Patent Document

BACKGROUND OF THE INVENTION 
     This invention relates to electromagnetic interference/radio frequency interference (EMI/RFI) shield assemblies for circuit boards and, more particularly, to a tool for removing the cover from such a shield assembly to expose the protected circuitry without damaging the shield assembly. 
     There are numerous applications where electronic circuit components mounted to a printed circuit board must be shielded from electromagnetic interference and/or radio frequency interference. To provide such shielding, metallic shielding assemblies have been developed which cover a group of electronic circuit components mounted to the printed circuit board, with the shield assembly being physically secured in some manner to the printed circuit board while also being grounded thereto. One such shield assembly includes a metallic base and a metallic cover. The base is a rectilinear box having an open side which is secured to the circuit board with the open side adjacent the circuit board, the box enclosing the electronic circuit components. The securing of the box to the circuit board is by using solder to surface mount the box to the board. In order to gain access to the electronic circuit components without removing the shield, the side of the box opposite the circuit board has an enlarged opening therein. This opening is then shielded by the cover, which itself is a metallic rectilinear box having an open side and which fits snugly around the base with the open side of the cover facing the circuit board. When it is desired to gain access to the shielded electronic circuit components, the cover must be removed from the base. In the past, this has presented a problem, since there is no known tool for removing the cover without causing damage to the shield assembly. It would therefore be desirable to provide such a tool. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a tool for removing such a shield cover from the shield base. The inventive tool includes a pair of gripper members each secured to a respective body member. The body members are held together with a slight separation therebetween and are movable toward and away from each other. In use, the tool is placed over the shield cover and the body members are moved toward the circuit board. The body members are then moved toward each other so that the gripper members are under the edges of opposed sides of the cover. The tool is then lifted away from the circuit board, taking the cover with it. 
     In accordance with an aspect of this invention, a spring is positioned between the body members to resiliently bias them apart. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing will be more readily apparent upon reading the following description in conjunction with the drawings in which like elements in different figures thereof are identified by the same reference numeral and wherein: 
     FIG. 1 is a perspective view of a circuit board showing a shield assembly with which the inventive tool may be used; 
     FIG. 2 is a view similar to FIG. 1 showing the cover separated from the base; 
     FIG. 3 is a perspective view of a tool constructed according to the present invention; 
     FIG. 4 is a front elevational view of the tool shown in FIG. 3; 
     FIG. 5 is a side elevational view of the tool shown in FIG. 3; and 
     FIG. 6 is a cross sectional view taken along the line  6 — 6  in FIG.  4 . 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 and 2 show a printed circuit board  10  with electronic components  12  mounted thereon. A shield assembly including a base  14  and a cover  16  encloses the components  12  and shields them from electromagnetic and radio frequency interference. Thus, the base  14  is a metallic rectilinear box having an open side. The base  14  is secured to the circuit board  10  by being surface mounted to surface mount solder pads  18 , as is known in the art. This securement places the open side of the base  14  against the circuit board  10 . The side  20  of the base  14  which is opposite the circuit board  10  is formed with an enlaced opening  22  to provide access to the shielded components  12 . 
     The cover  16  is a metallic rectilinear box having an open side. The cover  16 , like the base  14 , has an open side defined by distal edges  24  of lateral sides  26 . The lateral sides  26  of the cover  16  are sized so that the cover  16  fits snugly around the base  14 . To assist in providing and maintaining a snug fit, the lateral sides  26  are formed with slits  28  and small openings  30  between the slits  28 , and the lateral sides  32  of the base  14  are formed with outwardly extending bumps  34  corresponding in location to the openings  30 . The openings  30  and bumps  34  act as detents when the cover  16  is installed on the base  14 . The lateral sides  26  of the cover  16  are dimensioned so that when the cover  16  is installed on the base  14 , there is a gap between the distal edges  24  and the surface of the circuit board  10 , as best shown in FIG.  1 . 
     Referring now to FIGS. 3-6, the inventive tool, designated generally by the reference numeral  40 , includes a first body member  42  and a second body member  44 . The first body member  42  has a front face  46  and a mating face  48 . Similarly, the second body member  44  has a front face  50  and a mating face  52 . Preferably, the faces  46 ,  48 ,  50 ,  52  are all substantially planar. As best shown in FIG. 6, the body member  42  is formed with a pair of spaced bores  54  extending therein from the mating face  48  and orthogonal thereto. Similarly, the body member  44  is formed with a pair of spaced bores  56  extending therein from the mating face  52  and orthogonal thereto. The bores  54 ,  56  are spaced the same distance from the front faces  36 ,  50 , respectively, and are equally spaced from the side walls of the body members  42 ,  44  so that when the body members  42 ,  44  are aligned, as shown in FIG. 3, the bores  54  are aligned with the bores  56 . A pin  58  is installed in each bore pair  54 ,  56  to act as a guide member which orients the body members  42 ,  44  with respect to each other so that the mating faces  48 ,  52  face each other while at the same time allowing the body members  42 ,  44  to move relative to each other along a line of movement orthogonal to the mating faces  48 ,  52 . Each pin  58  must be free to move in at least one of the corresponding bores  54 ,  56 . 
     As shown in FIG. 6, the first body member  42  is formed with a bore  60  extending therein from the mating face  40  along an axis parallel to the line of movement, with the distal (innermost) end of the bore  60  being internally threaded. The bore  60  has an enlarged region  62  open to the mating face  48 . The second body member  44  is formed with a bore therethrough coaxial with the bore  60 . The bore through the second body member  44  includes an enlarged region  64  open to the mating face  52 , a central region  66 , and a further enlarged region  68  open at the side of the body member  44  opposite the mating face  52 . A shoulder screw  70  extends through the bore of the second body member  44  and is threadedly secured in the bore  60  of the first body member  42 . A helical spring  72  surrounds the shoulder screw  70  within the enlarged regions  62 ,  64 . Thus, the spring  72  provides a force to yieldably bias the body members  42 ,  44  away from each other along the line of movement and the head of the shoulder screw  70  abuts against the inner wall of the enlarged region  68  to provide an upper limit on the separation between the mating faces  48 ,  52 . 
     Secured to the first body member  42 , as by screws  74 , is a gripper member  76 . Similarly, a gripper member  78  is secured to the body member  44 , as by screws  74 . The gripper members  76 ,  78  are identical and therefore only the gripper member  76  will be described in detail. As shown, the gripper member  76  is substantially planar and is secured to its body member  42  on the side opposite the mating face  48 . The gripper member  76  extends in a plane forwardly beyond the front face  46  to a shoulder  80  formed on the gripper member  76  on the side facing the gripper member  78 . The shoulder  80  extends along the length of the gripper member  76  parallel to the front face  46  and is spaced from the front face  46  by a distance at least as great as the dimension of the shield cover  16  lateral side  26  orthogonally to the distal edge  24 . The distance from the shoulder  80  to the distal end  82  of the gripper member  76 , which distal end  82  runs parallel to the shoulder  80 , is less than the gap between the distal edge  24  of the cover  16  and the circuit board  10  when the cover  16  is installed on the base  14 . As shown, the planes of the gripper members  76 ,  78  are parallel to each other with the shoulders  80  of the gripper members  76 ,  80  facing each other and being aligned along a line parallel to the line of movement. 
     The body members  42 ,  44  are dimensioned so that they can be separated sufficiently that the gripper members  76 ,  78  can be moved along opposed lateral sides  26  of the cover  16  toward the circuit board until the shoulders  80  pass the distal edges  24 . The body members  42 ,  44  can then be moved toward each other against the force of the spring  72  until the shoulders  80  are separated by a distance less than the distance between the opposed lateral sides  26  of the cover  16 . Accordingly, subsequent movement of the tool  40  away from the circuit board  10  causes the shoulders  80  to engage the distal edges  24  to remove the cover  16  from the base  14 . This removal does not cause any damage to either the base  14  or the cover  16  since all forces are applied over a relatively large area without deforming either the base  14  or the cover  16 . 
     Accordingly, there has been disclosed an improved tool for removing the cover from an EMI/RFI shield assembly. While an illustrative embodiment of the present invention has been disclosed herein, it is understood that various modifications and adaptations to the disclosed embodiment will be apparent to one of ordinary skill in the art and it is therefore intended that this invention be limited only by the scope of the appended claims.

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