Abstract:
An optical connector includes a slug made from a malleable material and positioned behind a ferrule within a barrel member. The slug includes a capillary hole along its longitudinal axis for accommodating an optical fiber. One or more pins extend outwardly from the barrel and are generally orthogonal to the longitudinal axis. The pins provide several functions in the optical connector, including securing the slug within the barrel member, securing the optical fiber within the slug, and securing the barrel to a connector housing that includes a latch.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a connector for an optical fiber cable, and, more particularly, to an optical connector that can be readily installed in the field without the need for epoxy or anaerobic adhesives. 
     Optical fiber connectors and splices are an essential part of optical fiber communications systems. Connectors may be used to join lengths of optical fiber into longer lengths, or to connect optical fiber to active devices such as radiation sources, detectors, repeaters, or to passive devices such as switches or attenuators. 
     Many prior art connectors use adhesives or epoxies in securing connector components. For example, a typical connector includes a ferrule piece rigidly attached to a connector body. Adhesive is injected into a longitudinal bore of the ferrule. A cable is received into the connector body with the enclosed fiber projecting along the longitudinal bore of the ferrule. The adhesive wicks and adheres to the fiber, the ferrule, the connector body, and other connector parts to permanently secure the connector components to one another. 
     There is a growing demand, however, for a fiber optic connector that is simple to install or assemble in a field setting. In particular, there is a growing resistance to the use of epoxies that require special heat-curing ovens to facilitate solidification, and, in general, to the use of chemicals such as anaerobic adhesives. 
     Accordingly, what is sought, and what is not believed to be provided by the prior art, is a fiber optic connector that can be easily installed or assembled without the use of epoxies or adhesives. 
     SUMMARY OF THE INVENTION 
     Certain advantages and novel features of the invention will be set forth in the description that follows and will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. 
     To achieve the advantages and novel features, the present invention is generally directed to a fiber optic connector that can be installed in the field without the use of any adhesive or epoxy. The connector includes a housing that contains a barrel member. The barrel member has a ferrule disposed at one end, which terminates the optical fiber, and a barrel extension at the other end for receiving a buffered fiber. A slug made from a malleable material is confined within the barrel member. Both the barrel and the housing include an aperture, which are in substantial alignment with one another. A pin is disposed in the housing aperture that has a length such that when the pin is pressed to be substantially flush with the housing, the pin engages the slug contained within the barrel member. 
     The invention can also be viewed as providing a method for installing a fiber optic connector without using adhesives. In this regard, the method can be broadly summarized by the following steps: A slug of malleable material is inserted into a barrel member having an aperture formed therein. A pin is inserted into the aperture formed in the barrel member. The barrel member is surrounded with a housing that has an aperture formed therein that allows the pin to extend threrethrough. Finally, the pin is compressed until the pin engages the slug held within the barrel member, thereby causing the slug to grip the optical fiber running through the barrel member. 
     Advantageously, a technician can secure an optical fiber to the slug, the slug to the barrel, and the barrel to the connector housing by using a simple tool designed to compress the pin until it is substantially flush with the housing. Thus, the connector can be installed or assembled without the use of any adhesive or epoxy, which is particularly useful in a field setting. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     Other features of the present invention will be more readily understood from the following detailed description of specific embodiments thereof when read in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a cross sectional view of a prior art, optical fiber connector incorporating a ferrule member; 
     FIG. 2 is a perspective view of a quick-connect optical connector in accordance with the principles of the present invention; 
     FIG. 3 is a perspective view of the quick-connect connector of FIG. 2 with the housing cut away to reveal the internal structure; 
     FIG. 4 is a perspective view of the internal barrel assembly shown in FIG. 3; 
     FIG. 5 is a cross sectional view of the barrel assembly of FIG. 4; 
     FIG. 6 is a cross sectional view of a cylindrical slug used in the barrel assembly of FIGS. 4 and 5; 
     FIG. 7 is a cross sectional view of the quick-connect connector of FIG. 2 in which the connector is disposed in a receptacle; 
     FIG. 8 is a second cross sectional view of the quick-connect connector of FIG. 2 in which the connector is disposed in a receptacle; 
     FIG. 9 is a perspective view of a tool used in installing the quick-connect connector of FIG. 1; 
     FIG. 10 is a perspective view of the quick-connect connector of FIG. 2 received in the tool of FIG. 9; 
     FIG. 11 is a perspective view of an alternative embodiment of the quick-connect connector according to the present invention in which the ferrule is biased by an internal spring; 
     FIG. 12 is a cross sectional view of the quick connect connector of FIG. 11; 
     FIG. 13 is a perspective view of the quick-connect connector of FIG. 11 received in an installation tool. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof is shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. 
     With reference to FIG. 1, a portion of a prior art fiber optic connector  22  is shown to terminate a fiber optic cable  24 . The cable  24  comprises optical fiber  26 , which is surrounded by a thermoplastic buffer  28  providing protection and forming what is commonly referred to as a “buffered fiber.” The outside diameter of buffer  28  is typically 900 μm, which is a common standard for many connectors and splicing tools. Cable  24  is generally completed with a layer of aramid strength material  32  and an outer jacket of polyvinyl chloride (PVC)  34 . The aramid strength material typically comprises a KEVLAR® yarn, which provides crush resistance and withstands the tensile stresses applied to the cable. Outer jacket  34  is designed to protect against environmental hazards such as abrasion, oil, solvents and other contaminates. In addition, the jacket  34  generally defines the cable&#39;s duty and flammability rating. 
     Optical fiber cables comprising jacketed fibers are well known in the art. The outer jacket  34  is removed from a length of optical fiber  26  and a sleeve  36 , which is typically a stainless steel tube, is partially inserted between the buffer  28  and the fiber strength material  32  with part of the sleeve  36  extending beyond the outer jacket  34 . Ferrule  38  is held rigidly in the connector body or barrel  42  by adhesive means or other suitable means (e.g., a press fit). Connector housing  44  is held in place by a retaining ring  46  and a spring  48 . By partially filling the empty space  52  between the connector body  42  and the sleeve  36  with adhesive, a relatively strong bond will form in the region  53  between the outer jacket  34  and the connector body  42  once the adhesive cures. The adhesive, which is generally a themosetting epoxy, typically is transported along the strength material  32  by a wicking action, greatly increasing the bonding area between the sleeve  36  and the strength material  32 . 
     Before insertion of the cable  24  into the connector body  42 , an adhesive, typically also a thermosetting epoxy, is injected into the bore of the ferrule  38 , followed by threading the fiber  26  through the bore until the cable  24  is positioned substantially as shown in FIG.  1 . Lightly crimping the connector body  42  in the region indicated by numeral  54  preliminarily secures the cable  24  in the connector body  42  and prevents wicking of the adhesive past the crimping region. Once the adhesive cures, the fiber  26  protruding from the end  56  of ferrule  38  is severed using any appropriate means (e.g., scribing and breaking) and the fiber end is polished using standard polishing procedures that are well known in the art. 
     As discussed hereinbefore, the use of adhesives or epoxies in installing fiber optic connectors is inconvenient when performing field installations. Moreover, the use of epoxies and chemical adhesives is falling into disfavor because of the associated need for curing ovens and for environmental reasons. 
     A quick-connect fiber optic connector  60  that can be easily installed in a field setting without using epoxies or adhesives is shown in FIG.  2 . The fiber optic connector  60  according to the present invention is embodied in an LC type connector. It should be appreciated that the principles of the invention disclosed herein can be applied to other known optical connectors, such as ST, SC, and FC varieties, and that the choice of an LC type connector for the preferred embodiment is for illustrative purposes only. The quick-connect connector  60  includes a housing  62  having a ferrule  64  extending out of one end of the housing  62  and a barrel extension  66  extending out of the other end. A buffered fiber  68  of the type described hereinabove with respect to FIG. 1 (i.e., buffer  28 ) is received in the barrel extension  66  with the optical fiber carried by the cable terminating in the ferrule  64 . The quick-connect fiber optic connector  60  further includes a pair of metallic or hard plastic pins  72 — 72  (one shown) disposed in the sides of housing  62  and penetrating into the interior of connector  60 . In addition, a pair of windows or apertures  74 — 74  (one shown) are also formed in the sides of housing  62  allowing access to a portion of the barrel extension  66  from the outside of connector  60 . A latch  76  is included that facilitates mating of connector  60  with a complementary connector or receptacle. 
     Turning now to FIG. 3, the internal structure of connector  60  is shown in relation to a cross section of housing  62 . In particular, the housing  62  is shown to include a barrel member  78  that is configured to receive the pins  72  into openings in the barrel surface. FIG. 4 provides a perspective view of the entire barrel assembly comprising the barrel member  78 , which supports the ferrule  64  for terminating the optical fiber at one end, and supports the barrel extension  66  for receiving the buffered fiber  68  at the other end. Typically, the barrel member  78 , ferrule  64 , and barrel extension  66  are insert molded in the housing  62 . Pins  72 — 72  (one shown) are disposed in openings in the surface of barrel member  78 . 
     A cross section of the barrel assembly is shown in FIG.  5 . Most importantly, FIG. 5 shows a cylindrical slug  82  disposed within barrel  78  immediately behind ferrule  64 . Slug  82  is preferably made from a malleable material, such as fully-annealed aluminum or plastic, and contains a capillary channel  84  for holding the optical fiber. The capillary channel  84  can be round, triangular, or diamond shaped. To provide more flexibility in conforming the shape of the capillary channel  84  to the optical fiber, the slug can be split into two interlocking pieces  82   a  and  82   b  as shown in FIG.  6 . The pins  72 — 72  are in communication with slug  82  through the openings in barrel member  78 . 
     FIGS. 7 and 8 provide a more detailed illustration of the internal structure of connector  60 . FIG. 7 is a cross sectional view of connector  60  taken along lines  7 — 7  of FIG.  2 . In FIG. 7, the connector  60  is shown as received in a receptacle  86 . Note that the end of slug  82  is beveled where the optical fiber is received from barrel extension  66  to facilitate entry of the fiber into channel  84 . Likewise, the end of ferrule  64  is beveled at the junction with slug  82  to provide similar assistance in guiding the fiber into the channel opening. 
     FIG. 8 is a cross sectional view of connector  60  taken along lines  8 — 8  of FIG.  2 . 
     Like FIG. 7, the connector  60  is shown as received in a receptacle  86 . In addition to illustrating the foregoing features discussed with reference to FIG. 7, FIG. 8 also illustrates the windows  74 — 74  that provide access to the barrel extension  66  through the housing  62  of connector  60 . Moreover, openings  88  are shown that extend through barrel  78  and align with the openings in housing  62  holding pins  72 — 72  to allow the pins  72 — 72  to engage the slug  82 . 
     As will be described in more detail hereinafter, the unique operation of pins  72  and slug  82  allow connector  60  to be quickly, and easily installed in the field without the use of adhesives or epoxies. In the manufacturing process, slug  82  is inserted into the barrel  78  directly behind the ferrule  64 . This is followed by pressing the barrel extension  66  into the barrel  78  to effectively hold the slug  82  in place. Pins  72 — 72  are press fitted into openings  88  in the barrel  78 . The pins  72 — 72  abut slug  82  and are oriented orthogonally thereto. Generally, the pins  72 — 72  are pressed into the barrel member  78  during the manufacturing process and extend a prescribed distance outside of the barrel  78 . The barrel  78 , barrel extension  66 , ferrule  64 , slug  82 , and openings  88  can be insert molded within the housing  62  to form a single integrated part. 
     The fiber optic cable is prepared by stripping away the outer layers including the outer jacket, the strength material, and the buffer until the fiber is revealed. The fiber is then inserted into the connector  60  through the barrel extension  66  and into the capillary channel  84  in the slug  82  until the buffer (see FIG.  1 —buffer  28 ) contacts the slug  82 . Enough fiber should be exposed to ensure that the fiber extends out of the end of ferrule  64  before the buffer contacts the slug  82 . 
     Once the fiber has been inserted through connector  60 , a hand-held pliers like tool  92  shown in FIG. 9 is used to crimp the barrel extension  66  to the buffered fiber and to simultaneously press the pins  72 — 72  into the openings  88  in barrel  78 . FIG. 10 depicts the connector  60  received in the tool head  94 . Tool head  94  is dimensioned to conform to the geometry of the connector  60  such that when connector  60  is compressed between the two halves of tool head  94  the pins  72 — 72  are pressed substantially flush with the connector housing  62 . The inward movement of the pins  72 — 72  causes the slug  82 , which is made from a malleable material, to collapse around the fiber, thereby holding the fiber securely in place. The pins  72 — 72  are received in the openings  88  in the barrel  78  with a sufficiently tight fit to ensure that they do not loosen and relax the pressure upon slug  82 . Tool head  94  also includes raised regions that penetrate windows  74 — 74  in connector housing  62  to crimp barrel extension  66  to the buffered fiber. 
     Thus, the pins  72 — 72  used in the connector  60  according to the present invention allow a technician to secure the fiber to the slug  82 , the slug  82  to the barrel  78 , and the barrel  78  to the connector housing  62  by using a simple tool  92  and without the use of any adhesive or epoxy. Moreover, as a result of the windows  74 — 74  formed in the connector housing  62 , the buffered cable can be crimped to the barrel extension  66  coincidentally with the securing of the aforementioned internal connector  60  components. 
     The principles of the present invention can also be applied to connectors used with jumper cables that typically use an internal spring to provide an axial bias force for the ferrule and barrel components. FIG. 11 shows a quick-connect connector  160  in accordance with the present invention that can be used in jumper cable applications. Like connector  60 , connector  160  includes a ferrule  164 , a pair of pins  172 — 172 , a pair of windows  174 — 174  that provide access to the barrel extension  166 , and a latch  176 . Unlike, connector  60 , however, connector  160  includes a two part housing  162   a,b  and a pair of slots  173 — 173  that allow movement of the pins with respect to the housing  162   a,b.    
     A cross sectional view of the internal structure of connector  160  is shown in FIG.  12 . The basic structure is the same as that of connector  160  with the ferrule  164  being connected to the barrel member  178 , which in turn is connected to the barrel extension  166 . The slug  182  is positioned immediately behind the ferrule  164  as in connector  60 . To provide for movement of the barrel-ferrule assembly, however, a spring  167  is disposed about the barrel extension  166  and is confined between the barrel member  178  and a shoulder of housing part  162   b.  The spring is designed to provide a specific axial load on the ferrule interface and also to compensate for overtravel of latch  176 . Finally, housing part  162   a,  includes latching arms  163 — 163  that engage flanged regions in housing part  162   b  to secure the two housing parts  162   a,b  to one another. 
     The installation of connector  160  is substantially similar to the installation of connector  60 , however, in a jumper cable the aramid strength members or material (see FIG.  1 —strength material  32 ) are generally attached to the connector  160  structure. Thus, before inserting the buffered fiber into barrel extension  166 , a crimp sleeve  196  as shown in FIG. 13 is slid upon the outer jacket of the cable. The buffered fiber is then seated in the slug  182  and the fiber is threaded through the ferrule  164  as discussed hereinbefore. Then, using a pliers-like tool similar to tool  92  in FIG. 9, but having a modified head  194  as shown in FIG. 13, the crimp sleeve  196  is crimped, thereby joining the outer jacket of cable  168  to the barrel extension  166 . 
     Once the cable jacket is secured to the barrel extension  166 , the remainder of the installation process is the same as that used for connector  60 . Advantageously, the tool head  194  includes a second formed region  195  that is identical to the pattern formed in tool head  94  for pressing in pins  172 — 172  and for crimping the buffered fiber to the barrel extension  166 . 
     In concluding the detailed description, it should be noted that it will be obvious to those skilled in the art that many variations and modifications can be made to the preferred embodiment without substantially departing from the principles of the present invention. All such variations and modifications are intended to be included herein within the scope of the present invention, as set forth in the following claims.