Abstract:
A control module comprises a motherboard and at least one circuit board removably connected to the motherboard. There is at least one lever connected to the removable circuit board. The lever is moveable between a release and locked position. The lever contacts a bracket in the locked position to move the bracket against a spring force, such that a bias force maintains the at least one circuit board in contact with the motherboard. A circuit board and a chassis are also discussed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a structure and method for mounting circuit boards into a motherboard. 
         [0002]    Modern systems are becoming more and more complex. Thus, complicated controls are incorporated into many systems. As an example, one such system could be on aerospace systems such as an aircraft. 
         [0003]    A control module for such a system may include a chassis mounting a motherboard and a plurality of removable circuit boards. One type of circuit board, known as line removal modules, may provide a variety of functions. 
         [0004]    Designers of the control modules will mount a motherboard and then select appropriate LRMs to provide the particular function demanded by the system which will utilize the control module. It is known that the removable LRMs must be held against the motherboard such that electronic connections are made. 
         [0005]    In the past, levers have been utilized to lock the LRMs into the chassis and in contact with the motherboard. However, due to manufacturing tolerances, the known systems do not always provide sufficient LRM travel to ensure a reliable electrical connection. Also, various biasing arrangements have been proposed but are generally complex. 
       SUMMARY OF THE INVENTION 
       [0006]    A control module comprises a motherboard and at least one circuit board removably connected to the motherboard. There is at least one lever connected to the removable circuit board. The lever is moveable between a release and locked position. The lever contacts a bracket in the locked position to move the bracket against a spring force, such that a bias force maintains the at least one circuit board in contact with the motherboard. 
         [0007]    A circuit board and chassis are also disclosed. 
         [0008]    These and other features may be best understood from the following drawings and specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  shows a control module. 
           [0010]      FIG. 1B  schematically shows connection in the  FIG. 1A  module. 
           [0011]      FIG. 2  shows a locking assembly in an unlocked position. 
           [0012]      FIG. 3A  shows a locking assembly in a locked position. 
           [0013]      FIG. 3B  shows a detail. 
           [0014]      FIG. 4  shows geometric details of the locking system. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    A control module  20  is illustrated in  FIG. 1A . The control module may have applications such as to provide controls for a system on an aircraft. An outer chassis  22  provides a housing that mounts a motherboard  24 . The motherboard  24  is at an inner end  25 , and the circuit boards extend towards an opening  27  from the motherboard  24 . A plurality of line replaceable modules (LRMs)  26  are shown mounted to the motherboard. Any type of circuit board may be attached to the motherboard  24 . 
         [0016]    Motherboard  24  is shown communicating with a use, which may be an aircraft system. As known, module  20  provides control functions to the use. For example, the modules may be power distribution modules, power supply modules, communications modules, etc. 
         [0017]    Levers  28  are used at opposed ends of the LRMs  26  remote from the motherboard  24 . The levers  28  lock the LRMs within the chassis  22  and engaged to the motherboard  24 . The LRMs  26  are generally planar and levers  28  are at both ends of the plane. A bracket  30  is fixed on a side of the LRMs  26  and the levers  28  are pivotally mounted on the brackets  30 . A channel  32 , attached to the chassis  22  is used to guide the LRM&#39;s into place within chassis  22  and to align LRM&#39;s  26  to their appropriate connector on motherboard  24 . 
         [0018]    As shown in  FIG. 1B , schematically, a motherboard  24  receives an electrical connection  19  from an LRM  26 . Due to tolerance build-up, in the art, this connection has not always been fully mated to ensure a reliable electrical interface. A worker of ordinary skill would be able to calculate the tolerance build-up in any particular system. 
         [0019]      FIG. 2  shows the locking assembly in an unlocked position. The lever  28  is pivoted outwardly away from a lock bracket  38 . Lock bracket  38  is u-shaped, with sides  38 S and a bottom  38 B to define the u-shape. 
         [0020]    As can be seen, a holder, such as a bolt or pin  40  extends through the sides  38 S of lock bracket  38  and provides an abutment for a Belleville washer set or a spring of sufficient force  46  that is mounted in a fixed bracket  44 . Fixed bracket  44  is L-shaped. A nut  47  on holder  40  provides a stop. The bracket  44  is fixed on the chassis  22  while the lock bracket  38  is slidable along the chassis  22 . A head  42  of the holder  40  is on an opposed side of the bracket  38 . A head  34  of the lever  28  is illustrated along with a pivot pin  36 . A channel  37  is intermediate the pivot pin  36  and the head  34 . 
         [0021]    As shown in  FIG. 3A , the lever  28  has now been pivoted to a locked position. The head  34  cams against side wall  38 S on the lock bracket  38  to move the lock bracket in an outward direction. As can be seen, there is a space S between the brackets  44  and  38 . That is, when the lever  28  is moved to this position, it pulls the lock bracket  38  away from the fixed bracket  44 , and against the bias force of the Belleville washers  46 . When the lever  28  is in this position, the spring pushes the bracket  30  and hence the LRM  26  further into the chassis, such that the connection  27  between the motherboard  24  and the LRM  26  is fully closed. 
         [0022]      FIG. 3B  shows a locking pawl  90  which is pivotally connected to the lever  28 . Pawl  90  has arms  92  that can be pivoted to the position illustrated where they lock on pins  94  on the bracket  30 . The pawl  90  is moved to this position once the lever has been moved to the  FIG. 3A / 3 B position, and the pawl  90  locks the lever at that position. 
         [0023]    To remove the LRM  26 , the pawl  90  is pivoted away from the  FIG. 3B  position, releasing the lever. As can also be seen, the lever  28  has heads  34  spaced about a central member  96  of the bracket  30 . Thus, the pin  40  can extend between the spaced heads  34 . 
         [0024]    In a method of installing a circuit board into a motherboard according to this disclosure, a circuit board  26  is initially moved into the chassis  22 , and moved toward the motherboard  24  for connection. During this movement, it may be necessary to slightly pivot the levers  28  such that the head  34  can move beyond an outer side  38 S of the lock bracket  38  at both of the two locations. 
         [0025]    Once the circuit board  26  is moved into the chassis sufficiently such that the head  34  of the lever  28  can be moved between the side walls  38 S of the lock bracket  38 , the levers  28  are then pivoted to the position such as shown in  FIG. 2 . 
         [0026]    Next, the levers  28  are pivoted such that the head  34  cams against the sides  38 S on the lock brackets  38 , and the levers are further pivoted, drawing the lock brackets  38  against the force from the spring  46  until it reaches the  FIG. 3A  position. In this position, the Belleville washers  46 , or other bias members, pull the lock brackets  38  back into the chassis, thus causing the levers  28  to further pull the circuit board  26  into the chassis, ensuring an adequate connection. The pawl  90  is then moved to the  FIG. 3B  position. 
         [0027]    As shown in  FIG. 4 , a distance d 1  can be defined as between a center of the pivot point  36  and an end  78  on the head  34 . A second distance d 2  is the distance across the gap S between the faces  82  and  80 , respectively, of the brackets  44  and  38  ensures sufficient LRM movement to compensate for the tolerance accumulation of the system 
         [0028]    In embodiments, d2 is a subset or partial part of the overall LRM travel that results from the d1 moment arm length and movement. The LRM  26  required overall movement or engagement travel will be vary depending on the mating connector types used between the LRM  26  and the motherboard, Item  24 . Thus, d1 is selected to provide adequate LRM  26  movement to ensure a proper connection given the greatest possible tolerance stack-up for a given system. 
         [0029]    In one feature, a chassis for a control module provides a housing having an inner end  25  and a forward opening  27 . A fixed bracket  44  mounts a biasing member  46 , and a lock bracket  38  slides on the housing. Lock bracket  38  is spaced towards the opening  27  from the fixed bracket  44 . Biasing member  46  biases lock bracket  38  towards fixed bracket  44 . 
         [0030]    Although LRMs are disclosed, other circuit boards may come within the scope of this disclosure. In addition, while Belleville washers  46  are illustrated, other biasing members would come within the scope of this disclosure. 
         [0031]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.