System and method for inside of can curing

Abstract

An improved inside of can curing technology is provided. One implementation uses narrowband, semiconductor produced infrared energy which is focused into the inside of the can to affect a very high-speed curing result and will directly impact the coating covering the inside walls of the can to rapidly cure the coating. Detempering and annealing of the aluminum can body does not have time to occur, thus leaving a stronger can with the same amount of aluminum or a can of the same strength but with less aluminum. It is also possible to eliminate the natural gas fueled oven that is the current standard and replace it with a completely hydrocarbon-free curing alternative that has superior performance. This high powered radiant, narrowband energy will be digitally controlled to introduce only the needed heat and to not overheat the can.

We claim: 
     
         1 . A method for use in a can manufacturing inside coating and curing process wherein coating has been sprayed onto an inside surface of cans, the method comprising:
 serially transporting the cans toward at least one curing station; and,   individually and electrically heating the cans using narrowband semiconductor-produced radiant infrared energy and optical elements positioned outside of the cans in the at least one curing station such that the coating on the inside surface of each successive can in a series of single-filed production cans is brought to a critical temperature to accomplish a linking curing process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the can.   
     
     
         2 . The method as set forth in  claim 1  wherein each can is formed from manufacturing tooling reconfigured to reduce a diameter of the cut edge of a blank from which a starting cup for the can is drawn whereby the thickness of coil stock aluminum is substantially the same as before tooling reconfiguration but such that the coil stock is narrower, thus reducing the weight of aluminum required to manufacture each can by greater than 3%. 
     
     
         3 . The method as set forth in  claim 1  wherein each can is formed using a can design and tooling that is modified to manufacture the can out of thinner coil stock material to reduce the weight of the aluminum from which the can is manufactured, whereby the heating to accomplish the linking curing process in less than 20 seconds eliminates a reduction in strength of the can such that the can will have similar sidewall axial strength, bottom reversal strength, and overall strength as compared to thicker cans cured for a longer time, which longer time weakened the metal. 
     
     
         4 . The method as set forth in  claim 1  wherein a semiconductor-based system producing the narrowband radiant energy may be turned on or off within microseconds and can heat the coating and/or the can to the critical temperature in less than 10 seconds. 
     
     
         5 . The method of  claim 1  wherein, a conveyer transports the cans during the curing process and utilizes continuous rotary motion whereby the at least one irradiation curing station is in continuous rotary motion synchronous with the cans being cured thereby and at least one of electrical power, cooling liquid, and control signals are connected to the at least one curing station through a rotary union. 
     
     
         6 . The method of  claim 5  wherein at least one of DC power supply, cooling heat exchanger, cooling chiller, cooling recirculation pump, and control system which serve the at least one curing station are moving in a rotary motion and synchronously with the cans, providing for a continuous rotary motion curing system wherein the continuous motion of the system helps in the cooling function. 
     
     
         7 . The method of  claim 1  wherein, a conveyer transports the cans during the curing process and utilizes an indexing rotary motion whereby multiple irradiation curing stations are located around the periphery of, but not on, a turret such that a group of cans is serially loaded into a selected number of empty stations around the turret while the turret is rotationally indexing so that the cans are each under their respective narrowband curing stations, the curing stations are actuated to cure the cans and then the turret is again rotationally indexed, which takes the cured cans out while a new set of cans is indexed into their positions under the curing stations for curing and the process continues to repeat. 
     
     
         8 . The method as set forth in  claim 1  wherein each can is individually cured in less than 5 seconds. 
     
     
         9 . The method as set forth in  claim 1  wherein narrowband semiconductor devices emit the narrowband radiant infrared energy at a wavelength matched to an absorption characteristic of the coating on the inside surface of each successive can. 
     
     
         10 . The method as set forth in  claim 1  wherein a wavelength of the narrowband radiant infrared energy used to heat is in a wavelength range of one of 800 nm to 1200 nm, 1400 nm to 1600 nm, and 1850 nm to 2000 nm. 
     
     
         11 . The method as set forth in  claim 1  wherein the narrowband infrared radiant energy used to heat is produced using at least one of semiconductor-based irradiation devices, light emitting diodes (LEDs), and laser diodes. 
     
     
         12 . The method as set forth in  claim 11  wherein the semiconductor devices that produce the irradiation are configured in multi-device arrays which combine the optical output power of more than 10 individual semiconductor devices to produce a total optical output power of more than 100 watts. 
     
     
         13 . The method as set for in  claim 11  wherein the semiconductor devices are laser diodes and such that the full width / half max output bandwidth is narrower than 20 nanometers. 
     
     
         14 . The method as set forth in  claim 13  wherein the semiconductor devices are surface emitting laser diodes whose full width / half max output bandwidth is narrower than 2 nanometers. 
     
     
         15 . The method as set forth in  claim 11  wherein the energy sources are comprised of arrays of surface emitting laser diodes producing their photonic energy output between 825 to 1075 nanometers. 
     
     
         16 . The method as set forth in  claim 1  wherein can handling facilitates individual curing of one lane of cans at production speeds in excess of 300 cans per minute. 
     
     
         17 . The method of  claim 16  wherein multiple parallel curing stations are arranged to individually cure at a total throughput speed in excess of 1,800 cans per minute while running all lanes except one, that lane being available for any maintenance that may be required or to provide additional production if needed so that a higher level of overall up-time may be achieved. 
     
     
         18 . The method as set forth in  claim 1  wherein the method eliminates hydrocarbon-based fuel use and more than 3% of aluminum is saved in a can manufacturing process as a result of higher speed, under 20 second curing which eliminates annealing and weakening of aluminum of a can body. 
     
     
         19 . The method as set forth in  claim 1  wherein specific additives are added into the coating specifically to interact with wavelength of narrowband infrared light utilized to improve performance or facilitate new functionality from the cured coating. 
     
     
         20 . The method of  claim 1  wherein the method facilitates reformulation of the coating to eliminate BPA or other undesirable components in coating formulation. 
     
     
         21 . The method as set forth in  claim 1  wherein equipment configuration of the method can be started and stopped easily without deleterious effect on the cans or downstream portions of a production process. 
     
     
         22 . The method as set forth in  claim 1  wherein implementation provides the ability to instantaneously and while in motion respond to modulation of the method as a result of sensory gained information from an inspection system. 
     
     
         23 . A system for use in can or container manufacturing for curing a coating which has been sprayed onto the inside walls of said containers, the system comprising:
 an ingoing trackwork or conveyor configured to organize or facilitate movement of individual containers into single-file order toward a second conveyor;   the second conveyor being configured as a rotary turret to move the individual containers into and away from at least one curing station;   the at least one curing station comprising an optical configuration wherein photonic energy from at least one array of surface emitting laser diodes passes through columnating optics and then is focused by at least one condensing lens element through a pinhole or aperture where beyond the photonic energy diverges to irradiate inside sidewalls of a coated container, such pinhole or aperture being located at the vertex of a reflective cone, such reflective cone functioning to reflect photonic energy back into the container to effect further curing work;   wherein the coating is cured in less than 20 seconds, thus being fast enough to prevent weakening or annealing from taking place in aluminum comprising the container;   the second conveyor delivering the containers and being guided off to a third conveyor configured to bring the container out and away from the second conveyor so empty pockets are available to load waiting uncured cans to continue serial curing while the cured containers are transferred on the third conveyor toward subsequent container manufacturing operations.   
     
     
         24 . The system of  claim 23  wherein the subsequent manufacturing operations include an inspection station located on the third conveyor, the function of which inspection station is at least to verify veracity of the coating and curing, by way of imaging inside each container and searching for bare metal areas, and to the extent that an imaged quality level of the cured coating is not sufficient, rejecting the container with a faulty coating at a rejection station which is configured into the third after the inspection station and then sending signals to at least one of a coating system control system and a curing control system to correct the respective process. 
     
     
         25 . A system for use in can or open top container manufacturing for curing a coating which has been sprayed onto the inside surface of said container, the system comprising:
 an ingoing trackwork or conveyor configured to move single-filed individual containers toward a second conveyor;   the second conveyor being configured to use a rotary motion table to move said containers into and away from at least once curing station;   the at least one curing station incorporating one of an engineered reflector which will serve to re-direct the photonic energy from the arrays through the open top of the container and directly onto the sprayed coating on the inside surfaces of the container to effect a curing process;   wherein the coating is cured in less than 20 seconds, thus being fast enough to prevent weakening or annealing from taking place in aluminum comprising the container;   wherein the second conveyor is configured to rotate to provide an exit for already cured containers to a third conveyor while new, uncured cans are serially loaded into vacated positions;   wherein the third conveyor is configured to receive the already cured containers on exit and convey the already cured containers along toward a next container manufacturing operations.   
     
     
         26 . The system of  claim 23  wherein the second conveyor is a rotating configuration which has multiple curing stations located around a periphery, each of which can be functioning simultaneously to cure the inside of a container with infrared energy produced by at least one laser diode array. 
     
     
         27 . The system of  claim 26  wherein the multiple curing stations comprises more than 8 curing stations. 
     
     
         28 . The system of  claim 26  wherein the second conveyor is a rotating configuration which has multiple curing stations which are rotated in synchrony with the containers so curing can continue without starting or stopping rotation of a table and wherein at least one of the electrical power, cooling, and control signals are connected to the curing stations through at least one rotary union. 
     
     
         29 . The system of  claim 23  wherein the ingoing trackwork or conveyor is configured to use gravity to advance the containers which are single-filed and apply pressure of gravity to feed each individual can into the second conveyor. 
     
     
         30 . A system for use in a can manufacturing inside coating and curing process wherein coating has been sprayed onto an inside surface of a can, the system comprising:
 a can handling system configured to serially move production cans into at least one curing zone;   broadband infrared sources positioned to individually and electrically heat inside surfaces of each can moved into a curing zone using optical elements positioned to direct irradiation toward upper sidewalls of the inside surface of the can such that the coating on the inside surface of each successive can in a series of production cans is brought to a critical temperature to produce a linking curing process in the coating, in less than 20 seconds to prevent de-tempering or annealing from occurring in the can body; and,   a control system configured to use sensor information to modulate output of the broadband infrared sources to maintain consistent curing temperature and results.   
     
     
         31 . A system for use in a can manufacturing inside coating and curing process wherein coating has been sprayed onto an inside surface of a can, the system comprising:
 a can handling system configured to serially move production cans into at least one curing zone;   arrays of semiconductor-based narrowband irradiation devices positioned to individually and electrically heat inside surfaces of each can moved into a curing zone using optical elements positioned outside the open end of the can such that the coating on the inside surface of each successive can in a series of production cans is brought to a critical temperature to produce a linking curing process in the coating, in less than 20 seconds to prevent de-tempering or annealing from occurring in the can; and,   a safety system comprising at least one of control panels, guards, enclosures and sensors configured so any guards or enclosures are light tight and cannot be removed or bypassed when power is supplied to the arrays.