Abstract:
Unitary construction springs are provided for exerting an axial spring force for biasing a terminus of a connector outwardly so as to assure that the terminus abuts a corresponding terminus in a mating connector with sufficient force for maintaining proper contact when exposed to shocks and vibrations.

Description:
BACKGROUND OF THE INVENTION 
     Connectors for attaching optical fibers to one another comprise a housing within which at least one connector terminus is located. Each connector terminus holds an optical fiber such that the optical fiber is in desired alignment with respect to a corresponding optical fiber in a connector terminus in the mating connector. One of the connector termini applies a spring pressure which causes the terminus to extend outwardly from the connector. The spring pressure provides a force which assures that the two mating termini abut one another with sufficient force to maintain desired alignment and contact of the optical fibers during shock and vibration and with sufficient force to mitigate Fresnel losses due to the formation of undesirable air gaps therebetween. 
     It is therefore desirable that each terminus extend from a connector under a spring biasing force. However, it has been found that coil springs, which wrap around a terminus in a helical configuration, are not suitable. Coil springs are not capable of providing sufficient force, e.g., approximately five pounds, which is required for proper mating of the termini. A stack of Belleville washers, centered about the terminus, are typically used to form a Belleville spring to provide the desired spring biasing force. Each Belleville washer has a surface which tapers outwardly in a radially inward direction. The stack of Belleville washers generally contains approximately eleven washers oriented such that adjacent washers face in opposite directions, so as to provide the desired spring force. Thus, when a terminus is pushed inwardly, i.e., toward the connector, the Belleville washers tend to flatten so as to provide the desired outwardly directed spring biasing force. 
     Because of the small size of each terminus, Belleville washers having a diameter of approximately {fraction (1/10)} of an inch are necessary. As can be appreciated the handling of such small washers during assembly of the terminus is extremely difficult and time consuming. The individual Belleville washers must be painstakingly stacked about the terminus, one atop another, to form a spring. Not only is it difficult to pick up and handle such small washers one at a time, as is necessary during the stacking process, but it is also difficult to ascertain the orientation of each washer (to determine which side of the washer has the tapering surface). Further, it is necessary that such assembly be done using a microscope. 
     As such, it is desirable to provide a spring biasing mechanism which is not subject to the handling and assembly difficulties associated with the formation of a stack of Belleville washers. 
     SUMMARY OF THE INVENTION 
     Unitary construction springs are provided for spring biasing each fiber optic terminus of a connector outwardly, so as to assure that it abuts a corresponding terminus of a mating connector with sufficient force for maintaining proper contact when exposed to shocks and vibrations. A first embodiment spring has an annular construction defining an annular inwardly extending channel having two legs and a convex web therebetween. The two legs extend radially inward from the web. Each leg defines an annular flange. Externally, the convex web defines an annular concavity. When axially compressed, the annular flanges are flexed inward and provide an axial force as they try to extend outward to regain their original position. The convex web also allows for some axial compression of the spring and thereby also generates a spring force. 
     Optionally, the spring may be configured to have a split-ring construction such that it is insertable over the terminus probe without having to be slid over the end thereof. In other words, the spring may comprise a discontinuity or split formed along its length allowing the spring to be opened up so as to allow it to receive the terminus probe through the split thereof. 
     An optional retaining ring may be utilized to maintain the spring in position about the terminus and to prevent the accidental disengagement of the spring from the terminus. The ring is fitted in surrounding relationship to the annular spring and is preferably fitted within the concavity defined on the outer surface of the web. The retaining ring should preferably be a split ring such that it may be easily fitted over the annular spring. 
     An alternative embodiment of the unitary construction spring of the present invention is also of annular construction and comprises a cylindrical body having an edge beveled radially inward and a longitudinal split spanning the length of the spring. In operation the spring is pushed against a stop member on the terminus causing the spring beveled edge to ride against the stop member and the spring to radially expand about the split. The spring generates a spring force as the spring attempts to regain its original position and the beveled edge cams the spring against the stop member. 
     Another embodiment spring of the present invention comprises a generally cylindrical body having a plurality of pairs of cut-outs which define a plurality of deformable beams which deform so as to provide a spring action. This embodiment spring is formed by taking a hollow cylinder and cutting a series of first and second diametrically opposed pairs of cut-outs through the cylinder body. The first pairs of cut-outs are oriented at 90° with respect to the second pairs of cut-outs, thus defining the plurality of beams which bend when compressive force is applied to the spring. Each pair of cut-outs are preferably parallel to a plane perpendicular to the longitudinal axis of the cylinder. Moreover, to provide sufficient flexibility to the “beams” each cutout of each pair spans a major portion of half of the cylinder periphery. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of two prior art fiber optic connectors with fiber optic termini shown in side view. 
     FIG. 2 is a cross-sectional view of the connectors shown in FIG. 1 in a mated position. 
     FIG. 3 is partial cross-sectional view of a connector housing a terminus having a spring of the present invention which is shown in cross-section. 
     FIG. 4 is an end view of the spring shown in FIG.  3 . 
     FIG. 5 is partial cross-sectional view of a connector housing a terminus having another embodiment spring of the present invention which is shown in cross-section. 
     FIG. 6 is an end view of the spring shown in FIG.  5 . 
     FIG. 7 is a side view of a further embodiment spring of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides for a unitary construction spring for spring biasing each terminus of a connector outwardly, so as to assure that it abuts a corresponding terminus of a mating connector with sufficient force. 
     Referring now to FIG. 1 the mating of two prior art connectors  10 ,  12 , each having a corresponding terminus  14 ,  16  one of which (terminus  16 ) incorporates Belleville washers  18  for applying a spring force is shown. Each connector has a corresponding interface side  20 ,  22  for interfacing with the other connector. Each connector may be fitted with more than one termini. For illustrative purposes, however, the connectors are described herein as each accommnodating a single terminus. 
     A first terminus  14  is attached to one end of a fiber optic wire  25  and is fitted within a bore  24  formed in the first connector  10 . The first terminus comprises a contact probe  26  and a housing  28 . The contact probe  26  proximal end is fitted within the housing  28 . The fiber optic wire  25  is coupled to the contact probe  26  through the housing  28  at the proximate end of the first terminus. The fiber optic wire  25  extends coaxially within the probe to the tip  62  of the probe. Distally the probe diameter is stepped up, forming a larger diameter probe section  32  extending from a smaller diameter probe section  30 . The first terminus also comprises a sleeve  34  which is fitted over the base of the larger diameter section  32 . An expandable sleeve  36  of the first terminus is fitted over and in surrounding relationship to the smaller diameter section  30  and is positioned for receiving the sleeve  34 . 
     The first terminus housing  28  is loosely retained within the bore  24  in first connector  14 . The bore  24  accommodating the first terminus is designed to allow for slight side to side movement of the terminus housing  28  relative to the bore without allowing the first terminus to disengage from the bore and thus from the first connector. The connector may be molded around the terminus. An alignment sleeve  37  open at both ends is fitted over the first terminus contact probe  26  within the first connector. The alignment sleeve inner diameter is not as great as the outer diameter of the sleeve  34 . Consequently, the sleeve  34  limits the travel of the alignment sleeve relative to the probe. 
     A second terminus  16  is fitted within a bore  38  in the second connector  12 . The second terminus also comprises a contact probe  40  and a housing  42 . The proximal end of the contact probe  40  is fitted within the housing  42 . A fiber optic wire  39  is coupled to the contact probe  40  through a housing  42  at the proximate end of the second terminus. The fiber optic wire  39  extends coaxially within the probe to the tip  60  of the probe. Distally the probe diameter is stepped up forming a larger diameter probe section  43  extending from a smaller diameter probe section  44 . The second terminus also comprises a sleeve  46  which is fitted over the base of the larger diameter section  43 . An expandable sleeve  48  is fitted over and in surrounding relationship to the smaller diameter section  44 . 
     A stop washer  50  is fitted over the smaller diameter section  44  of the second terminus probe between the sleeve  46  and the expanding sleeve  48 . In prior art termini, a stack of Belleville washers  18  are fitted over the smaller diameter section  44  and are sandwiched between the stop washer  50  and the base  47  of the sleeve  46  at the base of the larger diameter section  43 . The stack of Belleville washers define an accordion or bellows-like structure. The distal end including the larger diameter section of the probe  40  of the second terminus extends beyond the interface side  22  of the second connector  12 . The second terminus housing  42  is also loosely retained within the bore  38  in the second connector  12 . 
     To guide the alignment and the mating of the two connectors, pins  52 ,  54  are typically fixedly attached to one connector (the first connector  10 , in FIG. 1) and are fitted in corresponding bores  56 ,  58  formed in the other connector. A fastener  68  extending from one of the connectors (as for example, connector  10  in FIG. 10) may be used to fasten the two connector members together by threading into a threaded bore  61  in the other connector (for example, connector  12  in FIG.  10 ). Other types of fastening configurations may also be used to keep the two connector members fastened to each other. 
     When the connector members are fastened together, the second terminus  16  extending from the interface side  22  of the second connector  12  is inserted into the bore  24  in the first connector from the interface side  20  of the first connector and penetrates the alignment sleeve  36  through the open end  63  of the alignment sleeve  37  as shown in FIG.  2 . The alignment sleeve ensures that the two contact probes  26 ,  40  from the two termini are properly aligned so as to properly align the fiber optic wires  25 ,  39  within the probes. The two contact probes contact each other at their distal tips  60 ,  62  causing the contact probe  40  of the second terminus to move distally and thereby compress the Belleville washers  18  between the sleeve  46  and the stop washer  50  which engages the second terminus expanding sleeve  48 . Consequently, the compressed Belleville washers  18  exert a force against the sleeve  46  forcing the second terminus probe  40  to maintain contact with the first terminus probe  26 . Simultaneously, the sleeve  34  of the first terminus engages the expanding sleeve  36  of the first terminus. As a result, a desired distal biasing force is created by the spring action of the Belleville washers when the connector is mated to a corresponding connector and a terminus abuts a corresponding terminus of the mating connector. As the stop washer  50  and the sleeve  34  engage their corresponding expanding sleeves  48  and  36 , they cause the expanding sleeves to expand and wedge in their corresponding bores  38  and  24  fixing the position of the termini relative to their corresponding connectors. By allowing the termini to be loosely retained within their corresponding connectors, the alignment sleeve  36  is able to properly align the two probes prior to the locking of the termini in their corresponding connectors. 
     Referring now to FIG. 3, in one embodiment, the present invention comprises a unitary construction spring  70  which takes the place of the Belleville  18  washers shown in FIGS. 1 and 2, thereby substantially simplifying the assembly process. The spring  70  is annular in construction, such that it surrounds a portion of the terminus contact probe smaller diameter section  44 , much as the Belleville washers shown in FIG. 1 do. The spring defines an annular inwardly extending channel  72  having two legs  74 ,  76  and a convex web  78  therebetween. Stated differently, the two legs extend radially inward from the web. Each leg defines an annular flange  80 ,  82 . Externally, the convex web defines an annular concavity  84 . 
     As the probe contacts the probe of another terminus during mating of the connectors, one of the flanges  82  engages the stop washer  50  while the other flange  80  engages the sleeve  46  fitted at the base of the larger diameter section  43  of the probe sandwiching the spring. When this occurs the stop washer and the sleeve deform the spring  70  by bending the inwardly extending flanges  80 ,  82  toward one another. The convex web  78  also allows for some axial compression of the spring. The bent flanges and compressed web provide the necessary spring force as they try to regain their original position for keeping the two probes in proper contact. 
     Optionally, the spring may be configured to have a split-ring construction such that it is insertable over the terminus probe without having to be slid over the end thereof. In other words, the spring may comprise a longitudinal discontinuity or split  90  formed along the entire length of the spring as shown in FIG. 4 such that it may be opened up so as to allow it to receive the terminus probe through the split thereof If the spring is not split, then it would have to fitted over the terminus during manufacturing of the terminus. 
     An optional retaining ring  92  may be utilized to maintain the spring in position about the terminus as shown in FIGS. 3 and 4 and to prevent the accidental disengagement of the spring from the terminus. The retaining ring  92  should also have a longitudinal split  94  like the split  90  of the spring, such that it may inserted over the spring in the same manner that the spring may be inserted over the terminus probe. The ring is mounted in surrounding relationship to the spring and is fitted within the external concavity  84  formed on the web. In this regard, the ring is axially retained within the concavity. Moreover, the concavity  84  allows for the use of a smaller diameter retaining ring that can be easily accommodated in the connector bore housing the terminus. 
     A second embodiment spring  91  of the present invention is shown in FIGS. 5 and 6. This second embodiment spring is also of annular construction and comprises a cylindrical body  96  having an edge  98  beveled radially inward and a longitudinal split  95  spanning the length of the spring. The outer surface diameter of the spring  96  is slightly greater than the outer diameter of the stop washer  50 . The spring is positioned over the smaller diameter section  44  of the probe with the beveled edge  98  facing the stop washer  50 . Because the outer surface diameter of the spring  96  is greater than the outer diameter of the stop washer  50  the beveled edge  98  of the spring engages a circumferential edge  100  of the stop washer. Consequently, the spring expands radially about the split as the beveled edge rides upon the stop washer edge  100  as the probe  40  and thus the spring are moved proximally toward the stop washer when the probe  40  engages the probe of another terminus during mating. 
     Spring force is created as the radially expanded spring attempts to collapse to regain its original non-expanded configuration. As the spring attempts to collapse, it tends to push itself distally as its beveled edge  98  cams against the stop washer circumferential edge  100 . 
     Referring now to FIG. 7, another embodiment spring  102  of the present invention comprises a cylindrical body  103  onto which are formed a plurality of deformable beams which define a plurality of deformable beams  106  which deform so as to provide spring action. This embodiment spring is formed by taking a hollow cylinder and cutting a series of first and second diametrically opposed pairs of cut-outs  104  through the cylindrical surface. The cut-outs are preferably formed by using Electrical Discharge Machining (EDM). The first pairs of cut-outs are oriented at 90° with respect to the second pairs of cut-outs, thus defining the plurality of beams  106  which bend when compressive force is applied to the spring. Each pair of cut-outs are preferably parallel to a plane perpendicular to the longitudinal axis of the cylinder. Moreover, to provide sufficient flexibility to the “beams” each cutout of each pair spans a major portion, preferably greater than 120° of half of the cylindrical body  103  periphery. 
     Each spring of the present invention may be mounted in a compressed state on its corresponding terminus. In such case, the spring further compresses when the terminus is mated with another terminus. 
     The springs of the present invention are preferably made from beryllium copper but may be made from other appropriate materials such as spring steel or other resilient metal. Beryllium copper is preferred, however, because it is non-corrosive and easy to heat treat and cut. Preferably, the springs of the present invention are formed by stamping or machining. Cuts are preferably formed by EDM. 
     The termini and connector features have been described herein by way of example and the present invention is not limited to use with the termini described herein. For example, the springs of the present invention may used with termini whose probe larger diameter section bases are not surrounded by a sleeve and/or may be used with termini which do not incorporate an expanding sleeve and which rely on other structures such as a shoulder formed on the connector for providing a barrier against the proximal movement of the spring.