US3618523A

US3618523A - Stab-electric detonator

Info

Publication number: US3618523A
Application number: US34931A
Authority: US
Inventors: Richard L Hiquera; H F Richard
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1970-05-06
Filing date: 1970-05-06
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

A detonator which can be initiated by either electrical or mechanical stimulii and which is safe against premature initiation until the fuze of which it is a component has been fired. The detonator consists of a length of tubing closed at one end by means of an extremely thin metal diaphragm which is loaded with a stab-sensitive priming mix in direct contact with the metal diaphragm and other explosives necessary for the desired output characteristics.

Description

United States Patent Primary Examiner- Sa Mason Dawson et a1. 89/28 Martin et al. 102/46 Sheehan l02/70.2 A X Tognola 102/70.2 A Peet et a1 102/70.2 A X muel W. Engle Attorneys-R. S. Sciascia and J. M. St. Amand ABSTRACT: A detonator which can be initiated by either electrical or mechanical stimulii and which is safe against premature initiation until the fuze of which it is a component has been fired. The detonator consists of a length of tubing closed at one end by means of an extremely thin metal diaphragm which is loaded with a stab-sensitive priming mix in direct contact with the metal diaphragm and other explosives necessary for the desired output characteristics.

CHARGE Rox, CLASS E\ PRESSED AT 30K P l LEAD AZIDE, 1x

PRESSED AT 30K PSI\ %/INOLI3O PRIMING MIX,\ PRESSED AT IOOK PSI IVRESISTANCE Q SEAM, 360

e.g. STAlNLESS STEEL FOIL 0.000| IN. THICK INERTIAL WEIGHT PATENTEU wuv 9mm 3,818,523

CHARGE R0x,cLAss E\ PRESSED AT 30K PSI LEA0 AZIDE,

PRESSED AT 30K ps1 NOLI3O PRIMING MIX, PRESSED AT 200K PSI 20 222mg i 01D s e.g. STAINLESS STEEL FOIL |NERT|AL WE GHT CHARGE 0.0001 IN. THICK FLASH CHARGE INERTIAL WEIGHT RICHARD L. HIGUERA RICHARD HF. STRESAU INVENTOR.

ATTORNEY STAB-ELECTRIC DETONATOR The invention herein described 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.

Currently if a fuze is to have both proximity and impact capability two detonators are provided, one an electric device and one a stab device. With such an arrangement it is usually necessary for the design to allow both of these detonators to be able to initiate an intermediate component which will in turn propagate the detonation to the main charge. Also, conventional electric detonators have wires connected to a sensitive explosive which must be switched from open to closed position to enable initiation.

A number of combination stab-electric detonators have been developed. Most of these have separate stab-sensitive and electroexplosive elements such as bridge-wires or thin films which are connected to electrodes. Because of their separate stab and electrical elements most prior combination stab and electric initiators are of more complex construction than of either stab or electric detonators which are sensitive to a single class of stimulus. The electrical elements are connected to terminals which can serve as antennae for the inadvertent collection of spurious signals sufficient to cause either premature initiation, destruction of the bridge system, or deterioration of the flash charge.

To eliminate the hazards of electrically initiated ordnance to premature initiation by spurious electrical signals, an electric initiator is provided which, in effect, does not become an electric initiator until the system of which it is a component is armed.

Electric initiation is used to fire explosive charge at a point, relative to the target, where it will be most effective. This is accomplished by means of a target-sensing-transducer system which emits an electrical signal upon initial contact or proximity. The great variability of target characteristics can sometimes cause failure of such electrical systems, so it is desirable to include a mechanical "backup system responding to inertia or impact to ensure firing at some point close to the target. A detonator, such as disclosed herein, which will respond to either electrical signals or mechanical impact results in considerable simplification of fuze design as well as economy of space, which is at a premium in small units. The small size of a bomblet or submissile results in limitations of both electrical and mechanical energy available for firing, and makes both electrical and stab sensitivity needed.

An object of the invention, therefore, is to provide a detonator which can be fired by either mechanical or electrical stimuli of energy content compatible with current fuzing systems, but only after arming has aligned the detonator with an electrode-firing pin.

The detonator design consists of a stainless steel tube, closed at one end with a thin foil disc (stainless steel 0.0001 inch thick) and loaded with explosives in the manner of a stab detonator. The priming mix is loaded in direct contact with the thin foil closure disc. Electrical sensitivity is attained when a pointed electrode is brought directly into contact with the foil or via a semiconductor film.

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 shows a detonator of the present invention in a safe or unarmed situation.

FIG. 2 shows a detonator as in FIG. 1, but in an armed situation.

FIG. 3 shows a detonator embodiment using a semiconductor film for electrical arming.

The typical stab-electric detonator of this invention, as shown in FIGS. 1 and 2, has a case of stainless steel tubing, for example, one end of which is closed by a very thin conductive film or diaphragm 12 (for example, stainless steel foil or silver formed by decomposition of silver azide) e.g. 0.0001- inch thick, secured to the case by means of a 360 resistance seam or weld 13. The detonator is loaded with a flash and priming charge 14 of NOL I30 pressed at approximately 100,000 p.s.i., an intermediate charge 15 of lead azide pressed at approximately 30,000 p.s.i., and an output charge 16 pressed at 30,000 p.s.i. The priming mix 14 is adjacent the foil diaphragm 12 of stainless steel and the output end is closed with an appropriate closure disk 18. Flash and priming charge 14, NOL 130, consists of 15 percent antimoney trisulfide (red technical grade, quality control Code No. 5 from Bell Co., Rutherford, N.J., 20 percent barium nitrate (Mallinckrodt Analytical Reagent, Mallinckrodt Chemical Works, St. Louis meets A.C.S. specifications,) 20' percent lead azide (RD-1333 (I-I) lead azide,) 40 percent basic styphnate and 5 percent tetracene. Intermediate charge 15 consists of lead azide, (RD-1333 and output charge 16 is RX, class E.

For example, an 0.05-inch-internal diameter tube 10, 0.200 inch in length loaded with 0.025-inch-priming mix, 0.087- flash charge and 0.087-inch output charge pressed as indicated above works satisfactorily.

The present detonator has both stab and electric sensitivities similar to those of separate stab and electric detonators. The detonator acquires the characteristics of an electric initiator only after contact with an external electrode, i.e. stab electrode 20. Such contact can be postponed until arming of the fuze of which it is a component, such as illustrated in FIG. 2. The detonator can be made smaller and more effective than either stab or electric detonators in current use.

The stab-electric detonator as shown in FIG. 1 is in an unarmed position. It can be armed by bringing it in contact with a stab-electrode 20, for example, as shown in FIG. 2. The detonator can be initiated by impact of stab-electrode 20 which would pierce diaphragm l2 and initiate the flash and priming charge 14. The detonator can also be initiated by application of an electrical signal between stab-electrode 20 and detonator case 10. The magnitude of the signal required is related to the area of contact between stab-electrode 20 and diaphragm 12 as well as to the thickness of the diaphragm and the thermal sensitivity of the priming mix. The means stabsensitivity, in tests, was 0.093 in./oz. with a standard deviation of 0.0128 in./oz. The electrical pulse-sensitivity tests showed a mean voltage of 27.3 v. from an 0.5 uf. capacitor with a standard deviation of 0.06 log units.

Both stab and electrical sensitivity can be varied by changing the dimensions of the stab-electrode for the stab and electric firing modes respectively.

Detonators of this type provide a means of including a mechanical backup" to an electrical fuzing system. The aim plicity of detonators as disclosed herein make the production cost much lower than those of other electric detonators and very much lower than those of stab-electric detonators of earlier designs in which separate stab and electric elements are included. The fact that its electrical sensitivity depends upon contact with a suitable electrode permits safety and arming devices which are both simpler than most in current use and have an unprecedented degree of electrical safety. Detonators of this type are as compact as it is possible for electric detonators to be and in addition, their combination of electrical and mechanical sensitivity as well as their unique electrical arming characteristics provide the means to the ultimate in fuze miniaturization.

The metal diaphragm 12 may be applied by welding or by chemical or vapor deposition or by the chemical decomposition of a surface film of the priming material to form a conductive film by means appropriate to its composition (for example, a composition containing a large proportion of silver azide can be decomposed at its surface to form a film of silver by exposure to ultraviolet light.) Where the protection provided by the metal diaphragm is not required, the film may be eliminated and an electrically conductive priming composition used. Other possible types of construction include the insertion of a disc in the pierced bottom of a cup and the reduction of the bottom thickness of a cup by hypersonic electropolishing, coining, grinding, or other processes for which sufficient control is attained to provide the fractional milthicknesses required for the sensitivity needed in most ordnance applications.

If desired, a semiconductor film 24 can be located between stab-electrode 20 and diaphragm 12 as shown in FIG. 3. Semiconductor 24 would electrically insulate electrode 20 from the detonator until a signal is applied to the semiconductor changing its electrical characteristics to allow it to become conductive in order to electrically arm the detonator.

What is claimed is:

l. A detonator initiated by either of electrical and mechanical stimuli and which is safe against premature initiation until armed, comprising:

a. a tubular metal casing,

b. a very thin-conductive closure at one end of said tubular casing, a 360 resistance seam between said thin-conductive closure and the end of said tubular casing,

c. a flash and priming charge in said casing adjacent said thin-conductive closure,

d. an intennediate charge adjacent said flash and priming charge, and filling an intermediate portion of said tubular casing,

e. an output charge adjacent said intermediate charge and filling the remaining portion of said tubular casing,

1. said flash and priming charge operable to be initiated by contact of an external electrode to said thin-conductive closure and application of an electrical pulse between said electrode and said tubular metal casing,

g. said flash and priming charge also operable to be initiated by impact of a stab-firing pin to pierce said thin-conductive closure and initiate the flash and priming charge.

2. A detonator as in claim 1 wherein said conductive closure is metal foil.

3. A detonator as in claim 2 wherein said resistance seam is formed by a resistance weld.

4. A detonator as in claim 1 wherein said thin conductive closure is formed by chemical decomposition of a surface film of priming material to form a conductive film.

5. A detonator as in claim 1 wherein said thin conductive closure is formed by decomposition of silver azide to form a film of silver by exposure to suitable light.

6. A detonator as in claim 1 wherein said flash and priming charge comprises 15 percent antimoney trisulfide, 20 percent barium nitrate, 20 percent lead azide, 40 percent basic styphnate and 5 percent tetracene pressed at approximately 100,000 p.s.i.

7. A detonator as in claim 1 wherein said intermediate charge comprises lead azide pressed at approximately 30,000 p.s.i.

8. A detonator as in claim 1 wherein said intermediate charge comprises RDX pressed at approximately 30,000 p.s .i.

9. A detonator as in claim 1 wherein a semiconductor film is provided adjacent said thin-conductive closure to prevent electrical contact with an external electrode until said semiconductor film becomes conductive.

10. A detonator as in claim 1 wherein said conductive closure is formed by chemical deposition.

11. A detonator as in claim 1 wherein said conductive closure is formed by vapor deposition.

12. A detonator as in claim 1 wherein said conductive closure is formed from electrically conductive priming mix.

Claims

1. A detonator initiated by either of electrical and mechanical stimuli and which is safe against premature initiation until armed, comprising: a. a tubular metal casing, b. a very thin-conductive closure at one end of said tubular casing, a 360* resistance seam between said thin-conductive closure and the end of said tubular casing, c. a flash and priming charge in said casing adjacent said thinconductive closure, d. an intermediate charge adjacent said flash and priming charge, and filling an intermediate portion of said tubular casing, e. an output charge adjacent said intermediate charge and filling the remaining portion of said tubular casing, f. said flash and priming charge operable to be initiated by contact of an external electrode to said thin-conductive closure and application of an electrical pulse between said electrode and said tubular metal casing, g. said flash and priming charge also operable to be initiated by impact of a stab-firing pin to pierce said thin-conductive closure and initiate the flash and priming charge.

2. A detonator as in claim 1 wherein said conductive closure is metal foil.

8. A detonator as in claim 1 wherein said intermediate charge comprises RDX pressed at approximately 30,000 p.s.i.