Patent Publication Number: US-10330408-B2

Title: Piston for a gas-operated firearm

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/428,643 filed on Dec. 1, 2016, entitled “PISTON-BASED METHOD OF GAS REGULATION FOR SELF-LOADING FIREARMS,” and also claims the benefit of U.S. Provisional Patent Application No. 62/525,546 filed on Jun. 27, 2017, entitled “METHODS FOR VENTING EXCESS GAS THROUGH AND/OR AROUND A PISTON,” which are hereby incorporated by reference in its entirety for all that is taught and disclosed therein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to firearms, and more particularly to a piston for a gas-operated firearm that is tunable to control how much energy from the expanding gas is converted into motion to cycle the firearm. 
     BACKGROUND OF THE INVENTION 
     Gas-operated firearms utilize a portion of the high-pressure gas resulting from the discharge of a cartridge to cycle the action of the firearm. The portion of high-pressure gas typically exits via a port in the barrel, and subsequently impinges on the surface of a piston head. Resulting movement of the piston unlocks the action, extracts the spent case from the chamber, ejects the spent case from the firearm, cocks the hammer, chambers a fresh cartridge from a magazine, and locks the action. 
     The high-pressure gas must be regulated to avoid either excessive or inadequate pressure. Excessive pressure generates unwanted wear and potential damage to components, if the energy is well more than that needed to cycle the action. Inadequate pressure may be insufficient to cycle the action, and generate malfunctions. Normally, a firearm is designed for a given application, such as a certain type of ammunition and certain accessories (such as a sound suppressor or lack thereof) within a suitable operating range for that application. However, when users wish to change some aspect of the application, they may face major tasks to modify or replace major components on their rifle to provide a suitable gas flow. Various methods have been used, including tuning the gas port size, adjusting the mass of the operating parts, and changing spring characteristics to prevent overly violent (or inadequate) movement of the action. While these traditional approaches are effective at controlling movement of the action, the use of a sound suppressor or specialized ammunition with a firearm can result in excessive gas pressure that accelerates wear and adversely affects accuracy. While some firearms have gas blocks that can be replaced with alternatives that reduce the gas pressure, some firearms have permanently-mounted gas blocks or gas blocks that are difficult to remove. 
     Therefore, a need exists for a new and improved piston for a gas-operated firearm that enables the user to easily adjust the gas pressure applied to the action components of the firearm. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the piston for a gas-operated firearm according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of enabling the user to easily adjust the gas pressure applied to the action components of the firearm. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved piston for a gas-operated firearm, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide an improved piston for a gas-operated firearm that has all the advantages of the prior art mentioned above. 
     To attain this, the preferred embodiment of the present invention essentially comprises an elongated body having a head portion adapted to be closely received in the cylindrical bore for reciprocation within the bore, the head portion having a first side toward a forward direction and a second side toward the rearward direction, the body having an operational facility on the second side adapted to transmit an operating force to the action in response to gas pressure on the first side, and the head portion defining a bypass passage between the first side and the second side. The bypass passage may have an adjustment facility adapted to provide selectable resistance to gas flow through the bypass passage. The adjustment facility may be a movable occlusion element that selectably occludes the bypass passage. The occlusion element may be a threaded element. The occlusion element may be a collar that receives a portion of the body. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims attached. 
     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional view of the current embodiment of the piston for a gas-operated firearm constructed in accordance with the principles of the present invention in use installed in a rifle. 
         FIG. 1A  is an enlargement of the rectangular area of  FIG. 1 . 
         FIG. 2  is an exploded isometric view of the current embodiment of the piston for a gas-operated firearm of  FIG. 1 . 
         FIG. 3  is a side sectional view of the current embodiment of the piston for a gas-operated firearm of  FIG. 1  installed in a gas block and tube. 
         FIG. 4  is a side sectional view of a first alternative embodiment of the piston for a gas-operated firearm installed in a gas block and tube. 
         FIG. 5  is an isometric exploded view of a second alternative embodiment of the piston for a gas-operated firearm. 
         FIG. 6  is a side sectional view of the second alternative embodiment of the piston for a gas-operated firearm of  FIG. 5  installed in a gas block and tube. 
         FIG. 7  is a front isometric view of a third alternative embodiment of the piston for a gas-operated firearm in the open position with dashed lines denoting a partially closed position. 
         FIG. 8  is a front isometric view of the third alternative embodiment of the piston for a gas-operated firearm of  FIG. 7  in the fully closed position. 
     
    
    
     The same reference numerals refer to the same parts throughout the various figures. 
     DESCRIPTION OF THE CURRENT EMBODIMENT 
     An embodiment of the piston for a gas-operated firearm of the present invention is shown and generally designated by the reference numeral  10 . 
       FIGS. 1 and 1A  illustrate the improved piston for a gas-operated firearm  10  of the present invention. More particularly, the piston for a gas-operated firearm is shown installed in a rifle  400 . The rifle  400  has a barrel  402  that defines a central barrel bore  404 . A gas port  406  is in fluid communication with the central barrel bore  404 . A gas block  408  is attached to the barrel. The gas block has a gas passage  410  that enables fluid communication between the gas port and a rearward-facing cylindrical central bore  412  that defines a bore axis  442  and flares at the rear  436 . A tube  430  has a central bore  414  that is in fluid communication with the central bore  412 . The piston  10  is an elongated body having a front piston head portion  106  received within the central bore  412  of the gas block and the central bore  414  of the tube for reciprocation within the central bores. The periphery of the head portion is closely received in the central bore  412  of the gas block to provide a gas seal. The front  418  of a pushrod  416  is attached to the rear of the piston. The front  424  of a piston rod  422  is attached to the rear  420  of the pushrod. A rear protrusion  426  contacts an operating system/action  428  such that when high-pressure gas passes through the gas port  406 , gas passage  410 , and central bore  412 , the high-pressure gas impinges upon the piston. Once sufficient gas pressure has accumulated within the central bore  412  to push the piston rearward, the rearward movement is communicated to the action via pushrod  416  and piston rod  422  such that the action is cycled. Thus, the pushrod and piston rod serve as an operational facility on the second, rearward side of the piston adapted to transmit an operating force to the action in response to gas pressure on the first, forward side of the piston. 
       FIGS. 2 and 3  illustrate the improved piston for a gas-operated firearm  10  of the present invention. More particularly, the piston for a gas-operated firearm is shown in  FIG. 3  installed in the gas block  408  and tube  430  with a fragmentary view of the barrel  402 . The gas block has a front  434 , rear  436 , top  438 , and bottom  440 . The bottom rear of the gas port defines the gas passage  410 , and the bottom rear of the gas block is attached to the barrel  402  such that the gas passage is in fluid communication with the gas port  406 . The rear of the gas block defines the central bore  412 . The front  432  of the tube  430  is attached to the rear of the gas block such that the central bore  414  of the tube is in fluid communication with the central bore  412 . 
     The piston  10  has a front  68  and a rear  70 . The front serves as a piston head portion  72  and defines a central bore  74  having a rear  80 . The rear portion of the central bore  74  has a smooth interior sidewall that defines two radial/lateral bypass passages  76  between the first, front side of the piston head and the second, rear side of the piston head. Thus, the central bore and bypass passages can also be viewed as a passage having a first portion extending from the first side through the head portion, and a second portion extending laterally from the first portion, with the passage having an inlet on the first side of the head portion and an outlet on the second side of the head portion. In addition, the outlet is rearward of a rear limit of the cylindrical central bore  412  of the gas block  408  defined by where the diameter of the central bore  412  flares at the rear  436 . The two radial bypass passages are in fluid communication between the central bore  74  and the central bore  414  of the tube. The exterior of the piston has a threaded portion  12  located immediately behind the bypass passages. A longitudinal slot  14  is defined in the piston immediately behind the threaded portion  12 . A lateral bore  16  is defined in the piston behind the longitudinal slot. The exterior of the piston has a threaded portion  18  at the rear. 
     An external collar  20  having a central bore  26  with a threaded portion  28  is threadedly connected to the threaded portion  12  of the piston  10  and receives a portion of the piston  10  within the central bore  26 . The external collar has a front  22 , rear  24 , and an exterior  30 . The exterior defines a plurality of flutes/recesses  32  to facilitate gripping and turning of the external collar. The rear of the external collar defines serrations  34 . 
     A snap ring  36  having a central bore  42  is received by the rear  70  of the piston  10 . The snap ring has a front  38  and rear  40 . The front of the snap ring defines serrations  44  that are of a suitable size and shape to mesh with the serrations  34  on the rear  24  of the external collar  20 . The snap ring defines two axially registered apertures  46 ,  48 . A snap ring pin  50  has one end  52  received by aperture  46 , and opposed end  54  received by aperture  48 , and a middle portion  56  that is received by slot  14  in the piston  10 . As a result, the snap ring is constrained to a limited amount of longitudinal travel relative to the piston  10  governed by the length of the slot  14 , and rotation of the snap ring is prevented. 
     A spring  58  abuts the rear  40  of the snap ring  36  and fits over the rear  70  of the piston  10 . A spring stop pin  60  has a middle portion  66  that is received within bore  16  in the piston  10 . The spring stop pin has opposed ends  62 ,  64  that protrude outwardly from bore  16  such that the spring is compressed between the rear of the snap ring and the opposed ends of the spring stop pin and thereby is retained on the piston  10 . 
     In  FIG. 3 , the solid lines show the external collar  20  in the fully open position that fully exposes the bypass passages  76 . As a result, high-pressure gas passing through the gas port  406 , gas passage  410 , and accumulating within the central bore  412  not only impinges upon the piston head  72  and enters the central bore  74  of the piston  10  to impinge upon the rear  80  of the central bore  74 , but a portion of the high-pressure gas can escape through the exposed bypass passages  76  into the central bore  414  of the tube  430 , and subsequently vent to the external environment. Thus, the force of the gas pressure exerted upon the piston  10  and the action  428  is maximally reduced. The dashed lines in  FIG. 3  denote the fully closed position of the external collar, in which the front  22  of the external collar completely covers the bypass passages. In this condition, no gas can escape from the central bore  74  of the piston  10 , and the force of the gas pressure exerted upon the piston  10  and the action is maximized. 
     Because the external collar  20  is threadedly connected to the threaded portion  12  of the piston  10 , the external collar can occupy a variety of positions determined by the pitch of the serrations  34 ,  44  between the fully closed and fully opened positions to enable partial exposure of the bypass passages  76  such that the force of the gas pressure exerted upon the piston  10  and the action  428  can be tuned to the desired amount to account for the presence or absence of a sound suppressor or specialized ammunition. The meshed engagement of the serrations  44  on the snap ring  36  with the serrations  34  on the external collar prevents the external collar from rotating once the external collar has been positioned to expose the desired portion of the bypass passages. The spring  58  ensures the serrations  34 ,  44  remain meshed together. 
     To change the portion of the bypass passages  76  that is exposed by the external collar  20 , the user pulls the snap ring  36  rearward until the serrations  44  on the snap ring have disengaged from the serrations  34  on the external collar. While continuing to hold the snap ring rearward to compress the spring  58  and keep the serrations  34 ,  44  disengaged from each other, the user grips the exterior  30  of the external collar and rotates the external collar clockwise to decrease the exposure of the bypass passages or counterclockwise to increase the exposure of the bypass passages. Once the external collar is in the desired position, the user releases the snap ring. The compressed spring  58  urges the snap ring forward and re-engages the serrations  34 ,  44  with each other to prevent undesired rotation of the external collar. Thus, the external collar serves as an adjustment facility adapted to provide selectable resistance to gas flow through the bypass passages that is a movable occlusion element that selectably occludes the bypass passages. It should be appreciated that a nonadjustable version of this embodiment can be created by eliminating the external collar, snap ring, spring, and pins, and providing bypass passages of a suitable size in the piston  10  to achieve the desired force of the gas pressure exerted upon the piston and the action. 
       FIG. 4  illustrates a first alternative embodiment of the improved piston for a gas-operated firearm  100  of the present invention. More particularly, the piston  100  is shown installed in the gas block  408  and tube  430  with a fragmentary view of the barrel  402 . The piston  100  has a front  102  and a rear  104 . The front serves as a piston head  106  and defines a central bore  108  having a rear  124 . The piston defines a radial/lateral bypass passage  110  that is in fluid communication between the central bore  108  and the central bore  414  of the tube. A ball  112  compresses a spring  114  against the rear of the  124  of the central bore  108 . The ball and spring serve as a ball check valve for the bypass passage. The strength of the spring determines how much of the gas entering the central bore  108  can escape through the bypass passage  110  (denoted by the dashed lines in  FIG. 4  showing the ball in a partially opened position). Thus, the force of the gas pressure exerted upon the piston  100  and the action  428  can be tuned to the desired amount to account for the presence or absence of a sound suppressor or specialized ammunition by using springs of different strengths. The rear of the piston  100  includes a threaded portion  116 . A pushrod  416  having a front  418  and rear  420  has the front threadedly attached to the rear of the piston. It should be appreciated that a nonadjustable version of this embodiment can be created by eliminating the ball check valve and providing a bypass passage of a suitable size in the piston  100  to achieve the desired force of the gas pressure exerted upon the piston and the action. 
       FIGS. 5 and 6  illustrate a second alternative embodiment of the improved piston for a gas-operated firearm  200  of the present invention. More particularly, the piston  200  is shown in  FIG. 6  installed in the gas block  408  and tube  430  with a fragmentary view of the barrel  402 . The piston  200  in the current embodiment is integral to the pushrod and has a forward-facing front  212  and rearward-facing rear  214 . The front serves as a piston head portion  216  and defines a central bore  218  having a rear  220 . The rear portion of the central bore  218  has a smooth interior sidewall that defines radial/lateral bypass passages  222  between the first, front side of the piston head and the second, rear side of the piston head. Thus, the central bore and bypass passages can also be viewed as a passage having a first portion extending from the first side through the head portion, and a second portion extending laterally from the first portion, with the passage having an inlet on the first side of the head portion and an outlet on the second side of the head portion. In addition, the outlet is rearward of a rear limit of the cylindrical central bore  412  of the gas block  408  defined by where the diameter of the central bore  412  flares at the rear  436 . The remaining forward portion of the interior sidewall is threaded. The radial bypass passages are in fluid communication between the central bore  218  and the central bore  414  of the tube. 
     A threaded plunger  224  is a threaded tube threadedly received within the threaded central bore  218  of the piston head portion  216 . The threaded plunger has a central bore  226 , exterior  228 , front  230 , and rear  232 . At least a forward portion of the central bore  226  defines a tool pocket  238  that extends through the front face of the piston head portion. The tool pocket is sized and shaped to receive a suitable tool to enable a user to apply torque to the threaded plunger to induce rotation. The exterior of the threaded plunger has a forward threaded portion  234  and a rearward smooth portion  236 . In  FIG. 3 , the solid lines show the threaded plunger in the fully open position that fully exposes the bypass passages  222 . As a result, high-pressure gas passing through the gas port  406 , gas passage  410 , and accumulating within the central bore  412  not only impinges upon the piston head  216  and enters the central bore  218  of the piston and the central bore  226  of the threaded plunger to impinge upon the rear  220  of the central bore  218 , but a portion of the high-pressure gas can escape through the exposed bypass passages  222  into the central bore  414  of the tube  430  and subsequently vent to the external environment. Thus, the force of the gas pressure exerted upon the piston  200  and the action  428  is maximally reduced. The dashed lines in  FIG. 6  denote the fully closed position of the threaded plunger, in which the smooth portion of the threaded plunger completely covers the bypass passages. In this condition, no gas can escape from the central bore  218  of the piston  200 , and the force of the gas pressure exerted upon the piston  200  and the action is maximized. 
     Because the threaded plunger  224  is threadedly received within the central bore  218 , the threaded plunger can occupy any position between the fully closed and fully opened positions to enable partial exposure of the bypass passages  222  such that the force of the gas pressure exerted upon the piston  200  and the action  428  can be tuned to the desired amount to account for the presence or absence of a sound suppressor or specialized ammunition. Thus, the threaded plunger serves as an adjustment facility adapted to provide selectable resistance to gas flow through the bypass passages that is a movable occlusion element that selectably occludes the bypass passages. It should be appreciated that a nonadjustable version of this embodiment can be created by eliminating the threaded plunger and providing bypass passages of a suitable size in the piston  200  to achieve the desired force of the gas pressure exerted upon the piston  200  and the action. 
       FIGS. 7 and 8  illustrate a third alternative embodiment of the improved piston for a gas-operated firearm  300  of the present invention. More particularly, the piston has a front portion  302 , a rear portion  304 , and a shaft  330  extending rearwardly from the front portion. The rear portion is rotatably mounted on the shaft such that the front  316  of the rear portion closely abuts the rear  308  of the front portion. The front portion has a front  306  that serves as a piston head  310  and an exterior  312  having a plurality of flutes  314  that serve as bypass passages. The rear portion has an exterior  320  defining a plurality of flutes  322  that serve as bypass passages that are sized and spaced to enable axial registration of the flutes  322  with the flutes  314 . 
     The rear of the rear portion defines serrations  324 . A snap ring  36  having serrations  44  is mounted on the shaft  330  and secured by a snap ring pin  50  with limited longitudinal movement and no rotational movement in the manner described previously in the discussion of piston  10 . Spring  58  is also mounted on the shaft and secured by a spring stop pin  60  in the manner described previously in the discussion of piston  10 . The rear  326  of the shaft has a threaded portion  328  to connect to a pushrod  416 . 
     In  FIG. 7 , the solid lines show the rear portion  304  in the fully open position that completely aligns the flutes  322  on the rear portion with the flutes  314  on the front portion. As a result, high-pressure gas passing through the gas port  406 , gas passage  410 , and accumulating within the central bore  412  not only impinges upon the piston head  310  and enters the flutes  314  of the front portion, but a portion of the high-pressure gas can enter flutes  322  on the rear portion and continue past the shaft  330  into the central bore  414  of the tube  430  and subsequently vent to the external environment. Thus, the force of the gas pressure exerted upon the piston  300  and the action  428  is maximally reduced. 
     The dashed lines in  FIG. 7  illustrate a partially closed position where the flutes  322  on the rear portion  304  are only partially aligned with the flutes  314  of the front portion  302 . As a result, some of the high-pressure gas entering the flutes  314  of the front portion impinges upon the front  316  of the rear portion prior to entering flutes  322  on the rear portion and continuing past the shaft  330  into the central bore  414  of the tube  430  and subsequently venting to the external environment. Thus, the force of the gas pressure exerted upon the piston  300  and the action  428  is partially reduced. 
       FIG. 8  shows the fully closed position of the piston  300  where the flutes  322  on the rear portion  340  are not aligned with the flutes  314  of the front portion  302 . In this condition, all the high-pressure gas entering the flutes  314  of the front portion impinges upon the front  316  of the rear portion, and no gas can enter the flutes  322  in the rear portion and vent to the external environment because the exteriors of the front and rear portions are closely received in the central bore  412  of the gas block to provide a gas seal. As a result, the force of the gas pressure exerted upon the piston  300  and the action  428  is maximized. Because the rear portion is rotatably mounted on the shaft  330  of piston  300 , the rear portion can occupy a variety of positions determined by the pitch of the serrations  44 ,  324  between the fully closed and fully opened positions to enable a variety of amounts of alignment of the flutes  322  of the rear portion with the flutes  314  of the front portion such that the force of the gas pressure exerted upon the piston  300  and the action can be tuned to the desired amount to account for the presence or absence of a sound suppressor or specialized ammunition. The meshed engagement of the serrations  44  on the snap ring  36  with the serrations  324  on the rear portion prevent the rear portion from rotating once the rear portion has been positioned to expose the desired portion of the front  316  of the rear portion. The spring  58  ensures the serrations  44 ,  324  remain meshed together. 
     To change the amount of alignment of the flutes  322  of the rear portion  304  with the flutes  314  of the front portion  302 , the user pulls the snap ring  36  rearward until the serrations  44  on the snap ring have disengaged from the serrations  324  on the rear portion. While continuing to hold the snap ring rearward to compress the spring  58  and keep the serrations  44 ,  324  disengaged, the user grips the exterior  320  of the rear portion and rotates the rear portion in either direction to increase or decrease the amount of alignment of the flutes  322  of the rear portion with the flutes  314  of the front portion. Once the rear portion is in the desired position, the user releases the snap ring. The compressed spring  58  urges the snap ring forward and re-engages the serrations  44 ,  324  to prevent undesired rotation of the rear portion. Thus, the rear portion serves as an adjustment facility adapted to provide selectable resistance to gas flow through the flutes/bypass passages that is a movable occlusion element that selectably occludes the flutes/bypass passages. Furthermore, the occlusion element is an end portion of the body rotatable about a major axis of the body with respect to a rear portion of the body. It should be appreciated that a nonadjustable version of this embodiment can be created by combining the front and rear portions into a fixed element and having them define flutes of a suitable size and shape to achieve the desired force of the gas pressure exerted upon the piston and the action. 
     While current embodiments of a piston for a gas-operated firearm have been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. For example, any quantity or size of bypass passage could be substituted for the bypass passage quantities described. 
     Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.