Ferrule holder for fiber optic connector

Technical Field

0001This invention relates generally to the field of optical cable connectors used in the telecommunications industry, and more particularly to a type in which the fiber optic core and surrounding cladding or buffer are supported in a slidably mounted ferrule to enable relative movement between the core and buffer and the surrounding jacket of the cable which forms a load supporting part of the cable. This type of construction has come into increased use in recent years because of the ability to absorb external loads on the cable without disturbing the positioning of the end of the fiber, movement of which would otherwise interfere with a transmitted communication carried by the cable.

Background Art

0002Connectors of this type are normally substantially fully assembled before permanent engagement with the end of the cable, which installation involves the adhesion of the fiber within the ferrule and the simultaneous cementing of the ferrule to a ferrule-supporting body. Care must be exercised to prevent any wicking of the adhesive to other parts of the connector so that the ferrule body will not be frozen in a single position when the adhesive cures. In one known device of this type, an elongated flexible sleeve is provided which communicates at an inner end thereof with the inner end of the ferrule, and in which the outer end extends outwardly of the connector to be severed after the epoxy has been injected therethrough. While effective, this construction requires an additional manufacturing operation, and is somewhat clumsy in operation.

0003Another problem occurs with the clamping of the rear part of the connector upon the outer jacket of the cable. The clamping action must be secure, but not include the clamping of the buffer or cladding which must be capable of limited axial movement within the jacket as is required with a floating ferrule construction.

0004One form of connector of this type also requires the use of an external key which engages a corresponding recess in a mating adapter. The free end of the key normally projects forwardly to a point where it interferes with the polishing of the finished end of the cable. In this type of connector, a key body includes a bore having internal keys which are not easily formed by machining operations, thus significantly adding to the cost of manufacture.

Disclosure of The Invention

0005Briefly stated, the invention contemplates the provision of improved fiber optic connectors of the class described, in which the above-mentioned disadvantages and requirements have been substantially addressed and complied with.

0006To this end, three of the disclosed devices include an internal guide forming a bore which accommodates the diameter of the needle of the syringe employed in injecting the adhesive in such manner that not only is the flow of adhesive outside the desired area avoided, but the needle itself is wiped free of adhesive as it is withdrawn, and then acts as a guide for the subsequent insertion of the fiber into the ferrule. The rear body of the connector which engages the jacket of the cable may take any of several alternative forms, one of which includes a collet type clamp which grips the jacket firmly without restraining the buffer. Another form includes the provision of internal threads in the rear body into which the outer surface of the jacket is deformed upon crimping. In this case, the buffer is protected from being restrained by the provision of a metal tube which is inserted between the buffer and the surrounding strength members which isolates the buffer from the crimping action. Installation of the cable within the connector, in one embodiment, is simplified by providing a selectively removable external key in all disclosed embodiments. Manufacturability is facilitated by effecting an internal key within the key body which is separately formed and press-fitted within a bore in the body.

Brief Description of the Drawings

0007In the drawings, to which reference will be made in the specification, similar reference characters have been employed to designate corresponding parts throughout the several views. <ul id="ul0001" list-style="none" compact="compact"><li>Figure 1 is a longitudinal central sectional view of a first embodiment of the invention.</li><li>Figure 2 is a longitudinal central sectional view of a subassembly of the embodiment including a ferrule, a ferrule supporting body, and an epoxy needle wiping member.</li><li>Figure 3 is a view in elevation, partly in section, of a key body assembly.</li><li>Figure 4 is a longitudinal central sectional view thereof as seen from the plane 4-4 in Figure 3.</li><li>Figure 5 is an end elevational view thereof, as seen from the left-hand portion of Figure 4.</li><li>Figure 6 is a longitudinal central sectional view of a second embodiment of the invention.</li><li>Figure 7 is a longitudinal central sectional view of a third embodiment of the invention.</li><li>Figure 8 is a longitudinal central sectional view of a rear body element comprising a part of the third embodiment.</li><li>Figure 9 is an end elevational view thereof.</li><li>Figure 10 is a fragmentary enlarged elevational view corresponding to the upper right-hand portion of Figure 8.</li><li>Figure 11 is a central longitudinal sectional view of a fourth embodiment of the invention.</li><li>Figure 12 is a view in perspective of an external key element forming part of the fourth embodiment.</li><li>Figure 13 is an enlarged fragmentary view corresponding to the left-hand portion of Figure 11.</li><li>Figure 14 is a similar view showing the external key element of Figure 12 in engaged condition.</li><li>Figure 15 is a fragmentary longitudinal sectional view corresponding to the central right hand position of Figure 1, but showing a fiber optic cable and buffer in position.</li><li>Figure 16 is an end elevational view corresponding to the left hand portion of Figure 15.</li></ul>

Best Mode For Carrying Out The Invention

0008In accordance with the first embodiment of the invention, the device, generally indicated by reference character 10 (Figures 1 and 2) comprises broadly: a coupling sleeve element 11, a key body element 12, a rear body element 13, a ferrule supporting body 14, a ferrule 15, a syringe needle engaging element 16, referred to hereinafter as a wiper, a ferrule body spring 17, a protective cap 18, and a buffer protective tube member 19.

0009The coupling sleeve element 11 is generally conventional, and is bounded by an outer surface 20 extending from a first end 21 to a second end 22. An interior bore 23 includes a partially threaded segment 24 which engages a corresponding part on a known adapter (not shown). A through bore 25 and an end wall 26 slidably accommodates the rear body element 13.

0010The key body element 12 is also generally conventional for a connector of the disclosed type, and extends from a first end 30 to a second end 31. Referring to Figures 3 to 6, inclusive, a forwardly positioned member 32 includes a radially projecting key 33. A rear cylindrically shaped member 34 defines a hollow bore 35 into which a separately machined key member 36 is press fitted to facilitate manufacture. The member 36 includes a longitudinally striated outer surface 37 to anchor member 36 against rotation relative to the hollow bore 35. An outer end rabbet 38 supports an anti-friction washer 39 (Figure 1).

0011The rear body element 13 is interconnected by an interference fit to the forward body element 12, and includes a forward member 40 and a rear member 41. The forward member 40 defines a cylindrical sleeve 43, a forward part 44 of which is provided with radial ribs 45 which provide an interference fit relative to the hollow bore 35 in the body element 12. A medially disposed flange portion 47 serves to captivate the coupling sleeve element 11 onto key body element 12 and rear body element 13. A chamfered opening 48 leads to a rewardly extending sleeve 49 having an internally threaded bore 50. An outer surface 51 defines an annular crimping area beginning at a radial groove 52 and a radial abutment 53 for engagement with a cable engaging protective member 54, as is known in the art.

0012Referring to Figure 2, the ferrule supporting body 14 is adapted to axially slide within the rear body element and key body element to which it is keyed. It includes a forward sleeve 60 defining a cylindrical bore 61 for the reception of the ferrule 15, and a rearwardly extending sleeve 62, a medially disposed flange 63 which engages the spring 17 which urges the body 14 leftwardly as seen in Figure 1 to permit the free end of the ferrule to abut a corresponding ferrule with which it is engaged (not shown). Keying member 36 engages keyway 68 and prevents rotation of the ferrule supporting body with respect to the key body element.

0013The ferrule 15 is preferably formed of ceramic materials, as is well known in the art, and extends between an outer end 70 and an inner end 71. It defines a centrally disposed bore 72 for the reception of an optical fiber (not shown), in cemented relation well known in the art.

0014The wiper element 16 may be of resilient synthetic resinous materials, and includes an elongated hollow shank 80 and a head portion 81. The shank 80 includes an outer surface 82 having an annular projection 83 which engages a corresponding bead 84 on the ferrule body to lock it in position. A bore 85 includes an inner constricted end 86 which serves as the fiber guide and needle wipe due to the interference fit with the needle diameter and the resilient nature of the material utilized. The outer end 87 is chamfered to assist in the insertion of a syringe needle, fiber, and buffer.

0015The head portion 81 is bounded by an outer surface 88 and an inner end surface 89 from which the chamfered end 87 of the bore 85 extends. A radially, outwardly extending shoulder 95a provides for an interference fit with a through bore 95b of the ferrule supporting body which effects a seal to prevent injected epoxy into the cavity 95c from flowing out to external surfaces of the ferrule supporting body or wiping element.

0016The spring 17 is of conventional wire wound type, extending from a first end 94 to a second end 95.

0017The buffer protective tube 19 may be formed as a screw machine product preferably from a hard material such as stainless steel. It includes a hollow shank 96 and an enlarged head 97. The position shown in Figure 1 is obtained after the device has been inserted onto the prepared end of a fiber optic cable by inserting the shank 96 about the buffer 98, and underlying the strength members 47 which are flared radially by the head 97 as seen, for example, in Figure 15. In addition to the buffer protection function due to the resistance of the hard material to external pressure from the crimping operation, the head enables maintenance of a uniform distribution of the strands of the strength members which enhances the cable retention ability after crimping.

0018Turning now to the second embodiment of the invention (Figure 6), to avoid needless repetition, parts corresponding to those of the first embodiment have been designated by similar reference characters with the additional prefix "2".

0019The second embodiment differs from the first embodiment principally in the provision of a deformable sleeve 101 positioned at an inner end of the rear body element 213, and the formation of the ferrule supporting body extension 219 which eliminates the need for a wiper element.

0020Another feature of the ferrule holder is the fact that in a free floating state (no external forces applied), the back of the holder extends beyond the back of the rear body of the connector. This feature has been designed to aid the process of "terminating" the connector. As epoxy is injected into the back of the ferrule of 3 prior art connector, some parts of epoxy may seep into other areas of the connector and harden; causing a defective product. The extended ferrule holder, as mentioned above, will act as a guide channeling any excess epoxy away from sensitive connector parts. Equally important is the fact that the holder will channel any excess epoxy out beyond the back end of the rear body to an area that is easy to clean by externally wiping clean.

0021The sleeve 101 is designed to be separately attached to the cable prior to connection with the connector, and includes a forward cylindrical member 102 and a rear cylindrical member 103. It is of metallic deformable material, such as aluminum. The rear body element 213 includes a stub-like sleeve 104 to receive the sleeve 101. Referring to the sleeve 101, an outer surface 105 includes a raised bead 106 which provides material for deformation into a corresponding recess 107 on the outer surface of the sleeve 104. The sleeve 104 is preferably knurled on its outer surface 105, so that when deformation occurs, the sleeve 101 is anchored not only against axial movement by virtue of the raised bead being collapsed radially or hexagonally inwardly into recess 107, but relative rotational movement as well. A thickened wall portion 109 defines a downward taper 110 for communication to the cylindrical section 110a and subsequently to cylindrical member 103. The member 103 is bounded by a stepped outer surface 111 providing a bead for a crimping tool (not shown), such that when crimped (deformed), the inner bore 114 collapses inwardly to grip and retain the cable jacket and strength members. The inner bore contains a buffer protecting tube 115 as described above. The strength members are uniformly radially dispersed by the head of the buffer protective tube and are folded back in known manner prior to insertion (see Figures 15 and 16).

0022Turning now to the third embodiment of the invention, generally indicated by reference character 120 (see Figure 7), parts corresponding to those of the first embodiment have been designated by similar reference characters with the additional prefix "3".

0023The third embodiment differs from the first embodiment principally in the provision of a collet-like clamp 121 for engaging the jacket and strength members of the engaged cable. The clamp includes a threaded sleeve 122 forming deformable fingers 123 between separating slots 124. As best seen in Figure 10, the tapered ends 126 of the fingers 113 include an undersurface 127 from which project thin backwardly tapered teeth 128. When engaged by a camming nut 129 and tightened, the undersurfaces 127 are contracted due to downward pressure of tapered ends and corresponding inward movement of the teeth 128 which grip the strength members and jacket and, hence, clench the cable without placing undue constrictive forces on the buffer as disposed radially inwardly thereof. The camming nut 129 is so configured, as best seen in Figure 7, that the camming surface 130 exerts only limited contractile effect, excess tightening resulting only in the fingers deforming until separating slots 124 close to the point where the fingers touch one another, thus stopping further contraction.

0024Turning now to the fourth embodiment of the invention 410 (Figure 11) parts corresponding to those of the first embodiment have been designated by similar reference characters with the additional prefix "4", thereby avoiding needless repetition.

0025The fourth embodiment is generally similar to the above disclosed embodiments, but is in the form of a so-called "D4" connector characterized in the presence of an external key element 141 (Figure 12) which mates with a corresponding keyway element in an adapter (not shown) with which it is engageable. It will be noted that the key element 141 projects forwardly a substantial distance, so as to lie in the area of the finished end of the ferrule, thus providing a degree of interference when the terminated fiber is polished in a manner known in the art. In the present embodiment, this problem is eliminated by making the key element detachable to permit proper polishing, and then replacing it to its original orientation.

0026To accomplish this, the forward end 142 of the forward body 412 is provided with an annular groove 143 which communicates with a longitudinal groove 144 terminating in an end surface 145. The key element 141 is similarly configured, to include an annular member 147 having split ends 148 and 149 to permit the same to be expanded for removal and replacement. The longitudinal member 150 terminates in an inner end 151 and an outer end 152. The key element 141 is simply removed by inserting a tool between the ends 148 and 149. When the polishing operation has been completed, a similar engagement permits replacement of the key element in its original axial and rotational orientation.