Abstract:
A system for ventilating electronic equipment and suppressing the radiation of electromagnetic interference (EMI) from the electronic equipment. More particularly, the present invention relates to a ventilation port and EMI wave-guide. There is provided corrugated spring member is compressed between a first plate and a second plate so as to define a plurality of ducts, each having a depth and a cross-sectional width. The spring member is in electrical contact with the first plate and the second plate.

Description:
TECHNICAL FIELD 
     The present invention is generally related to a ventilation port and wave-guide for suppressing electromagnetic radiation generated by an electronic component and, more particularly, is related to a system for air cooling of electronic components within an enclosure via ports. The ports are constructed to provide for attenuation of high frequency EMI radiation through the ports. 
     BACKGROUND OF THE INVENTION 
     In electronic equipment it is typically necessary to provide for cooling/ventilation of the electronic components during operation. Typical ventilation techniques incorporate air holes (ventilation ports) in the case or housing of the piece of electronic equipment to allow air flow to circulate through the case to cool the electronic components. An example of a typical configuration for cooling electronic components of a piece of electronic equipment  3  is shown in FIG.  1 . FIG. 1 shows a case  5 , having a fan  6  for inducing airflow “A” through a series of holes  10 , punched through the cabinet  5  to provide for cooling of components in the case  5 . 
     In electronic equipment which incorporate electronic devices having high operating frequencies, electromagnetic interference (EMI) is often generated by the high frequency electronic devices. This EMI can escape from the housing containing the electronic devices via typical ventilation ports  10  (FIG.  1 ). At high frequencies of operation, it is difficult to simultaneously provide for both cooling and EMI/ESD (electrostatic discharge) attenuation in an electronic equipment by simply providing for air holes (ventilation ports) in, for example, a cabinet  5  of the electronic equipment as is shown in FIG.  1 . Further, electrostatic discharge generated from external sources can radiate via the ventilation ports  10  into the case  5 . In short, while punching air holes in the sheet metal cabinet might provide for sufficient airflow A to properly cool an electronic device, such air holes typically are insufficient to provide for an appropriate level of attenuation of EMI and ESD radiation. 
     Certain properties of electromagnetic wave propagation allow for a “hole” in a sheet metal cabinet to provide for sufficient attenuation of electromagnetic wave propagation where the hole has sufficient depth. More particularly, where the depth of the hole is at least 50% or more of the maximum cross section length (diagonal), the “hole” will provide substantially greater attenuation of electromagnetic wave radiation than would be provided based simply upon the size of the hole alone. Wave-guide EMI filters have been developed in accordance with these properties. However, these wave-guide filters have typically required multiple parts and processing steps, including soldering of wave-guide components in order to obtain electrical conductivity. Thus, the cost of production of such a wave-guide is significant. These costs make the use of these types of wave-guides cost effective only for more expensive equipment or computer systems, such as mainframe computers. For smaller, less expensive electronic equipment assemblies such as individual input/output (I/O) modules including industry standard VersaModule Eurocard (VME), Compact Peripheral Component Interconnect (CPCI), and Peripheral Component Interconnect (PCI) modules, the cost of these types of wave-guides make them unfeasible. As the operational frequencies of electronic equipment, such as I/O modules, is increasing with frequencies of 2.5 GHz-10.0 GHz becoming common, a cost-effective wave-guide solution will be needed. 
     In order to attenuate the level of EMI radiated from a piece of electronic equipment, it has been common to provide for metal wave-guide structures to be used in place of typical ventilation ports or filtration screens. One example of a wave-guide structure of this type is illustrated in FIG.  2 . FIG. 2 illustrates an electronic component  3  having a case  5  that incorporates a typical wave-guide filter structure  20  (filter structure  20 ). This filter structure  20  is further illustrated in FIG.  3 A and FIG.  3 B. 
     With reference to FIG.  3 A and FIG. 3B, it can be seen that filter structure  20  is constructed of multiple individual hexagonal wave-guide tubes (ducts)  21  which are attached to each other via, for example, a solder joint or weld. The hexagonal wave tubes  21  are then attached to front and back plates  22   a  and  22   b , respectively, to form the filter structure  20 . Filter structure  20  is used as an air inlet port for a case  5  as illustrated in FIG.  2 . 
     With reference to FIG. 3B, if the individual hexagonal wave-guide tubes  21  are constructed for a depth T which is at least 50% or more of the maximum cross-section length D of the wave-guide tube  21 , then the wave-guide tube  21  will also function as an EMI filter and thus function to attenuate the radiation of any EMI radiation via the wave-guide tubes  21 . The filter structure  20  is a labor intensive structure to construct and is, thus, expensive and not suitable for less costly equipment applications in which profit margins are narrow. 
     Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system for ventilating electronic equipment and suppressing the radiation of electromagnetic interference (EMI) from the electronic equipment. More particularly, the present invention relates to a ventilation port and EMI wave-guide. Briefly described, in architecture, the system can be implemented as follows. A corrugated spring member is inserted (under tension) between a first plate and a second plate so as to establish electrical contact, as well as define a plurality of ducts, each having a depth and a cross-sectional width. 
     Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed descriptions. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
     FIG. 1 is a an illustration of a piece of electronic equipment having ventilation ports for cooling; 
     FIG. 2 is a diagram illustrating a wave-guide and ventilation port according to the prior art; 
     FIG.  3 A and FIG. 3B are detailed illustrations of a wave-guide according to the prior art; 
     FIG. 4 is a diagram illustrating an embodiment of a ventilation port and EMI seal wave; 
     FIG. 5 is a diagram illustrating a spring member  50 ; 
     FIG. 6 is a diagram illustrating nesting of spring members; 
     FIG. 7 is a diagram illustrating an alternate embodiment of the present invention; 
     FIG. 8 is a diagram illustrating a box-like structure  60  of the alternate embodiment shown in FIG. 7; 
     FIG. 9 is a diagram illustrating an embodiment of the present invention; 
     FIG.  10 A and FIG. 10B illustrate a printed circuit card in accordance with the present invention; and 
     FIG.  11 A and FIG. 11B illustrate examples of alternate corrugation patterns which can be used to form spring member  50 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 4, an embodiment of a ventilation port and EMI seal wave-guide  80  according to present invention is shown. A nested structure  70  is provided. Nested structure  70  is compressed between a plate  61  and a plate  62  so as to make an electrically conductive contact with the plate  61  and the plate  62 . The nested structure  70  is made up of spring members  50 ,  51  and  52  (see also FIG.  6 ), which are nested, or fit together, so as to form a series of ducts  53  and compressed between plates  61  and  62  to further form (enclose) ducts  54 . Each of the ducts  53  and  54 , preferably have a depth T which is 50% or greater than the longest maximum cross section (diagonal) D of the ducts  53  and  54 . 
     In FIG. 5 a spring member  50  is shown. Spring member  50  is preferably a corrugated metal sheet formed to provide a series of alternate troughs  55 . Each of troughs  55  has a width W, height H and depth T and are characterized by an open end. In an embodiment of the present invention in which only a single spring member is utilized, as opposed to the nested arrangement of two or more springs as shown in FIG. 4, the depth T of spring member  50  is preferably 50% or greater than the diagonal D in order to provide for cut-off of EMI radiation. 
     In FIG. 6, spring members  50 ,  51  and  52  are shown to illustrate how multiple spring members may be nested together to form a nested structure  70  which provides for multiple ducts  53 . At  100  in FIG. 6, it can be seen that each of the spring members  50 ,  51  and  52  have a height H1, H2 and H3, respectively. Further, the depth T of each spring member  50 ,  51  and  52  is preferably equal (FIG.  5 ). In order to achieve a desired cross sectional length (diagonal) D of duct  53 , the height H1, H2 and H3 of corrugated sheet members  52  and  51 , respectively, can be adjusted. In a preferred embodiment, the height H2 and H3 of spring members  51  and  52 , respectively, is less than the height H1 of the main spring member  50 . When spring members  51  and  52  are fit/nested with spring member  50 , ducts  53  are formed. Ducts  53  have a depth equal to the depth T of the longest spring member, for example  50  (FIG.  4  and FIG.  5 ). It will be noted that spring members  50 ,  51  and  52 , as well as plates  61  and  62  noted above, may be made of any number of metals, including, but not limited to, for example, beryllium copper or stainless steel. 
     With reference to FIG.  7  and FIG. 8, an alternate embodiment of the ventilation port and EMI seal wave-guide  80  is shown. In FIG. 7, nested structure  70  is inserted into a box-like structure  60  and provides for ducts  53  and  54 . In FIG. 8, it can be seen that box  60  includes an upper surface plate  61 , lower surface plate  62  and alternate side plates  63  and  64 . The interior of box  60  has a height Hi and a width Wi. Box  60  is constructed to accommodate the overall width, height and depth of the nested structure  70 . 
     In FIG. 9, an electronic component  3  having a case  5  is shown in which the ventilation port and EMI wave-guide  80  is incorporated to provide for ventilation and EMI attenuation. Airflow A is shown flowing through the ventilation port into the case  5  and out of the case  5  via fan  6 . Case  5  may contain an electronic device  7 . Electronic device  7  may be for example, an integrated circuit, such as a microprocessor, or other semiconductor device. Electronic device  7  is cooled/ventilated via the airflow A through case  5  and fan  6 . 
     FIG.  10 A and FIG. 10B illustrate an alternate embodiment of the present invention in which a spring member  50  is incorporated as a part of a printed circuit (PC) card  85  which includes a printed circuit board  88  having electrical edge connector  89 . More particularly, spring member  50  is connected to a spine  87  and aligned with openings formed in spine  87  via punch out tabs (flaps)  48 . Spring member  50  aligns with the openings to form ducts  44 . Ducts  44  have a depth T which is preferably 50% or greater than the diagonal D of the duct  44 . Spring member  50  is supported in place under tension on spine  87  via a support tab  49 . PC card  85  may be, for example, an Infiniband™ compliant I/O module, or a VME, CPCI, or PCI compliant I/O module. 
     It will be recognized by those skilled in the art that the corrugated sheet member  50  can be fashioned to provide for a number of corrugated patterns other than those depicted in FIG.  4  through FIG.  9 . With reference to FIG.  11 A and FIG. 11B, it can be seen that spring member  50  can be fashioned to provide for sizes  502  configured to form a generally saw-tooth pattern as shown in FIG.  11 B. Further, spring member  50  can be fashioned to provide for a generally clipped saw-tooth pattern as shown in FIG. I IA, in which the pinnacle of each saw-tooth is clipped to form a substantially flat surface  500  with angled sides  501 . 
     It should be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are merely possible examples of implementations, merely sot forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.