US 3432804 A
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United States Patent O 3,432,804 FLUID ULTRASONIC GENERATOR Basil B. Beeken, New Haven, Conn., assignor to Pitney-Bowes, Inc., Stamford, Conn., a corporation of Delaware Filed Oct. 25, 1966, Ser. No. 589,426 U.S. Cl. 340-15 Int. Cl. H04b 11/00 6 Claims ABSTRACT F THE DISCLOSURE This invention relates to a device for generating sonic energy. It more particularly relates to a device for the generation of ultrasonic energy by means of a iluid.
It is an object of this invention to provide a fluid powered ultrasonic generator.
It is a further object to provide a nid ultrasonic generator that may be easily constructed, is compact and may be operated under relatively low iluid pressure.
These and other objects of my invention will become apparent as the description thereof proceeds.
The invention consists of a device having a iluid supply chamber which feeds through a restricted orifice into at least one resonating chamber and to an outlet orice. The resonating cavities may be closed or open. The ultrasonic energy is detected at the outlet orifice when the cavities are closed and at the cavity outlets when the cavtities are open.
The various relative internal dimensions of the device result in the generation orf the ultrasonic energy.
The invention may be better understood by reference to the drawing which represent embodiments of the invention in which:
FIG. 1 is a perspective view of the device with a closed cavity, with the cover broken away to show the interior tluid passages or channels.
FIG. 2 is a perspective view of the device with open cavities with a rellector at one cavity, with the cover broken away to show the interior uid passages.
FIG. 3 is a cross-sectional view taken along the section line 3-3 of FIG. l.
FIG. 4 is a cross-sectional view of the device of FIG. 2, taken along the section line 4 4 of FIG. 2.
FIG. 5 is a diagrammatic partial plan view of the device of FIG. 1 showing relative dimensions.
FIG. 6 is a diagrammatic partial plan view of the device of FIG. 2 showing relative dimensions.
Referring to the drawings, FIG. l shows an embodiment of the invention where the sonic device has closed resonance cavities.
The generator is constructed of two flat plates olf any suitable material, a lower plate 10 into which the channels and cavities are cut, etched, molded and otherwise formed, and an upper cover plate 12 which serves to cover the channels. Plate 10 has a fluid supply channel `14 with a liuid inlet port 16 near one end. At the opposite end the air supply channel narrows to a constriction or throat 18. Beyond throat 1'8, resonance cavities 20a and 2Gb are spaced on each side. An outlet channel 22 leads out of the device. The outlet channel 22 has sub- 3,432,804 Patented Mar. 1l, 1969 ICC stantially the same width as the downstream end of the throat 1-8 with the result that the entrance oriiices of the cavities 20a and 20b are substantially parallel in the direction of uid flow and lie along the edges of the uid stream between the throat 18 and the upstream end of the outlet channel.
It will be obvious the channels could be etched in the underside of the cover 12 instead of in the base 10 and that fluid inlet 116 can be in either base 10 or cover 12 as desired.
The design of the generator is such that the frequency of the acoustic output is primarily a lfunction of its geometry and not the operating range of 0.5 to 3 p.s.i.g.
The cavity length L, measured from the center line of throat 18 is about one-half the wave length of the acoustic output frequency A. For optimum performance, the cavity width W is about 3 times the throat width t. 'Ihe cavity orices O are about 1.5 times the throat width t. The depth D of the channels and cavities is equal to or greater than throat width t. The outlet channel length L, must be about one-half the wave length orf the output frequency.
In operation, a fluid is fed through inlet r16 into iluid channel :14. 'Ihe fluid passes through throat 18, passes resonating cavities 20a and 20b. The acoustic energy is detected at outlet channel 22.
The embodiment of FIG. 2 is Igenerally similar to that of FIG. l and consists of a base plate with the channels formed in it and a cover plate 12. A fluid supply channel '14 is formed in base 10, and a uid inlet 16 is provided at one end of channel 14. At the opposite end of channel 14, it narrows to throat '18. On each side orf throat 18 are located cavities 24a and 24b. Cavities 24a and 24b are open at their outer ends 26a and 26b respectively. A reflector 28 may be used at one cavity opening to reflect the sonic energy to the other cavity and thereby increase the energy output at that cavity.
A uid outlet 30 is provided beyond cavities 24a and 24h. Outlet 30 is shaped dilferently than outlet 22 of the embodiment of FIG. 1. This is done to minimize impedance. However, as with the previous embodiment, at least the upstream end of the outlet channel 30 has substantially the saine width as the downstream end of the throat 18 with the result that the entrance on'ces of the cavities 24a and 24b are substtantially parallel in the direction of uid ow and lie along the edges of the lluid stream between the throat 1-8 and the upstream end of the outlet channel.
'I'he generator of FIG. 2 has an acoustic output energy of about 10 times that of the closed cavity type shown in FIG. 1. It also has the characteristic of broader ranging from 0.5 to `6 p.s.i.g. huid pressure for producing the fundamental frequency at which point the second harmonic appears. The output is greatest at one of the cavity openings 26a or 26b rather than in the direction olf the air stream.
The ultrasonic energy may be detected at both cavity openings 26a and 26b. As an alternative, a reflector 28 may be spaced from one opening 26 as shown at 26b, to reect the sonic energy to the other channel 26a, the spacing will be such that the reilected sonic waves will be in phase with the sonic waves in cavity 26a and therefore increased sonic energy may be detected at cavity opening 26a. It will =be understood that the reilector could be at cavity opening 26a and the sonic energy detected at cavity opening 26b if desired.
In the `device of FIG. 2, the cavity lengths L are about one half the wavelength of the acoustic output A, and the cavity width W is about 3 times the throat width t. The cavity orices 0 are about 1.5 times the throat width t. The depth D of the channel cavities is equal to or greater than the channel width t. The iiow output orilice 3 30, as previously indicated is designed to minimize flow impedance.
Although the device has been shown with a plate having channels and cavities formed in it and a Hat cover plate, it will be understood that the only requirement is that the channels and cavities be present. It would, of course, be possible to work grooves in both plates and place the plates together to form closed channels.
While I have disclosed certain specific embodiments and preferred modes of practice of my invention, it will be understood that this is solely for the purpose of illustration, and that various changes and modications may lbe made in the invention without departing from the spirit of the disclosure or the scope of the appended claims.
1. A uid powered ultrasonic generator comprising,
a uid supply chamber,
an inlet to said uid supply chamber adjacent one end thereof,
a throat at the opposite downstream end of said Huid supply chamber,
resonance cavities on each side of said throat and downstream thereof, the entrance orice of each said cavity being `about 1.5 times the width of said throat and the width of each said cavity being about 3 times said throat width, and the cavity length being about a multiple of one half the wave length of the acoustic output frequency,
and a uid outlet channel downstream from said cavities and said throat, at least the upstream end of said output channel being substantially equal to said throat width, the entrance orices of said cavities extending from the downstream end of said throat to the upstream end of said outlet channel and lying along the edges of the fluid stream flowing therebetween.
2. The ultrasonic generator of claim 1 wherein said cavities are closed, and the length of said fluid outlet channel is about .5 times the wave length of the acoustic output frequency.
3. The ultrasonic generator of claim 1 wherein said cavities are open.
4. The ultrasonic generator of claim 3 comprising in addition means to reflect the sonic energy at one of the cavity openings to the other cavity.
5. Apparatus as defined by claim 1 wherein said outlet channel diverges from said upstream end thereof.
6. Apparatus as defined by claim 1 wherein the outer end of one of said cavities is effectively blocked while the outer end of the other of said cavities is open.
References Cited UNITED STATES PATENTS 3,321,955 5/1967 Hatch IS7-81.5 X 3,071,145 1/1963 Blachard 181-.5 X 3,158,166 1l/1964 Warren 137-81.5 3,238,958 3/1966 Warren et al. 137-81.5
RODNEY D. BENNETT, Primary Examiner.
D. C. KAUFMAN, Assistant Examiner.