Abstract:
A method of producing a rifle scope having a body made in part of composite material. The method utilizes a composite material tubular housing element, having a rear and having an outer diameter and a metal eyepiece adapter in form of a tube having an inner diameter matching the outer diameter. In the method, the metal eyepiece adapter is adhered partially over the rear of the tubular housing element.

Description:
BACKGROUND 
     The invention is generally in the field of optical devices. More specifically, one form of the invention is a rifle scope made in part of composite material. 
     The traditional rifle sighting system body is a tube made of steel or aluminum, having an expanded front (objective) and rear (ocular) section. Although this design has many advantages, this results in a heavier rifle scope than is ideal for some applications. 
     SUMMARY 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 
     In a first separate aspect, the present invention may take the form of a method of producing a rifle scope having a body made in part of composite material. The method utilizes a longitudinal inner molding core (henceforth, “spud”), separable into a front piece and a rear piece, and which has a rigid-material tube placed where the front piece joins the rear piece. Woven-fiber material is placed about the spud and the rigid-material tube, thereby creating a work piece, which is placed into a mold. A charge of resin is introduced into the mold, which is then closed. The workpiece is heated until the resin infuses the woven-fiber material. The resin is permitted to cure, thereby creating a composite material piece. The mold is opened, either before or after the resin fully cures, and the workpiece is removed. The front piece is pulled from the front of the composite material shell and the rear piece is pulled from the back of the composite material shell, leaving the rigid-material tube contained within and connected to the composite material shell. The composite material shell is then used as a part in the construction of a rifle scope. 
     In a second separate aspect, the present invention may take the form of a method of producing a rifle scope having a body made in part of composite material. The method utilizes a composite material tubular housing element, having a rear and having an outer diameter and a metal eyepiece adapter in the form of a tube having an inner diameter matching the outer diameter. In the method, the metal eyepiece adapter is adhered partially over the rear of the tubular housing element. 
     In a third separate aspect, the present invention may take the form of an optical assembly that includes a compound material tubular housing element and a set of metal tube elements, into which are seated lens groups, adhered within the compound material tubular housing element, thereby forming an optical train. 
     In a fourth separate aspect, the present invention may take the form of a rifle scope having a front and a rear and including a main tube made of composite material. A zoom and erector assembly is positioned mostly in the main tube and a metal eyepiece adapter is rigidly attached to the rear of the main tube, and is adapted to brace the zoom and erector assembly against forward movement relative to the main tube, during rifle recoil. Finally, an eyepiece is rigidly attached to the rear of the eyepiece adapter. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments are illustrated in referenced drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
         FIG. 1  is a top side perspective view of a rifle scope, made in part of composite material, according to the present invention. 
         FIG. 2  is an isometric, exploded view of a work piece that may be used in the manufacture of the scope of  FIG. 1 . 
         FIG. 3  is a perspective view of the workpiece of  FIG. 2 . 
         FIG. 4  is a sectional view of the front portion of the workpiece of  FIG. 3 . 
         FIG. 5  is a detail view of the area shown by circle  5  in  FIG. 4 . 
         FIG. 6  is a detail view of the area shown by circle  6  in  FIG. 4 . 
         FIG. 7  is a sectional view of the front workpiece portion shown in  FIG. 4 , at a further stage of the production process, with composite material placed over it and placed into a mold. 
         FIG. 8  shows an isometric view of the workpiece of  FIG. 7 , at a further point in the manufacturing process, where it has been removed from the mold and the spud has been removed. 
         FIG. 9  is an isometric view of the workpiece of  FIG. 8 , at a further point in the manufacturing process, showing some apertures that have been formed in it. 
         FIG. 10  is an isometric view of the workpiece of  FIG. 8 , rotated about its longitudinal axis, to show an additional aperture. 
         FIG. 11  shows a sectional view of the workpiece of  FIG. 10 . 
         FIG. 12  shows the sectional view of  FIG. 11 , at a further point in the manufacturing process wherein lens assemblies have been added. 
         FIG. 13  shows a sectional view of a portion of composite material formed around the rear of the spud shown in  FIG. 2   
         FIG. 14  shows an enlarged sectional view of the composite material portion of  FIG. 13 , at a later stage of the manufacturing process with an eyepiece adapter added. 
         FIG. 15  shows an enlarged sectional view of the portion of  FIG. 14 , at a later stage of the manufacturing process, in which a zoom tube and an eyepiece have been added. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Definitions: 
     When the term “metal” is used as a modifier in this application, it means that the item that is the object of the modifier is largely metal, but could include other materials as well. 
     The term “spud” means inner molding core. 
     When the term “composite material” is used in this application, it means an engineered material made from two or more constituent materials with significantly different physical properties which remain separate and distinct within the finished structure. The term includes materials that combine a substrate of woven fibers, infused with a resin. The woven fibers may be made from carbon fibers, basalt fibers, glass fibers or para-aramid synthetic fibers. The resin may include an epoxy, polyester, nylon or vinyl ester. Also included are laminated materials made, at least in part, of composite material layers, and which may have a first layer or set of layers, made of a first composite material, and a second layer or set of layers, made of a second composite material. The term “composite-material” is a modifier indicating that the object of the modification interfaces with composite material. 
     The term “intermediate focus lens” refers to a Petzval lens or a Barlow lens placed between the objective lens and the erector tube. 
     Referring to  FIG. 1  in one preferred embodiment the present invention takes the form of a rifle scope  10 , having a composite fiber main tube  12 , which supports a turret  14  having an elevation adjustment knob  16 , a windage knob  18  and a focus knob  20 . Although it is not visible in  FIG. 1  an intermediate focus lens holder is supported inside tube  12  directly in front of the turret  14 , and in turn supports an intermediate focus lens set. A fiber optic objective bell  30 , similarly supports an objective lens holder  32  that supports an objective lens assembly  34 . Also, at the rear of scope  10 , an eyepiece adapter  38  supports eyepiece  40  and a zoom adjustment ring  42 . 
     Referring, now, to  FIGS. 2-3 , which collectively show a stage in the construction of scope  10 , a rifle scope is formed by first providing a spud  110 , generally in the shape of a scope, and divided into a front spud piece  112  and a rear spud piece  114 . An objective section  116  of front spud piece  112  is shaped to receive and support an objective lens insert  32 . In similar manner, an intermediate focus portion  120  at the rear of front spud piece  112 , is shaped to receive an intermediate focus assembly support insert  122 . Both the objective assembly support insert  32  and the intermediate focus assembly support insert  122  are each designed to receive a corresponding lens assembly and to act as an interface between the composite material shell described below and these lens assemblies. 
     Referring to  FIGS. 4, 5 and 6 , a set of circular grooves  124  are defined on both the objective insert  32  and the intermediate focus insert  122 . Also, O-rings  130  are set about front spud piece  112  prior to threading inserts  32  and  122  onto piece  112 . Also, it can be noted that front spud  112  and rear spud  114  are joined together by means of matching threads  132 . 
     Referring now to  FIG. 7 , a covering  140  of woven material, woven preferably of basalt or carbon fibers is placed about spuds  112  and  114  and the resultant work piece is placed into a mold  150 . A charge of resin, preferably epoxy, is also placed into the mold  150  and the work piece is heated to cure the resin charge. The resin must be added and the mold  150  heated and handled so as to cause the resin to cover, and to become thoroughly inculcated into, the woven material of covering  140 . 
     In a preferred embodiment woven material that has been pre-impregnated with resin (“prepreg” in industry parlance) is used. In one preferred embodiment a particular prepreg available from TCR composites of Ogden, Utah, designated as AS4D/UF3325, fiber volume 60%, is used. The “AS4D” portion of this designator refers to a carbon fiber that is available under the HexTow® mark from HexCel Corporation of Stamford, Connecticut. The “UF3325” portion refers to a proprietary TCR composites resin, with the following properties for the neat resin (properties of the essential polymers of the resin):
         Tg (RDS G″): 255° F. (123.89° C.)   Tensile strength: 10.5 ksi   Tensile modulus: 406 ksi   Elongation: 4.6%   Density (cured): 1.208 g/cc
 
Where T g  is the glass transition temperature.
       

     In a preferred embodiment this prepreg is placed about the spud and baked at an increasing temperature for two hours, at which point it should reach 300° F., at which temperature it is baked for two hours more and then permitted to slowly cool for two hours. 
     The finished product has approximately the following properties:
         Tensile strength: 315 ksi   Tensile modulus: 21.7 msi   Elongation: 1.3%   NOL short beam shear: 7.6 ksi   Typical pressure vessel hoop fiber strength translations: 80 to 95%       

       FIGS. 8 and 11 , show the work piece after it has been removed from the mold, the spuds  112  and  114  have been removed and excess covering  140  has been removed from the front. The covering  140  is now made of composite material, formed by resin curing and joining with the woven material and forms the main tube  12  and objective bell  30 . Inwardly directed ridges of the composite material covering  140  have entered the circular grooves  124 , thereby forming an enhanced bond between bell  30  and objective insert  32  and between main tube  12  and intermediate focus insert  124 . In an alternative preferred embodiment grooves are formed on the exterior of bell  30  and main tube  12 , where composite material has been introduced into grooves  124 . 
       FIGS. 9 and 10  show openings  142 ,  144  and  146  cut into main tube  12  to accommodate an elevation adjust knob stem, focus knob stem and windage/elevation adjust resistance spring (not shown), respectively. Windage/elevation adjust resistance spring (the “spring”) resists the erector tube (not shown) being pushed by the elevation adjust knob  16  or the windage adjust knob  18 , and urges erector tube to move when knob  16  or  18  are moved so as to retract the movement (not shown) used to adjust windage or elevation angle. The turret  14  ( FIG. 1 ) slides over opening  144  so that the spring does not protrude entirely through opening  144 , but rather a portion of the spring (in leaf form) lies within opening  144  contacting an interior surface of turret  14 . Accordingly, more space is made available inside main tube  12 , compared to a scope in which there is no opening  144  and the corresponding spring must be entirely accommodated within main tube. This added space may be exploited in various ways, including in one embodiment, by making thicker the walls of the cam tube  234  ( FIG. 15 ). 
     Next, referring to  FIG. 12 , main tube  12  is stood on end, with bell  30  pointed upward, and adhesive is introduced into the inside of intermediate focus insert  122  and objective insert  32 . Alternatively, or additionally, adhesive is applied to the exterior of an intermediate focus lens assembly  160  and an objective lens assembly  34  Then the intermediate focus lens assembly  160  and the objective lens assembly  34 , are lowered into intermediate focus insert  122  and objective insert  32 , respectively, and adhered into place. Interior ridges  172  and  174  of insert  122  are interior surface features adapted to enhance the bonding of the intermediate focus lens assembly. 
       FIG. 13  shows the rear end  210  of main tube  12  after it has been formed. In addition, a cut  212  has been made from the bottom and a round aperture  214  has been formed at its top. Referring to  FIG. 14  an eyepiece adapter  38  is adhered to the rear. Adapter  38  defines an aperture  218  that matches aperture  214 , and is aligned to aperture  214  to effect the alignment of adapter  38 . A peg  220  is adhered through both aperture  214  and  218  to maintain this alignment. A slot  222  is defined in adapter  38 , and will be discussed further below. Also, a set of square circumferential notches  224  are formed in the interior of adapter  38 , to accommodate adhesive during the process of adhering adapter  38  to main tube  12 . An inner circumferential rim  228  braces adapter  38  against the rear of main tube  12 . 
       FIG. 14  shows the portion of  FIG. 13 , but with an eyepiece  40  attached and with interior elements shown, although some are not shown, for clarity of presentation. When a rifle is fired, it undergoes a sudden rearward acceleration (typically referred to “recoil” or “kickback”) which is transferred to the rifle scope through the mounting mechanism (typically tubes). For scope  10 , this force is transferred from main tube  12  to the eyepiece  40  and to an erector tube assembly  238  ( FIG. 15 ), through the eyepiece adapter  38 . Because of inertia, eyepiece  40  and assembly  238  effectively exert forward force, by resisting the sudden rearward acceleration, during recoil. Accordingly adapter  38  braces assembly  238  against forward motion relative to main tube  12 . Many features of the design of adapter  38  and its joinder with tube  12  and eyepiece  40 , and the seating of the rear portion of assembly  238 , are designed to absorb the impact of recoil without suffering damage. 
     The erector tube assembly,  238  includes a cam tube  234  that is rotated by a zoom adjust actuator assembly, that includes a zoom adjustment ring  42  and a stem (not shown) that extends through slot and is joined with tube  234 . A ring  242  has an inner curved surface that matches an outer curved surface of a rear portion of assembly  238 , thereby permitting assembly  238  to swivel. Ring  242  is held in place during rifle recoil by the inner rim  228  defined by adapter  38 , and in turn restrains assembly  238  from forward movement relative to main tube  12 , which is rapidly accelerated rearward. 
     In a preferred embodiment inserts  32  and  122  and adapter  38  are made of  6061  aluminum alloy. Among other functions, insert  32  and adapter  38  serve to form a robust seal between composite material covering  140  and the interior elements of the scope  10 , thereby protecting the scope interior from moisture damage and other possible contamination. 
     While a number of exemplary aspects and embodiments have been discussed above, those possessed of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.