US2703052A - Magnetically controlled firing mechanism for marine mines - Google Patents

Description

March .1, 1955 J. B. GLENNON ETAL MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet 1 i. 1MB

ZIWuQ/W'IMS J. B- GLENNON C. M. VAN ATTA F. W. BROWN Ill March 1, 1955 .1. B. GLENNON ET AL MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES 8 Sheets-Sheet 2 Filed July 1, 1942 ll/llilll! r114! glwuonfoz J.' B. GLENNON c. M. VAN ATTA F. w. BROWN m March 1, 1955 J. B. GLENNON ET AL 2,703,052

MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES 8 Sheets-Sheet (5 Filed July 1, 1942 GLENNON VA N ATTA BROWN m March 1, 1955 J. B. GLENNON ET AL MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES 8 Sheets-Sheet 4 Filed July 1, 1942 mmm QrWQ/WY/MS J B. GLENNON C. M, VAN ATTA F. W. BROWN Ill //////vv//// Q issan-=5 March 1, 1955 J. B. GLENNON ET AL 2,703,052 MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet 5 m m N awn M3041 J. B, GLENNON G. M. VAN ATTA F. W. BROWN lll March 1 @555 a. a GLENNON ETAL 2,703,052

MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet 6 F. w. BROWN m March 1, 1955 .1. B. GLENNON ETAL 9 3 MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet '7 J. B. GLENNQN C. M. VAN ATTA F. W. BROWN HI March 1, 1955 J. B. GLENNON ET AL 2,73@52 MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet 8 arm 0W5 J. B. GLENNQN C. M. VAN ATTA W. BROWN Ill yk wi MAGNETICALLY CONTROLLED FIRING NECHANISM FOR E MINES James B. Glennon, Washington, D. C., Chester M. Van Atta, Bethesda, Md., and Frank W. Brown III, Rome, N. Y.

Application July 1, 1942, Serial No. 449,310

21 (Ilaims. (Cl. 102-18) (Granted under Title 35, U. S. Code (1952), see. 266) This invention relates to magnetically controlled firing ttes atent mechanisms for marine mines in which a pivoted magnetic needle or bar is moved from a predetermined setting under or by the magnetic attraction or influence of a mass of magnetic material within the vicinity of the mine to a firing position thereby to close a circuit from a source of electrical energy to an electro-responsive detonating device and explode the mine. More specifically, the magnetized element is automatically set to a predetermined sensitivity in accordance with the latitude at which the mine is planted whereby the magnetized element is adapted to be moved in either direction in a vertical plane in response to the approach or passage of a steel vessel within the vicinity of the mine sufiicient to establish a circuit connection from a source of electrical energy to an electro-responsive detonating device thereby to operate the device and fire the mine.

It may be stated that the lines of force comprising the earths magnetic field are perpendicular to the surface of the earth at the north and south magnetic poles, parallel to the earth at the magnetic equator and atan angle with the earths surface at different locations intermediate the equator and the magnetic poles depending upon the latitude of the location. If a balanced magnetic needle or bar be pivoted for rotation in a vertical plane, the needle will assume a position in accordance with the direction of the lines of magnetic force adjacent thereto at an angle with the surface of the earth depending upon the latitude in which the needle is placed, this angle of deviation from the horizontal plane being hereinafter referred to as the angle of inclination or dip of the needle.

It has been well established that within the vicinity of a 2,703,052 Patented Mar. 1, 1955 "ice above the mine. Such systems have not been found to be entirely satisfactory in cases where the vessel has been degaussed sufficiently to prevent movement of the magnetized needle into the firing position or in cases where the vessels have been overdegaussed for the reason that the magnetic needle is moved by the magnetic field set up by the overdegaussed vessel in a direction to increase the degree of separation between the firing contacts thereof.

In the system of the present invention a pivoted magnetic element comprising a pair of magnetized bars is yieldably held in a position preferably at a small angle with respect to a horizontal plane by an adjustable hair spring connected thereto such that the'firing contact element thereof is normally at rest intermediate a pair of contacting elements. The adjustable hair spring is connected .at the other end thereof to a clockwork mechanism which regulates the torque applied to the magnetized element such that a change in either direction in the magnetic field adjacent thereto causes the firing contact associated with the magnetized element to be moved selectively in steel vessel the lines of force of the earths magnetic field are distorted such that the intensity of the earths magnetic field within the vicinity of the vessel is altered. When such a vessel passes over a submarine mine having a magnetic dip needle therein, the angle of dip of the needle will vary in accordance with the degree of distortion of the earths magnetic field variably in accordance with the relative position of the vessel with respect to the mine.

It has also been found that a steel vessel has a certain 7 amount of magnetism imparted thereto during the construction of the vessel and acquires certain additional magnetic properties by reason of the movement of the vessel through the earths magnetic field particularly when the vessel is moved generally in an east-west directionor vice versa. This magnetic property which the vessel acquires is usually of a predetermined magnetic polarity and may be compensated for to a considerable degree by wrapping an electrical cable about the vessel and passing an electrical current through the cable thereby to dey, magnetize the vessel, such demagnetizing process being herein referred to as degaussing and the vessel to which this process has been applied as a degaussed vessel. In magnetically controlled systems of the type heretofore proposed for firing a marine mine such, for example, as

either direction into engagement with the upper or lower contact element, as the case may be, this adjustment of the hair spring being referred to herein as the sensitivity or sensitivity setting of the magnetic element.

It has been found that a degaussed vessel produces certain variations in the magnetic field opposite a point of reference as the vessel moves past the reference point by reason of the unequal distribution of the magnetic material comprising the vessel and the various masses of magneticmaterial carried thereby or secured thereto and it has been the practice in certain cases to apply an excess of demagnetizing current through the aforesaid cable thereby to impart apredetermined magnetic polarity to the vessel sufiicient to insure the safe passage of the vessel above mines in which the magnetic changes required to fire the mines are of the opposite polarity only. By employing a magnetically controlled mechanism in which movement of the magnetized bar in either direction from a predetermined setting thereof is employedto fire the mine, the possibility of the safe passage of a degaussed vessel thereover is extremely remote for the' reason that certain variations in the magnetic field of the vessel are found to be present afterthe degaussing process has been completed.

One of the objects of the present invention is to provide a mine firing control mechanism in which relatively small changes in the vertical component of the earths magnetic field of either polarity are employed to fire the mine.

Another object is the provision of new and improved means for preventing the premature explosion of the mine by countermining operations.

Another object is the provision of new and improved means for automatically and yieldably adjusting a pivoted magnetic element to a predetermined setting such that a mine firing circuit is closed by a predetermined change in the vertical component of the earths magnetic field adjacent thereto of increased or diminished strength, as the case may be, regardless of the latitude at which the mine g is planted. 1

Still another of the objects is the provision of a new and improved magnetic influence mine adapted to be fired by predetermined changes of either polarity in the earths magnetic field adjacent thereto in which the arrangement of parts and instrumentalities therefor comprises a structure of simple and rugged construction which is economical to manufacture and which possesses the desired qualities of reliability and efficiency in use and operation.

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

Fig. 1 is a view in section partly broken away of a mine employing the device of the present invention in accordance with a preferred embodiment thereof;

Fig. 2 is a greatly enlarged view in section partly broken away of the firing control mechanism of Fig. 1; Fig. 3 is a greatly enlarged view in elevation partly broken away of the firing control mechanism showing,

among other elements, the latitude setting device em ployed for controlling the sensitivity adjustment of the magnetic element;

Fig, 4 is a sectional view taken substantially on the line 44 of Fig. 3;

5 is a sectional view taken on the line 5'-5 of Fig. 6 is a view in section taken substantially along the line 6-6 of Fig. 4;

Fig. 7 is a view in elevation of the magneticelement and certain supporting and control elements therefor with the cover removed;

Fig. 8 is a view. of the reverse side of the device shown in Fig. 7;

Fig. 9 is an enlarged view partly broken away and partly 'in section of the magnetic element of Fig. 4 and certain supporting and control devices therefor with the magnetic element in a released position;

Fig. 10 is a view in elevation of hte trip switch mechanism 'of Fig. 3;

Fig. 11 is an end view of the trip switch mechanism of Fig. 10 showing the control elements and supporting plate therefor in section;

Fig. 12 is a view taken substantially along the line 12-42 of Fig. 11;

Fig. 13 is a view taken substantially along the line 13--13 of Fig. 11;

Fig. 14 is a view taken substantially along hte line 1414 of Fig. 9; and,

Fig. 15 illustrates diagrammatically the electrical circuit arrangement of the entire system.

Referring now to the drawings in which like numerals of reference are employed to designate like parts throughout the several views and more particularly to Fig. 1 thereof on which is shown a submarine mine indicated by the numeral 10 according to a preferred embodiment of the invention comprising a casing 11 having recessed portions 12 and 13 therein within which is arranged an extender hydrostat and clock hydrostat respectively. The extender hydrostat comprises a plunger 14 slideably supported within the member 15 and normally urged out-. ward by the spring 16 arranged thereon, the plunger being in engagement with the flexible diaphragm 17 secured in watertight relation with respect to the casing of the mine as by the bolts 18 and retaining ring 19'. The plunger 14 supports at one end thereof a detonating device 21 adapted to be inserted within a booster charge- 22 arranged within the well 23 as the hydrostat operates, the well being preferably braced to the casing of the mine as by the support 24.

Arranged within the recessed portion 13 of the mine casing is a member 25 adapted to support slideably a plunger 26 yieldably urged outward by a spring 27 into engagement with the flexible diaphragm 28 secured in watertight relation with respect to the'casing of the mine as by the bolts 29 and retaining ring 31. A starting clock or timing mechanism 32, hereinafter referred to as TM, is secured to the member 25 as by the bolts 33 in operative relation with respect to the plunger 26 whereby the timing mechanism is adapted to be set in operation by movement of the plunger inward in response to the pressure of the water against the flexible diaphragm 28.

There is also provided within the casing of the mine a chamber 34 within which is arranged a timing device 35, hereinafter referred to as TD2. The chamber 34 is in communication with the Well 23 as by the tube or duct 36 extending therebetween. A terminal box 37 is also preferably arranged within the chamber 34 having a plurality of electrical cables connected thereto for establishing circuit connections to the starting clock 32, the detonating device 21 and the timing device 35. There is also connected to the terminal box 37 a pair of conductors 38 and 39 connected at the other end thereof to the battery 41 hereinafter referred to as BA, suitable apertures being provided within the plate or partition 42 Within which the conductors 38 and 39 are arranged. The battery 41 is arranged within the chamber 43 and preferably insulated therefrom as by the cushion or yieldable pad 44 thereby to prevent injury or damage to the battery as the mine is launched. The pad 44 may be composed of any material suitable for the purpose such, for example, as felt, rubber or any of the synthetic placed by a clamping device to prevent movement of the battery relative to the chamber 43 during handling, transportation or planting of the mine. There is also provided within the mine case a suitable partition 45 thereby to form a chamber 46 within which is arranged the firing control mechanism 47 and yieldably supported with respect thereto as by the yieldable pad or cushion 48 composed preferably of rubber or'auy of the synthetic varieties thereof, the pad 48 having an aperture 49 within which is arranged the electrical cable 50 connected at one end thereof to the junction box 37 for establishing an external electrical connection to the firing control mechanism, the partition 45 having an aperture 51 therein within which the cable is arranged.

The casing of the mine is enclosed at one end thereof by a suitable cap 52 secured thereto as by the bolts 53, a gasket 54 being preferably arranged between the cap and the casing of the mine to insure a watertight joint therebetween. The casing of the mine also comprises a chamber 55 within which is disposed an explosive charge 56 of material suitable for the purpose such, for example, as material known in the art as TNT or the like, the casing also being provided with a scalable aperture through which the explosive charge is introduced, as is well known in the art to which the present invention pertains.

The clock or timing mechanism TM is provided with one or more spring members 57, Fig. 15, preferably of non-magnetic material suitable for the purpose such, for example, as Phosphor bronze, beryllium copper, or the like connected to a gear train having an escapement wheel 58 and an escapement member 59 provided with a pair of pins 61 adapted alternately to engage the teeth of the escapement whee as the clock mechanism operates. A stop pin 62 is brought into engagement with the arm 63 secured to the plunger 64 as the plunger is held in the unoperated position thereof by the spring member 65 prior to the launching of the mine. When the clock hydrostat operates, the arm 63 is moved out of engagement with the stop pin 62 by the hydrostat thereby setting the clock in operation and causing the cam member 66 thereof to be rotated until the end portion 67 of theslot 68 within the cam member engages the fixed pin 69 thereby preventing further movement of the cam member and bringing the clock mechanism to rest. The movement of the cam memberfifi causes the cam contacts A and B to be closed when a predetermined time such, for example, as twenty minutes has elapsed after the clock hydrostat is operated, and the cam C contacts to be closed when an additional period of time has elapsed such, for example, as twenty-five minutes after the A and B cam contacts close. The cam contacts A, B and C remain closed by reason of the cam being brought to rest as the end 67 of the slot therein engages the fixed pin Referring now to Fig. 2 there is shown thereon an annular member 71 having a pair of substantially hemispherical covers 72 and 73 secured thereto as by the bolts 74 and nuts 75 thereby to enclose the mine firing mechanism and prevent damage and injury thereto. a pair of gaskets 76 and 77 being arranged between the annular member 71 of the covers 72 and 73 respectively whereby the mine firing mechanism is hermetically sealed within the covers. The annular member 71 is provided with two bearing supports diametrically disposed thereon upon which is pivotally mounted as by the ball bearings 78 the gimbal ring 79. The ring 79 is provided with a pair of recessed portions therein respectively enclosed by a pair of circular plates 81 within which are arranged the ball bearings 82, Figs. 7 and 8, the ball bearings being fitted to the bearing supports 83 secured to the casing 184 as by the screws 85, the casing thus being suspended by gimbals and maintained in a vertical position by reason of a counterweight 86 secured to the lower side thereof in any suitable manner as by the screws 87.

Coaxial with the ball bearings 78 are the insulated pins '88 having a rounded or pointed end for establishing electrical connection with .the contact springs 89 se ured to the annular member 79 as by the screws 91 and insulated there-from in any well known manner such, for example, asby the insulating sleeves and washers illustrated. A second pair of insulated contact springs 92 are in electrical connection with the springs 89 by the conductors varieties thereof. Also, if desired, the pad 44 may be re- 93 and adapted to engage the insulated pins 94, Figs. 7

and 8, at the rounded or pointed ends thereof whereby no appreciable resistance tothe free movement of the gimbals is introduced by the engagement of the springs 89 and 92 with their respective contact pins. The contact pins 94, it will be understood, are'coaxial with the ball bearings 82 and insulated therefrom generally in the manner of the pins 88. The bearing supports 83 are each provided with an aperture or recessed portion within which is arranged the conductors 95 and 96 respectively secured at one end thereof to the insulating pins 94 thereby providing an arrangement in which two external circuits are adapted to be established to the mine firing and Iantude setting and control mechanism through the gimbal bearing supports indicated generally at GCl and GC2, Fig. 15, the common or ground circuit being established through the ball bearings by way of one of the conductors within the cable 49 secured to the annular member 71 as at 97, Fig. 1, adjacent one of the insulated pins 88, the external circuit to the other of the insulated pins 88 being established by way of a conductor as at 98 arranged within a recessed portion along the outer periphery of the annular member 71 and preferably secured thereto as by the straps 99 and screws '101.

The magnetic needle or element of Figs. 7 and 8 comprises two parallel magnetized steel bars 102 preferably tapered from the central portion toward the ends thereof and having an aperture in the center portion within which is disposed a shaft 103, a metal strip 1040f aluminum or other light non-magnetic material being provided with projecting portions or tabs 105 adapted to engage complementary recessed portions of the magnetic bars 102 and maintain the bars in parallel locked engagement with each other, the metal strip 104 also serving as an air bafiie to prevent sudden movement of the magnetic element within the air chamber 106. The supports 83 have their inner ends curved to impede the flow of air past the ends of the baffie plate or strip 104 as the magnetic element is moved angularly within the air chamber and a partition or baffie member 107 secured preferably to the upper portion of the air chamber impedes the flow of air at one end of the upper part of the air chamber to the other end thereof as the magnetic element is moved angularly within the air chamber 106.

The bushing members 108 are spun or otherwise secured to the magnetic bars 102 and clamped to the shaft 103 by the rivets 109 and clamping plate 111,'Figs. 4 and- 9. The shaft 103 is provided with an insulating bushing 1112 upon which is mounted the contact arm 1'13 as-"by the screws 114, Fig. 6. The contact arm has a turned up portion 115 to which the contact member 116 is secured as by the nuts 117. The contactmember 116 is prefer-- ably tapered or rounded at each end thereof and adapted to engage the contact springs 1-18 and 119, as the case may be, as the magnetized bar moves into the tiring position thereof by a change in the magnetic field adjacent the bar. The contact spring 118 is adapted to rest against the stop member 121 when the contact arm 113 is in the armed position. Prior to the launching of the min'qhowever, the contact member 1 16 is maintained in continuous engagement with the contact spring 118 by a fuse member as will more clearly appear as the description proceeds. The contact spring 118 and stop member 121 are clamped to a support 122 secured to an insulating member 123 of material suitable for the purpose such, for example, as Bakelite, hard rubber and the like in any suitable manner as by the rivets or screws 124. The member 122 is provided with a screw terminal 125 for establishing an external circuit thereto. The arm 126 secured to the insulating member 123 as at 127 is provided for adjusting the position of the spring 11 8 with respect to the contact member 116, the arm 126 and insulating member being pivotally supported by the screw 128 haing a washer 129 thereon about which the spring assembly is adapted to be moved. The end of the arm 126 is provided with a bent over portion 131 adapted to be engaged by the adjusting screws 132 threaded within the support 133 secured to.

the plate 134 as by the screws 135, the nuts 136 being employed to maintain the adjusting screws in the adjusted position thereof.

In a similar manner the contact spring 119 and stop member 130 are supported by an insulating member 137 secured to the adjusting arm 1-38 and pivotally supported by the screw 139 having a washer 141 thereon. A screw 142 in electrical circuit with the spring 119 is provided for connection to an electrical conductor. The end of the arm 138 is formed as at 143 to a shape suitable for engagement with the adjusting screws 1'44 threaded within the bracket 145 secured to the plate 134 as by the screws 146, a pair of nuts 147 being employed to maintain the arm 138 in any of its adjusted positions. An arrangement is thus provided in which the degree of separation between the contact member 116 and the contact springs 118 and 119 may be varied at will by adjustment of the screws 13-2 and 144 whereby the degree of angular movement of the firing element including the magnetized bars 102 in either direction from the armed position thereof necessary to tire the mine may be set to any desired angle.

The firing or contact arm 113 has connected thereto a biasing spring 148 for yieldably setting the magnetic element to a predetermined sensitivity by the latitude setting mechanism employed with the present invention, the biasing springalso being employed for establishing a circuit connection to the firing contact element 116. The shaft 103, Fig. 9, is formed to a V-shaped knife edge 149 at the ends thereof for engagement with the V-shaped jewel bearings 151 set within the threaded bearing screws 152 slideably mounted within the mounting plates 153 and 154 aflixed to the sides of the air chamber, a pin such as the pin 155, Fig. 14, passing through each of the plates 1'53 and 154 in the manner illustrated sufliciently to engage a slot 156 in each of the bearing screws to prevent rotation thereof as the screws are adjustably clamped in position against the mounting plates 153 and 1 54 by the nuts 157 threaded thereon.

A movable member 158 pivoted to the air chamber at 159 is provided with a block 161 having a serrated surface 162 thereon adapted to engage a complementary serrated surface on the plate 111 secured to the lower side of the shaft 103 and raise the shaft thereby to rotate the magnetic element to an initial position in which the con tact member 116 is maintained in continuous engagement with the spring 118 and the knife edges are disengaged from their jewel bearings until a predetermined period of time has elapsed after the mine has been launched within a body of water. The shaft 164 having an arm 165 thereon adapted to engage the member 158 is pivotally mounted to the sides of the air chamber and provided with a lever arm 166, Figs. 3 and 6, having a clamp 167 at one end thereof adapted to hold the fuse element 168 and thus maintain the shaft 164 in an operated position and the magnetic element in a position such that the knife edge supports therefor are clear of their bearings until the fuse is operated in response to the operation of the hydrostat cloak, as will more clearly appear as the description procee s.

The member 158 is moved by the spring 169 to the position shown in dashed outline on Fig. 7 thereby lowering the shaft 103 such that the magnetic element is in contact with and adapted to be moved about its jeweled bearing supports. The other end of the fuse element 168 is attached to the fuse block 171 as by the screw 172 and clamping member 173. The fuse block 171 is secured to the plate 134 and insulated therefrom as by the block of insulating material 174, the fuse block also being provided with the terminal screw 175 adapted to receive and clamp an electrical conductor for establishing a circuit connection with the fuse 168. The arm 166, it will be noted, is preferably of suitable insulating material such, for example, as material known in the art as Bakelite, havlng a clamping member 176 secured thereto adapted to coact with the complementary member 177 and clamp the arm to the shaft 164 as by the screws 178. The arm 166 is also provided with a projecting portion 179 adapted to be arrested by a back-stop pin 181 secured to the plate 134 and having a flexible conductor 18-2 connected thereto and to a terminal screw 183 on the clamping memher 167 for establishing an electrical connection between the fuse 168 and the plate 134. The air core coils 184 and 185 are mounted beneath the air chamber in any suitable manner as by the screws 186, Fig. 7, each of the coils when energized being adapted to maintain the magnetic element in the respective firing position in response to the closure of the firing contacts, the coils being respectively connected in series with the contact springs 118 and 119.

The mechanism employed for setting the magnetic element to a predetermined position such that the firing contact 116 thereof is intermediate the contact springs 118 and 119 will best be understood by -reference to Figs. 3,

4 and 5 of the drawings on which is shown, partly in section, the arrangement of parts and instrumentalities employed for mparting a predetermined degree of bias of tension to the biasing spring 148 which, as heretofore stated, is connected at one end thereof to the shaft 103 to which the magnetized bars 102 are afiixed. The latitude setting device comprises a gear train having an cscapement wheel 187 secured thereto adapted to engage the pins 188 alternately as the escapement wheel operates, the pins 188 being secured to the member 189 supported by the shaft 191. Also secured to the shaft 191 is an oscillating metallic member 192 provided with a counterweight 193 secured thereto as by the screw 194 and normally restrained from movement by the arm 195 pivoted at 196, Fig. 4, and normally urged out of engagementwith the arrnt195 by the spring 197, the arm being normally held in the restrained position by "the portion 179 of the lever arm 166 thereby providing an arrangement in which the lever arm 195 is moved out of engagement with the member 192 as the fuse 16S, Figs. 3 and' 6, is operated. A slot 198 is provided within the plate 199 to provide for movement of the arm 195. The plate 199, it will be noted, is secured to the plate 134 by the studs 201 and electrically insulated therefrom as by the insulating bushings 202, a plurality of nuts 203 being provided for this purpose. The studs 201 also sup port the plate 153 in spaced relation with respect to the plates 134 and 199 by reason of the spacing members 204 provided therebetween.

The escapement wheel 187 is connected by way of the gears 205 and 206 to the gear 207 having a ratchet 208, Fig. 5, by means of which the gear 207 is adapted to be driven by the gear 209. The gear 209, it will be understood, is adapted to rotate about the shaft which supports the gear 207 and is urged toward the gear 207 by the spring 211, the gears 207 and 209 being held in a predetermined position with respect to the escapement mechanism by the bearing support 212 secured to the plate 199 in the manner illustrated on Fig. 5. Afiixed to the .bearing support 212 is a plate 213 having a bearing therein for pivotally supporting a shaft upon which the gears 207 and 209 are mounted, a screw 214 and the dowel pins illustrated preferably being employed for maintaining the plate 213 in the assembled position. The gear 209 is in engagement with the teeth 215 of the spring barrel 216 within which is arranged a spring 217 composed preferably of non-magnetic material such, for example, as beryllium copper or Phosphor bronze having one end thereof connected to the spring barrel and the other end connected to a support 218, Fig. 4. The support 218 is secured to the plate 199 as by the screws 219.

Rotatably mounted on the support 218 is a drum 221 having an aperture therein within which is threaded a collar 222 in abutting relation with one end of the support 218. There is also provided within the drum 221 and collar 222 a shaft 223 having a shoulder at one end thereof in engagement with the collar 222 and locked thereto and to the drum by the nut 224 whereby the drum and shaft 223 are adapted to rotate as a unit about the support 218. Secured to the shoulder of the shaft 223 is an arm 225 having a flexible conductor 226 connected thereto and a bent over portion 227 to which is affixed as by the screws 228 a plate 229 to which the biasing spring 148 is secured to the outer end thereof as by the plate 231 and screw 232. From the foregoing it will be apparent that the degree of bias applied by the spring 148 is in accordance with the setting of the drum.

The drum 221 comprises an internal gear 233 secured thereto as by the screws 234 and having a pair of stoppins 235 adapted to engage a stud 236 secured to the plate 199 thereby to limit the degree of motion of the spring 217. Pivotally mounted on the support 218 is an arm 237 having a stud 238 thereon to which is pivotally secured a gear 239 in mesh with the internal gear 233' and the teeth 215 of the spring barrel 216, the stud 238 extending through an arcuate slot 241 within the plate 199 thereby to establish a circuit connection between the arm 237 and the firing contact member 116 by way of the flexible conductor 226 secured thereto in any suitable manner-as by soldering the conductor thereon to the arm 225. The arm 237 is provided with a pawl 242 pivotally secured thereto as at 243, a resilient spring member 244 being adapted to urge the pawl yieldably into engagement with a serrated or knurled surface on the outer periphery of the drum 221. The arm 237 is provided with a pair of turned up portions 245 and 246 within which one end of the pawl 242 is arranged. The pawl 242 has secured thereto as by the screws 247 a fuse clamp 248 to which is secured one end of the fuse 249, the fuse clamp being connected to the insulated screw 252 within the plate 199 by the flexible conductor 251 secured thereto, the other end of the flexible conductor being preferably soldered to a terminal on the fuse clamp in the manner illustrated. The fuse clamp is electrically insulated from the pawl 242 by suitable insulating washers, the pawl being tapered at the outer end thereof to engage the trip switch mechanism with the pawl in the initial locked position at the portion 253 thereof thereby to maintain the associated trip switch contacts in engagement with each other until the fuse 249 has operated. The opposite end of the fuse 249 is clamped by the screw 25,4 and clamping plate "255 secured to the metal strip 256 having a terminal 257 thereon for establishing a circuit connection to the fuse 249. The metal strip or plate 256 is secured in any suitable manner as by riveting to the support 258 of insulating material secured to the plate 199 as by the screws 260, a suitable spacing member being preferably arranged between the support 258 and the plate 199 to bring the fuse 249 into alined relation with respect to the plate 199. The bent up portion 246 of the arm 237, it will be noted, is maintained in engagementwith the support 258 by the fuse member 249 until the fuse 249 is blown by a flow of current therethrough, as will more clearly appear as the description proceeds. When this occurs the pawl 242 engages the outer periphery of the drum 221 which, as heretofore stated, is preferably knurled or serrated, thereby to insure a locking engagement between the pawl and the drum as the pawl is actuated by the spring member 244.

The arm 237 is provided with an electrical contact 259 adapted to engage contact screw 261 when the arm moves to the final s'et position shown in dashed outline on Fig. 3. The contact screw 261 is clamped by the stud 262 passing through an arcuate slot 263 within the plate 199 and insulated therefrom by the spacing member 264 composed of material suitable for the purpose such, for example, as Bakelite, hard rubber or the like.

The stud 262 is clamped in any desired position by the nut 265, Fig. 4, thereon in engagement with a conductor 266'thereby to establish an external circuit connection to thecontact screw'261, an insulating washer 267 being arranged between the conductor 266 and the mounting plate 199 thereby to insulate the conductor and nut from the plate. The plate 199 is also provided with a plurality of scale divisions or calibration marks 268 adjacent the aperture 263 therein whereby the contact screw 261 may be given any desired setting in accordance with a predetermined degree of sensitivity at which the device is to be set. The plates 134 and 269 comprising the casing 84 are extended downward beyond the spacing plate 271 and provided with a plate 272 secured thereto as by the screws 273 thereby to provide a compartment 274 within which is arranged a counterbalance weight 275 adapted to be shifted laterally in either direction by the threaded studs 276 and 277 journaled within the plates 134 and 269. The studs 276 and 277 are preferably slotted at one end thereof to enable the studs to be adjusted and each provided with a nut 278 to maintain the counterbalance weight 275 in the adjusted position thereof such I that the firing control mechanism including the pendulum device 312, hereinafter referred to as PM, secured thereto,

assumes a vertical position when the mine is at rest by reason of the gimbal mounting provided therefor.

There is secured to the mounting plate 199 as by the screws 279 av support 281 having a pair of electromagnets 282 in proximate relation with respect to the member 192 and adapted to attract the enlarged iron portion of the member 192 thereto and arrest the operation of the latitude setting mechanism during the time that the electromagnets are energized. For convenience in describing the operation of the system of the present invention, the electromagnets 282 are hereinafter identified by the designation EL.

Secured to the plate 199 as by the screws 283 and 284 and nuts 285 threaded thereon are a pair of trip switches T81 and TS2, Figs. 10 to 13, indicated generally by the numeral 286, a plate or cover 287 being provided to enclose and protect the mechanism of the switch TS1. A plurality of washers 288 are preferably provided between the screws 283 and 284 and the cover 287 to hold the switch assembly securely in position against the plate 199. Referring now particularly to Fig. 12 on which is shown a view of. the mechanism of the switch TS1, a casing 289 of suitable insulating material such as molded Bakelite, hard rubber or the like, is provided with a recessed portion therein within which are disposed the contact springs 291 and 292 normally held in engagement with each other by the rocker arm or hammer 293 pivotally mounted on the screw 284 and retained in the operated position by the tapered end 253 of the pawl member 242 until the fuse 249 operates. As the fuse 249 operates, the tapered end 253 of the pawl is moved out of engagement with the projection 294 of the rocker arm by the spring 244, Fig. 3, thereby causing the contact spring 291 to move out of engagement with the spring 292 and thus interrupt the circuit to a control relay as will hereinafter more clearly appear as the description proceeds.

The trip switch T82 is generally similar in construction to the switch TSl, the switch TS2 comprising a rocker arm 295 pivoted about the screw 284 and having a projecting portion 296 thereon adapted to be operated by the tapered end of the arm 237 until the arm has been moved by the latitude setting mechanism away from the initial locked position thereof. The operation of the rocker arm 295 to the released position thereof causes the contact spring 297 to be moved into engagement with the contact spring 298 thereby closing a circuit to the air coil 185, Fig. 15. Three terminals 299 are provided for establishing an external electrical circuit connection to the trip switches, the circuits being extended from the terminals by suitable conductors to the contact springs 292, 297 and 298 of the trip switches, the spring 291 being connected by the flexible conductor 301 to the screw terminal 302 on the plate 199. Secured to the shaft 103 as by the screw 303 is a hub or collar 304 having a plurality of radially extending arms 305, 306 and 307 thereon upon which are respectively mounted the ad: justable weights 308, 309 and 311, Figs. 4 and 9 thereby to apply a small mechanical bias to the shaft 103 variably in accordance with the settings of the weights 309 and 311, the speed of response of the magnetic bars 102 to a predetermined change in the magnetic field adjacent thereto being controlled by the setting of the weight 308. The weights 309 and 311, it will be noted, coact with the biasing spring 148 in applying the sensitivity adjustment to the magnetic bars whereby the sensitivity of the bars is controlled by the force of gravity on the weights 309 and 311 and the sensitivity setting of the biasing spring.

The pendulum employed with the system of the present invention is substantially identical with the pendultun disclosed on the aforesaid application of James B. Glennon and Chester M. Van Atta, Serial No. 395,230, filed May 26, 1941, for Firing Mechanism For A Submarine Mine, the pendulum comprising, among other elements, a tublular member 312 secured to the plate 269 by the supports 313 and screws 314, the pendulum being maintained in a predetermined position with respect -to the support by reason of the clamping screws 315 provided within the support. The pendulum mechanism comprises a bob pivotally supported from the screw member 316 and electrically insulated from the sleeve 312 as by the bushing 317 and secured thereto by the nut 318, a pair of nuts 319 being provided for establishing an external electrical connection to the pendulum. The pendulum includes an electrical contact arranged within an annular contact member connected to the terminal screw 321 passing through the tubular member 312 and insulated therefrom as by the bushings 322, the screw 321 being maintained in the assembled position by reason ofthe nut 323 threaded thereon, a nut 324 and washer being also provided on the screw, 321 for establishing an external, electrical connection to the annular contact member within the pendulum. The lower end of the pendulum is preferably enclosed by a suitable cap 325 secured thereto in any suitable manner as by threading the parts together thereby to exclude moisture and foreign matter from the interior of the pendulum casing. A structure is thus provided in which the pendulum closes a circuit between the screw terminals 316 and 321 whenever the pendulum is moved from the vertical position thereof or suddenly displaced from an initial position as by the shock received from a countermining operation.

Secured to the plate 269 in any suitable manner as by the support 326 is a relay 327 hereinafter referred to as R having an electromagnet 328 with a core of ferromagnetic material thereiri such, for example, as iron in substantial alinement with the shaft 103 of the magnetic element such that the field set up in response to the energization of the electromagnet is substantially in coaxial alinement with the axis of the pivoted magnetic bars 102 and for this reason the vertical component of the magnetic field acting on the electromagnetic bars is substantially unchanged when the relay operates. The relay R is also provided with a pair of contact springs 329 adapted to be electrically connected together as armature 331 moves to the operated position thereof in response to the energization of the electromagnet 328. The armature is normally retained in the unoperated position with the contact springs 329 thereof electrically disengaged by the adjustable retractile spring 332 connected thereto. Secured to the lower portion of the support 326 as by the screws 333 is preferably mounted a counterweight 334 for the reason that the relay 327 illustrated is of the type in which the parts thereof are of relatively light weight and it will, of course, be understood that by the selection of a heavier relay or by slight rearrangement of the parts or design of the structure supported by the gimbals, the counterweight 334 may be omitted.

Secured to the plate 272 as by the screws 335 is a time delay relay mechanism 336 hereinafter referred to as TD1 adapted to operate the contacts thereof when an energizing current has flowed through the relay winding for a predetermined period of time. As clearly shown in Fig. 15 relay TD1 comprises a rotatable armature 337 normally urged against a back-stop 338 by a retractile spring 339 secured thereto. The armature 337 is adapted to be actuated quickly by the energization of the electromagnet to the operated position thereof and return slowly to the released position by reason of a clockwork escapement mechanism connected thereto as is well known in devices of this character. As the relay operates, the armature 337 thereof causes a contact spring to be moved away from a normally engaged contact and into engagement with a second contact thereby to control certain circuit functions of the system in response to the operation of the pendulum as will more clearly appear as the description proceeds. The external circuit connections to the relay are established by way of the connecting screws 341, Figs. 7- and 8, and terminal connections 342 provided thereon. Preferably, though not necessarily, the relay mechanism is enclosed within a cover or casing indicated generally by the numeral 343 for preventing dirt or moisture from coming into contact with the relay clock mechanism and contact elements controlled thereby during the construction and assembly of the device.

The operation of the system will now be described. Let it be assumed, by way of example, that the fuse- elements 168 and 249, Fig. 15, have been placedin position, the spring motors of the clock timing mechanism TM and the latitude setting mechanism have been wound, the detonator 21 is connected, an explosive charge has been placed within the mine casing and the mine has been sealed and launched within a body of water adjacent the path of travel of a vessel. When the mine has descended. to a predetermined depth of submersion within the water, the pressure of the water causes the extender and clock hydrostats to operate thereby moving the detonator 21 into operative position with respect to the booster charge 22, the clock hydrostat causing the movement of the plunger 64 to withdraw the arm 63 out of engagement with the stop pin 62 thereby setting the clock timing mechanism TM in operation. Whereas in the illustrativeembodiment of the invention shown on the drawings two hydrostats are employed for extending the detonator within the booster charge and setting the clock timing mechanism in operation it will, of course, be understood that, if desired, a single hydrostat may be provided for this dual purpose.

When a periodof time such, for example, as twenty minutes has elapsed after the clock TM has been started, the cam contacts A and B thereof are closed by the cam member 66 thereby completing a circuit from ground at the cam contacts B by way of conductor 344 to the negative terminal of battery BA from whence the circuit is continued by way of the positive terminal of battery BA, conductor 345, contacts of cam A, conductor 346, gimbal contacts G01, conductor 347, contacts 348 of the time delay mechanism TD1, conductor 349, fuse element 168 and thence to ground at 351 thereby causing the fuse element 168 to blow and interrupt the circuit just described. The operation of the fuse element also causes shaft 164 and certain of the control mechanism associated therewith illustrated graphically by the member 352 to rotate by the action of spring 169 sufiiciently to disengage the member 192 thereby allowing the member 192 to oscillate and set the latitude setting mechanism into operation. As shaft 164 is rotated, the arm 165 thereof causes the member 158 to pivot about the bearing 159 and thereby unlock the magnetic element comprising the magnetized bars 102 by moving the shaft 103 thereof into engagement with its jeweled supports. The magnetic detecting element is now in readiness to be actuated by the latitude setting mechanism.

The operation of the latitude setting mechanism will best be understood by consideration of Fig. 3 of the drawings on which is clearly shown the spring barrel 216 urged by the spring 217 in a clockwise direction. When the member 192 begins to oscillate, the escapement mechanism allows the spring barrel to rotate slowly clockwise and thereby cause the gear 239 pivoted to the stud 238 on the arm 237 to rotate in a counterclockwise direction. The gear 239 is meshed internally with the gear 233 connected to the drum 221 thereby causing the drum and the shaft 223 connected thereto to be moved in a counterclockwise direction. The other end of the shaft 223 is connected to the arm 225, Figs. 4 and 9, thereby causing the arm 225 to be moved integrally with the drum in a counterclockwise direction and carry with it the outer end of the biasing spring 148 secured to the bent end 227 of the arm. As the drum 221 continues to move in a counterclockwise direction the bias applied by spring 148 to the shaft 103 is changed sufficiently to cause the magnetic detecting element to be moved angularly until the firing contact 116 thereof is brought into engagement with the contact spring 119.

When this occurs a circuit is closed from ground at contacts B of the timing mechanism TM by way of conductor 344, battery BA, conductor 345, contacts A of the timing mechanism, conductor 346, gimbal contacts (3C1, conductor 347, contacts 348 of the time delay mechanism TD1, conductor 349, air core coil 186, contact spring 119 and firing contacts 116, conductor 353, contact springs 291 and 292 of the trip switch TS1, conductor 354, winding of relay R and thence to ground thereby causing relay R to operate. As armature 331 of relay R moves into engagement with its make contact a circuit is closed from ground at cam B contacts of the timing mechanism TM, conductor 344, battery BA, condoctor 345, cam A contacts, conductor 346, gimbal contacts GCl, conductor 347, contacts 348 of time delay mechanism TD1, conductor 349, make contact and armature 331 of relay R, conductor 355, fuse element 249 and thence to groundat 356thereby causing the fuse 249 to blow and release the pawl 242. As the pawl 242 moves into locked engagement with the serrated outer periphery of the drum 221, the drum is locked to the arm 237 thereby preventing additional rotative movement of the drum with respect to the arm. The gear 239, Fig. 3, is thus locked to the arm by the drum and pawl there-by preventing further additional movement of the gear 239 with respect to the arm 237. The spring barrel 216, it will be recalled, is moved continuously in a clockwise direction and by reason of the locked relation of the gear 239 with respect to the drum 221, the drum is also locked to the spring barrel and moves integrally therewith in a clockwise direction, the direction of movement of the drum 221 and the arm 225 connected thereto now being reversed. As the pawl 242 moves into locking engagement with the drum 221 the tapered end 253 thereof quickly moves away from the projecting portion 294 of the hammer 293 of the trip switch T S1 thereby releasing the hammer and interrupting the circuit to the air core coil 184 and relay Rand causing relay R to release. As armature 331 of relay R moves away from its make contact, battery is removed from conductor 355.

As the spring 217 continues to unwind, the bias applied by the spring 148 to the shaft 103 is changed in a direction to cause the firing contact 116 to be moved away from the contact spring 119. The movement of the tapered end of the arm 237 away from its initial locked position releases the hammer 295 of the trip switch TS2 thereby causing spring 297 thereof to be moved into engagement with contact spring 298 thereby completing a circuit from battery on conductor 349 by way of the closed contacts of trip switch TS2, conductor 357 to one end of the winding of the air core coil from whence the circuit is continued by way of conductor 358 to contact spring 118 of the firing mechanism. The latitude setting arm 237 continues to rotate in a clockwise direction until the arm is arrested by the contact 259 thereof moving into engagement with the adjustable contact screw 261 thereby causing the latitude setting mechanism to be brought to rest with the magnetized element thereof set in an armed position such that the firing contact element 116 is intermediate the contact springs 118 and 119, the magnetic element and firing contact 1.16 being yieldably maintained in this position by the biasing spring 143. The mine is now in a condition such that the firing contact 116 is adapted to be moved upward or downward into engagement with the contact springs 118 and 119 respectively in accordance with a positive or negative variation in the earths magnetic field adjacent the magnetized element.

When a predetermined period of time has elapsed such, for example, as twenty-five minutes after cam contacts A and B close, the cam contacts C are closed by the clock timing mechanism TM thereby applying ground at cam 13 contacts by way of conductor 344, cam C contacts, conductor 359, and thence to contact spring 361 and one end of the winding of the time delay mechanism TD2. The mine is now in an armed condition. When the end 67 of the slot 68 within the cam member 66 engages the stop pin 69 the clock timing mechanism TM is brought to rest with the cam contacts A, B and C thereof maintained in a closed condition by the cam 66.

The time delay mechanism TD2 is generally similar to the time delay mechanism TD1 in which a rotatable armature is caused to be actuated by energization of an electromagnet thereby operating a clock escapement mechanism or similar device adapted to retard the movement of the armature sufiiciently to allow a predetermined period of timesuch, for example, as two and one-half seconds to expire after the electromagnet has been energized before the contact spring 361 is moved into circuit closing position by the rotatable armature thereby to delay the firing of the detonating device 21 for a period of time greater than that required for the operation of the anti-countermining feature which will be described with particularity as the description proceeds. Furthermore, by employing a time delay mechanism TD2 intermediate the firing contacts and the detonating device 21 the firing of the detonator is delayed thereby causing the explosion to occur more nearly toward the stern of the passing vessel.

The operation of the system caused by a disturbance of the mine such, for example, as may result from countermining, will now be described. When the mine is suddenly moved or disturbed the pendulum PM, Fig. 15, moves relative to the contacts thereof and applies ground to conductor 362, winding of time delay relay TD1 from whence the circuit is continued by way of conductor 349, contacts 348 of the timing mechanism TD1, conductor 347, gimbal contacts GCl, conductor 346, cam contacts A of the timing mechanism TM, conductor 345 to the positive terminal of battery BA thereby causing the time delay relay TD1 to operate the armature 337 thereof quickly to the operated position. As armature 337 operates, the contacts 348 are disengaged thereby interrupting the circuit of the winding of time delay mechanism TD1. As armature 337 of the time delay mechanism TD1 moves toward the unoperated position thereof, the clock escapement mechanism thereof is caused to operate and retard the movement of the armature such that the contacts 348 are maintained open for a suitable period of time such, for example, as thirty-five seconds after the operating circuit to the electromagnet of the time delay mechanism TD1 is interrupted.

As contact spring 363 moves away from contact 348 into engagement with contact 364, a circuit is closed from ground at cam B of the timing mechanism TM, conductor 344, battery BA, conductor 345, cam convtacts A of the timing mechanism TM, conductor 346,

gimbal contacts GCI, conductor 347, contact spring 363,

contact 364, conductor 365, electromagnet EL and thence to ground thereby energizing the electromagnet EL and causing the oscillating member 192 to be attracted there-' to and arrest the latitude setting mechanism in the event that the pendulum PM operated while the. latitude setting operation was in progress. In the event that the sensitivity setting of the magnetized element 102 has been completed the energization of the electromagnet EL is without effect. As contact spring 363 moves away from contact 348 in response to the operation of armature 337, battery is removed from conductor 349 whereby the air core coil 186 and, in the event that the trip switch TS2 had operated, the air core coil 185 are rendered ineffective to maintain the firing contacts in a closed position in the event that the shock or pressure impulse received by the mine had been suflicient to cause the firing contacts to be closed.

When a predetermined period of time has elapsed after the pendulum contacts are restored to their initial open position, armature 337 moves away from the operated position sufficiently to disengage contact spring 363 from contact 364 thereby deenergizing the electromagnet EL. As contact spring 363 engages the contact 348, battery is again applied to conductor 349 and the mine is again in an armed condition. In the event that the firing contacts 116 should be moved to closed position by a countermining operation before contact 348 of the time delay mechanism TDl is disengaged from contact spring 363, a circuit is closed from ground at cam B of the timing clock TM, conductor 344, battery BA, conductor 345, cam A, conductor 346, gimbal contacts GCI, conductor 347, contact spring 363 and contact 348 of the time delay mechanism TDl, conductor 349 and thence by way of the hold-on coils 184 or 185, as the case may be, the circuit of the hold-on coil 185 including the contacts of the trip switch TSZ, closed contacts 259 and 261, conductor 365, gimbal contacts 602, conductor 366, winding of the time delay mechanism TD2, conductor 359, contact C of the timing clock TM, conductor 344, contact B of the timing clock and thence to ground thereby energizing the winding of the time delay mechanism TD2 in the event that the countermining operation took place after a period of time has elapsed sufficient to allow contact C of the timing mechanism TM to close.

Armature 337 of the time delay mechanism TDl, it will be recalled, moves quickly to the operated position thereby disengaging contact spring 363 from contact 348 before the armature of relay TD2 has moved to a circuit closing position such that contact spring 361 thereof engages its make contact and an arrangement is thus provided in which the operating circuit of the time delay mechanism TD2 is invariably interrupted prior to the closing of the contacts 361 thereof when a countermining impulse or wave of pressure is received by the mine. By providing a relatively long period of time delay within the timing mechanism TD1 before the circuit to the hold-on coils 185 and 184 is again completed, sufficient time is allowed for the magnetic element or bars 102 to assume a state of rest with the firing contact 116 thereof intermediate the contacts 118 and 119 before the firing circuit is again made effective.

Furthermore, by arresting the latitude setting mechanism whenever the mine is disturbed as the result of a countermining operation in the event that the pendulum contacts are closed during movement of the magnetic element 102 from the initial locked position to the armed position, the degree of relaxation of the biasing spring 148 necessary to bring the contact member 116 into closed position with the contact spring 119 thereby to operate relay R and blow the fuse element 249 is thus invariably controlled by the azimuth position of the magnetic element which, it will be recalled, rotates in a vertical plane and the latitude of the location within which the mine is laid. The tension of the spring 148 is gradually increased after the contact element 116 has been brought into engagement with the contact spring 119 until the latitude setting arm 237 has moved to a predetermined angle of rotation and been brought to rest by the adjustable contact screw 261. The magnetic element is thus given a predetermined sensitivity setting regardless of countermining operations that may occur during the operation of the latitude setting mechanism.

Should the pendulum PM operate afterv the latitude setting arm 237 hasbeen released by the fuse element 249, the operation of the electromagnet EL causes the latitude setting mechanism to be arrested thereby preventing the engagement of the contact 259 of the arm 237 with the adjustable contact 261 until a predetermined period of time has elapsed after the pendulum has subsided sufiiciently for the contacts thereof to remain continuously disengaged. When this occursthe operate circuit for the time delay device TD2 is thus maintained open at contacts 259 and 261 and additionally interrupted at contact 348 of the time delay device TDI and contact C of the timing clock TM.

Let it now be assumed that a change occurs in the magnetic field adjacent the magnetic element such,. for example, as may be caused by a vessel approaching within the vicinity of the mine, sufiicient to cause the firing contact element 116 to be moved into engagement'with contact spring 119. When this occurs a circuit is closed from ground at cam B of the clock mechanism TM, conductor 344, battery BA, conductor 345, cam contacts A of the clock mechanism, conductor 346, gimbal contacts GCl, conductor 347, contact springs 363 and contact 348 of the time delay mechanism TD1, conductor 349, air core hold-on coil 186, contact spring 119, firing contact element 116 and the contact 259 of arm 237, contact 261, conductor 365, gimbal contacts GC2, conductor 366, winding of time delay mechanism TD2, conductor 359, cam C of the clock mechanism TM, conductor 344 and thence to ground at cam B of the clock mechanism thereby causing the time delay mechanism TD2 to attract the armature thereof. The energization of the hold-on coil 184 over the circuit just described maintains the firing contact 116 in continuous engagement with the contact spring 119 thereby maintaining a fiow of electrical current through the winding of the time delay mechanism TD2. When a predetermined period of time has elapsed after the firing contacts close such, for example, as two and one-half seconds contact spring 361 of time delay mechanism TD2 engages the make contact thereof thereby closing a circuit from positive terminal of battery BA, conductor 345, contact A of the clock mechanism, conductor 346, detonating device 21, conductor 367, make contact and contact spring 361 of time delay mechanism TD2, conductor 359, cam C of clock mechanism TM, conductor 344 and thence to the negative terminal of battery BA thereby causing the detonator to operate and fire the mine.

In the event that the approaching vessel caused a change in the magnetic field adjacent the mine in a direction and of strength suflicient to cause the contact element 116 to be moved into engagement with contact 118, the time delay mechanism TD2 will operate on a circuit including contact spring 118, hold-on coil 185, conductor 357 and the contacts of trip switch TSZ thereby energizing the hold-on coil 185 and maintaining the contact element 116 in continuous engagement with con.- tact spring 118 until the mine is fired by movement of the contact spring 361 of the time delay mechanism TD2 into engagement with its make contact thereof.

Whereas in the illustrated embodiment of the invention the time delay devices TD1 and TD2 have been shown as electromagnetically operated by clock mechanisms, it will be understood that this is by way of illustration only as various other electro-responsive delay devices comprising a dash-pot mechanism and other time delay means suitable for the purpose may be employed.

It will be understood that whenever a change in the magnetic field of relatively short duration is received such, for example, as a change produced by certain countermining operations, the magnetic element 102 is caused to close the firing contacts thereof ballistically and when this condition occurs the contacts 116 and 118 or 119, as the case may be, are opened by the rebound of the magnetic element and the firing arm regardless of the energized condition of the associated air core hold-on coils. The magnetic element is thus prevented from looking in the firing position when short magnetic pulses are received thereby preventing the operation of the time delay device TD2 and rendering the mine immune to this type of mine sweeping operations.

Briefly stated in summary the present invention contemplates the provision of a new and improved magnetic influence mine in which means are provided for arming the mine when a predetermined period of time has elapsed after the mine has been launched within a body of water,

for releasing the magnetized field sensing device thereof and automatically setting the magnetic sensing device to a predetermined sensitivity or setting such that the firing element thereof is brought to rest yieldably intermediate a pair of contact elements such that the mine is adapted to be fired in response to a predetermined change of either polarity in the magnetic field adjacent thereto, the mechanism also comprising means for preventing the premature explosion of the mine as the result of countermining or mine sweeping operations. In its broader aspects the present invention provides means for automatically setting a magnetized element yieldably in a predetermined position such that the movement of the element in either direction from the predetermined setting thereof in response to an increase or decrease in the intensity or a change in any direction in the lines of force composing the magnetic field adjacent thereto is sufiicient to cause the mine to fire.

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 modifications may be readily apparent to those skilled in the art, after understanding the invention herein disclosed, and that the terms employed in the claims are, therefore, to be considered as words of description rather than of limitation.

The invention herein described and claimed may be manufactured 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 secured by Letters Patent of the United States is:

1. In a marine mine of the character disclosed, a mine firing control mechanism comprising a magnetic dip needle, means including a shaft for pivotally supporting said clip needle for rotative movement about a horizontal axis, a firing contact connected to said shaft and adapted to be moved to difierent positions in accordance with the degree of rotation of the dip needle, a pair of contact elements arranged within the path of travel of said firing contact and adapted to be engaged selectively thereby, means for yieldably setting the firing contact intermediate said contact elements after the mine has been launched within a body of water, a firing circuit, and means for closing said firing circuit when said firing contact has engaged either of said contact elements in response to a predetermined change in the magnetic field adjacent the dip needle.

2. In a submarine mine adapted to be laid on the bed of a body of water, a mine firing control mechanism comprising a magnetized bar adapted to be moved angularly about a horizontal axis, a firing contact operatively connected to said magnetized bar and movable therewith, a pair of contact elements arranged on opposite sides of said firing contact and adapted to be engaged selectively thereby when the magnetized bar has moved through a predetermined angle of rotation, at source of electrical power, a pair of coils respectively connected to each of said contact elements and to said source of electrical power and adapted to urge the magnetic bar in a direction to maintain the firing contact in continuous engagement with the associated contact element as the coils are selectively energized, an electro-responsive time delay mechanism operatively connected to said firing contact and adapted to be controlled thereby, an explosive charge, electro-responsive means for detonating said explosive charge, and means including a pair of contacts adapted to be closed by said electro-responsive mechanism in time delayed relation with respect to the engagement of said firing contacts with either of said contact elements for causing said explosive charge to be fired by said detonating means.

3. In a mine firing mechanism of the character dis closed, the combination of a firing circuit having two branches therein, a pair of contact elements respectively associated with said branches, a movable firing contact arranged intermediate said contact elements and adapted to engage the contact elements selectively, a pivoted magnetic element adapted to be actuated by changes in the verticai component of the magnetic field adjacent thereto for controlling the movement of said firing contact, means for yieldably setting said magnetic element to an armed position with the firing contact disengaged from said contact elements, and means responsive to the engagement of said firing contact with either of said contact elements for closing said firing circuit through the associated branch thereof.

4. A mine firing control mechanism of the character disclosed comprising a magnetized bar pivotally supported for rotative movement about a horizontal axis, a contact arm operatively connected to said magnetized bar and rotatable therewith, a pair of contact elements arranged on opposite sides of said arm and adapted to be engaged selectively by the contact arm when the magnetized bar has moved through a predetermined angle, means for moving said contact arm into engagement with one of said contact elements, means controlled by said one of said contact elements for reversing the direction of motion of said contact arm, and means for bringing said contact arm to rest yieldably at a predetermined setting intermediate said pair of contact elements and disengaged therefrom.

5. A mine firing control device of the character disclosed comprising a magnetized bar pivotally supported for rotation about a horizontal axis, a firing contact operatively connected to said magnetized bar and rotatable therewith, a pair of contact elements disposed on opposite sides of said firing contact and adapted to be selectively engaged thereby, means for yieldably setting said firing contact to an armed position intermediate said contact elements and disengaged therefrom, a firing circuit, means for operatively connecting said firing circuit to said firing contact as the contact is yieldably set to said armed position, and means for closing said firing circuit when a predetermined period of time has elapsed after the firing contact has been moved into engagement of either of said contact elements by said magnetized bar in response to a change in the magnetic field adjacent thereto.

6. A mine firing control device of the character disclosed comprising a magnetized bar pivotally supported for rotative movement about a horizontal axis, a firing contact operatively connected to said magnetized bar and rotatable therewith, a pair of contact elements arranged on opposite sides of said firing contact and adapted to be selectively engaged thereby, means for yieldably setting said firing contact to an armed position intermediate said contact elements and disengaged therefrom, an electroresponsive time delay device, means for connecting said electro-responsive time delay device to said firing contact as the contact is yieldably set to said armed position, a firing circuit including a detonating device operatively connected to said electro-responsive device, and means included in said electro-responsive device for closing said firing circuit when a predetermined period of time has elapsed after the electro-responsive device has been operat'ed by the firing contact in response to the engagement of the firing contact with either of said contact elements.

7. In a magnetically controlled mine firing device, the combination of a pivoted magnetized element adapted to respond to changes in the vertical component of the earths magnetic field adjacent thereto, means including a shaft for pivotally supporting said magnetized element for movement about a horizontal axis, a pair of contact devices, a firing contact supported by said shaft and operatively connected to said magnetized element, means for yieldably actuating said firing contact into engagement with a predetermined one of said contact devices, means responsive to the engagement of the firing contact with said predetermined one of said contact devices for moving the firing contact reversely to an armed setting intermediate said pair of contact devices, a source of electrical energy, means for connecting said predetermined one of said contact devices to said source of electrical energy prior to the engagement of the firing contact therewith, means for connecting the other of said contact devices to said source of energy subsequent to the engagement of the firing contact with said predetermined one of said contact devices, a firing circuit, and means effective when the firing contact has been moved to said armed setting for causing the firing circuit to be operatively con nectcd to said source of electrical energy as the firing contact moves into engagement with either of said contact devices in response to a predetermined change in the magnetic field adjacent the magnetized element.

8. In a submarine mine, the combination of a pivoted magnetic needle responsive to changes in the vertical component of the magnetic field adjacent thereto, means for locking said magnetic needle in an initial position,

means responsive .to the pressure of the water within which the mine is planted for releasing said needle for pivotal movement about a horizontal axis, means for yieldably actuating the need; about said axis to a predetermined position thereof, a first pair of contacts .adapted to be closed as the magnetic needle moves into Said predetermined position, means responsive to the closure of said first pair of contacts -for reversing the. direction of movement of the needle about said axis, a contact device adapted to be closed when the needle has moved to ,a predetermined armed position with the first pair of contacts disengaged from each other, a second pair of contacts adapted to be closed when said magnetic .needle has been moved through a predetermined angle beyond said armed position, an electro-responsive time delay device, means effective when the contact device has been closed for operating said time delay device in re- ;sponse to the closure of either of said pairs of contacts by ..said magnetic needle, and means including a detonating device operatively connected-to said electro-responsive device for exploding the mine in predetermined time delay relation as the eiectro-responsive device is operated by either of said pairs of contacts.

9. In a mine having an explosive charge therein adapted tdbe laid on the bed of abody of water, a magnetic detecting device pivotally supported for rotation .movement above a horizontal axis, .said magnetic device .being-adapted-to be moved in either direction to diii'erent .settings selectively in accordance with changes in the vertical component of themagnetic fieldad acent thereto, a pair or normally open contactdevices, a firing element operatively connected to said magnetic detecting :device and vadapted to engage the contact devices selectively in accordance with the degreeof angular move- 'ment of ,said magnetic device, means including a resilient member for yieldably setting said firing element to an ,armed position intermediate said pair or' contact devices and disengaged thererrom, a firing circuit adapted to be closed as the firing element .is moved into engagement Withgeither of said contact devices .by a predetermined .changein saidmagnetic field, a pair oftn'ormally closed contactsin said firing circuit, a pendulum device having :meansforclosing anelectrical circuit as themine is dis- ,turoed, .and an =eiectro-responsive device controlled by said circuit closing means for quic ly disengaging said pairof normally closed contacts therebyto interrupt :said ,tiringcircuitior aiperiod, oftime sutficient forthe firing ..element to be ,broughttorestdn the armed position :-by ..saidresilient member.

10.,ln.a. submarine mine adaptedto be.la id :onthe bed of ..a .body of .water, :the combination of a magnetic element having afiring contactsecured thereto arranged .-.f,Or rotative movement ahouta horizontal. axis, means for yieldably ..setting said magnetic .element and .firing con- .tact to.a;predeterminedtarmed position, a,pair ofcon- ..taeLeiementsarranged on opposite sides of;said firing contact and adapted .to .be :engaged selectively thereby .in response to,ra.pre.determined degree ofangularmove- ,ment of .the .magnetic ..element in .either direction from said armed, position, ,acontroleircuit adapted to.be closed .as .the firing ..contact engages-either of said contact ,ele- .ments, said control. circuitincluding an electro responsive .device .having a pair .of normally open contacts :adapted .to he engaged in timedelay q-relationasthe device operates; .a firing ..circuit including a detonating device adapted to be controlledbysaidnormally opencontacts, ,apendulumdevice having ,contactmeansadapted to be -,closed as the mine is.disturbed,.,and.means controlled by said contact means forjnterrupting ,said controhcircuit before the detonating deviceisoperatedtby said electroresponsive means and for maintaining the control circuit interruptedfona period of time suflicient totenable said magnetic element and firing contact to be restored to said predetermined .armed position.

11. 'In aimagnetic mine adaptedtobearranged on the feed of a ,body of water within the. path of travel of a ,vessel, a pivoted magnetic elementselectively responsive to changes in the vertical component of the magnetic field adjacent thereto, said element having an initial position, an armed position and two firing positions, a firing circuit, means including a pair of contacts operatively connected to said magnetic element and adapted to be engaged selectively when the element is in either of said firing positions for closing said firing circuit, latitude setting means yieldably connected to said magnetic element for causing the magnetic element to ;be .moved from said initial position to said armed position, means for setting said latitude setting means in operation, an electro-responsive time delay device having a pair of normally closed contacts and a make contact adapted to close as the time delay device-operates, means including a pendulum device for operating the electro- -responsive device as the mine is disturbed, a control'circuit adapted to be interrupted as said pair of normally closed contacts of the time delay device are disengaged, and means controlled by said make contact for causing the operation of said latitude setting means to-be arrested during the movement of the magneticelement from said initial position to said armed position and for preventing the reoperation of the latitude setting .means until a predetermined period of time has elapsed after the'time delay device has been released.

12. In a mine firing mechanism of the character disclosed, the combination of a magnetized bar pivotally supported for rotativemovement about a hori-zontal axis, a contact arm operatively connected to said magnetized bar and rotatable therewith, a pair of contact elements arranged on opposite sides or said contact arm and adapted to be engaged selectively thereby, means including anelastic connection for yieldably setting said magnetized bar to an armed position with the contact arm intermediate said pair of contact elements and disengaged therefrom, a tirstcoil-connected to one of said contact elements and adapted to mad with the magnetized bar thereby to urge the contact arm into con- .tinuous engagement with said one of said contact-elements in response to movement of the arm into circuit closing position therewith, a second coil connected to the other of said contact elements adapted to coact with the magnetized bar and maintain the contact arm in continuous engagement with said other of the contact elements in response to -movement of thearm intoengagement therewith, asource of electricalenergy, means for connecting the first-coil'to said source of electrical energy, means controlled by the contact arm for connecting :the second coil to said source of electrical-err .ergy as the arm engages said one of-said contactlele- ,ments, a firing control circuihmeans,forconnectingthe firing control-circuit'to said-contact arm in time'delayed relationwith-respect-tothe connection ofthe second'coil to said sourceot electrical energy, a releasable electroresponsive deviceicontrolled by said-firingcontrol circuit including a pair of contacts adaptedtobe engaged when the firing control circuit has beentclosed for a predetermined period. of time, detonating means adapted tobe fired by saidelectro-responsive device as-the contacts thereof are. engaged, and meansincluding a-plurality of circuit connections-for maintaining a-continuous flow of current through said electro-responsive device fora period of time'sufiicient to cause the contactsthereofto be engaged and-firethedetonating device.

.13. In .a -mine of the character disclosed, a firing control mechanism comprising a magnetizedelement responsive to small changes in theearths magnetic field adjacent thereto, means maintaining-the mine in an un iarmed condition for apredetermi-nedperiod subsequent to the launching thereof and including a retaining ele- .ment forholding said magnetic element in a firstposi- :tion,-. means for arming said mine and including a spring operatively connected to said magnetic element and ,adapted to have the tension thereof adjusted to a preselected value forpositioning saidmagnetic element yield- -ab1y inasecond predetermined armed position, means forzadjustingsaidtension in accordance .with the latitude of the launching position, amine firing circuit, and -means controlled by-saidmagnetizedelement for closing the mine firing circuit when the strength of the vertical component of the earths magnetic field adjacent thereto is either increased by apredeterminedincrement-orde- ,creased by-a predetermined decrement.

14. A mine firing controlmechanism arranged within ,apmagnetic field, said mechanism comprising-a magnetized bar pivotally supported for rotative movement about a horizontal axis, means for applying a predetermined gravitational bias to said magnetized bar, means including a resilient member adapted to apply a predetermined additional degree of bias to said magnetized bar, means including a motor for varying the degree of bias applied by said resilient member, a pair of contacts adapted to be closed when the bias of said resilient member has been varied sufficiently to cause the magnetized bar to be moved rotatively to a predetermined position thereof, an electrical relay adapted to be operated by said pair of contacts as the magnetized bar moves into said predetermined position, a fusible locking device operatively connected to said relay and adapted to be released as the relay operates, means including a rotatable member controlled by said fusible device for reversely varying the bias applied by said resilient member sufliciently to disengage said pair of contacts, and means controlled by said rotatable member for preventing the reoperation of said relay by said pair of contacts as the contacts are subsequently closed by the magnetized bar in response to a predetermined change in the vertical component of said magnetic field.

15. A firing control mechanism of the character disclosed comprising a magnetic element pivotally supported for rotative movement about a horizontal axis, a contact arm operatively connected to said. magnetic element and rotatable therewith, a latitude setting mech- I anism having an elastic connection for yieldably setting said contact arm and magnetic element to a predetermined armed position, a pair of contact elements adapted to be engaged selectively by said contact arm when the magnetic element has moved through a predetermined angle in either direction from said armed position, a. firing control circuit adapted to be closed as the contact arm engages either of said contact elements, and means settable at will for varying the degree of rotative movement of said magnetic element and contact arm necessary to close said firing control circuit.

16. A firing control mechanism of the character disclosed comprising a magnetic element pivotally supported for rotative movement about a horizontal axis. a contact arm operatively connected to said magnetic element and rotatable therewith, a latitude setting mechanism having an elastic connection for yieldably setting said contact arm and magnetic element to a predetermined armed position, a pair of contact elements adapted to be engaged selectively by said contact arm when the magnetic element has moved through a predetermined angle in either direction from said armed position, a firing circurt, means operatlvely connected to said contact arm and responsive to the engagement of the contact arm with either of said contact elements for closing said firing circuit, and means settable at will for varying the degree of rotative movement of said magnetic element and contact arm necessary to operate said firing control circuit closing means.

17. A firing control mechanism of the character disclosed comprising a magnetic element pivotally supported for rotative movement about a horizontal axis, a contact arm operatively connected to said magnetic element and rotatable therewith, means including a resilient member for yieldably setting said magnetic element and contact arm to an armed position. a pair of contact devices adapted to be engaged by said contact arm selectively in accordance with the degree and direction of movement of the magnetic element and contact arm from said armed position. means for controlling the angle of the magnetic element with res ect to a horizontal plane when the magnetic element and contact arm are set to said armed position, and means settable at will for varying the degree of an ular movement of the contact arm from said armed osition necessary to engage each of said contact devices.

18. A firin mechanism for a submarine mine of the character disclosed comprising a shaft having a magnetic bar secured thereto. means for pivotally supporting said shaft and bar for rotative movement in a vertical plane. a contact arm secured to said shaft and rotatable therewith. a pair of contacts arran ed within the path of trave of said contact arm and adapted to be en aged thereby when the contact arm has moved through a pre determined angle. means for vieldably settin said contact arm in a predetermined armed position intermediate said pair of contacts and disengaged therefrom. means settable at will in accordance with the latitude at which the device is arranged for causing said contact arm to assume said predetermined armed position after the mine has been launched within a body of water, an electroresponsive time-delay device having a winding, an electric circuit including said contacts and said contact arm and said winding whereby the time-delay device is energized upon the closing of the circuit, and detonating means controlled by said time-delay device for exploding the mine a predetermined time after said electric circuit is closed.

19. Mine firing apparatus comprising a detonator, a normally open firing circuit for said detonator, a pivoted magnetic element adapted to be moved in response to changes in the vertical component of the magnetic field ambient thereto, an arm operatively connected to said element and adapted to move therewith, fuse means arranged within said mine for retaining said element in a first unarmed position for a predetermined period of time after the mine is launched, spring means adapted to have the tension thereof varied for subsequently setting said elementin a predetermined armed position in accordance with the latitude where the mine is launched, means for adjusting said tension, and means carried by said arm for closing said firing circuit when said element moves a predetermined distance in either direction from said armed position in response to a change in the magnetic field.

20. Mine firing apparatus comprising a detonator, a normally open firing circuit for said detonator, a pivoted magnetic element adapted to be moved in response to changes in the vertical component of the magnetic field ambient thereto, an arm operatively connected to said element and adapted to move therewith, means arranged 'within said mine for retaining said element in a first unarmed position for a predetermined period of time after the mine is launched, means controlled by said retaining means for subsequently setting said element in a predetermined armed position in accordance with the latitude where the mine is launched, and means carried by said arm for closing said firing circuit when the said element moves a predetermined distance in either direction from said armed position in response to a change in the magnetic field, said firing circuit including a timedelay device whereby said detonator is not exploded until a predetermined time has elapsed after the closing of the firing circuit.

21. In a mine of the character disclosed adapted to be laid on the bed of a body of water adjacent the path of travel of a vessel, the combination of an explosive charge, electro-responsive detonating means adapted to explode said charge, a dip needle having a pivot bearing, a. shaft adapted to be horizontally disposed, means mounting said needle on said shaft for rotation therewith about an axis, a contact arm connected to said needle and adapted to move in a plane upon rotation of said needle, a pair of contact elements disposed in said plane in the active path of said first named contact and on opposite sides of said arm respectively, means for selectively biasin: said contact arm in accordance with the strength and declination of the earths magnetic field where the mine is to be laid such that the contact thereon is in a predetermined position intermediate said pair of contact elements and normally disengaged therefrom, and a firing circuit including a source of electrical power and operable upon engagement of said contact arm with either one of said contact elements to energize said detonating means in response to the ma netic field of a vessel in the vicinity of the mine of sufiicient strength to change the setting of the dip needle to effect the engagement selectively of said contact arm and contact elements thereby to explode the mine.

References Cited in the tile of this patent UNITED STATES PATENTS 953,191 Bergstrom Mar. 29, 1910 1,382,374 Maxim June 21, 1921 1,388,658 Marshall Aug. 23, 1921

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