Circuit card guide assembly

Details Circuit card guide assembly Circuit card guide assembly

1999-11-15

2001-05-08

Picard, Leo P. (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S816000, C361S800000, C174S034000, C174S358000

Reexamination Certificate

active

06229715

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to the provision of electromagnetic interference and electrostatic discharge shielding of an electronic system and, more particularly, to a guide assembly for circuit cards which are part of such an electronic system.
Modern electronic systems equipment, such as for telecommunications purposes, is often constructed as modular circuit cards inserted into guide slots of mechanical card cages, or shelf units, for engagement with a backplane mounted to the shelf unit at the inward ends of the guide slots. The outward edge of each circuit card is fastened to a faceplate assembly which holds a latch for releasably retaining the circuit card in the shelf unit. Although the circuit cards are relatively closely packed, there are still gaps between adjacent faceplate assemblies. There are also gaps in the faceplate assemblies to allow portions of the latches to pass therethrough. All of these gaps allow electromagnetic interference radiation to leak therethrough. In addition, the gaps allow electrostatic discharge to pass therethrough, possibly causing damage to circuit components mounted on the circuit cards. A need therefore exists to provide shielding against electromagnetic interference and electrostatic discharge for such electronic systems equipment.
It is known to provide such shielding by encasing the electronic components within a conductive housing. While this“closed door” approach is satisfactory, there exists a need to provide such shielding under“open door” conditions, for example where a door to the enclosure is open to allow access to the equipment for maintenance purposes.
These needs have been addressed, for example, by a shielding assembly disclosed in co-pending U.S. patent application Ser. No. 09/309,930, filed May 11, 1999, and assigned to the assignee of this invention. As disclosed in the referenced application, each faceplate assembly secured to a circuit card includes an elongated conductive U-shape bracket member extending at least the length of the circuit card edge with the base wall of the U-shape being orthogonal to the circuit card. Secured to one side wall of each of the bracket members is a respective resilient compressible conductive gasket which extends the length of its respective bracket member. Each bracket member has its respective gasket secured to the same corresponding side wall as all the other bracket members so that between each adjacent pair of bracket members there is a single respective gasket. This seals all the gaps between adjacent faceplate assemblies.
While the aforedescribed assembly is effective, it has been found that the circuit card faceplate width can have dimensional variation that is considered acceptable in the manufacture process. However, this accumulation of variation (tolerance build-up) along with the springiness of the gaskets between adjacent faceplates can decrease the available opening for a circuit card to plug in between previously inserted cards. The tolerance build up is such that the first few circuit cards can be plugged in, but as there are more circuit cards in an adjacent group, the faceplates and gaskets start flaring out like an“accordion”. The build up can be such that the last few circuit cards are difficult or impossible to install. Accordingly, a need exists to overcome this problem without at the same time diminishing the shielding effect of the aforedescribed assembly.
SUMMARY OF THE INVENTION
According to the present invention, a plurality of guide fins are mount ed to the front of the shelf unit. Each of the guide fins is parallel to the guide slots and the guide fins are located and spaced so that each guide fin is between a respective pair of adjacent faceplate assembly bracket member side walls.
In accordance with an aspect of this invention, an elongated bracket is secured to the front of the shelf unit and extends across the plurality of guide slots. The plurality of guide fins are formed unitarily with the bracket.
In accordance with another aspect of this invention, an elongated angle bracket is secured to the front of the shelf unit and extends across a plurality of guide slots. The angle bracket has first and second orthogonally related sides and a plurality of aligned pairs of openings. One of the openings in each pair is in the bracket first side and the other opening in each pair is in the bracket second side. Each fin includes a pair of tabs each adapted for insertion in a respective opening of a respective pair of openings.
In accordance with a further aspect of this invention, each fin includes a third tab bent orthogonally to the fin and adapted to be spot welded to one of the angle bracket sides.


REFERENCES:
patent: 4857668 (1989-08-01), Buonanno
patent: 5233507 (1993-08-01), Gunther et al.
patent: 6038138 (2000-03-01), Dayton et al.
patent: 6043991 (2000-03-01), Sorrentino
patent: 6058025 (2000-05-01), Ecker et al.

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