Abstract:
The present invention relates to an optical transceiver unlatching device for disengaging the optical transceiver from a mounting cage found in a host computer device. The unlatching device converts rotational motion from a bail handle into reciprocating motion for a sliding latch member, which disengages spring fingers extending from the mounting cage from abutment surfaces formed in the sides of the optical transceiver. A return spring, extending between the sliding latch member and the optical transceiver housing, is provided to bias the unlatching device into the latched position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims priority from U.S. patent applications Ser. No. 60/409,232 filed Sep. 10, 2002, and Ser. No. 60/438,400 filed Jan. 7, 2003. 

   TECHNICAL FIELD 
   The present invention relates to an unlatching device for an optical transceiver, and in particular to a pivoting bail unlatching device used for unlatching an optical transceiver from a cage. 
   BACKGROUND OF THE INVENTION 
   Optical transceivers have become an ubiquitous link in the fiber optic data communication and telecommunication industries for transferring information between host computer devices and fiber optic networks. Typically, each transceiver module includes a transmitter optical subassembly (TOSA) and a receiver optical subassembly (ROSA), along with the circuitry for the control thereof. The TOSA converts electrical signals from the host device into optical signals for launching into an optical fiber. Conversely, the ROSA receives optical signals from an optical fiber and converts them to electrical signals for transmission to the host device. A front end of the transceiver module includes optical connector ports for receiving connectorized ends of optical fibers, while a rear end of the transceiver module includes an electrical connector for insertion into a mating electrical connector on a circuit board in the host device. 
   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 a 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. 6,439,918 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. 
   Recent designs for cages, in particular (see  FIGS. 1 ) a cage  1  designed for an XFP module  2  (according to the XFP Multi-Source Agreement), includes spring fingers  3  (one of which is shown), which are biased inwardly into the cage  1  for engaging a shoulder  4  on the transceiver housing  6 . During insertion through a bezel  7  and the open end of the cage  1 , the spring fingers  3  slide along a rear end of the transceiver housing  6  until the spring fingers  3  slide over the a shoulder  4  into engagement with abutment surfaces  8 , which prevents the module  2  from being removed. At the same time an electrical connector  5  on the transceiver module  2  engages an electrical connector  10  in the cage  1 , thereby electrically connecting the transceiver module  2  to a host board  9 . The XFP transceiver module  2  also includes a heat sink  11  mounted on the module  2  by a spring clip  12 . 
   An object of the present invention is to overcome the shortcomings of the prior art by providing an unlatching mechanism for disengaging a cage mounted spring finger from an abutment surface on a transceiver housing. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention relates to an optical transceiver for insertion into a mounting cage, of the type including at least one spring finger extending into engagement with at least one abutment surface on the optical transceiver, comprising:
         at least one optical sub-assembly for converting an optical signal into an electrical signal or for converting an electrical signal into an optical signal;   a housing for supporting each optical sub-assembly;   at least one optical connector port for receiving an optical fiber;   an electrical connector for transmitting electrical signals to and from each optical sub-assembly;   a sliding member reciprocatable on said housing between a latched and an unlatched position;   at least one camming member extending from said sliding member;   a bail handle pivotally mounted on said housing and engaged with said sliding member;   whereby rotation of said bail handle reciprocates said sliding member causing said camming member to disengage each spring finger from each abutment surface enabling the optical transceiver to be removed from the mounting cage.       

   Another aspect of the present invention relates to an unlatching mechanism for an opto-electronic device, of the type which is mountable in a cage attached to a circuit board in a host device, the cage having at least one spring finger for extending into contact with an abutment surface on a housing of the opto-electronic device, the unlatching mechanism comprising:
         a sliding member reciprocatable on the housing between a latched and an unlatched position;   at least one camming member extending from said sliding member;   a bail handle pivotally mounted on the housing and engaged with said sliding member;   whereby rotation of said bail handle reciprocates said sliding member causing said camming member to disengage each spring finger from each abutment surface enabling the opto-electronic device to be removed from the cage.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail with reference to the accompanying drawings, which represent preferred embodiments thereof, wherein: 
       FIG. 1  is an exploded view of a conventional transceiver module and cage assembly; 
       FIG. 2  is an isometric view of a transceiver module according to the present invention mounted in the transceiver cage of  FIG. 1 ; 
       FIG. 3  is an isometric view of the bail and sliding member of the unlatch mechanism according to the present invention; 
       FIG. 4  is an isometric view of the bail and sliding member of the unlatch mechanism of  FIG. 3 ; 
       FIG. 5  is a side view of a transceiver housing without the sliding member of  FIG. 3 ; 
       FIG. 6  is an isometric view of the transceiver housing is the latched position; 
       FIG. 7  is an isometric view of the transceiver housing of  FIG. 6  in the unlatched position; and 
       FIG. 8  is an isometric view of the sliding member of FIGS.  6  and  7 . 
   

   DETAILED DESCRIPTION 
   With reference to  FIGS. 2  to  4 , the unlatching mechanism according to the present invention includes a sliding member  21 , comprised of two rectangular sliding arms  22   a  and  22   b , and a rectangular cross brace  23  extending therebetween. The sliding arms  22   a  and  22   b  are mounted in channels  24  (one shown in FIG.  4 ), which are provided in opposite sides of the transceiver housing  6 . When in the channels  24 , the sliding arms  22   a  and  22   b  are flush with the sides of the housing  6 , so that the outside of transceiver module  2  matches the inside surface of the cage  1 , while enabling the transceiver module  2  to be slid into and out of the mounting cage  1  with relative ease. The cross brace  23  extends across the bottom of the transceiver housing  6  between the sliding arms  22   a  and  22   b . The outer free ends  26   a  and  26   b  of the sliding arms  22   a  and  22   b , respectively, are bent inwardly towards each other for extending into ramped sections  27  at an end of the channels  24 . The bent ends  26   a  and  26   b  enable the spring fingers  3  of the cage  1  to engage the abutment surfaces  8 , while in the latched position (FIG.  6 ). Alternatively, the outer free ends  26   a  and  26   b  can be thinner than the rest of the sliding arms  22   a  and  22   b  to enable the spring fingers  3  to engage the abutment surfaces  8  (FIG.  8 ). Camming members  28   a  and  28   b  are mounted on the ends  26   a  and  26   b , respectively, for disengaging the spring fingers  3  from the abutment surfaces  8 . In the latched position ( FIG. 6 ) the camming members  28   a  and  28   b  rest in recesses  29  in the sides of the transceiver housing  6  adjacent the ramped sections  27 . Reciprocation of the sliding member  21  causes the camming members  28   a  and  28   b  to lift the spring fingers  3  out of engagement with the abutment surfaces  8  until the spring fingers  3  are clear of the shoulder  4  and able to slide over the remaining portion of the transceiver housing  6  (FIG.  7 ). 
   A bail handle  30  is pivotally mounted on one end of the sliding member to actuate the sliding member  21 , as well as provide a handle by which the transceiver module  2  may be pulled out of the cage  1 . Ends  31  of the bail  30  are pivotally mounted to the transceiver housing  6 . Arcuate sections  32  of the bail  30  extend around semi-circular projections  33 , which extend from the sliding arms  22   a  and  22   b . Circular projections  34  also extend from the sliding arms  22   a  and  22   b  providing a bearing surface for the arcuate sections  32 . 
   In the latched position ( FIG. 6 ) the bail  30  is pivoted down and out of the way from in front of optical connector ports  35  enabling optical connectors to be received therein. The sliding arms  22   a  and  22   b  are rearwardly extending with the ends  26   a  and  26   b  positioned adjacent to the ramped sections  27 , and the camming members  28   a  and  28   b  positioned in the recesses  29 . As the bail  30  is rotated, the arcuate sections  32  apply a force to the semi-circular projections  33 , thereby forcing the sliding member  21  forward, which causes the camming members  28   a  and  28   b  to lift the spring fingers  3  away from the abutment surfaces  8  as the spring fingers  3  ride up the surface of the camming members  28   a  and  28   b . With the spring fingers  3  no longer in contact with the abutment surfaces  8 , any pulling force applied to the bail  30  causes the entire transceiver module  2  to be slid from within the cage  1 . 
   With reference to  FIG. 5 , another embodiment of the present invention includes a pair of return springs  41  extending from the cross brace  23 . Curved outer free ends of the return springs  41  extend into close proximity with a front face plate  42 , while in the latched position, whereby reciprocation of the sliding member  21  causes the return springs  41  to engage the front face plate  42  creating a restore force, which tends to return the sliding member  21  back to the latched position. 
     FIGS. 6 ,  7  and  8  illustrate another embodiment of the present invention, in which a sliding member  61  includes rearwardly-extending rectangular sliding arms  62   a  and  62   b , and a cross brace  63 . The ends  66   a  and  66   b  of the sliding arms  62   a  and  62   b , respectively, are not bent as in the aforementioned embodiment, but simply taper slightly providing access to the abutment surfaces  8 . Camming members  68   a  and  68   b  are provided for disengaging the spring fingers  3  from the abutment surfaces  8 , as hereinbefore discussed. A wire bail  70  pivots from a latched position ( FIG. 6 ) to an unlatched position ( FIG. 7 ) to initiate the disengagement of the transceiver module  2  from the cage  1 . A 90° bend, proximate each end of the bail  70 , form bearing shafts  71 , which are pivotally mounted on the housing  6 , defining an axis of rotation for the bail  70 . Arcuate sections  72 , of the bail  70 , extend around a curved projection  73 , which extend from the sliding member  61 . Retaining walls  74  extend from the sliding member  61  providing a bearing surface or a stop for the arcuate sections  72  during rotation of the bail  70 . Rotation of the bail  70  results in the arcuate sections  72  applying a force to the curved projections  73 , thereby reciprocating the sliding member  61 , which enables the camming members  68   a  and  68   b  to lift the spring fingers  3  away from the abutment surfaces  8 . Continued pulling force on the bail  70  disengages the mating electrical connectors  5  and  10 , and pulls the transceiver module  2  from the cage  1 . A pair of Y-shaped return springs  81  are provided for biasing the sliding member  61  back into the latched position. One arm  82  of the return spring  81  engages the front face plate  83 , while another arm  84  engages the cross brace  63 . By engaging both surfaces at once the spring force is increased, as well as the durability of the return springs  81 .