| 摘要 |
688,179. Piezo-electric crystals. BRUSH DEVELOPMENT CO. Oct. 17, 1951 [April 27, 1951], No. 24228/51. Class 40 (viii). Piezo-electric properties are imparted to a fired ceramic material by applying a unidirectional polarizing voltage between two spaced points on its surface for an appreciable time, and then applying the voltage between a further two points on the surface, one being spaced between the first two points and the other-being spaced outside. The material used is a bariuin titanate composition. A flat plate of material can be treated by moving two bars, formed into a unit by insulating spacers and connected each to one terminal of the voltage source, across the surface by a continuous or step-by-step motion. When, as shown, a hollow ceramic cylinder is being treated a unit 11, 12 may treat the outside and a unit 11<1>, 12<1> may treat the inside. The bars in this modification are provided with bristles 30 and 30<1> to make contact with the ceramic element. U.S.A. Specification 2,486,560 is referred to. |
