US2555352A - Air launched radio station - Google Patents

Description

82 60 E grwmbow PERCIVAL D. LQWELL WILLIAM HAKKARINEN QJJJLLL 5 sheets -sheet l FIG. I

P D LOWELL ET AL AIR LAUNCHED RADIO STATION FIG. 2

June 5, 1951 Filed June 20, 1945 June 1951 P. D. LOWELL ETAL 2,555,352

AIR LAUNCHED RADIO STATION I Filed .June 20, 1945 5 Sheets-Sheet 2 FIG. 3

June 5, 1951 P. D. LOWELL ETAL AIR LAUNCHED RADIO STATION 5 Sheets-Sheet 55 Filed June 20, 1945 R. FAME RESPONSIVE RESISTANCE FIG. IO

TO GROUND FIG.|O

FIG. II

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96 PERCIVAL D. LOWELL WILLIAM HAKKARINEN 5 Sheets-Sheet 4 gmwww PERCIVAL -D. LOWELL WILLIAM HAKKARlNEN P D LOWELL ETAL AIR LAUNCHED RADIO STATION June 5, 1951 Filed June go, 1945 June 1951 P. D. LOWELL ETAL 2,555,352 4 AIR LAUNCHED RADIO STATION Filed June 20, 1945 5 Sheets-Sheet 5 TO RELAXATION OSCILLATOR GRID FIG. II

To enouuo FIG. I:

TO FILAMENTS OF TRANS- MITTER TUBES FIG."

g wcwvtow PERCIVAL 0. LOWELL WILLIAM HAKKARINEN m QLL L p Patented June 5, 1951 STATES AIR LAUNCHED RADIO STATION Percival D. Lowell, Chevy Chase, and William Hakkarinen, Hyattsville, Md.

8 Claims.

Our invention relates to a radio station which may be dropped from an aircraft onto remote or hostile territory and there unattended will set itself into operation for transmission of signals, for example weather data such as pressure, temperature and humidity.

In accordance with one aspect of our invention, the station upon its release from a bombrack, or equivalent support, floats by parachute until contact with the earth initiates a series of events, including for example, release of the parachute, and elevation of an antenna, culminating in transmission, preferably periodically, of weather data or other intelligence.

Further in accordance with our invention, the release of the parachute, the elevation of the antenna and erection of the station, when erecting legs are employed, are efiected by explosive charges under control of a timing device, preferably the same device which controls the periods of transmission and silence of the radio transmitting equipment. Precautionary measures are taken to insure the explosive means are disabled until after the station is clear of the aircraft.

Further in accordance with our invention, to insure accuracy of the transmitted data despite possible deformation of relatively movable contacting parts due to landing impact, those parts are vibrated to ensure their proper relative posi tion in response to change in pressure, temperature or humidity, even though the deformation may greatly vary the contact pressure.

In accordance with other aspects of our invention, it is provided that change of electrical characteristics of circuit components after calibration shall not affect accuracy of the transmitted data and that response of the temperature element shall not be substantially afi'ected by incident radiation.

Our invention further resides, in features of construction, combination and arrangement hereinafter described or disclosed.

A later form of our invention having additional features not herein shown is disclosed in copending application Serial No. 613,151, filed August 28, 1945, by Robert P. Bennett.

Referring to the drawings:

Figure 1 is a general vertical sectional view showing the location of the various major components in one embodiment of our invention. The view shows the appearance of the device while being lowered by parachute and before the legs or antenna have assumed their erected positions.

amended April 30, 1928; 370 0. G. 757) Figure 2 shows the weather station after erection of the legs and antenna.

Figure 3 is an enlarged sectional view taken on section 3-3 of Figure 1 showing the para chute release pin and the tension spring used to eject the parachute cable.

Figure 4 is a sectional view taken on section 4-4 of Figure 1 showing the parachute release pin and the explosive charge used to release the parachute.

Figure 5 is an enlarged sectional view taken on section E5 of Figure 1 showing the means used to release the legs.

Figure 6 is a vertical sectional view of the telescoping antenna and the associated reservoir.

Figure 7 is a detailed sectional view of one of the joints of the antenna shown in Figure 6.

Figure 8 shows in partial section the housing used for the temperature-sensitive resistance element.

Figure 9 shows the pressure-sensitive device and the associated variable resistor.

Figure 10 shows the circuit used to provide sequential operation of the erecting and transmitting functions.

Figure 11 is a simplified schematic diagram of the relaxation oscillator and crystal oscillator.

Referring now to Figure 1 of the drawings we have shown a general sectional view of one embodiment of the device. It will be seen that the housing is shaped in the manner'of a bomb. This structure is indicated generally by the numeral 25! and consists of a nose portion 22, a longitudinal supporting member 2A, a transverse shelf or spider Z6, and longitudinal s11e1f-sup-- porting straps 26. A yoke Elli connecting the spider 2b and the nose portion 22 is provided to enable attachment to the bomb rack of an aircraft. Two additional transverse shelves 32 and 34 are used for the mounting of the Various components to be described. The compo nents are mounted so as to cause the center of gravity to be as close to the bottom as possible to increase the tendency of the device to remain upright. To make the device self-erecting without the use of legs, the center of gravity may be lowered by the addition of additional weight 36 placed as low as possible and, in addition, the diameter of the nose may be considerably increased.

Provision is made at the end opposite the center of gravity for the attachment of a parachute (not shown) having shroud lines 33. The shroud lines are connected to a rigid rod 4 extending down into the center of the structure for attachment. The rod 40 extends sufficiently beyond the top of the device so that the shroud lines 38 clear any components extending above the upper shelf 32. A lead line 42 is connected from a shroud to the dowel pin 44 of an arming switch 46, the functions of which will be described below. During transportation the parachute is packed in the space indicated generally by the numeral 48.

To erect the device, legs 50 are provided which are hinged to the spider 26 by hinges 52; springs 5 are provided to bias the legs downwardly toward the nose 22. The leg releasing mechanism indicated generally by the numeral 56 controls release wires 58.

The pressure-responsive device I38, the temperature-responsive device 62 and the humidity-responsive device 64 initiate the signals to be transmitted. These weather responsive devices are switched into the radio circuit by clock 66. The radio and electrical portion of the device is illustrated in block form in Figure l and consists of the relaxation oscillator 63, the transmitter IE, and the power supply consisting of dry batteries, I2. If desired the power supply may be mounted within the nose portion. The antenna for the radio transmitter consists of a telescoping vertical antenna "I4 which is elevated by gases generated in the explosive reservoir "5%. Switch 18 consists of concentric annular contacts 80 designed to be shorted by the shorting strips 82. This switch controls parachute release device 85.

Figure 2 shows the weather station in the erected position with the legs 50 drawn downwardly by the action of springs E i and with the antenna I i extended. The protection afiorded the weather responsive units by the legs has been removed by erection and the elements are fully responsive to ambient conditions.

Figure 3 shows in detail the device used for quickly releasing the parachute. A spring 86 is connected between the parachute rod 40 causing rapid ejection of the rod ii? upon removal of the pin 88. This spring serves both to eject the rod without delay and to apply constant lateral pressure on pin 83 to prevent accidental displacement of the pin. It will be obvious to one skilled in the art that instead of using the rigid rod extension it of the parachute line, much the same effect may be achieved by using a line flexible all n the way to the point of attachment to the release mechanism and by simultaneously increasing the upward extent of tube 24 suificiently to clear all obstructions projecting from the upper shelf 32. In lieu of extending tube 24 a lead through device or eyelet spaced from. shelf 32 could be used for this purpose.

The specific explosive release device used is shown in Figure 4. The explosive is housed in chamber 90 and is fired by fusible link 92 to which power is supplied by means of the electrical lead fl l. A similar device is shown in Figure 5 for releasing the legs 50 held in position by wires 58. The explosive contained in the chamber 96 is fired by the fusible element 98 supplied by electrical lead I03.

Figure 6 shows the telescoping antenna 14 and the reservoir I6. An explosive device I02 is used to provide gas pressure in the reservoir. This pressure feeds into the lower chamber I84 within the antenna barrel 15 at a reduced rate due to the relatively restricted path presented by the connecting tube I66. The antenna consists of a number of telescoping sections designated as I08, II 0, and H2 fittin within the barrel I5.

Gaskets H3 are provided to prevent the passage of gas between the respective walls of the tubes or sections. Split annular friction rings H l are mounted in the annular retaining caps I I6 at the top of each section. An enlarged portion H8 is provided at the base of each section to engage the split rings I'M as later described. Apertures I26 are provided to lead the expanding gas from each section to the section immediately above.

The function of the split rings H4 is shown to better advantage in Figure 7. Full extension of any antenna section relative to an adjacent section causes engagement of the enlarged portion H8 and the split rin I I i. This frictional engagement has two useful effects. The first is to absorb the kinetic energy or the moving antenna section, the second is to provide a frictional engagement which prevents the telescoping of the two sections with respect to one another except by the application of intentional effort. In operation pressure created within the reservoir 16 is applied to the lower chamber II'M of the antenna barrel 15. Due to the obstruction of the rapid flow of gases caused by interconnecting tube I06, the antenna barrel I5 and its sections I08 and Ht may be constructed of relatively light gauge material. Pressure in the chamber I04 is immediately effective toraise the first section I08 of the antenna. Admission of gas pressure to the chamber I22 immediately above is hindered by the relatively constricted orifice I28. Gas pressure appears in the second chamber I22 only after the high initial gas pressure has been effective to overcome any static friction existing between the first movable section I68 and the antenna barrel 55.

Figure 8 shows a detailed view in partial cross section of the housing for the temperature-responsive element. The housing consists of spaced overlapping cup members I24 surmounted by a cover I26. The outer surface of each cup member is provided with a light-reflecting surface. The inner surface may be darkened to prevent the reflection of light received from the outer surface of the cup immediately below to the temperature-sensitive element 134. Each cupshaped member is provided with a radially extending flange I28. Longitudinal pins I30 en gage the flanges and spacing is provided by the Washer-like spacers I323. The resistance element I34 sensitive to changes in temperature is resiliently suspended within the housing by any suitable means of low heat conductivity.

Figure 9 is a detailed view of the pressure-responsive device 613. It comprises a frame I36 to which a bellows I38 is attached by means of a bracket I60. The free end of this bellows terminates in'an axially movable rod I412 pivoted to a resistance-controlling lever M6. The collar I 46 is provided on the movable rod I42 to interfere with bracket I48 and thus prevent excessive expansion of the bellows when the device is carried at high altitudes. Lever I44 is effective to vary the wire wound resistance element I50. A buzzer I52 is mounted to cause vibration just prior to the insertion of resistor I50 into the relaxation oscillator circuit. Such vibration overcomes both the friction in the bearings, which may be increased by deformation of the members upon impact of the weather station upon the ground. The tensile spring I54 takes up the slack in the mechanical system. The hygrometer or humidity-sensitive device 54 also includes a buzzer to overcome the effect of friction. The hygrometer may be of the well known hair type and may move a resistance-controlling arm in the same manner as the pressure responsive device.

Figure shows the switching system used to provide sequential operation of the explosive de vices and sequential transmission of weather data. An electric clock I 54 provided with two sets of contacts performs the switching operation. The hour hand I55 makes contact with contacts I 51 once every three hours in the embodiment described while the minute hand I58 makes contact once every minute after the first contact of the series is engaged. Current is supplied to the winding I59 of the clock from battery I60, relay current is supplied by battery I62, and filament and fuse current is supplied by battery I 64. All three batteries are disconnected from their respective circuits by the action of the triple pole single throw arming switch 45, which is energized as the weather station is dropped from the aircraft.

Assuming that the hour hand I56 has made contact, negative potential will appear on the minute hand I58. As the minute hand touches the first contact IE6, relay I68 is energized, picking up contacts I It. Closing of these contacts supplies potential from battery IM to the fusible link 92 of the parachute releasing device 84. The making of the first contact is a safety precaution; the fuse 92 will normally have been operated by closing of the nose switch 18 upon contact with the ground. The second contact I12 is effective to energize the leg release relay II l. This results in the closing of contacts I I6 and the firing of the fusible element 98 in the leg releasing device. Contact of the minute hand I58 with the third contact I'IB causes the picking up of the relay I80, the closing of contacts I82 and the firing of the antenna-erecting explosive device I 02. Contacts controlling other erecting functions could be included if necessary at this point.

The subsequent making of the contact I8 3 causes relay I86 to be energized, which in turn closes contacts I88, putting the reference resistance ISil into the grid circuit of the relaxation oscillator as will be described. Contact I92 causes energization of relay I94, the closing of contacts I 93 and the insertion of the pressureresponsive resistor I98 into the oscillator grid circuit. In like manner contacts 2G0, 203, and 2I6 through the medium of relays 202, 2H], and ZIB cause the respective insertion of the temperature-responsive resistor 206, the humidityresponsive resistor 2 I i, and the identification resistor 222, into these circuits. The final making of contact 224 causes reinsertion of the reference resistor I90.

It will be noted that the firing of the leg re- ].easing fuse 98 is accompanied by operation of the buzzer or vibrator I52 associated with the pressure-responsive device 61]. In like manner, a buzzer 226 placed in parallel with the antenna erecting fuse I02 is effective to vibrate the humidity responsive device 64. It will also be noted that the buzzers I52 and 226 operate for an extended period, approximately 45 seconds, prior to the insertion of the associated resistance into the relaxation oscillator grid circuit. The vibration counteracts friction and enables the weatherresponsive device to assume a true equilibrium position.

The filaments of the transmitter tubes are turned on by relay 228 which is in series with the resistance-switching relays I86, I94, 202, M0, and 2 I 8. Thus, filament power is applied only during periods of actual transmission, as will be seen below, thereby saving the battery Hit. By putting the hands of the clock I56 and I58 in series as shown, the sequence described above will only take place once every three hours.

Figure 11 shows the relaxation oscillator circuit designated generally as 230, the crystal oscillator circuit 232 and the radio frequency '(R. F.) amplifier 234. The relaxation oscillator comprises a vacuum tube 236 of any well known type having a high value of trans conductance and a transformer 238, consisting of windings 2 3D and. 242. The time constant of the oscillator is determined by the capacitor 242 and the resister which may be inserted into the circuit. Such resistor, indicated generally by numeral 246, may be any one of the resistors I82, I98, 2&5, 22M, or 222, discussed in connection with Figure 10. The use of small additional, capacitors 241i and 258 in a relaxation oscillator circuit is well known. A relay 252 is provided in. the plate circuit of the relaxation oscillator tube. The contacts 252 of this relay short out the grid bias ap plied through resistor 255 associated with the crystal oscillator tube 256 to start oscillation of the crystal oscillator circuit. The interrupted oscillations are amplified and broadcast by the radio frequency amplifier 234.

The relaxation oscillator operates as follows: Assuming a sudden application of plate voltage, increasing plate current will result in a positive potential being applied to the grid of vacuum tube 235. This positive potential will result in the fiow of grid current which charges capacitor 244. When the plate current becomes constant at a saturated value, no positive voltage is induced at the grid terminal of the secondary 245-2 of the transformer. The plate current will there fore start to decrease, such decrease inducing a negative potential at the grid of the tube cutting off the plate current. The plate curreht is kept in the cut-off condition by the negative charge which has collected during the previous half cycle on the capacitor 242. This charge is dissipated through resistor 24% and, after the time interval required for such dissipation, the grid will lose its negative potential and. the cycle will be repeated. The capacitor 244 the time constant circuit is large, on the order of 8 microfarads, while the resistor 24%: is on the order of 10,000 ohms. This results in a desirable slow pulse rate on the order of to 3 pulses per second.

Before use the relaxation oscillator is calibrated with the weather-responsive elements so that each condition of pressure, temperature, and humidity corresponds to a certain pulse rate. The altered characteristics of other components in the circuit, caused for example by aging or damage, may cause a pulse rate somewhat slower or faster than the calibrated value for a given value of grid resistor. This error may be elin1i nated by the use of the reference resistor I983. The pulse rate resulting from the insertion of the reference resistor Hill in the grid circuit is noted at the time of initial calibration. Later in actual use the reference resistor Ififi is switched into the grid circuit by the clock 55 i prior to the resistors associated with the weathe --sensitive devices. If it is noted that the puls rate for the reference resistor is, say, 5 percent too the pulse rate noted for each of the other store will be corrected by being reduced proportionately before the pulse rate is interpreted as a weather condition.

The intended use of the device is as follows: The weather station with its legs 50, held in the position shown in Figure 1 and with the parachute packed in space 48 provided, is loaded on the bomb rack of an aircraft. A static line is rigged from the aircraft to the parachute to pull the parachute free immediately after the device is released. A lead line 42 is attached to one of the shrouds 38 of the parachute and to the dowel pin M which holds the arming switch 56 in an open position thus preventing the batteries from energizing any of the circuits. The clock IM may be present to energize the associated leg or antenna-erecting contacts after a dormancy period of up to approximately three hours after the arming switch ii has been operated.

When a suitable location for the station has determined, the station is dropped. The static line causes the parachute to open lowering the station at a rate of approximately 8 feet per second. At the same time opening of the parachute causes arming switch 46 to apply power to start the clock i 3 and to connect batteries M59, M22, and Mid into the circuit. Upon impact with the ground, the nose switch l5 will close, firing the parachute releasing device 84 and preventing the station from being pulled along the ground. The device will lie inert for the ore-set dormancy period until the first contact 566 is made by the clock I54. A long dormancy period may be 01 use where it is intended that the device lie unerected until darkness has fallen in order to escape enemy detection. Contact I56 is effective to release the parachute is nose switch 78 has failed to do so.

Contact of the minute hand with the second terminal. N2 of the clock will cause operation of the leg release device 56. Assuming that the device has landed on its side, the release of the 5% will. due to the urging of springs Ed. cause the device to become upright as shown in Figure 2. This be readily accomplished by springs 5d of this size if the device has a low center of gravity.

As the minute hand of the clock touches the third contact 2'58, the antenna erecting explosive device iii-'2 is fired causing erection of the antenna as discussed above.

lhe contact of the minute hand with contacts E92, 28d, 2&3, 255, and 22% results in the consecutive insertion of the reference resistor I99, the pressure-responsive resistor I98, the temperature-responsive resistor 268, the humidity-responsive resistor 2M, and the identification resistor While it will be obvious to one skilled in the art that the spacing of the clock contacts and the contact Width may be adjusted over wide limits, the following program has been found to be satisfactory:

Signal Timc (approximate) While the identification signal which notifies the operator to which station he is listening has a separate resistor in the embodiment described. the identification function could also be peroil 3 formed by using a distinctly difierent pulse rate for the reference signal of each weather station used.

At the receiving station the transmitted pulses are counted over a measured time interval and the pulses per unit time readily computed. Calibration charts enable the pulse rates to be inter-- preted as weather conditions. Assuming that dry batteries are used, reasonable battery power is suflicient to cause the station to transmit the above program of signals every 3 hours for a period in excess of 15 days.

When the station is to be used only as a beacon, the radio transmitter and its control mechanisms may be simplified merely to transmit a signal which may be used to guide for example other craft equipped with radio-direction-fiinding apparatus.

While we have shown and described particular embodiments of our invention, it will occur to those skilled in the art that various changes and modifications can be made without departing from our invention, and we, therefore, aim in the appended claims to cover all such changes and modifications that follow in the true spirit and scope of our invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What we claim is:

1. An automatic radio station adapted to be lowered by parachute comprising, an elongated housing having its center of gravity near the bottom end, a parachute suspension line having its point of exit at the top end of said housing remote from said center of gravity, an explosive para chute release device to release said suspension line, a nose portion on said housing at said bottom end, a set of electrical contacts mounted on said nose portion to operate said release device upon contact with the earth, a quick acting fusible element in said explosive release device operated by said electrical contacts whereby positive release is obtained with only momentary contact of said electrical contacts.

2. An automatic radio station adapted to be lowered by parachute comprising an elongated housing having its center of gravity near its bottom end, a plurality of legs hingedly attached to said housing at spaced points about said housing at a level above said center of gravity, said hinge attachment enabling each of said legs to swing in a plane which includes the axis of said housing, biasing means to urge said legs toward said bottom end of said housing, retaining means to hold said legs along the side of said housing against the action of said biasing means, and releasing means operable after contact with the earth to erect said housing into a leg-supported position.

3. An automatic radio station adapted to be lowered by parachute comprising an elongated housing including a frame, a parachute suspension line, a parachute suspension line lead through device mounted at the end of said housing at a point spaced surficiently far from the end of said housing so as to minimize the possibility of fouling of said suspension line with components projecting from the end of said housing, a parachute suspension line engaging member engaging said suspension line and mounted within said housing at a point of great mechanical strength of said frame whereby the likelihood of damage to said housing caused by the jerk of said parachute suspension line upon opening of said parachute is reduced.

4. The subject matter as claimed in claim 3 including a spring having one end engaging said parachute suspension line within said housing and the other end engaging said lead through device whereby said suspension line is quickly and forcibly ejected from said lead through device upon release of said line from said line-engaging member.

5. An automatic radio station adapted to be lowered by parachute comprising an elongated housing including a frame, a parachute suspension line, a parachute suspension rod fastened at the end of said suspension line to support said housing, said rod projecting outwardly from said housing to a point sufficiently far from said housing as to minimize possible fouling of said suspension line with components projecting from the end of said housing, said parachute suspension rod projecting into said housing to a point of great mechanical strength of said frame, a parachute release device engaging said rod and mounted at said point of great mechanical strength, and a spring having one end engaging said parachute suspension rod within said housing and the other end engaging said housing at the point of entry of said rod, whereby said suspension rod is quickly and forcibly ejected from said housing upon release of said rod by said parachute release device.

6. An automatic radio station adapted to be lowered by parachute comprising a housing, a nose portion on one end of said housing, a parachute supporting line entering said housing at a point remote from said nose portion, an explosive parachute release device engaging said parachute supporting line, a set of electrical contacts mounted on said nose portion to energize said explosive release device upon impact with the earth, an arming switch mounted on said housing having electrical contacts in series with said nose electrical contacts, an arming switch operator engaging said parachute supporting line effective to cause said arming switch to close upon opening of said parachute, whereby operation of said explosive release device is not possible until after said station is parachute-supported.

7. An automatic radio station adapted to be lowered by parachute comprising a housing, a parachute supporting line engaging said housing, an explosive release device to free said parachute supporting line from said housing, an explosive erecting device to erect said station for use, an arming switch having electrical contacts in series with said explosive release device and said explosive erecting device, an arming switch operator engaging said parachute supporting line and effective to cause said arming switch to close upon the opening of said parachute, whereby operation of any explosive devices is not possible until after said station is parachute-supported.

8. An automatic self-erecting radio station adapted to be dropped by parachute from aircraft comprising, an elongated housing having its center of gravity near its bottom end, a plurality of legs hingedly attached to said housing at spaced points about said housing at a level above said center of gravity, spring biasing means urging said legs to be swung outwardly from said housing toward said bottom end of said housing for the purpose of self-erection and support, retaining means efiective until said station is dropped to hold said legs adjacent the sides of said housing against the action of said biasing means, said legs being of such length and so positioned as to project beyond the top end of said housing forming a receptacle for the temporary storage of a self-contained parachute.

PERCIVAL D. LOWELL. WILLIAM HAKKARINEN.

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

UNITED STATES PATENTS Number Name Date 1,709,264 Holt Apr. 16, 1929 2,118,603 Hailey May 24, 1938 2,169,904 Schweller Aug. 15, 1939 2,228,060 Lescher et a1. Jan. 7, 1941 2,232,693 Dow Feb. 25, 941 2,300,847 Russel Nov. 3, 1942 2,311,491 Turner Feb. 16, 1943 2,327,163 Barrett Aug. 17, 1943 2,352,891 Graves July 4, 1944 2,373,413 Plummer Apr. 10, 1945 2,381,009 Siderman N Aug. 7, 1945 2,399,221 Freas Apr. 30, 1946 2,402,143 Arenstein June 18, 1946 2,452,990 Bush Nov. 2, 1948 2,492,501 Robins Dec. 27, 1949

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