Abstract:
An archer may levitate the front of an arrow in a magnetic field rather than resting the arrow against a mechanical arrow rest attached to a bow. From the first moment of release, the arrow has no contact with the bow or any apparatus attached to the bow.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to the field of archery, specifically to the problem of releasing an arrow with the least possible interference to its intended flight path.  
         [0003]     2. Prior Art  
         [0004]     At the moment just before an archer releases an arrow from a bow, the rear end of the shaft of the arrow is supported in a stable position against the bowstring, and the front end of the arrow is supported in a stable position with relation to the bow. An arrow is in a stable position with relation to a bow when any slight displacement of the arrow from that position results in a force pushing the arrow back to that position. The front end support, often called an arrow rest, may be as simple as a notch cut in the riser, or handle, near the middle of a bow. It is evident that friction between an arrow shaft and an arrow rest, or contact between an arrow&#39;s fletches (stabilizing vanes or feathers) and a bow or an arrow rest, may cause the arrow to deviate from its intended path after it is released.  
         [0005]     Many devices have been made to minimize such deviations. One class of such devices uses arrow rests formed from very light, flexible material that bends out of the way as the arrow passes. (See, for example, U.S. Pat. No. 5,896,849, “Arrow Rest”, to Branthwaite et al.) Another class of such devices uses very low friction coatings, such as Teflon, on arrow rests to minimize friction against the shaft of the arrow as it passes. (See, for example, U.S. Pat. No. 5,673,678, “Arrow Rest for Archery Bow”, to Savage.) A third class of such devices supports an arrow on high-friction prongs, which are held in position by a delicate balance of mechanical spring and magnetic forces. Immediately after release, the shaft of the arrow causes a slight drag on the high-friction prongs, which causes the balance of mechanical and magnetic forces to swing the prongs out of the way of the arrow for the remainder of its flight. (See, for example, U.S. Pat. No. 6,561,174, “Arrow Rest”, Afshari, and U.S. Pat. No. 6,082,348, “Arrow West” [sic], to Savage.) A fourth class of devices uses a magnet to hold the front of an arrow containing ferromagnetic material in direct contact with the magnet. (See U.S. Pat. No. 4,343,286, “Archery Bow”, to Thacker.) All of the arrow rests in the prior art require some direct contact between a bow, or an apparatus affixed to the bow, and an arrow during the arrow&#39;s flight.  
       Objects and Advantages  
       [0006]     The present invention eliminates all contact between an arrow and a bow, or an apparatus affixed to the bow, from the first moment of release. Thus friction or contact with the bow, or an apparatus affixed to the bow, causes no deviation of the arrow from its intended flight path.  
       SUMMARY  
       [0007]     A magnetic field supports a magnetic arrow in a stable position with relation to a bow just before the arrow is released from the bow. From the first moment of release, there is no contact between the arrow and the bow, or any apparatus affixed to the bow. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a perspective view of a radially magnetized magnetic arrow in release position at a bow levitated by a magnetic field from a ring magnet.  
         [0009]      FIG. 2  shows a ring magnet with a radially oriented magnetic field.  
         [0010]      FIG. 3  shows an edge, or side, view of a typical ring magnet with an axially oriented magnetic field.  
         [0011]      FIG. 4  shows three magnets embedded in a cross section of the shaft of a magnetic arrow.  
         [0012]      FIG. 5  is a perspective view of an axially magnetized magnetic arrow in release position at a bow levitated by a magnetic field from a ring magnet. The magnet in the magnetic arrow is set forward of the ring magnet.  
         [0013]      FIG. 6  is a perspective view of an axially magnetized magnetic arrow in release position at a bow levitated by a magnetic field from a ring magnet. The magnet in the magnetic arrow is set at the center of the ring magnet.  
         [0014]      FIG. 7  is a perspective view of an axially magnetized magnetic arrow in release position at a bow levitated by a magnetic field from a ring magnet. The magnet in the magnetic arrow is set behind the ring magnet.  
         [0015]      FIG. 8  is a perspective view of an axially magnetized magnetic arrow in release position at a bow levitated by a magnetic field from a ring magnet. The two magnets in the magnetic arrow are set one behind and one forward of the ring magnet  
         [0016]      FIG. 9  is a perspective view of a magnetic arrow in release position at a bow levitated by a magnetic field from a C-shaped magnet.  
         [0017]      FIG. 10  is a perspective view of an axially magnetized magnetic arrow in release position at a bow levitated by a magnetic field from two bar magnets.  
         [0018]      FIG. 11  shows a magnetic arrow formed by affixing a permanent magnet around the shaft of a non-magnetic arrow.  
         [0019]      FIG. 12  shows a magnetic arrow formed by inserting a threaded insert containing a permanent magnet in between the arrowhead and the shaft of a non-magnetic arrow.  
         [0020]      FIG. 13  is a perspective view of a magnetic arrow supported in release position at a bow by a magnetic field from a ring magnet, in which the ring magnet is covered with magnetic shielding on its outer surface.  
         [0021]      FIG. 14  is a perspective view of a magnetic arrow supported in release position at a typical bow by a magnetic support assembly attached to the bow with a bracket assembly.  
         [0022]      FIG. 15  is a perspective view of a magnetic arrow in release position at a bow levitated by a magnetic field from two electromagnets. 
     
    
     DETAILED DESCRIPTION  
     Preferred Embodiments: Structure and Operation  
       [0023]     In  FIG. 1 , a permanent ring magnet  35  is firmly affixed to a bow  18  somewhere near the middle section of bow  18  where an archer would normally grab bow  18 . The ring magnet has a front face  72 , an inner cylindrical surface  52 , an outer cylindrical surface  42 , and a rear face that is not visible in the drawing. The magnetism of ring magnet  35  is oriented radially, as shown in a front view of ring magnet  35  in  FIG. 2 . Inner cylindrical surface  52  is the north pole and outer cylindrical surface  42  is the south pole. Ring magnet  35  may be formed from a single piece of permanently magnetic material or it may be composed of a number of separate pieces, each of which is mounted with its magnetic field radially aligned.  
         [0024]     A magnetic arrow  22  in  FIG. 1  is poised in position just before release from bow  18 . Magnetic arrow  22  has much the same properties as a typical non-magnetic arrow except there are three magnets  62 ,  63 , and  64 , embedded in a perpendicular cross section  61  of the shaft of arrow  22 , as shown in  FIG. 4 . Magnets  62 ,  63 , and  64  are arranged radially, perpendicular to the axis of the shaft, with north poles facing outward and south poles facing inward.  
         [0025]     To get arrow  22  into the stable release position shown in  FIG. 1 , an archer slides arrow  22 , rear first from the front, through the hole in ring magnet  35 . The archer then places the rear end of the arrow against the bowstring and draws the bow into release position. The length of arrow  22  and the position of the bowstring at full draw are designed together to place cross section  61  near the center of ring magnet  35  at full draw just before release. The hole through ring magnet  35  is large enough to provide sufficient clearance for magnetic arrow  22  to pass through after being released without any part of arrow  22  touching ring magnet  35 .  
         [0026]     The front end of magnetic arrow  22  is shown in  FIG. 1  levitating in the hole of ring magnet  35 . This occurs because magnets  62 ,  63 , and  64  are each repelled by ring magnet  35 . Because of the shape of ring magnet  35 , the repulsive magnetic forces on arrow  22  are substantially radially inward. If cross section  61  is not in the exact center of ring magnet  35 , the repulsive magnetic forces may also be slightly forward (for forward of center positioning) or slightly rearward (for rearward of center positioning). Since the rear end of arrow  22  is held firmly against the drawn bowstring, the forward or rearward magnetic forces are counterbalanced. The radially inward magnetic forces center arrow  22  into a good, stable position for release. Gravity is counterbalanced by the repelling force from the lower part of ring magnet  35 . Thus ring magnet  35  affixed to bow  18  forms a magnetic support assembly. By providing bow  18 , providing magnetic arrow  22 , and arranging magnetic fields from this magnetic support assembly, arrow  22  is levitated in a stable position with respect to bow  18 .  
         [0027]     In  FIG. 5 , a permanent ring magnet  30  is firmly affixed to a bow  18  somewhere near the middle section of bow  18  where an archer would normally grab bow  18 . The ring magnet has a front face  70 , an inner cylindrical surface  50 , an outer cylindrical surface  40 , and a rear face  80  (shown in  FIG. 3 ). The magnetism of ring magnet  30  is axially oriented, as shown in an edge, or side, view of ring magnet  30  in  FIG. 3 . Front face  70  is the north pole and rear face  80  is the south pole.  
         [0028]     A magnetic arrow  20  in  FIG. 5  is poised in position just before release from bow  18 . Magnetic arrow  20  has much the same properties as a non-magnetic arrow except there is a small permanent magnet  60  in the shaft of arrow  20  on the centerline near the forward end behind an arrowhead  65 . Permanent magnet  60  is axially oriented with its north pole rearward and its south pole forward.  
         [0029]     To get arrow  20  into the stable release position shown in  FIG. 5 , an archer slides arrow  20 , rear first from the front, through the hole in ring magnet  30 . The archer then places the rear end of the arrow against the bowstring and draws the bow into release position. The length of arrow  20  and the position of the bowstring at full draw are designed together to place small magnet  60  just forward of ring magnet  30  at full draw just before release. The hole through ring magnet  30  is large enough to provide sufficient clearance for magnetic arrow  20  to pass through after being released without any part of arrow  20  touching ring magnet  30 .  
         [0030]     The front end of magnetic arrow  20  is shown in  FIG. 5  levitating in the hole of ring magnet  30 . This occurs because magnet  60  and ring magnet  30  repel each other. Because of the shape of ring magnet  30 , the repulsive magnetic forces on arrow  20  are radially inward as well as forward. Since the rear end of arrow  20  is held firmly against the drawn bowstring, the forward magnetic force is counterbalanced. The radially inward magnetic forces center arrow  20  into a good, stable position for release. Gravity is counterbalanced by the repelling force from the lower part of ring magnet  30 . Thus ring magnet  30  affixed to bow  18  forms a magnetic support assembly, which levitates arrow  20 .  
         [0031]     Other arrangements of magnetic fields may be chosen to successfully levitate the front of an arrow.  FIG. 6  is very similar to  FIG. 5  except that magnet  55  substitutes for magnet  60  of  FIG. 5 . Magnet  55  has polarity opposite to magnet  60 . Magnet  55  is positioned further toward the rear in the shaft of the arrow  27  so that magnet  55  is centered in the hole of ring magnet  30  when the bow is fully drawn just before release. In this arrangement, the forward-facing north pole of magnet  55  is repelled backward and radially inward by the north pole of front face  70  of ring magnet  30 . The rearward-facing south pole of magnet  55  is repelled forward and radially inward by the south pole of rear face  80  of ring magnet  30 . The inward forces center arrow  27  in ring magnet  30 . Gravity is counterbalanced by the upward repelling force from the lower portion of ring magnet  30 .  
         [0032]      FIG. 7  is very similar to  FIG. 5 , except that magnet  60  is positioned further toward the rear in the shaft of arrow  25  so that magnet  60  is just to the rear of ring magnet  30  when the bow is fully drawn just before release. In this arrangement, the forward-facing south pole of magnet  60  is repelled backward and radially inward by the south pole of rear face  80  of ring magnet  30 . The backward force is counterbalanced by the bowstring against the rear end of arrow  25 . The inward forces center arrow  25  in ring magnet  30 . Gravity is counterbalanced by the upward repelling force from the lower portion of ring magnet  30 .  
         [0033]      FIG. 8  is very similar to  FIG. 5 , except that a second magnet  67 , having the same polarity as magnet  60 , is positioned further toward the rear in the shaft of arrow  23 , just to the rear of ring magnet  30 , when the bow is fully drawn just before release. As in  FIG. 5 , magnet  60  and ring magnet  30  repel each other. Because of the shape of ring magnet  30 , the repulsive magnetic forces from the front of ring magnet  30  on magnet  60  in arrow  23  are radially inward as well as forward. Since the rear end of arrow  23  is held firmly against the drawn bowstring, the forward magnetic force is counterbalanced. The radially inward magnetic forces help to center arrow  23  into a good, stable position for release. Gravity is partially counterbalanced by the upward repelling force on magnet  60  from the lower part of ring magnet  30 . Simultaneously, the forward-facing south pole of magnet  67  is repelled backward and radially inward by the south pole of rear face  80  of ring magnet  30 . The backward force is counterbalanced by the bowstring against the rear end of arrow  23 . The inward forces on magnet  67  help to center arrow  23  in ring magnet  30 . The upward repelling force on magnet  67  from the lower portion of ring magnet  30  works in conjunction with the upward repelling force on magnet  60  to counterbalance gravity.  
         [0034]     In an alternative arrangement, shown in  FIG. 9 , a segment of the top portion of ring magnet  30  may be removed. This leaves a C-shaped permanent magnet  38  with the open side facing upward. The deletion of this segment removes some downward magnetic force on magnetic arrow  20 , allowing arrow  20  to levitate a bit higher. The upward-facing open side of the C-shaped magnet is convenient for placing an arrow quickly into release position.  
         [0035]     It is evident that circular arrangements of small bar magnets can replace ring magnets  30  or  35 . But a simpler minimal arrangement of bar magnets can also levitate magnetic arrows. In  FIG. 10 , two small bar magnets,  90  and  100 , are firmly affixed to bow  18  with their north poles facing upward and inward toward the shaft of arrow  20 . The space between bar magnets  90  and  100  is filled with a non-magnetic material  110 , such as wood, plastic, fiberglass, etc. As an archer draws arrow  20  back into the release position of  FIG. 10 , arrow  20  slides on non-magnetic material  110 . As the rearward-facing north pole of magnet  60  approaches the north poles of magnets  90  and  100 , magnetic arrow  20  is repelled forward, upward, and inward by bar magnets  90  and  100 . The forward force is counterbalanced by the archer pressing the rear of arrow  20  against the bowstring. The upward force is counterbalanced by gravity. The inward forces center arrow  20  between bar magnets  90  and  100 . Thus arrow  20  levitates above non-magnetic material  110 . The strength of the magnetic field is sufficient for the clearance between arrow  20  and non-magnetic material  110  to be large enough so that no part of arrow  20  will make contact with non-magnetic material  110  or any other part when it is released.  
         [0036]     Typical non-magnetic arrows may be changed into magnetic arrows for use in the present invention.  FIG. 11  shows a typical non-magnetic arrow  130  to which a tubular cylindrical magnet  120  has been added. Magnet  120  may be formed from sections of permanent magnetic material glued together around arrow  130 . Magnet  120  may also be formed by sections of permanent magnetic material surrounded by a plastic sleeve that snaps into place around the shaft of arrow  130 . In this example, the magnetic field of magnet  120  is oriented in the axial direction with a north pole facing rearward and a south pole facing forward, which is the same orientation as magnet  60  in  FIG. 5 .  
         [0037]     Another means of changing a non-magnetic arrow to a magnetic arrow is shown in  FIG. 12 . Typical non-magnetic arrows are often composed of multiple parts comprising a shaft  140  with a threaded hole at the front end and an arrowhead  160  with a screw protruding from its rear, which fits into the threaded hole. An insert  150  containing a small permanent magnet  60  may be inserted between shaft  140  and arrowhead  160 . Arrowhead  160  screws into a matching threaded hole in the front of insert  150 . A screw at the rear of insert  150  fits into the threaded hole of shaft  140 . The resulting assembly may be used like magnetic arrow  20 . As another alternative, arrowhead  160  and insert  150  may be permanently joined together to form a magnetic arrowhead component. Such a magnetic arrowhead may be screwed into a typical shaft instead of a typical non-magnetic arrowhead in order to form a magnetic arrow.  
         [0038]     Many arrowheads contain steel or other materials that are ferromagnetic. By exposure to a strong magnetic field, ferromagnetic material may be temporarily magnetized. Assume that typical non-magnetic arrow  130  of  FIG. 11  has an arrowhead  131  made of ferromagnetic material. Instead of converting arrow  130  to a magnetic arrow by using magnet  120 , arrowhead  131  may be magnetized shortly before use. Thus a magnetized ferromagnetic arrowhead may act in place of a permanent magnet such as magnet  120 .  
         [0039]     On the other hand, a ferromagnetic arrowhead may be considered a nuisance when it is not magnetized deliberately to enable levitation. Such an arrowhead may be attracted to ring magnets  30  or  35  or bar magnets  90  and  100 . Such attraction might annoy an archer during ordinary handling, or perturb the flight of a magnetic arrow immediately after release. This problem may be solved by providing an arrowhead that contains no ferromagnetic material.  
         [0040]     Ring magnet  30  in  FIG. 5  has a magnetic field that extends not only inward toward magnetic arrow  20  but also outward from its outer cylindrical surface  40 . This outward-extending field may be inconvenient to an archer because ring magnet  30  will attract, and possibly stick to, ferromagnetic objects such as automobiles, steel watches, belt buckles, etc. This problem may be mitigated by covering outer cylindrical surface  40  with magnetic shielding material  180  to shape the field. (For example, Mumetal® alloy, described in “Material Information: Mumetal® Magnetic Shielding Alloy”, Goodfellow Corporation, [retrieved on 2003-06-21], retrieved from &lt;URL: http://www.goodfellow.com/csp/active/static/A/NI03.HTML&gt;.) Such an arrangement is shown in  FIG. 13 .  
         [0041]     Many bows are built with threaded holes that allow an archer to attach many different arrow rests. A magnetic assembly for levitating the front of a magnetic arrow may be designed to accommodate such mounting holes and thus be attachable to many bows that were not originally designed for magnetic levitation.  FIG. 14  shows the magnetic levitation assembly of  FIG. 5  with the addition of a bracket  170  to make the assembly adaptable to a great variety of bows.  
         [0042]     The present invention may also be implemented by substituting electromagnets for permanent magnets.  FIG. 15  shows the substitution of electromagnets  200  and  210  for bar magnets  90  and  100  (shown in  FIG. 10 ).  
       Conclusion and Variations  
       [0043]     By levitating the front of an arrow in a magnetic field just before release, the present invention eliminates friction and contact between an arrow and a bow, or any apparatus attached to the bow. This eliminates known causes of deviation from an arrow&#39;s desired flight path.  
         [0044]     Besides the preferred embodiments described above, the present invention has a number of additional variations. Some examples are described below.  
         [0045]     The example of  FIG. 1  has radially oriented magnetic fields generated from both ring magnet  35  and magnetic arrow  22 . The example of  FIG. 5  has axially oriented magnetic fields generated from both ring magnet  30  and magnetic arrow  20 . It is easy to see that axially magnetized arrow  20  will also levitate in radially magnetized ring magnet  35 . Furthermore, any angle of orientation of the magnetic field in a ring magnet, which is at an angle between the forward-facing north pole of ring magnet  30  and the radially inward-facing north pole of ring magnet  35 , will repel and center magnet  60 , which is set forward in arrow  20 , and maintain levitation.  
         [0046]     It is easy to see that reversing all of the magnetic poles in any of the arrangements described above will maintain the repulsive forces in the same strength and orientation, thus levitating a magnetic arrow in the manner described above. This is because magnetic repulsion occurs between any like poles, whether they are both north or both south.  
         [0047]     The embodiments described above include a bow with limbs aligned generally in a vertical plane. It will be obvious to anyone skilled in the relevant arts that the present invention is also applicable to crossbows, which have limbs aligned generally in a horizontal plane.  
         [0048]     It is possible for an arrow to be levitated by the repulsive diamagnetic force between a magnet and a superconductor. The superconductor may be used in a magnetic support assembly with a magnetic arrow, or the superconductor may be used in an arrow with magnets used in the support assembly.  
         [0049]     In light of these numerous variations of the preferred embodiments, the scope of the present invention should be determined by the following claims.