Sonic signaling device
US 3125986 A
Description (OCR text may contain errors)
W. K. FORTMAN ETAL SONIC SIGNALING DEVICE March 24, 1964 2 Sheets-Sheet 1 Filed Nov. 15, 1962 INVENTORS. WILLIAM K. FORTMAN NORMAN C PICKERING March 24, 1 w. K. FORTMAN ETAL SONIC SIGNALING DEVICE 2 Sheets-Sheet 2 Filed NOV. 15, 1962 INVENTORS. WILLIAM R FoRmAfi' BY NORMAN c. PICKERING FIG. 3
ATTOR NEY United States Patent 3,125,986 SONIC SIGNALING DEVECE Widiiarn K. Fortman, 186 Cold Spring Road, Syosset, N.Y., and Norman C. Pickering, Sag Harbor, N .Y. Filed Nov. 15, 1962, Ser. No. 237,927 13 Claims. (Ci. 116-437) This invention relates to pulsed sound sources and in particular to means for producing a modulated sonic energy beam by means of a jet stream excited acoustical generator.
As disclosed in Yellott and Savory Patent No. 2,519,- 619, a gaseous jet stream may be directed from a nozzle into an opposed acoustically resonant cavity to generate sonic energy. The high intensity sonic wave energy field so generated finds many useful applications in spray devices, foam breakers, tank cleaning and the like, wherein a steady state sonic wave is maintained. The present invention, however, is directed towards an intermittent, selectable operation of such cavity resonators whereby the operation may be almost instantaneously halted and then regenerated, thus converting the resonator into a signal or control device responsive to programming. The utility of such a device will be apparent to those skilled in the art since sonic generators, in general, are very diflicult to regulate in terms of starting and stopping. Whistles, sirens, and the like, require a considerable time interval for regeneration of the sound once the device is stopped, and moreover, this interval is unpredictable. The use of standard cavity resonators, such as the Hartmann type, presents difiicultieis in practice, since valving of the pressure nozzle will again lead to a lengthy time interval for the generation of sonic velocity which is a prerequisite of the Hartmann generator. lnterposing a variable shutter between the nozzle and the resonator will disrupt the shock wave front generated in the cavity by the alternate filling and discharging of gas at the resonant frequency. Further, such an obstruction between the nozzle and the cup of the resonator will cause a greatly reduced output of sound. It is proposed in the present invention to provide means for modulating sound Waves having a constant frequency, with relatively sharp break between the start and stop. It will be readily appreciated that a device wherein the modulation can be controlled within very narrow limits can be extremely useful.
In order to illustrate a possible application of the present invention the following embodiment of the present invention is described.
The present invention is incorporated into an altitude indicating device wherein a pulse modulation system is utilized, for control purposes, to modulate the sonic energy transmitted by the apparatus of the present invention. This is achieved by the periodic filling and discharging of the resonator through the action of the hereinafter described cam-piston operation. A phase detection system is utilized, whereby phase difference between the received signal and a reference signal determines the modulating frequency. In this illustration the altitude defines the modulating frequency. For example, at an altitude of 50 feet (100 feet in total travel between the transmitting device and the receiving device), division by the speed of sound (-1000 feet per second) provides a travel time of -0.1 second. To achieve a maximum resolution of the phase detection system, one complete cycle of the modulated sonic energy is utilized. Thus a modulating frequency of one cycle per 0.1 second or cycles per second is required at the 50 foot altitude. A modulating frequency higher than 10 c.p.s. would create ambiguity in the phase detection system because more than one cycle of the modulated sonic energy would be utilized in the phase detection sample. A frequency of less than 10 c.p.s.
would cause deterioration of the resolution of the phase detection because less than one cycle would be utilized. These conditions establish the basic principle of measurement.
Thus it can be seen that a variable frequency pulse modulation technique is utilized, in which the modulating frequency is inversely proportional to the altitude. The modulating frequency is established, at a particular altitude, by comparing the phase between one complete cycle of received sonic energy and an equivalent complete cycle of a reference signal.
ince the modulating frequency varies inversely with the altitude, the minimum measurable altitude is restricted only by the upper limit of frequency modulation. The upper limit on modulating frequency is restricted primarily by mechanical modulator design consideration. These considerations present no problem with regard to the application as an altitude measuring device.
It is therefore a primary object of the present invention to provide an improved whistle type sonic signaling device adapted to generate timed pulses of sonic wave energy.
A further object of the present invention is to provide a whistle type sonic signaling device having a high power output, whereby a relatively high percentage of unidirectional jet stream energy is converted to sonic wave pulses.
Yet a further object of the present invention is to provide simple, highly reliable pulse forming means for a whistle type sonic signaling device.
These and other objects and advantages of the present invention will, in part, be pointed out with further particularity, or will, in part, be apparent from the following description and the drawing appended hereto wherein:
FIG. 1 is an elevational view, partly broken away to expose the internal supporting spider, shaft, nozzle resonator cup, of a sonic signaling device in the open position, or non-pulse generating condition.
FIG. 2 is an elevational view of the device of FIG. 1 in the closed or generating position. The figure is par tially broken away to expose the nozzle and resonator cup.
FIG. 3 is an elevational view of an alternate embodiment of the device shown in the non-pulse generating condition. The figure is partially broken away to expose the internal supporting spider, shaft, nozzle resonator cup. An electrical actuating circuit is shown schematically.
FIG. 4 shows the device of FIG. 3 with the bottom portion broken away to show the nozzle and resonator cup in a closed condition.
Referring more particularly to the drawing, the device of the present invention, characterized generally by the numeral 10, comprises a conduit 12 communicating with pressurized gas inlet 14. concentrically mounted within the longitudinal bore 16 of conduit 12 is a spider 18 slidably supporting a piston 20*, the functioning of which will hereinafter be described. At its lower end, conduit 12 terminates in a choked nozzle 22 having threadably secured thereto a reflector 24 which may, as in the illustrated embodiment, have a substantially parabolic shape. Webs 26, projecting radially inward at the open end 28 of reflector 24 support a centrally located cylindrical hub 29 having a bore 30 and a beveled seat 31.
Piston 2t is provided at its enlarged upper end 32 with biasing means such as compression spring 34. Spring 34 operates between piston end 32 and top surface 36 of conduit 12. Mechanically equivalent springless configurations may be employed. Piston 2.0 may be actuated mechanically by means such as cam 38, or by conventional intermittent motion linkages well known in the art. Alternatively, electrically energized solenoids, valves, hydraulic cylinders, or other means adapted to intermittent, repetitive motion, may be employed to displace piston 20 to the two positions shown in the drawings.
If a gaseous fluid is made to flow out of nozzle 22,
then as a result of the Bernoulli ellect, the flow velocity will become equal to and greater than that of sound. As the jet stream leaves the nozzle, a characteristic pressure distribution develops. This distribution is periodic in nature, and due to rapid variations in jet stream pressure and velocity, gas pile-ups and shock fronts are created. A properly positioned resonant cavity alternately becomes charged to the corresponding jet stream pressure until a condition of unstable equilibrium is reached and then discharges backwardly into the jet stream. As a result, high intensity sonic oscillations are produced which are focused by reflector 24 in a desired direction. The apparatus includes a resonant chamber 44 which is defined by bore 3i) and the top surface 46 of plug 40. Plug 40 is provided with a beveled outer surface 42 adapted to mate with beveled seat 31 in the closed condition, as shown in FIG. 2.
In the position shown in FIG. 1, with the resonator plug 40 axially displaced from seat 31 by piston the sonic waves are instantaneously disrupted and the gas vented downwardly through central bore of sleeve 29 and past the conical outside surface 42 of resonator plug 40.
It will readily be seen that displacing the resonator plug by any of the previously disclosed means creates time pulses which may be controlled within very close limits. Hence a square wave form may be readily generated. Due to the lengthy regenerating period associated with prior art sonic generators, this efiect was heretofore not readily achieved.
In FIGS. 3' and 4, an alternative embodiment is shown wherein the resonant chamber is opened by moving sleeve 50 away from bottom plug 52 permitting gas from nozzle 22 to escape in the space there bet-ween. In this embodiment, bottom plug 52 is maintained in a fixed position, being integrally secured to spider 18 by means of tube 51. Rod 54 extends coaxially through central bore in both tube 51 and plug 52. The upper end of rod 54 terminates at piston 2-1 and the bottom end of rod 54 mounts a spider 56, the free ends of which support axially movable sleeve member 50. In FIG. 3, the apparatus is shown in the non-resonating condition, and in FIG. 4 the sleeve member is shown in the pulse or resonating condition.
In this embodiment, cylinder 21 is shown stroked by solenoid coil 58 energized by source 60 under the control of switch 62. It will be understood that the mechanical stroking systems described earlier may likewise be employed.
There has been disclosed heretofore the best embodi-.
gas can be continuously discharged into said cylinder by said nozzle;
(0) a closure member disposed transversely to said cylinder and proximate thereto at a point remote from said nozzle; and
(d) actuating means to selectively displace said closure member and said cylinder relative to each other whereby said closure member in a first position is in a gas-tight, abutting relation to said cylinder to define an acoustically tuned cavity, said closure member in a second position being axially displaced from said cylinder, whereby in said first position a sonic wave is generated by said device.
2. The device of claim 1 wherein said cylindrical hollow member is maintained in a fixed position and said closure member is displaced.
3. The device of claim 1 wherein said cylindrical hollow member is displaced and said closure member is maintained in a fixed position.
4. The device of claim 1 wherein said actuating means is mechanically stroked.
5. The device of claim 1 wherein said actuating means is electrically stroked.
6. A sonic signaling device comprising:
(a) a conduit adapted to carry gas under pressure, said conduit terminating in a convergent-divergent nozzle;
(1)) a cylindrical hollow member disposed coaxially in spaced relationship to said nozzle, whereby said gas can be continuously discharged into said cylinder by said nozzle in the operational condition; I
(c) a closure member disposed transversely to said cylinder and'proximate thereto at. a point remote from said nozzle; and
(d) actuating means to selectively displace said closure member and .said cylinder relative to each other whereby said closure member in a ifirst position is in a gas-tight, abutting relation to said cylinder to define an acoustically tuned cavity, said closure member in a second position being axially displaced from said cylinder, whereby in said first position a sonic wave is generated by said device and in said second position said device is non-generating.
7. A sonic signaling device comprising:
(a) a conduit adapted to carry gas under pressure,
said conduit terminating in a nozzle;
(b) a cylindrical hollow member disposed coaxially in spaced relationship to said nozzle, whereby said gas can be continuously discharged into said cylinder by said nozzle in the operational condition;
(0) a closure member disposed transversely to said cylinder and proximate thereto at a point remote from said nozzle; and
(d) actuating means to alternately displace said closure member and said cylinder relative to each other whereby said closure member in a first position is in a gas-tight, abutting relation to said cylinder to define an acoustically tuned cavity, said closure member in a second position being axially displaced from said cylinder, whereby in said first position a sonic wave is generated by said device and in said second position said device is non-generating.
8. The device of claim 6 wherein said'actuating means controls the relative first and second position time;
9. The device of claim 7 wherein said cylindrical hollow member is maintained in a fixed position and said closure member is displaced.
10. The device of claim 7 wherein said cylindrical hollow member is displaced and said closure member is maintained in a fixed position.
11. The device of claim 7 wherein said actuating means is mechanically stroked.
. 12. The device of claim 7 wherein said actuating means is electrically stroked.
' 13. The device of claim 7 including sonic energy focusing means in operative relationship with said tuned cavity.
7 References Cited in the file of this patent UNITED STATES PATENTS 556,291 Turner Mar. 10, 1896 1,018,310 Frey Feb. 20, 1912 1,800,512 Daggett Apr. 14, 1931 2,238,668 Wellenstein Apr. 15, 1941 2,641,438 Arnold June 9, 1953 2,834,570 Harrison May 13, 1958 3,064,619 Fortman Nov. 20, 1962 3,070,313 Fortman Dec. 25, 1962