Abstract:
The present invention is directed to a revolver, where headspace is achieved differently and separately from the barrel, where [a cartridge is placed in the cylinder] and where that headspace is a function of caliber and varies per caliber/cylinder. 
     The system of the present invention links a unique barrel and cylinder relationship so that each may be exchanged with the other set on the same frame. A tension ring is used to threadedly engage the interchangeable barrel relative to the interchangeable cylinder and revolver frame such that the predetermined headspace is preserved. And all being fit to differing headspace points within the single revolver frame. Each could be numbered so that confusion of which cylinder with which barrel be reduced.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Provisional Patent Application No. 60/274,794, filed Mar. 9, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     The issue of barrel interchangeability was addressed in revolvers but led to a design that was so cumbersome [Dan Wesson design] that is no longer used. This design involved an entire barrel covering or shroud housing and neither the method nor the finished product was successful. 
     Another preexisting design is the Savage, a rifle design. 
     In the design of U.S. Pat. No. 5,987,797, headspace is achieved integral to a rifle barrel. Restated, the cartridge resides inside the barrel and is part of same. Therefore no consideration is given to a revolver, which requires the installation of a cylinder of a different caliber when a barrel of different caliber is placed on the gun. 
     To the extent that a .22 cal. barrel may be placed on the revolver frame while the frame continues to hold a .45 cal. cylinder, a most dangerous and possibly fatal situation would occur. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a revolver, wherein headspace is achieved differently and separately from the barrel [a cartridge is placed in the cylinder] and wherein that headspace is a function of caliber and varies per caliber/cylinder. 
     The system of the present invention links a unique barrel and cylinder relationship so that each may be exchanged with the other set on the same frame, and all being fit to differing headspace points within the single revolver frame. Each barrel and cylinder could be numbered to reduce confusion as to which cylinder corresponds with which barrel. 
     It is therefore desirable to provide for easy exchange of barrel length and caliber for an historic class of pistol using a minimum of parts or modification, and preserving the overall aesthetics of ie historic design. 
     It is further desirable to provide for easy exchange of barrel length and caliber for single action revolvers wherein different caliber and barrel length combinations are desirable and previously could only be obtained by purchasing a complete gun without the mentioned desirable features. The ability to switch barrel length and caliber gives the shooter ultimate flexibility while maintaining the classic look of the original design. See U.S. Pat. No. 158,957, Mason, William of Hartford, showing the class of fire arm (FIG.  1 ). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows exterior and sectioned views of Mason&#39;s design described in U.S. Pat. No. 158,957. 
     FIG. 1A shows typical view of the barrel of FIG. 1 before installation in frame. 
     FIG. 2 shows typical sectioned view of Mason&#39;s design. Barrel is shown fully installed or turned into the frame. 
     FIG. 2A shows cross section view of revolver spatial relationships. 
     FIG. 2B shows close up cross section view of headspace spatial relationship. 
     FIG. 3 is a sectioned view of new invention showing locking or tension ring installed. 
     FIG. 4 is a complete assembly view of new design, showing barrel installed, ring installed and modification of ejector housing to accommodate locking ring. 
     FIG. 5 is a modified barrel design showing new thread design for locking ring. 
     FIG. 6 is a locking ring showing tightening hole for wrench. 
     FIG. 7 is a modified ejector tube housing. 
     FIG. 8 is a tightening process shown with wrench installed. 
     FIG. 9 shows an assembly with wrench removed after installation. Unsightly hole is hidden under ejector tube housing after replacement. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 generally depicts a single-caliber, fixed-barrel revolver  10  the prior art. The revolver  10  includes a revolver frame  12 , a barrel  14  bored to accommodate a particular ammunition caliber, a grip  16 , a trigger assembly  18 , and a hammer  20 . The frame is provided with a recess  22  in which a cylinder  24  is rotatably mounted. The rearward face of the cylinder  26  is aligned in opposition to a bolster face  28  integral to the frame. The cylinder  24  has circumferentially-spaced chambers  30  for receiving ammunition cartridges of a preselected caliber. The aft end of the barrel  14  includes a threaded section  15 , as shown in FIG.  1 A. FIG. 2 depicts the barrel  14  threadedly engaged  17  with the frame  12 . 
     The present invention provides a revolver  50  with a frame  52 , having interchangeable barrels  54  and interchangeable cylinders  56  adapted to accept ammunition cartridges of differing caliber, as shown in FIG.  2 A. The revolver  50  includes a tension ring (not shown) which locks a barrel  54  bored to a particular caliber into a predefined spatial relationship with a cylinder  56  of the me caliber. A predefined gap between the bolster face of the frame and the base of the ammunition cartridge held in a chamber  58  of the cylinder  56 , called the headspace  60 , also is maintained by the tension ring. In addition, the tension ring maintains a desired spacing between the barrel  54  and the cylinder  56 , i.e., the barrel to cylinder gap  62 . Preferred embodiments of the invention include unique barrel-cylinder combinations fit to differing headspace points within the frame. 
     FIG. 2A shows the barrel  54  threadedly engaged  64  through the frame  52 , and held in a defined spatial relationship to the cylinder  56 . FIG. 3 demonstrates that the inner bore of the aft end of the barrel  54 , closest to the cylinder, is slightly flared to provide a forcing cone  82  for guiding the bullet portion of a cartridge into the barrel  54  upon firing, which forcing cone  82  slightly extends into the cylinder recess  53 . The linear distance between the rearward edge of the barrel forcing cone  82  and the frontward face of the cylinder  56  is defined as the “barrel-to-cylinder gap  62 ,” as illustrated by FIGS. 2A and 3. FIG. 2B demon rates that the aft end of each cartridge  66  has a base  70 , which slightly protrudes from the aft end of the cylinder  56 , limiting forward motion of the cartridge  66  in the cylinder chamber  58 . The linear distance between the bolster face  68  and the rearward face of the cartridge casing base  70  is defined as the “headspace  60 .” Headspace is a function of caliber and, in general, the larger the caliber in use, the greater the headspace required. 
     Operation is illustrated using FIGS. 2A and 2B. Coupled with the hammer (not shown) and the trigger assembly (not shown) is the firing in  72 , which is exposed to the cartridge through an aperture in the bolster face  74 . Upon actuation of the trigger assembly, the cylinder  56  rotates, bringing a chamber  58  into selective registration with the barrel  54 . The cartridge  66  within the selected chamber  58  is brought into coaxial alignment with the bore of the barrel  54 , such that the bullet  76  of the cartridge  66  is aligned with the barrel  54 , and the primer cup  78 , disposed in the cartridge casing  66 , is aligned with the firing pin  72 . When the trigger is pulled, the hammer is urged to strike the firing pin  72  using conventional cocking and releasing mechanisms well-known in the art. The firing pin  72  then traverses the headspace  60  and strikes the cartridge primer cup  78 . The perturbed primer cup  78 , in turn, ignites the main powder charge  80  in the cartridge casing  66 , rapidly generating a relatively large volume of gases. The expanding high-pressure gases displace the cartridge casing  66  rearwardly through the headspace  60  into engagement with the bolster face  68 , and then drive the bullet  76  to the forcing cone and forwardly through the barrel  54 . 
     It is important that the barrel-to-cylinder gap be properly dimensioned. If this gap is too small, the cylinder will not enter the frame recess. If the gap is too large, a significant amount of expanding gas and burning powder will escape, reducing the energy imparted to the bullet, and potentially injuring the shooter. However, the headspace is the most important dimension governing the safety of the shooter. When a firearm is fired, the cartridge tends to expand to the limits of the available volume within the chamber. If this volume is too great, as may be caused by too much headspace, the improperly supported cartridge expands excessively, and may rupture, seriously injuring the shooter. If there is to little headspace, the cylinder will not enter the frame recess, or if it does, it may cause damage to the firing pin. 
     For a single-caliber, fixed barrel revolver, dimensions such as headspace, and barrel-to-cylinder gap, typically are set at the factory. Unless adjusted by a gunsmith, or altered through use or damage, these spaces are rarely of import to a shooter. However, these dimensions, particularly headspace, must be properly and accurately adjusted when, as with the present invention, a revolver is adapted to accommodate ammunition of differing caliber and multiple barrel lengths. Cartridges for revolvers vary in length, primarily depending upon the caliber of the ammunition. Thus, the distance from the bolster face to the base of the cartridge, e.g., the headspace, when the cartridge is fully seated forwardmost in the chamber of the revolver cylinder, varies substantially from cartridge to cartridge. 
     A number of methods have been attempted for attaching different barrels, different cylinders, or both, to a firearm. One conventional technique is the so-called Savage barrel nut method employed by Savage Manufacturing Company, which is primarily intended for rifles and is well-known in the art. This involves employing a barrel set-nut having the same interior threads as the receiver, which threads are used to lock the barrel and action together in the correct relationship. However, because this method uses comparatively coarse barrel threads, it lacks the same degree of mechanical advantage possessed by other methods. In practice, a high degree of torque is required to lock together the barrel and action, making disassembly of the barrel and action difficult, and unsuitable for repeated, switch-barrel use. Additionally, such disassembly cannot take place with the action in the stock, due to the design of the locking barrel set nut. Thus, such an engagement system cannot accommodate the expedient switching of barrels of different caliber. 
     A conventional method of providing a firearm with multiple interchangeable barrels is shown in U.S. Pat. No. 4,288,938 (Kahn). Barrel installation is accomplished through conventional threads on the firearm&#39;s frame and barrel, modified only slightly, and secured by two set screws mounted perpendicular to the barrel&#39;s axis. However, recognizing that there must be clearance between the barrel threads and frame threads, such set screws when tightened act to thrust the barrel laterally within the frame, creating inconsistencies in a bullet&#39;s point of impact. The fact that U.S. Pat. No. 4,288,938 relies upon two set screws, each acting independently and in opposition to the other, means that there will be a large positional variation as to potential lock-ups, thus creating an unsatisfactory arrangement when accuracy is important. In addition, a related C-I-P patent, U.S. Pat. No. 4,297,801 (Kahn), a technique for providing a revolver employing multiple, interchangeable cylinders is described. Acknowledging that cylinders of different caliber can be of different lengths, this technique requires the use of barrels having a rearward extension to create a predetermined barrel-to-cylinder gap. In both U.S. Pat. No. 4,288,938, and related C-I-P patent, U.S. Pat. No. 4,297,801, the barrel-to-cylinder gap is the only caliber-related clearance that is addressed. There is no suggestion of how varying headspace requirements could be met by either invention. 
     A further technique disclosed in U.S. Pat. No. 5,020,260 (Houghton) includes a tensioning nut, but it does not have the benefit of seperate fine-pitch threads, relying instead on an extension of the standard barrel threads. Therefore, such a system lacks mechanical advantage and can be cumbersome for repeated barrel switches. In addition, the tensioning nut bears against a barrel bracket rather than the action itself, which design limits the available range of adjustment, making it unsuitable for fitting a cylinder of a particular caliber at a characteristic headspace point within a revolver frame. There is no teaching for adjusting headspace to accommodate ammunition cartridges, and cylinders, of different caliber, requiring different characteristic headspace. 
     U.S. Pat. No. 5,987,797 (Dustin) provides a rifle having the ability to accept a wide variety of interchangeable barrels of different caliber in a manner yielding a substantially invariant coaxial alignment of the receiver and barrel, by means of a rotatable, cylindrical locking ring, which is internally threaded with a series coaxially-aligned, fine-pitch “V” threads. The locking ring secures the barrel to the receiver at a threaded distal end of the receiver due to the torque exerted by the locking ring, which pulls the receiver and barrel toward a common center line. The substantially fine-pitch locking ring threads provide a maximized mechanical advantage upon rotation of the locking ring, which acts to sufficiently bind the receiver and barrel in substantially invariant coaxial alignment, without the requirement for excessive torque during tightening. This facilitates barrel exchange and provides the advantage of repeatable accuracy in firing with any given barrel. However, there is no teaching or suggestion of headspace adjustment, presumably because headspace in a rifle is achieved integrally to the barrel, in contrast with a revolver, where headspace is a function of caliber and is achieved independently of the barrel. Therefore, the disclosed technique is, in itself, lacking for applicability to revolvers. 
     Each of the aforementioned references is incorporated by reference in entirety herein. 
     FIG. 4 shows a revolver  100  according to the present invention, which essentially operates in the conventional manner described above. However, unlike techniques and apparatus found in the prior art, the invention herein provides an adaptable revolver that is capable of accommodating ammunition of differing caliber, for example, from .22 cal. to .45 cal., using the same revolver frame  110 , yet providing the predetermined headspace characteristic of each different caliber, and maintaining a desirable barrel-to-cylinder gap. The adaptable revolver  100  includes one or more interchangeable cylinders  120 , each adapted for a preselected caliber and each adapted to provide the predetermined headspace that is characteristic of the particular caliber. Also, the adaptable revolver includes one or more interchangeably barrels  130 , each adapted for a preselected caliber and each adapted to cooperate with a corresponding interchangeable cylinder of a preselected caliber to provide a desirable barrel-to-cylinder gap. The respective lengths of a set of barrels  130  and cylinders  120  for a particular caliber can be uniquely defined, so that each may be exchanged with another set on the same frame  110 . 
     To achieve barrel-to-frame lock-up, the adaptable revolver uses a tension ring  150 , as shown in FIG.  6 . The tension ring  150  maintains the aforementioned predetermined headspace characteristic of the particular ammunition caliber in use, as well as the desired barrel-to-cylinder gap, thus accommodating the aforementioned interchangeable cylinders and interchangeable barrels. 
     The tension ring  150  is internally threaded with a series of coaxially-aligned, fine-pitch “V” threads  160 , and includes a take-down recess  170  which allows the ring to be rotated to effect revolver assembly or disassembly. As shown in FIG. 5, an interchangeable barrel  200  can have coarse- or medium-pitch threads  210  to engage the revolver frame, and fine-pitch threads  220  to engage the tension ring. Alternatively, the revolver frame can be internally threaded with a series of coaxially-aligned, fine-pitch “V” threads, allowing a uniform thread surface on the barrel (not shown) to couple the tension ring  150  and the revolver frame. Also, the adaptable revolver can include a modified ejector tube  230 , adapted to couple with the tension ring  150 , and suitable for facilitating the extraction of spent casings, as shown in FIG.  7 . Furthermore, the present invention includes a take-down wrench  250  with a projection adapted to tightly engage the take-down recess  170  of the tension ring, as shown in FIGS. 8 and 9. 
     While this invention is described in connection with a preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Upon examination of the disclosure above, it is readily apparent that modifications may be made to the revolver by one skilled in the art without departing from the nature or scope of the invention. Therefore, all equivalent embodiments and modifications are to be included within the scope of the following claims.