Patent Publication Number: US-7708659-B2

Title: Fixed blade broadhead

Description:
This application claims benefit of U.S. provisional patent application 60/792,690 filed Apr. 18, 2006, which is hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to archery arrow broadheads, and more particularly to fixed blade broadheads including replaceable blades and a related method of manufacture. 
   When used to hunt game, archery arrows usually are tipped with broadheads having cutting blades designed to maximize penetration and cutting of tissue, which quickly and humanely harvests the game. A variety of broadheads are available, one of which is a fixed blade broadhead including blades that can be manually replaced if dulled or damaged during use. 
   Most fixed blade broadheads include a ferrule, a separate and replaceable sharpened tip, and separate and replaceable sharpened blades secured to the ferrule. In such broadhead constructions, the blades are usually triangular, with the forward and rearward portion both secured to the ferrule. Usually, the rearward portion of the blade includes a projecting tang. A ring slides over a rear portion of the ferrule and encircles the tang to secure the rearward portion of the blade to the ferrule. 
   Securing a rearward portion of a broadhead blade to a ferrule is generally considered an easier task than securing the forward portion of a blade to the ferrule. Broadhead manufacturers have used several different constructions for this forward securement. 
   One such construction is disclosed in U.S. Pat. No. 5,482,293 to Lekavich. Lekavich discloses a plastic ferrule, a replaceable blade positioned within lands defined by the plastic ferrule, and a metal injection molded tip. The tip includes a 45° rear inclined surface which engages the cutting edges of the blades. Lekavich requires that the ferrule must be plastic and deformable so that when the broadhead is installed on an arrow, the forward portions of the blades are driven down into the plastic lands, necessarily deforming the lands. Although this construction can secure the forward portion of the blade, the integrity of the ferrule is compromised due to the plastic deformation. Furthermore, if the blades are bent in use, this can tear or destroy the plastic lands of the ferrule. Thus, the broadhead is rendered a “one use” broadhead, which defeats the purpose of including replaceable blades. 
   Another broadhead construction that secures forward portions of replaceable blades is disclosed in U.S. Patent Publication 2005/0059516 to Davis and is offered under the Wac&#39;Em™ trade name. In the Davis construction, a forward portion of a blade forms an unsharpened, block-shaped tang. The ferrule of the Davis construction defines a complimentarily block-shaped retaining notch. This retaining notch is machined into the ferrule, that is, the ferrule material must be removed from the ferrule to define this block-shaped retaining notch. Although the Davis construction provides another way to secure the forward portion of the blade, it requires drilling or grinding away of the ferrule. In many cases, this is time consuming and wasteful of the ferrule material. In addition, additional care must be taken to ensure that excess heat is controlled so that the ferrule material is not weakened around the notch. 
   Conventional broadheads provide several ways to secure replaceable fixed blades; however, room exists for improvement. 
   SUMMARY OF THE INVENTION 
   The aforementioned problems are overcome in the present invention, which provides a broadhead including at least one replaceable blade and a ferrule, each of which include interlocking features to securely lock at least the forward portion of the blade to the ferrule. 
   In one embodiment, the broadhead includes a ferrule defining a blade slot that is bounded by a non-deformable metal land and a non-deformable metal inclined surface overhanging a portion of the metal land. A blade including a cutting edge and a slot engagement surface is positioned in the blade slot. The blade slot engagement surface is wedged against the blade slot inclined surface when the broadhead is installed on the arrow shaft by a user to securely trap the blade within the blade slot. 
   In another embodiment, the blade cutting edge terminates short of a forward portion of the blade, and the slot engagement surface is inclined relative to a land edge of the blade. The slot engagement surface of the blade directly engages a metal inclined surface overhanging a portion of the metal land. 
   In yet another embodiment, the forward portion of the blade forms a substantially triangular locking member, and the slot is formed with a substantially triangular forward portion of the blade slot. The blade locking member wedges within the slot triangular forward portion to secure the blade to the ferrule. 
   In a further embodiment, a blade slot land is constructed from a non-deformable metal material. Optionally, the ferrule can be constructed as a monolithic metal construction. 
   In yet another embodiment, a method is provided that includes: metal injection molding at least a ferrule defining a blade slot that is bounded by a land and an inclined surface, the inclined surface overhanging a portion of the land; sintering the ferrule; and joining a blade with the ferrule, the blade including a cutting edge coupled to a land edge in a forward portion of the blade. The forward portion of the blade wedges between the land and the inclined surface of the blade slot. Optionally, this wedging action is performed without deforming the land or the inclined surface of the slot. 
   In yet a further embodiment, the metal injection molding step includes forming the forward portion of the slot in a substantially triangular configuration. Optionally, the forward portion of the blade can also include a substantially triangular locking member that corresponds with the forward portion of the slot. The blade itself can be configured so that the cutting edge terminates short of the substantially triangular locking member and abuts against a portion of the inclined surface when the blade is joined with the ferrule. Further optionally, other components, such as the blade and/or the interlocking features may be formed via metal injection molding and/or powder injection molding. Other casting processes, such as die-casting, investment casting, thixotropic molding or injection molding, may be used to form the ferrule, the blade and the interlocking features of the broadhead of the present invention as desired. 
   The present invention provides a simple and easy way to manufacture broadheads including a ferrule and replaceable blades that securely lock to the ferrule. The resulting broadhead includes a rugged and sturdy blade locking system. Due to the locking features, the blades are quickly and easily replaced with minimal effort. Further, when the blade components are metal injection molded or powder injection molded, material can be conserved, and manufacturing time significantly reduced. 
   These and other objects, advantages and features of the invention will be more readily understood and appreciated by reference to the detailed description of the invention and the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a first embodiment of the broadhead installed on an arrow; 
       FIG. 2  is a side view of a ferrule of the broadhead; 
       FIG. 3  is a cross-sectional view of the ferrule taken along lines  3 - 3  of  FIG. 2 ; 
       FIG. 4  is a side sectional view of the ferrule of the broadhead with an exemplary blade being inserted into a blade slot of the ferrule; 
       FIG. 5  is a sectional view of a blade installed in the blade slot of the ferrule; and 
       FIG. 6  is a front view of the broadhead with multiple blades installed therein. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   I. Construction and Components 
   A broadhead constructed in accordance with an embodiment of the invention is illustrated in  FIGS. 1-6  and generally designated  10 . The broadhead  10  generally includes a ferrule  20  that defines an interlocking pocket  32 , and a blade including a locking member  42 . The locking member  42  can be wedged into the pocket  32  of the ferrule  20  when the broadhead  10  is installed on an arrow shaft  100 . An optional retaining member  50  can be disposed adjacent the rearward portion of the blade. For purposes of a disclosure, the broadhead is described in connection with use on an archery arrow; however, the broadhead is well suited for use with any projectile shooting device. 
   With reference to the figures, the components of the broadhead will now be described in further detail. Referring specifically to  FIGS. 2-3  and  6 , the forward most portion of the ferrule  20  includes a trocar tip  22  having multiple integral blades  24 . The number and configuration of these cutting edges  24  can vary as the application requires. The integral blades are aligned substantially in parallel with the blade cutting edges  44  of the corresponding blades  40 . However, the integral blades of the trocar tip are offset a distance above or below the blade cutting edge  44  when viewed from the side of the broadhead. The trocar tip  22  transitions to curved indentations  25  defined by the ferrule. Rearward of the curved indentation portions  25 , the ferrule  20  includes a shoulder  26 . Rearward of the shoulder  26 , the ferrule is reduced in cross section and forms a generally cylindrical portion  28 . The rearward portion of the cylindrical portion  28  can define threads  29 . These threads can be scaled and pitched to fit corresponding threaded bores of an archery arrow insert  101  and/or other threaded apertures. As will be appreciated, other fastening structures can be readily substituted for the threads  29 . 
   In the embodiment shown, the ferrule  20  is monolithic structure. Therefore, all components and structures associated with the ferrule can be integral with the ferrule and contiguous with other components of the ferrule. As will be discussed below, this monolithic configuration can be achieved via metal injection molding, powder injection molding or by other casting processes. 
   Referring further to  FIGS. 2-3 , the ferrule  20  defines a blade slot  30 . As used herein, the term slot can also refer to a groove, a recess, an aperture, an indentation, and a hole defined by the ferrule. The blade slot  30  can be defined from a forward portion of the ferrule  20 , near the trocar tip  22 , to the rearward portion of the ferrule, nearing the threads  29 . The exact location of blade slot can be modified as the application requires. In the embodiment shown, the blade slot includes opposing slot sidewalls  31  and  33 . Again, where the ferrule is monolithic and constructed from metal, the sidewalls accordingly will be constructed from metal. Generally, the sidewalls can extend the entire length of the blade slot from front to rear of the ferrule  20 . 
   The blade slot  30 , shown in  FIGS. 4 and 5 , can further be bounded by a land  34 . As desired, the land can include undulations or surface contours corresponding to features of the blade, further interlocking the blade with the land  34  as the application requires. Optionally, the land  34  can be uninterrupted by any surface undulations contours or projections as it transitions from the triangular shaped pocket  32  toward the rearward most portion of the blade slot  30 . For example, the land can be substantially linear and aligned in parallel with the longitudinal axis A of the ferrule  20 . The land  34  can transition to a contiguous inclined surface  35 , which overhangs at least a portion of the land  34 . The inclined surface  35  and the land  34  can cooperate to form a locking recess or pocket  32  generally in the shape of a triangle in the forward portion of the slot  30 . The angle of the inclined surface relative to the longitudinal axis A of the ferrule  20  and/or the land  34  can be about 15° to about 60°, optionally about 35° to about 50°, and further optionally about 45°. At the location where the inclined surface  35  and the land  34  transition, also referred to as the forward most portion of the slot, the slot structure can be pointed, rounded and/or angled relative to the land. 
   The monolithic ferrule  20  can be constructed entirely from metal. Optionally, this metal is substantially rigid and non-deformable. Accordingly, the land  34  and inclined surface  35  can be non-deformable so that when the blade  40  is installed in the blade slot  30  and wedged against and engages these two components of the blade slot  30 , these components do not deform. Slight scratching and/or marring of these components is not considered deforming. 
   With reference to  FIGS. 4 and 5 , the blade  40  of the broadhead  10  includes a forward portion  41  and a rearward portion  43 . In addition, the blade defines a blade cutting edge  44  coupled to a blade land edge  48  and a blade rear edge. The blade further includes opposing blade sides and defines a recess or aperture as desired. The rearward portion of the blade  43  can include an optional tang or tab  49  of any desired configuration. This tab  49  can be captured by an optional retaining member  50 . As shown, that retaining member is generally an annular or ringed shaped element that fits over a portion of the tab  49  when the blade is disposed in the slot  30 . 
   At the forward portion  41  of the blade  40 , the blade includes a locking member  42 . This locking member is generally substantially triangularly shaped. Of course, the forward most portion of this locking member  42  can be pointed, rounded or cut off at an angle relative to the land edge  48  as desired. Optionally, the forward portion of the blade includes a slot engagement surface  47  that is inclined relative to the land edge. The angle of inclination of this slot engagement surface  47  can be similar to that described above in connection with the inclined surface  35 . Indeed, the locking member  42  can be correspondingly shaped and include the same dimensions as the locking pocket  32 . 
   As shown in  FIG. 5 , the cutting edge  44  can terminate short of the forward portion  41  of the blade, specifically the cutting edge  44  can transition at a notch  45  to the forward portion. The forward portion can be offset a distance below or above the uppermost portion of the cutting edge  44 . 
   When the blade  40  is installed in the blade slot  30 , the forward portion  41  of the blade is trapped in the ferrule  20  via the locking member  42  engaging the pocket  32 . Specifically, when the ferrule is installed on an arrow and threaded or otherwise tightened relative to the arrow  100  or arrow insert  101 , the blade  40  is pressed forward so that the locking member  42  wedges within the pocket  32 . More specifically, the slot engaging surface  47  frictionally engages the inclined surface  35  of the blade slot  30 . Likewise, the land edge  48  frictionally engages the land  34  of the blade slot  30 . Again, where the ferrule  20  is constructed from an non-deformable material, this engagement does not cause deformation of the inclined surface  35  or the land  34 . 
   As shown in  FIG. 5 , the notch  45  can engage a portion of the trocar tip  22  adjacent the inclined surface  35  overhanging the blade slot  30 . In one embodiment, this engagement does not occur until after the triangular locking member  42  is fully wedged within the pocket  32  to frictionally secure the forward portion of the blade  41  within the blade slot  30 . 
   II. Method of Manufacture 
   A method of making a broadhead  10  will now be described. This method includes manufacturing the ferrule, and optionally the replacement blades from a metal, such as a steel alloy, using a metal injection molding (“MIM”) or powder injection molding (“PIM”) process. Features of the ferrule such as the blade slot  30  defining the interlocking pocket  32 , can be formed in a finished manner using the MIM or PIM process. 
   In general, the metal injection molding process includes injection molding a mixture of powdered metal and binder into a mold configured in the shape of the ferrule. The ferrule mold can define a blade slot, the blade slot being bounded by a land and an inclined surface that overhangs a portion of the land as described above. It will be appreciated the other features of the broadhead described above can be included in the ferrule mold as desired. 
   After the ferrule is metal injection molded, it undergoes a debinding step and a subsequent sintering operation, which is a form of heat treatment that bonds the particles and increases the density and strength of the finished ferrule. A more detailed description of the MIM process and the formation of broadhead components such as ferrules and blades is included in U.S. Pat. No. 6,749,801 to Louis Grace, Jr. et al, which is hereby incorporated by reference, and U.S. Pat. No. 6,290,903 to Louis Grace, Jr. et al, which is also incorporated by reference. 
   With the ferrule metal injected molded or otherwise formed, the blade  40  is joined with the ferrule. As shown in  FIGS. 3 ,  4  and  5 , the blade  40  is inserted into the blade slot  30  so that the land edge  48  engages the land  34 . In addition, the slot engagement surface  47  engages the inclined surface  35  of the ferrule  20 . Generally, the locking member  42  is inserted within the interlocking pocket  32  of the blade slot. Where the notch  45  is included, the notch may engage the rearward portion of a trocar tip  22 . 
   With the blade installed in the blade slot  30 , the annular member  50  is positioned over the tab  49  of the blade to secure the rearward portion of the blade  43 . The broadhead can be installed on an arrow by a user. As the broadhead is threaded into the arrow  100 , the arrow insert  101  and/or the arrow and/or the retaining member  50  engages the blade  40  thereby urging the blade forward while drawing the ferrule  20  into the arrow insert or arrow shaft. Accordingly, the locking member  42  is lockingly wedged within the pocket  32  of the ferrule. By way of this wedging action, the forward portion of the blade frictionally engages the inclined surface  35  and the land  34 , and traps the forward portion of the blade within the blade slot of the ferrule. Where the ferrule  20  is constructed from metal, the components of the blade  40  may scratch or slightly mar the blade slot, namely the land  34  and the inclined surface  35 . 
   Optionally, the monolithic ferrule  20  and the blades  40  can be manufactured using other processes. For example, where the ferrule is manufactured from a light metal alloy, it can alternatively be formed via a casting process such as die-casting, investment casting or thixotropic molding. 
   The above descriptions are those of the preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any references to claim elements in the singular, for example, using the articles “a,” “an,” “the,” or “said,” is not to be construed as limiting the element to the singular.