US2974588A - Shallow water mine and arming means therefor - Google Patents

Description

SHALLOW WATER MINE AND i MEANS THEREFOR Filed June 2, 1958, Ser. No. 739,442 7 Claims. (Cl. 102-16) (Granted under Title 35, Us. (Iode (1952);scc. 266) 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.

This invention relates to a marine mine for use in shallow water and more particularly to a shallow water mine which is armed by immersion in water independently of the hydrostatic pressure applied thereto and which includes means for effecting self destruction of the mine in the event that the mine is planted on the land.

In devices of this kind heretofore proposed it has been the usual practice to discriminate between the impact received by the mine or contact with water and the heavier impact of the mine when landing on a land target after being dropped from an aircraft in flight. Furthermore, such mines have usually employed hydrostatic pressure devices to actuate the various control mechanisms of the mine when the mine is planted in the Water. Such devices have been subject to the disadvantage that when the mine is planted in very shallow water, for example, there may be insufiicient pressure to operate the hydrostatic devices thereof, and furthermore, when launched in shallow water from an aircraft in flight, conditions may be such that it is impossible for the mine to distinguish by the shock received whether the mine is planted on land or in water.

The mine of the present invention does not rely upon the character of the shock received at the time of planting nor does it rely on hydrostatic pressure for its operation and for these reasons is free of the disadvantages which normally attend these prior art mines.

In accordance with the present invention the discriminating feature of the mine between water and land planting from an aircraft is achieved by a transducer element forming one arm of a balanced Wheatstone bridge and composed of material such that the impedance of this element is changed when the element becomes wet thereby causing an unbalance in the bridge circuit and an output signal therefrom which is employed to initiate the arming operation of the mine. As the mine is dropped from the aircraft a pull switch carried by the mine is actuated by a static line attached thereto and to the aircraft or the switch may be actuated by hand, as the case may be, thereby applying battery to an oscillator circuit to actuate the Wheatstone bridge aforesaid and to re move short circuits from the electric igniters of the various explosive elements of the explosively actuated switch mechanisms, as will more clearly appear as the description proceeds.

In the event that the mine does not land in the water, the Wheatstone bridge remains balanced and a self destruction circuit is rendered effective to fire a primer and thus destroy the vital components of the mine at the expiration of a predetermined interval of time. The unbalance of the Wheatstone bridge circuit, however, renders the self destruction circuit ineffective.

One of the objects of the present invention is to provide a shallow water mine having new and improved Z,74,588 Patented Mar. 14, 1961 means for distinguishing between a launching of the mine in shallow water or on dry land, as the case may be.

Another object is to provide a shallow water mine having means effective to destroy the vital components of the mine a predetermined period of time after the mine has been launched from an aircraft and landed on terra firma, in which means responsive to a wet condition thereof are employed to prevent the destruction of such vital components when the mine is planted in the water.

Still another object is the provision of a new and improved arming device for a shallow Water mine adapted it for launchingfr'om an aircraft in flight in which battery potential is operatively connected thereto as the mine leaves the aircraft and the unbalance of a normally balanced Wheatstone bridge having a water sensitive element in one of the arms thereof is employed toeffect the arming of the mine in predetermined time delay relation after the mine has been planted within the water.

A still further object is the provision of a new and improved arming and firing mechanism for a shallow water mine which discriminates between planting in the water or on dry land, as the case may be, to arm the mine when planted in water and to effectively destroy the mine mechanism when planted on land.

Still other objects, advantages and improvements will be apparent from the following description taken in connection with the accompanying drawing of which the single figure thereof illustrates the arming and self destructive features of a shallow water mine in accordance with a preferred embodiment of the invention.

Referring now to the drawing for a more complete understanding of the invention, there is shown thereon in diagrammatic form a complete system for arming an aircraft planted shallow water mine when the mine lands within water and the means for efiectively destroying the vital parts of the mine in predetermined time delayed relation with respect to the planting thereof when the mine lands on dry terra firma.

The system comprises several more or less well known components enclosed within dashed outlines, each ofthe componentshaving a legend designating the particular component enclosed by the dashed outline corresponding thereto. These components comprise a high voltage power supply to which battery is applied by the operation of a pull switch S1 preferably secured toa static line 13 and movable to an operated position as the mine falls away from the aircraft. The operation of the pull switch also applies battery potential both to an oscillater and signal amplifier and removes a short circuit from each of three explosive elements, the operation of which will be more clearly apparent as the description proceeds.

The water sensing element comprises a Wheatstone bridge supplied with alternating current from the oscillater, the bridge circuit having in one arm thereof a transducer 14 composed of barium titanate in a dry condition. The Wheatstone brigde is initially balanced such that no output signal is obtained therefrom when the transducer is dry. The transducer element is carried. by the mine in. suchvmanner. that it becomes wet when the mine is plantedwithin the water thereby changing the impedance thereof and causing an output signal to be generated by the Wheatstone bridge. The Wheatstone bridge and transducer element thus comprise a water discriminating device which is effective to apply an alternating current signal to the output thereof only when the transducer element has become wet. The output of the bridge is connected to a signal amplifier circuit comprising a plurality of transistors for amplifying the signal received from the, Wheatstone bridge when the mine has been planted within the water.

In the event that the mine is planted out of water, no bridge output voltage is obtained by reason of the balanced condition of the bridge. Under these conditions the high voltage power supply charges condenser C1 in the self. destruction circuit through resistance R1 connected; thereto. The resistance R1 and the capacity of condenser C1 are sufficiently large such that a time delay of substantially thirty minutes is required for the voltage of the condenser C1 to build up to a value sufficient to break down diode D1. When this occurs the self destruction primer 15 is operated by dischargecurrent from condenser C1 thereby firing an explosion charge, not shown, and destroying the vital mine components.

In the event that the mine is planted within water, a bridge output voltage is obtained. 'This voltage is amplified and rectified by the amplifier and destructor control circuits. The rectified A.-C. voltage so obtained is employed to perform three dififerent operations as follows: after a delay of approximately ten minutes, condenser C2 is charged through resistor R2 sufliciently to cause diode D2 to break down. When this occurs the discharge current from condenser C2 flows through the primer 16 causing primer 16 to operate and remove a lock from a movable arming member 20 having a length of explosive train carried thereby. The operation of primer 16 also closes all of the contacts of explosively actuated switch S2. The closure of contacts 17 of switch S2 completes an operating circuit to primer 18 whereby primer 18 is operated when diode D3 is triggered at the expiration of an additional predetermined period of time. This additional delay may be of the order of two hours during which condenser C3 has been charging through resistor R3 to a potential sufiicient to break down or trigger diode D3 at the completion of this additional delay period. When this occurs the discharge current of condenser C3 through primer 18 causes the primer 18 to operate and align an explosive train within the arming member 20 of the mine firing mechanism.

Switch S2 at contacts 19 thereof closes a circuit to set an arming clock into operation. The arming clock per se forms no part of the present invention and may be of any type suitable for the purpose such for example as the normally barred clock-work disclosed in Patent No. 913,524 for Submarine Mine which issued February 23, 1909, to K. 0. Leon, in which a pair of contacts are closed in time delayed relation following energization of the electromagnet M. When the clock has completed its arming cycle and the explosive train has been aligned by operation of primer 18 the mine is in an armed condition. The mine is exploded by a firing mechanism of any well known type suitable for closing a firing circuit to detonator 21 by way of closed contacts 22 of switch S2. Contacts 23 and 24 of switch S2 may be employed advantageously to apply battery to the firing mechanism of the mine and close a mine sterilizing circuit thereto respectively in the event that a sterilizing circuit is employed.

The unlocking and explosive train aligningvmechanism of arming member 20 controlled by primers 16 and 18 respectively may be of any type suitable for the purpose such, for example, as the mechanism disclosed and claimed in the copending application of Herbert E.

Ruehlemann et al., Serial No. 577,617, filed April 11, 1956, for Bomb Fuze and designated Arming Member on the single figure of the drawing, the control connections to primers 16 and 18 being shown by dashed lines respectively.

The third operation performed by the amplifier and the destruction control circuit is to provide a bucking or opposing voltage to the self destruction circuit. This is achieved by the circuit arrangement disclosedin which the voltage obtained from the amplifier and destructor control circuit when the mine lands in water is applied to condenser C4 by way of rectifier 25 and to resistor 26 in parallel with condenser C4, the rectifier 25 being so connected that the voltage of condenser C4 is in opposing relation with respect to the voltage of condenser C1 and insufficient to fire diode D1. With this arrangement the condenser C1, even though charged to its normal voltage at the end of the thirty minute self destruction period is insufficient to trigger diode D1 'for the reason that the voltage across diode D1 is the difierential voltage between the voltages on condensers C1 and C4. The diode D1 thus does not break down and cause destruction of the critical components of the mine in the event that the mine lands within the Water. The voltage of condenser C4, however, is sufficient to cause operation of diodes D2 and D3 in the order named.

From the foregoing it is ,clearly apparent thatthere has been provided a water discriminating arming and self destruction circuit for a shallow water mine in which the water sensing element comprises a balanced Wheatstone bridge having a barium titanate element disposed within one arm thereof and adapted to cause bridge unbalance when the barium titanate element becomes wet and the impedance thereof is thus changed. The bridge output voltage is amplified and rectified, the amplified and rectified voltage being employed to unlock a normally locked arming member having an explosive train carried thereby and simultaneously therewith close a plurality of control circuit contacts. At the expiration of an additional predetermined period of time a second primer 18 is operated to cause the arming member to be moved forcibly to an armed position in which an explosive train is in alignment with the detonator 21 and the usual booster charge of the mine. Normal firing of the mine is achieved in any well known manner, the firing circuit thereof including a pair of contacts 22 on the switch S2.

Should the mine land on the beach out of the water or elsewhere in such manner that the barium titanate transducer element remains in a dry condition, a slowly charging condenser C1 connected to the high voltage power supply is charged to a potential sufificient to trigger diode D1 and operate the electroresponsive primer 15 thereby to destroy the vital components of the mine and thus render identification thereof impossible.

The mine for which the present circuit is well suited may advantageously be of the type adapted for launching from an aircraft in which the static line usually employed with such launching is secured at one end thereof to a pull switch whereby battery is applied to the circuits at the. time the mine leaves the aircraft and a short circuit is removed from each of the unlocking, aligning and self destruction primers respectively as the pull switch is operated.

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 as new and desired to be secured by Letters Patent of the United States is:

1. An arming and self destruction circuit for a shallow water mine adapted to be laid by an aircraft in flight, comprising a source of electrical energy, means operable as the mine falls away from the aircraftfor connecting the circuit to said source of energy, an oscillator, means operatively connecting said oscillator to a normally balanced Wheatstone bridge, a barium titanate transducer arranged in one of the arms of said bridge for destroying the balance thereof as the transducer becomes Wet and thereby providing a bridge output signal, means for rectifying and amplifying said signal, a condenser connected to: be charged by said rectified and amplified signal, a first diode, means operatively connecting said diode to the condenser whereby the diode is triggered when the charge on the condenser hasreached a predetermined value, a primer connected to the diode for operation by the charge of the condenser as the diode is fired, and a normally looked arming member carrying a length of explosive train and movable from an initial safe position to an armed position, said primer being adapted to unlock said arming member as the primer operates.

2. An arming and self destruction device for an aircraft laid shallow Water mine comprising a source of electrical power, a switch operatively connected to the aircraft for establishing a circuit connection between the device and said source of power, an initially balanced Wheatstone bridge, a barium titanate transducer included in one of the arms of said bridge and adapted to destroy the balance thereof as the transducer becomes wet and thus produces an output bridge signal, amplifying means for said signal, rectifying means connected to the output of said amplifying means, a storage condenser having a resistance in parallel therewith connected to said rectifying means and chargeable thereby to the voltage of said amplified and rectified signal, a second condenser having a resistance in series therewith connected to the terminals of said storage condenser and chargeable in time delayed relation with respect to the time of charging said storage condenser, a diode connected to said second condenser in a manner to be fired when the charge on the second condenser is sufiicient to break down the diode, a primer in series With the diode and said second condenser and adapted to be fired by discharge current of the second condenser through the diode, an explosive actuated switch operable by the primer as the primer is fired, said switch having a plurality of normally open pairs of contacts movable to circuit closing position as the switch is operated, a third condenser and a third resistance connected in parallel therewith and to said storage condenser, the time constants of said third condenser and resistance being such as to cause the third condenser to be charged at a slower rate than the rate of charge of the second condenser, a second diode connected to said third condenser and adapted to be fired thereby when the charge on the third condenser has increased to a predetermined value, a second primer connected to said second diode and operable by the dis charge current of said third condenser as the second diode is fired, a movable arming member, and means for moving said arming member to an armed position in response to the operation of the said second primer.

3. A device according to claim 2 including a fourth condenser and a fourth resistor connected thereto through which the fourth condenser is charged, a high voltage power supply, means including a plurality of electrical connections for establishing a charging circuit between said fourth condenser and the power supply, a third diode operatively connected to said fourth condenser and adapted to be fired when the charge on the condenser has increased to a firing potential at the expiration of a prolonged period of time controlled by the fourth resistor and the capacity of the fourth condenser, and a third primer operable by discharge current from the fourth condenser as the third diode is fired for causing destruction of the components of the mine.

4. A device according to claim 3 in which said fourth condenser and storage condenser are connected in polarity opposition whereby the third diode is not fired when the storage condenser is charged in response to a signal received from said signal amplifying and rectifying means.

5. An arming and self destructive device for an aircraft launched shallow water marine mine comprising a normally balanced Wheatstone bridge having a Water sensitive element in one arm thereof for destroying the balance of the bridge as the element becomes wet and effecting a bridge output signal, signal amplifying and rectifying means connected to the output of said bridge, a storage condenser connected to the output of said signal amplifying and rectifying means and chargeable thereby, means including a pair of diodes connected to said condenser for arming the mine in response to a signal received from the condenser, means including a third diode for causing self-destruction of the mine in predetermined time delayed relation with respect to the launching thereof when no signal is received from said Wheatstone bridge, and means for rendering said last named diode ineifective to cause destruction of the mine when a signal is received from the Wheatstone bridge.

6. A device according to claim 5 in which the diodes of said pair of diodes operate in predetermined order of succession and the time of operation of the third diode is greater than the time of operation of the first of said pair of diodes and less than the time of operation of the second of said pair of diodes.

7. A device according to claim 6 including an explm sively actuated switch, means including a primer connected to the first of said pair of diodes for operating said switch as the primer is fired in response to the breakdown of the first diode, a second primer operatively connected to the second diode of said pair of diodes and adapted to be fired as the second diode breaks down, and means including a pair of normally open contacts on said switch for operatively connecting the second primer to said second diode as the switch operates.

References Cited in the file of this patent UNITED STATES PATENTS 2,574,261 Hagan Nov. 6, 1951

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