Patent Application
20060084535
1. Field of the Invention
The present invention relates to the field of archery. Specifically, the invention relates to arrowheads found on arrow devices.
2. Description of the Prior Art
Arrowheads and their associated aerodynamics are a key element for predictable flight of arrow assemblies. Prior art arrowheads can be broadly divided into two groups: those with little or no aerodynamic effect, such as the common field point, and those that do have a pronounced aerodynamic effect, whether intended or not, such as broadhead arrowheads.
Field point arrowheads are very simple devices that are commonly used for target practice. Field point arrowheads taper from a maximum diameter, equal to approximately the diameter of the arrow shaft, down to a point at the forwardmost end. Some variations of the simple field point geometry include three or four scallops in the field point surface. However these scallops are meant to provide a sharper point for penetration, not influence the aerodynamics of the arrow assembly. This simple point in all its prior art embodiments disturbs the air very little as the arrow assembly flies towards its intended target. A considerable drawback of the prior art field point is that the arrow assembly flight is governed entirely by the aerodynamics of the vanes at the aft end of the arrow. The arrow is essentially pushed through the air. This pushing can cause the flight path of the arrow to wander as the arrow is affected by random influences such as crosswind, oscillating vibration of the arrow shaft, and asymmetries between the arrow vanes. What the prior art lacks is a field point that is itself capable of stabilizing the flight of the arrow assembly.
Broadhead arrowheads were invented to increase effective hunting penetration and success potential. Typically two to four flat, triangular blades are arranged around the forward pointed tip. As the arrowhead enters the intended target, the blades slice a region much greater than a simple field point and increase the probability of inflicting mortal damage upon the intended target. These broad, flat blades have a pronounced aerodynamic effect that can radically affect the overall stability of the arrow in flight and significantly reduce the precision of flight. The forwardmost tip of such broadheads is typically either the flat blade itself, such as in the patents of Newnam (U.S Pat. No. 5,636,845) or Musacchia (U.S. Pat. No. 4,621,817); or the forwardmost tip is a field point-like cap that provides no aerodynamic effect, such as in the patents of Adams, jr. (U.S. Pat. No. 6,077,180) or Martinez, et. al. (U.S. Pat. No. 6,319,161). One recent improvement is the broadhead of Kuhn (U.S. Pat. No. 6,663,518) which employs blades whose geometry imparts an axial rotational spin on the arrow assembly during flight. However, the forwardmost tip of this broadhead is still basically a field point.
Mechanical broadhead arrowheads were developed to address problems associated with traditional bladed broadheads. Mechanical broadheads include deployable bladed or spiny bleeder appendages that remain closely attached to the main body of the arrowhead from release until impact. This reduces the overall aerodynamic effect of large, bladed structures during flight. Upon deployment, such appendages provide greater cutting surfaces and or means for lodging within the wounded target than a simple flat blade. Again, the forwardmost tip of such prior art broadheads is typically a field point-like cap, such as in the patents of Liechty, II (U.S. Pat. No. 6,171,206) and Maleski (U.S. Pat. No. 6,217,467), which provides no aerodynamic effect.
The present invention is a turbine tip arrowhead, used either strictly as a field point or as the forwardmost tip in concert with any prior art broadhead assembly. The key feature of this turbine tip arrowhead is the geometry, which includes a tapered tip and a plurality of helical rifles, consisting of either grooves or ridges, beginning at the tip of the field point and spiraling back towards the aft end. All rifles spiral in the same rotational direction giving the appearance of a turbine. This turbine tip design provides excellent rotation of the arrow shaft during flight without producing a large amount of aerodynamic drag. The invention is compatible with all contemporary arrow shafts.
When used as a replacement for the common field tip-like caps found on prior art broadhead assemblies, the turbine tip of the present invention again provides stabilizing, axial rotation of the arrow regardless of whether or not the broadhead main blades provide any axial rotation themselves. The rifling also inflicts additional damage while augering into the target upon impact. The invention is compatible with all contemporary broadhead assemblies.
With reference to
In the preferred embodiment there are between about three and about ten rifles 4 located symmetrically about the longitudinal axis of body 2. There are optimally about eight rifles 4 located symmetrically about the longitudinal axis of body 2. Too few rifles 4 will not provide enough rotational torque to produce the desired axial flow turbine aerodynamic effect. Too many rifles 4 must be so narrow or small that their aerodynamic effect becomes inconsequential as their aggregate surface approaches that of a smooth field point.
Rifles 4 are defined as grooves if the maximum diameter of the rifled portion of body 2 does not exceed the nominal maximum diameter of body 2. In other words, body 2 is tapered continuously from aft to point 3 and rifles 4 are cut into this otherwise smoothly tapered point. Rifles 4 are defined as ridges if the maximum diameter of the rifled portion of body 2 exceeds the nominal maximum diameter of body 2. Typically, rifles 4 will be V-shaped in cross section although other geometries would be obvious to one of ordinary skill in the art.
Field point 1 also includes an attachment means 5 used to mount field point 1 on a contemporary arrow shaft. Typically, attachment means 5 comprises a male-threaded post that is received by a female-threaded socket in the arrow shaft. However, attachment to an arrow shaft may comprise any method common in the art such as a press-fitting or gluing. In these embodiments, attachment means 5 of field point 1 may be a smooth socket or other means for mechanical engagement of the arrow shaft. Field point 1 may be made of any suitable material, such as, but not limited to, steel, aluminum, plastic, etc.
One of the features of the field point arrowhead of this invention is its ability to produce stabilized arrow flight without the use of fletching or tail fins (or feathers). The rotation induced in the arrow by the aerodynamically designed turbine tip is sufficient to stabilize the arrow in flight. Eliminating or reducing the size of the fletching in fact improves flight characteristics because the rotational drag normally induced by the fletching is avoided. It should be noted, however, that all embodiments of the arrowhead of the invention can be used with fletched arrow shafts as well.
The standalone point described above may be used in concert with any conventional broadhead. A conventional broadhead, as broadly defined, includes a ferrule, at least one blade coupled to the ferrule, a means for attachment of the broadhead to an arrow shaft, and a tip. In such a case, the cylindrical, pointed tip common on many contemporary broadheads is replaced by a tip having the same rifled geometry as the standalone point of the present invention.
One such novel broadhead, incorporating the turbine tip of the present invention, is described in
Broadhead arrowhead 100 further comprises a body or ferrule 107. At a first, or proximal, end, ferrule 107 incorporates a first end portion 108. First end portion 108 typically tapers to a reduced diameter at its most proximal end. Ferrule 107 also has a second, or distal, end portion 113. Second end portion 113 is of reduced diameter so that it may fit within the hollow end of a conventional arrow shaft. The aft portion of ferrule 107 may be slightly flared outwardly. It is not necessary that the aft portion of ferrule 107 be flared outwardly, however. As shown in the embodiment of
A mounting stub 114 extends rearwardly from second end portion 113 of arrowhead body 107. Typically, stub 114 is symmetrical about and coaxial with a longitudinal axis. Mounting stub 114, along with second end 113, is intended to fit into a mating recess typically located at one end of a standard arrow shaft. Stub 114 may be threaded to mate with matching threads in the arrow shaft recess or it may be seated in the recess in a press fit arrangement. Alternatively, mounting stub 114 may be glued or otherwise sealed into the mating recess of the arrow shaft.
In other variations of mounting means, instead of a stub 114, second end 113 of body 107 may be of diameter equal to or greater than that of an arrow shaft. Second end 113 may then be hollowed out to fit over said arrow shaft. In such an arrangement, the inside of hollow second end 113 may be threaded to mate with threads on the outer surface of the arrow shaft; or distal second end 113 may be press fit over the arrow shaft. Alternatively, second end 113 may be fitted over the end of the arrow shaft and glued or otherwise sealed to the arrow shaft.
A second key feature of broadhead arrowhead 100 is the inclusion of mechanically deployable blades 121 including an inertial trigger mechanism that both inhibits premature deployment during release and flight yet also facilitates deployment during impact with the intended target. Such a trigger is also found in the pending application of Kuhn (U.S. patent application Ser. No. 10/766,664). Each deployable blade 121 comprises an elongated third blade portion 123 that is sharpened on the side adjacent to body 107 when in the closed position. Integral to a first end of third blade portion 123 is a semi-circular, cam-shaped fourth blade portion 120. Integral to a second end of third blade portion 123 is a flag-shaped fifth blade portion 124. Fifth blade portion 124 comprises between about 20% and 50% of the total length of deployable blade 121.
Both elongated third blade portion 123 and integral cam-shaped fourth blade portion 120 are disposed in a plane at least substantially parallel to a longitudinal axis of body 107. Flag-shaped fifth blade portion 124 extends from third blade portion 123 at an angle thereto. Fifth blade portion 124 is preferably continuously curved, with a radius of curvature optimally between about 0.2″ and 0.5″, giving the blade the characteristics of an airfoil. The radius of curvature may vary over the surface of the blade. In the preferred embodiment, fifth blade portion 124 curves out of the plane of third blade portion 123 at a constant radius of curvature. The resultant leading edge region of fifth blade portion 124 is disposed at an angle to body 107 and also at an angle to third blade portion 123. This angle may be as great as 45 degrees or more, but optimally it is the range between approximately 5 and 5 degrees and most optimally in the range between approximately 5 and 25 degrees. In the closed position, fifth blade portion 124 resembles a swept forward wing.
Broadhead assembly 100 includes at least one associated deployable blade 121 and preferably three deployable blades 121. Cam-shaped fourth blade portion 120 fits into a deployable blade slot 110, which is cut into the side of ferrule body 107. Deployable blade slot 110 is substantially coplanar with a longitudinal axis of body 107 and is of a depth and geometry that permits deployable blade 121 to rotate freely about a pivot shaft 112 between the open position and the closed position as shown particularly in
As shown in the preferred embodiment in
Each of the fifth blade assembly portions 124 are angled out of the plane of their respective third blade portion 123 in the same rotational direction as shown in
Ferrule 107 further comprises an inertial trigger mechanism that both inhibits premature deployment of deployable blades 121 during release and flight, yet also promotes deployment of deployable blades 121 during impact with a target. Cylindrical cavity 109 begins at the leading face of the first end 108 of body 107 and continues down the longitudinal axis of body 107 to a depth approximately equal to the location of pivot shafts 112. The diameter of cylindrical cavity 109 is preferably in the range of 20% and 80% of the diameter of tip 101 and most preferably in the range of 25% and 50% of the diameter of tip 101. Cylindrical cavity 109 is symmetrical about the longitudinal axis of body 107.
Trigger 106 comprises a solid cylinder of outer diameter slightly less than the inner diameter of cylindrical cavity 109 such that trigger 106 can slide freely within cylindrical cavity 109 without binding or becoming cocked. Trigger 106 includes a trailing surface that interfaces with ledges 122 on both cam-shaped fourth blade portions 120 when deployable blades 121 are in the closed position. In the preferred embodiment, trigger 106 is a normal, right cylinder with walls perpendicular to its flat trailing surface. In this embodiment, ledges 122 are also flat so that they contact trigger 106 along their entire length when deployable blades 121 are rotated into the closed position. Trigger 106 may be made of any suitable material, such as, but not limited to, steel, aluminum, plastic, etc. Trigger 106 may also be coated with a lubricant, such as graphite, silicone oil, mineral oil, polytetrafluoroethylene, etc., in order to inhibit friction or binding along the inner surface of cylindrical cavity 109.
A mechanical tensioner 105 is located between the leading face of trigger 106 and the socketed aft end 104 of tip 101 and within cylindrical cavity 109. When tip 101 is integrated into broadhead assembly 100, the socketed aft end 104 of tip 101 compresses tensioner 105, which in turn urges trigger 106 in the aft direction and down upon ledges 122 of deployable blades 121. Tensioner 105 may comprise a coiled spring, a plug of reversibly compressible material, such as solid silicone, a collapsible volume filled with a compressible fluid, or any other means for storing mechanical energy that would be apparent to one of ordinary skill in the art.
During release and flight, inertial forces act to relieve compression on tensioner 105, thereby further urging trigger 106 in the aft direction and firmly retaining deployable blades 121 in the closed position by pressing firmly upon ledges 122. In the closed position, third blade portions 123 of deployable blades 121 are in close contact with the sides of ferrule body 107. Flag-shaped fifth blade portions 124 are disposed at angles laterally outward away from the sides of body 107.
During impact, flag-shaped fifth portions 124 of deployable blades 121 are forced laterally outward by contact with the surface of the target. At the same time, as rapid deceleration of the broadhead is occurring, trigger 106 is urged forward away from ledges 122 thereby compressing tensioner 105. The combination of torque applied by fifth blade portions 124 contact with the target and relieved rearward pressure applied by trigger 106 permits deployable blades 121 to overcome the engagement between ledges 122 and trigger 106 and rotate about pivot screws 112 toward the rear as shown in
The angle of deployment is limited by eventual contact between deployable blades 121 with ring 115. In the preferred embodiment, the maximum angle of deployment for blades 121 is preferably in the range of approximately 90 degrees and 170 degrees and more preferably in the range of approximately 100 degrees and 135 degrees as measured from the closed position. In the closed position, third blade portions 123 lie alongside body 107 and parallel to the longitudinal axis of body 107.
In the embodiment shown, ring 115 comprises a flat, annular device with an inner diameter equal to the outer diameter of second end 113 of body 107 and an outer diameter equal to the outer diameter of body 107. Ring 115 is placed over second end 113 prior to attaching second end 113 to an arrow shaft. Alternatively, ring 115 can be mechanically attached to body 107 by any means common in the art such as welding or adhesive bonding. Ring 115 may also be integrally formed along with body 107. Ring 115 may be made from any material such as steel, aluminum, plastic, etc., although metal is used in the preferred embodiment.
One of the features of the arrowhead of this invention is its ability to produce stabilized arrow flight without the use of fletching or tail fins (or feathers). The rotation induced in the arrow by the aerodynamically designed turbine tip used in combination with the deployable blades is sufficient to stabilize the arrow in flight. Eliminating or reducing the size of the fletching in fact improves flight characteristics because the rotational drag normally induced by the fletching is avoided. It should be noted, however, that all embodiments of the arrowhead of the invention can be used with all fletched arrow shafts as well.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
