Patent Publication Number: US-8967516-B2

Title: Wear tip holder for a VSI crusher, a kit comprising a wear tip holder, and a method of reducing the wear rate of a wear tip holder

Description:
RELATED APPLICATION DATA 
     This application is a §371 National Stage Application of PCT International Application No. PCT/EP2012/066753 filed Aug. 29, 2012 claiming priority of EP Application No. 11182571.7, filed Sep. 23, 2011. 
     FIELD OF THE INVENTION 
     The present invention relates to a wear tip holder for holding a wear tip adjacent to an outflow opening of a vertical rotor wall of a rotor of a VSI crusher. The invention also relates to a kit comprising such a wear tip holder, and to a method of reducing the wear rate of a wear tip holder. 
     BACKGROUND OF THE INVENTION 
     Vertical shaft impact crushers (VSI crushers) are used in many applications for crushing hard material, such as rocks, ore etc. A VSI crusher comprises a housing and a horizontal rotor located inside the housing. WO 2008133568 (A1) discloses an example of a rotor of a VSI crusher. Material that is to be crushed is vertically fed into the rotor, and with the aid of centrifugal force the rotating rotor ejects the material against the inner wall of the housing. On impact with the wall of the housing the material is crushed to a desired size. The housing wall could be provided with anvils or have a bed of retained material against which the accelerated material is crushed. 
     The rotor of a VSI crusher usually has a horizontal upper disc and a horizontal lower disc. The upper disc has an aperture for feeding material to be crushed into the rotor, such that the material lands on the lower disc. The upper and lower discs are interconnected by a vertical rotor wall, which guides the material to material outflow openings about the circumference of the rotor. The vertical rotor wall of WO 2008133568 is provided with a number of wear tips adjacent to the outflow openings in the rotor wall, to protect the rotor wall from wear caused by the material leaving the rotor at a high speed. The wear tips are provided with air flow directing ridges for reducing the wear of the wear tips and the rotor wall. 
     When the wear tips have become worn out they must be replaced. Replacement of the wear parts requires the VSI crusher to be shut down for a considerable time for maintenance. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to solve, or at least mitigate, parts or all of the above mentioned problems. To this end, there is provided a wear tip holder for holding a wear tip adjacent to an outflow opening of a vertical rotor wall of a rotor of a VSI crusher, said wear tip holder comprising a mounting plate for mounting the wear tip holder to said rotor wall, the mounting plate having a mounting face for facing the rotor wall to which it is to be mounted and a wear face for facing the interior of the rotor, the wear face being provided with at least one material retention hole for retaining, at the wear face, at least one of a wear-resistant insert and material to be crushed. When such a wear tip holder is used in a VSI crusher, material to be crushed may become firmly trapped in, and protrude from, the at least one material retention hole. Alternatively, a wear-resistant insert may have been located in the hole already before starting the crusher. The trapped material/wear-resistant insert will act as a wear surface, sparing the wear face of the wear tip holding plate. The trapped material/wear-resistant insert will also significantly increase the friction of the wear face, thereby assisting in forming and maintaining a bed of material on the rotor wall as well as on the wear tip holder. Thereby, the wear of the rotor wall as well as of the wear tip and wear tip holder will be reduced, such that an increase of the service interval of the crusher may be allowed. Throughout this disclosure, the term “wear-resistant” is to be construed as comprising a material having a higher resistance to wear than the wear face of the mounting plate. 
     According to an embodiment, said at least one material retention hole covers at least 10% of the area of the wear face. By covering a relatively significant portion of the wear face, a significant increase of the mounting plate wear face friction may be obtained, thereby improving the material bed maintaining ability of the wear tip holder. This even further reduces the wear of the mounting plate&#39;s wear face. 
     According to an embodiment, said material retention hole is a through-hole penetrating the mounting plate from the wear face to the mounting face. 
     According to an embodiment, at least a portion of the periphery of said at least one material retention hole is chamfered so as to form a retention surface facing the rotor wall to which the wear tip holder is to be mounted. Thereby, when in use, material to be crushed is wedged between the retention surface and the surface of the rotor wall facing the mounting surface of the mounting plate. Alternatively, when used together with a wear-resistant insert, the insert may be held in the material retention hole without the use of glue or other separate fastening means. Furthermore, should the insert crack into multiple pieces, e.g. due to the impact of a piece of rock to be crushed, the pieces may still be held in place by the retention surface. 
     According to an embodiment, said at least one material retention hole tapers in a direction from the mounting face towards the wear face. Such a design even more firmly wedges material to be crushed, or the wear-resistant insert as the case may be, in the material retention hole. In particular, any cracked insert will be held even more firmly in place by the tapering shape of the material retention hole. 
     According to an embodiment, said at least one material retention hole is essentially oval. Material retention holes of such a design have proven to be efficient in retaining material, while still being relatively practical to fabricate. 
     According to an embodiment, said at least one material retention hole is located at the vertical centre of the mounting plate. Such a design is particularly well suited for a wear tip holder configured for mounting to the rotor wall using a pair of threaded bars extending in the plane of the mounting plate, since the pair of threaded bars may, without compromising the integrity or wear resistance of the material retention hole, be screwed into the mounting plate on either side of the at least one material retention hole. Furthermore, the need for wear resistance has been found to be the highest near the vertical centre of the mounting plate. 
     According to an embodiment, said at least one material retention hole comprises a pair of material retention holes, said pair of material retention holes being vertically separated and located on either side of the vertical centre of the mounting plate. Such a design is particularly well suited for a wear tip holder configured for mounting to the rotor wall using a single threaded bar extending in the plane of the mounting plate, since the threaded bar may be screwed into the mounting plate at the vertical centre of the mounting plate. 
     According to another aspect of the invention, parts or all of the above mentioned problems are solved, or at least mitigated, by a wear tip holder kit comprising a wear tip holder according to what has been described above and at least one wear-resistant insert, said at least one wear-resistant insert fitting into said at least one material retention hole and comprising a material having a higher resistance to wear than the wear face of the mounting plate. The insert may be fixed in the hole, e.g. by gluing, or may be adapted to be removably inserted in the hole. Such a kit is of particular value when there is a need for increased wear resistance of the mounting plate, e.g. when processing highly abrasive industrial mineral. 
     According to an embodiment, said at least one wear-resistant insert comprises a ceramic material. According to an embodiment, said ceramic material comprises aluminium oxide. 
     According to an embodiment, said at least one wear-resistant insert is shaped so as to, when in use, be flush with or protrude from the wear face of the mounting plate. Such a design is particularly useful when very fine material, i.e. material having an average diameter of less than 10 mm, is to be crushed. 
     According to an embodiment, said at least one wear-resistant insert has a tapering shape, for form-fittingly engaging with a corresponding shape, tapering in a direction from the mounting face towards the wear face, of said at least one material retention hole. Thereby, should the insert crack into multiple pieces, e.g. due to the impact of a piece of rock to be crushed, the pieces may still be held in place by the tapering shape of the material retention hole. 
     According to yet another aspect of the invention, parts or all of the above mentioned problems are solved, or at least mitigated, by a method of decreasing the wear rate of a wear tip holder of a VSI crusher, the method comprising trapping at least one of a wear-resistant insert, and material to be crushed, in at least one material retention hole provided in a wear face of a wear tip holder mounting plate. Thereby, the wear-resistant insert and/or trapped material to be crushed will at least partly protect the mounting plate from wear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein: 
         FIG. 1  is a three-dimensional view and shows a rotor for a VSI crusher; 
         FIG. 2  is a three-dimensional view and shows the rotor of  FIG. 1  with the upper disc removed; 
         FIG. 3  shows the view of  FIG. 2  as seen from above in a two dimensional perspective; 
         FIG. 4   a  is a three-dimensional view of a wear tip holder according to a first embodiment; 
         FIG. 4   b  is a further three-dimensional view of the wear tip holder of  FIG. 4   a;    
         FIG. 5  is a diagrammatic view in section, as seen from above, of a detail of the rotor of  FIG. 3 ; 
         FIG. 6  is a diagrammatic view in section, as seen from above, of a wear tip mounting plate mounted onto a rotor wall segment; 
         FIG. 7   a  is a diagrammatic view in section, as seen from above, of a wear tip mounting plate in the process of being provided with a wear-resistant insert; 
         FIG. 7   b  is a diagrammatic view in section, as seen from above, of the wear tip mounting plate of  FIG. 7   a  as provided with a wear-resistant insert and mounted onto a rotor wall segment; 
         FIG. 8  is a diagrammatic view in section, as seen from above, of a detail of a wear tip mounting plate according to a second embodiment, mounted onto a rotor wall segment; 
         FIG. 9  is a diagrammatic view in section, as seen from above, of a detail of a wear tip mounting plate according to a third embodiment, mounted onto a rotor wall segment; 
         FIG. 10  is a diagrammatic view in section, as seen from above, of a detail of a wear tip mounting plate according to a fourth embodiment, mounted onto a rotor wall segment; 
         FIG. 11  is a schematic view in perspective of a detail of a wear tip mounting plate, according to a fifth embodiment, mounted onto a rotor wall segment; 
         FIG. 12  is a diagrammatic view in section, as seen from above, of a detail of a wear tip mounting plate according to a sixth embodiment, mounted onto a rotor wall segment; 
         FIG. 13   a  is a three-dimensional view of a wear tip holder according to a seventh embodiment; 
         FIG. 13   b  is a three-dimensional view of an aggregate wear tip holder comprising three wear tip holders of the type illustrated in  FIG. 13   a;    
         FIG. 14  is a three-dimensional view of a wear tip holder according to an eighth embodiment; and 
         FIG. 15  is a three-dimensional view of a wear tip holder according to a ninth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
       FIG. 1  shows a rotor  10  for use in a Vertical Shaft Impact Crusher, i.e., a VSI crusher. The rotor  10  has a roof in the form of a horizontal upper disc  12 , and a floor in the form of a horizontal lower disc  14 . The lower disc  14  has a hub  16 , which is welded to the disc  14 . The hub  16  is to be connected to a shaft (not shown) for rotating the rotor  10  inside the housing of a VSI crusher. The upper disc  12  has a central aperture  18  through which material to be crushed can be fed into the rotor  10 . 
     As is shown in  FIG. 2  the lower disc  14  is protected from wear by lower wear plates  20 . A distributor plate  22  is fastened to the centre of the lower disc  14 . The distributor plate  22  distributes the material that is fed via the aperture  18  in the upper disc  12  ( FIG. 1 ). 
     The upper and lower discs  12 ,  14  are separated by and held together by a vertical rotor wall  24 , which is separated into three separate wall segments  26 . Gaps between the wall segments  26  define outflow openings  28 , through which material may be ejected against a housing wall (not shown). At each outflow opening  28  the respective wall segment  26  is protected from wear by a wear tip  30  located at the leading edge of the respective wall segment  26 . Each wear tip  30  is mounted to the respective wall segment  26  by means of a wear tip holder  32 , which will be described further below. Each wall segment  26  is also provided with a respective pair  34  of cavity wear plates, which protect the rotor  10  and in particular the wear tips  30  from material rebounding from the housing wall and from ejected material and airborne fine dust spinning around the rotor  10 . 
       FIG. 3  illustrates the rotor  10  as seen from above and in operation. The upper disc  12  is not shown in  FIG. 3  for reasons of clarity. The arrow R indicates the rotational direction of the rotor  10  during operation of the VSI crusher. During operation of the rotor  10  a bed  36  of material is built up inside the rotor  10  against each of the three wall segments  26 . In  FIG. 3  only the bed  36  located adjacent to one of the wall segments  26  is shown. The bed  36 , which consists of material that has been fed to the rotor  10  and then has been trapped inside it, extends from a rear support plate  38  to the wear tip  30 . The bed  36  protects the wall segment  26  and the wear tip  30  from wear and provides a proper direction to the ejected material. The bed  36  of material forms an autogenous wear surface, which is regenerated as more material is fed into the crusher. The arrow A describes a typical passage of a piece of rock fed to the rotor  10  via the central aperture  18  and ejected via the outflow opening  28 . 
       FIGS. 4   a  and  4   b  illustrate a first embodiment of a wear tip holder  32 . The wear tip holder  32  has a wear body  40  with an elongate recess  42 , in which the wear tip  30  ( FIG. 2 ) is to be located. The wear tip  30 , which typically comprises a hard material such as tungsten carbide, may, by way of example, be welded or glued to the wear body  40 . Ridges  43  extend across the wear body  40 , and serve for forming an irregular turbulent air flow adjacent to the wear tip  30  in the manner described in greater detail in WO 2008/133568, such that the abrasive effect of dust laden air flowing past the wear tip  30  will be minimized. 
     The recess  42  and wear tip  30  extend, when the wear tip holder  32  is mounted to a horizontal rotor  10  ( FIGS. 1-3 ), in a vertical direction along the wear body  40 . The vertical centre of the wear tip holder  32 , when in use, is illustrated by a dashed line C. 
     A mounting plate  44 , which is a flat, rectangular plate for mounting the wear tip holder  32  to a vertical wall segment  26  of the rotor  10 , is attached to the wear body  40 . Two threaded bars  46 ,  48  extend from one end of the mounting plate  44 . By means of these two bars  46 ,  48  the wear tip holder  32  can be mounted to the wall segment  26  and fixed by nuts  50  ( FIG. 2 ). A holding flange  52 , extending from the wear body  40  at a distance from and in the same general direction as the mounting plate  44 , serves for gripping and holding the wall segment  26  in a manner which will be illustrated in greater detail in  FIG. 5 . Referring again to  FIGS. 4   a - b , the mounting plate has a wear face  54  ( FIG. 4   a ), which, when the wear tip holder  32  is attached to the rotor wall  24 , faces the interior of the rotor  10 , and which is exposed to wear at any location where it is not protected by the bed  36  of material ( FIG. 3 ). The mounting plate  44  also has a mounting face  56  ( FIG. 4   b ), which abuts the surface of the wall segment  26  when the wear tip holder  32  is attached to the wall  24 . 
     A material retention hole  58  penetrates the mounting plate  44  from the wear face  54  to the mounting face  56 . The material retention hole  58  has an elongate shape extending in the vertical direction of the mounting plate  44 . In the embodiment of  FIGS. 4   a - b , the material retention hole  58  essentially has the shape of an oval, or of a rectangle with curved short sides. Furthermore, the material retention hole  58  tapers in a direction from the mounting face  56  towards the wear face  54 , such that material retention hole&#39;s  58  aperture  60  in the mounting face  56  is larger than its aperture  64  in the wear face  54 . 
     The top view of  FIG. 5  illustrates how the wear tip holder  32 , when in use, is mounted to a rotor wall segment  26 . The mounting face  56  of the mounting plate  44  rests on, and abuts, a first portion  26   a  of the wall segment  26  in such a manner that the holding flange  52  of the wear tip holder  32  grips an edge  66  of the wall segment  26 . The threaded bars  46 ,  48  penetrate a second portion  26   b  of the wall segment, and nuts  50  are tightened on the threaded bars  46 ,  48  such that the holding flange  52  firmly grips the wall segment  26 . 
     The material retention hole  58  clearly illustrated in cross-section tapers from the mounting face  56  to the wear face  54 . When the wear tip holder  32  is mounted to the rotor  10 , the first portion  26   a  of the rotor wall segment  26  forms a bottom of the material retention hole  58 , such that the material retention hole  58  opens only towards the wear face  54 . 
       FIG. 6  illustrates the function of the material retention hole  58  when material to be crushed is present in the rotor  10 . Due to the tapering shape of the material retention hole  58 , the inclined inner wall of the hole  58  forms a material retention surface  68  obliquely facing the rotor wall segment  26 . 
     Even though not illustrated, it will be appreciated that there will be, on the wear face  54  of the mounting plate  44 , a bed  36  of material to be crushed. Pieces  70  of material to be crushed, e.g. pieces of rock, have, by operating the crusher, been trapped in the material retention hole  58  and wedged between the retention surface  68  and the rotor wall segment  26 . The pieces  70  of material form a rough, structured surface  72  facing the interior of the rotor  10 , thereby assisting in preventing the bed  36  of material ( FIG. 3 ) from sliding across the wear tip  30  and leaving the rotor  10 . Furthermore, the adjacency of the surface  72  to the wear tip  30  assists in extending the bed  36  of material very close to the wear tip  30 , thereby protecting the wear tip  30  from wear. 
       FIGS. 7   a - b  illustrate an alternative use of the material retention hole  58 . Before mounting the wear tip holder  32  ( FIG. 5 ) to the rotor wall segment  26 , a wear-resistant insert  74  is inserted into the material retention hole  58  via the aperture  60  of the mounting face  56 . The wear-resistant insert  74  has a tapering shape so as to fit snugly into the material retention hole  58 . Then, as is illustrated by  FIG. 7   b , the wear tip holder  32  is mounted to the rotor wall segment  26 , such that the insert  74  is trapped between the retention surface  68  and the wall segment  26 . 
     The wear-resistant insert  74  comprises a material having a higher resistance to wear than the material of the mounting plate  44  surrounding the insert  74 . Thereby, the insert  74  will operate so as to decrease the wear rate of the wear face  54 . The insert may also have a surface  76  that is rougher than the wear face  54  of the mounting plate  44 , such that the combined friction of the wear face  54  of the mounting plate  44  and the surface  76  of the insert  74  will be higher than would have been the friction of a wear face  54  having no insert  74 . Thereby, the insert will assist in maintaining a bed  30  of material ( FIG. 3 ) on the wall segment  26 . 
     The insert  74  may, by way of example, have a ceramic surface  76  comprising e.g. aluminium oxide. In fact, the entire insert may be a ceramic insert. The insert may also comprise any other suitable wear-resistant material, such as tungsten carbide, white iron or the like. 
     A wear-resistant insert  74  may be of particular value for sparing the mounting plate  44  when processing highly abrasive industrial minerals. Moreover, the risk of worn-off metal causing problems in any downstream industrial process will be reduced. The wear-resistant insert  74  may be inserted and removed as needed, e.g. when changing the composition or properties of the material to be crushed. By way of example, it has been found that the wear-resistant insert  74  may provide a better wear resistance of the wear tip  30  and wear tip holder  32  when processing wet, fine material, e.g. material having a mean diameter of less than about 10 mm. When processing dry material or material having a mean diameter of more than about 10 mm, the use of the material retention hole  58  without a wear-resistant insert  74  may provide the best wear resistance. Clearly, the material trapping efficiency of the material retention hole  58 , as well as the friction of the surface  76  of the wear-resistant insert  74 , depend on the properties of the material to be crushed. 
       FIGS. 8-12  illustrate exemplary alternative embodiments of material retention holes  158 ,  258 ,  358 ,  458 ,  558 . Each of the holes  158 ,  258 ,  358 ,  458 ,  558  may be used for retaining an autogenous wear layer of material to be crushed, as has been described hereinbefore with reference to  FIG. 6 , or for retaining a wear-resistant insert as has been described with reference to  FIGS. 7   a - b.    
       FIG. 8  illustrates a cross-section of a portion of a mounting plate  144  provided with a material retention hole  158 , wherein only a portion of the inner wall of the hole  158  is chamfered so as to form a material retention surface  168  facing the wall segment  26 . 
       FIG. 9  illustrates a cross-section of a portion of a mounting plate  244  provided with a material retention hole  258 , wherein the material retention hole  258  is provided with a bottom  200  formed in the mounting plate  244 . Even though the bottom  200  combined with a sloping material retention surface  268  may make it difficult to insert a single, solid and snugly fitting wear-resistant insert, a wear-resistant insert may still be inserted, e.g. by assembling it inside the hole from multiple pieces or by curing a liquid insert inside the hole  158 . 
       FIG. 10  illustrates a cross-section of a portion of a mounting plate  344  provided with a material retention hole  358 , wherein a portion of the periphery of the material retention hole  358  is chamfered so as to form a circumferential flange  302  having a retention surface  368  facing the rotor wall segment  26 . 
       FIG. 11  illustrates a cross-section of a portion of a mounting plate  444  provided with a material retention hole  458 . The material retention hole  458  is provided with a plurality of inwardly projecting material retention dogs  404 , each material retention dog  404  being chamfered to form a material retention surface  468  facing the rotor wall segment  26 . 
       FIG. 12  illustrates a material retention hole  558  with straight edges and having no material retention surface facing the rotor wall segment  26 . Material to be crushed may still be trapped in the material retention hole  558 , so as to form an autogenous wear layer protecting the mounting plate  544 . 
       FIG. 13   a  illustrates a wear tip holder  632  for use in an aggregate wear tip holder assembly. The wear tip holder  632  has a mounting plate  644  provided with a single threaded hole  647  for receiving a threaded bar (not shown). The threaded hole  647  is located at the vertical centre C of the wear tip holder  632 . A pair of material retention holes  658  are located on either side of the threaded hole  647 . 
       FIG. 13   b  illustrates an aggregate wear tip holder assembly  606  comprising three wear tip holders  632 . Each of the wear tip holders  632  comprises a pair of material retention holes  658 . 
     Clearly, it is not necessary that a material retention hole be oval.  FIG. 14  illustrates a wear tip holder  732  having a mounting plate  744  provided with two rectangular material retention holes  758 , whereas  FIG. 15  illustrates a wear tip holder  832  having a mounting plate  844  provided with three material retention holes  858 . 
     The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. 
     For example, the invention is not limited to any particular number of material retention holes in a single wear tip holder mounting plate. Moreover, the invention is not limited to any particular size or shape of the material retention hole(s), since many different hole sizes and hole shapes are suitable for holding, when the wear tip holder is in use, either a wear-resistant insert or material to be crushed. All such embodiments fall within the scope of the appended claims.