GB845299A - Acoustic-vibration generator - Google Patents

Abstract

845,299. Acoustic vibration generators. BOUYOUCOS, J. V., and HUNT, F. V. Feb. 15, 1957, No. 5304/57. Class 13. Acoustic vibrations are generated by pumping a fluid through a valve provided with acoustic feed-back. In Fig. 1, a pump P circulates fluid around a tube 2. The inlet 8 and the outlet 11 are separated by a diaphragm 5 carrying the piston 4 of a valve 1 which cuts off the flow when the diaphragm is displaced to the left. The increase in pressure at B is transmitted as a wave around the tube 2 and at A exerts a force on the diaphragm tending to open the valve again. The pump P is isolated from the vibrations by acoustic filters 12, 13. The filters are constituted respectively by a constriction 61, Fig. 1A, and a foam rubber lining 62, Fig. 1B. The piston 4 need not make actual contact with the seating 3 but may be drawn within the periphery of the seating so as to cut off the flow for more than 50% of the oscillation period. The vibrations are transmitted to a fluid medium 17, Fig. 4, by means of a rubber tube 14 closed at one end and connected to the tube 2. Alternatively, a helical rubber tube may be connected in the pump circuit in place of filter 13, the tube being immersed in the medium into which the vibrations are to be transmitted. The Specification describes a number of modifications with the inlet 8 and the outlet 11 on the same side of the diaphragm 5. Two hydraulic valve circuits may be arranged in push-pull, Fig. 6, the two pistons 4 being mounted on opposite sides of a single diaphragm 5. The generator is coupled to a fluid medium by a flexible tube 14. In another generator, Fig. 9, the valves comprise resilient tongues 305 which oscillate from side to side. The feedback circuits are bounded by the walls of a cylindrical casing 302 which has an acoustic window 40 of elastic material. A generator within an elastic spherical shell 32, Fig. 7, comprises a rigid circular valve disc 204 supported by bellows 205 against a conical valve seat 203 on the end of a hollow cylindrical block 206. Fluid driven into the shell by the pump P is admitted by the valve to a chamber 210 in the walls of the block 206 and thence back to the pump. Pressure changes in the shell caused by the closure of the valve are fed back to the valve disc through the hollow 202 in the cylindrical block. The right-hand face of the valve disc 204, as shown in the Figure, is maintained at a constant pressure within a chamber 30. The shell 32 is immersed in the medium in which the vibrations are to be transmitted. A generator in which the transmission medium itself is circulated, comprises an openended straight tube 118, Fig. 12, through which the fluid is driven by a pump P. A shutter valve 403 mounted on foam rubber at 62 is operated by feedback through tubes 402, 412 which are connected to tube 118 at points separated by half a wavelength. A tube 14 with flexible walls is connected to the tube 118 and the end opening 114 is constricted to keep the pressure high within the tube. Two generators may be coupled so that the second operates at twice the frequency of the first. Fluid driven into the channels 29, Fig. 14, oscillates the valve 5 to produce vibrations in the fluid outlet 10. The feed-back drives a flexible mounting 49 carrying the valve 51 of the second generator. Fluid pumped through the orifice 52 vibrates at twice the frequency produced by the first generator.