RU2009720C1 - Ultrasonic hf-transducer for sonication of bath fluid - Google Patents

Abstract

FIELD: cleaning of contaminated parts. SUBSTANCE: transducer has membranes secured to common base over its edges by means of fasteners. Installed on each membrane is piezoelectric plate rigidly connected to it. Thickness of isolating area of each membrane H (mm) is related to resonance frequency f (MHz) of its piezoelectric plate as h: f = 0.2-0.5; width of isolating area of membrane ΔR=(20-60)h, and membrane diameter D_м=D_o+2ΔR, where D_o is diameter of piezoelectric plate. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to ultrasonic piezoelectric transducers used for cleaning parts from contaminants and for physico-chemical effects on liquid media. It will find application in the semiconductor, chemical, metallurgical industries and in medicine.

 Known rod piezoelectric transducers containing a radiating pad that passes into an acoustic decoupling membrane, piezoceramic plates, reflecting the back pad, pulled together by a central bolt, and a housing for attaching to the bath, used to clean parts [1]. However, their resonant frequencies cannot exceed 100 kHz.

 In the known high-frequency piezoelectric transducer MHz - range [2], selected as a prototype, there is a mosaic system of piezoelectric plates glued to a single radiating membrane, and a housing for mounting the transducer to the bath.

 The disadvantage of this design is the insufficient radiation efficiency of the transducer due to the mutual damping effect of the piezoelectric plates on each other, as well as the inability to produce the membrane of optimal thickness for all piezoelectric plates at the same time, since each of them has its own resonant frequency.

 The purpose of the invention is to increase the radiation efficiency.

The goal is achieved by the fact that additional membranes and corresponding membrane attachment nodes along the periphery, mounted on a common base, are introduced in the converter. Additional membranes and piezoelectric elements are rigidly connected to each other in pairs, the thickness of the decoupling section of each membrane h (mm) is related to the resonance frequency of the piezoelectric plate f (MHz) fixed on it with the ratio hf = 0.2-0.5, the width of the decoupling section ΔR = 20- 60 h, and the membrane diameter D _m = D _о + 2 ΔR, where D _о is the diameter of the piezoelectric plate.

 The drawing shows a high-frequency transducer installed in an ultrasonic bath.

The transducer contains a piezoelectric plate 1 connected to a membrane 2 having an acoustic decoupling section 3 of radial intensity ΔR = (D _m -D _o ) / 2, where D _m is the outer diameter of the membrane; D _about - the diameter of the piezoelectric plate. Using the housing 4 having a sealing ring 5, the transducer is attached to the bath 6 with screws 7. Spring-loaded contacts 8 are connected to the inside of the piezoelectric plate.

 The converter operates as follows. High-frequency voltage in the range from 400 to 2000 Hz through spring-loaded contacts 8 is supplied to the inner side of the piezoelectric plate 1, its outer side through the membrane and the housing is grounded. When operating at the resonant frequency (piezoelectric plates and membranes), the vibrations are transmitted to the liquid. Prevention of the transmission of vibrations through the membrane portion 3 is carried out by choosing its thickness and length (radial length ΔR).

 The choice of the optimal thickness h and ΔR is determined by two factors: - the use of thicker membranes, for which hf> 0.5 and ΔR / h <20, leads to strong damping of the transducer due to a decrease in flexibility, while the radiation intensity decreases; - the use of thicker membranes, for which hf <0.2 and ΔR / h> 60, leads to a decrease in the strength of the membrane, as well as to the appearance of its flexural vibrations, which weakens the transmission of the useful signal and leads to a decrease in the radiation intensity.

For example, for a high-frequency converter with a resonant frequency of the piezoelectric plate equal to 1 MHz (thickness ≈ 2 mm) and a diameter of 50 mm, we will have: h = (0.2-0.5) / f, we take the average value h _cf = 0.35 / 1 = 0.35. In this case, the diameter of the membrane will be equal to D _m = D _о + 2 (40h) = 50 + 28 = 78 mm.

The use of this invention allows to obtain the following advantages:
- ensuring the operation of all piezoelectric plates of the mosaic system at their resonant frequencies. In addition, each converter is powered by its own modular generator with automatic frequency control;
- an increase in the radiation intensity of single transducers, and hence the greater efficiency of ultrasonic exposure to certain technological processes;
- ease of assembly of the transducers, their installation on the bottom and walls of the bath, as well as ensuring their maintainability. (56) 1. USSR Copyright Certificate N 1451875, cl. H 04 R 17/10, 1984.

 2. S. Shwartzman and A. Mayer. Megasonic Partical Removal from Solid - State Wafers RCA Review, v. 46, March, 1985, p. 81-105.

Claims (1)

An ULTRASONIC HIGH-FREQUENCY CONVERTER FOR SOUNDING LIQUID IN A BATH, containing a membrane, a membrane attachment unit according to the periphery, piezoelectric plates, one of which is rigidly connected to the membrane, which differs by adding additional membranes to the purpose of a peripheral membrane mounted on an introduced common base, additional membranes and piezoelectric elements are rigidly connected to each other in pairs, the thickness h (mm) of the decoupling portion of each membrane Anne is associated with the resonant frequency f (MHz) of the piezoelectric plate fixed on it by the ratio
hf = 0.2 - 0.5,
the width of the decoupling portion of the membrane
ΔR = (20-60) h,
and the diameter of the membrane
D _m = D _o + 2ΔR,
where D ₀ is the diameter of the piezoelectric plate.

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