Abstract:
A sieve tray for a sieve device that includes at least one sieve netting. The sieve netting includes wire netting having warp and weft wires mutually connected in a weave. The weave has mutually spaced alternating crossings extending diagonally with respect to the warp and weft wires.

Description:
CROSS-REFERENCE 
   This non-provisional application claims benefit of German Application Number 1889 24344DE filed on Jun. 6, 2002, which disclosure is hereby incorporated by reference herein. 
   BACKGROUND AND SUMMARY OF THE INVENTION 
   The present invention relates to sieve trays for a sieve devices. These sieve trays usually have at least one sieve netting consisting of a wire netting, and each wire netting contains warp and weft wires mutually connected by a weave. 
   The above-referenced sieve trays are known in many constructions. Each sieve tray has an upper sieve netting, relative to an installed position, and a supporting netting, situated below, which has a larger mesh size. The mesh sizes of the sieve nettings depend on the sizes of the particles to be sieved. The sieve trays normally have a round or square design. Frequently, the sieve trays are also provided with tensioning edges in order to tension the sieve netting either transversely to the flow direction of the material or in the longitudinal direction of the material. The so-called tensioning edges are also known in various constructions. In order to separate particles from a material such as a liquid, an emulsion, or the like, two different methods are known. There is sieving by a sieve device or filtering by a filter device. For the sieving, the above-mentioned sieve tray can be used which, by a vibration generator, is caused to carry out a swinging motion. 
   In the case of the above-mentioned sieve trays, the wire netting may consist exclusively of warp wires and weft wires which extend at a right angle thereto. As a result, square meshes or openings are created in the projection. Such sieve trays have been very successful but are not completely satisfactory for certain applications, such as the sieving of particles of a certain size from an emulsion. 
   An aspect of the present invention is having a sieve tray configured such that particles of a certain size can be sieved out of a material, such as a liquid, an emulsion or the like. 
   This aspect, at least, is addressed by having sieve netting that is provided with mutually spaced alternating crossings situated diagonally to warp and weft wires. 
   The size of meshes or openings are no longer necessarily determined by spaces between the warp and weft wires but gores are formed which are no longer square. The size of the gores is a function of the positions of the alternating crossings with respect to the warp and weft wires. The warp and weft wires may be in contact with one another in a twill-lace weave. The alternating crossings additionally contribute to stabilization of the sieve netting because they also include wires. 
   In a preferred embodiment, the alternating crossings extend in a zigzag shape from one edge to the opposite edge. The alternating crossings extend from the edges which extend parallel and at a distance from the warp wires. The zigzag-shaped course of the alternating crossings additionally increases the stability, so that the service life of a sieve tray can be extended. So that a uniform mesh size is achieved over the entire sieve surface, each straight-lined section of the alternating crossings extends over a constant number of warp wires. In a preferred embodiment, in which the warp wires and the weft wires are situated at equal mutual distances and therefore form square meshes, the straight-lined sections of the alternating crossings also extend over the same number of weft wires as warp wires. The individual straight-lined sections of the alternating crossings will then be situated at an angle of 45° with respect to the warp and weft wires. In a preferred embodiment, the straight-lined sections of the alternating weft wires maximally extend, for example, over 20 warp wires. 
   In a preferred embodiment, the weaves of the warp and weft wires are zz-weaves. As a result, favorable conditions are obtained for the weaves of the alternating crossings. In a preferred embodiment, a side change of the warp wires takes place when they have skipped a certain number of weft wires, and this number corresponds to the warp wires skipped by the weft wires. In a preferred embodiment, the number of skipped warp wires amounts to two. The respective sections of the warp and the weft threads situated on one side are offset from one warp wire to the next warp wire by one weft wire. The sections of the weft wires situated on one side are also offset with respect to one another by one warp wire from one weft wire to the next. 
   Depending on the construction, the diameters of the warp wires  14  and the weft wires  15  may be the same as or coincide or approximately coincide, but may also be different. The diameters of the alternating crossings may coincide with or be the same as the diameters of the warp wires and, if the diameters of the weft wires deviate therefrom, may also coincide with or be the same as the diameters of the weft wires or approximately coincide. However, constructions are also conceivable in which the diameters of the alternating crossings deviate from the diameters of the warp wires as well as of the weft wires. Depending on an application&#39;s purpose, a supporting netting also can be functionally assigned to the sieve netting. The mesh width of this supporting netting is normally larger than that of the sieve netting. 
   The sieve trays are considered to be fine-meshed. So that a uniform tension is ensured along the entire width or the entire length, the sieve tray is equipped with one tensioning edge respectively on two mutually opposite sides, which tensioning edge is formed by shaping. As an alternative, the sieve netting may also be clamped onto a frame. For compensating tension differences in the sieve netting, a flexible element, preferably a plastic element, may be worked into at least one tensioning edge. 
   The invention will be better understood and appreciated from the following detailed descriptions and with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a sieve tray, according to the principles of the present invention. 
       FIG. 2  is a top view of a starting product of a wire netting of a sieve tray, according to the principles of the present invention. 
       FIG. 3  is a sectional view of a weft wire and warp wires of the wire netting of  FIG. 2 . 
       FIGS. 4–6  are dobby cards in three different embodiments, according to the principles of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an embodiment of a sieve tray  10  having a sieve netting  11 . On two mutually opposite sides, the sieve tray  10  is provided with one tensioning edge  12 , 13  respectively, with each being of an essentially U-shaped design and essentially facing each other. Free end areas of the tensioning edges  12 ,  13  are bent in opposite directions and each contacts an area of it&#39;s own tensioning edge  12 ,  13 , respectively. Optionally, flexible plastic elements (not shown) can be worked into each tensioning edge  12 ,  13  in order to absorb tension differences in the sieve netting  11 . As shown in  FIG. 1 , the tensioning edges  12 ,  13  are provided on shorter sides of the tray  10 . In contrast to this construction, the tensioning edges  12 ,  13  may be shaped onto the longer sides (not shown). 
     FIG. 2  shows a starting product of the sieve netting  11  of  FIG. 1 , which is formed of warp threads or wires  14  and of weft threads or wires  15 . The warp wires  14  and the weft wires  15  are interwoven in a zz-weave. A wire netting  11  as shown in  FIG. 2 , is considered to be an example in which warp threads  14  and the weft threads  15  are arranged at a same mutual spacing so that square meshes  17  are obtained. In the embodiment of  FIG. 2 , a side change of the warp thread  14  takes place when the warp threads  14  have skipped two weft threads  15 . The side change of the weft threads  15  takes place in a similar manner; that is, when two warp threads  14  have been skipped.  FIG. 2  also shows that the side change of the warp threads  14  and of the weft threads  15  of two successive wires  14  or  15  is, in each case, offset by one wire  14  or  15 , respectively. 
     FIG. 3  shows a cross-sectional view of a weft wire interwoven with warp wires  14 . 
     FIGS. 4–6  show dobby cards representing embodiments of wire nettings  18 – 20  of  FIG. 2  that are equipped with alternating crossings  16  situated diagonally with respect to the warp wires  14  and the weft wires  15 . The alternating crossings  16  extend at an angle of 45° with respect to the warp wires and to the weft wires  15 . Spacing of the alternating crossings  16  is equal to two warp wires  14  and two weft wires  15  respectively. As a result, a fishbone-type pattern of the sieve netting  11  of  FIG. 2  is obtained.  FIGS. 4 to 6  show that the alternating crossings  16  extend in a zigzag shape. Each straight-line area to a change maximally skips, for example, 20 warp threads  14 . In the embodiments of  FIGS. 4–6 , the alternating crossings  16  have the same diameter as the warp wires  14  and the weft wires  15 . However, mutually deviating or different diameters are also conceivable. 
   The present invention is not limited to the embodiments described and shown herein. Other embodiments are possible that also have the sieve netting  11  equipped with alternating crossings  16  extending diagonally to the warp wires  14  and the weft wires  15 . 
   Although the present disclosure has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The spirit and scope of the present disclosure are to be limited only by the terms of the appended claims.