Ultraviolet bottom coating system and operation method thereof

Abstract

An ultraviolet bottom coating system includes a transport mechanism configured to transport a plurality of cans in a machine direction, where the plurality of cans each have a bottom surface and an uncured coating material applied on the bottom surface. The system also includes at least one ultraviolet light emitting diode (UV-LED) device configured to emit ultraviolet radiation to the plurality of cans, where the ultraviolet radiation is configured to cure the uncured coating material onto the bottom surface.

Description

[0001] This application is a divisional application of the application with application date of November 3, 2020, application number 202080076597.1, and invention name “Ultraviolet bottom coating system and its operation method”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. patent application No. 16 / 673,522, filed on November 4, 2019, the disclosure of which is incorporated herein by reference in its entirety as a part of this application. Technical Field

[0004] The present disclosure relates generally to coatings in can manufacturing and, more particularly, to systems and methods for curing coatings on bottom rim surfaces of cans. Background Art

[0005] Many known containers for providing food to consumers, such as metal cans, are coated to, for example, inhibit corrosion, improve the aesthetics of the container, and improve the handling of the container during the manufacturing process. When used to promote improved handling, an example coating may include an edge coating applied to the bottom edge surface of the container. The edge coating improves the handling of the container by providing an interface that reduces friction for the container as it travels along the production line. The edge coating is typically applied to the bottom edge surface in an uncured state and can then be cured with ultraviolet energy. However, many known ultraviolet energy emitters have inherent disadvantages, such as high power consumption, delayed output, limited available focal length, limited lamp life, and the need for an auxiliary support system with a large physical footprint. Summary of the Invention

[0006] In one aspect, a UV base coating system is provided. The system includes a conveyor mechanism configured to transport a plurality of cans in a machine direction, wherein each of the plurality of cans has a bottom surface and an uncured coating material applied to the bottom surface. The system also includes at least one UV-LED device configured to emit UV radiation toward the plurality of cans, wherein the UV radiation is configured to cure the uncured coating material on the bottom surface.

[0007] Advantageously, the at least one UV LED arrangement is water-cooled or air-cooled.

[0008] Advantageously, the conveying mechanism comprises a work surface having a width dimension perpendicular to the machine direction, wherein the at least one UV LED device is oriented to provide UV radiation across the entire length of the work surface in the width dimension.

[0009] Advantageously, the ultraviolet radiation emitted toward the conveyor mechanism defines a curing zone on the conveyor mechanism, the conveyor mechanism being further configured to transport the plurality of cans in the machine direction past the curing zone.

[0010] Advantageously, the at least one UV light emitting diode device is configured to emit UV radiation having only wavelengths defined within a range of about 200 nanometers (nm) to about 400 nm toward the plurality of tanks.

[0011] Advantageously, the at least one UV LED device is configured to activate to maximum power in less than about 1 second.

[0012] Advantageously, the at least one UV LED device is configured to provide a UV light emitting diode having a power consumption limited to approximately 2 watts per square centimeter (W / cm 2 ) to about 24 watts per square centimeter to emit the ultraviolet radiation.

[0013] In another aspect, a UV bottom coating system is provided. The system includes a conveyor mechanism configured to transport a plurality of cans in a machine direction, wherein each of the plurality of cans has a bottom surface. A coating applicator defines a coating zone on the conveyor mechanism, wherein the coating applicator is configured to apply uncured coating material to the bottom surfaces of the plurality of cans as they are transported through the coating zone. At least one ultraviolet light emitting diode (UV-LED) device defines a curing zone on the conveyor mechanism, the curing zone being located downstream of the coating zone in the machine direction. The at least one UV-LED device is configured to emit UV radiation toward the plurality of cans to cure the uncured coating material onto the bottom surfaces.

[0014] Advantageously, the at least one UV LED arrangement is water-cooled or air-cooled.

[0015] Advantageously, the at least one UV LED device has an activation time of less than about 1 second, the system further comprising a controller in communication with the delivery mechanism and the at least one UV LED device, the controller being configured to:

[0016] selectively activating and deactivating the at least one ultraviolet light emitting diode device; and

[0017] The transport speed of the conveying mechanism is controlled based on the activation time of the at least one ultraviolet light emitting diode device.

[0018] Advantageously, the coating applicator comprises a roller configured to contact the bottom surfaces of the plurality of cans conveyed through the coating zone.

[0019] Advantageously, the conveying mechanism comprises a work surface having a width dimension perpendicular to the machine direction, wherein the at least one UV LED device is oriented to provide UV radiation across the entire length of the work surface in the width dimension.

[0020] Advantageously, the at least one UV light emitting diode device is configured to emit UV radiation having only wavelengths defined within a range of about 200 nanometers (nm) to about 400 nm toward the plurality of tanks.

[0021] Advantageously, the at least one UV LED device is configured to activate to maximum power in less than about 1 second.

[0022] In another aspect, a method for forming an edge coating on a bottom surface of a metal can is provided. The method includes conveying a plurality of cans in a machine direction through a coating zone and then a curing zone; applying an uncured coating material to the bottom surfaces of the plurality of cans conveyed through the coating zone; and emitting ultraviolet radiation from at least one ultraviolet light emitting diode (UV-LED) device toward the plurality of cans conveyed through the curing zone. The ultraviolet radiation is configured to cure the uncured coating material on the bottom surface to form an edge coating.

[0023] Advantageously, the method further comprises cooling the at least one ultraviolet light emitting diode device with water or air.

[0024] Advantageously, emitting ultraviolet radiation comprises selectively activating and deactivating the ultraviolet light emitting diode arrangement based on a proximity of the plurality of tanks to the curing area.

[0025] Advantageously, the at least one UV LED device has an activation time to reach maximum power of less than about 1 second, wherein the plurality of cans are arranged in a plurality of groups, adjacent groups being spaced apart from each other by a distance in the machine direction, and wherein conveying the plurality of cans includes controlling a conveying speed of the plurality of cans based on the activation time and the distance between adjacent groups.

[0026] Advantageously, emitting ultraviolet radiation comprises emitting ultraviolet radiation having only wavelengths defined within a range of about 200 nanometers (nm) to about 400 nanometers toward the plurality of cans.

[0027] Advantageously, emitting ultraviolet radiation comprises emitting radiation at a temperature limited to about 2 watts per square centimeter (W / cm 2 ) to about 24 watts per square centimeter to emit the ultraviolet radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1is a block diagram of an exemplary UV bottom coating system.

[0029] Figure 2 for Figure 1 Schematic side view of a UV bottom coating system shown.

[0030] Figure 3 For use in Figure 1 A perspective view of an exemplary UV LED arrangement of a UV bottom coating system is shown.

[0031] Figure 4 for Figure 2 A schematic top view of a portion of a UV bottom coating system is shown.

[0032] Figure 5 A flow chart of an exemplary method for forming an edge coating on a bottom surface of a metal can. DETAILED DESCRIPTION

[0033] The embodiments described herein generally relate to systems and methods for curing a coating on the bottom edge surface of a can. For example, the system described herein includes a conveyor mechanism and one or more ultraviolet light emitting diode (UV-LED) devices. The conveyor mechanism receives a plurality of cans that have been formed from sheet stock on a production line. Coating areas and curing areas are defined on the conveyor mechanism, and the cans are conveyed through each area to form an edge coating on the bottom surface of each can. Uncured coating material is applied to the bottom surface of the cans conveyed through the coating area, and then the coating material is cured onto the bottom surface as the cans are conveyed through the curing area. The coating material is cured using ultraviolet radiation emitted from the UV-LED device.

[0034] In exemplary embodiments, the UV-LED device is cooled using a fluid, such as water or air. UV-LED devices offer numerous advantages over non-LED, air-cooled UV curing devices. For example, the power consumption of the UV-LED lamp is 50-90% lower than that of non-LED devices. Furthermore, UV-LED devices require less cooling than non-LED devices and are more easily cooled using fluids. Eliminating air supply equipment, such as ducting, housings, filters, blowers, and vacuum equipment, helps reduce the overall power consumption and physical footprint of the system described herein. Furthermore, a known drawback of non-LED, air-cooled UV curing devices is the tendency to draw airborne dust and oil mist into the non-LED device, which can damage the device and / or reduce its lifespan between maintenance intervals. Supplying a fluid, such as water, to the UV-LED device enables controlled cooling of the device, reducing the amount of contaminants introduced into the system. When activated, the UV-LED device also produces an instantaneous output of ultraviolet radiation, eliminates the need for precise focus to successfully complete the curing operation, and offers improved lamp life. Other advantages of UV-LED devices are that they generate less heat and lower surface temperatures of machine components, thereby improving the safety of machine operators and maintenance personnel. Therefore, the use of UV-LED devices in the UV bottom coating system described in this article helps to increase the production of cans in an efficient, safe and cost-effective manner.

[0035] As used herein, the term "can" refers to a one-piece or fully assembled multi-piece metal can, as well as a container portion of a multi-piece metal can that serves as a precursor to making a fully assembled multi-piece metal can.

[0036] Figure 1 is a block diagram of an exemplary UV bottom coating system 100, Figure 2 FIG1 is a side view schematic diagram of a UV bottom coating system 100. The UV bottom coating system 100 can be a stand-alone unit assembled off-line and incorporated into a production line (not shown), or it can be integrated as part of the production line itself. The system 100 can also be part of a new assembly or can be retrofitted into an existing assembly to upgrade its curing system. In an exemplary embodiment, the UV bottom coating system 100 includes a conveying mechanism 102, a coating applicator 104, and at least one UV-LED device 106. Figure 2As shown, the conveyor mechanism 102 conveys a plurality of cans 108 along a machine direction 110. The cans 108 can be manufactured along a production line and then conveyed to the conveyor mechanism 102 in any suitable orientation. As shown, each can 108 has a bottom surface 112, and the cans 108 are inverted on the conveyor mechanism 102 so that the bottom surface 112 faces upward. In such an embodiment, the conveyor mechanism 102 has a continuous working surface 114 that receives the cans 108 thereon, and the working surface 114 can be rotated by a track system that imparts motion using pulleys, rollers, etc. Alternatively, the cans 108 can be held on the conveyor mechanism 102 by a holding member (not shown) associated with each can 108. Therefore, the cans 108 can be oriented in any direction on the conveyor mechanism 102, which enables the UV base coating system 100 to function as described herein.

[0037] The coating applicator 104 defines a coating area 116 on the conveyor mechanism 102. In operation, the coating applicator 104 applies uncured coating material 118 to the bottom surfaces 112 of the plurality of cans 108 conveyed through the coating area 116. The coating applicator 104 can be any device that enables the UV bottom coating system 100 to function as described herein. Figure 2 As shown, coating applicator 104 is a roller 120 that may be covered with an elastomeric material, supplied with uncured coating material 118, and contacting bottom surfaces 112 of a plurality of cans 108 conveyed through coating area 116 to deposit uncured coating material 118 thereon. For example, roller 120 may rotate in a rotational direction 122 as cans 108 are conveyed through coating area 116. In an alternative embodiment, coating applicator 104 is a spray device oriented to discharge atomized uncured coating material toward conveyor mechanism 102. Thus, coating area 116 is defined by the size of roller 120 or by the discharge field of the spray device.

[0038] Any type of uncured coating material 118 may be applied to the bottom surface 112 of the can 108 to enable the UV bottom coating system 100 to function as described herein. For example, the uncured coating material 118 may be cured using UV energy, but does not require thermal energy to cure. Additionally, the uncured coating material 118 may be cured using less than about 500 mJ / cm 2 The coating is cured by energy of the UV-A radiation or in combination with UV-A radiation or alone and produces a clear varnish finish upon curing.

[0039] The UV-LED device 106 is located downstream of the coating applicator 104 in the machine direction 110 relative to the conveyor mechanism 102. The UV-LED device 106 defines a curing zone 124 on the conveyor mechanism 102. In operation, the UV-LED device 106 emits ultraviolet radiation 126 toward the plurality of cans 108 to cure uncured coating material 118 onto the bottom surface 112. For example, the ultraviolet radiation 126 emitted from the UV-LED device 106 defines a field of view 128 across the conveyor mechanism 102, and the field of view 128 defines the curing zone 124. The uncured coating material 118 reacts with the ultraviolet radiation 126, and the ultraviolet radiation 126 promotes the curing of the uncured coating material. As a result, the cans 108 conveyed through the curing zone 124 and then exiting the curing zone 124 have a cured edge coating 130 formed on their bottom surface 112.

[0040] In an exemplary embodiment, the UV-LED device 106 is a liquid-cooled or air-cooled device. Figure 1 , the UV bottom coating system 100 includes a cooling fluid supply device 132, which supplies cooling fluid, such as water or air, to the UV-LED device 106. Figure 3 , the UV-LED device 106 includes an outlet port 136 and an inlet port 134 in communication with the cooling fluid supply 132. In operation, the cooling fluid is directed into the UV-LED device 106 via the inlet port 134, heat generated by the UV-LED device 106 is transferred to the cooling fluid directed therethrough, and the heated cooling fluid is exhausted from the UV-LED device 106 via the outlet port 136. In this way, the UV-LED device 106 has operating parameters that help increase can production in an efficient, safe, and cost-effective manner.

[0041] For example, the UV-LED device 106 may be operated at approximately 2 watts per square centimeter (W / cm 2 ) to about 24W / cm 2 The UV-LED device 106 emits ultraviolet radiation 126 at a power output limited within a range of about 200 nanometers (nm) to about 400 nm, thereby enabling can production (e.g., curing) at a production speed of greater than about 80 feet per minute. In one embodiment, the UV-LED device 106 emits ultraviolet radiation 126 therefrom having a wavelength limited within a range of about 200 nanometers (nm) to about 400 nm. Alternatively, the UV-LED device 106 emits ultraviolet radiation 126 therefrom having a wavelength limited within a range of about 315 nm to about 400 nm and only within this limited range (i.e., the UV-A radiation band). Therefore, the operator of the ultraviolet base coating system 100 is not exposed to more harmful ultraviolet radiation bands, such as the UV-B and UV-C radiation bands.

[0042] The UV bottom coating system 100 also includes a power supply 138 for powering the UV-LED device 106. The UV bottom coating system 100 can include any suitable power supply 138 that enables the UV-LED device 106 to function as described herein. For example, the power supply 138 can be a DC power supply with a rated voltage within a range of approximately 40 volts to approximately 400 volts. In addition, in some embodiments, the power supply 138 is equipped with a monitoring feature that provides a signal output for input voltage failure, output voltage verification, internal fan failure, overheat warning, and / or fuse blown indication.

[0043] The UV base coating system 100 further includes a controller 140 that communicates with the conveyor mechanism 102, the coating applicator 104, the UV-LED device 106, and / or the cooling fluid supply 132. In some embodiments, the controller 140 controls the production speed of the work surface 114 moving along the machine direction 110, as well as the selective activation and deactivation of the coating applicator 104 and the UV-LED device 106. The tanks 108 can be arranged on the conveyor mechanism 102, or can be provided to the coating area 116 and the curing area 124 in a spaced or discontinuous manner. For example, referring to Figure 2 , the plurality of cans 108 are arranged in a plurality of groups 142, with each group being spaced apart from one another in the machine direction 110 by a distance D. The groups 142 may be spaced apart from one another in the machine direction 110 at regular or irregular intervals.

[0044] In operation, the controller 140 facilitates selective activation / deactivation of the coating applicator 104 based on the proximity of the plurality of tanks 108 to the coating area 116, and facilitates selective activation and deactivation of the UV-LED device 106 based on the proximity of the plurality of tanks 108 to the curing area 124. The UV-LED device 106 is capable of providing instant output without a warm-up time. The instant output can be defined by the activation time for the UV-LED device 106 to reach maximum power. The activation time can be less than about 1 second, less than about 0.75 seconds, less than about 0.5 seconds, or less than about 0.25 seconds. The activation / deactivation of the UV-LED device 106 can also be controlled by gradually energizing the UV-LED device 106 to maximum power over a duration greater than about 1 second.

[0045] The controller 140 controls the conveyance speed of the plurality of cans 108 based on the known activation times and the known distance D between adjacent groups 142 of cans 108 on the conveyor mechanism 102. For example, the conveyance speed is selected to increase the throughput of the UV base coating system 100 while also providing sufficient time for the coating applicator 104 and the UV-LED device 106 to be activated as the cans 108 are conveyed through the coating area 116 and the curing area 124, respectively. In this way, the controller 140 can selectively enable / activate and deactivate the coating applicator 104 and the UV-LED device 106 to reduce material costs, such as the cost of uncured coating material 118, and limit energy usage by the UV-LED device 106.

[0046] Figure 4 For UV bottom coating system 100 (such as Figure 2 In an exemplary embodiment, the working surface 114 of the conveyor mechanism 102 has a width dimension 144 that is substantially perpendicular to the machine direction 110. The UV-LED devices 106 can be oriented in any direction relative to the width dimension 144 to provide a direct current to each can 108 (both in FIG. 1 ) being conveyed through the curing area 124. Figure 2 14). As shown, the UV-LED device 106 is oriented substantially perpendicular to the machine direction 110 to provide curing for each can 108 conveyed through the curing zone 124. The UV-LED device 106 can be a single, elongated light emitting unit 146. Alternatively, the UV-LED device 106 can include a plurality of light emitting units 148 connected in series or otherwise coupled together and oriented to extend across the work surface 114 in the width dimension 144.

[0047] Figure 5 A flow chart of an exemplary method 150 for forming an edge coating on a bottom surface of a metal can is shown. The method 150 includes conveying 152 a plurality of cans in a machine direction through a coating zone and then through a curing zone, applying 154 an uncured coating material to the bottom surfaces of the plurality of cans conveyed through the coating zone, and emitting 156 ultraviolet radiation from an ultraviolet light emitting diode (UV-LED) device toward the plurality of cans conveyed through the curing zone.

[0048] Embodiments described herein relate to systems and methods for forming an edge coating on the bottom surface of a metal can. The systems and methods described herein achieve the aforementioned objectives by using a fluid-cooled UV-LED device to cure a coating material onto the metal can and form the edge coating in an efficient, safe, and cost-effective manner. Thus, the systems and methods described herein are capable of forming an edge coating on the bottom surface of a metal can during a high-speed production process.

[0049] An exemplary embodiment of a UV base coating system has been described in detail above. While the system is described and illustrated herein in conjunction with the production of metal beverage cans, the present invention may be used in any production system requiring UV curing of a coating onto an article. Furthermore, it should be noted that the components of the present invention are not limited to the specific embodiments described herein, but rather, aspects of each component may be utilized independently and separately from the other components and methods described herein.

[0050] This written description uses examples to disclose various embodiments, including the best mode, and to enable any person skilled in the art to practice the various embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A UV bottom coating system comprising: a conveyor mechanism configured to transport a plurality of cans in a machine direction, wherein each of the plurality of cans has a container portion including a bottom surface and a cylindrical body extending from the bottom surface; a coating applicator defining a coating zone on the conveyor mechanism, the coating applicator oriented above the conveyor mechanism and the plurality of cans to apply uncured coating material directly across bottom surfaces of the plurality of cans as the plurality of cans are conveyed through the coating zone; and a plurality of ultraviolet light emitting diode (UVLED) devices configured to emit UV radiation toward the plurality of cans, wherein the delivery mechanism is configured to orient the bottom surface toward the plurality of UV LED devices, wherein each of the plurality of UV LED devices is configured to emit the UV radiation at a power output defined within a range of about 2 watts per square centimeter to about 24 watts per square centimeter, wherein the UV radiation is configured to cure the uncured coating material onto the bottom surface such that when the coating material cures, the cured coating material produces a clear varnish finish on the cans, the plurality of UV LED devices comprising a cooling fluid inlet port and a cooling fluid outlet port; as well as A cooling fluid supply device is in communication with the cooling fluid inlet port and the cooling fluid outlet port of the plurality of ultraviolet light emitting diode devices to guide the cooling fluid through the plurality of ultraviolet light emitting diode devices.

2. The system according to claim 1, wherein: The cooling fluid includes water.

3. The system according to claim 1, wherein: The conveyor mechanism includes a work surface having a width dimension perpendicular to the machine direction, wherein the plurality of UV LED devices are aligned with each other perpendicular to the machine direction and oriented to provide UV radiation across the entire length of the work surface in the width dimension.

4. The system according to claim 1, wherein: Ultraviolet radiation emitted toward the conveyor mechanism defines a curing zone on the conveyor mechanism, and the conveyor mechanism is further configured to transport the plurality of cans through the curing zone in the machine direction.

5. The system according to claim 1, wherein: The plurality of ultraviolet light emitting diode devices are configured to emit ultraviolet radiation having only wavelengths defined within a range of about 200 nanometers to about 400 nanometers toward the plurality of tanks.

6. The system according to claim 1, wherein: The plurality of ultraviolet light emitting diode devices are configured to activate to maximum power in less than about 1 second.

7. The system according to claim 4, wherein: The plurality of ultraviolet light emitting diode devices have an activation time of less than about 1 second, the system further comprising a controller in communication with the delivery mechanism, the coating applicator, and the plurality of ultraviolet light emitting diode devices, the controller being configured to: selectively activating and deactivating the coating applicator based on proximity of the plurality of tanks to the coating area; selectively activating and deactivating the plurality of ultraviolet light emitting diode devices based on a proximity of the plurality of tanks to the curing area; and The conveying speed of the conveying mechanism is controlled based on the activation time of the plurality of ultraviolet light emitting diode devices.

8. The system according to claim 4, wherein: The conveyor mechanism includes a work surface having a width dimension perpendicular to the machine direction, wherein the plurality of UV LED devices are aligned with each other perpendicular to the machine direction and oriented to provide UV radiation across the entire length of the work surface in the width dimension.

9. The system according to claim 4, wherein: The plurality of ultraviolet light emitting diode devices are configured to emit ultraviolet radiation having only wavelengths defined within a range of about 200 nanometers to about 400 nanometers toward the plurality of tanks.

10. The system according to claim 4, wherein: The plurality of ultraviolet light emitting diode devices are configured to activate to maximum power in less than about 1 second.

11. The system according to claim 1, wherein: The plurality of cans are arranged in a plurality of groups, each of the plurality of groups being spaced apart from each other by a predetermined distance (D) in the machine direction.

12. The system according to claim 4, wherein: The conveyor mechanism is configured to convey the plurality of cans through the curing zone in a machine direction at a conveying speed greater than about 80 feet per minute.

13. The system according to claim 6, wherein: Ultraviolet radiation emitted toward the conveyor defines a curing zone on the conveyor, and the conveyor is further configured to convey the plurality of cans through the curing zone in a machine direction at a conveyance speed greater than about 80 feet per minute.

14. The system of claim 7, wherein the coating applicator comprises a roller oriented above the conveying mechanism and the plurality of cans to directly contact and apply uncured coating material directly across the bottom surfaces of the plurality of cans, the roller of the coating applicator being covered with an elastic material.

15. The system of claim 14, wherein the controller is further configured to rotate the roller of the coating applicator in a direction opposite to the machine direction of the conveyance mechanism.

16. The system of claim 1, wherein the coating applicator comprises a spray device oriented above the conveyor mechanism and the plurality of cans to discharge atomized uncured coating material toward the conveyor mechanism to cover bottom surfaces of the plurality of cans.

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