Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Radio frequency switch
Reexamination Certificate
2000-11-22
2001-12-11
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Radio frequency switch
C200S305000
Reexamination Certificate
active
06329891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high frequency relay for switching high frequency signals.
2. Description of the Prior Art
U.S. Pat. No. 6,100,606 discloses a high frequency relay which is contemplated to effectively shield an electric path carrying a high frequency signal. The relay includes three fixed contacts which are mounted on a relay base to define a common (COM) contact, a normally-open (NO) contact, and a normally-closed (NC) contact. A first movable contact spring bridges the COM contact and the NO contact to open and close a first signal path defined between the contacts, while a second movable contact spring bridges the COM contact and the NC contact to open and close a second signal path defined between the contacts. The first and second movable contacts are supported respectively by props extending from a movable part to be movable between contact closing and opening positions, respectively. The relay includes an electromagnetic shield upstanding from the base to surround the three fixed contacts as well as the movable contact springs. The shield is formed in its wall with notches which allow the props to extend through the shield for driving the movable contact springs between the contact closing and opening positions within the confine of the shield. However, due to the presence of the notches, the movable contact springs are exposed through the notches and cannot be fully surrounded by the shield, lowering a high frequency characteristic of the relay. Further, in this patent, the ground terminals are formed separately from the shield and are connected thereto. Thus, the ground terminals have to be prepared in addition to the shield, increasing the number of parts with an associated assembly cost increase.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of the above insufficiencies to provide an improved high frequency relay which is capable of effectively shielding a high frequency signal path, yet reducing a number of the parts forming the electromagnetic shield and the associated structure. The relay in accordance with the present invention includes a dielectric base mounting three fixed contacts defining a common (COM) contact, a normally-closed (NC) contact, and a normally-open (NO) contact, respectively. The NC and NO contacts are arranged on opposite of the COM contact, and each of the fixed contacts is defined at a tip of each corresponding one of three contact terminals extending through the base. A first movable contact spring is disposed to bridge the COM contact and the NC contact for closing and opening a high frequency signal path defined therebetween. Likewise, a second movable contact spring is disposed to bridge the COM contact and the NO contact for closing and opening another high frequency signal path defined therebetween. The relay further includes a driving mechanism which causes the first and second movable contact springs to move for closing and opening the high frequency signal paths alternately. Also included in the relay is a pair of electromagnetic shield plates upstanding from the base to define a shielded space between the shield plates for accommodating therein the three fixed contacts, the first and second movable contact springs. Each of the shield plates is configured to come into electrical contact with corresponding one of the first and second movable contact springs moved in the contact opening position. Each of the shield plates is integrally formed with at least one ground terminal which extends continuously from a bottom of the shield plate through the base, and each shield plate is configured to cover the first and second movable contact springs over the full length thereof without any interruption for completely shielding the first and second high frequency signal paths. Accordingly, the high frequency signal paths can be completely shielded simply by use of the two shield plates integrally formed with the ground terminals.
Preferably, the shield plates are of the identical configuration in order to reduce the number of parts and therefore improve productivity of the relay.
The base may be molded to have a pair of integral positioning studs which project on the base for abutting against opposite ends of the shield plates, respectively so as to accurately keep the spacing between the shield plates for giving an intended high frequency characteristic to the signal path.
Each shield plate is preferably formed with a bent recess which defines grounding shoulders at opposite bent ends of the recess for contact with the opposite ends of each corresponding one of the first and second movable contact springs. The grounding shoulder is located outwardly of an inner edge of the corresponding fixed contact with respect to a lengthwise direction of the corresponding movable contact spring. With this result, the movable contact spring can have its opposite ends rested on the shoulder only with a small projection towards the fixed contact, thereby improving isolation of the movable contact spring from the fixed contact.
Further, the opposite ends of each movable contact spring may be located at outer edges of the corresponding fixed contacts, respectively with respect to the lengthwise direction of the movable contact spring, for minimizing the projection of the opposite ends of the movable contact spring towards the fixed contact when the movable contact is in the contact opening position.
In a preferred embodiment, the shield plate has a pair of the ground terminals which are spaced along a length of the shield plate and positioned asymmetrically about a longitudinal center of the shield plate such that the two ground terminals of one shield plate stagger with respect to the two ground terminal of the other shield plate along the longitudinal direction of the shield plate. With this arrangement, a distance between either of the longitudinal ends of the shield plate and the adjacent ground terminal can be shorted sufficiently with respect to a wavelength of the high frequency signal, thereby avoiding an antenna effect which would otherwise occur between the longitudinal end of the shield plate and the adjacent ground terminal, while utilizing the shield plate of the identical configuration.
In this connection, the two spaced ground terminals are configured to extend from the bottom of the shield plate through respective anchor sections which are engaged with the base and have a greater width than the ground terminal with respect to the lengthwise direction of the shield plate. One of the anchor sections adjacent to the contact terminal of the COM contact is spaced therefrom by a distance greater than a distance by which another of the anchor sections adjacent to the contact terminal of the NC or NO contact is spaced therefrom. With this result, it is possible to reduce a capacitance between the contact terminal of the COM contact and the two adjacent ground terminal than a capacitance between the contact terminal of the NC or NO contact and the one adjacent ground terminal, thereby facilitating to achieve an impedance matching of the high frequency signal path to an intended overall impedance.
The driving mechanism of moving the first and second movable contact springs includes an electromagnet, an armature, and a card carrying the first and second movable contact springs at its lower end. The armature moves in response to the excitation of the electromagnet for driving the card to open and close the high frequency signal paths. The card is shaped into an elongated configuration aligned along the length of the shield plate and is located above the shield space. The card is formed at its upper longitudinal ends with pivot arms which are pivotally supported on top of end walls upstanding from opposite longitudinal ends of the base. Thus, the card can swing about a pivot axis which is fixed vertically relative to the base. With this result, the card can move the movable contact springs accurately while keeping the movable contact sprigs only at a small
Hayashi Tokatoshi
Nakahata Atsushi
Sagawa Koji
Taguchi Tomohiro
Takeyama Hidetoshi
Barrera Ramon M.
Matsushita Electric & Works Ltd.
Rader & Fishman & Grauer, PLLC
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