Patent Publication Number: US-11654380-B2

Title: Apparatuses, methods, and systems for vibratory screening

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/460,764, filed Jul. 2, 2019, which is a continuation-in-part of U.S. patent application Ser. No. 15/785,141, filed Oct. 16, 2017, which is related to and claims the benefit of U.S. Provisional Patent Application No. 62/408,514, filed Oct. 14, 2016, and U.S. Provisional Patent Application No. 62/488,293, filed Apr. 21, 2017. This application is also related to U.S. Design Application No. 29/644,138, filed Apr. 15, 2018. The disclosure of each of these applications is incorporated herein by reference in its entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG.  1    is a perspective side view of a vibratory screening machine, according to one or more embodiments of the present disclosure. 
       FIG.  2    is a perspective top view of the vibratory screening machine shown in  FIG.  1   . 
       FIG.  3    is a front view of the vibratory screening machine shown in  FIGS.  1  and  2   . 
       FIG.  4    is a rear view of the vibratory screening machine shown in  FIGS.  1 ,  2 , and  3   . 
       FIG.  5    is an isometric view of a screening deck having screen assemblies mounted thereon, according to one or more embodiments of the present disclosure. 
       FIG.  6    is an enlarged partial isometric view of the screening deck shown in  FIG.  5   , without screen assemblies mounted thereon, incorporated into the vibratory screening machine shown in  FIGS.  1 ,  2 ,  3 , and  4   . 
       FIG.  7    is an enlarged side view of a wash tray, which may be incorporated into the screening deck shown in  FIGS.  5  and  6   , according to one or more embodiments of the present disclosure. 
       FIG.  8    is an isometric view of a tensioning device with a ratchet mechanism, according to one or more embodiments of the present disclosure. 
       FIG.  9 A  is a side view of the screening deck shown in  FIGS.  5 ,  6 , and  7    with the ratchet mechanism shown in  FIG.  8   . 
       FIG.  9 B  is an enlarged view of the ratchet mechanism shown in  FIG.  9 A . 
       FIG.  10    is an enlarged partial isometric view of a feed assembly and the screening deck shown in  FIGS.  5 ,  6 , and  7    secured to the vibratory screening machine shown in  FIGS.  1 ,  2 ,  3  and  4   . 
       FIG.  11 A  is an isometric bottom view of an undersized material discharge assembly, according to one or more embodiments of the present disclosure. 
       FIG.  11 B  is an isometric top view of the undersized material discharge assembly shown in  FIG.  11 A . 
       FIG.  12 A  is an isometric bottom view of an oversized material discharge chute, according to one or more embodiments of the present disclosure. 
       FIG.  12 B  is an isometric top view of the oversized material discharge chute shown in  FIG.  12 A . 
       FIG.  13 A  is an isometric top view of an oversized material discharge trough, according to one or more embodiments of the present disclosure. 
       FIG.  13 B  is an isometric bottom view of the oversized material discharge trough shown in  FIG.  13 A , according to one or more embodiments of the present disclosure. 
       FIG.  14    is a cross-sectional side view of a screening deck having material flowing across the screening deck and featuring an impact area of a screen assembly incorporated into a screening deck assembly, according to one or more embodiments of the present disclosure. 
       FIG.  15    a side view of a tray showing material to be filtered falling on an impact area of a filter member, according to one or more embodiments of the present disclosure. 
       FIG.  16 A  is a front-side perspective view of a screen assembly, according to one or more embodiments of the present disclosure. 
       FIG.  16 B  is a side view of a screen filter for use in an embodiment of the present disclosure. 
       FIG.  17    illustrates a flow of undersized materials in a screening assembly, according to one or more embodiments of the present disclosure. 
       FIG.  18    illustrates a flow of oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. 
       FIG.  19    illustrates a flow of oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. 
       FIG.  20    illustrates a flow of oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. 
       FIG.  21    illustrates a flow of undersized and oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. 
       FIG.  22    is a perspective top and side view of a vibratory screening machine, according to one or more embodiments of the present disclosure. 
       FIG.  23    is a perspective bottom and side view of a vibratory screening machine, according to one or more embodiments of the present disclosure. 
       FIG.  24    is a top perspective view of a combined undersized/oversized collecting apparatus that includes an undersized collecting assembly with two oversized collecting troughs, according to one or more embodiments of the present disclosure. 
       FIG.  25    is a bottom perspective view of the collecting apparatus of  FIG.  24   , according to one or more embodiments of the present disclosure. 
       FIG.  26    is a further top perspective view of the collecting apparatus of  FIGS.  24  and  25   , according to one or more embodiments of the present disclosure. 
       FIG.  27    is a side perspective view of the collecting the apparatus of  FIGS.  24 ,  25 , and  26    with a plurality of installed screening deck assemblies, according to one or more embodiments of the present disclosure. 
       FIG.  28    is a further side perspective view of the collecting apparatus with installed screening deck assemblies of  FIG.  27   , according to one or more embodiments of the present disclosure. 
       FIG.  29    is a further side perspective view of the collecting apparatus with installed screening deck assemblies of  FIGS.  27  and  28   , according to one or more embodiments of the present disclosure. 
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to methods and apparatuses for screening materials, in particular, for separating materials of varying sizes. Embodiments of the present disclosure include screening systems, vibratory screening machines, and apparatuses for vibratory screening machines and screen assemblies for separating materials of varying sizes. 
     Vibratory screening systems are disclosed in U.S. Pat. Nos. 6,431,366 B2 and 6,820,748 B2, which are incorporated herein by reference thereto. Advantages of the present invention over previous systems include a larger screening capacity for separation of materials without an associated increase in machine size. Embodiments of the present invention include improved features such as: screening deck assemblies having first and second screens; tensioning devices that tension each screen in a front to back direction (i.e., in the direction of flow of the material that is being screened); wash trays positioned in between the first and second screens; feed chutes configured to connect directly to an over-mounted feed system, e.g., the feed systems described in U.S. Patent App. No. 2014/0263103 A1, which is incorporated herein by reference hereto; centralized discharge assemblies which collect undersized and oversized materials; and replaceable screen assemblies configured for front to back tensioning and impact areas for flow of material onto the screen assemblies. These features, among others described herein, provide for a compact design that allows for a direct overhead feed system, increased screening capacity, and reduced footprint. Additionally, the multiple screen assemblies that are tensioned front to back with wash trays in between and impact areas on the screen assemblies themselves provide for improved flow characteristics and efficiencies. The improved tensioning structures provide for quick and easy replacement of screen assemblies. The improved discharge assemblies are configured for optimal or nearly optimal flow characteristics as well as for providing the greatly reduced footprint. These improvements and advantages, and others, are provided by at least some embodiments in accordance with aspects of this disclosure. 
     Example embodiments of the present disclosure employ vibratory screening machines to separate materials of varying sizes. In some embodiments, a vibratory screening machine includes a framing assembly, a plurality of screening deck assemblies mounted to the framing assembly, an undersized material discharge assembly and an oversized material discharge assembly. The framing assembly includes an inner frame mounted to an outer frame. A plurality of screening deck assemblies are mounted to the inner frame and arranged in a stacked and staggered relationship. Each screening deck assembly includes a first screening deck and a second screening deck, a wash tray extending between first and second screening decks, and a tensioning assembly. At least one vibrating motor may be attached to the inner frame and/or at least one screening deck assembly. An undersized material discharge assembly and an oversized material discharge assembly, each of which may include at least one vibratory motor, are in communication with each screening deck assembly, and are configured to receive undersized and oversized screened material, respectively, from the screening deck assemblies. 
     In one embodiment of the present disclosure, a vibratory screening machine includes an outer frame, an inner frame connected to the outer frame, a vibratory motor assembly secured to the inner frame such that it vibrates the inner frame. A plurality of screen deck assemblies is attached to the inner frame in a stacked arrangement, each configured to receive replaceable screen assemblies. The screen assemblies are secured to the screen deck assemblies by tensioning the screen assemblies in a direction that a material to be screened flows across the screen assemblies. An undersized material discharge assembly is configured to receive materials that pass through the screen assemblies, and an oversized material discharge assembly is configured to receive materials that pass over a top surface of the screen assemblies. The undersized material discharge assembly includes an undersized chute in communication with each of the screen deck assemblies and the oversized material discharge assembly includes an oversized chute assembly in communication with each of the screen deck assemblies. 
     The oversized chute assembly may include a first oversized chute assembly and a second oversized chute assembly. The undersized chute, the first oversized chute assembly, and the second oversized chute assembly may be located beneath the plurality of screen deck assemblies, and the undersized chute may be located between the first and second oversized chute assemblies. At least one of the plurality of screen deck assemblies may be replaceable. Each screen deck assembly may include a first screen assembly and a second screen assembly. A wash tray may be located between the first screen assembly and the second screen assembly. A trough may be located between the first screen assembly and the second screen assembly. The trough may include an Ogee-weir structure. 
     The vibratory screening machine may include a screen tensioning system that includes tensioning rods that extend substantially orthogonal to the direction of flow of the material being screened. The tensioning rods may be configured to mate with a portion of the screen assembly and tension the screen assembly when rotated. The screen tensioning system may include a ratcheting assembly configured to rotate the tensioning rod such that it moves between a first open screen assembly receiving position to a second closed and secured screen assembly tensioned position. 
     The vibratory screening machine may include a vibratory motor, wherein the vibratory⋅motor is attached to the oversized chute assembly. The vibratory screening machine may include multiple feed assembly units, each feed assembly unit located substantially directly below individual discharges of a flow divider. The vibratory screening machine may include at least eight screen deck assemblies. 
     The oversized chute assembly may include a bifurcated trough that is configured to receive materials that do not pass through the screen assemblies and are conveyed over a discharge end of the screen deck assemblies. A first section of the bifurcated trough may feed the first oversized chute assembly, and a second section of the bifurcated trough may feed the second oversized chute assembly. 
     In one embodiment of the present disclosure, a screen deck assembly includes a first screen deck configured to receive a first screen assembly, a second screen deck configured to receive a second screen assembly located downstream from the first screen deck assembly; and a trough located between the first and second screen deck assemblies, wherein the first screen deck assembly is configured to receive a material to be screened and the trough is configured to pool the material to be screened before it reaches the second screen deck assembly. 
     The trough may include at least one of an Ogee-weir and a wash tray. The screen deck assembly may include a first and a second screen tensioning system, each having tensioning rods that extend substantially orthogonal to the direction of flow of the material to be screened. The first tensioning rod may be configured to mate with a first portion of the first screen assembly when rotated and the second tensioning rod may be configured to mate with a second portion of the second screen assembly when rotated. 
     The first screen tensioning system may include a first ratcheting assembly configured to rotate the first tensioning rod such that the first tensioning rod moves between a first open screen assembly receiving position to a second closed and secured screen assembly tensioned position. The second screen tensioning system may include a second ratcheting assembly configured to rotate the second tensioning rod such that the second tensioning rod moves between a first open screen assembly receiving position to a second closed and secured screen assembly tensioned position. 
     In one embodiment of the present disclosure, a method of screening a material includes feeding the material on a vibratory screening machine having a plurality of screen deck assemblies that are configured in a stacked arrangement, each of the screen deck assemblies configured to receive replaceable screen assemblies, the screen assemblies secured to the screen deck assemblies by tensioning the screen assemblies in the direction the material flows across the screen assemblies; and screening the materials such that a undersized material that passes through the screen assemblies flows into an undersized material discharge assembly, and an oversized material flows over an end of the screen deck assembly into an oversized material discharge assembly. The undersized material discharge assembly includes an undersized chute in communication with each of the screen deck assemblies and the oversized material discharge assembly includes an oversized chute assembly in communication with each of the screen deck assemblies. 
     The oversized chute assembly may include a first and second oversized chute assembly. The undersized chute and first and second oversized chute assemblies may be located beneath the plurality of screen deck assemblies, and the undersized chute may be located between the first and second oversized chute assemblies. 
     At least one of the plurality of screen deck assemblies may be replaceable. Each screen deck assembly may include a first and a second screen assembly. A. trough may be located between the first and second screen assemblies. The trough may include an Ogee-weir structure. 
     A screen tensioning system may be included having tensioning rods that extend substantially orthogonal to the direction of flow of the material being screened. The tensioning rods may be configured to mate with a portion of the screen assembly and tension the screen assembly when rotated. 
       FIGS.  1  to  4    illustrate a vibratory screening machine  100 . Vibratory screening machine  100  includes a framing assembly having an outer frame  110 , and an inner frame  120 , a feed assembly  130 , a plurality of screening deck assemblies  400 , a top vibratory assembly  150 , an undersized collecting assembly  160  and an oversized collecting assembly  170 . 
       FIG.  1    illustrates a side perspective view of vibratory screening machine  100 .  FIG.  2    illustrates a top perspective view of vibratory screening machine  100 , shown from the opposite side of vibratory screening machine  100  as is illustrated in  FIG.  1   . As is shown in  FIG.  2   , the opposite side of vibratory screening machine  100  includes mirror image components of outer frame  110  as is shown in  FIG.  1   . The mirror-image outer frame components are denoted by the addition of a prime (′) at the end of the corresponding component reference number. 
     As is shown in  FIGS.  1  and  2   , outer frame  110  includes a longitudinal set of base supports  111  and  111 ′, a latitudinal set of base supports  112  and  112 ′, and two sets of upstanding channels,  113  and  113 ′ and  114  and  114 ′. Upstanding channels  113  and  113 ′ and  114  and  114 ′ each have first ends  113 A and  113 ′A and  114 A and  114 ′A, mid-portions  113 B and  113 ′B and  114 B and  114 ′B, and second ends  113 C and  113 ′C and  114 C and  114 ′C, respectively. Each of first ends  113 A and  113 ′A and  114 A and  114 ′A are elevated relative to second ends  113 C and  113 ′C and  114 C and  114 ′C, with mid-portions  113 B and  113 ′B and  114 B and  114 ′B extending the length between the first and second ends, respectively. Outer frame  110  further includes upper angled channels  115  and  115 ′ and lower angled channels  116  and  116 ′. Upper angled channels  115  and  115 ′ and lower angled channels  116  and  116 ′ each have first ends  115 A and  116 A, mid-portions  115 B and  116 B, and second ends  115 C and  116 C, respectively. First ends  115 A and  116 A are elevated relative to second ends  115 C and  116 C, and mid-portions  115 B and  116 B extend the length between first ends  115 A and  116 A and second ends  115 C and  116 C, respectively. Outer frame  110  also includes three sets of declining channels:  117  and  117 ′,  118  and  118 ′, and  119  and  119 ′. Each declining channel has a first end,  117 A,  118 A, and  119 A which is elevated relative to its respective second end,  117 B,  118 B,  119 B. 
     Referring to  FIGS.  1  and  2   , the opposite ends of longitudinal base supports  111  and  111 ′ attach to the opposite ends of latitudinal base supports  112  and  112 ′ such that the four base supports create a rectangular shape. Second ends  113 C and  113 ′C and  114 C and  114 ′C of each respective upstanding channel attach to the four corners where base channels  111  and  111 ′ meet base channels  112  and  112 ′. Mid-portion  113 B and  113 ′B of upstanding channel  113  attaches to first end  119 A of declining channel  119 . Second end  119 B of declining channel  119  rests above longitudinal base support  111 . First end  113 A of upstanding channel  113  attaches to mid-portion  115 B of upper angled channel  115  and first end  118 A of declining channel  118 . First end  115 A of upper angled channel  115  attaches to first end  117 A of declining channel  117 . Second end  117 B of declining channels  117  attaches to mid-portion  116 B of lower angled channel  116  towards first end  116 A. Second end  118 B of declining channel  118  attaches to mid-portion  116 B of lower angled channel  116  toward second end  116 C. Second end  116 C of lower angled channel  116  attaches to and terminates at second end  119 B of declining channel  119 . 
     Referring to  FIG.  2   , outer frame  110  further includes a rear channel  109  having opposite ends that attach to one of each of mid-portions  113 B and  113 B′ of upstanding channel  113 . Additional rear channels  108  run parallel to rear channel  109 , each with opposite end attached to lower angled channel  116  and its counterpart lower angled channel  116 ′ from mid-portion  116 B toward second end  116 C to provide structural support to outer frame  110 . 
     As is shown in  FIG.  2   , inner frame  120  mounts top vibratory assembly  150  and screening deck assemblies  400  via securing mechanisms, such as bolts. Inner frame  120  includes upper angled channels  125  and  125 ′, lower angled channels  126  and  126 ′, upper declining channels  127  and  127 ′, and lower declining channels  128  and  128 ′. Upper and lower angled channels  125  and  126  of inner frame  120  run parallel to upper and lower angled channels  115  and  116  on the medial side of outer frame  110 . Upper and lower declining channels  127  and  128  of inner frame  120  run parallel to declining channels  117  and  118  on the medial side of outer frame  110 . Though not shown in  FIGS.  1  and  2   , inner frame  120  may be mounted to outer frame  110  with elastomeric mountings, or other similar mountings, which permit inner frame  120  to maintain vibratory motion while dampening the effects of vibration on the structural integrity of fixed outer frame  110 . In an embodiment, elastomeric mountings are made of a composite material including rubber and have female threads that accept male bolts from the inner frame and outer frame. The elastomeric mountings may be replaceable parts. While outer frame  110  is shown in the specific configuration described, it may have different configurations as long as it provides the structural support necessary for inner frame  120 . In embodiments, vibratory screening machine  100  may have an outer frame that includes feet that are configured to attach to an existing structure. 
     In some embodiments, top vibratory assembly  150  includes side plates  153  and  153 ′, a first vibrating motor  151 A and a second vibrating motor  151 B. Side plates  153  and  153 ′ have a top angled edge  154 , a bottom edge  155 , and an exterior surface  156 . Bottom edge  155  of side plate  153  is secured to a side channel  430  of screening deck assembly  400  via securing mechanisms, such as bolts. Exterior surface  156  includes ribs  157  that provide structural support to top vibratory assembly  150 . The opposing sides of vibrating motor  151 A and second vibrating motor  151 B are mounted to top angled edges  154  of side plates  153  and  153 ′. First and second vibrating motors  151 A and  151 B are configured such that they may vibrate all screening deck assemblies  400  mounted to inner frame  120 . While shown with a particular configuration in  FIGS.  1  and  2   , it is noted that top vibratory assembly  150  may have other arrangements that retain the functionality described herein. 
     As is shown in  FIG.  2   , vibratory screening machine  100  includes a feed assembly  130 . Feed assembly  130  includes support frame  134 , a plurality of vertical supports  136 , feed inlet ducts  131 , mounting arms  132 , and feed outlet ducts  133 . Mounting arms  132  are secured to support frame  134  and  134 ′ with securing mechanisms, such as bolts. Support frame  134  and  134 ′ is located above and parallel to declining channels  117  and  117 ′ of outer frame  110 . Vertical supports  136  secure support frame  134  and  134 ′ to declining channels  117  and  117 ′ of outer frame  110  such that feed assembly  130  is fixed relative to vibrating inner frame  120 . Inlet ducts  131  are configured to receive a flow of slurry from a flow divider device, such as shown in U.S. Patent Application No. 2014/0263103 A1, which is incorporated herein by reference in its entirety, or other material flow assemblies, and feed it to outlet ducts  133 . Outlet ducts  133  are positioned above elevated sides of screening deck assemblies  400  such that each outlet duct  133  is configured to discharge a flow of materials  500  to each screening deck assembly  400 . Earlier systems have hoses located a story above vibratory machines, whereas in assemblies of this disclosure, configurations of inlets on the vibratory machine provide for substantially distributed drops in flow and greatly reduce the height of the machine. This is an important space saving feature of at least some embodiments of the present disclosure. 
       FIG.  3    illustrates a front view of the vibratory screening machine  100 .  FIG.  4    illustrates a rear view of the vibratory screening machine  100 . As is shown in  FIGS.  3  and  4   , the vibratory screening machine  100  includes an undersized material collection assembly  160  and an oversized material collection assembly  170 . Referring to  FIG.  3   , undersized material collection assembly  160  includes a plurality of collecting pans  161  secured to the underside of each screening deck assembly  400 , a plurality of ducts  162  in communication with collecting pans  161 , and an undersized collecting chute  166 . Oversized material collection assembly  170  includes a plurality of oversized collecting chutes  171  mounted to lower end plate  428  of each screening deck assembly  400 , and two oversized collecting troughs  176  and  176 ′ in communication with oversized collecting chutes  171 . As is shown in  FIG.  4   , oversized collecting troughs  176  and  176 ′ include vibratory motors  179  and  179 ′. As is shown in  FIGS.  3  and  4   , undersized collecting chute  166  extends between oversized collecting chute  171  and oversized collecting troughs  176  and  176 ′ beneath screening deck assemblies  400  of vibratory screening machine  100 . Though shown in a specific configuration, oversized collecting troughs  176  and  176 ′ and vibratory motors  179  and  179 ′ may have different arrangements so long as they aid in conveying oversized material  500  discharged from screening deck assemblies across oversized collecting troughs  176  and  176 ′. 
       FIGS.  5  to  10    illustrate various views of a screening deck  400 .  FIG.  5    illustrates an enlarged isometric perspective view of screen assembly  400 . Screening deck assembly  400  includes a first screening deck  410 , a second screening deck  420 , side channels  430  and  430 ′, a wash tray  440 , and a tensioning device  450 . As is shown in  FIG.  5   , first screening deck  410  and second screening deck  420  are covered by a first screen assembly  409  and a second screen assembly  419 , respectively. First screen assembly  409  and second screen assembly  419  are replaceable screen assemblies which are attached to first and second screening decks  410  and  420 . When in operation, material to be screened  500  by vibratory screening machine  100  is discharged from feed outlet ducts  133  of feed assembly  130  to the elevated side of first screen assembly  409 , along feed end  409 A of first screen assembly  409 , and is vibrated across first screen assembly  409  of first screening deck  410 , over discharge end  409 B of first screen assembly  409 , and into wash tray  440 . Vibration carries material  500  over wash tray  440 , where material passes over feed end  419 A of second screen assembly  419 . As is described herein, material  500  hits second screen assembly  419  in screen impact area  448 , then vibrates across second screen assembly  419  of second screening deck  420 , and over discharge end  419 B of second screen assembly  419  along lower end plate  428 . First screen assembly  409  and second screen assembly  419  are configured such that undersized materials fall through first screen assembly  409  and second screen  419  into undersized material collecting pans  161 , and are funneled into undersized collecting chute  166  via ducts  162 . Oversized materials do not pass through screens  409  and  419  and are vibrated off lower end plate  428  and funneled through oversized collecting chutes  171  and  171 ′ to oversized collecting troughs  176  and  176 ′. Direction of the flow of material is represented with large arrows. While illustrated in this particular configuration in the figures, oversized collecting chutes  171  and  171 ′ and oversized collecting troughs  176  and  176 ′ may have different arrangements so long as they receive oversized materials discharged from each screening deck assembly and provide functionality as described herein. The flow of material through split outside oversized collecting chutes  171 ,  171 ′ and a central undistributed undersized collecting chute  166  provides for efficient flows in reduced space. The configuration of the chutes  166 ,  171 ,  171 ′ reduces the footprint of the machine  100  while providing for direct and efficient flow. 
     First screening deck  410  includes an upper end plate  416  and a lower end plate  418 . Second screening deck  420  includes an upper end plate  426  and a lower end plate  428 . Opposite sides of first screening deck  410  and second screening deck  420  are secured to the medial sides of side channels  430  and  430 ′ with securing mechanisms such as, e.g., bolts or welding. The lateral sides of side channels  430  and  430 ′ include a plurality of angled plates  432 . Angled plates  432  include holes through which securing mechanisms, such as bolts, may extend to secure side channels  430  and  430 ′ to upper declining channel  127  and  127 ′ and lower declining channel  128  and  128 ′ of inner frame  120 . While illustrated in this particular arrangement, side channels  430  and  430 ′ and angled plates  432  may have different configurations so long as they permit screening deck assembly  400  to vibrate such that materials  500  of varying sizes are separated as desired. 
       FIG.  6    illustrates a partial side perspective view of screening decks  410  and  420 , wash tray  440 , side channel  430 , and a portion of tensioning device  450 . As is shown in  FIG.  6   , a flexible material  405  covers outlet duct  133  of feed assembly  130 . Flexible material  405  is configured to control the flow of materials from outlet duct  133  to screening deck assembly  400  so that the flow of material is uniformly distributed across screening deck assembly  400 , thereby maximizing efficiency of vibratory screening machine  100 . As is shown in  FIG.  6   , first screening deck  410  and second screening deck  420  do not include screens  409  and  419 , but it will be appreciated that first and second screening decks  410  and  420  are covered by screens  409  and  419  when vibratory screening machine  100  is employed to separate materials of varying sizes, and can be changed out, as described herein, when worn or damaged. Referring to  FIG.  6   , first screening deck  410  includes a rib  412 , stringers  414 , an upper end plate  416  and a lower end plate  418 . Second screening deck  420  includes a rib  422 , stringers  424 , an upper end plate  426  and a lower end plate  428 . Opposite ends of ribs  412  and  422  extend from side channel  430  and  430 ′ at each of the midpoints between upper end plate  416  and lower end plate  418  of first screening deck  410 , and upper end plate  426  and lower end plate  428  of second screening deck  420 , respectively. A plurality of stringers  414  and  424  extend from upper end plates  416  and  426  to lower endplates  418  and  428 , respectively. A midpoint  415  of each stringer  414  and a midpoint  425  of each stringer  424  traverses the top surface of ribs  412  and  422 . Midpoints  415  and  425  are elevated with respect to opposite ends of stringers  414  and  424  such that stringers  414  and  424  create a “crown” or curvature across first and second screening decks  410  and  420 . Though first screening deck  410  and second screening deck  420  are shown with a single rib  412  and  422  respectively, it will be appreciated that first screening deck  410  and second screening deck  420  may include other configurations. First screening deck  410  and second screening deck  420  may include, respectively, a first plurality of ribs and a second plurality of ribs, so long as the additional ribs provide the functionality as described herein. In some embodiments at least one (or, in some embodiments, each one) of the first plurality of ribs and the second plurality of ribs can be assembled similarly to rib  412  or rib  422 . 
     Distinct from screening assemblies of other systems, such as those disclosed in U.S. Pat. No. 6,431,366, stringers  414  and  424  may be replaceable units, and may be bolted to ribs  412  and  422  rather than welded to ribs  412  and  422 . This configuration eliminates closely spaced weld joints between ribs  412  and  422  and stringers  414  and  424  that are commonly found in welded screening decks. This arrangement eliminates the shrink, heat distortion and drop associated with closely spaced weld joints, and enables rapid replacement of worn or damaged stringers  414  and  424  in the field. Replaceable stringers  414  and  424  may include plastic, metal, and/or composite materials and may be constructed by casting and/or injection molding. While not shown in  FIG.  6   , screening decks  410  and  420  are configured to support screens  409  and  419 , which extend across the surface of first screening deck  410  and second screening deck  420 , covering ribs  412  and  422  and stringers  414  and  424 , respectively, as is shown in  FIG.  5   . 
     With further reference to  FIG.  6   , upper end plate  416  of first screening deck  410  is elevated relative to lower end plate  418 . Similarly, upper end plate  426  of second screening deck  420  is elevated relative to lower end plate  428 . Wash tray  440  extends between lower endplate  418  of first screening deck  410  and upper endplate  426  of second screening deck  420 . First screening deck  410 , wash tray  440 , and second screening deck  420  are configured such that a flow of material from outlet duct  133  and flexible material  405  of feed assembly  130  traverses first screening deck  410  and wash tray  440  before traversing second screening deck  420 . This configuration enables a flow of materials to be effectively separated by increasing the surface area on which the flow of materials is screened into oversized material collecting assembly  170  and undersized material collecting assembly  160  without increasing the footprint of vibratory screening machine  100 . 
       FIG.  7    illustrates an isometric side view of wash tray  440  interfacing with first screening deck  410  and second screening deck  420 . As is shown in  FIG.  7   , wash tray  440  includes an upper side member  442  having a top portion  442 A and a bottom portion  442 B, a lower member  444  having a first end  444 A and a second end  444 B, and a curved side member  446  including a first end  446 A and a second end  446 B. Curved side member  446  includes an S-shape curve referred to as an “Ogee,” discussed in more detail below. Top portion  442 A of upper side member  442  connects to lower end plate  418  of first screening deck  410 . Bottom portion  442 B of upper side member  442  connects to first end  444 A of lower member  444 . Second end  444 B of lower member  444  connects to first end  446 A of curved side member  446 . Second end  446 B of curved side member  446  curves over upper end plate  426  of second screening deck  420 . 
     The resulting configuration of wash tray  440  generates a weir  447 , which is a trough or depression that provides a structure for pooling a flow of liquid or slurry material to be screened  500 . Embodiments of a wash tray  440  having an Ogee-weir structure possess functional significance in the field of fluid dynamics. An Ogee-weir structure is generally described as slightly rising up from the base of a weir and reaching a maximum rise  449  at the top of the S-shaped curve of the Ogee structure. Upon or after reaching maximum rise point  449 , fluid falls over the Ogee structure in a parabolic form. The discharge equation for an Ogee-weir is: 
     
       
         
           
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     As is shown in  FIG.  7   , incorporating wash tray  440  with an Ogee-weir curved side member  446  between first screening deck  410  and second screening deck  420  of screening deck assembly  400  may direct the flow of material screened by first screening deck  410  onto a desired impact point or impact area  448  near upper end plate  426  of second screening deck  420 , or another desired location, such that the discharge flow impacts the downstream screen panel at a predetermined wear surface as opposed to non-uniformly impacting downstream screen surfaces such as the screen openings. In this configuration, impact point/area  448  may remain unchanged despite changes in fluid parameters such as, e.g., flowrate and/or viscosity. Incorporation of Ogee-weir shaped curved side member  446  into wash tray  440  improves screening efficiency and consistency and reduces wear on second screening deck  420 . Flows of materials after impact are represented with large arrows in  FIG.  7   . 
       FIGS.  8 ,  9 A and  9 B  illustrate tensioning device  450 .  FIG.  8    illustrates an isometric perspective view of tensioning device  450 . Tensioning device  450  includes a tensioning rod  451 , brackets  454  and  454 ′, and ratchet mechanisms  456  and  456 ′.  FIG.  9 A  illustrates a partial side view of two ratchet mechanisms  456  and two brackets  454  mounted to side channel  430  of screening deck assembly  400 .  FIG.  9 B  illustrates an enlarged view of one of two ratchet mechanisms  456  and brackets  454  shown in  FIG.  9 A . As described in more detail below, each screening deck assembly  400  includes two tensioning devices  450 , one configured to enable tensioning of screen assembly  409  of first screening deck  410 , and the other configured to enable tensioning of screen  419  of second screening deck  420 . 
     Referring to  FIG.  8   , tensioning device  450  includes a tensioning rod  451 , brackets  454  and  454 ′, and ratchet mechanisms  456  and  456 ′. Tensioning rod  451  includes opposing, mirror image ends  452  and  452 ,′ a tubular midportion  453 , and a tensioning strip  455 . Opposing ends  452  and  452 ′ of tensioning rod  451  extend through holes  457  and  457 ′ in ratchet mechanisms  456  and  456 ′, respectively, and are secured to ratchet mechanisms  456  and  456 ′ by securing mechanisms, such as bolts. Ratchet mechanisms  456  and  456 ′ are secured to brackets  454  and  454 ′, which are in turn secured to side channels  430  and  430 ′, respectively, of screening deck assembly  400 , by securing mechanisms, such as bolts, as is shown in  FIGS.  9 A and  9 B . 
     While not shown in  FIG.  8   , tubular mid-portion  453  of tensioning rod  451  extends the width of screening deck assembly  400  from side channel  430  to side channel  430 ′. Tensioning rods  451  of each tensioning device  450  are located beneath upper end plate  416  of first screening deck  410  and upper end plate  426  of second screening deck  420 . Tubular mid-portion  453  and tensioning strip  455  of tensioning device  450  are configured to receive an end of screen assembly  409  and/or  419 . Opposing end  452 , tubular mid-portion  453 , and tensioning strip  455  of tensioning rod  451  are arranged so that when opposing end  452  and tubular mid-portion  453  rotate in a counter-clockwise direction, tensioning strip  455  rotates in a clockwise direction, thereby pulling screen assembly  409  and/or  419  towards upper end plate  416  of first screening deck  410  and/or upper end plate  426  of second screening deck  420 . While shown in  FIG.  8    as having tubular mid-portion  453  and tensioning strip  455 , tensioning device  450  may include other components so long as it is configured receive an end of screen assembly  409  and/or  419  and is connected to ratchet mechanism  456  so as to permit ratchet mechanism  456  to rotate tensioning rod  451  and pull screen assembly  409  and/or  419  toward upper end plates  416  and/or  426 . 
       FIG.  9 A  illustrates a partial side view of two ratchet mechanisms  456  and two brackets  454  of two tensioning devices  450  mounted to side channel  430  of screening deck assembly  400 .  FIG.  9 B  illustrates an enlarged view of ratchet mechanism  456  and bracket  454 . Though not shown, tensioning rods  451  extend from each ratchet mechanism  456  on side channel  430  of screening deck assembly  400  to each ratchet mechanism  456 ′ on opposing side channel  430 ′ beneath upper end plates  416  and  426  of screening deck assembly  400 . 
       FIG.  10    illustrates an enlarged partial perspective view of ratchet mechanism  456  mounted to side channel  430  below first screening deck  410 . First screening deck  410  is shown interfacing with feed assembly  130  and flexible flow controlling material  405 . As is shown in  FIG.  10   , ratchet mechanism  456  includes an upper portion  458  and a lower portion  460 . Upper portion  458  includes a locking bar  459  that interfaces with a multitude of teeth  461  on lower portion  460 . Lower portion  460  includes an actuation point  462  where second end  452  of tensioning rod  451  extends through hole  457  of ratchet mechanism  456 . Referring to  FIG.  10   , a wrench  463  is configured to rotate actuation point  462  of ratchet mechanism  456 . In response to application of a counter-clockwise rotational force to wrench  463 , actuation point  462  and tubular mid-portion  453  of tensioning rod  451  are configured to rotate in a counter-clockwise direction, and tensioning strip  455  is configured to rotate in a clockwise direction such that tensioning device  450  pulls an end of screen assembly  409  toward upper end plate  416 . In response to rotation of wrench  463  and actuation point  462  of ratchet mechanism  456 , locking bar  459  of upper portion  458  and teeth  461  of lower portion  460  are configured to lock the tensioning device in place and retain tension. Whereas tensioning devices used in vibratory screening machines disclosed in the prior art apply tension in a side-to-side direction, or towards side channels  430  and  430 ′ relative to vibratory screening machine  100 , tensioning device  450  disclosed herein applies tension in a front-to-back direction, or towards upper end plate  416  and lower end plate  418  of first screening deck  410  and/or upper end plate  426  and lower end plate  428  of second screening deck  420  relative to vibratory screening machine  100 . Unlike tensioning devices disclosed in the prior art, the front-to-back direction of tensioning provided by tensioning device  450  corresponds with the direction of the flow of material such as, e.g., slurry, across first and second screening decks as it is separated by vibratory screening machine  100 . Though shown with wrench  463  in  FIG.  10   , other tools may be employed to rotate actuation point  462  of ratchet mechanism  456 , so long as it provides functionality as described herein. 
       FIGS.  11 A and  11 B  illustrate an embodiment of undersized material collection assembly  160 . Undersized material collection assembly  160  includes a plurality of collecting pans  161  secured to the underside of each screening deck assembly  400  (see  FIGS.  3  and  4   ), a plurality of ducts  162  in communication with collecting pans  161 , and an undersized collecting chute  166 . As is shown in  FIGS.  11 A and  11 B , undersized collecting chute  166  includes a mounting end  167 , which may be secured to outer frame  110  of vibratory screening machine  100  by securing mechanisms, such as bolts, a top surface  168  that runs the length of collecting chute  166 , and a discharge port  169 . Each duct  162  includes an inlet  163 , a chamber  164 , and an outlet  165 . Inlet  163  of each duct  162  is configured to receive undersized material from collecting pans  161  and funnel the material through chamber  164  of duct  162  to outlet  165 . Each outlet  165  communicates with a portion of top surface  168  of undersized collecting chute  166  such that material discharged from outlets  165  of ducts  162  enters collecting chute  166  and exits through discharge port  169 . An undersized material hopper may be configured to receive undersized material discharged from discharge port  169 . Though not shown, inlets  163  of ducts  162  may include radial clearances to accommodate vibratory motion from collecting pans  161  (see  FIGS.  3  and  4   ), which are mounted to screening deck assemblies  400 , whereas ducts  162  and collecting chute  166  are mounted to fixed outer frame  110 . The placement of the undersized collecting chutes directly beneath ducts  162  increases the efficiency of vibratory screening machine  100  and saves space by centralizing the flow of all undersized material into a central channel. 
       FIGS.  12 A and  12 B  to  FIGS.  13 A and  13 B  illustrate oversized material collection assembly  170 . Oversized material collection assembly  170  includes a plurality of oversized collecting chutes  171  mounted to lower end plate  428  of each screening deck assembly  400 , and two oversized collecting troughs  176  and  176 ′ in communication with oversized collecting chutes  171  (see  FIGS.  3  and  4   , for example). 
       FIGS.  12 A and  12 B  illustrate an embodiment of oversized collecting chute  171 .  FIGS.  13 A and  13 B  illustrate an embodiment of oversized collecting trough  176 . Referring to  FIGS.  12 A &amp;  12 B , each oversized collecting chute  171  includes a first side  172  and a second side  172 ′ mirroring first side  172 , both having an inlet  173  with a mounting arm  173 A, a chamber  174 , and an outlet  175 . Mounting arms  173 A of each oversized collecting chute  171  are secured to each lower endplate  428  of screening deck assemblies  400  with securing mechanisms, such as bolts, such that material that does not pass through screens  409  and/or  419  to undersized discharge assembly rolls off lower endplate  428  of screening deck assemblies  400  into inlet  173  of oversized material collecting chute  171  (see  FIGS.  3  to  4   , for example). Upon or after entry into inlet  173 , oversized material is funneled through chamber  174 , and discharged from outlet  175  into oversized collecting trough  176 . While shown having a trapezoidal shape, it will be appreciated that oversized collecting chute  171  is not limited to this configuration. Oversized collecting chute  171  may have other arrangements, so long as such a chute can receive oversized material from lower endplate  428  of screening deck assemblies  400  and can transfer oversized material to one of oversized collecting troughs  176  and  176 ′. 
     Referring to  FIGS.  13 A and  13 B , oversized collecting trough  176  includes a mounting end plate  177 , a back surface  178 , an outlet  180 , and a channel  181 . Mounting end plate  177  is secured to rear channel  129  of inner frame  120  with securing mechanisms, such as bolts (see  FIGS.  3  and  4   , for example). Channel  181  extends from mounting end plate  177  to outlet  180  beneath each outlet  175  of oversized collecting chutes  171  such that oversized material discharged from each of oversized collecting chutes  171  falls into channel  181  of oversized collecting trough  176 . A vibratory motor  179  is mounted to back surface  178  of oversized collecting trough  176  with securing mechanisms, such as bolts, to increase the rate at which oversized material passes through channel  181  to outlet  180 , thus increasing the volume of material that vibratory screening machine  100  may process overall. Though not shown, an oversized material hopper may be configured to receive oversized materials discharged from outlet  180  of oversized collecting trough  176 . 
       FIG.  14    is a side view similar to  FIG.  7    of screening deck assembly  400  showing details of tensioning assembly  450  tensioning second screen  419  along second screening deck  420 . As indicated in  FIG.  14   , material to be screened  500  flows via vibration across first screen assembly  409  toward discharge end  409 B of first screen assembly  409 . During passage, appropriately sized particles of material  500  pass through openings or pores  488 A of first screen assembly  409 . After passing over the discharge end  409 B of first screen assembly  409 B, material  500  passes into wash tray  440  and over curved side member  446  and maximum rise  449 . After passing over maximum rise  449 , the material  500  lands on an impact area  448  of second tray  419 , and then vibrates across second screen  419 , passing from input end  419 A to discharge end  419 B, with appropriately sized particles of material  500  passing through second screen  419  along the way. Screens  409 ,  419  are selectively affixed to decks  410 ,  420  via deck clips  455 B of the decks  410 ,  420  and tensioning strips  455  of the tensioning devices  450 , in a manner described in greater detail below. 
     As it can be understood from  FIG.  14    and as is explained in further detail below, a discharge end  409 B,  419 B of screen assemblies  409 ,  419  is attached to a fixed deck clip  455 B, while an opposing input end  409 A,  419 A is attached to a tensioning strip  455  of tensioning device  450 . When tensioning strip  455  is rotated, the screen assembly  409 ,  419  is tensioned front-to-back across the associated deck  410 ,  420 , in the same direction that material to be screened flows across the screen deck assembly  400 . This is an improvement over earlier systems, where screen assemblies were tensioned from the sides, leaving a crown that was perpendicular to the flow of the material to be screened, creating valleys and inefficiencies in flows. 
       FIG.  15    is a side perspective view of a screening deck assembly  400  showing additional details of first and second screen assemblies  409 ,  419  tensioned over first and second screening decks  410 ,  420 , respectively. In  FIG.  15   , portions of screens  409 ,  419  have been cutaway to show aspects of decks  410 ,  420  below the screens. Material  500  is shown passing over wash tray  440  and crashing onto impact area  448  of second filter  419 . 
       FIGS.  16 A and  16 B  show views of a screen assembly  419  for use with the vibratory screening machine  100  and screening deck assembly  400  described above. While the following description of embodiments depicted in  FIGS.  16 A and  16 B  is made with reference to second screen assembly  419 , it is noted that this discussion applies equally to first screen assembly  409 ; first screen assembly  409  can typically be identical to screen assembly  419 , but optionally may have different sizes and configurations, e.g. different sized impact area  448  (smaller or larger), different size opening configurations, a combination thereof, or the like. 
       FIG.  16 A  is a front-side perspective view of screen  419  in accordance with one or more embodiments of the disclosure. Screen  419  is configured for removably securing to deck  420  under tension in the manner described herein. Screen  419  includes feed end  419 A and opposing discharge end  419 B. Screen  419  has a widthwise dimension between ends  419 A and  419 B, and a lengthwise dimension between opposing side edges  483 . A filter area  488  is defined by a plurality of individual openings or pores  488 A extending substantially across the surface of the screen  419 . The openings  488 A are of a selected size, such as a size determined by side lengths having respective magnitudes in a range from about 20 microns and about 100 microns. In some embodiments, the openings  488 A can be rectangular shaped and can have a substantially uniform width or substantially uniform thickness in a range between about 43 microns to about 100 microns, and a substantially uniform length in a range between about 43 microns to about 2000 microns. 
     In the embodiment of  FIG.  16 A , the filter area  488  is framed by an impact zone  448  formed along feed end  419 A, a strip  486  along discharge end  419 B, and opposing side strips  484  along respective side edges  483 . Ends of the impact zone  448 , strip  486 , and side strips  484  integrally join together at abutment points, and together provide structural support to the filter area  488 , preventing tearing and the like during placement and use on the machine  100 . With reference to  FIG.  14   , as material  500  flows over the curved member  446  of the wash tray  440 , the material  500  lands on impact zone  448 . Impact zone  448  protects the integrity of the individual openings  488 A and prevents or decreases the likelihood of large particles becoming lodged in the openings  488 A. As indicated in  FIG.  14   , as material  500  flows from feed end  419 A to discharge end  419 B, appropriately sized particles of material  500  pass through openings  488 A. Impact zone  448  may have different sizes and configurations depending on the screening application and desired flow characteristics. 
     As is shown in  FIGS.  16 A and  16 B , a first binder strip  481 A is provided along feed end  419 A, while a second binder strip  481 B is provided along discharge end  419 B. Each binder strip  481 A,  481 B may be a generally U-shaped strip of metal that is integrated into feed ends  419 A,  419 B, substantially along the length of each respective end  419 A,  419 B. While alternative means may be used to attach binder strips  481 A,  481 B to screen  419 , the binder strips  481 A,  481 B are configured to withstand substantial forces during operation of the vibratory screening machine  100  without separating from screen  419  or otherwise allowing screen  419  to come loose from deck  420 . 
       FIG.  16 B  is a side view of a screen filter  419  for use in an exemplary embodiment of the present disclosure. When viewed from the side as in  FIG.  16 B , screen  419  presents a thin profile. As seen in  FIG.  16 B , the screen filter  419  includes a material input surface  485 A on an upper side, and a material output surface  485 B on an opposing lower side thereof. Individual screen openings  488 A extend from input side  485 A to output side  485 B, such that during vibratory screening, individual particles pass through the screen area  488 . In the embodiment depicted in  FIG.  16 B , first and second binder strips  481 A,  481 B depend downward from the lower side of screen  419 . Each binder strip  481 A,  481 B curves back toward a center of screen  419 , such as in an L-shape or C-shape. 
     The screen assembly  409 ,  419  is dimensioned to match the size of deck  410 ,  420 . In some embodiments, screen assembly  409 ,  419  preferably has a length of about 56 cm, a width of about 30 cm, and a thickness of about 0.25 cm. Impact area  448  is about 3 cm wide; narrower or wider impact areas  448  can be used, with the former decreasing protection and the latter decreasing the number of openings  488 A. Strip  486  and side strips  484  are about 1 cm wide. The screens  409 ,  419  are preferably made of polyurethane. While exemplary embodiments of screens  419  are depicted in FIG.  16 A and  FIG.  16 B  for use with the vibratory screening machine  100  described herein, it will be appreciated that the machine  100  can be configured for use with alternative configuration of screens, screen materials, and screen characteristics (opening/pore size, connection mechanisms, and the like). Examples of screens, screen materials and screen characteristics that can be incorporated into screens  409 ,  419  for use with machine  100  are found in applicant&#39;s U.S. Pat. No. 9,409,209, U.S. Patent Application Publication 2013/313,168A1, U.S. Patent Application Publication 2014/0262978A1, and U.S. Patent Application Publication 2016/0310994A1, the disclosures of which are incorporated herein by reference in their entirety. 
     A method of attaching a screen assembly  409 ,  419  to a deck  410   420  will now be described. As is seen in  FIG.  14   , deck clips  455 B are fixed adjacent to respective output ends  410 B,  420 B of decks  410 ,  420 . Deck clips  455 B are sized and configured for attaching output ends  409 B,  419 B of screens  409 ,  419  to screening decks  410 ,  420 . In an embodiment, deck clips  455 B extend substantially along a length of discharge end  410 B,  420 B, in a manner analogous to binder strips  481 A,  481 B extending along lengths of screen assembly  409 ,  419 . In  FIG.  14   , deck clip has an L-shaped aspect when viewed in side profile, although other engagement configurations, such as curved C-shaped aspects, can be used. As can be understood from  FIG.  14   , second binder strip  481 B along discharge end  409 B,  419 B of a screen assembly  409 ,  419  is engaged to deck clip  455 B, such that the L- or C-shaped aspect of binder strip  481 B interdigitates with L- or C-shaped aspect of deck clip  455 B. Tension is applied to spread screen assembly  409 ,  419  across the deck  410 ,  420  toward input end  410 A,  420 A, such that binder clip  481 B remains interconnected with deck clip  455 B. With screen assembly  409 ,  419  spread across deck  410 ,  420 , first binder strip  481 A of screen assembly  409 ,  419  is then engaged to tensioning strip  455  of tensioning device  450 , such that an L- or C-shaped aspect of tensioning strip  455  interconnects with first binder strip  481 A. Tension is then applied to screen assembly  409 ,  419  via tensioning device  450  to thereby selectively lock first binder strip  481 A to tensioning strip  455 , whereby filter  409 ,  419  is tensioned tightly along deck  410 ,  420  for use in screening particles of material  500  during operation of the machine  100 . 
     After a period of use, screens  409 ,  419  can be selectively removed from deck  410 ,  420  for replacement with new screens  409 ,  419 . In a method of screen removal, tensioning device  450  is used to release tension strip  455  from first strip  481 A. Screen assembly  409 ,  419  is then pulled or slid toward discharge end  410 A,  420 A of deck  410 ,  420  to release second binder strip  481 B from deck clip  455 B. 
       FIG.  17    illustrates a flow of undersized materials in a screening assembly, according to one or more embodiments of the present disclosure. In this example, a screen deck assembly  400  includes a screen  409  and an undersized material collection assembly  160 . Undersized material collection assembly  160  includes a collecting pan  161  which collects fluid and undersized materials that flow through a screen surface of screen  409 . Undersized material collection assembly  160  is configured to allow fluids and undersized materials to leave screen deck assembly  400  and to flow into an inlet  163  of ducts  162  of an undersized collection chute  166 . 
       FIG.  18    illustrates a flow of oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. In this example, an oversized material collection assembly  170  includes an oversized collecting chute  171  that is mounted to lower end plate  428  of screening deck assembly  400 . Oversized material collection assembly  170  further includes two oversized collecting troughs  176  and  176 ′ in communication with oversized collecting chute  171 . As shown, oversized material that does not flow through the screen surface of screen  409  is collected by oversized collecting chute  171  and fed to collecting troughs  176  and  176 ′. 
       FIG.  19    illustrates a flow of oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. In this example, oversize material collection assembly  170  does not have oversized collecting chute  171  (e.g., see  FIG.  18   ). Rather, in this embodiment, a deflector  1902  causes oversized material that does not pass through the surface of screen  409  to flow past deflector  1902  to thereby be guided to collecting troughs  176  and  176 ′. In this example, deflector  1902  may be a triangular deflector that is configured to reside on the surface of screen  409 . 
       FIG.  20    illustrates a flow of oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. This example shows an alternative embodiment to that described above with reference to  FIG.  19   . In this example, the triangular shaped deflector  1902  of  FIG.  19    has been replaced, in this embodiment, by a wedge-shaped deflector  2002 . In other embodiments, many other configurations of deflectors may be employed, including defectors that are external to screen deck assembly  400 . 
       FIG.  21    illustrates a flow of undersized and oversized materials in a screening assembly, according to one or more embodiments of the present disclosure. In this example, undersized collecting chute  166  (e.g., see  FIG.  17   ) and oversized collecting troughs  176  and  176 ′ (e.g., see  FIGS.  18  to  20   ) have been replaced by a single structure  2100  that has first  2102 , second  2104   a , and third  2104   a  channels. First channel  2102  is configured to collect fluids and undersized materials from collecting pan  161  that flow through the surface of screen  409 . Second  2104   a  and third  2104   b  channels are configured to collect oversized materials that do not flow through the surface of screen  409 . This embodiment is shown having deflector  1902 . Other embodiments, however, may include other deflector structures, such as deflector  2002  (e.g., see  FIG.  20   ) or may include an oversized collecting chute  171  (e.g., see  FIG.  18   ). For simplicity,  FIG.  21    is shown in a geometry in which screen deck assembly  400  makes a shallow angle  2107  relative to structure  2100 . In practice, angle  2106  is larger to thereby accommodate a plurality of screen deck assemblies  400 , as shown above in other examples, and in examples illustrated in  FIGS.  27  to  29   . 
       FIG.  22    is a perspective top and side view of a vibratory screening machine  2200 , according to one or more embodiments of the present disclosure. Vibratory screening machine  2200  has many of the same features as vibratory screening machine  100 , described above with reference to  FIGS.  1  to  4   . In this embodiment, however, undersized collecting chute  166  and oversized collecting troughs  176  and  176 ′, have been replaced by the single structure  2100 . As described above, with reference to  FIG.  21   , structure  2100  has first  2102 , second  2104   a , and third  2104   a  channels as shown in further detail in  FIG.  23   . 
       FIG.  23    is a perspective bottom and side view of vibratory screening machine  2200 , according to one or more embodiments of the present disclosure. As described above, structure  2100  has first  2102 , second  2104   a , and third  2104   a  channels. First channel  2102  collects undersized materials, while second  2104   a  and third  2104   a  channels collect oversized materials. Undersized and oversized materials may be removed from vibratory screening machine  2200  through first  2102 , second  2104   a , and third  2104   b  channels as described above in other embodiments. 
       FIG.  24    is a top perspective view of a combined undersized/oversized collecting apparatus  2400  that includes an undersized collecting assembly  2402  with two oversized collecting troughs (only one trough  2404   a  visible in this view), according to one or more embodiments of the present disclosure. Undersized collecting assembly  2402  includes a plurality of ducts  2406  in communication with a collecting pan  2408 . Undersized collecting assembly  2402  has a similar structure to undersized collecting assembly  160 , and performs a similar function to undersized collecting assembly  160 , as described above with reference to  FIGS.  11 A and  11 B . Similarly, oversize collecting troughs  2404   a  and  2404   b  (e.g., see  FIG.  26   ) each have a similar structure to, and perform a function similar to, oversized collecting troughs  176  and  176 ′ described above with reference to  FIGS.  4 ,  13 A, and  13 B . 
     Collecting apparatus  2400  of  FIG.  24    collects oversized and undersized materials and functions similarly to systems described above with reference to  FIGS.  11 A to  13 B . Collection apparatus  2400 , however, eliminates the need for oversized collecting chutes  171 , described above with reference to  FIGS.  12 A and  12 B . In this regard, undersized collecting assembly  2402  further includes an angled surface  2410  (described in greater detail below with reference to  FIG.  26   ) that diverts oversize materials flowing over end plate  428  of screening deck assembly  400  (e.g., see  FIG.  5   ) into oversize collecting trough  2404   a  (and oversize collecting trough  2404   b  shown in  FIG.  26   ). In this regard, angled surface  2410  plays a role that is similar to the role played by oversized collecting chutes  171  in previously-described embodiments. Further, the presence of angled surface  2410  eliminates the need for deflectors  1902 , described above with reference to  FIGS.  19  and  21   , and deflector  2002 , described above with reference to  FIG.  20   . Collecting apparatus  2400  further includes a plurality of diverting structures  2412  that act to guide oversized materials toward oversized collecting troughs  2404   a  and  2404   b  (e.g., see  FIG.  26   ) and away from ducts  2406 . Collecting apparatus  2400  may further include splash guards  2414 . 
       FIG.  25    is a bottom perspective view of collecting apparatus  2400  of  FIG.  24   , according to one or more embodiments of the present disclosure. In this view, both oversized troughs  2404   a  and  2404   b  may be seen. Further, oversized trough  2404   a  has an outlet  2502   a  and oversized trough  2404   b  has an outlet  2502   b . Outlets  2502   a  and  2502   b  are similar to, and serve a similar function as, outlet  180  of oversized collection trough  176 , described above with reference to  FIGS.  13 A and  13 B . Undersized collecting assembly  2402  further includes discharge port  2504  that has a similar structure to, and serves a similar function as, discharge port  169  of undersized collecting assembly  160 , described above with reference to  FIGS.  11 A and  11 B .  FIG.  25    also shows a view of collecting chute  2506  of undersized collecting assembly  2402 , which is similar to, and serves a similar function as, collecting chute  166 , described above with reference to  FIGS.  11 A and  11 B . 
       FIG.  26    is a further top perspective view of collecting apparatus  2400  of  FIGS.  24  and  25   , according to one or more embodiments of the present disclosure. In this view, both oversized collecting troughs  2404   a  and  2404   b  are shown. Further, angled surface  2410  of  FIG.  24    is shown in  FIG.  26    as having a first angled portion  2602   a  and a second angled portion  2602   b . First angled portion  2602   a  is sloped downwardly toward oversized collecting trough  2404   a  and second angled portion  2602   b  is sloped downwardly toward oversized collecting trough  2404   b.    
     As described in greater detail below with reference to  FIGS.  27  to  29   , oversize materials flowing over end plate  428  of screening deck assembly  400  (e.g., see  FIG.  5   ) may fall on first angled portion  2602   a  or on second angled portion  2602   b . In this way, oversized materials that land on first angled portion  2602   a  are diverted to oversized collecting trough  2404   a  while oversized materials that land on second angled portion  2602   b  are diverted to oversized collecting trough  2404   b . Thus, angled portions  2602   a  and  2602   b  respectively play a similar role to chambers  174  and  174 ′ of oversized collecting chutes  171 , described above with reference to  FIG.  12 B . As described above with reference to  FIG.  24   , collecting apparatus  2400  further includes diverting structures  2412  that act to guide oversized materials toward oversized collecting troughs  2404   a  and  2404   b  and away from ducts  2406 . 
       FIG.  27    is a side perspective view of the collecting the apparatus  2400  of  FIGS.  24 ,  25 , and  26    with a plurality of installed screening deck assemblies  400 , according to one or more embodiments of the present disclosure. In this configuration, oversized material flowing from a top screening surface of screening deck assemblies (e.g., see  FIG.  5   ) is directed by first  2602   a  and second  2602   b  (e.g. see  FIG.  26   ) angled portions of angled surface  2410  (e.g., see  FIG.  24   ). Diverting structures  2412  further act to guide oversized materials toward oversized collecting troughs  2404   a  and  2404   b  and away from ducts  2406 , as described above with reference to  FIGS.  24  and  26   . 
       FIG.  28    is a further side perspective view of collecting apparatus  2400  with installed screening deck assemblies  400  of  FIG.  27   , according to one or more embodiments of the present disclosure. Each screening deck assembly  400  includes a first screening deck  410 , a second screening deck  420 , and a wash tray  440 , as described above with reference to  FIGS.  5  to  10   . When in operation, material to be screened is deposited on first screening deck  410  by feed outlet ducts  133  (e.g., see  FIG.  2    and related description above). Vibration causes material to flow over first screening deck  410 , over wash tray  440 , and onto second screening deck  420 , as described above with reference to  FIGS.  5  to  10   . 
     Undersized material flows through screens  409  and  419  (e.g., see  FIGS.  5 ,  15 ,  16 A , and  16 B and related description above) and is collected by ducts  2406  of undersized collecting assembly  2402  (e.g., see  FIG.  24   ). Oversized materials remain on a screening surface of screening decks  410  and  420  and are discharged over lower end plate  428  of screening deck  420  by vibration, as described in greater detail above with reference to  FIG.  5   . After leaving lower end plate  428 , oversized materials then hit one of the first  2602   a  or second angled portion  2602   b  (e.g., see  FIG.  26   ) and are thereby directed to respective oversize collecting troughs  2404   a  or  2404   b  (e.g., see in  FIG.  26   ) as described above. 
       FIG.  29    is a further side perspective view of the collecting apparatus with installed screening deck assemblies of  FIGS.  27  and  28   , according to one or more embodiments of the present disclosure. This view shows further structural details of screening decks  410  and  420  and should be compared with  FIG.  6   , described in greater detail above. In this regard, upper screening deck  410  includes a first plurality of stringers  414  and lower screening deck  420  includes a second plurality of stringers  424 . First plurality of stringers  412  is supported by ribs  412  and the second plurality of stringers  424  are supported by ribs  422 . First  414  and second  424  pluralities of stringers provide mechanical support for screens  409  and  419  (e.g., see  FIGS.  5  and  15    and related description above). Screens  409  and  419  (e.g., see  FIGS.  5 ,  14 , and  15   ) may be respectively installed on screen decks  410  and  420  and held in place by a tensioning mechanism (e.g., tensioning strip  455  of  FIG.  14   ) that exerts tension to screens  409  and  419  along a front-to-back direction, that is, in the same direction that material to be screened flows across the screen deck assembly  400 . 
     Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language generally is not intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation. 
     This specification and annexed drawings disclose vibratory screening machines that include stacked screening deck assemblies. It is, of course, not possible to describe every conceivable combination of elements for purposes of describing the various aspects of the disclosure. Thus, while embodiments of this disclosure are described with reference to various implementations and exploitations, it is noted that such embodiments are illustrative and that the scope of the disclosure is not limited to them. Those of ordinary skill in the art can recognize that many further combinations and permutations of the disclosed features are possible. As such, various modifications can be made to the disclosure without departing from the scope or spirit thereof. In addition or in the alternative, other embodiments of the disclosure can be apparent from consideration of the specification and annexed drawings, and practice of the disclosure as presented herein. It is intended that the examples put forward in the specification and annexed drawings be considered, in all respects, as illustrative and not restrictive. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.