Patent Publication Number: US-4733474-A

Title: Bow sight

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 803,384, filed Nov. 29, 1985, entitled Bow Sight, and now U.S. Pat. No. 4,646,444. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to sights and, more particularly, to a sight for a low speed projectile, such as an arrow fired from a bow. 
     II. Description of the Prior Art 
     As is well known in the art, in the sport of archery, the bow is cocked by the archer and, upon release, projects the arrow forwardly of the bow. Furthermore, since the bow is typically cocked to the same position each time the arrow is fired, the arrow is initially fired along a predetermined path of travel and at a predetermined initial and rather low speed. The arrow follows a generally parabolic path after it is fired and until it hits its target or the earth. 
     A major difficulty in the sport of archery is the degree of elevation of the bow necessary to obtain the desired distance for the arrow. There have been a number of previously known bow sights which, when calibrated, provide the archer with the proper elevation of the bow over a wide range of distances. Such previously known sights are acceptable when shooting targets at predetermined or known distances. 
     A major disadvantage of these previously known bow sights, however, is that they require that the archer determine the distance between himself or herself and the target prior to firing the arrow. When shooting game with bow and arrow, however, the distance between the archer and the target can only be approximated so that these previously known sights provide only an approximation of the necessary elevation for the bow in order to hit the game. Since these previously known bow sights provide only an approximation when used for shooting game, many archers simply disregard them altogether and shoot using their own natural instincts rather than a bow sight. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides a split image bow sight which overcomes all of the above mentioned disadvantages of the previously known devices. 
     In brief, the bow sight of the present invention provides an elongated housing having a front side, a rear side and an interior housing chamber. The housing is secured to the bow so that its rear side faces the archer while its front side faces in the direction of travel for the arrow when fired. 
     A first opening in the housing extends through both housing sides and is open to the housing chamber. Conversely, a second housing opening is open only to the front side of the housing at a position longitudinally spaced from the first opening and this second opening is also open to the housing chamber. 
     A parabolic mirror is contained within the housing chamber in alignment with the second housing opening. This parabolic mirror is arranged to reflect incoming light through the second housing opening downwardly through the interior of the housing and towards the first opening. Similarly, a planar mirror is diagonally arranged across one side of the first opening so that light reflected longitudinally through the housing by the parabolic mirror is reflected by the planar mirror rearwardly through the first opening and towards the archer. The other side of the first opening, however, is transparent so that light passes directly through this other half of the first opening from the target to the archer. 
     In practice, the archer, by looking through the first housing opening, views an image which is split along a vertical center line. One side of the image represents the image as reflected by the parabolic and planar mirrors, while the other side of the image represents the straight line of sight between the archer and the target. By adjusting the elevation of the bow, the reflected half of the split image will vertically slide due to the reflection from the parabolic mirror. Once both sides of the image are aligned with each other, the proper elevation for the bow is obtained so that, when fired, the arrow will strike the target. Furthermore, one can adjust the bend or shape of the parabolic mirror to calibrate the sight for different archers and different bows. 
     In a second embodiment of the invention, two planar mirrors are contained within the interior of the housing while a parabolic mirror is disposed across the second housing opening. A prism can also be used to form the mirrors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views and in which: 
     FIG. 1 is a side view illustrating a preferred embodiment of the present invention; 
     FIG. 2 is a plan view showing the rear side of the preferred embodiment of the invention; 
     FIG. 3 is a plan view showing the front side of the preferred embodiment of the invention; 
     FIG. 4 is a side view of the preferred embodiment of the invention and with parts removed for clarity; 
     FIGS. 5-7 are diagrammatic views illustrating the operation of the preferred embodiment of the invention; 
     FIG. 8 is a side view illustrating a second preferred embodiment of the invention; 
     FIG. 9 is a crossectional view of the embodiment of FIG. 8; and 
     FIG. 10 is a crossectional view similar to FIG. 9 but illustrating a modification thereof. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     With reference first to FIGS. 1-3, a preferred embodiment of the bow sight 10 of the present invention is thereshown and comprises a vertically elongated housing 12 having a front side 14, a rear side 16, two lateral sides 18, a top 20 and a bottom 22. All sides 14-18 of the housing 12 are relatively thin walls so that the housing 12 defines an interior chamber 24. 
     As best shown in FIG. 1, the housing 12 is secured to an archery bow 26 by any conventional means, such as a bracket 28, so that the front side 14 of the housing 12 faces the direction of trojectory of an arrow 30 fired by the bow 26 while the rear side 16 faces rearwardly towards the archer using the bow 26. In addition, the housing 12 is secured to the bow 26 so that the housing 12 extends generally vertically along the bow 26, and thus perpendicular to the direction of travel of the arrow 30. 
     With reference now particularly to FIGS. 2 and 3, an opening 32 is formed through the housing 12 adjacent its bottom 22 so that the opening 32 is open to both the front side 14 and rear side 16 of the housing 12 as well as the housing chamber 24. Similarly, a second opening 34 (FIG. 3) is formed in the housing 12 adjacent its top 20 and this opening 34 is also open to the housing chamber 24. Unlike the lower opening 32, however, the opening 34 is open only to the front side 14 of the housing 12. 
     With reference now to FIGS. 2-4, a planar mirror 36 is attached to the housing 12 so that it extends diagonally (see FIG. 4) across the lower opening 32. This planar mirror 36, however, extends across only the right hand side, as viewed in FIG. 2, of the lower opening 32. The left side 38 of the opening 32 (as viewed in FIG. 2) is transparent thus allowing unobstructed vision between the archer and the target. Consequently, a split image of the target is viewed by the archer through the opening 32. 
     Referring now particularly to FIGS. 3 and 4, a second mirror 40 is secured to the housing 12 so that the mirror 40 extends generally diagonally with respect to the axis of the housing 12 and is aligned with the second housing opening 34. Unlike the planar mirror 36, however, the mirror 40 is curved in the shape of a parabola from its forward end 42 and towards its rearward end 44 for a reason to be shortly described. 
     Although any means can be employed to form the parabolic mirror 40, in the preferred form of the invention, the mirror 40 is preferably formed of a slightly flexible material, such as thin glass, having a reflective surface on one side, which is attached to the housing 12 at a fulcrum point 46 adjacent one end. The mirror 40 narrows linearly in width from its front end 42 and towards its rearward end 44 (FIG. 4). A knob 48 having a threaded shaft 49 is threadably mounted in a hole in the housing 12 and the shaft 49 abuts against the mirror 40 adjacent its rearward end 44. Consequently, by turning the knob 48, the amount of bend of the mirror 40 and thus the shape of the mirror 40 can be adjusted for a reason to be subsequently described. Furthermore, the degree of curvature of the amount of bending of the mirror 40 increases from the front side 14 of the housing 12 and to its rear side 16. 
     With reference now to FIG. 4, both the planar mirror 36 and the parabolic mirror 40 are angled generally diagonally with respect to the axis of the housing 12. Consequently, light passing through the upper housing opening 34 as shown by arrow 50 is reflected by the parabolic mirror 40 generally longitudinally through the housing chamber 24, as shown by arrow 52. This light ultimately is reflected by the planar mirror 36 rearwardly through the lower housing opening 32, as shown by arrow 54, towards the archer. 
     All projectiles which are fired along a predetermined path of travel and with a predetermined initial velocity travel along a predetermined parabolic curve. Consequently, by matching the curve of the parabolic mirror 40 to the characteristics of the archer by adjustment of the knob 48, and thus the shape of the mirror 40, the reflective image from the parabolic mirror 40 via the planar mirror 36 can be matched to the shooting characteristics of the archer and/or bow. 
     For example, with reference to FIG. 5, the elevation of the bow 26 is initially too high. When this occurs, the non-reflected image half 62 of the target 63 as seen through the side 38 of the opening 32 is positioned above the reflected image half 60 of the target 63, i.e., the image of the target 63 as reflected by the mirrors 40 and 36. 
     By lowering the elevation of the bow to the position shown in FIG. 6 so that the image halves 60 and 62 of the target 63 are aligned with each other as viewed by the archer through the opening 32, the bow 26 is properly aimed. Consequently, once the bow is fired, the arrow will strike the target 63 as represented by the image halves 60 and 62 as desired. 
     Similarly, in FIG. 7 the elevation of the bow 26 is also properly adjusted so that the image halves 60 and 62 are aligned with each other. In this case, the image halves 60 and 62 align at a lower position in the opening 32, as contrasted with FIG. 6, since the target 63 is positioned further from the archer. Furthermore, in all cases, the reflected image half 60 is more vertically elongated than the non-reflected half 62 of the target 63. 
     As best shown in FIG. 1, the bow sight 10 is preferably mounted to the bow 26 so that the sight 10 is nested behind the bow limb. This mounting minimizes tangling or snarling of the bow sight 10 on tree branches, shrubbery and the like when in use. Furthermore, as shown in FIGS. 2 and 3, the housing 12 is angled so that the upper end of the bow sight 10 is positioned to one side of the bow limb while a portion of the lower end is nested behind the bow limb. 
     With reference now to FIGS. 8 and 9, a second preferred embodiment of the bow sight 10&#39; of the present invention is thereshown. The bow sight 10&#39; is mounted to the bow 26 as before by any conventional means so that a front side 14&#39; of the bow sight 10&#39; faces the target while a rear side 16&#39; of the bow sight faces the archer. Furthermore, elements designated by primed numbers correspond to the like numbered unprimed elements and the previous description for such elements is incorporated by reference. 
     With reference now particularly to FIG. 9, the bow sight 10&#39; is thereshown in greater detail and includes a housing 12&#39; having an opening 32&#39; adjacent its lower end and a second opening 34 adjacent its upper end on the front side 14&#39;. Consequently, as thus far described, the bow sight 10&#39; shown in FIGS. 8 and 9 is substantially the same as the bow sight 10 illustrated in FIGS. 1-7. 
     The bow sight 10&#39;, however, differs from the bow sight 10 in that two planar mirrors 100 and 36&#39; are contained within the interior of the housing 12&#39; which are spaced apart and generally parallel to each other. Furthermore, the mirrors 100 and 36&#39; are angled with respect to the axis of the housing so that the path of light 103 entering the housing opening 34&#39; is first reflected by the mirror 100 to the mirror 36&#39; and then from the mirror 36&#39; out through the opening 32&#39;. 
     Referring now particularly to FIG. 9, a parabolic lens 103 having a degree of curvature which increases from one end 120 of the lens 103 to the opposite end 122 is positioned across the second housing opening 34&#39;. This parabolic lens 103 refracts the incoming light through the housing opening 34&#39; in order to produce the range finding operation like that illustrated in FIGS. 5-7 of the drawing. Furthermore, the planar mirror 36&#39;, like the mirror 36, extends only halfway across the width of the housing 12&#39; while the other half 38&#39; of the mirror 36&#39; is transparent. The transparent half 38&#39; thus allows light to pass directly through the transparent half 38&#39; of the mirror 36&#39; in the fashion that has been previously described. 
     Consequently, it can be seen that the embodiment of the invention illustrated in FIGS. 8 and 9 differs from that illustrated in FIGS. 1-7 in that the parabolic lens 103 and planar mirror 100 are substituted for the parabolic mirror 40 shown in FIGS. 1-7. 
     With reference now particularly to FIG. 10, a still further modification of the present invention is thereshown in which the housing 12&#39; (FIG. 9) as well as the mirrors 100, 36&#39; and lens 103 are replaced by a prism 106. This prism 106 includes flat surfaces 108 and 110 which form the mirrors 100 and 36&#39;, respectively, while a parabolically shaped surface 112 on the prism 106 forms the parabolic lens 103 (FIG. 9). The operation of the FIG. 10 embodiment, however, is substantially identical to that shown in FIG. 9 and for brevity will not be repeated. 
     Although the present invention has been described for use in conjunction with archery, it will be understood that it is equally adaptable to other low speed projectiles which are fired at a predetermined initial velocity and along a predetermined path of travel. Consequently, the present invention is easily adaptable to short range artillery and the like. 
     Having described my invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.