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  Hydraulic bolt buffer for firearmUSPTO Application #: 20060236853Title: Hydraulic bolt buffer for firearm Abstract: A hydraulic bolt buffer assembly for an automatic firearm, the firearm including a receiver having a longitudinal chamber, a bolt and carrier assembly mounted in the chamber for reciprocating movement between a recoil position and a battery position, a spring for urging the buffer into contact with the bolt and carrier assembly for movement therewith and for biasing said bolt and carrier assembly toward the battery position. The buffer assembly includes a housing having an inner cavity, as well as a piston disposed within the inner cavity of the housing that is movable between an extended position and a depressed position, the piston being in contact with the bolt and carrier assembly. The buffer further includes a spring for biasing the piston in the extended position, as well as a bearing member in fixed relation in the housing and permitting a fluid tight seal with the interior of the buffer housing. The bearing further includes a cavity for retaining an accumulator disposed in a fluid chamber and in which movement of the piston based on movement of the bolt and carrier assembly causes hydraulic fluid contained in a first fluid chamber of said cavity to be moved to a second fluid chamber of said cavity containing the accumulator to slow the firing rate of the firearm. (end of abstract)
Agent: Wall Marjama & Bilinski - Syracuse, NY, US Inventors: Timothy J. Boersching, Brian C. Bucholtz USPTO Applicaton #: 20060236853 - Class: 089198000 (USPTO) Related Patent Categories: Ordnance, Automatic, Buffers And Brakes The Patent Description & Claims data below is from USPTO Patent Application 20060236853. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The invention relates in general to firearms capable of automatic or semi-automatic operation, and in particular to a buffer for reducing or slowing the cyclic rate of firing for such firearms. BACKGROUND OF THE INVENTION [0002] Firearms that are capable of automatic or semi-automatic operation, such as the M-16 rifle, are replete and extremely well known. Accuracy using such firearms is not successful unless the firearm is fired in short bursts due to the recoil of successive rounds causing the barrel of the firearm to climb upwardly and to the right, for the right handed shooter. The M-16 rifle, for example, fires at a cyclic rate of approximately 750 rounds per minute (RPM) wherein this rate, as combined with the impulse produced by a 5.56 mm cartridge makes it difficult for the shooter of such a firearm to consistently produce a controlled pattern of shots. [0003] There have been numerous attempts that have been made to reduce the cyclic rate of fire of automatic and semi-automatic firearms, using a buffer assembly, wherein the recoil force is stored by the action or operating spring of the firearm and the bolt is returned from the recoil position to the battery position. For example, U.S. Pat. No. 3,977,296 describes a typical hydraulic buffer assembly used for decreasing the cyclic firing rate. According to the design of the '296 buffer assembly, the bolt carrier, bolt and the buffer are each accelerated rearward from the battery position when the automatic firearm is fired. Each of the bolt, bolt carrier and the buffer are moved in unison toward the recoil position against the action or operating spring of the firearm. An elastomeric bumper provided on the end of the buffer contacts the end wall of the receiver extension. At this point, the buffer compresses and forces hydraulic fluid contained within the buffer through an orifice provided in a cylinder, thereby creating a resisting force. This resisting force decelerates the bolt as well as the bolt carrier, thus extending the recoil period. Furthermore and during counter-recoil (e.g., return of the bolt/bolt carrier assembly and buffer to the firing position), there is less rebound energy from the end of the recoil stroke such that the buffer/bolt are returned at a slower rate, which further delays the return of each of the assemblies back to the battery position. This delay thereby results in a slower firing rate of the firearm. Upon return to the battery position, the buffer also absorbs some of the kinetic energy of the bolt and the bolt carrier as they stop on the breech end of the barrel, such that these elements do not "bounce" off the breech end of the barrel. [0004] There are a number of problems noted with regard to the above-described buffer design. First, the '296 buffer relies upon the use of dynamic seals. Dynamic seals, however, are more prone to leakage than static seals. The design of the above described '296 buffer includes a pair of dynamic seals, each of which create a potential leakage path. Hydraulic fluid loss can result in degraded performance. The internal spring of the '296 buffer continually acts upon the damping fluid, which in turn acts to hydraulically extend the piston rod. If the buffer unit leaks enough fluid, the piston will be compressed by the action spring thus reducing or eliminating the stroke in the buffer. The buffer would then merely act as a single mass only within the gun recoil system--which may only marginally reduce the firing rate and perhaps no longer reduce the condition known colloquially as "bolt bounce" from occurring. Bolt bounce has the potential for stopping the automatic firing sequence before the operator has the intention to do so. [0005] In addition, the seals that are used in the '296 design are simple O-rings, each sealing dynamically upon an internal diameter bore, upon which can be difficult to obtain a smooth, hard, defect-free surface finish. This form of seal is prone to "weeping", and is also more prone to rolling or twisting within its groove--the latter also leading to potential leakage. The '296 buffer design further relies upon a spring--loaded accumulator to provide a force that is sufficiently high enough to exceed the preload of the action spring of the firearm and thereby maintain the piston rod in the extended position. This form of accumulator provides a positive internal pressure within the buffer at all times. This pressure further acts to force the hydraulic fluid out of the buffer at all times. [0006] Furthermore, the above-described '296 hydraulic buffer has four (4) separate stroke lengths that require size considerations in the placement of same in the firearm and making application of this design difficult in guns having shorter stocks. A buffer, such as the above-described '296 design, further includes the elastomeric plug or bumper which holds the spring in place, which in turn loads the sliding seal separator. If this plug or bumper were to loosen even partially, the function of the buffer would degrade. SUMMARY OF THE INVENTION [0007] According to one aspect of the present invention, there is described a hydraulic bolt buffer assembly for an automatic firearm, said automatic firearm including a receiver having a longitudinal chamber, a bolt and carrier assembly mounted in said longitudinal chamber for reciprocating movement between a recoil position and a battery position, a spring for urging the buffer into contact with the bolt and carrier assembly for movement therewith and for biasing said bolt and carrier assembly toward the battery position, said buffer assembly comprising: a housing having an inner cavity; a piston disposed within the inner cavity of said housing and movable between an extended position and a depressed position, said piston being in contact with said bolt and carrier assembly; a spring disposed within the inner cavity of said housing, said spring biasing said piston in said extended position; and a bearing member in fixed relation in said housing cavity, said bearing including means for providing a fluid-tight seal in said inner cavity and further including a cavity for retaining a compressible foam material contained in a variable fluid chamber. [0008] According to one version, a hydraulic fluid is contained within the inner cavity of the housing wherein the piston causes the fluid to move between a first variable volume fluid chamber and a second variable volume fluid chamber as the piston is moved therethrough, the compressible foam material being contained in the second variable fluid chamber such that hydraulic fluid is caused to compress the foam material when the firearm reaches the recoil position. As the piston is extended under the bias of the contained spring within the buffer and as the bolt and carrier assembly is moved towards the battery position, the hydraulic fluid is again moved from the second variable fluid chamber to the first variable fluid chamber, decompressing the foam material. [0009] According to one version, an elastomeric bumper is also disposed on an opposing end of the buffer relative to the piston, the bumper being configured to engage the operating spring of the firearm. The bumper is fitted to the end of the buffer housing covering a fill plug which is used to fill the inner cavity with hydraulic fluid. [0010] An advantage of the present invention is that the herein described buffer assembly only requires a single dynamic seal provided on the piston rod. Therefore, the number of potential leak paths is significantly reduced from previously known designs. [0011] In addition, the herein described buffer design utilizes a U-cup type seal, sealing upon a hard plated shaft, which can be easily ground and plated in order to obtain a smooth, hard running surface for the rod seal lip. The U-cup type seal is also less prone to twisting, rolling, and weeping due to its geometry. [0012] Another advantage of the present buffer design is the use of a closed cell-foam accumulator which provides only a positive pressure in the buffer assembly when the piston rod is compressed or when the buffer assembly becomes hot. While the piston assembly is extended and the buffer is at room temperature, the internal pressure of the buffer is at atmospheric pressure, thus there is no pressure that is attempting to force the hydraulic fluid from the buffer the majority of the time. [0013] Advantageously, the new buffer design has an elastomeric plug or bumper which is installed in a blind cavity at the end of the buffer housing. If the bumper were to dislodge partially, the buffer will still properly function because the bumper is not influencing other portions of the damper. [0014] Another advantage of the present buffer design is that the herein described assembly is more fail-safe in the event the buffer should wear out and leak hydraulic fluid. A buffer assembly made in accordance with the present design having no hydraulic fluid contained within the inner cavity will still stroke because the spring acts directly upon the piston rod and is thus independent of hydraulic damping. Due to this continuation of the stroke action, the buffer will still continue to function as an inertial spring-mass buffer (i.e., inertia of internal components) to help reduce cycle rate and bolt bounce. [0015] Another advantage of the present design is the buffer can be designed to fit in firearms having shorter or collapsible stocks due to the more efficient use of space. The present design incorporates the buffer's stroke in two areas as opposed to 4 areas in previous designs. [0016] These and other features and advantages will be readily apparent from the following Detailed Description which should be read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a perspective view of a hydraulic bolt buffer assembly in accordance with an embodiment of the present invention; [0018] FIG. 2 is a side view of the hydraulic bolt buffer assembly of FIG. 1; [0019] FIG. 3 is a side sectional view of the hydraulic bolt buffer assembly of FIGS. 1 and 2, taken in a recoil position thereof; [0020] FIG. 4 is the side sectional view of the buffer assembly of FIG. 3, taken in a battery position thereof; Continue reading... Full patent description for Hydraulic bolt buffer for firearm Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Hydraulic bolt buffer for firearm patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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