| 摘要 |
1,082,874. Ultrasonic wave couplings; valve oscillating circuits. M.E.L. EQUIPMENT CO. Ltd. Nov. 23, 1965 [Feb. 22, 1965], No. 7546/65. Headings H3F and H4J. [Also in Division B3] Printed circuits are soldered by a mound of molten solder locally raised by discrete pulses of acoustic vibrations. The mound height is increased compared with that achieved by continuous vibrations. A magnetostrictive element 13 and probe 15 are immersed in a solder bath. In use, an intense acoustic wave is generated in the solder and pressure effects at the solder-air interface produce a solder mound following the outline of the probe 15. Printed circuit boards are passed across the mound and their surfaces are wetted by the solder. Cavitation effects assist wetting and radiation pressures cause solder to adhere neatly to joints. A 50 c/s. voltage supply is applied to line 5 and the potential at the anode 2 of triode 1 is varied above and below the cathode potential. When the anode 2 is positive with respect to the cathode 6, triode 1 conducts and current flows through the primary 3 of transformer 4 which in turn causes current flow in the secondary 11. The magnetostrictive element 13 is energized and the vibratory energy produced causes a pick-up transducer 17 to vibrate. By the reverse magnetostrictive effect a potential is produced across a winding 16 and applied to grid 8. This potential alternates at a frequency decided by the mechanical resonance of the magnetostrictive system. Loop phase and gain are arranged so that the initial vibrations are maintained and automatic frequency control is obtained. In the arrangement described the transducer vibrates and is interrupted for identical periods of 10 m/s. If unequal periods are required a switched D.C. power source is used. The transducer may then vibrate for 20 m/s. and cease for 1 to 10 m/s. Reference has been directed by the Comptroller to Specification 846,961.
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