Patent Abstract:
A screening machine of the type used to separate or classify mixtures of solid particles of different sizes includes a fixed base and a perforate screen mounted for movement relative to the base during a screening operation. The screens are pre-tensioned and mounted in a perimeter frame for separating various granular and particulate material. The frame is slid into the side of the machine in a direction parallel with two opposing bevel lips at the ends of the frame which mate in the screening machine with a complementary channel such that when the screen is raised into sealing contact in the screening machine, the bevel ends of the screen panel frame align the screen panel in the machine. The bevels on the screen panel frame provide a positive sealing surface for contact with the adjacent portions of the channel to prevent product from escaping off of the screen during use.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    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. 
         [0002]    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 which 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 comprise 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. 
         [0003]    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. 
         [0004]    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 which 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 which 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. 
         [0005]    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 which 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. 
       SUMMARY OF THE INVENTION 
       [0006]    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 one or more pre-tensioned screens mounted in a perimeter frame for separating various granular and particulate material. One aspect of this invention is the profile or contour of opposite ends of the perimeter frame for the screen. The mesh screen is mounted to a rigid perimeter frame. The screen is pre-tensioned in the frame as opposed to screens which are stretched or tensioned during the screening machine set up. The frame is slid into the side of the machine in a direction parallel with two opposing contoured profile ends of the frame. In one embodiment, the profile of the frame along each end includes a downwardly directed bevel relative to the plane of the screen. The profile or contour of these ends align with and mate in the screening machine with a complementary channel such that when the screen is raised into sealing contact in the screening machine, the bevel ends of the screen panel frame align the screen panel in the machine through a comparably dimensioned and configured channel on the screening machine. Likewise, the bevels on the screen panel frame provide a positive sealing surface for contact with the adjacent portions of the channel to prevent product from escaping off of the screen during use. 
         [0007]    Therefore, according to this invention, the screening operation is much more efficient and more easily accomplished while offering significant advantages in screen service life, installation and removal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The objectives and features of the invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      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; 
           [0010]      FIG. 2  is a perspective view of the screen panel of  FIG. 1 ; 
           [0011]      FIG. 3  is a top plan view of the screen panel of  FIG. 2 ; 
           [0012]      FIG. 4  is a side elevational view of the screen panel of  FIG. 2 ; 
           [0013]      FIG. 5A  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; and 
           [0014]      FIG. 5B  is a view similar to  FIG. 5A  with the screen panel engaged with a screen panel carrier according to one aspect of this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    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 shown for illustrative purposes. 
         [0016]    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 . 
         [0017]    The screening machine  10  is supported structurally by a base 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, other motion or combinations thereof (herein collectively referred to as “vibratory” motion or variations of that term) to at least the head end  16 . 
         [0018]    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 decks  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 the foot or 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, direction or attitude. The direction of travel of the material being screened from the head end to the foot end 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 is a lateral direction. 
         [0019]    In the embodiment of the screening machine  10  shown in  FIG. 1 , upper and lower screen decks  30  each include four screen panels  28  mounted generally coplanar with each other in the associated screen deck  30 . Accordingly, as the material to be screened is deposited from the inlet port  12  onto the upper screen deck  30 , the vibratory motion of the screening machine advances the material longitudinally across the top of the screen panels  28  of the upper screen deck  30  toward the foot end  32 . Appropriately sized and configured material passes through the upper screen deck  30  and falls onto the lower screen deck  30 . The screen panels  28  of the upper screen deck  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 deck  30  and is deposited on the lower screen deck  30 . Therefore, the lower screen deck  30  is included to provide an additional separating mechanism for the appropriately sized particles to pass through the second lower screen deck  30  for collection in the lower pan (not shown) and discharge through an outlet or exit section  36 . 
         [0020]    The unacceptably sized particles remain atop the first upper screen deck  30  and fall off the terminal edge thereof into a collection basin for discharge through the outlet section  36 . Material that passes through the upper screen deck  30  and remains atop the lower screen deck  30  falls off the terminal edge thereof and into the collection basin for discharge through a reject port (not shown). The discharge and reject ports are separated by a baffle (not shown) to keep the classified particles separate from one another. 
         [0021]    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 on the opposite side of the screening machine  10  may also be provided. Advantageously, the screen panels  28  are inserted laterally or perpendicularly to the longitudinal direction of travel of the material being screened in the screening machine  10  from the head end  16  to the foot end  32  of the machine  10 . 
         [0022]    As shown generally in  FIG. 5A , when the screen panel  28  is inserted into the screening machine  10 , it is supported on a vibratory carrier  44 . In one embodiment, the vibratory carrier  44  may include a ball tray  46  capturing a number of balls or other agitation producing members (not shown) which repeatedly impact the screen panel  28  to dislodge particulate material that might accumulate on the screen material  34  and inhibit occlusion of the screen material  34  as is well known in the art. 
         [0023]    Referring to  FIGS. 2-4 , one embodiment of the screen panel  28  according to this invention includes a generally perforated mesh screen material  34  including a number of intersecting longitudinal  48  and lateral  50  threads, wires or strings which are oriented orthogonally to each other to provide appropriately sized and configured openings  52  in the mesh screen material  34  to prevent/permit the passage particulate material there through. The screen panel  28  includes a generally rigid perimeter frame  54  having a leading side edge  56  opposite from a trailing side edge  58 . In one aspect, the screen material  34  of the screen panel  28  of this invention does not require tensioning by the screening machine  10  upon installation into the screen deck  30 . Many prior screening machines tension the screen mesh material or pull it taught during the installation process. The screen mesh material  34  of the screen panel  28  according to this invention does not require tensioning and in that sense is considered pre-tensioned in that it is mounted in the screen panel frame  54  in a ready-to-use state. 
         [0024]    The panel  28  may be manufactured by a variety of processes, one of which utilizes a bare metal frame which is dipped into an epoxy and allowed to air dry. The epoxy is hard to the touch but has not cured. The frame  54  with dry epoxy is then placed on a table with mesh screen material  34  on top. This stack-up is then bonded together with a heat press for a few minutes. The edges are then cleaned up with a hand grinder, if necessary. 
         [0025]    A further benefit of this aspect of the invention is that the process leaves the panel  28  feeling tensioned although no time or fixture is required to pull (tension) the screen material  34  prior to bonding it to the frame  54  or when installing the screen frame panel into the screening machine  10 . The new panel  28  design incorporates this approach such that open area is maximized but the tension level is comparable to known tension techniques, such as spring clips. 
         [0026]    The leading side edge  56  of the screen panel frame  54  is typically inserted laterally into the screening machine  10  while a user or operator grasps the trailing side edge  58  for manipulation. In particular, a downwardly turned elongate handle  60  is formed on the trailing side edge  58  of the screen panel  28 . In one embodiment, the handle  60  is oriented approximately 90° relative to the plane of the screen panel  28  and provides a convenient and easy access for the user or technician to grasp or manipulate the screen panel  28 . Additionally, the handle  60  or adjacent surfaces of the screen panel frame  54  provide a convenient location for identifying indicia and labels indicating various service parameters, design characteristics and other aspects of the screen panel  28 . 
         [0027]    One or more tabs  62  each located proximate a head end  64  or a tail end  66  of the screen frame  54  are located along the trailing side edge  58  of the frame. The tabs  62  are each oriented approximately 90° relative to the plane of the screen panel  28  and along with the handle  60  provide a convenient location for the user or technician to grasp and manipulate the screen panel frame. Likewise, upon insertion of the screen panel  28  into the screening machine  10 , the tabs  62  and handle  60  provide a detent when juxtaposed against the vibratory carrier  44  for proper orientation and location of the screen panel  28  in the screening machine  10 . 
         [0028]    Another aspect of the screen panel  28  and associated frame  54  according to this invention are beveled edges or lips  68  along the longitudinal head end  64  and/or foot end  66  of the screen panel frame  54 . Each bevel  68  is oriented approximately 45° relative to the upper surface or plane of the screen panel  28  and extends substantially the entire width of the frame  54 . While the bevel  68  are shown along both the longitudinal head and foot ends  64 ,  66  of the screen panel frame  54 , one of ordinary skill in the art will readily appreciate that the bevel edge  68  may be provided at either or both of the head and foot ends  64 ,  66  within the scope of this invention. 
         [0029]    Referring to  FIGS. 5A and 5B , the configuration of the screen panel frame  54  relative to the remainder of the screening machine  10  will now be described. The downwardly turned bevel edges  68  along the head and foot ends  64 ,  66  of the screen panel frames  54  are supported by a similarly inclined face  70  of the vibratory carrier  44  as shown in  FIG. 5A . The carrier  44  also includes a compressible seal member  72  juxtaposed to the terminal edge  74  of the bevel edge  68  and mounted in the carrier  44 . Likewise, the lower surface of the screen panel frame  54  is supported along a similarly configured profile of the carrier  44  as shown in  FIG. 5A . 
         [0030]    The screening machine  10  includes a bracket  76  in which a rotational cam  78  is seated to support the carrier  44 . The rotation of the cam  78  is accomplished by an actuator  80  accessible to the operator or technician when the door  38  of the screening machine  10  is open. One known mechanism suitable for use with this invention to raise/lower the carrier  44  and screen panel  28  is disclosed in Rotex&#39; U.S. Pat. No. 6,070,736 which is incorporated by reference herein. The screening machine  10  also includes a downwardly depending channel  82  initially spaced from the bevel lip  68  of the screen frame  54  as shown in  FIG. 5A . 
         [0031]    Upon rotation in the direction of arrow A of the actuator  80 , the cam  78  is rotated thereby raising the carrier  44  and screen panel  28  supported thereon upwardly to sealing engagement with an upper portion  84  of the screen deck  30  as shown in  FIG. 5B . As the carrier  44  supporting the screen panel  28  is raised, a face  86  of the channel  82  is juxtaposed against the bevel lip  68  of the screen panel  28  and the seal  72  is compressed against the channel  82 . As a result, the portion of the screen deck  84  and upper surface of the screen panel frame  54  are sealed to prevent and inhibit the discharge of material being screened. Due to the design and configuration of the screen panel frame  54  and associated screen deck  30 , the seal  72  and associated components are neither damaged nor compromised during the lateral installation and removal of the screen panel  28  thereby extending the service life of the associated components while maintaining effective sealing and associated screening operations. The orientation of the seal  72  is generally parallel with the lateral direction in which the screen panel is inserted and removed from the machine  10 . 
         [0032]    The bevel edges  68  on two opposite ends in conjunction with the lift system described in U.S. Pat. No. 6,070,736 permits insertion and proper location, alignment, sealing, and securing of the screen panel  28  to the screening machine  10  while maintaining a smooth transition (no bumps or wear points). This invention 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, nestable for storage and shipping. The bevel lip  68  also acts as a seal holder for reusable seal strips  72 . 
         [0033]    Referring to  FIGS. 1-3 , the screen panel  28  of this invention includes a number of smaller cells  88  defined around the interior of the perimeter frame  54  by plurality of transverse and longitudinally extending ribs  90 . Because the screen material  34  is flat and pressed, smaller cells  88  result in greater tension in the screen mesh material  34  since it has very little length and is held on both ends and it cannot deflect for a given load. The orientation of the ribs  90  may be skewed or not aligned with the orientation of the openings  52  defined by the threads  48 ,  50  of the screen material  34 . Alternatively, the ribs  90  and threads  48 ,  50  of the screen material may be aligned with each other in the lateral and longitudinal direction. In one embodiment of the screen panel  28 , the wire mesh screen material  34  is not bonded directly to the ribs  90 , only the perimeter frame  54 . Silicone may be used either as an adhesive to bond the screen material  34  to the frame  54  and/or as a buffer between the screen material  34  and another suitable adhesive known in the industry. It is believed that the silicone retards fatigue of the screen material  34  in use. As such, the service life of the screen panel  28  is extended and the economic benefit of this invention is maximized. It is expected that this general design provides improved throughput, service live and screening accuracy. 
         [0034]    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, I desire to be limited only by the scope of the following claims and equivalents thereof.

Technology Classification (CPC): 1