Abstract:
The Fuze Safety Logic is disclosed that guards against erroneous responses created by accidents or by accidental releases of submunitions of payloads being carried by explosive ordnances. The fuze safety logic provides provisions for conservation of battery internal power, while at the same time ensures the maintenance of proper safety features of the explosive ordnances.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein was made by an employee of the United States Government and may be used by or for the government for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND OF THE INVENTION 
     1.0 Field of the Invention 
     This invention relates to a submunition of a projectile having a fuzed warhead and, more particularly, to a submunition that provides an explosive ordnance with provisions for conservation of its internal battery power or power source, a programmable timer for controlling its self-destruct/neutralizer functions, and other programmable timers that ensure the maintenance of the proper safety features of the explosive ordnance. 
     2.0 Description of the Prior Art 
     The U.S. Military is increasingly demanding that all explosive ordnances being developed incorporate a fuzing system, such as an electronic fuzing system, for neutralizing or otherwise self-destructing such explosive ordnance once they have completed their intended mission. The U.S. Military is also concerned that ammunitions, such as explosive ordnances, containing submunitions not release the submunitions under any accidental scenarios. 
     In accident scenarios, a battery or power source activation event or a submunition release event related to the post-launch system, may occur at the same time or within a few seconds of the primary accident event or a secondary event. The electronics may misinterpret either an accidental submunition release event or an accidental battery activation event causing the submunition to function or to start a self-destruct or self neutralize process thus causing the functioning of the explosive ordnance. It is of primary importance that an apparatus be provided that eliminates any accidental electronic functioning for submunitions that would otherwise cause damage from the explosion of the ordnance. 
     The U.S. Military is increasingly demanding that the lethality associated with the submunitions be improved. This improvement in the lethality may be accomplished by a known proximity functional mode. It is desired that an apparatus be provided that incorporates a proximity mode so as to not only increase the lethality of the operation of the submunitions, but also the reliability and safety of the submunitions by the introduction of this proximity functional mode. 
     OBJECTS OF THE INVENTION 
     It is a primary object of the present invention to provide an apparatus for controlling a post-launch sequence of an explosive ordnance having a fuzed head that substantially eliminates any accidental electronic arming or functioning of submunitions associated with the explosive ordnance. 
     It is an additional object of the present invention to provide for a proximity function mode used to control the operation of the submunitions of the explosive ordnance. 
     It is a further object of the present invention to provide safety logic inhibiting any erroneous functional responses of submunition fuze electronics after it is placed on its internal battery or power source. 
     It is a further object of the present invention to increase the lethality of the submunitions related to the explosive ordnance. 
     It is a further object of the present invention to increase the overall reliability of the submunitions which, in turn, increases the overall reliability of the projectile. 
     It is a further object of the present invention to conserve the internal power supply of the fuze, which increases the ability to use smaller batteries or power sources for powering the electronics associated with the submunition fuze which, in turn, reduces the size of the fuze. 
     It is still a further object of the present invention that allows for better control of the submunitions while still employing the control for the self-neutralization and self-destruct functions for the explosive ordnance. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus that provides an initiation system that controls an explosive ordnance while at the same time provides provisions for the conservation of the associated battery or power source, and provides provisions for programmable timers for setting the self-destructing and/or self-neutralizing functions, as well as other programmable timers that ensure the maintenance of the proper safety features of the explosive ordnance, especially those related to the submunitions of the explosive ordnance. 
     The apparatus of the present invention controls the submunition of a projectile having a fuzed warhead. The functioning or safely securing of a submunition is dependent upon the occurrence of a battery or power source activation control signal, the occurrence of both the presence and absence of a nesting switch open control signal, and the presence of a valid target control signal. The successful submunition functioning or safely securing is also dependent upon the generation of four commands, (1) self-dud, (2) charge firing capacitor, (3) turn on proximity mode, and (4) fire firing capacitor. The successful submunition functioning is also dependent upon the inhibiting of the self-dud command. The successful submunition being made safe is also dependent upon the activation of the self-dud command. The apparatus comprises a microprocessor having a plurality of routines and subroutines, preferably seven routines, with the seventh routine having three subroutines. The routines and subroutines of a microprocessor provide a method to conserve internal power for the explosive ordnance, while at the same time incorporate self-destruct/neutralizer timers and providing safety logic to eliminate responses to accidents involving submunitions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention will be had upon reference to the detailed description when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block diagram that shows the interrelationship between the apparatus of the present invention and the payload and other submunitions; 
     FIG. 2 is composed of FIGS. 2A,  2 B,  2 C and  2 D that cumulatively illustrate a flow chart showing the overall operation of the safety logic related to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, wherein the same reference number indicates the same element throughout there is illustrated in FIG. 1 a block diagram showing the elements associated with a projectile  10 . The projectile  10  may be type known as Extended Range Guided Projectile (ERGM) which is fired from a naval gun. ERGM, among other sections, has an electronics section (not shown) and a payload section  12 . The electronics section of ERGM causes the payload section  12  to be ejected from the projectile  10 . Once free of the projectile  10 , the payload section  12  ejects the submunitions, such as the submunitions  14  and  14 A (Adjacent Submunitions) shown in FIG.  1 . Each submunition  14  or  14 A has a warhead (not shown) and a fuze  16 . The present invention is particularly concerned with the logic within the electronics of the fuze  16  on the submunition  14 . Except for the connection shown in FIG. 1 of the adjacent submunitions  14 A connected to the nesting switch  18  of submunition  14 , there is no electrical connection between the other submunitions or between the payload section or between the ERGM electronics. 
     The projectile  10  controls the launch of the payload  12  of the projectile, such as an explosive ordnance, to a predetermined target. The payload  12  releases the submunition  14 , which contains the fuze  16 . As shown as being arranged in FIG. 1, the fuze  16  contains the nesting switch  18 , an internal battery or power source  20 , a microprocessor  22  and other electronic components, a proximity sensor  24 , and a firing circuit  26  which controls a firing capacitor  28  which, in turn, controls an electric detonator  30 . 
     The microprocessor  22  eliminates any electronic reaction of the submunition  14  to an accidental release by the payloads or an accident involving the payload. Without the present invention, these accidental releases may interfere with the intended purpose of the explosive ordnance, that is, the submunitions of the payload being carried by the payload. 
     The submunition  14  is known in the art and may be of the type known as M80 grenade or EX 433 Proximity Fuze or M234 Self-Destruct Fuze. The projectile  10  functions in such a way as to cause, via signal path  32 , activation of the internal battery or power source  20 , thus supplying a signal on signal path  34  in the form of power to the microprocessor  22 . The projectile  10  also acts in such a way as to cause the payload  12 , via signal path  36 , to generate a release signal on signal path  36 A to the submunition  14  and adjacent submunitions  14 A. The release signal causes the nesting switch  18  to supply an open signal on signal path  38 , which is sent to the microprocessor  22 . The microprocessor  22  in response to the two control signals  42  (battery activation), and  44  (nest switch open), on signal paths  34 ,  38 , respectively, to be further described with reference to FIG. 2, provides four output commands which are (1) self-dud  48  on signal path  50 , or (2) charge firing capacitor  52  on signal path  54 , or (3) turn on proximity mode  56  on signal path  58 , and or (4) fire firing capacitor  60  on signal path  62 , with the signals  48 ,  52  and  60  being fed to the input stage of the firing circuit  26 . The proximity sensor  24  detects a target and correspondingly sends a valid target signal on signal path  40  to the microprocessor  22 . The microprocessor  22  in response to control signal  46  (valid target control) on signal path  40  provides output command fire firing capacitor  60  on signal path  62  with the fire firing capacitor signal  60  being fed to the input stage of the firing circuit  26 . Firing circuit  26  generates an output signal  64  on signal path  66  that is routed to firing capacitor  28  which, in turn, generates an output signal  68  on signal path  70  which is routed to electric detonator  30 . 
     The internal battery  20  of the fuze  16  supplies the battery activation signal  42 , on signal path  34 , which powers up the electronics of the fuze  16  including the microprocessor  22 . The nest switch open signal  44  on signal path  38  indicates to the microprocessor  22  that the associate munition has been released from the adjacent submunitions  14 A. The valid target control signal  46  on signal path  40  indicates that the radar proximity sensor has acquired a valid target. The self-dud subroutine  72  being run in the microprocessor  22  ensures the submunition  14  will not be capable of electrically detonating the system. Charge firing capacitor subroutine  74  being run in the microprocessor  22  indicates to the electronics that is, firing circuit  26 , to output signal  64  on signal path  66  to the firing capacitor  28 . Turn on proximity mode routine  76  being run in the microprocessor  22  indicates to the microprocessor  22  to broadcast a signal, look for a return signal, and then analyze the return signal for a valid target. The fire firing capacitor routine  78  being run in the microprocessor  22  causes the electronics to discharge the firing capacitor  28  connected to the electrical detonator  30 , thus functioning the warhead. All of the routines  72 ,  74 ,  76  and  78  are to be further described hereinafter with reference to FIG.  2 . 
     FIG. 2 is composed of FIGS. 2A,  2 B,  2 C, and  2 D that cumulatively illustrate a flow chart that includes the identification of the input control signals  42 ,  44 , and  46  of FIG. 1, as well as the command signals  48 ,  52 ,  56 , and  60  of FIG.  1 . The battery activation signal  42  is referred to in FIG. 2 as battery activated  42 . Still further, the nesting switch open signal  44  is referred to in FIG. 2 as Nest Switch Open. Further, the signals  42 ,  44 ,  46 ,  48 ,  52 ,  56  and  60  of FIG. 1 are sometimes referred to as events in FIG.  2 . 
     A normal functional scenario, partially illustrated in FIG. 2A, has the internal battery  20  of the fuze  16  being activated by a signal on signal path  32  (see FIG. 1) at gun firing by a setback G-force or by having the associated payload being dropped or expelled from an explosive ordnance as represented by program segment  82 . Program segment  82  creates the battery-activated event  42  which, in turn, is handled by a first routine residing in microprocessor  22 . 
     The first routine is in response to the battery activated signal  42  and the nest switch open control signal  44  being present at the same time, indicated by program segment  84 , generates the self-dud command  48  which, in turn, activates the self-dud subroutine  72 , which may be further described with reference to FIG.  2 B. 
     As seen in FIG. 2B, the self-dud subroutine  72  is initiated by the self-dud command  48  which causes a discharge firing capacitor event  86  to be created and also causes a discharge battery  88  event to be created. The events  86  and  88  are indicative of an abnormal situation. Both events together ensure that the submunition will not electrically function in the future, that is, will remain dormant. Furthermore, for this condition, the firing capacitor  28  of FIG. 1 does not release its energy to the electrical detonator  30 . Although the self-dud subroutine  72  is preferred, the self-dud sequence can be any method that ensures the electronics of the fuze  16  do not cause the functioning of the explosives. 
     Under normal situations, the nest switch open event  44 , shown in FIG. 2A, is not immediately present when the battery activated event  42  occurs so that the first routine generates a first output signal on signal path  90  which starts a second routine residing in the microprocessor  22 . 
     The second routine is responsive to the first output signal on signal path  90 , as well as to the present and absence of the nesting switch control signal represented by presence and absence of event  44 . The second routine comprises three program segments  92 A and  92 B, and  92 C (shown on FIGS. 2C and 2D) with program segment  92 A starting a first timer t=0, with program segment  92 B keeping track that a first predetermined maximum time for first timer t has not exceeded a typical value, such as 30 seconds, and program segment  92 C keeping track that a second predetermined maximum time for the first timer, t, has not exceeded a typical value, such as 8 minutes. The second routine creates the self-dud command signal on path  94  of FIG.  2 (A), which is at the output of program segment  96 , upon the occurrence of the presence of the nest switch open event  44  before the predetermined maximum time (30 seconds) of the first timer controlled by program segment  92 B expires. If the nest switch open event  44  is not present, the second routine returns to program segment  92 B, by way of program segment  98  and signal path  100  as shown in FIG.  2 A. Furthermore, if the nest switch open event  44  is not present before the 30 seconds has expired, the second routine generates a second output control signal on signal path  102 , which is delivered to program segment  104  of the third routine which may be further described with reference to FIG.  2 C. 
     The third routine generates a third output signal present on signal path  106  in response to the nest switch open event  44  being present after the expiration of the 30 seconds controlled by program segment  92 B of FIG.  2 A. The third output signal on signal path  106  of FIG. 2C is generated by program segment  108 . The third routine also includes program segments  110 ,  92 C,  112  and  114  and the sensing of the self-dud command signal  48  which activates the self-dud subroutine  72 , previously described with reference to FIG.  2 C. More particularly, if the second output signal is present on signal path  102  and if the nest switch open event  44  is not (program segment  110 ) present, then the program segment  92 C (Is T greater than 8 minutes?) is examined and if the answer of this examination is No (program segment  112 ) the third routine returns, via signal path  116  of FIG. 2C, to its event  44  for sensing for the nest open switch signal  44 ; however, if the 8 minutes, associated with program segment  92 C has expired, program segment  114  causes the generation of self-dud command signal  48  and which, in turn, causes the response previously described with reference to FIG.  2 B. 
     A fourth routine in response to the presence of the third output signal on signal path  106  causes the examination of program segment  92 C. The fourth routine will generate the self-dud control signal  48  upon the expiration of the 8 minutes controlled by program segment  92 C and by the activation of program segment  118 , but it also generates a fourth output signal on signal path  120  if the predetermined maximum time of 8 minutes set by program segment  92 C has not expired, as indicated by program segment  122 . The fourth output is routed to charge firing capacitor subroutine  74 , which is also part of a fifth routine. 
     The fifth routine, in particular, the charge firing capacitor subroutine  74  causes the firing circuit  26  of FIG. 1 to generate output signal  64  so as to supply voltage to the firing capacitor  28  in response to the fourth output signal on signal path  120 . The fifth routine includes program segments  124  and  126 , wherein program segment  124  starts a self-destruct (SD) timer TT=0, and wherein program segment  126  (shown in FIG. 2D) sets a predetermined maximum time for the self-destruct (SD) timer, which may have a typical timer value of 30 seconds. The fifth routine supplies a fifth output signal on signal path  128 , which is routed to a sixth routine. 
     The sixth routine starts at a second timer, controlled by program segment  130  having a predetermined maximum time, which may be one (1) second and upon the expiration of the one (1) second duration, the second timer generates the command, turn on proximity mode signal  56  of FIG. 1, which is shown in FIG. 2C by event  76 . The output of turn on proximity mode event  76  is routed to a seventh routine by way of signal path  132 , which may be further described with reference to FIG.  2 D. 
     The seventh routine is responsive to the presence and absence of the valid target event  46  of FIG. 1, shown in FIG. 2D as event  46 , and the expiration of the self-destruct (SD) timer (TT) controlled by program segment  126 , previously mentioned with reference to the fifth routine of FIG.  2 C. The seventh routine is also responsive to the presence and absence of the expiration of the second predetermined maximum time of the first timer, t, defined by program segment  92 C previously discussed with regard to the second routine of FIG.  2 A. The seventh routine includes three subroutines. 
     The first subroutine, in particular program segment  134 , of the seventh routine generates the firing capacitor command signal  60  of FIG. 1 which, in turn, activates the fire firing capacitor routine  78  upon the presence of a valid target event  46 . The fire firing capacitor routine  78  commands the firing circuit  26  to cause the discharge of the firing capacitor  28  connected to the electrical detonator  30 . Further, the fire firing capacitor routine  78  causes the generation of the self-dud command signal  48 . 
     The second subroutine of the seventh routine, in response to the absence of the valid target event  46  indicated by program segment  136 , and the expiration of the 30 second timer for the self-destruct (SD) timer (TT) defined by program segment  126  and indicated by program segment  138 , causes the activation of the fire firing capacitor routine  78  and the generation of the self-dud command signal  48 . The second subroutine, in particular program segment  140 , generates an output signal on signal path  142  upon the absence of a valid target control event  46  and upon the absence of the expiration of the 30 second for the self-destruct (SD) timer (TT) defined by program segment  126 . 
     The third subroutine of the seventh routine, in particular program segment  144 , activates the fire firing capacitor routine  78  in response to the output signal being present on signal path  142 , and upon the expiration of the maximum time (8 minutes) controlled by program segment  92 C. The fire firing capacitor routine  78  also causes the generation of the self-dud command  48 . If the maximum time, typically 30 seconds, for the self-destruct timer, TT, controlled by program segment  126  has not expired indicated by program segment  140 , and if 8 minutes predetermined second maximum duration of the timer, t, of program segment  92 C has also not expired indicated by program segment  146 , then the third subroutine of the seven routine transfers control back to the first subroutine of the seven routine starting at the valid target event  46  by way of signal path  148 . 
     It should now be appreciated that the practice of the present invention in response to a normal function scenario that has a battery activated at gun firing by the setback G-force indicated by event  82  of FIG. 2A, provides a program safety logic that allows 30 seconds, controlled by program segment  92 B, for a minimum flight. This 30 seconds may typically be increased to 45 seconds. The maximum flight time for the projectile  10  is 8 minutes and is controlled by program segment  92 C of FIGS. 2C and 2D. Thus, the fuze control logic mandates that the submunitions remain nested together for at least 30 seconds after the battery is activated, but allows for up to 8 minutes for unnesting to occur. Accounting for typical battery rise time and electronic timer tolerances, these times may be adjusted between 30 to 45 seconds and between 8 to 10 minutes. It should also be appreciated that programmable timers are ordnance dependent and can be changed to match different performance requirements. 
     It should be further appreciated that the present invention provides for a proximity fuze mode. The proximity fuze mode, that is, turning on the proximity sensor  24 , shown in FIG. 2C, is coordinated with the valid target information indicative that the correct height of the explosive ordnance has occurred prior to ground impact. This allows the submunition to be more lethal. Further, the integration of the timing logic with turning on the proximity fuze mode has allowed the battery capacity to be reduced by not requiring the proximity mode to be broadcasting considerable RF energy, which, in turn, allows for the reduction in size of the internal battery being carried by the explosive ordnance, which, in turn, allows for the reduction in size of the entire fuze. Further, the proximity mode not only increases the lethality, but also increases the reliability of the operation of the submunitions. 
     The present invention eliminates electronic functioning by any accidental release of the submunitions. More particularly, in an accident scenario, the battery activation event is considered to occur at the same time or within a few seconds of the submunition release event. It is assumed that if the submunitions are nested during this time, they will remain somewhat together for a sufficiently long time. The use of a programmable timer takes this into account and does not react immediately to the nest switch open signal  44 . Although in an accident where the battery is activated and the submunitions are nested, the ability of the fuze control logic does not prevent the fuze to be functioned mechanical, but it does at the same time greatly reduce the probability of allowing for the entering of the self-destruct or self-neutralizing mode. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the above-described embodiments of the present invention without departing from the scope or spirit of the invention. Thus, it is intended that the present invention covers such modifications and variations provided they come within the scope of the appended claims and their equivalence.