Ignition Circuit For Projectile Fuses

Abstract

A projectile with an electrically ignitable fuse is provided with a control circuit in which piezo electric cells are provided which develop a potential upon acceleration of the projectile and then develop a reverse potential upon relaxing of the acceleration on the projectile when it emerges from the firing weapon. The piezo electric cells are serially arranged and connected thereacross is a pair of condensors, the juncture of which is fastened to the juncture of the cells with one capacitor charging during the acceleration period of the projectile and the other charging during the relaxing period. A resistor connected across the capacitors provides for reversing of the charge on the one capacitor and which reversing triggers a control circuit. The control circuit releases the charge from a third capacitor which is charged by one of the cells during the relaxing period thereby to ignite the fuse. An impact control source of voltage is also provided for igniting the fuse upon impact of the projectile.

Description

The present invention relates to an electronic projectile fuse which is provided with a source of voltage, a reloading circuit, and an electronic switch arranged between the voltage source and the ignition means, said electronic switch being adapted to be controlled by means of an impact switch and/or the reloading circuit. With a fuse of the above identified type, for instance, there is suggested between a first voltage source of a discharge circuit which voltage source is adapted to be charged with a definite charge during the firing, and a time element forming a reloading circuit, to provide a valve which through the intervention of an impact detector is pivotable into its switch-on position, and to connect to the outlet of the time element an ignition transfer element which only when reaching the minimum voltage required for switching through tilts into the turn-on position and discharges an ignition voltage source to the ignition means.

With the fuse of the above identified type, as structural element with a threshold value behavior, there is provided a four-layer diode. Four-layer diodes, however, have the property that for purposes of igniting they require not only a minimum voltage, but also a considerable ignition current. This requires a voltage source of a corresponding output.

It is, therefore, an object of the invention to provide an electronic fuse of the type disclosed which will have a low consumption of energy so that the charge required for controlling the circuits and for igniting the igniting means can be generated in a piezo electric or a magnetic generator which becomes effective during the firing.

It is a further object of this invention to provide an electronic fuse as set forth in the preceding paragraph, in which not only the impact ignition, but also automatic ignition controlled by a time member will operate safely.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, illustrating the essential portion of the fuse according to the present invention.

The view of the drawing illustrates an ignition circuit for projectile fuses having features in accordance with the present invention.

The electric projectile fuse according to the present invention is characterized primarily in that the reloading circuit which in the form of a time element is located between a voltage source and a control member of the electronic switch comprises two condensers which are adapted to be charged by opposite potentials and different magnitude of charge, and also comprises a reloading resistor which interconnects the voltage poles of said condensers, while the voltage pole of the condenser which is adapted to be charged by a lower blocking charge is connected to the control inlet of the switch or its control part, and while the control part is so designed that after the reversing of the poles of the condenser will open the switch only when a voltage of a predetermined magnitude is attained at the input, which voltage is opposite to the blocking voltage.

As voltage sources, piezo electric cells may be employed which are connected in such polarized condition and which through current direction-dependent elements communicate with the condensers of the reloading circuit, that the blocking charging condenser is adapted to be charged during the firing or acceleration phase, whereas the recharging condenser is adapted to be charged only in the relaxing phase.

By generating the blocking charge during the firing phase and the greater polarity reversing charge only in the relaxing phase, the mechanical and the retarding times caused by the reversing load circuit add to each other. As a result thereof, a sufficiently long delaying time is obtained up to the self-ignition regardless of small charge magnitude, but also an absolute safety is assured against an accidental premature switch actuation of the electronic switch as well as a better ignition after the expiration of the predetermined operating time.

Referring now to the drawing in detail, it will be noted that piezo electric ceramic cells K1 and K2 serve as voltage source, which cells become positive at their outer cover in the pressure phase at the central pole and during the relaxing phase at their outer cover. The charge of cell K1 as produced during the pressure phase, is short circuited through the intervention of a diode D2 or by a leakage resistance. The charge generated during the relaxing phase passes through a diode D4 to a condenser C1. The charge generated in cell K2 during the pressure phase, passes through a diode D1 to a condenser C2 which, in its turn, is in series with the condenser C1. The voltage poles of the condensers C1, C2, which voltage poles are connected to each other by a recharge resistor R1 first have an oppositely directed potential. A minus charge is applied to a joint A while a plus charge is applied to the joint B. By correspondingly dimensioning the piezo ceramic cells K1, K2 and/or by other means it will be assured that the charge at the condenser C1 is greater than that of the condenser C2. Additionally, as already mentioned, the charge at the condenser C1 is introduced later. The charge occurring on the cell K2 during the relaxing phase, is available as ignition charge. By means of this last mentioned charge, a condenser C3 is charged at least partially through the intervention of a diode D3. Arranged in parallel to the condenser C3 and the cell K2 and the diode D3 there is provided an electronic thyristor (switch Th), and furthermore in series with the switch Th is an ignition means Z, for instance, in the form of an electrically ignitable ignition cap.

The switch Th is adapted to be controlled through, on one hand, by a piezo abutment cell P having arranged thereto in parallel a resistor R3, and also having a diode D5 arranged in series thereto and on the other hand is adapted to be controlled through by a control element which comprises two transistors T1, T2 and a resistor R2.

Arranged in parallel to the condenser C2 is a zener diode ZD. In order to make sure that the condenser C2 after effected pole reversal over a resistor R1 will not automatically discharge itself through this zener diode, a further diode D6 is in series to the zener diode. During the firing operation, due to the occurring acceleration at the piezo ceramic cells K1 and K2 charges are brought about and more specifically plus charges at the central pole of the cells K1, K2 and condensers C1, C2. Through the intervention of the diode D1, the condenser C2 is charged in such a way that a minimum potential will prevail at the point A. The charge generated at K1 is passed through the diode D2 or a resistor. At the end of the acceleration phase, which means during the discharge of the cells K1, K2, the positive charge generated at the outer pole of the cell K2 flows off through the diode D3 to the ignition charge condenser C3 and remains in part at the cell K2. The condenser C1 is charged by cell K1 through the diode D4. At its point B a positive charge exists.

In view of the above mentioned sequence of the charging operation it will be assured that no faulty ignition can occur. First, in cell K2, the blocking boltage is generated and is fed into the condenser C2, and only then -- in the relaxing phase -- which means after the projectile has left the firing system, for instance, a weapon tube, will the ignition charge be generated in cell K2 and the pole reversing for the condenser C1 will be generated in cell K1. This charging sequence of the individual condensers C2, C3, C1 is thus of great importance for the function and safety of the fuse. The condensers C1 and C2 and the charges fed thereinto together with the recharging resistance R1 determine the time period up to the self-destruction. In view of the already mentioned smaller dimensioning of the piezo ceramic cell K2 relative to cell K1, the condenser C2 receives a smaller charge than the condenser C1 which, for instance, has the same capacity as the condenser C2. Through the recharging resistance, the charge on the condenser C2 is first equalized whereupon the point A moves into the positive range. When point A reaches the control voltage of the transistor T1 of, for instance, 0.6 volts, current will flow through T1. As a result thereof, also the transistor T2 opens. Both transistors are controlled as to transmission. The charge of the condenser C1 passes to the control inlet of the control thyristor Th. As a result thereof the thyristor Th is switched through and discharges the condenser C3 to the ignition means Z. The discharging time constant is determined substantially only by the capacity of the condenser C3 and the resistance of the ignition means Z. The energy available at the condenser C3 is thereby within a sufficiently short time conveyed to the ignition means Z.

As mentioned above, the charge at the condenser C2 must be lower than that conveyed to the condenser C1. Inasmuch as the charging quantity which is made available by the cell K2, but as the case may be, is greater than is required at the condenser C2, it may be necessary under certain circumstances to withdraw the excessive charge through the zener diode ZD which is arranged in parallel with the condenser C2, in which instance the diode D6 arranged in series thereto will prevent the condenser C2 after its polarity reversal from discharging through the zener diode ZD and thus will prevent a switching of the transistors T1 and T2.

In order also to equalize possible strays of the piezo ceramic cell K1, it may become necessary or expedient to arrange a zener diode of suitable dimension in parallel with the condenser C1.

By means of the recharging circuit C1, C2, R1, the time period is determined after which the fuse will carry out its decomposition. In addition thereto, for instance, the thyristor switch Th may by a current pulse be adapted to switch through which current impulse is furnished by the impact detector P, which may be in the form of a piezo electric cell. The diode D5 is intended to separate the circuits from each other, which means they prevent a rearward discharge, for instance, through the resistor R3 forming a leakage resistance and being arranged in parallel to the cell P. During the impact of the projectile, the electronic switch Th is switched through in the same manner as by the reversing circuits C1, C2, R1. The condenser C3 and/or the charge of cell K2 are discharged through diode D3 and switch Th to the ignition means Z.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawing, but also comprises any modifications within the scope of the appended claims.

Claims

1. An igniting system for an electrically operated projectile fuse comprising; a voltage source and circuit means connecting the voltage source to said fuse, said voltage source developing voltage pulses upon acceleration of the projectile containing the fuse, said circuit means comprising a time controlled charge reversing circuit connected to said source, control means connected to said charge reversing circuit and actuated thereby at the expiration of the time period pertaining to said reversing circuit, and means connecting said control means to said fuse for igniting the fuse by said control means upon actuation thereof, said voltage source comprising a pair of piezo electric cells in serial relation with a common center terminal, said charge reversing circuit comprising a capacitor connected across each cell and a resistor connected in parallel with said capacitors, and diode means interposed between said cells and the respective capacitors and so poled that one cell charges its capacitor during the acceleration period of the projectile while the other cell charges its capacitor following the acceleration period of the

2. An igniting system according to claim 1 in which said circuit means includes a further capacitor adapted to be charged by said one cell at the end of said acceleration period of the projectile and connected to said fuse, said control means when actuated releasing the charge on said

3. An igniting system according to claim 1 which includes a zener diode connected in parallel with the capacitor pertaining to said one cell to limit the voltage rise thereof during the acceleration period of said projectile to a value less than that supplied to the capacitor pertaining to said other cell following the acceleration period of said projectile.

4. An igniting system according to claim 3 which includes a diode in series with said zener diode and poled to prevent discharge of the capacitor pertaining to said one cell following the acceleration period of said

5. An igniting system according to claim 1 which includes an impact sensitive voltage source connected to said fuse and operable to supply igniting voltage to said fuse upon impact of said projectile.