Image Number 2 for United States Patent #4304134.
Apparatus for ultrasonically inspecting material radially bounding a circular bore into which the apparatus is insertable. The apparatus includes a central housing adapted to lie along the bore's longitudinal axis, three support arms which are engageable with the bounding wall of the bore and are circumferentially equally spaced about the central housing, linkage arms joining the support arms and the central housing for maintaining a predetermined relative configuration between the support arms and the bore wall, a transducer carrier which protrudes radially inside the support arms' engageable surfaces and is supported by each support arm, an ultrasonic transducer carried in each ultrasonic transducer carrier, means for biasing the transducers radially outward relative to their associated transducer carrier, and a pneumatically actuated cylinder which rotates the linkage arms and displaces the support arms radially outward into engagement with the bore wall. The transducers are restrained in the transducer carriers within predetermined displacement limits by a pin extending from each transducer carrier into an opening formed in each transducer. The transducers' openings are radially larger than the pins extending thereinto so as to permit limited radial displacement of the transducers relative to the carriers. Suitable relative radial positioning of the transducer carriers and support arms and selection of appropriate strength biasing means enables application of high centering forces on the support arms to coaxially align the housing with the bore's center line while independently providing relatively small, optimum engagement forces between the transducers and bore wall.