Patent Description:
Contact rings are known in the form of compression spring contacts which are made of electrically conductive materials and can therefore establish electrically conductive connections between contact elements. These contact rings are typically flat and have, for example, a wave shape so that they alternately touch the surfaces of the contact elements.

<CIT> relates to a shield sleeve having a sleeve member. The sleeve member has a first end, and at least one radially protruding contact finger. Each contact finger has a cantilevered end connected to the first end, and at least one contacting protrusion positioned proximate to an opposite free end and protruding outward in a radial direction with respect to the sleeve member.

<CIT> relates to a conductor connection washer arranged between two conductors in order to connect them electrically, which has a metal plate with a washer hole in the center, and <NUM> or more contact protrusions formed on the opposite sides of the plate integrally therewith. Out of the <NUM> contact protrusions, <NUM> or more contact protrusions are bent alternately to one side and the other side along the outer periphery of the plate, and <NUM> or more contact protrusions are bent alternately to one side and the other side along the inner periphery of the washer hole.

<CIT> relates to a grounding spring ring made of resilient conductive material for a connector shell, which comprises an annular portion with an axial split. At the front end of spring a plurality of cantilever spring fingers are provided which are engaged between the external surface of shell and internal surface of outer shell. The rear end of spring has a lip which engages behind shoulder on the internal surface of the connector shell to prevent axial movement.

<FIG> illustrate a conventional arrangement of two contact elements <NUM> and <NUM> without a connecting member (<FIG>) and two contact elements with a connecting member <NUM> (<FIG>). Connecting member <NUM> in <FIG> is a typical contact ring <NUM> as is known from prior art. Contact ring <NUM> is flat and wave-shaped and is typically made of spring steel which has good mechanical but poor electrothermal properties, which can also hardly be compensated for by a thick silver plating. The contact sections of the known contact ring are also not able to reliably penetrate electrically insulating surface layers, such as aluminum oxide, with typical contact forces. They are also prone to corrosion.

Contact elements, though containing electrically conductive materials whose surfaces, however, are made of electrically insulating layers, such as natural oxides, cannot be connected in an adequate electrically conductive manner by the contact elements described in prior art. In addition, the contact elements are not configured to avoid air gaps between the contact elements. The electromagnetic shielding of such a connection is therefore inefficient in the event of high frequencies. There is therefore a need for connecting members that provide electrically conductive connections between contact elements with surfaces made of electrically insulating layers and efficient electromagnetic shielding.

This problem is solved by the subject matter of the independent claims. Advantageous embodiments of the present invention are presented in the dependent claims.

For connecting contact elements having an electrically conductive core and an electrically insulating surface layer, the present invention is based on the idea of using a contact member which is made of electrically conductive material and respectively penetrates the electrically insulating surface layers of the contact elements.

The contact member according to the present invention has the shape of a ring, where the term "ring" in the present application refers to circular ring structures as well as structures that are topologically equivalent to circular ring structures. This includes, for example, non-overlapping polygonal structures. In order to ensure better understanding, only the term "ring" shall be used in the following without further specification. The figures show circular ring structures by way of example, although structures that are topologically equivalent to circular ring structures are also included.

The ring shape of the contact member enables, in particular, the efficient connection of cylindrical contact elements with a corresponding base area, since the latter has the appropriate architecture for use in a limited ring-shaped installation space. It is created in that a strip of an electrically conductive material, for example, a copper alloy, which can be silver-plated, is closed to form a ring-shaped structure. The use of a copper alloy, which can be silver-plated, is advantageous since it represents a good compromise between mechanical and electrothermal properties.

The strip comprises projections on at least one longitudinal side. The projections have tips or sharp edges which penetrate the electrically insulating surface layers of the contact elements and thereby establish an electrically conductive connection between the electrically conductive cores of the contact elements. By using a large number of short projections, the contact member according to the present invention benefits from the advantages of multi-contact physics and has favorable electrothermal properties. The projections each establish an electrically conductive contact, whereby a plurality of electrically conductive connections between the contact elements is created, which leads to many short current flows and redundant contacting.

In contrast to known contact rings, which have planar contact sections for touching the contact elements, the contact sections of the contact ring according to the present invention are very limited and thereby reduce the occurrence of corrosion.

According to an advantageous embodiment, the strip of the contact ring is arranged in the shape of a cylinder and can therefore be well adapted to cylindrical contact elements.

The projections of this embodiment taper to a tip and have an S-shaped cross section, so that their tip impacts the surfaces of the contact elements at an obtuse angle. This avoids greater lateral contact or surface contact of the projections with the surfaces of the contact elements. This in turn reduces the occurrence of fretting corrosion.

At least one pair of adjacent projections has flat segments disposed between the two projections. Said flat segments serve as overstretch protection for the projections during pre-assembly and final assembly between the contact elements. With a coil spring that engages around the cylindrically arranged strip, the contact ring on the cylindrical contact element can optionally be even more stable.

According to a further advantageous embodiment, the strip is closed to form a ring-shaped structure and is arranged in a flat manner.

The contact ring according to the invention is used in a contact system which, in addition to the contact ring according to the present invention, comprises a ground cylinder and a shielding cylinder which are shaped such that gap-free assembly with the flat contact ring is possible, thereby creating perfect electromagnetic shielding. The connection is established by a double press fit and is therefore particularly robust. It additionally reduces relative motions and vibrations. Due to this connection, the contact system according to the present invention comprises efficient electromagnetic shielding, in particular in the event of high frequencies, and can advantageously be used in multi-position connectors.

The shielding cylinder according to the present invention also has three centering projections which enable the efficient centering of the shielding cylinder relative to the ground cylinder and prevent relative motions and vibrations between them, thereby additionally stabilizing the connection.

A cylinder of the contact system preferably comprises the electrically conductive material aluminum. Other materials are also conceivable.

The contact rings according to all embodiments have a high degree of adaptability with regard to the orientation, arrangement, number, and configurations of the projections.

For better understanding of the present invention, it shall be explained in detail by way of the embodiments illustrated in the figures below. Same elements are there designated with same reference numerals and same component designations. Furthermore, some features or combinations of features from the different embodiments shown and described can also be independent inventive solutions by themselves or solutions according to the invention.

Embodiments of the present invention shall be described hereafter in detail with reference to <FIG>.

<FIG> show a contact ring <NUM> according to a first embodiment of the present invention. As shown in <FIG>, contact ring <NUM> comprises a strip <NUM> made of electrically conductive material. Strip <NUM> is provided with projections <NUM> on at least one longitudinal side. Projections <NUM> taper and form a tip at their end. <FIG> shows that strip <NUM> can be equipped at the ends with a closure <NUM> which allows strip <NUM> to be closed to form a ring-shaped cylindrically arranged structure, as can be seen in <FIG>. This structure allows for simple and inexpensive production of contact ring <NUM> by punching and bending. As shown in <FIG>, projections <NUM> are bent outwardly and have an S-shaped cross section.

A coil spring (not shown) can optionally surround contact ring <NUM> concentrically so that the connection between contact ring <NUM> and cylindrical contact element <NUM> is even more stable.

In addition, it is also possible for the strip to be open at the ends without a closure. In this case, the coil spring can optionally hold the strip together. Another possibility is for the strip to be a little longer without a closure and comprises an overlap at the ends.

The material of contact ring <NUM> preferably comprises a copper alloy which can be silver-plated. In contrast to spring steel, this material has good mechanical as well as good electrothermal properties.

<FIG> shows an application example of contact ring <NUM>. Contact ring <NUM> is arranged between two contact elements <NUM> and <NUM> such that it touches the oppositely disposed surfaces of contact elements <NUM> and <NUM> with the tips of S-shaped projections <NUM>. If contact elements <NUM> and <NUM> are pressed against one another, then the tips of projections <NUM> penetrate electrically insulating surface layers such as a layer of aluminum oxide which naturally forms on the surface of a contact element made of electrically conductive aluminum.

An electrically conductive connection can thus be established with the aid of contact ring <NUM> between the electrically conductive core of first contact element <NUM> and the electrically conductive core of second contact element <NUM>, even if contact elements <NUM> and <NUM> comprise insulating surfaces that electrically separate them from one another. A large number of projections <NUM>, for example <NUM>, like in <FIG>, on both sides of contact ring <NUM> has a physically positive effect on the electrothermal properties of the connection between the two contact elements <NUM> and <NUM>.

The structure of contact ring <NUM> with its pointed projections <NUM> for touching contact elements <NUM> and <NUM> also minimizes the area of the contact sections in which a protective surface of contact elements <NUM> and <NUM> is damaged. Corrosion of contact elements <NUM> and <NUM> can thereby be counteracted.

<FIG> shows a contact ring <NUM> according to a second embodiment of the present invention. This contact ring <NUM> comprises a flat ring made of electrically conductive material. The flat ring is provided with projections <NUM> on the two narrow sides. Projections <NUM> taper towards their end. Projections <NUM> are bent such that they point out of the plane spanned by ring <NUM>, wherein projections <NUM> on the outer side of ring <NUM> and projections <NUM> on the inner side of ring <NUM> point in opposite directions. Projections <NUM> are preferably, but not necessarily, arranged with regular spacings, where internal projections <NUM> can also have individual greater spacings.

Projections <NUM> on the outer side of ring <NUM> have an S-shaped cross section. They are oriented such that they surround a common inscribed circle that they touch with one flat side. Projections <NUM> on the inner side of ring <NUM> are oriented such that they each touch a common inscribed circle with an edge. This edge is sharp and therefore able to penetrate insulating surfaces. Projections <NUM> on the outer side of the ring can also optionally be oriented such that they each touch a common inscribed circle with an edge that is sharp and can therefore penetrate insulating surfaces.

Like contact ring <NUM> according to the first embodiment, the material of contact ring <NUM> according to the second embodiment preferably comprises a copper alloy which can be silver-plated and which has good mechanical as well as good electrothermal properties.

The structure of contact ring <NUM> can be created in a simple and inexpensive manner as a reel-to-reel strip by punching and bending.

<FIG> shows how contact ring <NUM> according to the second embodiment can be arranged in a contact system <NUM> together with a ground cylinder <NUM> and a shielding cylinder <NUM>. Projections <NUM> on the outer side of the ring engage around shielding cylinder <NUM>. Projections <NUM> on the inner side of the ring are spread apart from the inside against ground cylinder <NUM>. The connection is established by press-fitting, so that contact ring <NUM>, ground cylinder <NUM>, and shielding cylinder <NUM> touch each other without any air gaps therebetween.

As shown in <FIG>, contact ring <NUM> contacts ground cylinder <NUM> with a sharp edge of projections <NUM> on the inner side of the ring. As a result of the pressure of the press fit, the sharp edges penetrate the surface of ground cylinder <NUM>. As described in relation to contact ring <NUM> according to the first embodiment, this creates an electrically conductive connection between contact ring <NUM> and the electrically conductive core of ground cylinder <NUM>. Due to the expansion of the contact section between contact ring <NUM> and ground cylinder <NUM>, corrosion is additionally reduced.

As shown in <FIG>, shielding cylinder <NUM> comprises three centering projections <NUM>. Shielding cylinder <NUM> is connected to contact ring <NUM> in such a way that centering projections <NUM> are each positioned where contact ring <NUM> comprises internal projections <NUM> with greater spacings. As a result, centering projections <NUM> can be bent around contact ring <NUM> so that they touch ground cylinder <NUM> from the inside without being obstructed by a projection <NUM> of contact ring <NUM>.

Centering projections <NUM> hold shielding cylinder <NUM> firmly at ground cylinder <NUM>. As a result, they facilitate the centering of shielding cylinder <NUM> relative to ground cylinder <NUM> and stabilize contact system <NUM>. Centering projections <NUM> and the press-fit of contact system <NUM> thereby ensure that the connection composed of contact ring <NUM>, ground cylinder <NUM>, and shielding cylinder <NUM> does not have any air gaps nor any relative motions and vibrations of the components. As a result, efficient electromagnetic shielding can be ensured, in particular in the event of high frequencies.

As shown in <FIG>, contact ring <NUM> according to second example not forming part of the invention can comprise a toothing <NUM> instead of internal projections <NUM>. This alternative of contact ring <NUM> can be produced in a simple and inexpensive manner by deep drawing, punching, and bending.

<FIG> shows a contact ring <NUM> according to a second example not forming part of the invention. Like contact ring <NUM> of the second embodiment, contact ring <NUM> consists of a strip which is closed to form a flat, ring-shaped structure. In addition, contact ring <NUM> has a meander structure with sections alternately pointing inwardly <NUM> and outwardly <NUM>. This arises from the strip being provided with cutouts <NUM> and <NUM> which alternately start out from the inner and outer edge of the strip and extend into the interior of the strip (see <FIG>). The meanders pointing inwardly are bent out of the plane of the ring and in this manner form projections <NUM> for the electrically conductive contacting of the contact elements. Projections <NUM> can point in the same direction, as shown in <FIG>, or in different directions, as shown in <FIG>.

<FIG> shows a possible application of contact ring for connecting two contact elements <NUM> and <NUM>. Due to its structure, contact ring <NUM> is elastic in several directions of expansion. On the one hand, the angle between outer <NUM> and bent-over inner sections <NUM> and therefore the expansion of contact ring <NUM> out of the plane of the ring can be varied by moving contact elements <NUM> and <NUM> towards or away from one another. On the other hand, the radius of contact ring <NUM> can be varied by expanding or compressing the meander structure, thereby increasing or reducing the circumference of contact ring <NUM>. In the example of contact element <NUM> shown in <FIG>, this property allows the radially elastic contact ring <NUM> to be pulled over a latching step <NUM> which is provided with a ramp <NUM> on one side. In the target position, contact ring <NUM> rests on a retaining ring <NUM> and is prevented from slipping off contact element <NUM> by latching step <NUM>.

The meander structure allows for a mechanically advantageous connection of the contact elements since they can be effectively decoupled and vibrations can thus be reduced. The configuration is also very variable and can be easily adapted to the given spatial conditions. For example, <FIG> show a variation of contact ring <NUM> which comprises an additional section of outer meanders <NUM> pointing out of the plane of the ring and is therefore suitable for the attachment to cylindrical contact elements. The length and shape of the cutouts pointing inwardly and outwardly can then be varied and the spatial elastic properties of contact ring <NUM> can thereby be adapted to the respective conditions. <FIG> also show variations with attachment projections which can be connected to a contact element, for example, by welding.

Claim 1:
Contact system (<NUM>) comprising at least a first (<NUM>, <NUM>) and a second (<NUM>, <NUM>) electrically conductive contact element wherein the first electrically conductive contact element is a ground cylinder (<NUM>), and the second electrically conductive contact element is a shielding cylinder (<NUM>), a contact ring (<NUM>, <NUM>) disposed within said two cylinders for connecting the at least first (<NUM>, <NUM>) and second (<NUM>, <NUM>) electrically conductive contact elements, the contact ring (<NUM>, <NUM>) being formed from:
a strip (<NUM>) comprising electrically conductive material,
wherein said strip (<NUM>) comprises a plurality of projections (<NUM>, <NUM>) on each longitudinal side,
wherein said projections (<NUM>, <NUM>) are configured such that they contact the electrically conductive materials of said contact elements and establish an electrically conductive connection therebetween,
wherein the contact ring (<NUM>, <NUM>) is connected to the first and second electrically conductive contact elements (<NUM>, <NUM>) by press-fitting, and
wherein at least some of the projections (<NUM>, <NUM>) have tips or edge sections with sharp edges that penetrate electrically insulating surface layers of the first or second electrically conductive contact elements (<NUM>, <NUM>).