Patent Publication Number: US-9415420-B2

Title: Laminated screens

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application, pursuant to 35 U.S.C. §119(e), claims priority to U.S. Provisional Application Ser. No. 61/061,906, filed Jun. 16, 2008. That application is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     Embodiments disclosed herein relate generally to apparatuses and methods of assembling screens for vibratory separators. More specifically, embodiments disclosed herein relate to apparatuses and methods of assembling laminated screens for vibratory separators. 
     2. Background Art 
     Vibratory separators have long been used for the separation of both dry and wet materials, and are used in industries as varied as the chemical, food and beverage, powder coating, pharmaceutical, plastic, pulp and paper, ceramic, oilfield, and laundry industries. Vibratory separators, as used herein, generally refer to any type of separator or sifter used in the industrial processing of materials. Examples of materials and applications of industrial separators include metal powder, flour, sugar grinding, salt, steel shot, meat meal, sugar scalping, plastics, resin, fertilizer, petroleum coke, pharmaceuticals, wheat, soybean and oilseed, pellets and crumbles, and clay. Such separators may be circular or rectangular in cross section, and may include a vibration-generating device and resiliently mounted housings. Screens are fixed to the vibratory housings such that material fed to the vibrating screens may be screened. Various vibratory motions may be employed to work the material on the screen in the most advantageous manner. Frequently, discharge openings are provided both above the screening mechanism and below for retrieving the separated materials. 
     Some factors for selecting a particular vibratory separator include general material information, material characteristics, wet material data, material safety information, separator efficiency requirements, and desired use for the vibratory separator. For example, general material information may include the material to be screened, the temperature of the material, bulk density, specific gravity, and particle shape (spherical, fibrous, platelet, etc.). Materials may be characterized as granular, powder, abrasive, electrostatic, sticky, corrosive, free flowing, and agglomerates, among other characterizations. Key wet material data may include whether the material is viscous, greasy/oily, thixotropic, paste-like, sticky, or fatty. Furthermore, standard process data such as feed rate and minimum/maximum percentage of solids are important factors for selection of a vibratory separator. MSDS information, including numbers representing the severity of health, flammability and reactivity may be important depending on industry and application. Efficiency requirements vary by industry and application and are also important factors. Finally, those of ordinary skill in the art will appreciate that a vibratory separator may be used to scalp, dedust, or dewater, among other alternative uses. 
     In operation, a vibratory separator may be actuated to provide a flow of materials through the vibratory separator, such that solid particles are divided according to relative size. Thus, as the materials flow over a screen, larger particles exit the vibratory separator through a discharge outlet, while smaller particles exit through a secondary discharge area. The screen may include one or more filtering elements that may be manufactured from metals, plastics, cloth, and/or composites. Screens may be selected based on mesh size or micron size, among other sizing selection alternatives. 
     Over time, screens may be exposed to erosive and/or corrosive substances and operational conditions that degrade the screen effectiveness or efficiency of the filtering elements. Examples of operational conditions that may cause such an effect include typical actuation of the vibratory separator to impart movement in vertical and lateral directions. Over time, the vibratory motion, for example, in the vertical direction, may decrease the integrity of the screens due to structural damage, filtering element loosening, and the like. Such decreases in integrity may manifest as a slackening of the screen or parting of the screen from the frame, frame warpage or failure, or failure of the filtering element at the intersection with the frame. Further, screen failure may result from a broken screen, a screen tear, or bypass around a screen from improper sealing. 
     Screen failure may result in oversized particles entering the discharge underflow line of a vibratory separator. In wet screening of certain products, a maximum particle size may be important to manufacturing processes, and failure to screen to such a maximum size may lead to a large amount of final product being rejected or having to be reworked at a significant expense. 
     Accordingly, there exists a need for screens for use in the separation of dry and wet materials. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, embodiments disclosed herein relate to a laminate screen for a vibratory separator, the screen including a product screen mesh layer having a plurality of wires. The screen further including a structural screen mesh layer having a plurality of wires secured to the product screen mesh layer with a thermoplastic polymer, wherein the structural screen mesh layer is configured to provide structural integrity to the laminate screen, and wherein a diameter of the product screen mesh layer wires is less than a diameter of the structural screen mesh layer wires. 
     In another aspect, embodiments disclosed herein relate to a method of assembling a laminate screen for a vibratory separator, the method including selecting a product screen mesh layer and selecting a structural screen mesh layer. The method further including disposing a thermoplastic layer between the product screen mesh layer and the structural screen mesh layer, laminating the product screen mesh layer to the structural screen mesh layer to produce a laminate screen, and forming a retaining portion along at least a portion of the laminated screen. 
     In another aspect, embodiments disclosed herein relate to a vibratory separator including a first screen frame, a second screen frame disposed below the first screen frame, and a laminated screen disposed between the first screen frame and the second screen frame. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a breakaway perspective view of a screen according to embodiments of the present disclosure. 
         FIG. 2  is a breakaway perspective view of a screen according to embodiments of the present disclosure. 
         FIG. 3  is a top view of a screen according to embodiments of the present disclosure. 
         FIG. 4  is a perspective view of a screen according to embodiments of the present disclosure. 
         FIG. 5A  is a side perspective view of a screen according to embodiments of the present disclosure. 
         FIG. 5B  is a close perspective view of a portion of  FIG. 5A  according to embodiments of the present disclosure. 
         FIG. 6A  is a vibratory separator according to embodiments of the present disclosure. 
         FIG. 6B  is a close perspective view of a portion of  FIG. 6A  according to embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments disclosed herein relate generally to apparatuses and methods of assembling screens for vibratory separators. More specifically, embodiments disclosed herein relate to apparatuses and methods of assembling laminated screens for vibratory separators. 
     Screens for vibratory separators have traditionally been manufactured from composite or carbon steel structural supports with one or more layers of screen mesh disposed thereon. The screen mesh is typically attached to the structural supports through the use of glues, such as epoxy resins, and then sealed with other materials, such as silicon. Additionally, traditional screens include structural components used to pretension the screens, or may otherwise include attachment structures for securing the screens to the vibratory separator. Such traditional screens often fail during use due to a loss of structural integrity from failing structural support members, loss of tensioning, seal failure, etc. Embodiments disclosed herein provide alternative screens and methods of assembling such screens for use in wet and/or dry separatory operations. 
     Referring to  FIGS. 1 and 2 , breakaway perspective views of screens according to embodiments of the present disclosure are shown. Separator screen  100 , prior to the completion of manufacturing, includes three layers, a product screen mesh layer  101 , a structural screen mesh layer  102 , and a thermoplastic layer  103 . 
     Product screen mesh layer  101  may be formed from a plurality of wires interwoven to provide a mesh having perforations of a desired size. The perforation size may be changed by, for example, varying the number of wires used, the spacing of the wires, and the diameter of the wires. A range of wire diameters may be used in constructing product screen mesh layer  101 . Exemplary ranges include wires having a diameter of between 0.0008 inches to 0.0075 inches. By decreasing the diameter of the wire, more wires may be used, thereby resulting in a smaller perforation size, and allowing finer materials to be separated. Similarly, by increasing the diameter of the wires, perforation size may be increased, and coarse materials may thus be separated with greater efficiency. The diameter of the wires, as well as the number of wires and layout of the wires may be changed based on the material being separated and design requirements of the operation. Furthermore, those of ordinary skill in the art will appreciate that the wires may be formed from a number of different materials, for example, stainless steel and/or heat resistant polymer. 
     Structural screen mesh layer  102  may also be formed from a plurality of wires interwoven to provide a mesh having perforations of a desired size. Generally, the wires used to form structural screen mesh layer  102  will have a greater diameter than the wires used to form product screen mesh layer  101 . Thus, structural screen mesh layer  102  provides a coarse screen surface relative to the fine screen surface of product screen mesh layer  101 . Exemplary ranges of wire diameter for structural screen mesh layer  102  include wires ranging in diameter between 0.012 inches and 0.135 inches. Those of ordinary skill in the art will appreciate that generally, increasing wire diameter results in a more rigid mesh. Thus, the diameter of the wire used in constructing structural screen mesh layer  102  may be varied to achieve a desired rigidity for the screen. 
     When selecting a wire diameter size for structural screen mesh layer  102 , a wire diameter greater than the diameter of wire used in product screen mesh layer  101  should be selected. By using a layer of screen mesh with greater wire diameter (structural screen mesh layer  102 ) relative to the wire diameter used for product screen mesh layer  101 , screen  100  may have increased structural integrity after assembly. Structural integrity, as used herein, refers to a level of rigidity of the screen for a particular application. A screen with structural integrity may have greater rigidity, and thus less flexibility, than a screen without structural integrity. Those of ordinary skill in the art will appreciate that generally, the wire diameters used for product screen mesh layer  101  will not provide sufficient structural integrity to support a screen when installed in a vibratory separator, without additional components. In the present disclosure, structural screen mesh layer  102  provides the rigidity to screen  100  that is necessary for the screen to have structural integrity. 
     Thermoplastic layer  103  is a layer of thermoplastic material that may be used to secure product mesh screen layer  101  to structural mesh screen layer  102 . The specific thermoplastic used may vary depending on the requirements of the separatory operation. For example, separation of product in the food or pharmaceutical industries may require use of a different thermoplastic than separation of products in the drilling and refining industries. Additionally, the thermoplastic may vary depending on the melting temperature of the wires that form product screen mesh layer  101  and/or structural screen mesh later  102 . Various thermoplastic materials may be used, so long as the melting temperature of the thermoplastic material is less than the melting temperature of the wire of product screen mesh layer  101  and/or structural screen mesh later  102 . Examples of thermoplastics that may be used in accordance with embodiments of the present disclosure include polypropolyene, polyethylene, polybutylene, polybutadiene, polyester, polyimide, polychlorotrifluoroethylene, polycarbonate, polyketone, polystyrene, and fluoroplastic. Those of ordinary skill in the art will appreciate that other thermoplastic materials may also be used in certain aspects. Similarly, those of ordinary skill in the art will appreciate that more than one thermoplastic material may be used in assembly of a screen. 
     During assembly, product screen mesh layer  101  and structural screen mesh layer  102  may be secured to one another by applying heat to thermoplastic layer  103 . The assembly process for laminate screens in accordance with the present disclosure will be described below in detail. Initially, a product screen mesh layer  101  and a structural screen mesh layer  102  are selected for an operation. The perforations of product screen mesh layer  101  define the largest particle size that may pass through the screen, while structural screen mesh layer  102  is selected to include a larger diameter wire than product screen mesh layer  101 , thereby providing structural integrity to the assembled screen. 
     After selection of desired screen mesh layers, thermoplastic layer  103  is disposed between product screen mesh layer  101  and structural screen mesh layer  102 . The three layers,  101 ,  102 , and  103  are then laminated together to produce a laminated screen  100 . Lamination may include melting thermoplastic layer  103  disposed between products screen mesh layer  101  and structural screen mesh layer  102  to a specified temperature, such that thermoplastic layer  103  melts, thereby bonding product screen mesh layer  101  to structural screen mesh layer  102 . The laminating may further include pressing product screen mesh layer  101 , thermoplastic layer  103  and structural screen mesh layer  102  between two heated platens. Those of ordinary skill in the art will appreciate that one or more of the platens should be heated to a temperature at or above the melting point of thermoplastic layer  103  and below the melting point of the mesh layers  101  and  102 . Furthermore, the temperature of the platens should be less than a temperature that may damage either product screen mesh layer  101  or structural screen mesh layer  102 . For example, in an embodiment where the screen mesh layers are stainless steel and the thermoplastic layer is polypropylene, because polypropylene achieves flow properties sufficient to allow it to fuse the mesh layers together between 400° F. and 450° F., and the melting point of stainless is far greater than the melting point and flow rate of polypropylene, the polypropylene may fuse product screen mesh layer  101  to structural screen mesh layer  102  without damaging either layer. 
     Those of ordinary skill in the art will appreciate that other methods of assembling laminated screens in accordance with the present disclosure may also be possible. For example, rather than use platens to heat thermoplastic layer  103 , in certain embodiments, heat may be applied to a particular area of screen  100  to laminate certain portions of screen  100 . Such a process may allow for customized screens to be assembled for specialty applications. Additionally, the process of heating only a portion of screen  100  may allow for localized repairs of damaged screens. 
     After product screen mesh layer  101  is laminated with structural screen mesh layer  102 , the thermoplastic will remain moldable for a short period of time. While the thermoplastic is moldable, additional features may be formed on screen  100 , such as a retaining portion  104 . Retaining portion  104  is a portion of at least structural screen mesh layer  102  that is bent into a desired configuration to allow the screen to be placed in a vibratory separator. In certain aspects, retaining portion  104  may include both product screen mesh layer  101  and structural screen mesh layer  102 , while in other aspects, only structural screen mesh layer may be used to form retaining portion  104 . Those of ordinary skill in the art will appreciate that due to the physical properties of thermoplastics, if retaining portion  104  is formed out of specification, the thermoplastic may be reheated, such that it is moldable again, and a desired shape of the screen reformed. The ability to reheat thermoplastics may also allow for product screen mesh layers  101  or structural screen mesh layers  102  to be replaced should they fail or become worn during use. 
     Referring to  FIGS. 3, 4, and 5A , top and side perspective views of laminated screens according to embodiments of the present disclosure are shown. In these embodiments, varied retaining portion geometries that may be formed after or during lamination are illustrated. Generally, retaining portions include a section of a screen  100  that is used to secure or otherwise hold screen  100  in place within a vibratory separator. Retaining portions may include, for example, flaps, extensions, and bent sections integrally formed from the structural and/or product screen mesh layers. Referring specifically to  FIG. 3 , screen  100  is formed to include a retaining portion  104  on one side of the periphery of the screen. Retaining portion  104  may be formed during assembly so that it may be used to secure screen  100  in a vibratory separator. Those of ordinary skill in the art will appreciate that additional features may be added to screens, such as holes for rivets, bolts, screws, or other attachment mechanisms to further secure screen  100  in a vibratory separator. 
       FIG. 4  also illustrates a screen  100  with retaining portions  104 . In  FIG. 4 , screen  100  includes retaining portions  104  at two locations along the periphery of the screen. Retaining portions  104  are bent to a desired orientation, which may vary according to the type of vibratory separator they are designed to be installed in. In other aspects, retaining portions may be formed on three, four, or more surfaces, if the screen is either an irregular or nonrectangular shape. 
       FIG. 5A  shows a perspective view of a corner portion of screen  100 . Screen  100  illustrates product screen mesh layer  101  disposed on top of structural screen mesh layer  102 . Referring briefly to  FIG. 5B , a close-up view of section A of  FIG. 5A  is shown.  FIG. 5B  illustrates layering product screen mesh layer  101  on top of structural screen mesh layer  102 . In this embodiment, both product and structural screen mesh layers  101  and  102  are bent to include a retaining portion  104 , however, retaining portion  104 A illustrates a tapered configuration wherein product screen mesh layer  101  extends further than structural screen mesh layer  102 . In contrast, retaining portion  104 B illustrates a tapering of product screen mesh layer  101 , while structural screen mesh layer  102  extends to the periphery of screen  100 . Those of ordinary skill in the art will appreciate that retaining portion  104  may be formed in various configurations of product and structural screen mesh layers  101  and  102 . 
     Referring back to  FIG. 5A , various design features may be present along the periphery of screen  100 . In one aspect, screen  100  includes a plurality of notches  105  formed along retaining portion  104 . The notches may be used to retain screen  100  in a vibratory separator, and as such, may be cut or formed after lamination of product and structural screen mesh layers  101  and  102 . In still other aspects, screens  100  may include various design features, such as retaining portions  104  bent to specific orientations, notches  105 , grooves (not shown), and/or attachment mechanisms (not shown). 
     Referring to  FIG. 6A , a perspective view of a vibratory separator according to embodiments of the present disclosure is shown. In this embodiment, vibratory separator  106  is illustrated having three screen slots  107  formed by a first screen frame  108  and a second screen frame  109 . First screen frame  108  forms a top portion of the screen slot  107 , while second screen frame  109  forms a bottom portion of the screen slot  107 . Disposed within screen slot  107  are slidable trays  110  configured to allow a screen  100  to be placed thereon. Thus, screen  100  may be removed from vibratory separator  106  by sliding the trays  110  out of screen slot  107 . In certain aspects screen  100  may be secured to trays, or other components of vibratory separator  106  with attachments mechanisms, such as screws, bolts, rivets, etc. Additionally, those of ordinary skill in the art will appreciate that other methods of disposing screens  100  within vibratory separator  106  are known in the art. 
     Referring to  FIG. 6B , a close perspective view of section B of  FIG. 6A  according to embodiments of the present disclosure is shown. In this embodiment, screen  100  is illustrated disposed on tray  110 , which consists of rains extending from a vibratory separator body. Screen  100  includes retaining portions  104  disposed on three sides of screen  100 , thereby allowing screen  100  to be slid onto tray  110  during installation, and slide off of tray  110  during replacement. Screen  100  also illustrates structural screen mesh layer  102  forming a widely spaced wire substrate. Product screen mesh layer  101  is illustrated as including a plurality of wires forming sized perforation to allow for the operation to produce a desired particle side distribution. Particle size distribution may be adjusted by changing the wire diameter, spacing, and number of wires used to form the mesh, as discussed above. 
     Advantageously, embodiments of the present disclosure may provide for screens for vibratory separators, including sifters, that use thermoplastic to secure a product screen mesh to a structural screen mesh. Because the wire diameter of the structural screen mesh is greater than the wire diameter of the product screen mesh, the structural screen mesh may provide structural integrity to the screen without requiring the use of screen frames and/or components to provide tension to the mesh. Thus, the mesh provides the structural integrity for the screen. 
     Also advantageously, embodiments of the present disclosure may provide for screens for vibratory separators that do not require the use of additional seals and/or sealing compounds, such as epoxy resins. Because the thermoplastic secures the product screen mesh to the structural screen mesh without the use of frames, and the screen thus has requisite structural integrity, the mesh does not need to be bonded to a frame. Because there are no frames, neither physical seals nor sealing components have to be added to the screen frame. Thus, the screen frame is lighter, and does not require additional components that may increase the cost to produce the screen, as well as potentially result in screens that cannot be used in, for example, the food industry due to the use of toxic sealing compounds. 
     Furthermore, the screens may provide the advantage of allowing the screens to be disassembled and subsequently reassembled if the mesh becomes worn during use. Because the mesh layers are secured to one another with a thermoplastic, after use, the thermoplastic may be reheated, the mesh separated from one another, and then one of the mesh components may be replaced. The thermoplastic may then be reheated, once the replacement mesh is positioned appropriately, and the screen may be reformed. By recycling screen components, the cost of remanufacturing screens may be decreased, thereby decreasing the net cost of the separatory operation. 
     Also advantageously, because the products screen mesh is secured to the structural screen mesh with a thermoplastic, the resulting laminate screen may be shaped before the thermoplastic sets, thereby allowing for additional design features, such as retaining portions, to be integrally formed on the screen. Additional features that may be formed on the screen include alignment portions, notches, and attachment portions. Additionally, when the thermoplastic hardens, the screen may become pretensioned, thereby removing the need for pretensioning components from the screen. Removing the pretensioning components may decrease the cost of the screen. Because the screen does not require tensioning components, the screen may be handled and installed without distorting or inadvertently adjusting the tension of the screen wires. 
     Finally, the screens disclosed herein may provide the advantage of replacing a steel or carbon steel frame typically found in screens. By removing the carbon steel frame, the laminate frames are more corrosion resistant, thereby decreasing the likelihood of premature screen failure. Additionally, the thermoplastic bonding provides a more rigid screen, thereby easing installation, and improving its resistance to operational failure. 
     While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.