The present invention deals generally with firearms. More particularly, it deals with noise and flash suppressors for firearm muzzles.
Reducing muzzle noise and flash from military and security personnel firearms (e.g., long guns and pistols) provide a significant tactical advantage in the field. Existing suppression technology reduces noise and flash, but comparatively little science exists to explain how current designs can be modified or replaced to provide enhanced suppressor performance, including the useful life span of the suppressor. Furthermore, even less design guidance exists that can lead to integration of suppressors into a firearm's barrel assembly. Lessons learned as a result of the ongoing military and homeland security based conflicts have indicated that increased use of current suppressors, as part of everyday operations, have led to shortened life cycles of suppressors, increased maintenance (and sometimes damage) of weapons, and considerable variability in weapon accuracy.
To set the stage for developing improved suppressors, it is necessary first to identify the critical elements of the attendant flow fields as thoroughly documented in Klingenberg, Firearmter and Heimerl, Joseph M., Firearm Muzzle Blast and Flash, AIAA Progress in Astronautics and Aeronautics, Volume 139, 1992.
These characteristics can be broken down into three core elements. The first two core elements are: the precursor blast; and a main blast set up by the expanding gases. The precursor blast consists of mostly air with a small amount of propellant and the main blast is made up of spherical pressure waves that quickly overtake the fired projectile. Both of these blasts are sources of low frequency noise that carry very far distances. The third core element is the highly visible gas flash which follows the blast.
In general, a gas flash occurs because air mixes with the fuel rich propellants and the high temperatures from the blast waves. The result of this mixture forms a gas flash which is greatly increased in the secondary flow region that occurs away from the muzzle of a firearm.
When a gas flash forms, it occurs in three parts: primary, intermediate, and secondary flashes. The primary flash forms at the muzzle in the supersonic flow region and is very small. An intermediate flash occurs directly behind the projectile, but in front of the Mach disk leading any supersonic flow region. (Not all firearms have supersonic discharge flows.) The secondary flash is the most severe, and it occurs downstream of the firearm muzzle, and after the normal shock resulting from the muzzle gas over-expansion. The large flash seen when firing a projectile is actually the secondary flash.
With an understanding of the three core elements involved in the blast and flash from a projectile, the individual components can be analyzed to assess their critical components. Considering the principal characteristics of the blast wave, Applicants have found that it is essentially a spherical blast wave that travels rapidly but also decays rapidly both strength-wise and time/distance-wise. Relative to the flow-field attendant to the flash, it establishes after or behind the main blast wave with a structure very similar to that of a traditional under-expanded jet plume often seen in propulsion applications. The key elements of the post-blast wave flow field are the free jet boundary and the highly under-expanded jet flow region all flowing strongly in the downstream axial direction. The over-expanded gas results in the normal shock or Mach disk, which causes the secondary flash and a significant portion of the noise. The important point is that the key physics of this type of flow structure is common in propulsion aerodynamics, and can be used to generate performance correlations for use in developing more efficient suppressor designs.
There are a wide range of firearm suppressor designs. See, for example, the Prior Art shown in Applicants'
An alternate means of controlling supersonic flows, originally developed for propulsion applications, involves the use of flow mixer-ejectors, as discussed in U.S. Pat. No. 5,884,472 to Walter M Presz, Jr. and Gary Reynolds. Ejectors are well-known and documented fluid jet pumps that draw flow into a system and thereby increase the flow rate through that system. Mixer/ejectors are short compact versions of such jet pumps that are relatively insensitive to incoming flow conditions and have been used extensively in high-speed jet propulsion applications involving flow velocities near or above the speed of sound. See, for example, U.S. Pat. No. 5,761,900 to Walter M. Presz, Jr., which also uses a mixer downstream of a gas turbine nozzle to increase thrust while reducing noise from the discharge. Dr. Presz is a co-inventor in the present application. An ejector is a fluid dynamic pump with no moving parts.
Ejectors use viscous forces to lower the velocity and energy of a jet stream by ingesting lower energy flow which can lead to flow characteristics that may augment thrust, cool exhaust gases, suppress jet infrared signature, and importantly to ballistic applications, reduce attendant noise and flash. Mixers improve the performance characteristics of ejectors by inducing stirring, or axial vortices, that promote rapid mixing of the high velocity primary jet with the cooler, and sometimes heavier, ingested gas; thus resulting in more compact devices. Numerous patented products have derived from this concept. The mixer/ejector concept is well accepted within the aviation and jet propulsion community as an extremely efficient solution to aircraft noise and exhaust temperature suppression.
Gas turbine technology has yet to be applied successfully to firearm muzzle suppressors. If one were to replace an under-expanded jet engine exhaust for a ballistic blast from a firearm, in which hot gases are mixed and expelled with a projectile over the length of the barrel, it may be seen that such a technology could significantly reduce noise, flash, and provide outside air to the barrel that could be employed to cool and clean the suppressor components.
Accordingly, it is a primary objective of the present invention to provide a firearm suppressor that employs advanced fluid dynamic ejector pump principles to consistently deliver levels of noise and flash suppressor equal to or better than current suppressors.
It is another primary objective to provide an improved firearm suppressor with significantly increased useful life span over that of current firearm suppressors.
It is another primary objective to provide a self-cleaning, self-cooling firearm suppressor using mixer/ejector technology.
It is another primary objective to provide an improved firearm suppressor using mixer/ejector technology to control the muzzle blast wave and overexpansion flow for better suppression.
It is another object, commensurate with the above-listed objects, to provide an improved suppressor which is durable and safe to use.
Applicants have developed an improved firearm suppressor through the use of advanced mixer/ejector concepts. By recognizing and analyzing the blast and plume characteristics, inherent in ballistic discharges, Applicants have created a new two-step controlled unaided surge and purge system (nicknamed “CUSPS”) for firearm suppressors.
This new CUSPS approach attends to the blast surge effects by controlling the flow expansion into the suppressor, and attends to the flash effects by controlling inflow and outflow gas purging. The CUSPS suppressor rapidly reduces the pressure energy associated with a firearm muzzle blast before it exits the suppressor, thereby reducing noise and muzzle flash. The blast surge is mitigated through a rapid, divergent nozzle volume increase and thereafter through a series of vent holes strategically located around the suppressor outer wall. Applicants anticipate the noise frequency spectrum of the blast will be controllable through careful design of the hole contours, size and placement. The vent holes preferably converge towards the outside of the CUSPS. Alternatively, the holes could be contoured with divergent or convergent/divergent area distributions.
Following this, air is ingested inward through the same holes, mixed with the muzzle gases and purged axially through the exit port and vent holes. Preferably a two-stage supersonic mixer/ejector is used in the CUSPS suppressor to control or eliminate the Mach disk, while rapidly mixing and diluting the propellant with ambient air.
Based upon preliminary testing, Applicants believe that their CUSPS suppressor will generate the following benefits: lower noise; hide or eliminates flash; integrate cooling and self-cleaning; maintain firearm accuracy at longer distances, and lessen the amount of powder residue inside barrels.
FIG. SB shows the same two-stage mixer/ejector system of
Referring to the drawings in detail,
In the preferred embodiment 100 (see
The preferred embodiment (see
Though not shown, the vent holes 104 are preferably convergent. They narrow towards the outside of the suppressor.
FIGS. SB and 8C depict additional embodiments of Applicants' CUSPS suppressor, in which:
While the preferred CUSPS has lobed internal nozzles 116, 117, it could instead have slotted rounded internal nozzles. Both types have divergent area distributions to minimize flow overexpansion and reduce noise and flash.
Tubular housing 102 need not be circular in cross section. Its major axis is preferably horizontal (i.e., co-axial with the firearm barrel 103, or alternatively vertical (not shown), or in between (not shown).
Experimental and analytical analyses of the preferred CUSPS embodiment 100 performed by the Applicants indicate: the CUSPS can reduce the noise induced by the firearm's muzzle blast wave, reduce the radiant flash caused by the propellant gases and ingest ambient an to both cool the suppressor and purge it of residual gases, thereby increasing its useful life span.
Based on their experimental and analytical results, and the observation that the vent holes permit easier flushing of the interior volume with cleaning fluids, the Applicants believe the preferred CUSPS embodiment 100 will reduce the blast wave induced noise at three feet from the muzzle exit by 20 db or more, make the gas flash visually undetectable to an observer at any distance greater than 1000 muzzle diameters, and have an indefinite useful lifetime if properly maintained.
In the preferred embodiment 100, the entrance and lobed nozzle 116 serves to control and reduce the static pressure of the gases exiting the muzzle while the vent holes 104 first dissipate the blast wave from the muzzle gases and thereafter ingest ambient air to purge, dilute and cool the residual gases. The ejector 117 lobes assist and amplify the air ingestion process, stir the ingested air into the muzzle gases to enhance their cooling and reduce the strength of the shock waves produced, which are further assisted by the convergent/divergent diffuser 127. Applicants believe their other disclosed embodiments will do the same.
The internal diameter of Applicants preferred suppressor housing 102 is between two and ten muzzle external diameters to accommodate the range of propellant gases used in the firearm. The CUSPS suppressor length is set between three and ten times its internal diameter to tailor its sound reduction to a desirable level.
Applicants have also presented, in
The placement, number and size of the vent holes 104 are established to assure sufficient dilution of the muzzle gases to reduce flash and purging of the residual gases.
The entrance divergent nozzle's exit diameter and length are established using classic gas dynamic principals to produce isentropic, or near isentropic, expansion of the muzzle gases into the suppressor.
The exit nozzle diameter and length are established using classic gas dynamic principals to produce isentropic, or near isentropic, expansion of the muzzle gases out of the suppressor.
The mixer lobes, slots, tabs or swirl vanes have longitudinal, azimuthal and/or radial dimensions approximately equal to the radial dimensions of the entrance nozzle exit diameter and the suppressor internal diameter.
The ejector diameter is set between that of the entrance nozzle exit diameter and the suppressor internal diameter.
While the preferred embodiments are detachable from a gun, they can be affixed, more permanently, to the barrel.
Each of Applicants embodiments can be thought of as a firearm suppressor comprising:
Each of Applicants' CUSPS embodiments also can be thought of in method terms. For example, a method for firearms, and other guns, comprising:
It should be understood by those skilled in the art that obvious structure modifications can be made without departing from the spirit or scope of the invention. For example, the same technique could be used for artillery or other guns.
This application claims priority from Applicants U.S. Provisional Patent Application, Ser. No. 29/317,238, filed Sep. 17, 2007 (hereinafter “Applicants' Provisional Application”). Applicants hereby incorporate the disclosure of Applicants' Provisional Application by reference.