US2702003A - Antisweep device for submarine mines - Google Patents

Description

Feb. 15,1955 E. A. JOHNSON 2,702,003

ANTISWEEP DEVICE FOR SUBMARINE MINES Filed Aug. 51, 1942 2 She'ets-Sheet 1 gwue/wbo'b LLIS A. JOHNSON Feb. 15, 1955 E. A. JOHNSON 2,702,003

ANTISWEEP DEVICE FOR SUBMARINE MINES Filed Aug. 31, 1942 2 Sheets-Sheet 2 United States Patent Oflice Patented Feb. 15, 1955 ANT ISWEEP DEVICE FOR SUBMARINE MINES Ellis A. Johnson, Chevy Chase, Md.

Application August 31, 1942, Serial No. 456,754

21 Claims. (Cl. 102-18) (Granted under Title 35, U. S. Code (1952), sec. 266) This invention relates to an anti-sweep device for a submarine'mine in which the mine is prevented from being fired by impulses received from a sweep cable or sweep tail towed by a vessel. More specifically, the invention relates to means operatively connected to a marine mine in communication with the water within which the mine is planted having electro-responsive means operatively connected thereto and controlled by the gradient of the voltage and current of an electric field set up within the water by a sweep cable employing a sea water return as an impulse of electric current is caused to flow through the sweep cable whereby the mine is prevented from being fired or swept by signals received from the sweep cable.

It is the general practice to employ a sweep cable or tail adapted to be towed by a vessel, hereinafter referred to as a mine sweeper, through the water and insulated therefrom throughout the length of the cable, an electrode being usually provided at the trailing end of the cable thereby to establish an electrical connection between the sweep cable and the water. An electric current is caused to pass through the sweep cable and the aforesaid electrode periodically at predetermined intervals of time, the current returning by way of the sea water to the hull of the vessel or to an electrode arranged on the trailing end of a second cable secured to the sweep cable such that the second electrode is disposed within the water at arelatively short distance from the mine sweeper. The passage of the electric current through the sweep cable causes a strong electromagnetic field to be set up within the water of sufiicient strength to explode a submarine mine planted within the vicinity of the cable of the type adapted to be fired by changes in the terrestrial magnetic field adjacent thereto. A relatively large electric current is usually passed through the sweep cable thereby to set up an electromagnetic field thereabout of considerable proportions and thus increase the effectiveness of the sweep cable, this current, as heretofore stated, being applied at predetermined intervals of time to the sweep cable. An electromagnetic field is thus set up about the sweep cable periodically at intervals, this electromagnetic field being of considerably greater strength than the magnetic field of a steel vessel whereby a considerable portion of a mine field is adapted to be swept by a single passage of the towed sweep cable thereacross.

The present invention employs the gradient of the voltage and current set up within the sea water by the sweep cable to control the operation of a sensitive relay having the winding thereof connected to a pair of electrodes secured to the mine casing in insulated relation thereto and in communication with the sea water. The relay is not sufficiently sensitive to be operated by voltage and current gradients set up within the water by a passing vessel but of sufficient sensitivity to respond to the relatively larger gradients of voltage and current set up by a sweep cable. The relay is employed to disarm the mine for a period of time suflicient to prevent the firing of the mine by electromagnetic signals received from the sweep cable.

One of the objects of the present invention is the provision of new and improved means for preventing the firing of a marine mine by signals received from a sweep cable.

Another of the objects is to provide an anti-sweep device for a submarine mine controlled by the gradient. of the voltage and current received through the water from asweep cable.

Another of the objects is the provision of new and improved means responsive to the gradient of the voltage and current of the water adjacent the mine for disarming the mine until a predetermined period has elapsed after the gradient signal has abated.

Still another object is the provision of a new and improved anti-sweep device for a submarine mine which will be economical to manufacture, reliable in operation and which possesses all of the qualities of ruggedness and durability.

Still other objects, advantages and improvements will be apparent from the following description taken in connection with the accompanying drawings wherein like numerals of reference are employed to designate like parts throughout the several views and in which:

Fig. 1 is a view of a marine mine employing an antisweep device according to one embodiment of the invention:

Fig. 2 shows in diagrammatic form an arrangement of circuits and parts therefor suitable for use with the mine of Fig. l;

Fig. 3 is a view of a mine employing an'anti-sweep device according to another form of the invention;

Fig. 4 is a plan view of the mine of Fig. 3; and,

Fig. 5 shows in diagrammatic form an arrangement of circulit s1 and parts suitable for use with the mine of Figs. 3 an Referring now to the drawings and more particularly to Fig. 1 thereof there is shown thereon a submarine mine indicated generally by the numeral 10 arranged on the bed of a body of water within the path of travel of a vessel or sweep cable, as the case may be. The casing 11 of the mine is composed of any non-magnetic material suitable for the purpose preferably cylindrical in shape and provided with a pair of electrodes 12 and 13 arranged near the opposite ends thereof and insulated from the casing in any suitable manner as by the insulating members 14 and 15 by means of which the electrodes are supported by the mine casing. The explosive charge and firing control mechanism-are arranged within the mine casing in such a manner as to insure that the mine will come to rest in substantially the position shown on the drawing after being launched within a body of water with the electrodes 12 and 13 thereof in contact with the water. The electrodes may be composed of any conductive material suitable for the purpose but I prefer to use electrodes composed of silver chloride for this purpose for the reason that this material is adapted to maintain at all times the electrical potential of the electrodes at substantially the potential of the sea water with which they are in contact. The electrodes 12 and 13 are connected to the winding of a sensitive relay R as by the conductors 16 and 17 respectively connected thereto. The relay R is adapted to be operated by a predetermined gradient of the voltage and current of the sea water with which the electrodes are in contact such, for example, as may be caused by the magnetic sweep cable 18 within the vicinity of the mine in which the sea water is employed for the return path of the electrical current flowing through the cable. The sweep cable 18 is towed through the water by a mine sweeper 19 to which the sweep cable is connected and provided with a strong electric current at regular intervals which may be obtained from any suitable source of electrical power 21 such, for example, as a storage battery, the battery being electrically connected to a generator in such a manner as to maintain the battery in a predetermined charged condition, the arrangement also including a circuit closing device adapted to connect the sweep cable to the source of electrical power at regular predetermined intervals of time as is well known in the art to which the present invention pertains.

The mine is provided with a firing control mechanism 22 of the type adapted to close a firing circuit from a source of potential in response to a change in the terrestrial magnetic field caused by a vessel within the vicinity of the mine, a suitable arming device such, for example, as the hydrostat 23 being provided to connect the firing mechanism to a battery 24 after a soluble washer S has dissolved or been softened sufiiciently by the water vto permit the hydrostat to operate. A sensitive relay R is.adapted to apply battery potential to a'tiine'delay device TD having a pair of normally closed contacts included within the firing circuit'ofthe mine therebyto cause the timing device to operate and prevent the detonator 25 from being operated by the firing mechanism 22 until sufiicient time has elapsed for the time 'delay'device to release. -The time'delay device TD isof the slow-torelease type by reason of-the provision of a' dash pot or similar time-delay mechanism whereby the firingcircuit is adapted to be held open for a predeterminedperiod of time after relay R releases. An arrangement is thus provided in which the closure of the firing circuit at the contacts'of the time delay deviceis prevented until sufiicient time has elapsed to allow the mine firing mechanism 22 to be restored .to the armed condition after performing a cycle of firing operations in response to the electromagnetic'signal received from the sweep cable The detonaton25, it will be understood, is adapted to fire an explosive charge '26 such, for example, as TNT arranged within the mine casing. 1 -Whereason-Figs; l and 2'of the drawings there is shown a marine -mine'ernploying two electrodes. arranged in space relationship at opposite ends of the mine, it will be understood that various other arrangements of electrons may be employed and the number 'of' the electrodes may be increased without departing from the present invention, Furthermorethe electrodes may be arranged inany suitable manner such, for example, as circumferentially about the casing of the mine in two groups, itbeing merely necessary to connect the electrodes of one group together and to the conductor 16 and the electrodes of the other group to the conductor 17, whereby the gradient of the voltage and current setup within the water by a sweep cable causes the sensitive relay R to operate and thereby disarm the mine. It will bealsound'erstood that Whereas'in Fig. 2 of the drawings the' arming device for the mine firing mechanism 'is'shown as a hydrostat switch. it will be understood that this is by way of illustration only as various other arming devices such, for example, as clock'rnechanisms adapted to be controlled bya hydrostat. arming wire or the like may be employed for arming the mine. On Figs. 3 and 4 is shown a submarine mine'according tov another embodiment of the invention, the mine. comprising a casing 27 provided with electrodes 28, 29, 31 and 32 arranged in predetermined space relation with with respect to one another on thejupper and outerportionof the mine casing 27. The electrodes are composed preferably' of silver chloride and 'insulated'from'the casing 27 'by the insulators 33" generally similar to the insulating r'nembers Hand of-Fig. 2. The pair of electrodes 28"and 29 are connected to the winding of a sensitive relay-R1, Fig. 5. In a'similar manner the electrodes 31 anrl 32 are connected to'the winding of a sensitive relay R2; 'Each of the relays R1 and R2 is providedwith apair of normally opencon'tactsadap'ted to'befclosedas the relay operates. .The contacts are-connected together in parallel-and adapted to closea' circuit from batteryB to the winding of a time delay mechanism-.TDl whenever relaysRlfor R2 operate. When this occurs, 'the armature 34 of the time delay relay TDI is "operated about thepivotsupportGS thereby quickly openingtheipair of contacts 36. :These contacts remain open until a predetermined period of time has elapsed after the operate circuit .to the time delay mechanism TDl has been interrupted by reason of the provision of an escapement mechanismadapted to be actuated by a.retractile spring 37 secured to the armature .34 and thereby delay the returnof the armature. to the unoperated position thereof in;engagement with the back stop 38 until theaforesaid predetermined period of time has elapsed. The contacts 36, .it will be understood, are maintained disengaged until armature 34 has again movedv into engagement'with the back stop'38fat the completion of the release movement of the armature.

Each of the relays'Rl and "R2 is also provided with a pair of normally closed contactsconnected-in' series with the contacts 360i th'e'timefdelay mechanism TD1 andjwithseach other whereby thejfiringfcircuitis opened immediately as relay R1 or R2 operates andisinaintained opened by thecontacts. 36 until apr'e'det'ermined period of time has elapsed afterrelays'RI and R21are'Ire leased. Suitable means are employed: for armingthe mineof Fig' 3 after the-mine has. been launchediandsfor firingthe mine in response to changes in the-"magnetic new adjaaefit matte, causes by a vessel Within the vicinity of the mine, the hydrostatically controlledarm ing device 39 and mine firing mechanism 40, illustrated diagrammatically on Fig. ,5 being generally similar to the arming device and mine firing mechanism of Fig. 2.

The operation of the system of Fig. 1 will now be described. Let it be assumed, by way of example, that the mine 10 has been launched within a body of water and thatthe hydrostat-23 thereoj-isoperated thereby operatively connecting'the battery 24 to the mine firing mechanism 22 andv arming the mine. Let it also be assumed that the sweep cable 18 is towed by the mine sweeper 19 within the vicinity of the'mine and that the sweep cable has applied thereto atintervals an electric current from the source of electrical power 21 of sufficient strength to cause .relay R; to be operated by the current returning'through the's'ea 'water between the electrodes 41 and 42. Th gradient of the voltage and current between the electrodes 12 and 13 of the mine is of sufiicient order of magnitude'to'causethe sensitive relay R, Fig. 2, to operate. "When this occurs, the firing. circuit is interrupted at armature 30 and breakcontact of relay R. A c'ircuitis also closed from'the battery 24 by wayof conductor 43, contacts 23'of the arminghydrostat switch, conductor 44, make contact and armature 45 ofrelay R, conductor 46, winding oftime'delay relay TD and thence to ground thereby causing relay TD to operate and at contacts 47 thereof additionally interrupt the firing cireuitforthe detonator 25 The mine firing control mechanism may be of any type suitable for the purpose such,- for example, as the mine firing mechanism disclosed in Pate'nt 1,446,915 of Ernest F.-Nichols, issued September 4, 1923 for Submarine Mine in which the firing circuit controlled thereby is adapted toxbe closed by .a pair of firing contacts in response to a magnetic signal received by the mine firing mechanism.

By including a break contact of relay R within the firing circuit in series with'the contacts 47 of relayTD, an arrangement isprovided in which the firing circuit is interruptedby' the'operation of the sensitive relay. R before the firing contacts of the mine firing mechanism 22 are closed and the firing'circuit is rendered ineffective until a predetermined period of time has elapsed after the sensitive'relay R iszreleased, this period of time being controlled-by the slow releasing relay TD. The time of release of relay TD is longer thanthe time required for the firing mechanism 22 to be restored to the armed condition in response to the sudden cessation of electromagnetic signals transmitted from a sweep cable. and thusr'the-detonating device 25 is prevented from being prematurely'fired'by a protracted interruption'of the sweep impulses'within theyicinity of the mine asthe contacts: 47 close at the end of the aforesaid predetermined period of time. r The electric signals received from a sweep cable are offconsiderably greaterstrength than the signals received from an approaching'vessel and thus the anti-sweep mechanism comprising the electrodes. 12 and 13 and the relay Rf'rnay' be made sufiiciently'insensitive for therelay R to' be operated. by the passage. of a vessel. within the vicinitylof the mine. For this reason the contacts 47 of" the time delay'relayiTD remain closed during .the time a vessel is withinjthe vicinity of'the mine .and. at all. othertimes' except when signals. are being received from a sweep'cable' and for apredeterrnined time thereafter. The sensitivity of response of relay R to the gradient of thevoltage and current of an electric field may be accomplished in a variety of ways such, for example,'as by including a resistance element in the circuit ,of relay "R in series with the winding of the relay or in parallelflthereto,'a's'may be desired, but I prefer. to control-the sensitivity of the relayto current and voltage" gradientreceived by the'electrodes 12 and 13 by the space relationship or degree .of separation of. the .electrodes 12:and"13 fromeach other. The relay :R'is thus prevented from being operated bybackground currents produced from natural causes or by currents received from armoving vessel byreasorr of the'fact that these currentsarewery weak with respect to the electriccurreritsxproduced,by-..the...sweep cable and, therefore, the anti-sweep arrangement herein'disclosed is rendered'effective to;disarm the'mine whenfthe1relativelyrstrQng currents andvvoltage.fgradients.set upfiwithin. the water by;-.a: sweep cable'tare :i'eceivfednbythe'electrodes 12 and 13 and to prevent the mine from being disarmed from natural causes or by a vessel disposed within the vicinity of the mine.

The operation of the mine of Figs. 3 and 4 in response to electrical impulses received from a sweep cable will best be understood by consideration of Fig. 5 on which is shown in diagrammatic form an arrangement of circuits and parts therefor in accordance with an alternative form of the invention. Let it be assumed, by way of example, that the mine has been planted within a body of water and that the soluble washer 50 has dissolved sufiiciently for the hydrostat switch 39 to be moved to the closed position thereby closing a circuit from battery B to the mine firing mechanism and causing the mine to become armed. Let it further be assumed that a sweep cable such, for example, as the sweep cable 18 of Fig. l is towed by the mine sweeper 19 within the vicinity of the mine and that current impulses are applied thereto by the source of electrical power 21. When this occurs, the gradient of the voltage and current picked up by the pair of electrodes 28-29 or 3132, as the case may be, is suflicient to operate the sensitive relay R1 or R2 respectively associated therewith. Whether relay R1 or R2 or both of the relays R1 and R2 are operated, will depend upon the azimuth position of the mine with respect to the sweep cable. For the purpose of explanation it may be assumed that the pair of electrodes 28-29 are generally parallel to the sweep cable and'thepair of electrodes 31-32 generally perpendicular to the sweep cable. The gradient of the voltage and current picked up by the pair of electrodes 28-29, therefore, will be considerably greater than the gradient of the voltage and current picked up by the pair of electrodes 3132 and thus relay R1 may be assumed to operate as the result of the difference in potential between the electrodes 28 and 29 and relay R2 may be assumed to be unoperated by the difference in potential between the electrodes 31 and 32.

The operation of relay R1 at armature 49 and make contact thereof applies ground to conductor 51, winding of the electromagnet of time delay relay mechanism TD1 from whence the circuit is continued by way of conductor 52, contacts 39 of the hydrostat switch mechanism and thence to one terminal of the battery B, the other terminal of battery B being connected to ground, thereby-causing the electromagnet of relay TD1 to move the armature 34 thereof quickly to the operated position. As armature 34 of relay TD1 moves away from the back stop 38 the contacts 36 of relay TD1 are opened and remain open until armature 34 has again moved to the released position in engageemnt with the back stop 38, this return movement of the armature being retarded, as heretofore stated, by a suitable escapement mechanism adapted to be actuated by the retractile spring 37 when the operate circuit to relay TD1 is interrupted.

The movement of armature 53 of relay R1 away from its break contact as relay R1 operates causes the firing circuit for the detonating device 54 to be interrupted, the firing circuit including the break contact and armature 55 of relay R2, contacts 36 of the time delay relay TD1 and a source of electrical power B adapted to-be operatively connected thereto by the firing contacts of the mine firing mechanism 40. An arrangement is thus provided in which the contacts 36 of relay TD1 are opened before armature 53 of relay'Rl again moves into engagement with its break contact and thus the firing circuit for the detonator 54 is maintained open and ineffective until contacts 36 close again at the end of a predetermined period of time after relay R1 releases in response to the abatement or cessation of electric impulses received from the sweep cable. Furthermore, by including the armature 53 and break contact of relay R1 within the firing circuit an arrangement is provided in which the firing circuit is invariably interrupted by relay R1 before sufiicient time has elapsed for the firing impulse to be transmitted thereto by the mine firing mechanism in response to the electromagnetic signal received from the sweep cable.

When the flow of current within the sweep cable is discontinued at the expiration of the first impulse, relay R1 irel'eases and at armature 49 thereof interrupts the operate. circuit to the time delay relay TD1. As the electromagnet of relay TD1 is deenergized in response to the interruption of the aforesaid operate circuit the retractile spring 37 causes armature 34 to be moved slowly toward the unoperated position, the movement of the armature being retarded by a suitable escapement mechanism. As relay R1 releases, armature 53 moves into engagement with its break contact. The firing circuit, however, is prevented from being made effective at this time by contacts 36 of relay TD1 which, it will be recalled, remain disengaged until a predetermined period of time has elapsed after relay R1 releases. When the second impulse is received from the sweep cable relay R1 again operates thereby reenergizing the electromagnet of relay TD1 and causing armature 34 thereof to be moved from a partially released position to the fully operated position. The movement of armature 53 of relay R1 away from its break contact additionally interrupts the firing circuit. The foregoing cycle of operations is continued until the gradient of the voltage and current between the electrodes 28 and 29 has decreased sufficiently to prevent the further operation of relay R1 and relay TD1, therefore, is thus caused to operate the escapement mechanism thereof for a continuous period of time of predetermined length sufiicient to allow the armature 34 to be moved by the retractile spring into engagement with the back stop 38 and the contacts 36 thereof to be closed. The firing circuit is now in readi-- mess to be closed by the mine firing mechanism in response to the approach of a vessel within the vicinity of the mine.

In the event that the mine should be disposed on the bed of the body of water such that the electrodes 31 and 32 are substantially parallel to or at a small angle with the sweep cable, the gradient of the voltage and current picked up by the electrodes 31 and 32 would be sufiicient to operate relay R2 and at armature 56 and make contact thereof apply ground to one end of the winding of relay TD1 thereby causing relay TD1 to operate. As armature 55 of relay R2 moves away from its break contact the firing circuit to the detonator 54 is interrupted. The successive operation of relays R2 and TD1 is repeated as impulses of current and voltage are received in succession by the electrodes 31 and 32 thereby to maintain the firing circuit continuously interrupted until the contacts 36 of relay TD1 are closed.

in the event that the mine should be so arranged with respect to the sweep cable that the electrodes 2829 and 31-32 make substantially equal angles with the sweep cable, both the relays R1 and R2 would be operated concurrently thereby causing relay TD1 to operate and the contacts 36 thereof to be disengaged until the gradient of the voltage and current received by the electrodes was insufficient to operate the relays R1 and R2. The mine is thereby disarmed during this period and for a predetermined period of time thereafter sufiicient to permit the armature 34 of relay TD1 to be restored to its unoperated position in engagement with the back stop 38. When this occurs, the mine is again in an armed condition.

In each of the foregoing examples it will be understood that the mine firing mechanism 40 is caused to close a pair of firing contacts thereby to apply electrical potential to a portion of the firing circuit when the electromagnetic field received by the mine firing mechanism has undergone a predetermined change and to cause the firing contacts to be restored to an open or disengaged position when the electromagnetic signal received by the mine firing mechanism has ceased or decreased to a predetermined degree of strength.

When an impulse of-electric current flows through the sweep cable the electric field caused by the flow of this current through the sea water is relatively large and substantially coincident with the electromagnetic field set up by the sweep cable. The arrangement of the pairs of electrodes on the mine casing and the sensitive relays R1 and R2 connected thereto is such that the associated sensitive relay is caused to operate by the electric field of an approaching sweep cable before the electromagnetic field set up by the sweep cable has reached a degree of strength necessary to cause the mine firing mechanism to close the firing contacts thereof and apply electrical energy to the firing circuit. Furthermore,"when the sweep cable moves away from the mine the; electromagnetic field detected by the mine firing mechanism decreases to a strength insufficient to actuate thefiring con-1 tacts thereof before the electric field of the sweep cable. has decreased sufiiciently to prevent the operation ,of the. sensitive relays R1 or R2. The sensitive relays are therefore invariably operated and the firing circuit rendered inefiective upon-the '5 approach-of a sweep cable within the .vicinityof .'the mine' before *the'mine 'firi n g 'mechanism responds -sufiiciently 'to the electromagnetic field of the' sweep cableto'close the firing contacts thereof and, furthermore, the-firing contacts of the mine firing mechanism are invariably opened whileithesweepcable' is "receding from"the-mine"before the firing circuitis closed bythe release of relay -TD1. in*whi'chthereis no p'ossibility'of firing" the mine as'the result 'ofsignals received from a 'sweep'cable;

*Whenever a ponderous mass of magnetic material such, for-example, as a' vessel approaches within the'vicinity of the mine the electromagnetic field adjacent' themine is' altered and when 'the vessel has moved into a predetermined relative: position with respect to ;the mine the change-in-the-electromagnetic field' is suflicient'to cause the mine firingimechanism to close the'firin'g contacts thereof and fire the-'detonator '54; RelaysiRl, R2 and TD'l'are unoperated by'themass of-magnetic material for the reason'that the electromagnetic field isunaccom= panied by an electricfield ofstrengthsufficient tooperate-the sensitive -relays: t

Brifly statedinsummary, the "present invention pro vide's' an" anti-sweep devicesuitable for usewith asub marine mine or the'likeadapted to be firedby a change in the magnetic field adjacent thereto'in which the gradient of the voltage and current of an electric'field is em"- ployed to prevent themine from being fired by a sweep cableor sweep tail of 'the type generallyemployed with mine sweepers. I

While the invention has been described with*particularity with respect totwo examples which give satisfactory results it will-'beunderstood bythose skilled in the art, after understanding the invention, that various changes and'modificat-ions may be'made without departing from-the spirit and scone of the invention and it is my intention, therefore,-in the appended claims to cover allsuch changes and modifications;

The invention herein described and claimed-may be manufactured andused "by or forthe Government of the United States of America for governmental purposes without the payment-of any=royaltiesthereon or therefor.

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

1. 'In a marinemine adapted'to be laid on the bed of a body of water adjacent the path of travel of a vessel, a casingflfor said mine having an explosive charge therein, means'responsive to 'a change in the magnetic field adjacent =the mine for-firing saidexplosiv'e charge, means 'included in said lfiring means and adapted when operated to render the'firing means inetie'ctive for a'predetermined interval, and means controlled by the gradient of a changing electricfield adjacent themine for operating'said last namedmeans when said gradient has reached or exceeded a predetermined value;

2. An anti-sweep device of the character disclosed adapted to control a marine mine,1a'casing for said mine,

firing mechanism within said casing, a firing'circuit' adapted'to'be, closedbysaid firing mechanism in'response to 'a-prede'terminedchange in the magnetic field adiacent the minefa pair of electrodes in'communication with the water "within which the mine is planted, means for supporting said electrodes by said casingin insulated relation therewith, and electro-responsive means operatively connected to said electrodes adapted to interrupt said firing circuit when the gradient of the voltage and current within the water between the electrodes reaches a predetermined value.

3. In a submarine mine adapted to be fired by a change inzthe magnetic field adjacent thereto, a firing circuit having 1a detonatingjdevi'c'e therein, a source of electrical energy,'a firing mechanism adapted to close said firing circuit in response to a predetermined change in said magnetic field'thereby to operate said detonating device by said source ofelectrical energy, a pair of electrodes in contact with the water within which the mine :issubmerged, means :for maintainingisaid electrodes in predetermined-spaced rrelation with respect to each other, and anz'feleetro-responsive device operatively connected to said pairof electrodes adapted to vbe operated'when the gradienti ofthevoltage and current within the'wate'r between :the electrodesreaches a predetermined "value,

said electro responsive"device having means for inter-' An 'arrangementiis' thus provided 4. In a submarine mine adapted to-be fired b yja'ch ange" in the magnetic field adjacent'thereto, a' firingcirfcuit havinga'detonating device-therein, a: source ofelec'trical energy, a firing mechanis'madaptedto close"-said"firi'ng. circuit in response'to a'predetermined change in'saijdimage' netic field thereby' to operate said 'detonatin'g idevice"by7 the source of electricalfenergy, apair'of electrodesin' contact with the 'waterwithin which the minefis sub merged, means for maintaining said electrodes in prede termined'spaced relation withrespect toeach othely'an electro-responsive device operatively connected to said. pair of electrodes adapted to be operated whenfthej'gradi ent of the voltage and current within the-water between the electrodes reaches a predetermined value, saidelectroresponsive device having means for interrupting said -fir-" ing c'ircuitas the electro-responsive deviceoperates,";and means controlled by said electro re'sponsive"device fol additionally interrupting ,said firing pcircuit fora prede terminedperiod of time aftertheelectro-responsive device has released. p g

5. A mine of the characterfdi'sclosedfladapted tobe laid on the bed of 'a' bodyof water withinthe'ipath-ot travel of a vessel, anexplosive charge -arranged*within said mine, a detonating device adaptedto'explo'de s'aid' explosive charge, a normally open firing circuit--including a source of electrical energy, adapted to firesaid den onating device, -means responsive to themagnetic field' adjacent the mine adapted to close said firingcircuit when the magnetic field has been altered by a predeterf mined amount, and means controlled by-' the gradient of an electric field adjacent the mine for preventing' the closure'of thefiring-circuit by said, circuitclosing means when the gradient has increased to a predetermined value:

6. A .mine 'of the character disclosed adapted to be laid on the bed-of a body of water withinthe-pathfof travel of a vessel, an. explosive chargearrangedwithin said mine, a detonating device "adapted toexplode'naid explosive charge,- anormallyopen firing circuit including" a source of electrical energy adapted tofire'said' detonating device, means responsiveto'the magneticfiel'd adja' cent the mine adapted 'to close said firing *circuit when the magnetic'field hasbeen altered by,a'predetermined" amount, electrore'sp-onsive means controlled byfl'the gradient of an electric field'adj acentthe minetorpre venting the closure of the firings cir'cuitbysaid circuit closing means when the gradient has increased to a" predetermined value, and means controlled by said electr-oresponsive means for additionally preventing the closure-of the firing circuit by said circuit'closingmeans until a predetermined period of time has'elapsedmfter the gradient has decreased to' a predetermined value: 7

' 7. A submarine mine having an explosive charge therein,- means for armingthe mine, meansinclu din'gia' device responsive to ach'ange in the magnetic'field ad jacent the mine for firing said' explosive charge-when the mine has been armed by said arming means,':con-' trol means included within said firing means 'anda'dapt ed to render the firing means ineffective when "a prede' termined value of voltage is applied thereto and "means responsive to an electric field adjacent thereto 'forapplying said voltage to said control means when the gradient of the electric-field reaches a predetermined value;

8. A marine mine of the character disclosed 'havingan explosive charge therein, means responsive to the'pressure of the water within which the mine is planted for arming the mine, a detonatingdevice-adapted to "fire said explosive charge, a minefiring circuit including said detonating device, means included in said "firing'circuitfor operating the detonating device in response-'to a'pre determined changein the magnetic field adjacent thereto when themine has been armed by said armingmeans, means included in said firing circuit and'adaptedwhen operated to interrupt the firing circuit for"a'prede'ter-' mined interval and means controlled .by thefgradientof an electric field adjacent themine .for operating said interrupting means thereby to disarm .the -mine when the gradient of .the electric field reaches 'orz-exceeds' a predetermined-value. r H

9. In a submarine mineadaptedlto be fired bya change in themagnetic field adjacent thereto, a casingQfon-saidmine, firing mechanism within. said -casing,,,a firing fill}: cuit"adapted tobe c-losed bytsaidSfii'ing,mechanism in response to a predeterminedcha'nge in th'e'magneticfield adjacent the mine, a pair of electrodes in contact with the water within which the mine is planted, a second pair of electrodes in communication with the water, means supported by said casing for maintaining each pair of electrodes in predetermined spaced relation with respect to the other pair of electrodes, a pair of electroresponsive devices respectively connected to each of said pairs of electrodes and adapted to be operated by the gradient of the voltage and current in the water there- 'between, each of said electro-responsive devices having means adapted to interrupt said firing circuit as the electro-responsive device operates, and means adapted to be controlled by either of said electro-responsive devices for additionally interrupting said firing circuit for a predetermined period of time after the electro-responsive device has released.

10. A marine mine of the character disclosed having an explosive charge therein, means for arming the mine, a firing circuit having a detonating device therein adapted to explode said explosive charge as the firing circuit is closed, firing mechanism adapted to close said firing circuit in response to a predetermined change in the magnetic field adjacent the mine, a pair of electro-responsive devices adapted to interrupt said firing circuit as either of the devices operates, a plurality of electrodes in contact with the water within which the mine is planted operatively connected to said electro-responsive devices and adapted to operate the electro-responsive devices when the gradient of an electric field within the water adjacent the mine reaches or exceeds a predetermined value, and means controlled by said electro-responsive devices for preventing the closure of the firing circuit by said firing mechanism until a predetermined period of of time has elapsed after the electro-responsive devices have released.

11. An anti-sweep device of the character disclosed adapted to prevent a marine mine from being fired by signals received from a sweep cable, a casing for said mine having an explosive charge therein, means for detonating the explosive charge, a firing circuit, firing mechanism responsive to a change in the magnetic field adjacent the mine adapted to close said firing circuit and thereby operate said detonating means, a sensitive relay adapted to interrupt said firing circuit as the relay operates, and means including a pair of electrodes in contact with the water for causing said sensitive relay to interrupt said firing circuit in response to a predetermined gradient of the electric field received from the sweep wire before the firing circuit is closed by said firing mechanism.

12. In a submarine mine arranged within a body of water and adapted to be fired by a change in the magnetic field adjacent thereto, a casing for said mine having an explosive charge therein, means responsive to a change in the magnetic field adjacent the mine for firing said explosive charge, a firing circuit connected to said firing means, electro-responsive means controlled by the gradient of an electric field adjacent the mine for interrupting said firing circuit in response to an electric impulse received through the water from a sweep cable, and means controlled by said electro-responsive means for maintaining said firing circuit continuously interrupted while a plurality of electric impulses from said sweep cable are received in succession and for a predetermined period of time after said impulses have ceased.

13. A mine of the character disclosed adapted to be laid on the bed of a body of water within the path of travel of a vessel, an explosive charge arranged within said mine, a detonating device adapted to explode said explosive charge, a normally open firing circuit including a source of electrical energy adapted to fire said detonating device as the firing circuit is closed, means responsive to the magnetic field adjacent the mine adapted to close said firing circuit when said magnetic field has been altered by a predetermined amount, electro-responsive means controlled by the current and voltage gradient of an electric field set up with-in the water by a sweep cable, said electro-responsive means having a pair of contacts adapted to interrupt said firing circuit, and :means controlled by said electro-responsive means for maintaining said firing circuit continuously interrupted while the electro-responsive means operates successively in response to a plurality of electromagnetic fields received in succession from the sweep cable.

14. In a submarine mine adapted to be fired by a 10 i p change in the magnetic field adjacentthereto, a casing for said mine, firing mechanism disposed within said casing adapted to be operated by a predetermined change in said magnetic field, a firing circuit adapted to be closed by said firing mechanism, a sensitive relay having means for interrupting said firing circuit as the relay operates, means including a pair of electrodes in contact-with the water adapted to operate said sensitive relay in response to a predetermined current and gradient of the voltage of the electric field received from a sweep cable as the sweep cable approaches the mine thereby to interrupt said firing circuit before the firing mechanism operates in response to a change in said magnetic field caused by the electromagnet field set up by the sweep cable, and means controlled by said sensitive relay for maintaining the firing circuit continuously interrupted until the sweep cable has passed beyond the mine to a safe distance therefrom such that the electromagnetic field received from the sweep cable is of insuflicient strength to operate said firing mechanism.

15. In a marine mine in combination, a firing circuit, a pair of electrodes in communication with the surrounding water carried by said mine, and a relay having the winding thereof connected to said electrodes and a pair of contacts included in said firing circuit for interrupting said circuit as the relay operates in response to a predetermined value of voltage and current gradient sensed by said electrodes.

16. In a mine of the character disclosed, a firing circuit, magnetically controlled means for closing said circu-it, a pair of electrodes in communication with the surrounding water, and means controlled by said electrodes as an electric field adjacent the mine is sensed thereby for interrupting said circuit in response to a magnetic sweep operation before the circuit is closed by said magnetically controlled circuit closing means.

17. In a marine mine, a pair of electrodes disposed in mutually spaced relation in communication with the surrounding water for sensing a gradient of an electric field, an electroresponsive device operatively connected to said electrodes and adapted to be operated by a current received therefrom as the gradient is sensed by the electrodes, said device having a pair of normally closed contacts adapted to be disengaged as the device operates, and a mine firing circuit connected in series with said pair of contacts whereby the firing circuit is interrupted as the gradient of an electric field is sensed by said electrodes.

18. In a submarine mine adapted to be fired by a change in the magnetic field adjacent thereto, means including a normally open circuit for firing the mine when the circuit is closed, means for closing said circuit in response to a predetermined change in the magnetic field adjacent thereto as a vessel moves within the vicinity thereof, electroresponsive means for preventing the closure of said circuit when the gradient of the voltage and current of an electric field caused by a mine sweeping operation has increased to a predetermined value, and a pair of sensing electrodes in communication with the surrounding water for actuating said electroresponsive means as said gradient is sensed thereby.

19. In a marine mine, the combination of an initially unarmed firing circuit including an electroresponsive detonator, means responsive to a change in the magnetic field adjacent the mine for closing said firing circuit when said magnetic field has been altered by a predetermined amount, and means responsive to the gradient of an electric field adjacent the mine for preventing closure of the firing circuit by said magnetic field responsive means when said gradient has increased to a predetermined value, said gradient responsive means including at least two electrodes carried by the mine in mutually spaced relation and in communication with the surrounding water.

20. In a marine mine, an electroresponsive detonator, a firing circuit for the detonator including a normally open switch and a normally closed switch, means responsive to a change in the magnetic field adjacent the mine for closing the normally open switch, and means controlled by an electric field adjacent the mine for opening said normally closed switch in response to an electric impulse received through the water from a magnetic sweep cable, said last named means including a pair of electrodes in communication with the surrounding water for sensing said field.

21. In a firing mechanism for a marine mine, in comginatipn means inc ludingemegneie respqnsivfielemen, 7 References Cited in the file of this patent Qr'fii'ifigthe'mine; a'pfiir'ofdectw ve's'irll'mutua y space T relatiin commfini'ca'tibn wi h the'sui'l ounding water, UNITED T PATENTS. az'i'd an el 'e ctrbrd 'jjdflsivjdevice operatively connected to 310,568 7 Healpeff'alp I1 1ly'22', 191 9. sai d"e1ect r0des;and having means forrendering the"n1ag- 5 1,382,374 Maxim Jnne. '21,-1921 netiefiiingelement' ineffective tofir'e the mine when the 1,466,915 Nichols Sep'tf4, 1923 gr'a dient'of an electric. field between said electrodes is sliflici'en't' to operate said electroresponsi've' means.

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