Abstract:
A radio transmitter assembly for use in tracking an arrow employs an insert containing a radio transmitter that can inserted through the open end of an arrow and into the interior of the arrow shaft. After the insert has been secured within the arrow shaft, an arrow head can be secured to a connector on the insert.

Description:
RELATED APPLICATION  
       [0001]    The present application is based on, and claims priority to the applicant&#39;s U.S. Provisional Patent Application No. 60/244,030, entitled “Radio Frequency Trackable Arrow With Receiver,” filed on Oct. 27, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to the field of remote tracking systems. More specifically, the present invention discloses a radio transmitter assembly for tracking an arrow.  
           [0004]    2. Statement of the Problem  
           [0005]    Modern hunting arrows can be relatively expensive. After being fired, arrows can become lost, broken, or become embedded in a wounded animal. Therefore, a need exists for a system to assist in tracking arrows.  
           [0006]    The prior art in this field includes several examples of radio transmitters for tracking arrows, but these approaches have serious limitations or shortcomings. Placing a radio transmitter and its associated batteries in the head of an arrow results in an assembly that is too heavy and awkward for proper flight characteristics. Placing the radio transmitter within the shaft of the arrow creates a risk that the transmitter could be damaged if the shaft is broken, as is often the case when a wounded animal runs through heavy brush or woodlands. In that event, the hunter could lose his investment in both the arrow and the transmitter assembly.  
           [0007]    Another difficulty associated with prior art approaches has been the limited life of the battery. Due to space and weight constraints, only a very small, light-weight battery can be used to power the radio transmitter. Therefore, a need also exists for a means to quickly and easily activate the transmitter before firing the arrow, so that battery life is maximized.  
           [0008]    3. Prior Art  
           [0009]    The following prior art patents disclose radio transmitters used to track the location of an arrow:  
                                                       Inventor   Patent No.   Issue Date                           Ratkovich   3,790,948   Feb. 5, 1974           Robinson et al.   4,675,683   June 23, 1987           Boy et al.   Re. 33,470   Dec. 4, 1990           Treadway   4,976,442   Dec. 11, 1990           Rodriguez   5,450,614   Sep. 12, 1995                      
 
           [0010]    Ratkovich discloses a radio-transmitting hunting arrow in which the battery and transmitter are housed in the arrow head. The antenna extends from the arrow head along the hollow shaft of the arrow.  
           [0011]    Robinson et al. disclose a radio transmitter for tracking spent hunting arrows in which the transmitter is placed in a cylindrical housing having the same cross-sectional diameter as the arrow shaft. The transmitter section is connected in series between the arrow head and the shaft of the arrow. However, this approach lengthens the arrow and changes its flight characteristics.  
           [0012]    Boy et al. disclose a system for recovering a hunting arrow. A radio transmitter is housed within the arrow shaft. An inertial switch is employed to activate the transmitter.  
           [0013]    Treadway discloses an arrow with a removable radio transmitter. The transmitter fits into a notch or slot in the arrow shaft. A curved hook attached to the transmitter projects through the notch or slot. If the arrow strike an animal, the hook engages the hide, bone, or tissue of the animal so that the transmitter will remain with the animal, regardless of the location of the arrow.  
           [0014]    Rodriguez discloses an arrow tracking apparatus in which a radio transmitted is housed in a jacket that fits over the arrow shaft.  
           [0015]    4. Solution to the Problem.  
           [0016]    None of the prior art references discussed above show a radio transmitter assembly for tracking the location of an arrow in which the transmitter is housed in an insert within the hollow arrow shaft. To minimize weight, most conventional hunting arrows have a hollow shaft. The arrow head is normally secured to the end of the shaft by means of threads that engage a threaded metal insert that has been permanently bonded into the end of the shaft. The present invention employs an insert that largely matches the weight and size of a conventional insert, but also houses a radio transmitter. This enables the present invention to be used in conjunction with conventional hunting arrows without significantly changing the length or weight of the arrow, or otherwise altering its flight characteristics.  
           [0017]    In addition, the radio transmitter in the present invention is protected within the arrow shaft and insert. If the arrow strikes a hard object, the force of the impact is largely carried through the wall of the insert and the arrow shaft itself, rather than through the radio transmitter. If an animal is wounded by an arrow, the animal will often seek cover in heavy brush or woodlands, which can result in the arrow being snagged or broken. The insert used in the present invention minimizes the risk that the radio transmitter might be damaged or become detached from the animal if the arrow shaft is broken. In particular, the insert containing the radio transmitter is screwed securely onto the arrow head, which minimizes any risk that it will become detached from the animal. In addition, the insert is permanently bonded with adhesive into the end of the arrow shaft. This reinforces the end of the arrow shaft and makes its more likely that the shaft would break at a different point along its length. This configuration maximizes the probability that the arrow head and at least the adjacent portion of the arrow shaft containing the insert will remain with the animal.  
         SUMMARY OF THE INVENTION  
         [0018]    This invention provides a radio transmitter assembly for use in tracking an arrow. An insert containing a radio transmitter is inserted through the open end of an arrow and into the interior of the arrow shaft. After the insert has been secured within the arrow shaft, an arrow head can be secured to the insert.  
           [0019]    These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    The present invention can be more readily understood in conjunction with the accompanying drawings, in which:  
         [0021]    [0021]FIG. 1 is an exploded cross-sectional view of an arrow with the present radio transmitter assembly.  
         [0022]    [0022]FIG. 2 is a detail cross-sectional view of the radio transmitter assembly.  
         [0023]    [0023]FIG. 3 is a schematic diagram of a radio transmitter circuit using amplitude modulation.  
         [0024]    [0024]FIG. 4 is a schematic diagram of a radio transmitter circuit using frequency modulation.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    Turning to FIG. 1, an exploded cross-sectional view is provided of an arrow with the present radio transmitter assembly. The arrow itself can be conventional. For example, the arrow shown in FIG. 1 has a conventional shaft  10 , fletching  12 , nock  14 , and head  15 . The arrow shaft  10  is conventionally made of fiber glass or another suitable composite material. It typically has a hollow interior that is accessible through the open end of the arrow shaft  10 . The arrow head  15  has a threaded base  16  that would allow it to be threaded into a conventional insert in the end of an arrow shaft  10 .  
         [0026]    In the present invention, the conventional insert is replaced with a radio transmitter assembly. FIG. 2 is a detail cross-sectional view of the radio transmitter assembly. The components of this assembly are housed in a generally cylindrical insert  20 . This insert  20  has a socket  22  to receive the base of the arrow head  15  and threads  25  to engage the threads  16  on the arrow head  15 . In the preferred embodiment of the present invention, an interior passageway extends along the longitudinal axis of the insert  20  from the socket  22  through the threads  25 . The lower portion of the interior passageway contains a radio transmitter  30  and a number of batteries  32 , as will be discussed below. The lower end  27  of the insert  20  can be constricted or crimped to hold the radio transmitter  30  and batteries  32  in place within the insert. Alternatively, these internal components could be potted or bonded with adhesive within the insert  20 .  
         [0027]    The insert  20  has exterior dimensions that allow it to be inserted through the open end of the arrow shaft  10  into the hollow interior of the arrow shaft  10 . Insertion of the insert  20  continues until the upper end of the socket  22  is generally even with the open end of the arrow shaft  10 . The insert  20  can be designed with substantially the same diameter as a conventional insert to result in a snug, friction-fit against the interior of the arrow shaft  10 . This configuration allows the present invention to be directly substituted in place of a conventional insert without modifications to existing arrows. The insert  20  can be permanently bonded to the arrow shaft with adhesive or other equivalent means.  
         [0028]    Either metallic or non-conductive materials can be used to fabricate the insert. If a conductive material is used, the body of the insert provides a degree of electromagnetic shielding for the radio transmitter  30  and can form part of the power circuit between the radio transmitter  30  and the batteries  32 . However, a non-conductive insert simplifies assembly of the device and eliminates the risk that the insert might accidentally short the radio transmitter  30  or its antenna  35 .  
         [0029]    In the embodiment shown in FIGS. 1 and 2, the socket  22  and threads  25  serve as a connector to secure the arrow head  15  to the insert  20 . This is largely a matter of convention to enable the present invention to be used in conjunction with existing arrow heads  15  having a threaded base  16 . However, it should be understood that other types of connectors could be readily substituted to secure an arrow head  15  to the insert  20 . For example, a bayonet-type connector could be used.  
         [0030]    The output signal from the radio transmitter  30  is broadcast by an antenna  35  extending from the radio transmitter  30  through the insert  20  and along the interior of the shaft  10  of the arrow. For example, the antenna  35  can be a wire having a length of approximately one-quarter wavelength (e.g., approximately 6-15 inches).  
         [0031]    The radio transmitter  30  is powered by a number of batteries  32  (e.g., two conventional 1.5 volt watch or calculator batteries providing a total of about 3.0 volts to the radio transmitter  30 ). In the preferred embodiment of the present invention, the batteries  32  are stacked in axial alignment with the radio transmitter  30  within the passageway of the insert  20 . Two springs  41  and  42  form part of the circuit between the batteries  32  and the radio transmitter  30  in the embodiment depicted in FIG. 2.  
         [0032]    If the arrow head  15  is not secured to the insert  20 , the outer spring  42  pushes the batteries  32  upward and out of contact with the inner spring  41 , as illustrated in FIG. 2. In this state, there is no electrical continuity between the batteries  32  and the radio transmitter  30 . Thus, the radio transmitter  30  remains off while the arrow head is detached and battery power is conserved.  
         [0033]    Screwing the arrow head  15  into the threads  25  of the insert  20  causes the base  16  of the arrow head  15  to come into contact with the upper battery  32 . The arrow head  15  pushes both batteries  32  downward so that the lower battery will come into contact with the inner spring  41 , which establishes electrical continuity between the batteries  32  and radio transmitter  30 . In this state, radio transmitter  30  is turned on.  
         [0034]    It should be expressly understood that other methods could be substituted to switch the radio transmitter on only when the arrow is about to be fired. For example, a simple set of electrical contacts could be closed in attachment of the arrow head  15  to the insert  20 . A pressure-sensitive switch could be also be substituted.  
         [0035]    The radio transmitter  30  can be designed to transmit any conventional radio signal that can be detected at a reasonable distance by a directional radio receiver (not shown). For example, FIG. 3 is a schematic diagram of a radio transmitter circuit using amplitude modulation. FIG. 4 is a schematic diagram of a radio transmitter circuit using frequency modulation. A frequency of approximately 100 to 300 MHz can be used for AM modulation, and a frequency of approximately 300 to 500 MHz can be used for FM modulation. The radio transmitter  30  can be fabricated in a very compact size using surface mount technology (SMT) with a phenolic printed circuit board. A transmitter output power of approximately 0.1 to 0.5 mW can be readily detected at a range of approximately 150 to 200 feet with a conventional radio receiver.  
         [0036]    The above disclosure sets forth a number of embodiments of the present invention. Other arrangements or embodiments, not precisely set forth, could be practiced under the teachings of the present invention and as set forth in the following claims.