US3670653A - Self-powered fuze firing system - Google Patents

Abstract

1. A self-powered fuze firing system that will initiate moderate energy wire-bridge detonators comprising: A. PIEZOELECTRIC IMPACT GENERATOR HAVING FIRST AND SECOND ELECTRODES FOR GENERATING AN OUTPUT SIGNAL VOLTAGE WHEN DEFORMED ON IMPACT, B. A TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, C. SAID PRIMARY WINDING BEING CONNECTED ACROSS SAID IMPACT GENERATOR, D. A DIODE RECTIFIER CONNECTED IN SERIES WITH SAID SECONDARY WINDING AND BEING POLED SO AS TO BLOCK CURRENT FLOW IN SAID SECONDARY WINDING DURING THE TIME A RISING COMPRESSIVE FORCING FUNCTION IS BEING APPLIED TO THE PIEZOELECTRIC IMPACT GENERATOR, E. ELECTRIC CHARGE STORAGE MEANS COUPLED ACROSS SAID SECONDARY WINDING AND SAID RECTIFIER SERIES CONNECTED CIRCUIT, F. AND A DETONATOR CONNECTED IN SERIES WITH A VOLTAGE RESPONSIVE SWITCHING MEANS.

Description

United States Patent Lunt et al.

SELF-POWERED FUZE FIRING SYSTEM inventors: Wilbur B. Lunt, Arlington; Robert A.

Haskell, Long Beach, both of Calif.

The United States of America as represented by the Secretary of the Navy Oct. 16, 1963 Assignee:

Filed:

Appl. No.:

US. Cl. 102/70.2 R Int. Cl ..F42c 11/02, F42c 7/00, F42c 15/20 Field of Search 102/702, 70.2 G1

References Cited UNITED STATES PATENTS Allison l02/70.2 R

lips

[ 1 June 20, 1972 EXEMPLARY CLAIM l A self-powered fuze firing system that will initiate moderate energy wire-bridge detonators comprising:

a. piezoelectric impact generator having first and second electrodes for generating an output signal voltage when deformed on impact,

b. a transformer having a primary winding and a secondary winding,

c. said primary winding being connected across said impact generator,

d. a diode rectifier connected in series with said secondary winding and being poled so as to block current fiow in said secondary winding during the time a rising compressive forcing function is being applied to the piezoelectric impact generator,

e. electric charge storage means coupled across said secondary winding and said rectifier series connected circuit,

f. and a detonator connected in series with a voltage responsive switching means.

6 Claims, 2 Drawing Figures KM \l/ PATENTEnJuuzo I972 W. B. LUNT R. A. HASKELL INVENTORS ATTORNEY SELF-POWERED FUZE FIRING SYSTEM The present invention relates to a self-powered fuze firing system and more particularly to a self-powered fuze firing system which allows the initiation of moderate-energy wirebridge electro-explosive devices from an unamplified piezoelectric output of a poled ferroelectric ceramic disc.

In known fuzing systems employing wire-bridge initiators and piezoelectric impact generators, the impact-generated electrical signal is used as a trigger to discharge a stored energy circuit. For example, the common circuit consists of a thyratron which is triggered into conduction to discharge a charged capacitor through the electro-explosive initiators.

An object of the present invention is to provide a selfpowered fuze firing system that will initiate moderate energy (nominally 2,500 to 10,000 ergs) wire-bridge detonators.

Anotherobject of the invention is to provide a self-powered fuze firing system using only the energy delivered by a ferroelectric ceramic disc piezoelectric impact generator.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a schematic diagram of a preferred embodiment of the invention.

FIG. 2 is a diagram illustrating the various currents and voltages pertaining to the embodiment of FIG. 1.

Referring now to the drawings, there is shown in FIG. 1 a poled ferroelectric ceramic (piezoelectric) impact generator which under compressive impact releases a charge of the polarity indicated and a flow of current in primary winding 12 of transformer 14 which is wound so as to have the polarity shown. The secondary winding 16 is connected through a silicone diode 18 across a storage capacitor 20. An avalanche or Shockley diode 22 is connected in series with detonator 24 across capacitor 20.

In operation generator 10 should be mounted in the fuzed vehicle so as to receive as high distorting forces as possible from anticipated impacts. Under compressive impact the generator 10 releases a charge of the polarity shown and a current flows in primary 12 of transformer 14. With all polarities as shown, no current flows in secondary 16 due to the blocking action of diode 18.

Under a transient impact forcing function 30, FIG. 2, the resulting crystal deformation, curve 32, (and hence its charge generation) may closely follow its leading face; i.e., the rise of the forcing function. But as the sensor of generator 10 is electrically loaded by primary 12 of transformer 14, the freed charge is rapidly bled ofi. Even though such charge draining is inhibited by the primary l2 inductance, the voltage, curve 34, across the sensor (generator 10) falls to zero soon after peak force and peak deformation have been reached. At this same time the current, curve 36, through primary 12 is a maximum, and by inductor flywheel action continues to flow, piling the charge accrued during forcing function rise time up on the opposite sensor electrode and establishing a sensor voltage of polarity opposite to that shown in FIG. 1. Following the time of peak deformation the forcing function falls ofi, but sensor relaxation does not necessarily follow the force fall-off curve. If the rate of forcing function fall-off is slower than the natural relaxation rate of the sensor seismic system, the deformation relaxation will follow it, but if the forcing function falls faster than the relaxation time the deformation cannot follow and will relax at its natural rate. Thus there is a minimum deformation relaxation time which depends upon the physical characteristics of the sensor mounting. The continuing primary current derived from charges freed on the forcing function rise must fall to zero and then actually reverse itself due to oscillatory characteristics of the LC circuit formed by sensor capacity and transformer primary 12, with the rate of current collapse and reversal being dictated by the natural oscillatory period created by the L and C values. During this same period of current collapse and reversal, sensor deformation relaxationis creating charges of an opposite sign, curve 38, to those originally freed with the charge now bemg proportional to the magnitude of relaxation return from peak deformation. At the time when the oscillatory electrical action reverses the risegenerated current, the two current components are inphase and a heavy current pulse, curve 40, passes back through the the transformer primary. At this time all polarities indicated in FIG. 1 are reversed and the diode 18 allows the inductively coupled energy in the secondary to be applied to the firing capacitor 20.

It is critical that the reversal of the component of current derived from the force rise occur at the proper time for maximum reinforcement of the deformation relaxation current. The electrical oscillation period of the total L and C components seen in the primary 12 circuit must be considerably less than the mechanical free oscillation period of the generator l0 mounting. When the voltage across capacitor 20 reaches a predetennined value, avalanche diode 22 breaks down and capacitor 20 is very rapidly discharged through detonator 24.

Obviously many modifications and variations of the present invention are possible in the 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:

l. A self-powered fuze firing system that will initiate moderate energy wire-bridge detonators comprising:

a piezoelectric impact generator having first and second electrodes for generating an output signal voltage when deformed on impact,

b. a transformer having a primary winding and a secondary winding,

c. said primary winding being connected across said impact generator,

d. a diode rectifier connected in series with said secondary winding and being poled so as to block current flow in said secondary winding during the time a rising compressive forcing function is being applied to the piezoelectric impact generator,

e. electric charge storage means coupled across said secondary winding and said rectifier series connected circuit,

f. and a detonators connected in series with a voltage responsive switching means.

2. A self-powered fuze firing system that will initiate moderate energy wire-bridge detonators comprising:

a. a piezoelectric impact generator for generating an output signal voltage when deformed on impact,

b. a transformer having a primary winding coupled to said impact generator and having a secondary winding,

c. rectifier means connected in series with said secondary winding and having the same relative polarity as the output signal generated by said impact generator on impact,

d. electric charge storage means coupled to said rectifier means for receiving electric charges when said rectifier is in a conducting condition,

e. a voltage responsive switching means coupling said electric charge storage means to a detonator and being responsive to a predetermined voltage on said charge storage means for discharging said charge storage means through said detonator.

3. The system of claim 2 wherein said impact generator is of the poled ferroelectric ceramic type.

4. The system of claim 2 wherein said voltage responsive means is of the Shockley avalanche diode type.

5. The system of claim 2 wherein said detonator is of the moderate energy wire-bridge type.

6. The system of claim 2 wherein said wire-bridge detonator is of the type requiring electrical energy for initiation in the range of from 2,500 to 10,000 ergs.

Claims (6)

1. A self-powered fuze firing system that will initiate moderate energy wire-bridge detonators comprising: a piezoelectric impact generator having first and second electrodes for generating an output signal voltage when deformed on impact, b. a transformer having a primary winding and a secondary winding, c. said primary winding being connected across said impact generator, d. a diode rectifier connected in series with said secondary winding and being poled so as to block current flow in said secondary winding during the time a rising compressive forcing function is being applied to the piezoelectric impact generator, e. electric charge storage means coupled across said secondary winding and said rectifier series connected circuit, f. and a detonators connected in series with a voltage responsive switching means.

2. A self-powered fuze firing system that will initiate moderate energy wire-bridge detonators coMprising: a. a piezoelectric impact generator for generating an output signal voltage when deformed on impact, b. a transformer having a primary winding coupled to said impact generator and having a secondary winding, c. rectifier means connected in series with said secondary winding and having the same relative polarity as the output signal generated by said impact generator on impact, d. electric charge storage means coupled to said rectifier means for receiving electric charges when said rectifier is in a conducting condition, e. a voltage responsive switching means coupling said electric charge storage means to a detonator and being responsive to a predetermined voltage on said charge storage means for discharging said charge storage means through said detonator.

3. The system of claim 2 wherein said impact generator is of the poled ferroelectric ceramic type.

4. The system of claim 2 wherein said voltage responsive means is of the Shockley avalanche diode type.

5. The system of claim 2 wherein said detonator is of the moderate energy wire-bridge type.

6. The system of claim 2 wherein said wire-bridge detonator is of the type requiring electrical energy for initiation in the range of from 2,500 to 10,000 ergs.

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