US2341351A - Aerial mine - Google Patents

Description

Feb. 8, 1944. J. A, BARKLl-:Y

AERIAL MINE 2 sheets-sheet 1 AF'iled May l5. 1941 'IIIIIIIl Feb. 8, 1944. J. A. BARKLEY 2,341,351-

AERIAL MINE Filed'May 1S, 1941 2 sheets-sheet 2 TDME DELAY CONTROL Patented Feb. 8, 1%44 v artist MINE Joseph Amos Barkley, Silvercroft-,Del. l Application May is, 1941, serial Nassasiv 1 o1aim.'- '(ci. 1oz-9) This invention relates to aerial mines, and more particularly, to a mine adapted to operate at a given height above the earth and to explode in response to sound waves or vibrations from a source, such as a hostile aircraft, in predetermined proximity to the mine.

An important object of the invention is the provision in a mine of this character of means for preventing response of the mine to extraneous disturbances, such as the explosion of anti-aircraft fire.

A further object of the invention is to provide a construction preventing response'of the mine to even those vibrations to which it is sensitive until it has reached a predetermined height above the terrain from which itis launched. I

A still further object of the invention is the provision of means whereby the mine will be maintained at all times at a predetermined level.'

Another object of the invention is the provision of means whereby the mine will only explode upon an approach thereto by the aircraft which it is designed to destroy within certain limits. y

A further object of the invention is the inclusion in the structure of certain safety devices precludlng accidental detonation of the mine during launching or landing thereof.

Other objects and advantages of the construe tion will become obvious throughout the course of the following description.

In the drawings, wherein for the purpose of illustration I have shown a preferred form of my invention,

Fig. l is a pictorial representation of the use of mines constructed in accordance with my invention;

Fig. 2 is a` vertical sectional view through the mine unit;

Fig. 3 is' a vertical mine unit taken at Fig. 2;

Fig. 4 is a side elevation of the mine unit;

Fig. 5 is a detail sectional view of the baromesectional view through the right angles to the view of tric switch partially in section of one modiable gas-inflated supporting balloon which may be employed either singly or in multiple with the mine unit hereinafter to be described. This balloon element is equipped with means whereby it will move to aselected height and remain at that height. This may be accomplished, for example, by providing the balloon Iwithan outlet neck Ii, the upper end of which aords a seat for a springseated check valve I2 preventing the escape of the supporting gas therefrom. As at present shown, this check valve is connected toa remote portion of the balloon, indicated at I3, byA the flexible element I6, with the result that when the balloon distends beyond a predetermined diameter, as it will when `it reaches a sufficiently rareed atmosphere, the flexible element iii will lift the valve i2 from its seat, permitting release of a portion of the contents until the balloon is restored to its predetermined maximum size. Since the rarecationof the atmosphere may be at least generally said to be proportional to the distance from the earth, such an arrangement will serve to maintain the balloon at an approximate selected altitude. By adjusting the length of element I6 and the amount of gas in the balloon, the maxlmurnaltitude can be regulated.

Suspended from the balloon,` as by means of ilexible element I5, is a mine unit I6. Preferably a parachute I5a is attached to the mine unit so as to lower the same gradually in the event that the balloon should burst. Unit I6 comprises an upper casing element I1 at present shown as adapted to receive the explosive (see Figs. 2 and 3), and a lower casing element I8, detachable from the casing element i i as by means of quickdetachable fasteners indicated at i9, and at present shown as spring plates rotatable about' pivots 20 and engaging pins 2| carriedby the elements I8. The bottom casing element I 8 carries, preferably at its lower end. a series of vibrationreceiving horns or sound collectors 22. This element likewise affords a housing for the electrical control apparatus 23 including a sensitivity control 26 which may be adjusted through an externally disposed knob 25 and a time delay control 59 similarly adjustable by knob 62.

In addition to affording space for the electrical control apparatus hereinafter to be more fully described, the element I8 likewise houses a barometric switch 2o. Switch 26 (see Fig. 5) cornprises a closed chamber 2l, one vface of which is in the form of a flexible diaphragm 28 carrying the switch contact 29. The chamber 27 is bodily adjustable toward and away from one wall of the element i8 by means of a screw 30 rotatably iounted in this wall and having at its outer end n adjusting knob 9i. The contact 29 of diahragm 29 is opposed by a contact 92 on the mer end of a screw 33 adjustable through the ame wall as that mounting the screw III and conrollable through a knob 94 coacting with a suitbie dial 35 (see Fig. 4) which may be coneniently graduated in thousands of feet.

The electrical control apparatus is connected to detonator 99 and to a switch 21 by means of ack sockets 39 and associated jack plugs on umper connections 39. The ,detonator is renovably held in a receptacle 40 within the exploive chamber I1 by means of a clip 4I. A pair .f jack sockets 42 are disposed adjacent the jack ockets 38 for a purpose which will be described ater. It will be noted that the detonator is luickly removable merely by operation of clip II and removal of the jack plugs electrically coniecting it to the other elemen Moreover, the entire explosive charge may be quickly sepa- .'ated from the rest of the mine simply by de- ;aching section I1 from section I8.

The voltage produced by the vibration-respon sive device 45 may be supplied to a step-up transformer 59 which is preferably peaked to the frequencies above mentioned. The voltage across the secondary of transformer 50, or a portion thereof, is supplied `to an electron tube amplifier which may comprise/as many cascaded stages as may be desired. The sensitivity control device 24, previously referred to, may take the form of a potentiometer interposed between transformer 50 and the ilrst l,ube 5I. as illustrated, and serving to control the sain of the amplliler. Tube 5I may take the form of a simple triode, as illustrated, or it may take any other suitable form. In the speciilc circuit illustrated, tube 5I is coupled to a diode-triode tube l2 by means of a transformer 53, which is also preferably peaked to the desired frequencies. A by-pass condenser 6I serves to control the frequency response. This condenser may have a l capacity of about .002 microfarad. Tube 52 serves The switch 91 is normally biased to its open position, as shown in Fig. 2, for example by the resilience ol' arm 43 and the weight of hook 44 secured thereto. By means of the hook, the flexible element of the sustaining balloon or balloons is connected to the mine. Thus when the element I5 is not under tension, i. e., when the balloon is on the ground or in the event that the balloon bursts while in the air, the switch 31 is opened and prevents explosion of the mine. When the weight of the mine is sustained by the balloon, switch 31 will be closed. 'I'his will, of course, occur immediately upon proper inflation of and release of the balloon, and, under ordinary circumstances, the mine would then be ready for detonation. Any possibility of such detonation is, however, prevented through the barometric switch 2B which, prior to release of the balloon, is set to prevent closure of such switch until the balloonA has reached a predetermined elevation above the terrain from which it is released.

Referring now to the electrical system illustrated in Fig. 7, there is provided a suitable vibration-responsive device 45 which isarranged to receive the sound vibrations collected by the collectors 22. This device may take any suitable form, for example, it may comprise one or more vibrative reeds 46 and an associated electromagnet 41 forming a simple electric generator, as will be well understood. This device serves, of course, to translate the vibrations received by the vibrative element 46 into electrical currents. The vibrating reeds may be designed and arranged to vibrate over a predetermined frequency range. By mounting the reed or reeds in rubber, or by damping the reeds in any suitable manner, a wider frequency response range may be obtained.

It will be apparent that the device 45 may take other well-known forms; for example, it may take the form of a. microphone. In any case, this device should be designed so that it has a resonance frequency or frequencies of vibration within a predetermined frequency range including the noise or sound frequencies commonly produced by aircraft.

A common battery energy in the circuit also serve to energize tron tubes employed. trois the energiz'ation of the apparatus.

48 may serve as a source of of the device 45, and may the laments of the elec- A manual switch 49 con- 'nsi to control a relay 54, which in turn controls -the energization of the detonator 36, as will be described presently. If desired, suitable iilters 55 and 55 may be connected as illustrated in order to further improve the frequency response of the circuit, and each iilter maycomprise an adjustable resistor and condenser.

While it is preferred to employ the diode-triode tube 52 for reasons which will be apparent later, it is within the contemplation of the invention to employ any suitable single or multistage amplier. Moreover any suitable type of interstage coupling may be employed; for example resistance-capactance coupling could be used.

The diode-triode 52 is arranged so that it is normally inoperative or quiescent, and it is adapted to be triggered by incoming vibrations, provided such vibrations are of a sustained nature and are not merely of a transient nature. To this end, the triode section of the tube is biased substantially to plate current cut-off by means of a biasing source 51. The diode rectifier circuit is connected to the control grid of tube'52 through a condenser 58 and a variable resistor 59. The rectified voltage appearing in the rectier circuit is thus impressed on condenser 58 through variable resistor 59 which controls the rate at which the condenser is charged by the said voltage.

Condenser 58 may have a capacity of about 8 microfarads, while resistor 59 may have a resistlance of about one megohm. A resistor 60 which is also of very high resistance slowly discharges the condenser. The condenser-charging voltage is polarized in opposition to the negative bias voltage on the grid of tube 52, and, therefore, when the condenser becomes suillciently charged, it overcomes the negative bias and causes plate current to iiow in the triade section .of tube 52. It will be apparent that by varying the resistance 59, the time delay or time required to charge the condenser 59 may be varied. By this arrangement, the circuit is caused to discriminate between sustained vibrations and vibrations of short duration, and the discriminating action may be varied by means of resistor 59. Continuous or sustained vibrations will cause the condenser 59 to accumulate a charge until it triggers the tube, whereas transient vibrations will not charge the condenser suiiciently to trigger the tube and any charge due to such vibrations will be dissipated by resistor 60. Thus, the device is caused to operate in response to the sustained vibrations produced by approaching aircraft, and at the same time it is prevented from responding to vibrations of short duration such as may be caused by antiaircraft lire, the explosions of nearby mines, etc.

It will be apparent also that the circuit may be designed and adjusted to operate at a predetermined noise level corresponding to predetermined proximity of an aircraft. Obviously any desired threshold level may be established by the tube bias and the condenser.

The employment of the particular circuit illustrated also conserves the plate supply battery,

since the tube 52 is non-conductive except when' it is triggered.

Since the switches 26 and 31 will have been previously closed, as described above, the energization of relay' 54 completes an energizing circuit for the detonatorASB which may be energized `from the plate supply source 62. The detonator, when thus activated, causes the explosion of the explosive material within the chamber I1.

In order to assure proper operation of the baronetric switch 26 and to compensate for surface elevation and local barometric conditions, this ;witch may be pre-adjusted in the manner now '.o be described. The jack plugs are removed from lack sockets 38, and a special jack plug 63, as :hown in Fig. 8, is inserted in the jack sockets 38 ind 42. The prongs 64 of this plug are connected iogether and serve to bridge sockets 42, while the rongs 65, which are received by sockets 38, are :onnected to a voltmeter or a lamp 66. It will be :een that this disconnects the Vdetonator 38 and he switch 31 and places the voltmeter, or lamp, n circuit with the battery 62 and the barometric witch 26. The handle 34 is set to zero altitude, nd the zero adjustment knob 3| is rotated in a lirection to close the contacts of the barometric witch which will be indicated by the lamp or 'oltmeten This adjustment establishes the conact 29 in proper position for zero altitude. 'I'he :nob 34 is then turned until it indicates the altiude at which it is desired that the barometric witch shall close. This adjustment, of course, stablishes the contact 32 at a. certain distance rom contact 29.

It will be apparent to those skilled in the art hat other forms of trigger type control circuits ray beemployed. For example, in Fig. 9 there sshown another form of such a circuit employing gas lled ionic-cathode glow-discharge tube 63 commonly known as a gas trigger tube. The voltage across the secondary of transformer 53 is applied to a suitable rectifier, such as the oxide rectiiier 64. The rectied voltage is applied to condenser 58 which is connected to the starter grid of the gas tube. The starter grid may be maintained at a potential Just below the trigger potential of the tube by means of the tap on battery 62. The voltage on condenser 58 is polarized the same as the potential applied to the grid.

In response to sustained vibrations the condenser 58 will acquire |a charge sumcient to trigger the tube, causing plate current to iiow and thereby energizing relay 54. Transient vibrations, however, will not charge, the condenser suiliciently to trigger the tube, and the resistor 60 will dissipate any charges due to such vibrations.

Aside from the above-noted differences, the circuit of Fig. 9 is similar to that of Fig. l and operates in the same manner. It should be noted, however, that in theuse of the gas tube it may ibe unnecessary toamplify the voltage generated by device I5, as such voltage may be suflicient to trigger the tube, but it is desirable to employ one or more stages of amplication.

From the above description, it will be seen that the invention provides a novel Iaerial mine having various novel features. It will be understood. of course, that the invention is not limited to the specific structure illustrated, but is capable of various modiilcations within the scope of the appended claim.

I claim:

In an aerial mine, an elevating balloon, la mine unit, means for suspending said unit from said balloon, detonating means for exploding the mine, an electrical energizing circuit for said detonating means, vibration-responsive means for closing said energizing circuit, a normally open safety switch included in said circuit and operable by said suspension means to closed position whenever sad unit is lifted by said balloon, and a normally open barometric switch included in said circuit serially with said safety switch and operable by predetermined atmospheric pressure to closed position when said unit is lifted by said balloon to a predetermined altitude.

JOSEPH AMOS BARKLEY.

Images