Patent GB-1145134-A (GB)
Title: Rolling ultrasonic transducer
IPC: G01N29/24
Filed: 1967-07-11
Abstract: 1,145,134. Ultrasonic probes; ultrasonic testing. PANAMETRICS Inc. 11 July, 1967 [20 July, 1966], No. 31817/67. Headings H4D and H4J. An ultrasonic transducer comprises a roller 11 (Figs. 1, 3, 4) having a central axial opening 25 and a plurality of ultrasonic energy generators 28 located for transmitting generated ultrasonic energy radially outward through the roller 11. The roller 11 is rotatably supported in pressure rolling contact with a material 19 to be measured. Electrical connections are made to successive generators 28 as the roller is rotated. The roller 11 is mounted in a housing 12 and pressure on the bottom surface 13 ensures pressure rolling contact. It has a hollow hexagonal opening 25 and is of tungsten, tungsten carbide or other material having high wear, high melting point and excellent sonic transmission characteristics. Each generator 28 is of lead zirconate titanate. Steel coverplates 30, held by screws 32, close the opening 25. The roller 11 is supported on needle bearings 35 and further bearings 38, pivoted on screws 39, provide alignment of the roller 11. Each cover-plate 30 contains a circular groove 40 in which the point of a screw 41 engages, merely to retain roller 11 in housing 12 when it is being transported. An insulated, fixed axle 51 has a contact shoe 50 and, as the roller rotates, shoe 50 contacts successive generators 28. Current passes through the axle 51, the shoe 50, a generator 28, the roller 11, the bearings 35 and the housing 12. Alternatively, the axle 51 is tubular and a coaxial cable inside has its inner connected to the shoe 50. Rotation of the roller 11 is either by frictional contact at the moving test piece 19 or by a motor and gear drive (not shown), the cover-plates 30 being formed with gear teeth. Shear or longitudinal waves may be coupled to the test piece 19. Coolants or coupling fluids enhance longitudinal wave coupling. Preferably, the radial thickness of the roller 11 is such that the round trip transit time of a sonic pulse through it is substantially greater than the round trip transit time of the pulse from the surface of the test piece 19 to a solid-liquid interface 20. Alternative embodiments.-The roller 60 (Fig. 5) is of steel with radial inserts 62 retained by brazing, welding, taper fitting, press fitting or threading. Each insert 62 is a single crystal of tungsten or titanium carbide. Needle or roller bearings 78 are provided. Current is conveyed from a connector (Fig. 7) through a lead 76 to a shoe 50 and to an electrode extension 73 on one of the generators 28 when this is aligned. An axle 51 is prevented from rotating by screws 70, 71. Circuit.-Pulses from a pulser 14 (Fig. 1) trigger a crystal exciting circuit 15, thereby exciting an ultrasonic generator 28 within the roller 11. The reflected pulse from the interface is applied through a filter 16 to an amplifier detector 17 which provides an output signal to an oscilloscope or other display 18. The display 18 is also triggered by the pulse from the pulser 14. Electrical delays and acoustic delay in the roller 11 may be compensated for.