RETROFIT ADJUSTABLE GAS VALVE FOR LONG-STROKE PISTON-OPERATED FIREARM

Abstract

Provided is a retrofittable adjustable gas valve for an AK-pattern firearm having a standard gas block that receives a head portion of a gas piston. The gas valve includes a valve body configured to be at least partially received by a piston head-receiving portion of a standard AK-pattern gas block and has a gas passageway through it. A threaded adjustment valve member in the valve body has a stem portion configured to adjust gas flow through the gas passageway.

Claims

1. An adjustable gas valve for an AK-pattern firearm having a standard gas block that receives a head portion of a gas piston, comprising: a valve body configured to be at least partially received by a piston head-receiving portion of a standard AK-pattern gas block and having a gas passageway therethrough; and a threaded adjustment valve member in the valve body having a stem portion configured to adjust gas flow through the gas passageway.

2. The adjustable gas valve of claim 1, wherein the valve body includes a portion configured to mate with a gas cylinder tube.

3. The adjustable gas valve of claim 1, further comprising a replacement gas piston and replacement gas cylinder tube that are each shortened in length relative to standard AK-pattern parts they replace.

4. The adjustable gas valve of claim 1, wherein the valve body includes a brace portion that is in contact with a barrel outer surface when installed.

5. The adjustable gas valve of claim 1, wherein the adjustment valve member is situated outside of the head-receiving portion of the gas block.

6. The adjustable gas valve of claim 1, wherein the valve stem portion is adjustable between fully open and fully closed positions.

7. The adjustable gas valve of claim 5, wherein the adjustment valve member includes a head portion for hand adjustment thereof, the head portion including a circumferential series of notches at a periphery thereof, and further comprising a spring latch mounted on the valve body to engage at least one notch to prevent rotation of the adjustment valve member until released.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Like reference numerals are used to indicate like parts throughout the various drawing figures, wherein:

[0010] FIG. 1 is a fragmentary isometric view showing relevant parts of a prior art AK-pattern firearm gas operating system;

[0011] FIG. 2 is an exploded view thereof;

[0012] FIG. 3 is a fragmentary isometric view of an adjustable gas regulating valve assembled on the gas block of an AK-pattern firearm gas operating system;

[0013] FIG. 4 is a longitudinal sectional view thereof; and

[0014] FIG. 5 is a similar view showing the gas block and gas tube in phantom.

DETAILED DESCRIPTION

[0015] With reference to the drawing figures, this section describes particular embodiments and their detailed construction and operation. Throughout the specification, reference to one embodiment, an embodiment, or some embodiments means that a particular described feature, structure, or characteristic may be included in at least one embodiment. Thus, appearances of the phrases in one embodiment, in an embodiment, or in some embodiments in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the described features, structures, and characteristics may be combined in any suitable manner in one or more embodiments. In view of the disclosure herein, those skilled in the art will recognize that the various embodiments can be practiced without one or more of the specific details or with other methods, components, materials, or the like. In some instances, well-known structures, materials, or operations are not shown or not described in detail to avoid obscuring aspects of the embodiments. Forward will indicate the direction of the muzzle and the direction in which projectiles are fired, while rearward will indicate the opposite direction. Lateral or transverse indicates a side-to-side direction generally perpendicular to the axis of the barrel. Although firearms may be used in any orientation, left and right will generally indicate the sides according to the user's orientation, top or up will be the upward direction when the firearm is gripped in the ordinary manner.

[0016] Referring first to FIGS. 3-5, therein is shown an adjustable gas regulator 30 according to one embodiment of the present invention installed in the gas operating system of an AK-pattern firearm. The structure and function of the gas block 10, barrel 12, gas port 16, and gas passageway 18 described above remain unchanged. The regulator 30 includes a body 32 with an internal gas flow passageway 34 that operably communicates with the gas passageway 18 of the gas block 10. The body 32 includes a portion that fits closely into the cylindrical chamber 24 of the gas block 10, where the piston head 22 of a prior art gas piston 20 would ordinarily rest. Another portion of the regulator body 32 extends outwardly beyond the cylindrical chamber 24. This portion includes a threaded bore 36 configured to adjustably receive a threaded valve member 38. The threaded bore 36 is configured to intersect the gas passageway 34 of the body 32 so the valve member 38 may be adjusted between positions where the passageway 34 is completely closed, completely open, or at any number of positions in between where the gas passageway 34 is partially restricted. The body 32 may also include a leg portion 40 configured to rest against the barrel 12 and support the regulator 30 when installed in the gas block 10.

[0017] Various mechanisms may be used to retain the valve member 38 at a preselected adjustment position. In the illustrated embodiment, a detent spring 42 is mounted on a lateral extension of the body 32 with ends pivotally engaged in offset openings 44. This configuration allows the detent spring 42 to be manually pivoted to the side, causing temporary flexing of the spring's legs. Release of the manual deflection causes the detent spring 42 to return to its at rest position (as shown), bearing against a peripheral edge 46 of an enlarged head portion 48 of the treaded valve member 38. Rotation of the head portion 48 causes axial movement of the valve member 38. Detent engagement between the detent spring 42 and notches in the peripheral edge 46 of the head portion 48 releasably hold the valve member 38 in a selected position.

[0018] Because the gas regulator 30 extends outwardly behind the gas block 10, a shortened gas piston member 20a and shortened gas tube 28a are used in place of the corresponding original parts 20, 28. A forward end of the gas tube 28a engages the body 32 of the gas regulator 30, much like the original gas tube 28 engaged the gas block 10. Likewise, the head portion 22a of the piston 20a seats against an outlet opening 50 that is on a rear face of the body 32, downstream of the valve member 38. The head portion 22a may seat directly against the outlet opening 50 in the body 32, guided by the gas tube 28a. The replacement gas piston 20a includes a connector portion 26 mimicking that of the original gas piston 20 for connection to a forward extension of the bolt carrier (not shown). If desired, the gas tube 28a may include an internal shoulder 52 and a compression spring 53 can be inserted between the internal shoulder 52 and head portion 22a to bias the piston 28a toward the forward, in-battery position. If desired, the replacement piston 20a may be constructed with the head portion 22a and connector portion 26 as separate parts (as depicted in FIG. 4). This allows the head portion 22a to be returned forward by the spring 53 separate from the connector portion 26, which moves with the bolt carrier (not shown).

[0019] In operation, expanding propellant gases flow from the bore 14 of the barrel 12, through the gas port 16 and gas passageway 18 of the gas block, as before. With the adjustable gas regulator 30 of the present invention installed in the cylindrical chamber 24 of the gas block, propellant gasses now flow through the internal passageway 34, regulated by placement of the threaded valve member 38, before impinging on the head portion 22a of the gas piston 20a to displace it rearward, cycling the bolt carrier.

[0020] An adjustable gas regulator 30 of the present invention may be installed in an existing AK-pattern firearm without replacement or removal of the gas block 10 from the barrel 12. Instead only the original gas piston 20 and gas tube 28 are replaced, along with insertion of the gas regulator unit 30. The regulator 30 is accessible for operator adjustment without further modification to the AK-pattern firearm because it is situated forward of the handguard and handguard ferrule at a position where a forward portion of the original gas tube 28 would otherwise be exposed.

[0021] While one or more embodiments of the present invention 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. Therefore, the foregoing is intended only to be illustrative of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not intended to limit the invention to the exact construction and operation shown and described. Accordingly, all suitable modifications and equivalents may be included and considered to fall within the scope of the invention, defined by the following claim or claims.