Abstract:
A screen basket with replaceable profiled bars and method of making such screen basket are described herein. The screen basket includes profiled bars evenly spaced circumferentially to form a plurality of continuous slots that covers the whole basket length. The profiled bars are fixed in place by a backing structure, including support rings. In pulp and paper industry, this type of basket is mainly used for pulp screening and is commonly referred to as wedge wire basket. As opposed to conventional wedge wire baskets, in which the profiled bars are permanently joined to the rings, the present invention allows replacing the profiled bars when required and to fully re-use the main structural elements. This is achieved with an assembly that allows to insert the profiled bars, preferably consecutively sled into each aligned ring grooves in a vertical movement. The ring grooves are profiled such that there is sufficient clearance for sliding in the profiled bars. The mounting clearance is then removed radially to hold the profiled bars in place. According to an illustrative embodiment, this is achieved by squeezing an element made of compressible material, and placed between each ring pair.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of application Ser. No. 11/920,139 filed Nov. 9, 2007 which in turn was a U.S. national phase filing under 35 USC §363 and §365 of PCT International Application Serial No. PCT/CA2006/000722 filed May 5, 2006 claiming priority of U.S. Provisional Patent Application Ser. No. 60/678,819 filed May 9, 2005. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to screen baskets used for screening fiber suspensions, and more particularly to a screen basket which can be applied in the pulp and paper industry, for example in pressure screen applications. The innovations of the present invention can also be advantageously applied for basket manufacturing used for screw presses or other filtration or dewatering devices. 
       BACKGROUND OF THE INVENTION 
       [0003]    Pulp screening in the pulp and paper industry is generally achieved with pressure screens in which the furnish is pumped to remove oversized contaminants, fiber bundles, wood fragments, and/or sort long and short fibers, and/or stiff and soft fibers. Several pressure screen configurations are in use today. The two main configurations are pressure screens using substantially cylindrical outward flow basket, and screens using substantially cylindrical inward flow basket. All the pressure screens generally require the accepted stock to pass through the holes or slots of a screen basket. Rejects too large to pass through the screen basket or wedge-wire basket openings leave through a rejects outlet. A rotor is used to prevent the slots or holes from plugging. The rotor creates pressure pulsations resulting in sufficient cleaning action of the screening surface to avoid plugging condition. 
         [0004]    In applications with aggressive rotor, screen baskets are subjected to high dynamic loading from the pressure pulsations generated by the rotor. In such applications, ring fatigue failure of wedge wire basket is commonly observed and the mills are often forced to get back to milled slot or drilled baskets, resulting in a loss of capacity and/or efficiency for obtaining acceptable screen basket life. 
         [0005]    Wedge wire baskets are most commonly welded assemblies. Baskets from these constructions suffer to various degrees from distortion, residual stress, stress concentration from welded joint geometry and weld defects, which can normally be associated with most welding processes. 
         [0006]    Among the screen baskets commercially available, the wedge wire baskets are the ones offering the highest open area because of their continuous slots extending over the entire basket length. The accuracy of the cold drawing process used in wire manufacturing can be advantageously used to achieve exceptionally accurate slot width and highly repeatable contour geometry, which contribute in providing better efficiency and capacity than milled slot or drilled baskets. 
         [0007]    Conventional wedge wire screen baskets generally comprise a plurality of wedge wires (profiled bars) that are permanently joined to support rings by various methods. It should be understood by the term “permanently joined” that a destructive method, such as cutting, grinding, chemical attack, etc., would be required to remove the profiled bars. Support rings are necessary to withstand the loading to which the basket is subjected during screening. For severe applications, the screen basket are often reinforced using additional welded or shrink fit rings or backing jacket. 
         [0008]    Some efforts have been made by manufacturers to re-use a portion of the main structure by using replaceable screening elements. However, the manufacturing of these elements is costly and requires several steps and more material at each rebuild. Also, loss in open area is sometimes generated because of the fixing devices such as cage or backing jacket. Finally, the slot and contour accuracy and uniformity are also compromised because of the assembly method. An example of a wedge wire screen basket which has its main structure re-use can be seen in International Patent Application No. WO 02/083263 A1, published Oct. 24, 2002, naming Lutz et al. as the inventors and titled “Screen Cylinder and Method”. 
         [0009]    U.S. Pat. No. 5,791,495, issued to Gero et al. on Aug. 11, 1998 and titled “Paper Pulp Screen Cylinder” describes a basket made with milled bars to obtain a basket with replaceable profiled bars. However, the proposed basket is not provided with continuous slots over the entire basket length, which compromises its capacity. Also, the manufacturing of the profiled bars adapted for the proposed screen basket requires additional steps, such as milling, cutting, and machining. Furthermore, the quantity of parts to be assembled becomes very high because each row requires a set of milled bars. 
         [0010]    U.S. Pat. No. 6,051,103 issued to Aikawa on Apr. 18, 2000 and titled “Paper-Making Screen Apparatus” concerns an inward-flow screen basket provided with both replaceable bars and continuous slots. A drawback of Aikawa&#39;s basket is that a minimum clearance has to be provided between the rod-shaped members and the engaging sections of the support members to allow insertion of the rod-shaped members therein. This clearance may cause the movements of the rod-shaped members in the engaging sections during operations and even vibrations, which in turn can cause fatigue and premature wear of the parts. 
       OBJECTS OF THE INVENTION 
       [0011]    An object of the present invention is therefore to provide an improved screen basket. 
         [0012]    Another object of the invention is to provide a demountable screen basket having replaceable profiled bars which can be locked in place. 
       SUMMARY OF THE INVENTION 
       [0013]    More specifically, in accordance with a first aspect of the present invention, there is provided a screen basket comprising: 
         [0014]    a plurality of profiled bars generally aligned along a longitudinal axis so as to define a slotted cylindrical wall having an inner side and an outer side extending between two longitudinal ends; each of the profiled bars having a radial profiled portion and a radial locking portion joined at an intermediate cross section; the radial locking portion having an irregular cross section including at least one radial cross section wider than the intermediate cross section; and 
         [0015]    a plurality of support ring assemblies, each removably mounted to at least some of the plurality of profiled bars for assembling the plurality of profiled bars into the slotted cylindrical wall; each of the plurality of support ring assemblies including a stack of first and second annular support rings; at least one of the first and second support rings including a plurality of grooves; each groove being configured and sized for complementary receiving the radial locking portion of a respective one of the profiled bars; the first and second support rings being mounted to each other and to the plurality of profiled bars so as to yield a locking force towards the radial locking portion of the profiled bars, thereby locking the profiled bars thereonto. 
         [0016]    According to a second aspect of the present invention, there is provided a method for assembling a screen basket comprising: 
         [0017]    providing a plurality of support ring assemblies including first and second support rings; at least one of the first and second support rings including a plurality of grooves; 
         [0018]    providing a plurality of profiled bars, each having a radial profiled portion and a radial locking portion joined at an intermediate cross section; the radial locking portion having an irregular cross section including at least one radial cross section wider than the intermediate cross section; the radial locking portion being configured for complementary insertion into one of the grooves of first and second support rings; 
         [0019]    inserting the locking portions of the profiled bars into the grooves of the first and second support rings so as to generally align the profiled bars along a longitudinal axis and to define a slotted cylindrical wall having an inner side and an outer side extending between two longitudinal ends; and 
         [0020]    applying a locking force towards the radial locking portion of the profiled bars for releasably locking the profiled bars in the support ring assemblies. 
         [0021]    It is to be noted that the magnitude of the locking force is such that it is several times that generated by pressure differential and pressure pulsations from the rotor of the apparatus into which the screen basket is used, which prevents movement of the profiled bar during normal operation. 
         [0022]    One of the benefits of the present invention is that it provides a basket assembly for which the profiled bars and other parts thereof can be replaced. Some other benefits that also substantially improve screen basket technology are: 
         [0023]    The profiled bar assembly does not require any welding. This provide substantial increase of the profiled bar fatigue strength since it avoids detrimental conditions that can be created in a welded assembly (notches, cracks, distortion, residual stresses, metallurgical problems, etc.). 
         [0024]    The profiled bars are integral, i.e., the assembly does not require any hole that would weaken the bars. 
         [0025]    No forming stress is present in the rings since they are cut round from plate before assembly. 
         [0026]    The present screen basket can be adapted for both inward flow and outward flow basket configurations. 
         [0027]    The present screen basket can also be used advantageously for conical screens or open shape panels such as flat screens, curved section screens, or any imaginable and practical shapes of screens using bar assembly. 
         [0028]    A screen basket according to the present invention is not limited to the paper or pulp industry. It can also be used in other industries using profiled bars to generate a plurality of screening, draining, filtering, classifying or sorting slots such as but not limited to mining, petrochemical, food and beverage, and water treatment industries, in various forms and configurations of screening surface (cylinders, curved sectors, flat sections, etc.). It can further be used in the manufacturing of special drainage rolls. 
         [0029]    Other objects, advantages and features of the present invention will become more apparent upon reading the following non restrictive description of illustrated embodiments thereof, given by way of example only with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    In the appended drawings: 
           [0031]      FIG. 1  is a perspective view of a demountable screen basket according to a first illustrated embodiment of the present invention; 
           [0032]      FIG. 2  is a perspective partly sectional view of  FIG. 1 ; 
           [0033]      FIG. 3  is a partial close-up view illustrating the assembly of support ring assemblies and profiled bars from  FIG. 1 ; 
           [0034]      FIGS. 4A-4B  are isolated radial cross sections of the assembly of one support ring assembly and profiled bars from  FIG. 1 ;  FIG. 4A  illustrating the compressible ring before being compressed and  FIG. 4B  illustrating the compressible ring compressed; 
           [0035]      FIGS. 4C-4D  are cross sections taken respectively along line  4 C- 4 C on  FIG. 4A  and along line  4 D- 4 D on  FIG. 4B ; 
           [0036]      FIGS. 5A and 5B  are isolated radial cross sections of the assembly of a profiled bar and a support ring assembly according to a second illustrative embodiment of the present invention;  FIG. 5A  illustrating the compressible insert before being compressed and  FIG. 5B  illustrating the compressible insert compressed; 
           [0037]      FIGS. 6A and 6B  are isolated radial cross sections of the assembly of a profiled bar and a support ring assembly according to a third illustrative embodiment of the present invention;  FIG. 6A  illustrating the compressible insert before being compressed and  FIG. 6B  illustrating the compressible insert compressed; 
           [0038]      FIG. 7  is a perspective partly sectional view of a demountable screen basket according to a fourth illustrated embodiment of the present invention; 
           [0039]      FIG. 8  is a perspective partly sectional view of a screen basket according to a fifth illustrated embodiment of the present invention; 
           [0040]      FIGS. 9A and 9B  are isolated radial cross sections of the assembly of a profiled bar and a support ring assembly of the screen basket from  FIG. 8 ;  FIG. 9A  illustrating the compressible inserts before being compressed and  FIG. 9B  illustrating the compressible inserts compressed; 
           [0041]      FIGS. 10A and 10B  are isolated radial cross sections of the assembly of a profiled bar and a support ring assembly of a screen basket according to a sixth illustrated embodiment of the present invention;  FIG. 10A  illustrating the open ring opened and  FIG. 10B  illustrating the open ring closed; 
           [0042]      FIGS. 10C and 10D  are isolated top-plan cross sections of the assembly the support ring assembly from  FIGS. 10A-10B  with profiled bars;  FIG. 10C  illustrating the open ring opened and  FIG. 10D  illustrating the open ring closed; 
           [0043]      FIGS. 11 to 13  are top-plan cross sections illustrating back contours for the locking portions and for the corresponding complementary grooves of the support ring assemblies of screen baskets according to seven, eight and ninth illustrative embodiments of the present invention; 
           [0044]      FIGS. 14A-14B  are partial top plan cross sections of a clamping mechanism for a screen basket according to a tenth illustrated embodiment of the present invention;  FIG. 14A  illustrating the clamping mechanism in a mounting position;  FIG. 14B  illustrating the clamping mechanism in a pressed position; and 
           [0045]      FIGS. 15A-15B  are partial side cross sections of the clamping mechanism from  FIGS. 14A-14B ;  FIG. 15A  illustrating the clamping mechanism in a mounting position;  FIG. 15B  illustrating the clamping mechanism in a pressed position. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0046]    In the following detailed description, same or corresponding elements are generally indicated by same reference numerals. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. Also, the entire content of the specification, claims, and drawings of parent application Ser. No. 11/920,139 is hereby incorporated by reference herein. 
         [0047]    Turning now to  FIGS. 1-3  of the appended drawings, a demountable screen basket  10  according to a first illustrated embodiment of the present invention will be described. 
         [0048]    The demountable screen basket  10  comprises a plurality of profiled bars  12  aligned along a longitudinal axis  14  and positioned so as to define a slotted cylindrical wall  15  having an inner side  16 , defining a screening surface, and an outer side  18  both extending between two longitudinal ends  20 , a plurality of support ring assemblies  22  and  22 ′ mounted to the plurality of profiled bars  12  transversally therefrom for assembling the plurality of profiled bars  12  into the slotted cylindrical walls  15 , a pair of annular end flanges  24 , each for receiving a respective end  20  of the plurality of profiled bars  12 , and a plurality of clamping posts  26  secured to both annular flanges  24  for compressing the support ring assemblies  22 . 
         [0049]    As can be better seen from  FIG. 3 , each profiled bar  12  has a profiled portion  28  and a tapered locking portion  30  joined at an intermediate cross section  32 . Turning briefly to  FIG. 4C , the tapered locking portion  30  has two angled faces  31  extending from an outer face  33 , thereby defining a dovetail. 
         [0050]    Each support ring assembly  22  includes a stack of first and second identical support rings  34  provided with equidistanced grooves  36  configured for complementary receiving the tapered locking portion  30  of a profiled bar  12 . Since the locking portions  30  are tapered, the profiled bars  12  are prevented from being released radially. Each profiled bar  12  is however slidable along the support ring assemblies  22  and therefore removably mounted thereto. 
         [0051]    The grooves  36  are located on the inner side diameter of the rings  34  for outward flow screen basket configuration, such as screen basket  10 . For inward flow screen basket configuration (not illustrated), the grooves  36  are located on the outer side diameter of the rings  34 , and the clamping posts  26  are positioned on the inner side of the basket. 
         [0052]    It should be noted that the rings  34  are manufactured before assembly and already include the assembly grooves  36 . 
         [0053]    To ease the mounting of the profiled bars  12  into the grooves  36 , the locking portions  30  and grooves  36  are dimensioned as to yield a clearance. However, this clearance may result in slight movements between the profiled bars  12  and the support ring assemblies  22  and  22 ′ when the screen basket  10  is under stress. 
         [0054]    As will now be described in more detail, the screen basket  10  includes means to bias the locking portions  30  of the profiled bars  12  towards respective contours of the grooves  36  so as to lock the profiled bars  12  therein for applications wherein relative movements of the profiled bars  12  and support ring assemblies  22  can be detrimental. 
         [0055]    The screen basket  10 , as well as any screen basket from the present invention, can be used in a screening apparatus either held fixed or put in constant or intermittent rotation along axis  14 , or put under constant or intermittent vibration or displacement. 
         [0056]    With reference to  FIG. 3 , each support ring assembly  22  includes a compressible insert, in the form of an elastomer ring  38  mounted between the two rings  34 , adjacent to the locking portions  30  of the profiled bars  28 . 
         [0057]    As can be seen from  FIGS. 4A and 4C , the elastomer ring  38 , which has a circular cross section, is initially positioned between the two support rings  34  and around the circumference defined by the profiled bars  12 , after the mounting of the profiled bars  12  into the ring grooves  36 . Then, the two rings  34  are pressed together axially, forcing the insert  38  towards the profiled bars  12  as illustrated in  FIGS. 4B and 4D . This forces the locking portions  30  of the profiled bars  12  towards the grooves  36 , eliminating the above-mentioned clearance, thereby locking the profiled bars  12  into the grooves  36  as discussed hereinabove. 
         [0058]    Even though the elastomer ring  38  is illustrated as having a circular cross section, an elastomer ring having other another regular or irregular cross section, including for example a rectangular cross section, can also be provided. 
         [0059]    Now referring to  FIG. 2 , to press the stack of support rings  34 , each pair of rings  34  are clamped together at preferably equally spaced circumferential locations by the clamping posts  26 . The clamping posts  26  are in the form of combs  26  provided with longitudinal notches  40  for receiving the pair of rings  34 . More specifically, the notches  40  are tapered to thereby axially compressing the pair of rings  34  when they are inserted therein as shown in  FIG. 2 . 
         [0060]    Even though, the clamping combs  26  are illustrated as V or U-shaped elongated members, they can also be tubular for example. The clamping combs  26  can further be in the form of elongated beam-like members provided with V-shaped brackets (not shown) mounted thereon for receiving the support ring assemblies  22 . 
         [0061]    The notches  40  are distributed to locate the support ring assemblies  22  at desired locations along the basket length with uniform or variable spacing, to have for example tighter ring pair spacing in a more critical region of the basket  10 . 
         [0062]    The clamping combs  26  are secured to the end flanges  24  via mounting rods  42 . 
         [0063]    More specifically, the annular end flanges  24  and the rings  34  are provided with respective co-axial holes  44  and  46  for receiving the rods  42 . The rods  42  are provided with longitudinal threaded ends for securing directly into holes in one of the two flanges  22  and for receiving a nut  48  through respective counterbores at the other end. Other means can also be used to removably secure the rods  42  to the flanges  24 . 
         [0064]    Also, the clamping combs  26  can alternatively be positioned so as to show an angle with both the support ring assemblies  22  and  22 ′ and the profiled bars  12  and are thus not limited to the position aligned with the profiled bars  12  illustrated for example in  FIGS. 1-2 . 
         [0065]    Still referring to  FIG. 2 , each of the end support ring assemblies  22 ′, which are mounted at each of the longitudinal end of the clamping combs  34  so as to abut the flanges  24 , include a first grooved ring  34  contacting the combs  26  and a non-grooved ring  50 , having a larger inside diameter than the first grooved ring  34 , contacting a respective flange  24 . A compressible insert  38  is provided between the non-grooved ring  50  and the circumference created by the locking portions  30  of the profiled bars  12  for biasing the bars  12  into the grooves of the rings  34  of the assembly  22 ′, the face of the flange  24  contacting the inside ring  50  acting as a second support ring for compressing onto the insert  38 . 
         [0066]    The thickness of the non-grooved ring  50  is selected so that it is smaller than the uncompressed insert  38 . 
         [0067]    Each of the two end flanges  24  includes a recess  54  on its peripheral inner side for respectively receiving the first and second longitudinal ends  20  of the profiled bars. 
         [0068]    An illustrated method of assembling the basket  10  includes: 
         [0069]    Inserting the profiled bars  12  into the grooves of the support ring assemblies  22 - 22 ′; 
         [0070]    Inserting the inserts  38  within the support ring assemblies  22 - 22 ′; 
         [0071]    Installing the clamping combs  26  onto the support ring assemblies  22 - 22 ′ in line with the holes  46 ; 
         [0072]    While the clamping combs  26  are maintained in place, inserting the rods  42  into the holes  46 , thereby locking the combs  26  in place; and 
         [0073]    Securing the end flanges  24  as described hereinabove. 
         [0074]    Other method of assembling the basket  10  can also be used. 
         [0075]    A person skilled in the art will appreciate that the basket  10  is completely demountable. Therefore, when worn or broken components of the basket  10  need to be replaced, the basket  10  can be disassembled so as to remove these components and reuse the other, still usable, components. 
         [0076]    It has been found that any elastomeric material having a Young&#39;s modulus lower than about 20 GPa is suitable to be used as the insert. 
         [0077]    Even though the basket  10  is illustrated with equally distanced clamping combs  26 , a screen basket according to the present invention can be provided with unequally spaced clamping combs  26 . 
         [0078]    Also, the number of profiled bars  12 , support ring assemblies  22  and/or  22 ′, and clamping combs  26  may vary. 
         [0079]    Furthermore, even though the screen basket  10  has been described as a screen suitable for outward flow, it is believed to be within the reach of a person skilled in the art to adapt the present teaching for an inward flow application. For example, in such a case, the support ring assemblies  22  and  22 ′ and the clamping combs  26  are positioned on the inner side of the cylinder formed by the profiled bars  12 , with the profiled portions thereof located on the outside of the cylinder. 
         [0080]    Also, the support ring assemblies can take many forms.  FIGS. 5A-5B  illustrates a support ring assembly  56  according to a second illustrated embodiment of the present invention. Since the support ring assembly  56  is similar to the support ring assembly  22 , and for concision purposes, only the differences between the two assemblies  56  and  22  will be described herein in more detail. The compressible insert  58  is in the form of a wide ring having a rectangular cross section and a width similar to the width of the rings  34 . Again, the insert  58  is forced against the profiled bars  12  when the two metallic rings  34  are pressed together. 
         [0081]      FIGS. 6A-6B  illustrates a support ring assembly  60  according to a third illustrated embodiment of the present invention. Since the support ring assembly  60  is similar to the support ring assembly  22 , and for concision purposes, only the differences between these two assemblies  60  and  22  will be described herein in more detail. The support ring assembly  60  includes a compressible insert  62  in the form of a narrow ring having a width preferably smaller than the width of the metallic rings  34  and characterized by a thickness at rest. The assembly  60  further includes an intermediate ring  64  positioned between the support rings  34  and having a thickness smaller than the insert  62  thickness at rest. The insert  62  is forced against the profiled bars  12  when the stack of metallic rings  34  and  64  is axially compressed. 
         [0082]    Turning now to  FIG. 7  of the appended drawings, a demountable screen basket  66  according to a fourth illustrative embodiment of the present invention will be described. Since the screen basket  66  is very similar to the screen basket  10 , and for concision purposes, only the differences between the two screen baskets  10  and  66  will be described herein in more detail. 
         [0083]    The screen basket  66  further includes fasteners  68  for pressing the two rings  34  together axially and then forcing the insert  38  towards the profiled bars  12  as illustrated in  FIGS. 4B and 4D . The fasteners  68  can take any form including rivets, bolts, clips, etc. 
         [0084]    The use of such fasteners  68  allows limiting the number of clamping combs  26  and rods  42 . 
         [0085]    A screen basket  70  according to a fifth illustrative embodiment of the present invention will now be described with reference to FIGS.  8  and  9 A- 9 B. Since the screen basket  70  is very similar to the screen basket  10 , and for concision purposes, only the differences between the baskets  10  and  70  will be described in more detail. As will now become more apparent, the main difference between the two baskets  10  and  70  is the support ring assemblies  72  of the screen basket  70  which differ from the support ring assemblies  22 . 
         [0086]    Each support ring assembly  72  includes first and second integral rings  74  which, similarly to the rings  34  of the basket  10 , extend along all the periphery of the basket  10 , and an intermediary grooved disk  76 , which is made of a plurality of angular segments  78 , mounted between the first and second rings  74 . 
         [0087]    The grooved disk  76  includes grooves  36  for complementary receiving the locking portions  30  of the profiled bars  12  as discussed hereinbelow in more detail. 
         [0088]    The support ring assembly  72  further comprises two compressible inserts in the form of rings  38  positioned between a respective support ring  74  and grooved disk  76  adjacent to the profiled bars  12 . The inner side of each support ring  74  is provided with a chamfer  80  for biasing the inserts  38  towards profiled bars  12  when the support ring assembly  72  is compressed as illustrated in  FIG. 9B . Also, as illustrated in  FIG. 9B , the support ring assembly  72  allows forcing the locking portion of the bars  12  towards the grooves  36 , providing the locking effect discussed in further detail hereinabove. 
         [0089]    Of course, the support rings  74  and intermediary ring  76  are provided with holes  82 , similar to holes  46  of the basket  10 , for securing the rods  42 . To provide better stability, the holes  46  are positioned so that each segment  78  includes at least one hole and therefore receives at least one rod  42 . Moreover, the joints  84  between two segments  78  are preferably offset for two adjacent support ring assemblies  72 . 
         [0090]    The use of a grooved disk  76  made of segments  78  allows minimizing the lost of material. For example, when only a portion of the disk  76  is damaged, only the corresponding segments can be changed. 
         [0091]    The number of sections  78  forming the grooved disk  76  may of course vary. Typically, 6 angular segments  78  are used. 
         [0092]    Turning now to  FIGS. 10A-10D , a support ring assembly  86  for a screen basket according to a sixth illustrative embodiment of the present will now be described. Since the support ring assembly  86  is very similar to the support ring assembly  72 , only the differences between these two assemblies, relating mainly to the support ring assembly, will be further described herein. 
         [0093]    Instead of compressible inserts, such as the elastomer rings  38 , the support ring assembly  72  includes open rings  88 , having a triangular cross section for respective complementary insertion in the chamfers  80 . 
         [0094]    As illustrated in  FIG. 10C , the rings  88  are sized so as to yield a gap  92  between its two extremities  90  when no pressure is exerted onto the two exterior support rings  74 . However, when such a pressure is exerted onto the support rings  74  (see arrow  94  in  FIG. 10C ), its diameter shrinks, as allowed by the gap  92 , bringing the two extremities  90  towards each other (see arrows  96 ) and immobilizing the locking portion of the bars  12  into the grooves  36 . 
         [0095]    The open rings  88  can be made for example of metal. 
         [0096]    It is to be noted that the rings  88  can be replaced by any other suitable elements or materials which expand in a confined space. 
         [0097]      FIGS. 11 to 13  illustrate examples of back contours for the locking portions and for the corresponding complementary grooves of the support ring assemblies of screen baskets according to seven, eight and ninth illustrative embodiments of the present invention. In all three cases, since the grooves contours are complementary to the locking portion contours and therefore identical in shape, only the locking portion contours will be described herein in more detail. 
         [0098]      FIG. 11  shows a first alternate configuration of locking portions  98  characterized by having an outer or abutting face  100 , a first face  102  extending generally perpendicularly from the outer face  100 , and a second face  104  opposite the first face  102 , extending at an angled therefrom. 
         [0099]      FIG. 12  illustrates locking portions  106  having multiple teeth  108  on both sides.  FIG. 13  illustrates locking portions  110  with multiple teeth  112  on a single side, the other opposite side  114  being generally planar. 
         [0100]      FIGS. 14A-14B  and  15 A- 15 B illustrate a clamping mechanism  116  according to a tenth illustrated embodiment of a screen basket of the present invention. Since the screen basket according to this tenth illustrated embodiment is very similar to the screen basket according to the second illustrated embodiment (see  FIGS. 5A-5B ), and for concision purposes, only the differences between these two embodiments will be described herein in more detail. 
         [0101]    The clamping bar  116  includes sequentially alternating integral narrow portions  118  and wide portions  120 . 
         [0102]    As illustrated in  FIGS. 15A and 15B , the narrow portions  118  have a height slightly less than the overall thickness of the two support rings  34  with the insert  58  when the support ring assembly  56  formed thereby is not compressed (see  FIG. 15A ) and generally corresponding to the overall thickness of the support ring assembly  56  when it is compressed (see  FIG. 15B ). 
         [0103]    Each wide portion  120  has a height generally corresponding to the inter-space between two adjacent support ring assemblies  56 . 
         [0104]    Elongated holes  122  are provided in both the support rings  34  and inserts  58  at generally equally distanced circumferential position to receive the plurality of clamping posts  116 . 
         [0105]    As illustrated in  FIGS. 14A and 15A , the elongated holes  122  are configured and sized to receive the posts  116  when the posts are oriented along the elongated side of the holes  122 . 
         [0106]    As illustrated in  FIGS. 14B and 15B , the clamping posts  116  are then rotated 90 degrees from mounting position to obtain a pressed position (see arrows  124  on  FIG. 14B ). This rotation forces the wide portions  120  to engage over the support ring assemblies  56 , thereby exerting a force onto the support ring assemblies  56  (see arrows  126 ). While in this pressed position, the support ring assemblies  56  are therefore compressed, yielding the locking effect described hereinabove in more detail. 
         [0107]    The clamping post  116  can then be removably secured to the end flanges (not illustrated). 
         [0108]    The present invention is not limited to a screen basket having support disk assemblies provided with two (2) or three (3) support rings. For example, four, or more rings pressed together with deformable inserts placed between some of those rings to obtain stronger joints can be provided. It is also possible for example to use a single support ring located at a certain distance in between two ring pairs. One or more rings could also be added to a ring pair without adding supplementary compressible insert. 
         [0109]    A screen basket according to the present invention can be provided with profiled bars, support ring assemblies or support conforming to any shape or contour and clamping posts so configured and sized as to yield a screening surface which is flat, curved, stepped, conical, etc. 
         [0110]    A screen basket having different combinations of aspects of the above illustrated embodiments can also be provided according to the present invention. 
         [0111]    Even though the screen baskets according to the illustrated embodiments are all completely demountable, it is believed to be within the reach of a person skilled in the art to modify one of the illustrated screen baskets and/or use the above teaching to provide a screen basket which is only partly demountable so as to recycle only parts of its components for example. 
         [0112]    Although the present invention has been described hereinabove by way of illustrated embodiments thereof, it can be modified without departing from the spirit and nature of the subject invention, as defined in the appended claims.