Patent Application
20100242773
Not Applicable
Not Applicable.
Not Applicable
1. Field of the Invention
This invention relates to the field of gas-propelled projectiles. More specifically, the invention comprises a marker flare projectile having an improved delay column ignition system
2. Description of the Related Art
Although the present invention can be configured to operate from a variety of different launchers, it was primarily developed to be fired from launchers adapted to fire 40 mm grenades (such as the U.S. Army's M433). The invention incorporates elements from a prior design reduced to practice by the same inventor. The prior design is disclosed and claimed in U.S. Pat. No. 7,004,074 to Van Stratum (2006), which is hereby expressly incorporated by reference.
Gas-propelled projectiles typically use solid propellant encapsulated in a cartridge case. A projectile is seated in the open mouth of the cartridge case. Ignition of the propellant is provided by percussive or electrical means. The burning propellant generates pressurized gas which forces the projectile out of the mouth of the case and then typically through a barrel bore.
This type of system is typically used to launch 40 mm grenades. The same approach can be used to launch other types of projectiles, however. An example of such a projectile is a marker flare. A marker flare projectile has a mass which is similar to that of a grenade round. Thus, the propulsion system developed for use with grenade rounds can be used to launch a marker flare. The incorporated U.S. Pat. No. 7,004,074 illustrates and describes an effective approach to the problem of launching large masses at low velocities. The '074 invention uses a high-pressure cartridge embedded within a low-pressure larger cartridge. A burst cup metering system is used to meter propellant gases from the high pressure cartridge into the low pressure cartridge, thereby accelerating the projectile in a smooth and controlled fashion. This approach helps to reduce the peak recoil loads experienced by a user. The high pressure found within the high pressure cartridge also ensures the reliable ignition and combustion of the propellant it contains.
The burst cup approach results in hot metered gases exiting the high pressure case in the direction of the mouth of the low pressure case. The present invention makes use of this phenomenon. In addition to propelling the marker flare down the bore of the firing weapon, the hot gases exiting the high pressure case are used to ignite a delay column in the aft end of the marker flare round.
The present invention is a modified marker flare round which is configured to function with a propellant cartridge such as described in U.S. Pat. No. 7,004,074.
When the high pressure cartridge is ignited, the solid propellant burns and hot propellant gases rupture the burst cup. The gases then shoot out through charge vent hole 52 (toward the mouth of low pressure cartridge 38). These propellant gases expel marker flare round 124 from the mouth of the low pressure cartridge and accelerate it down the bore of the weapon.
The hot propellant gases also impinge against the exposed aft end of delay carrier 96. The contents of the delay carrier are thereby ignited. The delay carrier includes one or more delay columns ultimately terminating in a flare igniter charge. The delay columns burn as the marker flare round is in flight. A specified amount of time later, the flare igniter charge ignites the flare itself (generally after the marker flare round has struck the earth and buried its nose cone in the ground). The flare's aft closure is detached from the balance of the round and the flare then burns brightly.
Cylindrical candle 88 is made of suitable flare material. It is housed within hollow cylindrical tube 86. Nose cap 18 covers the forward end of the candle. The nose cap is hollow, leaving a space between the nose cap and the forward end of the candle. This space is preferably filled by cushion 84, which is made of a low density foam.
The aft end of the candle is covered by aft closure 94. Aft closure 94 is connected to flare sleeve 90 by conventional means, such as a threaded engagement. Flare sleeve 90 is a hollow cylinder which slides over tube 86. The forward extreme of the flare sleeve engages with the aft extreme of nose cap 18 in a sliding fit (which will be explained in more detail subsequently).
The assembly of aft closure 94, candle 88, tube 86, flare sleeve 90, nose cap 18, and cushion 84 together makes up marker flare round 124. This assembly is expelled from the weapon upon firing, travels downrange, and strikes the target area. Thus, it must be able to withstand the substantial acceleration of the firing cycle as well as the impact with the target. It is therefore important to eliminate any open space within the projectile in order to prevent unwanted deformations. As an example, potting 92 is used to fill a gap existing between aft closure 94 and candle 88. The potting can be any suitable compound which transitions from a liquid to a solid in order to fill the volume.
The reader will note additional significant features of the marker flare round in
A variety of burstable covers can be used in high pressure cartridge 42, including a simple “wad” crimped into the cartridge's open mouth. However, a hollow hemispherical burst cup 40 is preferably used. This is retained within the high pressure cartridge by a suitable mechanical interference. The burst cup is preferably embossed with rupture lines so that it will burst in a predictable fashion.
Delay carrier 96 is aligned with high pressure cartridge 42 so that the propellant gases exiting the high pressure cartridge will strike the aft end of the delay carrier.
Igniter charge 98 is located within the internal passage proximate input opening 104. When the high pressure cartridge ignites, the hot propellant gases ignite igniter charge 98, which in turn ignites the adjacent delay column 100. Delay column 100 is a specialized type of combustible which takes a fixed amount of time to burn from one end to the other. Two or more such delay columns can be stacked within the passage inside the delay carrier in order to establish a set delay. When the last delay column burns through, it ignites flare igniter charge 102. The flare igniter charge is located proximate a surface of the flare candle, so its ignition actually starts the burning of the flare candle.
It is important that the delay carrier be firmly retained in the aft closure, so that it is not dislodged during the firing cycle. While many methods of securing the delay carrier can be used, one good approach is to peen or otherwise deform a portion of the aft closure into the delay carrier. This plastic deformation will create an interference fit which then securely retains the delay carrier in the aft closure.
The operation of the marker flare round will now be described, beginning with
It may take many seconds for the projectile to reach the target area and impact the ground. For most applications, it is desirable to light the flare after impact. As an example, two ten-second delay columns can be used to provide a twenty second delay between the ignition of the high pressure cartridge and the ignition of the flare. During this delay, the projectile flies through the air and strikes the ground in the target area.
In
Returning now to
Looking back at
Those skilled in the art will realize that the components thus described can be used to create a delayed ignition of many types of ignitable payloads in a projectile round. A marker flare candle is a common example of such an ignitable payload. However, the system described could be used to ignite an explosive payload as well. The explosive payload could be ignited while airborne (using a short delay in the delay carrier) or after it has landed in the target area (using a long delay in the delay carrier). The system could also be used to ignite a smoke-generating payload.
Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the preferred embodiment of the invention. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.
