Abstract:
A fiber otic connector assembly includes a receptacle for receiving a fiber optic connector along an optic axis. A housing has an open end for receiving the fiber optic connector. A pair of shutter members are pivotally mounted on the housing at opposite sides of the open end for pivotal movement toward and away from each other to close and open the open end. One of the shutter members is shorter than the other shutter member so that the one shutter member closes before the other shutter member and, thereby, prevents binding therebetween. The receptacle has a bottom mating face, and the fiber optic connector has a plurality of alignment pins insertable into guide holes in the mating face. The fiber optic connector assembly include particular dimensional relationships to prevent the alignment pins from engaging the mating face rather than entering the guide holes.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention generally relates to the art of fiber optic connectors and, particularly, to a fiber optic connector which includes a pair of shutter members, and a connector assembly which is particularly dimensioned to prevent alignment pins of one connector from damaging an internal mating face of a second connector.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fiber optic connectors of a wide variety of designs have been employed to terminate optical fiber cables and to facilitate connection of the cables to other cables or other optical fiber transmission devices. A typical optic fiber connector includes a ferrule which mounts and centers an optical fiber or fibers within the connector. The ferrule may be fabricated of such material as ceramic. A ferrule holder or other housing component of the connector embraces the ferrule and may be fabricated of such material as molded plastic. A spring may be disposed within the housing or ferrule holder such that the ferrule is yieldably biased forwardly for engaging another fiber-mounting ferrule of a mating connecting device.  
           [0003]    A plurality of fiber optic connectors often are mated in an adapter with another connector or connectors, with the adapter aligning the fibers to provide low insertion losses. The adapter couples the mating connectors together so that their encapsulated fibers connect end-to-end. The adapter may be an in-line component, or the adapter can be designed for mounting in an opening in a panel, backplane, circuit board or the like.  
           [0004]    Various problems are encountered when terminating optical fibers in fiber optic connectors versus terminating electrical conductors in electrical connectors, when situations arise wherein a fiber end of an “active” fiber optic connector is exposed. A typical situation might arise when one of the fiber optic connectors at one end of an adapter is removed, leaving the other “active” fiber optic connector or connectors in the adapter.  
           [0005]    In particular, an exposed fiber end may be damaged by adverse environmental hazards, and the accumulation of dust and dirt may impair the optical transmission capabilities of the fiber. Another very important problem is to protect an operator&#39;s eyes from dangerous light beams from the exposed end of an active optical fiber. For instance, an operator&#39;s eyes may be damaged from dangerous light beams exiting an unprotected receptacle or adapter.  
           [0006]    Heretofore, dust covers, end caps or spring-loaded shutter members have been used to close an open end of an adapter to, thereby, cover the exposed fiber ends to protect the fiber ends from adverse environmental hazards and to prevent light energy from the fiber ends from exiting the adapter. One such spring-loaded shutter member is pivotally mounted on the adapter adjacent the open end thereof and is pivotally movable to close and open the open end. The shutter member extends across the optic axis of the connector/adapter assembly when the shutter member is closed. The shutter member may be pivotable away from the optic axis to its open condition.  
           [0007]    In some connector assemblies, a pair of opposing shutter members are used, versus a single shutter member. The pair of shutter members are pivotally mounted at opposite sides of the connector receptacle, and the use of a pair of opposing shutter doors has a number of advantages. First, the two shutter members save considerable axial space which otherwise would be required to accommodate the full pivoting action of a single shutter member which would be approximately twice the size of a pair of shutter members. Second, it is easier to open the two smaller shutter members because smaller springs can be provided. When a mating connector has alignment pins, the pins generally are at the center of the connector and, thereby, most forces are applied near the edges of the pair of shutter members, whereas with a single shutter member a large force is required on one side of the centerline than the other side. Third, the wiping surface of either of the pair of shutter members is one-half the wiping surface of a single shutter member. With the single shutter member, dust collected on the outside of the shutter member is carried all the way into the interface area between the connectors. With a pair of shutter members, any dust which accumulates on the outer surfaces thereof will be deposited away from the mating interface rather than being carried further inwardly.  
           [0008]    However, the use of a pair of opposing shutter members continue to create problems in being able to completely close an open end of a receptacle without causing binding between the shutter members. The present invention is directed to solving this problem by a simple arrangement whereby one shutter member is shorter than the other shutter member and, thereby, the shorter shutter member closes before the longer shutter member and there can be no binding.  
           [0009]    The invention herein is directed to solving other problems in mating such fiber optic connectors by providing specific dimensional relationships between a receptacle and a plug of a connector assembly to prevent alignment pins on the plug from damaging the mating interface within the receptacle.  
         SUMMARY OF THE INVENTION  
         [0010]    An object, therefore, of the invention is to provide a new and improved fiber optic connector assembly of the character described.  
           [0011]    According to one aspect of the invention, a connector receptacle is provided for receiving a fiber optic connector along an optic axis. The receptacle includes a housing having an open end for receiving the fiber optic connector inserted thereinto on the optic axis. A pair of shutter members are pivotally mounted on the housing at opposite sides of the open end for pivotal movement toward and away from each other toward and away from the optic axis to close and open the open end. One of the shutter members is shorter than the other shutter member in a direction radially of the axis so that the one shutter member closes before the other shutter member and, thereby, prevents binding therebetween.  
           [0012]    In the exemplary embodiment of the invention, the shutter members are generally planar and rectangular for closing a generally rectangular open end of the housing. An inner edge of the longer shutter member overlaps an inner edge of the shorter shutter member when the shutter members are closed. A spring is operatively associated between each shutter member and the housing to bias the respective shutter member toward its closed positions. The springs have generally equal spring constants to apply a generally equal spring force on each shutter member.  
           [0013]    According to another aspect of the invention, a fiber optic connector assembly includes a first connector having a housing with a receptacle defining an optic axis. A bottom of the receptacle defines a mating face with a pair of transversely spaced pin-receiving guide holes. A second connector includes a housing forming a plug insertable into the receptacle of the first connector on the optic axis. The second connector has a pair of transversely spaced alignment pins projecting axially from the plug for insertion into the guide holes in the mating face at the bottom of the receptacle of the first connector. The plug and the receptacle have respective cross-dimensions such as to provide a sufficiently close fit, and the receptacle is of sufficient depth in relation to the length of the plug and the projecting alignment pins, to prevent the alignment pins from engaging the mating face at the bottom of the receptacle rather than entering the guide holes in the mating face.  
           [0014]    According to still another aspect of the invention, an elongated guide rib is provided on one of the outside of the plug of the second connector or the inside of the receptacle of the first connector, insertable into an elongated groove in the other of the outside of the plug or the inside of the receptacle when the plug is inserted into the receptacle. The rib and the groove extend generally parallel to the optic axis. The rib has a sufficiently close fit in the groove, and the rib and groove have sufficient lengths in relation to the length of the alignment pins, to prevent the alignment pins from engaging the mating face at the bottom of the receptacle rather than entering the guide holes in the mating face.  
           [0015]    Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which:  
         [0017]    [0017]FIG. 1 is perspective view of a fiber optic connector assembly according to the invention, in unmated condition;  
         [0018]    [0018]FIG. 2 is a perspective view of the assembly in mated condition;  
         [0019]    [0019]FIG. 3 is a horizontal section through the assembly as viewed in FIG. 2;  
         [0020]    [0020]FIG. 4 is a vertical section through the assembly as viewed in FIG. 2;  
         [0021]    [0021]FIG. 5 is an enlarged side elevational view of the adapter assembly, partially in vertical section to show the shutter members in closed condition;  
         [0022]    [0022]FIG. 6 is an enlarged perspective view of the adapter assembly, partially cut-away to show the pivotal mounting and one of the springs for one of the shutter members;  
         [0023]    [0023]FIG. 7 is an end elevational view looking toward the right-hand end of the adapter assembly shown in FIGS. 5 and 6; and  
         [0024]    [0024]FIG. 8 is a perspective view of the connector assembly of FIGS. 1 and 2, with the adapter assembly cut-away to show the condition when an attempt is made to insert the plug connector at an angle or skewed orientation. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    Referring to the drawings in greater detail, and first to FIGS. 1 and 2, the invention is embodied in a fiber optic connector assembly, generally designated  10 , which includes a plug connector, generally designated  12 , insertable on an optic axis  14  into a receptacle  16  of an adapter assembly, generally designated  18 . FIG. 1 shows the plug connector and the adapter assembly in unmated condition. The plug connector is inserted in the direction of arrow “A” (FIG. 1) into an open end  16   a  of receptacle  16  of adapter assembly  18  to a mated condition shown in FIG. 2.  
         [0026]    Plug connector  12  includes a housing  20  which mounts one or more ferrules (not visible in the drawings) that terminate the individual optical fibers  22  of a large fiber optic cable or ribbon  24 . As is known in the art, the individual fibers are exposed at a front mating face  26  of a plug  28  of plug connector  12 , the plug being insertable into open end  16   a  of receptacle  16  of adapter assembly  18 . A pair of transversely spaced alignment pins  30  project forwardly of mating face  26 . Housing  12  also journals a pair of transversely spaced jack screws  32  for free rotation relative to the housing, the jack screws having externally threaded distal ends  32   a  projecting forwardly of mating face  26 . A pair of transversely spaced, forwardly opening guide grooves  34  are formed in each of the top and bottom of housing  20 . For purposes to be described in greater detail hereinafter, each guide groove is 12.5 mm long and 3.0 mm wide.  
         [0027]    Referring to FIGS. 3 and 4 in conjunction with FIGS. 1 and 2, adapter assembly  18  has a housing which basically includes two parts, namely a front housing part  36  which defines receptacle  16  and a rear housing part  38  which receives a plurality of terminal modules, generally designated  40 . Rear housing part  38  is connected to front housing part  36  by a plurality of fasteners  42 . The rear housing part defines a mating face  44  at the bottom of receptacle  16 . Each terminal module terminates a separate, small fiber optic cable or ribbon  46 . The individual fibers of each cable or ribbon are terminated in respective ferrules  48  of terminal modules  40 . The ferrules have mating faces which are generally flush with mating face  44 . As best seen in FIG. 1, a pair of guide ribs  50  project inwardly from opposite sides of receptacle  16  for insertion into guide grooves  34  on the top and bottom of plug connector  10 . Receptacle  16  of adapter assembly  18 , and plug  28  of plug connector  12 , are rectangular in configuration defining major sides extending horizontally in FIGS. 1 and 2 and as represented by the section direction of FIG. 3, along with minor sides extending in the vertical direction in FIGS. 1 and 2 and as represented by the section direction of FIG. 4. Guide ribs  50  and guide grooves  34  are transversely spaced on the major sides of this rectangular configuration. Each guide rib is approximately 2.0 mm wide and substantially the same length as guide grooves  34 .  
         [0028]    [0028]FIG. 5 shows a feature of the invention which comprises a pair of shutter members or doors  60  and  62  which are pivoted at  64  and  66 , respectively. The shutter members are pivotally mounted on opposite major sides of adapter assembly  18  within receptacle  16 . The shutter members are pivotally movable toward and away from each other and toward and away from optic axis  14  to close and open end  16   a  of receptacle  16 . FIGS. 5 and 7 show the shutter members in their closed condition. FIG. 4 shows the shutter members in their open condition, having been moved thereto by plug  28  of plug connector  12 .  
         [0029]    [0029]FIG. 6 shows that each shutter member  60  and  62  includes a pivot shaft  68  at each opposite end thereof. The pivot shaft is journalled in opposite minor side walls of front housing part  36  of adapter assembly  18 . A torsion spring  70  is wrapped around the pivot shaft at each opposite end of each shutter member. As seen in FIG. 5, each torsion spring has one end  70   a  abutting the back side of one of the shutter members and an opposite end  70   b  abutting an inside wall of front housing part  36  of the adapter assembly. The torsion springs, thereby, bias the shutter members to their closed positions shown in FIG. 5. The torsion springs are fabricated to have equal spring constants to apply generally equal forces to each opposite end of each shutter member.  
         [0030]    The invention contemplates a unique arrangement to prevent binding of shutter members  60  and  62  when they move to their closed position shown in FIGS. 5 and 7. Specifically, shutter member  60  is shorter than shutter member  62 . Therefore, the shorter shutter member  60  will close before the longer shutter member  62  because of the smaller length and smaller turning or pivoting radius. The shutter members are generally rectangular as best seen in FIG. 7, and the free edge of the longer shutter member overlaps the free edge of the shorter shutter member as seen in FIG. 5, when the shutter members are closed.  
         [0031]    [0031]FIG. 8 represents a situation when an operator may attempt to insert plug  28  of plug connector  12  into receptacle  16  of adapter assembly  18  at an angle or skewed orientation which could cause problems if alignment pins  30  could engage mating face  44  at the bottom of receptacle  16  before the alignment pins are aligned with a pair of pin-receiving guide holes  72  in the mating face of rear housing part  38  of the adapter assembly. Distal ends  32   a  of jack screws  32  are threaded into internally threaded holes  74 , but the projecting ends of the jack screws are shorter than the projecting ends of the alignment pins, so the jack screws would not create any problems. If alignment pins  30  were able to engage mating facing  44  before the pins are aligned with guide holes  72 , the alignment pins could damage ferrules  48  of terminal modules  40 , along with the ends of the optical fibers which are terminated by the ferrules. The alignment pins also could damage any one of a plurality of smaller guide pins  76  which project from the ferrules.  
         [0032]    In order to ensure that alignment pins  30  are aligned with guide holes  72  (FIG. 8), a redundant dimensional system is provided between plug connector  12  and adapter assembly  18 , particularly front housing part  36  of the adapter assembly which defines receptacle  16 . First of all, guide ribs  50  within receptacle  16  and guide grooves  34  on plug connector  12  have a sufficiently close fit and are of sufficient lengths to prevent alignment pins  30  from engaging mating face  44  at the bottom of receptacle  16  before the alignment pins are aligned with guide holes  72 . Specifically, as stated above, guide grooves  34  are 12.5 mm long and 3.0 mm wide. Guide ribs  50  are 2.0 mm wide so that a close fit is provided between the guide ribs and the guide grooves. The ribs have lengths of approximately the same lengths as the guide grooves so that the ribs bottom-out in the guide grooves as seen in FIG. 3. Therefore, with this close fit, plug  28  of plug connector  12  cannot be inserted into receptacle  16  at a sufficiently severe angle as shown in FIG. 8, because the tips of guide ribs  50  must enter guide grooves  34  and, with the close fit between the ribs and the grooves along with the lengths of the ribs and grooves, this intermitting relationship will cause plug connector  12  to “straighten-out” on insertion into receptacle  16 . As a result, the straightened plug connector will cause alignment pins  30  to be aligned with and enter guide holes  72  without engaging mating face  44  or damaging ferrules  48  and the terminated optical fibers.  
         [0033]    A redundant dimensional relationship exists between plug  28  and alignment pins  30 , along with receptacle  16 , to also prevent plug connector  12  from being inserted into receptacle  16  at a severe angle, i.e., without straightening the plug connector so that the alignment pins are aligned with guide holes  72 . Specifically, double-headed arrow  80  in FIG. 3 represents the major or “X” dimension of receptacle  16  and double-headed arrow  82  in FIG.  4  represents the minor or “Y” dimension of receptacle  16 . In the illustrated embodiment, the major or “X” dimension  80  is 46.6 mm, whereas the “Y” or minor dimension  82  is 20.75 mm. Still referring to FIGS. 3 and 4, double-headed arrow  84  represents the “X” or major dimension of plug  28  and is 46.0 mm. Double-headed arrow  86  in FIG. 4 represents the “Y” or minor dimension of plug  28  and is 20.0 mm. Therefore, it can be seen that the dimensions (46.0 mm×20.0 mm) of plug  28  establishes a close fit within receptacle  16  which has very slightly larger dimensions (46.5 mm×20.75 mm).  
         [0034]    In addition, receptacle  16  has a depth as represented by double-headed arrow  88  in FIG. 5 in relation to the combined length of plug  28  and the projecting alignment pins  30 , as indicated by double-headed arrow  90  in FIG. 8, to prevent the alignment pins from engaging mating face  44  within the receptacle. Specifically, the depth of receptacle  16  in a “Z” direction as represented by double-headed arrow  88  in FIG. 5, is on the order of 25.75 mm. The combined length of plug  28  and projecting alignment pins  30  in the “Z” direction as indicated by double-headed arrow  90  in FIG. 8, is on the order of 25.85 mm. Therefore, with the sufficiently close fit between plug  28  and receptacle  16  as described above, along with receptacle  16  being of a sufficient depth in relation to the length of plug  28  and the projecting alignment pins  30 , the alignment pins are prevented from engaging mating face  44  at the bottom of the receptacle before the pins are aligned with guide holes  72  in mating face  44 . This positional relationship is a redundant dimensional relationship in addition to that of guide ribs  50  and guide grooves  34 , to ensure that the alignment pins do not ever engage mating face  44  of ferrules  48  during mating of plug connector  12  and adapter assembly  18 .  
         [0035]    It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.