US3511182A

US3511182A - Apparatus for controlling the firing of an explosive charge

Info

Publication number: US3511182A
Application number: US510798A
Authority: US
Inventors: Frank A Hester Jr
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1943-11-18
Filing date: 1943-11-18
Publication date: 1970-05-12
Anticipated expiration: 1987-05-12

Description

May 12., v19'70 F. A. HESTER, JR

APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE Filed Nov. 18, 1943 .4 Sheets-Sheet l III! r. M H.

Frank Gttorneg Mayv 12., 1970 F. A. HESTER, JR 3,511,132

APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE Filed Nov.` 18,1945 .4 sheetssheet 2 Zsnventor Cttorneg .May 12, `19701 F. A. HEsTER, JR 3,511,132

4IFPARA'IUS FOR CONTROLLING THE FIRING 0F AN EXPLOSIVE CHARGE Filed Nov. 18, 1943 .4 Sheets-Sheet 5 lI-.IIlIIIlIlIlIL I LLAA AAAAAAA .Inlllllll 'III Il..

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MgylZ., 1970 F. A. HEs'rER, JR

APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE 4 Filed NOV. 18, 1945 .4 Sheets-Sheet 4 l'aa /aa FBF. (76255 PEI? 5661 :inventor mkg@ Fran/Z.

Gttorncg Uhitedr States Patent O U.S. Cl. 102-70.2 14 Claims Aus'TRl/wr oF THE Ds'cLosURnV This invention relates to apparatus for and a method of controlling the firing of an explosive charge, and more particularly to an apparatus and method of this type which are especially suitable for submarine use.

In submarine operations, it is sometimes necessary to set off `an explosive charge for destroying a target located below the surface of the water. For example, in naval warfare, the problem of destroying submarines after they have been located is an exceedingly important one. Various attempts have been made heretofore to lire explosive charges which have been directed toward submarines so that they will produce maximum damage to the submarines. Obviously, this can only be done if the explosive charges` are detonated or fired when they are in close proximity` to their targets. In this respect, however, the prior art methods of and devices for controlling the firing of depth charges have not been very successful.

It is the primary object of my present invention to provide an improved method of and apparatus for ring depth charges in a manner which will not be subject to the limitations of those of the prior art.

More particularly, it is an object of my present invention to provide an improved method of and apparatus for controlling the tiring of depth charges so that such charges will not explode until they have reached a minimum distance from the target.

Another object of my present invention is to provide an improved apparatus as aforesaid which will be protected against tiring in response to countermine shock, such as that resulting either from the explosion of another charge in the vicinity of the controlled charge or from other undesirable vibrations set up in the water and reaching the controlled charge.

Still another object of my present invention is to provide improved apparatus as above set forth which can be made either to expend itself when striking the bottom of the ocean or not, as may be found most desirable.

A further object of my present invention is to provide an improved method and apparatus of the type set forth both of which are extremely eicient in operation, and the apparatus of which is very compact in construction and relatively inexpensive in cost.

In accordance with my present invention, I provide a heterodyne detecting device consisting of a magnetostriction loudspeaker-microphoneoscillator unit provided with a vibratory diaphragm and a three-quarter wavelength magnetostriction rod secured at one end to the diaphragm. At the two motional nodes of the magnetostriction rod, I couple a pair of coils thereto coaxially with the rod, one coil constituting a driving or transmitting coil and the other a driven or receiving coil. The two coilsare connected to two vacuum tubes which, in turn, are connected in cascade, one tube receiving its signal from the receiving coil, and the second tube receiving its signal from the first tube, the second tube being connected so as to supply a signal to the driving coil. This circuit is arranged to oscillate at the frequency of the vibratorysystem comprising the magnetostriction rod and the vibratory portion of the diaphragm and introduces an acoustic signal into the water through the diaphragm.

lf the singal emitted by the unit thus far described is reflected from an object moving relative thereto, the Doppler effect shift in the frequency of the reflected signal will occur. Upon striking the diaphragm, the reflected signal will set up in the rod very small vibrations which will regenerate around the oscillator circuit, thereby resulting in the detection of a heterodyne between the reected and the outgoing signals. The heterodyne frequency will depend upon the relative speed of the refleeting target or other object and the transducer unit above described and will fall to zero at the minimum distance between them. A selective amplifier and tiring circuit, set to fire the explosive charge when some suitable low heterodyne frequency is reached, are connected to the output of the detector. An anticountermine switch is connected to the diaphragm and is suitably coupled to the ring circuit to prevent firing of the charge when another charge detonates or some other undesirable sonic vibrations appear in the vicinity of the controlled charge. The tiring circuit may be arranged so that, notwithstanding said switch, it will operate to re the charge when it strikes the bottom of the ocean, or it may be arranged not to do so, depending upon whether or not it is desired that the controlled charge shall re upon striking the bottom.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description of two embodiments thereof, when read in connection with the accompanying drawings, in which FIG. 1 is a central, sectional view of one form of control apparatus constructed in accordance with the present invention, certain of the parts being removed for the sake of clearness,

FIG. 2 is a top plan view of the apparatus with the cover shown in dash lines,

FIG. 3 is a wiring diagram of one circuit in accordance with the present invention, this circuit being useful when it is desired that the charge be not fired upon striking the bottom of the ocean,

FIG. 4 is a wiring diagram showing a modied form of circuit useful when it is desired that the charge be fired upon striking the bottom of the ocean,

FIG. 5 is a circuit diagram of the limiter with reference to which its operation will be described in greater detail hereinafter,

FIGS. 6a and 6b are sets of curves showing instantaneous plate voltage values for various sine wave inputs to the limiter,

FIGS. 7a and 7b are curves showing the direct current components of the limiter plate voltages corresponding, respectively, to the inputs of 6a and 6b,

FIG. 8 is a diagrammatic view illustrating the relation between a falling depth charge and a submarine target, and with reference to which the operation of the control apparatus of the present invention will be described in greater detail hereinafter, and

FIG. 9 is a curve showing the response of the amplifier of the present invention.

Referring more particularly to the drawings, wherein similar reference characters designate corresponding parts throughout, there is shown in FIGS. 1 and 2, a control device 1 comprising a diaphragm 3 of magnetic material having a vibratory, central portion S coupled to the outer portion thereof by a thin, exible, annular portion 7 whereby the central portion 5 is capable of acting substantially as a piston. A magnetostrictive rod or the like 9 is secured to the vibratory portion 5 of the diaphragm and forms therewith a vibratory system. The diaphragm 3 is also provided with an annular recess 11 in which a casing or cover 13 is received against a suitable gasket 15 to provide a water-tight connection between the casing 13 and the diaphragm 3. The latter is also formed with a plurality of openings 17 through which suitable bolts may be inserted for securing the device 1 to a depth charge or other similar explosive 19, as shown in FIG. 8. Surrounding the magnetostrictive rod in coaxial relation therewith and in proximity to the diaphragm 3 is a winding 21 constituting a driving coil. An annular magnet 23 disposed about the 'coil 21 is secured to the'di'aplragm 3 and supplies a biasing flux to the vibratory system. The flux path is completed by a yoke plate 25 and a spacing member 27 disposed between the yoke plate 25 and the magnet 23. An alternating current magnetic shield 29 of copper or the like is placed around the yoke plate 25, the spacer 27, the magnet 23, and the coil or winding 21.

Above the shield 29 is a cylindrical supporting member 31 which supports a second coil or winding 33. The coil 33 is also disposed about and in coaxial relation with the rod 9 and acts as a receiving coil in a manner to be presently described, the shield 29 serving to shield the

coils

21 and 33 from each other against induction. The space above the shield 29 may also be utilized to compactly house the other components of the device to be presently described, and a suitable terminal plug 35 is provided at the upper end of the casing for connection of these components to suitable power sources and the like. A gasket 37 of rubber or other suitable material is interposed between a flange on the plug 35 and the casing 13 to provide a water-tight connection therebetween. The casing 13 may be secured in place by means of a pair of screws 39 which are threaded into a pair of upstanding brackets 41 secured to the diaphragm 3 in any suitable manner.

The receiving or driven coil 33 is connected to the input circuit of a pentode vacuum tube 43, such as a type 1T4 tube, which operates as a combined detector and amplifier. The output circuit of the tube 43 is connected to the input circuit of a vacuum tube amplifier 45, such as a type 3A4 tube, the latter acting as a power amplifier. The driving coil 21 is connected in the output or plate circuit of the power amplifier 45. The arrangement is such that the vibratory system constituted by the piston-like diaphragm portion 5, the magnetostrictive rod 9, the two

windings

21 and 33, and the tubes 43 and 45 form an oscillating circuit or system which generates the outgoing signal. The tube 43 excites the tube 45 which then drives the rod 9 through its output or plate coil 21, while the rod 9, in turn, excites the tube 43 through the receiving or grid coil 33 thereof. This oscillatory system is arranged to oscillate at the natural frequency of the vibratory system comprised of the diaphragm portion 5 and the rod 9, and this frequency may be approximately 25 kc. The length of the rod 9 is equal to three-fourths of the wave length at the natural frequency of the oscillating system, and the

windings

21 and 33 are preferably arranged about the rod 9 at the two motional nodes thereof. In actual practice the rod 9 is, of course, somewhat longer than three-fourths of the wavelength at the natural frequency of the oscillating system so as to provide a short end beyond its lower node region within the coil 21 for attachment to the diaphragm 3, as clearly shown in FIG. l.

The output of the tube 43 is also coupled to a three stage selective amplifier which includes a pentode 47, such as a type 1S5 tube, and a pair of triodes 49 which may be enclosed in a single envelope, as in the type 3A5 tubes. The output of the amplifier 49 is connected to a limiter amplifier 51 through a multi-stage, low-pass filter comprised of resistors 53 and grounded capacitors 55 connected in tandem. A two-stage filter of this type is shown in FIG. 3 by way of illustration. The attenuation of the4 filter network 53, 55 increases as the frequency is raised. Thus, to obtain a given output from the filter with rising frequency, the input to the filter must be increased greatly as the frequency is raised. The limiter amplifier 51 is of a type which responds only to signals of a voltage above a certain minimum. Hence, the input voltage to the filter network 53, 55 must be relatively high to obtain any limiter response. Now, the maximum voltage which can be applied to the lter network is limited to the maximum output voltage of the amplifier tube 49 which drives it. As a result, there is a frequency dependent upon (a) the maximum output voltage of the driving tube 49, (b) the filter network 53, 55 and (c) the minimum voltage required to operate the limiter 51 above which operation of the limiter cannot be obtained. This cut-off frequency, so to speak, may be selected at any suitable or predetermined point and the filter network 53, 55 arranged to pass on to the limiter amplifier 51 only voltages of a frequency less than said predetermined frequency for a purpose which will become apparent presently.

The output of the limiter amplifier 51, which may also be a pentode of the 155 typefis coupled through a network consisting of a resistor 57 and a grounded capacitor 59 to a normally blocked, cold cathode discharge device 61 which acts as a firing tube. The tube 61 may be a type 359A tube, for example. A capacitor 63 is connected in series with the tube 61, as is also a detonator 65 associated with the depth charge 19 in well-known manner. The capacitor 63 is normally charged through a resistor 66 from a suitable D.C. voltage source connected at the point A.

Before proceeding with a description of the operation of the apparatus thus far described, it may be pointed out that the well-known Doppler effect is employed to obtain ring of the charge at substantially the point of closest approach to the target, such as a submarine 67. The method of utilizing this effect will now be explained with reference to FIG. 8.

Assuming that the submarine 67 has been located, a depth charge 19 is dropped at a point as nearly over the submarine as can be judged. When the charge has reached a certain depth below the surface of the water, pressureoperated switches therein function in a well-known manner immaterial to the present invention to close the various circuits to the several power sources indicated schematically in FIG. 3. As soon as the oscillatory system consisting of the diaphragm portion 5, the magnetostrictive rod 9, the coils Z1 and 33, and the tubes 43 and 45 begins to function, the vibratory diaphragm portion 5 projects a continuous, high frequency acoustical wave toward the submarine which reflects the wave back to the diaphragm 3. This all takes place while the depth charge is moving relative to the submarine. Due to the relative velocity which exists between the depth charge 19 and the submarine 67, the received, reflected signal and the outgoing, transmitted signal will differ slightly in frequency, pursuant to the Doppler effect, the frequency difference depending upon the magnitude of the relative velocity between the charge 19 and the submarine 67.

If the angle 0 shown in FIG. 8 is the angle made at any instant between a line from the depth charge 19 to the center of the submarine 67 and the horizontal, f is the frequency of the transmitted signal, V is the downward velocity of the depth charge 19, and C is the velocity of sound, the difference frequency fd between the two signals at that instant is given by the expression As the device 1 of the depth charge 19 passes by the submarine 67, the frequency difference fd will vary from a maximum value when the device first starts operating (for example, cycles per second) to 0, the value 0 occurring at the instant of closest approach of the depth charge 19 to the submarine 67; that is, when the charge 19. and the submarine 67 are substantially both on the same horizontal plane. This is the ideal point at which the charge should be tired. However, in practice, this is very diiicult to realize. Consequently, the charge is made to fire when the frequency difference fd is in the neighborhood of about cycles per second which corresponds to an angle 0 of about 11.5 from the horizontal.

Referring once more to FIG. 3, it will be seen that when thereiiected signal, which is extremely weak, is received bythe diaphragm portion 5, the rod 9 is caused to vibrate, thereby setting up weak signals in the receiving coil 33. Signals generated in the coil or winding 33 are then amplified by regeneration around the oscillator loop. Due to the regeneration, the amplitude of the received signal is sufficient to produce a heterodyne on the grid of the tube 43. Thus, a component whose frequency is the difference in frequency between the outgoing and reiected signals appears in the output of the tube 43, since this tube also acts as a simple grid leak detector, as shown in FIG. 3. The circuit is designed so that the tube 43 will operate at maximum detector sensitivity, while the tube 45 operates at maximum power output. It is for this rea son that the two tubes 43 and 45 are employed instead of a `single tube in which either sensitivity or power would have to be sacrificed.

The heterodyne signal representing the difference in frequency between the transmitted and reflected waves is applied to the input of the tube 47. The low pass filter 53, is designed to pass only very low frequencies. If desired or found necessary, the networks which couple the various amplifier stages may be similarly designed more or less. Thus, when the frequency difference between the transmitted and received signals is in the order of 30 cycles,` the signal is passed by the selective amplifier and is applied to the limiter tube 51. The characteristic of this circuit is such that it will not respond at all to Weak signals, While its response to strong signals is independent of signal strength. This may be understood more readly from the following description in connection with FIGS. 5, 6a, 6b, 7a and 7b:

The instantaneous value of the plate current of a tetrode or pentode is principally dependent on the instantaneous values of the control grid and screen grid voltages and is dependent only to a minor degree upon the instantaneous value `of the plate voltage, provided this value exceeds a certain minimum. If the value of the control grid voltage ec of the tube 51 be maintained at its constant zero signal voltage, increases in the screen voltage Es will result in nearly proportionate decreases in the plate voltage ep, provided Es is not allowed to increase beyond a certain limiting value. As Es approaches this limiting value, the plate current, ip, approaches its maximum value of ip (max.)=Ep/Rp. Thus, a value 0f Es may be found which reduces ep substantially to zero. Further increases in Es will essentially produce no effect 0n ep. If Es is maintained at the minimum value required to reduce ep substantially to zero, and an alternating voltage ec be applied to the control grid, the circuit acts as an average value rectifier. During the positive portion of the cycle of ec, ep will remain at zero. During the negative portion of the cycle, ep will vary in proportion to ec. The direct current component of the plate voltage will be the average value of ep, which will be porportional to the average value of eC rectified. FIGS. 6a and 7a show the result of applying a sine wave input to the circuit. For large `values of input voltage, the output D.C. voltage component is limited to the value 1/2E.

If the value of Es be set higher than the minimum value required to reduce the plate voltage substantially to zero in the absence of an input signal, small amplitudes of input signal will produce no output, while the output for large inputs will be unchanged. An input large enough to allow its negative peaks to compensate the excess of Es over the minimum value is required to produce output. FIGS. 6b and 7b illustrate the operation of this circuit with a sine wave input. This condition of operation is employed in the heterodyne depth charge units according to my present invention.

It will be apparent from the foregoing description that the selective amplifier will pass on to the limited 51 only signals of a frequency below the predetermined frequency which is the high frequency cut-off frequency of the filter network 53, 5S. It will also be apparent that the limiter 51 does not respond at all to the voltages supplied by the selective amplifier having an amplitude less than a predetermined amplitude (for example, about 5 volts), whereas for voltages above this amplitude, the tube 51 will respond. When these two conditions are met, the limiter tube 51 applies its output voltage pulses to the capacitor 59, thereby gradually charging this capacitor. The

network

57, 59 has a time constant of about 0.2 sec. after which the charged capacitor 59 will fire the tube 61. As soon as the tube 61 is fired, there is provided a current discharge path for the capacitor 63 through the tube 61 and the detonator 65, thereby firing the charge 19.

In order to prevent premature firing of the charge 19 by extraneous noises, such as that produced, for example, by the explosion of another charge in the vicinity of the controlled charge, there is provided an anti-countermine switch 6'9. This switch comprises a relatively stiff leaf spring 71 which is connected at one end to the diaphragm 3 or to some other suitable member rigidly connected with the diaphragm. To the other end of the leaf spring 71 is connected a mass 73 which is tuned with the spring 71 to some suitable frequency, say, for example, approximately 200 cycles per second. At one end of the mass 73 there is secured a second and relatively exible spring 75, the mass and resilience of which are also tuned to approximately the same frequency as that at which the spring 71 and the mass 73 are resonant (say, within 10 cycles per second thereof). The diaphragm 3 may be grounded and the spring 71, the mass 73 and the spring 75 are conductively connected thereto. A terminal 77 having an adjustable terminal screw 79 thereon is mounted in insulated relation to the mass 73. Any abnormally intense, undesirable waves having a component frequency of the order of the resonant frequency of the switch 69 which strike the diaphragm 3 will cause the spring 71 and the mass 73 to vibrate at the resonant frequency thereof. This, in turn, will cause the spring 75 to vibrate at the resonant frequency, but with much greater amplitude, to contact the screw 79 and thereby complete a circuit through a resistor 81 connected to the capacitor 63 in shunt relation with the discharge tube 61 and the detonator 65. Thus, when an abnormally intense wave strikes the diaphragm 3, the circuit through the resistor 81 is completed before the one through the discharge tube 61, and the capacitor 63 discharges through the resistor 81 instead of through the detonator 65. In this way, premature firing of the depth charge is avoided. If the source of the abnormal or undesired vibrations should be at a considerable distance from the controlled depth charge 19, the amplitude of the abnormal vibrations striking the diaphragm 3 may be very small. It is for this reason that the switch 69 is arranged as above described so as to greatly multiply the amplitude of vibration in the spring 75 and thereby insure engagement thereof with the terminal screw 79 to complete the alternative current discharge path through the resistor 81 for the capacitor 63.

The design of the firing circuit in the heterodyne depth charge of my present invention is such that a definite time duration of firing signal is required before the circuit will fire the detonator. As the charge drops in relation to the submarine, the frequency of the heterodyne signal applied to the amplifier input varies from its maximum value to zero, zero occurring at the instant of closest approach. The rate at which this frequency change is dependent on the distance from the submarine, being fast for a close approach and slow for a more distant approach. The amplitude of the heterodyne signal applied to the input of the amplifier is greater for a close approach than for a more distant one. The frequency response curve of the amplifier, shown in FIG. 9, is designed so that these two effects tend to produce at the grid of the limiter tube 51 a tiring signal for a length of time which is roughly independent of the nearness of approach to the submarine.

For a distant approach, the heterodyne signal is relatively Weak, and the output of the amplifier is sufficient to produce firing only when the frequency is very near the peak of the response curve. For this distance, however, the frequency varies slowly, producing a firing signal for the required length of time. For a close approach,

the heterodyne signal is very strong, and an amplifier output of firing amplitude is realized over a much wider range of frequencies, this range being governed by the response curve. Since at this distance the frequency varies much more rapidly, this additional range of frequencies is required to provide the necessary time duration of firing signal. The response curve is designed to provide a very nearly constant firing signal time for all distances and to provide detonation at very nearly the point of closest approach to the submarine.

Should there be no submarine or other target in the vicinity of the charge 19, it is apparent that the charge will continue to fall until it reaches the bottom of the ocean where it will come to rest in the soft mud. ln some cases, it may `be desirable to have the charge fired at that point. For this purpose, the circuit shown in FIG. 4 may be employed for coupling the output of the amplifier 49 to the limiter 51 in place of the filter` network 53, 55. The frequency difference between the signal transmitted to the ocean bottom and that reflected thereby when the charge is close to the bottom may be of the order of 150 cycles per second. With the filter network S3, 55 in the circuit as in FIG. 3, the heterodyne frequency is thus too high to cause firing of the charge, regardless of the signal strength, since this frequency is above the cut-off frequency described above. Now, with the filter network 53, 5S removed, as in FIG. 4, although the relatively high frequency heterodyne signal still may be greatly attenuated depending upon the frequency response characteristic of the

amplifier

47, 49, when the charge is very close to the bottom of the ocean (say, within two or three feet thereof), the signal strength of the heterodyne will be sufficient to cause the charge to be fired. In general, however, it is preferable not to have the explosive charge fired when it reaches the bottom of the ocean because the waves which it then sets up in the water and the disturbance produced by the gases generated thereby may interfere with readings or other operations on board ship.

Although I have shown and described but two forms of my invention in considerable detail, it will be apparent to those skilled in the art that many other modifications thereof as well as changes in the ones described are possible. For eXatnble, the vibratory system need not be limited to one of the magnetostrictive type, but may be of any other suitable type. Furthermore, even where the vibratory system is of the magnetostrictive type, the diaphragm 3 need not itself be of magnetic material, but may be made of non-magnetic material and a magnetic plate or the like secured thereto so as to provide a suitable flux return path. Also, in place Of the particular tubes specified above, other suitable tubes may 'be employed. Other changes will, no doubt, readily suggest themselves to those skilled in the art. I therefore desire that my invention shall not be limited except insofar as is made necessary by the spirit of the appended claims.

I claim as my invention:

1. Apparatus for controlling the firing of an explosive charge comprising a sonic transducer adapted to project sonic waves toward a target and to receive sonic waves reflected back thereto from said target While said transducer and said target move relative to each other, the relative movement of said transducer and said target resulting in a continually varying frequency difference between said projected and received waves in accordance with the Doppler effect and producing in said transducer a correspondingly varying heterodyne signal, means associated with said transducer for detecting said varying heterodyne signal, an amplifier coupled to said detecting means for amplifying said detected signal, and means associated with said charge coupled to said amplifier and responsive to the output signal thereof for firing said charge when said heterodyne signal has reached a frequency less than a predetermined frequency.

2. Apparatus according to claim 1 wherein said transducer comprises a vibratory system including a vibratory diaphragm and magnetostrictive means secured to and movable with said diaphragm, and characterized further in that said detecting means includes electron discharge means forming with said vibratory system an oscillatory system, said oscillatory system being arranged to oscillate at the natural frequency of said vibratory system.

3. Apparatus according to claim 1 wherein said transducer comprises a vibratory system including a vibratory diaphragm and a magnetostrictive element secured to and movable with said diaphragm, characterized further in that said detecting means includes electron discharge means forming with said vibratory system an oscillatory system, said oscillatory system being arranged to oscillate at the natural frequency of said vibratory system, and characterized still further in that said magnetostrictive element has a length substantially equal to three-quarters of the wave length at said natural frequency.

4. Apparatus according to claim 1 wherein said transducer comprises a vibratory system including a vibratory diaphragm and a magnetostrictive element secured to and movable with said diaphragm, characterized further in that said detecting means includes electron discharge means forming with said vibratory system an oscillatory system, said oscillatory system being arranged lo oscillate at the natural frequency of said vibratory system, characterized still further in that said magnetostrictive element has a length substantially equal to three-quarters of the wave length at said natural frequency whereby said element has a pair of motional nodes, and characterized still further by the addition of a pair of windings around said element, one at each of said nodes, said windings being connected to said electron discharge means.

5. Apparatus according to claim 1 wherein said transducer comprises a vibratory system including a vibratory diaphragm and a magnetostrictive element secured to and movable with said diaphragm, and characterized further 1n that said detecting means includes a pair of electron discharge tubes connected in cascade and a pair of windings each connected to a separate one of said tubes, said windings being disposed around said magnetostrictive element at predetermined points thereon, one of said windings being connected in the output circuit of one of said tubes and the other of said windings being connected 1n the input circuit of the other of said tubes.

6. Apparatus according to claim 1 wherein said transducer comprises a vibratory system including a vibratory diaphragm and a magnetostrictive element secured to and movable with said diaphragm, characterized further in that said detecting means includes a pair of electron discharge tubes connected in cascade and a pair of windings each connected to a separate one of said tubes, said tubes and windings forming with said vibratory system an oscillatory system and said oscillatory system being arranged to operate at the natural frequency of said vibratory system, characterized further in that said magnetostrictive element has a length equal substantially to three-quarters of the wave length of said natural frequency whereby said element has a pair of motional nodes, and characterized still further in that said windings are arranged coaxially around said element one at each of said nodes.

7. Apparatus according to claim 1 wherein said transducer comprises a vibratory system including a vibratory diaphragm and a magnetostrictive element secured to and movable with said diaphragm, and characterized further in that said detecting means includes a vacuum tube detector and a vacuum tube power amplifier connected to the output of said detector, and a pair of windings arranged coaxially around said element at predetermined points thereon, said detector and said power amplifier together with said pair of windings and said vibratory system forming an oscillatory system, one of said windings being connected in the output circuit of said power amplifier and constituting a driving winding for said vibratory system, and theother of said windings being connected in the inputcircuit of said detector tube and constituting a receiving Winding in which signal impulses are generated by vibrations of said vibratory system in response to the reflected waves received back by said diaphragm.

8.Apparatus according to claim 1 characterized in that said amplifier includes a filter in the output circuit thereof adapt-ed to reject all frequencies above said predetermined frequency.

9. Apparatus for controlling the firing of an explosive charge comprising a sonic transducer adapted to project sonic waves toward a target and to receive sonic waves reected back thereto from said target while said transducer and target move relative to each other, the relative movement of said transducer and said target resulting in a continually varying frequency difference between said projected and received waves in accordance with the Doppler eiect and producing in said transducer a correspondingly varying heterodyne signal, means associated with said transducer for detecting said varying heterodyne signal, an amplifier coupled to said detecting means for amplifying said detected signal, a low pass filter connected in the output circuit of said amplifier for passing only signals of a frequency below a predetermined frequency, a limiter connected `to the output of said filter for supplying voltage pulses, means in the output circuit of said limiter for storing the energy of said voltage pulses, and means associated with said explosive charge coupled to said storage means and responsive to a predetermined voltage thereon for effecting firing of said charge.

10. Apparatus according to claim 9 characterized in that said limiter is responsive only to signals having an amplitude in excess of a predetermined minimum amplitude.

11. Apparatus according to claim 9 characterized in that `saidstorage means comprises a resistance-capacitance network having a predetermined time constant.

12.. Apparatus according to claim 9 characterized in that said firing means includes a normally blocked, cold cathode discharge device and a normally charged capacitor connected thereto, and characterized further in that said explosive charge includes a conductive charge detonator also connected to said discharge device, said discharge device being adapted to be red in response to said storage means to provide a current discharge path for said capacitor through said detonator for ring said explosive charge.

13. Apparatus according to claim 9 characterized in that said firing means includes a normally blocked, cold cathode discharge device and a normally charged capacitor connected thereto, and characterized further in that said explosive charge includes a conductive charge detonator also connected to said discharge device, said dis- 10 charge device being adapted to be red in response to said storage means to provide a current discharge path for said capacitor through said detonator for firing said explosive charge, and characterized still further by the Yaddition of means associated with said capacitor and providing therefor an additional current discharge path in shunt with said first named path, said last named means including a normally open circuit adapted to be closed in response to abnormal waves whereby to provide an alternative current discharge path for said capacitor to thereby avoid firing of said explosive charge `in response to said abnormal Waves.

14. Apparatus according to claim 9 characterized in that said transducer includes a vibratory diaphragm, characterized further in that said firing means includes a normally blocked, cold cathode discharge device and a normally charged capacitor connected thereto, and characterized further in that said explosive charge includes a conductive charge detonator also connected to said discharge device, said discharge device being adapted to be fired in response to said storage means to provide a current discharge path for said capacitor through said detonator for firing said explosive charge, and characterized still further by the addition of means associated with said capacitor and providing therefor an additional current discharge path in shunt with said first named path, said last named means including a normally open inertia switch device connected to said diaphragm and means connecting said switch device to said capacitor, said switch device being adapted to be closed 4 in response to abnormal Waves received by said diaphragm whereby to provide an alternative current discharge path for said capacitor to thereby avoid tiring of said explosive charge in response to said abnormal Waves.

References Cited UNITED STATES PATENTS 1,683,692 9/192s Ogden 102-7 1,780,592 11/1930 Johansson 102-7 2,319,107 5/1943 Brandt 20o-s2 2,325,908 s/1943 Edstmm 20o-52 2,060,198 11/1936 Hammond 114-21 2,193,361 3/1940 Rice 25o-1.25

VERLIN R. PENDEGRASS, Primary Examiner Us. c1. xn. 102-7,1s

Claims

1. APPARATUS FOR CONTROLLING THE FIRING OF AN EXPLOSIVE CHARGE COMPRISING A SONIC TRANSDUCER ADAPTED TO PROJECT SONIC WAVES TOWARD A TARGET AND TO RECEIVE SONIC WAVES REFLECTED BACK THERETO FROM SAID TARGET WHILE SAID TRANSDUCER AND SAID TARGET MOVE RELATIVE TO EACH OTHER, THE RELATIVE MOVEMENT OF SAID TRANSDUCER AND SAID TARGET RESULTING IN A CONTINUALLY VARYING FREQUENCY DIFFERENCE BETWEEN SAID PROJECTED AND RECEIVED WAVES IN ACCORDANCE WITH THE DOPPLER EFFECT AND PRODUCING IN SAID TRANSDUCER A CORRESPONDINGLY VARYING HETERODYNE SIGNAL, MEANS AS-