WO1994019716A1 - Ferrule holder for fiber optic connector - Google Patents

Abstract

An improved fiber optic connector of the type in which a fiber supporting ferrule (15) is slidably and resiliently biased independently of the surrounding load-bearing parts of the connector so that forces applied to the fiber optic cable jacket are not transmitted to the ferrule (15) and supported fiber to interrupt communications then in progress. In one of the embodiments, the needle of a syringe is inserted into a positioning tube (16) which confines an adhesive to the needed area, and prevents wicking of the adhesive to surrounding areas where it might interfere with the sliding action of the ferrule (15). It also wipes the needle as the syringe is withdrawn. A rear body element (13) provided with internal threads (50) which surround the cable jacket, which during a crimping operation, causes the jacket to deform into the threads for superior cable retention. Alternate embodiments include a rear body having means for engaging a sheath of a fiber optic cable, key means, and crimping operations with collet-like fingers.

Description

FERRULE HOLDER FOR FIBER OPTIC CONNECTOR

Technical Field

This invention relates generally to the field of optical cable connectors used in the telecoitimunications 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

Connectors 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.

Another 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.

One 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

Briefly 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. To 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. anufacturability 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

In 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.

Figure 1 is a longitudinal central sectional view of a first embodiment of the invention.

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.

Figure 3 is a view in elevation, partly in section, of a key body assembly.

Figure 4 is a longitudinal central sectional view thereof as seen from the plane 4-4 in Figure 3. Figure 5 is an end elevational view thereof, as seen from the left-hand portion of Figure 4.

Figure 6 is a longitudinal central sectional view of a second embodiment of the invention.

Figure 7 is a longitudinal central sectional view of a third embodiment of the invention.

Figure 8 is a longitudinal central sectional view of a rear body element comprising a part of the third embodiment.

Figure 9 is an end elevational view thereof. Figure 10 is a fragmentary enlarged elevational view corresponding to the upper right-hand portion of Figure δ. Figure 11 is a central longitudinal sectional view of a fourth embodiment of the invention.

Figure 12 is a view in perspective of an external key element forming part of the fourth embodiment. Figure 13 is an enlarged fragmentary view corresponding to the left-hand portion of Figure 11.

Figure 14 is a similar view showing the external key element of Figure 12 in engaged condition.

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.

Figure 16 is an end elevational view corresponding to the left hand portion of Figure 15. Best Mode For Carrying Out The Invention

In 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.

The 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.

The 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).

The 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.

Referring 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.

The 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. The 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.

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

The 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.

Turning 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".

The 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.

Another 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 a 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.

The 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) .

Turning 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".

The 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.

Turning 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.

The 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.

To 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. Claims:

1. In a fiber optic cable connector of a type including a ferrule holder arranged for axial movement within a connector body, said ferrule holder defining a bore for the reception of a ferrule, and the adhesive interconnection of the ferrule within said ferrule holder, the improvement comprising means communicating with said bore and defining an interior bore produced utilizing resilient material and of diameter forming an interference

Claims

fit with the outer surface of the needle of a syringe, and larger than that of a buffer of a fiber optic cable, whereby said bore provides a passage for the injection of an adhesive, and serves to wipe the needle of the syringe upon withdrawal therefrom prior to the insertion of said buffer.

2. The improvement set forth in Claim 1, in which said last-mentioned means is formed integrally with the body of the ferrule holder.

3. The improvement set forth in Claim 1 , in which the ferrule holder defines a socket, and said means comprises a separate member engaged in said socket defining said interior bore through which the adhesive is injected.

4. In a fiber optic connector having a rear body including means for engaging the sheath and folded-back strands of a strength member of a fiber optic cable, the improvement comprising: said rear body including a deformable sleeve defining an internally threaded bore, the diameter of which accepts the diameter of a cable sheath and folded-back strands of said strength member, which, after engagement of said sheath and said strength member within said bore and the subsequent crimping of said sleeve causes said sheath and strength member to be deformed into the interstices of said internally threaded bore to be retained thereby with substantially improved retention therebetween.

5. In a fiber optic connector having a rear body including means for engaging the sheath and a stranded strength member of a fiber optic cable, the improvement comprising: said rear body including a hollow sleeve forming flexible collet-like fingers, said fingers having an inner arcuate surface and sharpened projections projecting radially inwardly of said arcuate surfaces, whereby upon engagement of a cable sheath and strands of said strength member under said fingers, and the clamping of said fingers thereupon, said projections are capable of gripping said sheath and strands to only a limited degree, thereby preventing constriction upon parts of said cable disposed within said sheath.

6. The improvement set forth in Claim 5, further comprising: a camming nut member engaging said fingers, said nut member including an arcuate interior camming surface and a coaxially aligned cylindrical bore communicating with said camming surface; whereby after said fingers have reached a predetermined degree of clamping action upon said cable sheath, the tips of said fingers contact each other to thereby maintain said predetermined degree of contraction.

7. In a fiber optic connector having a cylindrical body and a ferrule supporting body arranged for relative longitudinal movement therein, said body having an external keying means thereon, a free end of which projects to lie adjacent the exposed end of a supported ferrule, the improvement comprising: said cylindrical body defining an annular groove and a longitudinal groove communicating therewith; said external keying means including an expandable annular member and a longitudinal member precisely engageable within said annular and longitudinal grooves to provide for selective removal and engagement without the loss of rotational orientation relative to said cylindrical body to facilitate access to the finished end of said ferrule during polishing operations.

8. The method of making a hollow keyed body having a longitudinally extending bore and at least one key projecting radially inwardly within said bore comprising the steps of: a) forming said hollow body to include a smooth longitudinal bore; b) forming a second hollow cylindrical member of outer diameter corresponding to that of said first mentioned bore; c) forming said at least one key on said second cylindrical member; and d) press fitting said second cylindrical member within said first cylindrical member to fixed relation therewith.

9. In the method set forth in Claim 8, the additional step of forming longitudinally oriented striations on at least one of said first and second cylindrical members to prevent relative rotational movement between said first and second members, after mutual engagement.

10. In a fiber optic connector having a rear body including means for engaging the sheath of a fiber optic cable, the improvement comprising: said rear body having a rearwardly projecting sleeve having an outer surface, said outer surface defining an annular recessed area and raised knurl sections on both sides of said annular recessed area and a separate crimp body including first and second tubular segments, said first segment including a medially positioned annular crimpable portion adapted to overlie said annular recessed area of said sleeve, and upon the occurrence of a crimping operation to be deformed to fill said area and to make intimate contact with said knurl sections, and anchor said crimp body against relative rotational and longitudinal movement relative to said sleeve; said second crimpable portion defining a bore for the reception of a sheath of an engaged fiber optic cable, and being radially or hexagonally crimpable to engage said sheath.

11. A device for preventing constriction upon the buffer of a fiber optic cable having a surrounding sheath and a stranded strength member disposed thereabout, upon engagement with a fiber optic connector, and the crimping of a part of the connector upon said cable, comprising: an elongated headed hollow sleeve insertable into the end of said cable between said buffer and said strength member and sheath of the cable for preventing the transmission of crimping forces applied to the sheath to said buffer, and for spreading and maintaining the strands of said strength member in uniform radial distribution to improve cable retention.

12. In a fiber optic connector having a rear body including means for engaging the sheath and a stranded strength member of a fiber optical cable, the improvement comprising: said rear body including a hollow sleeve forming flexible collet-like fingers, said fingers having an inner arcuate surface and sharpened projections projecting radially inwardly of said arcuate surfaces, whereby upon engagement of a cable sheath and strands of said strength member under said fingers, and the clamping of said fingers thereupon, said projections are capable of gripping said sheath and strands to an extent that securely retains said sheath and strands within said connector but limits inward displacement of said sheath and strands so that the buffered fiber, disposed within said sheath and strands, is not constricted from axial movement.