GB1236999A - Method and apparatus for applying ultrasonic energy to a workpiece - Google Patents

Abstract

1,236,999. 999. Cleaning metals. BRANSON INSTRUMENTS Inc. Dec.3, 1968 [Dec.7, 1967], No.57280/68. Heading C7E. [Also in Division B3] A method of applying ultrasonic energy to a workpiece 20 immersed in a liquid 19 comprises setting up pressure waves in the region of the workpiece by displacing the liquid with high intensity pulsed energy produced electrically said pulses being at a rate of at least 20, 000 pulses per second, and the duration of each pulse being equal to or less than, one half of the interval between the commencement of successive pulses. The pulses may be produced by switching a source of D.C. potential, applying the pulses to a transducer 15 that moves in substantial correlation with said pulses, and arranging the transducer in communication with the liquid to produce pressure waves in the region of the workpiece. The method may be used for deburring, cleaning, or polishing workpieces, or separating parts. In apparatus described for deburring workpiece 20 the workpieces are placed in a liquid 19 within a plastic walled container 18 which is itself supported in a liquid 17 within a steel tank 16. A transducer 15 is attached to the sides or, as shown, bottom of the tank or placed within the tank and receives pulses from a generator 10 comprising a device for switching D.C. such as a blocking oscillator, multi-vibrator, flip-flop, or tunnel-diode. The D.C. voltage may be 600- 2500 and the pulse rate up to 100, 000 pulses per second or more. The transducer 15 may be a crystal, e.g. a Piezo-electric crystal, or an electro-strictive or magnetostrictive device, and in use operates above its resonant frequency in a pulse range in which it is tuned for a flat response. The liquids 17 and 19 may be water including a wetting agent. The liquid 19 may also include an abrasive material such as ground, powdered, or beaded glass diamond dust, carborundum, or aluminium oxide. The liquid 19 preferably includes an embrittling agent for the workpieces when these are of metal. A hydrogen embrittling agent such as a solution in water of nitric, hydrochloric and phosphoric acids is used for ferrous metals, an oxygen embrittling agent such as a solution of hydrofluoric, phosphoric, and glacial acetic acids for aluminium, and a solution of sulphur dioxide for copper. The liquid 19 may also include a detergent and an oxygen inhibitor. The workpiece may be tumbled during the deburring process. In an alternative method, workpieces to be cleaned are placed in an open basket or tumbler in the liquid 17 which may include a cleaning agent. The method may also be used to separate lenses from a lens block.