Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1997-04-29
1999-04-27
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310351, 310348, H01L 4108
Patent
active
058982566
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a container for enclosing a piezo-electric transducer therein with a cylindrical case the sectional shape of which is elliptical or nearly elliptical and a base for sealing an aperture part of the cylindrical case and, more particularly, to a press-fitting allowance of a case and base.
DESCRIPTION OF THE RELATED ART
Piezo-electric transducers such as clock piezo-electric transducers used in electronics including watches are enclosed in containers and mounted, for example, on printed-circuit boards. Piezo-electric transducers are near U or rectangular thin plates. In order to efficiently house piezo-electric transducers having such shapes, the mounting height from the surface of printed-circuit boards must be lowered as much as possible. To achieve this, cylindrical containers for enclosing a piezo-electric transducer the sectional shape of which is nearly elliptical have been suggested. For example, Japanese Utility Model Application No. Hei 2-55727 has disclosed a cylindrical container for enclosing a piezo-electric transducer the sectional shape of which is nearly elliptical as mentioned above. With this container, a piezo-electric transducer is held in a case the sectional shape of which is nearly elliptical and an aperture of the case is sealed with a base. The joint of the case and base has a given press-fitting allowance width which is used to make the container airtight.
If the sectional shape of a container is nearly elliptical as in the above publication, pressure on the contact surface of a case and base varies along the circumference. Therefore, leakage occurs at the parts where pressure on the contact surface is low, which can make it impossible to perfectly seal the container. In order to reliably seal a container, press-fitting allowance having a maximum value at the arc parts corresponding to the minor axis of an ellipse and a minimum value at the arc parts corresponding to the major axis of the ellipse has been suggested in Japanese Patent Laid-Open Publication No. Sho 53-61294.
However, even with the technology described in the latter publication, sometimes a container cannot be perfectly sealed. A problem to be solved still exists.
DISCLOSURE OF THE INVENTION
The present invention is intended to solve the above problem. That is, its object is to provide a container for enclosing a piezo-electric transducer having an elliptical or nearly elliptical section which can be reliably sealed.
In order to achieve the above object, a container for enclosing a piezo-electric transducer according to the present invention includes a cylindrical case for housing a piezo-electric transducer therein and a base for sealing an aperture of the case, the base having an elliptical or nearly elliptical transverse section at the contact part with the case, and the cylindrical case with one end closed and one end open having a transverse section the inner shape of which is elliptical or nearly elliptical at the contact part with the base and is smaller than the transverse section of the base. A piezo-electric transducer is enclosed by fitting the base into the open end of the case. In this case a press-fitting allowance has a maximum value at arc parts between the minor and major axes of the ellipse or near ellipse.
Experiment has shown that with a container for enclosing a piezo-electric transducer having an elliptical or nearly elliptical section, leakage occurs at arc parts between its minor and major axes. The above container has larger press-fitting allowance at these parts than the other parts, which prevents leakage at these parts. As a result, it can be reliably sealed.
Furthermore, it is possible that the press-fitting allowance at the parts where the major axis and arc of the ellipse or near ellipse intersect has a minimum value. In addition, it is possible that the press-fitting allowance at the parts where the minor axis and arc of the ellipse or near ellipse intersect has a greater value than those at the parts where the major axis and arc inte
REFERENCES:
patent: 5568006 (1996-10-01), Luff et al.
Ide Toshinori
Uchibori Kiyoshi
Wakasugi Makoto
Budd Mark O.
Citizen Watch Co. Ltd.
Miyota Co., Ltd.
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