Patent Publication Number: US-10309754-B2

Title: Self locking broadhead blade

Description:
TECHNICAL FIELD AND BACKGROUND 
     The technical field of the present invention relates generally to broadheads, a well known type of arrowhead, and more particularly to an expanding broadhead, a type of broadhead with an in-flight configuration in which the blades are retracted, and upon striking a target converts to a deployed, or target penetrating position in which the blades are expanded outward. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a cut-away side view of a broadhead in accordance with the present invention, with a portion of the broadhead body removed to show a single self-locking blade in the retracted, or in-flight position; 
         FIG. 2  is a perspective side view of a fully assembled two-bladed broadhead in accordance with the invention, with the self-locking blades locked in the retracted position; 
         FIG. 3  is a front view the self-locking blade of  FIG. 1 ; 
         FIG. 4  is a close-up view of the portion of  FIG. 1  proximate a blade locking lug of the broadhead body; 
         FIG. 5  is another close-up view of the broadhead of  FIG. 1  illustrating a ramp angle of a locking surface in the trailing edge of the self-locking blade; 
         FIGS. 6 through 8  illustrate a process of moving the self-locking blade from an unlocked position into the locked, or retracted position; 
         FIG. 9  is a side view of the broadhead of  FIG. 1  showing the blade in a hyper-extended position that occurs after contact with a target; 
         FIG. 10  is a side view of the broadhead of  FIG. 1  showing the blade in the deployed position; and 
         FIG. 11  is a side view of a complete two-bladed broadhead, also with the self-locking blades shown in the deployed position. 
         FIGS. 12 and 13  depict another embodiment of the blade portion of the broadhead with a spring member having a fixed end secured to the blade. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The instant invention is described more fully hereinafter with reference to the accompanying drawings and/or photographs, in which one or more exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be operative, enabling, and complete. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention. Moreover, many embodiments, such as adaptations, variations, modifications, and equivalent arrangements, will be implicitly disclosed by the embodiments described herein and fall within the scope of the present invention. 
     Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Unless otherwise expressly defined herein, such terms are intended to be given their broad ordinary and customary meaning not inconsistent with that applicable in the relevant industry and without restriction to any specific embodiment hereinafter described. As used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one”, “single”, or similar language is used. When used herein to join a list of items, the term “or” denotes at least one of the items, but does not exclude a plurality of items of the list. 
     For exemplary methods or processes of the invention, the sequence and/or arrangement of steps described herein are illustrative and not restrictive. Accordingly, it should be understood that, although steps of various processes or methods may be shown and described as being in a sequence or temporal arrangement, the steps of any such processes or methods are not limited to being carried out in any particular sequence or arrangement, absent an indication otherwise. Indeed, the steps in such processes or methods generally may be carried out in various different sequences and arrangements while still falling within the scope of the present invention. 
     Additionally, any references to advantages, benefits, unexpected results, or operability of the present invention are not intended as an affirmation that the invention has been previously reduced to practice or that any testing has been performed. Likewise, unless stated otherwise, use of verbs in the past tense (present perfect or preterit) is not intended to indicate or imply that the invention has been previously reduced to practice or that any testing has been performed. 
     Referring now specifically to the drawings, a broadhead and self-locking broadhead blade in accordance with one exemplary embodiment of the present disclosure are illustrated in  FIGS. 1 through 3 , and indicated generally at reference numerals  1  and  10 . Beginning with  FIG. 1 , a broadhead blade  10  is shown assembled to a broadhead body  22 . Only one blade is shown for clarity of illustration in several of the drawings, including  FIG. 1 , although a broadhead in accordance with the present disclosure would typically have a symmetrical configuration including at least two expanding blades, such as the fully assembled configuration of  FIG. 2 . 
     The broadhead body  22  may be similar in certain respects to prior art designs, including a target penetrating end or tip  23  at the front, an arrow shaft attachment end  24  at the back, and a longitudinal passage or slot  26  for receiving one or more blades. A blade retaining lug  28  and a blade locking lug  30  traverse the slot  26  substantially perpendicular to a longitudinal axis of the broadhead body. The blade retaining lug  28  is positioned forward of the locking lug  30  in slot  26 , or in other words closer to the penetrating end  23  of broadhead body. The lugs  28 ,  30  may be any type of cylindrical member or bar, such as press-fit metal dowel pins, screws, rivets, or the like that are installed in holes or recesses formed in the broadhead body. Alternatively the lugs may be fabricated as integrally formed portions of the broadhead body. In one particular embodiment the lugs are steel rivets (see  FIGS. 2 and 11 ) installed in holes that are simply cross-drilled through the broadhead body  22 . 
     The broadhead blade  10  has a perimeter defined by a front end  11 , a distal end  12 , an outward facing, sharpened leading edge  13  between the front end and distal end, and a trailing edge  14  opposite the leading edge. In the retracted blade position of  FIGS. 1 and 2 , the front end  11  faces generally forward, and includes a target contacting portion  32  that extends out from the broadhead body. The target contacting portion  32  is on an opposite side of the broadhead body  22  relative to the distal end  12  as shown in  FIG. 1 , however the blade could also be configured with the contacting portion  32  and distal end on the same side of body  22 . 
     The broadhead blade further includes an aperture  18  that captures the blade retaining lug  28  as shown, thereby functioning cooperatively with lug  28  to effectively retain the blade to the broadhead body. The aperture  18  has a contour that includes a deployed blade retaining surface  20  in a forward portion of the contour proximate the front end  11  of the blade, and a blade locating pocket  34  in an aft portion of the aperture contour substantially opposite the forward portion. The blade locating pocket  34  is configured to substantially restrict lateral movement of the blade  10  relative to the blade retaining lug  28  with the blade retracted. 
     Referring now also to  FIG. 4 , blade  10  further incorporates a locking system with an integral spring member  16  configured to bear against one of the blade retaining lug  28  or locking lug  30  when the blade is in the retracted, in-flight position. The spring member  16  may be integrally formed from the blade material, such as for example stainless steel, or fabricated as a separate element attached with conventional methods such as by bonding or welding. 
     The depicted locking system embodiment is intended to represent a spring member integrally formed from the blade material by forming or cutting a pair of adjacent grooves  41  through the blade. The grooves  41  essentially cooperate to define a spring in the form of an elongated, cantilevered, flexible bar that extends into the aperture  18 , or more specifically into the pocket  34  portion of aperture  18 , from a cantilevered end  45  to a free end  43 . The grooves may be parallel and arcuate in shape to produce the curved spring shape depicted, although other shapes such as straight, angled, or a zig-zag pattern are also feasible. In any case, a contact surface  15  at the free end is configured to bear against the blade retaining lug  28  when the blade is in the retracted position. 
     The spring member  16  works in conjunction with the locking surface  19  in the blade trailing edge to restrain the blade in the retracted position. To that end, spring member  16  is configured to create an interference fit so that in order for the locking surface  19  in the blade trailing edge to be forced over the blade locking lug  30 , the spring member must be deflected toward the distal end  12  of the blade. This elastic deflection of the spring member results in a forwardly directed force being exerted against the blade retaining lug  28  by the spring member, and an equal and opposite force being exerted by locking surface  19  against the blade locking lug  30 . 
     Referring to  FIG. 5 , the locking surface  19  may be configured with a ramp angle α. The ramp angle α is the angle between a line  29  defined by the locking surface  19 , and a perpendicular line  31  to a line “CL” passing through the center of lugs  28  and  30 . The ramp angle is selected to have sufficient slope to prevent the blade from unintentionally slipping off the locking lug  30  during arrow flight or from normal handling, while still allowing the blade to come off of the locking lug when the blade strikes a target. In one embodiment the ramp angle is between about zero and five degrees, and in another more particular embodiment the ramp angle is about one degree. 
     Although in the depicted embodiments the spring member  16  engages the blade retaining lug  28  in the aperture  18 , other configurations are possible. For example, the spring member may instead be located on the blade trailing edge, and configured to bear against (from above or below) the blade locking lug  30 . In such a configuration the spring member could incorporate a ramp angle or a detent feature to double as a blade locking surface. 
     It should be further appreciated that still other configurations and orientations of the spring member and/or locking surface may be beneficially utilized, any of which would be well within the spirit and scope of the invention. Generally stated, the blade retention system may be arranged in any manner that provides a first contact surface on an integral spring configured to bear against a first lug or blade locating feature of a broadhead body, and a second contact surface on the blade configured to bear against a second lug or blade locating feature of the broadhead body, such that the spring must be deflected or compressed for the blade to be placed in the retracted position in which the first and second contact surfaces are bearing against the respective first and second blade locating features. 
     The process of placing the blades in the retracted or in-flight position is illustrated by the sequence of  FIGS. 6-8 .  FIG. 6  depicts the blade  10  in an unlocked position wherein an outer corner  50  of locking surface  19  rests against the the side of locking lug  30 , and the spring member  16  rests against the blade retaining lug  28 . The lug  28  is near the bottom or aft portion of the aperture  18  in the blade locating pocket  34 . In this position the spring is undeflected, and there is no force being exerted against either of lugs  28  and  30  by the blade. 
     The blade may be moved toward the locked position by applying a lateral force “F 1 ” to the forward outer corner  47  of the blade forward end  11 . In a fully assembled broadhead with two blades, the lateral force may be conveniently applied by pinching the two corners  47  together. The applied force F 1  is reacted at lug  28  against one side of the blade locating pocket  34 , creating a couple tending to rotate the blade. For the single depicted blade, the reaction force is against the right side of the locating pocket  34 , and the direction of the applied couple is counterclockwise, tending to drive outer corner  50  of the locking surface  19  against lug  30 . 
     By applying enough force, the corner  50  of the locking surface will begin to ride up on lug  30 , pushing the blade in a forward direction toward the broadhead tip  23 , and causing the spring member  16  to deflect in a rearward direction as it bears against lug  28 . With sufficient continued force the blade rotation will continue, overcoming the resisting force of the spring member, while the locking surface  19  moves forward and laterally onto lug  30 .  FIG. 7  depicts an interim condition in which the blade has rotated counterclockwise far enough to move the outer corner  50  to the forward side of lug  30  approximately coincident with a line through the centers of lugs  28  and  30  (see line CL in  FIG. 5 ). In this condition the spring member  16  is at its maximum rearward deflection, and the lug  28  is at its rear-most position within the blade locating pocket  34 . 
       FIG. 8  shows the end result of continued application of force F 1 , with the blade rotated to the fully retracted position, and lug  30  seated in the inner corner  51  of the locking surface with the trailing edge  14 . In this position the spring member is still deflected rearward, applying a forward directed force to lug  28 , with an equal and opposite reaction force in a rearward direction being applied by locking surface  19  to lug  30 . This force between surface  19  and lug  30  created by spring member  16  together with the previously described ramp angle of surface  19 , tends to keep lug  30  seated in corner  51 , and laterally stabilized. 
     At the same time the forward end of the blade is laterally restrained and stabilized by the blade locating pocket  34 . As best seen in  FIG. 4 , the lateral width of the blade locating pocket is only slightly greater than the diameter of lug  28 . In one embodiment the width of blade locating pocket  34  measured adjacent the middle of lug  28  is between about 0.001 and 0.010 inches greater than the diameter of lug  28 . 
     The above described blade locking sequence is essentially reversed when the broadhead strikes a target and the blades deploy. Referring initially still to  FIG. 8 , upon initial target penetration, the contacting portion  32  of the blade is forced against the target, creating a wedging force against the blade at an outwardly directed angle. The wedging force (Indicated by arrow “F 2 ”) is reacted laterally at lug  28 , creating a clockwise couple or torque tending to rotate the blade clockwise about lug  28 , and swing the distal end of the blade  12  outward and away from the broadhead body  22 . The applied torque is resisted by friction between the locking surface  19  and lug  30  due to the interference fit of the blade against the lugs combined with ramp angle of locking surface  19 . However, as the momentum of the arrow continues driving the broadhead forward, the wedging force eventually overcomes the friction at lug  30 , and the blade abruptly releases from lug  30  swinging rapidly and freely outward. The rotational momentum of the swinging blade initially carries it out to a hyper-extended position shown in  FIG. 9 , unguided in the process by either of lugs  28  and  30 . In this position the contact between the blade and the broadhead body is at the blade retaining lug  28 , and specifically where the blade retaining surface  20  at the forward portion of aperture  18  bears against the blade retaining lug  28 . 
     As the broadhead continues to penetrate further into the target, the blade leading edge  13  eventually contacts the target, pushing the blade rearward and causing it to rotate counterclockwise, back toward the broadhead body. The rotation will continue until the blade again comes into contact with lug  30  at a blade bracing surface or notch  21  in the blade trailing edge  14 , as depicted in the deployed configuration of  FIGS. 10 and 11 . In this blade position the combination of the blade bracing surface  21  bearing against lug  30 , together with the blade retaining surface  20  bearing against lug  28 , act to brace the blade and prevent any further inward rotational movement. The blades will remain in the braced, deployed position and cut through the target for as far as momentum carries the broadhead forward. As in prior art broadheads, the blades are free to swing forward, allowing the broadhead to be pulled backward out of the target without any barbing effect. 
       FIG. 12  illustrates an embodiment in which the spring member  16 , while still forming a part of blade  10 , is not integrally formed from the blade material itself. Rather, it is formed separately, from any suitably springy or elastic material, and then installed in blade  10  within aperture  18 , either permanently or removably. For example, the blade may be made of stainless steel, and the spring  16  made of a high carbon spring steel. Other suitable spring materials may include high temper aluminum such as 6061 T6, high strength polymers such as graphite or carbon matrix composites, or other polymers with sufficiently high strength and stiffness. 
     In the depicted embodiment, the spring  16  coplanar with the blade, and made of a flat material having substantially the same thickness. The spring may include a cantilevered, or fixed end  45  that is enlarged in the manner of a flange and configured to fit securely inside a corresponding pocket  61  within aperture  18 . The remaining portion of spring member  16  from the fixed end  45  to the free end  43  is spaced away from the adjacent edges of aperture  18  to allow the spring to elastically deflect under load in the manner previously described. 
     The fit of the fixed end  45  in pocket  61  is configured to prevent the spring from falling out, and to prevent any slipping or rotation of the fixed end relative to the pocket when the free end of the spring is deflected, such as occurs when the blade  10  is forced into the retracted position. The means for ensuring a secure arrangement may comprise simply friction, or more positive measures such as creating an interference fit or bonding the spring to the blade with a braze or adhesive material. In addition, the profile shape of a contacting interface between fixed end  45  and the pocket  61  may be non-circular, or elongated, such that rotation of fixed end  45  cannot occur without permanently deforming either the pocket  61  or the spring, or both. 
     The spring member  16  and aperture  18  may be further configured with one or more features designed to facilitate an interference fit. Referring to  FIG. 13 , a keyhole slot  63  is formed in fixed end  45 , defining legs  64  on either side of the slot. The width of the fixed end  45  at the outside edges of the legs  64  is slightly greater than the width of the pocket  61 , creating an interference. Thus, in order to install the spring member in aperture  18 , the legs  64  must be first squeezed together while the fixed end  45  is fit into the pocket. Once the fixed end is sufficiently far inside the pocket, the legs may be released, causing them to push outward against the pocket, and thereby firmly securing the spring in the aperture. The position of the spring may then be adjusted as needed to ensure that the spring and blade are coplanar to each other. The spring may be removed from the blade, if desired, by simply applying enough force to the spring in a direction perpendicular to the surface of the blade to dislodge it from the pocket. 
     For the purposes of describing and defining the present invention it is noted that the use of relative terms, such as “substantially”, “generally”, “approximately”, and the like, are utilized herein to represent an inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     Exemplary embodiments of the present invention are described above. No element, act, or instruction used in this description should be construed as important, necessary, critical, or essential to the invention unless explicitly described as such. Although only a few of the exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in these exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the appended claims. 
     In the claims, any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. Unless the exact language “means for” (performing a particular function or step) is recited in the claims, a construction under § 112, 6th paragraph is not intended. Additionally, it is not intended that the scope of patent protection afforded the present invention be defined by reading into any claim a limitation found herein that does not explicitly appear in the claim itself.