Self-destructive electronic fuse

Abstract: The object of the present invention relates to a self-destructive electronic fuse that acts, by means of an inertia switch, when the ammunition hits the target and if there is no hit or such takes place at an inappropriate angle, after a set time, the fuse shall destroy itself and cause the ammunition to which it is attached to explode. The fuse, light in weight, small in size, compact, capable of resisting a sharp acceleration, is specially designed to be used in subammunition using a projectile opening up in the air as a carrier vector. This self-destructive fuse comprises mechanical and electronic elements acting together, a frame, a body and a printed circuit fitted with the electronic components.

Description: SPECIFICATION The present invention relates to a self-destructive electronic fuse. Ammunition abandoned in the battlefield without exploding can cause in one's own army the same effects that were designed for the enemy's army, which problem is ever more serious if the ammunition used is multiple. Consequently, it is often wise for the ammunition to destroy itself if it fails to explode at the desired time. This self-destructive electronic fuse acts, by means of an inertia switch when the ammunition hits the target or if there is no hit or such takes place at an inappropriate angle, after a set time, so as to destroy itself and cause the ammunition to which it is attached to explode. CH-A-534 860 on which document the preamble of independent claim 1 is based, discloses a self-destructive electronic fuse having an impact switch for actuating the fuse upon an impact. The fuse comprises a timing circuit for actuating the fuse and, hence, the ammunition, after a certain time interval after launching of the ammunition, in order to achieve a self-destruction in case no impact occurs. Further, the fuse is provided with an acceleration switch serving as pre-launching safety measure, which acceleration switch applies voltage to the actuation circuit after closure. US-A-3 815 505 discloses a self-destructing apparatus for impact-detonating explosive devices. After firing or dropping of the explosive device, the detonator is actuated after a predetermined time delay so as to ensure self-destruction of the device in case of lack of prior explosion. US-H-136 discloses a fuse for a grenade which is provided with an electrical backup system for detonating the grenade for self-destruction in case no prior detonation should take place. The present invention provides a self-destructive electronic fuse in accordance with claim 1. Some further details of the present invention are defined in the subclaims. The fuse of the invention is light in weight, small in size, compact, capable of resisting a sharp acceleration and specially designed to be used in subammunition using a projectile opening up in the air as a carrier vector. During ammunition storage and handling the fuse receives no electric power supply and the status of its electrical circuit is stable and disabled. Upon firing, from the time the power supply is connected, the fuse receives an electric power supply that is stored. When the fuse is disconnected from the power supply, two timers are switched on, one of which works as a distance interrupter preventing the instantaneous actuation of the fuse and the other, in the event that the fuse should not act upon a hit, activates the elements causing the same to destroy itself. Though self-destructive fuses already exist, the fuse in respect of which the present patent application is being made, contributes a number of improvements and original elements in respect of existing fuses that allow the following: Its use, though not exclusively, is possible in subammunition using as the carrier vector a mortar grenade, an artillery grenade, a rocket or other projectile type opening up in the air and expelling the subammunition items. Absolute safety to be achieved during carriage and handling, because the fuse cannot work until firing takes place and it is connected to and disconnected from the power supply. It works when the ammunition hits the target. It is self-destructive, for if the fuse does not act upon the hit, because the ammunition may be hanging from the branch of a tree, it may have been tipped by a nearby explosion or otherwise, after a preset time the fuse will destroy itself and with it the ammunition to which it is attached. The description is illustrated with a set of drawings in which an embodiment has been shown, that is by no means restrictive and may consequently be changed to the extent that its characteristic objective is not essentially changed. In the drawings: Figure 1 shows the fuse and the subammunition together at rest. Figure 2 shows the fuse and the subammunition together in flight. Figure 3 shows the electronic fuse circuit. Because the field of application of this fuse is so large, the description shall be considered using the same in a mortar projectile subammunition, without this description limiting the invention to only this embodiment, which can be extended to others for which it is equally suitable. The self-destructive fuse (Fig. 1) comprises mechanical and electronic components working together. There are provided: a frame (1), a body (2) and a printed circuit (100) fitted with the electronic components. These three elements are joined to each other by means of screws (3). The body (2) is used to couple the fuse to a subammunition (4) and houses inside a centre stop (5) for an electric detonator (120). By action of a spring (9) a guide (7), fitted with a stopper disc (8), slides along the centre stop (5) when it is released from the abutment that prevents it from moving, the abutment being in this case another subammunition (4). When at rest, the stopper disc (8) provides a barrier between the electric detonator (120) welded to the printed circuit (100) and the subammunition (4), thereby preventing a chance detonation of the electric detonator (120) from causing the subammunition (4) to explode. When the guide (7) slides with the stopper disc (8), its barrier effect is eliminated and the detonation of the electric detonator (120) causes the subammunition (4) to explode. In order to enhance contact of the electric detonator (120) with the printed circuit (100), the electric detonator (120) is surrounded by and in contact with a spring (10). Inside the frame (1) there are electronic components welded to the printed circuit (100) and there is a cavity (6) housing a contact disc (12) with a counterweight (11). The contact disc (12) acts as an inertia switch (112) for when the subammunition (4) hits the target, the deceleration caused by such hit folds the contact disc (12) and when a contact (13) welded to the top printed circuit (121) simultaneously touches a washer (14) the electronic circuit is made and the detonator (120) detonates, thereby causing the subammunition (4) to explode. In order to enable the subammunition (4) to arrive at the target vertically, the fuse, by means of a stay (21) and a pin (22), is coupled with a band (23), with a curved reinforcement (24), that is rolled over the fuse body (2) before firing and after firing (Fig. 2) acts as a parachute causing the subammunition (4) to brake aerodynamically. The cables, for positive (101) and negative (102) supply welded to the printed circuit (100) and a contact (104) connect the self-destructive fuse to an external electric power supply (200), that in the subject case is the carrier projectile fuse. A short-circuit cable (103) also welded to the printed circuit (100) and the contact (104) holds the electric detonator (120) in short-circuit until it is disconnected. The cable (101), (102) and (103) connections disappear when the subammunition items (4) are released from one another upon firing. All the electronic components are welded to the printed circuit (100) and the circuit is shown in Fig. 3. It has a storage condenser (105) storing the power received from the external electric power supply (200), which power returns to the circuit when the fuse is disconnected from the outer power supply (200). When the circuit is powered by the power supply (200), analogue switches (106) and (107) are powered through a diode (118). When power is eliminated from the circuit, a resistor (114), resetting the control line, and a diode (119), preventing the storage condenser (105) from driving the positive power line, allow the analogue switches (106) and (107) to be turned off. The analogue switch (106) through condenser (108) and the resistor (115) acting as a timer, controls powering of an analogue switch (110). This timing takes place in order for there to be no premature explosion. The analogue switch (107) through the condenser (109) and a resistor (116) acting as a timer, controls powering of an analogue switch (111). This timing takes place in order for there to be self-destruction after the fuse may have acted upon a hit in normal circumstances. The analogue switch (110) controls powering of an inertia switch (112). The inertia switch (112) or if it fails the analogue switch (111) govern powering of a drive transistor base (113). When the base is not powered, the drive transistor (113) stays set by a bias resistor (117) and when its base is powered, it drives the electric detonator (320) causing it to detonate, which in turn causes the subammunition (4) to explode. OPERATION Before firing, the subammunition items (4) are at rest, supported by and fitted to each other and with their self-destructive fuses all connected to each other, and further with the short-circuit cable connected to the negative power cable. In this original position, the circuit is disabled and stable, for there is no circuit powering and through the short-circuit cable (103) the detonator (120) remains short-circuited. The loading stage begins upon firing and when the power supply (200) is triggered, powering the fuse though the contact (104) and the power cables (101) and (102). When the fuse is powered, the storage condenser (105) is charged, storing energy. In this position, the analogue switches (106) and (107) stay on because they are powered through the diode (118). Since all the analogue switches (106) and (107) are on, the delay condensers (108) and (109) remain unloaded and hence the analogue switches (110) and (111) stay off, leaving the inertia switch (112) and the drive transistor base (113) powerless. The load condition is stable while there is a powering and the detonator (120) remains short-circuited through the short-circuit cable (103). The tripping state begins when the fuse is disconnected from the storage condenser (105) charged from the power supply and occurs when the subammunition (4) is sent off. When the subammunition (4) is sent off the connector (104) is disconnected from the power supply (200), the band (23) unwinds and the guide (7) with the stopper disc (8) moves along the centre stop (5) to render the electric detonator (120) communicated with the subammunition explosive (4). When the connector (104) is disconnected, system powering is eliminated and the electric detonator (120) short-circuit is disabled. When powering is eliminated, the analogue switches (106) and (107) are turned off for their control line is reset through the resistor (114) and the diode (119) prevents the storage condenser (105) from driving the line. When the analogue switches (106) and (107) are turned off, the power stored in the storage condenser (105) is used to begin charging the delay condensers (108) and (109) through the delay resistors (115) and (116) calculated for the charge level in the delay condensers (108) and (109) to cause the analogue switches (110) and (111) to be switched over with different timings. The delay resistor (115) and the condenser (108) act as a distance interrupter and are calculated for the analogue switch (110) to be turned on when the flight of the subammunition (4) is already stable. When the analogue switch (110) is turned on, the inertia switch (112) is powered, and hence when the ammunition hits the target, due to the deceleration effect there is, the contact disc (12) folds and turns the inertia switch (112) on. When the inertia switch (112) is turned on, the drive transistor base (113), that remained set by action of the bias resistor (117), is powered, and the electric detonator (120) detonates and causes the subammunition (4) to explode. If the fuse is not actuated upon a hit, because the ammunition may be hanging from the branch of a tree, it may have been tipped by a nearby explosion or otherwise, after a preset time controlled by the resistor (116) and the condenser (109), sufficient for the subammunition (4) to have already arrived at the target, the analogue switch (111) shall be turned on. When the analogue switch (111) is turned on, the drive transistor base (113) will be powered and the electric detonator (120) detonated and the fuse will destroy itself and with it the subammunition (4) to which it is attached.

Claims: A self-destructive electronic fuse comprising mechanical and electronic elements, and used in a subammunition items with the mechanical elements (7, 8, 12) providing safety features and hit detection, characterized in that the electronic elements (101 to 120) are providing a double timing (108, 109, 115, 116), both starting when the subammunition items (4) are released: the first timing (108, 115) preventing instantaneous operation of the fuse, and the second timing (109, 116), larger than the first, ensuring that self-destruction will only take place if operation by a hit fails. A self-destructive electronic fuse, as in claim 1, characterized in that its mechanical elements include a frame (1), body (2), stop (5), centre, guide (7), contact disc (8) and band (23), allowing the electronic components to be coupled to the fuse to work upon an impact. A self-destructive electronic fuse, as in claim 1 or 2, characterized in having an electronic circuit, fitted with a printed circuit (100), comprising diodes, capacitors, resistors, analogue switches, an analogue transistor and an electronical detonator (120), which circuit allows the fuse to work by a hit or by self-destruction. A self-destructive electronic fuse, as in claim 3, characterized in that the detonator (120) is short-circuited thereby to prevent operation of the fuse during transport and handling of the ammunition. A self-destructive electronic fuse, as in claim 3 or 4, characterized in that a spring (10) is provided to improve the electric connection of the detonator (120). A self-destructive electronic fuse, as in claims 1, 2, 3, 4 or 5, characterized in that a guide (7) is provided having a stopper disc (8) preventing the operation thereof until the guide (7) moves.

Inventors: MORLAS NADAL EMILIO, MUNOZ BUENO LEONCIO, MORLAS NADAL, EMILIO, MUNOZ BUENO, LEONCIO
Applicants: INSTALAZA SA, INSTALAZA S.A.
Application year: 1993
Main classification: F42C9
IPC codes: F42C9