Abstract:
An optic fiber connector includes a self-contained optical fiber cartridge ( 12 ), that can be easily inserted into a passageway ( 16 ) of a connector housing ( 14 ), and easily removed and replaced, without exposing the coil spring ( 52 ) that urges the terminus forwardly. The cartridge includes a frame ( 20 ) that completely encircles the spring in all terminus positions and that also surrounds much of the terminus.

Description:
BACKGROUND OF THE INVENTION 
   Optic fiber connectors in current use, include a housing with one or a plurality of passages that each holds a terminus through which an optic fiber projects. A coil spring lies in the passage to urge the terminus forwardly and allow the terminus to be pushed back by a mating terminus. A sheet metal clip prevents rearward movement of the terminus out of the passageway, but allows such removal when a special tool is inserted to expand the tines of the clip and pull out the terminus. In some prior connectors, the spring was removed with the terminus, and the spring was sometimes damaged when it caught on other parts at the rear of the connector. In another design, the spring remained in the passageway when the clip tines were expanded to remove the terminus. However, there often was damage to the spring when the removal tool was slid closely within the spring to expand the clip tines. The presence of a coil spring and a resilient clip through which or around which a removal tool had to be inserted, reduced the reliability of the connectors. Where the spring was left behind when the terminus was removed, the housing passageway had to be enlarged to retain the spring. A connector that enabled easy removal and replacement of a terminus, which minimized the number of deflectable and moving parts while protecting the movable parts especially the spring at all times, and which minimized the required diameter occupied by each terminus and surrounding parts would be of value. 
   SUMMARY OF THE INVENTION 
   In accordance with one embodiment of the present invention, a self-contained optic fiber cartridge is provided, that can fit into a small diameter connector housing passageway, and with the cartridge having a minimum number of deflectable and movable parts and providing maximum protection for such movable parts, especially a coil spring. The cartridge includes a tubular frame, a terminus that lies in a through passage of the frame, and a coil spring that also lies in the passage. The coil spring has a rear spring end abutting an inner shoulder in the frame and has a front spring end abutting a body shoulder that lies rearward of the front end of the frame, in all positions of the terminus. 
   An easily operated retainer at the rear end of a connector housing passageway, enables easy removal and replacement of the cartridge. The cartridge does not require a deflectable clip for removing the terminus from the frame because the terminus is not removable from the frame. The spring is never exposed, either to the surroundings when the cartridge is removed or to a removal tool. The coil spring lies closely around a small diameter terminus body rear portion and the frame is thin immediately around the coil spring, so the cartridge has a small outside diameter. 
   The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded side elevation view of a connector housing and of an optic fiber cartridge of the present invention. 
       FIG. 2  is an exploded front isometric view of the housing and cartridge of FIG.  1 . 
       FIG. 3  is a sectional view taken on line  3 — 3  of FIG.  2 . 
       FIG. 4  is a sectional view taken on line  4 — 4  of  FIG. 2 , but showing a modified retainer at the rear of the housing, and with the retainer body rear end not yet swaged. 
       FIG. 5  is a sectional view of a connector with multiple passageways that each holds a cartridge of the design as taken on line  5 — 5  of FIG.  4 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  illustrate a connector  10  which includes an optic fiber cartridge  12  and a housing  14  with a passageway  16  that receives the cartridge. The cartridge includes a frame  20  and a terminus  22  that extends through a through passage  24  of the frame. An optic fiber cable  30  extends through a bend limiting sleeve  32  and through a bendable coupling  34 , and through the terminus to a tip  42  of a ferrule  40  of the terminus. 
     FIG. 3  shows that the terminus  22  includes a body  50  that holds the rear end of the ferrule  40 , preferably in a press fit. A spring  52  has a rear end that abuts a largely forwardly-facing internal shoulder  54  of the frame  20  and that has a front end that abuts an external largely rearwardly-facing shoulder  56  on the terminus body. The terminus body has an enlarged front portion  60  with a front end forming a largely forwardly-facing shoulder  62  that abuts a largely rearwardly-facing internal shoulder  64  on the housing  14 .  FIG. 3  shows the terminus in its most forward position, wherein the entire spring  52  is protected by the frame  20 . The body has a narrow rear portion  70  with a rear end  72  that is swaged, to form an external flange shoulder  73  that is in line with an internal frame shoulder  74  to limit forward movement of the terminus within the frame  20  and prevent substantial exposure of the spring  52 , and to prevent the ferrule from falling out of the frame. 
   The frame  20  has an external flange  80  near its rear end, which is used in conjunction with a retainer  82  to releaseably hold the cartridge  12  in the housing passageway  16 . It is possible to merely form a groove where the flange  80  lies, to provide a shoulder. The particular retainer  82  is in the form of a sheet metal clip with tines  86  that abut a largely rearwardly-facing shoulder  90  of the frame. A rear end of the clip abuts a forwardly-facing and clip-retaining housing rear shoulder  91 . A tool can be inserted into the rear  92  of the housing passageway  16  (by first pulling the coupling  34  rearward) to expand the tines  86  and withdraw  12  from the housing passageway. Such tool does not slide across the spring  52  or against any part of the terminus, so it cannot damage the spring or terminus. As mentioned above, when the cartridge  12  lies outside of the housing, the spring is protected. Since the spring  52  is a permanent part of the cartridge, no clip is required to remove the terminus from the frame of the cartridge. 
   The cartridge is assembled by pressing the ferrule  40  rearwardly into the front portion  60  of the body. The optic fiber cable is prepared by stripping protective material from around the glass fiber  100  and inserting the glass fiber through a corresponding bore in the ferrule until the tip of the fiber lies slightly forward of the ferrule tip  42 . The fiber tip is polished flush with the ferrule tip. A flowable epoxy has been placed in the bore  102  of the body to fix the cable in the terminus. The spring  52  has been earlier threaded onto the cable and is slid forwardly F against the body shoulder  56 . The terminus, with the spring  52  thereon, is then slid rearwardly R into the front end of the through passage  44  of the frame  20 . The rear end  72  of the terminus body is swaged to enlarge it so that it can abut the shoulder  74  of the frame to prevent the terminus from moving forwardly from the position shown in FIG.  3 . The bendable coupling  34  is moved forward, the strength member  110  of the optic fiber cable is wrapped around a rear portion  112  of the frame, and a crimp sleeve  114  is crimped around them. 
   In  FIG. 3 , the body is formed with an elongated undercut recess  120  for receiving the clip retainer  82 . The cartridge  12  is installed by merely inserting it forwardly into and through the housing passageway  16 . Forward movement of the frame is limited by the frame front end  130  abutting a corresponding internal shoulder  132  of the housing. Also, a rear flange front end  134  abuts a housing internal shoulder  136  which also limits forward movement of the cartridge within the housing. 
     FIG. 4  illustrates a modified housing  14 A that is identical to that of  FIG. 3 , except that the housing has interfering parts  150  on opposite sides of the housing passageway  16 A, that deflect apart to allow the frame external flange  80  to pass therethrough, and which have largely forwardly-facing shoulders  152  that then prevent cartridge removal unless the interference parts  150  are spread apart. A variety of retainers can be used to hold the optic fiber cartridge  12  in place and allow its removal when necessary. The presence of the flange  80  facilitates operations of such releaseable retainers. 
   The cartridge  12  has a relatively small diameter C. The ferrule  40  is required to have a predetermined diameter A to fit into a standard diameter alignment sleeve  160  that is contained in an alignment cartridge  162  that fits into a recess  164  at the front end of the housing. The terminus body front portion  60  must have a somewhat larger diameter than the ferrule to robustly hold the rear end of the ferrule  40 . The frame front end  166  can be thin and have only a slightly greater diameter than the terminus body front portion  60 . The body rear portion  70  has a small diameter, so the spring  52  can readily fit between the inside of the frame front portion  166  and the outside of the body rear portion  70 . This results in a cartridge of small diameter, with the flange  80  at the rear adding only a small addition diameter. In  FIG. 4 , the ferrule has a standard outside diameter A of 1.6 mm, the cartridge  12  has an outside diameter B of 3.3 mm (about 190% of A) along most of its length, and the flange  80  has an outside diameter C of 3.9 mm (about 240% of A). Where the housing holds a single terminus, this results in the cartridge being installable in a housing of small size. Where the housing has multiple passageways, the small diameter of each cartridge enables the multiple passageways of such connector to be closely spaced so that a large number of termini can be installed in a connector of small size. The fact that the body front portion  60  projects partially forward of the frame front end  130 , results in a connector of smaller length. 
     FIG. 5  illustrates a connector  200  with six optic fiber cartridges  12  installed therein. A prior art installation, which included a releaseable retention clip that engaged the terminus body and a spring with space for a release tool to fit around or within the spring, might allow only five termini to be placed in a connector of the same diameter. 
   Thus, the invention provides a removable optic fiber cartridge that is self-contained, with a spring that biases a terminus forwardly, wherein the spring is protected against damage when it lies outside a connector housing and where the spring is protected against damage from any removal tool. This is accomplished by mounting a terminus and spring permanently within a frame to form an optic fiber cartridge, and providing for the cartridge to be insertable and retained, and later removable from a passageway in a connector housing. The elimination of a retention clip or the like within the frame of the cartridge, also results in a cartridge of small diameter, which allows the termini to be mounted at small spacings in a connector that has multiple termini, or to allow the cartridge to be mounted in a connector housing of small size. 
   Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.