GB1379955A - Ultrasonic transducer - Google Patents

Abstract

1379955 Seaming non-metallic sheet material EASTMAN KODAK CO 10 March 1972 [11 March 1971] 11214/72 Heading B5K [Also in Division H4] An ultrasonic transducer comprises (Fig. 1) a metal rear mass 11, a first piezoelectric vibration generator 15, a metal separator 19, a second piezoelectric vibration generator 17 arranged so as to expand axially during axial contraction of the generator 15 and a metal output member comprising a front mass 13. The components are so dimensioned so that, when the transducer is operated at a predetermined frequency, the ends thereof are at antinodes (A) of the vibrations, and the vibration generators 15, 17 are at nodes (N) separated by #/2. Preferably a horn 25 is formed integral with or attached to the front mass 13. The components are preferably cylindrical and are clamped together by a central bolt 27, by a number of peripheral bolts or by a surrounding tension shell. Masses 11 and 13 and the separator 19 are of the same or different metals, e.g. aluminium, titanium or steel. If different metals are used, the rear mass 11 has the greater or greatest density, the separator 19 has a density less than the rear mass 11 and the front mass 13 has a density the same as, or less than, the separator 19. One construction has a combined horn 21 and front mass 13 of titanium, an aluminium separator 19 and a steel back mass 11. If desired, the separator 19 may comprise two elements (35, 37) Fig. 3 (not shown), of equal dimensions, the rear element 35 being of light weight metal (titanium or aluminium) and the front element 37 being of relatively heavy metal (steel). The piezoelectric generators 15, 17 are of barium titanate or lead zirconate-titanate. The shoulder 23 is at a node. Heat generated by the piezoelectric generators 15, 17 is removed by conduction through members 11, 19 and 13. In an alternative construction (Fig. 2, not shown) each piezoelectric vibration generator comprises a pair of piezoelectric discs (15<SP>1</SP>, 161 and 17<SP>1</SP>, 18<SP>1</SP>) with a metal plate (31, 33) between these discs. The plates (31, 33) are connected to one side of an energizing circuit and the members 11, 19, 13 are connected to the other side of the circuit. For dissipating heat produced in the piezoelectric generators 15<SP>11</SP>, 17<SP>11</SP> (Fig. 4) the separator 19<SP>11</SP> may carry longitudinally extending radial cooling fins 39. Circumferential fins could also be used. The transducer T is mounted within a cylindrical housing 40 by a mounting plate 41 provided with circumferentially extending overlapping slots 43, 45 (see also Fig. 5, not shown). Cool air is circulated through an inlet 49 to outlet slots 43, 45. Preferably the housing 40 is supported by a second mounting plate 50. The plates 41, 50 are at vibration nodes. One application is the splicing of webs of plastics material.