Abstract:
A circuit board standoff including a fastener mechanism and a body for disposition between first and second boards and having an upper portion for contacting the first board, fastener portions for engaging the fastener to secure the body to the first board and engagement portions arranged to be forced into penetrating engagement with the second board.

Description:
[0001]    This application is a continuation of co-pending application Ser. No. 09/654,361 filed Sep. 1, 2000, entitled Circuit Board Standoff. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates generally to electrical circuit board apparatus and, more particularly, to improved standoff elements for separating and supporting printed circuit boards.  
           [0003]    Printed circuit boards are used extensively in various types of electrical equipment. Typically, standoff elements are used to support and provide spacing for circuit boards. Standoffs are used, for example, to separate, support and electrically insulate a printed circuit board from either a metal chassis or other printed circuit boards. In many applications, separated circuit boards include ground circuits that must be interconnected. Standoff elements of that type are disclosed, for example, in U.S. Pat. Nos. 4,952,158; 5,281,149; 5,345,366 and 5,380,211. Such prior standoff elements exhibit certain deficiencies such as structural complexity, limited specialized use and high cost.  
           [0004]    The object of this invention, therefore, is to provide an improved standoff device that can both separate and electrically ground printed circuit boards.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention is a circuit board standoff including a fastener mechanism and a body for disposition between first and second boards and having an upper portion for contacting the first board, fastener portions for engaging the fastener mechanism to secure the body to the first board, and engagement portions arranged to be forced into penetrating engagement with the second board. The engagement portions facilitate securement of a structurally simple standoff between the first and second boards.  
           [0006]    According to one feature of the invention, the body further includes a plurality of legs having lower portions shaped and arranged to be tightly received by an opening in the second board and defining the engagement portions. The legs can be expanded to penetrate the second board.  
           [0007]    According to another feature of the invention, the engagement portions are defined by extremity portions of the legs, the extremity portions being shaped and arranged for outward expansion to penetrate perimeter portions of the opening in the second board. The extremity portions are expanded to penetrate the second board and secure the body thereto.  
           [0008]    According to an important feature of the invention, the fastener mechanism produces outward expansion of the legs in response to engagement with the fastener portions. The outward expansion maintains the penetrating engagement between the engagement portions and second board.  
           [0009]    According to yet another feature of the invention, the legs include at least one leg in which the lower portion thereof is outwardly convex and has opposite edge portions defining the extremity portions. The concave legs provide the engagement portions in a simple, easily fabricated structure.  
           [0010]    According to still another feature of the invention, the legs include at least one leg in which the lower portion thereof defines outwardly directed engagement tabs further defining the extremity portions. The tabs further secure the body to the second board.  
           [0011]    According to an additional feature of the invention, the legs include at least one leg in which said lower portion thereof defines an outwardly directed flange shaped and arranged to engage a surface of the second board facing opposite to the first board. The flange assists in positioning and retaining the body in the opening of the second board.  
           [0012]    According to a further feature of the invention, the fastener mechanism is a screw having a threaded shank engaging the fastener portions and a head for contacting a surface of the first board facing opposite to the second board. The screw secures the body to the first board.  
           [0013]    According to another feature of the invention, the fastener portions include an inwardly directed annular collar in the upper portion and having an inner fastener edge threadedly engaged with the threaded shank.  
           [0014]    According to yet another feature of the invention, the fastener portions also include inwardly directed fastener tabs formed in an intermediate portion of the body and threadedly engaged with the threaded shank.  
           [0015]    According to an important feature of the invention, the body is a substantially cylindrical, unitary member stamped from an electrically conductive material. The provision of a unitary stamped body reduces the cost of the standoff. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0016]    These and other objects and features of the invention will become more apparent upon a perusal of the following description taken in conjunction with the accompanying drawings wherein:  
         [0017]    [0017]FIG. 1 is a perspective view of a standoff according to the invention;  
         [0018]    [0018]FIG. 2 is a top view of the standoff illustrated in FIG. 1;  
         [0019]    [0019]FIG. 3 is a cross-sectional view taken along lines  3 - 3  of FIG. 2;  
         [0020]    [0020]FIG. 4 is a cross-sectional view taken along lines  4 - 4  of FIG. 2;  
         [0021]    [0021]FIG. 5 is a perspective view of another standoff embodiment of the invention;  
         [0022]    [0022]FIG. 6 is a top view of the standoff illustrated in FIG. 5; and  
         [0023]    [0023]FIG. 7 is a cross-sectional view taken along lines  7 - 7  of FIG. 6.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    A standoff  11  includes a body  12  (FIG. 1) and a screw faster  13  (FIGS. 3 and 4). The body  12  is a substantially cylindrical member having an intermediate portion  15  straddled by an upper portion  16  and a lower portion  17 . Preferably, the body  12  is a unitary member stamped from a suitable electrically conductive, spring tempered material such as electro-tin plated carbon steel. Forming the body  12  are a first pair of diametrically opposed legs  21 ,  22  separated by a second pair of diametrically opposed legs  23 ,  24 . The screw fastener  13  has a slotted head  27  and a threaded shank portion  28  as shown in FIGS. 3 and 4.  
         [0025]    Defined by the upper portion  16  of the body  12  is an annular inwardly directed collar  31  terminating with a fastener helical edge  32  shaped and dimensioned for threaded engagement with the shank portion  28  of the screw fastener  13 . Each of the first pair of legs  21 ,  22  has an outwardly convex lower portion  34  with circumferentially spaced apart lower opposite edge extremities which define engagement portions  35 ,  36 . A flange  41  is directed outwardly at the bottom of each of the second pair of legs  23 ,  24 . Closely adjacent to the flange  41  in each of the second pair of legs  23 ,  24  are a pair of circumferentially spaced apart engagement tabs  42 ,  43  directed outwardly from lower edges of each of the second pair of legs  23 ,  24 . Extremity edges of the tabs  42 ,  43  form additional engagement portions of the body  12 . Also formed in intermediate portions of each of the first pair of legs  21 ,  22 , respectively, are inwardly directed fastener tabs  46 ,  47 , dimensioned and arranged for threaded engagement with the shank portion  28  of the screw fastener  13 .  
         [0026]    A plurality of spaced apart standoffs  11  are used to maintain separation between a pair of boards. Typically, each standoff  11  is positioned between a first printed circuit board  51  and a sheet metal baseboard  52  as depicted in FIGS. 3 and 4. During assembly of each standoff  11 , the lower portions of the first and second pairs of legs  21 ,  22  and  23 ,  24  are retracted inwardly to facilitate insertion through an opening  54  in the second board  52 . After insertion, the first and second pairs of legs  21 ,  22  and  23 ,  24 , are allowed to extend radially producing tight engagement between the lower portions thereof and an inner perimeter  55  of the opening  54 . In addition, the outwardly directed flanges  41  contact a lower surface  56  of the second board  52  facing opposite to the first board  51 . A conventional impact tool then is inserted through the opening  54  into the body  12  and actuated to induce further outer expansion of the first and second pairs of legs  21 ,  22  and  23 ,  24 . Such expansion produces penetration of the inner perimeter  55  of the opening  54  by the engagement tabs  42 ,  43  of the second pair of legs  23 ,  24  and the engagement extremities  35 ,  36  of the first pair of legs  21 ,  22 .  
         [0027]    The printed circuit board  51  then is placed on the assembled body members  12  and supported by contact between the collars  31  thereof and a lower surface of the board  51  facing the second board  52 . After proper positioning, an opening  58  in the first board  51  is aligned with the collar  31  in each body member  12 . A screw fastener  13  then is inserted through each opening  58  and turned to provide threaded engagement of the shank portion  28  with the fastener edge  32  and fastener tabs  46 ,  47  of each body member  12 . Each fastener screw  13  is tightened to produce secure engagement between its slotted head  27  and an upper surface  59  of the first board  51  facing away from the second board  52 . During the assembly of the fastener screws  13 , the fastener edge  32  maintains axial alignment of the shank portion  28  with the fastener tabs  46 ,  47  and engagement therebetween produces a radially outward expansion force on the first pair of legs  21 ,  22 . That outward force maintains the previously induced penetration of the second board  52  by the engagement extremity portions  35 ,  36  of the first pair of legs  21 ,  22 .  
         [0028]    Illustrated in FIGS.  5 - 7  is another standoff embodiment  71  including a body member  72  and a screw fastener  13 . Portions of the standoff  71  which are the same as those of the standoff  11  have been given the same reference numerals. The standoff  71  is substantially identical to the standoff  11  except for an absence of the diametrically opposed second pair of legs  23 ,  24 , thereof. One other difference is the formation in the legs  23 ,  24 , respectively, of inwardly directed fastener tabs  75 ,  76  arranged and dimensioned for threaded engagement with the shank portion  28  of the screw fastener  13 . The standoff  71  is used to provide separation between first and second boards  51 ,  52  in the same manner as described above for the standoff  11 .  
         [0029]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is to be understood, therefore, that the invention can be practiced otherwise than as specifically described.