Electrical connectors – Metallic connector or contact having movable or resilient... – Spring actuated or resilient securing part
Reexamination Certificate
1998-12-02
2001-04-17
Nguyen, Khiem (Department: 2839)
Electrical connectors
Metallic connector or contact having movable or resilient...
Spring actuated or resilient securing part
C439S839000
Reexamination Certificate
active
06217395
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a contact spring. The contact spring includes the following parts: a bottom spring with a centrally disposed spring arm base formed by a rectangular frame, a connection part formed on one end of the spring arm base for electrical conductors, and two spring arms adjoining an opposite end and formed onto broad sides of the spring arm base. The spring arms converge toward one another on a free end and then open into a plug-in funnel. Respective indentations facing one another and disposed on long edges keep the spring arms spaced apart, in the vicinity of a contact zone. A detent sleeve connected to the spring arm base surrounds the spring arms.
It is well known that in disconnectable electrical contacting devices, in particular plug devices of the kind formed by a female part, such as a contact spring, and a connecting part, such as a contact blade, the contact force is of decisive significance for the reliability of the electrical connection.
There is also a demand for contact surfaces capable of good conduction, that is, which are not corroded or are non-scaling, so as to assure interference-free current transfer at the contact surface and to minimize the contact resistance.
Furthermore, disconnectable contacts constructed as a plug device should be simple to manipulate, both in the manufacture of the electrical terminals and in making the plug connection.
German Published, Non-Prosecuted Patent Application DE 196 11 698 A1 discloses a contact spring of the type defined at the outset, with resilient contact legs on both sides for contact blades intended to carry high current, in which the above demands are maximally met. However, in the use of that known contact spring, it has been found that while the contact force is still at about greater than 3 N after a certain number of plug-in operations and thus does not fall below the specified holding force for an introduced blade contact, nevertheless the requisite plugging force rises to approximately 10 N, thereby making manipulation more difficult. Under some circumstances, that can make the connection defective, or if the holding force is too low the connection can come loose or be interrupted.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a contact spring, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which is simple in structure and which can be manufactured at reasonable expense.
With the foregoing and other objects in view, a contact spring is provided in accordance with the invention. The contact spring comprises a bottom spring having a centrally disposed spring arm base formed by a rectangular frame. The spring arm base has broad sides and two opposite ends. A connection part is formed onto one of the ends of the spring arm base for electrical conductors. Two spring arms are each formed onto the broad sides of the spring arm base at the other ends of the spring arm base. The spring arms converge in a wedge-like manner toward a free end and then widen into a plug-in funnel in a contact zone. The plug-in funnel having an opening angle less than thirty degrees (<30°) over its entire length. The spring arms have long edges with respective indentations oriented toward one another for keeping the spring arms spaced apart in the vicinity of the contact zone. The spring arms are shaped spherically in the vicinity of the contact zone. Each spring arm forms a respective contact dome. A detent sleeve surrounds the spring arm base and the spring arms.
The wording “over its entire length” herein means that the sides or legs of the plug-in funnel extend quasi-linearly without curving or kinking. The opening angle between the legs should be as acute as possible, or in other words as small as possible.
In order to assure contact security in all cases, the spring arms are curved in a dome-like manner in the region of the contact zone. The contact zone is the region where the plug contact cooperates with the associated blade contact. Due to the curved contact surfaces of the legs, it is assured that regardless of the location of the contact blade in question when plugged in, an adequate electrical contact will always exist, so that problems in the electrical power and/or signal transmission are practically prevented.
In accordance with another feature of the invention, in order to additionally improve the contact reliability, at least the spring arms are covered on all sides with a layer of tin, and the layer thickness is approximately 1.5 &mgr;m. The tin layer is preferably applied as a so-called fire tin-plating, that is in a molten bath of tin.
It is known that while tin is a metal with good conductivity, mechanically it cannot be stressed very much, because it only affords low wear resistance due to its low strength.
In accordance with a further feature of the invention, in order to overcome that vulnerability to wear, the tin layer is mechanically consolidated through the use of stamping in the region of the contact dome.
In accordance with an added feature of the invention, through the use of this stamping, which is also called strain-hardening, the tin layer is indeed locally reduced by about 0.3 &mgr;m as compared with the non-consolidated region. This does bring about a considerable rise in wear resistance, so that the surface thus treated has less wear from friction and is abrasion-proof. In accordance with an additional feature of the invention, the tin layer has a smoothed surface. As a result, while simultaneously preserving the good corrosion protection by the tin layer, a marked reduction in the forces required to plug in and pull out the contact blades again is attained.
In accordance with yet another feature of the invention, the tin layer, at least in the mechanically consolidated region, has an intermetallic phase with a proportion of the total layer volume of 50% to 75%. This intermetallic phase additionally contributes to increasing the strength of the intrinsically very soft tin layer.
In accordance with a further feature of the invention, the spring arms of the contact spring are each formed by two parallel spring legs, which are formed onto the broad sides of the spring arm base. In accordance with an added feature of the invention, the spring legs are separated from one another by a longitudinal gap. In accordance with an additional feature of the invention, the spring legs of a spring arm, per contact spring, are joined at their free end through the use of a cross piece.
In other words, the spring arms converging in a wedge-like manner and disposed opposite one another, each have two elongated strips that each form one spring leg and are joined to the spring arm base. These spring legs are separated from one another as far as their free end by a longitudinal gap. However, the longitudinal gap is closed off on the free end by a crosspiece, for one of the two pairs of strips, each forming one spring arm.
In accordance with again another feature of the invention, each spring leg is curved spherically in the region of the contact zone and forms a contact dome, as a result of which the afore-mentioned contact reliability is not merely assured but is even improved, since the elasticity of two pairs of spring legs necessarily has a more-favorable performance than two individual spring arms.
In accordance with a concomitant feature of the invention, in a time-tested way, the detent sleeve of the contact spring cooperates in a form-locking and force-locking manner with the spring arm base and serves to secure the installation of the contact spring in existing mounting openings of housings and the like. A form-locking connection is one which connects two elements together due to the shape of the elements themselves, as opposed to a force-locking connection, which locks the elements together by force external to the elements.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the in
D'Hulster Freddy
Flieger Richard
Greenberg Laurence A.
Lerner Herbert L.
Nguyen Khiem
Stemer Werner H.
Tyco Electronics Logistics AG
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