Ordnance – Fuse setters – Combined with projecting – launching or releasing devices
Reexamination Certificate
1999-04-29
2001-01-23
Eldred, J. Woodrow (Department: 3644)
Ordnance
Fuse setters
Combined with projecting, launching or releasing devices
C089S006000, C102S215000
Reexamination Certificate
active
06176168
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an improved transmitter coil of a fuze setter and improved fuze setter circuitry for adaptively tuning the circuit for resonance and current difference circuitry for interpreting a fuze talkback message.
Inductive fuze setters are well known in the art. U.S. Pat. No. 5,343,795, entitled “Settable Electronic Fuzing System For Cannon Ammunition”, issued Sep. 6, 1994 to General Electric Co. is directed to one such system. The entire contents of U.S. Pat. No. 5,343,795 are hereby incorporated by reference. Inductive fuze setters are used to transmit detonation data to a projectile warhead, such as time-of-flight or turns-to-burst data, as is well known in the art. Rapid-fire canons can have a fire rate ranging from 10 rounds per minute to 10 rounds per second or greater, and therefore it is very important to be able to quickly transmit data to a projectile as it is moving from a magazine to the cannon. Moreover, it is extremely important to verify that the projectile has correctly received the transmitted data.
NATO has a standard STANAG 4369 and the AOP-22 which govern the communications between a fuze setter and a fuze. This specifies a 100 KHz carrier signal which is pulse width modulated (PWM) for the forward message, which transmits the detonation data to the projectile and pulse code modulated (PCM) for the reverse or talkback message, in which the faze confirms the transmitted data.
As is well known in the art, the magnetic interface between the fuze setter and the fuze must allow energy transfer to “charge” the fuze circuit as well as be sensitive enough to detect and interpret the talkback signal transmitted by the fuze circuit with the power available from the “charge” portion of the communication from the fuze setter.
The prior art detected and interpreted the talkback message by detecting the phase change that occurs between the fuze setter circuit voltage and current during talkback, as the fuze is modulating the fuze coil impedance. However, this method suffers from the problem of a loss of signal when the LC circuit of the fuze setter is at resonance due to a null in the phase response. In order to work properly the system must be tuned a little off of resonance to be near the maximum power transfer of resonance, but to also be away from the null point. A small change in the inductive fuze setter parameters, such as a drift in capacitance values or inductance values caused by temperature variations can shift the operating point back to resonance, resulting in a null and loss of phase response, so that no talkback message can be interpreted.
BRIEF SUMMARY OF THE INVENTION
The inventive transmitter coil utilizes an “L” shaped coil cross section, with the wrapped coil portion being at right angles to the return coil portion, in order to increase the coupling efficiency between the fuze setter coil and the fuze receiver coil, as compared to the prior art “C” coil. The inventive “L” shaped cross section also eliminates counter magnetic field due to the return coil portion being at right angles to the wrapped coil portion.
The inventive fuze setter includes a controller which is conductively connected to a transmitter and a receiver, the transmitter and receiver each being conductively connected to a first inductive coil, the first inductive coil being part of a resonant LC circuit. The electronic fuze is incorporated into a projectile and includes a second inductive coil in an inductively coupled relationship with the first inductive coil, the fuze including circuitry for sending a talkback message back to the controller using the second inductive coil, the talkback message confirming data sent by the transmitter to the electronic fuze using the first inductive coil. The fuze setter further includes circuitry for adaptively tuning the resonant LC circuit for resonance by adjusting the capacitance in the LC circuit to maximize current in the LC circuit. The inventive fuze setter utilizes a switched capacitor network circuit to tune the LC circuit for resonance. The forward message is transmitted by pulse width modulating a 100 KHz carrier signal and the reverse message is transmitted by pulse code modulating the 100 KHz carrier signal
The fuze pulse code modulates the 100 KHz carrier signal by modulating its impedance, by “shorting” its inductance, which the circuit accomplishes by using a transisitor switch. The modulated impedance of the fuze circuit results in changes in the current in the resonant LC circuit of the fuze setter which are detected and interpreted by the fuze setter circuit.
The current difference in the fuze setter circuit is at a maximum at resonance, unlike the prior art phase change. This eliminates the problems of losing the talkback signal due to a null point. Adaptively tuning the fuze setter circuit for each projectile also eliminates any problems due to aging circuitry or temperature variations by ensuring the maximum signal detection for detecting and interpreting the talkback message.
The inventive system also utilizes a positioning mechanism, which is comprised of two proximity sensors and a vertical stepper motor driven linear cylinder for vertical motion and a solenoid with guide rods for horizontal motion. The positioning mechanism positions the fuze setter so that each projectile is inductively coupled with the fuze setter as the projectile moves from the magazine to the cannon. The positioning mechanism allows the fuze setter to maintain a fire rate of at least 10 rounds per minute and handle projectiles up to 1000 mm.
REFERENCES:
patent: 4144815 (1979-03-01), Cumming et al.
patent: 4649796 (1987-03-01), Schmidt
patent: 5113766 (1992-05-01), Grosch
patent: 5117732 (1992-06-01), Munzel et al.
patent: 5117733 (1992-06-01), Fischer et al.
patent: 5343795 (1994-09-01), Ziemba et al.
patent: 5497704 (1996-03-01), Kurschner et al.
Humbert Randy E.
Keil Robert E.
Alliant Techsystems Inc.
Eldred J. Woodrow
Vidas, Arrett & Steinkraus PA
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