Electronic equipment shelf with blank for unequipped position

Details Electronic equipment shelf with blank for unequipped position Electronic equipment shelf with blank for unequipped position

1999-02-12

2001-10-30

Joyce, Harold (Department: 3744)

Ventilation

Electronic cabinet

C361S695000

Reexamination Certificate

active

06309295

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the packaging of electronic apparatus in an equipment shelf. More particularly, the invention relates to the use of a blank in an unequipped shelf position to equalize airflow back pressure in the shelf, and to retain optical cables provided for future use at the unequipped position.
BACKGROUND OF THE INVENTION
Complex electronic apparatus may require the interconnection of thousands of individual electronic devices. To manage the large number of required interconnections, such apparatus is often configured by affixing devices to a circuit boards (circuit packs), and by interconnecting these circuit packs via one or more printed wire backplanes. Collections of interconnected circuit packs are often contained in housings referred to as equipment shelves.
As circuit and power densities increase, heat dissipation presents a significant challenge. Increasingly, forced air convective cooling is used in equipment shelves to provide the required cooling capacity. In a typical shelf configuration, circuit packs are positioned vertically with sufficient spacing to allow for airflow between adjacent packs. Airflow is generated by fans located above or below the shelf, and directed past the packs by enclosing the sides, rear and front of the shelf to be relatively airtight. Air flowing past the boards carries heat away from the electronic devices on the boards, and is then exhausted from the shelf. Ambient air is drawn into the shelf by the fans to refresh and continue the airflow.
The effectiveness of this approach can be impacted by imbalances in the equipment shelf. For example, to allow for future increases in system capacity, fewer than all circuit pack positions may be equipped. Fan assemblies for shelves that are partially equipped may generate uneven airflow backpressures across the equipped and unequipped positions.
In an equipped position, electronic devices are present in the airflow path, and these devices create resistance and an associated pressure drop over the airflow path. In an unequipped position, no electronic devices sit in the airflow path, and pressure differentials over the path are substantially less. Because air moving through the shelf seeks a path of least resistance, the presence of unequipped positions leads to an increased airflow through the unequipped positions and a decreased airflow through the equipped positions. While fans with increased capacity can substantially overcome this problem, they may also generate increased noise, require added space, consume additional power, generate additional cost, and experience reduced life. In addition, fan failures may occur, increasing the risks of overheating and reducing the life of the electronic devices.
SUMMARY OF THE INVENTION
Uniform airflow backpressure is substantially maintained across airflow paths in partially-equipped equipment shelves through use of a novel circuit pack blank for unequipped positions. Each blank includes a base for retaining the blank in an unequipped position, and one or more diffuser blades attached to the base to create resistance in an adjacent air plenum. The diffuser blade is designed to generate a backpressure in the adjacent air plenum that is substantially equivalent to backpressures generated in air plenums adjacent to the equipped positions.
In a preferred embodiment of the blank, two diffuser blades are attached to the base to provide resistance both at the entrance and exit of the adjacent airflow path. In addition, the blank incorporates a faceplate that supports insertion and removal, and that contains a novel tray for retaining associated cables in position for future use. In a preferred embodiment of the shelf, the blank is inserted into an unequipped position in the shelf via an apparatus guide, and positioned so that an air plenum is formed between the blank and an adjacent equipped position. The diffuser blades attached to the blank effectively reduce the cross-sectional area of this air plenum, so that a backpressure generated by air flow in the air plenum is substantially equivalent to a backpressure generated by air flow in an air plenum adjacent to the equipped position.


REFERENCES:
patent: 4620265 (1986-10-01), Lerude et al.
patent: 4659349 (1987-04-01), Rodi et al.
patent: 5361188 (1994-11-01), Kondou et al.
patent: 5544012 (1996-08-01), Koike
patent: 5563768 (1996-10-01), Perdue
patent: 5707282 (1998-01-01), Clements et al.
patent: WO 98/21922 (1998-05-01), None
D. Flockton, “It's all in the packaging”,Mechanical Engineering, Feb. 1999, pp. 58-59.

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