Abstract:
An apparatus for cutting residual cakes within a bottom-unloading centrifuge so that the residual cake can be discharged without putting the operator in jeopardy. The apparatus comprises first and second cutting members that are vertically spaced from each other and an elongated support member secured to the cutting members. The cutting members and the elongated support member are rotatably and vertically moveable within the centrifuge. The apparatus also includes a locking system for securing and maintaining the cutting members in a first, cutting position and a second, rest position.

Description:
[0001]     The present invention relates to an apparatus for cutting material within a bottom-unloader centrifuge basket, more particularly, the present invention relates to a device that cuts the residual cake within the basket of a centrifuge so that the residual cake is safely removed from a surface of the basket without requiring an operator to hand clean the interior of the basket.  
       BACKGROUND OF THE INVENTION  
       [0002]     Use of a centrifugal separation device allows the extraction of the solid particles from other portions of a mixture. In a centrifugal separator, the separation of the solid from the liquid is commonly accomplished by pumping the contaminated liquid into a high speed rotating chamber or basket. The centrifugal forces created by high speed rotation of the basket cause the contaminated liquid to conform to the interior surface of the rotating basket. The centrifugal energy causes the heavier solids to concentrate in a solid cake form for easy removal, reclamation, reuse or disposal. Since the basket is rotating at a high speed, the solid material adheres to the side of the basket while a cleansed coolant or liquid exits through an opening or openings commonly located at the bottom basket. Centrifugal separation is preferable to the more traditional medium of filtration. However, when centrifugal filtration is performed, a cake begins to form within the basket and the filter screen within the basket becomes clogged, thereby limiting the efficiency of the centrifuge.  
         [0003]     Known devices, such as plows, are used to rapidly remove the cake from within the basket. However, plows do not remove the entire cake because the plow cannot come into contact with the filter screen or it will damage the screen. In many centrifuges, as much as two inches of the cake can remain in the basket after the operation of the plow. This remaining portion of the cake that is packed against the filter screen is known as the residual cake or heel. In most instances, the residual cake has to be removed because it slows down the filtration, because the user wishes to recover the entire product or because the user wishes not to mix multiple batches or products. To remove the residual cake, it may require that the operator manually introduce a member, such as a hand trowel, into the basket while the basket is spinning. This exposes the operator to physical danger and may result in the operator being seriously injured. Alternatively, the removal of the residual cake requires the shutting down and opening the centrifuge. It either instance, an operator may come into contact with toxic, flammable or other dangerous products. What is more, the product may deteriorate when it comes into contact with the open air.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     An aspect of the present invention includes an apparatus for cutting residual cake within a centrifuge so that the residual cake can be discharged without putting the operator in jeopardy. The apparatus comprises first and second cutting members that are vertically spaced from each other and an elongated support member secured to the cutting members. The cutting members and the elongated support member are rotatably and vertically moveable within the centrifuge. The apparatus also includes a locking system for securing and maintaining the cutting members in a first, cutting position and a second, rest position.  
         [0005]     A manual system or powered drive system can be used to vertically and rotationally move the elongated shaft and cutting members toward and away from the lower inner surface of the basket. After the cutting members move from a first rest position to a second, lower rest position, the elongated shaft and cutting members are rotated into a residual cake cutting position. When the cutting members are rotated into the first, cutting position, the cutting members are located immediately adjacent to the wall surface of the filter, yet not in physical contact with the wall surface. At this position, the cutting members can contact and create up to a two inch score in a residual cake within the basket of the centrifuge.  
         [0006]     Each cutting member includes a blade having a cutting surface that faces the cutting surface of the opposing blade. These opposing cutting surfaces cause the cut portions of the residual cake to be directed away from the lower and upper surfaces of the basket, thereby preventing the cut portions from being wedged between the cutting blades and portions of the basket. The cut portions of the residual cake are discharged from the basket through the main solids discharge opening. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a schematic view of a portion of a centrifuge including a material cutting apparatus according to an aspect of the present invention with cutting members being shown in both rest and cutting positions;  
         [0008]      FIG. 2  is a partial broken away schematic view of a portion of the centrifuge of  FIG. 1  with the cutting members in a rest position;  
         [0009]      FIG. 3  is a schematic top view of the portion of the centrifuge of  FIG. 1  with the cutting members shown in a lower rest position and a lower engaged position;  
         [0010]      FIG. 4  is a cross section of a support shaft shown in  FIG. 1 ;  
         [0011]      FIGS. 5 and 6  illustrate portions of a locking mechanism shown in  FIG. 1 ;  
         [0012]      FIG. 7  illustrates a housing for the locking mechanism shown in  FIG. 1 ;  
         [0013]      FIGS. 8A and 8B  illustrate a lower cutting member of  FIG. 1 ;  
         [0014]      FIGS. 9A-9C  illustrate an upper cutting member of  FIG. 1 ;  
         [0015]      FIGS. 10 and 11  illustrate an indexing plate of a rotational positioning system shown in  FIG. 1 ;  
         [0016]      FIG. 12  illustrates a stopping plate of a rotational positioning system shown in  FIG. 1 ;  
         [0017]      FIG. 13  illustrates a spacing washer that cooperates with the stopping plate of  FIG. 12 ;  
         [0018]      FIGS. 14 and 15  illustrate a retainer plate of a rotational positioning system shown in  FIG. 1 ; and  
         [0019]      FIG. 16  illustrates a handle for turning the shaft and cutting members shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]      FIGS. 1 and 2  illustrate a portion of a basket  2  of a top loading, bottom discharge centrifuge  1  as known in the art. An example of such a centrifuge  1  is a TOLHURST centrifuge. As understood in the art, the basket  2  can be connected to a drive shaft and motor (riot shown) and rotated about a vertically disposed axis that extends through the centrifuge  1 . The basket  2  comprises an inner bottom surface  4  and a vertically extending sidewall  6 . The basket  2  also includes a wire-mesh cloth or screen  8  that extends along the length of the vertical sidewall  6 . As appreciated by those skilled in the art, the basket  2  may include, as necessary, the appropriate bearings and seals that support the basket  2  as it rotates at a high rate and separates the subject material located within the basket  2 , while maintaining an isolated environment within the basket  2 .  
         [0021]     As shown in  FIGS. 1 and 2 , the centrifuge  1  also includes a material removal apparatus  10  for cutting (scoring) a residual cake  3  that remains within the basket  2  of the centrifuge  1  after operation of the centrifuge  1 . The apparatus  10  comprises a positioning assembly  20  that provides both vertical and rotational positioning to cutting members  54 ,  56  of a cutting assembly  50 . The positioning assembly sets the cutting members  54 ,  56  at desired heights and locations within the basket  2  so the residual cake  3  can be cut (scored) by cutting members  54 ,  56  and removed from within the basket  2  through the bottom discharge opening (not shown).  
         [0022]     The positioning assembly  20  is secured to the cover  8  of the centrifuge  1  as shown in  FIGS. 1 and 2 . The positioning assembly  20  comprises a housing  21  that includes an internal passage  22  sized and shaped to receive a centrally positioned support shaft  100 . The positioning assembly  20  also includes a spacing member  23  having an internal bearing surface and guide collar  25  that spaces the cutting members  54 ,  56  a predetermined distance below the inside surface of the cover  8  and within the basket  2 .  
         [0023]     As illustrated in  FIGS. 1 and 2 , the support shaft  100  extends vertically through at least a portion of the basket  2  and the cover  8 . The shaft  100  is moveable toward and away from the bottom surface  4  of the basket  2  along an axis that extends through the cover  8 . In the illustrated embodiment, the shaft  100  has a total length of between about 37 and 41 inches. In an embodiment, the shaft  100  has a length of about 39.4 inches. The shaft  100  also has a width of between about 1.15 and 1.35 inches. In an embodiment, the width is about 1.27 inches. However, the length and width of the shaft  100  may change with the size of the centrifuge  1 .  
         [0024]     As shown in  FIG. 4 , the support shaft  100  has a substantially octagonal cross section with four substantially planar sides  102  connected by angled sections  101 . In the illustrated embodiment, each planar side  102  has a length of about 1.25 inches. This shape provides the support shaft  100  with additional strength to resist torsion and other forms of deformation while cutting of the residual cake occurs. The support shaft  100  is formed of a known material. One such material includes DELRON plastic. Other known materials that resist torsion could also be used.  
         [0025]     The shaft  100  is held in either a raised or lowered vertical position by a release system  44 , illustrated in  FIGS. 1, 3  and  5 . The release system  44  comprises a sliding, cylindrical member  45  that is received within an opening  103  in the support shaft  100 . A handle  46  that can be grasped by an operator extends from the sliding member  45 . A spring  47  or other known resilient member biases the cylindrical member  45  in the direction of the support shaft  100 . During use, the operator pulls on the handle  46  to retract the cylindrical member away from the shaft  100  and against the force of the spring  47 . In response to the operator pulling on the handle  46 , the cylindrical member  45  moves within a channel  48  ( FIG. 7 ) extending through a support housing  113  that is secured to, and extends from, the housing  21 . When this occurs, the support shaft  100  is separated from the cylindrical member  45  and free to move vertically and rotationally relative to the basket  2 .  
         [0026]     The shaft  100  carries a stopping member  110  for limiting the length of its vertical travel within the basket  2 .  FIGS. 1 and 2  illustrate a stop collar  110  that is moveable along the length of the support shaft  100 . The collar  110  can be secured to the support shaft  100  at any point along its length in order to set the height of the lower end  104  of the shaft  100  and the cutting members  54 ,  56  above the bottom surface  4  of the basket  2 . The collar  110  can be secured using a well known manner including a friction fit between a bolt  114  advanced through a portion of the collar  110  and into engagement with the support shaft  100 . Alternatively, the stop collar  110  can be secured to the support shaft  100  using a detent and sliding member. As the shaft  100  is advanced into the basket  2  and the cutting members  54 ,  56  moved toward the bottom surface  4 , the collar  110  will contact an upper surface of an indexing plate  210 . When this occurs, the vertical movement of the shaft  100  and the cutting members  54 ,  56  stops and the cutting height of the cutting members  54 ,  56  above the bottom surface  4  is set.  
         [0027]     As shown in  FIGS. 1 and 2 , the cutting assembly  50  comprises a pair of vertically spaced cutting members  54 ,  56  secured proximate the lower end  104  of support shaft  100 . The cutting members  54 ,  56  can be formed of any known cutting tools including knife blades  57  having cutting edges  58 . However, other known cutting members could also be used to cut the residual cake within the centrifuge  1 . The cutting edge  58  of each blade  57  is shaped to follow the contour of the screen  8  and effectively cut the residual cake  3 . In the illustrated embodiment, the cutting edge  58  has a radius of curvature of about 6 inches. The terminal end  59  of the cutting edge  58  is slightly rounded. The terminal end  59  has a radius of curvature of about 0.25 inch.  
         [0028]     As shown in  FIG. 1 , the cutting edge  58  of the lower cutting member  54  is angled away from the bottom surface  4  of the basket  2  in order to prevent a cut portion of the residual cake from being thrown and wedge between the lower cutting member  54  and the bottom surface  4 . Similarly, the cutting edge  58  of the upper cutting member  56  faces away from the cover  8  so that cut portions of the residual cake  3  are not thrown between the cutting member  56  and an upper surface of the basket  2 .  
         [0029]     The cutting members  54 ,  56  can vary in length depending on the size of the basket in the centrifuge  1 . In the illustrated embodiment, the cutting members  54 ,  56  extend between about eight inches and nine inches from the shaft  100  and score a two inch slit in the residual cake. The cutting members  54 ,  56  are vertically spaced from each other in a direction parallel to the length of the shaft  100 . The upper cutting member  56  is vertically spaced between about 0.75 inch and 1.0 inch above the lower cutting member  54 . The distance between the two cutting members  54 ,  56  is maintained by a spacer nut  57 . The cutting members  54 ,  56  can be secured to the spacer nut  57  by bolts, screws, welds, adhesives or other known securing techniques. The cutting members  54 ,  56  could be spaced by a greater or lesser distance depending on the size of the basket  2  and the residual cake within the basket  2 . While the cutting members  54 ,  56  are shown to be vertically aligned, in an alternative embodiment the cutting members  54 ,  56  can be rotationally offset from each other (not shown).  
         [0030]     The lower cutting member  54  includes an angled section  72  that operatively secures the lower cutting member  54  to the lower end  104  of the support shaft  100 . The offset positioning of the cutting edge  58  relative to the lower end  104 , created by the angled section  72 , locates the cutting edge  58  closer to the bottom of the basket  2  than the lower end  104  of the support shaft  100 . An angled bracket could be used in place of angled section  72  to secure the lower cutting member  54  to the support shaft  100 . The offset created by the angled section  72  positions the lower cutting member  54 . The offset also spaces the bottom surface of the lower cutting member  54  from the bottom of the basket  2  by a distance of about 0.25 inch or less when the collar  110  is in contact with the indexing plate  210 . Alternatively, the distance between the lower cutting member  54  and the bottom of the basket  2  could be greater than 0.25 inch.  
         [0031]     The positioning apparatus  20  also includes a rotational positioning system  200  secured to the housing  21  for limiting the rotational movement of the support shaft  110  and the secured cutting members  54 ,  56  within the basket  2 . The rotational positioning system  200  limits how far the cutting members  54 ,  56  can rotate within the basket  2  in response to the rotation of their support shaft  100 . The rotational positioning system  200  includes the indexing plate  210  positioned within a recess in a positioning system housing  205 . The indexing plate  210  includes at least two recesses  211  that receive elongated members  215 , such as threaded bolts. The threaded members  215  also extend through washer  219  ( FIG. 13 ) that extends above a stopping plate  220 . As shown in  FIG. 12 , the stopping plate  220  is substantially arcuate in shape. The stopping plate  220  is positioned within an open region  232  of a retainer plate  230 . The open region  232  has a substantially hemispherical shape as illustrated in  FIG. 14 . The open region  232  also includes two stopping surfaces  234 ,  236  that contact the stopping plate  220  to stop the rotation of the shaft  100  and the arcuate travel of the cutting members  54 ,  56  as discussed below.  
         [0032]     The stopping plate  220  is allowed to travel between about 82 and 92 degrees within the open region  232 . This, in turn, limits the arcuate travel of the cutting members  54 ,  56  to between 82 and 92 degrees. In a preferred embodiment, the arcuate travel of the stop plate  220  and cutting members  54 ,  56  would be between about 84 and 88 degrees. In one embodiment, the arcuate travel is about 85 degrees. Greater or lesser amounts of arcuate travel of the stop plate  220 , and thus the support shaft  100  and cutting members  54 ,  56 , can be provided to compensate for wear of the cutting edges  58 , materials being cut or the like.  
         [0033]     During the operation of the centrifuge  1 , the cutting members  54 ,  56  are maintained in the upper rest position A. In upper rest position A, the cutting members  54 ,  56  are vertically spaced above the residual cake and adjacent to the cover of the basket  2 , as shown in  FIG. 2 . In the rest position A, the cutting members  54 ,  56  are positioned out of engagement with the cake and other portions of the centrifuge  1 . This allows for normal operation of the centrifuge  1 . The cutting members  54 ,  56  are held in rest position A by the cylindrical member  45  being engaged with the support shaft  100 . As the handle  46  is pulled backwards, away from the support shaft  100 , the cylindrical member  45  slides out of engagement with the support shaft  100 . An operator can then advance the support shaft  100  into the basket  2 , thereby simultaneously lowering the cutting members  54  in the direction of the bottom surface  4  of the basket  2 . When the collar  110  engages the indexing plate  210 , the vertical movement of the cutting members  54 ,  56  stops and the cutting members  54 ,  56  assume a lower rest position B. In this position B, the cutting members  54 ,  56  achieve their intended cutting height, but they have not been rotated into engagement with the residual cake. As illustrated, when in the partially engaged position B, the first cutting member  54  will be substantially adjacent the bottom surface  4 . In such an embodiment, the lower surface of the lower cutting member  54  can be positioned about 0.25 inch from the bottom surface  4 . The cutting members  54 ,  56  can also be incrementally lowered so that the residual cake can be cut at incremental heights, thereby allowing the residual cake to be cut away in stages. The support shaft  100  can include indicia to identify the depth of the cutting members  54 ,  56  within the basket  2 .  
         [0034]     After the cutting height of the cutting members  54 ,  56  is achieved, the support shaft  100  is rotated and the cutting members  54 ,  56  are moved from the lower rest position B to the engaged position C. The support shaft  100  is rotated by an operator turning a drive wheel  240  or a motor and drive arrangement attached to the support shaft  100  (not shown). The drive wheel  240  or motor and drive arrangement can also be used to raise and lower the support shaft  100  and cutting members  54 ,  56 . A counter weight  250  can be secured to the drive wheel  240  to secure the centrifuge  1 .  
         [0035]     In the illustrated embodiment, the rotation of the wheel  240  causes the support shaft  100  to engage and rotate the indexing plate  210 , which carries the stopping plate  220 . When the forward edge  224  of the stopping plate  220  engages the stop surface  234 , the rotation of the indexing plate  210 , the shaft  100  and the cutting members  54 ,  56  toward the screen  8  is stopped because the cutting members  54 ,  56  have assumed the cutting position C, shown in  FIG. 1 . In the cutting position C, a terminal end of each cutting member  54 ,  56  is positioned immediately adjacent to the inner surface of the screen  8 . As shown, the cutting members  54 ,  56  are not in physical contact with the wall of the screen  8 , thus the screen  8  is free of contact and damage from the cutting members  54 ,  56 .  
         [0036]     After the residual cake has been cut sufficiently for removal, the support shaft  100  is rotated in the opposite direction and the cutting members  54 ,  56  move away from the screen  8  toward the lower rest position B. When a rearward edge  226  of the stopping plate  220  engages the stopping surface  236 , the stopping surface  236  prevents any additional movement of the shaft  100  and indexing plate  210  in the direction away from the screen  8  because the cutting members  54 ,  56  have returned to the lower rest position B. The cylindrical member  45  is again backed away from the support shaft  100  by the operator pulling on the handle  46 . The shaft  100  may then be raised to return the cutting members  54 ,  56  to the upper rest position A. The handle  46  is then released and the spring  47  forces the cylindrical member  45  back into secure engagement with the support shaft  100 .  
         [0037]     Numerous characteristics, advantages and embodiments of the invention have been described in detail in the foregoing description with reference to the accompanying drawings. However, the disclosure is illustrative only and the invention is not limited to the illustrated embodiments. Various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.