Abstract:
An equipment rack includes a shelf and a backplane which supports and receives an electronic module having a rear connector. The backplane includes a complementary connector for engaging the rear connector along an insertion axis. An extraction tool is coupled to the shelf and to the module for disengaging the rear connector from the complementary connector while producing an extraction force having a first component substantially along the insertion axis and a second component substantially perpendicular to the insertion axis. A hold-down bracket is coupled to the module and slidably engages the shelf to counteract the second component of the extraction force until the rear connector disengages from the complementary connector and thus avoids upward movement of the module.

Description:
TECHNICAL FIELD 
     This invention relates generally to the mounting of electronic equipment, and more particularly to an apparatus for facilitating the extraction of modules from a shelving system. 
     BACKGROUND OF INVENTION 
     Amongst the generalized inner-workings of multifaceted apparatus, electronic equipment can be said to have significant value. The architecture of such equipment often entails significant production cost, and electronic equipment often performs vital processing functions producing direct or indirect results in response to data input or operator commands. Thus, any damage done to electronic equipment may be relatively costly, and any malfunction in electronic equipment may lead to incorrect results or greater mechanical and/or electrical failures. The architecture of electronic equipment is usually inherently delicate. Thus, protecting such equipment is important for several reasons. In particular, it is desirable that a housing apparatus, cabinet, or shelving system for receiving and retaining electronic modules: (1) protect the electronic equipment and (2) provide precise alignment of the electronic interfaces (e.g. male and female connectors). Under certain conditions, these basic criteria may be more difficult to meet. Electronic equipment undergoing transport, for instance, experiences an increased risk of damage due to constant subjection to vibrations and other aberrant forces. This is also true for electronic systems of the type employed in aircraft since such electronic systems frequently experience forces that threaten to dislodge and damage them. 
     To provide better protection of electronic equipment and maintain proper couplings between interfaces, hold-down mechanisms have been introduced. Early hold-down mechanisms secured electronic units onto a rack through the application of a constant pressure. Such hold-down mechanisms effectively protected electronic units from damage and consequently became commonly employed in aircraft electronic shelving systems. However, the design of these hold-down mechanism suffered from several shortcomings. For example, such mechanisms increased the weight of the electronic units. Additionally, early hold-down mechanisms were capable of generating forces greater than necessary potentially damaging the equipment. Several other limitations were also inherent in the architecture of these hold-down mechanisms such as the lack of means to prevent loosening of set-screws and the like during flight. 
     A more desirable hold-down apparatus is shown and described in U.S. Pat. No. 3,640,141 issued to Hollinsead et al. on Feb. 8, 1972, the teachings of which are herby incorporated by reference. This device, referred to as an extractor hold-down apparatus, is improved over the previous hold-down device in several ways, For example, a singular extractor hold-down apparatus provides sufficient force to suitably secure an electronic unit in place thus reducing the undesirable accumulation of weight. Furthermore, unlike the initial hold-down mechanisms, this extractor hold-down apparatus does not generate excessive forces and provides a convenient way to gauge the applied force. The device is capable of generating a forward driving force for inserting an electronic module to provide proper connection between the module and backplane connectors and an extraction force for dislodging the module from its connections and extracting it (e.g. an extraction force of 100 pounds would not be uncommon). This extractor hold-down device became commonly used in the field of avionics and is now required by the Air Transport Avionics Equipment Interface, ARINC Specifications 600. 
     Unfortunately, an undesirable upward-directed force is produced by the above described hold-down apparatus during extraction. That is, due to its design, the spindle or axis of the device forms an angle with the plane of the engaging male and female connecters which may be as high as 9 to 25 degrees. Thus, the extraction force is not limited to a desired axis but includes a component which acts perpendicularly to the axis of the connector pins of the male/female connector interface (hereinafter referred to as the axis of the connector interface). In the case of heavier electronic units, this aberrant force is compensated for by the mass of the unit and is not a significant issue. However, lighter electronic units are increasingly being developed and introduced. Unfortunately, the perpendicular force generated by the hold-down extractor apparatus on such lighter units becomes problematic. Specifically, the extraction force generated perpendicular to the desired axis of the connector interface is sufficient to bend the connector pins damaging the module and may perhaps cause the module to wedge preventing further removal. It should also be noted that undesirable forces of this nature may be exacerbated via other sources; for example, by lifting upwards on a handle of a module being removed instead of extracting the module along the line of the connector interface axis. 
     In view of the foregoing, it should be appreciated that it would be desirable to provide a lightweight, module-extracting apparatus which avoids the generation of forces perpendicular to the axis of the electronic interface. Such a device would be especially suited for use in an avionics shelving apparatus. Additional desirable features will become apparent to one skilled in the art from the foregoing background of the invention and following detailed description of a preferred exemplary embodiment and appended claims. 
     SUMMARY OF THE INVENTION 
     According with a first aspect of the invention, there is provided an equipment rack including a shelf and a backplane which supports and receives an electronic module having a rear connector. The backplane includes a complementary connector for engaging the rear connector along an insertion axis. An extraction tool is coupled to the shelf and to the module for disengaging the rear connector from the complementary connector while producing an extraction force having a first component substantially along the insertion axis and a second component substantially perpendicular to the insertion axis. A hold-down bracket is coupled to the module and slidably engages the shelf to counteract the second component of the extraction force until the rear connector disengages from the complementary connector. 
     In accordance with a further aspect of the invention, there is provided an electronic module capable of being supported on a shelf and comprising a housing having at least a front surface, a rear surface, and a bottom surface, the bottom surface for slidably engaging the shelf. The module includes at least a first connector in the rear surface thereof, and a hold-down bracket is fixedly coupled to the bottom surface and cooperates therewith to form a channel capable of slidably engaging at least a portion of the shelf. 
     According to a still further aspect of the invention, there is provided a hold-down bracket for forming a receiving channel with an undersurface of an electronic module which slidably engages a portion of a shelf. The bracket comprises a cross member having an upper surface and a lower surface, the lower surface for fixedly engaging the undersurface of the module. At least one longitudinal member extends from the cross member and is spaced from the undersurface to form the receiving channel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements, and: 
     FIG. 1 is an isometric view of a shelf or equipment rack configured to receive a plurality of electronic modules; 
     FIG. 2 is an isometric view of a module of the type shown in FIG. 1; 
     FIG. 3 is a side view of the module depicted in FIG. 2 positioned on the shelf depicted in FIG.  1  and equipped with an extraction tool which cooperates with the shelf and the module; 
     FIG. 4 is an isometric view of the extraction tool shown in FIG. 3; 
     FIG. 5 is a front isometric view of a portion of the module shown in FIG. 2; 
     FIG. 6 is an isometric view of hold-down bracket in accordance with the first embodiment of the present invention; 
     FIG. 7 is side view of a front lower portion of the module depicted in FIG. 2 equipped with one embodiment of a hold-down bracket; 
     FIG. 8 is an isometric of a hold-down bracket in accordance with a second embodiment of the invention; 
     FIG. 9 is a side view of the module depicted in FIG. 2 positioned on a shelf and further equipped with the hold-down bracket shown in FIG. 8; 
     FIGS. 10 and 11 are isometric and front views respectively of a third embodiment of a hold-down bracket; and 
     FIG. 12 is a side view of the hold-down bracket shown in FIGS. 10 and 11 fixed to an underportion of the module shown in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description of a preferred embodiment of the invention is mainly exemplary in nature and not intended to limit the invention or the application or use of the invention. 
     FIG. 1 is an isometric view of an equipment shelf or rack  100  configured to receive a plurality of electronic modules  102 . Modules  102  slidably engage and are received, for example, in slots  104 , and sockets of rear female connectors receive and engage pins of complementary male connectors such as is shown at  106  in backplane  108 . The floor  110  of shelf  100  is provided with a downward extending flange  112  having a plurality of openings  114  therein. An extraction tool or mechanism  116  is associated with each module  102  and is configured to engage a module  102 , pass through one of openings  114 , and secure to a lower or undersurface of floor  110  in a manner to be more fully described hereinbelow. 
     Referring now to FIG. 2, there is shown an isometric view of one of the modules  102  shown in FIG.  1 . Each module  102  may contain one or more circuit cards which communicate with other modules or with external circuitry by means of female connectors  202  shown in the rear surface of module  102 . The front portion of module  102  is provided with a concavity  204  comprised of a first surface  206  extending downward and inward from the front surface  208  of module  102  and a second surface  210  which extends upward from the bottom surface  212  of module  102  until it reaches surface  206 . A bottom portion of surface  210  includes a flange portion  214  which extends beyond and below bottom surface  212  of module  102 . This flange  214  is engaged or captured by extraction device  116  to aid in the extraction of module  102  from the shelf assembly  100  as will be more fully described hereinbelow. 
     FIG. 3 is a side view of module  102  positioned on floor  110  of shelf  100 . FIG. 3 also illustrates how extraction device  116  cooperates with flange  112 , floor  110  of shelf  100 , and module  102 . As stated previously, extraction device  116  is utilized to extract and secure module  102  on shelf  100 . Extraction device  116  includes an externally threaded spindle  302  which extends through aperture  114  (shown in FIG. 1) in downward extending flange  112  and is pivotally coupled to hinge  304  which is, in turn, fixedly coupled to the undersurface of floor  10 . 
     Extraction device  116  further includes a carriage  306  which is configured for engagement with module  102 . Carriage  306  includes a capture portion  308  which hooks or grabs the flange  214  of module  102 . Carriage  306  also includes an axial slot  410  (shown in FIG. 4) which receives a forward extending curved portion  513  of toe  512  which is fixedly coupled to surface  210  as for example by screws  402  shown in FIG.  5 . Referring again to FIG. 4, a cup portion  416  is adapted to be pivotally mounted within carriage  306  and includes a handle  418  integrally formed therewith extending outwardly through transverse slot  410 . Cup portion  416  and handle  418  may be pivoted across the carriage so as to enable cup  416  to extend over the lower extremity  513  of toe  512  thereby retaining toe  512  and front wall  210  in a secure position. 
     Carriage  306  is adapted to be driven forward by a drive assembly along the spindle  302  to apply translational force on module  102  rearwardly into engagement with rear connectors  106  and to maintain module  102  in a secure position with a desired amount of force. Carriage  306  is also rearwardly driven to function as an extractor. The drive assembly adapted to drive carriage  306  along spindle  302  is provided with a knob shell  422  which rotates spindle  302 . Thus, as knob shell  422  is rotated in a clockwise manner, module  102  is driven inwardly. When knob shell  422  is rotated in a counterclockwise manner, module  102  is extracted. A more detailed description of the structure and operation of extraction device  116  can be found in the above referred to cited U.S. Pat. No. 3,640,141. 
     As stated previously, the angle formed between the axis of the spindle and the axis of the connector interface (the insertion axis) creates an unwanted force substantially perpendicular to the axis of the male of female connector pins and sockets respectively when module  102  is being extracted through the action of extractor device  116 . This unwanted force perpendicular to the insertion axis can damage the connector pins and render extraction of module  102  much more difficult. It has been discovered that this problem can be solved through the use of a hold-down bracket of the type described below. 
     FIG. 6 is an isometric view of hold-down bracket  600  in accordance with a first embodiment of the present invention. As can be seen, it includes a longitudinal plate  602  having a generally flat upper surface  604  and, for the major portion thereof, a generally flat lower surface  606 . The plate includes a thicker portion  608  which likewise has a flat lower surface  610 . Openings  612  are provided through the thicker portion of the plate for receiving attachment mechanisms such as screws for securing to the lower surface  212  of module  102 . Portion  608  has a cutaway  609  for receiving capture portion  308 . The resulting structure is shown in FIG. 7, which is side view of a front lower portion of module  102  with hold-down bracket  600  affixed thereto. As can be seen, flat surface  610  of hold-down bracket  600  engages surface  212  of module  102  and is in abutment with a rear portion  702  of lip  214 . The hold-down bracket is secured to module  102  by means of screws  704 . In this manner, a slot or channel  706  is created between surface  606  and  212  for receiving floor  110  of shelf  100 . 
     FIG. 8 is an isometric view of a hold-down bracket in accordance with a second embodiment of the invention. In this case, a central portion of plate  602  has been removed leaving legs  804  and  806 . Module  102  is secured in position by a receiving channel formed between the bottom surface of module  102  and legs  804  and  806  of what now may described as a U-shaped hold-down bracket. As was the case previously, this channel receives a front portion of shelf  110 . The space between longitudinal legs  804  and  806  reduces the weight of the hold-down bracket. As was the case previously, cutaway  609  enables capture unit  308  to engage lip  214 . 
     FIG. 9 is similar to FIG. 3 except that module  102  is now equipped with the hold-down bracket  900  shown in FIG.  6 . As can be seen, module  102  is in a fully inserted position such that channel  706  has fully received a front portion of floor  110 . As module  102  is extracted by means of extraction device  116  as previously described, both a horizontal and vertical extraction force is imparted to the front portion of module  102 . However, since the front portion of shelf  110  is slidably secured within channel  706 , module  102  is prevented from moving upward. The length of channel  706  (i.e. the depth to which the front portion of floor  110  is received in channel  706 ) is preferably equal to or greater than the depth to which pins of connectors  106  are received in female connectors  202 . Therefore, when channel  706  clears the front portion of floor  110 , the pins of connectors  106  have been fully extracted from female connectors  202 . Thus, the vertically upward extraction force produced by extraction device  116  as it is operated to extract module  102  is counteracted by a downward vertical force produced by hold-down bracket  600  and exerted upon the front portion of floor  110 . 
     FIGS. 10 and 11 are isometric and front views of a third embodiment of a hold-down bracket, and FIG. 12 is a side view illustrating how the hold-down bracket shown in FIGS. 10 and 11 cooperate with module  102 . The hold-down bracket shown in FIGS. 10 and 11 is similar to that shown in FIG. 8 except that the base or cross-member  1002  of the U-shaped bracket is offset from the plane of leg members  804  and  806  such that the upper surface of cross member  1002  resides below the upper surfaces of leg members  804  and  806 . The lower surface of cross member  1002  lies below the lower surfaces of cross members  804  and  806  as is shown in FIG.  11 . This hold-down bracket is mounted similarly to the hold-down bracket shown in FIG. 7 except that cross member  1002  will now seat in a groove  1204  in the bottom surface  212  of module  102 . This provides for both greater clearance and increased bracket stability. 
     Thus, there has been provided a mechanism for preventing the connectors which couple electronic modules to the backplane of a rack or shelf from being damaged when the modules are extracted. This is accomplished by providing a hold-down bracket which counteracts any vertical force of extraction exerted on the module which would tend to shift the direction of extraction upward and away from the insertion axis of connection. 
     While preferred exemplary embodiments have been presented in the foregoing detailed description, it should be appreciated that a vast number of variations in the embodiment exist. It should also be appreciated that the preferred embodiments are only examples and not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description provides those skilled in the art with a convenient roadmap for implementing the preferred exemplary embodiments of the invention. Various changes may be made in the function and arrangement described in connection with the exemplary preferred embodiments without departing from the spirit and scope of the invention as set forth in the appended claims.