| 摘要 |
600,190. Piezo-electric crystals. BENDIX AVIATION CORPORATION. Feb. 8, 1944, No. 2358. Convention date, Aug. 10, 1942. [Class 40 (v)] [Also in Group XX] Bar stock from which piezo-electric crystals are to be made is prepared by roughening a surface of the slab of material from which the bars are to be cut, passing a narrow beam of light through this surface to produce a dispersion pattern on it, and marking the material with lines in accordance with this pattern to indicate the cutting planes. In carrying out the method, a quartz crystal is cut into slabs in planes parallel to the optical and mechanical axes, the surfaces being then etched with hydrofluoric acid. A slab 3 is then placed on the apparatus shown in Fig. 3, comprising a lamp 7 in an enclosure 8 having a pinhole 9 which allows a narrow beam of light to pass through the slab. When the piece of quartz is left-handed and the upper face is negative, a bright-line dispersion pattern is produced in the form of a parallelogram 10, of which the short sides are parallel to the optical axis 2, and the long sides are at an angle of 52 degrees with it. Cutting planes 12, Fig. 6, for bars from which AT cut crystals are to be cut are thus marked on the slab by lines parallel to the long sides of the parallelogram 10. The minor or transverse axis of these bars make an angle of 90- 52 degrees, i.e. 38 degrees with the optical axis, 'and since an AT cut crystal makes an angle of approximately 35 degrees with this axis, such crystals may be cut from the bars in planes inclined at not more than 4 degrees to their minor axes. For BT cut crystals, the cutting planes of the bars are perpendicular to the long sides of the parallelogram. If the quartz is right - handed, the parallelogram 11 is seen and is similarly used as a guide. When the positive face of the slab is uppermost the dispersion pattern takes the form of a double-headed arrow. |
