US2499012A - Tow target carrier - Google Patents

Description

Feb. 28, i950 J. P. WELSH ETAL TOW TARGET CARRIER Filed April l5, 1943 y www w. W2# fw MW I i l Patented Fei. 28, 195() TOW TARGET CARRIER James P. Welsh, Buialo, and John L. Jewett, Cheektowaga, N. Y., assignors to the United States oi' America as represented by the Secre.-

tary of the Air Force Application April 13, 1948, Serial No. 20,634

9 Claims. l

The invention described herein may be manuiactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to a remotely actuable control for a towed object, more particularly an airplane-towed target. The invention is, however, capable of general application.

One object of the invention is to provide an explodable connector for a cable by which an object is towed, such connector being explodable through the cable without other conductor circuit being necessary.

Another object is the provision of an explodable connector for insertion in a tow cable, in combination with such an electric circuit that the connector is explodable only by an electric current of pre-selected frequency.

Another object is the provision of explodable means by which the position of an airplanetowed target may be altered from horizontal to vertical or vice-versa.

Another object is the provision of remote-controlled means for selectively inverting a jettisoning a towed object.`

In the drawings:

Fig. 1 is a side elevation of the explodable connector, partly in section.

Fig. 2 is an edge View of the connector.

Fig. 3 is a detail of the ignition.

Fig. 4 is a diagrammatic representation oan electric current embodying my invention in that form in which a steel tow cable can be used for transmission of an exploding signal.

Fig, 5 is a diagrammatic representation of an electric circuit between a towing airplane and a towed target in which means are provided to turn or to jettison the target selectively.

Fig. 6 is a diagrammatic detail of the assembly of a weight on the target, which weight may be jettisoned. An explosive charge and frequency responsive means for exploding the charge to jettison the weight are also shown.

Referring now to Figs. l and 2, the explodable connector ID comprises a flattened ring II of a tough, strong, synthetic linear polyamid polymer plastic. A central opening I2 is slightly elongated as to one of its axes, i. e. the horizontal one, in the present showing. At each arcuate end of the elongated axis there is attached over the inner surface of the opening edge I3, a metallic highly conductive shoe I4 over each of which is intended that a hook (not shown) attached to the tow cable, be tted. One such hook is the outer terminal o f the cable extending fromthe air- 2 craitand the other is the inner terminal of the cable connecting the explodable connector I0 and the towed target. The purpose of the hooks and the shoes I4 is to furnish an electrical path for the ingress of signal to a pair of explodersl 5 -which are mounted radially in holes I6 formed in the ring II. The shoes I4 are preferably formed withoutwardly extending nns Il as is best shown in Fig. 2, which serve to retain the hooks in po!- sition in case momentary slack occurs in the cable.

The edge oi ring ll has-a groove I8 in which there is positioned a bleeder resistor I9 (see Eig. 2) which may be preferably of the carbon type. A 7.5 megohm V2 watt resistor with 1eads.2.75" long has been found satisfactory. The leads' 2i make contact with one of the shoes I4 and to do so are radially embedded in the ring Il. A conductive wire 22 connects the two exploders iik-I5 around the lower half of the groove I8 `andrivetsllS connect the exploders to the shoes Ill. Since thereis a spark gap, as will be later -clescribed, in each exploder, the bleeder-resistor I9 and conductors 20 and 2| offer a leakage path, although a high resistance one, for any stray high-voltage static charges which might otherwise build upon the cable and shoes- It and'lso explode the connector prematurely. A high voltage power signal along the tow cable will, howeverhave enough potential and power to jump the exploder gaps as well asto dissipateitseli to a certain extent through the high resistance leakage path. n Y

Referring now to Fig. 3, the structure of an 'explode-rp It is shown. It is in general, similar to that of a cartridge fuse, having a non-conductive cylindrical .body 2li, vcopper caps '2S-on `each end thereofl and central electrodes 26 incontact with respective caps. The electrodes' have sharp ends, which are about 35 apart. vThe gap 38 is iilledwith photographers negative guncotton 27 which Vserves to hold apart two charges 28 of about v1.84 grains of small grain smokeless powder around'each electrode. As will be seen from Fig. el, `the exploders l5 f abut the' conductive rivets 23 and brass retaining screws 29 which are compound so as to. be able to make contact .with the connecting wire 22. 7 A

' In Fig. 4 the dashed box 3!) indicates the aircraft which will tow the target 3|. Within the aircraft area 24 volt battery or. generator 32', a switch 33 tri-energize the exploder circuit anda ground connection 34 to the airframe. An inverter 35 convertsthe 24 v. D.` C. to 400 cycle A.

` proportions.

and delivers the output to a step-up transformer 36 which delivers its approximately 10 M. A. output at 20,000-45,000 volts to the tow cable 31 in which there is the explodable connector l0. A spark gap 38 and a bleeder resistor |9 for the connector I are shown. 31a is that part of the tow cable which joins the connector |U and the target 3|;

In operation, the switch 33 is closed, thereby sending a high-tension power signal along cable 31, due to the capacity effect distributed between the connected parts of the tow cable and the airplane, which acts as a ground. The signal jumps the gap 38, ignites the gun cotton 21 which ignites the smokeless powder charges 28, resulting in the fragmentation of the ring and the release of the tow target 3| together with cable section 31a.

Fig. 5, which shows a frequency-respective selective system, contemplates the use of a two `frequency channel radio transmitter 40 on the aircraft.V The transmitter 40 has preferably an output of 50 to 100 watts. The two frequency channels may be derived from frequency generators 4| and 42 which are selectively connectible to the transmitter 40 through a control box 43 which is manually operable. A coaxial transmission line 44 or a wave guide connects the transmitter 49 with an antenna tuning unit 45 which may be a manually variable inductance (loading coil). A tow cable 31 joins an explodable connector l0 as before with a tow target 3| and a second section 31a of a tow cable. There is the difference in the construction of the connector l0 however. that a high-low pass (band rejection) resonant filter 45 is incorporated to shunt the spark gap. The inductance in filter 46 has a low D. C. resistance and a high impedance at the frequency at which it is to be used. Radio frequency is preferred and the Lfrequency should be chosen in relation to the cable length so that current nodes will be developed. 493 kc. or whole harmonics thereof have been found to be satisfactory. y

As shown in Fig. 5, the tow target 3| is provided with a stiff spreader 41, to which two spreader cables 48a and 4817 are attached. These cables are pulled by rear cable portion 31a. The latter continues past the'point at which cables 48a and 4817 are attached to it, to contact electrically a weight 49 which can be jettisoned by the explosion of an explosiven charge attached thereto. The exploding signal follows the cable 31a through an electrical lter 50 shown in Fig. 6, to an exploder (not shown) which may be attached to the weight fastenings (not shown).

The filter 50 is a conventional one, but of small It comprises an inductance and a capacitance 52. Its circuit leads 53 and 54 connect to an exploder (not shown), the explosive capacity of which is sufcient to tear loose 41 but is insuicient to damage the latter. The

' filter 50 is proportioned so that it will pass 4an eX- ploding signal to the weight exploder at the frequency of tap 2 on the control dial 43. In such case the current will go through the lower loop 46h of the lilter 46 and will not go through the upper loop 46a which contains the exploder |5.

As long as there are two weights, 49 and 56, which in the aggregate, weigh the same, on opposite ends of the spreader 41, the target will ily horizontally. If weight 46 is jettisoned by explosion, then weight 56 will assume the lowermost position and the target 3| will ily vertically.

If it is now desired to jettison the entire target, the control dial 43 is set at position 3 and a different frequency sent over the cable 31 which frequency will be able to go through loop 46a and exploder I5. Explosion then occurs and the target 3| and cable section 31a drop off. The cable 31 can then be reeled in and another target attached. By the use of the antenna tuning unit 45 it may be possible to vary the wave length of the R. F. current passing over the cable 31 so that only one frequency generator 4| or 42 is necessary.

A ground for the circuit is not necessary since there is suflicient static dissipation and corona loss to allow enough current to pass to fire the exploders. If the cable is 1000 feet long, the wave `length of the signal should be about 2G00 feet (493 kc.) 'so that the exploders will be located at a point where there is current and voltage, not at a node where bothare absent or of low value. Competent electrical engineers can design selective filters for any given wave length.

We claim as our invention:

l. An explodable connector comprising a ring of tough plastic resinous material, conductive metallic shoes at opposite sides of the hole therein gripping the rim thereof, a pair of exploders having outer terminals, said exploders being embedded in the ring, each one extending substantially from one shoe to the outer rim of said ring, an embedded electrical circuit connecting the outer terminals of the said exploders and a second electric circuit of high resistance value connecting said shoes with each other.

2. An explodable connector according to claim l in which the exploders are of the type which can be energized by the pass of an electric spark through them.

3. An explodable connector which comprises a ring of a tough synthetic linear polyamid plastic, contact means for a pair of hooks on opposite sides of the opening in said ring, a high resistance static-dissipating shunt connecting said shoes, a pair oi' electric-spark-explodable devices embedded in said ring, one extending substantially radially from each shoe to the outer rim of said ring, a low resistance electric circuit joining the outer ends of said explodable devices, said devices being capable, on the explosion of one or both, of destroying the connecting power of the said ring.

4. An explodable connector comprising a strong frangible ring, a pair of conductive shoes attached on opposite sides of said ring to the inner ranged around the other side of said ring and connecting only the said shoes, each of said circuits being conductive to an electrical signal of substantially different frequency, the exploder circuit being inoperable by a signal which will pass through the remaining circuit.

5. In combination, an airplane, a tow cable trailable from said airplane, a tow target attached to said cable at the outer end thereof, an explodable connector responsive to an electrical current of a certain frequency in said tow cable in the neighborhood of said tow target and means on said airplane for applying an electrical signal of such frequency through said cable to said explodable connector to explode the latter.

6. In combination, an airplane, a tow cable trailable therefrom, a tow target attached to the outer end of said cable, a pair of weights attached to the inner end of said tow target, electrical and explosive means attached to one of said weights, actuable from said airplane, for jettisoning said Weight.

7. In combination, an airplane, a tow cable trailable from said airplane, a tow target attached to said cable at the outer end thereof, a pair of weights near the inner end of said tow target and attached thereto, one of said weights including an electrical frequency responsive exploding device, an electrical frequency-responsive explodable connector in said cable in the neighborhood of said tow target, means on said airplane for generating and applying electrical signals of a plurality of A,frequencies to said tow cable, a signal one of said frequencies being capable of exploding the weight-associated ex- I ploding device and ofpassing the explodable connector without exploding same and a signal of the second frequency being capable of exploding the connector to jettison the tow target.

8. In combination, an airplane, a tow cable trailable therefrom and a tow target attached to the outer end of said tow cable, a spreader on the inner end of the tow target, a weight attached to each end of said spreader, a band pass iilter attached between the end of said tow cable and one of said weights, an explosive charge containing a spark-responsive exploder attached between said filter and said weight and means on said airplane for generating and applying an electrical signal to said tow cable to pass said alter and to explode said explosive charge xvhereby to jettison said weight.

cable lbetween said weight and said airplane butA 9. In combination, an airplane, a tow target,

,4 near said tow target, said connecting means .being able to pass a signal of a frequency which @will jettison the weight without exploding the connecting means, and means on the airplane f' fior generating and selectively applying electrical ysignal oi' a. frequency which will either jettison `fthe weight or explode the connecting means.

JAMES P. WELSH. JOHN L. JEWETT.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 30 2,118,603 Hailey May 24, 1938 2,331,058 Stock Oct. 5, 1943 2,370,909 Martin Mar. 6, 1945 2,422,662 Fahrney June 24, 1947

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