Abstract:
A base mounted remote set digital time fuze permits a chambered round to  e power, time setting information and cartridge case firing voltage available at an electric primer terminal of the cartridge case. Fuze power, time setting information and cartridge firing are performed sequentially over the same hardwire line.

Description:
GOVERNMENTAL INTEREST 
     The invention described herein was made in the course of Government Contract DAAA09-76-C-2055 and may be manufactured, used and licensed by or for the Government for Governmental purposes without the payment to me of any royalties thereon. 
    
    
     BACKGROUND OF THE INVENTION 
     Modern weapon system development has improved the range, accuracy, rapidity of fire, and lethality of guns and ammunition under a variety of battlefield conditions. The general improvement in weapon lethality supplied to ground troops has made it extremely important for personnel in armored vehicles to spot the enemy and fire an air burst before being fired upon. The amount of time that an armored vehicle commander has to make a decision and see that a fire command is executed can be very short. To overcome or shorten these lift threatening time constraints, personnel in armored vehicles, such as tanks, frequently travel with a round chambered in its gun. The problem with these chambered prior art rounds was that the range is preset and cannot be quickly changed without unchambering the round. Thus an armored vehicle traveling with a chambered round may be at a severe disadvantage, when an air burst is desired, if the preset fuze range is incorrect. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a projectile which is fully telescoped into its cartridge case and has a fuze which may be remotely set after it is chambered in a gun. A communication link is provided via a hardwire through the cartridge case primer to a digital time fuze located in the base of the projectile body. 
     An object of the present invention is to provide a hardwire remote set digital time fuze for which no internal fuze power generator is required. 
     Another object of the present invention is to provide for a digital time fuze which is powered and set only after the round is chambered and the breech of the gun is sealed. 
     Another object of the present invention is to provide a hardwire remote set digital time fuze which requires no modification to the weapon to accommodate the fuze setting technique. 
     Another object of the present invention is to provide a hardwire remote set digital time fuze which has a low cost design. 
     A further object of the present invention is to provide a hardwire remote set digital time fuze which has high system reliability due to the limited number of parts required in the design. 
     For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following descriptions taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cutaway isometric view of a telescoped round positioned in a cartridge case. 
     FIG. 2 is a partial enlarged cross sectional view of the primer-to-fuze hardwire link mechanization taken along line 2--2 of FIG. 1. 
     FIG. 3 is a further enlarged partial cross sectional view of the primer-to-fuze hardwire link mechanism taken from within circle line 3 of FIG. 2. 
     FIG. 4 is a functional schematic diagram of the hardwire remote set digital time base fuze. 
     Throughout the following description, like reference numerals are used to denote like parts of the drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, a cartridge case 10 has a telescoped round 12 axially supported therein. The front end of round 12 has a dummy nose cover 14. The rear end 16 of round 12 operatively supports fin assembly 18 and includes the base fuze 20 which is electrically and mechanically coupled to the cartridge primer 22. The round warhead in this particular instance diagrammatically shows flechette type charge 24 for illustrative purpose of what may be used in an air burst round. A propellant charge 26 is operatively disposed between round rear end 16 and the cartridge case 10. A black powder charge 28 is operatively axially positioned in the cartridge case rear end 30 between the primer 22 and the round rear end 16. 
     Referring now to FIGS. 2 and 3 the electric primer terminal 22 has an electrically initiated pyrotechnic charge 32 therein which is used to ignite the black powder charge 28 which in turn initiates the propellant charge 26. A primer-to-fuze hardwire link is comprised of a contact pin 34 which is electrically isolated from the cartridge case 10 by an insulator 36. The forward end 28 of contact pin 34 makes electrical contact with the base fuze 20 through helical contact spring 40 and the rear end 42 of contact pin 34 makes electrical contact with a primer firing voltage source, not shown, through pyrotechnic charge 32. 
     Referring now to the functional schematic electrical diagram and waveform of FIG. 4, once the round shown in FIG. 1 is chambered, a fire control system determines target range, via a laser range finder, and computes time-of-flight of the round 12 based upon the known exterior ballistics of that round. Fire control converts this information into a data train consisting of a finite number of +15 volt pulses 46 and a -160 volt firing signal 48. 
     In operation, these +15 volt pulses are applied to the primer 22 and carried via the hardwire data link of FIGS. 3 and 4 to the fuze circuitry within the round 12. All of the elements forward of the primer 22 are considered part of the projectile fuze. The +15 volt pulse signals are fed to a blocking diode 48 via an electrical conductor 50 which is connected to the primer 22 through helical spring 40 and contact pin 38. Diode 48 allows the +15 volt signal from the primer 22 to pass and charge capacitor 52 but blocks the -160 volt signal. This prevents the -160 volt signal from discharging capacitor 52. Once the storage capacitor is charged to voltage Vcc it supplies power to the electronics as indicated by the arrows marked Vcc. The data pulse train is fed via electrical conductor 54 to the input of signal conditioner 56. The signal conditioner 56 is used to condition the pulse train coming from the primer 22 so as to be properly inputted via conductor 58 to a presettable counter 60. The number of pulses fed into the counter 60 from the signal generator 56 is always less than a full count. The difference is made up from the frequency scaler 62 input via input conductor 64 once the round 12 is in flight. An oscillator 66 which serves as a time base for the fuze 20 has its output via electrical conductor 68 to the frequency scaler 62 inhibited until a set back switch 70 is enabled at the first motion of the projectile 12. Projectile motion is initiated when fire control applies a -160 volt firing signal to the primer 22. From that point on, the counter 60 which has a capacity of about 8,000 counts, for an 8 second time-of-flight, is driven from the scaler 62. When the counter 60 is filled, it produces an output via conductor 72 through a safing and arming system 74 to an electric squib 76 via electrical conductor 78. The safe and arming 74 is a mechanical system which aligns an explosive train, not shown, to an armed state once the necessary gun launch environmental conditions have been properly sensed. The electric squib 76 then initiates the warhead 80 via electrical conductor 82. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.