US2881702A - Mine firing mechanism - Google Patents

Description

April 14, 1959 J. B. GLENNON ET AL 2,881,702.

- MINE FIRING MECHANISM I Filed Aug. 9, 194; v 5 Sheets-Sheet 1 Ei'li'llllllliiQ-Ffilllll" INVENTORS J.B. G NNON R.H. P K W.R. MALTBY BY c. HOBBS 9W ATTORNEY April 14, 1959 J. B. GLENNON ET AL 2,

MINE FIRING MECHANISM I Filed Aughs, 1941 I 5 Sheets-Sheet 2 .a. GLENNON .H. PARK W.R.MALTBY BY gmnoass ATTORNEY INVENTORS April 14, 1959 J. B. GLENNON ET AL 2,

. MINE FIRING MECHANISM Filed Aug. 9.;1941 s Sheets-Sheet 3 ATTORNEY J. B. GLENNON ET AL 2,881,702

April 14, 1959 I MINE FIRING MECHANISM 5 Sheets-Sheet 4 Filed Aug. 9, 1941 INVENTORS J.B. GLENNON R.H. PARK W. C

R.MALTBY A. HOBBS ATTORNEY April 1959 J. B. GLENNON ET AL 2,881,702

MINE FIRING MECHANISM Filed Aug. 9. 1941 5 Sheets-Sheet 5 INVENTORS B. GLENNON .H. PARK MALTBY H 03 B 3 BY W ATTORNEY J. R W

United States Patent 2,881,702 MINE FIRING MECHANISM James B. llennon, Washington, 1).c., Robert H. Park, Pluckemm, N .J., Wilson R. Maltby, Washington, D.'C., and Charles A. Hobbs, Atlanta, Ga.

Application August 9, 1941, Serial No. 406,236 36 Claims. Cl. 102-18) (Granted under Title 35, US. Code (1952), sec. 266) instrument in which the field continues to change over a predetermined period of time and controlling the firing .of the mine in accordance with the changing nature of the magnetic field detected by the device.

In devices of this character heretofore proposed in which a changing magnetic field is employed for firing a submarine mine, it has been found that an impulse of heavy current applied to an electrical conductor attached to a vessel moving within the vicinity of the mine and insulated from the sea water within which it is immersed except at the furthermost end thereof, causes a magnetic field to be set up within the water about the conductor of sufficient intensity to cause the mine to explode. This method of detonating a mine is referred to herein as mine sweeping, the electrical conductor employed for this purpose is also referred to herein as a sweep wire, and the vessel as a mine sweeper. Thus with the types of submarine mines heretofore devised employing firing mechanisms controlled by changes in the terrestrial magnetic field, a mine field may be swept and the mines thereof detonated by a mine sweeper systematically cruising over the field and applying current impulses at periodic intervals of time to a sweep wire trailing from the vessel.

In order to establish an effective magnetic field of considerable size about the sweep wire, it has heretofore been foundnecessary to employ an electric current of such strength that the source of electrical energy is only sufiicient to. allow the current to be applied to the sweep wire periodically for short periods of time.

In the system of the present invention the mine firing mechanism includes certain selecting and time delay elements in combination with the field sensing device whereby the detonation 'of the mine is effected only when the magnetic'field continues to change for a predetermined period of time such, for example, as the continuing change of magnetic field caused by the movement of a steel vessel or any vessel having a considerable amount of magnetic material therein past the mine disposed adjacent the path of travel of the vessel. By reason of the selecting and time delay elements and circuit connections therebetween the detonation of the mine by a mine sweeping operation of the type referred to hereinbefore is highly improbable.

Furthermore, the mine is rendered absolutely safe for transportation and handling and assumes an armed condition only after being launched by reason of the provision of certain safety control devices and circuits therefor, the operation of which will become more clear- 1y apparent as the description proceeds. In the event that the mine should fail to become armed within a prede- 2,881,702 Patented Apr. l4, 1959 2 termined time after being launched, or if the mine should be raised from the bed of the body of water within which it had been planted to a predetermined depth beneath the surface of the water, means are provided for automatically causing the mine to be exploded.

One of the objects of the present invention is toprovide a new and improved magnetic influence mine firing mechanism, selectively responsive to a changing magnetic field, of simple and rugged construction which will be economical to manufacture and possess the desired qualities of reliability and eificiency in use and operation.

Another object is to provide a mine firing device of the above general character having new and improved means for sensing changes in the magnetic field adjacent the device periodically during a predetermined period of time and detonating the mine when the changing magnetic field has continued during the predetermined period of time.

Another of the objects resides in the provision of new and improved means responsive to a changing magnetic field for firing a submarine mine in proximate amidship relation to a vessel moving past the mine.

Another of the objects resides in means in which different portions of a ships magnetic signature are employed in succession for firing a submarine mine.

Another object is the provision of means for arming a submarine mine under control of a predetermined number of vessels moving past the mine.

Another object is the provision of means responsive to a changing magnetic field for comparing the continuance of a changing magnetic field with a plurality of predetermined intervals of time and selectively firing an explosive in accordance with the results of such comparison.

Another of the objects resides in the provision of means responsive to a changing magnetic field for storing indications representing changing conditions of the field at intervals and controlling the operation of a detonating device in accordance with the indications stored.

Another of the objects is the provision of new and improved means responsive to the launchingv of the mine within a body of water for automatically resetting a 'signal storing device adapted to be subsequently controlled by a changing magnetic field.

A further object is the provision of means for storing a plurality of indications of changes in a magnetic field received at predetermined intervals of time and restoring the storing means to a predetermined condition when any of the changing indications are not received, in regular order within a predetermined period of time. d

A further object is the provision of a system vhaving means for causing a mine firing mechanism to perform a test cycle of operations as the" mineis launched and either to arm or destroy the mine in accordance with the result of the test. H 1

A still further object resides in the provision 'of' new and improved means for causingthe destruction of a submarine mine in response to movement of the mine toward the surface of the body of water within which the mine is planted.

Still further objects, improvements and advantages will be apparent from the following detailed description, taken in connection with the accompanying drawings, of which:

Fig. 1 is a view partly in section of a submarine mine employing the system of the present invention;

Fig. 2 is a view somewhat enlarged taken substantially along the line 22 of Fig. 1 showing the extender hydrostat and contacts controlled thereby;

Fig. 3 is a view taken along the line 3-3 of Fig. 2;

Fig. 4 is a view in perspective of the firing control mechanism of Fig. 1 withthecover removed;

detected by the device of Fig. 4;

Fig. taken in connection with Fig.8, illustrates graphically the variations in a magneticfield caused by the passage of each of two undegaussed vessels of different sizepast a point of reference; I

Fig. it) taken in connection with Fig 8, illustrates graphically the variations ina magnetic field caused by the passage of each of two degaussed vessels of different size past point of reference; and I Fig. 11 illustrates in diagrammatic form the entire s st m- Referring first to Fig. 1 of the drawings there is shown thereon a submarine mine indicated generally by the numeral 1 within which is disposed a field changing detection mechanism comprising an induction or search coil 2 connected as by the cable 3 to a mine firing control unit 4 operatively connected to a detonator 5 The mine is provided with a suitable aperture 6 within which is disposed a hydrostat 7 in sealed relation to the casing of the mine adapted to extend the detonator within the explosive booster charge 8 contained within the compartment 9. An explosive charge 11 surrounds the compartnient Q and completely fills the explosive chamber 12. The mine is also provided preferably with a plurality of fins 13 by means of which the mine is directed along apredetermined line of flight as to the mine is launched. A soluble washer 14 is provided within the aperture 6 for preventing the operation of the extender hydrostat for a predetermined period of time after the mine has been launched; u

The extender hydrostat comprises a flexible diaphragm 15, Fig. 2, securely held in position at the outer edge thereof as by the retaining ring 16 and bolts 17. The diaphragm is normally held in an outward position by a spring 18 acting against a shoulder 19 secured to the shaft 20in any suitable manner as by brazing the parts together. A detonator 21 is secured to the shaft 20 as by the screws 22. The casing of the mine is provided with "an extended portion 23 within which the shaft 20 is adapted to move. Secured to the plunger as by the screw 24 is a cam member 25 of insulating material suitable for the purpose such, for example, as Bakelite, hard rubber, fiber or the like having cam surfaces adapted to engage the contact springs 26 and 27 and move them into engagement with the contact springs 28 and 29 respectively as the hydrostat is operated by the pressure of the water within "which the mine is immersed. The cam member '25 is provided with a slotted cam portion 31 adapted to be engaged by the cam follower 32 secured to the end of the contact spring 33 and adapted to move the contact spring into engagement with the contact spring 34 in the event that the shaft '20 is returned to its flannel position by the spring 18 as the mine is raised to a predetermineddepth beneath the surface of the body of water within which the mine is laid. The contact springs 26, 27, 28, 29, 33 and 34 are electrically insulated from each other and from the casing of the mine as by the insulating bus'hings 35, and securely clamped in V the assembled position as by the screws 36, a projecting boss 30 being provided on the extended portion 23 to support the "contact springs 33 and 34. In order that the description of the operation of the system may be facilitated, the contactsprings 26 and 28 are hereinafter referred to as contact 1, springs 27 and 29 as contact 2,

and 33 and 34 as contact 3. A soluble washer 14 having a suitable aperture therein adapted to receive the shaft 20and secured thereto as by the nuts 40 is disposed within the aperture 6 in abutting relation with a shoulder 4 37 whereby movement of the hydrostat shaft is prevented until the soluble washer has become dissolved or softened sufliciently to permit movement of the shaft. The soluble washer may be composed of any material suitable for the purpose such, for example, as salt, glycerin, sugar and glue or similar ingredients.

The control mechanism of Fig. 4 comprises the mounting plates 38, 39, and 41 held together in spaced relation as by the studs 42 and nuts 43, the plate 41 forming a base having a plurality of lugs 44 secured thereto in any suitable manner as by welding or brazing the parts together. Each of the lugs is provided with a tapped hole adapted to receive a screw or bolt whereby a suitable enclosing cover 50, Fig. 5, may be secured thereto. A pad 47, Fig. 1, of resilient material suitable for the purpose, such, for example, as sponge rubber is provided for engaging the cover 50 and yieldably supporting the control mechanism within the mine casing. The plate 41 is provided preferably with formed portions or tabs 45 adapted to secure a battery 46 in clamped position between the plates 39 and 41 or, if desired, the battery 46 may be mounted within a suitable compartment and yieldably insulated therefrom by the pad or cushion 10 in the manner indicated on Fig. 1.

A sensitive control relay 48 such, for example, as the relay known in the trade as a sensitrol relay, is mounted within a resilient cushion mounting 51 of material suitable for the purpose such, for example, as rubber secured to the plate 38 as by the mounting ring 52 and screws 53, Figs. 4 and 6. A relay 54 is secured to the plate 38 as by the mounting studs 55 and provided with terminals 56 for external electrical connection. A selection switch SS is also mounted on the plate 38 and settable to different positions in accordance with the number of ships which may be allowed to pass the mine in succession before the mine is detonated. Three switches designated T81, T82, and T53, are provided for changing the number of successive operations of the detecting mechanism required to complete a cycle of operations thereof. A terminal strip 57 is secured to the plate 38 as by the screws 58 and provided with a plurality of terminals 59 electrically connected to the unit by the conductors 61. A cable 62 comprising a plurality of electrical conductors 63 connected at one end thereof to the terminals 59 is employed for establishing a circuit connection between the control unit and the extender hydrostat. The cover 50 is provided preferably with a bushing 60 of suitable insulating material having an aperture therein adapted to receive the cable 62.

On Fig. 7 is shown the plate 39 on which is mounted a time delay relay TD2 comprising an electrically oper ated clock mechanism having a pair of electrical contacts adapted to be closed in response to engagement by the arm 80 preferably of insulating material within a predetermined interval of time such, for example, as nine seconds after electrical energy is first applied to the relay mechanism. A second time delay relay TD4 comprising clock mechanism is also attached to the plate 39, the mechanism comprising a pair of electrical contacts 81 adapted to be closed in response to engagement by the arm with a delay of approximately two seconds as the operate circuit to the electrical Winding mechanism of the relay is interrupted. Each of the delay mechanisms TDZ and TD4 is provided with a resilient mounting 64 of rubber or similar material held to the mounting plate 39 as by the mounting ring 65 and screws 66. A selector switch A having two terminal banks adapted to be engaged by wipers is also attached to the plate 39, and a selector switch B having a single termi nal bank is also secured to the plate.

Fig. 8 shows a typical vessel having a preponderance of magnetic material distributed unequally throughout the vessel and adapted to influence the earths magnetic field in varying degrees as dilferent portions of the vessel move past a fixed point of reference. The magnetic field adjacentthe point of reference or observation is thus varied or changed and the direction of the field is also changed in accordance with that portion of the vessel moving past the reference point. Stated differently, each portion of the vessel may be regarded as exerting a magnetic influence upon the terrestrial magnetic field of varying degree whereby the influence of the terrestrial magnetic field is increased or decreased by the presence of the vessel, as the case may be. A steel vessel, for example, may acquire a certain degree of magnetism imparted thereto during the process of fabrication of the vessel and may additionally acquire magnetic properties by reason of the movement of the vessel in the earths magnetic field, and thus a steel vessel casts a particular magnetic shadow or zone of magnetic influence about the vessel in accordance with a particular pattern referred to herein as a ships signature.

Referring now to Fig. 9 and more particularly to curve A thereof in which the signature of a ship such as the ship of Fig. 8 is illustrated, the various portions of the curve A correspond generally to the adjacent portions of the vessel. The dashed line H extending across the figure indicates the earths magnetic field at the latitude corresponding to the path of travel of the vessel and the numerals 10, 20, and 25 appearing directly below the dashed line indicate the interval of elapsed time in seconds since the bow of the vessel passed the point of reference. The magnetic field represented by the curve A, it will be noted, is decreased slightly ahead of the bow of the vessel and increased as the vessel moves along a point of reference until the central portion of the vessel is opposite the reference point, thereafter decreasing to the initial strength of terrestrial field as the vessel continues its movement past the reference point, the variation in the strength of the magnetic field being discontinued shortly after the stern of the vessel passes the point of reference.

The curve A may be regarded as the signature of a small undegaussed vessel moving at a relatively slow rate of speed and the curve B as the signature of a larger vessel moving at a higher rate of speed whereby the same interval of time is required for each of the vessels to pass the point of reference. The curve B, it will be noted, is generally similar to the curve A but represents a greater change in the earths magnetic field caused by the passage of the larger vessel than the change represented by the curve A.

The curve C, Fig. 10, illustrates by way of example, the magnetic signatureof a degaussed vessel such, for example, as the vessel of Fig. 8 in which, by reason of the disposition of the magnetic material throughout the vessel and the method employed for degaussing the same, the magnetic field of the ship is caused to make several reversals as the ship passes the point of reference, there being six such reversals of the field in the ships signature represented by the curve C. -It will also be noted that the intensity of the magnetic field is varied from a positive to a negative value with respect to the earths magnetic field indicated by the letter H such that a substantially symmetrical curve is produced about the dashed line H attenuating somewhat as the stern of the vessel approaches the point of reference. The curve C may be regarded as the magnetic signature of the vessel corresponding to the curve A when the vessel is in a degaussed condition. In a similar manner the curve D, Fig. 10, may be regarded as the signature of the vessel of the curve B when in a degaussed condition, the degaussed vessel passing the point of reference during the same time interval as the vessel of curve C.

The manner in which the signature of a vessel, whether degaussed or undegaussed, is employed during a plurality of intervals of time for selectively firing a submarine mine as the vessel moves past the mine will now be described.

The operation of the system of the present invention shown on Fig. 11 will best be understood by consideration of a specific illustration. Assume, by way of example, that a;soluble plug 14 has been placed in operative position within the aperture 6, and that the selector switches A and B have been set to their normal or initial positions with the wipers of switch A in engagement with contact 1 of their respective switch banks, ,the wiper of switch B in the position shown on Fig. 11, switch SS has been set to position 1, switches T82 and T83 are operated, switch T81 is unoperated, and the mine has been launched in a body of water of depth sufficient to cause the extender hydrostat to operate.

Upon striking the water the mine sinks .and comes to rest on the bed of the body of water and, after a predetermined period of time, the soluble plug dissolves or is softened sufiiciently to allow the extender hydrostat to be operated by the pressure of the water. As the hydro stat is moved from its initial position, contact 1 closes momentarily and completes a circuit from positive terminal of battery BA, conductor 67, winding of the reset magnet RS-A of the switch A, conductor 68, contact 1 of the extender hydrostat, conductor 69 and thence to the negative terminal of battery BA thereby causing the reset magnet RS-A to operate and restore the wipers of the switch A to their normal or initial position in engagement with terminal 1 of their respective switch banks in the event that the wipers have been moved from their initial or home position prior to the launching of the mine or as the result of the violent shock received when the mine was launched. As the extender hydrostat continues its movement, contact 1 opens thereby interruptingthe operate circuit to the winding of the reset magnet RS-A and causing the reset magnet to release. As the hydrostat continues its movement contact 2 closes and remains closed during the life of the mine.

A test cycle of operation is now made as follows. Relay TD2 operates over the following circuit: Positive pole of battery BA, conductor 67, winding of relay TD2, conductor 70, wiper 1 and terminal 1 of switch A, conductor 74, contact 2, conductor 69 and thence to the negative pole of battery BA. Relay TD2 is a time delay relay arranged to close its contacts after a predetermined period of time such, for example, as nine seconds after an operate circuit has been completed to the winding thereof. Relay D operates over the following circuit: Positive terminal of battery BA, conductor 67, high resistance 71, winding of relay D in parallel with the search coil SC, high resistance 72, conductor 73, terminal 1 and wiper 2 of switch A, conductor 74, contact 2, conductor 69, and thence to the negative terminal of battery BA. The operation of relay D at its armature closes a circuit from positive terminal of battery BA, conductor 67, armature 75 and make contact 76 of relay D, conductor 77, winding of relay P, conduct0r 74, contact 2, condoctor 69 and thence to negative battery, thereby causing relay P to operate. As armature 78 of relay P moves into engagement with its make contact, a circuit is closed from positive battery BA by way of conductor 67, winding of time delay relay TD4 in parallel with the stepping magnet STP-B of switch B, conductor 79, make contact and armature 78 of relay P, conductor 74, contact 2, conductor 69 and thence to negative battery, thereby causing the operation of the time delay relay TD4 and the stepping magnet STP-B. The operation of relay TD4 causes the armature 81 thereof to move into engagement with its make contact and there to remain for a period of time such, for example, as three seconds after the operate circuit to the winding of relay TD4 has first been completed. As armature 81 of relay TD4 moves into engagement with its make contact, positive battery is applied to conductor 82, winding of reset magnet DR I of relay D from whence the circuit is continued by way of conductor 74, contact 2, conductor 69, and thence to negative battery thereby causing the reset magnet DR-to operate and restore. the armature 75 of relayv D to -a position intermediate the contacts 76 and 83 regardless of the energized condition of the operate magnet of relay D.

The operation of stepping magnet STP-B causes the switch wiper thereof to be moved into engagement with terminal 1. As the wiper of switch B moves from its initial or rest position, contacts ON-B are closed.

As armature 75 of relay D is disengaged from its contact 76, the operate circuit to relay P is interrupted. Relay P is a slow releasing relay by reason of a copper slug encircling the core of the operate magnet thereof and for this reason does not release until approximately three-tenths'of a second after the circuit to the relay winding has been interrupted. As armature 78 of relay P moves out of engagement with its make contact, negative battery is removed from conductor 79 thereby deenergizing the operate winding of relay TD4 and the stepping magnet STP-B. The stepping magnet STP-B releases but, as heretofore stated, armature 81 of relay TD4 does not move out of engagement, with its make contact until three seconds after the winding of relay TD4 was deenergized. At the completion of the three second period hereinbefore referred to, armature 81 of relay TD4 moves away from its make contact thereby removing positive battery from conductor 82 and causing the reset magnet DR of relay D to release, whereby the armature 75 of relay D is free to respond to a signal received by the operate winding of relay D.

As the wiper 2 of switch A is still resting on its terminal 1 at this time, negative battery is applied to conductor 73, resistance 72 and the operate magnet of relay D remains energized, thereby causing armature 75 of relay D to be again moved into engagement with its contact 76. When this occurs, relay P operates and applies negative battery to conductor 79 thereby causing the operation of relay TD4 and the stepping magnet STP-B. The operation of the stepping magnet causes the wiper of switch B to be moved into engagement with its terminal 2. The operation of relay TD4 causes the reset magnet DR to operate and restore the armature 75 of relay D to its intermediate position. As armature 75 of relay D moves away from its contact 76 the operate circuit to relay P is interrupted and, after a delay of three-tenths of a second, relay P releases and at its armature 78 interrupts the circuit to relay TD4 and the stepping magnet STP-B. As armature 81 of relay TD4 moves away from its make contact, positive battery is removed from conductor 82 thereby releasing the reset magnet DR and allowing the armature 75 to be again brought under control of the operate magnet D.

As the operate magnet of relay D is still energized at this time, armature 75 again moves into engagement with its contact 76 thereby causing relay P to operate and, at its armature 78 and make contact thereof, apply negative battery to relay TD4 and the stepping magnet STP-B thereby causing relay TD4 to operate and the stepping magnet STP-B to advancethe wiper of switch B into engagement with its terminal 3. A circuit is now completed from positive battery, conductor 67, winding of stepping magnet STP-A, conductor 84, contacts of switch TS3, contacts of switch TSZ, terminal 3 and wiper of switch B, conductor 74, contact 2, conductor 69 and thence to negative battery thereby causing the stepping magnet STP-A to operate and advance the wipers of switch A ahead to their terminals 2. The operation of relay TD4 at its armature 81 and make contact thereof,

1 causes the reset magnet DR of the switch D to restore the armature 75 thereof to its neutral position between the contacts 76 and 83 thereby causing relay P to release. The release of relay P removes negative battery from conductor 79 thereby releasing the stepping magnet STP-B and deenergizing the time delay relay TD4. As armature 81 of relay TD4 moves away from its make contact, positive battery is removed from the reset magnet DR thereby removing the restraint from armature 75 of relay D whereby the armature is free to respond to subsequent signals received by the operate winding of relay D. As wiper 2 of switch A moves out of engagement with its terminal 1, negative battery is removed from conductor 73 thereby deenergizing the operate magnet of relay D, and rendering the relay responsive to changes in the magnetic field detected by the search coil SC. As wiper 1 of switch A moves off terminal 1 of its switch bank, the operate circuit to relay TD2 is interrupted but, regardless of this circuit interruption, the clock mechanism of relay TD2 continues to function until armature thereof engages the make contact. The wiper of switch B, it will be recalled, is now resting on its terminal 3, and the Wipers of switch A on their terminals 2.

Shortly after the foregoing cycle of operations has been completed and at the end of the nine second period following the completion of the operate circuit to the winding of relay TD2, armature 85 of relay TD2 engages its make contact momentarily thereby applying negative battery by way of conductor 86 to the winding of the reset magnet RS-B of switch B, the circuit continuing by way of conductor 67 to positive battery thereby causing the reset magnet RS-B to operate and restore the wiper of the switch B to its normal position. As armature 85 is disengaged from its contact, reset magnet RS-B releases. The test cycle of operation is now complete, and the mineis in a condition to respond to a change in the magnetic field adjacent the mine.

The operation of the system in response to a change in the magnetic field caused by a mine sweeping operation will now be described. Assume, by way of example, that an impulse is received from a sweep Wire by the search coil SC of sufficient magnitude and duration to cause the armature 75 of relay D to be moved into engagement with one of its contacts as, for example, the contact 76. Positive battery at armature 75 of relay D is applied by way of contact 76 to conductor 77 thereby causing relay P to operate. As armature 78 of relay P moves into engagement with its make contact, negative battery is applied to conductor 79 thereby causing relay TD4 and the stepping magnet STP-B to operate. The operation of the stepping magnet STP-B causes the wiper of switch B to be moved into engagement with terminal 1 of the switch bank and the off-normal switch contacts ON-B to close. A circuit is now completed from positive battery, conductor 67, winding of relay TD2, conductor 70, wiper 1 and terminal 2 of switch A, conductor 87, contacts ON-B, conductor 74, contact 2 of the extender hydrostat, conductor 69, and thence to negative battery thereby causing relay TD2 to operate and close its contacts nine seconds later. The operation of relay TD4 at its armature 81 and make contact thereof causes the reset magnet DR of relay D to operate and reset the armature 75 thereof. As armature 75 of relay D moves away from contact 76 the operate circuit to relay P is interrupted and relay P releases. The release of relay P at its armature 78 causes the release of the stepping magnet STP-B and the deenergization of the operate magnet of the time delay relay TD4. Armature 81 of relay TD4, it will be recalled, does not become disengaged from its make contact until a period of three seconds has elapsed following the energization of the operate winding thereof. When this occurs, positive battery is removed from one end of the winding of the reset magnet DR, thereby removing the restraint from armature 75 of relay D and allowingthe relay to respond to a subsequent signal received from the search coil SC generated by the search coil in response to a changing magnetic field. The wipers of switch A are now resting on their terminals 2, and the wiper of switch B on its terminal 1.

If a second impulse should now be received from the sweep Wire such, for example, as would be caused by an interruption or reversal of the current flowing within the sweep wire, an electromotive force of opposite polarity would be generated within the search coil SC and such an impulse might be of sufficient intensity and duration to cause armature 75 of relay D to. be moved'into engagement with contact 83. Should this occur, positive battery at armature 75 of relay D is applied by way of contact 83 and conductor 77 to one end of the winding of relay P, thereby causing relay P to operate and at its armature 78 apply negative battery to relayTD4 and the stepping magnet STP-B. The operation of the stepping magnet STP-B advances the wiper of switch B into contact with terminal 2 of the switch bank. The operation of relay TD4 causes the reset magnet DR .to operate and restore the armature 75 of relay D to its neutral or intermediate position three seconds after the operate circuit of relay TD4 has been completed. As armature 75 of relay D moves away from contact 83, relay P releases thereby removing negative battery from conductor 79 and cansing relay TD4 and the stepping magnet STP-B to release. A time interval of approximately seven seconds has now elapsed since a change in the magnetic field was first detected by the search coil SC and, as is the general practice in mine sweeping operations at present employed, no further impulses will be transmitted by the sweep wire during the three second interval immediately following the release of the reset magnet DR.

At the completion of the nine second interval of time following the first operation of relay D in response to an impulse set up by a sweep operation, armature 85 of relay TD2 is moved into momentary engagement with its make contact thereby applying negative battery by way of conductor 86 to the reset magnet RS-B of switch B and causing the wiper of switch B to be'restored to its home or initial position and the switch contacts ON-B to open. The mine is now restored to its original partially armed condition.

In the event that a single impulse only is received from the sweep wire the wiper of switch B is stepped ahead to terminal 1 as relay P operates and remains on terminal 1 until armature 85 of relay TD2 engages its make contact after a time delay of nine seconds, thereby operating the reset magnet RS-B and restoring the switch wiper to its normal or initial position.

The operation of the mine in response to a changing magnetic field caused by a moving ship will now be described. Let it be assumed,by way of example, that an undegaussed ship having a magnetic signature such as shown by curve A, Fig. 9, is approaching a mine planted adjacent the path of travel of the vessel, at a rate of speed such that the time required for the vessel to travel a distance equal to the length of the vessel is substantially 25 seconds. As the bow of the vessel moves past the mine the intensity of the magnetic field adjacent the mine is increased, thereby causing "an electromotive force to be generated by the search coil 2, hereinafter referred to as SC, of sufficient magnitude to cause movement of the armature 75 of relay D from its neutral position, this movement of the armature occurring during that portion of the curve A indicated by the letter X. The movement of armature 75 continues until it is arrested by engagement with contact 76, the point on the curve A at which this occurs being indicated by the numeral 88, Fig. 9. The vessel at this time will have moved through a distance M and the magnetic field will be changed by an amount N during the time required to operate relay The operation of relay D, Fig. 11, causes relay P to operate and apply negative battery to the stepping magnet STP-B and the time delay relay TD4. The stepping magnet operates and advances the wiper of switch B to terminal 1 of the switch bank. Relay TD4 operates and at its armature 81 causes the operation of the reset magnet DR which forcibly restores the armature 75 of relay D to a neutral position intermediate the contacts 76 and 83 and maintains the armature in a neutral position until the reset magnet is released. As-armature 75 is disengaged from contact 76 the operate circuit to relay P is interrupted and relay P releases after a delay of threetenths of .a second, thereby interrupting the operate circuit to the stepping magnet STP-B and the time delay relay TD4. Relay TD4, it will be recalled, releases after a three second delay thereby removing positive battery from one end of the winding of reset magnet DR. ,The reset magnet DR releases thereby removing the restraint from armature 75 of relay D and permitting the detector relay D to respond selectively to a subsequent signal re ceived from the search coil SC.

The point on the magnetic curve A at which restraint is removed from armature 75 of relay D is indicated by the numeral 89 and the ship, it will be noted, has advanced a fractional part of its length since the first change in the magnetic field was detected by the search coil SC. The continued movement of the ship past the mine causes the magnetic field sensed by the search coil at 89 to be increased untilthat portion of the vessel corresponding to the point 91 on the curve A is opposite the mine, at which time relay D again closes its contacts by reason of an increase in the intensity of the magnetic field indicated by the letter O for a period of time represented by the letter R. As armature 75 again moves into engagement with contact 76 the cycle of operations just described is repeated and the wiper of switch B is moved into engagement with terminal 2 of the switch bank. As armature 81 of relay TD4 engages its make contact, the reset magnet DR operates and restores armature 75 of relay D to its neutral position and prevents further movement of the armature therefrom until the reset magnet DR releases. After a three second delay armature 81 of relay TD4 moves away from its make contact thereby releasing the reset magnet DR and permitting movement of the armature 75. By this time the vessel will have moved ahead until that portion of the vessel corresponding to the point 92 of the curve A representing the magnetic signature of the vessel is opposite the mine. Continued movement of the vessel causes the magnetic field to be changed until the point 93 of the curve A is reached, the ship having moved ahead a distance from the point 92 by an amount S and the magnetic field having changed by an amount T, at which time armature 75 of relay D again engages contact 76. An interval of approximately eight seconds has now elapsed since relay D was first operated by the change in magnetic field caused by the movement of the ship, during which time the ship has moved ahead sufficiently to bring the central portion thereof opposite the mine.

The operation of relay D in response to the increase T of the magnetic field causes relay P to operate, and at its armature 78 apply negative battery to conductor 79 thereby operating relay TD4 and the stepping magnet STP-B. The operation of stepping magnet STP-B causes the wiper of switch B to be moved into engagement with contact 3 of the switch bank. A circuit is now completed from positive battery BA, conductor 67, winding of stepping magnet STP-A, conductor 84, contacts of switches T83 and T82, terminal 3 andwiper of switch B, conductor 74, contact 2 of the extender hydrostat, conductor 69 and thence to negative battery thereby causing the stepping magnet STB-A to operate and advance the wipers of switch A to position 3.

a of the settable switch SS having a wiper 94 adapted to engage the contacts selectively in accordance with the set position of the switch. The wiper 94 is connected by the conductor 95 to the detonator 96. If it be assumed that the switch SS was set to position 1 with the wiper thereof in connection with contact 3 of bank 2 of switch A before the mine was launched, a circuit is now closed from negative battery by way of conductor 69, contact 2 of the extender hydrostat, conductor 74, wiper 2 and terminal 3 of switch A, contact 1 and wiper 94 of switch SS, conductor 95, detonator 96, conductor 67 and relay to operate.

11 thence to positive battery thereby operating the detonator and causing the mine to explode.

As the switch STP-B operated in response to the first operation of relay D, the Wiper of switch B was moved from the initial or home position to position 1 thereby closing contact ON-B. The closure of contact ON-B completed a circuit from positive battery, conductor 67, winding of relay TD2, conductor 70, wiper 1 and terminal 2 of switch A, conductor 87, contact ONB, conductor 74, contact 2 of the extender hydrostat, conductor 69 and thence to negative battery thereby causing the winding of relay TD2 to be energized and the Relay TD2, it will be recalled, does not close its contacts until nine seconds after the relay winding has been energized. A predetermined delay of nine seconds is thus provided as contact ON-B closes before the reset magnet RS-B may be operated to restore the wiper of switch B to its initial position. In the case of .a changing magnetic field caused by the passage of a vessel within the vicinity of the mine, armature 75 of relay D is repeatedly moved to circuit closing position by a change in the magnetic field immediately following the release of the reset magnet DR and three impulses are thus transmitted by relay P to the stepping magnet STP-B to cause the wiper of switch B to be advance-d to position 3 before sufficient time has elapsed to allow the wiper thereof to be restored to its normal position by the operation of the reset magnet RSB. In the case just described of a changing magnetic field caused by a moving vessel in which the switch SS has been set to position 1 whereby conductor 95 is in circuit with terminal 3 of bank 2 of switch A, the operation of the stepping magnet STP-A as the wiper of switch B moves into engagement with terminal 3 of its switch bank, causes a firing circuit to be closed and the mine to be exploded.

In the event that the ship of curve A has been degaussed before the ship moved into the vicinity of the mine, the operation of the mine in response to the signature of the degaussed ship will best be understood by reference to curve C of Fig. in which the first operation of relay D would take place at a point 97 on the curve C, the second operation at the point 98 and the third operation at the point 99, at which point the mine is exploded. Whereas the point 99 corresponds generally to the point 93 of the curve A, by reason of the difierence in configuration of the curves A and C as a result of the degaussing process employed, the mine may explode at a somewhat different position with respect to the portion of the vessel opposite the mine at the instant of detonation, and in either case the explosion will occur generally amidships.

If it be assumed, by way of example, that switch SS is set to posit-ion 2 thereby connecting conductor 95 to terminal 4 of bank 2 of switch A, the detonation of the mine is delayed until wiper 1 of switch A is brought into engagement with contact 4 of the switch bank. The manner in which this is accomplished will now be described.

Shortly after stepping magnet STP-A operates to advance the wipers of switch A to position 3, armature 85 of relay TD2 moves into closed position thereby applying negative battery by way of conductor 86 to one end of the winding of the reset magnet RS-B and causing the reset magnet to operate and restore the wiper of switch B to its initial or home position. When this occurs, the succeeding operation of switch B by a subsequent change in the magnetic field resulting from the continued movement of the ship past the mine causes the operation of relay D and the wiper of switch B to be advanced to position 1. The second operation of relay D by the changing field due to the ships signature causes the wiper to be advanced to position 2, and the third operation causes the wiper of switch B to he stepped ahead to terminal 3 and the wipers of switch A to be moved into engagement with their terminals 4. The engagement of wiper 2 of switch A with terminal 4 of the switch bank completes a circuit from negative battery by Way of conductor 69, contact 2, conductor 74, wiper 2 and terminal 4 of switch A, terminal 2 and wiper 94 of switch SS, conductor 95, detonator 96, conductor 67 and thence to positive battery, thereby causing the detonator to operate and explode the mine under the .aft portion of the ship.

In the event that an insufficient portion of the ships signature remains after switch B has been restored to normal by the operation of relay TD2 to allow relay D to operate a sufiicient number of times to cause the wipers of switch A to be advanced to their terminals 4, the operation of relay TD2 in response to the closure of contacts ON-B, at armature thereof causes the wiper of switch B to be restored to normal without again advancing the wipers of switch A. Thus, by the selective setting of switch SS, any of the terminals 3 to 10 of bank 2 of switch A may be operatively connected to the detonator 96 whereby the first, second, third, fourth, fifth,

sixth, seventh, or eighth ship passing the mine may be 7 selected at will for destruction. It will noted that means are provided for partially arming the mine in response to the operation of the hydrostat and for additionally arming the mine as each additional vessel passes the mine in succession thereafter. Thus, if the mine firing mechanism was set to cause the mine to explode as the Nth vessel passes the mine, the mine would be additionally armed as each of the vessels from the N(N1) vessel to the (N-2) vessel moves past the mine and fully armed as the (N-l) vessel moves past the mine.

When none of the switches T31, T82, and T83 are operated to closed position, five operations of the switch B arerequired within the time interval controlled by relay TD2 to advance the wipers of switch A to their next succeeding position. Also, if switch TS3 only is closed, four operations of switch B are required to advance the wipers of switch A, and when all of the switches T51, T52, and T83 are closed, two operations of switch B are required to advance the switch A.

Whereas in the illustrative embodiment of the invention shown on Fig. 4, three switches TSl, T S2, and TS3, are employed for changing the number of operations of the field sensing mechanism required to identify a ships signature, it will be understood that additional switches or other means may be employed, if desired, for increasing the number of sensing operations required to identify a ships signature, by merely removing the strapping between the terminals 5 to 10 of switch B as required and connecting the additional switches or other means to the terminals 5 to 10 in successive order in the manner of the switches TSl to T83.

In the event that the mine is raised from the bed of the body of water within which the mine is laid to a depth sufficient to cause the hydrostat to be forced outward by the spring 18, contact 3 closes and applies negative battery to the detonator thereby causing the mine to explode. Also, in the event that contact ON-A fails to open within nine seconds after the extender hydrostat contact 2 is closed, the operation of relay TD2 causes a circuit to be closed from negative battery, conductor 69, contact 2, conductor 74, armature 85 and make contact of relay TD2, conductor 86, contact ON-A, conductor 95, detonator 96, conductor 67, and thence to positive battery thereby causing the detonator to operate and explode the mine.

Self-destruction of the mine is also caused by the failure of switch B to step to position 2, 3, 4, or 5, as the case may be, within the operating time of relay TD2 following the closure of contact 2 of the extender hydrostat. Other conditions which may cause the self-destruction of the mine are the failure of relay D to reset, the continual operation and resetting of relay D, the failure of relay TD4 to operate or the armature 81 thereof to move to open position after the relay has been :operated, or the failure of relay P to operate orto release after operation.

Briefly stated in summary, the present invention contemplates the provision of a mine firing mechanism in which changes in a magnetic field are detected at successive intervals of time and compared with a predetermined interval of time and the firing of the mine is controlled in accordance with the results of such comparison. Furthermore, means are provided for insuring that the mine will be detonated only by a predetermined number of changing magnetic field conditions detected successively at intervals during a predetermined interval of time, and in the event that an insufiicient number of changing field conditions is detected within the predetermined interval of time, the mine is restored to a detecting condition in which a predetermined number of successive detection operations must be completed before the mine is detonated.

While the invention has been described with particularity as to one preferred embodiment of a combination of mechanisms and of each of the various elements of the combination, it is to be understood that this has been done for purposes of disclosure and that various changes and substitutions may be readily apparent to those skilled in the art, after understanding the invention herein disclosed, and that the terms employed in the appended claims are, therefore, to be considered as words of description rather than of limitation.

The invention herein described and claimed 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.

What is claimed as new and desired to be securedb Letters Patent of the United States is: I

1. In a submarine mine of the character disclosed arranged within a magnetic field, a relay, means including said relay for detecting a plurality of changing magnetic conditions within said field, means controlled by said relay for counting signals corresponding to said changes of the field detected by said detecting means, means efiective when the first of said conditions has been detected for measuring a predetermined interval of time, and means controlled by said counting means for causing said mine to explode when a predetermined number of changes in said magnetic field have been counted within said predetermined interval of time.

2. In a submarine mine of the character disclosed, an

electrical relay, means including said electrical relay for detecting magnetic changes in a magnetic field within which the mine is disposed, normally open contact means on said electrical relay adapted to be closed as the relay operates, a source of electrical power, means efiective after the mine has been launched for causing the relay to be operated by said source of electrical power, a slow releasing relay operatively connected to said contact means, a time delay mechanism controlled by said slow releasing relay, means for forcibly restoring and maintaining said contact means in open position during the operation of said time delay mechanism, means controlled by said slow releasing relay for counting the number of operations of said electrical and slow releasing relays, and means efiective when a predetermined number of operations of said electrical and slow releasing relays have been counted for preventing an additional closure of the normally open contact means of said electrical relay by said source of power. 1

3. In a submarine mine of the character disclosed, an electrical relay, means including said electrical relay for detecting magnetic changes in a magnetic field within which the mine is disposed, means adapted to be operated in time delayed relation to the launching of the mine for partially arming the mine, and means controlled by said detecting means in response to a predetermined number of changes in said magnetic field for completely arming the mine.

-tively in response to the number of signal indications counted by said counting means, and means effective 4.-In a submarine mine of the character disclosed, means for sensing the movement of a vessel within the vicinity of the mine, means controlled by said sensing means for counting signal indications, each of said signal indications corresponding respectively to one of a predetermined number of vessels moving past the mine in successive order, means for arming the mine selectively in response to the number of signal indications counted by the counting means, and means effective when the mine has been armed for causing the mine to explode opposite the next succeeding vessel passing the mine.

5. In a submarine mine of the character disclosed, means for sensing the movement of a vessel within the vicinity of themine, means controlled by said sensing means for counting a variable number of signal indications, each of said signal indications corresponding respectively to one of a plurality of vessels moving past the mine in successive order, means settable at will for setting said counting means to count a predetermined number of signal indications, means for arming the mine selecelectrical relay, means including said electrical relay for detecting the movement of a vessel within the vicinity of the mine arranged adjacent the path of travel of the vessel, means. operated in time delayed relation to the launching of the mine for partially arming the mine, means for initiating a plurality of cycles of operations of said elec- .trical relay and the. armingmeans, means settable at will for controlling the number of said cycles of operations of said arming means, and. means effective when said cycles of arming operations'have been completed for additionally. operating said arming means in response to the passage of a vessel past-the mine.

7. In a submarine mine of the character disclosed, an electrical relay, means including said electrical relay for detecting themovement of-ai vessel within the vicinity of the mine arranged adjacent the path of travel 'of the vessel, means operated in time delayed relation to the launching of themine for initiating a plurality of cycles of operations of said electrical relay, arming means cyclically controlled by said electrical relay, means settable at will for controlling the number of said cycles of operations of said arming means, means efiective when said cycles of arming operations have been completed for additionally operating said arming means in response to the passage of a vessel past the mine, detonating means, means effective when apredetermined number of vessels vhave passed themine in successive order for causing the mine to be fully armed by said arming means,

and means for causing the mine to be exploded by said detonating means as the next succeeding vessel moves a past the mine.

controlled by said relay for rendering the detecting means effective to detect magnetic variations in the magnetic field at predetermined intervals of time, an electrical circuit, a first device for counting a predetermined number of operations of said relay, said first counting device ,having means for closing said electrical circuit when a predetermined number of operations of said relay'have 1 been counted, a second counting device adapted to be operated by said circuit closing means, a contact element on said second counting-device and settable to a plurality of difierent positions, a plurality of electrical contacts adapted to be engaged successively by said contact element as said second counting device is set to each of said different positions in, succession, a detonating device,

means settable at will for operatively connecting said detonating device selectively to the contacts of said second counting device, and means for causingthe mine to be exploded by said detonating means as the selected contact of said second counting device is engaged by said contact element.

9. In a submarine mine of the character disclosed arranged within a magnetic field, an electrical relay, means including said electrical relay for detecting a plurality of changing magnetic conditions within said field, means controlled by said relay for counting signals corresponding respectively to said changes of the field detected by said detecting means, means effective as the first of said signals is counted by said counting means for measuring a predetermined interval of time, and means controlled by said time measuring means for restoring said countingmeans -to an initial counting position when less than a predetermined number of changes in said magnetic field have been counted by the counting means within said predetermined interval of time.

10. In a submarine mine of the character disclosed arranged within a magnetic field, a relay, means including said relay for detecting a plurality of uniform groups of changing magnetic conditions within said field, means controlled by said relay for counting in succession signals corresponding respectively to each of said changing conditions detected by said detecting means, means effective as the first signal of each of said groups is counted by said counting means for measuring a predetermined interval of time, means controlled by said time measuring means for restoring said counting means to an initial counting position after each of said groups of signals has been counted, an electro-responsivedevice adapted to count the number of uniform groups of signals counted by said counting means, and means controlled by said electro-responsive device for causing the mine to explode when a predetermined number of uniform groups of changes in said magnetic field have been counted by said electro-responsive device.

11. In a submarine mine of the character disclosed arranged within a magnetic field, a relay, means including said relay for detecting a plurality of uniform groups of changing magnetic conditions within said field, means controlled by said relay for counting in succession signals corresponding respectively to each of said changing conditions detected by said detecting means, means eifective as the first signal of each of said groups is counted by said counting means for measuring a predetermined interval of time, an electro-responsive device adapted to count the number of uniform-groups of signals counted by said counting means, means controlled by said time measuring means for restoring said counting means to an initial counting position after each of said groups of signals has been counted by saidelectro-responsive device, and means including a device settable at will for causing the mine to explode when a predetermined number of uniform groups of changes in said magnetic field have been counted by said electro-responsive device.

12. In a submarine mine of the character disclosed arranged within a magnetic field, a relay, means including said relay for detecting a plurality of uniform groups of changing magnetic conditions within said field, means controlled by said relay for counting in succession signals corresponding respectively to each of said changing conditions detected by said detecting means, means effective as the first signal of each of said groups is counted by said counting means for measuring a predetermined interval of time, an clectro-responsive device adapted to count the number of uniform groups of signals counted by said counting means, means controlled by said time measuring means for restoring said counting means to an initial counting position after each of said groups of signals has been countedby said electro-responsive device, means settable at will for changingthe number of signals of each group counted by said electro-responsive device, and means including a detonator controlled by said electr'o-responsive device for causing the mine to explode when a predetermined number of said uniform groups of signals have been counted by said counting means.

13. In a submarine mine of the character disclosed disposed Within a magnetic field, a relay, means including said relay for detecting in succession a plurality of changing magnetic conditions within said field occurring during different intervals of time, means controlled by said relay for counting in succession signals corresponding respectively to each of said changing conditions detected by said detecting means within a predetermined interval of time, means eifective when less than a predetermined number of signals are counted by said counting means within said predetermined interval of time for restoring said counting means to an initial condition, a detonating device, and means including said detonating device controlled by said counting means for causing the mine to explode when said predetermined number of signals are counted in said counting means.

14. In a submarine mine of the character disclosed disposed within a magnetic field, a relay means including said relay for detecting in succession a plurality of changing magnetic conditions within said field occurring during different intervals of time, means controlled by said relay for counting in succession signals corresponding respectively to each of said changing conditions detected by said detecting means, within a predetermined interval of time, means eifective when less than a predetermined number of signals are counted by said counting means within said predetermined interval of time for restoring said counting means to an initial condition, electro-responsive means adapted to be set by said counting means to different settings when said predetermined number of signals are counted in said counting means, a detonating device, and means including said detonating device for causing the mine to explode when said electro-responsive means has been set to a predetermined setting.

15. In a submarine mine of the character disclosed arranged within a magnetic field, mine firing mechanism, means included within said mine firing mechanism for sensing changing magnetic conditions within said field during different intervals of time, relay means operatively connected to said sensing means and adapted to be operated thereby, a source of electrical power, an electrical circuit, means for closing said electrical circuit to cause said relay means to be operated cyclically by said source of power, a counting device controlled by said relay means, said counting device having an initial setting and a plurality of move settings, and means effective when said counting device has been moved to a predetermined moved setting for interrupting said electrical circuit.

16. In a submarine mine of the character disclosed arranged within a magnetic field, mine firing mechanism, means included Within said mine firing mechanism for sensing changing magnetic conditions Within said field during different intervals of time, relay means operatively connected to said sensing means and adapted to be operated thereby, a source of electrical power, an electrical circuit, means for closing said electrical circuit to cause said relay means to be operated cyclically by said source of power, a counting device controlled by said relay means, said counting device having an initial setting and a plurality of moved settings, means effective when said counting device has been moved to a predetermined moved setting for interrupting said electrical circuit, detonating means, a device controlled by said relay means for measuring an interval of time, and means controlled by said interrupting means for causing the mine to be exploded by said detonating means when the interrupting means has not been moved to said predetermined setting during the interval of time measured by said time measuring device.

17. In a submarine mine of the character disclosed arranged Within a magnetic field, a relay, means including d N for detecting changing magnetic conditions withi 17 I in said field, normally open contacts on said relay and adapted to be engaged as the relay operates, a source of electrical power, means controlled by the pressure of the body of water within which the mine is laid for causing said relay to be operated by said source of electrical power for a predetermined number of cycles of operation, means controlled by said relay contacts during said cycles of operation for partially arming the mine, and means controlled by said relay contacts for additionally arming the mine in response to a plurality of. subsequent changing conditions within said magnetic field detected in succession by said detecting means within predetermined intervals of time.

18. In a submarine mine of the. character disclosed arranged within a magnetic field, a relay, means including said relay for detecting changing magnetic conditions within said field, normally open contacts on saidrelay and adapted to be engaged as the relay operates, a source of electrical power, means controlled by the pressure of the body of water within which the mine is laidfor causing said relay to be operated by said source of electrical power for a predetermined number of cycles of operation, means,

controlled by said relay contacts during said cycles ofop:v eration for partially arming the mine, means controlled by said relay contacts for additionally arming the mine in response to a plurality of subsequent changing condi tions within said magnetic field detected in succession by said detecting means within predeterminedintervalsof time, a detonating device, and means effective when said mine has been additionally armed for causing the mine to. be exploded by said detonating device in response to a plurality of additional changing conditions within the magnetic field detected in succession by said detecting means within an additional predetermined interval of time.

19. In a submarine mine of the character disclosed.

arranged within a magnetic field,,an induction coil for sensing changing magnetic conditions within said field, a source of electrical power, a relay adapted to be controlled successively by said source of electrical power and by said induction coil, normally open contacts on said relay adapted to be engaged as the relay operates, an electrical control connection between said andthe relay, means responsive to the pressure of the body of water within which the mine is laid for establishing said electrical control connection, means efiective when said control connection has been established for causing the relay to make a predetermined number of cycles of operation, electro-responsive switching means .controlled by said relay contacts for'interrupting said control connection when said, predetermined number of cycles of operation has been completed, and means controlled by said relay contacts for exploding the mine when a predetermined number of uniform groups of changing conditions within said magnetic field have been sensed by said induction coil during predetermined intervals of time after said control connection has been interrupted.

In a submarine mine'of the character disclosed arranged within a magnetic field, the combination of means including a control relay for sensing magnetic changes Within the field, electrical contacts on said relay and adapted to be closed as the relay operates, a source of electrical energy, an electro-responsive time measuring device, circuit closing means controlled by the pressure of the body of water within which the mine is laid for simultaneously initiating the operation of said control relay and the time measuring device, means controlled by said relay contacts for causing the relay to make a predetermined number of cycles of operation within the interval of time measured by said time measuring device,

means for counting said cycles of operation, said counting means having an initial position and a plurality of set positions, a normally open contact on said counting means adapted to be closed as the counting means is moved from said initial position to the first of said plurality of set source of power 18 positions, switching mechanism adapted to be operated by said counting means when the counting means has been set to a position corresponding to said predetermined number of cycles of operation, means controlled by said time measuring device for restoring said counting means to said initial posiction after said switching mechanism has been operated, and means for transferring the subsequent control of said time measuring means from said circuit closing means to said normally open contact on said counting means.

21. In a submarine mine of the character disclosed arranged within a magnetic field, the combination of mine firing mechanism, a detecting coil included within said mine fin'ng mechanism and adapted to respond to changing magnetic conditions within the field, a relay connected to said coil and adapted to be operated thereby, circuit closing means controlled by the pressure of the water within which the mine is laid for operating said relay, electro-responsive means controlled by said circuit closing means for measuring apredetermined interval of time, detonating means, and means for causing the mine to be exploded by said detonating means when the relay is not operated within said predetermined interval of time.

22. In a submarine mine of the character disclosed arranged within a magnetic field, the combination of mine firingmechanism, a detecting coil included within said mine firing mechanism and adapted to respond to changing magnetic conditions within the field, a relay connected to said coil and adapted to be operated thereby, circuit closing means controlled by the pressure of thewater within which the mine is laid for operating said relay, electro-responsive means controlled by said circuit 1 closing means for measuring a predetermined interval of time, means for resetting said relay after the relay has been operated by said circuit closing means, detonating means, and means for causing the mine to be exploded by said detonating means when the relay is not reset within said predetermined interval of time.

23. In a submarine mine of the character disclosed arranged within a magnetic field, the combination of mine firing mechanism, a detecting coil included within said mine firing mechanism and adapted to respond to changing magnetic conditions within the field,"a sensitive relay connected to said coil and adapted to be operated thereby, circuit closing means controlled by the pressure of the water within which the mine is laid for operating said sensitive relay, electro-responsive means controlled by said circuit closing means for measuring a predetermined interval of time.

24. In a submarine mine of the character disclosed arranged within a magnetic field, the combination of mine firing mechanism, a detecting coil included within said mine firing mechanism and adapted to respond to Chang ing magnetic conditions within the field, a sensitive relay connected to said coil and adapted to be operated thereby, circuit closing means controlled by the pressure of the water within which the mine is laid for operating said sensitive relay, electro-responsive means controlled by said circuit closing means for measuring a predetermined interval of time, a slow releasing relay adapted to be operated by said sensitive relay, switch stepping mechanism adapted to be operated by said slow releasing relay -to different settings including a predetermined setting,

detonating means, and means for causing the mine to be exploded by said detonating means when the switch stepping mechanism is not operated to said predetermined setting within said predetermined interval of time. T

25. In a submarine mine of the character disclosed arranged within a magnetic field, the combination of mine firing mechanism, at detecting coil included within said mine firing mechanism andadapted to respond to changing magnetic conditions within the field, a sensitive relay connected to said coil and adapted to be operatedthereby, circuit closing means controlled by the pressure of the water within which the mine is laid -'for operating said sensitive relay, electro-responsive means controlled by said circuit closing "means for measuring a predetermined interval .of time, a slow releasing relay adapted to be operated "by said sensitive relay, means operated by'said slow releasing relay for counting the number ofi operations of saidsensitive relay, electro-responsive switching mechanism operatively connected to said counting means and adaptedtoxbe moved from an initial position when a predetermined number of operations of sai'd sensitive relay have been counted, contact means adapted to be disengaged as said switching mechanism is moved from said initial position, detonating means, and means for causing the mine to be exploded by said detonating means when said contact means are not disengaged within-said predetermined interval of time.

26. In a mine firing mechanism disposed within a magnetic field, means responsive to a changing magnetic condition of .said field for detecting in succession a plurality of changing conditions of the field within a predetermined interval of time, signal. counting means, and means for selectively voperating said signal counting means in accordance with a predetermined plurality ofchanging conditions of said field detectedby said detectingimearis Within, said. predetermined interval of time.

27; In a mine firing mechanism of the character disclosed, a signal; relay, means including said signal-relay responsive to a changing magnetic fieldfor detecting intime, means controlled by said relay for selecting uniform groups of signals correspondingrespectively 'to a predetermined number of said changing conditions in the field, detonating means, and means controlled by said selecting means for causing the mine tobe exploded by said detonating means when a predetermined number of said uniform groups of signals has beenselected bysaid selecting means.

28'. In a mine firingmechanismof the character disclosed arranged. within a magnetic field, a signal relay, means including said signal relay responsive to a changing magnetic condition within said magnetic field' fordetectinginsuccession. a plurality of subsequent changing magnetic conditions in the field occurring within a predetermined period of time, means controlled by said ingmeans toan initial condition aftersaid groups of] signals have been transferred to said secondary registering means. i

29.. In a. submarine mine of the character disclosed arranged within a magnetic field, meansfor detectinga plurality-offs changes in magnetic conditionswithin-said field-,- means controlled by said detecting means for countingsaid changes, means effective after the first of said changes has been counted for resetting said-counting means to an initial position after a predetermined interval-of time, and means controlledby said counting means forcausmgsaidmine to explode when-a predeterminedsplurality of changes in said-magnetic conditions have beencounted by the counting-means within said predeterminedinterval of time.

30. In amine firingvmechanism of the-character disclosed, means for: generatinga plurality of'signals inresponse td a. plurality of changing magnetic conditions associated with a vessel in motion, means controlled by said signals for selecting predetermined groups of the signals, step-.by-step switch means adapted to be moved forward one step-aseachof saidgrou-ps' of signalsis generated, and means controlled by said switch means for causing the mine'to'be fired when a predetermined numberof steps'has been taken thereby.

31-. In amine firing mechanism of the character disclosed, means forgenerating-aplurality of signals in response to a plurality of changing magnetic conditions associated with a 'vessel in motion, means controlled by said generating means for counting said signals from an initial signal counting position thereof, means adapted to be rendered effective to measure a predetermined interval oftime as operation of said counting means is initiated and adapted to restore the counting means to said initial position thereof at the end of said interval, step-by-step'switch means adapted to be moved forward one step'under control of said counting means each time a number or signals equal to or greater than a predetermined-number is counted thereby from said initial position, and means controlled by said switch means for causing the mine to be fired when a predetermined numben-ofstepshas been taken thereby.

32-. Ina marine mine, in combination, a hydrostat having-apressure responsive element in communication with the surrounding water, amember securedjto said element and adapted to be moved from an initial position to an extended position, means including said pressure responsiveelement formovingsaid member in either direction to andfromeither one of said positions selectively as thehydrostat responds tochanges in pressure of the surrounding water, a, first; switch controlled by said member and adapted to be closed thereby when the member is moved from said initial position, a second switch controlled by said member and adapted to be closed thereby when; the member is movedfrom said extended position. a predetermined distance, a mine firing circuit including ed to bemoved between initial-and extended positions.

thereof as the element responds. to,changes in pressure o f the surroundingwater, first, second and third switches adapted to be actuated by saidmember, said first switch being closed m mentarily by the member upon movement thereof from its initial position, said second switch being closed by the member upon movement thereoffrom said initialposition, said third switch being closed by the member upon predetermined movement thereof from said extended position, a first mine firing circuit including said, second and third switches and adapted to fire the mine when both the second and third switches are closed and a. second, mine firing circuit adapted to be rendered efiective as the secondswitch is closed and including a stepper switch adapted to be reset by said first switch.

34, In a marine mine, incombination, a pressure responsive element in communication-,with the surroundwater, ,a member associated'with said element and adapted to-be moved betweeninitial and extended positions thereof as theelement responds to changes in pressure of the surroundingwwater, first'and second'switches adaptedto -beactuatedby said member, said first switch beingclosed momentarily by the member upon movementthereof; from its initial jposition, said second switch being closed'by the-member upon movement thereof from saidrinitial position, and a minefi'ring circuit, including means adaptedto be reset to-an initial position thereof by said first-switch,'the'firing circuit being armedas saidv second switch is operated.

35. In a marine mine, in combination, a pressure responsive element in communication with the surrounding water, a member associated with said element and adapted to be moved between initial and extended positions thereof as the element responds to changes in pressure of the water, a mine firing circuit, and means including a pair of switches actuated by said member in predetermined sequential order and effective as said member moves from said initial position for causing said firing circuit to be first reset to an initial condition thereof, and thereafter set in an armed condition.

36. In a marine mine, the combination of a hydrostatic device including a member adapted to be moved between initial and extended positions in response to variations in pressure of the surrounding water caused by changes in the depth of submergence of the mine, three switches constructed and arranged for operation by said member in sequential order in response to a predetermined movement of the member between said positions as the mine 22 is lowered and thereafter raised within the water, a resettable mine firing circuit, and means including said switches for resetting, arming, and firing said firing cir' cuit in the order named during said predetermined movement of the member.

References Cited in the file of this patent UNITED STATES PATENTS 1,382,374 Maxim June 21, 1921 1,390,768 Dorsey Sept. 13, 1921 1,538,316 Duffie May 19, 1925 1,766,524 Loftin June 24, 1930 2,066,211 McCreary Dec. 29, 1936 FOREIGN PATENTS 803,907 France July 20, 1936 836,663 France Oct. 17, 1938

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