Abstract:
A pre-assembled pivoting lens unit is disclosed that includes a pivot cartridge capable of being at least partially received by an optical sighting device housing, along with a pivot tube defining a first end movably coupled to the pivot cartridge and a second end capable of moving transversely to the longitudinal axis of the device housing. Disposed in the pivot tube between the first and second ends is a lens assembly capable of focusing an image when the lens unit is at least partially received by the device housing. A fastener is used to secure the pivot cartridge to the first end of the pivot tube, and a resilient member interposes the fastener and pivot tube first end to enable relative pivoting movement of the pivot tube.

Description:
TECHNICAL FIELD 
     This application relates to devices for pivotally mounting lenses within the housing of an optical sighting device such as a riflescope and, in particular, to a pivoting lens unit that is pre-assembled prior to installing within the housing of the optical sighting device. 
     BACKGROUND OF THE INVENTION 
     Optical sighting devices have long been used in conjunction with weapons, such as rifles and handguns, to allow a user to accurately aim the weapon. Optical sighting devices such as riflescopes typically include eyepiece and objective lenses positioned at opposite ends of a tubular housing. A lens assembly is positioned medially of the eyepiece and objective lenses, and may be movable along a longitudinal axis of the housing for adjustment of the optical power of the optical sighting device. An aiming reticle is positioned in the optical path of the optical sighting device, typically between the lens assembly and the eyepiece lens. Because bullet trajectory, wind conditions and distance to the target can vary depending upon shooting conditions, quality riflescopes typically provide compensation for variations in these parameters by allowing a user to make small adjustments to the optical characteristics or the aiming of the weapon relative to the rifle or handgun on which it is mounted. These adjustments are known as windage and holdover adjustments and are typically accomplished by pivotal movement of the lens assembly within the housing of the optical sighting device to divert the optical path of the observed light before it reaches the reticle, as shown in U.S. Pat. Nos. 3,297,389 and 4,408,842 to Gibson, which are incorporated herein by reference. 
     To aid in pivotal movement of the lens assembly, the optical sighting device industry has developed a pivoting lens unit and lens assembly, which includes a pivot cartridge mounted to the housing of the device, a pivot tube disposed within the housing and supporting the lens assembly, and a resilient member that biases the pivot cartridge toward the pivot tube while allowing pivotal movement of the pivot tube and lens assembly. In these designs, the pivoting lens unit is generally positioned proximate the eyepiece of the housing. However, it is also known to position the pivoting lens unit proximate the objective end of the housing. A pivot end of the pivot tube that extends along the longitudinal axis of the housing is pivotally mounted to the interior of the housing near the eyepiece end of the housing. The lens assembly is supported near a free end of the pivot tube opposite the pivot end. Adjustment of windage and holdover is accomplished by turning an adjustment mechanism that operatively engages a leaf spring, thereby driving the free end of the pivot tube, including the lens assembly, transversely of the housing longitudinal axis and thereby altering the optical path between the eyepiece and objective lenses. 
     However, current manufacturing and assembly processes require the pivoting lens unit to be manufactured and assembled with the housing. These processes are time-consuming and expensive because each component of the pivoting lens unit is manufactured and then separately assembled with the housing. The pivoting lens unit is provided on an “as-needed basis” and is typically manufactured and assembled by the same manufacturer at the same time the optical sighting device is built, thereby reducing flexibility in the manufacturing and assembly processes. In addition, the assembly process is complicated by the number of loose components that an installer must assemble in a particularized order. The process involves great efforts and requires substantial skill because the fit between components requires precise dimensional coordination, which is of substantial significance for the accurate operation of the optical sighting device. Imprecision of one component leads to re-manufacture and re-assembly of that component and possibly re-assembly of other components that followed in the assembly process. 
     The assembly process is further slowed and complicated by the requirement to use a special tool to assemble some components of the pivoting lens unit. The pivot tube is installed in the housing following installation of the leaf spring; however, to install the pivot tube, the installer must use a special hand tool to compress the leaf spring, which in final assembly is disposed between the housing and the pivot tube. 
     Thus, there exists a need to simplify the manufacturing and assembly processes associated with optical sighting devices, and the pivoting lens unit in particular, to reduce the costs of manufacturing and assembling a pivoting lens unit while maintaining or even improving the precision of optical sighting devices. 
     SUMMARY OF THE INVENTION 
     The present invention is directed in part to a pre-assembled pivoting lens unit that facilitates the manufacturing and assembly processes for an optical sighting device. Therefore, consistent with one aspect of the invention, a pre-assembled pivoting lens unit is disclosed that includes a pivot cartridge capable sized to be at least partially received by an optical sighting device housing, along with a pivot tube defining a first end movably coupled to the pivot cartridge and a second end extending from the pivot cartridge and capable of moving transversely to the longitudinal axis of the device housing. Disposed in the pivot tube between the first and second ends is a lens assembly capable of focusing an image when the lens unit is at least partially received by the device housing. A fastener such as a nut is used to pivotally secure the pivot cartridge to the first end of the pivot tube, and a resilient member such as a spring interposes the fastener and pivot tube first end to enable relative pivoting movement of the pivot tube. 
     Consistent with another aspect of the invention, the above-described lens assembly may be positionally fixed between the first and second ends of the pivot tube to provide an optical sighting device with fixed magnification. Alternatively, the lens assembly may include a cam sleeve supported around at least a portion of the pivot tube and communicating with the lens assembly to drive the lens assembly along the longitudinal axis, thereby selectively adjusting the optical magnification provided by the optical sighting device. 
     In another embodiment of the invention, the above-described lens assembly may include a key formed in the pivot cartridge that engages a keyway formed in the first end of the pivot tube, thereby restricting rotation of the pivot tube relative to the pivot cartridge and cam sleeve. Alternatively, the lens assembly may include a key formed in the housing that engages a keyway formed in the pivot cartridge for orienting and rotationally fixing the pivot tube about the housing longitudinal axis. Fixing the position of the pivot tube facilitates use of the cam sleeve for adjusting optical magnification. 
     Other aspects and embodiments of the present invention include an optical sighting device incorporating such a pre-assembled pivoting lens unit, as well as a method for manufacturing the same. 
     Pre-assembly of the pivoting lens unit in accordance with these aspects and features results in a cost-effective technique for producing the optical sighting device, since rather than tracking a series of components, the manufacturer need only track one component—the pre-assembled pivoting lens unit. Moreover, consistent with an embodiment of the present invention, the entire pivoting lens unit can be pre-assembled at an off-site pre-assembly facility and shipped to the optical sighting device manufacturer as a single unit. Once the pivoting lens unit is pre-assembled, it can be pre-tested off-site or by the optical sighting device manufacturer before installing in the optical sighting device. Pre-assembly of the pivoting lens unit increases the availability of such units, for the unit can be manufactured, assembled, and tested separately from the optical sighting device and stored as an off-the-shelf item. 
     Further still, pre-assembling the pivoting lens unit in accordance with the disclosed embodiments of the invention simplifies the final assembly process and eliminates the need for special assembly tools to install the pre-assembled pivoting lens unit within the optical sighting device. In addition, the pre-assembled pivoting lens unit can be easily removed to expose components mounted within the optical sighting device for service or replacement as needed. 
     Additional aspects and advantages of this invention will be apparent from the following detailed description of particular embodiments thereof, which proceeds with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of an optical sighting device including a pre-assembled pivoting lens unit in accordance with an embodiment of the present invention. 
     FIG. 2 is an enlarged cross-sectional view of the pre-assembled pivoting lens unit shown in FIG.  1 . 
     FIG. 3 is an exploded perspective view of the pre-assembled pivoting lens unit shown in FIG.  2 . 
     FIG. 4 illustrates assembly of an optical sighting device, including the pre-assembled pivoting lens unit, in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following description relates to an example of an optical sighting device incorporating features and aspects of the present invention, specifically a riflescope, and references the attached drawings. A riflescope is usually mountable to a firearm, a rifle or a handgun. FIG. 1 is a cross-sectional view of a riflescope  100  that has an outer tubular housing  102  having a bore  104  that extends along a longitudinal axis  106  of the housing  102 . An adjustment mechanism  108  is located proximate the midpoint of the riflescope  100 , and a power magnification selector ring  110  is located proximal of an eyepiece end  112 . A pre-assembled pivoting lens unit  114  in accordance with an embodiment of the invention is disposed within the bore  104  and movably mounted to an interior wall  116  of the housing  102 . 
     FIG. 2 shows an enlarged cross-sectional view of the pre-assembled pivoting lens unit  114  of FIG.  1 . FIG. 3 is an exploded view of the pre-assembled pivoting lens unit  114  of FIG. 2, showing the various elements that comprise the pre-assembled pivoting lens unit  114  and their order of assembly. With reference to both FIG.  2  and FIG. 3, the pre-assembled pivoting lens unit  114  includes a pivot tube  202  with a pivot end  204  sized for a sliding fit against a pivot cartridge  200 . The pivot tube  202  extends longitudinally from the pivot end  204  and terminates in a free end  206 . A lens assembly  208 , preferably including two separately locatable doublet lens assemblies as shown in the embodiments of FIG.  2  and FIG. 3, is slidably disposed between the pivot end  204  and the free end  206  of the pivot tube  202 . A field lens assembly  209 , used, for example, for correcting field distortion in an image or magnifying an image, is mounted to the free end  206  of the pivot tube  202 . A lens unit extender  222  is threadably coupled to the free end  206  of the pivot tube  202  for engagement by adjustment mechanism  108  to pivotably adjust the pivot tube  202  within the pivot cartridge  200 , as further described below. A fastener  210  such as a nut is externally threaded to mate with interior threads in the pivot cartridge  200 , thereby pivotally securing the pivot tube  202  to the pivot cartridge  200 . 
     In the embodiment shown in FIG. 2, the lens assembly  208  is slidably mounted within the pivot tube  202 , thereby providing a variable power feature. A set of cam followers  211  is mounted to the lens assembly  208 . A cam sleeve  212  circumscribes the pivot tube  202  and drives the cam followers  211  for movement along the pivot tube  202 , generally along the longitudinal axis  106  of the housing  102  when the pre-assembled pivoting lens unit  114  is installed, in response to manual rotation of the power magnification selector ring  110  rotatably mounted around the housing  102  and mechanically coupled to the cam sleeve  212 . Those ordinarily skilled in the art will appreciate that the pre-assembled pivoting lens unit  114  could also be assembled with the cam sleeve  212  omitted and the lens assembly  208  rigidly secured to the pivot tube  202  (not shown), so that the optical power of the riflescope  100  is fixed. 
     As shown in FIG. 2, a resilient member  214 , such as a wave spring, a set of coil springs or any other resilient material, biases the pivot cartridge  200  toward the pivot end  204  of the pivot tube  202  to enable relative pivoting movement of the pivot tube  202 . The fastener  210 , as previously discussed, is externally threaded to mate with interior threads in the pivot cartridge  200 , thereby compressing the resilient member  214  so that the desired amount of force is applied against the pivot end  204  of the pivot tube  202 , as well as securing the pivot tube  202  to the pivot cartridge  200 . A step washer  220  is installed for transitioning from a larger inner diameter  221  to a smaller inner diameter  223  of the pivot cartridge  200 , so that a ridge  225  of the step washer  220  seats against an inner shoulder  219  of the pivot cartridge  200 . This prevents threading the fastener  210  into the pivot shoulder  219  to the extent of complete compression of the resilient member  214 . 
     In FIG. 2, a wire reticle  218  is disposed between the fastener  210  and the step washer  220  in a focal plane of the riflescope  100  generally perpendicular to the longitudinal axis  106  of the housing  102  so that cross-hairs (not shown) of the reticle  218  are centered at a pivot point (not shown) when the pre-assembled pivoting lens unit  114  is installed. The pivot point is determined by the curvature of a socket joint  216 , which, in FIG. 2, is where the pivot tube  202  slides against the pivot cartridge  200 . The size of the pivot cartridge  200 , the pivot tube  202  and the bore  104  in the housing  102  is such that the pivot point will coincide with the focal plane of the riflescope  100  when the pre-assembled pivoting lens unit  114  is installed in the housing  102 . Those skilled in the art will appreciate that the socket joint  216  may include a conical or spherical socket surface against which the pivot tube  202  is seated, either in a full-socket or half-socket configuration. The socket joint  216  may also include an equalized pivot mount of the type described in U.S. Pat. No. 6,469,829, the specification of which is incorporated herein by reference. 
     As further shown in FIG. 2, a pivot tube keyway slot  224  extends longitudinally along the pivot end  204  of the pivot tube  202  and mates with a pivot cartridge key  226  extending transversely into the interior of the pivot cartridge  200  to limit rotation of the pivot tube  202  about its longitudinal axis relative to the pivot cartridge  200  and cam sleeve  212  (some play is necessary to accommodate the motion of the windage and holdover adjustments described below). The key  226  is preferably a pin that is press-fit into a small transverse hole through pivot cartridge  200 . In alternative embodiments, the keyway slot may be formed in the pivot cartridge  200  and the key formed on the pivot tube  202 . 
     FIG. 4 is a perspective view of an order of assembly for elements as they relate to an optical sighting device, such as, for example, the riflescope  100  that may be found mounted to a firearm, a rifle or a handgun (not shown), consistent with an embodiment of the invention. In the prior art, it has been necessary to manufacture and separately assemble each element shown in FIG. 3, in addition to the elements shown in FIG. 4, with the housing  102  of the riflescope  100 . Pre-assembly of the pivoting lens unit  114 , however, significantly reduces the amount of assembly required. To visually understand the magnitude of reduction, replace the pre-assembled pivoting lens unit  114  shown in FIG. 4 with the exploded view of the pre-assembled pivoting lens unit  114  shown in FIG.  3 . 
     In the embodiment shown in FIG. 4, installation of the pre-assembled pivoting lens unit  114  is preceded by a series of O-rings  402 , which are installed with the power magnification selector ring  110 , which is rotatably mounted around the outside of the housing  102 . Before installing the pre-assembled pivoting lens unit  114  in the bore  104  of the housing  102 , a leaf spring  400  is mounted within the housing  102  adjacent where the free end  206  of the pivot tube  202  will be located. The leaf spring  400  biases the free end  206  toward the adjustment mechanism  108 . With reference to FIG. 1 the adjustment mechanism  108  extends from the housing  102  and includes a plunger  118  that operatively engages the free end  206  of the pivot tube  202  when the pre-assembled pivoting lens unit  114  is installed. The adjustment mechanism  108  adjustably extends into the bore  104  and is manually adjustable to drive the pivot tube  202  for movement transversely of the longitudinal axis  106  in a vertical direction to adjust an elevation setting of the riflescope  100 . Ordinarily skilled persons will appreciate that a second adjustment mechanism (not shown) could also be applied to adjust the horizontal position of the pivot tube  202  in a direction perpendicular to the adjustment mechanism  108 , to thereby allow adjustment of windage in addition to elevation. 
     Returning to FIG. 4, after the leaf spring  400  is attached, the pre-assembled pivoting lens unit  114  is then installed in the bore  104  of the housing  102  such that the pivot cartridge  200  is rigidly secured, bonded, or press-fit to the interior wall  116  of the housing  102 . Recall that in the prior art, the leaf spring  400  is installed in the bore  104  of the housing  102  using special assembly tools prior to installing the pivoting lens unit  114 . Attaching the leaf spring  400  to the free end  206  of the pivot tube  202  before installing the pre-assembled pivoting lens unit  114  can eliminate the need for such special assembly tools. 
     A second key  227  (FIG. 1) extends inwardly within the interior of the housing  102  and mates with a second keyway slot  228  extending longitudinally along the outer surface of pivot cartridge  200  to orient the pivot tube  202  in a generally fixed rotational position about the longitudinal axis  106  of the housing  102  when the pre-assembled pivoting lens unit  114  is installed in the bore  104  of the housing  102 . Fixing the rotational position of the pivot tube  202  about the longitudinal axis  106  of the housing  102  facilitates use of the cam sleeve  212  to move lens assembly  208  longitudinally by preventing rotation of the pivot cartridge  200  and the pivot tube  202  relative to the housing  102  in response to rotation of the cam sleeve  212  about the longitudinal axis  106 . In alternative embodiments (not shown), the second key  227  may be formed in the pivot cartridge  200  and the second keyway slot  228  may be formed in the housing  102  to perform a similar function. 
     Returning to FIG. 4, a second series of O-rings  403  is installed immediately following installation of the pre-assembled pivoting lens unit  114  to form a gas tight seal at eyepiece end  112 . A retainer, such as lock ring  406 , is externally threaded to mate with the interior threads in the housing  102 , thereby retaining the pre-assembled pivoting lens unit  114  and the reticle  218  within the housing  102 . An eyepiece  404  is threaded onto the end of the housing  102  and environmentally sealed by the second O-rings  403  to protect the pre-assembled pivoting lens unit  114  from dust and debris. 
     It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments of this invention without departing from the underlying principles thereof. For example, in other embodiments, different mechanical fittings may be used to achieve the same effect. The scope of the present invention should, therefore, be determined only by the following claims.