Abstract: An improved ultrasonic cleaning system employs a plurality of electroacoustic transducers located at different positions on the wall surfaces of a tank containing a cleaning liquid in combination with a source of electrical power and a selective switching system. The switching system applies the electrical power selectively, sequentially and intermittently to any specified one or more of said plurality of electroacoustic transducers to achieve substantially increased cavitation intensity levels in the cleaning liquid and thereby greatly improves the cleaning efficiency of the inventive system as compared to the conventional ultrasonic cleaners which are in widespread use.

Abstract: A deep-water low-frequency transducer employs a collapsible air chamber to equalize the internal transducer air pressure with the external hydrostatic pressure at the submerged operating depth. A capsule containing a highly pressurized gas is mounted inside the collapsible air chamber and an automatic valve mechanism releases the gas to inflate the collapsed air chamber at a predetermined depth, beyond which any further reduction in the air volume would impair the operation of the transducer. With the collapsed air chamber restored to its original full volume, the transducer will operate satisfactorily at increased water depths.

Abstract: An improved ultrasonic transducer designed for rugged outdoor applications uses a thin-walled cylindrical tube of polarized ceramic operating in the fundamental circumferential resonant frequency mode. The major portion of the external surface area of the vibrating cylinder is covered by a sound insulating barrier, thereby preventing sound radiation from the covered non-radiating surface area portion of the cylinder. Specific unique relationships between the diameter, length and wall thickness of the ceramic tube, which are necessary to achieve the objects of the invention, are described.

Abstract: A wide-range audio frequency underwater transducer is designed to make use of a massive small diameter vibratile piston driven by electromagnetic oscillatory forces to transmit omnidirectional uniform sound pressure level over the frequency range 100 Hz to 5 kHz. The rugged transducer design is adapted for low-cost mass production and can be used as a highly reliable expendable reference standard of source level for the calibration of in-situ stationary or moving sonar receiving systems. The magnitude of the source level can be accurately controlled by the magnitude of the electrical current supplied to the electrical winding over the entire frequency range of operation. A pressure equalization system is included in the design that permits use of the transducer at any depth down to 500 feet.

Abstract: An electromagnetically driven vibratile piston underwater transducer element generates acoustic intensity levels in excess of 25 peak Watts per square inch of radiating surface in the low audible frequency region within the approximate range 500 to 2500 Hz. The design achieves an efficiency greater than 50% and a very low Q of less than 2. The electromagnetic design employs two separate independent air gaps and a unique mechanical coupling system that combines the electromechanical forces generated in each gap in the proper phase and transmits the combined oscillatory force to drive the vibratile piston.

Abstract: The power handling capacity of a high-power low-frequency underwater transducer including an inertial mass-loaded vibratile piston assembly is greatly increased by increasing the heat conduction from the inertial mass member by designing the vibrating structure to place a surface area portion of the inertial mass member in direct thermal contact with the water environment in which the transducer is submerged. In order to reduce the sound radiation from the exposed surface of the submerged inertial mass member and to obtain a broadband response with a Q equal to 1 or less, a novel rigid hollowed piston construction is described which greatly reduces the weight-to-stiffness ratio of the vibratile plate and achieves the desired low Q as well as a reduction of sound radiation from the exposed inertial mass surface by at least 20 dB below the radiation from the surface of the vibratile plate member.

Abstract: An electromagnetically driven vibratile piston underwater transducer element generates acoustic intensity levels in the order of 50 peak Watts per square inch of radiating surface in the low audible frequency region in the vicinity of 1 kHz. The design achieves an efficiency greater than 50% and a very low Q of less than 2. The air gap is designed to seat mechanically if the unit is operated accidentally at high-power levels while acoustically unloaded thereby protecting the spring assembly from unsafe amplitudes of vibration. The mechanical protective design also serves to protect the transducer vibrating structure from failure if the transducer is exposed to the proximity of an underwater explosive shock wave. The transducer construction results in a minimum overall length so that when the transducer element is mounted in a planar array attached to the hull of a vessel the projection of the radiating surface of the array from the surface of the hull is minimized.

Abstract: A novel configuration of a low-frequency lightweight sonar system is described comprising a coaxial assembly of a transmitting transducer and a directional receiving array contained within a cigar-shaped streamlined cylindrical housing less than 1 ft. diameter which operates in the 3 to 4 kHz frequency region and achieves submarine target detection ranges in the order of 20,000 meters with a bearing accuracy within 2.degree.. The small cylindrical streamlined structural assembly results in a very great reduction in drag resistance while it is being towed underwater at high speeds as compared to conventional sonar domes which must be an order of magnitude larger in diameter to accommodate the larger conventional scanning sonar transducers which are several wavelengths in diameter at the operating frequency.

Abstract: A piezoelectric ceramic cylinder is positioned between a vibratile piston and a matched rigid mass element. To prevent corona, the electrodes on the ceramic cylinder are covered with an insulating material in the region near the edges of the electrodes where a corona might otherwise form. A low-loss rubber compound and a molded rubber support cradles the transducer assembly. A special manufacturing technique uses a standard weight supported on the cylinder to affect the resonant frequency of the cylinder and enable them to be segregated into classes according to their resonant characteristics.

Abstract: A fixed array of three identical directional receivers, each having a carid directional pattern, are arranged in a symmetrical configuration with each receiver having its principal axis of maximum sensitivity oriented 120.degree. from the corresponding axes of its neighbors. By comparing the relative magnitudes of the voltages generated in each of the three cardioid receivers upon receiving a signal, the bearing of the signal source is automatically determined and displayed. The tri-cardioid receiving array overcomes the prior art need for large-sized directional receiving transducers, and also overcomes the need for mechanically rotating or electronically scanning the receiving array to find the bearing of the signal source.

Abstract: An improved method of manufacturing electroacoustic transducers which emp vibratile transducer elements includes an automatic method of measuring the motional impedance vs. frequency characteristics of a plurality of transducer elements and an automatic method of segregating the transducer elements into separate groups which are selected in accordance with the similarities of the measured motional impedance characteristics of the elements. The separate groups of selected transducer elements are then processed by changing a mechanical dimension of the elements in each separate group by a different specified amount which adjusts the motional impedance vs. frequency characteristic of each separate group to the same specified desired value. The processed transducer elements are then assembled into complete transducers, thereby achieving improved uniformity in the performance characteristics of the transducers which is obtained at relatively low cost.

Abstract: A transducer of the flexural resonant vibratile rectangular type is described in which a housing includes a square frame-like mounting structure with a square opening for receiving the vibratile plate assembly. V-shaped projecting ribs from the center of the inner sides of the square opening provide locating points for precisely positioning the periphery of the square vibratile plate assembly concentrically with the square opening. A second set of four V-shaped ribs are located at right angles to the ribs projecting from the inner sides of the square opening and lie in a plane to provide support for the face of the vibratile plate assembly. All of the V-shaped ribs are located near the nodal regions of the vibratile plate and present minimal area of contact with the vibratile plate.

Abstract: An improved transducer utilizes an acoustic delay line to reverse the phase f the sound vibrations generated by the peripheral area of a bi-laminar vibratile disc operating at its free fundamental resonance mode. When the diameter of the vibratile disc is dimensioned within specific limits in comparison with the wavelength of sound being radiated at the frequency of operation, the radiation efficiency of the transducer is significantly increased over the efficiency of the same vibratile disc operating in the prior art manner with an acoustic shield placed over the peripheral area of the disc to prevent destructive interference from the out-of-phase sound radiation generated by the peripheral area.

Abstract: An improved transducer utilizes an acoustic delay line to adjust the phase f the acoustic output from the out-of-phase portion of a free resonant flexural disc so that it is constructively added to the acoustic output generated from the remaining portion of the resonant flexural disc. The improved transducer combines an acoustic coupler with the housing structure of the transducer for the purpose of increasing the radiation resistance load on the vibratile disc to achieve increased acoustic output from the transducer.

Abstract: Improved ultrasonic cleaning of large surfaces is achieved by modifying conventional transducers of either the cylindrical or piston vibratile type so that the transducer vibratile element is brought in closer proximity to the surface being cleaned. For efficiently cleaning the wall surface of a circular water-filled tank, such as a toilet bowl, a ceramic disc operating in the planar resonant mode is provided with an acoustic transmission line comprising a solid annulus bonded to the periphery of the ceramic. The radial dimension of the annulus is equal to one-half wavelength of sound in the material at the frequency of operation. The annulus serves as an acoustic transmission line to extend the peripheral vibrating surface of the ceramic to a region closer to the wall of the tank. The transmission line also increases the radiating area of the transducer which achieves increased sonic power density in the vicinity of the wall surface.

Abstract: This invention discloses a mold design which limits the maximum pressure that can be developed inside a closed cavity containing a polarized ceramic as a result of the volume expansion of the molding compound during the curing cycle. The pressure control is achieved by interposing a spring member between the mold and the pressure source which closes the mold. The spring will deflect slightly to absorb any volume expansion of the molding compound during the curing cycle, thus preventing any significant increase in pressure in the cavity and thereby preventing depolarization of the ceramic.

Abstract: This invention discloses an improved process for applying electrodes to the surfaces of thin ceramic discs which permits the coating of the entire disc with a conducting film and then automatically removes the conducting film from the peripheral edge of the disc as it is rolling down an inclined plane while being held within a guide slot. The bottom of the guide slot is provided with a moving abrasive belt which automatically removes the conducting film from the peripheral edge of the disc as it passes over the belt. The inventive process will permit the advantageous use of plated electrodes such as electroless nickel without entailing the costly expense of masking the edges of the discs before plating.

Abstract: A mathematical analysis reveals the existence of circular motion in the head of a rotating phasor which represents the received signal in a Doppler intrusion alarm system in the presence of a moving target. The circular motion is virtually nonexistent when a moving target is absent regardless of the presence of environmental disturbances such as air turbulence and noise transients. The mathematical revelations are confirmed by a considerable amount of experimental data representing hundreds of thousands of measurements under various environmental conditions. The invention makes use of these new findings in combination with a new signal processing system which incorporates a circle detector for recognizing the presence of circular motion in the head of a rotating phasor when it occurs in the received signal, thus permitting absolute detection of a moving target even in the presence of environmental disturbances, such as air turbulence, while the system remains immune to false alarms due to these disturbances.

Abstract: A movie camera is provided with an automatic focusing adjustment mechanism which is responsive to a control signal which is generated by an ultrasonic range finder attached to the camera. The camera is automatically kept in focus as the distance of the subject from the camera is varied.

Abstract: A coin-operated vending machine accepts any combination of valid coins which are deposited and automatically returns the correct change when the merchandise is dispensed. The amount of change represents the difference between the total value of the accepted coins and the price of the selected merchandise. A digital data processing circuit is employed for recognizing the validity and denomination of all deposited coins and any unacceptable coin that falls outside the established tolerance limits for a genuine valid coin is automatically rejected and immediately returned.