Patent ID: 7411335

Claim:
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.