Patent Application
20070114060
1. Field of the Invention
The present invention relates to an electromagnetic compatibility (EMC) sealing apparatus and related method; and more particularly to a dynamic EMC sealing apparatus and method for an electrical enclosure used in computing system environments.
2. Description of Background
It is an industry goal to continuously increase the number of electronic components inside an electronic device. This goal is driven by several key and important reasons. The first and more obvious one is for the convenience of compactness. Compactness allows for selective fabrication of smaller and lighter devices that are more attractive to the consumer. Some of the reasons for such appeal stem from a desire for easier transportation, shipping, installation and storage of such devices. In other instances, when compactness per se is not a driving factor, providing the same number of devices in only a fraction of available footprint allows the remaining space to be filled with more components which will increase system performance and speed. In addition, compactness also allows many of the circuits to operate at higher frequencies and at higher speeds due to shorter electrical distances in these devices. Unfortunately, despite many of the advantages associated with this industry goal, there are several important challenges that have to be overcome by the designers of these systems.
One area where the challenges and advantages provided by such compact densities is increased is in the computer industry. The reliance of many businesses on computers and computer networks in recent years, demands an ever increasing need to provide fast and accurate systems in the smallest and lightest allowable footprint. In a computing environment, whether comprising of a simple personal computer, or a complex system comprising of a number of computers in processing communication with one another, a plurality of printed circuit boards and cards are provided that house many electronic components and even devices.
A particularly challenging area for the designers of these systems is the issue of resolving electromagnetic interference (EMI). As the number of components are increased, electromagnetic leakage concerns continue to grow. This is because every electronic device, emits some form of electromagnetic radiation. If unresolved, EMI can affect both system performance, data integrity and speed. Obviously, in larger system environments, the increased number of components that are stored in close proximity to one another, greatly increases the EMI concerns. This is because while such effects can be tolerated when few devices and components exist, the increasing number of components and devices can seriously impact system integrity and performance. This problem is further exacerbated by the improvement in semiconductor devices which allow them to operate at higher speeds, generally causing emission in higher frequency bands where interference is more likely to occur.
Prior art attempts have been made to minimize the interference problem. Electromagnetic compatibility (EMC) requires that emissions from a given device be reduced by shielding or other similar means. Such shieldings are designed not only to reduce emissions from the device itself, but also to reduce sensitivity of the device to external fields such as fields from other devices. One type of such EMI shieldings are EMI gaskets.
In recent designs, it is necessary to use a metallic type of electromagnetic gaskets to provide better conduction with an electrical enclosure in which the printed circuit boards or cards are engaged. A common problem with such gaskets, however, are that they are easily damaged as a result of deflection of gasket during insertion or removal of printed circuit cards that reside in the computing system environment during mundane activities such as during servicing calls. Once the gasket has been damaged, not only does it no longer provides EMI protection for the device but it may even pose a threat for a potential short.
Related patent U.S. Pat. No. 6,794,571 by Barringer et al. (hereinafter Barringer patent), owned by the same assignee, International Business Machines Corporation, and coauthored by at least some of the inventors of this application, provided a method and apparatus for providing an electromagnetic conduction seal in a device disposed within an electrical enclosure including a metal EMC gasket.
Related patent solved the prior art problem of minimizing damages to such gaskets. This is especially true with EMC metal gaskets that have a spring design. In such gaskets, often one end of the gasket is only attached to a chassis with the other end left hanging without any retention. This other end is especially vulnerable to being damaged by being for example caught in some other object. The Barringer patent introduced a retention mechanism that provided for a lock strip to be fixed to the device. The gasket in that patent was secured to a device that provided limits of deflection of an intermediate portion to the gasket using an external part.
While the Barringer patent solves many of the prior art problems, it is desirable to introduce a mechanism that can be fabricated at the same time as the chassis itself. In addition, providing a mechanism that does not provide a lock strip can allow the gasket to be used in environments where the installation or later exposure to high temperatures (such as caused by heat dissipation issues) can cause the lock strip to come unhinged. An example would be where glue is used and heat or installation can cause the glue to come undone.
The shortcomings of the prior art are overcome and additional advantages are provided through the method and associated apparatus for providing an electromagnetic seal in electrical enclosure of a device. The apparatus comprising of an electromagnetic gasket formed of a thin conductive material, having a first end and an opposing end. The apparatus also includes a conductive chassis disposed in the electrical enclosure and having protrusions for securing at least one end of the gasket. The other end of the gasket is also secured to the chassis in a manner to provide facility of compression. The other end of the gasket is secured to the chassis either through adhesive bonding, through use of other alternate protrusions or another similar manner.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features, refer to the description and to the drawings
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The embodiments provided in conjunction with the following figures provide for a preferred embodiment where the EMC gasket of present embodiment is disposed in a computing environment. It should be noted that this embodiment is only provided for ease of understanding and the teaching of the present invention can equally apply to other devices and in conjunction with other electrical disclosures.
FIGS. 5 provides a cross sectional illustration of one embodiment of the present invention. The illustration of
Before discussing the unique features comprising the EMC gasket of the present invention,
Elements referenced as 24 and 26 in
In addition to the removal of the cover 10, the illustration of
The removal of the cover 10 provides for a view of cavity 14 and walls 12. Referring back to
The components 24 and 26 as discussed in
The housing wall 12 also preferably includes other elements such as a cable opening 18 (shown in
The printed circuit board 16 is disposed inside the cavity 14 of the docking apparatus 1. In the example of
In
In the isometric view of
The linkage mechanism includes linkage arm 83 and clevis 84 which can be pivotally coupled to the linkage arm 83 and configured to receive a shaft 88 at one end, while an opposing end includes a thread 86 engaged with an operably fixed nut (not shown) secured to either housing 2 and or housing bezel 6. In one embodiment, linkage mechanism 4 can be operably mounted within housing cavity 14 via a complimentary configured aperture 89 for receiving linkage mounting screw 91 allowing pivotal movement of linkage arm 83 about screw 91 or with any other suitable mounting device as known to those skilled in the art, including but not limited to a clip. Furthermore, linkage mechanism 4 is operably mounted within housing cavity 14 via the nut operably secured to housing bezel 6 and associated with thread 86.
Linkage arm 83 include first and second linkage arms 92 and 94 respectively substantially extending from aperture 89 and preferably perpendicular to one another. First link arm can also include an aperture provided for operable connection with corresponding aperture 98 shown and aligned therewith so as to connect printed circuit board 16 to first link arm 92 (also see
The gasket 400 as illustrated in the embodiment of
In conclusion of the discussion relating to topography and placement of the gasket, the focus can now be turned back to the illustration of
FIGS. 5 provides a cross sectional depiction of one of the gasket 400. It should be noted, that since a cross sectional view is provided, however, the gasket 400 as a whole is not visible and only the shape of a single strip 405 is visible. Since all such segments 405, however, are nearly identical in this embodiment and the gasket 400 is provided of a plurality of such strips, discussing the topography of a single segment 405 of the gasket 400 also reveals the topography of the gasket 400 as a whole.
In the illustration of
Gasket segment 405 is fabricated of a thin sheet of a conductive material, referenced as 505. In a preferred embodiment the gasket 405 is fabricated out of a thin sheet of metal, such as copper. The thin sheet of material 505 has opposing ends respectively referenced as 501 and 502 and top and bottom surfaces 503 and 504 respectively.
One of the ends 501 of the thin sheet of material (505) forming the gasket section 405 is disposed over the chassis 500 and adhesively bonded (510) to its top side 503. The thin sheet of material 505 is then looped around and secured to the chassis at its opposing end 502 by the use of the protruding element 550 as illustrated in such a manner that it provides facility of compression. The length of the strip 505 along with the percentage of strip 505 that is adhesively bonded to the chassis 505 determines the flexibility of the gasket 400 as a whole. In the illustration of
It should be noted that in a preferred embodiment, the gasket is made out of a single sheet transversally segmented, for example by creating slits selectively preferably such that the opposing ends of the gasket/material are not segmented (and still connected) and the gasket can be put in place as a single units. The slits, once the gasket is secured, form individual loops that independently enhance compression of the gasket. In such an embodiment, the portion that is being marked for adhesive bonding and the end disposed under the protruding element 550, for example, have not slits cut out on them.
The protruding element 550 serves multiple functions. The more obvious purpose of the protruding element 550 is to hold the gasket securely at one end and also allow the gasket to maintain its ability to compress. A less obvious purpose is that since the protruding element 550 is preferably made of the same rigid material that forms the chassis 500, it provides support to the thin gasket material such that gasket is not easily torn, damaged or displaced.
The number of the protruding elements provided can also be selectively adjusted to provide more protection if desired. In a functional regard, it is not necessary to have more that a few protruding element for the entire gasket. In such a respect, it would only be necessary to provide a protruding element for every few strip 405. The few protruding element will hold the gasket 400 securely, but if more secure fastening is desired, the number of elements 550 as discussed above can be increased.
The illustration of
While the preferred embodiment to the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.
This application contains subject matter which is related to the subject matter of the following co-pending applications, filed on the same day, which is assigned to the same assignee as this application, International Business Machines Corporation of Armonk, New York. The application listed below is hereby incorporated herein by reference in its entirety the following U.S. Pat. No. 6,794,571
