GB568468A - Improvements in and relating to piezo-electric crystals - Google Patents

Abstract

568,468. Piezo - electric crystals. TENENBAUM, B. Aug. 31, 1943, No. 17949/42. [Class 40 (v)] A flexural vibration crystal has the interior cut away to provide a space or spaces extending in the longitudinal direction of the crystal bar and is supported by terminal wires inserted into the hollow space and connected to internal metallic coatings. Figs. 3 and 5 show suitable forms of crystal. In Fig. 3, the interior of the crystal is cut away leaving two plates a<1>, a<2> joined by integral webs b<1>, b<2> which may be situated at the ends or at nodal points. Fig. 5 shows a form in which the crystal is divided into two plates a<1>, a<2> by grooves cut into each of the longer edges of the crystal to leave a central longitudinal web b. If the poles of an alternating supply are connected respectively to the metallized internal and external surfaces of the crystal, it will exhibit flexural vibrations dependent on the length and thickness of the crystal, which may suitably be an X-cut quartz. Fig. 6 shows a crystal of the form shown in Fig. 5, mounted for use as an oscillator. The crystal is supported by wires j<1>, j<2>, k<1>, k<2>, connected to the internal coatings and to rods m connected to a pair of pins o. The external coatings are connected by wires p and springs q to a second pair of pins r. An arrangement for a filter circuit is also described, Figs. 9 and 10 (not shown), in which the external electrodes are transversely divided to form input and output electrodes, the internal electrodes forming an earthed common electrode.