Abstract:
A screening machine of the type used to separate or classify mixtures of solid particles of different sizes includes a machine frame and a perforate screen panel mounted for movement relative to the machine frame during a screening operation. The screen panels are pre-tensioned mesh screen material mounted in a peripheral rim for separating various granular and particulate materials. The screen panel is slid into the side of the machine frame in a direction orthogonal to the direction particulate matter moves when the screening machine is operating. The screen panel peripheral rim has a shaped or other cross section adapted to hold a large seal member that provides a positive sealing surface for contact with the machine frame to prevent particulate matter from escaping off of the screen panel during use.

Description:
This claims priority to U.S. Provisional Patent Application Ser. No. 61/060,833, filed Jun. 12, 2008, and is a continuation in part of and claims priority to U.S. patent application Ser. No. 11/382,353, filed May 9, 2006, which in turn was a continuation in part of and claimed priority to U.S. patent application Ser. No. 11/295,259, filed Dec. 6, 2005. Each of these identified prior applications is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to screening machines of the type used to separate or classify mixtures of solid particles of different sizes. The invention also relates to screening machines of the type used for liquid/solid separations, i.e., for separating solid particles of specific sizes from a liquid in which they are carried. More particularly, the invention relates to an improved screen panel for use within the screening machine. 
     In screening machines of the type described, a screen (which may be woven, an aperture plate or another design) is mounted in what is often called a “screen frame” or “screen deck” which includes a supporting peripheral frame around the perimeter of the screen. Some screens are tensioned when they are installed in the screening machine and other screens are pre-tensioned in a frame prior to being installed in the machine. Typically associated with the screen deck are other material handling elements that are moved with the screen and form walls or partitions above or below the screen for containing the liquid and/or particulate materials adjacent to the screen and directing them to appropriate outlets. These elements may include a top cover and a pan beneath the screen deck. In the case of screening machines with multiple screens or deck units, spacer pans or frames are provided between the multiple screens. 
     The screens are often removed from the screening machines for cleaning, replacement, readjustment, or installation of a screen of a different mesh size or the like. The screen is releasably mounted to a carrier, table or box to which vibratory motion is imparted, typically by one or more eccentric motors or other means of excitation. The carrier, table or box is referred to herein as a “vibratory carrier”. The vibratory carrier may be moved in oscillatory, vibratory, gyratory, gyratory reciprocating, fully gyratory, rotary or another type of motion or combinations thereof, all of which are herein collectively referred to as “vibratory” motion or variations of that term. 
     In large commercial screening machines, the weight of the various components including the screen assembly carried by the vibratory carrier, and the weight of the material being processed on the screen assembly may total several hundred pounds or more. Screening machines which tension the screen, as opposed to those utilizing pre-tensioned screens, include the added weight associated with the screen tensioning mechanism and related components. This presents a very substantial inertial mass that resists the changes of motion applied thereto by the vibratory drive acting through the vibratory carrier. As a result of these inertial forces, a relative motion may exist between the vibratory carrier and the screen assembly. Typically, the screen assembly and vibratory carrier are each constructed of metal that could result in significant noise, wear and damage due to the relative motion or rubbing action there between. The resulting impact forces between the screen assembly and vibratory carrier significantly increase the stresses on the components and reduce their useful life. 
     Reducing the metal-to-metal contact minimizes the wear on the various metal components and the noise associated with the operation of the screening machine. Currently, certain screen assembly designs may not be sealed or secured relative to the remainder of the screening machine, particularly in larger screening machines. This results in the above-described metal-to-metal contact between the screen assembly and the remainder of the screening machine and prevents the screening of very fine material, such as sand or the like. The screens in larger screening machines are typically inserted and/or removed from the machine in a generally horizontal, longitudinal direction typically through an opening or slot at the head or foot end of the machine. This method of installation and removal of the screen is detrimental to known sealing arrangements because a seal that would engage the screen assembly could be torn or damaged during the installation/removal of the screen. In other screening machines, the screen is inserted vertically, typically from the top of the machine. Access to the screens from the top of the machine or the longitudinal ends is often very inconvenient and difficult. 
     Thus, it would be desirable to provide a screen panel and screening machine to overcome these and other aspects of screening machines and screen panels. 
     SUMMARY OF THE INVENTION 
     The above-described and other problems with prior art screening machines and associated screen panels have been resolved by this invention. Screening machines according to one embodiment of this invention utilize a machine frame, a perforate screen assembly engaging the machine frame, and a driver imparting vibratory motion to the screen assembly, the machine frame and screen assembly designed to hold particulate matter to be screened. The screening machine also includes a first outlet which discharges a first portion of the particulate matter that remains on top of the screen assembly and a second outlet which discharges a second portion of the particulate matter that passes through the screen assembly. 
     One aspect of this embodiment is the screen assembly including a screen panel having a generally planar screening surface and a peripheral rim or outer edge extending around at least a portion of the screening surface and being recessed, offset or beveled relative to the screening surface. A seal member positioned relative to the screening surface. The peripheral profile of the screen panel also enhances the strength of the panel so that the tensioning forces of the screen material will not alter the shape of the screen panel. In one embodiment, the rim on the screen panel has a shaped cross section designed to hold the seal member. The rim in one embodiment can also include rounded corners so that the seal member is one continuous seal attached around the perimeter of the screen panel. 
     The machine frame in one embodiment includes lining rails that engage the seal member of the screen panel when the screen panel is inserted into the screening machine. The seal member closes any gap between the lining rails of the machine frame and the screen panel so that particulate matter cannot escape to the interior components of the screening machine. The machine frame may also include transition caps permanently sealed to each lining rail, and the transition caps help ensure a proper seal between the screen panel and the machine frame. 
     Therefore, according to various embodiments of this invention, the screening operation is much more efficient and more easily accomplished while offering significant advantages in screen service life, strength, installation and removal while avoiding the opportunities for operator error when installing the screen panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objectives and features of the various embodiments and features of the invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an exemplary screening machine and associated screen panel being installed therein according to one embodiment of this invention; 
         FIG. 2  is a top plan view of the screen panel of  FIG. 1 ; 
         FIG. 2A  is a bottom plan view of an alternative embodiment of a screen panel frame; 
         FIG. 3  is a front, partially cross-sectional view of the screen panel of  FIG. 2 ; 
         FIG. 4A  is a side elevational view of a portion of the screening machine of  FIG. 1  and a screen panel inserted therein prior to a screening operation; 
         FIG. 4B  is a view similar to  FIG. 4A  with the screen panel engaged with the machine frame of the screening machine in preparation for a screening operation; and 
         FIGS. 5A-5E  are side cross-sectional views of alternative embodiments of a seal member attached to the screen panel. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , an exemplary embodiment of a screening machine  10  in which this invention may be used is shown. Screening machines of many types are sold commercially by Rotex, Inc. of Cincinnati, Ohio, the assignee of this invention. However, this invention is not limited to any particular type of screening machine design or application and the machine shown and disclosed herein is only for illustrative purposes. 
     The screening machine  10  includes an inlet port  12  near an inlet section  14  proximate a head end  16  of the machine  10 . The screening machine  10  may also include a top cover  18  in any one of a variety of forms. Particulate or other material to be screened is fed into the inlet port  12  from a hopper (not shown) for screening and processing by the machine  10 . 
     The screening machine  10  is supported structurally by a machine frame  20  including beams  22  connected together by laterally oriented struts  24  on each end of the screening machine  10 . The screening machine  10  includes an electric motor  26  coupled to a drive weight (not shown) to impart an oscillatory, vibratory, gyratory, gyratory reciprocating, fully gyratory, or other motion or combinations thereof (herein collectively referred to as “vibratory” motion or variations of that term) to at least the head end  16 . 
     Within a screening chamber of the screening machine  10 , one or more screen panels  28  are each mounted in combination to form one or more screen assemblies  30  to receive the material being screened from the feed chute  12  at the head end  16  of the machine  10 . The screen panels  28  are mounted on slightly sloping planes (approximately 4°) with the head end thereof being slightly elevated relative to a foot end so that during the screening process the material advances, in part by gravity, over the screen panels  28  toward a discharge end  32  of the machine  10 . Even though the screen panels  28  of the screening machine  10  may be on a slightly sloping plane, to provide a reference for the purposes of clarity herein, these components will be considered to be generally horizontal and the direction perpendicular or orthogonal to the screen panels  28  will generally be referred to as a vertical orientation or direction. The direction of travel of the material being screened from the head end  16  to the discharge end  32  across the screen panels  28  is referred to as the longitudinal direction and the perpendicular orientation extending from side to side on the screen panels  28  is a lateral direction. 
     In the embodiment of the screening machine  10  shown in  FIG. 1 , upper and lower screen assemblies  30  each include four screen panels  28  mounted generally coplanar with each other in the associated screen assembly  30 . Accordingly, as the material to be screened is deposited from the inlet port  12  onto the upper screen assembly  30 , the vibratory motion of the screening machine  10  advances the material longitudinally across the top of the screen panels  28  of the upper screen assembly  30  toward the discharge end  32 . Appropriately sized and configured material passes through the upper screen assembly  30  and falls onto the lower screen assembly  30 . The screen panels  28  of the upper screen assembly  30  may include a fine mesh screen material  34  adjacent the inlet port  12  through which dust and other fine particulate matter passes for collection and discharge. Certain material also passes through the upper screen assembly  30  and is deposited on the lower screen assembly  30 . Therefore, the lower screen assembly  30  is included to provide an additional separating mechanism for the appropriately sized particles to pass through the lower screen assembly  30  for collection in a lower pan (not shown). 
     The unacceptably sized particles remain atop the first upper screen assembly  30  and fall off the terminal edge thereof into a collection basin for discharge through a first outlet (not shown) in the exit section  36 . Material that passes through the upper screen assembly  30  and remains atop the lower screen assembly  30  falls off the terminal edge thereof and into the collection basin for discharge through a second outlet (not shown) in the exit section  36 . The first and second outlets are separated by a baffle (not shown) to keep the classified particles separate from one another. The acceptably sized particles that pass through both the upper and lower screen assemblies  30  are collected in a lower pan and discharged through a third outlet (not shown) located at the discharge end  32  of the machine  10 . 
     Referring to  FIG. 1 , one or more doors  38  are each pivotally connected by a hinge  40  to a lateral side  42  of the screening machine  10 . When opened, the doors  38  provide access for insertion and removal in the lateral direction of the screen panels  28 . It will be appreciated that although one side  42  of the screening machine  10  is shown in  FIG. 1 , additional doors  38  on the opposite side of the screening machine  10  may also be provided. Advantageously, the screen panels  28  are inserted horizontally and laterally or perpendicularly to the longitudinal direction of travel of the material being screened in the screening machine  10 . 
     Referring to  FIGS. 2-3 , one embodiment of the screen panel  28  includes a generally perforated mesh screen material  34  making a screening surface  44 . The mesh screen material  34  includes a number of intersecting longitudinal threads or wires  46  and lateral threads or wires  48  which are oriented orthogonally to each other to provide appropriately sized and configured openings  50  in the screening surface  44  to prevent or allow the passage of particulate matter. The screen panel  28  includes a generally rigid frame  51  with a peripheral rim  52  extending around at least a portion of the screening surface  44 . At least a portion of the peripheral rim  52  is recessed, offset or beveled relative to the screening surface  44 , and the peripheral rim  52  can have a shaped cross section designed to accept a seal member  54 . Alternatively, the peripheral rim  52  includes a cross section with a generally horizontal first portion  58  adapted to hold the mesh screen material  34 , a generally vertical second portion  60  integral with first portion  58 , and a generally horizontal third portion  62  integral with the second portion  60 . The portion  62  may be offset or recessed relative to the screening surface  44  and/or may be positioned at a lower surface of the screen panel  28 . Alternatively, the rim  52  may be of a different configuration or location relative to the screening surface  44  including spaced from the lower surface of the screen panel  28 . The portion  62  is shown in  FIG. 3  as being oriented perpendicularly to the portion  60  and generally parallel to the screening surface  44 . Alternatively, the rim  52  may be of a different configuration or orientation relative to the screening surface  44  including obliquely oriented relative to the screening surface  44 . 
     An alternative embodiment of a frame  51   a  of the screen panel  28  according to this invention is shown in  FIG. 2A . Frame  51   a  includes a lattice arrangement  53  inside the peripheral rim  52  to provide added stiffness to the screen panel  28 . The added stiffness assists in maintaining tension on the screen material  54  (not shown in  FIG. 2A ). The lattice arrangement  53  of  FIG. 2A  includes longitudinal members  55   a  intersecting lateral members  55   b  oriented orthogonally to each other. The members  55   a ,  55   b  may be generally flat members with rectangular cross sections, rounded bars with circular cross sections, or of another shape within the scope of this invention. Further alternative embodiments of this invention include screen panels  28  with only longitudinal members  55   a , only lateral members  55   b  and members  55   a ,  55   b  intersecting in non-orthogonal orientations. 
     The members  55   a ,  55   b  may be tack welded to each other at their common points of intersection and at their intersection with the peripheral rim  52 . Adhesive is an alternative to the welding according to alternative embodiments. Moreover, the lattice arrangement  53  may be integral with the peripheral rim  52  as a result of a burnout design or other production technique. 
     The seal member  54  in one embodiment is coupled to the peripheral rim  52  along the second portion  60  and third portion  62  of the cross section of the peripheral rim  52 . Alternatively, the seal member  54  may be positioned at other locations on the screen panel  28  relative to the rim  52 . The peripheral rim  52  in one embodiment also has rounded corners  56  which allow the seal member  54  to be a continuous seal member  54  that follows the rounded corners  56  without buckling. The rounded corners  56  also allow for clearance room for internal hardware (not shown) inside the machine frame  20 . The corners  56  may be produced by a stamping operation to enhance quality and lower production costs. The rim  52  in  FIG. 2  is shown as extending entirely around the perimeter of the screen panel  28 , but other configurations are possible within the scope of this invention, including portions of the rim only along the trailing and/or leading edges of the screen panel  28 . 
     The screen panel  28  may be manufactured by a variety of processes, including stretching a mesh screen material  34  to put longitudinal wires  46  and lateral wires  48  in tension, robotically applying adhesives to a peripheral rim  52 , raising the peripheral rim  52  up into the mesh screen material  34 , curing with ultraviolet light for about 30 seconds, and trimming or grinding off any excess wire  46 ,  48 . The screen material  34  may be bonded to the peripheral rim  52  via adhesive or welding in alternative embodiments. A seal member  54  is then permanently mounted on the peripheral rim  52 . In some embodiments, a silicone bead can be installed on the perimeter where the ends of wires  46 ,  48  are exposed. This silicone bead is not necessary in all embodiments, as the seal member  54  can be large enough to cover the exposed ends of wires  46 ,  48 . In another embodiment, the screen panel  28  can be manufactured by dipping the peripheral rim  52  in epoxy and pressing the mesh screen material  34  onto the peripheral rim  52  with a heat press. Additionally, the screen panel  28  of  FIG. 2  is shown with the screen material  34  tensioned uninterrupted within the confines of the rim  52 . Other embodiments are included within the scope of this invention, including smaller cells defined within the interior of the rim  52  by transverse and longitudinally extending ribs within the peripheral rim  52 . Additionally, one or more labels  57  can be included on a lower surface of the frame  51  ( FIG. 2A ) to permit identification of the panel  28  while it is installed in the machine  10 . 
     Another aspect of this invention is the ability to recondition existing screen panels  28  when the screen material  34  is torn, worn, used or otherwise in need of replacement. The frame and rim  52  of the screen panel typically are not damaged or worn and are capable of repeated use. As such, the used screen material  34  is removed from the frame and rim  52  and likely the seal member  54  as well. New screen material of the same type, material mesh and the like or of different characteristics relative to the used screen material is positioned on the frame, tensioned, bonded to the frame and trimmed to size as appropriate and previously described herein above. A new seal member  54  is then applied to the screen panel  28  and it is ready to be returned to service. 
     The screen panel  28  of the current embodiment has several advantages over conventional screen panels. The shaped cross section of the peripheral rim  52  allows for a large seal member  54  to be permanently attached to the screen panel  28 , removing the need to carefully position the screen panel  28  within the machine frame  20  to ensure a good seal. The shaped cross section also allows for a continuous seal  54  around each panel  28  in one uniform plane while maintaining a flush product flow surface between the panels  28  and internal components of the machine  10 . Screen panels  28  of other embodiments include interior lattice arrangement  53  ( FIG. 2A ) connected to the peripheral rim to support the tension levels of the mesh screen material. With a shaped cross section, the peripheral rim  52  has an increased stiffness allowing for the optional removal of the lattice network and promoting better conveying and blinding control. Conventional screen panels required calibration of seal size to varying wire thicknesses in the mesh screen material, but the current embodiment&#39;s large compliant seal member  54  makes the seal effectiveness far less sensitive to varying wire  46 ,  48  sizes in the mesh screen material  34 . These improvements create more economical manufacturing processes and more reliable seals in a screening machine  10 . 
     The leading side edge  64  of the screen panel  28  is typically inserted laterally into the machine frame  20  through door  38  as shown by arrow  68  in  FIG. 1 . A user or operator can easily grab the trailing side edge  66  thanks to the shaped cross section of the peripheral rim  52  and the large seal member  54  protecting the hands of the user or operator from exposed wire. In some embodiments, the user slides the screen panel  28  over a vibratory ball tray (not shown) or other device that has balls or agitation producing members that bounce against the underside of screen panel  28  to reduce blinding or other occlusion of the mesh screen material  34  when the electric motor  26  provides vibratory motion to the machine  10 . Advantageously, the screen panel  28  in this embodiment can be removed and replaced for manual cleaning or other maintenance without removing the heavier ball tray. 
     Referring now to  FIGS. 4A-4B , the placement and configuration of a screen panel  28  inside the screening machine  10  according to one embodiment will now be described. The machine frame  20  of the screening machine  10  includes lining rails  70  permanently attached to the interior of machine frame  20 , the lining rails  70  including a downwardly-angled portion  72  and a horizontal portion  74  below the angled portion and designed to engage the screen panel  28 . The lining rails  70  can be slightly resilient to allow vibration with the machine frame  20  to force particulate matter onto the screening surface  44 . Also permanently attached to the interior of the machine frame  20  are transition caps  76 , generally horizontal edge pieces that engage the screen panel  28  and the lining rail  70  to eliminate leakage concerns and eliminate any time needed for fixturing during assembly. Below the lining rails  70  and adjacent to the transition caps  76  is an upper portion  77  of screen assembly  30 . A flat seal member  78  on the underside of the transition caps  76  rests between the lining rails  70  and the transition caps  76  and upper portion  77 . 
     The machine frame  20  further includes a bracket  80  in which a rotational cam  82  is located. The peripheral rim  52  in one embodiment of the screen panel  28  is supported on the rotational cam  82  when initially inserted in the screening machine  10  as illustrated in  FIG. 4A . The rotation of the cam  82  is accomplished by an actuator  84  accessible to the operator or user when the door  38  of the machine  10  is open. For example, one known mechanism suitable for use with this invention to raise/lower the screen panel  28  is disclosed in Rotex&#39; U.S. Pat. No. 6,070,736, which is incorporated by reference herein. 
     Upon rotation of the actuator  84  in the direction of arrow A, the cam  82  is rotated, thereby raising the screen panel  28  supported thereon upwardly to sealing engagement with upper portion  77  of screen assembly  30  as shown in  FIG. 4B . As the screen panel  28  is raised, the mesh screen material  34  is juxtaposed on the upper portion  77  and the seal member  54  is compressed against transition cap  76 , upper portion  77 , and lining rail  70 . As a result, the upper portion  77  of screen assembly  30 , the screen panel  28 , and the lining rails  70  are sealed to prevent and inhibit the discharge of particulate matter being screened into other interior components of the machine frame  20 . Due to the design and configuration of the screen panel  28 , machine frame  20  and seal member  54 , the seal member  54  is neither damaged nor compromised during lateral installation of the screen panel  28 , thus extending the service life of the associated components. The invention thus offers a screen panel  28  that is pre-tensioned, ready to use, lightweight, standardized in size to lower cost, simple design, mass producible, easy to handle, and stronger or stiffer than conventional screen panels of similar weight. 
     Referring now to  FIGS. 5A-5E , alternative embodiments of large seal members  54  for use on screen panel  28  are illustrated. In  FIG. 5A , a typical round seal member  54  is attached to screen panel  28 . The embodiment in  FIG. 5A  includes a seal lip  86  which helps cover exposed wire ends of mesh screen material  34  and also extends to further fill the gap between the machine frame  20  and the screen panel  28  when the screen panel  28  is raised by cam  82  into engagement with the machine frame  20  as shown in  FIG. 4B . This seal lip  86  allows for minor manufacturing tolerances and insertion forgiveness. The embodiment illustrated in  FIG. 5B  is another possible large seal member  54  with an irregular cross section for more resiliency or seal effectiveness. Seal members  54  of FIGS.  5 A and  5 C- 5 E each include ridges  88  which assist in improving the overall sealing effectiveness of the member  54 . One skilled in the art will recognize that many other possible configurations are possible of seal members used with the screen panel  28  of this invention. 
     In another unillustrated embodiment, screening machine  10  could also include a removable seal holder as well as the machine frame  20  and the screen panel  28 . The removable seal holder would include the large seal member  54  and be a resilient holder to be sandwiched between the machine frame  20  and the screen panel  28  when screen panel  28  is raised into engagement with the machine frame  20 . This would allow the seal to be reuseable and extend the life of individual components of the screening machine  10  beyond the previously described embodiments. 
     From the above disclosure of the general principles of the present invention and the preceding detailed description of at least one preferred embodiment, those skilled in the art will readily comprehend the various modifications to which this invention is susceptible. Therefore, we desire to be limited only by the scope of the following claims and equivalents thereof.