Abstract:
A demolition shear and a piercing tip insert and nose configuration for a demolition shear which resists nose wear and resists retract forces exerted on the piercing tip insert in jamming situations and in the event of snagging of the piercing tip insert. There is a need for a demolition shear having a piercing tip insert and nose configuration to reduce nose wear and to resist retract forces exerted on the piercing tip insert in jamming situations and in the event of snagging of the piercing tip insert.

Description:
BACKGROUND 
       [0001]    There is a need for a demolition shear having a piercing tip insert and nose configuration to reduce nose wear and to resist retract forces exerted on the piercing tip insert in jamming situations and in the event of snagging of the piercing tip insert. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a right side perspective view (from the position of the operator) of one embodiment of a demolition shear attachment. 
           [0003]      FIG. 2  is a left side perspective view of the demolition shear attachment of  FIG. 1 . 
           [0004]      FIG. 3  illustrates the shear attachment of  FIG. 1  in a typical operating position showing the movement of the upper jaw with respect to the lower jaw during a shearing operation. 
           [0005]      FIG. 4  is an exploded perspective view of the jaw pivot shaft of the shear attachment of  FIG. 1   
           [0006]      FIG. 5  is an enlarged view of  FIG. 1  showing the jaws of the shear attachment. 
           [0007]      FIG. 6  is the same view as  FIG. 5  but with the blade inserts and piercing tip inserts removed. 
           [0008]      FIG. 7  is an enlarged view of  FIG. 2  showing the jaws of the shear attachment. 
           [0009]      FIG. 8  is a perspective view of the lower jaw of  FIG. 1  with the upper jaw removed to better show the blade-side shear blade inserts and guide blade insert. 
           [0010]      FIG. 9  is another perspective view of the lower jaw of  FIG. 1  with the upper jaw removed to show guide-side guide blade insert and cross-blade insert. 
           [0011]      FIG. 10  is the same view as  FIG. 7  with the blade inserts and piercing tip insert removed. 
           [0012]      FIG. 11  is the same view of the lower jaw as  FIG. 9  with the blade inserts removed. 
           [0013]      FIG. 12  shows different views of an embodiment of a shear blade insert, wherein  12 A is a front perspective view,  12 B is a front elevation view,  12 C is an end elevation view and  12 D is rear elevation view. 
           [0014]      FIG. 13  shows different views of an embodiment of a guide blade insert, wherein  13 A is a front perspective view,  13 B is a front elevation view,  13 C is an end elevation view and  13 D is rear elevation view. 
           [0015]      FIG. 14  shows different views of an embodiment of a cross-blade insert, wherein  14 A is a front perspective view,  14 B is a rear perspective view,  14 C is an end elevation view,  14 D is a front elevation view and  14 E is rear elevation view. 
           [0016]      FIG. 15  shows different views of an embodiment of a blade-side piercing tip half, wherein  15 A is a front perspective view,  15 B is a rear perspective view,  15 C is a front end elevation view,  15 D is an outer side elevation view and  15 E is an inner side elevation view. 
           [0017]      FIG. 16  shows different views of an embodiment of a guide-side piercing tip half, wherein  16 A is a front perspective view,  16 B is a rear perspective view,  16 C is a front end elevation view,  16 D is a inner side elevation view and  16 E is outer side elevation view. 
           [0018]      FIG. 17  is a perspective view of the upper jaw of the shear attachment of  FIG. 1  in isolation with the piercing tip inserts shown exploded with respect to the nose seat. 
           [0019]      FIG. 18  is an enlarged side elevation view of the upper and lower jaws of the shear attachment of  FIG. 1  with the upper jaw in the fully open position. 
           [0020]      FIG. 19  is an enlarged side elevation view of the upper and lower jaws of the shear attachment of  FIG. 1  with the upper jaw in a partially closed position. 
           [0021]      FIG. 20  is an enlarged side elevation view of the upper and lower jaws of the shear attachment of  FIG. 1  with the upper jaw about to enter the slot in the lower jaw. 
           [0022]      FIG. 21  is an enlarged side elevation view of the upper and lower jaws of the shear attachment of  FIG. 1  with the upper jaw fully closed and extending into the slot of the lower jaw. 
           [0023]      FIG. 22  is an enlarged side elevation view of the upper and lower jaw illustrating forces acting on the piercing tip in a jamming situation. 
           [0024]      FIG. 23  is an enlarged side elevation view of the upper and lower jaw illustrating forces acting on the piercing tip in another type of jamming situation. 
           [0025]      FIG. 24  is an enlarged side elevation view of the upper and lower jaw illustrating forces acting on the piercing tip in the event of snagging of the upper end of the piercing tip due to wear of the parent material from the nose of the upper jaw. 
       
    
    
     DESCRIPTION 
       [0026]    Referring to the drawings wherein like reference numerals designate the same or corresponding parts throughout the several views,  FIGS. 1 and 2  are perspective views from right and left sides, respectively (from the position of the operator), of one embodiment of a demolition shear attachment  10 . The shear attachment  10  has a main body  12  with a forward end  14  and a rearward end  16 . The rearward end  16  is adapted to be operably mounted to the boom or stick  18  ( FIG. 3A ) of an excavator such as by a swivel attachment  19  or other suitable mounting attachment as recognized and understood by those of skill in the art. At the forward end  14  of the main body  12  is a movable upper jaw  40  and a fixed lower  42  (discussed in detail later). 
         [0027]      FIGS. 3A-3C  show the shear attachment  10  mounted to the boom or stick of an excavator  18  of an excavator, and positioned in a typical operating position, and illustrating the movement of the upper jaw  40  closing with respect to the lower jaw  42  over an object  11  to be sheared. The object  11  to be sheared may be any structural member, such as a steel I-beam or channel, steel plate, pipe or some other material, such as scrap metal, sheet metal or any other object or material for which a demolition shear is suited for handling or processing. 
         [0028]    Referring to  FIGS. 1-4 , the main body  12  is typically constructed of steel side plates  20 ,  22 , a top plate  24  and a bottom plate  26  which together define a substantially enclosed area within which a hydraulic actuator  30  ( FIGS. 3A-3C ) and other hydraulic components of the shear attachment  10  are substantially enclosed and protected. The hydraulic actuator  30  is pivotally secured at a rearward end within the main body  12  by an actuator pivot pin  32  extending through the side plates  20 ,  22 , internal gussets (not shown) and the cylinder rod clevis  34 . The forward end of the hydraulic actuator  30  is pivotally attached to the movable upper jaw  40  by a cylinder pin  36  extending through the cylinder body clevis  38  and cylinder pin bore  42  (see also  FIG. 16 ) in a rearward lobe of the upper jaw  40 . Thus, it should also be appreciated, that as the hydraulic actuator  30  extends and retracts as illustrated in  FIGS. 3A-3C , the upper jaw  40  rotates about the longitudinal axis of the jaw pivot shaft  60  (discussed below) to open and close the upper jaw  40  with respect to the lower jaw  42 . An access opening with an access cover  25  ( FIG. 2 ) may be provided in the top plate to gain access to the interior of the body  12  for installation, maintenance, servicing and repair of the hydraulic actuator and other components of the hydraulic system. 
         [0029]    As best illustrated in  FIGS. 4 ,  8  and  9 , jaw bosses  44 ,  46  on each side of the forward end  14  of the main body  12  include hub bores  48 ,  50 . A jaw pivot shaft assembly  60  received within the hub bores  48 ,  50  and through a pivot shaft bore  54  (see  FIG. 17 ) pivotally supports the upper jaw  40 . 
         [0030]    The jaw pivot shaft assembly  60  comprises flanged bushings  56 ,  58  fitted within the hub bores  48 ,  50 . A main shaft  62  is press-fit into the pivot shaft bore  54  for rotation with the upper jaw  40 . The main shaft  62  includes a central bore  64  which receives a tie rod  66  having threaded ends  68 . End caps  70 ,  72  are secured to the flanged bushings  56 ,  58  by threaded connectors extending through aligned holes in the flange bushings  56 ,  58  and are threadably received by aligned internally threaded holes in the hubs  44 ,  46 . Tie rod nuts  74  threadably receive the threaded ends  68  of the tie rods  66 . The tie rod nuts  74  are secured to the end caps  70 ,  72  by threaded connectors threadably received into internally threaded aligned holes in the flange bushings  56 ,  58 . It should be appreciated that the tie rod  66  and tie rod nuts  74  laterally restrain the hubs  48 ,  50  against lateral forces exerted on the jaws during the shearing operation. 
         [0031]    As best viewed in  FIGS. 4 and 8 , lateral jaw stabilizing puck assemblies  80 , such as disclosed in U.S. Pat. No. 7,216,575, may be provided along with corresponding wear plates or wear surfaces  82  ( FIG. 17 ) on the adjacent side or sides of the upper jaw  40  to resist lateral movement of the upper jaw  40  during the shearing operation until the upper jaw enters the slot  96  of the lower jaw  42  (discussed below). 
         [0032]    Referring to  FIGS. 5-11 , the lower jaw  42  includes forwardly extending, laterally spaced and substantially parallel jaw beams  90 ,  92  and a cross-beam  94  extending transversely between the forward ends of the laterally spaced jaw beams  90 ,  92 . The laterally spaced jaw beams  90 ,  92  and the cross beam  94  together define a slot  96  into which the upper jaw  40  is received during the shearing process (see  FIG. 3C  and  FIG. 4 ). As discussed in more detail below, the forwardly extending jaw beam  90  is adapted to receive shear blade inserts and guide blade inserts and is hereinafter referred to as the blade-side jaw beam  90 . The other forwardly extending jaw beam  92  serves to provide structural rigidity to the lower jaw and also serves to laterally restrain and guide the upper jaw into the slot  96  during the shearing process and is hereinafter referred to as the guide-side jaw beam  92 . 
         [0033]    As best viewed in  FIG. 10 , the inner side of the blade-side jaw beam  90  includes a shear blade seat  100  which is adapted to receive a set of hardened steel shear blade inserts  110  ( FIGS. 7 and 8 ). An embodiment of the shear blade inserts  110  is illustrated in  FIG. 12 . The shear blade inserts  110  each have generally planar vertical wear surfaces  114 ,  116  and generally planar horizontal wear surfaces  118 ,  120 . The intersection of the vertical and horizontal wear surfaces define four shearing edges  122 . The shear blade inserts  110  have parallel sloping end surfaces  124 ,  126  creating a parallelogram configuration so that when the shear blade inserts  110  are positioned and oriented in the shear blade seat  100  the adjacent end surfaces bear against each another in a downward apex (see  FIGS. 7 and 8 ). It should be appreciated, that because the shear blade inserts  110  are in the shape of identical parallelepiped, they may be rotated and oriented with respect to one another within the shear blade seat  100  so that all four shearing edges  122  may be used as the shearing edges wear during use. The planar vertical wear surfaces  114 ,  116  include counterbore holes  130  for receiving threaded connectors  132  (preferably socket headed cap screws) to removably attach the shear blade inserts  110  within the shear blade seat  100 . The counterbore holes  130  permit the heads of the threaded connectors  132  to be seated within the counterbore. The threaded ends of the threaded connectors  132  extend through the counterbore holes  130  and through aligned holes  134  ( FIG. 10 ) in the shear blade seat  100  and are secured by nuts  136  ( FIGS. 5 and 9 ), received within counterbore holes  138  on the outer side of the blade-side jaw beam  90 . 
         [0034]    As best viewed in  FIG. 10 , the inner side of the blade-side jaw beam  90  also includes a guide blade seat  200  which is adapted to receive a hardened steel guide blade insert  210  (best viewed in  FIG. 8 ). An embodiment of the guide blade insert  210  is illustrated in  FIG. 13 . The guide blade insert  210  has generally planar vertical wear surfaces  214 ,  216  and generally planar horizontal wear surfaces  218 ,  220 . The intersections of the vertical and horizontal wear surfaces define four shearing edges  222 . The guide blade insert  210  has parallel sloping end surfaces  224 ,  226  creating a parallelogram configurations. The sloping end surfaces  224 ,  226  of the guide blade insert  210  are complimentary to the sloping end surfaces  124 ,  126  of the shear blade inserts  110  so that when the guide blade insert  210  is positioned and oriented in the guide blade seat  200  one of its end surfaces  224 ,  226  will bear against one of the end surfaces  124 ,  126  of the adjacently positioned shear blade insert  110  (as best illustrated in  FIG. 8 ). It should be appreciated, that because the guide blade insert  210  is in the shape of a parallelepiped, it may be rotated and oriented within the guide blade seat  200  (and switched with the guide-side guide blade seat  300  discussed below) so that all four shearing edges  222  may be used as the shearing edges wear during use. The vertical wear surfaces  214 ,  216  include tapped internally threaded holes  230  for receiving threaded connectors  232  (e.g., bolts) to removably attach the guide blade insert  210  within the guide blade seat  200 . The threaded ends of the threaded connectors  232  extend through aligned counterbore holes  234  ( FIGS. 5 and 9 ) on the outer side of the blade-side beam  90  and are threadably received by the tapped internally threaded holes  230  in the guide blade insert  210 . 
         [0035]    As best viewed in  FIGS. 9 and 11 , the guide-side beam  92  also includes a guide-blade seat  300  ( FIG. 11 ) which is adapted to receive the same guide blade insert  210  as received in the blade-side guide blade seat  200  so that the guide blade inserts  210  are interchangeable between the guide-side guide blade seat  300  and the blade-side guide blade seat  200 . Accordingly, the guide blade insert  210  is retained and secured in the guide-side guide blade seat  300  in substantially the same manner as the blade-side guide blade seat  200  in that the same threaded connectors  232  (e.g., bolts) extend through aligned counterbore holes  334  ( FIGS. 7 ,  8 ,  10 ) on the outer side of the guide-side jaw beam  92  and are threadably received by the tapped holes  230  in the guide blade insert  210 . 
         [0036]    As best viewed in  FIGS. 9 and 11 , the cross-beam  94  includes a cross-blade seat  400  ( FIG. 11 ) which is adapted to receive a hardened steel cross-blade insert  410  ( FIG. 9 ). An embodiment of the cross-blade insert  410  is illustrated in  FIG. 14 . The cross-blade insert  410  has a generally planar front wear surface  414 , generally planar top and bottom wear surfaces  418 ,  420 , generally planar end surfaces  424 ,  426  and a back side  428 . The back side  428  includes four equally radially spaced internally threaded holes  430 . The back side  428  is also keyed with a projection  432  which seats within a recess  434  ( FIG. 11 ) in the cross-blade seat  400 . The intersection of the front vertical wear surface  414  with the top and bottom wear surfaces  418 ,  420  and end surfaces define four cutting edges  422 . The cross-blade insert  410  is preferably square with four radially spaced holes  430  so that it may be rotated 90 degrees four times within the cross-blade seat  400  so that all four cutting edges  422  may be used as the shearing edges wear during use. The cross-blade insert  410  is secured within the cross-blade seat  400  by threaded connectors  436  (such as bolts) extending through counterbore holes  438  ( FIGS. 5 and 7 ) in the cross-beam  94 . The ends of the threaded connectors  436  are received within the aligned internally threaded holes  430  in the back side surface  428  of cross-blade insert  410 . 
         [0037]    The upper jaw  40  has a blade-side and a guide-side which correspond to the adjacent blade-side jaw beam  90  and guide-side beam  92  of the lower jaw  42 . The blade-side of the upper jaw  40  includes a shear blade seat  500  ( FIG. 6 ) which is adapted to receive the same shear blade inserts  110  ( FIG. 5 ) as used in the shear blade seat  100  of the lower jaw  42  so that the shear blade inserts  110  are interchangeable between the upper and lower jaws, thereby reducing the number of different blade configurations needed for the shear attachment  10 . However, in the upper jaw, the shear blade inserts  110  are oriented in an upward apex as opposed to the downward apex in the lower jaw (compare  FIGS. 5 and 7 ). The shear blade inserts  110  are secured in the upper jaw in substantially the same manner as the lower jaw. The threaded ends of the threaded connectors  132  extend through the counterbore holes  130  and through aligned holes  534  in the upper shear blade seat  500  and are secured by nuts  136  received within counterbores  538  ( FIG. 7 ) on the guide-side of the upper jaw  40 . 
         [0038]    Referring to  FIGS. 6 ,  10  and  17 , the forward most end of the upper jaw  40  or nose  601  includes a nose seat  600  adapted to receive a hardened steel piercing tip insert  610  ( FIGS. 5 ,  7 ,  17 ) to protect the parent material of the upper jaw nose from wear during use. The nose seat  600  includes a blade-side nose seat  602  ( FIGS. 6 and 17 ), a guide-side nose seat  604  ( FIG. 10 ), and a front nose seat  606  ( FIGS. 6 ,  10 ,  17 ) which results in a narrowed nose portion  608 . The forward most nose tip  609  of the nose seat  600  is preferably radiused to minimize stress concentrations on the nose portion  608 , both during the manufacturing process and during use. The piercing tip insert  610  is comprised of two halves  620 ,  622  which are substantially mirror images of each other except for the connector holes in each half (discussed later). The half which extends over the blade-side of the nose is hereinafter referred to as the blade-side half  620 , and the half which extends over the guide-side of the nose is hereinafter referred to as the guide-side half  622 . 
         [0039]      FIG. 15  shows various views of an embodiment of the blade-side half  620 .  FIG. 16  shows similar views of an embodiment of the guide-side half  622 . Each of the piercing tip halves  620 ,  622  includes an outer sidewall  630  having a substantially planar vertical wear surface  632  and a substantially planar vertical inner bearing surface  634 . Each half  620 ,  622  also includes a laterally inward projecting front wall  636  having an outer curved wear surface  638  and an inner bearing surface  640 . Each piercing tip half  620 ,  622  also includes a laterally inward projecting bottom leg  642  having a bottom planar wear surface  644  and an upper leg bearing surface  646 . Each of the piercing tip halves  620 ,  622  further includes an end bearing surface  648  and an ear  650  having upper ear bearing surface  651  and a lower ear bearing surface  653 . The ear  650  may have a radiused periphery to reduce stress concentrations. The lower ear bearing surface  653  extends rearwardly of the end bearing surface  648 , the purpose of which is discussed later in connection with  FIGS. 22 and 23 . The intersection of the planar vertical wear surface  632  and the bottom planar wear surface  644  defines a shearing edge  652 . The intersection of the curved wear surface  638  of the front wall  636  and the bottom planar wear surface  644  defines a front piercing edge  654  (the front piercing edge may be chamfered). 
         [0040]    As best viewed in  FIGS. 6 ,  10  and  17 , the nose seats  602 ,  604 ,  606  define peripheral bearing edge surfaces  656  which complimentarily receive the outer peripheries of the piercing tip halves  620 ,  622 . It should be appreciated that the inner surface  640  of the laterally inward projecting front wall  636  and the upper surface  646  of the laterally inward projecting bottom leg  642  of each piercing tip half  620 ,  622  is approximately half the width of the narrowed nose portion  608  so that when the piercing tip halves  620 ,  622  are mounted in the nose seat  600 , the inner bearing surfaces  640  of the sidewalls  630  and the upper leg bearing surfaces  646  of the bottom legs  642  of the piercing tip halves  620 ,  622  bear against the respective bearing surfaces of the blade-side nose seat  602 , the guide-side nose seat  604  and the front nose seat  606 . Additionally, the upper ear bearing surface  651  and the lower ear bearing surface  653  of the tip halves  620 ,  622  bear against peripheral bearing edge surfaces  656  of the nose seat  600 . On the blade-side of the nose  601 , one of the sloping ends  124 ,  126  (depending on orientation) of the upper shear blade insert  110  abuts and bears against the back end bearing surface  648  of the blade-side half  620 . As such, the blade-side piercing tip half  620  is rotationally restrained from outward rotation (as discussed later) by both the blade insert  110  and the peripheral bearing edge surfaces  656  which mateably receive of the upper ear bearing surface  651  and the lower ear bearing surface  653  of the blade-side nose seat. The guide-side piercing tip half  622  is rotationally restrained from movement by the peripheral bearing edge surfaces  656  which mateably receive of the upper ear bearing surface  651  and the lower ear bearing surface  653  of the guide-side nose seat  604 . 
         [0041]    It should be appreciated that when the two piercing tip halves  620 ,  622  are mounted in the nose seat  600 , the narrowed nose portion  608  is completely surrounded by the hardened steel piercing tip insert  610  thereby protecting the parent material of the nose  601  from wear during use. 
         [0042]    In addition to being rotationally restrained by the peripheral bearing edge surfaces  656 , the two piercing tip halves  620 ,  622  are secured to the narrowed nose tip  608  with threaded connectors  670 . In a preferred embodiment, the threaded connectors are socket headed cap screws. The two halves  620 ,  622  include aligned holes  660  through their respective outer sidewalls  632 . Corresponding aligned holes  664  are provided through the narrowed nose tip  608 . Concentric counterbores  668  are provided over the holes  660  in the outer wall  632  of the blade-side half  620 . The aligned holes  660  in the outer wall  632  of the guide-side half  622  are tapped with internal threads. The counterbores  668  permit the heads of the threaded connectors  670  to be seated within the counterbores  668 . The threaded ends of the threaded connectors  670  extend through the holes  660  in blade-side half  620  and through the aligned holes  664  in the narrow nose tip  608  and are threadably received by the internally threaded aligned holes  660  of the guide-side tip half  622 . Obviously, the counterbores  668  and the internal threaded holes  660  in the two tip halves  620 ,  622  could be reversed if desired. Alternatively, counterbores  668  could be provided in outer walls  632  of both tip halves  620 ,  622  for receiving the heads of the threaded connectors  670  and to receive a nut (not shown) on the opposing tip half rather than tapping the holes  660  of one of the halves. As discussed in more detail later in connection with  FIGS. 18 and 22 , the holes  660 ,  664  are aligned along an arc concentric with the front edge of the piercing tip  610  (i.e., the outer curved wear surface  638 ) to ensure a more uniform loading across the threaded connectors  670 . 
         [0043]    It should be appreciated that when mounted to the upper jaw  40 , the planar vertical wear surfaces  114 ,  116  (depending on orientation) of the shear blade inserts  110  are substantially co-planar with the vertical wear surface  632  of the blade-side tip half  620  and the shearing edges  122 ,  652  of the shear blade inserts  110  and piercing tip insert  610  are substantially aligned. Similarly, on the lower jaw  42 , the planar vertical wear surfaces  114 ,  116  (depending on orientation) of the shear blade inserts  110  are substantially coplanar with the vertical wear surface  214  of the blade-side guide blade insert  210  and their respective shearing edges  122 ,  222  are substantially aligned. It should also be appreciated that the substantially coplanar vertical wear surfaces  114 ,  116 ,  632  and shearing edges  122 ,  652  of the upper shear blade inserts and piercing tip insert  610  are slightly laterally, inwardly offset from the shearing edges  122 ,  232  of the shear blade inserts  110  and blade-side guide blade insert  210  of the lower jaw (preferably between a range of about 0.01 inches and 0.05 inches), to permit the upper shearing edges to pass by the shearing edges of the lower jaw as the upper jaw moves through its range of motion and into the slot  96  of the lower jaw  42 . Likewise, the shearing edge  652  of the guide-side piercing tip half  622  is laterally inwardly offset from the shearing edge  222  of the guide-side guide blade insert  210  preferably between a range of about 0.01 inches and 0.05 inches. Accordingly, the width of the piercing tip insert  610  is less than the width between the opposing shearing edges  222  of the blade-side and guide-side guide blades  210  (preferably between a range of about 0.02 and 0.1 inches), such that the piercing tip insert  610  can pass between the lower dual guide blades  210  as the upper jaw closes into the slot  96  of the lower jaw  42 . Shims may be inserted between the various inserts  110 ,  210 ,  610  and their respective seats  100 ,  200 ,  300 ,  500 ,  600  to maintain the close tolerances between the respective shearing edges. 
         [0044]      FIGS. 18-22  are enlarged side elevation views of the jaws  40 ,  42  to better illustrate the relationship of the blade inserts  110 ,  210  and piercing tip insert  610  cross-blade insert  410  during movement of the upper jaw—i.e., from the fully open position ( FIG. 18 ), to the fully closed position ( FIG. 21 ) in which the upper jaw reaches full depth into the slot  96  of the lower jaw  42 .  FIG. 19 , shows the upper jaw partially closed wherein the front piercing edge  654  of the piercing tip insert  610  is perpendicular or normal to the ground surface.  FIG. 20 , shows the upper jaw in a position where the front piercing edge  654  intersects the lower jaw  42 . 
         [0045]    A nose wear shoe  700  is secured (such as by welding) to the nose  601  of the upper jaw  40  above the piercing tip insert  610  to protect the parent material of the upper jaw from wear during use. As the nose wear shoe  700  wears down, it may be removed and replaced with another wear shoe  700 . The wear shoe  700  may be fabricated from the same material as the parent material or it may be fabricated from hardened steel. Referring to  FIG. 20 , the nose wear shoe preferably extends along the nose a sufficient distance to ensure that the parent material of the nose is protected to at least the full depth of entry of the upper jaw  40  into the lower jaw  42 . In an alternative embodiment, the piercing tip insert  610  may be extended along the nose  601  to the full dept of entry of the upper jaw into the lower jaw. In such an embodiment, the nose seat  600  would likewise be extended and additional holes  660  may be necessary to adequately restrain the longer piercing tip insert  610  to the narrowed nose  608 . 
         [0046]    It should be appreciated that the parent material of the nose  601  above the piercing tip insert  610  is more susceptible to wear than the hardened steel piercing tip insert  610 . Accordingly, without a wear shoe  700 , the nose  601  could wear down to the point that the upper edge of the piercing tip insert  610  projects above the nose. If the upper edge of the piercing tip insert  610  projects outwardly from the nose  601 , the projection could potentially snag on material caught in the jaws as the upper jaw re-opens or is retracted from the lower jaw. If sufficient retract force is exerted on the upper jaw, the piercing tip insert could be pulled away from the nose by the snagged material, shearing the threaded connectors in the process or breaking the piercing tip insert. Accordingly, as hereinafter described, the nose  601  of the upper jaw is configured to minimize the risk of snagging, even when a wear shoe  700  is not mounted to the nose  601  or where the wear shoe itself is worn down such that the parent material of the nose is no longer protected by the wear shoe. 
         [0047]      FIGS. 18 and 21  illustrate a preferred configuration of the nose  601  to avoid or minimize occurrences of snagging. The phantom line designated by reference numeral  800  identifies the arc created by the forward most front piercing tip edge  654  of the piercing tip insert  610  as the upper jaw moves through its range of motion. The arc  800  has a radius R 1  to the center axis of the jaw pivot shaft  60 . The outermost periphery of the nose  601  from the forward piercing edge  654  of the piercing tip  610  to the end of the nose wear shoe  700  or to the point on the nose which corresponds to the maximum depth that the nose  601  penetrates the lower jaw is configured to transitions away from the front piercing tip edge arc  800  in a substantially smooth nose arc  802 . The nose arc  802  has a radius R 2  which is less than the radius R 1 , such that radial distances from the central axis of the jaw pivot shaft  60  to points along the nose  601  or nose arc  802  continually decrease relative to the front piercing tip edge arc  800 . Stated another way, the distance between the piercing tip front edge arc  800  and the nose arc  802  continually increases along the nose  601  or nose arc  802  from the piercing tip front edge  654 . This configuration allows the nose  601  to only make contact at the piercing tip front edge  654 , thereby avoiding or reducing the likelihood of the nose  601  scraping along objects being pierced by the piercing tip  610 , thereby minimizing wear along the nose. Additionally, because the nose increasingly transitions away from the piercing tip edge arc  800 , it reduces the likelihood of snagging of material caught in the jaws even if the parent material of the nose becomes worn down to where the upper edge of the piercing tip insert  610  projects outwardly from the worn parent material of the nose. 
         [0048]    Furthermore, the piercing tip seat  600  and piercing tip insert  610  are configured to ensure retention of the piercing tip if a projecting edge of the piercing tip becomes snagged or if the upper jaw becomes jammed by material trapped in the jaws. For example, in  FIG. 22  the hatched area  900  is intended to represent trapped or lodged material caught between the wear surfaces of the piercing tip insert  610  and the guide shear blade inserts  210  causing the upper jaw to become jammed within the slot  96  of the lower jaw  42  such that the upper jaw  40  cannot retract or re-open. The retract force F of the upper jaw  40  (exerted by the hydraulic actuator  30  pulling on the upper jaw) attempts to pull the piercing tip insert  610  in the direction perpendicular to the radial line  806  extending from the center axis of the jaw pivot shaft  60  to the midpoint of the trapped material  900 . It should therefore be appreciated that any bearing surface which is less than 90 degrees to the radial line  806 , will resist the retract force F. Accordingly, the rearwardly projecting ears  650  of the piercing tip insert  610  ensure that a bearing surface is provided to resist the retract force F. 
         [0049]    Referring to  FIG. 22 , the lower ear bearing surface  653  is at an angle less than 90 degrees to the radial line  806  and therefore provides a bearing surface designated by arrows R against which the peripheral bearing edge surfaces  656  of the nose seat  600  engage to resist the retract force F. Similarly, the inner bearing surface  640  of the front wall  636  bears against the nose seat  606  as designated by arrows R to resist the retract force F. Thus, the resistance or reactionary forces R will reduce the shearing forces being exerted on the connectors  670  by the retract force F, thereby preventing or minimizing the piercing tip insert  610  from being pulled off the nose or otherwise fracturing. 
         [0050]    Furthermore, because the holes  660  in the piercing tip insert  610  are aligned along an arc  804  having a radius R 3  which is less than the radius R 2  but which is concentric with the nose arc  802 , a more uniform load is applied across all of the connectors  670  thereby further reducing the shearing stresses exerted on any one connector or causing stress concentrations which could shear the connectors or cause the piercing tip insert to fracture. 
         [0051]      FIG. 23  illustrates another example wherein the hatched area  902  is intended to represent material trapped between the piercing tip insert  610  and the cross-blade insert  410 . In this example, the retract force F again pulls the piercing tip in the direction perpendicular to the radial line from  806  extending from the center axis of the jaw pivot shaft  60  to the center point the trapped material, which, in this example, is assumed to be at the piercing tip front edge  654 . The retract force F will cause the piercing tip insert  610  to attempt to roll outwardly or away from the nose  601  as indicated by arrow  810 . However, the upper ear bearing surface  651  engages with the peripheral bearing edge surfaces  656  of the nose seat  600  as designated by reactionary forces R to resist the outward rotation of the piercing tip insert  610  thereby reducing shearing forces on the connectors  670  and preventing or reducing stress fracturing of the piercing tip insert  610 . 
         [0052]      FIG. 24  illustrates an example of the retract force F acting on the upper edge of the piercing tip insert  610  in the unlikely event that the nose  601  is worn down to create a ridge upon which material could snag as described above. Such an occurrence is unlikely in view of the configuration of the nose  601  having a continually increasing distance between the nose arc  802  and the piercing tip front edge arc  800  for the reasons explained above, but nevertheless, if the nose is worn down to create a ridge on which material could snag, the upper ear bearing surface  651  would engage against the peripheral bearing edge surfaces  656  of the nose seat  600  as indicated by reaction forces R to resist the retract force F attempting to roll the piercing tip edge outwardly as indicated by arrow  810  thereby reducing shearing forces on the connectors  670  and preventing or reducing stress fracturing of the piercing tip insert  610 . 
         [0053]    The foregoing description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the embodiments described herein, and the general principles and features of the embodiments described herein will be readily apparent to those of skill in the art. Thus, the present invention is not to be limited to the embodiments described herein and illustrated in the drawing figures, but is to be accorded the widest scope consistent with the spirit and scope of the appended claims.