Abstract:
A vibrating screen for conducting material in a longitudinal direction while screening the material comprises a screening deck, exchangeable modular screening media, and an adapter arrangement for mounting the screening media on the deck. The screening deck includes transverse carriers oriented transversely of the longitudinal direction. The adapter arrangement comprises longitudinal support carriers arranged substantially in the longitudinal direction, and connecting elements oriented transversely of the longitudinal direction for interconnecting the support carriers and connecting the interconnected support carriers on the transverse carriers.

Description:
The present application claims priority under 35 U.S.C. §119 to Patent application Ser. No. 0400789-4 filed in Sweden on Mar. 27, 2004. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to an adapter arrangement for mounting cross-tensioned or pre-tensioned screening media on a screening deck, normally provided with a special sub-frame, and to exchangeable modular screening elements for screening of material, such as crushed stone, gravel or the like. 
   In mining and stone industries, it is often important to fractionate crushed stone and gravel into fractions of stones with different sizes. Mostly, fractionating is done by supplying an unfractionated stream of crushed stone or gravel to a vibrating screen provided with screening elements having screening holes for allowing stones smaller than the screening holes to pass through the holes. 
   Today, there are vibrating screens that are manufactured to use only cross-tensioned or pre-tensioned screening media. The cross-tensioned screening media can be either wire mesh screening media or polyurethane/rubber screening media with reinforcement. The pre-tensioned screening media can either be made of a metal sheet or be made of polyurethane/rubber material in a frame with metal reinforcement. The wire mesh screening media has the advantage that it is easy to mount, cheap and has the highest percentage open area. 
   The cross-tensioned screening media is bought in the desired length and hooks or other fastening means are attached on the two opposite sides of the screen by simple actions. The cross-tensioned screening media is mounted in the vibrating screen with the hooks or the fastening means attached to fastenings means on the side walls of the vibrating screen. 
   Several support beams are arranged between the side walls of the vibrating screen having their longitudinal direction parallel to the side walls of the vibrating screen. The support beams are arranged at different heights in order to support the cross-tensioned screening media between the side walls of the vibrating screen, causing the cross-tensioned screening media to have a crowned or slightly upwardly curved shape and to support the cross-tensioned or pre-tensioned screening media when being mounted. These vibrating screens have the disadvantage that they are manufactured to only have cross-tensioned screening media, and the wire meshes are not suitable for running larger batches since they have shorter lifetime compared with vibrating screens having screening media made of polyurethane (PU) or rubber. 
   There are also vibrating screens having screening decks with modular screening elements, e.g. as described in SE-A-0 460 340 (corresponding to U.S. Pat. No. 5,085,324). This document shows a system with modular screening elements in a vibrating screen for screening of crushed rocks or gravel. The vibrating screen according to this document includes a multitude of screening elements. The modular screening elements and cross-tensioned polyurethane/rubber screening media are more expensive than the wire mesh screening media, but they have a longer lifetime. The modular screening elements are, however, supplied from the specific manufacture of the system of modular screening elements and therefore not as easily accessible as the cross-tensioned screening media. There are also manufacturers that deliver specific manufactured modular elements with a pre-tensioned screening media, e.g. the WS 83 module for the WS S5 modular screening system from the company Isenmann. The latter has the disadvantage of being more expensive than cross-tensioned wire mesh. 
   Another vibrating screen with exchangeable modular screening elements is shown in the Swedish patent application, SE0400337-2, “Screening deck”. 
   In many cases, especially in the set-up of the vibrating screen, there is a need for running-in the screening deck of the vibrating screen in respect of the size of the screening holes. It might also be the case that a small batch of crushed stones or gravel should be fractionated with a specific size of the holes. In both cases there is a need for a quick, temporary and cheap solution. The cross-tensioned screening media is the best solution in these cases, but the present vibrating screens require to be substantially re-built before can be used with the cross-tensioned screening media if they are of the modular type. If they already are of the cross-tensioned screening media type, they have the disadvantage of not being able to use modular screening elements after the running-in period due to the construction with support beams arranged at different heights. 
   A difference between wire mesh and the cross-tensioned or the pre-tensioned screening media of polyurethane (PU) or rubber is that the wire mesh provides a larger open area, i.e. an area used for screening. This is caused by the fact that cross-tensioned and pre-tensioned screening media are provided with larger closed areas between the holes to get enough rigidity in the screening media, whereas the wire mesh has enough rigidity in wires forming the wire mesh and need not additional material between holes. The cross-tensioned or the pre- tensioned screening media of polyurethane (PU) or rubber needs also reinforcement material, e.g. wires, incorporated in the polyurethane (PU) or rubber to get enough rigidity. 
   Faced with the above prior art screening systems and the disadvantages and problems therewith, the object with the present invention is to improve the screening systems in a way that combines the advantages of the system with modular screening elements and the system with cross-tensioned screening media. 
   Another object of the present invention is to provide a way of providing a vibrating screen with a sub-frame for modular screening elements at the time it is provided with cross-tensioned or pre-tensioned screening media. 
   SUMMARY OF THE INVENTION 
   The above-mentioned objects are achieved by an adapter arrangement, which comprises longitudinal support carriers for supporting the cross-tensioned or pre- tensioned screening media, and connecting elements for connecting the support carriers to transverse carriers of the screening deck. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention will be explained with reference to the accompanying drawings, wherein 
       FIG. 1  is a schematic perspective assembly view of a prior art screening deck with modular screening elements, 
       FIG. 2  is a schematic perspective assembly view of a prior art screening deck with a cross-tensioned screening media, 
       FIG. 3  is a schematic perspective assembly view of a screening deck with modular screening elements and the adapter arrangement according to the present invention, 
       FIGS. 4A ,  4 B,  4 C are perspective views of first, second and third adapter parts, respectively, of the adapter arrangement according to the present invention, 
       FIG. 5  is a perspective view of a support carrier in the adapter arrangement according to the present invention, 
       FIGS. 6A ,  6 B, and  6 C are cross-sectional views taken at circles a, b, c, respectively in  FIG. 6D , showing how first, second, and third connecting elements, respectively, are attached to transverse carriers, 
       FIG. 6D  is a side elevational view showing a transition between screening elements according to the present invention, 
       FIG. 7  is a schematic perspective assembly view of a vibrating screen having a screening deck with both modular screening elements and the cross-tensioned or pre-tensioned screening media, where the screening media has been mounted by means of an adapter arrangement according to the present invention, and 
       FIG. 8  is a schematic perspective assembly view of a screening deck with longitudinal carriers for holding modular screening elements, where a cross-tensioned or pre-tensioned screening media have been mounted by means of an adapter arrangement according to the present invention. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  schematically shows a prior art screening deck  100  in a vibrating screen for screening of crushed stones, gravel or the like comprising exchangeable modular screening elements  110  and transverse carriers  120 . The modular screening elements  110  differ in height to improve the screening of crushed stones or gravel. The modular screening elements  110  are normally alternately placed so that the neighboring screen elements always will be at different heights. Each carrier  120  has two parallel, elongated stanchions  130   a ,  130   b . The modular screening elements  110  have snap locks  140 , which interact with the elongated stanchions  130   a ,  130   b  for fastening the screening elements to the transverse carriers  120 . The transverse carriers  120  are fastened by bolting, welding or other suitable fastening means to cross members (not shown) arranged in a vibrating screen mechanism. In a surface  150  of the modular screening element  110 , through-holes H have been provided for fractionating crushed stone and gravel into fractions of stones with different sizes. A longitudinal direction of the screening deck is indicated with an arrow A in  FIG. 1 . The longitudinal direction of the screening deck is also the travelling direction for the material, i.e. stones or gravel, on the vibrating screen. 
     FIG. 2  schematically shows a part of a prior art vibrating screen  250 , where a cross-tensioned screening media  200  has been mounted. The screen  250  comprises a hook arrangement  210  in each end of the screening media  200 . Fastening means  220  fasten the hook arrangements  210  to the walls  230  of the vibrating screen. 
   The means for fastening the screening media  200  to the vibrating screen  250  or the side walls  230  of the vibrating screen  250  can be designed in many ways, e.g. the hook arrangement shown or a screw/bolt joint etc., but is not part of the present invention. The hook arrangement is typically jammed over the edges of the screening media  200  and fixed by a bolt and nut arrangement. If pre-tensioned screening media is to be used in the vibrating screen, the fastening means  220  will only have a down- holding function, whereas the fastening means have an outwardly stretching function when using cross-tensioned screening media to form the crowned shape of the screening media. 
   The fastening means  220  are flexibly mounted by a bolt arrangement or similar. The fastening means  220  also have a second function in that they function as side covers in the vibrating screen protecting the vibrating screen from wear due to the material being screened. When the modular screening elements are mounted in a vibrating screen (see  FIG. 7 ), special cover plates  820  can instead be mounted on the side walls to protect the vibrating screen from wear caused by the material being screened. 
   Further, supporting carriers  240  are shown in  FIG. 2  that are mounted rigidly in the vibrating screen  250  to support the screening media. The supporting carriers  240  are arranged substantially parallel to the longitudinal direction A of the vibrating screen  250 . The difference in height of the support carriers  240  can be seen from a virtual reference line B extending from the fastening points of the screening media  200  to the side walls of the vibrating screen  250 . Due to the difference in height of the support carriers  240  the screening media  200  will form a crowned or slightly curved shape as is shown in  FIG. 2 . 
     FIG. 3  schematically shows the screening deck after two rows of modular screening elements have been removed and an adapter arrangement  300  has been mounted, in accordance with the present invention. The adapter arrangement  300  comprises longitudinal support carriers  310 , first connecting elements  320 , second connecting elements  330 , third connecting elements  390  and cappings  340 . 
   As is shown in  FIGS. 6A-6D  each of the longitudinal support carriers  310  extends between two transverse carriers  120  and is provided with snap locks  410 ,  420  (also shown in  FIG. 5 ) at each end to interact with fastening means  321 ,  322 ,  331 ,  391  on respective first, second and third connecting elements  320 ,  330 ,  390 . Each of the first, second and third connecting elements  320 ,  330 ,  390  is provided with snap locks  350 ,  360 ,  380  and  392 , respectively, at its underside ( FIG. 3 ). The snap locks interact with the elongated stanchions  130   a ,  130   b  for fastening the first, second and third connecting elements  320 ,  330 ,  390  to the transverse carriers  120 . 
   The cappings  340 , shown in  FIG. 3 , are arranged on the upper edge of the supporting carriers  310  facing the screening media and protect the support carriers  310  from wear from the screened material and also from the screening media. In  FIG. 3  the cappings  340  are shown as extending over two adjacently arranged longitudinal support carriers  310  that are interconnected by a first connecting element  320 , but the length of the cappings  340  can instead be equal to the length of a single support carrier  310 . In  FIG. 7  it is shown that the cappings  340  extend over three adjacently arranged support carriers  310 . 
   In  FIG. 3  an adapter arrangement is schematically shown, only covering a part of the length of the transverse carriers  120 , but in practice the adapter arrangement  300  will be mounted along the entire length of the transverse carriers  120  (see  FIG. 7 ) to fully function as support for the mounting of screening media on the screening deck. The cross-tensioned screening media typically extends between the side walls of the vibrating screen, a length which substantially equals the length of the transverse carriers  120 . 
     FIGS. 4 ,  4 B,  4   c  show a first set of adapter parts, the adapter parts including a first connecting element  320 , a second connecting element  330 , a third connecting element  390 . In  FIG. 4A  it is shown that the first connecting element  320  further is provided with a slot  370  having fastening means  321 ,  322  for receiving the respective ends of two support carriers  310 . The fastening means  321  is partly shown, but the fastening means  322  is concealed in  FIG. 4 . Both fastening means  321 ,  322  are shown in  FIG. 6 . The fastening means  321 ,  322  are arranged to interact with snap locks  420 ,  410 , respectively, of the support carriers  310 . In  FIG. 4  is also shown that the snap locks  350 ,  360  are arranged to adapt to the difference in height between the stanchions  130   a ,  130   b.    
   In  FIG. 4B , it is shown that also the second connecting element  330  is provided with a slot  385  having fastening means  331  (concealed in  FIG. 4 , but shown in  FIG. 6 ) for receiving the snap lock  410  arranged at the end of the support carriers  310 . The second connecting element  330  is also provided with a snap lock  380  at its underside. The snap lock  380  interacts with the shorter, elongated stanchion  130   a  on the transverse carrier  120  for fastening the second connecting elements  330  to the transverse carrier  120 . The second connecting element  330  is typically used as an end element of the adapter arrangement, adjacent to modular elements  110  (see  FIGS. 3 and 6 ). 
   In  FIG. 4C  the third connecting element  390  is shown as provided with a slot  393  having fastening means  391  (concealed in  FIG. 4 , but shown in  FIG. 6 ) for receiving the snap lock  420  arranged at the end of the support carriers  310 . The third connecting element  390  is also provided with a snap lock  392  at its underside. The snap lock  392  interacts with the longer, elongated stanchion  130   b  on the transverse carrier  120  for fastening the third connecting element  390  to the transverse carrier  120 . The third connecting element  390  is typically used as an end element of the adapter arrangement, adjacent to the end of the screen (see  FIGS. 4 and 6 ). 
   As an alternative to the configuration to the first set of adapter parts shown in  FIG. 4 , a second set of adapter parts can be used, adapted to transverse carriers having stanchions of equal height. This alternative configuration of the first, second and third connecting element would otherwise have the same functional structure as the earlier described first, second and third connecting elements  320 ,  330 ,  390 . 
   In  FIG. 5  a support carrier  310  is shown having two snap locks  410 ,  420  provided at its two ends. The support carrier  310  has an upper edge or side  430 , where a capping  340  (shown in  FIG. 3 ) would be mounted to protect the support carrier  310  from the screened material and the screening media. The support carrier  310  is further configured: (i) so that the snap lock  410  interacts with the fastening means  331  of the second connecting element  330  or the second fastening means  322  on the first connecting element  320 , and (ii) so that the snap lock  420  interacts with the fastening means  391  of the third connecting element  390  or the first fastening means  321  on the first connecting element  320 . 
   The longitudinal support carriers  310  preferably have different heights to support the screening media in a manner forming the crowned or slightly upwardly curved shape, when mounted. Typically the support carriers  310  arranged closest to the side walls of the vibrating screen will be lower in height than the support carriers arranged halfway between the side walls to create the slightly upwardly curved shape of the cross-section of the screening media. The support carriers  310  also serve to support the screening media, when it is mounted. 
   As an alternative to having longitudinal support carriers  310  of different heights to create the slightly upwardly curved shape of the cross-section of the screening media, all support carriers  310  could have the same height and the cappings  340  could be of different respective heights to create the same effect. Cappings of different heights will be further discussed in connection with a vibrating screen having longitudinal carriers to hold modular screening elements, where the longitudinal support carriers  310  and the adapter parts are not needed. 
     FIGS. 6A-6C  show respective cross sections of the adapter arrangement  300  mounted on transverse carriers  120 . The adapter arrangement  300  comprises: (i) two of the support carriers  310  joined together by a first connecting element  320 , (ii) a second connecting element  330  to which one end of the support carriers  310  has been fastened, (iii) a third connecting element to which an opposite end of the support carriers  310  has been fastened, and (iv) a capping  340  mounted on top of the two support carriers. In  FIGS. 6A ,  6 B and  6 C it is shown how the respective first, second and third connecting elements  320 ,  330 ,  390  are attached to the transverse carriers  120  and how the support carriers  310  are attached to the first, second and third connecting elements  320 ,  330 ,  390 . Further  FIG. 6D  shows the transition between screening elements  110  and the adapter arrangement  300  for the screening media. 
   In  FIG. 7  a screening deck  100  of a vibrating screen  800  according to the invention is shown schematically, after three rows of modular screening elements  110  have been removed and a cross-tensioned screening media  810  has been mounted on top of the adapter arrangement  300 . Even though only one screening media  810  is shown in  FIG. 7  covering three rows, it is possible to use several screening media with possibly different hole sizes or different configuration of the holes extending between the side walls that are mutually parallel to and successively arranged in the longitudinal direction of the vibrating screen  800 . 
   In  FIG. 8  a screening deck  900  is shown after modular screening elements  110  have been replaced by a cross-tensioned screening media  920  (i.e., the vibrating screen combines different types of screens). On the top edge of longitudinal carriers  910 , cappings  940   a ,  940   b ,  940   c  are arranged facing a cross-tensioned screening media  920  and protecting the support carriers  900  from wear from the screened material and also from the cross-tensioned screening media  920 . Similar to the transversal carriers  120 , the longitudinal carriers  910  are provided with two parallel, elongated stanchions. The stanchions have the same height. The modular screening elements  110  have snap locks  140 , which interact with the elongated stanchions for fastening the modular screening elements  110  to the longitudinal carriers  910 . The cappings  940   a ,  940   b ,  940   c  are provided with similar snap locks, which interact with the elongated stanchions for fastening the cappings  940   a  to the longitudinal carriers. To form the crowned or the slightly curved shape of the screening media and support the cross-tensioned screening media  920 , the cappings  940   a  have different heights. The screening media  920 , which also can be a pre-tensioned screening media, is fastened by any previously disclosed fastening method. 
   When the vibrating screens are very wide, there would be provided an additional holding-down or fixing point with down holding means for holding down the middle of the cross-tensioned screening media so that the crowned shape is not so high as to cause the material being screened to deviate to the sides and producing poor screening results. Thereby two crowned shapes are arranged with the cross-tensioned screening media over the width of the vibrating screen. 
   It is an advantage if modular screening elements and one or several screening media can be provided in the same vibrating screen as shown in  FIG. 7 , since the two solutions complement each other. Modular screening elements are very good since they have a long lifetime, and wire meshes are very good for screening the gravel into the right fractions of gravel. It is therefore an advantage that both types can be combined in the same vibrating screen by simple actions. 
   The present invention is implemented in a vibrating screen of the type shown in the Swedish patent application, SE0400337-2, but could of course be modified to function with other vibrating systems having exchangeable modular screening elements without deviating from the scope of the invention. 
   Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, modifications, substitutions and deletions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.