Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-08-29
2002-12-10
Martin, David (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S802000, C361S741000, C361S747000, C174S034000, C174S051000, C312S223100, C312S223200
Reexamination Certificate
active
06493235
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to guides, guide assemblies and/or guide mechanisms for use in conjunction with pluggable cartridges for inserting printed circuit cards into and for removing them from printed circuit boards. More particularly, the present invention is directed to an integral guide structure which provides a guiding, alignment and locking function. Even more particularly the present invention includes a cartridge which mates with the desired guide structure so that cartridges are firmly locked into position to permit a self-contained actuation mechanism within the cartridge to slidably move a printed circuit card within the cartridge so as to forcibly mate a card edge electrical connector to a matching printed circuit board mounted connector.
The past twenty-five or so years have seen the development of ever smaller electrical circuit components at the chip level. However, to take fullest advantage of achievements in electrical circuit miniaturization, one must package the resultant printed circuit cards containing these chips in an efficient manner. Clearly, the packaging of printed circuit cards in tight spaces is a direct logical extension of increasing chip level circuit densities. It should also be noted that the tight packaging of integrated circuit chips on printed circuit cards and the correspondingly dense packaging of the printed circuit cards is a design goal that is carried out for more than just the convenience of compactness. Compactness provides shorter distances between circuit components which, in turn, serves the very desirable goal of being able to operate the circuits effectively at higher frequencies, thus increasing the speed of numerous different forms of electrical systems, including but not limited to data processing systems.
Moreover, mainly for reasons associated with long-term system operation and reliability, it is likewise very desirable to be able to easily insert and remove these printed circuit cards even when they are disposed in very tight spaces. The insertion and removal operations are also provided as an important part of a “hot-pluggability” function which is very desirable for “on the fly” repairs, replacements, maintenance and upgrades.
With increased circuit density there has also been a concomitantly driven increase in the number of power, signal and control lines which require electrical connections to be made between printed circuit cards and printed circuit boards. This means that the electrical connectors that carry these various electrical circuits between the cards and the boards have been required to carry more and more separate individual connections. A significant consequence of the increase in the number of individual electrical connections, all of which require surety of contact, is the corresponding increase in the force needed to insert printed circuit connectors into mating printed circuit board sockets. This aspect provides special design considerations for self-contained cartridges that carry printed circuit cards which are meant to be inserted into printed circuit boards via actuating mechanisms contained within the cartridge itself.
The increase in the number of connections also poses other problems in the design of desirably compact packaging systems, particularly those designed for easy cartridge insertion and removal. In particular, the increased number of connections results in the use of connectors with an increased number of pins and socket holes. Since these structures are present in larger and larger numbers, the pin-and-socket connections (or the like) are themselves packed together with smaller and smaller distances between them. This aspect of the packaging problem brings along with it the problem of connecting pin alignment for the purpose of physically connecting oppositely disposed mating pins and socket holes. Alignment failure can severely and permanently damage both the printed circuit card and the printed circuit board into which the card is to be inserted.
Also of note is the fact that one of the principle purposes of the present invention is to provide cartridges which are capable of this self-contained insertion actuation function. Even more particularly, the present invention employs cartridges which are designed to have no physical contact with any external structure except the printed circuit board itself. This means that cartridges of the present invention do not require any form of actuation mechanism which relies upon external structures such as an enclosure, cabinet or frame or upon any form of adaptation provided in a surrounding cabinet, frame or enclosure. This also means that there are no frictional elements disposed between the printed circuit board and its surrounding structures. And this is turn implies that the entire printed circuit board may be inserted and removed as an integral, fully populated structure, that is, with a full set of printed circuit cards inserted (within cartridges). However, this desirable feature makes cartridge design more difficult in that there still must be provided some mechanism for resisting insertion forces, however, slight they may sometimes be.
Additionally, if the printed circuit board is itself intended to be inserted and removed with its complement of printed circuit cards in place, it should also be substantially rigid particularly in those circumstances in which the horizontal dimensions of the board are large with respect to its vertical height. If the printed circuit board is wide and long but thin, then insertion in particular can result in undesirable bending and flexing of the board which is commonly referred to as “oil canning.”
As an additional constraint on packaging design, it should be appreciated that, with increased circuit density, there is also a concomitant increase in power density and heat dissipation. Accordingly, packaging designs should be fully compatible with those aspects of system design associated with cooling functions. Also, to whatever extent possible, packaging designs should be: economical to produce; function smoothly; require little or no maintenance; be producible from inexpensive, readily available materials; and be reliably operable over a large number of insertion and removal operation cycles.
Yet one other concern arises in electrical systems as circuit feature size shrinks, operating frequencies increase and packaging densities grow larger, namely, the generation of electromagnetic interference (EMI). Electronic circuit packaging designs should thus also be compatible with structures and configurations that are employed to prevent the leakage of electromagnetic interference. To whatever extent possible, packaging designs should also include structures which actually contribute positively to the containment of electromagnetic interference.
Furthermore, it is noted that whatever guide and locking mechanism is employed, it is ultimately placed on the printed circuit board which is intended for printed circuit card insertion (and later removal, as needed or desired). Accordingly, the guide should be compatible with printed circuit board function and, if possible, contribute to its structural rigidity to counteract the above-mentioned oil-canning effect.
It is also noted that the present discussion refers to printed circuit boards and printed circuit cards. As contemplated herein, the printed circuit board is the larger component into which at least one printed circuit card is inserted for purposes of electrical connection. The present invention places no specific limits on either the size of a printed circuit board or the size of a printed circuit card. In the most general situation, a circuit board will be populated with a plurality of printed circuit cards. That is, the printed board will have a number of printed circuit cards inserted therein. Accordingly, as used herein, the terms “printed circuit board” and “printed circuit card” are considered to be relative terms.
Accordingly, the present inventors are presented with the following sometimes competi
Barringer Dennis R.
Notohardjono Budy D.
Seminaro Edward J.
Toffler Harold M.
Bui Hung
Cutter Lawrence D.
International Business Machines - Corporation
Martin David
LandOfFree
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