Abstract:
An electropolishing or electroplating system and method for metal conveyor belts is described. In some embodiments, the system has a metal conveyor belt held in constant tension; a tank for holding an electrolytic fluid, the tank having an interior space suitable to contain the fluid, a metal plate and the metal conveyor belt; and an electrical current supply. In an electropolishing application, the current passes from the metal conveyor belt, through the fluid and into the metal plate. In an electroplating application, the current passes from the metal plate, through the fluid and into the metal conveyor belt.

Description:
BACKGROUND 
     Field 
     Embodiments of the claimed invention relate to electropolishing and electroplating, and in particular, systems and methods for electropolishing or electroplating continuous assemblies of interconnected components, such as conveyor belts. 
     Description of Related Art 
     Conveyor belt systems are used in various industrial fields for material handling and processing purposes. For instance, conveyor systems are used within food processing systems in which food items are placed on the support surface of a conveyor belt and processed, while being conveyed from one location to another. Various types of conveyor belts exist, including modular conveyor belts, which are especially popular in food processing systems. Moreover, conveyor systems are often used in a helical accumulator such as that disclose in U.S. Pat. No. 5,070,999 to Layne et al. which allows storage of a large number of items in the conveyor system. 
     In the food processing industry, it is of the utmost importance that conveyors belts are sanitary. To accomplish this, conveyor belts are conventionally wiped down, washed, and/or steamed on a regular basis. However, conveyor belts are often very long, extending hundreds or even thousands of feet. In these cases, the belts can be difficult to clean and may become less durable over time due to the thorough process needed to maintain their sanitation. 
     Electropolishing and electroplating has been previously used in a number of applications. U.S. Pat. No. 4,895,633 to Seto et al. discloses a conventional molten salt electroplating apparatus for forming plating on steel strips, sheets, and wires. A steel strip is continuously unwound from a pay-off reel, passed through a looper, and sent to a pretreatment apparatus. Next, the surface of the steel strip is plated as it passes between electrodes immersed in electroplating solution. The steel strip is then washed and dried, passed through a looper and a shearing machine, then wound onto a tension reel. 
     U.S. Pat. No. 7,407,051 B1 to Farris et al. discloses a stainless steel sprocket support shaft for a nozzleless conveyor belt and sprocket cleaning apparatus. The stainless steel sprocket may be surface finished by electropolishing. U.S. Pat. No. 5,491,036 to Carey, II et al. generally discloses an electrolysis process for applying a tin coating of carbon steel. 
     SUMMARY OF THE INVENTION 
     The above described patents propose a variety of methods for electropolishing or electroplating various materials. However, there still exists a need for a system and method for electropolishing and electroplating metal conveyor belts that improves sanitation and product release characteristics, particularly with respect to conveyor belts used in food processing. There also exists a need for a system and method for electropolishing and electroplating metal conveyor belts that reduces wear and friction on the conveyor belts. 
     In view of the foregoing, one aspect of the present invention provides a continuous electropolishing and/or electroplating process for metal conveyor belts. This process provides benefits such as improved sanitation, improved product release characteristics, and reduced wear and friction, which are particularly important for conveyor belts used in food processing. 
     To create a continuous process, the belt is fed from an infeed roll, passed through an electrolytic fluid bath, and collected on a take-up roll after the electropolishing or electroplating process. Guide rolls keep the belt in tension, direct the belt into the bath and position the belt between two metal plates parallel to a surface of the belt that are immersed in the electrolytic fluid, while also maintaining conductivity through the belt. As the belt leaves the electrolytic bath, it passes by an air knife that removes excess electrolyte, before being rinsed to neutralize the electrolyte. The electrolytic fluid that is used in the process is cooled and filtered continuously to maintain a temperature greater than or equal to 120° F. and less than or equal to 150° F. The filter size is preferably less than 3 microns, but can be other sizes as well. 
     The belt may be guided past one or multiple sets of metal plates. In one embodiment, by directing the belt 180° around a roller, the belt may pass on opposite sides of the same plate, such that both sides of the plate may be used in the electropolishing or electroplating process. The plates may be fixed in the electrolytic bath, or some plates may be movable to facilitate the loading of the belt into the belt path. 
     Belts are separated into smaller sections, typically 50 to 100 feet long, for ease of handling and shipping. These sections may be connected sequentially, such that the leading end of a new roll of belt is connected to the trailing end of the previous roll of belt, to maintain a continuous process. These sections can be disconnected and placed on separate take-up rolls after processing. Leader chains may also be used to guide the ends of the belt into and out of the bath while maintaining tension. Materials used in the process, such as the plate material and electrolyte material, may be of any suitable type such as are currently used or may be developed for electropolishing and electroplating. 
     According to one embodiment, an electropolishing or electroplating system is provided that comprises an inner tank configured to hold electrolytic fluid, the inner tank comprising a conductive plate, an outer tank surrounding the inner tank, a tension device configured to maintain tension in a continuous assembly of interconnected components between a first roller and a second roller, and a system drive configured to move the continuous assembly of interconnected components from the first roller through the inner tank and onto the second roller. 
     A method for electropolishing or electroplating a continuous assembly of interconnected components is also described. According to one embodiment, the method comprises unrolling a continuous assembly of interconnected components from a first roller, guiding the continuous assembly of interconnected components into an electrolytic bath comprising at least one conductive plate, applying current to at least one of the continuous assembly of interconnected components and the at least one conductive plate, moving the continuous assembly of interconnected components out of the electrolytic bath, and rolling the continuous assembly of interconnected components onto a second roller. Tension is maintained in the continuous assembly of interconnected components between the first roller and the second roller. 
     Still other aspects, features and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating a number of exemplary embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention also is capable of other and different embodiments, and its several details can be modified in various respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only. 
         FIG. 1  is a cutaway view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 2  is a cutaway view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with another embodiment. 
         FIG. 3A  is a top view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 3B  is a side view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 3C  is a perspective view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 4A  is a top view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 4B  is a side view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 4C  is a perspective view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 4D  is a cutaway side view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
         FIG. 4E  is a cutaway perspective view of a system for electropolishing or electroplating a continuous assembly of interconnected components in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A system and method for electropolishing or electroplating a continuous assembly of interconnected components is described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments. It is apparent to one skilled in the art, however, that the present invention can be practiced without these specific details or with an equivalent arrangement. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  is a cutaway view of a continuous system  100  for electropolishing or electroplating metal conveyor belts in accordance with one embodiment of the invention. The system  100  has an inner tank  160  surrounded by a larger, outer tank  150 . Inner tank  160  is adapted to receive one or more conductive plates  180   a - c , and comprises one or more guide rollers  200   b ,  200   c . Conductive plates  180   a - c  can be made of any conductive material. In one embodiment, conductive plates  180   a - c  are made of copper. 
     Both inner tank  160  and outer tank  150  are adapted to hold electrolytic fluid  170 . Electrolytic fluid  170  is allowed to overflow from inner tank  160  into outer tank  150 . Electrolytic fluid  170  may flow into inner tank  160  and/or outer tank  150  via one or more input pipes  105 , and out of inner tank  160  and/or outer tank  150  via one or more output pipes  103 . Electrolytic fluid  170  exiting inner tank  160  and/or outer tank  150  is filtered by screen filter  110  and bag filter  120  achieve filtration of electrolytic fluid  170 . Screen filter  110  and/or bag filter  120  can have a size of 3 microns or less. Although shown and described with respect to both an inner tank and an outer tank, it is contemplated that the electrolytic fluid  170  can be recirculated by means of input and output pipes in inner tank  160  only, and outer tank  150  can be omitted. 
     Electrolytic fluid  170  is then passed through pump  130  to chiller  140 , where it is cooled before being returned to inner tank  160  and/or outer tank  150  via input pipe  105 . In one embodiment, electrolytic fluid  170  is cooled to a temperature between 120° F. and 150° F. by chiller  140 . Thus, according to system  100 , electrolytic fluid  170  can be filtered and cooled continuously. The illustrated arrows within output pipes  103  and input pipes  105  show the exemplary travel of electrolytic fluid  170  therein. 
     Although shown and described as screen filter  110 , bag filter  120 , pump  130  and chiller  140  being consecutively positioned, any suitable configuration may be employed. For example, screen filter  110  and bag filter  120  can be entirely separate from chiller  140 , the order of the components can be changed, the path of electrolytic fluid  170  can be varied, and more or less output pipes  103  and/or input pipes  105  can be employed. In another embodiment, one or more of screen filter  110 , bag filter  120 , pump  130  and chiller  140  may be positioned within inner tank  160  and/or outer tank  150 . 
     To create a continuous electropolishing or electroplating process, a continuous assembly of interconnected components (in this embodiment, a conveyor belt  190 ) is guided through the illustrated system according to the arrows alongside conveyor belt  190 , which indicate one exemplary direction of travel of the conveyor belt  190 . Conveyor belt  190  is metal, and may be stainless steel. Guide roller  200   a  directs the conveyor belt  190  into the electrolytic fluid  170 , and positions the conveyor belt  190  between plates  180   a  and  180   b  immersed in the electrolytic fluid  170 . In one embodiment, conveyor belt  190  passes horizontally above outer tank  150  and inner tank  160 , and turns vertically downward via guide roller  200   a  into inner tank  160  comprising electrolytic fluid  170 . Below plates  180   a ,  180   b , conveyor belt  190  passes around guide roller  200   b  and is directed toward guide roller  200   c . Conveyor belt  190  then passes upward toward guide roller  200   d . In one embodiment, guide roller  200   d  is adapted to allow conveyor belt  190  to travel horizontally away from outer tank  150  and inner tank  160 . In this embodiment, guide rollers  200   b  and  200   c  are submerged in electrolytic fluid  170 , while guide rollers  200   a  and  200   d  are outside of electrolytic fluid  170 . However, any other suitable configuration of guide rollers  200   a - d  may be employed. 
     As shown in  FIG. 1 , plates  180   a - c  are submerged in electrolytic fluid  170  comprised in inner tank  160 . In this embodiment, conveyor belt  190  passes vertically between plate  180   a  and  180   b ; along the edge of plate  180   b ; then vertically between plates  180   b  and  180   c . Thus, all sides and angles of conveyor belt  190  are exposed to plates  180   a - c . Also, although conveyor belt  190  is shown entering and exiting inner tank  160  from above, other configurations, including a horizontal configuration, may be used in accordance with other embodiment of the invention. 
     In the illustrated embodiment, metal plates  180   a - c  each have a surface parallel to a surface of conveyor belt  190 . These surfaces of plates  180   a - c  can be vertical, as shown in  FIG. 1 . In another embodiment, the surfaces of plates  180   a - c  can be angled from horizontal such that gas pockets cannot form on the surface and interfere with current transfer between the plates  180   a - c  and conveyor belt  190 . 
     Although three plates are shown in  FIG. 1 , it is understood than any suitable number and combination of plates may be used, as well as any suitable path for conveyor belt  190 . In one embodiment, by directing conveyor belt  190  180° around one or more guide rollers, conveyor belt  190  may pass on opposite sides of the same plate  180 , such that both sides of the plate  180  may be used in the electropolishing or electroplating process. In this manner, belt  190  may be guided in a serpentine path around multiple plates  180 . 
     Conveyor belt  190  may be a single, continuous belt or may comprise a plurality of component parts (e.g., links and rods) that are connected together to form the belt. When conveyor belt  190  is traveling in a generally straight line, the component parts may be aligned in the same direction, and interconnecting parts of each component part may be covered by interconnecting parts of another component part in a default or straight-line position or orientation. As conveyor belt  190  passes over rollers  200   a - d  and passes through turns, such as in the serpentine path shown in  FIG. 1 , the component parts may be allowed to turn with respect to one another into multiple positions, thereby more directly exposing previously covered portions of the component parts to electrolytic fluid  170  and plates  180   a - c . As such, in the embodiment shown in  FIG. 1 , by passing the belt  190  through the serpentine path shown, the system  100  facilitates exposure of certain portions of component parts that are not otherwise exposed or exposed well if a simple linear path were to be used during the electropolishing or electroplating process. 
     In the embodiment shown in  FIG. 1 , it is noted that conveyor belt  190  and its component parts have an upper and lower side, and that guide rollers  200   b  and  200   c  in inner tank  160  facilitate improved exposure of the lower side of the interconnecting parts of each component part. Although not shown in  FIG. 1 , configurations may be employed whereby guide rollers  200   a  and  200   d  are provided in electrolytic fluid  170  so as to facilitate improved exposure of the upper side of the interconnecting parts of each component part. In still other embodiments, other configurations may be adapted to facilitate exposure of interconnecting parts of each component part to electrolytic fluid  170  and plates  180   a - c.    
     Current may be applied to conveyor belt  190  with a conductive brush or roll contact, or other suitable dynamic electrical connection. In an electropolishing application, the current passes from conveyor belt  190 , through electrolytic fluid  170 , and to plates  180   a - c . In an electroplating application, the current passes from plates  180   a - c , through electrolytic fluid  170 , and to conveyor belt  190 . In the embodiment illustrated in  FIG. 1 , plates  180   a - c  are fixed within inner tank  160 . 
     Turning now to  FIG. 2 ,  FIG. 2  illustrates another cutaway view of a continuous system  100  for electropolishing or electroplating metal conveyor belts in accordance with an embodiment of the invention. In this embodiment, plate  180   b  is movable to facilitate loading of conveyor belt  190  into inner tank  160 . However, it is contemplated that any combination of plates  180   a - c  can be similarly movable. 
     As shown in  FIG. 2 , plate  180   b  is removed from inner tank  160  to ease loading of conveyor belt  190  into inner tank  160 . When retracted, plate  180   b  is housed in roller frame  210 . Roller frame  210  comprises guide rollers  200   b  and  200   c , and has an open configuration such that electrolytic fluid  170  can flow freely therethrough when positioned within inner tank  160 . Once conveyor belt  190  is positioned within inner tank  160 , roller frame  210  and plate  180   b  can be inserted into inner tank  160  by means of hydraulic cylinder  230 , which is also operable to retract roller frame  210  and plate  180   b  from inner tank  160 . Although described with respect to a hydraulic cylinder, it is contemplated that any vertical displacement device may be used to vertically position roller frame  210  and plate  180   b.    
     Thus, according to this embodiment, conveyor belt  190  can be placed over guide roller  200   a , into inner tank  160  between plates  180   a  and  180   c , and over guide roller  200   d  when loading conveyor belt  190 . Roller frame  210  (having guide rollers  200   b  and  200   c ) and plate  180   b  can then be placed into inner tank  160 , and the placement of guide rollers  200   a - d  and plates  180   a - c  shown in  FIG. 1  can be achieved with a movable plate  180   b . In another embodiment, hydraulic cylinder  230  can vertically displace plate  180   b , while roller frame  210  remains stationary. 
       FIGS. 3A, 3B and 3C  show a top view, side view and perspective view, respectively, of a system for electropolishing or electroplating a metal conveyor belt according to an embodiment of the invention. In this embodiment, plate  180   b  is movable to facilitate loading of conveyor belt  190  into inner tank  160 . Thus, system housing  300  includes hydraulic cylinder  230  and roller frame  210 . As shown in  FIGS. 3A-3C , conveyor belt  190  is unrolled from an in-feed roll  105  onto guide roller  200   a  and through the remainder of system  100 , and exiting via guide roller  200   d . Conveyor belt  190  is guided by guide roller  200   e  over tank  375 , where excess electrolytic fluid is dripped from conveyor belt  190 . 
     Conveyor belt  190  is moved along its path by system drive  192 . System drive  192  may be, for example, a motor. System drive  192  is used to create torque or tension to pull conveyor belt  190  from in-feed roll  105 , through the system and onto take-up roll  195 . A tension device  102  is used in conjunction with in-feed roll  105  to create a resistive torque or tension in conveyor belt  190  as it is fed from in-feed roll  105 . Tension device  102  may be, for example, a brake, a clutch, a motor, and combinations thereof, both mechanical and electrical. Thus, conveyor belt  190  can remain under tension throughout the electropolishing or electroplating process from the in-feed roll  105  to the take-up roll  195 . However, it is contemplated that the goals of the described embodiments can be accomplished by providing tension in conveyor belt  190  at least while it is immersed in electrolytic fluid  170 . 
     The tension maintained in conveyor belt  190  ensures good physical and electrical contact between component parts of conveyor belt  190  (e.g., links and rods), and allows the current to pass through the immersed portion of conveyor belt  190  evenly. Such tension creates larger points of contact between the current generation device and conveyor belt  190  (as well as between the component parts of conveyor belt  190 , such as links and rods), resulting in less electrical resistance. This increased conductivity ensures more uniform current flow throughout conveyor belt  190 , resulting in a more uniform polishing or plating effect. 
     To further increase contact area between links and rods, thus increasing conductivity, conveyor belt  190  can comprise coined links, such as those shown and described in U.S. Pat. No. 4,932,925, which is herein incorporated by reference in its entirety. Such coined links can have a work-hardened area having a radius equal to the radius of the rod, such that the rod has a relatively large area of contact with the link when the belt is kept in tension. With the belt in tension, the rod is maintained in coined area of the link with constant contact maintained between the rod and the link. 
     Embodiments of the invention can be used to electropolish or electroplate conveyor belts that are separated into smaller sections, for example 50′ to 100′ long, for ease of handling and shipping. In accordance with the described embodiments, these sections may be connected sequentially, such that the leading end of a new roll of belt is connected to the trailing end of the previous roll of belt, to maintain a continuous process. These sections can be disconnected and placed on separate take-up rolls after processing. Leader chains may also be used to guide the ends of the belt into and out of the electrolytic fluid  170  while maintaining tension. 
       FIGS. 4A, 4B and 4C  show a top view, side view and perspective view, respectively, of a system for electropolishing or electroplating a metal conveyor belt according to another embodiment of the invention.  FIGS. 4D and 4E  show a front cutaway view and perspective cutaway view of the system illustrates in  FIGS. 4A-4C , which has been cut away at line  4 D as shown in  FIG. 4A . In this embodiment, conductive plates  480   b  and  480   c  are movable to facilitate loading of conveyor belt  490  into inner tank  460 . Conductive plates  480   b  and  480   c  are movable on roller frame  410  by displacement device  430 . Displacement device  430  may be a hydraulic cylinder, for example. 
     As shown in  FIGS. 4A-4E , conveyor belt  490  is unrolled from an in-feed roll  405  onto guide roller  400   a . Conveyor belt  490  continues into outer tank  450  and inner tank  460 , which comprises an electrolytic bath  470 . Current is applied to conveyor belt  490 . Conveyor belt  490  passes between conductive plates  480   a  and  480   b  in electrolytic bath  470 , and is guided along guide rollers  400   b  and  400   c  along the bottom of conductive plates  480   b  and  480   c . Conveyor belt  490  then passes out of electrolytic bath  470  between conductive plates  480   c  and  480   d.    
     Electroplating or electropolishing is achieved while conveyor belt  490  is immersed in electrolytic bath  470 . With respect to electroplating, a current is applied to conductive plates  480   a - d , oxidizing the metal atoms that comprise the conductive plates and allowing them to dissolve into electrolytic bath  470 . The dissolved metal ions in electrolytic bath  470  are moved by the electric field to coat conveyor belt  490 . Thus, a layer of metallic material is deposited on the surface of conveyor belt  490 . 
     With respect to electropolishing, a current is applied to conveyor belt  490 , oxidizing the metal atoms on the surface of conveyor belt  490  and allowing them to dissolve into electrolytic bath  470 . The dissolved metal ions in electrolytic bath  470  are moved by the electric field to conductive plates  480   a - d . Thus, a smoother, polished surface results on conveyor belt  490 . 
     Once conveyor belt  490  has been electropolished or electroplated, it is moved along guide roller  400   d  past a first dryer  462  positioned above outer tank  450 . First dryer  462  removes excess electrolyte from conveyor belt  490  and directs it download into outer tank  450  and/or inner tank  460 . Conveyor belt  490  is guided along guide roller  400   e  under rinse nozzles  465   a  and  465   b , which pours a rinsing fluid (such as water, for example) onto conveyor belt  490 . Rinse nozzles  465   a  and  465   b  are positioned over rinse tank  475 , which collects the excess water dripping from conveyor belt  490 . Although shown and described with respect to two rinse nozzles  465   a  and  465   b , it is contemplated that one or both rinse nozzles can be omitted. Further, one or both of rinse nozzles  465   a  and  465   b  can be pressurized to decrease rinse time and increase rinse efficiency. 
     Conveyor belt  490  moves under a second dryer  467  that removes excess rinsing fluid from conveyor belt  490 . Second dryer  467  is positioned above rinse tank  475  such that rinse tank  475  continues to collect excess water dripping from conveyor belt  490  while it is being dried by second dryer  467 . First dryer  462  and second dryer  467  may be air knifes, for example, to accelerate drying. Although shown and described with both first dryer  462  and second dryer  467 , it is contemplated that one or both dryers can be omitted. Conveyor belt  490  is then rolled onto take-up roll  495 . 
     Conveyor belt  490  is moved along the above-described path by a system drive  492 . System drive  492  can be a motor, for example, and is connected to take-up roll  495 . Tension is maintained in conveyor belt  490  at least between guide roller  400   a  and guide roller  400   d  (in other words, while conveyor belt  490  is submerged in electrolytic bath  470 ). This tension can be accomplished by creating a resistive torque or tension at tension device  402 , which is connected to in-feed roll  405 . Tension device  402  may include, for example, a brake, a clutch, a motor, and combinations thereof, both mechanical and electrical. 
     Although described herein with respect to conveyor belts, it is contemplated that the methods and systems described herein can be applied to any rollable and/or conductive materials, including chains or other continuous assemblies of interconnected components. Such electropolishing or electroplating applied in accordance with the described embodiments results in improved sanitation, reduced wear and friction on the treated parts, and improved product release characteristics, particularly with respect to food processing applications. 
     The present invention has been described in relation to particular examples, which are intended in all respects to be illustrative rather than restrictive. Those skilled in the art will appreciate that many different combinations of materials and components will be suitable for practicing the present invention. 
     Other implementations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. Various aspects and/or components of the described embodiments may be used singly or in any combination. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.