# Patent

## Title
Arrowhead

## Abstract

A broadhead arrowhead having fully retractable blades wherein a plunger of the tip of the arrowhead causes the blades to shear a shear pin and deploy when the arrowhead strikes a target. In an alternative embodiment, the blades are retained in the arrowhead by a friction fit that is overcome to deploy the blades when the arrowhead strikes a target.

## Background
The instant invention relates to retractable blade arrowheads. The instant application claims priority to U.S. Provisional Patent Application Ser. Nos. 62/285,679; 62/389,059; and 62/392,245 filed Nov. 5, 2015; Feb. 16, 2016; and May 24, 2016 respectively. Broadhead arrowheads are known and comprise either fixed or retractable blades. Fixed blade broadheads are mechanically simple but suffer from relatively high aerodynamic drag from the exposed fixed blades. Fixed blade broadheads also require care in handling and storage to prevent blade dulling and accidental injury. The blades of many retractable blade broadheads do not fully retract into the body of the arrowhead and thus suffer from the same aerodynamic drag and safety problems as fixed blade broadheads.


BACKGROUND OF THE INVENTION
As discussed in U.S. Pat. No. 4,998,738 and U.S. Pat. No. 5,112,063, the objective for any hunting arrow with deployable cutting blades is to have the blades retracted to a more aerodynamic position during the flight of the arrow and to have the blades open to a cutting position which causes maximum hemorrhaging when the arrow strikes its quarry. As discussed above, traditional broadheads have fixed, exposed cutting blades which are subject to wind drag and other adverse wind effects during the flight of the arrow. It has been found that broadheads designed with deployable blades overcome the problems associated with wind effects and are more accurate than traditional fixed blade broadheads.
U.S. Pat. No. 2,859,970 discloses a cone which houses a pair of cutting blades therein where the cutting blades are mounted on a pivot pin. The Doonan device is frictionally fit over the tip of a target arrow. The intended design of the Doonan device is such that during the flight of the arrow, the cutting blades stay within the cone, thereby overcoming adverse wind effects on the flight of the arrow. When the cone strikes the animal, the arrow shaft rams the target tip into the back of the cutting blades such that they open up from the cone by pivoting on the pivot pin. One problem with the Doonan device is that the shaft of the arrow is likely to ram the cutting blades of the cone open just as the arrow is shot because of the inertia of the cone relative to the speed of the arrow. Another problem with the Doonan device is that the frictional engagement of the cutting blades against sidewalls of slots in the cone is not easily controllable.
U.S. Pat. No. 4,932,671 shows a phantom bladed broadhead where the cutting blades remain inside a cylindrical ferrule body during flight and are rammed open by a plunger, positioned to slide rearward from the front of the body, when the plunger impacts against the body of the animal. In Anderson, the cutting blades are not connected to the plunger but are pivotally connected to the cylindrical body by a ring which passes through a forward cut out section of each blade.
U.S. Pat. No. 4,504,063 discloses a broadhead which is designed to have a slimmer profile during flight and a wider, cutting profile upon impact. In LeBus, a plunger, which extends from the front of the broadhead while it is in flight, includes a weight at its rear section that acts against notches formed on the inside surfaces of the cutting blades when the broadhead strikes an animal. LeBus utilizes an O-ring to help hold the cutting blades in their slimmer profile during flight wherein the O-ring fits in a notched portion at the base of each cutting blade and the O-ring expands when the weight at the rear of the plunger forces the cutting blades open. Since the blades of the LeBus broadhead are always slightly open, the archer must be very careful when installing the O-ring so as not to get cut on the sharp blades of the broadhead.
U.S. Pat. No. 5,102,147 and U.S. Pat. No. 8,118,694 disclose broadheads having fully retracting blades. U.S. Pat. No. 7,713,152; U.S. Pat. No. 7,905,802; U.S. Pat. No. 8,905,874; and US Patent Application Publication 2015/0184986 disclose broadheads having partially retracting blades. The instant invention is directed at providing a better retractable blade arrowhead having fully retracting blades.
SUMMARY OF THE INVENTION
The instant invention is an important advance in the art of retractable blade arrowheads. The instant invention is an arrowhead comprising: (a) a cylindrical ferrule; (b) a tip; (c) a first blade; (d) a second blade; (e) a hinge pin; and (d) a shear pin, the ferrule having a longitudinal axis, the ferrule having a passageway thereinto along the longitudinal axis of the ferrule, the tip having a shank dimensioned to pass into the passageway, the ferrule having a first elongated aperture into said passageway on one side of the ferrule into which the first blade is positioned, the ferrule having a second elongated aperture into said passageway on the other side of the ferrule into which the second blade is positioned, the first blade having a first aperture near one end and a second aperture near the other end, the second blade having a first aperture near one end and a second aperture near the other end, the hinge pin positioned through the first aperture of the first and second blades, the hinge pin positioned near the shank of the tip, the ferrule having a bore therethrough transverse to the longitudinal axis of the ferrule, the shear pin positioned through said bore and through the second apertures of the first and second blades so that when the arrowhead strikes a game animal the shank of the tip pushes the hinge pin and blades to move in a direction along the longitudinal axis of the ferrule away from the tip to shear the shear pin so that the blades swing out from the ferrule on the hinge pin.
In another embodiment, the instant invention is an arrowhead comprising: (a) a cylindrical ferrule; (b) a tip; (c) a first blade; (d) a second blade; and (e) a hinge pin, the ferrule having a longitudinal axis, the ferrule having a passageway thereinto along the longitudinal axis of the ferrule, the tip having a shank dimensioned to pass into the passageway, the ferrule having a first elongated aperture into said passageway on one side of the ferrule into which the first blade is positioned within the ferrule, the ferrule having a second elongated aperture into said passageway on the other side of the ferrule into which the second blade is positioned within the ferrule, the first blade having a first aperture near one end and a detent projection near the other end, the first blade detent projection being an interference fit in the first elongated aperture, the second blade having a first aperture near one end and a detent projection near the other end, the second blade detent projection being an interference fit in the second elongated aperture, the hinge pin positioned through the first aperture of the first and second blades, the hinge pin positioned near the shank of the tip so that when the arrowhead strikes a game animal the shank of the tip pushes the hinge pin and blades to move in a direction along the longitudinal axis of the ferrule away from the tip so that the blades swing out from the ferrule on the hinge pin.
In yet another embodiment, the instant invention is a kit of parts packaged for retail sale, comprising: the arrowhead of the instant invention employing a shear pin made of an elastomer; and (b) a plurality of shear pins colored coded to correspond to the durometer value of the shear pin.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded view of the parts of a highly preferred embodiment of the instant invention;
FIG. 2 is a side view of the assembled arrowhead of FIG. 1;
FIG. 3 depicts the arrowhead of FIG. 1 in flight;
FIG. 4 depicts the arrowhead of FIG. 1 upon impact with the target;
FIG. 5 depicts the blades of the arrowhead of FIG. 1 fully deployed after impact with the target; and
FIG. 6 is an exploded view of the parts of another highly preferred embodiment of the instant invention.



DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, therein is shown an exploded view of the parts of a highly preferred arrowhead 10 of the instant invention. Arrowhead 10 includes cylindrical ferrule 13, tip 11 and tip retraction spring 12. The term “cylindrical” is defined herein to include a conical shape. Tip 11 has the terminal shape of a three sided pyramid and is notched with notches 11a. Tip plunger 11b is passed through spring 12 into ferrule 13. Set screw 15 retains tip 11 in ferrule by engagement near tip plunger flat portion 11c. Blade 20 is inserted into elongated aperture 17 in ferrule 13. Blade 21 is inserted into an elongated aperture (not shown) opposite elongated aperture 17 in ferrule 13 so that pin 24 is passed through aperture 20b in blade 20 and aperture 21b in blade 21. Then pin 24 is slid up elongated aperture 16 in ferrule 13 so that shear pin 18 can be passed through an aperture (not shown) opposite aperture 25 in ferrule 13, through aperture 21a of blade 21, through aperture 20a of blade 20 and then through aperture 25 of ferrule 13 so that bulbous portion 18b of shear pin 18 is positioned in aperture 25 with shear pin tail 18a extending from ferrule 13. Threaded shank 19 permits arrowhead 10 to be screwed into the shaft of an arrow or into the shaft of a crossbow bolt. A preferred shear pin 18 of the instant invention has a central diameter of 0.093 inches and is molded of an elastomer having a durometer value selected to shear upon impact of the arrowhead with a target. The preferred durometer value for use with a compound bow is a value on the A scale of between 40 and 45. Since a crossbow typically has a higher bolt acceleration upon firing, the preferred durometer value for use with a crossbow is a value on the A scale of between 50 and 60.
Referring now to FIG. 2, therein is shown a side view of an assembled arrowhead 10 with shear pin tail 18a shown extending from ferrule 13. Shear pin tail 18a is removed before use of arrowhead 10. Blades 20 and 21 are positioned on top of each other and folded into body 13 as seen through elongated aperture 17 in ferrule 13.
Referring now to FIG. 3, tip 11 is shown in its extended position retained by set screw 15. Shear pin 18 retains the blades of the arrowhead within ferrule 13. Hinge pin 24 is shown at one end of elongated aperture 16. FIG. 3 shows arrowhead 10 of FIG. 1 in flight.
Referring now to FIG. 4, when arrowhead 10 of FIG. 1 strikes a target game animal (such as a deer) tip plunger 11b is forced into ferrule 13 to force blades 20 and 21 from ferrule 13 shearing shear pin 18 as pin 18 is slid in the direction away from tip 11 along elongated aperture 16. Notch 20c in blade 20 and notch 21c in blade 21 are preferred to better enable blade 20 and blade 21 to fully deploy as shown in FIG. 5. The spring constant of tip retraction spring 12 and shear strength of shear pin 18 are readily confirmed by experiment. For example, if the spring constant of tip retraction spring 12 and shear strength of shear pin 18 are too low, then blades 20 and 21 will deploy in the air upon firing of the arrowhead thereby increasing the aerodynamic drag of the arrowhead. And, if the spring constant of tip retraction spring 12 and the shear strength of shear pin 18 are too high, the blades will fail to deploy upon striking the target. High power crossbows typically require higher shear strength shear pins while longbows typically require lower shear strength shear pins. Notches 11a in tip 11 shown in FIG. 1 are highly preferred because the pointed edges thereof increase the initial force of the tip shank 11b into ferrule 13 when arrowhead 10 strikes a game animal. It should be understood that an arrow tip terminating in a pyramid point wherein the edges of the faces of the pyramid are notched with cylindrical notches transverse to the edges of the pyramid is novel and unobvious as a separate invention disclosed herein. It should also be understood that tip 11 shown in FIG. 1 is not critical in the instant invention and that any tip shape can be used in the instant invention. Preferably, the arrowhead 10 of FIG. 1 is sold in a package that includes spare color coded shear pins of different shear strength together with recommendations for use with different bows, compound bows and crossbows.
Referring now to FIG. 6 therein is shown an exploded view of the parts of another highly preferred arrowhead 30 of the instant invention similar in many respects to the arrowhead 10 of FIG. 1. Arrowhead 30 includes ferrule 33, tip 31 and tip retraction spring 32. Tip plunger 31b is passed through spring 32 into ferrule 33. Set screw 35 retains tip 31 in ferrule by engagement near tip plunger flat portion 31c. Blade 40 is inserted into elongated aperture 37 in ferrule 33. Blade 41 is inserted into an elongated aperture (not shown) opposite elongated aperture 37 in ferrule 33 so that pin 44 is passed through aperture 40b in blade 40 and aperture 41b in blade 41. Then pin 44 is slid up slot 36 in ferrule 33. Detent projection 40a on blade 40 and detent projection 41a on blade 41 are an interference friction fit in their respective elongated apertures of ferrule 33 and serve to retain blades 40 and 41 in ferrule 33 before arrowhead 30 strikes a game animal or other target. The spring constant of tip retraction spring 12 and the friction of the interference fit of the detent projections 40a and 41a on blades 40 and 41 are readily confirmed by experiment. For example, if the spring constant of tip retraction spring 12 and the friction of the detent projections are too low, then blades 20 and 21 will deploy in the air upon firing of the arrowhead thereby increasing the aerodynamic drag of the arrowhead. And, if the spring constant of tip retraction spring 12 and the friction of the detent projections are too high, the blades will fail to deploy upon striking the target. High power crossbows typically require stronger springs and higher detent friction while longbows typically require weaker springs and less detent friction of the detent projections. Threaded shank 39 permits arrowhead 30 to be screwed into the shaft of an arrow or into the shaft of a crossbow bolt.
The tip and blades of the instant invention can be made of any suitable material but preferably are made of a metal such as stainless steel. The ferrule of the instant invention can be made of any suitable material but preferably is made of aluminum shaped by automatic machine tools. The shear pin of the instant invention can be made of any suitable material (such as brass, tin or a thermoplastic) but preferably is made of an elastomer such as silicone rubber.
CONCLUSION
While the instant invention has been described above and claimed below according to its preferred embodiments, it can be modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the instant invention using the general principles disclosed herein. Further, the instant application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains.

## Claims

1. An arrowhead comprising: (a) a cylindrical ferrule; (b) a tip; (c) a first blade; (d) a second blade; (e) a hinge pin; and (f) a shear pin, the ferrule having a longitudinal axis, the ferrule having a passageway thereinto along the longitudinal axis of the ferrule, the tip having a shank dimensioned to pass into the passageway, the ferrule having a first elongated aperture into said passageway on one side of the ferrule into which the first blade is positioned within the ferrule, the ferrule having a second elongated aperture into said passageway on the other side of the ferrule into which the second blade is positioned within the ferrule, the first blade having a first aperture near one end and a second aperture near the other end, the second blade having a first aperture near one end and a second aperture near the other end, the hinge pin positioned through the first aperture of the first and second blades, the hinge pin positioned near the shank of the tip, the ferrule having a bore therethrough transverse to the longitudinal axis of the ferrule, the shear pin positioned through said bore and through the second apertures of the first and second blades so that when the arrowhead strikes a game animal the shank of the tip pushes the hinge pin and blades to move in a direction along the longitudinal axis of the ferrule away from the tip to shear the shear pin so that the blades swing out from the ferrule on the hinge pin.

2. The arrowhead of claim 1, wherein the tip terminates at the point of a pyramid with the edges of the faces of the pyramid being notched.

3. The arrowhead of claim 2, wherein the notches are cylindrical in shape and transverse to the longitudinal axis of the ferrule.

4. The arrowhead of claim 2, wherein the pyramid has three faces and wherein the notches are cylindrical in shape and transverse to the longitudinal axis of the ferrule.

5. The arrowhead of claim 4, wherein the shear pin is made of an elastomer.

6. The arrowhead of claim 1, wherein the shear pin is made of an elastomer.

7. A kit of parts packaged for retail sale, comprising: (a) the arrowhead of claim 6; and (b) a plurality of shear pins each being colored coded to correspond to the durometer value of the shear pin.

8. The kit of parts of claim 7, wherein the tip of the arrowhead terminates at the point of a pyramid with the edges of the faces of the pyramid being notched.

9. The kit of parts of claim 7, wherein the pyramid has three faces and wherein the notches are cylindrical in shape and transverse to the longitudinal axis of the ferrule.