GB1024358A - Improvements in ultrasonic generators - Google Patents

Abstract

1,024,358. Vibrator supply arrangements. MULTISONIC CORPORATION. April' 24, 1964, No. 17115/64. Heading G4F. [Also in Division H3] Ultrasonic cleaning apparatus comprises a liquid-containing tank T (Fig. 3, not shown) to the bottom of which is attached a transducer comprising a metal bar 61 forming a loading element for a piezo-electric crystal 53 which is fixed to its lower face. The transducer is driven from a self-oscillating triode valve 23 via a tapping point on an autotransformer 42, which may have a ferrite core and is tuned by the capacities of the crystal (Fig. 2, not shown). The anode and grid of the valve 23 are connected via capacities 46, 37 respectively to either end of transformer 42, a tap 47 on which is earthed so as to form a Hartley oscillator circuit. The valve is supplied with A.C. by means of a transformer 11; in a modification means are provided to vary the output, comprising a separate anode transformer 62 (Fig. 4, not shown) with two seriesconnected primary windings, one of which is shunted by a variable auto-transformer 65. The arrangement is stated to be such as to avoid the production of standing waves as the transducer is driven both at its own resonant frequency and also at that of the crystal alone, due to harmonics generated in the autotransformer 42. It is also stated to be insensitive to changes in resonant frequency; the output of the auto-transformer tends to a square waveform and so increases the efficiency since the mass loaded transducer has two or more side resonances either side of the main resonances.