US3722408A - Anti-swimmer charge - Google Patents

Abstract

An anti-swimmer explosive charge device having a capacitor for energy storage and a water activated switch. The water activated switch consists of two terminals separated by a salt impregnated insulator. When the insulator becomes wet it conducts current from the energy source to a timing circuit.

Description

ie States Patent 11 1 Fox et a1. 5] Mar. 27, 1973 [54] ANTl-SWIMMER CHARGE 3,127,485 3/1964 Vitolo ..200/6l.05 3,343,493 9/1967 A lds ta]... ..102/70.2 [75] lnvenmrs: F" 3,395,640 8/1968 Ts mr ..102/16 7 both of Arlington, Va. 3,502,024 3/1970 Mountjoy ..102/70.2

[73] Assignee: The United States of America as represented by the Secretary of the Pnmary Exammerfvqlm pendegass Navy. Attorney-R. S. Sciasc1a and P. Schneider 22 Filed: I M110, 1970 i [57 ABSTRACT 21 Appl 1 02 An anti-swimmer explosive charge device having a capacitor for energy storage and a water activated switch. The water activated switch consists of two ter- [52] US. Cl ..102/16, 102/702 R, ZOO/61.05 minals separated by a salt impregnated insulator. [51] Int. Cl ..F42c 3/00, F42c 15/38 When the insulator be m we i onducts current 58 Field of Search 102/16, 70.2; ZOO/61.05 from t energy Source to a timing circuit- 3 Claims, 5 Drawin Figu' res [56] References Cited 8 UNITED STATES PATENTS 1,648,197 11/1927 Roodhouse ..200/61.05

SALT mew- PATENTEDHARZTIHYS ,722,40

FIG. 2

' 1NVENTOR$ JOHN 0. FOX THOMAS H ROSL/ G /Awa ATTORNEY PATENIEDmznms 3 7 2 SALT I IMPREGNATED MATERIAL I I 22 25 I I 2a SALT 9 IMPREGNATED I MATERIAL 27 2o 23' T 26 FIG 4 /5 SALT 4 IMPREGNATED MATERIAL /5' 22 SALT IMPREGNATED MATERIAL ANTl-SWIMMER CHARGE STATEMENT OF GOVERNMENT INTEREST 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.

BACKGROUND OF THE INVENTION This invention relates generally to an explosive charge that may be launched or thrown into the water and more particularly to a charge that may be set to detonate at specific water depths.

Many prior art designs have been developed around mechanical methods of detonation such as pressure switches and mechanically activated devices. As well as being unsafe and expensive, these devices cannot function properly in shallow depths of less than feet. Further, the usual energy source has been a battery which greatly increases the required package size and decreases performance reliability as it is difficult to keep charged batteries in portable units. Also, a battery maintains available detonating power and keeps the device potentially ready and dangerous regardless of malfunctions.

SUMMARY OF THE INVENTION The present invention provides an explosive charge device that is capable of functioning properly at any depth including depths of less than 15 feet. A water activated switch is disclosed which comprises a salt impregnated material connected between two terminals of thetiming circuit. When dry, the salt impregnated material acts as an insulator and blocks the energy source from the timing circuit. Upon entry of the device into the water, the salt impregnated material becomes wet. In this wet condition, the salt impregnated material is capable of conducting an electric current. Thus, the explosive charge device is armed and detonation timing begun by placing the entire device in the water. The need for pressure sensitive switches and other mechanical devices is eliminated. The explosive device of the present invention may be set to detonate at any time, following entry into the water, without waiting for a sufficient pressure head to develop to actuate a mechanical switch. 7

This disclosure further eliminates the battery as an energy source. A capacitor is substituted to take advantage of the fact that energy stored in a capacitor will leak off over a period of time. Should a malfunction occur, this leak will discharge the capacitor and thereby render the device harmless. The elimination of a battery also allows a decrease in package size.

OBJECTS OF THE PRESENT INVENTION Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a partial cut away of a preferred embodiment of the invention;

FIG. 2 shows a chamber containing elements of the present invention;

FIG. 3 shows a schematic drawing of a preferred em- DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1, which illustrates a preferred embodiment of the invention, shows an explosive charge 10 packaged with an electronic timer and detonator mounted within housing 11. Aqua switch 12, mounted within housing 11 (see FIG. 2) comprises a water tight chamber 14 housing a salt impregnated material 15 and baffle 16. A water port 18 in the side of water tight chamber 14 is sealed with pull ring 19. With pull ring 19 in place, the entire housing 11 is water tight. Removal of pull ring 19 allows water to flow through water port 18 past baffle 16 to salt impregnated material 15. A charging plug 20 is located on the bottom of housing 11 to deliver energy to the energy storage means located within housing 1 1.

Referring now to the schematic of FIG. 3, the energy needed to operate the timer and to detonate the charge is stored within the anti-swimmer charge (ASC) by a capacitor 22. Capacitor 22 may be charged through charging plug 20 by a hand held DC generator. Switches 23 and 23' are actuated by pull ring 19 to arm the charge and timer before it is thrown into the water.

Predetonation timing is controlled by the salt impregnated material 15. When dry, this material acts as an insulator thus blocking the charge on capacitor 22 from the timing circuit. When the insulator 15 becomes wet, it is made ready for conduction of electric current. The charge is armed and an RC circuit begins its timing. Capacitor 24 is initially charged by capacitor 22 and blocks the charge on capacitor 22 from the SCR 25 gate. SCR 25 acts as a switch between detonator 28 and its power source, capacitor 22, and remains open while capacitor 24 remains charged. Capacitor 24 discharges through variable resistance 27 according to the RC time constant. Resistance 27 is adjusted manually according to the desired water depth for explosion. When capacitor 24 is fully discharged the gate on SCR 25 becomes positive in potential with respect to its cathode. SCR 25 then fires (switch closes) and allows the detonator 28 to detonate through capacitor 22. Zener diode 26 is used to keep the sensitive SCR 25 from firing on interfering and spurious voltages. Diode 26 breaks down (the switch closes) only if a sufficiently large voltage is applied.

FIGS. 4 and 5 show design variations of the circuits in FIG. 3. Similar references numerals have been used to designate functionally similar elements in all of the circuits. It is obvious that within the guide lines of the concept disclosed these and other circuits may be used to achieve the results of the present invention.

During storage and handling pull ring 19 is in place, sealing chamber 14. Also there is no charge on capacitor 22. In this condition, the ASC device is safe for handling and storing as the timing circuitry is open and there is no internal energy available.

To prepare for firing, capacitor 22 is charged by a DC generator through charging plug 20. Next, the pull ring 19 is removed thereby opening water port 18 and closing switches 23 and 23. In this condition, the device is moderately safe and becomes neutralized when the capacitor becomes discharged.

The presence of the aqua switch delays predetonation timing until the charge enters the water. This allows the charge to be detonated at any preselected depth. The detonation depth is set by changing the RC time constant through variable resistor 27.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings.

What is claimed is:

1. In an electronic detonator for use in a device having an explosive charge, said electronic detonator including a detonator charge connected to a timing circuit:

a capacitor for energy storage having a charge thereon electrically connected to said timing circuit and being the sole source of power for said device; and

a water activated switch means delaying the initiation of predetonation timing until such time as the charge enters the water;

wherein the switch means comprises a salt impregnated insulator interposed between said capacitor and timing circuit whereby the timing circuit is not activated until the switch means enters the water.

2. The device according to claim 1 and further comprising:

a water tight housing enclosing said detonator;

a water tight chamber having a water port within said housing and having therein said salt impregnated material; and

a pull ring seal removably mounted upon said housing and sealing said chamber when in place;

whereby removal of said pull ring seal will open the water port to allow a flow of water to reach said salt impregnated material.

3. The device according to claim 2 and further comprising an externally mounted charging plug means for electrically connecting the energy storage capacitor to an external source of DC power.

Claims (3)

1. In an electronic detonator for use in a device having an explosive charge, said electronic detonator including a detonator charge connected to a timing circuit: a capacitor for energy storage having a charge thereon electrically connected to said timing circuit and being the sole source of power for said device; and a water activated switch means delaying the initiation of predetonation timing until such time as the charge enters the water; wherein the switch means comprises a salt impregnated insulator interposed between said capacitor and timing circuit whereby the timing circuit is not activated until the switch means enters the water.

2. The device according to claim 1 and further comprising: a water tight housing enclosing said detonator; a water tight chamber having a water port within said housing and having therein said salt impregnated material; and a pull ring seal removably mounted upon said housing and sealing said chamber when in place; whereby removal of said pull ring seal will open the water port to allow a flow of water to reach said salt impregnated material.

3. The device according to claim 2 and further comprising an externally mounted charging plug means for electrically connecting the energy storage capacitor to an external source of DC power.

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