Ordnance – Automatic – Buffers and brakes
Reexamination Certificate
2001-06-11
2003-07-22
Johnson, Stephen M. (Department: 3641)
Ordnance
Automatic
Buffers and brakes
C089S007000, C089S194000, C089S162000, C089S177000, C089S178000
Reexamination Certificate
active
06595103
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the field of ballistics, and it particularly relates to recoilless gun systems such as the “Davis gun” system described in U.S. Pat. No. 1,108,714. More specifically, the present invention relates to a contained Davis gun system that enables misfire and hang-fire handling for fire out of battery, that decreases structural dynamic activity of the gun barrel during launch with resulting increases in system accuracy, that possesses an almost infinitely variable chamber volume and a potential for direct fire “zoning”, with a reduced system weight, and that presents synergistic advantages when combined with a conventional recoil system in a double recoil design.
BACKGROUND OF THE INVENTION
A “Davis gun” system is known where the propellant gas pressure is inertially contained. A projectile is fired toward the front and a compensating mass toward the rear from an equal-caliber barrel open on both ends. The axial forces are transmitted to the gun only by friction of the projectile and/or the compensating mass on the inner wall of the barrel; propellant gas forces in this case do not contribute toward recoil during firing, and the friction forces can be kept lower by several orders of magnitude than the propellant gas forces, while the friction forces of the projectile and of the compensating mass, at least in part, compensate each other. For this reason, the so-called “Davis gun” is an essentially recoilless gun.
Conventional gun systems still present some or all of the following concerns and none provided an integral, fully satisfactory solution to such concerns.
Conventional gun systems are awkward to operate in the fire out of battery mode. Fire out of battery is a technique to reduce the magnitude of the forces applied between the gun mount/platform and those parts of the gun that recoil during firing. It is achieved by pre-accelerating the recoiling gun mass forward, prior to firing. Thus, upon firing, the rearward momentum applied to the recoiling gun parts by the containment of the propellant gas pressure is directly offset by that portion imparted to the gun prior to firing. Theoretically, since half of the momentum may be applied prior to firing, the maximum speed of recoil may be cut exactly in half. Since the kinetic energy is related to the square of velocity and is achieved by the recoil forces applied over the available recoil stroke, the recoil forces may be theoretically cut by a factor of four. Conservation of momentum is achieved by increasing the duration of the recoil forces, again by a factor of four.
Two principal engineering challenges hinder the application of fire out of battery to conventional gun systems. First, in the event of a misfire, the forward momentum of the pre-accelerated recoiling gun parts is not reversed by the reaction of the gun to firing the projectile forward. As a consequence, the forward momentum and its associated kinetic energy must be extracted in a controlled fashion to prevent damage resulting from the impact of the gun against the gun mount as it reaches the end of the available recoil travel stroke. This requires a shock isolator termed a misfire snubber. Since fire out of battery is applied principally to attenuate the recoil forces (or reduce the required recoil stroke), the magnitude of the snubber loads are also generally limited. In the event the snubber loads are required not to exceed the same maximum loads as the pre-acceleration loads, it may be seen that kinetic energy imparted to the gun over the intended recoil stroke prior to firing will require exactly the same stroke length to safely decelerate the gun to a standstill in the event of a misfire. Thus half of the total available recoil stroke would have to be dedicated to misfire snubbing. Since the same kinetic energy is required to pre-accelerate to half of the forward momentum regardless of how misfire is addressed, it may be seen that under the assumptions made, the maximum recoil forces must be doubled relative to those of the theoretical minimum. Thus, relative to the standard fire in battery mode, the fire out of battery mode that incorporates such a misfire snubber may only cut recoil loads by a factor of two.
The second principal challenge that hinders the application of fire out of battery to conventional gun systems is hang fire. Hang fire is the delayed ignition of a round of ammunition and is relatively rare. The extreme situation of hang fire for a fire out of battery gun system would be the delay of shot start ignition until after the misfire snubber had brought the forward momentum of the gun system to rest; thus, in this context, a misfire is a necessary prerequisite to a hang fire, but only a few misfires become hang fires. When such a hang fire occurs, no forward momentum remains to offset the rearward momentum imparted to the gun system by its reaction to firing. Therefore, the recoiling gun mass may recoil with double the speed of the ideal fire out of battery design, and thus four times the kinetic energy. This dramatic increase in kinetic energy must be extracted using the integral of recoil force over recoil stroke. It is obvious that design of a conventional gun system to withstand hang fire is the exact same problem as the conventional fire in battery mode of operation, thus negating much of the impetuous for incorporating a fire out of battery design in the first place.
“Gun whip,” that is the motion of a gun barrel during in bore gun dynamics, can become excessive when the gun barrel itself recoils. This recoil acceleration of a traditional barrel is a significant contributor to the gun barrel dynamic flexure that results in increased round dispersion. In addition, the ability to increase the structural stability of conventional gun systems using external “truss like” structures to increase the flexural rigidity of the launch tube is hindered by concerns about the effects of recoil upon such structures. Furthermore, in the absence of such external structures high emphasis is placed upon the flexural rigidity of the gun barrel itself, therefore, the application of non-homogeneous manufacturing techniques, such as composite or wire wrapped guns are impeded.
The required flexural rigidity of Conventional gun systems impairs “fine tune” stabilization capability for enabling the gun muzzle to bend to the target. In the absence of recoil acceleration, most of the remaining gun dynamic loads associated with launch including centripetal acceleration of the projectile and gases increase as a function of the non-ideal curvature of the centerline of the gun barrel and the projectile velocity which is quite low near the breechblock end.
Conventional gun systems employ the integrity of steel to contain the rearward reaction force of the gun launch created by the internal pressures applied over the exposed breechblock area using stress developed as the breechblock material undergoes strain. They require a breech ring, breechblock, and threads applied to the rear of the gun barrel to contain the rearward force of the high pressure propellant gases, thus increasing the ultimate weight of the gun system.
Numerous attempts were proposed to address the foregoing concerns. One such attempt that aims at reducing the recoil forces associated with the reaction of a recoiling gun to firing is to increase the recoil stroke. Compared with the theoretical limit of implementation of the current invention, increasing the recoil stroke of any gun system by a factor of four may reduce the recoil force by a factor of four. Long recoil strokes are undesirable for a number of reasons for most applications. First, the longer the recoil stroke the more substantial and complicated the gun mount becomes. For turreted gun systems, the need to be able to point the gun at different elevations and azimuthal orientations results in a spherical sweep volume that increases with the cube of the distance between the furthest extent of recoil and the trunnion bearings. This sweep volume is very wasteful and requires substantial a
Johnson Stephen M.
Moran John F.
Sachs Michael C.
The United States of America as represented by the Secretary of
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