Abstract:
Apparatus for adjusting the vertical placement of a bow sight on an archery bow is provided with a belt extending over a drive pulley and an idler pulley. A sight mount is secured to the belt for movement therewith between the pulleys and a sight is attached to the sight mount. A sight adjustor lock locks the sight in position by preventing rotation of the drive pulley.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to adjustable sight assemblies for archery bows. More particularly, the present invention relates to adjustment control of an adjustable archery sight through the use of a driver pulley, an idler pulley, and a belt operatively engaging the pulleys. The sight is attached to the belt for movement therewith. 
     PRIOR ART 
     Archery bows and the use of adjustable sights therewith are well known in the art. Such adjustable archery sights vary from simple to complex assemblies each varying with respect to ease of use and cost. 
     One type of prior art archery sight control mechanism provides an adjustable sight with a rotatable sight adjustor shaft near the bow draw string. In one example of this type of archery sight control mechanism, a flexible shaft is coupled between a rotatable adjustor shaft and a lead screw for transmitting the rotational movement of the adjustor shaft to rotational movement of the lead screw. A sight mount, threadedly engages the lead screw and is vertically movable as the lead screw rotates. This type of mechanism tends to be imprecise and is difficult to properly adjust; further, such flexible shaft mechanisms fail to give a “smooth” feel to the adjustment that is desirable with modern compound bows and auxiliary equipment and is relatively expensive. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the invention to provide an inexpensive adjustable sight assembly for use on an archery bow. 
     It is another object of the invention to provide an inexpensive adjustable sight assembly for use on an archery bow that provides smooth and precise control over the vertical movement of the sight. 
     It is yet another object of the invention to provide a reliable and easily adjusted sight for use on an archery bow. 
     SUMMARY OF THE INVENTION 
     The present invention is an inexpensive adjustable sight assembly which provides firm and direct control over vertical movement of a bow sight. According to one embodiment of the invention, the rotation of a sight adjustor knob, mounted at one end of a rotatable adjustor rod is transmitted to a drive pulley mounted on an opposite end of the adjustor rod such that when the sight adjustor knob is rotated, the drive pulley correspondingly rotates. An idler pulley, spaced from the drive pulley, is provided and a belt is wrapped around both pulleys. Rotation of the drive pulley imparts linear motion to the belt as it travels vertically between the pulleys. A sight block is attached to that portion of the belt between the drive pulley and the idler pulley. Movement of the belt thus translates into vertical movement of the sight block between the drive pulley and the idler pulley. One embodiment of the invention also includes an adjustor rod lock to restrict movement of the drive pulley, thereby maintaining a predetermined position of the sight block. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The nature of the present invention as well as other embodiments of the present invention may be more clearly understood by reference to the following detailed description of the invention, to the appended claims, and to the drawings herein, wherein: 
     FIG. 1 a side view, partly in section, of a prior art adjustable sight assembly; 
     FIG. 2 is an isometric view, partly in section, an adjustable sight assembly constructed according to the teachings of the present invention. 
     FIG. 3 is a isometric view of an alternate embodiment of adjustable sight assembly constructed in accordance with the teachings of the present invention. 
     FIG. 4 is a cross-sectional view of a portion of the adjustable sight assembly of FIG. 3, taken along line  4 — 4 . 
     FIG. 5 is a diagram of a typical archery bow including a sight assembly according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One type of prior art archery sight assembly, a side view of which is shown in FIG. 1, involves an adjustable sight assembly  2  for mounting on an archery bow (not shown) which provides a user of the bow with a sight adjustor knob  4  near the bow draw string for rapid sight adjustment when the bow is raised into the shooting position. The adjustable sight assembly  2  includes a cable guard  6  and bow mount  8  found on conventional bows, but also includes a sight adjustor knob  4 , an adjustor rod  10  extending through the center of the cable guard  6 , a sight block  12  for mounting a sight pin, and a lead screw  14  to which the sight block  12  is threadedly engaged. To transmit the rotational movement of the sight adjustor knob  4  to vertical movement of the sight block  12 , the sight assembly  2  further incorporates a flexible shaft  16  coupled between the adjustor rod  10  and a lead screw  14 . When the adjustor knob  4  is rotated, the flexible shaft  16  similarly rotates, thus rotating the lead screw  14 . As the lead screw  14  rotates, the sight block  12 , which is threadedly coupled to the lead screw  14 , slides up or down on the lead screw  14  in relation to the direction of rotation of the sight adjustor knob  4 . 
     One difficulty experienced with the use of a flexible shaft  16  to translate rotational movement between the sight adjustor knob  4  and the sight block  12 , is that the rotational movement does not always evenly transfer to the sight block  12 . Because the flexible shaft  16  inherently includes a degree of elasticity, initial movement of the sight adjustor knob  4  does not move the sight block  12 . The initial rotational movement of the sight adjustor knob  4  rotates one end of the flexible shaft  16  to build up enough rotational force within the flexible shaft  16  to overcome an initial static friction force between the lead screw  14  and the sight block  12 . Furthermore, due to variances in the frictional force between the lead screw  14  and the sight block  12 , the flexible shaft  16  may release rotational force to the lead screw  14  unevenly, thus, reducing control accuracy over the vertical movement of the sight block  12 . In other words, use of the flexible shaft  16  to translate rotational movement from the sight adjustor knob  4  to the lead screw  14  is difficult to accurately control. Additionally, use of a lead screw  14  to adjust the vertical position of the sight is susceptible to dirt and other debris clogging up the threads of the lead screw  14  or the sight block  12 , thus, further restricting movement of the sight block  12  and causing the transfer of rotational movement through the flexible shaft  16  to be even more uneven. 
     Referring now to FIG. 2, an adjustable sight assembly  20  according to a first embodiment of the present invention is shown. In this embodiment of the invention, a sight  21 , including a sight block  22 , is attached to a side of a drive belt  24  between a drive pulley  26  and an idler pulley  28 . As used herein, the term “belt” is intended to include belts having rectangular cross-sections such as those belts shown in the various embodiments, as well as belts having round, oval, square, or other shaped cross-sections, chains, cables, and any other drive transferring apparatus known in the art which frictionally or otherwise engages a drive pulley, thereby enabling transmission of rotational drive pulley movement to sight translational movement. Rotation of the drive pulley  26  causes the drive belt  24  to move around the drive pulley  26  and idler pulley  28 , and the sight  21  to move between the drive pulley  26  and the idler pulley  28 . Although the sight  21  may be directly mounted on the drive belt  24 , in the embodiment chosen for illustration, the sight  22  is secured to a sight mount  30  which in turn is secured to the drive belt  24 . The sight mount  30  slides along a sight mount track  32 . In this manner, the sight movement is smooth and less responsive to bow movements or jolts. 
     In the embodiment shown in FIG. 2, an outer surface of the drive pulley  26  includes radially extending indentations  34 , and the drive belt  24  includes corresponding teeth or protrusions  36  on its inside surface. By providing such corresponding indentations  34  and protrusions  36  on the pulley  26  and belt  24  respectively, the belt and pulley “mesh” with each other to thus prevent belt slippage. Such indentations may also be included on the idler pulley  28  if desired. It will be clear to one of ordinary skill in the art that in a much simpler embodiment of the present invention, a belt without protrusions and a belt support, such as a rod, may be used in place of the idler pulley  28  to support the upper portion of the drive belt  24  and provide tension in the drive belt  24 . Similarly, it will be clear to one of ordinary skill in the art that the meshing indentations and protrusions  34  and  36  respectively, while desirable, may not be necessary to every embodiment of the present invention. The friction required to transfer rotational movement of the drive pulley  26  to the drive belt  24  may be established through sufficient tension in the drive belt  24 , or alternatively by other forms of protrusions on either the drive pulley  26 , the drive belt  24 , or both. 
     The idler pulley  28  is rotationally mounted on a sight housing  38  to maintain an operable distance between the idler pulley  28  and the drive pulley  26 . A mount  40  for mounting the. sight assembly to a bow is securely coupled to the sight housing  38 . The bow mount  40  may be integrally formed with the sight housing  38 , or may alternatively be formed as a separate piece and coupled to the housing  38  through adhesive, screws, welding, or any other method known in the art. The drive pulley  26  is coupled to the sight adjustor  42  through the adjustor rod  44  to permit rotation of the pulley  26  by rotating the sight adjustor and thus the adjustor rod  44 . 
     As shown in FIG. 2, the adjustor rod  44  is formed with a knob  48  at one end thereof to permit convenient rotation of the rod  44  by an operator. Because the sight adjustor  42  is directly coupled to the drive pulley  26  by the adjustor rod  44 , rotating the sight adjustor  42  as indicated by the arrow  43 , correspondingly rotates the drive pulley  26  proportionally, as indicated by arrow  27 , thereby providing direct control over the vertical position of the sight  21 . Though not required, a protective covering may be placed around the drive belt  24 , drive pulley  26  and idler pulley  28 . 
     The drive belt  24  may be formed of rubber compounds, silicon, metal parts (i.e. chain), or other materials which may be formed to contact the surfaces of the drive pulley  26  and the idler pulley  28 . The sight adjustor  42 , sight  21 , mount  40  and sight housing  38  may be formed of any rigid material, such as aluminum or other metal, or may be formed using available rigid plastic materials. 
     In another embodiment of the present invention, as shown in FIG. 3, the sight block  22  (shown in FIG. 2) is replaced by a sight pin  50 . As will be clear to one of ordinary skill in the art, the sight pin  50  may be replaced by or formed into any of a number of sight tools including, but not limited to, cross-hairs, a scope, a laser sight, a fiber optic sight, and the like. Additionally, a distance indicator  52  is attached to the sight mount  30  and adjusts up and down with the sight pin  50 . The position of the distance indicator  52  relative to a range scale  58  may be used to indicate a chosen distance an arrow will travel to hit the target when using the sight  21  in that position. In this way, an archer may select a range setting to impart an appropriate trajectory to an arrow to cause the arrow to strike a target at a given distance. 
     In the embodiments shown in FIGS. 2 and 3 a sight adjustor lock  54  for restricting the rotational movement of the drive pulley  26  is shown. The sight adjustor lock  54  restricts the rotational movement of the drive pulley  26  by directly contacting either the adjustor rod  44 , or the sight adjustor knob  48 . Alternatively, the sight adjustor lock  54  may be configured to restrict rotational movement of the drive pulley  26  by directly contacting the drive pulley  26 . 
     Referring to FIG. 4, the sight adjustor lock  54  may take the form of a simple lock nut or jam nut that threadedly engages the adjuster rod  44  and may be manually tightened in abutment with cable guard  46  to thereby restrict the rotation of the adjustor rod. The sight adjustor knob  48  and the sight adjustor lock  54  also preferably include textured surfaces to better enable an archer to grip them securely for rotational movement. Other locking mechanisms for restricting rotational movement are well known in the art and may be substituted for the sight adjustor lock shown and described herein without departing from the invention. 
     FIG. 5 is a diagram of an archery bow  60  incorporating a sight assembly  62  constructed in accordance with the teachings of the present invention. It will be understood by one of ordinary skill in the art that the sight assembly may be secured to the bow through a mounting plate such as that shown in FIGS. 2 and 3 or may be formed using part of the bow riser  64  as an integral part of the sight assembly. 
     Although the present invention has been shown and described with reference to particular preferred embodiments, various additions, deletions and modifications that are obvious to a person skilled in the art to which the invention pertains, even if not shown or specifically described herein, are deemed to lie within the scope of the invention as encompassed by the following claims.