper collection unit; the size of a microwave UV single lamp has an effective curing area of ​​170 mm. Arranging the lamp group to the required size according to the curing width requirements can meet the curing and drying requirements of printed materials of different lengths and formats. 3) Improved resonant cavity: a. Under ideal conditions, the resonant cavity can fully transmit electromagnetic waves. During the conversion of electromagnetic wave energy into light energy, the proportion of heat generated by induction is minimal. With a 4.5mm aperture, multiple tests and extended burn-in periods, coupled with a 10W dual-roller bearing DC blower and monitored by a thermal imager, achieved a maximum cavity shell temperature of 60°C and a maximum lamp tube temperature of 176.7°C, adequately meeting heat dissipation requirements. b. Improved and secured reflector and shield: The reflector and shield of the present invention utilize a flat, narrow-edged design and are positioned where the resonant cavity opening and the housing fit tightly. The housing, constructed of cast aluminum, aligns evenly with the resonant cavity, effectively securing the reflector and shield and thoroughly shielding electromagnetic waves. 4) Electromagnetic waves are rationally moved through the elongated aperture and the elliptical through-hole for heat dissipation, and the apertures are adjusted and tested to match the resonant cavity, the lighting power range of the lamp assembly, and the temperature of the magnetron lamp. A 24-hour test showed that the mercury lamp and magnetron temperatures were controlled between 60°C and 120°C when the lamp power was between 500W and 1500W, an average reduction of 30°C compared to the original setup, significantly extending the magnetron's service life. b) The fixed edge of the reflector is bent 90 degrees, 5mm wide, and a sealing strip is added to the bottom, reducing the width of the lamp assembly while also addressing electromagnetic wave sealing issues. 5) The shielding cover adopts a flat design, with a conductive silicone sealing strip attached to a narrow 5mm edge. This provides optimal hardness and elasticity, ensuring a good seal and preventing sparks and heat from igniting the shielding cover seal. 6) A separate fan outlet is used to dissipate heat from the magnetron, directing hot air to the substrate surface. The small opening and high air velocity help remove solvents. The resonant cavity generates relatively low heat, primarily dissipating heat to the lamp, cavity walls, and reflector. This results in lower magnetron temperatures than existing technologies, meeting heat dissipation requirements and extending the magnetron's service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a front view of a first embodiment of the present invention;

[0024] FIG2 is a right side view of a first embodiment of the present invention;

[0025] FIG3 is a schematic diagram of a three-dimensional structure of the first embodiment of the present invention;

[0026] FIG4 is a second schematic diagram of the three-dimensional structure of the first embodiment of the present invention;

[0027] FIG5 is a front view of the shielding cover according to the first embodiment of the present invention;

[0028] FIG6 is a cross-sectional view taken along line AA in FIG5 ;

[0029] Figure 7 is an enlarged view of point B in Figure 6;

[0030] FIG8 is a front view of the resonant cavity of Example 1 of the present invention;

[0031] FIG9 is a perspective view of a cavity housing according to a first embodiment of the present invention;

[0032] FIG10 is a front view of the cavity housing according to the first embodiment of the present invention;

[0033] FIG11 is a front view of a reflector according to a first embodiment of the present invention;

[0034] FIG12 is a side view of a reflector installed in a resonant cavity according to a first embodiment of the present invention;

[0035] FIG13 is a top view of a reflector installed in a resonant cavity according to a first embodiment of the present invention;

[0036] FIG14 is a perspective view of a reflector installed in a resonant cavity according to a first embodiment of the present invention.

[0037] The following are marked in the figure:

[0038] Magnetron; 11. Cylindrical head; 12. Annular heat sink; 2. Waveguide; 3. Resonant cavity; 31. Cavity shell;

[0039] "C"-shaped semicircular step; 32, reflector; 321, long through hole; 322, elliptical through hole;

[0040] Semicircular reflective plate; 324, skirt; 33, microwave lamp; 34, first through hole; 35, second through hole; 4, shielding cover; 41, square frame; 42, woven mesh; 43, conductive silicone sealing strip; 44, pressure strip; 45, mounting through hole; 6, first cooling fan; 7, second cooling fan. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings: Example

[0042] As shown in Figures 1 to 14, a microwave UV curing and drying system for printing includes a magnetron 1, a waveguide 2, a resonant cavity 3, and a shielding cover 4. The magnetron 1 is connected to the waveguide 2 through a cylindrical head 11 at its lower portion, and the waveguide 2 is connected to the resonant cavity 3. The magnetron 1, waveguide 2, and resonant cavity 3 are connected longitudinally in sequence from top to bottom.

[0043] The resonant cavity 3 includes: a cavity shell 31, a reflector 32, and a microwave lamp 33. The front wall of the cavity shell 31 is set to be open. A first through hole 34 is set in the middle of the upper wall of the cavity shell 31. The waveguide 2 is connected to the resonant cavity 3 through the first through hole 34. The reflector 32 and the microwave lamp 33 are both set in the cavity shell 31.

[0044] The reflector 32 is rectangular and has two longitudinal long through holes 321 arranged horizontally thereon. A plurality of regularly arranged elliptical through holes 322 are provided on both sides of the two long through holes. The long through holes 321 and the elliptical through holes 322 are both provided in the upper half of the reflector 32. The lower half of the reflector 32 is a non-porous reflective mirror panel.

[0045] The left and right side walls of the cavity shell 31 are symmetrically provided with "C"-shaped semicircular steps 311, and the lower ends of the steps are located at the front ends of the left and right side walls of the cavity shell 31; the left and right sides of the reflector 32 are respectively in close contact with the left and right side walls of the cavity shell 31 at the intersection of the height of the "C"-shaped semicircular steps 311. After the close contact, the reflector 32 also presents a "C"-shaped semicircular shape, with its "C"-shaped bottom facing the rear wall of the cavity shell 31 and its "C"-shaped opening facing the cavity shell 31. 1. The open opening of the front wall; the elongated through hole 321 and the elliptical through hole 322 are located at the upper part of the "C"-shaped semicircular arc top of the reflector 32, and the lower part of the "C"-shaped semicircular arc top is a non-hole reflector panel; the microwave lamp tube 33 is arranged horizontally in the middle part of the cavity shell 31, and the "C"-shaped opening of the reflector 32 faces the microwave lamp tube 33. The two ends of the microwave lamp tube 33 are respectively connected to the lower end of the "C"-shaped semicircular step 311 on the left and right side walls of the cavity shell 31;

[0046] Semicircular reflective plates 323 are respectively inserted at the lower ends of the "C"-shaped semicircular steps 311 on the left and right side walls of the cavity housing 31. The arc edges of the two semicircular reflective plates 323 are connected to the two side edges of the reflector 32. The straight edges of the two semicircular reflective plates 323 are pressed against the left and right side walls of the cavity housing 31 by the shielding cover 4.

[0047] The upper and lower edges of the reflector 32 are both provided with a 90-degree bent skirt 324, and a sealing strip is provided inside the skirt 324; the skirt 324 is pressed onto the left and right side walls of the cavity shell 31 by the shielding cover 4;

[0048] The shielding cover 4 is positioned outside the opening of the front wall of the cavity housing 31. It comprises a square frame 41, a braided mesh 42, a conductive silicone sealant 43, and a pressure strip 44. The square frame 41 is provided with slots on all four sides, and the braided mesh 42 is nested within these slots. The conductive silicone sealant 43 is nested within the slots above the braided mesh 42, while the pressure strip 44 is nested within the slots above the conductive silicone sealant 43. The braided mesh 42, conductive silicone sealant 43, and pressure strip 44 are stamped and connected to the square frame 41. The square frame is provided with mounting holes 45. The braided mesh 42 is cross-woven and made of tungsten wire.

[0049] It also includes a sealing cover, which is buckled on the front surface of the shielding cover 4 and the magnetron 1; a light-transmitting square hole is set at the lower part of the sealing cover, and the light-transmitting square hole corresponds to the position of the open opening of the front wall of the cavity shell 3; a small square hole is set at the upper part of the sealing cover.

[0050] It also includes a first cooling fan 6 and a second cooling fan 7. The magnetron 1 is connected to the first cooling fan 6 through an air duct. An annular heat sink 12 is provided on the outer surface of the main body of the magnetron 1. A second through hole 35 is provided on the rear wall of the cavity shell 3, and the second cooling fan 7 is connected to the resonant cavity 3 through the second through hole 35.

[0051] The working principle of the present invention is:

[0052] As shown in Figures 1 to 13, a high-frequency DC power supply is used to provide DC power to the magnetron 1. The magnetron 1 generates electromagnetic waves through its cylindrical head 11. The electromagnetic waves are transmitted to the resonant cavity 3 through the waveguide 2. The electromagnetic waves store electromagnetic wave energy in the resonant cavity 3. The electromagnetic wave energy is transmitted to the microwave lamp 33 through the long through hole 321 of the reflector 32, and stimulates the gas and mercury in the microwave lamp 33 to emit ultraviolet light. The first cooling fan 6 dissipates heat from the magnetron 1 through the cooling air duct. The second cooling fan 7 dissipates heat from the resonant cavity 3, the reflector 32, and the microwave lamp 33.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A microwave UV curing and drying system for printing, characterized in that: A microwave UV curing and drying system for printing, comprising a magnetron, a waveguide, a resonant cavity, and a shielding cover. The magnetron is connected to the waveguide through a cylindrical head at its lower part, and the waveguide is connected to the resonant cavity. It is characterized in that the magnetron, the waveguide, and the resonant cavity are longitudinally connected in sequence from top to bottom; The resonant cavity includes: a cavity shell, a reflector, and a microwave lamp tube. The front wall of the cavity shell is set as an open mouth, and a first through hole is arranged in the middle of the upper wall of the cavity shell. The waveguide is connected to the resonant cavity through the first through hole; the reflector and the microwave lamp tube are both arranged in the cavity shell; The reflector is rectangular, and two longitudinal long through holes are arranged horizontally thereon. A plurality of regularly arranged elliptical through holes are arranged on both sides of the two long through holes. The long through holes and the elliptical through holes are both arranged in the upper half of the reflector, and the lower half of the reflector is a non-porous reflecting mirror panel; On the left and right side walls of the cavity shell, a semi-circular step in the shape of "C" is symmetrically arranged. The low end of the step is located at the front ends of the left and right side walls of the cavity shell; the left and right sides of the reflector are respectively in close contact with the left and right side walls of the cavity shell at the high and low joints of the semi-circular step in the shape of "C". After close contact, the reflector also presents a semi-circular shape in the shape of "C", with the bottom of its "C" shape facing the rear wall of the resonant cavity and the opening of its "C" shape facing the open mouth of the front wall of the cavity shell; the long through holes and the elliptical through holes are located above the arc top of the "C" shape of the reflector, and the lower part of the arc top of the "C" shape of the reflector is a non-porous reflecting mirror panel; the microwave lamp tube is horizontally arranged in the middle part of the cavity shell, the opening of the "C" shape of the reflector faces the microwave lamp tube, and both ends of the microwave lamp tube are connected to the left and right side walls of the cavity shell and the low ends of the semi-circular steps in the shape of "C"; At the low ends of the semi-circular steps in the shape of "C" on the left and right side walls of the cavity shell, a semi-circular flat plate is respectively inserted. The arc edges of the two semi-circular flat plates are connected to the two sides of the reflector, and the straight edges are pressed by the shielding cover on the left and right side walls of the cavity shell; Both the upper and lower edges of the reflector are provided with skirts bent at 90 degrees, and sealing strips are arranged in the skirts; the skirts are pressed by the shielding cover on the left and right side walls of the cavity shell; The shielding cover is arranged outside the open mouth of the front wall of the cavity shell; the shielding cover includes a square frame, a woven mesh, a conductive silicone sealing strip, and a pressing strip. Embedding grooves are arranged on the four peripheries of the square frame, and the four peripheries of the woven mesh are embedded in the embedding grooves; the conductive silicone sealing strip is arranged in the embedding groove and above the woven mesh, and the pressing strip is arranged in the embedding groove and above the conductive silicone sealing strip; It further includes a sealing cover, and the sealing cover is buckled on the front surfaces of the shielding cover and the magnetron; a light-transmitting square hole is arranged at the lower part of the sealing cover, and the position of the light-transmitting square hole corresponds to that of the open mouth; a small square hole is arranged at the upper part of the sealing cover.

2. The microwave UV curing and drying system for printing according to claim 1, wherein: It further includes first and second cooling fans. The magnetron is connected to the first cooling fan through an air duct; a second through hole is provided on the rear wall of the resonant cavity, and the second cooling fan is connected to the resonant cavity through the second through hole.

3. The microwave UV curing and drying system for printing according to claim 2, wherein: An annular heat sink is sleeved on the outer surface of the magnetron body.

4. The microwave UV curing and drying system for printing according to claim 3, wherein: The woven mesh is cross-woven and made of tungsten wire.

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