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Publication numberUS3161716 A
Publication typeGrant
Publication dateDec 15, 1964
Filing dateFeb 19, 1962
Priority dateFeb 19, 1962
Publication numberUS 3161716 A, US 3161716A, US-A-3161716, US3161716 A, US3161716A
InventorsDonald J Burris, John L Maulbetsch
Original AssigneeRedfield Gun Sight Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Variable power riflescope with tilting reticle and erector tube
US 3161716 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

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Dec. 15, 1964 D. J. BURRIS ETAL 3,161,716 VARIABLE POWER RIFLESCOPE WITH TILTING RETICLE AND ERECTOR TUBE Filed Feb. 19, 1962 2 Sheets-Sheet 1 INVENTORS DONALD J. BUR/PIS JOHN L. MAuLBETscH ,4T ORNEYS 1964 D. J. BURRIS ETAL 3,161,716

VARIABLE POWER RIFLESCOPE WITH TILTING RETICLE AND ERECTOR TUBE Filed Feb. 19, 1962 2 Sheets-Sheet 2 INVENTORS DON/71.0 J. BUR/P/S Joli/34V L, M/IULBETSOH ATTORNEYS United States Patent 3,161,716 VARIABLE POWER RIFLESCOPE WITH TILTING RETICLE AND ERECTOR TUBE Donald J. Burris, Broomfield, Colo., and John L. Maulbetsch, Northampton, Mass., assignors to Redfield Gun Sight Company, Denver, Colo., a limited partnership of Colorado Filed Feb. 19, 1962, Ser. No. 173,922 8 Claims. (Cl. 88--32) This invention relates to optical sighting devices and, more particularly, to improvements in telescopic rifle sights of the internally adjustable type that include a reticle.

This application is a continuation in part of our application for Letters Patent of the United States Serial Number 100,100 filed April 3, 1961, now abandoned.

A number of significant advances in the design and construction of internally adjustable rifiescopes have been made in recent years which have contributed materially to their versatility, ruggedness, dependability and accuracy. Among the most important of these have been the feature by which the reticle appears to always remain centered in the field of view irrespective of the adjustments made in the scope to introduce corrections in the line of sight to compensate for windage, the distance to the target, the ballistic characteristics of a particular cartridge and, primarily, to 2ero-in the scope to the axis of the gun barrel because, due to the dimensional variations in the mounts, the mechanical axis of the scope is rarely exactly in line with the gun barrel. The fact that the trajectory of a bullet does not coincide with the line of sight which is always straight necessitates these corrections.

A riflescope includes a reticle which provides some means for defining an aiming point supposedly coincident with the point of impact of the bullet on the target. Reticles take many forms, the most common of which are the cross-hair, dot and post types and these patterns may take either the form of filaments or other materials mounted in a frame or a design engraved, etched or otherwise deposited on a piece of glass. There are certain rather standard design requirements insofar as reticle placement within the optical system are concerned that must be followed and many of the refinements in scope design, such as the centered reticle feature, should take these standard requirements into account. For instance, there are usually two image planes within a riflescope in which a sharp image of the target is produced. One lies at or near the focal plane of the objective lens system which is near the front of the scope (at or near depending on whether the objectives are set for viewing at infinity or at a nearer target, 100 yards, for instance, the latter being the usual case), and the other is at or near the focal plane of the lens system consisting of objective lenses and erector lens system. This second image plane is the one usually viewed by the observer through the eyepiece and is, therefore, adjacent to the shooters eye and may be referred to as an eyepiece image plane. The first one may be referred to as objective image plane. If the image of the reticle, as viewed by the shooter is to be superimposed upon the viewed image of the target in a sharp and well defined manner without showing any parallax, then the reticle must be located either in the first image plane or in the second image plane. Actually, neither of these planes is accurately fixed as they vary with the distance to the target being sighted; however, from a practical standpoint, they are substantially fixed, as most targets that require the use of a scope in the first place are far enough away that variations in distances introduce only a minute displacement of these image planes and therefore only a slight amount of parallax between target image and reticle image will result.

A well designed scope must also include a diaphragm that limits the field of view as seen through the optical system and is known as a field stop. The purpose of this diaphragm is to give a sharply delineated boundary to the field, and further, it serves to prevent unwanted internal reflections. If a diaphragm is not used the field is limited by various apertures in the optical system which are not in sharp focus to the shooter producing a fading out of the field which is a most undesirable eifect.

This diaphragm should also be located in one of the two image planes of the scope it a sharp and well-defined field is to be maintained. It may be in the same image plane as the one where the reticle is placed or the reticle may be placed in one image plane and the diaphragm in the other. For practical reasons and also because of optical considerations, this diaphragm may be slightly displaced longitudinally relative to the center of the image plane. The reticle is focused mainly for the central region of the field while the diaphragm acts on the edges of the field.

Bearing in mind the foregoing relationships, the optical system in a riflescope should, in addition, provide means for maintaining the aiming point of the reticle centered in the field of view defined by the diaphragm throughout the maximum adjustment range of the system to compensate for windage and elevation. This refinement presents a much more difficult problem. One possible solution is to mount the reticle within the main scope barrel at the eyepiece image plane to maintain same in sharp focus as aforementioned, and mount the tube of other adjustable support for the erector lens system for limited universal movement relative to the barrel about a center that also falls within the eyepiece image plane. From the practical standpoint, it becomes extremely difficult, if not impossible, mechanically to locate and maintain the center of universal movement of the erec tor lens system support coincident with the aiming point defined by the reticle or, for that matter, even in the same plane; however, this is not an overriding consideration as the off-center relationship that results when the center of universal movement of the erector lens tube is displaced a small fraction of an inch from the image plane containing the reticle, while noticeable, is not too disturbing to the viewer. Any greater separation between the center of universal movement of the erector lens system and adjustable support therefor from the image plane in which the reticle is located does, however, materially affect the centering of the reticle assuming that the diaphragm is mounted for movement with the erector lens system. In other words, when the center of universal movement of the erector lens system and mount therefor are displaced any appreciable distance from the reticle and the latter is located in the eyepiece image plane, some relative movement between the diaphragm carried in the erector lens tube and the reticle which 0ccupies a fixed position within the barrel must take place when angular adjustments of the erector lens system are made to introduce windage and elevation corrections; thus, the reticle will not remain centered within the field of view defined by the diaphragm.

A better solution to the centered reticle problem is to mount the reticle in the same adjustable support that carries the erector lens system and the diaphragm thus eliminating any relative movement therebetween due to the fact that a fixed relationship exists among all elements that cooperate to establish the line of sight and, even though they are adjustable by reason of their common adjustable support, all of them move in fixed ratio to one another thus maintaining true centering of the aiming point within the field of view. The US. patent to Kolhnorgen et a1. 2,955,512 which is now owned by the assignee of this application, recognized this important relationship; however, at the time it was felt that the center of universal movement of the erector lens system should be located approximately in the eyepiece image plane much in the same manner as in the centered reticle system previously discussed in which the reticle was separately and fixedly mounted in the main barrel, if true centering was to be achieved. It has now been found in accordance with the teaching of the instant application that the location of the center of universal movement of the erector lens system in relation to the eyepiece image plane is not particularly significant insofar as the centered reticle feature is concerned as long as both the diaphragm and reticle are mounted on the optical axis of the erector lens system for movement therewith. From a different standpoint, however, it is still highly desirable to locate the center of universal movement of the erector lens system adjacent one end of the erector lens tube and the means for adjusting same to correct for windage and elevation at the other end as, by so doing, utilization is made of a long lever arm having the advantage of extremely fine windage and elevation adjustments and, more important, the field of view through the scope will remain more or less centered in the eyepiece lenses. In other words, the more closely the center of movement of the erector lens assembly and the adjustment mechanism therefor approach one another, the coarser the adjustment becomes because, with a short lever arm a greater angular shift takes place in the optical axis of the erector lens system relative to the fixed optical axis defined by the centers of objective and ocular lens systems. The net result of this is that the center of universal movement of the erector lens system is, in fact, preferably located in close proximity to the eyepiece image plane but for the purposes of maintaining the field of view centered in the eyepiece lenses and to realize fine windage and elevation adjustments rather than to preserve the centered reticle feature which is more or less independent of the location of this center of universal movement when both the diaphragm and reticle are carried by the same mount as the erector lenses.

Now, the Kollmorgen et al. reticle-centering system previously described wherein the reticle is carried by the erector lens tube and located in the objective image plane along with the other system where the reticle is mounted in fixed position in the main barrel and located in the eyepiece image plane, have both proven reasonably satisfactory for use in fixed-power riflescopes; however, neither one will perform well in a variable-power scope as each introduces new problems even though the reticle remains farily Well centered. For example, if the optical system of the Kollmorgen et a1. Patent 2,955,512 were adopted for use in a variable-power scope, the reticle would be magnified in direct proportion to the degree of magnification of the image whenever the latter was varied due to the location of the reticle essentially in the objective image plane. This apparent change in size of the reticle upon varying the degree of magnification of the image is disturbing to the user and, more important, makes it difficult to accurately locate the aiming point on the target due to the relative enlargement of the intersection of the cross-hairs, post-tip or dot. If, on the other hand, the reticle size remained constant and that at which it would appear at the minimum power, an increase in magnification of the target image would result in the sighting point obscuring a smaller area of the target and permit extremely accurate location of the point of impact. This desirable end can be attained without disturbing the centered reticle feature in accordance with the teaching of the instant invention by relocating the reticle in the rear extremity of the erector lens tube and in the eyepiece image plane. For best results, the diaphragm should remain, as in the Kollmorgen construction, located in this eyepiece image plane so that the size of the field of view will, likewise, remain constant and in sharp focus through the entire range of target image magnification.

The construction wherein the reticle is fixedly mounted in the main scope barrel at the eyepiece image plane is subject to a much more serious deficiency in variablepower scopes even though there is no apparent increase or decrease in reticle size accompanying changes in the degree of target image magnification. Unless the sighting point defined by the reticle is positioned exactly on the optical axis of the erector lens system, the point of impact of the bullet will appear to move in relation to the target as the power of the scope is changed. When this happens, the accuracy of the rifiescope as a sighting device is lost. In other words, the aiming point will no longer coincide with the point of impact nor can this discrepancy be compensated for by introducing appropriate windage and elevation corrections as the error will still be present at other degrees of magnification. This is not a factor in fixed-power scopes because, once the scope is assembled, the center of the reticle and the axis of the erector lens system occupy a fixed relationship to one another and to the trajectory of the bullet which does not change. Any displacement of the reticle off the optical axis of the erector lens system remains constant and will, therefore, be compensated for by the windage and elevation corrections even though the actual adjustments made are not all caused by wind conditions and the drop of the bullet but include increments to correct for misalignment of the reticle with the optical axis.

No such simple solution is available in a variable-power scope wherein the reticle is mounted in the eyepiece image plane because, for true accuracy, the aiming point must be exactly on the optical axis of the erector lens system or, any error present, will show up immediately as the image size is varied relative to the reticle size in the form of a shift in the point of impact. Now, it is a practical impossibility to keep the aiming point of a reticle fixedly mounted within the main scope barrel always on the optical axis of the erector lens system which is moveable in order to introduce windage and elevation corrections. Theoretically, of course, the aiming point of a reticle mounted in the main barrel could be placed exactly on the optical axis of the erector lens system and the latter be mounted for limited universal movement about the aiming point to produce the desired result; however, mechanically, this theoretical condition cannot be achieved with any system that would be practical for use in a riflescope.

It is possible, however, to mount the reticle on the erector lens tube and also provide means for relocating the aiming point of the latter exactly on the optical axis of the erector lens system thus achieving true accuracy in a variable-power riflescope while, incidentally, retaining the centered reticle feature, maintaining both the reticle and field of view defined by the diaphragm or field stop a constant size throughout the entire range of variation in image magnification, and accomplish these desirable ends substantially independent of the center of universal movement of the erector lens system. It is the foregoing that comprises the most significant contribution of the present invention.

Accordingly, it is the principal object of the present invention to provide a novel and improved internally adjustable riflescope of the type having a reticle incorporated therein capable of defining an aiming point and point of impact with great accuracy.

A second object is the provision of an internally adjustable riflescope wherein the reticle always remains apparently centered within the field of view and in focus irrespective of the windage and elevation corrections introduced in the optical axis of the erector lens system or the location of the center of universal movement of the latter relative to the image plane in which said reticle is positioned.

Another objective is to provide an optical system especially suited for use in a variable-power internally adjustable riflescope that maintains the reticle image a constant size despite variations in the degree of magnification of the target image.

Still another object is the provision of an adjustable reticle assembly that enables the aiming point of the reticle to be located precisely on the optical axis of the erector lens system.

An additional object of the invention is to provide an improved and simplified universal mounting for the erector lens system in an internally adjustable riflescope.

Further objects of the invention herein described are the provisions of a telescopic sighting device for rifles and the like which is rugged, versatile, easy to operate, compact, accurate, relatively free of service problems, lightweight and decorative in appearance.

Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description that follows, and in which:

FIGURE 1 is a vertical diametrical section showing the internally adjustable riflescope of the present invention;

FIGURE 2 is a fragmentary diametrical section to an enlarged scale, portions of which have been broken away to conserve space, showing the details of the erector lens assembly and associated adjustment structure;

FIGURE 3 is a transverse section taken along line 33 of FIGURE 2 illustrating the externally-located ring which is rotated to vary the spacing and longitudinal position of the erector lenses thus altering the degree of image magnification;

FIGURE 4 is a transverse section taken along line 44 of FIGURE 2 showing the windage and elevation adjustment controls and their operative connection with the erector lens assembly;

FIGURE 5 is a top plan view of the erector lens tube and the means operatively associated therewith for changing the position of the erector lenses to change the power of the scope;

FIGURE 6 is a development of the rotating cam tube and cam slots therein which envelops the erector lens tube and turns relative thereto to alter the position of the erector lenses;

FIGURE 7 is a rear elevation of a cross-hair-type reticle assembly showing the means for centering same;

FIGURE 8 is a diametrical section through the reticle assembly of FIGURE 7; and,

FIGURE 9 is a fragmentary diametrical section to an enlarged scale illustrating a modified ball and socket type pivotal connection between the erector lens tube and barrel that may be substituted for the elastic coupling of FIGURES l and 2.

Referring now to the drawings for a detailed description of the present invention and, in particular, to FIGURES 1 and 2 for this purpose, the riflescope will be seen to include basically a tubular barrel 10 having an objective lens assembly 12 mounted on its remote end, an eyepiece or ocular lens assembly 14 mounted on the near end of the barrel, and an erector lens assembly mounted inside the barrel, the latter having been designated in a general way by reference numeral 16. The invention that forms the subject matter hereof has been illustrated and will be discussed in detail as it relates to a riflescope although it is by no means restricted to this specific application and the principles thereof would be equally useful in other optical sighting instruments. In fact, the particular riflescope shown is of the variable-power type as contrasted with those employing fixed magnification as it is the former scope in which many of the features to be set forth herein find their greatest utility although all of them, with the possible exception of the features relating specifically to the means for maintaining a fixed reticle size throughout changes in the degree of image magnification, are also useful in fixed-power sighting devices.

In the particular construction illustrated herein, the objective lens assembly 12 includes a flared barrel extension 18 that threads into the main barrel 10, a lens holder 20 into which the objective lens 22 is cemented or otherwise mounted, and a threaded ring 24 that cooperates with the barrel extension 18 to hold the lens holder 20 in place. Lens 22 may, of course, be of the compound type or the single element type illustrated depending upon the par ticular optical system employed in the scope. Functionally, the objective lens assembly reproduces an inverted and reversed image of a real object in a plane normal to the optical axis defined by the centers of the objective and ocular lens systems. The location of this plane depends upon the distance to the target; however, for practical purposes the target viewed through a riflescope can be considered an infinite distance away meaning that the light reflected therefrom enters the scope in the form of parallel rays which place the image plane at the focal length of the lens where it stays. In the present optical system, objective lens image plane would be located a slight distance ahead of collector lens 26 mounted in the front end of erector lens tube 28 as represented by plane AA. The collector lens merely functions to concentrate the rays from the objective lens system and direct them into the erectors. The unit will function quite well without the collector lens, however, and it has been included merely to illustrate the preferred optical arrangement.

At the other or rear extremity of the barrel 10 is the eyepiece or ocular lens assembly 14 which in several respects is quite similar to the objective lens assembly just described. For instance, it also includes an internallythreaded barrel extension 30 which has a flared portion 32 interconnecting small diameter and large diameter tubular sections that have been designated by numerals 34 and 36, respectively. The small tubular section 34 threads onto the externally-threaded end of the main barrel 10 enabling the optical system to be adjusted to cooperate with the users eye which forms a part thereof. Lock ring 38 locks the barrel extension 30 in adjusted position. As shown, the larger tubular section 36 is internally-threaded and provides a shoulder 40 against which compound lens 42 rests and is secured in place by retaining ring 44. The remaining lens element 46 is mounted within a ring 48 that threads into the rear extremity of tubular section 36. Here again, the particular construction and arrangement of lens elements and mounts therefor can be varied to suit particular requirements and the ones shown herein are intended as being merely illustrative of one ocular lens assembly that will function to focus upon the erected image reproduced by the erector lens assembly in the erector lens image plane designated B-B in FIGURES l and 2. It should be mentioned that the objective and erector lens assemblies cooperate with one another to locate the second image plane B-B which remains fixed for all practical purposes assuming the optical system is focused upon a target located a considerable distance from the scope. Adjustment of the eyepiece or ocular lens system merely brings the erect image in the erector lens image plane B-B into sharp focus and the precise location of said ocular lens will, therefore, vary with the requirements of the viewers eye.

The erector lens assembly 16, in a fixed-power riflescope, has one prime function, namely, the reinversion and reversal of the inverted and reversed target image reproduced by the objective lens system although in some scopes it may also be used to accomplish angular adjustment of the line of sight relative to the optical axis defined by the centers of the objective and eyepiece lens systems to compensate for errors inherent in the trajectory of the bullet. In a variable-power riflescope such as that illustrated herein, a third function is added to those already mentioned and this is to increase or decrease the degree of target image magnification. In a fixed-power scope the foregoing functions are accomplished by at least one and preferably two erector lens elements 50 and 52 mounted within an erector lens tube 28 in position to produce a.

focused erect image of the target in a focal plane BB located, in most instances, adjacent the rear end of the barrel 10. The erector lens tube 28 is housed within the barrel and is of a lesser diameter than the latter so as to permit limited movement relative thereto about a point of more-or-less universal movement defined by a coupling 54 located in spaced longitudinal relation to the windage and elevation adjustment mechanisms that have been designated in a general Way by reference numeral 56 and which also interconnect the barrel and erector lens tube.

In a variable-power scope on the other hand, these same elements are required although at least two erector lens elements 50 and 52 are necessary and provision must be made for adjusting their longitudinal positions relative to one another and with respect to the ocular and objective lens systems for purposes of accomplishing variation in target image magnification, Even though these erector lenses move back and forth along the erector lens tube, the erect focused target image produced thereby must remain substantially fixed in focal plane BB.

In the specific embodiment illustrated herein, a ring 58 containing a rearwardly-facing shoulder 60 is mounted within the rear extremity of the main lens barrel 10 and retained non-rotatably in place with set screws 62. The rear end of the erector lens tube 28 is provided with an internally-threaded enlargement 64 that defines a shoulder 66 spaced rearwardly of shoulder 60 and in opposed relation thereto. Between these shoulders 60 and 66 and the radially-spaced opposed wall surfaces of the ring 58 and erector lens tube 28 is placed an elastic coupling 54 that is preferably bonded to these surfaces in accordance with the teaching of US. Patent 2,948,188 that is owned in common with the instant application. This bonded and preferably vulcanized coupling 54 perm-its limited universal movement of the erector lens tube and associated elements relative to the main barrel and thus provides the means by which corrections for elevation and windage may be introduced into the optical system.

The specific mechanism 56 by which the line of sight is adjusted relative to the optical axis can best be seen in FIGURES 1, 2 and 4 to which reference will now be made. The interior surface of the main barrel 10 is provided with a longi-tudinally-extending groove 68 within which is retained a bowed leaf spring 70. The intermediate portion of this spring bears against the erector lens tube 28 at a point spaced longitudinally from its center of limited universal movement and biases the latter toward a diametrically opposed point on the inside surface of the main barrel.

Angularly spaced approximately 135 on opposite sides of spring 70 are the .points of contact of windage and elevation control screws 72 and 74, respectively, that are carried by the main barrel for movement against the erector lens tube in opposition to the bias exerted thereon by said spring. When the scope is mounted on a rifle barrel, it occupies the position shown in FIGURE 4 wherein the axis of the windage control screw 72 is substantially horizontal, that of the elevation control screw is substantially vertical and the spring 70 is equiangularly spaced therebetween to urge the erector lens tube against both controls simultaneously irrespective of their adjusted positions. Obviously, with the axes of these two adjustment screws disposed at 90 to one another, using one screw to shift the line of sight in one plane does not shift the line of sight in a plane normal thereto due to the broad flat ends on the screws and the limited angular adjustment provided within the confines of the barrel.

The mount for these screws comprises a saddle-forming element 76 which is secured to the exterior surface of the barrel by internally and externally threaded flanged tubular members 78 that also screw into the barrel wall. Each of the latter members has a radial flange 80 bordering the outer extremity thereof and an externally-threaded outstanding rim encircling the flange 82 to define a recess 84 adapted to receive the slotted head 86 of the adjustment screw 72 or 74. A protective cap 88 is detachably mounted upon the externally threaded rim 82 to prevent moisture, dust and other foreign matter from entering the assembly 56 and possibly the optical system. The abovedescribed windage and elevation controls can assume any one of several different forms and those shown are intended as merely being illustrative of one type that is simple, accurate and able to withstand considerable recoil without becoming damaged or moving out of adjustment.

Again with reference to FIGURES 1 and 2, it will be seen that the reticle 90 along with the diaphragm 92 are both located in the eyepiece image plane BB and, in addition, are carried by the erector lens tube for movement therewith; yet, the center of universal movement of the erector lens assembly 16 as defined by resilient coupling 54 is not in this same plane. In fact, the center of universal movement defined by coupling 54 may be located anywhere along the erector lens tube as long as it is spaced longitudinally from the elevation and windage adjustment mechanism 56 to provide a lever arm about which the line of sight can shift relative to the optical axis in order to preserve the centered reticle feature; however, it is preferably located in close proximity to the eyepiece image plane, as aforementioned, to keep the field of view more or less centered in the eyepiece. As long as the diaphragm 92 and reticle 90 are both moveable with the erector lens assembly, the reticle will remain centered in the field of view defined by the aperture in the diaphragm. In addition, as is the case here, the reticle and diaphragm will remain in focus because they are located in eyepiece image plane BB. In a fixedpower scope, as aforementioned, either the reticle or the diaphragm or both may also be located in the objective image plane AA and remain centered and in sharp focus. A variable-power scope such as that illustrated herein, however, necessitates placement of both the reticle and diaphragm in the eyepiece image plane BB if the apparent size thereof is to remain constant throughout the entire range of change in the degree of image magnification. This alone is not enough as the sighting point 94 of the reticle 90 must also be located precisely on the optical axis of the erector lens system in order to avoid a shift in the point of impact when the degree of magnification is decreased or increased as has already been explained in considerable detail. 1

Reference will now be made to FIGURES 1, 2, 7 and 8 for a detailed description of the mechanism by which the aforementioned desirable ends have been realized in the riflescope forming the subject matter of the instant inven- .tion. An internally and externally threaded ring 96 having an annular interrupted stop-forming flange 98 on the forward end thereof is threaded into the internally threaded enlargement 64 on the rear extremity of the erector lens tube. The diaphragm 92 comprises a ring having a frusto-conical inner surface 100 terminating at its forward extremity in a circular edge 102 that defines an aperture restricting the field of view through the optical system to an area less than that encompassed by other elements of the optical system. Preferably, the aperture defined by edge 102 is such that the maximum deviation in the erector lens tube relative to the main barrel will not be sufiicient to allow the lens holder 20 for the objective lens 22 to appear in the field of view. The exterior surface 104 of diaphragm 92 is, in the form shown, smooth and generally cylindrical. Most important, however, is the fact that the outside diameter of this diaphragm-forming ring 92 is somewhat less than the minimum inside diameter of mounting ring 96 as defined by the lands of the internal threads, This allows ring 92 to be shifted radially, i.e. in a plane normal to the optical axis of the erector lens system, relative to mounting ring 96. In that the diaphragm-forming ring 92 performs the secondary function of the mount for the reticle 90, this adjustable feature makes it possible to locate the sighting point 94 of the cross-hair-type reticle precisely on the optical axis of the erector lens system thereby eliminating any shift in the point of impact when the degree of mag nification of the scope is changed. The necessity for such an adjustment arises because of the mechanical problems associated with fastening the cross-hairs of the reticle to the diaphragm ring such that their intersection which defines the sighting point will be exactly at the center of the ring. There are, of course, other possible reasons for misalignment of the sighting point relative to the optical axis of the erector lens system which may or may not be correctable with the structure just described although this radial reticle adjustment feature is almost always adequate to compensate for the eccentricity of the sighting point occasioned by mechanical errors in fabricating the reticle.

The diaphragm and associated reticle carried thereby are secured in adjusted position by means of an externallythreaded lock ring 106 that is screwed into the rear end of mount 96 forcing ring 92 against stop-forming flange 98.

In the assembly of the reticle and diaphragm, they are first loosely mounted in the mounting ring 96 and the latter is screwed into the end of the erector lens tube. The sighting point 94 of the reticle is then relocated to place same exactly on the optical axis of the erector lenssystem and any tilt in a cross-hair or post type reticle relative to the axes of the windage and elevation adjustment screws is eliminated by rotating the diaphragm ring in its mount before tightening the lock ring 106.

Next, the means by which the positions of the front and rear erector lenses 50 and 52 are shifted relative to one another and along the erector lens tube 28 will now be set forth in connection with FIGURES 1-6, inclusive. Each of these erector lenses which, in the particular form shown are of the compound double-convex type, are carried in separate mounts 108 and 110 that are sized to fit inside the erector lens tube and slide longitudinally therein between collector lens 26 and reticle 90. Each mount has a shoulder 112 against which the lens rests and a retaining ring 114 that fits over the end of the mount holding the lens in place against the shoulder. The erector lens tube is provided with a longitudinal slot 116 adapted to receive a pair of slide blocks 118 and 120 for slideable movement in the direction of the length thereof. These slide blocks 118 and 120 are secured, respectively, to mounts 108 and 110 by screws 122 and 124 which each have heads projecting outwardly beyond the surface of the erector lens tube in position to be received within cam slots 126 and 128 provided in the walls of rotatable cam tube 130.

Cam tube 130 encircles the erector lens tube 28 between the points of contact of the windage and elevation adjustment screws 72 and 74 therewith and ring 58. This tube 130 is mounted for rotation relative to the erector lens tube which, as previously noted, is nonrotatably attached to the main scope barrel 10. Rotation of cam tube 130 is accomplished by means of externally-located adjusting ring 132 that encircles the barrel immediately ahead of lock ring 38. An annular slot 134 in barrel opens onto the exterior surface of the cam tube and the inside surface of the adjusting ring 132, the latter elements being operatively interconnected by screw 136 that has the cylindrical portion thereof moving within slot 134 protected by a plug 138. Slot 134, of course, prevents longitudinal movement of the cam tube, screw 136 and adjusting ring 132 relative to the erector lens tube; therefore, upon rotation of the cam tube by means of said external adjusting ring, the heads of screws 122 and 124 moving within cam slots 126 and 128 will cause the erector lens mounts 108 and 110 along with the erector lenses carried thereby to move along the erector lens tube while varying the spacing between one another thus either increasing or decreasing the degree of magnification of the target image.

The inclination, shape and arrangement of cam slots 126 and 128, as it is most clearly revealed in the develop- 10 ment of cam tube shown in FIGURE 6, are selected such that the focal plane of the system remains at image plane B--B yet the degree of magnification of the target image steadily increases as the positions of these erector lenses is varied.

The inside of adjusting ring 132 is preferably provided with a pair of annular grooves spaced on opposite sides of screw 136 that are adapted to receive O-rings 140 These O-rings prevent the metal-to-metal contact and resultant abrasion between the ring and barrel as the former is rotated relative to the latter. Also, they prevent the introduction of moisture and other foreign material into the interior of the scope as well as the escape of the dry nitrogen sometimes introduced and sealed into the optical system to prevent moisture condensation and the resultant fogging of the lenses. Furthermore, these O-rings absorb any slight tilt of the adjusting ring relative to the barrel that might be transferred thereto when the erector lens tube is shifted laterally to correct for windage and elevation although such deflection is so small as to be of no consequence especially when, as in the instant construction, the mechanism for rotating the cam tube is positioned quite close to the coupling 54.

Finally, with brief reference to FIGURE 9, a modified form of universal coupling 54m between the erector lens tube 28m and main barrel 10m will be described. As shown, sleeve 58, has been eliminated and a section of increased inside diameter 142 provided at the rear end of the barrel 10m. The rear extremity of the erector lens tube 28m has been changed to provide a spherical outer surface 144 which slides against the enlarged cylindrical section 142 of the main barrel somewhat in the same manner as is found in a ball-and-socket joint. A hollow cylindrical bushing 146 is mounted on the spherical wall section 144 of the erector lens tube with its axis extending substantially radially and normal to said spherical surface. A spherically-surfaced pivot pin 148 is attached within the enlarged cylindrical section of the barrel in position to fit inside the bushing and form a universal coupling 54m therewith. Such a coupling has certain advantages over the resilient bonded rubber coupling 54 shown in FIGURES 1 and 2, perhaps the most significant of which is the fact that the center of universal movement defined thereby does not remain fixed, but rather, shifts around depending upon the distribution of the compression and tension loads to which it is subjected when adjustments are made, whereas, the ball-and-socket connection 54m will remain fixed. It might appear that displacing the center of universal movement of the erector lens system from a point substantially on the optical axis thereof to one eccentrically located on the inside surface of the barrel would cause problems in keeping the reticle in focus, the edge of the field sharp, etc. As a practical matter, however, when the coupling 54m is located near one extremity of the erector lens tube and the windage and adjustment mechanism at the other, the maximum that the sighting point can move out of the eyepiece image plane B-B amounts to a very few thousandths of an inch which is well within the design tolerances of other elements of the system.

Having thus described the several useful and novel features of the riflescope of the present invention, it will be seen that the many worthwhile objectives for which it was designed have been realized. Although but two different embodiments of the invention have been shown in the accompanying drawings, we realize that certain changes and modifications therein may well occur to those skilled in the art within the broad teaching hereof; hence, it is our intention that the scope of protection provided hereby shall be limited only insofar as said limitations are expressly set forth in the appended claims.

What is claimed is:

1. A rifiescope which comprises, an elongate tubular barrel, objective lens means mounted in the forward end of the barrel adapted to reproduce an inverted and reversed image of a real object in a first image plane located intermediate the ends of said barrel, a second tubular element of smaller diameter than the barrel mounted therein for limited universal tilting movement relative thereto, means adapted to receive the image from the objective lens means and reproduce same in erect unreversed form at varying degrees of magnification in a second image plane located a fixed distance behind the first image plane, said means comprising a pair of erector lens elements carried by the second tubular element forwardly of the center of universal movement thereof that cooperate to define an optical axis and are mounted for longitudinal adjustment relative to one another, ocular lens means located in the rear extremity of the barrel and adapted to focus upon the erect unreversed image in the second image plane, first external adjustment means carried by the barrel and operatively connected to the second tubular element in longitudinally spaced relation to its center of limited universal tilting movement, said adjustment means including control means adapted upon'actuation to tilt the second tubular element and shift the optical axis defined by the erector lens elements so as to introduce corrections for windage and elevation, second external means located on the outside of the barrel connected to the erector lens elements and operable upon actuation to change the spacing therebetween, said second external means including a coupling extending into the barrel and accommodating the tilting movement of the second tubular element, a reticle carried by the second tubular element Within the second image plane which includes means defining an aiming point located on the optical axis defined by the erector lens elements, and a diaphragm car-- ried by the second tubular element for movement therewith, said diaphragm having an aperture therein defining a field of view which remains substantially unobstructed at maximum deflections of the second tubular element relative to the barrel.

2. The riflescope as set forth in claim 1 in which the second external means comprises an elongate slot in the wall of the second tubular element, a circumferential slot in the barrel opening onto the surface of the second tubulare element, a pair of tubular mounts for the erector lens elements, each of said mounts being independently adjustable relative to one another and longitudinally of the second tubular element, a cam tube mounted exteriorly of the second tubular element for rotational movement relative thereto over the slot therein and underneath the slot in the barrel, means carried by the cam tube projecting through the circumferential slot in the barrel for rotating said cam tube relative to the second tubular element, said cam tube having a pair of cam slots therein intersecting the slot in the second tubular element at longitudinally-spaced points varying in location and spacing depending upon the relative rotarial positions thereof, said points of intersection defining the positions of the erector lens elements corresponding to a range of changes in degree of image magnification while maintaining said image focused in the second image plane, and cam follower means operatively interconnecting each of the erector lens element mounts with one of the cam slots in the cam tube 12 through the longitudinal slot in the second tubular element.

3. The riflescope as set forth in claim 2 in which, the means carried by the cam tube projecting through the circumferential slot in the barrel comprises a pin, an adjusting ring is mounted on the barrel for relative rotational movement, and the adjusting ring and pin are interconnected such that rotation of said ring accomplishes the adjustment of the erector lens elements.

4. The riflescope as set forth in claim 3 in which the coupling of the second external adjustment means that accommodates the tiltable movement of the second tubu lar element comprises, a loose fit between the adjusting ring and barrel, a pairof longitudinally-spaced continuous annular grooves on the inside of the adjusting ring on opposite sides of the pin, and a pair of compressible elastic O-ring seals located within the annular grooves in contact with the barrel, said seals permitting said adjusting ring to tilt on the barrel the amount required to accommodate the tilt of the second tubular element while sealing the interior of the assembly against the entry of moisture-laden air.

5. The riflescope as set forth in claim 1 in which the diaphragm is positioned closely adjacent the second image plane.

6. The rifiescope as set forth in claim 1 in which, the diaphragm carries the reticle and both are located within the second image plane.

7. The riflescope as set forth in claim 1 in which, the diaphragm carries the reticle and comprises a ring of lesser diameter than the inside of the second tubular element at the second image plane, the second tubular element includes abutment-forming means positioned and adapted to engage the diaphragm ring and locate same in the second image plane when placed thereagainst, said ring being adjustable both rotarially and eccentrically within said second image plane to place the aiming point of the reticle carried thereby on the optical axis of the erector elements, and means comprising a lock ring cooperating with the second tubular element to secure the diaphragm ring in adjusted position against the abutment means.

8. The riflescope as set forth in claim 1 in which center of universal movement of the second tubular element lies closely adjacent the second image plane.

References Cited by the Examiner UNITED STATES PATENTS DAVID H. RUBIN, Primary Examiner.

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Classifications
U.S. Classification356/247, 359/428, 359/422, 42/122
International ClassificationG02B23/14
Cooperative ClassificationG02B23/145
European ClassificationG02B23/14Z