Abstract:
An enclosure protects electronic equipment from physical contact and electromagnetic interference. The enclosure includes a base portion which is attachable to a circuit board and which surrounds all sides of the electronic equipment. A cover is attachable to the base in order to cover the top of the electronic equipment. The cover is attachable to the base by snap-in tangs formed on the base which cooperate with projections formed on the cover. The base is attachable to the circuit board by snap-in fasteners formed on the base. The base and the cover are made of a material which reflects and/or absorbs EMI. The EMI shielding enclosure protects the electronic equipment and allows access to the electronic equipment for replacement or repair without having to take the time to manipulate separate mechanical fasteners.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to shielding of electromagnetic interference (EMI). More particularly, the present invention relates to a snap-in enclosure for shielding (EMI) from electronic equipment. 
     2. Description of Related Art 
     Electronic equipment is often sensitive to physical contact as well as electromagnetic fields. For example, electronic equipment which operates at a radio frequency (r.f) level is very susceptible to EMI from radio frequency fields. Accordingly, EMI sensitive electronic equipment is usually enclosed within a housing which protects the electronic equipment from physical contact and from EMI. In addition, electronic equipment which produces EMI may also be enclosed within a housing to protect adjacent EMI sensitive electronic equipment. 
     It is often necessary to provide enclosures on a circuit board in order to protect various pieces of electronic equipment mounted on the circuit board. Enclosures of this type are usually made of a material which either reflects or absorbs electromagnetic radiation. These housings usually include some type of a mechanical fastener for opening and closing the housing to gain access to the electronic equipment inside. Mechanical fasteners such as threaded fasteners provide a sufficient connection between parts; however, access to the electronic equipment is very time consuming which increases the cost of repair. The threaded fasteners must be detached and then reattached once repairs are completed. 
     Accordingly, there is a need for an enclosure which protects electronic equipment from EMI and which allows quick access to the electronic equipment without having to detach numerous mechanical fasteners. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an alternative technique for shielding electronic equipment from EMI which makes up for the above-mentioned deficiencies. 
     It is another object of the present invention to decrease the time required to gain access to the electronic equipment in order to decrease the cost of electronic equipment manufacture, repair and testing. 
     It is yet another object of the present invention to provide an enclosure which can be made in small and large sizes and in various shapes to accommodate numerous applications. 
     These and other objects of the present invention are fulfilled by providing an enclosure for protecting electronic equipment from electromagnetic interference comprising a base made of an EMI absorbing or reflecting material which includes a plurality of fastening elements and at least one securing element formed thereon. Furthermore, a cover made of an EMI absorbing or reflecting material includes at least one securing element formed thereon for engaging with the securing element on the base. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a perspective view of an EMI shielding enclosure according to a first embodiment of the present invention; 
     FIG. 2 is a left side elevational view of the enclosure of FIG. 1; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a top perspective view of the cover of the enclosure according to the first embodiment of the present invention, 
     FIG. 5 is a bottom perspective view of the cover of the enclosure according to the first embodiment of the present invention; 
     FIG. 6 is a top perspective view of the base of the enclosure according to a second embodiment of the present invention; 
     FIG. 7 is a bottom perspective view of the base of the enclosure according to the second embodiment of the present invention; 
     FIG. 8 is a detail view of a retaining tab of FIG. 7; 
     FIG. 9 is a detail view of a snap-in fastener of FIG. 7; 
     FIG. 10 is a perspective view of the enclosure according to a third embodiment of the present invention; 
     FIG. 11 is a top view of the enclosure according to the third embodiment of the present invention; 
     FIG. 12 is a top perspective view of the base of the enclosure according to the third embodiment of the present invention; 
     FIG. 13 is a bottom perspective view of the base of the enclosure according to the third embodiment of the present invention; 
     FIG. 14 is a cross-sectional view of the enclosure taken along the line  14 — 14  of FIG. 11; 
     FIG. 15 is a cross-sectional view of the enclosure taken along the line  15 — 15  of FIG. 10; 
     FIG. 16 is a top perspective view of the cover of the enclosure according to the third embodiment of the present invention; 
     FIG. 17 is a bottom perspective view of the cover of the enclosure according to the third embodiment of the present invention; 
     FIG. 18 is a perspective view of the enclosure according to a fourth embodiment of the present invention; 
     FIG. 19 is a top view of the enclosure according to the fourth embodiment of the present invention; 
     FIG. 20 is a cross-sectional view of the enclosure taken along the line  20 — 20  of FIG. 19; 
     FIG. 21 is a top perspective view of the base of the enclosure according to the fourth embodiment of the present invention; 
     FIG. 22 is a bottom perspective view of the base of the enclosure according to the fourth embodiment of the present invention; 
     FIG. 23 is a top perspective view of the cover of the enclosure according to the fourth embodiment of the present invention; 
     FIG. 24 is a bottom perspective view of the cover of the enclosure according to the fourth embodiment of the present invention; 
     FIG. 25 is a top perspective view of the enclosure according to a fifth embodiment of the present invention; 
     FIG. 26 is a bottom perspective view of the enclosure according to the fifth embodiment of the present invention; 
     FIG. 27 is a top view of the enclosure according to the fifth embodiment of the present invention; 
     FIG. 28 is a cross-sectional view of the enclosure taken along the line  28 — 28  of FIG. 27; 
     FIG. 29 is a detail view of a connection between the cover and the base of the enclosure of FIG. 28; 
     FIG. 30 is a detail view of a snap-in securing tang of FIG. 28; 
     FIG. 31 is a perspective view of the base of the enclosure according to the fifth embodiment of the present invention; and 
     FIG. 32 is a perspective view of the cover of the enclosure according to the fifth embodiment of the present invention; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described with reference to the accompanying drawings. It is noted that the same reference numerals are used to indicate the same or similar elements throughout the several views. 
     Referring in detail to FIGS. 1-5, an EMI shielding enclosure  1  according to a first embodiment of the present invention includes a base  3  and a cover  5 . The base  3  includes a plurality of side walls  7  connected to each other end-to-end and forming a space therebetween. 
     Referring specifically to FIGS. 1-3, each of the plurality of side walls  7  includes at least one snap-in fastener  9 . The snap-in fasteners  9  are used to connect the base  3  to a circuit board (not shown) which includes electronic equipment thereon. Each of the snap-in fasteners  9  includes a narrow end portion  11  and a wide portion  13 . The snap-in fasteners  9  are aligned with holes (not shown) in the circuit board and are pushed in through the holes in order to secure the base  3  to the circuit board. The snap-in fasteners  9  flex in order to allow the wide portion  13  to pass through the holes so that the circuit board is located between the wide portions  13  of the snap-in fasteners  9  and a lower surface  15  of each of the side walls  7 . 
     Referring to FIGS. 1 and 3, one of the side walls  7  includes a recessed portion  17  which allows the cover  5  to slide onto the base  3 . The recessed portion  17  is formed by a top of the side wall  7  being shorter than the remaining side walls  7 . Furthermore, the side wall opposite to the side wall with the recessed portion  17  includes two snap-in securing tangs  19  for engaging with the cover  5 . The remaining side walls  7  include reinforcing tabs  21  which also engage an upper surface of the cover  5 . 
     Referring to FIG. 3, a lip  23  extends from the side wall  7  below each of the snap-in securing tangs  19 . The lips  23  engage with the cover  5  to hold the cover  5  in a proper vertical location on the base  3  and in contact with the snap-in securing tangs  19 . The lips  23  are illustrated in FIG. 3 as square-shaped projections formed on an inner surface of the side wall  7 ; however, the lips  23  can be of any shape as long as they are sufficiently sized to hold the cover  5  in position. 
     Referring now to FIGS. 4 and 5, the cover  5  includes a generally planar body portion  25  with an enlarged end  27  and a narrow end  29 . An upper surface  31  of the cover  5  includes two projections  33  formed thereon for engaging with the snap-in securing tangs  19  of the base  3 . Referring to FIG. 5, a bottom of the cover  5  includes an edge having a first recessed cut-out portion  35  formed therealong. Furthermore, the enlarged end  27  includes a second recessed cut-out portion  37  formed on a bottom surface thereof Referring to FIG. 3, the first recessed cut-out portion  35  is for engaging with the lips  23  when the cover  5  is attached to the base  3 . Furthermore, the second recessed cut-out portion  37  is for engaging with an upper surface of the side wall  7  which includes the recessed portion  17 . 
     The operation of the first embodiment of the present invention will now be described with reference to FIGS. 1 and 3. First, the base  3  is attached to a circuit board by aligning the snap-in fasteners  9  with holes formed in the circuit board (not shown). The snap-in fasteners are designed for easy alignment, since the narrow end portions  11  readily fit in the holes in the circuit board. The snap-in fasteners  9  are secured by pushing the base  3  toward the circuit board to engage the snap-in fasteners  9  within the holes formed in the circuit board. The snap-in fasteners  9  flex in order to allow the wide portion  13  to pass through the holes formed in the circuit board so that the circuit board is located between the wide portions  13  of the snap-in fasteners  9  and the lower surface  15  of the base  3 . 
     Second, the narrow end  29  of the cover  5  is inserted into the recessed portion  17  of the side wall  7 . The body portion  25  of the cover  5  is slid below the reinforcing tabs  21  and the narrow end  29  is brought into engagement with the lips  23  formed on the side wall  7 . Furthermore, the projections  33  formed on the upper surface  31  of the cover  5  engage the snap-in securing tangs  19  to retain the on the base  3 . 
     Referring to FIG. 3, the recessed portion  17  includes a projecting portion  18  for engaging with the second recessed cut-out portion  37  formed in the enlarged end  27 . A lower surface  22  of the reinforcing tabs  21  tapers toward the recessed portion  17 . Furthermore, the lips  23  are located a predetermined distance below the snap-in securing tangs  19  so that the cover  5  slides in at an angle. The angular sliding of the cover  5  allows several enclosures  1  to be located adjacent to each other in close proximity without interference between adjacent enclosures when a cover  5  is removed or attached. 
     The cover  5  can be easily removed from the base  3  by merely pressing down on the upper surface  31  of the cover  5  adjacent to the snap-in securing tangs  19  in order to disengage the projections  33  from the snap-in securing tangs  19 . The cover  5  is then slid away from the lips  23  and out of the recessed portion  17  in order to disengage the cover  5  from the base  3  to allow access to the electronic equipment which is secured to the circuit board within the base  3 . 
     A second embodiment of the present invention will now be described with reference to FIGS. 6-9. The second embodiment of the present invention is substantially the same as the first embodiment; however, instead of providing the lips  23  below each of the snap-in securing tangs  19  as in the first embodiment, a plurality of elongated lips  39  are provided on three of the side walls  7  between the snap-in securing tangs  19  and the reinforcing tabs  41 . Furthermore, elongated lips  39  are provided extending from adjacent the reinforcing tabs  41  to a position adjacent to the side wall  7  which includes the recessed portion  17 . The elongated lips  39  engage the first recessed cut-out portion  35  formed in the cover  5 . The cover  5  of the first embodiment illustrated in FIGS. 4 and 5 is usable in the second embodiment as well. 
     Referring to FIG. 8, a detail view of the reinforcing tab  41  is shown. The reinforcing tab  41  includes a projecting portion  42  formed thereon. The projecting portion  42  engages the upper surface  31  of the cover  5  when the cover  5  is attached to the base  3 . The elongated lips  39  and the reinforcing tab  41 , according to the second embodiment of the present invention, provide a more secure attachment between the cover  5  and the base  3 . Therefore, the protection against EMI is enhanced. 
     Referring to FIG. 9, a detail of one of the snap-in fasteners  9  is illustrated. The snap-in fastener  9  includes the narrow end portion  11  and the wide portion  13  substantially the same as in the first embodiment. The shape of the snap-in fasteners  9  promote ease of assembly. The narrow end portions  11  readily fit in the holes in the circuit board and the wide portions  13  sit on a top of the hole until they are pressed through the holes by application of a force on the base  3 . FIG. 9 also illustrates the lower surface  15  of the base  3  including a curved portion  14  formed thereon. The lower surface  15  of the base  3  may engage a complimentary groove (not shown) formed in the circuit board. It is noted however, that the lower surface  15  of the base  3  may have a flat construction for engaging with a flat surface of the circuit board. Alternatively, the curved portion  14  may be used with a circuit board which does not include a complimentary grooved portion. Other shapes may also be used for the lower surface  15  and the snap-in fasteners  9  as long as the base  3  is securely held to the circuit board. 
     The operation of the second embodiment of the present invention is similar to the operation of the first embodiment. The base  3  is secured to a circuit board by pushing the snap-in fasteners  9  through holes formed in the circuit board. The cover  5  is then inserted, narrow end  29  first, through the recessed portion  17  formed in one of the side walls  7 . The first recessed cut-out portion  35  of the cover  5  engages with the elongated lips  39  and is slid under the reinforcing tabs  41 . The narrow end  29  of the cover  5  is inserted under the snap-in securing tangs  19  so that the snap-in securing tangs  19  engage with the projections  33  formed on the upper surface  31  of the cover  5 . Furthermore, the projecting portion  18  engages with the second recessed cut-out portion  37  formed in the enlarged end  27  of the cover  5 . 
     Referring again to FIG. 8, the projecting portions  42  include an angled lower surface and the elongated lips  39  are angled downwardly to allow the cover  5  to slide downwardly along the elongated lips  39  to a position substantially the same as the position of the cover  5  in the first embodiment. Once again, the angular sliding of the cover  5  allows enclosures  1  to be located adjacent to each other without interfering with each other. 
     The cover  5  can be easily removed from the base  3  by merely pressing down on the upper surface  31  of the cover  5  adjacent to the snap-in securing tangs  19  in order to disengage the projections  33  from the snap-in securing tangs  19 . The cover  5  is then slid along the elongated lips  39  and out of the recessed portion  17  in order to disengage the cover  5  from the base  3  to allow access to the electronic equipment which is secured to the circuit board within the base  3 . 
     A third embodiment of the present invention will now be described with reference to FIGS. 10-17. The third embodiment of the present invention is substantially the same as the first and second embodiments of the present invention, except that the base  3  includes only one snap-in securing tang  19  and no reinforcing tabs  21  or  41  are provided. Furthermore, instead of providing the lips  23  or the elongated lips  39  on three of the side walls, as in the first and second embodiments, a groove  45  is formed on an inside surface of the three side walls  7  extending generally around the entire circumference of the three side walls  7 . This arrangement is advantageous since there are no spaces remaining between the cover  5  and the base  3  which would allow electromagnetic radiation to pass therethrough. 
     Although the third embodiment includes only one snap-in securing tang  19  and no reinforcing tabs  21  or  41 , it will be understood that additional snap-in securing tangs  19  can be provided and that reinforcing tabs  21  or  41  may also be provided in order to further enhance the connection between the cover  5  and the base  3 . Not providing securing tangs  19 ; however, makes more space available within the base  3  for testing or repair of the electronic equipment within the base. 
     Referring to FIGS. 12 and 13, the groove  45  is angled downwardly away from the recessed portion  17 . Furthermore, the groove  45  is located a predetermined distance away from the snap-in securing tang  19  so that the cover  5  slides in at an angle to a position as illustrated in FIG.  15 . 
     Referring to FIGS. 16 and 17, the cover  5  includes a third recessed cut-out portion  47  formed along the edges of upper surface  31  of the body portion  25  as well as the first recessed cut-out portion  35  formed along the edges of the bottom of the cover  5 . This allows the edges of the cover  5  to slide within the groove  45  formed in the base  3 . The cover  5  also includes one projection  33  formed on the upper surface  31  for engaging with the snap-in securing tang  19  formed on the base  3 . 
     The operation of the third embodiment of the present invention is substantially the same as the first and second embodiments. The base  3  is first secured to the circuit board (not shown) by snapping the snap-in fasteners  9  through holes formed in the circuit board. The narrow end  29  of the cover  5  is then inserted through the recessed portion  17  formed in one of the side walls  7  and slid along the groove  45  so that the narrow end  29  is located beneath the snap-in securing tang  19  in order to engage the projection  33  formed on the cover  5  with the snap-in securing tang  19 . 
     The cover  5  can be easily removed from the base  3  by merely pressing down on the upper surface  31  of the cover  5  adjacent to the snap-in securing tang  19  in order to disengage the projection  33  from the snap-in securing tang  19 . The cover  5  is then slid along the groove  45  in order to disengage the cover  5  from the base  3  to allow access to the electronic equipment which is secured to the circuit board within the base  3 . 
     A fourth embodiment of the present invention will now be described with reference to FIGS. 18-21. The fourth embodiment of the present invention is substantially similar to the first through third embodiments; however, the cover  5  includes a curved body  55 . The cover  5  is curved in order to decrease interference with adjacent parts and adjacent enclosures  1 . Referring to FIGS. 21 and 22, the base  3  includes a lip  57  extending from an upper surface  59  of the base  3 . The lip  57  is divided into separate pieces by cut-out portions  61 . Furthermore, a plurality of tabs  63  are provided below the lip  57  and aligned with the cut-out portions  61 . 
     Referring to FIGS. 23 and 24, the cover  5  includes a pair of projecting tabs  65  which engage with the cut-out portions  61  formed in the side wall  7  which is opposite to the side wall which includes the recessed portion  17 . The cover  5  includes a recessed cut-out portion  67  formed along the edge of the upper surface  31  thereof. The projecting tabs  65  extend into this recessed cut-out portion  67 . 
     The operation of the fourth embodiment of the present invention is similar to the operation of the first through third embodiments. Specifically, the base  3  is secured to a circuit board (not shown) by pushing the snap-in fasteners  9  through holes formed in the circuit board. The cover  5  is then inserted through the recessed portion  17  and slid along the lip  57  such that it is below the lip  57  and above each of the tabs  63 . The lip  57  engages the cut-out portion  67  of the cover  5 . The narrow end  29  of the cover  5  is then slid to engage the projecting tabs  65  within the cut-out portions  61  formed on the side wall  7  opposite to the side wall with the recessed portion  17 . The cover  5  is then securely attached to the base  3  in order to protect the electronic equipment within the base  3  from electromagnetic radiation. 
     Referring to FIGS. 18-20, when the cover  5  is attached to the base  3 , the upper surface  59  of the base  3  and the upper surface  31  of the cover  5  form a single continuous surface. The upper surface  59  of the base  3  is curved in order to accommodate the curvature of the cover  5 . 
     In order to remove the cover  5  from the base  3 , the cover is slid out of the base  3  in the reversed direction to the inserted direction. It is unnecessary to press down on the cover  5 , since there are no snap-in securing tangs which must be disengaged. The geometry of the curved body  55  ensures that the cover  5  remains in place without the necessity of providing snap-in securing tangs. Furthermore, it is envisioned that the curvature of the curved body  55  and/or the recessed cut-out portion  67  would be slightly greater or less than the curvature of the lip  57  of the base  3 . Therefore, the natural resilience of the curved body  55  and/or the recessed cut-out portion  67  would cause frictional engagement to assist in holding the cover  5  in the closed position. 
     A fifth embodiment of the present invention will now be described with reference to FIGS. 25-32. The enclosure  71  according to the fifth embodiment of the present invention includes a base  73  and a cover  75 . The base  73  includes a plurality of side walls  77  connected to each other to form a space therebetween. A plurality of snap-in fasteners  79  are formed on a lower surface of the side walls  77 . Furthermore, a plurality of snap-in securing tangs  89  are formed on each of the side walls  77  extending parallel to the side walls  77 . The snap-in tangs  89  cooperate with projections  83  formed on the cover  75 . Furthermore, the base  73  includes a plurality of cut-out portions  81  formed in an upper surface  82  of each of the side walls  77 . The cut-out portions  81  each receive a tab  84  formed on the cover  75 . 
     Referring to FIG. 31, the base  73  includes a lip  85  formed along an inside surface of each of the side walls  77 . The lip  85  includes a plurality of gaps  87  which are located aligned with each of the snap-in securing tangs  89 . Referring to FIG. 32, the lip  85  engages a shoulder  91  which is formed by a recessed portion of the cover  75 . 
     The fifth embodiment of the present invention operates in a manner different than the first through fourth embodiments. The fifth embodiment is specifically used in areas where insufficient access to the enclosure is provided on sides of the enclosure. The cover  75  is inserted from the top of the base  73  in a vertical direction. The cover  75  is pushed into the space formed by the base  73  so that each of the projections  83  align with a respective snap-in securing tang  89  and each of the tabs  84  align with a respective cut-out portion  81  formed in the base  73 . The cover is pushed downwardly until it reaches a position as illustrated in FIGS. 25-30. In this position, the upper surface  93  of the cover  75  is generally parallel to the upper surface  82  of the base  73 . Furthermore, the shoulder  91  of the cover  75  engages the lip  85  of the base  73 . 
     In order to gain access to the electronic equipment within the base  73 , one needs to use a tool such as a screw driver to disengage the snap-in securing tangs  89  from the projections  83 . This will allow the cover  75  to be removed from the base in a vertical direction opposite to the insertion direction. 
     The EMI shielding enclosure of the present invention can be made from numerous EMI reflecting and/or absorbing materials or electrically conductive materials. The preferred materials of the present invention are Ni coated graphite and polycarbonate or similar materials. The EMI enclosure can also be made of other polymers. In addition, the above-mentioned materials may be further coated with Ni—Cu or Ni—Cu—Ni electrolessly applied. Alternatively, the EMI shielding enclosure of the present invention can be made of metal, such as magnesium or aluminum. Magnesium is preferable, since it can be made thinner than aluminum. 
     It is noted that the first through fifth embodiments of the present invention include four side walls  7  connected together in the shape of a rectangle; however, the number and shape of the side walls and how they are connected together can be of any number and shape depending upon the electronic equipment which is being enclosed. Furthermore, the base  3 ,  73  of the enclosures  1 ,  71  in the first through fifth embodiments may include separators therein in order to separate various pieces within an enclosure from each other. Separators within the enclosures form individual cavities which provide protection against EMI between electronic equipment within the cavities of the enclosures. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.