Abstract:
A robotic spray system is provided for accurately spraying mold release onto any size or shaped green tire. The system analyzes individual green tires using an integrated vision system. The system controls the robotic spray position, the fan, fluid, atomizing air, and tire rotation speed for optimal spray coverage on both the inside and outside of green tires. The system includes a conveyor, an overhead mounted camera located over an infeed station, and a second camera located perpendicular to the green tire&#39;s tread and several feet away from the center of the tire. Pictures of the green tire in the station are used to estimate the center and radius of the tire and locate the angle of the bar code with respect to the center of the tire. Reference points are provided from the camera images and robot positions are calculated to control the spraying.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method of and an apparatus for coating green or uncured tires. More particularly, the invention is directed to a system for robotically spraying a coating on predetermined areas both inside and outside green tires. 
     BACKGROUND OF THE INVENTION 
     Conventionally, pneumatic rubber tires are produced by molding and curing a green, or uncured, tire in a molding press in which the green tire is pressed outwardly against a mold surface by means of an inner fluid expandable bladder. By this method, the green tire is shaped against the outer mold surface which typically defines the tire&#39;s tread pattern and configuration of sidewalls. By application of heat, the tire is cured. Generally, the bladder is expanded by internal pressure provided by a fluid such as hot gas, hot water and/or steam which also participates in the transfer of heat for curing or vulcanization purposes. The tire is then usually allowed to cool somewhat in the mold, sometimes aided by added cold or cooler water to the internal surface of the bladder. Then the mold is opened, the bladder collapsed by removal of its internal fluid pressure and the tire removed from the tire mold. Such tire curing procedure is well known to those having skill in such art. 
     The use of synthetic rubber compounds in the manufacture of tires makes it necessary to apply suitable coating materials to the rubber surfaces of the fabricated tire carcasses to ensure proper distribution of rubber during the curing operation and the production of finished tires with unblemished surfaces. These coatings are generally liquid in form and are known as lubricants and anti-blemish paints, where the lubricants are applied to the interior surface of a green tire and the anti-blemish paints are applied to the outer surface at the sidewall areas. 
     The outside green tire paints serve the functions of allowing the rubber to slip as it comes in contact with the metal mold and the paints also serve as a release agent when at the end of the vulcanization cycle, the tire must separate from the mold. Another function of the paint is to provide bleeding of air which becomes trapped between the tire and the mold. Outside green tire paints also aid in the appearance of the finished tire. 
     Care must be taken that certain areas of the green tire are not coated and that the lubricant employed at the interior of the carcass does not reach any exterior surface of the carcass. Also, applying the coatings manually by either spraying or brushing is time consuming and laborious. Automatic applications, are well known in the art, however, these prior art applications require presorting and separate applicator apparatuses for tire size differences and outer spraying. 
     U.S. Pat. No. 3,507,247 discloses a coating apparatus including a work-actuated expandable chuck for holding a green tire as the tire is moved through coating and drying zones. The lubricant and paint applying apparatus includes an indexing mechanism for a turret structure which supports identical tire carcass-holding chucks. 
     The mechanism indexes the carcasses through the spraying and drying steps. Each chuck is manually adaptable to support any size tire carcass. The spray nozzles are manually located relative to the chuck location. 
     U.S. Pat. No. 5,631,028 discloses a green tire conveyor system for use in a molding machine zone, vulcanizing zone and finishing zone that includes a visual sensor attached to the center of a chuck for locating the center of a green tire via guide marks stamped on the tires. The visual sensor identifies the presence of a green tire and the type of tire. A second distance sensor is attached to a robot for height adjustment of a robot arm corresponding to the type of tire. 
     U.S. Pat. No. 4,778,060 discloses a tire processing system for sorting tires according to the Department of Transportation&#39;s assigned code to each tire manufacturer. The code is optically read by a line-scan camera and sorts green tires using additional information such as: the height of the tire measured from the upper bead, the tire centerline, and other digital optical images transmitted from a camera system located within a painting booth. 
     Other conventional methods for sorting and spraying the internal and external surfaces of green tires are illustrated in U.S. Pat. Nos. 4,125,639; 5,188,904; and 6,077,469. 
     While it is known in the art to implement cameras to aid in the locating, conveying and sorting of green tires, it is desirable to provide a vision system that can generate spray positions and fan data based on a two-dimensional image. Further, it is desirable to provide such a system for accurately spraying any size or shaped object with no part specific setup. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a robotic spray system is provided for accurately spraying mold release onto any size or shaped green tire. The system analyzes individual green tires using an integrated vision system. The system controls the robotic spray position, the fan, fluid, atomizing air, and tire rotation speed for optimal spray coverage on both the inside and outside of green tires. 
     In one embodiment, the components of the system include at least one conveyor for transporting a green tire through the vulcanizing process. At least one overhead mounted camera is located over an infeed station. This camera will preferably take a picture of the green tire in the station, estimate the center and radius of the tire and locate the angle of the bar code with respect to the center of the tire. A first robot then uses this angle to rotate or clock the tire to the desired position. 
     At least a second camera is preferably pointed toward the green tire&#39;s tread surface and several feet away from the center of the tire. Lighting is provided and positioned to point towards the tire so that the second camera only sees a shadow of the tire. The second camera checks for a transition from the black shadow of the tire to the white background, defining reference points for the outside tire spraying system. 
     The advantages of the tire spraying system of the present invention include fully programmable spray and spray positioning for fluid, fan and atomizing, maximizing the efficiency of spray material used and the positioning of the spray. By having a precise spray, overspray is drastically reduced, resulting in a reduction in material costs. 
     Using vision cameras to dynamically adjust robot spray positions based on varying tire profiles provides the ultimate flexibility to run different tire sizes. 
     Implementing modern technology with traditional conveying and chucking allows retro-fitting of existing systems with the present invention. Implementing the novel system in an existing or newly constructed system, such as a dual conveyor system, will produce a coated green tire approximately every 7-9 seconds while accurately placing the proper amount of inside and outside tire lube in only the areas specified with minimal overspray. A single conveyor system will deliver a coated green tire approximately every 12-14 seconds. 
     With this system, the green tires are measured while hanging on a chuck. A tire stretcher pulls the bottom bead out and the vision system takes the image. However, the tire stretcher is optional and the vision system can take the image without pulling the bottom bead out. The system then processes the necessary values fractional seconds before actual spray. 
     The system verifies through flow metering and pressure sensing that the spray has been dispensed. 
     The system can be equipped with an HMI (human/machine interface) providing operator fault status and diagnostics. These could include; tire mis-chuck, tire not sprayed, gun plugged, fluid delivery tank level low, limit not made, I/O status, etc. 
     The robot is the main motion element of the system. Robots are highly reliable and repeatable. The system does not index heavy tires on swing arms using traditional mechanical indexers. 
     The system according to the present invention is built for the ultimate in flexibility. Calculated robot spray positions are based on individual tire profiles. 
     Flexible variables include: infeed conveyor speed (VFD), spray fan, fluid, and atomizing air (proportional valves), tire rotation speed and position (servo controlled), exhaust intake (VFD), automatic gun purge, gun fluid/fan test, and chuck cycles (HMI selectable), robot to gun maintenance position, quick change spray guns, etc. 
     The system is able to handle bead diameters of 13″ to 24″, Tire Diameter of 20″ to 44″ and bead to bead height of 10″ to 22″. Custom engineered systems can be made for larger and/or smaller sizes. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
         FIGS. 1A and 1B  illustrate the robotic tire spray application system of the present invention for a single conveyor; 
         FIG. 2  illustrates the robotic tire spray application system of the present invention for a dual conveyor; 
         FIG. 3  illustrates a schematic view of the tire spray application system of the present invention; 
         FIGS. 4A-4C  illustrate a preferred embodiment of a green tire and method of the present invention; and 
         FIGS. 5A-5F  illustrate the analysis of two green tire profiles using the method of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. 
     A traditional tire sprayer employs high pressure, high volume guns resulting in overspray, requires a large footprint and has a cycle time of approximately 7-10 sec. These sprayers require large exhaust fans and a different model sprayer for different tire ranges. Further, these sprayers do not typically include a bar code mask, or pressure or flow sensing. 
     The present invention advantageously combines robotics with a vision system, eliminating the disadvantages of traditional tire sprayers. The robots are preferably provided with an integrated 7th axis control for servo chuck assembly. The system includes a flow meter and pressure sensor, along with vision cameras for reading bar code location and tire profile. A process valve control is included for complete spray control. The ultimate in flexibility is provided with this system where the robots follow tire profile. An overspray catch pan and removable filters are also provided. 
     With reference to  FIG. 1A , a first preferred embodiment of the green tire painting system  10  of the present invention is there shown and comprises a typical single feed station conveyor  12  and chuck system  14  that is well known in the art.  FIG. 2  illustrates a second preferred embodiment of the green tire painting system  100  of the present invention comprising a typical dual feed station conveyor  112  and chuck system  114  that is well known in the art. Generally, both systems  10 ,  100  include an overhead camera  16 ,  116  and a camera  18 ,  118  located to view toward the tread surface of the conveyed green tire  20 ,  120 . Each system  10 ,  100  also comprises an exhaust fan and stack  22 ,  122 . Lighting and a white backdrop can be used to aid the cameras  18 ,  118  in imaging each tire profile. A vision system of the present invention preferably includes cameras  16 ,  116  and  18 ,  118  used in conjunction with a vision PC and a robot controller. The green tires  20 ,  120  are positioned on the conveyors  12 ,  112  with one sidewall facing down and an opposite sidewall facing up. As shown in  FIG. 1B , the green tire  20  positioned as shown in  FIG. 1A  has an upwardly facing first sidewall outer surface  20 A a downwardly facing second sidewall outer surface  20 B and a tread surface  20 C extending in an annular lane connecting the sidewall surfaces. 
     Generally, the method of the present invention is illustrated in  FIGS. 1A ,  2  and  3  in use with a typical dual infeed conveyor system and comprises mounting an overhead camera  16 ,  116  over each feed station  12 ,  112 . The camera  16 ,  116  takes a picture of the tire  20 ,  120  and uses this information to estimate the center and radius of the tire  20 ,  120  along with locating the angle of the bar code (not shown) with respect to the center of the tire  20 ,  120 . 
     The second camera  18 ,  118  is preferably located perpendicular to the tire&#39;s tread and slightly upstream to clear the stack  22 ,  122 . These cameras  18 ,  118  are preferably 7′ to 12′ away from the center line of the tire  20 ,  120 . A white backdrop with lighting  24  ( FIG. 1B , where the illustrated set up applies to both the single and dual conveyor system) is positioned just downstream from the robots  26 ,  126 . The lighting  24  is preferably positioned to point towards the tire  20 ,  120  so that the cameras  18 ,  118  see only a shadow of the tire  20 ,  120 . The cameras  18 ,  118  field of view is preferably set up to see one half (½) of the largest tire to be handled. 
     With reference to  FIGS. 4A and 4B , the vision process for the pair of cameras  18 ,  118  is to first fit a line through the top and bottom edge of the tire  20 ,  120  and outer edge of the tread  28 ,  128 . Based on the location of these lines, the vision system places a series of calipers  30  perpendicular to each line. These calipers  30  start near the center of the tire  20 ,  120  and gradually move out. Each caliper  30  checks for transition from the black shadow of the tire  20 ,  120  to the white background as shown. When the vision system determines that this distance is equal to or greater than a predefined distance (approximately ½″ to 1″), the vision system saves the x-y reference position coordinates of the transition from white to black. The calipers  30  may be positioned tighter than shown to assure sufficient resolution if necessary. The reference position coordinates  32 ,  34 , a shown in  FIG. 4C , are used in conjunction with a computer program, such as the KAREL® program owned by Fanuc Robotics America, Inc. (located in Auburn Hills, Mich.), provided with the robot  26 ,  126  to determine the center of the line  36  and a position  38  that is a predefined distance away from the center of the line  36 . The KAREL® program may also calculate an equivalent point on the inside of the tire  20 ,  120  using a predefined parameter to set the thickness of the tire.  20 ,  120 . 
     Testing: Processing and Analysis were performed on two differently configured green tires. These tires were photographed and the PFD was set up to sample every two pixels and collect up to 600 data points. The PFD algorithm was run on both tires. The average processing time per tire was 2.98 seconds. The digitized tire profiles were exported to EXCEL® for plotting and analysis. A PC based software routine was created to perform the following: 
     1) Start on the top of the left side wall and find the 1st point that varies from calculated slope by a given distance. This is the start of the 1st spray area. 
     2) Start in the middle of the tread and move to the left finding the 1st point that varies from calculated slope by a given distance. This is the end of the 1st spray area and the beginning of the 2nd. 
     3) Start in the middle of the tread and move to the right finding the 1st point that varies from calculated slope by a given distance. This is the end of the 2nd spray area and the beginning of the 3rd. 
     4) Start on the top of the right side wall and find 1st point that varies from calculated slope by a given distance. This is the end of the 3rd spray area. 
     5) Calculate the length of each spray area (used for fan control) and a point that is perpendicular to the center and offset at the desired spray height. 
     6) The spray positions are sent to the robot for processing. 
     With reference to  FIGS. 5A-5C , an analysis was performed initially on a typically configured green tire as is well known in the art as best shown in  FIG. 5A . The following measurements and analysis was determined using the vision system described above: 
     
       
         
               
             
               
             
           
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
             
          
           
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Resulting in the digitized images illustrated in  FIGS. 5B and 5C . As described above, the camera  18  is utilized to locate the right sidewall surface  20 A or top edge portion of the tire  20  and fit a straight line  40  thereto, the left sidewall surface  20 B or bottom edge portion and fit a straight line  42  thereto, and the tread surface portion  20 C and fit a straight line  44  thereto. Then the calipers  30  are applied to locate the reference position coordinates  32 ,  34 , the center of the line  36  is determined and the position  38  ( FIG. 4C ) is calculated. 
     A second green tire configuration illustrated in  FIG. 5D  was proposed. In this configuration, the bead on both edges is bulged, providing a more pronounced angle between reference points  32 ,  34 . The following measurements and analysis was determined using the vision system described above: 
     
       
         
               
             
               
             
           
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
             
          
           
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     Resulting in the digitized images illustrated in  FIGS. 5D and 5E . As described above, the camera  18  is utilized to locate the right sidewall surface  20 A or top edge portion of the tire  20  and fit the line  40  thereto, the left sidewall surface  20 B or bottom edge portion and fit the line  42  thereto, and the tread surface portion  20 C and fit the line  44  thereto. Then the calipers  30  are applied to locate the reference position coordinates  32 ,  34 , the center of the line  36  is determined and the position  38  ( FIG. 4C ) is calculated. 
     The preferred green tire carcass of the present invention is provided with the pronounced double bead bulge indenting toward the central tread as best shown in  FIG. 5D . Thus the reference points illustrated in  FIG. 4C  are determined for both the upper and lower beads of each green tire carcass. 
     Using the preferred green tire carcass embodiment and with reference to  FIG. 1A , the following sequence of events provide a method for accurately spraying an outer and/or inner coating onto any size or shaped green tire when using a single conveyor tire spraying machine: 
     
       
         
               
             
           
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     The method for accurately spraying an outer coating on a preferred embodiment of a green tire carcass using a dual robot, single conveyor tire spraying machine of the present invention processes each tire in approximately 12 seconds. 
     Using the preferred green tire carcass embodiment and with reference to  FIG. 1B , the following sequence of events extending from a time lapse of one to seven seconds, eight to fourteen seconds, fifteen to twenty-one seconds, and twenty-two to twenty-eight seconds, provides a method for accurately spraying an outer and/or inner coating onto any size or shaped green tire when using a dual conveyor tire spraying machine: 
     
       
         
               
             
           
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
         
       
     
     The method for accurately spraying an outer and/or inner coating on a preferred embodiment of a green tire carcass using a dual robot, dual conveyor tire spraying machine of the present invention processes each tire in approximately 7 seconds. 
     As is illustrated above, once the reference points  32 ,  34  are determined, the outer spray is directed to the area between these points by robots  26 . This method prevents overspray, minimizes material waste and provides for spraying any size green tire carcass. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.