US 3343493 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
p 9 D. D. AULDS ETAL 3,343,493
ARMING AND FIRING CIRCUIT Filed Jan. 11, 1966 zavo'c POWER SUPPLY INVENTOR8 DARRELL D. AULDS HAROLD R. SOHE/BE, JR.
ATTORNEY United States Patent 3,343,493 ARMING AND FIRING CIRCUIT Darrell D. Aulds, Ruston, La., and Harold R. Scheibe, J12, King George, Va., assignors to the United States of America as represented by the Secretary of the Navy Filed Jan. 11, 1966, Ser. No. 520,316 6 Claims.'(Cl. 102-70.2)
ABSTRACT OF DISCLOSURE The specification and drawing disclose a time delay fail-safe firing system utilizing two SCRs and a capacitor discharge firing circuit to enable the SCRs. The firing circuit is initiated when the power and ground circuits are broken thereby causing the capacitor to discharge through the gate circuit of the SCR and then causing the SCR to conduct and thereby detonate the load.
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention relates to firing circuits for electronic fuze systems and in particular to timing circuitry employing semi-conductor devices to provide a safe, compact and reliable circuit for the purpose intended.
More specifically, the invention relates to an ignition circuit for detonating explosives in which a predetermined time delay may be produced between the disconnection of the circuit from the related electrical system and the detonation of the explosive charge.
Such a circuit would, for example,be incorporated with a positive destruct system in aircraft equipment that is designed to be jettisoned or dropped while in flight such that at a predetermined time after jettisoning the circuit will detonate the explosive charge associated therewith.
The description of the use is for illustrative purposes only and it will be understood that such a circuit is readily adaptable for use with any load that would require a signal at a predetermined time after the circuit was disconnected from the associated electrical system.
Such a circuit must be compact and as efiicient as possible due to the severe space limitations and the high reliability requirements imposed by the aircraft environment. It is also desirable that such a circuit will not be susceptible to stray electromagnetic radiation which might accidentally detonate the associated explosive charge and that the circuit will drain very little current from the associated electrical system.
Accordingly, it is an object of the present invention to provide an electrical circuit capable of producing a time lag of the aforesaid nature. I
Another object of the present invention is to provide an electrical circuit capable of producing a signal at a predetermined time after the circuit has been disconnected from the associated power supply and electrical grounds.
A further object of the present invention is to provide an electrical circuit for use with electronic fuze systems and which circuit will produce a time lag of the aforesaid nature.
Still another object of the present invention is to provide a new and improved circuit for use with a fuze system which will produce a predetermined time delay between the initiating occurrence and the detonation of the explosive charge that is associated with the fuze system.
Yet another object of the present invention is the provision of a firing circuit for use with electronic fuze 3,343,493 Patented Sept. 26, 1967 systems which circuit is not susceptible to stray electromagnetic radiation which might accidentally detonate the associated explosive charge.
Still a further object of the present invention is to provide a firing circuit which will have a low current drain on the electrical system in which it is connected.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing wheren:
The figure shows a schematic of the circuit of the present invention with the associated casing.
Referring now to the drawing in detail, the ground 10 is-electrically coupled to the cathode of Zener diode 12 via the positive plate of a first feed through capacitor 14, diode 16 and resistor 18. The 28 volt direct current power supply or potential source means 20 is electrically coupled to the anode of a first silicon controlled rectifier 22 via the positive plate of a second feed through capacitor 24, diode 26 and current limiting resistor 30. The anode of Zener diode 12 is electrically coupled to one terminal of plug 32 via resistors 34, 36 and is also electrically connected to the control gate of the first silicon controlled rectifier 22. A lead 38 electrically connects a second terminal of plug 32 with ground 40. The anode of the first silicon controlled rectifier 22 is electrically connected to the anode of a second silicon controlled rectifier 42 and to the positive plate of firing capacitor 44. The negative plate of firing capacitor 44 is electrically connected to ground 40 via lead 38. The cathode of the first silicon controlled rectifier 22 is electrically connected to the control gate of the second silicon controlled rectifier 42 and also 'to the line between resistors 34 and 36. The cathode of the second silicon controlled rectifier 42 is electrically connected to the same line and the same terminal of plug 32 as the anode of Zener diode 12.
A resistor 46 is electrically connected between the cathodes of diodes 16 and 26. The negative plate of timing capacitor 48 is electrically connected to the cathode of Zener diode 12 via resistor 18. The positive plate of timing capacitor 48 is electrically connected to the cathode of Zener diode 12 via potentiometer 50 and is also electrically connected to the anode of silicon controlled rectifier 22. The timing capacitor and potentiometer 50 form a network means for producing a time lag of predetermined duration as will hereinafter be described. A two pole single throw switch 52 electrically grounds, when closed, the positive plate of firing capacitor 44 and both the anode and cathode of the second silicon controlled rectifier 42 such that the circuit is incapable of operation and thus acts as an arm-safe switch.
The entire circuit is shown in case 56 which together with feed-through capacitors 14 and 24 acts 'as a filter means to eliminate any stray electromagnetic radiation from affecting the circuit. The negative plates of feedthrough capacitors 14 and 24 are shown attached to the case 56 and with the case 56 grounded at 40 via connection at 58. The leads extending beyond casing 56 to plug 32 are encased in shielded cable which is grounded to the casing 56 as indicated at 60.
The plug 32 is shown connected to a detonator 62 for illustrative purposes only and it will be obvious that the circuit of the present invention could be employed with any load which requires a signal or needs to be controlled at a determined time after the circuit has been disconnected from the power supply means.
In operation the application of power supply means 20 with the switch 52 in armed or open position will charge the positive plate of timing capacitor 48 and the positive plate of firing capacitor 44. After the capacitors 48 and 44 are charged, the only source of continuous current drain will be through resistor 46 since potentiometer 50 will be almost an open circuit due to its large ohmic value in comparison to resistors 30 and 46, and the circuit will therefore be in a ready state. If the circuit is now disconnected from the power supply means 20 and grounds and 40, the positive plate of capacitor 48discharges at a predetermined time rate, through potentiometer 50 until the potential across Zener diode 12 has risen to a predetermined value due to the negative plate of capacitor 48 becoming more positive, at which time the Zener diode 12 conducts and places a voltage on the control gate of the first silicon controlledrectifier 22. Rectifier 22.then conducts and places a voltage on the control gate of the second silicon controlledrectifier 42 thus allowing'the second rectifier42 to conduct. With the: second siliconcontrolled rectifier 42 conductive, the firing capacitor 44 discharges through the rectifier 42 and actuates the squib of detonator 62. The explosive system isthus set off after a predetermined time delay. The cir-- cuit may be disarmed by simply turning off the power supply. from the circuit, while leaving grounds 10 and 40 connected, whereby the capacitors-44 and 48-are discharged through resistors and 46. to ground 10. If switch 52 is closed orin the safe position, the firing capacitor 44 will not be charged and the circuit will be incapable of accidentally actuating detonator 62.
While applicants-do not wish to be limited to any particular set of circuit constants, the following constants;
have proven to be useful in the'particular circuit shown.
Capacitors 14, 24 6.8 microfarads. Diodes 16, 26 GE type 1N538. Resistor 46 1 kilohm. Resistors 18, 30 270 ohms. Capacitor 48' 220 microfarads. Potentiometer 50 25 kilohms. Zener diode 12 GE type 1N1771A. Silicon controlled rectifier 22 GE type 2N2323. Silicon controlled rectifier 42 GE type C40F. Capacitor 44 4000 microfarads. Resistor 34- 4.7 kilohms. Resistor 36 15 kilohms.
Obviously many. modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims. the invention may. be practiced otherwise than as specifically described.
What is claimed is:
1. A circuit for controlling. a loadcomprising electrical ground means;
a firstand'a second silicon, controlled rectifier, each of said rectifiers having an anode, a cathode anda control gate, said cathode of said firstrectifier connectedto said gate of said second rectifier, the anodes of said first'and second: rectifiers electrically.
coupled to said ground means;
a firing capacitor electrically'connected to said anode of said second rectifier;
a Zener diode electrically connected to said control gate of said first rectifier;
a resistance-capacitance network means electrically connected in parallel betweensaid Zener diode and saidanode of said first rectifier;
a potential source means electrically coupled to said circuit for charging both the capacitance of said network means and said firing capacitor whereby if the circuit is disconnected from both said potential source means and said electrical ground means the capacitance discharges through the resistance of said network means and causes said Zener diode to conduct after a predetermined time lag which in turn allows the first and second rectifiers to conduct and thus permits the firing capacitor to discharge through said second rectifier to a load to be controlled.
2. A circuit as described in claim 1 wherein said network means includes a timing capacitor having a positive and a negative plate, the positive plate being charged by said potential source means whereby the disconnection of said circuit from said potential source means allows the positive plate of said timing capacitor to discharge through the resistance of said network means to allow the Zener diode to conduct.
3. A circuit as described in claim 1 for use in an electronic fuze system having a detonator wherein:
said Zener diode includes an anode and a cathode, the anode being electrically coupled to the control gate of said first rectifier; and
said network means includes a, timing capacitor and a potentiometer, said timing capacitor having a positive and a negative plate, both said timing capacitor and said potentiometer being electrically coupled in parallel between the anode of said first rectifier and the cathode of said Zenerdiode, said positive plate of said timing capacitor being charged by said potential source means whereby the disconnection of said circuit from said potential source means and said electrical ground means allows said positive plate to discharge through said potentiometer to make said Zener diode conductive and which ultimately results in said firing. capacitor discharging through said second silicon controlled rectifier to said detonator of said fuze system.
4; A circuit as described in claim 3 including a switch electrically grounding said firing capacitor and said cathode of said second rectifier when said switch is closed.
5. A circuit as defined in claim 3 including filter means References Cited- UNITED STATES PATENTS 4/1965, Urban 30788.5
8/1965 Carrol 30788.5
BENIAMIN A. BORCHELT, Primary Examiner..
W. C. ROCH, Assistant Examiner.