Patent Application
20140256484
The present invention pertains generally to projectiles. More particularly, the present invention pertains to projectiles that are suited for use with man-powered weapons, such as a crossbow. The present invention is particularly, but not exclusively, useful as a projectile having a center of gravity located towards the forward end of the projectile and having cutting edges mounted towards the rear of the projectile.
Two of the most important considerations in the design and manufacture of projectiles are accuracy and effectiveness. In particular, these considerations may have greater importance when the projectile is to be fired from a so-called “man-powered” weapon, such as a crossbow or a compound bow. In general, projectiles that are used with such weapons will be constructed with an elongated shaft. Further, for hunting activities, these projectiles will typically employ a broadhead (cutting element) that is mounted at the fore-end of the shaft, and they will have some type of fletching (stabilizing element) that is mounted at the aft-end of the shaft. Both of these additions onto the shaft of a projectile (i.e. the cutting and stabilizing elements) can, however, have a profound effect on both the accuracy and the effectiveness of the projectile.
Insofar as accuracy is concerned, the in-flight stability of the projectile is critical. On this point, it is well known that stabilizing elements are most effectively located aft of the center of gravity, or center of pressure, of the projectile. Increased stability, of course, contributes to overall accuracy. On the other hand, unwanted aerodynamic forces that may be generated forward of the center of gravity, such as by an imperfect broadhead, may have substantial adverse effects on both the stability and accuracy of the projectile.
As for the effectiveness of a projectile, it is crucial that the projectile be accurately propelled. Further, it is important that the projectile have sufficient penetrating power upon contact with a target. With this in mind, it is recognized that establishing a relatively high momentum for the projectile (mass and velocity) at the time of its impact with the target is very desirable.
The result to be attained here is that the projectile needs to achieve an optimal penetration into the target. Of particular importance is that the cutting element of the projectile effectively penetrates the target.
In light of the above, it is an object of the present invention to provide a projectile that is predictably accurate. Another object of the present invention is to provide a projectile having enough momentum to be especially effective for hunting large game animals. Yet another object of the present invention is to provide a projectile that is easy to use, is relatively simple to manufacture, and is relatively cost effective.
In accordance with the present invention, a projectile is provided having an elongated shaft with a center of gravity that is located axially in the forward half of the projectile. Specifically, the location of the center of gravity in the forward end of the projectile is established in either of two ways. For one, two materials having different densities may be used for the structure of the projectile. For another, a single-type material can be configured to locate the center of gravity in the front quarter of the projectile. In either case, an array of cutting edges is mounted onto the shaft at the rear portion of the projectile.
When two materials are used for manufacture of the projectile, a nose portion consisting primarily of heavier, denser material is affixed to the forward end of the shaft. At the same time, a lighter, less dense material is used to manufacture the rest of the shaft. Thus, the projectile has more mass concentrated toward its forward half. Furthermore, the nose portion is aerodynamically clean; meaning the effects of aerodynamic forces on the nose portion during flight are minimized. For this purpose, the outer surface of the nose portion may be any of various geometrical shapes, such as ellipsoidal, cylindrical, or spherical. In any event, it is important that the center of gravity be located ahead of the midpoint, and preferably in the forward quarter of the projectile.
When the projectile of the present invention is manufactured using a single-type material, the projectile can be configured to locate its center of gravity ahead of the midpoint. To accomplish this, the projectile is constructed with the bulk of its material in its forward half. Stated differently, the mass of the projectile is not distributed equally along the length of the shaft.
In addition to the location of the center of gravity, the location of the cutting edges is an important aspect of the present invention. Structurally, an array of cutting edges is mounted on the projectile at the aft-end of the elongated shaft. In a preferred embodiment, the cutting edges will be configured to also function as stabilizing fins for the projectile, and three or more cutting edges will be used. More specifically, each cutting edge is preferably triangular in shape and the vertices of the cutting edge are coplanar with the shaft axis of the projectile. Also, in a preferred embodiment the cutting edge will be inclined in a rearward manner relative to the axis of the shaft.
Certain structural features of the present invention make it particularly suited for use with a man-powered weapon such as a crossbow. One such feature is the shape of the projectile that allows it to interact with the launch rail of a crossbow. For this purpose, the projectile is formed with two contact points; one contact point being near the fore-end of the shaft and one being near the aft-end of the shaft. At its aft-end, the shaft of the projectile is outwardly flared in a radial direction away from the shaft to create a substantially circular cross-section having a diameter “Dmax.” Thus, the contact point near the aft-end is established. This diameter, Dmax, at the aft-end of the shaft is substantially the same as the maximum diameter of the nose portion. Consequently, contact points at the fore-end and aft-end of the shaft will maintain the axis of the projectile shaft substantially parallel to the launcher rail of the crossbow.
Other features suited for use with a man-powered weapon include a nock and threaded receptacle that are located at the aft-end of the shaft. In detail, the nock is aligned perpendicularly to the shaft and is formed to engage with a bow string of a man-powered weapon such as a crossbow. On the other hand, the threaded receptacle extends from the aft-end of the shaft forwardly along the axis and into the shaft.
As envisioned for the present invention, when a projectile strikes a target, the projectile may become embedded in the target. Thus, a tool is provided that can engage with the threaded receptacle to more easily retrieve the projectile. More specifically, the tool for this purpose will be constructed with complementary threading designed for use with the threaded receptacle of the projectile.
The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
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While the Projectile with Aft-Mounted Cutting Edges as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.
