GB1580175A

GB1580175A - Electronic projectile fuse

Info

Publication number: GB1580175A
Application number: GB798672A
Authority: GB
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1971-03-02
Filing date: 1972-02-21
Publication date: 1980-11-26
Also published as: FR2443186A5; BE780024A; IT1040525B; NL7202662A; DE2109849A1

Description

(54) ELECTRONIC PROJECTILE FUSE (71) We, DYNAMIT MOBEL AKTIENGESELLSCHAFT, a German company, of 521 Troisdorf, Postfach 1209, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: According to one aspect of the invention, there is provided a fuse for use on board a projectile to electrically detonate an explosive charge carried by the projectile, the fuse comprising means for supplying electrical energy during the flight of the projectile, an output terminal for connection to electrically operable detonating means, switch means connected between the energy supplying means and the output terminal so that when the switch means is operated it enables an electrical firing signal to be delivered to the output terminal, an electronic signal delaying device for ensuring that said firing signal cannot be delivered to said output terminal as aforesaid until after the expiry of a predetermined safety delay time starting from the time the projectile is launched, an electronic signal delaying device for delaying the delivery of said firing signal to said output terminal until the expiry of a target penetration delay time starting from the time of operation of said switch means, an electronic device for causing a self-d;estruct firing signal to be delivered to said output terminal after the expiry of a self-destruction time delay whether or not the switch means is operated, and electronic programming means for controlling the said self-destruction time delay.

Preferably, the energy supplying means comprises means for causing it to become operable to supply energy as aforesaid only after the projectile is launched.

The said devices may comprise respective threshold trigger components having the same physical construction. Advantageously, these threshold trigger components each consist of an electronic integrated circuit component having two main current carrying terminals and a control terminal for controlling the passage of current between the main terminals, the characteristics of the circuit component being such that it acts as a thyristor as re gards current flow between said main ter minals, and as a trigger diode as regards its control path including said control terminal.

Each threshold trigger component can be connected to an adjustable time delay setting device, for example a capacitance and a resis tor connected together.

Said energy supplying means can comprise a d.c. voltage generator for example, or a single cell battery connected to a d.c. voltage transformer.

Advantageously, the safety delay time signal delaying device is connected to receive energy from said energy-supplying means and to pass it, after said safety delay time, to a capacitor which is connected to the output of this device.

In this case, it is preferred that the said switch means is connected between said capacitor and said terminal and comprises an impact switch which closes on impact of the projectile and then passes energy from said capacitor.

Preferably, the fuse includes further switch means, which switch means is connected to said target penetration delay time signal delaying means for causing the latter to become operable or inoperable as desired.

The fuse may include means for causing said target penetration delay time to vary as a function of the time elapsed since launching of the projectile, for example there may be a resistor connected in parallel with said capacitor to gradually discharge it.

Preferably the said programming means is adapted to be activated independently of the energy supplying means. Such programming means can include a coil for responding to a magnetic field through which the projectile passes as it is launched to programme the said self-destruction delay time in dependence upon said field. Along with the coil, there may be a diode, a capacitor and a field effect transistor, the diode being connected to pass signals induced in the coil to the capacitor, the capacitor being connected to control the field effect transistor, and the field effect transistor being connected to con trol the self-destruction delay time.Alternatively, the programming means can include a Zener diode and a further diode, the further diode being connected between the coil and the Zener diode, and to a capacitor the charging of which controls said selfdestruction delay time.

According to a second aspect of the invention, there is provided a projectile carrying an explosive charge, an electrically operated detonator for firing the charge, and a fuse for producing an electrical signal which operates the detonator, the fuse being as described above.

The aforementioned coil is preferably mounted flush on the surface of the projectile.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a sectional elevation of part of an explosive shell having an electronic fuse for detonating the explosive charge, Figure 2 is a simplified circuit diagram of the electronic fuse used in the shell of Figure 1, Figure 3 is a circuit diagram of a modi fication of a part of Figure 2, Figure 4 is an elevation of the fuse showing its physical construction, and Figure 5 is a perspective view correspond- ing to Figure 4 showing how the component parts of the fuse are connected together.

The shell 1 shown in Figure 1 comprises in its nose 9 an electronic fuse 3 with an impact switch 2 at the tip. Instead of the impact switch 2, there may equally well be employed an electronic proximity switch. The electronic fuse 3 is mounted above an electrically operated detonator 4, for example an electric detonating cap in which the electric ignition is effected, for example, by the electrical current passing through a resistive metal layer. Beneath the detonator 4 is the main explosive charge 7 and a booster charge 6.

Initially, the shell is made safe by a detonator safety device 5 positioned between the detonator and the explosive charge. The device 5, which may be for example a mechanical device released by the rotational acceleration of the shell, prevents a premature explosion of the detonator 4 from setting off the charges 6 and 7. The point 8 at which the nose of the shell is screwed to the rear portion thereof is constructed to form an easy break- ing point in order to further reduce the chance of premature ignition of the detonator setting off the charges while the device 5 is in the "safe" position.

Referring to Figure 2, the fuse consists of an energy supply part 10 adapted to be activated by the firing of the shell, a device 20 for ensuring that a firing signal is not produced until after the expiry of a predetermined bore safety delay time following the firing of the shell, a device 30 for delaying the firing signal for a time starting from the time of impact of the shell, a part 40 for "self destroying" the shell after a certain time delay even if it does not meet a target and a part 50 for programming the self destruction time delay. The energy supply part 10 comprises a single cell battery 11 connected to a d.c. voltage transformer 12.

It could instead comprise a d.c. generator.

The supply part 10 is activated by the acceleration of the shell as it is fired and only then becomes operable to supply the rest of the fuse, the part 10 being inoperable 'before then. The device 20 comprises a threshold trigger component 21 having two main current carrying terminals and a control terminal. The control terminal is connected via a Zener diode 23 to the point of connection between a resistor and a capacitor forming a safety time delay setting device 22. The resistor passes current from the part 10 to charge the capacitor. One main terminal of the component 21 is connected to the common ground connector by way of a capacitor 25 and to the supply connection from the part 10 by way of a resistor 24. A resistor 26 and a capacitor 27 are connected in parallel between the ground connector and the other main terminal of the component 21.The component 21 comprises an electronic integrated circuit the characteristics of which are such that it acts as a thyristor as regards current flow between its main current carrying terminals and as an accurate trigger diode as regards its control path comprising its control terminal, in other words the component is triggered so that current can flow between its main terminals when the signal at its control terminal exceeds an accurately defined trigger potential.

As a preferred example, the component may have a maximum control current of 10 ,aA, a main terminals voltage range of 5 to 80 volts and an impulse current capacity of 10 amps, the component not being erroneously triggered by rates of rise (slope) of the main terminal voltage up to 10SVoks/sec. The resistor 24 and capacitor 25 are provided in order to prevent too rapid a rise of the main terminal voltage across the component 21, and hence premature triggering thereof, when the part 10 is switched on. After such switching, the capacitor 22 is gradually charged up and, when the potential on this capacitor has exceeded the threshold voltage defined by the component 21 plus the threshold voltage of the Zener diode 23, the component 21 conducts so that energy is passed from the part 10 to rapidly charge up the capacitor 27. The function of the Zener diode 23 is to extend the possible choice of threshold vokage at which the component 21 conducts, i.e. to extend the range of possible safety time delay, using the same component 21.

The resistor 26 gradually discharges the capa citor 27 as the flight of the projectile con tinues-This being for a purpose to be described later.

The purpose of the device 20 is to ensure that the firing signal for the detonator cannot be produced until after the expiry of a preset time delay starting from the time when the shell is fired even if the impact switch 2 closes before then. In the case of a shell, this time delay ensures that the shell does not explode within the barrel of the gun or rear to it and hence may be called the bore safety time.

If and when the shell hits a target, the contacts 28 of the impact switch 2 are closed so connecting the device 20 to the device 30.

The device 30 delays the firing signal after impact to enable the shell to penetrate the target before exploding. The device 30 comprises a threshold trigger component 31, which is exactly like the component 21, and an adjustable RC timing member 32. When the impact switch 2 closes, the potential on the capacitor 27 is applied to one main terminal of the component 31 and also via the resistor to the capacitor of the timing member 32.

When this capacitor has charged to a poten tidal exceeding the threshold value associated with the control terminal of the component 31, ie. after the expiry of the target penetration delay time, the component 31 is triggered and current flows through it to the detonator 4 which is thus ignited.

The rate of charging of the capacitor of the timing member 32, and hence the target penetration delay time, depends upon the potential on the capacitor 27 at the time when the switch 2 is closed. As mentioned before, the resistor 26 gradually discharges the capacitor 27 so the potential thereon will be inverse-exponentially proportional to the time elapsing between the end of the safety time set by the device 20 and the time at which the switch 2 is closed, i.e. the target penetration delay time will depend on the time length of the flight of the shell between firing and target impact. The delay time is inversely proportional to the velocity of the shell and the time taken for the shell to penetrate to a given depth into a given target also depends on its velocity.The fuse is preferably arranged so that the penetration depth at which the shell explodes in a given target is as nearly as possible constant irrespective of the target distance.

A switch is connected between the main terminals of the component 31 so that when the switch is closed the device 30 becomes inoperative and, as soon as the impact switch 2 is closed, current flows from the capacitor 27 to the detonator 4 and the shell explodes without any target penetration delay. In the embodiment shown, the further switch takes the form of short-circuiting bridge contacts 33 connected to the respective main terminals of the component 31. During production of the fuse, the contacts 33 are initially connected together by a short-circuting bridge which can be removed in order to produce a fuse which will delay the explosion of the shell for a required penetration delay time after impact, or left in place in order to produce a fuse in which such a delay does not occur.

The "self-destruction" part 40 of the fuse comprises a threshold trigger component 41 which is exactly like each of the components 21 and 31, an R.C. timing number 42 and a Zener diode 43, the function of which is similar to that of the diode 23, connected between the control terminal of the component 41 and the timing member. The selfdestruction time delay can be adjusted by selecting appropriate values for the resistance and capacitance of the timing member 42 when the fuse is made. This delay can also be adjusted at the time of firing the shell by means of the programming part 50 connected to the part 40 at the terminal 44.

The programming part 50 comprises a coil 54 which is flush mounted at the surface of the shell. Means are provided for forming a magnetic field at the muzzle of the gun from which the shell is fired so that, as the shell passes through the magnetic field, a voltage is induced in the coil 54. This voltage is fed to a capacitor 53 by way of a diode 52 and so becomes present at the gate of a field-effect transistor 51 the main current path, Le. the source-drain path, of which is arranged to form part of the resistance of the R.C. timing member 42. By varying the dimensions or magnitude of the magnet field at the gun muzzle, the voltage induced in the coil and hence the voltage stored by the capacitor 53 are varied. This in turn varies the source-drain path resistance of the fieldeffect transistor 51 and hence the self-destruction delay time.

The magnetic field at the gun muzzle can be produced by means of a coil surrounding the path taken by the shell just forward of the gun muzzle. The self-destruction delay time is then programmed by varying the intensity or the length of the field.

The capacitor 53 and the field-effect transistor 51 could be replaced by a Zener diode 56 and a further diode 55 as shown in Figure 3 which also shows the coil 54 and the diode, here referenced 57, for collecting the voltage induced in the coil. In this modification, the effect of the voltage induced in the coil is to pre-charge the capacitor of the timing member 42. The magnetic field is made sufficient so that the voltage induced in the coil 54 causes the Zener diode 56 to conduct.This of course causes the voltage level at the cathode of the Zener diode 56 to be constant irrespective of the magnitude of the coil voltage so, in this modification, the self-destruction delay determined by the amount of pre charging of the capacitor 42, is varied by varying the length of the magnetic field through which the shell passes and hence the time during which the precharging is applied to the capacitor of the timing member 42.

In either case, it is necessary for the magnetic field strength of the muzzle coil, through which the shell passes on firing, to have a certain minimum value, i.e. it should be large enough to exceed the threshold value of the Zener diode 56 according to Figure 3 or the threshold value of the field effect transistor 51 according to Figure 2.

To vary the length of the field through which the shell passes, the muzzle coil on the gun is subdivided into a number of longitudinal sections. For the shortest self-destruction time, the largest charge must be preprogrammed at the capacitor of the timing member 42 in the case of the Figure 3 embodiment, or on the capacitor 53 in the case of the Figure 2 embodiment, and so all the coil sections, Le. the entire coil length, are fed with electrical current. For longer self-destruction times, only some, or even none, of the coil sections are fed with current.

Since the muzzle velocities of a number of shells of one particular type fired from the same gun vary by only small amounts, the time required by each shell to pass through a particular coil length is very constant so the charging time of capacitor 53 or 42, and hence the self-destruction time delay, for these shells is substantially depen, dent only upon the number of coil sections which are supplied with current.

As mentioned before, the energy supply part 10 becomes activated during firing of the shell. There could be provided means (not shown) which short-circuits the supply part 10 before the shell is fired, so that in the event of unintentional premature activation of the part 10, the fuse is still not rendered effective, for example where the part 10 includes a battery such short circuiting would cause destruction of the battery. Simultaneously with the activation of the energy supply part 10, the detonator safety device 5 is dislodged by the rotational acceleration of the shell and hence the detonator 4 becomes able to fire the charge 6 and 7. In the course of the building-up of the voltage of the energy supply part 10, the part 20 for setting the bore safety time and the part 40 for setting the self-destruction time start to operate.Depending upon the distance of the target, which is measured by radar for example, the programming part 50 can if desired be acted on by means of the coil mounted at the muzzle of the gun so as to preprogramme the self-destruction time to a value different from that which would occur if no preprogramming were to occur. Ir will be noted that for this preprogramming, it is not necessary to vary the supply voltage of the energy supply part 10, i.e. the preprogramming means is independent from the part 10.

The self-destruction delay time could be programmed by using appropriate magnetic field producing means before the shell is fired.

After the expiry of the preset bore safety time, the firing voltage is transmitted to the firing capacitor 27 and held available. If the impact switch 2 closes as a result of the impact of the projectile before expiry of the set self-destruction time, the detonator 4 is fired with or without a target penetration delay depending upon whether or not the contacts 33 are bridged.

If the projectile has not reached a target within the programmed self-destruction time, the detonator 4 is automatically fired by the part 40.

The various delay times provided by the parts 20, 30 and 40 may for example be in the range from about 1 millisecond to 10 seconds.

There is shown in Figure 4 the compact construction of the electronic fuse with the impact switch 2 at the tip. The parts 10, 20 and 30, and the parts 40 and 50 together, are produced as separate units and tested as such. Thereafter particular ones of the appropriate units are selected and assembled together in a pyramid shape to form a fuse having the desired characteristics.

The impact switch 2 is disposed at the nose of the shell and below it is the device 30 for obtaining the penetration delay time.

Below this is situated the part 20 including the bore safety time obtaining means and the firing capacitor 27, followed by the combined unit comprising the programming part SO and the self-destruction part 40. The programming coil 54 (not shown) is arranged flush on the upper outside surface of the shell casing. The base of the pyramid is formed by the energy supply part 10 with the detonator 4 just below that. The individual units are connected together by acceleration resistant plug and socket contacts equispaced around the peripheries of the top and bottom surfaces of the units as shown in Figure 5. This figure is a diagram showing the positions 60 of the contacts but not their construction. The whole electronic part is therefore mechanically combined to form a component unit with detonator and switch in order to withstand high accelerations and to ensure sufficient safety in transport.

The electronic fuse shown is especially suitable for shells having calibres of more than 20 mm. Instead of a shell, the fuse may be used for other explosive projectiles such as rocket missiles and the like.

It will be seen that the self-destruction delay time can be programmed without gal vanic connections to the fuse from the external programming apparatus, and that the various delay times can be adjusted by selecting appropriate values of the components in the timing members 22, 32 and 42.

WHAT WE CLAIM IS: 1. A fuse for use on board a projectile to electrically detonate an explosive charge carried by the projectile, the fuse comprising means for supplying electrical energy during the flight of the projectile, an output terminal for connection to electrically operable detonating means, switch means connected between the energy supplying means and the output terminal so that when the switch means is operated it enables an electrical firing signal to be delivered to the output terminal, an electronic signal delaying device for ensuring that said firing signal cannot be delivered to said output terminal as aforesaid until after the expiry of a predetermined safety delay time starting from the time the projectile is launched, an electronic signal delaying device for delaying the delivery of said firing signal to said output terminal until the expiry of a target penetration delay time starting from the time of operation of said switch means, an electronic device for causing a self-destruct firing signal to be delivered to said output terminal after the expiry of a self-destruction time delay whether or not the switch means is operated, and electronic programming means for controlling the said selfdestruction time delay.

2. A fuse according to claim 1, wherein the energy supplying means comprises means for causing it to become operable to supply energy as aforesaid only after the projectile is launched.

3. A fuse according to claim 1, wherein the said devices comprise respective threshold trigger components having the same physical construction.

4. A fuse according to claim 3, wherein the threshold trigger components each consist of an electronic integrated circuit component having two main current carrying terminals and a control terminal for controlling the passage of current between the main terminals, the characteristics of the circuit component being such that it acts as a thyristor as regards current flow between said main terminals, and as a trigger diode as regards its control path including said control terminal.

5. A fuse according to claim 3 or 4, wherein each threshold trigger component is connected to an adjustable time delay setting device.

6. A fuse according to claim 5, wherein each time delay setting device comprises a resistor and a capacitance connected together.

7. A fuse according to any preceding claim, wherein said energy supplying means comprises a single-cell battery connected to a d.c. voltage transformer.

8. A fuse according to any one of claims 1 to 6, wherein said energy supplying means comprises a d.c. voltage generator.

9. A fuse according to any preceding claim, wherein the safety delay time signal delaying device is connected to receive energy from said energy supplying means and to pass it, after said safety delay time, to a capacitor which is connected to the output of this device.

10. A fuse according to claim 9, wherein the said switch means is connected between said capacitor and said terminal and comprises an impact switch which closes on impact of the projectile and then passes energy from said capacitor.

11. A fuse according to any preceding claim, including further switch means, which switch means is connected to said target penetration delay time signal delaying means for causing the latter to become operable or inoperable as desired.

12. A fuse according to any preceding claim, including means for causing said target penetration delay time to vary as a function of the time elapsed since launching of the projectile.

13. A fuse according to claim 12, when appended to claim 9 or 10, wherein said means for causing said penetration delay time to vary comprises a resistor connected in parallel with said capacitor to gradually discharge it.

14. A fuse according to any preceding claim, wherein the said programming means is adapted to be activated independently of the energy supplying means.

15. A fuse according to claim 14, wherein the programming means includes a coil for responding to a magnetic field through which the projectile passes as it is launched to programme the said self-destruction delay time in dependence upon said field.

16. A fuse according to claim 15, wherein the programming means further includes a diode, a capacitor and a field effect transistor, the diode being connected to pass signals induced in the coil to the capacitor, the capaci- tor being connected to control the field effect transistor, and the field effect transistor being connected to control the self-destruction delay time.

17. A fuse according to claim 15, wherein the programming means further includes a Zener diode and a further diode, the further diode being connected between the coil and the Zener diode, and to a capacitor the charging of which controls said self-destruction delay time.

18. A fuse for use on board a projectile to electrically detonate an explosive charge carried by the projectile, the fuse being substantially as hereinbefore described with refer

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. vanic connections to the fuse from the external programming apparatus, and that the various delay times can be adjusted by selecting appropriate values of the components in the timing members 22, 32 and 42. WHAT WE CLAIM IS:

1. A fuse for use on board a projectile to electrically detonate an explosive charge carried by the projectile, the fuse comprising means for supplying electrical energy during the flight of the projectile, an output terminal for connection to electrically operable detonating means, switch means connected between the energy supplying means and the output terminal so that when the switch means is operated it enables an electrical firing signal to be delivered to the output terminal, an electronic signal delaying device for ensuring that said firing signal cannot be delivered to said output terminal as aforesaid until after the expiry of a predetermined safety delay time starting from the time the projectile is launched, an electronic signal delaying device for delaying the delivery of said firing signal to said output terminal until the expiry of a target penetration delay time starting from the time of operation of said switch means, an electronic device for causing a self-destruct firing signal to be delivered to said output terminal after the expiry of a self-destruction time delay whether or not the switch means is operated, and electronic programming means for controlling the said selfdestruction time delay.

ence to Figures 1, 2, 4 and 5, or with reference to Figures 1, 2, 4 and 5 as modified by Figure 3, of the accompanying drawings.

19. A projectile carrying an explosive charge, an electrically operated detonator for firing the charge, and a fuse for producing an electrical signal which operates the detonator, the fuse being in accordance with any preceding claim.

20. A projectile according to claim 19, wherein the fuse is in accordance with claim 15, 16 or 17 and said coil is mounted flush on the surface of the projectile.