Electricity: circuit makers and breakers – Snap – Single snap
Reexamination Certificate
2000-01-07
2001-02-13
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Snap
Single snap
C200S407000
Reexamination Certificate
active
06188033
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electrical switches and more particularly to snap-acting switches of the over-centering kind and such switches which can be made in small size.
BACKGROUND OF THE INVENTION
Snap-acting electrical switches having a switching element of the type disclosed in U.S. Pat. Nos. 2,777,032 and 3,105,886, the details of which are incorporated herein by this reference, have been successfully built for many years and are still in wide use. Such switching elements comprise a blade of a flat resilient material having a pair of outer legs and a center leg extending essentially in the same direction from a junction portion. The free ends of the outer legs are connected to a support by a pair of connections which are spaced from one another such that the outer legs are distorted or warped toward one another, thus urging the center leg toward a position of relative equilibrium into electrical engagement with a first stationary electrical contact thereby providing a pair of normally closed contacts. An actuating element is disposed adjacent at least one of the outer legs and is movable into engagement with one or both outer legs to bias the outer leg(s) into the opposite warped configuration away from each other thereby causing the center leg to move in the opposite direction away from the first electrical stationary contact and into engagement with a second, normally open, electrical stationary contact disposed at a location on the opposite side of a plane, passing through the support location of the outer legs, from the position of the first electrical stationary contact.
Even though the above described switches and switching elements have been very effective, it would be desirable to improve the operational performance of such switches and switching elements, for example, with regard to lowering the electrical contact resistance of the normally closed contacts and increasing the normally closed contact force.
SUMMARY OF THE INVENTION
Briefly stated, a snap-acting switch made in accordance with the invention, comprises a switching element formed of a blade of a flat, resilient material having a pair of outer legs and a center leg extending in substantially the same direction from a junction portion. The outer legs are each formed with a generally semi-annular band portion which at one end blends into the junction portion and with a mounting portion extending from the opposite end of the band portion. Although other annular configurations may be employed, a generally semicircular configuration is suitable. A mounting aperture is formed adjacent the free distal end of each outer leg for reception on a respective mounting pin as described in the above referenced patents. According to a feature of the invention, a strengthening portion is formed in the semi-annular band portion of a each outer leg, preferably on the outer portion thereof, i.e., the portion closer to the respective distal free end. In one embodiment, the strengthening portion comprises at least two permanently formed dimples or recesses, i.e., portions where the blade is deformed out of the plane of the blade, positioned generally equidistant to the inner and outer edges of the respective band portion. In another embodiment the strengthening portion is configured as a rib extending along a curved line equidistant from the inner and outer edges of the band portion. The strengthening portions stiffen an otherwise low stressed region of the outer legs in the mounted or warped condition and thereby more evenly distribute stress throughout the switching element and increase the contact force of the normally closed contact. This in turn lowers the electrical resistance of the normally closed contact and serves to increase device reliability. Additionally, the switching element made in accordance with the invention has a quicker response time and thereby reduces dead break or blackout issues.
REFERENCES:
patent: 2777032 (1957-01-01), Burch et al.
patent: 3105886 (1963-10-01), Burch et al.
patent: 4159563 (1979-07-01), Bauer et al.
patent: 4168412 (1979-09-01), Smith
patent: 4214136 (1980-07-01), Rossi et al.
patent: 4224488 (1980-09-01), Rossi
patent: 4278855 (1981-07-01), Rossi
patent: 4941254 (1990-07-01), Davis
patent: 5617946 (1997-04-01), Acampora et al.
Bentley William J.
Berg Peter G.
Koczwara David A.
Baumann Russell E.
Friedhofer Michael
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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