Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-02-10
2001-11-06
Gaffin, Jeffrey (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S740000, C361S752000, C361S756000, C361S759000, C361S800000, C361S802000, C361S818000
Reexamination Certificate
active
06313997
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to communication systems, and is particularly directed to a printed circuit card housing architecture having upper and lower perforated card metallic guide panels, that contain staggered arrangements of bumps distributed among a matrix of air flow perforations in the panels, the bumps forming card installation channels for guiding printed circuit boards into engagement with backplane connectors therefor, while providing minimal interruption of cooling air flow perforations, without EMI leaks.
BACKGROUND OF THE INVENTION
Telecommunication equipment installations customarily employ electronic hardware racks, respective shelves of which have backplane connectors into which printed circuit boards are inserted. For this purpose, a typical housing architecture may contain mutually aligned sets of elongated U-shaped card guides that are affixed to upper and lower frames of the shelf. These card guides are sized to receive and guide upper and lower edges of printed circuit boards into physical and electrical engagement with backplane connectors, that are vertically installed in a side-by-side arrangement at a backplane of the shelf. The front edge of each printed circuit board is usually terminated by a face plate, having a latch that engages the shelf frame, when the printed circuit board is fully inserted into its slot, so that the front plates of multilayer printed circuit board forms a front panel closure for the shelf.
With such a compact and nested arrangement these are two operational issues that must be addressed: providing sufficient air flow over the printed circuit boards for cooling; and constraining electromagnetic interference (EMI). To constrain EMI emissions, the shelf is customarily surrounded by conductive (metallic) shielding plates, two of which serve as upper and lower mounting supports for the mutually aligned sets of card guides. In order to provide air flow to the printed circuit boards, a plurality (e.g. matrix) of holes or perforations may be formed in each mounting plate.
Unfortunately, this configuration suffers from several drawbacks. First, in order to support the card guides, the perforated mounting plates must have sufficient thickness for rigidity and strength. Secondly, because of the presence of the card guides, relatively large air flow apertures must be formed in the mounting plates between the card insertion channels in order to afford adequate air flow to the cards. However, since large air flow apertures undesirably provide a path for EMI emissions, it is necessary to install additional perforated EMI shielding plates adjacent to the card guide mounting plates. Such additional shielding plates undesirably increase hardware volume, complexity and cost, especially since a different tooling set is required for each type of shelf arrangement.
SUMMARY OF THE INVENTION
In accordance with the present invention, the shortcomings of conventional printed circuit board housing architectures described above are effectively obviated by a new and improved shelf structure having upper and lower perforated guide panels, or sheet metal plates, that contain mutually opposed staggered arrangements or patterns of bumps or ‘upsets’. As will be described these mutually opposed bump arrangements form guide channels for guiding printed circuit boards into engagement with respective card slot backplane connectors, thereby eliminating the need for attachment of a separate set of card guides.
The patterns of card guide upsets are arranged so as to direct, yet constrain, the travel paths of printed circuit boards from their points of insertion through grooves in rails at the front of the chassis to the backplane connectors, while providing minimal interruption of a matrix or gridwork of air flow perforations through the sheet metal plates. The upsets themselves do not penetrate the sheet metal plates, so that there are no EMI leaks, thus eliminating the need for and assembly of additional perforated plates. The staggered pattern of upsets is the same for each card slot, so that a single punch tool can be configured to be engaged in a numerically controlled (NC) press, with the pitch between bumps programmably variable, thereby providing a much less costly tool, that is applicable to a variety of shelf shapes and sizes.
REFERENCES:
patent: 4519016 (1985-05-01), Bradley et al.
patent: 5019948 (1991-05-01), Steketee et al.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Gaffin Jeffrey
Pliant Systems, Inc.
Vu Phuong T.
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