Ordnance – Accelerating
Reexamination Certificate
1998-12-18
2001-02-13
Johnson, Stephen M. (Department: 3641)
Ordnance
Accelerating
C102S472000, C042S084000
Reexamination Certificate
active
06186040
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 197 57 443,2 filed Dec. 23, 1997, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a plasma burning device for electrothermal and electrothermal/chemical gun systems. The device has a high-voltage electrode which passes perpendicularly through a bottom zone of a container (case) accommodating the plasma material. The high-voltage electrode and the gun tube which functions as a counter electrode, are connected to a high-voltage source. The high-voltage electrode has an energy supply bar (current conductor bar) provided with an insulation.
U.S Pat. No. 5,287,791 discloses a precision generator for an electrothermal/chemical gun system, having an anode and a cathode for igniting the plasma. A thin wire disposed in the plasma channel electrically connects the anode and the cathode with one another. Upon applying a high voltage, the wire is combusted, whereby an arc is generated which ignites a propellant charge for launching a projectile.
U.S. Pat. No 5,355,764 likewise discloses a plasma generator for an electrothermal/chemical gun. The generator disclosed therein has an anode and a cathode as well as a thin metal wire therebetween within a plasma channel for igniting the plasma.
It is a disadvantage of both above-outlined conventional generators that long insulating paths are necessary to prevent an arc discharge from the high-voltage side (anode) to the grounded gun tube.
An annular plasma injector for an electrothermal/chemical driving system is described in U.S. Pat. No. 5,503,081. In one of the embodiments, a grounded cathode is electrically connected by an igniting wire externally of the plasma chamber with a high-voltage side. The igniting wire has the function of generating an arc. The element serving as the igniting wire is disposed in the fuel chambers, and the ground side is grounded via the gun tube. The element serving as the igniting wire is separated from the plasma by an insulating sleeve. If the intensity of current passing through the igniting wire is sufficiently high, the element is evaporated and supplies for the plasma the fuel mass contained in the element.
German Offenlegungsschrift No. 196 17 895 discloses a plasma injection device for electrothermal guns, having a multipart propellant case through which only one electrode passes; the second electrode is constituted by the grounded gun tube.
Because of the expansion of an arc between the inner electrode and the gun tube and the accompanying phenomenon, according to which the generated gas streams and arc root-points are driven into the gun tube, significant corrosion appears in the conical zone of the breech zone and occasionally also in the muzzle zone of the gun tube.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved plasma burning device of the above-outlined type in which corrosion phenomena in the conical zone of a gun tube breech are prevented or at least minimized.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the plasma burning device for an electrothermal/chemical gun system includes a case having a bottom and an interior; a plasma material accommodated in the interior; and a high-voltage electrode passing through the case bottom into the case interior. The high-voltage electrode is adapted to cooperate with a gun tube acting as a counter electrode for generating an arc to combust the plasma material. The high-voltage electrode includes a conductor bar adapted to be coupled to a high-voltage source; an insulation surrounding the conductor bar; a conductor sleeve electrically connected to an end of the conductor bar and extending towards the case bottom along a length portion of the conductor bar. The conductor sleeve surrounds the insulation and the conductor bar and has a non-insulated outer surface. Further, an insulating cap is provided which covers the end of the conductor bar.
According to the basic principle of the invention, a magnetic field which builds up in the gun tube is utilized in such a manner that the arc needed for a proper functioning of the plasma burner remains in the rearward zone of the gun breech. For this purpose the high-voltage electrode is so configured that the arc which is generated between the high-voltage electrode and the gun tube acting as the second electrode, is driven in the rearward direction of the gun tube by the magnetic field which builds up in a non-insulated region of the high-voltage electrode. During this occurrence the arc acts on the end face of the propellant which may be flat powder grains or compressed powder disks, causing combustion or vaporization in a direction opposite to the propellant gas flow.
According to the invention the high-voltage electrode has an inner conductor bar which delivers electric energy and which is surrounded by an insulation. The conductor bar is adjoined at its end by a non-insulated conductor sleeve which surrounds the insulation. Thus, the high-voltage electrode has along its terminal length portion a larger circumference than along its remaining length portion The end face of the high-voltage electrode which is oriented towards the muzzle of the weapon tube (that is, oriented away from the case bottom) is capped with an additional insulation.
According to an advantageous feature of the invention, the outer surface of the conductor sleeve is slotted. As a result, the arc rotates about the high-voltage electrode and thus ensures a homogenous combustion or evaporation of the propellant. If, in addition, the non-insulated conductor sleeve conically tapers from the free end of the high-voltage electrode in the direction of the case bottom, the arc may expand in a loop-like manner about the high-voltage electrode, whereby the arc moves more rapidly Such a phenomenon is also of advantage for the ignition, because at the beginning of the plasma ignition the arc is driven in the desired direction. By virtue of the configuration of the high-voltage electrode according to the invention, propellant powder which in prior art plasma burning devices is, as a rule, constituted by cylindrical parts, may be disk-shaped grains or plates, whereby a higher packing density and thus a higher energy conversion is achievable. The electrode configuration according to the invention ensures that the arc effects combustion on the disk surface of the powder propellant uniformly and efficiently. As a result, a higher acceleration of the projectile out of the gun tube is achieved
If a metal cartridge is used, the latter may function as the second electrode, in which case it is electrically connected with the gun tube When a propellant case made of plastic, such as Durostone or PMNA, is used, the electrode configuration according to the invention drives the arc to the plasma and only thereafter reaches the inner breech wall functioning as the counter electrode.
Damages caused by erosions and ablations are minimized in the conical region of the gun tube breech by the particular configuration of the high-voltage electrode according to the invention.
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Haak Hans Karl
Weise Thomas
Wisken Holger
Johnson Stephen M.
Kelemen Gabor J.
TZN Forschungs- und Entwicklungs-zentrum
Venable
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