Patent Publication Number: US-2011067284-A1

Title: Porting feature for firearm

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to firearms. More particularly, the present application involves a port that can function to expel gas during discharge of a firearm. 
     BACKGROUND 
     Firearms can be provided with various features to improve their performance. For example, it is known to employ ports that function to expel combustion gases out of the bore of a barrel of the firearm during discharge. The combustion gases are expelled radially from the bore through the ports so that energy associated with the expelled combustion gases does not contribute to recoil of the firearm. Additionally, porting of combustion gases from the barrel acts to dissipate heat generated during firing and prevents temperature elevation of the firearm after multiple shots are fired. 
     Additional features that can be incorporated into firearms include knife edges that are arranged longitudinally along the interior of the barrel that act to score a wad as it passes through the bore. The wad may house a plurality of pellets or flechettes. Scoring of the wad by the knife edges may facilitate its rapid opening upon exiting the barrel so that the wad does not interfere with the string of pellets as they travel to their target. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended Figs. in which: 
         FIG. 1  is a perspective view of a choke with a port in accordance with one exemplary embodiment. 
         FIG. 2  is a top view of the choke of  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 1 . 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 2 . 
         FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 2 . 
         FIG. 6  is a cross-sectional view of the choke of  FIG. 1  when used during the discharge of a firearm. 
         FIG. 7  is a front view of a rifle with a plurality of ports defined in the barrel in accordance with another exemplary embodiment. 
         FIG. 8  is a side view of a wad stripped through use of a port forming a knife edge in accordance with one exemplary embodiment. 
         FIG. 9  is a side view of a wad stripped through use of a ported choke. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations. 
     It is to be understood that the ranges mentioned herein include all ranges located within the prescribed range. As such, all ranges mentioned herein include all sub-ranges included in the mentioned ranges. For instance, a range from 100-200 also includes ranges from 110-150, 170-190, and 153-162. Further, all limits mentioned herein include all other limits included in the mentioned limits. For instance, a limit of up to 7 also includes a limit of up to 5, up to 3, and up to 4.5. 
     The present invention provides for a port  34  for use with a firearm  12  that allows firing gas to be expelled from a bore  18  of the firearm  12  during discharge. The port  34  may also be arranged to form a knife edge  62  that functions to more easily strip a wad  22  during discharge. For example, the port  34  may function to assist in stripping a wad  22  so that the wad  22  opens rapidly upon exiting the bore  18  so as not to interfere with a string of shot  24  as they travel to their target. A method of forming a port  34  to aid in the stripping of a wad  22  is also disclosed. 
       FIG. 1  is a perspective view of a choke  10  in accordance with one exemplary embodiment. The choke  10  can be attached to a firearm  12  to afford a tapered portion through which a wad  22  and shot  24  can travel. When used in conjunction with a firearm  12  that is a shotgun, the choke  10  acts to force the shot  24  into a tighter stream upon exiting. Various chokes  10  can be placed onto the firearm  12  in order to achieve a desired shot pattern for a particular purpose. A plurality of ports  34  are defined in the choke  10 . The ports  34  act to reduce recoil force as gas  36  generated during firing of the wad  22  and shot  24  is vented through the radially disposed ports  34 . Additionally, the ports  34  are arranged so as to provide a knife edge  62  that aids in the stripping of a wad  22  so that the wad  22  is hindered in interfering with a shot  24  pattern. 
     The choke  10  is releasably attachable to the firearm  12  through a threaded engagement. As shown, choke  10  includes external threading  60  that engages internal threading present on an interior passage of the firearm  12 . The choke  10  can be attached to and removed from the firearm  12  by the user as desired. A different choke  10  that includes different features may be subsequently attached to the firearm  12  to result in a desired shot pattern or to achieve some other desired benefit. Although described as being releasably attachable, the choke  10  may be permanently attached to the firearm  12  in accordance with various exemplary embodiments. Additionally, the choke  10  can be integrally formed with the firearm  12  or may be a separate component that is either permanently or releasably attached to the firearm  12  in accordance with other embodiments. Although described as being attached through the use of external threading  60 , the choke  10  can be attached to the firearm  12  through various means such as clips, welding, a snap-fit engagement, screws, or various types of mechanical fasteners. 
     The choke  10  includes a body  16  that defines a bore  18  therethrough. Bore  18  has a longitudinal axis  20  that may be coaxial with a longitudinal axis of the firearm  12  when the choke  10  is attached. The bore  18  extends from one open end  26  to an opposite open end  28 . Open end  26  receives wad  22  and shot  24  traveling from the other portions of the firearm  12 . The wad  22  and shot  24  are subsequently expelled from the choke  10  through open end  28  of bore  18  to exit the firearm  12 . Choke  10  can be made of a strong material such as high-hardness stainless steel in order to resist deformation due to explosive forces and elevated temperatures that result upon firing a wad  22  and shot  24  therethrough. 
     Referring now to  FIG. 2 , body  16  has a mounting segment  54  and a choking segment  56 . The mounting segment  54  and choking segment  56  are located next to one another in the longitudinal direction  42  of body  16 . As shown, the mounting segment  54  is located proximal to the choking segment  56  in the longitudinal direction  42 . Open end  26  of bore  18  opens into the mounting segment  54  which also includes the external threading  60 . The choking segment  56  includes open end  28  of bore  18  along with one or more ports  34 . Bore  18  does not have a consistent diameter extending all the way from end  26  to end  28 . Instead, a conical section  50  of bore  18  is present in the mounting segment  54 . Bore  18  has a larger diameter at end  26  which tapers to a smaller diameter at the location in which mounting segment  54  contacts choking segment  56 . In effect, the conical section  50  of bore  18  narrows as the wad  22  and shot  24  traverse therethrough. Conical section  50  functions to constrict the wad  22  and shot  24  and thus causes certain desired effects to be achieved. Bore  18  has a parallel section  52  in choking segment  56 . Bore  18  has a constant diameter through the parallel section  52  from the point of contact between the choking segment  56  and mounting segment  54  until the end  28  of bore  18 . In this regard, the inner surface  30  of the body  16  at the choking segment  56  has a constant inner diameter. Parallel section  52  of bore  18  may also function to impart a constriction onto the wad  22  and shot  24  traveling therethrough to achieve certain desired effects. 
     The shape and length of conical section  50  and parallel section  52  can be varied in order to achieve various results. For example, a steep taper angle of the conical section  50  will cause shot  24  to quickly compress which may result in a larger shot pattern spread. A flatter taper angle of conical section  50  will cause the shot  24  to compress more gradually and may result in a tighter and more consistent shot pattern. The length of the parallel section  52  in the longitudinal direction  42  of body  16  may also effect the resulting shot  24  pattern. For example, a larger length of parallel section  52  may cause a more uniform shot column to develop which can create consistently tighter shot patterns. A shorter length in the longitudinal direction  42  of parallel section  52  may cause a larger shot pattern to be produced from parallel section  52 . Further, the use of a longer parallel section  52  may increase the benefits realized by the presence of ports  34 . As stated, ports  34  cause firing gas  36  to be released which in turn acts to slow down the speed of the wad  22  and shot  24  upon traversing bore  18 . In some instances, the presence of ports  34  function to slow the speed of a wad  22  which may be prevent the wad  22  from breaking up a column of shot or pellets  24 . Allowing the shot  24  to develop into a column without interference of wad  22  can result in a more desirably consistent shot pattern. Modification of the length of parallel section  52  acts to modify the effectiveness of the ports  34  and thus effects the resulting shot pattern. 
     Although described as having both a conical section  50  and a parallel section  52 , it is to be understood that bore  18  can be variously configured in accordance with other exemplary embodiments. For example, the bore  18  may have a constant diameter from one end  26  to the other end  28 . In this regard, the bore  18  is parallel throughout. Alternatively, the bore  18  may be conical from end  26  to end  28 . Here, the bore  18  may be larger at end  26  and smaller in diameter at end  28 . Further, the diameter of bore  18  may be varied in accordance with various exemplary embodiments to modify the size of the resulting shot patterns. Although described as having a mounting segment  54  and choking segment  56 , it is to be understood that the wad  22  and shot  24  can be restricted or choked in either one of or both of these segments  54  or  56 . 
     The choke  10  as shown with reference to  FIGS. 1 and 2  has a circumference that has a curved shape. However, it is to be understood that other exemplary embodiments exist in which the circumference need not be curved in shape. For example, the circumference of the body  16  can have one or more flat sections in the mounting segment  54  or choking segment  56  of body  16 . The ports  34  are shown located in the choking segment  56  of the body  16 , but can be located in the mounting segment  54  in addition to or alternatively to the choking segment  56  in accordance with other exemplary embodiments. The ports  34  are located around the entire circumference of the body  16  and may be radially symmetrical about the body  16 . However, the ports  34  need not be radially symmetrical in accordance with other exemplary embodiments. 
     Referring now to  FIG. 3 , a cross-sectional view taken along line  3 - 3  of  FIG. 1  is shown. The arrangement of the ports  34  at the inner surface  30  of the body  16  is displayed. Port  34  has a distal end  38  at the inner surface  30  that extends in the radial direction  40  of the body  16  but does not extend in the longitudinal direction  42  of the body  16 . As such, the distal end  38  of the port  34  at the inner surface  30  may be perpendicular to the longitudinal axis  20  and may be perpendicular to the direction of travel of the wad  22  and shot  24  through the bore  18 . The port  34  has a side  44  and a side  46  at the inner surface  30  that extend in the longitudinal direction  42  of the body  16  but do not extend in the radial direction  40  of the body  16 . The sides  44  and  46  are parallel with one another at the inner surface  30  and are each contiguous with the distal end  38  at the inner surface  30 . 
     The port  34  also has a proximal end  48  at the inner surface  30  that extends both in the radial direction  40  and in the longitudinal direction  42 . The proximal end  48  of the port  34  is contiguous with the sides  44  and  46  at the inner surface  30 . The proximal end  48  at the inner surface  30  may be described as being curved with a radial component. The port  34  is thus completely defined at the inner surface  30  by the distal end  38 , side  44 , side  46 , and proximal end  48 . As shown, the port  34  is asymmetrical in shape at the inner surface  30 . However, it is to be understood that other arrangements are possible in which the port  34  is not asymmetrical in shape at the inner surface  30 . For example, the port  34  may be configured as shown in  FIG. 3  with the exception of the proximal end  48  that may be arranged in a manner similar to the distal end  38 . In these embodiments, the port  34  may be symmetrical in shape. As shown in  FIG. 3 , the port  34  may be described as having an elliptical shape at the inner surface  30  with a flattened distal end. 
     The port  34  functions to expel firing gas  36  from the bore  18  so that the resulting recoil due to discharge of the firearm  12  is reduced. Additionally, the port  34  is arranged so that the distal end  38  functions to aid in stripping of wad  22 . In this regard, the orientation of the distal end  38  of port  34  may create friction that slows down an outer portion of the wad  22  traversing across the port  34  to prevent interference.  FIG. 6  shows one exemplary embodiment in which a firearm  12  is discharged that includes a wad  22  and shot  24 . The shot  24  may escape the wad  22  upon exiting end  28  or shortly thereafter. The wad  22  is slowed upon crossing the distal ends  38  of the ports  34  so that it does not interfere with the shot  24  to thus allow the shot  24  to more accurately hit its target. Although not wishing to be bound by a particular theory of operation, the distal ends  38  may also function to score the wad  22  so that the wad is weakened and thus more easily opens upon exiting the bore  18  to thus minimize interference with the shot  24  string. The firing gas  36  that pushes the wad  22  and shot  24  through the choke  10  is at least partially vented through the ports  34  once the wad  22  and shot  24  have passed the ports  34  to allow sufficient space for venting. Ports  34  are arranged so as to vent some of the firing gas  36  in a direction different than that of the direction of force of the wad  22  and shot  24 . 
     The ports  34  may be sized so as to have a fairly large length in the radial direction. Use of larger ports  34  may more easily allow portions of the wad  22  to be pulled into the ports  34  when traversing across the ports  34 . Although not wishing to be bound by any theory of operation, a vacuum may be formed that acts to pull the surface of the wad  22  into the port  34 , or combustion gases inside of the bore  18  may force the wad  22  against the inner surface  30  and hence inside of the ports  34  when traversing across ports  34 . As the wad  22  is pulled slightly inside of the ports  34  or at least tightly against the inner surface  30  during traversal, the wad  22  will eventually contact the distal end  38  so that the knife edge  62  can more effectively engage and distort the wad  22  as it passes. However, it is to be understood that other arrangements are possible in which the wad  22  is not slightly pulled into the ports  34  or even held tightly against the inner surface  30  upon discharge of the firearm  12 . As such, various exemplary embodiments are possibly in which the ports  34  are generally small in the radial direction  40  and do not function to easily allow the wad  22  to enter the port  34  to more easily facilitate stripping by the knife edge  62 . 
       FIG. 8  is a side view of the wad  22  upon discharge in accordance with one exemplary embodiment. As illustrated, the knife edge  62  has significantly distorted the wad  22  to the point that it is more significantly damaged than the wad  22  illustrated in  FIG. 9 . The wad  22  shown in  FIG. 9  was produced by through discharge of a firearm  12  that does not include the port  34  and associated knife edge  62  as presently discussed. Comparison of the two wads  22  illustrates the significant distortion imparted by the knife edge  62  which results in a wad  22  that is more easily opened upon exiting the bore  18  and more significantly slowed during traversal through the bore  18 . The wad  22  associated with the knife edge  62  interferes less with string of shot  24  produced upon discharge. The wad  22  used in conjunction with the firearm  12  that does not have the port  34  and associated knife edge  62  is less distorted upon discharge and may not be as slowed upon traversal such that a greater interference with the string of shot  24  is realized. 
     Although an aforementioned comparison has been made between wads  22  it is to be understood that the distortion of the wad  22  illustrated in  FIGS. 8 and 9  are only exemplary. As such, certain exemplary embodiments are possible in which the wad  22  is distorted exactly or substantially like that shown in  FIG. 9 . Further exemplary embodiments exist in which the wad  22  is not distorted as that illustrated in  FIG. 8 . 
       FIG. 4  shows a cross-section of the choke  10  along lines  4 - 4  of  FIG. 2 . The port  34  extends from the inner surface  30  to the outer surface  32  of the body  16 . The port  34  increases in size from the inner surface  30  to the outer surface  32  such that the port  34  is larger at the outer surface  32  than at the inner surface  30 . In this regard, the sides  44  and  46  remain a constant size from the inner surface  30  to the outer surface  32 , but the distal end  38  and the proximal end  48  both increase in size from the inner surface  30  to the outer surface  32 . However, it is to be understood that other configurations of the port  34  are possible. For example, side  44  and/or side  46  may increase or decrease in size from the inner surface  30  to the outer surface  32 . Further, the proximal end  48  may decrease in size or remain the same size from the inner surface  30  to the outer surface  32 . The distal end  38  may form a knife edge  62  upon extending from the inner surface  30  to the outer surface  32 . The knife edge  62  can additionally function to slow a portion of the wad  22  passing across. The knife edge  62  may extend from the inner surface  30  to the outer surface  32  at any angle with respect to the longitudinal axis  20 . For example, the knife edge  62  may extend at an angle from 30° to 60° to the longitudinal axis  20  from the inner surface  30  to the outer surface  32  in accordance with various exemplary embodiments. The knife edge  62  may act to cut or otherwise scar the wad  22  as it traverses across the knife edge  62 . Damage of a portion of the wad  22 , such as the petals of the wad  22 , causes it to weaken and thus more easily open or expand once it is no longer contained against the inner surface  30  of the bore  18 . The knife edge  62  can be arranged in a number of manners in accordance with various exemplary embodiments. Increasing the size of the port  34  in the radial direction  40  may act to increase the surface area of the knife edge  62  so as to more effectively strip a portion of the wad  22 . 
     As shown in  FIG. 4 , the distal end  38  at the outer surface  32  is located distal to the distal end  38  at the inner surface  30 . The proximal end  48  at the outer surface  32  is located proximal to the proximal end  48  at the inner surface  30 . Other arrangements are possible. For example, the proximal end  48  at the outer surface  32  may be distally located to the proximal end  48  at the inner surface  30 . As used herein, the terms distal and proximal refer to relative positions with respect to the longitudinal axis  20 . Proximal refers to a location generally closer to the user of the firearm  12 , and distal refers to a location generally farther from the user of the firearm  12  when using the firearm  12 . Likewise, the wad  22  and shot  24  travel from the proximal to the distal direction when traversing the choke  10 . With reference to  FIG. 2 , the port  34  is asymmetrical at the outer surface  32 . In this regard, the port  34  at the outer surface  32  is generally elliptical with a distal end that is flattened. However, other arrangements are possible in which the port  34  has a symmetrical shape at the outer surface  32 . 
       FIG. 5  shows a cross-sectional view along line  5 - 5  of  FIG. 2 . As shown, a plurality of ports  34  extend about the circumference of the body  16 . Any number of ports  34  can be used in accordance with various exemplary embodiments. For example, fourteen ports  34  can be used in accordance with one embodiment in which the ports  34  are divided into two sets of seven. The first set is located distal to the second set, and the ports  34  are arranged so as to be radially symmetrical about the body  16 . However, it is to be understood that any number of ports  34  can be employed in accordance with various exemplary embodiments. For example, up to thirty ports  34  can be used in certain embodiments. In accordance with one exemplary embodiment, a single port  34  can be present. Further, when using a number of ports  34 , they can be positioned in a non-symmetrical manner about the body  16 . 
     Although described as being incorporated into a choke  10 , the port  34  need not be located in a choke  10  in accordance with other exemplary embodiments. For example, as shown in  FIG. 7 , the port  34  can be formed directly into the barrel  14  of a firearm  12  that in this embodiment is a rifle. The rifle is capable of discharging a projectile  58  that in this case is a bullet. The port  34  may be arranged in the same manners are previously discussed. Additionally, the barrel  14  may include the same features as the choke  10  as previously discussed. In this regard, the barrel  14  may have a curved inner surface  30  and a curved outer surface  32 . Further, the barrel  14  may have a body  16 , bore  18  and a longitudinal axis  20 . The barrel  14  may include a choke  10  in accordance with certain exemplary embodiments. In this regard, the ports  34  may be located in either the choke  10  portion of the barrel  14  and/or in another portion of the barrel  14  that does not include the choke  10  portion. As such, it is to be understood that as used herein the barrel  14  may or may not include a choke  10  that is releasably attachable to the barrel  14 . It is to be thus understood that the choke  10  is a part of the barrel  14  in accordance with certain exemplary embodiments. The portions of the barrel  14  that include the choke  10  portion and that do not include the choke  10  portion may be arranged as previously discussed. The firearm  12  can be a shotgun, a rifle, or a pistol in accordance with various exemplary embodiments. 
     The ports  34  need not be incorporated into a firearm  12  that has a feature that functions to constrict the object traversing therethrough. When used in conjunction with a rifle or a pistol, the ports  34  may act to facilitate the stripping of a sabot from the projectile  58  at the muzzle of the firearm. Additionally, the ports  34  will act to reduce recoil of the firearm  12  upon discharge due to venting of the firing gases  36 . The ports  34  can be arranged about the circumference of the body  16  so that a greater amount of firing gases  36  are expelled from the upper portion of the body  16  than the lower portion of the body  16  in order to reduce upward kick of the firearm  12  upon discharge. 
     The ports  34  can be formed by a number of processes. For example, the ports  34  can be formed by a milling process, a drilling process, or by electrical discharge machining. The port  34  can be formed by removing a portion of the body  16  first at the outer surface  32  and then subsequently removing material down to the inner surface  30 . The removal of material, or the cuts, may proceed from the proximal to the distal direction. In this regard, should a milling process be employed, the cutting instrument may be oriented at an angle to the outer surface  32  in the longitudinal direction  42 . The cuts made to form the ports  34  may proceed such that the cut is not all the way through the body  16  from the outer surface  32  to the inner surface  30 . In this regard, the cutting “stops” before removing all of the material near the distal end  38  to leave the port  34  in the shape that may be seen, for instance, in  FIG. 4 . Should the cutting instrument proceed all the way through to the inner surface  30 , the resulting port would be of the same size on the inner surface  30  as on the outer surface  32  and would be symmetrical in shape at both the inner and outer surfaces  30  and  32 . In accordance with one exemplary embodiment, the port  34  is formed by removing material from the outer surface  32  to the inner surface  30  from the proximal to distal direction. Other methods of manufacture are possible in order to form a port  34  that is asymmetrical at the inner surface  30 . Asymmetry of the port  34  at the inner surface  30  may be capable of facilitating removal of one portion of the wad  22  from a different portion of the wad  22 . In accordance with one exemplary embodiment, the port  34  at the inner surface  30  may be symmetrical with regard to a longitudinally oriented axis running through its center, yet asymmetrical with regard to a radially oriented axis running through its center. Here, although the port  34  at the inner surface  30  may be symmetrical in accordance with one axis, it is asymmetrical with respect to a second axis and is in effect an asymmetrical in shape. 
     In accordance with certain exemplary embodiments, apertures through the body  16  may be present that do not function to vent gas  36 . For example, a choke  10  may be present with a hole located through the mounting segment  54 . The hole can be used to help hold the mounting segment  54  to a firearm  12  with an associated pin or bolt, in accordance with certain embodiments. The ports  34  that vent gas  36  need not be configured in a similar manner. In this regard, one or more of the ports  34  may have a distal end  38  at the inner surface  30  that extends in the radial direction  40  but not the longitudinal direction  42  while other ports  34  in the body  16  have distal ends  38  that do extend in the longitudinal direction  42 . 
     While the present invention has been described in connection with certain preferred embodiments, it is to be understood that the subject matter encompassed by way of the present invention is not to be limited to those specific embodiments. On the contrary, it is intended for the subject matter of the invention to include all alternatives, modifications and equivalents as can be included within the spirit and scope of the following claims.