Patent Publication Number: US-11033910-B2

Title: Wire member and method of making wire member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Stage of International Application No. PCT/AU2017/050925, filed on Aug. 30, 2017, which claims the benefit of Australian Application No. 2016903443, filed on Aug. 30, 2016. All of the foregoing are incorporated as though set forth herein in their entirety. 
     FIELD OF THE INVENTION 
     The present invention relates generally to the manufacture and use of wire members used in separating centrifuges. Separating centrifuges are commonly used in many sorting and dewatering processes. More specifically the invention relates to wedge wire used in improved screen baskets for use in separating centrifuges. 
     BACKGROUND TO THE INVENTION 
     Centrifuges, such as screen scroll centrifuges, are often used to filter or dewater crystalline or amorphous solid/liquid slurries. These centrifuges typically utilize a screen to separate the solid portion of the slurry from the liquid phase. The screen, moreover, is typically sized to retain the larger solids portion of the slurry while allowing the liquid to pass through and thus, the two phases of the slurry may be separately collected. Instead of relying on gravity to filter the slurry through the screen, however, filtration occurs under large centrifugal forces (on the order of many times the force of gravity), caused by high rotational speed of the centrifuge. These large centrifugal forces substantially increase the separation efficiency of the centrifuge. 
     Specifically, the slurry is delivered to the interior of a rotating basket that includes a frusto-conical screen body. The screen body is typically formed from a plurality of wedge wires that are spaced side-by-side. For structural support, the wedge wires may be welded to circumferential ribs spaced out along the rotational axis of the body. Rotation of the screen basket drives the slurry against the inner surface of the body and the liquid phase is forced through the slots formed between adjacent wedge wires. The larger solid particles do not pass through the slots and are instead collected on the inside of the basket. 
     To convey the solids out of the inside of the basket, a scroll conveyor having a helical blade is typically mounted concentrically within the basket. The tip of the blade, however, is spaced from the inner surface of the basket by a small radial clearance. The scroll conveyor is rotated in the same direction as the basket but at a slightly different rotational speed relative to the basket. Through this differential speed, the solids accumulating along the inside surface of the basket are conveyed by the helical blade from the small diameter end and toward the basket&#39;s larger end where they are dumped in a discharge chute and collected. 
     Another type of separating centrifuge is a vibrating centrifuge. Vibrating centrifuges also include a screen basket that is similar in design to the basket of screen scroll centrifuges. A vibrating centrifuge, however, does not utilize a helically bladed scroll to move the solid particles collecting on the inside surface of the basket to the discharge chute. Instead, the vibrating centrifuge includes a mechanism for shaking the basket back-and-forth along its axis. By shaking or vibrating the basket along its rotational axis, solid particles accumulating on the inside of the basket are conveyed axially toward the discharge chute and collected. 
     Therefore, as described above, scroll and vibrating centrifuges are very useful for separating liquid/solid slurries. Nonetheless, these centrifuges are subject to significant wear requiring frequent maintenance and corresponding down time. For example, solid particles of the slurry often get trapped in the slots of the basket, damaging the screen and reducing the separation efficiency of the centrifuge. Furthermore, the slurries often include highly abrasive components that wear out the body of the screen basket. The corresponding maintenance and replacement of parts significantly increase operating costs. 
     A conventional method of manufacture of the centrifuge baskets described above includes manufacture of the body from stainless steel wedge wire cut from flat sheets. Commonly, wedge wires are arranged as a screen cylinder which is then split and flattened into a sheet form. The frusto-conical body forming the basket is then developed and a layout made on this flat wedge wire sheet. To minimize the material used, the body is usually divided into several sections. Each section is cut from the flat sheet and rolled into a frusto-conical shape. A set of panels is placed on an appropriate jig and welded into the required complete frusto-conical form. However, when the sections are joined to form a body, the welded joints located between each adjacent section end up having a “herring bone” or V shaped pattern similar to the V shaped pattern found in twill fabric. 
     This also results in a cone with slots on the inside of the basket running in a relatively vertical pattern (i.e., slots are in the general longitudinal direction of the cone). 
     The inner surface of the body is produced by wedge wires which are welded to a network of support rods at the exterior of the body. The support rods run at right angles to the internal wedge wires and generally run circumferentially on the outside of the basket. The wedge wires have a wedge shaped cross sectional shape. An example of such a basket is described in U.S. Pat. No. 4,487,695. 
     However, in this arrangement, there is usually only one wire in each section which is parallel to the rotation axis of the body. This cannot be avoided using current materials and techniques. This means that for reasons explained hereinafter that as the particles in mine slurries (e.g. coal slurries) travel outwardly of the centrifugal basket due to centrifugal force and vibration, some coal particles will cut across the wedge wires, resulting in excessive wear and premature failure of the basket. 
     To complete a useable basket, mounting flanges of various styles are welded to the ends of the basket body and often there are reinforcing ribs and, depending on design, strengthening and wear plates added. 
     Thus, the manufacture of a screen basket involves a number of processes, is time consuming and labour intensive and the quality of the end product is dependent on the skill of personnel involved in the manufacturing. In a large part, the time and expense in building a screen basket is brought about by the method of fabricating the body of the basket from a number of panel sections. Depending on the size of the basket, the process of cutting these panel sections from flat sheet can also be wasteful of expensive stainless steel materials. 
     Another problem with the conventional centrifuge baskets as described above is that they did not process coal slurries in an efficient manner. In this regard coal generally has a stratified form and thus, in other words, has a laminar structure. Thus, in use coal may travel from a smaller diameter end of the centrifuge basket to a larger diameter end. However, due to its structure, coal tends to split into smaller particles or dust. The presence of the herring bone pattern in the welded joints between each section of the body as described above also was detrimental to the coal particles as it tended to cut the coal particles. In this regard, it was necessary that the coal particles were caused to travel on the internal surfaces of each longitudinal wedge wire to avoid fracturing. Therefore because of the herring bone pattern in each welded joint it was necessary to spin the centrifuge at 300 rpm to introduce vibration into movement of the basket to facilitate the coal particles to travel on the internal surfaces of each wedge wire. However, such vibration also resulted in fracturing of the coal particles. 
     OBJECT OF THE INVENTION 
     It is an object of the invention to overcome or at least alleviate one or more of the above problems and/or provide the consumer with a useful or commercial choice. 
     SUMMARY OF THE INVENTION 
     In one form, although it need not be the only or indeed the broadest form, the invention resides in a screen basket for centrifuges comprising a wedge wire having a broad end and an opposite narrow end, wherein the wedge wire narrows in width from the broad end to the narrow end. 
     The wedge wire may increase in depth from the broad end of the wedge wire to the narrow end of the wedge wire. 
     The wedge wire suitably has a generally triangular-shaped profile in cross-section. 
     The degree of narrowing may be uniform over the length of the wedge wire. 
     The wedge wire may have a flat planar head face having edges between which the width of the wedge wire is defined. The head face tapers inwardly from the broad end of the wedge wire to the narrow end of the wedge wire. 
     In another form, the invention resides in a screen basket for centrifuges, the screen basket having a body of frusto-conical shape, the body including a plurality of wire members and a number of support rods, wherein each wire member is oriented in a common plane with a rotational axis of the body and the support rods are oriented circumferentially of the body and there are longitudinal slots located between adjacent wire members. 
     The wire members suitably have a broad end and an opposite narrow end, wherein the wire members narrow in width from the broad end to the narrow end. 
     The wire members may be wedge wires as defined and described in the first form of the invention. 
     The support rods may have a plurality of teeth spaced around an annulus of the support rod, wherein each pair of adjacent teeth defines a recess for receiving a wire member. 
     The longitudinal slots may have a constant width. Alternatively, the longitudinal slots may have a varying width. 
     In yet another form, the invention resides in a method of manufacture of a screen basket for centrifuges, the method including: 
     feeding a feed wire between rollers in a rolling operation; 
     gradually displacing at least one of the rollers closer to an adjacent roller as the feed wire is fed between the rollers to form a wedge wire; and 
     forming a centrifuge basket from the wedge wire. 
     A rolling machine for forming a wedge wire from a feed wire includes two rollers which are displaced relative to each other as the feed wire is fed between the rollers. 
     Each roller may have a rotational axis and a groove which has a floor inclined relative to the rotational axis. 
     The rolling machine includes a controller which controls the rate of displacement of the rollers relative to each other as the feed wire is fed between the rollers. The controller also controls the rate of feed of the feed wire by controlling the rotation of at least one of the rollers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, exemplary embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a wire member in the form a wedge wire in accordance with the invention; 
         FIG. 1A  is a side view of the wedge wire shown in  FIG. 1 ; 
         FIG. 2  is a series of cross-sectional views along the wedge wire shown in  FIG. 1 ; 
         FIGS. 3 and 4  are perspective views of the wedge wire shown in  FIG. 1  from each end of the wedge wire, respectively; 
         FIGS. 5, 6 and 7  show a side view, plan view and perspective view of the body of a screen basket including a multiplicity wedge wires of  FIG. 1 ; 
         FIG. 8  is a perspective view of the geometry of the body of  FIGS. 5-7 ; 
         FIG. 9  is a perspective view of one embodiment of a rolling operation to form the wedge wire of  FIG. 1 ; 
         FIG. 10  is an end view of a jig used in the rolling operation of  FIG. 9 ; 
         FIG. 11  is a different end view of the jig of  FIG. 10 ; 
         FIG. 12  is a perspective of another embodiment of a wedge wire in accordance with the invention; 
         FIG. 13  is a different perspective view of the wedge wire of  FIG. 12 ; 
         FIG. 14  is an end view of the broad end of the wedge wire of  FIG. 12 ; 
         FIG. 15  is an end view of the narrow end of the wedge wire of  FIG. 12 ; 
         FIG. 16  is a perspective view of part of a rolling machine for forming the wedge wire of  FIG. 12 ; 
         FIG. 17  is a diagram of the rolling machine of  FIG. 16 ; 
         FIG. 18  is a cross-sectional view of the rollers of the rolling machine of  FIG. 16  in a start position; 
         FIG. 19  is a cross-sectional view of the rollers of the rolling machine of  FIG. 16  in an end position; 
         FIG. 20  is a front view of one of the rollers of the rolling machine of  FIG. 16 ; 
         FIG. 21  is a cross-sectional view of one of the rods used in the screen basket of  FIGS. 5 and 6 ; 
         FIG. 22  is a top view of a rotating table on which wedge wires of  FIGS. 12-15  and the rods of  FIG. 21  are arranged for assembling the body of a screen basket; 
         FIG. 23  is a perspective view of a conical jig used in assembling the body of a screen basket including the rods of  FIG. 22 ; 
         FIG. 24  shows a perspective view of the body of a screen basket including a multiplicity of wedge wires of  FIG. 1  and support rods; and 
         FIG. 25  shows a plan view of a segment of a support rod of  FIG. 24 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In this patent specification, adjectives such as first and second, left and right, top and bottom, etc., are used solely to define one element or method step from another element or method step without necessarily requiring a specific relative position or sequence that is described by the adjectives. Words such as “comprises” or “includes” are not used to define an exclusive set of elements or method steps. Rather, such words merely define a minimum set of elements or method steps included in a particular embodiment of the present invention. In the drawings, like reference numerals refer to like parts. 
       FIG. 1  shows a perspective view of a wire member in accordance with one embodiment of the invention. The wire member is in the form of a wedge wire  10  of a screen basket (shown in  FIG. 5 ) for centrifuge. It will be noted from  FIG. 1  that the wedge wire  10  is of a triangular-shaped cross-section as shown in  FIG. 2 . The wedge wire  10  is used in the manufacture of a centrifugal screen basket. 
     The wedge wire  10  has three planar faces, namely head face  11  and two side faces  12 ,  13 . Head face  11  has edges  14  and  15  which are common with side faces  12  and  13 . A head width (w) of the wedge wire  10  is defined across the head face  11  extending between the edges  14  and  15 . The head width (w) is measured perpendicularly to the longitudinal axis  20  of the wedge wire  10 . 
     The wedge wire  10  has a broad end  17  and a narrow end  18 . It will be noted that edges  14  and  15  of head face  11  taper or converge inwardly from the broad end  17  to the narrow end  18 . That is to say the head width (w) decreases from the broad end  17  to the narrow end  18 . 
     The side faces  12  and  13  share a common edge  16 . A depth (d) of the wedge wire  10  is defined as the shortest distance from the edge  16  to the head face  11 . In regard to side face  12 , side edges  15  and  16  taper or diverge outwardly from end  17  to end  18 . In regard to side face  13 , side edges  14  and  16  taper or diverge outwardly from end  17  to end  18 . That is to say the depth (d) increases from the broad end  17  to the narrow end  18 . 
     The broad end  17  is in the shape of approximately an isosceles triangle and narrow end  18  is also approximately in the shape of an isosceles triangle. The narrow end  18  thus has a greater depth (d) than broad end  17 , which has a greater width (w). 
       FIGS. 3 and 4  show different isometric views of wedge wire  10  from each of the different ends  17  and  18 . The wedge wire  10  is indefinite in length although  FIGS. 1-2  indicate a finite length for convenience. 
       FIGS. 5, 6 and 7  show the body  19  of a centrifuge screen basket. The body  19  includes wedge wires  10  described in  FIGS. 1-4 . It will be appreciated that the body  19  has a plurality of wedge wires  10  and also a plurality of support hoops  21 ,  22  and  23  comprising support rods. 
     The body  19  has a frusto-conical shape (truncated cone) as shown, having a smaller diameter end  24  and a larger diameter end  25 . The wedge wires  10  are circumferentially spaced about a rotational axis  56  of the body  19 . Each of the wedge wires  10  are welded to support hoops  21 ,  22  and  23  at points  26 . There are also provided longitudinal or axially oriented slots  27  between adjacent wedge wires  10  having a constant width as shown by distance “X” in  FIGS. 5, 6 and 7 . It will also be noted that narrower ends  18  of each wedge wire  10  are located on the smaller diameter end  24  and broader ends  17  are located on the larger diameter end  25 . Furthermore, it will be appreciated that the slots may have a tapered width or varying width between adjacent wedge wires  10 . This varying width can be achieved by having the narrower ends  18  of each wedge wire  10  located on the larger diameter end  25  and the broader ends  17  on the smaller diameter end  24 . The varying width can also be achieved by placing adjacent wedge wires  10  so that one wedge wire  10  has a narrower end  18  located on the larger diameter end  25  and broader end  17  on the smaller diameter end  24  and an adjacent wedge wire  10  has a narrower end  18  located on the smaller diameter end  24  and a broader end  17  on the larger diameter end  25 . 
     The wedge wires  10  and each longitudinal slot  27  are in a common plane with the rotational axis  56  of the body  19 . 
       FIG. 8  shows wedge wires  10 , or slots  27 , represented by lines in phantom  50 ,  51  and  52  each of which form a common plane  53 ,  54  and  55  with rotational axis  56  of the body  19 . 
     In the case that lines  50 ,  51  and  52 , represent wedge wires  10 , the longitudinal axis  20  of each wedge wire  10  will lie on one of the lines  50 ,  51  and  52 . 
     End faces of the wedge wires  10  at their narrow ends  18  are to square to the rotational axis  56 . Similarly, the end faces of the wedge wires at their broad ends  17  are square to the rotational axis  56 . 
     One method of manufacturing wedge wire  10  is described in  FIG. 9 , wherein preformed feed wire  35  is rolled in a die plate  31 . The feed wire  35  has a constant triangular cross-section in the shape of approximately an isosceles triangle. The die plate  31  has a continuous longitudinal groove  32  which has a shape which is complementary to the wedge wire  10 . The groove  32  thus has a constantly changing triangular shape as shown in  FIGS. 10 and 11 . 
       FIG. 10  shows an end  33  of the groove  32  in the die plate  31  which corresponds with the narrow end  18  of the wedge wire  10 . 
       FIG. 11  shows an end  34  of the groove  32  which corresponds with the broad end  17  of the wedge wire  10 . 
     The process includes an initial step of placing annealed feed wire  35  in groove  32  as shown in phantom in  FIG. 9  and moving die plate  31  between opposed rollers  36  and  37 . The feed wire  35  after passage through rollers  36  and  37  will be the wedge wire  10  having the cross-sectional shape as shown in  FIGS. 1-4 . 
       FIG. 12  shows an elongate wire member in the form of wedge wire  100 . The wedge wire  100  is another embodiment of a wire member in accordance with the invention. The wedge wire  100  is similar to the wedge wire  10 , with the main difference being that side faces  120 ,  130  of wedge wire  100  each comprise two planar surfaces as discussed below. 
     The side face  120  of wedge wire  100  has a body surface  122  and a nose surface  124 . The body surface  122  and nose surface  124  are contiguous along an edge  126 . The flat plane of the body surface  122  is angled relative to the flat plane of the nose surface  124 . Similarly, the side face  130  of wedge wire  100  comprises a body surface  132  and a nose surface  134 . The body surface  132  and nose surface  134  are contiguous along an edge  136 . The flat plane of the body surface  132  is angled relative to the flat plane of the nose surface  134 . 
     The nose surfaces  124  and  134  share a common leading edge  160  of the wedge wire  100 . 
     A nose  102  of the wedge wire  100  is defined between the nose surfaces  124  and  134 . A body  104  of the wire  100  is defined between the body surfaces  122 ,  132 . The wedge wire  100  is symmetrical about a symmetrical plane (p) extending square from the head face  110  to the leading edge  160 . The symmetrical plane (p) extends through a longitudinal axis  200  of the wedge wire  200 . 
     The body surfaces  122 ,  132  are slanted at about a 3 degree angle to the symmetrical plane (p) along the whole of the wire  100 . Although an approximately 3 degree angle may be advantageous, it will be appreciated that the angle could be of varying degrees. The angle may advantageously fall within the range of 1 degree to 15 degrees, and more particularly in the range of 1 degree to 10 degrees, and even more particularly in the range of 1 degree to 6 degrees, and still more particularly between about 2 degrees and about 4 degrees. 
     The depth (d) of the wedge wire  100  increases from the broad end  170  to the narrow end  180 . As such, depth d 1  measured at the broad end  170  is shallower than depth d 2  measured at the narrow end  180 . In order for the depth to increase and the body surfaces  122 ,  132  to remain at around 3 degrees, the body  104  elongates in the depth direction. 
     The head width (w) decreases from the broad end  170  to the narrow end  180 . The head width w 1  measured at the broad end  170  is thus wider than the head width w 2  measured at the narrow end  180 . 
     The wedge wires  10  of the screen basket body  19  depicted in  FIGS. 5 to 8  may be substituted by wedge wires  100 . 
     The wedge wire  100  is formed from constant cross-section feed wire using a rolling process.  FIG. 16  shows part of a rolling machine  200  for forming the wire  100 . The rolling machine  200  includes an upper roller  202  and a lower roller  204 . The upper roller  202  has a rotational axis  206  and the lower roller  204  has a rotational axis  208 . The rotational axes  206 ,  208  of the rollers  202 ,  204  are parallel to one another. The rollers  202 ,  204  are held relative to each other in a frame  210 . 
     The upper roller  202  is selectively displaceable in the frame  210  relative to the lower roller  204  so that the spacing between the rotational axes  206 ,  208  vary. Even though the spacing between the axes  206 ,  208  may vary, the rotational axes  206 ,  208  remain parallel. 
     The upper roller  202  is displaced upwardly or downwardly by electric motors  216  of the rolling machine  100  mounted on top of the frame  210 . The rollers  202 ,  204  have axles  212 . The axle  212  of the upper roller  202  is journaled at either end in a block  214 . The blocks  214  are movable up and down in the frame  210 . The motors  216  rotate screws which engage the blocks  216  to translate the blocks  214  up and down in the frame  210 . 
     The axles  212  are driven via drive shafts  218 . The drive shafts  218  are connected to the axles  212  via universal joints  220 . The universal joints  220  allow the upper roller  202  to be displaced while still driving the axle  212  of the upper roller  202 . 
     It will be appreciated that although the upper roller  202  has been described as being displaceable, the lower roller  204  may also be displaceable. Either way, the upper roller  202  and the lower roller  204  are displaceable relative to each other. 
     The speed of rotation of the drive shafts  218 , govern the rate of feed of wedge wire between the rollers  202 ,  204 . The drive shafts  218  are driven by a hydraulic motor (not shown). 
       FIG. 17  shows a diagram of the rolling machine  200  and its control by a controller  300  of the machine  200 . The speed of rotation of the drive shafts  218  is controlled by a controller  300  which controls motor  222 . Displacement of the upper roller  202  is also controlled by the controller  300 . Specifically, the controller controls the electric motors  216 . The controller  300  thus controls the taper of the wire  10  over the length of the wire  10  by controlling the rate of displacement of the upper roller relative to the feed rate of wedge wire between the roller  202 ,  204 . 
       FIG. 18  shows the upper roller  202  at a start position when forming the wire  100 . The upper roller  202  is spaced from the lower roller  204 . The wide end  170  of the wire  100  is located between the rollers  202 ,  204  in the start position. The wide end  170  has the shape of the pre-formed feed wire fed between two rollers  202 , 204 . 
       FIG. 19  shows the upper roller  202  at an end position wherein the upper roller  202  has been displaced to be substantially against the lower roller  204 . The narrow end  180  of the wedge wire  100  is located between the rollers  202 ,  204  in the end position. 
     In one example, the upper roller  202  is displaced 0.88 mm from the start position to the end position over 750 mm of travel of feed wire between the roller  202 ,  204 . That is to say that between the start position and the end position, the upper roller  202  moves about 0.11733 . . . mm closer to the lower roller  204  for every 100 mm of pre-formed feed wire fed between the rollers. In the example, the head width of the wedge wire  100  decreases from 3 mm to 2.12 mm over 750 mm. The decrease in head width is at a constant rate over the length of the wedge wire  100 . The depth of the wedge wire  100  increases as the head width decreases. The depth of the wire  100  is 6.22 mm at the wide end  170  and 6.92 mm at the narrow end  180 . 
       FIG. 20  shows a front view of the upper roller  202 . The lower roller  204  is the same as the upper roller  202 . The upper roller  202  is generally cylindrical and has an annular groove  230 . The groove  230  has an inclined floor  232 . The floor  232  is inclined at an acute angle of about 3 degrees relative to the rotational axis  206  of the roller  202 . The floor  232  is tapered at about 3 degrees relative to the rotational axis  206 . A shoulder face  234  of the groove  230  extends to the deepest end of the floor  232 . The shoulder face  234  is square relative to the rotational axis  206 . The lower roller  204  is the same as the upper roller  202 . 
     In use, the body surface  122  or  132  of the wedge wire  100  is supported between the floors  232  of the grooves  230  with its head face against the shoulder faces  234  of the grooves  230 . 
     The steps to manufacture a screen basket from either wedge wire  10  or  100  is described herein below as the process is the same irrespective of whether wedge wire  10  or  100  is used. Wedge wire  10 ,  100  is straightened and in one step may be placed in a rotating table  40  as shown in  FIG. 22 . Table  40  has a series of circumferential grooves  41  into which rods  42  are placed. The rods  42  have a cross-sectional shape as shown in  FIG. 21 , which resembles a house-like shape. The straightened wedge wire  10 , 100  is then laid across rods  42  as shown in  FIG. 22  and welded to rods  42  as the wedge wire  10 ,  100  is located in position on table  40 . Wedge wire  10 ,  100  may then be cut to the desired length and the table  40  rotated or indexed by a desired amount and the next series of wedge wires  10 ,  100  laid across and welded to rods  42 . The wedge wire  10 ,  100  may then be cut and the process repeated until a frusto-conical body formed from rods  42  and wire  10  is formed with the mutually adjacent edges being welded to each other. 
     Alternatively, use may be made of a split conical jig  43  shown in  FIG. 23  which would be formed from heavy steel and machined to the desired shape with a series of circumferential grooves  44  which would retain rods  42  having a cross-sectional shape as shown in  FIG. 23 . The jig  43  would be split into two components  45  and  46 . The two components  45 , 46  are releasably joined at join line  47 . This may allow loading of rods  42  into retaining grooves  44 . This would also allow for removal of the completed body from jig  43 . 
     Alternatively, a screen basket  240 , shown in  FIG. 24 , may be formed from a support rod in the form of an support hoop  250  which is formed from heavy steel and machined to the desired shape to receive a plurality of wedge wires  10  as described above. It will be appreciated that wedge wire  100  as described herein could also be used with the toothed hoop  240 . 
     The support hoop  250 , shown in more detail in  FIG. 25 , has a series of circumferentially located spaced teeth  251  projecting inwardly from the annular body  252  of the support hoop  250 . A recess  253  is defined by each pair of adjacent teeth  251  and retains a wedge wire. Each tooth  251  has a narrow end  254  distally located from the annular body  252  and a broad end  255  proximally located from the annular body  252 . The narrowing from the broad end  255  to the narrow end  254  is uniform. The broad end  255  ensures the wedge wire (not shown) is held in the recess  253  against the annular body  252 . In some embodiments, each tooth  251  has a width of approximately 0.61 cm. 
     Alternatively, a plurality of individual frusto-conical segments may be formed and then connected together to form the frusto-conical body. The segments may be connected to each other using any suitable affixing means, such as bolting or welding. Each segment may be constructed as a flat panel first and then curved to the desired frusto-conical segment shape. The plurality of segments may include at least 4 segments, more particularly at least 8 segments, and even more particularly 12 segments. However, it will be appreciated that the number of segments may be varied according to the size and shape of the desired frusto-conical body. 
     In practice, wedge wire  10 ,  100  is laid across rods  42  as shown in  FIG. 22  and this may be done manually or automatically. A wire guide or carrier (not shown) would carry or progress wire  10 ,  100  to the small end  48  of jig  43  and set it in the desired position wherein subsequently it would be welded to rods  42 . As the carrier is withdrawn from smaller end  48  to larger end  49 , the wire  10  would then be cut to the correct length and the cone jig  43  would then be rotated or indexed on appropriate support bearings (not shown) to the desired location for the next series of wedge wires  10  to be laid across rods  42  and welded thereto. This process would be completed until the body of the centrifuge basket is completed. 
     It will be appreciated from the foregoing with the wires  10 ,  100  having the cross-sectional shapes described above, that centrifugal screen basket body  19  may be produced having a longitudinal slot  27  of uniform or constant width which is also in a common plane with the rotational axis of body  19 . This means that coal particles included in a slurry being processed by centrifugal screen basket body  19  will travel from one end  24  to the other end  25  on tapered head face  11 , thereby reducing fracturing and providing a greater harvest of coal from processing of the coal slurries. 
     It will be appreciated from the foregoing that because each wedge wire and thus each longitudinal slot is in a common plane with the rotational axis of the frusto-conical body, and also each slot has a constant width, that fracturing of particles in coal slurries is substantially reduced and thus the magnitude of the coal harvest from the processing of coal slurries is considerably increased.