Abstract:
A strain relief boot that attaches to and can be removed from a pre-assembled fiber optic cable and connector, as well as, related strain relief boot designs and methods of assembly are disclosed. The strain relief boot may be overmolded, formed of a unitary unit, include two components, or even a coil element. The strain relief boot may be used during original assembly or as a replacement part. A variety of strain relief boot design alternatives and fiber optic assemblies that include the strain relief boot are disclosed.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to fiber optic cable connectors, strain relief of boots for such connectors, and methods of assembling such connectors. More particularly, the invention is directed to a fiber optic cable connector having a strain relief boot that can be easily attached to and removed from an assembled fiber optic assembly, as well as, related strain relief boot designs and methods of assembly. 
     BACKGROUND OF THE INVENTION 
     Various types of connectors have been developed for connecting optical cables to optical system components such as active or passive optical devices, or to other optical cables. Numerous factors influence the design of such connectors, including the diameter and makeup of the optical fiber used in the cable, the environment into which the cable and connector are placed, the space available for connection, and the number of connections required in a given location, to name but a few. Several of the optical cable connectors currently in common use include SC, DC, Unicam, LC, FC, ST, MTP, MU, MTRJ, and similar connectors. 
     Many such connectors are attached to a flexible member, commonly known as a strain relief boot, on the end of the connector opposite the terminated fiber. As the name suggests, the strain relief boot reduces strain on the fiber optic cable and connector, such as, for example, during pulling on the cable, so as to avoid violating the minimum bend radius of the optical fiber within the cable. Such bending could lead to attenuation and even breakage of the optical fiber or other damage to the connector. 
     Boots typically are annular with one wider end and one narrower end. The fiber optic cable passes through the boot with the wider end typically attaching to the connector and with the cable exiting the narrower end. In connectorizing a fiber optic cable, the first step is typically sliding a boot over the cable from the end being connectorized. Afterwards, various other parts such as a crimp band, a crimp body, a ferrule, a ferrule holder, a connector housing, etc., are attached to the end in sequence while various manipulations are performed to the cable and the parts. Once most if not all of the connector assembly steps are completed, the boot is slid along the fiber optic cable until the boot engages and is secured to the connector. 
     While connectorizing a fiber optic cable is typically not a complicated or time consuming task for a trained technician, a certain amount of time is required to properly achieve such connectorization. If one forgets to attach the boot before some of the connectorization steps are performed, the fiber optic cable will have to be cut and all of the steps will have to be performed again, thereby causing delay and a waste of otherwise acceptably assembled parts. Further, if a boot were to become damaged, one would have to recut and reconnectorize the cable in order to replace just the boot. Also, if one were to wish to change the type of boot on the connector, one would also have to recut the cable and reconnectorize it. As compared to many of the connector parts, the boot is not subject to high manufacturing tolerances and precise assembly requirements. Thus, to replace a “low tolerance” part of a connector assembly, more precisely manufactured and assembled parts must be discarded and replaced. As can be seen, in each of these scenarios, potentially acceptable connector parts are discarded, and additional effort and expense is required to reconnectorize the cable in order to add or change the boot. 
     SUMMARY OF THE INVENTION 
     This invention addresses the above needs by providing a strain relief boot for that is configured to be easily installed after a connector and an fiber optic cable, ribbon, or other device have been assembled in a fiber optic assembly. Further, the strain relief boot of this invention provides means for repeatedly removing and reinstalling the strain relief boot to the fiber optic assembly without damage to the connector or to the fiber optic cable, ribbon, or other device of the fiber optic assembly. While the embodiments below describe the fiber optic assembly having a connector and a fiber optic cable, this is not to be limiting and should be understood that alternate embodiments of the fiber optic assembly may have a connector and a fiber optic ribbon or an optical device. 
     The strain relief boot includes an extending member having a first end configured for attachment to the connector, a second end opposite the first end, and a passageway extending from the first end to the second end configured to receive a portion of the fiber optic cable and a portion of the connector. The extending member is flexible so as to be bendably deflectable along with the portion of the fiber optic cable relative to the connector. Further, the extending member includes attachment means for attaching the extending member to the connector and to the portion of the fiber optic cable after the connector and the fiber optic cable are positioned together. In alternate embodiments, the extending member is rigid so as to not bend. 
     The attachment means may include an overmolded extending member configuration, or a slit extending from the first end to the second end in communication with the passageway, the slit configured for passing at least the fiber optic cable into the passageway in a radial direction. The attachment means may alternatively include two parts configured to be attached together to form the passageway therebetween, at least one hinge formed unitarily with and between the two parts, an adhesive, a hot melt, an ultrasonic weld, and/or mating elements disposed on the extending member. The attachment means may also include a coil element extending member configuration and a collar disposed at an end of the coil element. 
     Also, the extending member may include two parts configured to be attached together to form the passageway therebetween. The extending member may include at least one hinge formed unitarily with and between the two parts, or the two parts may be formed nonunitarily. The two parts may attached together at least partially by an adhesive, by a hot melt, by an ultrasonic weld, by mating elements disposed on each of the two parts, by an interference fit, by a snap fit, or by other suitable techniques. 
     The extending member may include a coil element, and the coil element may have two ends. The extending member may include a collar disposed at one of the ends. The collar may include a first part and a second part, the second part being movable relative to the first part to open or close a slit extending axially along the collar. 
     The collar may be configured to be attachable to or removable from the fiber optic cable and the connector when the slit is opened, and the collar may be configured to secure the extending member to the fiber optic cable and the connector when the slit is closed. 
     The extending member may be at least partially curved along its length, and the extending member may be configured so that a curvature of the extending member has a radius of curvature greater than a minimum bend radius of the fiber optic cable. The extending member may curved from about 179 degrees to about 90 degrees. Alternatively the extending member may be substantially straight or about 180 degrees. 
     The extending member may include a tapered portion having an outer diameter that decreases in the direction of the second end of the extending member. The extending member tapered portion may taper uniformly or nonuniformly. The extending member may define openings extending substantially radially, and the extending member may be configured to be rotatable relative to the connector. 
     According to another aspect of the invention, a method of assembling a connectorized end of a fiber optic cable is provided, the method including the steps of preparing the end of a fiber optic cable for connectorizing, connectorizing the fiber optic cable by attaching a connector to the end of the fiber optic cable, and attaching a flexible strain relief boot to the connector and a portion of the fiber optic cable after the connectorizing step. 
     The attaching step may include overmolding the strain relief boot. Alternatively, the attaching step may include sliding at least the fiber optic cable through an opening in the strain relief boot into a passageway extending through the strain relief boot. The attaching step may also include attaching two parts of the strain relief boot together to enclose at least a portion of the fiber optic cable within a passageway extending through the strain relief boot. This may be accomplished by attaching the two parts using an interference fit, a snap fit, an adhesive, a hot melt, an ultrasonic weld, and/or mating elements disposed on the two parts. Further, the two parts may be formed unitarily with a hinge, and attaching the two parts may include pivoting the two parts at the hinge so as to provide contact between the two parts. 
     The attaching step may also include threading a coil around the fiber optic cable, opening a collar attached to the coil, threading the fiber optic cable through the opened collar, and closing the collar after the fiber optic cable has been threaded through the collar. 
     The attaching step may also include the substeps of placing the strain relief boot around the fiber optic cable spaced from the connector, and sliding the strain relief boot along the fiber optic cable into engagement with the connector. Alternately, the attaching step may include placing the strain relief boot simultaneously around the connector and the fiber optic cable. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
     For better understanding of this invention, reference is made to the following description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other aspects and advantages of this invention are apparent from the detailed description below in combination with the drawings, in which: 
     FIG. 1 is a partially broken away perspective view of a connectorized fiber optic cable with a strain relief boot formed by an overmolding process, according to one embodiment of the invention. 
     FIG. 2 is a perspective view in partial section showing one example of molds suitable for overmolding the strain relief boot (not present in FIG. 2) onto the connectorized fiber optic cable of FIG.  1 . 
     FIG. 3 is a perspective view of another embodiment of a connectorized cable and strain relief boot assembly wherein the boot has radial slots. 
     FIG. 4 is perspective view of another embodiment of a connectorized cable and strain relief boot assembly wherein the boot has a stepped tapered section. 
     FIG. 5 is perspective view of another embodiment of a connectorized cable and strain relief boot assembly wherein the boot is at least partially curved. 
     FIG. 6 a  is a perspective view of an embodiment of a two-part strain relief boot prior to attachment to a fiber optic cable and connector according to another embodiment of this invention. 
     FIG. 6 b  is an end view of the embodiment of FIG. 6 a.    
     FIG. 7 a  is a perspective view of another embodiment of a two-part strain relief boot prior to attachment to a fiber optic cable and connector according to this invention. 
     FIG. 7 b  is an end view of the embodiment of FIG. 7 a.    
     FIG. 8 a  is a perspective view of another embodiment of a two-part strain relief boot prior to attachment to a fiber optic connector according to this invention. 
     FIG. 8 b  is an end view of the embodiment of FIG. 8 a.    
     FIG. 8 c  is an enlarged partial view of the embodiment of FIG. 8 a  in a connected condition. 
     FIG. 9 a  is a perspective view of another embodiment of this invention in which two parts of the strain relief boot are connected by a living hinge. 
     FIG. 9 b  is an end view of the embodiment of FIG. 9 a.    
     FIG. 10 a  is another embodiment of a strain relief boot according to this invention including a coil element and a collar. 
     FIG. 10 b  is an end view of the embodiment of FIG. 10 a.    
     FIG. 11 a  is a perspective view of another embodiment of a strain relief boot including a coil element and a collar. 
     FIG. 11 b  is an end view of the embodiment of FIG. 11 a.   
    
    
     DETAILED DESCRIPTION 
     Detailed reference will now be made to the drawings in which examples embodying this invention are shown. The drawings and detailed description provide a full and detailed written description of the invention and of the manner and process of using it so as to enable one skilled in the pertinent art to make and use it as well the best mode of carrying out this invention. However, the examples set forth in the drawings and detailed description are provided by way of explanation of the invention and are not meant as a limitation of this invention. This invention thus includes any modifications and variations of the following examples as come within the scope of the appended claims and their equivalents. 
     The detailed description uses numerical and lettered designations to refer to figures in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of this invention, in particular with reference to corresponding parts in different embodiments. 
     FIG. 1 shows an embodiment of a connectorized fiber optic assembly  20  including a fiber optic cable  22 , a connector  24 , and a strain relief boot  26 . It should be understood that connector  24  may comprise any type of connector suitable for use with fiber optic cables, fiber optic ribbons, and optical devices. Thus, the specific connector type an the fiber optic cable shown should thus not be considered limiting of the invention in any way. A connector like that shown in FIG. 1 is discussed in more detail in U.S. patent application Ser. No. 09/737,040, filed Dec. 14, 2000, the entire disclosure of which is incorporated by reference into this application. 
     As generally shown in FIGS. 1 and 2, connector  24  is attached to an end  28  of fiber optic cable  22  (the end face of cable  22  is located within connector  24 , and is thus not visible in FIG.  1 ). Connector  24 , as shown in FIG. 1, includes a housing  30 , a trigger member  32 , a dust cap  34 , a crimp body  36 , a crimp ring  38 , and a tube portion  40  of a ferrule assembly (not otherwise shown). 
     Strain relief boot  26  includes an extending member  42  having a first end  44  configured for attachment to connector  24 , a second end  46  opposite the first end, and a passageway  48  extending from the first end to the second end. The passageway  48  is configured to receive a portion of fiber optic cable  22  and a portion of connector  24 . In the connector shown in FIG. 1, strain relief boot  26  is disposed around crimp body  36  and crimp ring  38  and encloses portions of cable  22  inside and adjacent to connector  24 . 
     Optionally, extending member  42  of boot  26  may include a tapered portion  50  having an outer diameter that decreases in the direction of second end  46  of extending member  42 . As illustrated in FIG. 1, tapered portion  50  is located between a first portion  52  of greater diameter and a second portion of  54  of lesser diameter. 
     Boot  26  and/or connector  24  may include mating structure to retain boot  26  on connector  24 . For example, as shown in the broken away part of FIG. 1, boot  26  may have a ridge  56  that seats in a groove  58  of crimp body  36  (or some other portion of connector  24 ) to maintain boot  26  in position on connector  24 . Multiple mating ridges and grooves may be provided, or the position of the ridge and groove could be reversed, or other such retaining structure could be utilized, within the scope of the invention. 
     Extending member  42  is flexible as to be bendably deflectable along with the portion of fiber optic cable  22  disposed within passageway  48  relative to connector  24 . Thus, extending member  42  may be made of a flexible material such as thermoplastic. Alternately other materials, flexible as well as rigid, may be used, including polypropylene, polycarbonate, stainless steel, and aluminum. In alternate embodiments, the extending member is rigid so as to not bend along the portion of the fiber optic cable disposed within the passageway relative to the connector. 
     Extending member  42  is configured to be attachable to connector  24  and the portion of cable  22  that will be disposed within the extending member after the connector and the cable are secured together. Thus, extending member  42  is connected to connector  24  and cable  22  radially or circumferentially. Extending member  42  is not therefore fit over cable  22  prior to its attachment to connector  24  and then simply slid along cable  22  until the extending member engages connector  24 . 
     According to one embodiment of the invention, extending member  42  is overmolded onto the connectorized connector  24  and cable  22 . FIG. 2 shows a sectional view of a mold having two halves  60  and  62  suitable for forming extending member  42  over the connectorized fiber optic assembly  20 . The mold halves  60 ,  62  have mating interior surfaces  64 , 66  that define the outer shape of extending member  42 . If extending member  42  is overmolded, various methods and formulations may be used. 
     An alternate embodiment of an extending member suitable for use with a cable and connector is shown in FIG.  3 . Extending member  142  is shaped roughly similar to extending member  42 . For example, extending member  142  includes a first end  144 , a second end  146 , a passageway  142  therebetween, a tapered portion  150 , a wide portion  152 , and a narrow portion  154 . Tapered portion  150  tapers uniformly between portion  152  and portion  154 , as described in the embodiment of FIGS. 1 and 2. However, if desired, the tapered portion could have a different (curved or otherwise) unusual tapered cross section, if desired. Extending member  142  defines openings  168  extending substantially radially. As shown in FIG. 3, openings  168  take the form of slots. These openings provide additional flexibility for tapered portion  150  to allow smoother bending of extending member  142  at that area. 
     FIG. 4 shows another embodiment of an extending member, wherein extending member  242  includes a tapered portion  250  that tapers nonuniformly (step wise) between wide portion  252  and narrow portion  254  at first end  244  and second end  246 . 
     FIG. 5 shows another embodiment of an extending member, wherein extending member  342  is at least partially curved along its length. As shown, tapered portion  350  is curved between wide portion  352  at first end  344  and a narrow portion  354  at second end  346 . Although the previous embodiments of the extending members may be curved by virtue of force applied to the respective cables, in some applications such a pre-curved extending member  342  may be desired. 
     Extending member  342  may be configured, for example, so that a curvature of the extending member has a radius of curvature greater than a minimum bend radius of cable  22 . It may also be desirable to have extending member  342  curve from about 179 degrees through about 90 degrees for some plug-in applications. 
     The overmolded extending members can be made so as to be rotatable relative to cable  22  and connector  24 . Thus, connector  24  may be made circumferentially symmetrical or cylindrical so as to improve rotatably, either continuously, or to a number stop positions. 
     For each of the above embodiments, it should be understood that the respective extending members may all be overmolded using mold halves as described above, or using some other commonly molding process. The interior surfaces of the mold halves could readily be altered to create the disclosed extending member shapes or other shapes within the scope of the invention. Also certain features of the disclosed embodiments could readily be combined with each other (for example, the openings  168  shown in FIG. 3 may be combined with the curvature in the tapered portion  350  of the embodiment shown in FIG.  5 ). 
     As an alternative to overmolding, other structures may be used for the extending member so as to be able to attach it to a connector and cable after the connector and cable are secured together. For example, the extending member may include two parts attached together to form the passageway for receiving the cable and connector. As shown in FIGS. 6 a  and  6   b , extending member  442  includes a first part  443  and a second part  445 . Flanges  447  may be provided along parts  443  and  445  to provide additional surface area for securing the two parts together, for example, by securing with an adhesive, hot melt, an ultrasonic weld, etc. Extending member  442  may have shapes other than that shown (including non-cylindrical shapes with uniformly extending members). 
     As shown in FIGS. 7 a  and  7   b , an alternative design for an extending member  542  is provided. In this embodiment, a first part  543  and a second part  545  include mating elements to attach together the two parts of extending member  542 . The mating elements comprise ridges  549  and grooves  551  that align and attach the two parts of extending member  542  together. As shown, ridges  549  and grooves  551  are substantially rectangular in cross section, although many alternative shapes may be utilized if desired. The mating elements may secure the two parts together by way of an interference fit or a snap fit, or elements such as adhesives, hot melts, or an ultra sonic weld may also be used to further secure the parts together. It is notable that extending member  542  tapers continuously from first end  544  to second end  546 . 
     Another alternate embodiment is shown in FIGS. 8 a - 8   c . In this embodiment, two mating parts  643  and  645  are provided to form extending member  642 . In this embodiment, the ridges are replaced by projections  649  having an under-cut cross sectional shape for mating with edges  653  of grooves  651 . Thus, a more secure fit may be achieved than that of FIGS. 7 a  and  7   b , thereby potentially not requiring any additional attaching and securing means (e.g., use of adhesive, holt melt, ultrasonic weld, etc.). 
     Another embodiment of an extending member is shown in FIGS. 9 a  and  9   b . In these figures, extending member  742  includes two parts  743  and  745  that are unitarily formed. As shown, parts  743  and  745  may be connected by a living hinge  755  formed by a partial slit  757  formed in extending member  742 . A full slit  759  is provided also to allow parts  743  and  745  to be separated. In alternative embodiments, partial slit  757  may be made smaller and/or may be eliminated. 
     Edges  761  of slit  759  thus may be joined to secure together extending member  742 . If desired, a ridge  763  may be provided on one of the edges  761  to fit into a mating groove  765 . Ridge  763  extends radially outward, unlike ridges  649  and  549  which extend substantially circumferentially or tangentially, relative to the center of the respective extending members. Again, adhesives, hot melts, ultrasonic welds, or other such means may be used to further secure edges  761  together. 
     For all of the previous two-part embodiments, if no adhesive or other permanent securing means is used, the parts may be readily separated without destruction if removal or replacement of the extending members is desired. Further, the embodiments comprising two molded halves may be molded from the same material as described above for the overmolded embodiments. 
     Another embodiment of an extending member is shown in FIGS. 10 a  and  10   b . Extending member  842  includes a coil  867  attached to a connecting portion or collar  869  (shown schematically). Collar  869  may include a threadable interior surface (not shown) that is capable of engaging and connecting to coil  867 . Coil  867  is flexible and can be threaded around cable  22  and connector  24 . Connecting portion  869  includes an inner portion  871  including a slit  873  and an outer portion  875 . Inner portion  871  is moveable relative to outer portion  875  to expose slit  873  to allow cable  22  to pass therethrough. Further outer portion  875  may be configured as a locking mechanism that securely attaches inner portion  871 . The outer portion  875  and inner portion  871  can then be moved back to cover the slit. 
     A modified version of the device of FIGS. 10 a  and  10   b  is shown in FIGS. 11 a  and  11   b . In this embodiment, inner portion  971  of collar  969  moves back and forth within channels  977  located in outer portion  975  to open or close slit  973 . Otherwise, extending member  942  is similar to extending member  842 . 
     It should be understood that various features of the embodiments set forth above can be combined with each other in order to create new embodiments. Thus particular elements or particular shapes of elements may be mixed and matched within the scope of this invention to achieve various different shapes of extending members suitable for use as a strain relief boot. All of the embodiments disclosed above are attachable to a fiber optic assembly, such as, for example a connector and cable subassembly after the cable has been permanently attached to the connector (other fiber optic assemblies include a connector with a fiber optic ribbon subassembly and a connector with an optical device assembly). Thus, the assembly of a connectorized fiber optic cable is simplified. Also, a strain relief boot may be replaced in the field to alter the characteristics of the boot, or if the original boot has become damaged. 
     In accordance with another aspect of the invention, a method of assembling a connectorized end of a fiber optic assembly with the strain relief boot is provided. The method includes the steps of: (1) preparing the end of a fiber optic assembly for connectorizing, connectorizing the fiber optic assembly by attaching a connector to the end of the fiber optic cable, ribbon, or optical device; and (2) attaching a flexible strain relief boot to the connector and a portion of the fiber optic cable, ribbon, or optical device after the connectorizing step. 
     The attaching step may include overmolding the strain relief boot, or may include sliding at least the fiber optic cable, ribbon, or optical device through an opening in the strain relief boot and into a passageway in the strain relief boot. This sliding step may include sliding the cable, ribbon, or optical device through an opening in a substantially radial direction, or threading the cable into a coil. 
     The attaching step may alternatively include attaching the two molded halves of the strain relief boot to enclose at least a portion of the fiber optic cable, ribbon, or optical device within a passageway extending through the strain relief boot. Further, the attaching step may include securing (either temporarily or permanently securing) the two molded halves using an interference fit, a snap fit, an adhesive, a hot melt, an ultrasonic weld, mating elements disposed on the two halves, or similar securing means. The two halves may be formed unitarily, and may include a hinge, and the two halves may be attached by pivoting the two halves at the hinge so as to provide contact between the two parts. The attaching step may also include threading a coil around at least the fiber optic cable, ribbon, or optical device. Further, the attaching step may include opening a collar attached to the coil and threading the fiber optic cable through the open collar, as well as closing the collar after the fiber optic cable has been threaded through the collar. The attaching step may also include the substeps of placing the strain relief boot around the fiber optic cable spaced from the connector, and sliding the strain relief boot along the fiber optic cable into engagement of the connector. Alternatively, the attaching step may include placing the strain relief boot simultaneously around a portion of the connector and the fiber optic cable, ribbon, or optical device. 
     It will be apparent skilled in the art that various modifications and variations can be made at this invention without departing from the scope and spirit of the invention. For example, specific shapes of various elements of the illustrated embodiments may be altered to suit particular connector or receptacle applications. Further, the extending member may be formed of a flexible material so as to bendably deflect along a portion of the fiber optic cable, or it may be formed of a rigid material so as to not deflect. Alternatively, the extending member may be a combination of flexible and non-flexible material. Also, specific method steps may be similarly altered. It is intended that this invention include such modifications and variations as come within the scope of the appended claims and their equivalents.