A RING-LIKE NOZZLE INSIDE A FLASHTUBE
Patent No.: 9,249,759
Date of Patent: February 2, 2016
Inventors: DONALD S. CHIU (ARDEC), SANDOR L. EINSTEIN, ALEXANDER COLLETI (FORMER ARDEC EMPLOYEES)
PICATINNY ARSENAL, N.J. -- In recognition of their latest invention, one Picatinny Arsenal employee and two contractors recently were granted a U.S. patent. Their invention-- a ring-like nozzle placed in a flashtube--aims to increase the reliability of mortar ignition cartridges and thus improve the system's overall performance.
The patent holders are Donald S. Chiu, Sandor L. Einstein, and Alexander Coletti. Chiu is a chemical engineer at the U.S. Army Armament Research, Development and Engineering Center or ARDEC. Einstein and Coletti are former ARDEC employees who developed the concept during their Government employment.
Mortars are weapons that fire projectiles at low velocities and short ranges. They include ignition cartridges, which ultimately propel projectiles forward. Inside the cartridge, there is a flashtube, or tube-like compartment, that vents a bed of black powder pellets contained in the primer head. This tube is designed with small holes that vent combustion products, such as gas.
When the system's primer is ignited, it in turn ignites the black pellets, generating combustion products. The venting of the combustion products through the vent holes in the flashtube ignite the propellant in the ignition cartridge which starts the motion of the projectile through the gun's launch tube. If additional propellant is included on the mortar boom, it is ignited by the ignition cartridge.
Currently, though, the system's black pellets are consumed by the combustion process, shrinking their size and letting them travel freely in the flashtube. In doing so, the pellets are able to oscillate over the flashtube's holes, which cause pressure waves within the ignition cartridge and mortar tube combustion chamber. This can cause erratic performance as well as inaccurate trajectories and safety problems.
However, by adding this ring-like nozzle within the flashtube, the motion of black powder pellets is restrained. The flashtube is now separated into two compartments: a flashtube venting chamber and a pellet combustion chamber. Therefore, there are less pressure waves within the flashtube and the mortar's performance is more consistent, especially in terms of its velocity and the combustion of its black powdered pellets. Additionally, with the black powder pellets contained within the base of the flashtube, they burn at a higher pressure with more consistency.
When asked about lessons learned, Einstein said that the nozzle was inspired by reviewing acceptance data and realizing that by better controlling the combustion environment more reproducible results could be obtained.
He advised other engineers not to overlook such simple solutions.
"Sometimes simplicity is overlooked because of the power of computers," said Einstein. "But, complex problems are sometimes more easily solved as a series of simple solutions."
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The U.S. Army Armament Research, Development and Engineering Center is part of the U.S. Army Research, Development and Engineering Command, which has the mission to ensure decisive overmatch for unified land operations to empower the Army, the joint warfighter and our nation. RDECOM is a major subordinate command of the U.S. Army Materiel Command.
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