Abstract:
The present invention relates to a latching system for an optical transceiver module that eliminates the use of compound latching mechanisms by providing a single latching lever for unplugging the module from its mounting cage. The latching lever includes a pair of arms with a bail handle on one end to facilitate actuation of the latching lever and manipulation of the module. The other end of the latching lever applies a force to the cage to separate first and second mating latching members on the module and the cage, respectively. The fulcrum of the lever is provided by a bend in each arm, which acts like a journal, mounted in a bearing depression formed in the module housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present invention claims priority from U.S. Patent Applications No. 60/361,654 filed Mar. 5, 2002; No. 60/381,256 filed May 17, 2002; No. 60/382,612 filed May 24, 2002 and No. 60/426,937 filed Nov. 15, 2002. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to a latching device for an optical transceiver, and in particular to a pivoting bail latching device used for latching an optical transceiver within a cage.  
         BACKGROUND OF THE INVENTION  
         [0003]    With the advent of “hot pluggable” optical transceivers, latching devices have become a popular safety feature to ensure that the transceiver module is held within the guide rail or cage until purposely removed. Bail latching devices have become particularly popular, due to their functional and ergonomic advantages. Previous bail designs are disclosed in U.S. Pat. No. 5,901,263 issued to IBM Corp., and U.S. Pat. No. 6,439,916 issued to Finisar Corp. The bail in the IBM device forces plastic arms, which are normally biased inwardly, outwardly into engagement with the guide rail system. The bail in the Finisar device pivots a separate pivoting latch member, which is normally biased into engagement with the cage by a specially designed extension of the housing. Both of these devices require specially designed housings, and the use of a separate pivoting latch member or arm, which moves into or out of engagement with the guide rail or cage system. The Finisar device in particular requires a complex assembly process to ensure that the bail, the pivoting latch member and the housing all interact correctly.  
           [0004]    An object of the present invention is to overcome the shortcomings of the prior art by providing a simpler bail latching device with fewer movable parts, providing a more robust structure, and facilitating a much easier assembly process.  
         SUMMARY OF THE INVENTION  
         [0005]    Accordingly, the present invention relates to an opto-electronic device for transmitting signals between an optical waveguide and a host computer of the type including a mounting cage for receiving the opto-electronic device, the opto-electronic device comprising:  
           [0006]    an optical sub-assembly for converting optical signals into electrical signals or electrical signals into optical signals;  
           [0007]    a housing for supporting the optical sub-assembly, the housing including a first latching member for engaging a corresponding second latching member on the mounting cage;  
           [0008]    an optical connector on a first end of said housing for receiving the optical waveguide, and for aligning the optical waveguide with the optical sub-assembly;  
           [0009]    a printed circuit board mounted in the housing including circuitry for controlling the optical sub-assembly;  
           [0010]    an electrical connector extending from a second end of said housing for transmitting electrical signals between the printed circuit board and the host computer; and  
           [0011]    a latching lever pivotally mounted on said housing having a grasping section extending from the first end of said housing for manually rotating the latching lever, and a force applying section for applying a force to the mounting cage to disengage the first and second latching members when the latching lever is rotated. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein:  
         [0013]    [0013]FIG. 1 is an isometric view of the bottom of an optical transceiver device according to the present invention;  
         [0014]    [0014]FIG. 2 is an isometric view of the top of an optical transceiver device according to the present invention;  
         [0015]    [0015]FIG. 3 is an exploded view of the device of FIGS. 1 and 2;  
         [0016]    [0016]FIG. 4 is a partially exploded view of the device of FIGS. 1 and 2;  
         [0017]    [0017]FIG. 5 is a isometric view of the housing of the device of FIGS. 1 and 2;  
         [0018]    [0018]FIG. 6 is a side view of two of the devices of FIGS. 1 and 2 mounted on a host circuit board in a belly to bell arrangement;  
         [0019]    [0019]FIG. 7 is an isometric view of several of the devices of FIGS. 1 and 2 mounted on a host circuit board;  
         [0020]    [0020]FIG. 8 is a partially exploded view of the front end of the device of FIGS. 1 and 2;  
         [0021]    [0021]FIG. 9 is a partially exploded view of a front end of another embodiment of the present invention;  
         [0022]    [0022]FIG. 10 is a partially exploded view of a front end of another embodiment of the present invention;  
         [0023]    [0023]FIG. 11 is an isometric view of another embodiment of a transceiver module of the present invention mounted in a guide rail;  
         [0024]    [0024]FIG. 12 is an exploded view of the transceiver module of FIG. 11;  
         [0025]    [0025]FIG. 13 is an isometric view of the pivoting latch mechanism of the transceiver module of FIGS. 11 and 12;  
         [0026]    [0026]FIG. 14 is an isometric view of the front end of the transceiver module of FIGS. 11 and 12 with the bail in the locked-in position; and  
         [0027]    [0027]FIG. 15 is an isometric view of the front end of the transceiver module of FIGS. 11 and 12 with the bail in the removal position. 
     
    
     DETAILED DESCRIPTION  
       [0028]    With reference to FIGS.  1  to  5 , an optical transceiver  1  according to the present invention includes a thermally conductive housing base  2 , e.g. cast metal, with a receiver optical subassembly (ROSA)  3  and a transmitter optical sub-assembly (TOSA)  4  mounted in the front end thereof, and a printed circuit card  5  extending from the back end thereof.  
         [0029]    L-shaped electrical leads  6   a  and  6   b  extend from the back end of the ROSA  3  and TOSA  4 , respectively, into contact with the printed circuit card  5  for transmitting power and electrical signals therebetween. An extra wire  7  is provided for connecting the ROSA ground to a logic ground on the underside of the printed circuit card  5  A pair of cylindrical optical connectors  8  extend from the front ends of the ROSA  3  and the TOSA  4  for receiving a duplex optical connector  9 , e.g. an LC optical connector. The front end of the housing base  2  forms a shroud for receiving the duplex optical connector  9 , as is well known in the art. The duplex optical connector  9  couples optical fibers  11  and  12  with the TOSA  4  and the ROSA  3 , respectively. An internal electro-magnetic interference (EMI) shield  13  includes radially extending spring fingers  14  for frictionally engaging the outer surface of the optical connectors  8 , and outwardly extending EMI fingers  16  for engaging a mounting cage  17 , which will be discussed in greater detail with reference to FIGS. 6, 7 and  8 .  
         [0030]    An electrical card-edge connector  18  is provided at the outer free end of the printed circuit card  5  for “hot plugging” the transceiver  1  into an electrical connector (not shown) provided in the cage  17 , thereby electrically connecting the transceiver  1  with a host device for the exchange of power and data signals.  
         [0031]    A thermal pad  19  is positioned between the printed circuit card  5  and a thermal boss  21 , which is cast into the housing base  2  A threaded fastener  22  secures the printed circuit card  5  to a T-shaped projection  23  (FIG. 5), which is also cast into the housing base  2 . Heat is dissipated from the printed circuit card  5  through the combination of the thermal pad  19 , the thermal boss  21 , the threaded fastener  22  and the T-shaped projection  23 .  
         [0032]    The T-shaped projection  23  also separates and shields the ROSA leads  6   a  from the TOSA leads  6   b , thereby reducing electrical crosstalk between the two components, without the use of separate shields. The crosstalk originates from the radiated fields caused when the laser is driven at high (multi-gigahertz levels) electrical frequencies. The metal in the T-shaped projection  23  shunts the electrical fields from crossing to the other side of the printed circuit card  5 . Metal to metal contact is provided by a mating top surface, e.g. made of copper, on the printed circuit card  5 .  
         [0033]    The housing  2  base is provided with a chamfered or bevelled rear edge  25  to prevent the housing base  2  from short circuiting the circuit board mounted electrical connector (not shown), if the user attempts to incorrectly plug the transceiver  1  into the cage  17  upside down.  
         [0034]    The housing base  2  is enclosed by a front sheet metal cover  26  and a rear sheet metal cover  27 . The front cover  26  is connected to the housing base  2  using cleats  28 , formed in the sides of the front cover  26 , which engage projections  29  extending from the side of the housing base  2 . Coined-in bumps  31  are provided in the cover  26  for applying a retaining force directly onto the ROSA  3  and the TOSA  4 , when the transceiver module  1  is assembled. The openings  32  are necessary to enable the EMI fingers  16  to extend into contact with the cage  17 . A Z-shaped bend  33  in the front of the front cover  26  acts like a spring to ensure that the front cover  26  is secure at all times.  
         [0035]    The rear cover  27  also includes cleats  34 , which engage projections  36  extending from the housing  2 . Metal tabs  37  are provided in the rear cover  27  for holding the rear part of the circuit card  5  firmly in place in the housing base  2 . The front and rear covers  26  and  27  are independent to enable access to test points on the transceiver  1 . Moreover, the two covers  26  and  27  are manufactured with different widths to conform to mechanical standards. A laser safety label  38  is provided covering parts of both the front and rear covers  26  and  27 . Similarly, a customer label  39  is provided covering a portion of the lower surface of the housing  2 .  
         [0036]    With reference to FIGS. 6, 7 and  8 , the optical transceivers  1  are guided by the cages  17  for hot-plugging into electrical connectors (not shown), which are mounted on a printed circuit board  41  of a host device, represented by faceplate  42 . Each cage  17  includes a resilient tongue  43  with a triangular recess  44  for receiving a mating latch projection  46  extending from the transceiver housing  2 . The latch projection  46  is provided with a sloped front side, which acts as a camming surface to lift the tongue  43 , during insertion of the transceiver  1  into the cage  17 .  
         [0037]    A bail latching lever  50  is provided for disengaging the transceiver  1  from the cage  17 . The bail latching lever  50  includes a laterally extending grasping section  51 , which enables the user to both pivot the bail latching lever  50  and pull the transceiver  1  from the cage  17 . The grasping section  51  can be color coded to differentiate the different optical wavelength transceivers. Two elongated arms  52  extend from the grasping section  51  into the front end of the housing base  2 . A small downwardly angled offset  53  is provided in the arms  52  to ensure that the grasping section  51  does not interfere with the coupling of the duplex optical connector  9  with the optical connectors  8 . Journal bearing sections  54  extend from the arms  52  inwardly towards each other and get seated in bearing surfaces, e.g. depressions  56  (FIGS. 5 and 8) provided in the housing base  2 . Force applying fingers  57  extend from the journal bearing sections  54  on each side of the latch projection  46 . The ends of the fingers  57  are bent downwardly in the direction of the housing base  2  providing a solid stop defining one extreme of the bail latching lever&#39;s throw travel to prevent the bail latching lever  50  from over rotating, and to ensure the fingers  57  do not have any sharp edges, which could damage the cage  17  during insertion of the transceiver  1 . A second stop is provided inside the housing base  2  defining the other extreme of bail latching lever&#39;s throw travel. The front cover  26  applies a small amount of force to the journal bearing sections  54  to hold them in the bearing surfaces  56 , and to prevent any rattling. Furthermore, the force ensures that the bail latching lever  50  is always electrically grounded to the transceiver housing base  2  and cover  26  to prevent EMI during use. A hole  58  is provided in the front cover  26  to enable the fingers  57  to pivot into contact with the tongue  43  on each side of the recess  44 .  
         [0038]    Accordingly, during insertion, the bail latching lever  50  remains freely rotatable, and thereby interferes with the connection of the duplex optical connector  9  with the optical connectors  8 . Just prior to latching, the bent ends of the fingers  57  act as a camming surface with the outer end of the cage  17 , and pivot the bail latching lever  50  into a down position, as in FIG. 8. Subsequently, the latch projection  46  simply deflects the tongue  43  until engaging the triangular recess  44 . During removal, the bail latching lever  50  is rotated into an up position by rotating the grasping section  51  in one direction which rotates the fingers  57  in the opposite direction, thereby disengaging the tongue  43  from the latch projection  46  and enabling the transceiver  1  to be pulled out of the cage  17 .  
         [0039]    With reference to FIG. 6, the top arrangement illustrates how the present invention prevents the connection of the duplex optical connector  9  into the transceiver  1  until the transceiver  1  is fully inserted into the cage  17  and the bail latching lever  50  is in the down position. Furthermore, the aforementioned bail latching arrangement prevents the transceiver  1  from being unplugged from the cage  17 , while the duplex optical connector  9  is seated in the transceiver  1 , because the duplex optical connector  9  prevents the grasping section  51  from being rotated. Moreover, the transceivers  1  can be plugged in “belly to belly”, because the throw travel of the grasping section  51  always remains within the end-face dimensions of the transceiver  1 , and therefore will never interfere with the other devices.  
         [0040]    Variations of the bail latching lever  50 , facilitating access to the grasping section  51 , are illustrated in FIGS. 9 and 10. The bail latching lever  50 , illustrated in FIG. 9, includes a lateral offset  61  in one of the arms  52 , whereby the grasping section  51  does not extend the full distance between the arms  52 . The open area created by the offset  61  enables the user to more easily access the grasping section  51  of another transceiver  1 , positioned in the “belly to belly” position illustrated in FIG. 6.  
         [0041]    Alternatively, as in FIG. 10, a rectangular pull tab  71  can be attached to the grasping section  51  to provide a greater amount of surface area to grasp. The pull tab  71  can also be color coded to identify various characteristics of the transceiver module.  
         [0042]    With reference to FIGS.  11  to  15 , another embodiment of the present invention includes a transceiver module  100  having an integrated locking feature in the form of a pair of latch mechanisms, generally indicated at  101 . The transceiver module  100  is “hot pluggable” in a guide rail or cage assembly  102 , which is mounted on a printed circuit board  103  of a host device represented by chassis  104 .  
         [0043]    The transceiver module  100  includes a housing  106  for supporting and enclosing opto-electronic components, e.g. a transmitter optical sub-assembly (TOSA) and a receiver optical subassembly (ROSA), which are both electrically connected to a printed circuit board (PCB). The PCB includes signal processing electronics with digital and analog circuitry for controlling and monitoring the transmitter and receiver optical sub-assemblies. An electrical connection for the transceiver module  100  to the host printed circuit board  103  is usually made through an edge connector disposed at an extremity of the PCB or via a multi-pin connector disposed at an extremity of the transceiver module  100 . The optical connection of light signals to the transceiver module  100  is made through optical fiber connectors disposed at an end of optical fibers and inserted into optical connector receptacles  107  disposed at an end of the transceiver module  100 . The housing  106  includes heat-dissipating projections  108  for dissipating heat generated by the electronics and optics of the of the transceiver module  100 .  
         [0044]    As best seen in FIG. 13, each latch mechanism  101  includes a rotating pin  110  supporting a pivoting arm  111 , which comprises an actuating end  112  and a latching end  113 . The latching end  113  includes a shoulder  114  for engaging a locking hole  116  formed in the guide rail  102 , thereby preventing accidental disengagement of the transceiver module  100 . A pair of kick back springs  117  normally bias the latching end  113  into the locking hole  116 . Preferably, the kick back springs  117  are metallic leaf springs extending from a base  118  into contact with the latching end  113 . A bail  119 , including longitudinally extending side arms  121  and lateral handle  122 , is pivotally connected to the housing  106  for releasing the latching end  113  from the locking hole  116 . In use the bail  119  is lifted and the side arms  121  push against angled camming faces on the actuating ends  112 , thereby producing a lateral force that pushes the actuating ends  112  outwardly, causing the latching ends  113  to pivot inwardly overcoming the force of the kick back springs  117 . With the bail  116  in the lowered position, as in FIGS. 13 and 14, the kick back spring  117  is free to bias the latching ends  113  outwardly causing them to engage the locking holes  116  thereby fastening the transceiver module  100  to the guide rail assembly  102 .  
         [0045]    When no fiber connector is connected to the connector receptacles  107 , the bail  116  can be lifted, as shown in FIG. 15, and the transceiver module  100  may be removed from the guide rail assembly  102 . When a fiber connector is connected to the connector receptacles  107  the bail  119  is prevented from moving, thereby ensuring that the transceiver module  100  does not get accidentally removed while optically coupled to other devices.