Abstract: A mechanical filter including resonators, a coupler for longitudinally coupling the resonators, electro-mechanical transducers coupled to the opposite ends of the coupler, and lead wires led out from the transducers. Each of the transducers comprises a piezoelectric ceramic resonator adapted for longitudinal resonance and having electrodes attached to the opposite end faces thereof, and one of the end faces of the piezoelectric ceramic resonator is formed with a coupling hole which is located substantially on the axis thereof and extends lengthwise of the ceramic resonator. Each end of the coupler is inserted into the coupling hole with an electrically conductive adhesive to thereby couple the coupler and ceramic resonators. The aforementioned lead wires may be connected to the electrodes and wound about the piezoelectric ceramic resonators through a predetermined number of turns, and may be secured to the ceramic resonators by an adhesive having rubber-like elasticity.

Abstract: A container for a mechanical filter is provided in which the internal pressure is reduced to prevent propagation in the air of sound waves to thereby prevent deterioration of the filter characteristics. A recess with an aperture therethrough is formed in one of the walls of a metal casing which constitutes the container. Further, an adhesive tape-like member is disposed on the surface of the recess in such a manner as to cover the aperture. After the casing has been evacuated through the aperture, hermetic sealing means is provided on the adhesive tape-like member within the recess.

Abstract: In a mechanical filter, a pair of transducer elements of truncated circular cross-section are disposed at the input and output sides respectively, and they are mechanically connected in cascade to each other by means of a coupler member. The areas of the truncated cross-section of the transducer elements are made different from each other. Between said pair of transducer elements may be provided one or more resonator elements each provided with a recess and connected to each other and to said transducer elements by said coupler member. Each of the transducers and resonators are mounted on a mount base plate by means of a bent wire-like support member having a pair of legs. The foregoing mechanical filter is accommodated in a container which is pressure-reduced and hermetically sealed.