# US 7,411,335 B2 · Sonic or ultrasonic transducer

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- Number: US 7,411,335 B2
- Document ID: US7411335B2
- Status: Granted
- Kind: B2
- Application number: 10/573,420
- Filed: 2004-09-20
- Published: 2007-11-29
- Granted: 2008-08-12
- Earliest claimed: 2003-09-25
- Assignees: Endress + Hauser GmbH + Co. KG
- Inventors: Manfred Eckert; Frank Volz
- Web page: https://patentgrep.com/patent/US7411335B2

## CPC

- B06B 1/067: {which is used as, or combined with, an impedance matching layer}
- B06B 1/0662: {with an electrode on the sensitive surface}
- B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R)

## Abstract

A sonic or ultrasonic transducer, which is embodied as a radial oscillator. So that the sonic or ultrasonic transducer can be used at high temperatures, a matching layer is located between the radial oscillator and the atmosphere into which the ultrasonic signals are transmitted The matching layer is made from a material that has a dimensional stability up to a temperature which lies above the temperature at the installation location of the sonic or ultrasonic transducer. Furthermore, the matching layer is selected such that its material-specific coefficient of thermal expansion is greater than that of the materials of a piezoelectric unit and a coupling ring, and that the modulus of elasticity of the material of the matching layer is at least one order of magnitude smaller than that of the piezoelectric unit and/or the coupling ring.

## Claims

### Claim 1

A sonic or ultrasonic transducer, comprising:
a disc-shaped piezoelectric unit; a ring-shaped coupling element surrounding said piezoelectric unit with a form- and force-fit;
a matching layer arranged in front of said piezoelectric unit in the direction of radiation of the sonic or ultrasonic waves; and
a transmitting/receiving unit which excites said piezoelectric unit to execute radial oscillations, wherein:
said matching layer is made of a material which has dimensional stability up to a temperature lying above the temperature at the installation location of the sonic or ultrasonic transducer; the material-specific coefficient of thermal expansion of the material of said matching layer is greater than that of the materials of said piezoelectric unit and/or said coupling element; and
the modulus of elasticity of the material of said matching layer is at least one order of magnitude smaller than that of said piezoelectric unit and/or said coupling ring element.

### Claim 2 (depends on 1)

The sonic or ultrasonic transducer as claimed in claim 1, wherein:
said matching layer is made of a hard foam material.

### Claim 3 (depends on 1)

The sonic or ultrasonic transducer as claimed in claim 1, wherein:
said coupling element is made of metal or ceramic.

### Claim 4 (depends on 1)

The sonic or ultrasonic transducer as claimed in claim 1, further comprising:
a protective foil provided in front of said matching layer in the direction of radiation of the sonic or ultrasonic waves, and is arranged such that it protects said matching layer, on the side of said matching layer facing in the direction of radiation, from the penetration of moisture and other foreign matter.

### Claim 5 (depends on 4)

The sonic or ultrasonic transducer as claimed in claim 4, wherein:
said protective foil is made of metal.

### Claim 6 (depends on 1)

The sonic or ultrasonic transducer as claimed in claim 1, further comprising:
a housing provided, in which said matching layer and said piezoelectric unit with said coupling element are arranged; and
a potting compound provided, which is arranged at least in some areas between said matching layer, said piezoelectric unit, said coupling element, and the inner wall of said housing.

### Claim 7 (depends on 1)

The sonic or ultrasonic transducer as claimed in claim 1, wherein:
said potting compound is an elastomeric potting compound.

### Claim 8 (depends on 7)

The sonic or ultrasonic transducer as claimed in claim 7, further comprising:
a diffusion barrier provided, which is arranged on said potting compound facing away from the direction of radiation.