Abstract:
A broadhead with expandable front pivot cutting blades has the cutting blades connected to the broadhead by low-friction rotary connections. The connections reduce frictional forces during outward rotation of the blades and permit locked blade deployment before the blades hit the target.

Description:
BACKGROUND OF THE INVENTION 
     Conventional broadheads have expandable front pivot cutting blades. The blades are in collapsed positions in the broadhead ferrule during flight and, upon impact, automatically deploy out from the ferrule to locked impact positions. The blades must rapidly rotate outwardly from the collapsed to the impact positions during the short interval between when the ferrule first contacts the target and when the blades contact the target. 
     Conventional broadheads have rotary connections between the blades and the ferrule. These connections have high frictional forces when the blades rotate and deploy upon impact. The friction slows outward rotation of the blades and can prevent the blades from locked deployment before the blades come into contact with the target. If the blades are not locked in the deployed position, the impact of the broadhead on the target is undesirably reduced. 
     Thus, there is a need for an improved broadhead having expandable front pivot cutting blades where, during impact of the broadhead on a target, the blades very rapidly rotate outwardly to the deployed position and are locked before continued movement of the broadhead brings the locked blades into contact with the target. The rapid outward rotation of the blades should be facilitated by low-friction rotary connections between the blades and ferrule. 
     SUMMARY OF THE INVENTION 
     The invention is an improved broadhead with expandable front pivot cutting blades where the blades are connected to the broadhead by low-friction rotary connections. The connections reduce frictional forces during outward rotation of the blades and permit locked blade deployment before the blades hit the target. 
     The broadhead is mounted on the lead end of an arrow fired by a crossbow or archery bow. Alternatively, the broadhead may be mounted on a spear, harpoon or like device. During flight of the broadhead, the blades are in a trailing, streamlined position to reduce aerodynamic drag so that the broadhead is similar to a field tip point and permits a more accurate shot. 
     The blades are mounted on the head in longitudinally extended slots by sliding and rotary connections that permit rapid rearward movement and rapid outward rotation of the blades to a locked, fully deployed position upon impact. Before impact, latches hold the blades in the streamlined position to reduce drag. 
     Initial impact of the blades with a target slides the blades rearwardly along the ferrule, releases the latched connections and quickly rotates the blades outwardly from the streamlined position to the outwardly extended deployed and locked position before the blades impact the target. To maximize impact, the blades must be locked in the deployed position before engagement with the target. 
     Rotational frictional forces exerted on the blades during outward rotation are reduced by providing a low-friction line contact rotary connection between each blade and a mounting member supporting the blade on the broadhead ferrule. The small area contacts between the blades and mounting members reduce frictional forces during outward rotation of the blade and deployment so that the blades are deployed and locked when the blades impact the target. 
     The mounting members are fitted in grooves to either side of blade slots in the ferrule. On impact, the mounting members and blades move rearwardly along the slots and are unlatched as the blades are rapidly rotated outwardly around the mounting members from the streamlined position to the fully deployed position. Outward rotation of the blades is facilitated by cams on the ferrule which engage follower surfaces on the blades. The blades include lock surfaces which lock the blades in the deployed position. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The improved broadhead is illustrated in the drawings where: 
         FIG. 1  is a perspective view of a broadhead with the blades retracted; 
         FIG. 2  is an exploded view of the broadhead shown in  FIG. 1 ; 
         FIG. 3  illustrates one cutting blade and a metal ball which is fitted in the blade to mount the blade on the head; 
         FIG. 4  illustrates the ball mounted in the blade; 
         FIG. 5  is a broken-away transverse sectional view taken through the forward end of the broadhead illustrating the connection between a blade and the head; 
         FIG. 6  is a view illustrating one blade mounted on the broadhead prior to impact with a target; 
         FIG. 7  is a view like  FIG. 6  showing initial impact with the target and rearward and outward rotation of the blade; 
         FIG. 8  is a view like  FIG. 7  showing the blade fully deployed and locked prior to penetrating the target; 
         FIG. 9  illustrates a latch member; and 
         FIG. 10  is a sectional view taken along line  10 - 10  of  FIG. 6 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Broadhead  10  includes a metal ferrule or body  12  mounted on the lead end of an arrow and three cutting blades  14  positioned in three slots  16  in ferrule  12 . The slots  16  extend longitudinally and outwardly along ferrule  12  and are spaced apart 120 degrees around the ferrule. Ferrule  12  includes a trocar tip  18  on the lead end of the ferrule, an indexing shaft  20  extending from the trailing end of the ferrule and a reduced-diameter, threaded end  22  extending rearwardly from shaft  20 . Ferrule  12  is preferably formed from steel. 
     Each blade  14  is preferably formed from uniform-thickness stainless steel. The blades have opposed parallel sides  24 , an elongate arm  26  extending from the front to the rear of the blade, and an inwardly extending mounting portion  28  below the forward end of arm  26 . Cylindrical hole or passage  30  extends through the front or forward end of portion  28 . Mounting member  32 , preferably a spherical steel ball, is positioned in hole  30 . The ball may be chrome-plated. The balls  32  engage the interior surfaces of the holes  30  at low-friction rotary line contact surfaces  34 , illustrated in  FIG. 5 . The surfaces  34  are located in the blades between blade sides  24 . 
     Slots  16  may have a width of 0.138 inches. Blades  14  may have a thickness of 0.136 inches so that the blades have close sliding fits in the slots. Holes  30  in the blades may have a diameter of 0.0938 inches with spherical mounting members  32  having a diameter of 0.093 inches for close, low-friction rotary fits in the bores. 
     The diameter of ball  32  is greater than the thickness of the arm so that, as illustrated in  FIG. 5 , the sides of ball  32  extend outwardly beyond blade sides  24 . 
     The mounting portion  28  of each blade  14  has a maximum depth at the lead end of the blade, adjacent hole  30  and a minimum depth at end  35  so that edge  38 , across from arm  26 , slopes inwardly toward the arm from hole  30  to end  35 . Latch recess  40  extends into blade  14  between end  35  and arm  26 . 
     Broadhead  10  includes a blade latch  42 , flat aluminum cam washer  44  and a resilient O-ring  46  fitted on shaft  20 . 
     The longitudinal slots  16  are formed in ferrule  12  and extend from tip  18  to ferrule end  48 . Each slot  16  has opposed, flat and parallel side walls  50  and a bottom wall  52  between the side walls. The side walls extend from the bottom wall to the outer surface of ferrule  12 . Semi-circular grooves  54  are formed in side walls  50 . The grooves lie on the surface of a cylindrical surface. Each groove extends along the length of the side wall from body end  48  to groove front end  56  adjacent tip  18 . The portions of balls  32  extending out from blades  14  have low-friction, line contact sliding fits in grooves  54  to permit ready sliding movement of the blades along slots  16  upon impact. The blades quickly rotate out from the retracted position shown in  FIGS. 1 and 6  to an extended or deployed position shown in  FIG. 8  around low-friction line contact surfaces  34 . 
     The slots  16  may be formed in ferrule  12  by first drilling cylindrical bores into the main body from ferrule end  48 . The bores angle down toward the axis of the ferrule as illustrated in  FIGS. 6 ,  7  and  8 . Then, the slots  16  are milled through the bores leaving grooves  54  in side walls  50 . The grooves slope inwardly from end  48  so that movement of the blades from the inner ends  56  of the grooves to outer ends  48  move the blades radially outwardly on the ferrule. 
     Blade latch  42  as shown in  FIG. 9  has a triangle-shaped, flat plastic body  70  having straight sides  72  and latch recesses at the corners of the body. The mouth of each recess  74  includes two inwardly extending retention projections  76 . The projections  76  reduce the width of recesses  74 . The outer and inner surfaces of the projections are angled to facilitate movement of the blades into and out from the recesses, as described below. 
     Broadhead  10  is mounted on an arrow (not illustrated) by positioning blade latch  42  onto the shaft  20  with the latch abutting ferrule end  48  as illustrated in  FIG. 6 . Washer  44  is placed on the shaft and O-ring  46  is placed on the shaft. The cutting blades  14  are positioned in slots  16  as illustrated in  FIG. 1  with balls  32  in holes  30  resting against the inner groove ends  56  illustrated in  FIGS. 7 and 8 . The blades are rotated to the retract position to move blade ends  35  past projections  76  and into latch recesses  74 . The projections hold the blades in the retracted position. See  FIG. 10 . 
     Threaded end  22  of ferrule  12  engages the forward end of a hollow connecting member  58  mounted on the lead end of the arrow. O-ring  46  is sandwiched between the lead end of the connecting member and washer  44  to secure head  10  on the arrow. The blade latch  42  holds blades  14  in the retracted, rearwardly extending position to reduce drag and improve accuracy when the arrow is fired at a target, indicated by vertical line  60  shown in  FIGS. 6 ,  7  and  8 . 
       FIG. 6  illustrates broadhead  10  in flight immediately prior to hitting target  60 . The blades  14  are positioned on ferrule  12  with balls  32  seated against groove ends  56 . Blade latch  42  holds the blades inwardly with edges  38  engaging washer  44 . 
       FIG. 7  illustrates broadhead  10  after initial contact of ferrule  12  with target  60 . Trocar tip  18  has penetrated the target. The surface of the target has engaged from shoulders  62  on blades  14  to push the blades rearwardly and outwardly from the ferrule. The balls  32  move back along grooves  54 . Edges  36  ride along lock washer  44  so that the blades are simultaneously moved rearwardly and rotated outwardly around balls  32  as illustrated in  FIGS. 7 and 8 . Outer rotation of blades  14  moves ends  35  past projections  76  and out from recesses  74 . Projections  76  slide along the sides of the blades as the blades are moved to the locked deployed positions. 
       FIG. 8  illustrates blades  14  fully deployed with lock surfaces  64  engaging lock washer  44 . Engagement of the blades with washer  44  locks the blades in the fully deployed position before the blades hit target  60 . 
     During movement of blades  14  from the retracted to the extended and latched positions, the blades and mounting members  32  move rearwardly along the line sliding connections between the portions of the mounting members extending outwardly of the blades and grooves  54 . At the same time, the blades rotate outwardly along rotary connections at circular line contact surfaces  34 . Frictional engagement between the blades and the mounting members is reduced because of the very small area of contact at the line surfaces. Reduction of friction at the rotary connections permits the blades to rotate outwardly very quickly so that they are locked in the extended position of  FIG. 8  before the outer target cutting surfaces of the blades engage the target.