Abstract:
A capture device for use with circuit boards of varying thicknesses prevents the spacing between the boards from increasing and has a unitary body including a flexible arm, a clip cavity and multiple living hinges that enable the device to be pivotally self-locked between the circuit boards. The capture device can be engaged and disengaged in poor visibility and limited access areas densely packed with circuit boards. The capture device may be made of a semi-rigid material that provides enough flexibility for the living hinges, yet is rigid enough to exert pressure on the boards and prevent the spacing between the boards from increasing. In alternative embodiments, more than two circuit boards may be secured using alternative configurations of the capture device with either multiple arms or multiple clip cavities.

Description:
FIELD OF THE INVENTION 
     The invention relates to electrical circuit boards, and more specifically, to a capture device for use with circuit boards having variable thickness to prevent the space between the circuit boards from increasing. 
     BACKGROUND OF THE INVENTION 
     Computers and other devices that include digital logic components typically employ one or more circuit boards populated with any of small, medium, or large scale logic components, typically in the form of integrated circuits, as well as occasional discrete components. Electrical signals and power are transferred between boards through electrical connectors, typically complimentary mating pin connectors. It is common for a primary circuit board (a mother board) to provide power and signals to a secondary or supplemental circuit board (a daughter board), such as a memory card. In such instances, the electrical connection between the mother board and daughter, board must be maintained in order for the daughter board to function properly. The preferred spacing between the circuit boards, therefore, is defined by the spacing necessary for optimal mechanical and electrical contact between the complimentary electrical connectors on each respective board. Accordingly, the space between the interior or facing surfaces of two connected circuit boards is fairly well defined by the combined profile of the connectors. If the only feature mechanically coupling the mother board to the daughter board is an electrical pin connector, it is possible for the daughter board to work loose or “back-out” from the mother board, particularly since the daughter board may be of smaller size than the mother board. This problem also arises when two similar size boards are mechanically and electrically coupled through only a pin connector. One prior art solution to this problem has been to mechanically secure the boards together using a spacing post, sometimes called a standoff, and screws. However, such devices are sometimes difficult to install and uninstall, particularly when boards are being swapped in existing installed system where space may be very limited. Accordingly, a need exists for a device that mechanically secures a plurality of circuit boards, including mother boards and daughter boards, in a fixed relation to prevent the space between the boards from increasing, i.e. back-out. 
     In addition, although the space between the interior or facing surfaces of two connected circuit boards is typically defined by the combined profile of the connectors on the circuit boards, the height between the exterior surfaces of the joined boards may vary depending on the thickness of the boards. Current fabrication techniques allow circuit boards to have multiple layers of signal paths therein, increasing the thickness of the boards. As such, the required spacing between the respective non-connecting surfaces of two circuit boards may vary depending on the thickness of the circuit boards to be joined. Accordingly, a need exists for a device that can mechanically clamp two circuit boards together and that can accommodate a variety of spacing distances between the exterior, non-facing surfaces of the boards. 
     Further, circuit boards are often mechanically and electrically coupled during both assembly of a computer system as well as during upgrading and maintenance of a computer system once assembled. For example, daughter boards that add additional functionality and/or memory to a mother board are often inserted by a field engineer. Typically, the existing space into which the board must be inserted has limited access making it very difficult to use mechanical fasteners, i.e., screws and standoffs to secure circuit boards together. In addition, mechanical coupling of such boards is often done without the benefit of the technician being able to see the boards and components clearly. Accordingly, a need exists for a device that can be used to capture and mechanically join circuit boards with limited access thereto. A further need exists for a device that can be clamped and unclamped from circuit boards using primarily the tactile sense, without the benefit of sight. 
     SUMMARY OF THE INVENTION 
     A capture device for use with circuit boards having variable thickness includes a unitary body including a flexible arm, a clip cavity and multiple living hinges that enable the capture device to be pivotally locked between multiple circuit boards whose intermediate spacing height varies. The capture device can be engaged and disengaged in poor visibility and limited access areas with densely packed circuit boards. The capture device may be made of a semi-rigid material that provides enough flexibility for the living hinges, yet is rigid enough to maintain the boards at respective distances. In alternative embodiments, more than two circuit boards may be secured using alternative configurations of the capture device with either multiple arms or multiple clip cavities. 
     According to a first aspect of the present invention, an apparatus for removably securing multiple circuit boards comprises (a) a main body capable of receiving a first circuit board; (b) a first arm pivotally joined to the main body; and (c) an engaging mechanism formed at an end of the first arm for engaging and removably securing another circuit board in spaced relation to the first circuit board. In one embodiment, the first arm and the main body are joined with a first living hinge. In another embodiment, an elbow is integrally formed in the first arm and joined with a living hinge which forms an angle of less than ninety degrees between the elbow and the first arm. In other embodiments, the capture device further comprises a second arm pivotally joined to the main body and a second engaging mechanism formed at an end of the second arm for engaging and removably securing another circuit board in spaced relation to the first circuit board. 
     According to a second aspect of the present invention, an apparatus for removably securing multiple circuit boards comprises (a) a main body capable of receiving a first circuit board; (b) a first arm; (c) means for pivotally attaching the first arm to the main body; and (d) engaging means formed at the end of the first arm for engaging and removably securing another circuit board in spaced relation to the first circuit board. In one embodiment, the means pivotally attaching the first arm to the main body comprises a first living hinge. In another embodiment, an elbow is integrally formed in the first arm and joined with a living hinge which forms an angle of less than ninety degrees between the elbow and the first arm. In other embodiments, the capture device further comprises a second arm pivotally joined to the main body and a second engaging mechanism formed at an end of the second arm for engaging and removably securing another circuit board in spaced relation to the first circuit board. 
     According to a third aspect of the present invention, a method for removably securing multiple circuit boards comprising: (a) providing a capture device comprising: i) a main body capable of removably receiving a circuit board; ii) a first arm pivotally joined to the main body, and iii) an engaging mechanism formed at an end of the arm for engaging and removably securing another circuit board in spaced relation to the first circuit board; (b) engaging a first circuit board with the capture device; and (c) pivoting one of the main body and first arm to engage a second circuit board with the capture device. In another embodiment the method further comprises, applying force on the circuit boards with the capture device to maintain the circuit board in a spaced relation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in that: 
     FIG. 1 is a top/side perspective view of the capture device of the present invention; 
     FIG. 2 is a side view of the capture device of FIG. 1; 
     FIG. 3 is a front view of the capture device of FIG. 2; 
     FIGS. 4A-B illustrate configurations of the capture device of FIG. 1 during and after capture of a pair of circuit boards; 
     FIG. 5 is a side view of an alternative embodiment of the inventive capture device of FIG. 1; 
     FIG. 6 is a side view of an another alternative embodiment of the inventive capture device; and 
     FIG. 7 is a side view of yet another alternative embodiment of the inventive capture device. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1-4, a capture device  10  is shown in accordance with an illustrative embodiment of the invention. Capture device  10  comprises a main body  12  having a clip formed therein and connected to an arm  16 . Three “living hinges” or flexible joints facilitate attachment of the capture device  10  securely between multiple circuit boards. In the illustrative embodiment, capture device  10  may be of a unitary design and manufactured by an injection molding process. Materials suitable for use in manufacturing capture device  10  include any rigid or semi-rigid material, such as natural or synthetic resin, including polypropylene and related families of plastic. 
     Referring specifically to FIGS. 1-3, capture device  10  comprises a main body  12  joined to an arm  16  by living hinge  14 . The living hinge is implemented with an extreme narrowing of the cross sectional area between arm  16  and main body  12 . Living hinge  14  allows arm  16  to bend in relation to main body  12 . Main body  12  further comprises a clip cavity formed therein and defined by a clip base  20  and projection  22 . A hemispherical nub  24  on the top surface of base clip  20  interacts with the lower ridge portion at the maximum width of projection  22  to form a pinch into which a circuit board may be received and removably secured. As illustrated, the point at which projection  22  is secured to main body  12  includes a second living hinge  18  characterized by a narrowing cross-sectional area that allows projection  22  to bend or flex slightly in relation to main body  12  to receive a circuit board. In the illustrative embodiment, it is contemplated that the circuit board received within the clip cavity formed by clip base  20  and projection  22  has a complimentary shape aperture, depression, or other feature into which nub  24  may be disposed. The lower ridge portion of projection  22  rests on the surface of the circuit board or, alternatively, within a feature, such as a hole or depression, in the circuit board. Living hinge  18  causes projection  22  to apply downward force on the circuit board to maintain the board within the clip cavity of main body  12 . 
     Arm  16  has integrally formed therein an elbow  15  having a living hinge  30  that separates the arm into upper and lower portions  16 A and  16 B, respectively. In the illustrative embodiment, the angle between the upper and lower portions of arm  16  may be approximately 85° but should be less than ninety degrees (90°) in order to provide appropriate downward force from upper arm portion  28  onto the second circuit board, as explained hereinafter. Extending downward from the bottom portion of upper arm portion  16 B is a substantially conical nub  32  with a founded peak which frictionally engages an aperture in a second circuit board once in place. A tab  34  projects from the top surface of upper arm portion  16 B and is provided with a support  36 . The tab  34  facilitates manual attachment and removal of the capture device  10 , from between a pair of circuit boards. Force substantially normal to tab  34  causes device  10  to bend a living hinge  14  allowing arm  16  to pivot in relation to main body  12 . Referring to FIG. 3, the end surfaces of clip base  20 , as well as upper arm portion  16 B and tab  34  are rounded, in the illustrative embodiment. 
     Referring to FIGS. 4A-B, the position of capture device  10  in relationship to a pair of circuit boards  36  and  38  is illustrated during and after capture thereof. Specifically, in FIG. 4A, the device  10  shown in phantom has the clip cavity joined to first board  36  while arm  16  is yet to be joined. The device  10  shown in solid lines is joined to second circuit board  38  while the clip cavity in main body  12  is yet to be joined. As illustrated, either the clip cavity or arm may be used to capture a first of the boards. Thereafter device  10  is pivoted at living hinge  14  to position either of the clip cavity or arm, whichever is still free, to capture a second of the boards, as illustrated in FIG.  4 B. Once device  10  is in place, nub  32  of upper portion  16 B rests within an aperture, depression or other feature of a circuit board. Because of the displacement angles of upper arm portion  16 B relative to lower arm portion  16 A, and the living hinge  30  formed therebetween, upper arm portion  16 B exerts force against the surface of the circuit board while arm  16  exerts counter force, helping to maintain nub  32  within the aperture, depression or other feature of the other circuit board. Note that the inward clamp-like force exerted on boards  36  and  38  by device  10  prevents the boards from moving apart, however, the device  10  does not secure the boards at a fixed distance or prevent the boards from being moved closer together if necessary. 
     It will be obvious to those reasonably skilled in the art that the size and shape of nubs  24  and  32 , as well as projection  22  may vary according to the designer&#39;s discretion so long as the shapes are compatible with the features in the circuit boards into which the nubs and/or projections are received. For example, FIG. 5 illustrates an alternative embodiment of the capture device  10  in which the conical nub  32 , extending downward from the bottom surface of upper arm portion  16 B in FIG. 1, has been replaced with a projection  32 B that frictionally engages a second circuit board once in place. The projection  32 B has a profile similar to a ratchet tooth, instead of a cone. Otherwise, all other aspects of capture device  10  may be the same as illustrated in FIG. 1 described herein. 
     Referring specifically to FIG. 6, an alternative embodiment of the capture device  10  is illustrated. In FIG. 6, capture device  10  comprises a main body  12  joined to an arm  16  by living hinge  14 , similar to that illustrated in FIG.  1 . However, main body  12  includes a second clip cavity defined by base clip  40  and projection  42 . A hemispherical nub  44  on base clip  40  interacts with the ridge at the maximum width of projection  42  to form a pinch into which a circuit board may be received and removably secured. As illustrated, the point at which projection  42  is secured to main body  12  includes a fourth living hinge  48  characterized by a narrowing of the cross-sectional area that allows projection  42  to bend or flex slightly in relation to main body  12  to receive a circuit board. In the illustrative embodiment, it is contemplated that the circuit board received within the second clip cavity formed by clip base  40  and projection  42  also has an aperture, depression or other feature into which nub  44  may be disposed. The lower ridge portion of projection  42  rests on the surface of the circuit board. Living hinge  48  causes projection  42  to apply force on the circuit board to maintain the board within the second clip cavity of main body  12 . Otherwise, all other aspects of capture device  10  may be the same as illustrated in FIG.  1  and as described herein. The embodiment of capture device  10  illustrated in FIG. 6 may be used to removably secure three circuit boards in which the distance between at least two adjacent circuit boards is variable. Alternatively, capture device  10  of FIG. 6 may removably secure two circuit boards in which the distance between the circuit boards is greater than the distance that can be accommodated by the first clip cavity defined by a clip base  20  and projection  22 . 
     In an alternative embodiment of the capture device  10  illustrated in FIG. 6, a plurality of clip cavities may be formed into main body  12 . In such embodiment, the clip cavities may be implemented with a clip base, projection and living hinge, as previously described with reference to FIG.  1 . Such an embodiment may be used to removably secure multiple circuit boards in which the distance between at least two end adjacent circuit boards is variable, or, alternatively, to removably secure two circuit boards by selecting the clip cavity that most closely matches the distance between the circuit boards. 
     Referring specifically to FIG. 7, another alternative embodiment of capture device  10  is illustrated. In FIG. 7, capture device  10  comprises a main body  12  joined to an arm  16  by living hinge  14 , similar to that illustrated in FIG.  1 . However, main body  12  includes second arm  56  joined by living hinge  54 . Living hinge  54  allows arm  56  to bend in relation to main body  12 . Arm  56  has integrally formed therein a living hinge  70  that separates the arm into lower and upper portions  56 A and  56 B, respectively. In the illustrative embodiment, the angle between the upper and lower portions of arm  56  may be approximately 85° but is typically less than 90° in order to provide appropriate downward force from upper arm portion  56 B onto the second circuit board, as explained hereinafter. Extending downward from the lower surface of upper arm portion  56 B is a substantially conical nub  72  that frictionally engages a third circuit board once in place. A tab  74  projects from a surface of upper arm portion  58 B and is provided with a support  76 . The tab  74  facilitates manual attachment and removal of the capture device  10  from multiple circuit boards. Otherwise, all other aspects of capture device  10  may be the same as illustrated in FIG.  1  and as described herein. The embodiment of capture device  10  illustrated in FIG. 7 may be used to removably secure three circuit boards in which the distance between at least two adjacent circuit boards relative to the center circuit board is variable. 
     Having described herein illustrative embodiments of the present invention, persons of ordinary skill in the art will appreciate various other features and advantages of the invention apart from those specifically described above. It should therefore be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications and additions can be made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, the appended claims shall not by the particular features that have been shown and described, but shall be construed also to cover any obvious modifications and equivalents thereof.