| 摘要 |
663,422. Electrostatic switches. BRUSH DEVELOPMENT CO. June 3, 1949. [June 12, 1948] No. 14947/49. Class 38 (v). [Also in Groups XXXV and XL (b)] An electrostatic relay comprises an elongated element of electro-mechanically sensitive dielectric material convoluted into a space the largest dimension of which is a small fraction of the length of the elongated element. Fig. 1 shows a relay having a helical piezo-electric element 11 which operates by bending mounted on a frame 12, 13, 14, 16, 17, the lower end being fixed to the frame at 18, and the upper end being fixed to a yoke 26 on an arm 24 coupled through a driving spindle 22 to an insulating arm 27 carrying a contact 28 for engaging a fixed contact 31. A voltage applied to terminals 49, 51 connected to opposite electrodes of element 11, causes the element to bend, giving a large cumulative displacement at the upper end of the helix for operating the contact arm 27. The frame members 13, 14, 16 are covered with felt or like fabric. The helix 11 may be formed of two strips of electroded piezo-electric material cemented together and arranged so that on the application of a voltage, one strip expands while the other contracts, such as the titanate members described in Specifications 648,403 and 648,404 [both in Group XL (b)]. Alternatively the helix may be formed from a hollow flattened tube of piezo-electric material having one internal electrode, and a pair of opposite external electrodes, for example as described in Specification 663,423 [Group XL (b)]. In the case of titanate elements, they may be continuously polarised by an external source, or they may be pre-polarised during formation of the element. Instead of a helix, a flat spiral element may be used, Figs. 5 and 6 (not shown). In Fig. 7 the element 100 is cut from a piece of piezoelectric material so as to comprise a number of limbs 101 ... 107 joined at alternate ends. One end is fixed at 117, and the electrodes on the sides of the limbs are joined in pairs as shown so that on the application of a voltage at 49, 51, the limbs alternately expand and contract to give an additive displacement of the end 118 relative to the fixed end 117 to operate contacts 119,120. The limbs are guided in comb-like members 122, 123 lined with a resilient fabric. Specifications 659,869, [Group XL (c)], and 663,424, [Group XL (b)], are referred to. |
