JPS5797716A - Ceramic filter - Google Patents

Abstract

PURPOSE:To prevent looseness and displacement at the assembling time or due to vibration from the external, by arranging respective filter elements with required insulating gaps after assembling them individually and immersing them in a thermoplastic resin to seal them as one body. CONSTITUTION:A filter element 1 of a small capacity consisting of a thick piezoelectric resonator 11 of a small capacity which is provided with electrodes 11a and 11a' on both faces and consists of piezoelectric porcelain, an insulating frame 12 of a synthetic resin provided with an aperture part 12a where the resonator 11 is stored and small projecting pieces 12b- and 12b'- in four corners of both faces, and a pair of terminal plates 13 and 13' which cover both faces with small holes 13b- and 13b'- fitted to small projecting pieces 12b- and 12b'- and are provided small projections 13a and 13a' brought into contact with the node of vibration of the piezoelectric resonator 11 in their centers and a filter element 2 of a large capacity assembled similarly are immersed in a thermoplastic resin with an insulating gap G interposed between these elements 1 and 2 and are sealed as one body. As a result, each piezoelectric resonator is held in a stable state in the center, which becomes the node of vibration, and all of outside circumferential parts in the insulating frame.