WO2016033492A1

WO2016033492A1 - Centrifugal basket with openings of varying widths

Info

Publication number: WO2016033492A1
Application number: PCT/US2015/047482
Authority: WO
Inventors: Charles H. Flansburg; Steven Douglas DEHN; Michael Richard EKHOLM
Original assignee: Bilfinger Water Technologies, Inc.
Priority date: 2014-08-28
Filing date: 2015-08-28
Publication date: 2016-03-03

Abstract

A screen assembly (40) formed with a truncated cone may include a plurality of spaced screen elements defining slots of differing predetermined widths. The panel or panels of the screen assembly (40) may extend from the first end (46) to the second end (44) of the truncated cone, and each panel may be formed from a single piece of screen material secured to one or more adjoining panels to form the truncated cone. The plurality of screen elements may include a first plurality of screen elements defining a first plurality of slots having a first predetermined width, and a second plurality of screen elements defining a second plurality of slots having a different, second predetermined width. Different combinations of slot widths and configurations may be provided to vary the performance of the assembly, and substantially horizontal seams in panels may be omitted in some embodiments.

Description

CENTRIFUGAL BASKET WITH OPENINGS OF VARYING WIDTHS

CROSS-REFERENCE TO PRIORITY APPLICATION

[0001] This application claims the benefit of U.S. Patent Application Ser. No. 62/043,152 for a Centrifugal Basket with Openings of Varying Widths (filed August 28, 2014), which is hereby incorporated by reference in its entirety.

FIELD

[0002] Aspects of the disclosure generally relate to a centrifugal basket screen, and in particular may relate to a centrifugal basket including screen elements that provide openings of varying widths in the screen.

BACKGROUND

[0003] Centrifugal baskets are commonly used in sugar processing. The baskets generally include an internal screen or a thin perforated plate that is used to separate sugar elements from raw feed and to dewater a slurry. These baskets, however, may need to be replaced frequently and do not always provide performance that accesses the full yield potential of the centrifugal machine. Depending on the material to be processed, binding of solid particulate material in slots or openings in the screen or plate of the basket may be prevalent. In addition, expensive customized adapters may be needed to operate the same centrifugal machine with either an internal screen or a perforated plate. Therefore, there is a continuous need for new and improved centrifugal baskets systems that are cost effective and efficient.

BRIEF SUMMARY

[0004] In accordance with one embodiment of the concepts disclosed herein, a screen assembly is provided including a base and a truncated cone extending from the base at a first end to a second, open end having a larger diameter than the first end. The truncated cone includes at least one panel with a plurality of spaced screen elements defining slots, with certain

predetermined slots of the at least one panel having different predetermined widths than other slots of that panel.

[0005] In some embodiments and in combination with the above embodiment, the at least one panel includes a plurality of panels each extending from the first end to the second end. Each panel is formed from a single piece of screen material and is secured to one or more adjoining panels to form the truncated cone.

[0006] In some embodiments and in combination with any of the above embodiments, the plurality of screen elements includes a first plurality of screen elements defining a first slot having a first width, and a second plurality of screen elements defining a second slot having a different, second width.

[0007] In some embodiments and in combination with any of the above embodiments, the first plurality of screen elements is adjacent to the second plurality of screen elements.

[0008] In some embodiments and in combination with the above embodiments, each slot of the first and second pluralities of slots has a different predetermined width.

[0009] In some embodiments and in combination with any of the above embodiments, the second plurality of screen elements is disposed between the first plurality of screen elements and the second end, and the first plurality of screen elements defines a first plurality of slots whose widths gradually change in one direction.

[0010] In some embodiments and in combination with any of the above embodiments, the second plurality of screen elements defines a second plurality of slots whose widths gradually change in one direction.

[0011] In some embodiments and in combination with any of the above embodiments, the first plurality of screen elements is disposed starting from the first end and ending at a first location spaced from the first end toward the second end, and the second plurality of screen elements is disposed starting from the first location spaced from the first end and ending at the second end.

[0012] In some embodiments and in combination with any of the above embodiments, the first predetermined width is narrower than the second predetermined width, while in other embodiments the first predetermined width is wider than the second predetermined width.

[0013] In some embodiments and in combination with any of the above embodiments, the first plurality of screen elements forms at least one quarter of the truncated cone starting from the first end toward the second end.

[0014] In some embodiments and in combination with any of the above embodiments, the screen elements comprise wires spaced from each other to define the slots. [0015] In some embodiments and in combination with any of the above embodiments, the screen elements comprise perforated plates that define the slots.

[0016] In some embodiments and in combination with any of the above embodiments, the second plurality of screen elements is disposed between the first plurality of screen elements and the second end; wherein the first plurality of screen elements comprises a bottom wear plate defining a first wear slot having a third width, the first wear slot being disposed between the first end of the truncated cone and the first slot; wherein the second plurality of screen elements comprises a top wear plate defining a second wear slot having a fourth width, the second wear slot disposed between the second end of the truncated cone and the second slot; and wherein the third width and the fourth width are less than the first width and the second width.

[0017] In some embodiments and in combination with any of the above embodiments, the second plurality of screen elements is disposed between the first plurality of screen elements and the second end; wherein the first plurality of screen elements comprises a bottom wear plate defining a first wear slot having a third width, the first wear slot being disposed between the first end of the truncated cone and the first slot and wherein the third width is less than the first width and the second width.

[0018] In some embodiments and in combination with any of the above embodiments, the first width is lesser than the second width.

[0019] In some embodiments and in combination with any of the above embodiments, the first width is greater than the second width.

[0020] In some embodiments and in combination with any of the above embodiments, the second plurality of screen elements further comprises a top wear plate defining a second wear slot having a fourth width, the second wear slot disposed between the second end of the truncated cone and the second slot; and wherein the fourth width are less than the first width and the second width.

[0021] In some embodiments and in combination with any of the above embodiments, the screen assembly comprises at least one slot which defines a first length along a central longitudinal axis of the truncated cone that is smaller than a second length along the

circumference of the truncated cone.

[0022] In some embodiments and in combination with any of the above embodiments, the screen assembly comprises at least one slot which defines a first length along a central longitudinal axis of the truncated cone that is greater than a second length along the circumference of the truncated cone.

[0023] In accordance with another embodiment disclosed herein, a screen assembly having a central longitudinal axis is provided. The screen assembly includes an upper portion and a lower portion. The upper portion includes a first plurality of screen elements forming a first truncated conical arrangement having an axis, with the central longitudinal axis being coincident with the axis of the upper portion, the upper portion having a first top limit and a first bottom limit, the transverse dimension of the first top limit being larger than the transverse dimension of the first bottom limit. The lower portion includes a second plurality of screen elements forming a second truncated conical arrangement having an axis, with the central longitudinal axis being coincident with the axis of the lower portion, the lower portion having a second top limit and a second bottom limit, the transverse dimension of the second top limit being larger than the transverse dimension of the second bottom limit and substantially the same as the first bottom limit, the second top limit being continuous with the first bottom limit to form a larger truncated conical arrangement.

[0024] In accordance with another embodiment disclosed herein, a method of making a screen assembly is provided. A plurality of flat screen panels are fabricated, with each flat screen panel of the first plurality of flat screen panels having an axis and comprising screen elements spaced from one another to define slots of a plurality of predetermined widths. The screen panels and a base are assembled to form a truncated conical arrangement about a central longitudinal axis, wherein the slots have at least two different widths at different locations along the central longitudinal axis. The method may also include, prior to assembling the screen panels, forming each flat screen panel into a curved shape to conform to the shape of a portion of the truncated conical arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a more complete understanding, reference should now be had to the

embodiments shown in the accompanying drawings and described below. In the drawings:

[0026] FIG. 1 is a perspective view a centrifugal device according to one embodiment.

[0027] FIG. 2 is a perspective view of a screen according to a first embodiment of FIG.

1. [0028] FIG. 3 is a side view of the screen of FIG. 2.

[0029] FIG. 4 is a top view of the screen of FIG. 2.

[0030] FIG. 5 is a side view of the screen of FIG. 2, offset 90 degrees from the view of

FIG. 3.

[0031] FIG. 6 is a top view of a half panel of the screen of FIG. 2, after forming and prior to assembly.

[0032] FIG. 7 is a top view of a quarter panel of the screen of FIG. 2, prior to forming and assembly.

[0033] FIG. 8 is a perspective view of a screen according to a second embodiment of

FIG. 1.

[0034] FIG. 9 is a top view of the screen of FIG. 8.

[0035] FIG. 10 is a top view of a quarter panel of the screen of FIG. 8, prior to forming and assembly.

[0036] FIG. 11 is a detail view of a section of the screen of FIG. 2, including

embodiments of stabilizing/retaining members.

[0037] FIG. 12 is a detail view of the screens of FIGS. 2 and 8.

[0038] FIG. 13 is a partial section view of screen elements and a support member of the screen of FIGS. 2 and 8.

[0039] FIG. 14 is a top view of a quarter panel of the screen of FIG. 2, prior to forming and assembly, according to another embodiment of the invention.

[0040] FIG. 15 is a top view of a quarter panel of the screen of FIG. 2, prior to forming and assembly, according to another embodiment of the invention.

[0041] FIG. 16 is a side view of the screen according to another embodiment of the

invention

[0042] FIG. 17 is a side view of the screen according to another embodiment of the

invention DETAILED DESCRIPTION

[0043] The following detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments. Other embodiments having different structures and operation do not depart from the scope of the present disclosure.

[0044] Certain terminology is used herein for convenience only and is not to be taken as a limitation on the embodiments described. For example, words such as "top", "bottom", "upper," "lower," "left," "right," "horizontal," "vertical," "upward," and "downward" merely describe the configuration shown in the figures or the orientation of a part in the installed position. Indeed, the referenced components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise. Throughout this disclosure, where a process or method is shown or described, the method may be performed in any order or simultaneously, unless it is clear from the context that the method depends on certain actions being performed first.

[0045] Embodiments of concepts disclosed herein are directed to a centrifugal basket screen having screen elements (e.g. wires or plates with openings) forming slots that vary in size. For example, each screen element may be spaced apart from adjacent screen elements at a plurality of predetermined distances or widths. In this way, spaces in the screen between adjacent screen elements define slots, each of which may vary in width. Some embodiments provide screen elements that form slots with two or more predetermined widths. In one embodiment, screen elements spaced apart from adjacent screen elements at a first

predetermined distance form a lower portion of the screen, while screen elements spaced apart from adjacent screen elements at a second predetermined distance form an upper portion of the screen. In some embodiments, the spacing between screen elements may increase incrementally over a distance along the screen from top to bottom or bottom to top, with a gradually increasing width of the slots.

[0046] The screen is configured to separate a liquid component and a solid component from a slurry. During operation, the slurry is poured into the screen while it is rotating. The slurry is forced both radially outward and upward along the inner surface of the screen by centrifugal force. In some embodiments, screen elements that are spaced apart from adjacent screen elements at different predetermined distances have different performance characteristics. For example, screen elements that are spaced apart a first predetermined distance from adjacent screen elements so that slots formed between the spaced-apart adjacent screen elements may effectively remove the fluid component of the slurry, while prohibiting removal of the solid component of the slurry. Conversely, screen elements that are spaced apart a second

predetermined distance from adjacent screen elements, where the second predetermined distance is shorter than the first predetermined distance so that slots formed between adjacent screen elements spaced apart the first predetermined distance are substantially narrower than the slots formed between screen elements spaced apart the second predetermined distance, may also help remove the fluid component of the slurry, but may further effectively capture the solid component of the slurry and direct the solid component of the slurry up along the inner surface and over the upper edge of the screen. Therefore, because the screen elements are spaced apart from one another at varying distances and form slots of various widths in the screen, differently sized particulate of the solid component of the slurry may be trapped and retained within the interior of the centrifugal basket more efficiently.

[0047] Referring to the drawings, where like reference numerals refer to the same or similar parts, FIG. 1 shows an apparatus that may be referred to as a centrifugal screen basket, a screen basket, a screen assembly, or a screen 40 in a processing or refining device 42. The screen 40 is generally conical and has a top edge 44, a bottom edge 46, an inner surface 48, and an outer surface 50 (illustrated in FIG. 2). The screen 40 is disposed within a rotatable member 52 of the device 42. The top edge 44 defines a second side of the screen 40, while the bottom edge 46 defines a first side of the screen 40, opposite to the second side. The first side and the second side define a longitudinal axis between them, about which the rotatable member 52 and/or the screen 40 rotate or spin. The longitudinal axis may be oriented vertically, horizontally or along any suitable incline. In some embodiments, the longitudinal axis may be centrally located and may extend from the center of the first side to the center of the second side.

Although the longitudinal axis is termed and described as a central longitudinal axis hereinafter in this disclosure, embodiments of the invention may comprise the longitudinal axis being offset from one or both the centers of the first and second sides. The longitudinal axis also defines an axial direction. In some embodiments, the axial direction is the longitudinal axis projected onto the screen 40. The screen 40 may also comprise a circumferential direction along the circumference of the screen 40. Typically, the circumferential direction, as referred to elsewhere in the specification, may be parallel to the wires and/or screen elements along the circumference of the screen 40. Typically the circumferential direction and the axial direction are oriented at an angle with respect to each other. For instance, in some embodiments, the circumferential direction is perpendicular to the axial direction. The present invention typically finds applications in processes that require separating a slurry into one or more components, for example: sugar processing, coal mining, petroleum refining, cement manufacturing, meat processing, and the like. Although the invention is described with respect to sugar processing below, it is understood that the invention is applicable in other industries as well. During a sugar refining process, a slurry containing fluid and solid components (for example: molasses, water, and sugar crystals) is poured into the center of the rotatable member 52 while it is spinning. The slurry may be input at the bottom edge 46 either from the first side or the second side depending on the design of the refining device 42. The slurry incident at the bottom edge 46 is forced outward against the inner surface 48 of the screen 40 due to centrifugal forces created by the rotation of the rotatable member 52. Because not all of the slurry can flow through the screen 40 instantaneously, some portions immediately move out through the screen 40, and some portions move up the slanted inner surface 48 by the centrifugal force of the rotatable member 52 before moving out through the screen 40. The transverse dimension of the top edge 44 is in this embodiment greater than the transverse dimension of the bottom edge 46, where the transverse dimension is the diameter of each circle formed at the edges 44, 46. In this way, the screen 40 is in a conical arrangement that is truncated, or more specifically forms a truncated or frustoconical cone, as it does not terminate at a point or apex.

[0048] Particularly, the screen 40 is designed for sugar production and/or dewatering purposes so that molasses and/or water are filtered out through the screen 40, while sugar crystals are left behind and captured by the screen 40. The screen 40 is configured to

circumferentially rotate within the centrifugal refining device 42 during operation. As illustrated in FIGS. 3-5, the screen 40 is rotatable about central longitudinal axis X--X. Sugar slurry is incident at the bottom edge 46 of the spinning rotatable member 52. Centrifugal forces created by the rotation of the rotatable member force the slurry outward, away from the central longitudinal axis. This outward propulsion of the slurry causes at least a portion of the slurry to be dewatered. Dewatering is the process that causes fluids and solid components with sizes smaller than the openings in the incident area of screen to shear off away from the screen, while larger components remain in the interior of the screen 40. The remaining slurry comprising fluid and solid components now moves up along the inner surface 48 with the impetus from the centrifugal force. In some embodiments, this motion along the inner surface 48 is aided by the inclination of the inner surface 48 with respect to the central longitudinal axis X— X. Spinning of the rotatable member 52 causes the sugar crystals to continue moving up the inner surface 48, with progressive dewatering along the path. When the sugar crystals reach the top edge 44, they are ejected out of the rotatable member 52 and collected for further processing. In some embodiments, the sugar crystals that reach the top edge 44 have significantly less fluid content than the input slurry at the bottom edge 46. In some embodiments, a larger portion of fluid and/or solid components is ejected proximate the bottom edge 46 in comparison with the portion of fluid and/or solid components ejected proximate the top edge 44. In some embodiments, the slurry incident at the bottom edge comprises a turbulent flow that transitions into a laminar or less turbulent state as the slurry moves along the inner surface 48.

[0049] The screen 40 is dimensioned to prohibit sugar crystals of a desired size from flowing out through the screen 40. Specifically, openings (e.g., slots) in the screen 40 are appropriately dimensioned so as to inhibit the flow of sugar crystals of a desired size from flowing through the slots in the screen 40. The slots are typically defined by spaces between a plurality of screen elements 70, 80 used to inhibit the flow of sugar crystals through the screen 40. The slots may vary in width at various locations on the screen 40 so as to efficiently inhibit the flow of sugar crystals through the screen 40. For example, FIGS. 2-7 illustrate a first embodiment where the screen 40 includes relatively narrow slots on a lower portion 62 of the screen 40 and relatively wide slots on an upper portion 60 of the screen 40. Conversely, FIGS. 8-10 illustrate a second embodiment, the shape and form of which are also represented by FIG. 2 where the screen 40 includes narrow slots 102 on an upper portion 60 of the screen and wide slots 102 on a lower portion 62 of the screen 40. When a dimension herein is described as being different than, wider than, or narrower than another dimension, it should be understood that such differences are as would be understood by one of ordinary skill in the art to exceed differences that might result purely from manufacturing tolerances.

[0050] The screen 40 may include, for example, an upper portion 60 and a lower portion

62; other intermediary portions may also be provided. The upper portion 60 may have a first top limit, which may or may not be the same as the top edge 44 of the screen 40, and a first bottom limit. The lower portion 62 may have a second top limit, which may coincide with the first bottom limit of the upper portion 60, and a second bottom limit, which may or may not be the same as the bottom edge 46 of the screen 40. Preferably, the upper portion 60 and the lower portion 62 are both comprised in or manufactured from a continuous section of the screen 40 so as to form a panel (discussed in detail below) of screen 40 that is seamless from top to bottom, i.e., lacks a seam that may be crossed by a line extending from top to bottom of the screen 40. A seamless screen 40 may provide several benefits during fabrication and operation. First, a seamless screen panel may be advantageous because coupling the upper portion 60 and the lower portion 62 via a weld or similar connection may be time consuming. Therefore, utilizing a seamless screen panel may reduce the amount of time and manual labor required to fabricate the screen 40. As such, utilizing a seamless screen 40 may increase the operational life of the screen 40 while providing increased structural integrity and durability during operation. Although, a welded or other seam in the screen 40 may wear down quicker than the rest of the screen during operation, screens with seams may also be employed when the design and process benefits exceed the overheads of utilizing screen panels attached together with seams. Therefore, the upper portion 60 may be connected to the lower portion 62 by a permanent (e.g. welded) connection or a releasable (for example, bolted, threaded, clamped, or sealed) connection, but such a configuration may provide similar or different advantages than those described above.

[0051] The proportion of the height of the lower portion 62 of the screen 40 to the upper portion 60 of the screen 40 may be as shown in FIGS. 2-10, or other proportions. In one embodiment, a transition point for the change from the lower portion 62 to the upper portion 60 (e.g., a point where width, sizing, or orientation of slots, or spacing of screen elements 70, 80 changes) is about one-third of the overall height of the screen 40, meaning that the lower portion 62 may form about one-third of the height of the screen 40. In one embodiment, the height of the lower portion 62 may be less than the height of the upper portion 60. In one embodiment, the heights of the lower portion 62 and the upper portion 60 may be substantially the same. In one embodiment, the height of the lower portion 62 may be greater than the height of the upper portion 60. Changing the spacing, size, and/or orientation of the screen elements 70, 80 as well as the slots 102 formed between the spaced screen elements 70, 80 in the screen 40 may occur at multiple heights along the height of the screen 40 (e.g., changes may occur multiple times within each of the upper portion 60 and the lower portion 62). As such, the screen 40 of the present invention may include more than two portions. [0052] In one embodiment, the screens 40 may include wire with a substantially triangular cross-section and may include Vee-Wire® type screens (VEE-WIRE is a registered trademark of Bilfmger Water Technologies, Inc.) or wedge wire type screens. Utilizing Vee- Wire® type screens has the advantage of preventing clogging or obstruction of spacing or slots between the wires. In one embodiment, such screens 40 may include substantially solid plates having perforations, slots, and/or other filter-type openings. In one embodiment, the wires and plate openings may be oriented symmetrically, asymmetrically, horizontally, vertically, tangentially, and combinations thereof relative to an axis of the section or portion (e.g., the upper portion 60 or the lower portion 62) of the screen 40 that they form. In one embodiment, the spacing and sizes of wires (e.g., screen elements 70, 80) and/or openings (e.g., slots 102) vary along the lengths of such screens 40 to provide for different opening widths in different locations on the screen 40. In one embodiment, such screens 40 may include one or any combination of screen elements 70, 80 (e.g., filter wires, plates, features with perforations, or features that otherwise provide a plurality of filter-type openings (e.g., slots 102)). Such screens 40 may include the embodiments like those disclosed in U.S. Patent No. 6,663,774, filed on October 16, 2001 and specifically with respect to the filter wires 28 and the support rods 20 described therein, and embodiments like those disclosed in U.S. Patent No. 7,425,264, filed on July 18, 2005 and specifically with respect to the wires 16 and the support rods 17 described therein, the contents of both of which patents are herein incorporated by reference in their entirety.

[0053] In one embodiment, the screen 40 may have a tapered angle of its walls (formed by the screen elements 70, 80) of about 30 degrees to about 35 degrees relative to the central longitudinal axis X— X. In one embodiment, the screen 40 may have a diameter of about 12 inches to about 18 inches to about 24 inches at its lower edge 46. In one embodiment, the screen 40 may have a diameter of about 24 inches to about 36 inches to about 48 inches at its top edge 44. However, it is noted that screens with different angular and linear dimensions may be utilized based on optimizing a merit function associated with one or more target parameters (for example: the purity of components received at the top edge 44 of the screen, dewatering efficiency, operation time and the like). Furthermore, the dimensions of the slots and the screen 40 may be chosen based on the type of slurry being used, fluid content in the slurry, viscosity of the slurry, desired size of final product and other relevant parameters. [0054] FIGS. 4 and 9 show top views of different embodiments of the screen 40. The truncated conical arrangement of the screen 40 is typically formed by a plurality of

symmetrically-shaped, formed panels 88A, 88B; each comprising an upper portion 60 and a lower portion 62 with spaced screen elements 70 and 80, respectively. Two substantially semicircular panels 88A, 88B typically are combined to form the screen 40, as seen in FIGS. 4 and 9. Sides of the panels 88A, 88B are joined together at one or more interfaces 94 as shown in FIGS. 2, 4, and 9. Alternatively, four quarter panels 88A, 88B, 88C, and 88D as depicted in FIGS. 7 and 10 may also be utilized to form the screen 40. Although two-panel and four-panel conical arrangements are shown in the figures herein, any number of appropriately dimensioned panels may be used to form the screen 40.

[0055] As seen in FIGS. 6, 7, and 10, each panel 88A, 88B (as well as 88C and 88D) may be formed from a continuous screen material as described herein so that an upper portion 60 and a lower portion 62 are seamlessly positioned within each panel 88 A, 88B. A lower edge of each panel's upper portion 60 is typically adjacent to an upper edge of each panel's lower portion 62 so that each panel 88A, 88B may be seamless (e.g., has no welds or other couplings) between the upper portion 60 and the lower portion 62.

[0056] Panels 88A, 88B of the screen 40 (as illustrated in FIGS. 6, 7, and 10) may, in one embodiment, be made from helically wrapped wire cylinders, with wire resistance (e.g., spaced- apart screen elements 70, 80) welded to support members 72. The wrapping machine controls the width of the slots formed by the wires, and may be adjusted. The cylinders of wire are then cut and made flat in to a blank. Then the panels 88 A, 88B may be cut out of the flat blank in a direction that orients the screen elements 70, 80 (e.g. wires in this case) in the desired direction. The cut, flat screen panels 88 A, 88B are then rolled to conform to the shape of a portion of the conical arrangement and resemble the panel 88 A, 88B in FIG. 6. Lastly, the screen 40 may be assembled on an appropriately sized and shaped mandrel by joining two (or more) panels 88A, 88B together at the interfaces 94.

[0057] Discussed further below, the screen elements 70, 80 may be spaced on the screen

40 and/or cut from the screen material according to predetermined measurements so as to create slots 102, 104 (see FIG. 11) of specific or different widths between the spaced-apart screen elements 70, 80. In some embodiments, the spacing of the screen elements 70, 80 (and therefore the width of the slots 102, 104 between the spaced-apart screen elements 70, 80) may be different for various portions (e.g., in the upper portion 60 and the lower portion 62) of the panels 88A, 88B. Further, any desired angles of orientation of the screen elements 70, 80 may be provided, and the angles may differ between the upper portion 60 and the lower portion 62, or in other various locations throughout the panels 88 A, 88B. The width of the slots 102 in such a design, while generally consistent when the panels 88 A, 88B are flat, may be tighter at the bottom edge 46 than the top edge 44 when formed to be the wall of the conical arrangement. The width of slots 102, 104 may also vary throughout the panels 88A, 88B as described herein. For example, another slot width or gradually increasing slot widths provided in the broken part of FIG. 11 may be provided.

[0058] While FIG. 6 shows the shape of a panel 88A, 88B in a formed state prior to being joined to form a section of the screen 40, FIGS. 7 and 10 show the shape of a panel 88A, 88B in a flat state prior to being formed and joined to form a section of the screen 40. The top edge 44 of the panel 88A, 88B may be curved, the sides may be tapered, and the bottom edge 46 of the panel 88A, 88B may be curved. Two panels 88A, 88B may be coupled together by any one or more of a welded connection, a bolted connection, a clamped connection, or other types of connections known in the art at an interface 94. The panels 88A, 88B may include other shapes, sizes, including symmetrical or non-symmetrical configurations. Again, the screen elements 70, 80, which may be, for example, spaced-apart wires or plates defining openings (e.g., slots 102), are shown schematically to provide a representation of their general orientation.

[0059] FIG. 11 shows an enlarged portion of an edge or wall of the conical arrangement

(e.g., the screen 40). As illustrated, the upper portion 60 and the lower portion 62 of the screen 40 are formed by screen elements 70, 80, respectively. The screen elements 70, 80 are supported by support members 72, which in some embodiments may be rods. One or more stabilizing and/or retaining members 84, 86 may be coupled to the top edge 44 and the bottom edge of the screen 40 for support while rotating. These retaining members 84, 86 may extend fully or partially around the circumference of screen 40 along the top edge 44 or the bottom edge 46 of the screen 40. In the embodiment shown, the coupling is by welding and may connect the retaining members 84, 86 to the top edge 44 and/or the bottom edge 46 of the screen 40.

However, other coupling means may be used. The retaining members 84, 86 may also be formed as part of the panel 88A, 88B. For clarity, the support members 72 and the stabilizing/retaining members 84, 86, shown in FIG. 11, are not shown in FIGS. 1-4, but are shown in FIGS. 5-7 and 10. In some embodiments, the stabilizing and/or retaining members while increasing the structural stability of the screen 40 also facilitate easy handling of the screen 40 even when the edges of the support members 72 and/or the wires of the screen have sharp edges. The panels of the screen 40 (88A, 88B, 88C, 88D) are adaptable and can be used in conjunction with a variety of hold down members, stabilizing members and retaining members employed in the field. In the embodiment of a screen 40 shown in FIGS. 2-10, the screen elements 70, 80 are shown schematically, but generally each represent an orientation that, for example, wires and/or slots 102 may take.

[0060] As the result of the curvature of the screen, the screen elements 70, 80 of the upper portion 60 and the lower portion 62 of the screen 40 may be oriented differently with respect to the central longitudinal axis X— X (FIGS. 3, 5, and 8) and with respect to planes that are perpendicular to the central longitudinal axis X— X. The screen elements 70, 80 may be the same or different in size, shape, and/or orientation between the upper portion 60 and the lower portion 62. The embodiments disclosed herein represent screen elements 70, 80 that may be substantially parallel to each other throughout both the upper portion 60 and the lower portion 62. The screen elements 70, 80 may also be generally or substantially non-horizontal (e.g., positioned at an angle in relation to a plane perpendicular to the central longitudinal axis X— X) when the screen 40 is in the operating position, with the central longitudinal axis X— X being positioned vertically. The screen elements 70, 80 may also be positioned generally or substantially horizontally, vertically, or in another configuration. In some embodiments, the wires of the screen elements 70 and 80 may comprise a concentric arrangement with respect to the central longitudinal axis. While other embodiments the screen elements 70 and 80 may comprise helical or curved wires.

[0061] Typically, screen elements 70 of the upper portion 60 are spaced apart from one another (e.g., adjacent screen elements 70) so as to form a slot 104 (e.g., a gap, or the like) between each adjacent screen element 70. The same is true for screen elements 80 of the lower portion 62, where screen elements 80 of the upper portion 62 are spaced apart from one another (e.g., adjacent screen elements 80) so as to form a slot 102 between each adjacent screen element 80. Therefore, in some embodiments, the slots 102, 104 formed by spacing screen elements 70, 80 may cause the screen 40 to resemble a grate or a lattice through which the slurry is permitted to flow. The slots 102 and 104 are illustrated in FIGS. 3-11 as being substantially horizontal slots, in that, the dimensions of each slot (102, 104) in the circumferential direction, parallel to the extent of the screen element, is greater than the dimensions of the slot in the

longitudinal/axial direction. The horizontal slots may extend a first length along the axial direction, the first length being smaller than a second length along the circumferential direction, parallel to the extent of the screen element.

[0062] However, embodiments of the invention can also comprise screen elements (70,

80) that comprise vertical slots to improve the dewatering process. In some embodiments, vertical slots may be created by arranging the wires of the screen elements in the axial direction and the support rods 72 in a substantially circumferential direction, parallel to the extent of the screen element. In some embodiments, the vertical slots may be created by arranging the support rods 72, closer together in the axial direction with the wires remaining in the circumferential direction, parallel to the extent of the screen element. The vertical slots may extend along a first length along the axial direction and a second length along the circumferential direction such that the first length is greater than the second length. FIGS. 14 and 15, illustrate screen panels (88 A, 88B, 88C, 88D), prior to forming and assembly. Second screen elements 70 are illustrated in FIG. 14 as comprising larger slots than the first screen elements 80, while the converse is illustrated in FIG. 15. In some embodiments, one or both of the first screen elements and second screen elements may comprise vertical slots, while being otherwise substantially similar in construction to the screen panels described elsewhere in this disclosure. In some embodiments with vertical slots, screen elements 70 and/or 80 may comprise wires (for example: Vee- Wires®) oriented along the axial direction and support rods 72 extending along the circumferential direction. In some embodiments the screen panels (88A, 88B, 88C, 88D) illustrated in FIGS. 14 and 15 are seamless in construction, while in other embodiments the screen elements 70 and 80 may associated with two or more sub-panels that are attached together to form the screen panels with horizontal and/or vertical seams.

[0063] In some embodiments, the first length and the second length may be equal, creating substantially square slots. Although the slots (102, 104) have been illustrated with substantially quadrilateral contours, any polygonal, circular, elliptical or suitable curvilinear contour may be employed with dimensions described above. The screen elements (70, 80) may comprise one contour and/or orientation (horizontal, vertical, and the like) of slots or the screen elements may comprise a combination of contours and or orientations. Furthermore, the screen elements (70, 80) may each comprise the same contour and orientation of the slots; or each screen element (70, 80) may comprise a different contour and/or orientation. In the

embodiments described above, each screen panel (88A, 88B, 88C, 88D) may be seamless or may comprise a first sub-panel with the screen portion 70 and an adjacent second sub-panel with screen portion 80, joined together long the circumference with a suitable seam. The screen elements are illustrated as being oriented in the circumferential direction, parallel to the extent of the screen element, however the screen elements may be oriented in any suitable angle with respect to the circumferential direction, parallel to the extent of the screen element. For example, in some embodiments, the screen elements (70 and/or 80) may be oriented in the axial direction and support members 72 may be oriented along a different direction (for instance the

circumferential direction).

[0064] The spacing of screen elements 70, 80 may vary throughout the sheet 40. In some embodiments, the spacing between screen elements 70 of the upper portion 60 form slots 104 of a first predetermined width (e.g., a distance between screen elements 70), while the spacing between screen elements 80 of the lower portion 72 form slots 102 of a second predetermined width (e.g., a distance between screen elements 80). The first predetermined width may be equal to, less, than, or greater than the second predetermined width. For example, as depicted in FIGS. 2-7 and 11 , the screen elements 70 of the upper portion 60 may be more widely spaced apart from each other than the screen elements 80 of the lower portion 62. As noted previously, the each slot may define a first length along the axial direction and a second length along the circumferential direction, parallel to the extent of the screen element. In this regard, in some embodiments, the first lengths of slots in the screen element 70 may be greater than the first lengths of the slots in the screen element 80. In some embodiments, the second lengths of slots in the screen element 70 may be greater than the second lengths of the slots in the screen element 80, singularly or in combination with the dimensions of first lengths described above, achieved by varying the positioning or contour of the support members 72 and/or the positioning of the wires. Conversely, FIGS. 8-10 depict an opposite configuration, where the screen elements 70 of the upper portion 60 may be spaced more narrowly from each other that the screen elements 80 of the lower portion 62. In this regard, in some embodiments, the first lengths of slots in the screen element 70 may be smaller than the first lengths of the slots in the screen element 80. In some embodiments, the second lengths of slots in the screen element 70 may be lesser than the second lengths of the slots in the screen element 80, singularly or in combination with the dimensions of first lengths described above. In some embodiments, with respect to FIGS. 2-11, the smaller of the first length and the second length of the slots is varied between screen elements 70 and 80. For example, if the first length of a slot is smaller than the second length of the slot, as in the case of horizontal slots, the first length (sometimes referred to as width) of the slots of screen elements 70 may be configured to be smaller or greater than the first lengths of slots of screen elements 80, to achieve variation in flow of slurry components through the screen 40. Alternately, if the second length of a slot is smaller than the first length of the slot, as in the case of vertical slots, the second length (sometimes referred to as width) of the slots of screen elements 70 may be configured to be smaller/greater than the second lengths of slots of screen elements 80. In this way, variably spacing the screen elements 70, 80 defines slots 102, 104 of different or variable widths in the screen 40 in the space between the spaced screen elements 70, 80 for each of the upper portion 60, the lower portion 62, and/or the screen 40 as a whole.

[0065] Furthermore, the spacing of screen elements 70, 80 may vary throughout each of the upper portion 60 and the lower portion 72. In this way, slots 104 formed in the upper portion 60 may have varying widths, and slots 102 formed in the lower portion 62 may also have varying widths. For example, the screen elements 80 of the lower portion 62 may be spaced in such a way that the widths of slots 102, 104 between the spaced screen elements 80 gradually increase throughout the lower portion 62 of the screen 40 (e.g., the widths of slots 102, 104 being narrowest at the bottom edge 46 of the screen 40 and the widths of slots 102 being widest at the top of the lower portion 62 with gradual increases in widths of adjacent slots 102 between the bottom edge 46 and the top of the lower portion 62). Conversely, the screen elements 80 of the lower portion 62 may be spaced in such a way that widths of slots 102 between the spaced screen elements 80 gradually decrease throughout the lower portion 62 of the screen 40 (e.g., the widths of slots 102 being widest at the bottom edge 46 of the screen 40 and the widths of slots 102 being narrowest at the top of the lower portion 62 with gradual decreases in widths of adjacent slots 102 between the bottom edge 46 and the top of the lower portion 62). The same or reverse may be true for spacing of the screen elements 70 of the upper portion 60. Alternatively, the spacing of screen elements 70, 80 may be uniform throughout the upper portion 60 and separately uniform to a different dimension in the lower portion 62. In another embodiment, each slot 102, 104 in the screen may have a different width, or a width independent of any adjacent slots 102, 104. In one other embodiment, there may be, for example, small slots 102 at the bottom, gradually increasing up the screen 40 to large slots, and then back to small slots at the top. In this way, the screen 40 may be configured with screen elements 70, 80 spaced apart from one another so as to provide an optimal inhibition of sugar crystal flow through the screen 40.

[0066] Shown in FIG. 12 and 13 is an embodiment of a plurality of spaced apart screen elements 70, 80 (e.g. wires) coupled to and supported by support members 72. The screen elements 70, 80 may be welded to the support members 72, with welding, brazing, soldering, riveting, bolts, wires or any other suitable fastening means, and spaced apart to form a plurality of slots 102 for filtering fluid flow out of the screen 40 during operation.

[0067] FIG. 13 shows a cross section of the screen elements 70, 80 mounted to support members 72 according to one embodiment. As shown and discussed herein, the screen elements 70, 80 may in one embodiment have a substantially triangular cross sectional shape, and may be positioned substantially parallel to each other. The support members 72 typically have a circular cross-sectional shape as shown in FIG. 13, but may have a triangular cross-sectional shape as shown in FIG. 12, or may be another shape. The support members 72 may be positioned parallel to each other, and may be positioned substantially perpendicular to the screen elements 70, 80 as seen in FIGS. 5-7, 10, and 11-13. Alternatively, the support members 72 may be positioned at another orientation in relation to the screen elements 70, 80. Additionally, in one embodiment, the same support member or members 72 may be used to support the screen elements 70, 80 of the upper portion 60 and lower portions 62 of the screen 40. In one embodiment, one or more support members 72 may extend continuously and substantially vertically along the outer circumference of the screen from the bottom edge 46 to the top edge 44. The one or more support members 72 may also be positioned in a different orientation (e.g., positioned at an angle in relation to a vertical axis, or in relation to an orientation of the screen elements 70, 80).

Typical spacing of support members 72 from adjacent support members 72 may fall within a range from 0.25 inches to 1.5 inches, with a preferable range extending from 0.25 inches to 0.5 inches.

[0068] When poured into the rotating screen 40, the slurry initially contacts the smaller- diameter lower portion 62 of the screen 40. The screen elements 80 of the lower portion 62 and slots 102 may effectively and efficiently remove fluid from the slurry (e.g. perform dewatering). Fluid passes through the slots 102 and exits the screen 40, while the screen elements 80 capture solids in the slurry and retain them within the interior of the centrifugal basket. The screen elements 80 are typically spaced at a first predetermined distance so that the slots 102 define an opening with a first predetermined width (first length of the slots). The first predetermined width of the slots 102 may be chosen based on expected particulate size of solids in the slurry so that the solids may be optimally trapped and contained within the interior of the centrifugal basket (e.g., the screen 40) during operation.

[0069] The slurry subsequently contacts the larger-diameter upper portion 60 of the screen 40 purposed to further filter fluid flow out of the screen 40, as well as direct particulate matter (e.g., solids) along the inner surface of the screen 40 to the top edge 44. The screen elements 70 and slots 104 of the upper portion 60 may remove any remaining fluid from the slurry. Additionally, the screen elements 70 and slots 104 of the upper portion 60 spaced a second predetermined distance and defining a second predetermined width, respectively, may prevent significant damage to the solid particular matter of the slurry more effectively and efficiently than the screen elements 80 spaced the first predetermined distance and slots 102 dimensioned with the first predetermined width of the lower portion 62. The solid particulate matter may move along and in the same direction as the slots 102 and/or upper faces of the screen elements 70 in a less impacting manner. For example, with the slots 104 of the upper portion 60 being different in width and perhaps orientation as the slots 102 of the lower portion 62, damage or fracture of the solid particular matter into smaller sizes capable of filtering through the screen 40 may be reduced, thus reducing generation of product waste. In some embodiments, the narrower slots may reduce damage or fracture of the solid particulate matter (for example: sugar crystals) while also providing improved wear resistance to the screen 40. In some embodiments, the wider slots employed may enhance the dewatering process.

[0070] The different sizing, shaping, and/or orientation of screen elements 70, 80 and slots 102, 104 between portions of the screen 40 as disclosed herein may provide different performance effects from a conventional screen 40. The screen 40 may improve overall product quality by increasing dewatering efficiency and decreasing solid particulate damage. The novel design of screen 40 also provides resistance to wear by utilizing slots of varying sizes in addition to improving the dewatering process. The screen 40 may enable replacement of either the upper portion 60 or the lower portion 62, as opposed to replacing the entire screen 40, in the event of damage or wear. The screen 40 enables the use of variable or different slot sizes (e.g. larger or smaller) in different areas, including the upper portion 60 and/or the lower portion 62, of the screen 40 and may also combine the advantages of differently shaped or oriented screen elements 70, 80.

[0071] In one embodiment, the distance between adjacent screen elements 80 of the lower portion 62 may be the same as, less than, or greater than the distance between adjacent screen elements 70 of the upper portion 60. In one embodiment, the distance between adjacent screen elements 70 may be the same, different, or may vary along the length and/or

circumference of the lower portion 62. In one embodiment, the distance between adjacent screen elements 80 may be the same, different, or may vary along the length and/or circumference of the upper portion 60. Spacing of the screen elements 70, 80 may range, in some embodiments of screens, from 0.001 inches to 0.250 inches, and may preferably be, for example, 0.001 inches to 0.010 inches.

[0072] Accordingly, the width of the slots 102 (e.g., the space between adjacent screen elements 70, 80) may be determined by the spacing of the screen elements 70, 80, and therefore the width of slots 102, 104 may vary throughout the screen 40. Additionally, with reference to the screen 40 being formed using a plate (such as a thin, metallic plate) and having one or more openings disposed through the plate, the openings may be oriented in a similar manner as the screen elements 70, 80 or slots 102. The screen 40 may be formed from one or more sections of plates coupled together, each of which may define an upper portion 60 and a lower portion 62 in a similar way as the panels 88 A, 88B. Each plate section may further include openings of various sizes, widths, lengths, and/or orientations in either of an upper portion 60 or a lower portion 62 of the plate, or the plate as a whole. For example, openings may extend the entire length, width, and/or height of the sections of plates. The openings may be symmetrically or non-symmetrically spaced relative to each other. The sections of plates may be supported by one or more support members, such as support members 72, or other support mechanisms that are known in the art.

[0073] In some embodiments, the slurries used during the operations of the refining device 42 are abrasive and induce wear in a screen that has prolonged exposure to the slurry. In this regard, the portions of the screen with wider/large slots may be more susceptible to wear as the fluid and solid components of the slurry shear off around the outer surface of the wires of the screen. Furthermore, as mentioned earlier, slurry with a greater thrust due to larger centrifugal effects impacts the inner surface of the portion of the screen proximate to the bottom edge 46, causing greater wear in this region in comparison with the rest of the screen. While the embodiments described above may address these concerns, at least partially, other embodiments of the invention are illustrated in FIGS. 16 and 17 to further alleviate these concerns.

Specifically, the screen 40 comprises one or more screen panels. Each panel may comprise three or more screen elements. In this regard, in some embodiments, one or more of the screen elements may be associated with a wear plate. For example, each panel may comprise first screen elements 80, second screen elements 70, third screen elements 80a and fourth screen elements 70a; with third screen elements 80a and fourth screen elements 70a being associated with a bottom wear plate and a top wear plate respectively. In this regard embodiments of the invention may comprise one or both of the top and bottom wear plates (70a, 80a) depending on the requirements. The screen elements associated with the wear plate may be disposed between the bottom edge 46 and other screen elements; between the top edge 44 and other screen elements and/or between two screen elements. The screen panels may be seamless, or may comprise seams formed due to joining separate screen elements (70a, 70, 80, 80a) using suitable fastening means. The adjacent second screen elements 70 and first screen elements 80 may be substantially similar in construction and assembly to those described above. Second screen elements 70 are illustrated in FIG. 16 as comprising larger slots than the first screen elements 80, while the converse is illustrated in FIG. 17. The embodiments described in FIGS. 16 and 17 may comprise one or both of the first and second screen elements (70, 80). The screen 40 further comprises third screen elements 80a adjacent to the first screen elements 80, disposed between the bottom edge 46 and the first screen elements 80. The third screen elements 80a, also referred to as the bottom wear plate comprise wires or screen elements that are tightly arranged with narrow or small slots. In some embodiments, the wires of third screen elements 80a are arranged substantially adjacent to one another. The slots formed by the third screen elements 80a may have dimensions (first and/or second lengths defined above) smaller than the dimensions of both the second and first screen elements 70 and 80. This tight arrangement of wires in the third screen elements 80a improves the strength and functioning of the screen as the screen 40. The bottom wear plate 80a is stronger and withstands the impact of turbulent, outward flowing slurry proximate the bottom edge 46 without flexure or deformation during operation, and the narrow spacing significantly resists wear. [0074] The screen 40 may also comprise fourth screen elements 70a adjacent the second screen elements 70, arranged between the top edge 44 and the second screen elements 70. The fourth screen elements 70a, also referred to as the top wear plate, may be substantially similar to the third screen elements 80a. The fourth screen elements 70a may comprise slots of similar or different dimensions with respect to the third screen elements 80a, although typically, the slots of the fourth screen elements 70a may be smaller than the slots of both the second and first screen elements 70 and 80. In some embodiments, the screen 40 may comprise slots (associated with one or all of the screen elements 70a, 70, 80 and 80a) with progressively and/or gradually varying sizes along a predetermined direction. For instance, the dimensions of the slots may vary gradually along a predetermined direction, such that the slots collectively form a

substantially curvilinear shape. For example the screen 40 may comprise slots with gradually varying dimensions, collectively forming a substantially streamlined shape in the axial direction, with the largest slots in towards the center of the screen 40. Specifically the screen 40 may start with small/narrow slots near the bottom edge 46 which may develop into progressively larger and subsequently progressively smaller slots along an axial direction towards the top edge 44, which terminate at the top edge 44 with small/narrow slots. Typically, significant improvement in wear resistance and increase in longevity of the screen can be obtained by utilizing the bottom and/or top wear plates. Furthermore, in some embodiments, the bottom and/or top wear plate may further aid in preventing the damage or fracture of solid particulate matter during operation of the refining device 42.

[0075] Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the embodiments herein have other applications in other environments. This application is intended to cover any adaptations, combinations or variations of the embodiments and elements described in the present disclosure. The following claims are in no way intended to limit the scope of the disclosure to the specific embodiments described herein. While the foregoing is directed to embodiments of a variable geometry centrifugal basket, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

WHAT IS CLAIMED IS:

1. A screen assembly comprising:

a base; and

a truncated cone extending from the base at a first end to a second, open end having a larger diameter than the first end, the truncated cone comprising at least one panel comprising a plurality of spaced screen elements defining slots, with certain predetermined slots of the at least one panel having different predetermined widths than other slots of that panel.

2. The screen assembly of Claim 1, wherein the at least one panel comprises a plurality of panels each extending from the first end to the second end, wherein each panel is formed from a single piece of screen material and is secured to one or more adjoining panels to form the truncated cone.

3. The screen assembly of Claim 1, wherein the plurality of screen elements includes a first plurality of screen elements defining a first slot having a first width, and a second plurality of screen elements defining a second slot having a different, second width.

4. The screen assembly of Claim 3, wherein the second plurality of screen elements is disposed between the first plurality of screen elements and the second end, and the first plurality of screen elements defines a first plurality of slots whose widths gradually change in one direction.

5. The screen assembly of Claim 4, wherein the second plurality of screen elements defines a second plurality of slots whose widths gradually change in one direction.

6. The screen assembly of Claim 3, wherein the first plurality of screen elements is disposed starting from the first end and ending at a first location spaced from the first end toward the second end, and the second plurality of screen elements is disposed starting from the first location spaced from the first end and ending at the second end.

7. The screen assembly of Claim 6, wherein the first width is narrower than the second width.

8. The screen assembly of Claim 6, wherein the first width is wider than the second width.

9. The screen assembly of Claim 6, wherein the first plurality of screen elements forms at least one quarter of the truncated cone starting from the first end toward the second end.

10. The screen assembly of Claim 3, wherein:

the second plurality of screen elements is disposed between the first plurality of screen elements and the second end;

the first plurality of screen elements comprises a bottom wear plate defining a first wear slot having a third width, the first wear slot being disposed between the first end of the truncated cone and the first slot;

the second plurality of screen elements comprises a top wear plate defining a second wear slot having a fourth width, the second wear slot disposed between the second end of the truncated cone and the second slot; and

the third width and the fourth width are less than the first width and the second width.

11. The screen assembly of Claim 3, wherein:

the first plurality of screen elements comprises a bottom wear plate defining a first wear slot having a third width, the first wear slot being disposed between the first end of the truncated cone and the first slot; and

the third width is less than the first width and the second width.

12. The screen assembly of Claim 11 , wherein the first width is lesser than the second width.

13. The screen assembly of Claim 11, wherein the first width is greater than the second width.

14. The screen assembly of Claim 11, the second plurality of screen elements further comprising:

a top wear plate defining a second wear slot having a fourth width, the second wear slot disposed between the second end of the truncated cone and the second slot; wherein the fourth width is less than the first width and the second width.

15. The screen assembly of Claim 1, wherein the screen elements comprise wires spaced from each other to define the slots.

16. The screen assembly of Claim 1, wherein the screen elements comprise perforated plates that define the slots.

17. The screen assembly of Claim 1, wherein at least one slot defines a first length along a central longitudinal axis of the truncated cone that is smaller than a second length along the circumference of the truncated cone.

18. The screen assembly of Claim 1, wherein at least one slot defines a first length along a central longitudinal axis of the truncated cone that is greater than a second length along the circumference of the truncated cone.

19. A method of making a screen assembly comprising:

fabricating a plurality of flat screen panels, each flat screen panel of the first plurality of flat screen panels having an axis and comprising screen elements spaced from one another to define slots of a plurality of predetermined widths; and

assembling the screen panels and a base to form a truncated conical arrangement about a central longitudinal axis, wherein the slots have at least two different widths at different locations along the central longitudinal axis.

20. The method of making a screen assembly of Claim 19, further comprising prior to assembling the screen panels forming each flat screen panel into a curved shape to conform to the shape of a portion of the truncated conical arrangement.