Abstract:
A single-shot break action firearm includes a receiver, a barrel, and a stock. The receiver has a breach portion that defines a cavity that is sized and shaped to house a breechblock therein. The breechblock is constructed from a powdered metal formed by metal-injection-molding. The breechblock is form from a higher strength material than the receiver to contain explosive forces produced during discharge of the firearm. The barrel is connected with the receiver and extends forward therefrom. The stock is connected with the receiver and extends rearward therefrom.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    room This application claims the benefit of U.S. Provisional Application No. 61/367,950, filed Jul. 27, 2010, entitled “UNITARY BREECH BLOCK ASSEMBLY”, the aforementioned application being hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to firearms and, more particularly, to single-shot break action firearms. 
       BACKGROUND OF THE INVENTION 
       [0003]    Single-shot break action firearms, typically, have a barrel enclosing a bore that extends from a breech end to a muzzle end of the barrel. The barrel is pivotally mounted to a receiver disposed near the breech end of the barrel. The receiver includes a breechblock, which blocks the breech end of the barrel when the barrel is in a closed position. Pivoting motion of the barrel on the receiver shifts the barrel to an open position wherein the breechblock does not block the breech end of the barrel. The breechblock typically houses a firing pin, which is aligned with an inner diameter of the barrel bore when the barrel is closed. The receiver typically houses a pivotally movable hammer and a trigger, by which the firing pin may be actuated toward the muzzle end of the barrel when the barrel is closed. Typical firearms also include ergonomic parts, such as a stock and a fore end, which are attached to the receiver. Typical break action firearms further include some sort of mechanism for securing the barrel in the closed position. 
         [0004]    For loading the typical break action firearm, the barrel opened and a single cartridge of ammunition is inserted into the breech end of the barrel with the bullet toward the muzzle end of the barrel and with the primer rim fitted snugly to the breech end. The barrel then is closed. For firing, the trigger is pulled to release the hammer, which drives the firing pin forward against the primer rim of the cartridge, discharging the round down the bore. 
         [0005]    Break action firearms typically are marketed either as economical sporting goods, or as finely crafted works of gunsmithing. In a gunsmithed break action firearm, all of the metal parts including the receiver and the firing mechanism are forged and machined from high quality materials such as steel. The use of high quality materials and time-intensive manufacturing processes results in high costs. On the other hand, for casual sporting firearms, it is common to economize on materials and modes of manufacture. In particular, the receiver of a break action firearm typically is die cast, with moving parts such as the hammer and trigger being pivoted on pins pressed through the receiver. 
         [0006]    One potential problem with economical firearms is that the breechblock portion of the receiver can become worn by pivoting motion of the barrel. This wear, in turn, may adversely affect the performance of cartridges—for example, by permitting the rim of a cartridge to shift in the gap between the breechblock and the breech end of the barrel. 
         [0007]    Accordingly, there is a need for an economically manufactured single shot firearm, in which the wear parts are formed from high quality materials at low cost, while non-moving parts are cast from lower cost materials. 
       SUMMARY OF THE INVENTION 
       [0008]    According to the present invention, a firearm receiver is die cast at low cost and is adapted to receive a slide-in unitary breechblock and barrel catch assembly, which provides sturdy wear surfaces at minimal cost of manufacture. 
         [0009]    Additionally, upper interior surfaces of the die cast receiver are machined to provide interference flats, which engage complementary flats formed on a barrel tang, thereby enhancing engagement of the barrel catch with the barrel tang. 
         [0010]    Additionally, the barrel tang, barrel catch, trigger, and hammer are mutually positioned to provide an interlock that prevents closing the barrel with the hammer cocked, and that also prevents releasing the hammer unless the barrel is fully closed or fully opened. 
         [0011]    These and other objects, features and advantages of the present invention will become apparent in light of the detailed description of the best mode embodiment thereof, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a side view of a break action firearm according to an embodiment of the present invention. 
           [0013]      FIG. 2  shows a left side sectional assembled partial view of a receiver, barrel assembly, catch mechanism, and firing mechanism of the firearm shown in  FIG. 1 , with the barrel assembly in a closed position. 
           [0014]      FIG. 3A  shows a left side view of the firing mechanism without the receiver of the break action firearm shown in  FIGS. 1 and 2 . 
           [0015]      FIGS. 3B  shows a left side view of the receiver without the firing mechanism of the break action firearm shown in  FIGS. 1 and 2 . 
           [0016]      FIG. 4  shows a front exploded view of the break action firearm shown in  FIGS. 1 through 3 . 
           [0017]      FIG. 5  shows a perspective exploded view of the firearm shown in  FIGS. 1 through 4 . 
           [0018]      FIG. 6  shows a right side sectional exploded view of the receiver, catch mechanism, and firing mechanism shown in  FIG. 2 . 
           [0019]      FIG. 7  shows a forward partially exploded view of the firing mechanism and the barrel catch mechanism shown in  FIGS. 1 through 6 . 
           [0020]      FIG. 8  shows a right side sectional exploded view of the firing mechanism and the barrel catch mechanism shown in  FIGS. 1 through 7  in a partially open position. 
           [0021]      FIG. 9  shows a top perspective view of the receiver shown in  FIGS. 1 through 7 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Referring to  FIG. 1 , a break action rifle  10  includes a barrel  12 , which is pivotally mounted to a receiver  14  that supports a fore end  16  and a stock  18 . The receiver also houses a firing mechanism  20 , of which a hammer  22  and a trigger  24  are shown in  FIG. 1 , and a catch mechanism  66  (shown in  FIG. 2 ). The barrel  12  has a breech end  26  and a muzzle end  28 . 
         [0023]    Referring to  FIG. 2 , the barrel  12  is connected to the receiver  14  by way of a barrel tang  30  and a pivot pin  32 , located near the barrel breech end  26 . The barrel tang  30  is attached to the barrel  12  by bolts  34  threaded into holes  35  tapped into the outer surface of the barrel  12 . The barrel tang  30  includes a transverse through hole  36 , while the receiver  14  includes transverse holes  38 . The pivot pin  32  is inserted through the transverse holes  36 ,  38  to pivotally mount the barrel  12  to the receiver  14 . The barrel  12  is pivotal between a closed position, where the breech end  26  rests against a breech portion  40  of the receiver  14 , and an open position, where the breech end  26  is raised away from the receiver  14  permitting access to the barrel bore  41 , as shown in  FIG. 8 . 
         [0024]    With additional reference to  FIGS. 5 through 7 , the breech portion  40  of the receiver  14  houses a breechblock  42 . When the barrel  12  is in the closed position, the breechblock  42  secures a cartridge  43  into the breech end  26  of the bore  41 . The receiver  14  may be die cast from base metal or even from a thermoset plastic or fiber-resin composite. However, the breechblock  42  is injection-molded from high quality metal (such as steel powder) to form a high-strength, temperature- and wear-resistant structure suitable for containing the explosive forces produced by discharge of a rim fire rifle cartridge  43 . In addition to enhanced strength over what can be achieved by die casting, metal-injection-molding (MIM) offers dimensional tolerances approaching what can be achieved by machining stock metal, so that MIM parts do not require the same level of finish machining as do conventionally die-cast parts. Thus, the separate structures of the receiver  14  and of the breechblock  42  offer optimal strength and fit at the critical location surrounding the breech end  26  of the barrel  12 , with lower cost of manufacture than can be achieved by machining the receiver  14  and breechblock  42  as a single piece. 
         [0025]    The breechblock  42  houses a firing pin  44  and a firing pin spring  46 , which are parts of the firing mechanism  20 . The firing pin  44  is positioned to be driven forward by the hammer  22 , which is forwardly biased around a hammer pin  48  by a hammer spring  50 . When the hammer  22  is pulled back to a cocked position, the trigger  24  is biased rearward around a trigger pin  52  by a trigger spring  54  so that a sear finger portion  56  of the hammer  22  engages a cocking notch  58  formed on the top end  25  of the trigger  24 , thereby restraining the hammer  22  in the cocked position. By pulling the finger part  60  of the trigger  24  rearward, a shooter can release the hammer  22  to drive the firing pin  44  forward against the rim of a cartridge  43  loaded into the barrel bore  41 . 
         [0026]    Additionally, the breechblock  42  includes laterally extending pivots  62 , which support a barrel catch  64  that is part of the catch mechanism  66  mentioned above. The barrel catch  64  is forwardly biased around the pivots  62  by a catch spring  68 , which presses downwardly against a heel  70  of the barrel catch  64  to push the barrel catch  64  into a notch  72  formed in the rearward part of the barrel tang  30 . Engagement of the barrel catch  64  into the notch  72  of the barrel tang  30  secures the barrel  12  in the closed position. The catch mechanism  66  also includes a trigger guard  74 , which is pivotally mounted on a transverse pin  76 , and a guard spring  78  with one end fastened to the receiver  14 . The other end of the guard spring  78  rests against an inner surface  80  of the trigger guard  74  to downwardly bias the trigger guard  74  around the transverse pin  76 . When a shooter pulls the trigger guard  74  rearward and upward against the guard spring  78 , an upper finger  82  of the trigger guard  74  pushes upward on the heel  70  of the barrel catch  64  to release the barrel catch  64  from the barrel tang  30 , thereby permitting the barrel  12  to pivot to the open position. 
         [0027]    Referring briefly to  FIG. 8 , it can be seen that when the barrel  12  is opened, a knuckle  73  formed on the barrel tang  30  presses the barrel catch  64  rearward against the trigger  24 . In case the hammer  22  is cocked when the barrel  12  is opened, pressure of the barrel catch  64  against the trigger  24  captures the sear finger portion  56  into the cocking notch  58 , so that the trigger  24  cannot be pulled rearward to release the hammer  22 . Thus the cocked weapon cannot be discharged unless the barrel  12  is fully closed; alternatively, the hammer  22  cannot be decocked unless the barrel  12  is fully opened. This interlock averts discharging a loaded cartridge with the barrel  12  less than fully latched closed. 
         [0028]    Referring briefly to  FIG. 9 , the barrel tang  30  includes protruding side posts  83  with flattened lower faces  85 . When the barrel  12  is fully closed, the lower faces  85  of the side posts  83  rest against complementary flats  87  machined into the receiver  14 . The barrel catch  64  wedges into the notch  72  of the barrel tang  30  to firmly seat the complementary flats  87  together, and the opposed flats reciprocally push the notch  72  upwards to maintain the barrel catch  64  firmly engaged. 
         [0029]    Referring back to  FIG. 2 , between the barrel  12  and the barrel tang  30 , an extractor  84  is captured on the bolts  34 . The extractor  84  includes longitudinal slots  86  (better shown in  FIG. 3A ) for receiving the bolts  34  so that the extractor  84  can slide lengthwise along the barrel  12  between forward (retracted) and rearward (extended) positions when the barrel  12  is pivoted to the opened position, as further explained below. 
         [0030]    Referring to  FIGS. 3A through 4 , the receiver  14  encloses an action cavity  88  housing the firing mechanism  20  and the catch mechanism  66 , a barrel tang slot  89  for receiving the barrel tang  30 , and a breech cavity  90  for receiving the breechblock  42 . For assembly of the hammer  22  and the trigger  24 , the receiver  14  includes pinholes  92  and  94 , respectively, as well as a hammer slot  93  and a trigger slot  95 . For assembly of the catch mechanism  66  into the receiver  14 , the receiver  14  also includes a catch spring groove  96 , lateral pivot grooves  98 , a guard spring groove  100 , a guard recess  102 , a guard pinhole  103 , and a breech bolt hole  104 . The breechblock  42  is fastened to the receiver  14  by a breech bolt  106  threaded into the breechblock  42  via the breech bolt hole  104 . For operation of the extractor  82 , the receiver  14  also includes a camming surface  108  offset from the pivot pin  32  at the forward end of the receiver  14 . When the barrel  12  is pivoted to the open position, the forward end of the extractor  84  contacts the camming surface  108  so that the extractor  84  is pushed rearward to pull the cartridge  43  out of the breech end  26  of the bore  41 . For assembly of the stock  18 , the receiver  14  also includes a stock bolt hole  110 . 
         [0031]    In addition to the breechblock  42 , the hammer  22 , the trigger  24 , the firing pin  44 , the barrel catch  64 , and the extractor  82  preferably are metal-injection-molded for enhanced dimensional accuracy and durability. 
         [0032]    Opposite the barrel tang  30 , a sight mount  111  is fixed to the upper side of the barrel  12  by screws  112  threaded into tapped holes  113 . The sight mount  111  also can be metal-injection-molded, or can be die cast. 
         [0033]    The fore end  16  is fastened to the barrel  12  by bolts  113 , while the stock  18  is fastened to the receiver  14  by a single large bolt  114 . The stock  18  includes an aesthetic cap  116  snapped over the large bolt  114 , and also includes a shock-absorbing butt piece  118 , which is secured to the stock by screws  120 . 
         [0034]    One advantage of the present invention is that the pre-assembled breechblock and catch ensure proper alignment of the catch with the notch formed in the barrel tang. Also, the pre-assembled breechblock and catch reduce the number of holes that must be formed at mutually accurate positions in the receiver. The catch spring and guard spring grooves further simplify assembly of the catch mechanism relative to previously known designs. 
         [0035]    Although this invention has been shown and described with respect to detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and the scope of the invention.