Patent Publication Number: US-8978559-B2

Title: Cartridge cases and base inserts therefor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. application Ser. No. 13/224,590 filed Sep. 2, 2011, pending, which claims the benefit of U.S. provisional patent application No. 61/381,609 filed Sep. 10, 2010, the disclosures of which are herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the munitions arts. More particularly, the present invention relates to cartridge cases and base inserts therefor. 
     BACKGROUND 
     In the munitions arts, a cartridge includes a case, a bullet, propellant, and a primer. Such cartridges are used in firearms and the operation of such cartridges is generally well known in the art. To discharge a cartridge in a firearm, a user typically squeezes a trigger to activate a firing pin and the firing pin strikes the primer, causing the propellant to ignite. The ignited propellant creates substantial pressure within the cartridge, and the bullet is forcefully ejected from the cartridge and from the firearm. 
     A cartridge case generally extends between two ends, a base end and a forward end. The base end is generally closed and includes features for receiving the primer. The forward end is generally open, with the bullet being inserted into this forward open end of the cartridge case. A volume is defined within the cartridge case between the base end and the forward end, and the propellant is contained within that volume. Modern cartridges use so-called “smokeless powder” as the propellant, and for the purposes of this disclosure, the volume where the propellant is contained will be called the powder fill pocket. The cartridge case also includes a generally tubular outer wall having a generally constant diameter, and a web that extends transverse to the outer wall proximate the base end. A primer pocket is formed between the web and the base end and a flash hole connects the primer pocket with the powder fill pocket. 
     The exterior of a cartridge case can take on any suitable shape. Known cartridge cases have bases with several different profiles. Proximate the base end, cartridge cases are generally cylindrical in shape. When viewed in the cross section taken along the diameter and showing the length axis of a cartridge case, the outer wall has a generally constant diameter, except for near the base end. Proximate the base end structures such as rims, extraction grooves and belts may be found. In one known example, the diameter of the cartridge case is smaller than a rim positioned at the base end of the cartridge case. Such a design is referred to in the art as a rimmed cartridge case. In another known cartridge case design, the outer wall of the cartridge case tapers radially inwardly to form an extraction groove proximate the base end, and the extraction groove includes a lip that does not extend beyond the diameter of the outer wall. Such design is known in the art as a rimless cartridge case because the lip of the extraction groove does not extend beyond the outer wall. Such is different from the rim of the rimmed design, which extends beyond the diameter of the outer wall. In yet another cartridge case design, the outer wall of the cartridge case tapers near the base end to define an extraction groove and a lip extends slightly beyond the diameter of the outer wall. Such a design is known as a semi-rimmed cartridge case. In another known cartridge case design, a belt extends radially outwardly from the outer wall proximate the base end, then tapers radially inwardly to define an extraction groove and a lip, much like the extraction groove and lip found in rimless designs. Such a design is known as a belted cartridge case. In yet another cartridge case design, the outer wall tapers radially inwardly near the base end to define a groove, and the groove has a lip that does not extend as far as the diameter of the outer wall. Such a design is known as rebated cartridge case. 
     SUMMARY OF THE INVENTION 
     The present invention is generally directed to a cartridge case of the type having a base insert and a case overmolded or otherwise connected thereto. More particularly, the present invention is direct to a base insert for the cartridge case comprising a base end having a lip and a groove proximate the lip and having a primer pocket defined in the base end, and an insert end having a base wall and a cylindrical wall extending there from, said base wall and cylindrical wall defining a powder fill pocket. The base wall has a flash hole disposed therein and an inner surface facing the powder fill pocket. The cylindrical wall has an inner surface intersecting with the inner surface of the base wall and an outer surface defining the outer circumference of the base insert. The intersection of the inner surface of the base wall and the inner surface of the cylindrical wall is curved, while the outer surface of the insert end is not curved. 
     A further aspect of the present invention may include the inner surface of the base wall being substantially orthogonal to the outer surface of the cylindrical wall, while the inner surface of the cylindrical wall in substantially parallel to the cylindrical wall. Alternatively, the inner surface of the base wall may be substantially orthogonal to the outer surface of the cylindrical wall, while the inner surface of the cylindrical wall is substantially slanted and not parellel to the cylindrical wall. In one embodiment, the cylindrical wall has a tapering thickness, wherein the cylindrical wall is thicker proximate its intersection with the base wall and thinner distal from the base wall. In another embodiment, the inner surface of the base wall includes a curved cut-out contiguous with the curvature of the intersection of the inner surface of the base wall and the inner surface of the cylindrical wall. Still further, another embodiment may provide that the inner surface of base wall include a curved cut-out adjacent to and surrounding the flash hole. Yet another embodiment may combine both the curved cut-out adjacent to and surrounding the flash hole with the curved cut-out contiguous with the curvature of the intersection of the inner surface of the base wall and the inner surface of the cylindrical wall. Other embodiments provide that the base wall may include an annular flashhole cutoff pit disposed therein. 
     Another aspect of the present invention may be achieved by a base insert for a cartridge case comprising a base end having a lip and a groove proximate the lip and having a primer pocket defined in the base end, and an insert end having a base wall and a cylindrical wall extending there from, said base wall and cylindrical wall defining a powder fill pocket. The base wall has a flash hole disposed therein and an inner surface facing the powder fill pocket. The cylindrical wall has an inner surface intersecting with the inner surface of the base wall and an outer surface defining the outer circumference of the base insert. The intersection of the inner surface of the base wall and the inner surface of the cylindrical wall forms an oblique angle, while the intersection of the base wall with the outer surface of the of the cylindrical wall does not form an oblique angle. 
     Another aspect of the present invention may be achieved by a base insert for a cartridge case made from the base insert with a polymer over molded with the base insert, the base insert comprising a cylindrical wall, a first radially indented polymer groove adjacent the cylindrical wall, and a second radially indented polymer groove in the cylindrical wall. An extraction groove is formed in the cartridge case near the first radially indented polymer groove when the polymer is molded over the base insert. 
     Any one of these aspects of the present invention, as well as potentially other features and advantages of the present invention, will be better understood with regard to the following description of the invention as set forth herein below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Any advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein: 
         FIG. 1  is a cross section of a portion of a base insert constructed according to the concepts of the present invention. 
         FIG. 2  is a cross section of a portion of another base insert constructed according to the concepts of the present invention. 
         FIG. 3  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 4  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 5  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 6  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 7  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 8  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 9  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 10  is a cross section of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 11  is a side elevation view of a portion of a base insert constructed according to the concepts of the present invention. 
         FIG. 12  is a side elevation view of a portion of another base insert constructed according to the concepts of the present invention. 
         FIG. 13  is a side elevation view of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 14  is a side elevation view of a portion of yet another base insert constructed according to the concepts of the present invention. 
         FIG. 15  is a cross section of a portion of a cartridge case. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     The concepts of the present invention will be described in the context of a rimless cartridge case, but the teachings contained herein are equally applicable to other designs for cartridge cases, including those described herein. Some embodiments of the present invention relate to components of a cartridge case that includes a metal base insert and a polymer portion. 
     Turning to  FIG. 15 , a portion of an exemplary cartridge case is shown and is generally indicated by the numeral  10 . In particular,  FIG. 15  shows a base end  12  and an insert end  13  defining a portion of a powder fill pocket  14 . An outer surface  15  of a cylindrical wall  16  defines the radial outer boundary of a cartridge case body  18  of cartridge case  10 . Case body  18  includes an inner wall  20 , generally radially defining the powder fill pocket  14 . Case body  18  tapers radially inwardly at  21  between the insert end  13  and base end  12  to define an extraction groove  22 . Extraction groove  22  has a lip  24  whose diameter is approximately equal to the diameter of outer surface  15  of the cylindrical wall  16 . A primer pocket  26  is defined in cartridge case  10  proximate base end  12 . Cartridge case  10  includes a transversely extending base wall or web  28  proximate base end  12 . A flash hole  30  extends through base wall  28  and connects primer pocket  26  and powder fill pocket  14 . As shown in  FIG. 15 , flash hole  30  is generally cylindrical in shape, and a flash hole wall  32  extends from a primer pocket wall  34  to an inner surface  36  of base wall  28 . 
     A cartridge case can be made from a combination of pieces, any or all of which may be made from metal or plastic materials. In one known arrangement, a metal base insert has a polymer portion molded over it, so that the combined polymer portion and metal base insert constitute the cartridge case. In any event, such cartridge cases have the same general overall shape as the cartridge case designs that are of unitary construction. 
     In the present invention, the angle of intersection between the inner surface  20  of the cylindrical wall  16  and inner surface  36  of the base wall  28  is important. Generally, in one embodiment, the thickness of the cylindrical wall tapers in thickness from a thick wall proximate the base wall  28  to a thinner wall distal from the base wall  28 . However, the tapering of the wall is set forth on the inside of the cylindrical wall, not the outside. The shape of the flash hole, including the shape of the flash hole wall as it intersects with the base wall is also important. In one embodiment, there may be a curved cut-out  52  surrounding the flash hole  30 , such that the flash hole wall  32  is less thick than the base wall  28  in general. 
     Turning to the figures, shapes of portions of several base inserts used to make cartridge cases will now be described. The figures are cross section views taken along a diameter and show a portion of a base insert, in particular where the base end, the web, and a portion of the outer wall and inner wall of a cartridge case are formed using the base inserts shown in the figures. 
       FIG. 1  shows a prior art base insert where the inner surface  20  of the cylindrical wall  16  is substantially parallel to the outer surface  15  of the cylindrical wall  16 , and the base wall  36  extends generally perpendicular or orthogonal to cylindrical wall  16 , so that the inner surface  36  of base wall  28  and inner surface  20  of base wall  16  intersect at a right angle. The flash hole  30  and flash hole wall  32  are generally perpendicular to base wall  28  and flash hole wall  32  intersects base wall  36  at approximately a right angle. 
     The base insert of  FIG. 2  is substantially similar to the base insert of  FIG. 1  in that the inner surface  20  of cylindrical wall  16  is substantially parallel to outer surface  15  of cylindrical wall  16  and inner surface  36  of base wall  28  extends generally perpendicular or orthogonal to cylindrical wall  16 . However, in this embodiment, the inner surface  20  of cylindrical wall  16  intersects and connects with the inner surface  36  of base wall  28  through a curved portion  40 , while the outer surface  15  of the cylindrical wall  16  is not so curved and does not include such a curved portion. 
     In  FIG. 3 , a portion of the inner surface  20  of cylindrical wall  16  extends at an angle and is tapered with respect to outer surface  15  of the cylindrical wall  16 . Base wall  28  extends generally perpendicular or orthogonal to the outer surface  15  of the cylindrical wall  16 , while the inner surface  20  of the cylindrical wall  16  intersects with the inner surface  36  of the base wall  28  at an oblique angle  42 . 
     In  FIG. 4 , the base insert is similar to that in  FIG. 3 , inasmuch as a portion of inner surface  20  of the cylindrical wall  16  extends at an angle with respect to the outer surface  15  of the cylindrical wall  16 , and base wall  28  extends generally perpendicular to the outer surface  15  of the cylindrical wall  16 . However,  FIG. 4  differs from  FIG. 3  in that the inner surface  20  of the cylindrical wall  16  and the inner surface  36  of the base wall  28  intersect and connect through a curved portion  44 . 
     In  FIG. 5 , the inner surface  20  of cylindrical wall  16  extends at a larger angle with respect to outer surface  15  of cylindrical wall  16  as compared to  FIG. 4 . Because of this shape, inner surface  36  of base wall  28  is much smaller in length and may be essentially non-existent. Thus, the inner surface  20  of cylindrical wall  16  may be considered to be connected to the flash hole wall  32  of flash hole  30  through a curved region  46 . 
     The base insert of  FIG. 6  is substantially similar to the base insert of  FIG. 4 , with the essential difference being the thickness of base wall  28 . As a result, the length of flash hole  30  is greater than the length of the flash hole shown in  FIGS. 1-5 . 
     In  FIG. 7 , a portion of the inner surface  20  of cylindrical wall  16  again extends at an angle with respect to the outer surface  15  of cylindrical wall  16 . Inner surface  20  of cylindrical wall  16  intersects and connects to the inner surface  36  of base wall  28  through a curved portion  50 . In addition, another curved portion or cut-out  52  in base wall  28  surrounds and is adjacent to flash hole  30  such that flash hole wall  32  is shorter than in previous designs, i.e., where the flash hole would extend to in the absence of curved portion or cut-out  52 . 
     In  FIG. 8 , a portion of the inner surface  20  of cylindrical wall  16  again extends at an angle with respect to the outer surface  15  of cylindrical wall  16 . Moreover, the inner surface  36  of base wall  28  extends generally perpendicular or orthogonal to the outer surface  15  of cylindrical wall  16 . Further, the inner surface  20  of cylindrical wall  16  intersects and connects with base wall  28  through a curved portion  54 . However, the curved portion  54  extends beyond and cuts out a portion of the inner surface  36  of the base wall  28 . Thus, the curved portion  54  is contiguous with the curved intersection of the inner surface  36  of base wall  28  and inner surface  20  of cylindrical wall  16   
     In  FIG. 9 , the contiguous curved intersection shown in  FIG. 8  and the curved portion surrounding and adjacent the flash hole are shown in combination. That is, a portion of inner surface  20  of cylindrical wall  16  again extends at an angle with respect to outer surface  15  of cylindrical wall  16 . Flash hole wall  32  is connected to inner surface  20  through an inner surface of base wall  28  having two intermediate curved portions,  58  and  62 . The first curved portion  58  surrounds and is adjacent to the flash hole wall  32 . The curvature ends at one end of inner surface  36 , and the second curved portion  62  begins and extends from the other end of inner surface  36  to cut out a portion of base wall  28  and is formed contiguously with the curve formation at the intersection of the inner surface of the cylindrical wall  16  and the inner surface of the base wall  28 . 
     In  FIG. 10 , a portion of the inner surface  20  of cylindrical wall  16  again extends at an angle with respect to the outer surface  15  of cylindrical wall  16 . Further, base wall  28  extends generally perpendicular to outer wall  16 . The inner surface  20  of the cylindrical wall  16  intersects and connects with the inner surface  36  of base wall  28  through a curved portion  66 . In addition, an annular flashhole cutoff pit  68  is defined in base wall  28  radially inside curved portion  66 . As shown, base wall  28  is interrupted by flashhole cutoff pit  68 , so that a portion of base wall  28  extends both radially inside and outside of flashhole cutoff pit  68 . 
     In the case where the cartridge cases are made from a base insert with a polymer over molded with the base insert, the base insert can have different profile configurations proximate the base end  12 . Turning to  FIGS. 11-14 , four examples are shown. 
     In  FIG. 11 , a standard insert  80  shown. The standard insert  80  includes a radially indented polymer groove  82 . Once the polymer is molded over insert  80 , an extraction groove is formed in the area near  84 . 
     The insert of  FIG. 12  is substantially similar to what is shown in  FIG. 11 , but also includes a second polymer groove  86  formed in the outer wall. 
       FIG. 13  shows a metal base insert having a polymer fill groove  88  with a similar diameter through where the extractor groove. 
     In  FIG. 14 , the base insert has no polymer filled groove. 
     Cartridge cases may be made using base inserts having any combination of the features disclosed in herein. 
     In light of the foregoing, it should thus be evident that a base insert of the present invention, for use with a cartridge case, substantially improves the art. While, in accordance with the patent statutes, only the preferred embodiments of the present invention have been described in detail hereinabove, the present invention is not necessarily to be limited thereto or thereby. Rather, the scope of the invention shall include all modifications and variations that fall within the scope of the attached claims.