Abstract:
An electromagnetic gasket ( 110 ) combines a compressible substrate ( 300, 504/504′, 804 ) carrying a conductive material ( 302, 502, 802 ) and a hook-and-loop fastener ( 114/304, 400/504/504′, 804 ) to provide both the mechanical function of removably mounting a door ( 102 ) on a cabinet ( 100 ) and the electromagnetic function of shielding against EMI emissions even if the door becomes warped.

Description:
[0001]    This invention relates to electromagnetic interference (EMI) shielding.  
         BACKGROUND OF THE INVENTION  
         [0002]    The prior art contains myriad designs of EMI shielding gaskets for doors or access panels of cabinets for housing electrical or electronic equipment. Some designs, such as a woven conductive sheath applied over a strip of pliable foam material, or a strip of rubber impregnated with particles of conductive metal, provide a good seal against electromagnetic emissions through the space between the door or panel and the rest of the cabinet, sometimes even when the door or access panel warps. However, they require the use of a latching mechanism therewith to attach the door or panel to the cabinet and to keep it closed. The trouble of latching and unlatching the latching mechanism encourages service personnel to simply remove the door or panel and keep the cabinet open, thereby defeating the purpose of EMI shielding.  
           [0003]    Magnetic latches and gaskets, which rely upon magnetic attraction between a door or a panel and a cabinet, are also known. For example, U.S. Pat. No. 6,429,370 B1 discloses use of magnetic tape to form an EMI seal between a cabinet and a door and to adhere the door to the cabinet. The magnets are hard, that is, not compressible, physically. Therefore, a “gasket” consisting of a magnetic strip does not always provide a good seal between the door or panel and the cabinet, and may allow electromagnetic emissions to leak out if the panel or door warps.  
         SUMMARY OF THE INVENTION  
         [0004]    This invention is directed to solving these and other problems and disadvantages of the prior art. Generally according to the invention, a pliable (e.g., compressible) gasket provides both the mechanical function of keeping a door or a panel mounted on (e.g., closed and tightly sealed against) a cabinet and the electromagnetic function of shielding against EMI emissions even if the door or panel becomes warped.  
           [0005]    Specifically according to the invention, a gasket for preventing emissions of electromagnetic radiation from a cabinet having an opening and a panel for mounting over the opening comprises a first and a second half of the gasket, with the first half of the gasket comprising a first half of a self-engaging disengageable and reengageable fastener, such as a hook-and-loop fastener, for surrounding the opening, and with the second half of the gasket comprising a second half of the fastener for engaging the first half of the fastener when the panel is mounted over the opening, and a material that blocks electromagnetic radiation carried by a pliable substrate for surrounding the opening and conforming to the shape of the space between the periphery and the panel when the panel is mounted over the opening.  
           [0006]    This structure not only effectively seals the cabinet against emission of electromagnetic radiation from the cabinet, but also mounts the panel on the cabinet to keep the opening into the cabinet closed and tightly sealed, yet allows for easy removal and subsequent remounting of the panel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0007]    These and other features and advantages of the invention will become more apparent from the following descriptions of illustrative embodiments of the invention considered together with the drawing, wherein:  
         [0008]    [0008]FIG. 1 is a perspective view of an electronic-equipment cabinet that includes an illustrative embodiment of the invention;  
         [0009]    [0009]FIG. 2 is a perspective-view diagram of a first illustrative embodiment of a gasket of the cabinet of FIG. 1;  
         [0010]    [0010]FIG. 3 is a cross-section diagram of a first half of the gasket of FIG. 2.  
         [0011]    [0011]FIG. 4 is a perspective-view diagram of a second illustrative embodiment of the gasket of the cabinet of FIG. 1;  
         [0012]    [0012]FIG. 5 is a cross-section diagram of a first half of the gasket of FIG. 4;  
         [0013]    [0013]FIG. 6 is a perspective-view diagram of a third illustrative embodiment of the gasket of the cabinet of FIG. 1;  
         [0014]    [0014]FIG. 7 is a perspective-view diagram of a fourth illustrative embodiment of the gasket of the cabinet of FIG. 1; and  
         [0015]    [0015]FIG. 8 is a cross-section diagram of a first half of the gasket of FIG. 7. 
     
    
     DETAILED DESCRIPTION  
       [0016]    [0016]FIG. 1 shows a cabinet  100  for holding electronic equipment  104 . One side of cabinet  100  defines an opening  101  into cabinet  100 . Opening  101  is normally closed by an access panel (e.g., a door)  102  that is openably, and preferably removably, mounted on cabinet  100  over opening  101 . The outer periphery of opening  101  carries a first half  112  of an EMI shielding gasket  110 , while the outer periphery of panel  102  carries a second half  114  of gasket  110 .  
         [0017]    According to the invention, gasket  110  provides both the electromagnetic function of shielding against EMI emissions from equipment  104  out of cabinet  100  and the mechanical function of keeping panel  102  mounted on, closed, and tightly sealed against, the rest of cabinet  100 . Gasket  110  uses a combination of a self-engaging disengageable and reengageable fastener, such as a Velcro® hook-and-loop fastener, and a pliable (e.g., compressible) EMI shielding material to provide these functions.  
         [0018]    [0018]FIGS. 2 and 3 show a first illustrative embodiment of gasket  110 . As shown in FIG. 2, second half  114  of gasket  110  is merely a strip of one of the hook and the loop material of the hook-and-loop fastener. First half  112  of gasket  110  is shown in cross-section in FIG. 3. It comprises a material  302  that blocks EMI radiation, such as a conductive foil or a conductive woven material, and a pliable material  300 , such as foam, that carries material  302 . As shown in FIG. 3, material  302  illustratively encapsulates pliable foam material  300  which has an “I”-shaped cross-section. One channel of the “I”-shape is occupied by the other  304  of the hook and the loop material of the hook-and-loop fastener, and the other channel of the “I”-shape is occupied by an adhesive  306  that attaches first half  112  of gasket  110  to cabinet  100 . The width of second half  114  of gasket  110  is preferably no more than the width of material  304 . Of course, the positions of the two halves  112  and  114  of gasket  110  can be interchanged, with first half  112  being mounted on panel  102  and second half  114  being mounted on cabinet  100 .  
         [0019]    During use, when panel  102  is mounted on cabinet  100 , the two halves of the hook-and-loop fastened adhere to, or engage, each other, and keep panel  102  mounted on and pulled tightly against cabinet  100 . The adhesion between the two halves of the hook-and-loop fastener compresses foam  300  between panel  102  and cabinet  100  and foam  300  and material  302  conform to the shape of the space between panel  102  and cabinet  100 , thus forming a tight seal between them and compensating for any irregularities, such as those caused by buckling of panel  102 . Material  302  around foam  300  provides a double-layer of protection against electromagnetic radiation leakage out of cabinet  100 . The two halves of the hook-and-loop fastener are disengaged and panel  102  is dismounted from cabinet  100  merely by pulling panel  102  off of cabinet  100 .  
         [0020]    Use of a full strip of hook or loop material for second half  114  of gasket  110  may make removal of panel  102  from cabinet  100  too difficult because of the strength of adhesion between the two halves of gasket  110 . To adjust, or lessen, this force of adhesion, first half  114  of gasket  110  may be formed of periodically-spaced strips, instead of an uninterrupted strip, of the hook or loop material. Alternatively, the density of the hooks in the hook material may be reduced, thereby lessening the force of adhesion between the two halves of gasket  110 . Also, the two halves of gasket  110  need not be attached to cabinet  100  and panel  102  by adhesive, but rather may be attached by any desired means, e.g., rivets, screws, through-hole pop plugs, etc.  
         [0021]    A second illustrative embodiment of gasket  110  is shown in FIGS. 4 and 5. In this embodiment, first half  112  of gasket  110 , shown in cross-section in FIG. 5, is made of patches or strips  502  of the conductive shielding material woven into or adhered onto the hook or loop material  504 / 504 ′ through periodically-spaced slots  500 . In this embodiment, portion  504 ′ of material  504 / 504 ′ provides the function of foam  300  of the embodiment of FIG. 3. Second half  114  of gasket  110  is made of strips  400  of the complementary hook or loop material, with gaps  402  in-between strips  400  being sized and shaped to accommodate strips  502  when panel  102  is mounted on cabinet  100 . So long as the spacing between strips  502  of the conductive material is less than one-half the wavelength of the highest frequency of radiation that the EMI-shielding gasket  110  is to block, strips  502  of conductive material suffice. However, it is easily envisioned that, instead of using strips of material  502 , a single continuous strip  604  of the conductive material may be used and would be woven into or adhered onto material  504 / 504 ′ through a single, long, continuous slot  600 , as shown in FIG. 6. In such an implementation, only the outer portion  504  of material  504 / 504 ′ would provide the gripping action to adhere first half  112  of gasket  110  to second half  114 . In this implementation, second half  114  of gasket  110  is formed of two side-by-side strips  606  of the complementary hook or loop material with a space  608  in-between them to accommodate strip  604 , also as shown in FIG. 6.  
         [0022]    As in the case of the embodiment of FIGS. 2 and 3, illustratively a layer of adhesive  506  attaches first half  112  of gasket  110  to panel  102  or cabinet  100  in the embodiments of FIGS.  4 - 6 .  
         [0023]    A fourth illustrative embodiment of gasket  110  is shown in FIGS. 7 and 8. In this embodiment, second half  114  of gasket  110  remains unchanged from FIG. 2. But in first half  112  of gasket  110 , shown in cross-section in FIG. 8, shielding material  802  completely encapsulates hook or loop material  804  except for periodically-spaced cutouts  808 . Cutouts  808  allow hook or loop material  804  of first half  112  of gasket  110  to protrude and engage the loop or hook material of second half  114 , and second half  114  is preferably no wider than the width of cutouts  808 . Alternatively, in the embodiment of FIGS.  7 - 8 , second half  114  of gasket  110  may be constructed identically to first half  112  but using the other of the hook or loop material from the one used in the construction of first half  112 .  
         [0024]    As in the case of the embodiments of FIGS.  2 - 6 , a layer of adhesive  806  attaches first half  112  of gasket  110  to panel  102  of cabinet  100  in the embodiments of FIGS.  7 - 8 .  
         [0025]    Of course, various changes and modifications to the illustrative embodiments described above will be apparent to those skilled in the art. For example, the pliable material may be made magnetic by embedding pieces or a strip of magnet therein, and if the cabinet is magnetic (e.g., steel), the hook-and-loop fastener may be dispensed with because the magnet and the cabinet will together act as a self-engaging disengageable and reengageable fastener. Such changes and modifications can be made without departing from the spirit and the scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the following claims.