Patent Publication Number: US-2017348696-A1

Title: Secondary shredder

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     BACKGROUND 
     Tire shredder systems are employed to convert whole tires into shredded particles that can be employed for a number of different purposes. Many tire shredder systems employ a two-stage shredding process. First, whole tires are fed through a primary shredder which converts the tires into larger-sized shreds (e.g., a rough shred down to a 2 inch shred). Next, these larger-sized shreds can be fed through a secondary shredder which will convert them into small-sized particles (e.g., into approximately 0.25 to 2 inch particles). Also, in many systems, the secondary shredder is employed to remove the metal wire from the rubber particles. Therefore, the typical output of the secondary shredder is a wire-free rubber mulch. 
     Many secondary shredders employ a rotor design in which a single rotating head (or rotor) to which blades are mounted is rotated as the larger-sized shreds are fed into the secondary shredder. These rotor-based designs also typically include a number of stationary knives that are positioned in close proximity to the rotating blades thereby forming a shredding interface as the rotor rotates. At the shredding interface, the larger-sized shreds will be forced between the rotating blades and the stationary knives resulting in the shreds being cut/ripped into the small-sized particles. These secondary shredders will also typically have a screen through which appropriately sized particles of rubber and wire can fall to exit the shredding area and which will cause particles that have not yet been reduced to the appropriate size to be recirculated through the shredding interface. After falling through the screen, the particles can be passed by a magnet that will remove the wire particles from the rubber particles thereby producing the rubber mulch. 
     BRIEF SUMMARY 
     The present invention extends to a secondary shredder and components of a secondary shredder. A secondary shredder can include a rotor assembly that employs a modular rotor design. Each rotor of the rotor assembly can include a number of blades that are symmetrical around a horizontal and a vertical axis. Each rotor can include a number of radial extensions forming gaps between adjacent radial extensions into which the blades insert. Each blade can be secured within a gap by a wedge that presses the blade against the radial extension. The radial extensions and blades can include keyways into which keys insert to prevent the blades from escaping the gaps and which provide consistent orientation of the blade within the gap. The secondary shredder may also include a stationary knife assembly that includes multiple stationary knives that are positioned on the same side of the rotor assembly. 
     In one embodiment, the present invention is configured as a secondary shredder that includes a body having an internal compartment and an opening into the internal compartment, a stationary knife assembly comprising one or more stationary knives positioned within the internal compartment, and a rotor assembly positioned within the internal compartment. The rotor assembly has one or more rotors that each has a plurality of blades which form a shredding interface with each of the one or more stationary knives. Each blade is symmetrical around a horizontal axis and a vertical axis. 
     In another embodiment, the present invention is configured as a secondary shredder that includes a body having an internal compartment and an opening into the internal compartment, a stationary knife assembly comprising a first set of stationary knives and a second set of stationary knives that extend along a width of the internal compartment and protrude into the internal compartment, and a rotor assembly comprising a plurality of rotors. Each rotor comprises a number of radial extensions that are spaced around a circumference of the rotor thereby forming a number of gaps. Each gap includes a blade and a wedge that secures the blade to an adjacent radial extension. The rotor assembly is positioned within the internal compartment such that the blades form a shredding interface with the first and second sets of stationary knives. 
     In another embodiment, the present invention is implemented as a rotor for use in a secondary shredder. The rotor includes a circular shaped body having a number of radial extensions spaced around a circumference of the body thereby forming a number of gaps. For each gap, the rotor includes a blade and a wedge that insert into the gap. The wedge secures the blade to the corresponding radial extension. Each radial extension and each blade includes opposing keyways into which keys insert to prevent the blade from escaping the gap. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates a top perspective view of a secondary shredder that is configured in accordance with embodiments of the present invention; 
         FIG. 1A  illustrates a detailed view as identified in  FIG. 1 ; 
         FIG. 2  illustrates a front view of the secondary shredder of depicted in  FIG. 1 ; 
         FIG. 2A  illustrates a cross-sectional view as identified in  FIG. 2 ; 
         FIG. 3  illustrates a single rotor of a rotor assembly that can be employed within a secondary shredder configured in accordance with embodiments of the present invention; 
         FIG. 3A  illustrates a detailed view as identified in  FIG. 3 ; 
         FIG. 4A  represents a front or rear perspective view of a blade that can be employed on a rotor of the rotor assembly; 
         FIG. 4B  represents a front or rear view of the blade; 
         FIG. 4C  represents a left side or right side view of the blade; 
         FIG. 4D  illustrates how the configuration of a blade allows the blade to be coupled to a rotor in four different orientations; 
         FIG. 4E  illustrates how the leading edges of a blade can be ground down without altering how the blade is secured to the rotor; and 
         FIG. 5  illustrates an exploded perspective view of a rotor assembly that can be employed within a secondary shredder configured in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A secondary shredder as described herein may typically be used to shred rubber tires. However, a secondary shredder configured in accordance with embodiments of the present invention could be employed to shred other types of materials. Also, the term secondary should not be viewed as limiting the shredder of the present invention to use within a shredding system that employs a primary shredder. Instead, the term secondary refers to the fact that the shredder is employed to shred material of relatively smaller size. Accordingly, the present invention should not be limited to use in any particular system or for use in shredding any particle type of material. The present invention extends to a secondary shredder and components of a secondary shredder. A secondary shredder can include a rotor assembly that employs a modular rotor design. Each rotor of the rotor assembly can include a number of blades that are symmetrical around a horizontal and a vertical axis. Each rotor can include a number of radial extensions forming gaps between adjacent radial extensions into which the blades insert. Each blade can be secured within a gap by a wedge that presses the blade against the radial extension. The radial extensions and blades can include keyways into which keys insert to prevent the blades from escaping the gaps and which provide consistent orientation of the blade within the gap. The secondary shredder may also include a stationary knife assembly that includes multiple stationary knives that are positioned on the same side of the rotor assembly. 
     In one embodiment, the present invention is configured as a secondary shredder that includes a body having an internal compartment and an opening into the internal compartment, a stationary knife assembly comprising one or more stationary knives positioned within the internal compartment, and a rotor assembly positioned within the internal compartment. The rotor assembly has one or more rotors that each has a plurality of blades which form a shredding interface with each of the one or more stationary knives. Each blade is symmetrical around a horizontal axis and a vertical axis. 
     In another embodiment, the present invention is configured as a secondary shredder that includes a body having an internal compartment and an opening into the internal compartment, a stationary knife assembly comprising a first set of stationary knives and a second set of stationary knives that extend along a width of the internal compartment and protrude into the internal compartment, and a rotor assembly comprising a plurality of rotors. Each rotor comprises a number of radial extensions that are spaced around a circumference of the rotor thereby forming a number of gaps. Each gap includes a blade and a wedge that secures the blade to an adjacent radial extension. The rotor assembly is positioned within the internal compartment such that the blades form a shredding interface with the first and second sets of stationary knives. 
     In another embodiment, the present invention is implemented as a rotor for use in a secondary shredder. The rotor includes a circular shaped body having a number of radial extensions spaced around a circumference of the body thereby forming a number of gaps. For each gap, the rotor includes a blade and a wedge that insert into the gap. The wedge secures the blade to the corresponding radial extension. Each radial extension and each blade includes opposing keyways into which keys insert to prevent the blade from escaping the gap. 
       FIGS. 1-2A  each illustrate a view of a secondary shredder  100  that is configured in accordance with one or more embodiments of the present invention. Secondary shredder  100  generally comprises a body  101  having an internal compartment  101   a  in which a rotor assembly  102  is housed. An opening  101   b  is formed through body  101  and into compartment  101   a.  Material to be shredded can be input into internal compartment  101   a  via opening  101   b . The diameter of internal compartment  101   a  can be slightly larger than the outer diameter of rotor assembly  102  thereby allowing rotor assembly  102  to be rotated within internal compartment  101   a.    
     With reference to  FIG. 1A , rotor assembly  102  can include a number of rotors  104  which are secured together along an axis of rotation. In the depicted example, rotor assembly  102  includes four rotors  104 . However, a rotor assembly could equally include greater or fewer rotors  104  in some embodiments. In fact, as will be further described below, rotor assembly  102  can employ a modular design to facilitate the addition or removal of a rotor  104  from the assembly. 
     As is best shown in  FIG. 2A , each rotor  104  has a generally circular or cylindrical shape and includes a number of radial extensions  104   a  that are equally spaced around the circumference of the rotor. These radial extensions  104   a  form a number of gaps between adjacent radial extensions that are spaced around the circumference of the rotor. The role of each of these gaps is to receive and secure a blade  105 . As will be further described below, these blades  105  can be secured to rotor  104  by employing a wedge  106 . 
     Secondary shredder  100  can also include a stationary knife assembly  103  which includes two (or possibly more) sets of stationary knives  103   a  and  103   b  that span the width of rotor assembly  102  (or more particularly, the combined width of rotors  104 ). Stationary knives  103   a  and  103   b  can extend inwardly into internal compartment  101   a  and can have a cutting profile that corresponds to the cutting profile of blades  105 . For example, as best shown in  FIG. 1A , stationary knives  103   a  and  103   b  can be structured with a triangular pattern that corresponds to the triangular pattern of blades  105  thereby allowing the tips of blades  105  to insert between the tips of stationary knives  103   a  and  103   b  to form a shredding interface. In other words, the close proximity of stationary knives  103   a  and  103   b  to blades  105  will form a shredding interface when rotor assembly  102  is rotated. 
     In  FIG. 2A , the direction of rotation during normal operation is represented by the arrow. Accordingly, materials input through opening  101   b  will first be forced through the shredding interface formed between blades  105  and stationary knives  103   a  and then through the shredding interface formed between blades  105  and stationary knives  103   b.  As shown, stationary knives  103   a  can be positioned near or at opening  101   b  (i.e., towards the top of rotors  104 ) so that the materials quickly come into contact with the stationary knives. One benefit of positioning stationary knives  103   a  near the top of rotors  104  is that it causes stationary knives  103   a  to be oriented nearly vertically which will prevent the materials from building up against the stationary knives. In other words, due to the near-vertical orientation of stationary knives  103   a,  gravity will prevent the materials from building up against the leading face of stationary knives  103   a.    
     Stationary knives  103   b  can also be positioned on the same side of rotor assembly  102  as stationary knives  103   a.  For example, as shown in  FIG. 2A , stationary knives  103   b  can be positioned within the same quadrant as stationary knives  103   a.  This will cause the materials to be shredded twice before reaching a screen  101   c  that is positioned at the bottom of body  101 . Because the materials will be subjected to two sets of stationary knives before reaching screen  101   c,  it is much more likely that the materials will have been reduced to the appropriate size upon reaching the screen and will therefore exit body  101 . This can minimize the amount of materials that will be recirculated around internal compartment  101   a  which in turn will increase the efficiency of the shredding process. 
     Turning to  FIGS. 3 and 3A , a rotor  104  is shown in isolation. Each rotor  104  can be ring-shaped (i.e., each rotor  104  can have an opening passing through its middle) which can allow a cooling fluid or air to be circulated through rotor assembly  102  during the shredding process. As mentioned above, rotor  104  can include a number of radial extensions  104   a  that form gaps  104   b  along the circumference of the rotor. The width of gaps  104   b  can generally correspond to the combined width of blade  105  and wedge  106  thereby allowing a blade  105  and a wedge  106  to be inserted into each gap  104   b.    
     To secure and position blade  105  within gap  104   b,  each radial extension  104   a  can include keyways  104   a   1  into which keys  107  can insert. Each blade  105  can also include corresponding keyways  105   a  that are centered on each side of the blade. Accordingly, blade  105  can be positioned against radial extension  104   a  with keys  107  inserting into both keyways  104   a   1  and  105   a.  Then, to lock blade  105  in this position, wedge  106  can be inserted into gap  104   b  alongside blade  105  and bolted down via holes  106   a.  The wedge shape of wedge  106  will cause a sandwiching or pressing force to be applied to blade  105 . This sandwiching force combined with keys  107  will retain blade  105  in place. 
     The wedge shape also increases the tolerances of gap  104   b  and blade  105 . In other words, because wedge  106  will apply a greater sandwiching force as it is tightened further into gap  104   b,  there is no need for the width of blade  105  to be precise. If one blade  105  happens to have a slightly smaller width, or equally if the width of one gap  104   b  happens to be slightly larger, wedge  106  can simply be tightened further into gap  104   b  to apply the necessary sandwiching force to hold the blade in place. 
       FIGS. 4A-4C  illustrate blade  105  in isolation. Blades  105  can be symmetrical about a horizontal axis and a vertical axis as represented by the dotted lines in  FIGS. 4B and 4C  respectively. This symmetry allows blades to be positioned within gap  104   b  in any of four different orientations. Because the leading edge of blade  105  (e.g., the leftward-facing edge in  FIG. 2A ) performs the shredding function, this leading edge will become worn over time. For example, this leading edge, which would form a vertical edge when new, can begin to taper backwards (especially at the tip) due to the wear and tear of shredding the materials. However, due to the symmetrical design of blade  105 , any one of the four edges can serve as the leading edge. Because keyways  105   a  are positioned on the horizontal axis of symmetry and are formed on both sides of blade  105 , these keyways will align with keyways  104   a   1  regardless of which of the four possible orientations blade  105  is placed in. 
     Also, because blade  105  is symmetrical about the vertical axis, the tips of blade  105  will always be appropriately positioned with respect to stationary knives  103   a  and  103   b .  FIG. 4D  illustrates this. As shown, each blade  105  can include a body portion  105   c  and tip portions  105   b  that extend from a top and bottom side of body portion  105   c.  The combined height of body portion  105   c  and one of tip portions  105   b  can be approximately equal to the height of radial extension  104   a  as represented by the dashed lines. As a result, the outer edge of body portion  105   c  will substantially align with the outer edge of radial extension  104   a  while the exposed tip portion  105   b  will extend beyond the outer edge of radial extension  104   a.  Due to the symmetry, this will be the case regardless of the orientation of blade  105 . 
     A primary benefit of having symmetrical blades  105  is that it allows the blades to be repositioned into one of the other three orientations when the leading edge in the current orientation becomes worn. This repositioning can be performed in a relatively quick and easy manner due to the fact that blades  105  are properly positioned using keyways and keys and easily secured in place by wedge  106 . In particular, by removing wedge  106 , a blade  105  can also be removed from gap  104   b,  reoriented to use a different leading edge, and re-secured with the wedge. Because wedge  106  is coupled to rotor  104  using bolts that are accessible from the outer/exposed surface of the wedge, a blade  105  could be reoriented even without removing rotor assembly  102  from body  101  (e.g., by accessing wedge  106  and blade  105  via opening  101   b.    
     By using wedge  106 , there is no need to directly bolt blade  105  to rotor  104  thereby facilitating the repositioning of blade  105 . In particular, if blade  105  was configured to be bolted to rotor  104 , the location of the bolt holes would minimize the number of orientations that blade  105  could be positioned in. By using keyways  105   a  and a wedge  106 , a symmetrically designed blade can be employed. 
     The use of wedge  106  and keys  107  to secure blade  105  also allows a worn edge to be reground without affecting how blade  105  couples to rotor  104  and interfaces with stationary knives  103   a  and  103   b.  This is represented in  FIG. 4E . As shown on the left side of the figure, a blade  105  includes leading edges  105   b   1  that have become worn. These leading edges  105   b   1  can be ground flat to remove the worn (or rounded edge) as is represented on the right side of the figure. This grinding can be performed only on the tip portion  105   b  of blade  105  so that keyways  105   a  are not affected. As a result, blade  105  can again be secured in any of the four orientations using wedge  106 . This ability to grind the edges of blade  105  can greatly increase the useful lifespan of the blade. For example, in some instances, each leading edge can be ground up to 2 mm at a time for a total of 6 mm (i.e., each leading edge may be ground at least three times). With four available leading edges, this would allow a single blade to be reused at least 12 times. 
     In some embodiments of the present invention, rotor assembly  102  can be modular as is represented in  FIG. 5 . As shown, rotor assembly  102  can include a first endplate  109   a  to which a first rotor  104  is secured. A second rotor  104  is also shown as being secured to the first rotor  104  while a third and fourth rotor  104  are shown separated from the other two rotors. Each of these rotors  104  can be configured to couple to another rotor  104  or to endplate  109   a  via bolts  108 . Then, once the desired number of rotors  104  has been coupled together, a second endplate  109   b  can be secured to the outermost rotor  104 . By coupling the rotors directly to one another between opposing endplates, rotor assembly  102  can have a hollow interior to facilitate cooling. However, other rotor designs could equally be used in conjunction with the other features of the present invention including designs in which the rotors are pressed onto or otherwise secured to an axle or shaft. 
     As shown in  FIG. 5 , each adjacent rotor  104  is offset slightly so that the blades  105  on one rotor are staggered with respect to an adjacent rotor. In one non-limiting configuration, the blades  105  are staggered in a slight spiral configuration. In this manner, only one blade  105  of a given rotor will interface with a given set of stationary knives at a specific time. 
     This modular design facilitates creating rotor assemblies of varying lengths. For example, to produce a shredder having a larger/longer shredding interface, additional rotors  104  could simply be added to the four rotors  104  shown in  FIG. 5 . The modular design also facilitates replacing an individual rotor without needing to replace the entire rotor assembly. For example, if one rotor  104  is damaged, the rotor assembly  102  can be disassembled to the point that the damaged rotor can be removed (e.g., by first removing any intervening rotors) and replaced while any undamaged rotors can continue to be used. 
     Endplates  109   a  and  109   b  can be configured with the necessary components (e.g., gears) to allow rotor assembly  102  to be rotated. Also, although not shown in  FIG. 5 , endplates  109   a  and  109   b  can be configured to allow a cooling fluid or air to be injected through each of rotors  104 . For example, a cooling fluid may be pumped through first endplate  109   a  then through each of rotors  104  prior to exiting through endplate  109   b.  In this way, rotors  104  can be cooled during the shredding process. 
     Returning to  FIG. 2A , in some embodiments, a demagnetizer may be employed in conjunction with stationary knife assembly  103 . When shredding tires, the wires that are oftentimes included in the tires may become magnetized during the shredding process. These magnetized wires may then be attracted to the stationary knife assembly  103 , particularly between the two stationary knives, and will therefore never reach screen  101   c.  As a result, it may be necessary to periodically remove the magnetized wires. This results in downtime and additional burden when operating a shredder. To address this issue, the present invention may incorporate a demagnetizer (not shown) as part of or adjacent to stationary knife assembly  103 . This demagnetizer can remove the magnetization that may have built up in the wires and/or the stationary knife assembly thereby allowing the wires to pass through stationary knife  103   b  towards screen  101   c.    
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description.