Electromagnetic Interference Shielding Device

The invention relates to an electromagnetic interference shielding device in the form of a contract spring element for closing a gap or clearance between housing or covering-panel members of a cabinet or rack containing electronic equipment.

From German Pat. No. 2,039,681 there is known one such shielding device, which consists of spring contact elements freely cut out of a sheet metal strip having an L-shaped cross section. The shielding device is capable of being inserted into the grooves of housing members. One housing member, e.g. a corner profile, comprises specially shaped grooves in which the contact spring strips as well as the respective neighbouring housing members (closing plates) are slipped. With the aid of the contact spring strips, the housing members are connected in an electrically conductive manner and, at the same time, electromagnetic interference shielding for the interior of the housing is provided. The disclosed type of shielding device, however, is only suitable for use with fixed housing members, hence not with doors or similar moving parts.

For the electromagnetic interference shielding of door joints there is disclosed, for example, in the German Pat. No. 2,522,186, a sealing element which is disposed in the door. In this construction, behind an angled-off door edge, there is mounted a flexible ledge. Between this ledge and a parallel-extending angle section there is clamped the flap of an electrically conducting sealing strip which is rolled over at its free end and, in this part, may be filled with an elastic core. Upon closing the door, the rolled part is compressed and establishes the contact between the door and the housing.

Another door-joint shielding is known from German Offenlegungsschrift No. 3,219,263 which, however, is only for use on the hinge side. On this side, the door panel is bent at least semicircularly, with the rounding being covered by a spring plate connected on one hand to the door and, on the other hand, to the door frame.

Finally, from German Offenlegungsschrift No. 3,210,843, there is known a contact device for housing members capable of being moved in relation to one another, in which a knife-shaped extension of one housing member comes into snap-engagement with a groove lined with contact springs, of the other housing member.

It is the object of the invention to provide an electromagnetic interference shielding device which is easy to manufacture and to assemble, and which can be used for closing gaps or clearances between stationary as well as between movable housing members. This device is to ensure a good contact-making. On the other hand, when attached to a door, the closing pressure is not to become excessively high.

This object is achieved by providing a contact spring having a generally triangular profile that is open at one point. The legs adjacent the open point are slipped over an edge of one of the housing members forming a gap, and a leg is applied to another housing member forming the gap. The advantages of this solution reside in that it not only meets the given requirements, but that the contact springs, also without any special measures, are capable of being used on the housing members. That is, they are neither in need of the guiding grooves of special sections, nor of additional mounting means. The seating of the contact springs can be improved with the aid of small flaps engaging into simple openings, which is of particular advantage in the case of moving parts, such as doors.

FIG. 1 shows a shielding device according to the invention in the shape of a contact spring, in a perspective representation,

FIG. 2 shows a double contact spring resembling the one of FIG. 1, in perspective representation, and

FIG. 3 is the cross-sectional view of a contact spring placed on to the edge of a door.

The contact springs 1 as shown in FIGS. 1 to 3 have a triangular profile which almost corresponds to that of an isosceles triangle. One of the triangular points is open, that is, where the two nearly equally long legs 2 and 3 form an acute angle. The leg 2 is bent off inwardly at its free end to form a narrow lip 4 extending almost in parallel with the connecting, short leg 9.

The free ends of the two legs 2 and 3 are each provided in their centers with a flap 5 or 6, each of which, in turn, is slightly bent toward the inside. While FIG. 1 shows one single contact spring 1, FIG. 2 shows a double contact spring 1 (as seen from the other side with respect to FIG. 1). The difference merely resides in that two contact springs are joined by a remaining web 8 on one of the legs. The two can be separated with the aid of a transversely extending incision 7 in the profile. The web 8 is appropriately within the edge area of the smooth leg 3. In this way, the contact spring 1 can be manufactured on a production line and then divided, in accordance with requirements, by cutting the web 8, into single, double or multiple contact springs. The contact spring 1 is made from a relatively thin spring plate, such as spring steel, spring bronze, etc. It is featured by small dimensions, a large spring deflection and a small pressure rise throughout the entire spring excursion. Its contact resistance is low-ohmic.

As is illustrated in FIG. 3, the contact spring 1 is simply slipped on to the edge of the housing member 10 and is self-lockingly retained in position by the flaps 5 and 6 engaging into the opening 11. In the normal position, the leg 2 is applied to the housing member 12. The housing member indicated by the reference numeral 10 is a door of a housing or cabinet or of the covering panel of a rack containing electronic equipment which, when being closed, is swivelled against the housing member or wall 12 of the housing in the direction as indicated by the arrow 13. The contact spring 1, in the course of this, deflects toward the other side as indicated by the arrow 14. By the contact spring 1 there is established a metallic connection in the gaps of the housing, so that all housing members or parts of the covering panels, such as doors, side walls, etc., are electrically connected among each other and to the racks, and are thus also grounded. At the same time, it is also easily possible to achieve RF shielding. Considering that the arrangement of the contact springs is variable, the spacings can be easily adapted to the frequencies in order thus to respectively obtain a complete shielding of the housing.