WO1998018035A1

WO1998018035A1 - Push and pull resistant fiber optic connector for coupling to an enclosure

Info

Publication number: WO1998018035A1
Application number: PCT/US1997/018747
Authority: WO
Inventors: Soren Grinderslev
Original assignee: The Whitaker Corporation
Priority date: 1996-10-18
Filing date: 1997-10-16
Publication date: 1998-04-30
Also published as: AU4906897A

Abstract

A fiber optic connector for terminating a fiber optic cable comprises an intermediate housing having opposite engaging ends being rotatable about the fiber optic cable. A first crimp member having a first physical stop and a second crimp member having a second physical stop are disposed adjacent the opposite ends of the intermediate housing. The first and second physical stops limit movement of the intermediate housing along the cable when the first and second crimp members are actuated through engagement with the ends. The fiber optic connector further comprises a mating housing engageable with the intermediate housing and a securing housing engageable with the intermediate housing. A method of terminating a fiber optic cable comprises the steps of stripping a fiber optic cable jacket to expose strength members, an inner tube and individual fibers, positioning a securing housing, a first crimp member, an intermediate housing, a second crimp member, and a crimping tool over the fiber optic cable jacket, actuating the first and second crimp members by threading the securing housing and the tool to the intermediate housing, partially disengaging the securing housing from the intermediate housing, removing the tool, and threading a mating housing to the intermediate housing.

Description

PUSH AND PULL RESISTANT FIBER OPTIC CONNECTOR FOR COUPLING TO AN ENCLOSURE

The present invention relates to a connector used for attaching a multiconductor cable to an enclosure and more particularly to a connector that may be coupled to an enclosure without rotation of the cable or the enclosure.

An emerging information infrastructure is hybrid fiber coax in which a fiber optic cable stretches from a central office or head end to a distribution point. A copper coaxial cable extends from the distribution point to a recipient of the information service. This architecture is also referred to as fiber to the feeder. Conversion from the fiber distribution media to the copper distribution media occurs at the distribution point in an enclosure referred to as a node . The node is commonly positioned in aerial mounts for pole to pole connections. The node may feed anywhere from 1 - 200 users depending upon the application. The node is also subject to harsh environmental conditions as it is typically exposed to the elements. The node is an important link in the infrastructure. Accordingly, the viability of the node connection is very important both to providers of the information service as well as recipients of the same service. The interconnection at the node enclosure is a vulnerable link in the distribution system.

In a hybrid fiber coax CATV distribution system, the CATV node receives a multiple conductor fiber optic cable. The cable is held by a feed through connector which is mounted to a wall of the node enclosure. In an interior of the node enclosure, the cable is broken out into its individual fibers for distribution and interconnection with electronics held within the node enclosure. Due to the harsh environment in which the node enclosure resides, the enclosure, the feed through connector, and the fitting of the cable to the connector must sufficiently protect the fiber optic cable so as not to degrade performance of the signal and consequently the system. In order to assure reliability of the system, the CATV industry has dictated certain requirements of the equipment used at the distribution point or node. Requirements of the CATV node enclosure interconnection include the ability of the connection between the feedthrough connector and the enclosure to withstand a minimum 150 lb. tensile force on the fiber optic cable. Reliable node interconnection also requires tolerance to the mechanical movement of the constituent parts of the fiber optic cable and connector due to thermal fluctuations, physical protection of the fibers, and resistance to moisture penetration. In addition, it is important that the fitting for the cable that is to go into the node enclosure be reliably field mountable and able to withstand tensile, compressive and rotational forces imposed on the cable, node enclosure and feed through connector when the node enclosure is hoisted up and down a pole during installation and repair. The feed through connector must be mounted onto the enclosure of the node without rotating the cable or the enclosure and when mounted must resist rotation when the cable is subjected to rotational forces.

Conventionally, node enclosures can receive two styles of fiber optic cable, a dielectric style and an armored style. Currently, there is a different style of connector to accommodate each style of cable. There is a need, therefore, for a single connector capable of reliable termination of either cable style while providing a high quality ground for an armored cable.

U.S. Patent Numbers 5,371,821 and 5,315,684 disclose a fiber optic connector comprising an intermediate housing engageable with a mating section and a securing section. A crimp member comprising a split sleeve is actuated by axial movement of the sleeve urged into the intermediate housing by axial movement of the securing section. Advantageously the connector may be terminated to a cable and coupled to a housing without rotating the cable. In addition, the coupled connector resists rotational displacement of the cable relative to the connector in response to rotational forces placed on the cable. Disadvantageously, the crimp member and intermediate housing are disengageable with the fiber optic cable upon disengagement of the securing member rendering the resistance to movement in response to tensile and compressive forces less than optimum. There is a need, therefore, for a fiber optic connector capable of being coupled to an enclosure without rotation of the cable or enclosure that is more resistant to displacement between the connector and the cable in response to tensile and compressive forces placed on the cable than prior art connectors. Moreover, when the connector is decoupled from the enclosure for example, during maintenance procedures, it is desirable that the connector and cable be decoupled from the enclosure, while in addition ensuring that the connector remains in place on the cable after decoupling. This makes handling and re- coupling of the connector and cable to the enclosure easier and more reliable.

Accordingly, a fiber optic connector for terminating a fiber optic cable comprises an intermediate housing having opposite engaging ends being rotatable about the fiber optic cable. A first crimp member having a first physical stop and a second crimp member having a second physical stop are disposed adjacent the opposite ends of the intermediate housing. The first and second physical stops limit movement of the intermediate housing along the cable when the first and second crimp members are actuated through engagement with the ends. The fiber optic connector further comprises a mating housing engageable with the intermediate housing and a securing housing engageable with the intermediate housing.

A method of terminating a fiber optic cable comprises the steps of stripping a fiber optic cable jacket to expose strength members, an inner tube and individual fibers, positioning a securing housing, a first crimp member, an intermediate housing, a second crimp member, and a crimping tool over the fiber optic cable jacket, actuating the first and second crimp members by threading the securing housing and the tool to the intermediate housing, partially disengaging the securing housing from the intermediate housing, removing the tool, and threading a mating housing to the intermediate housing. It is an advantage of a fiber optic connector according to the teachings of the present invention that the connector has improved resistance to tensile and compressive forces placed on the cable while being more compact than prior art connectors . It is another advantage of a connector according to the teachings of the present invention, that a single connector is appropriate for use with at least two different styles of known fiber optic cables.

It is a further advantage of a connector according to the teachings of the present invention that a reliable ground path is provided from the armor of an armored cable to the connector.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a side view of an armored fiber optic cable prepared for termination with a fiber optic connector according to the teachings of the present invention. Figure 2 is a cross-sectional view of an intermediate housing. Figure 3 is a cross-sectional view of a securing housing.

Figure 4 is a cross-sectional of a mating housing.

Figure 5 is a cross-sectional view of one embodiment of a crimp member.

Figure 6 is a cross-sectional view of an alternate and preferred embodiment of a crimp member.

Figure 7 is an exploded cross-sectional view of constituent parts of a fiber optic cable connector according to the teachings of the present invention shown relative to the fiber optic cable prior to termination of the cable assembly.

Figure 8 is cross-sectional detailed view of a crimp member as shown in figure 5 prior to actuation. Figure 9 is cross-sectional detailed view of a portion of a crimp member similar to that shown in Figure 8 but shown upon actuation.

Figure 10 is a cross-sectional detailed view of a crimp member shown in Figure 6 prior to actuation. Figure 11 is a cross-sectional detailed view of a crimp member as shown n Figure 6 upon actuation.

Figure 12 is a side view of a partial assembly of a fiber optic connector according to the teachings of the present invention. Figure 13 is a cross-sectional view of a fiber optic connector according to the teachings of the present invention shown subsequent to termination of the fiber optic cable and prior to termination of the individual fibers. Figure 14 is a perspective view of the mating end and of a fiber optic connector according to the teachings of the present invention shown subsequent to termination of the fiber optic cable and prior to termination of the individual fibers. Figure 15 is a perspective view of the securing end of a fiber optic connector according to the teachings of the present invention shown subsequent to termination of the fiber optic cable and prior to termination of the individual fibers.

Figure 16 is a cross-sectional view of a terminated fiber optic connector and cable according to the teaching of the present invention shown as connected to an enclosure.

With specific reference to Figure 2 of the drawings there is shown a substantially tubular intermediate housing (1) defining a longitudinal axis (9) along the length of the housing (1) . An inner diameter of the intermediate housing (1) is slightly greater than the outer diameter of a jacketed fiber optic cable. A center section (2) of the intermediate housing (1) comprises an area of large outer diameter the outer cross-section of which is a hexagonal configuration.

Opposite walls of the center section that are transverse to the longitudinal axis (9) create first and second o- ring shoulders (3,4). The intermediate housing (1) further comprises opposite engaging ends (5) distal from the center section (2) . The threads (6) of each engaging end (5) extend from the outermost ends of the intermediate housing to a position short of the first and second o-ring shoulders (3,4). An innermost end of the threads (6) positioned a distance from the first and second o-ring shoulders (3,4) create an o-ring seat (7) in which is disposed an o-ring. Each engaging end (5) further comprises a 45° angular chamfer (8) angled toward the inner diameter of the intermediate housing (1) . As one of ordinary skill in the art can appreciate, the intermediate housing is symmetrical about both a plane intersecting the longitudinal axis (9) as well as a plane transverse to the longitudinal axis (9) and cutting through the center section (2) . In a preferred embodiment, the intermediate housing is made of nickle plated aluminum. With specific reference to Figure 3 of the drawings, there is shown a substantially tubular securing housing (10) made of nickle plated aluminum and having a hexagonal cross-sectional outer diameter profile. An inner geometry of the securing housing comprises a complimentary engaging end (11) designed to be threadably engageable with the engaging end (5) of the intermediate housing (1) . The threads (12) are positioned slightly internal to the complimentary engaging end (11) creating an o-ring recess (13) adjacent the threaded portion of the complimentary engaging end (11) . The securing housing (10) further includes an area where the inner diameter converges from a larger inner diameter in which the threads (12) are positioned to a smaller inner diameter section toward a sealing end (14) of the securing housing (10) . The sealing end (14) further comprises an area of annular relief creating an o-ring seat (15) positioned close to and adjacent the sealing end (14) of the securing housing (10) . The area of transition from a larger inner diameter to a smaller inner diameter section of the securing housing (10) can be a linear transition creating an angled annular transition (not shown) or, and in a preferred embodiment, the transition is radiused to create an annular force transmitting element (16) .

With specific reference to Figure 4 of the drawings, there is shown a substantially tubular nickle plated aluminum mating housing (17) having a threaded coupling section (18) and an attachment section (19) . The coupling section (18) has external threads for coupling to a CATV node enclosure. Adjacent to the threads of the coupling section (18) is a relief area creating an o-ring seat (20) on an outer diameter of the mating housing (17) . The attachment section (19) has an internal threaded coupling and an outer diameter the cross section of which has a hexagonal configuration. The internal threads of the attachment section (19) are appropriate for interconnection with the external threads on the engaging end (5) of the intermediate housing (1) . The threads of the attachment section (19) do not extend to an end of the mating housing (17) distal from the coupling section (18) thereby creating an annular o-ring recess (21) . With specific reference to Figure 5 and 6 of the drawings, there is shown two embodiments of first and second crimp members (22,23) according to the teachings of the present invention. Figure 5 shows the cross-section of one embodiment of the first and second crimp members. First and second crimp members (22,23) comprise an annular clamp ring preferably made of halfhard brass. Relative to a longitudinal axis (9) that extends through the center of the annular clamp ring, the first and second crimp members have a non uniform outer diameter with a maximum outer diameter being positioned at a center of the first and second crimp members (22,23) along their length. It is preferred that the outer diameter transition in thickness from an initial thickness at the outermost ends of the crimp members increasing along a line angled at 20° with respect to the longitudinal axis (9) . The area of maximum outer diameter comprises a physical stop (24) to be described more fully hereinafter. With specific reference to Figure 6 of the drawings, there is shown an alternate and preferred embodiment of the first and second crimp members (22,23). The preferred embodiment includes the nonuniform outer diameter having at its center a maximum outer diameter. The preferred embodiment further comprises a relief area created by inwardly angled hinge walls (26) positioned on an inner diameter that is directly in line with the area of maximum outer diameter. The hinge walls (26) are preferable at 90° with respect to each other defining a pivot point 27 at an intersection of the two hinge walls (26) . With specific reference to Figure 7 of the drawings, there is shown an exploded cross-sectional view of constituent parts of a fiber optic connector according to the teachings of the present invention shown relative to a prepared armored fiber optic cable. The fiber optic connector according to the teachings of the present invention is assembled by first stripping and preparing a fiber optic cable for receipt of the connector. In the case of the non armored fiber optic cable, the jacket (100) is stripped to expose the strength members (101) , the gel filled inner tube (102) , and fibers (103) of the fiber optic cable. Preparation of an armored fiber optic cable includes stripping the jacket (100) to expose a length of the armor (104) , the strength members (101) , the inner tube (102) , and the fibers (103) . The armor (104) that is exposed and is not covered by the jacket is cut to form a strip of metal which is then retroflexed over the jacket of the fiber optic cable as shown in Figure 7 of the drawings. The securing housing (10) , the first crimp member (22) , the intermediate housing (1) , and the second crimp member (23) are threaded onto the jacketed cable and positioned over the strip of retroflexed armor (104) . The intermediate housing (1) is positioned at an appropriate distance from an end of the jacket (100) of the fiber optic cable. First and second crimp members (22,23) are positioned adjacent each engaging end (5) of the intermediate housing (1) . At this point in the assembly process, the engaging end (5) of the intermediate housing (1) closest to the exposed fibers (103) of a fiber optic cable, defines a coupling end (28) of the intermediate housing (1) . The engaging end (5) of the intermediate housing (1) opposite to the coupling end (28) is defined as the securing end (29) of the intermediate housing (1) . When the intermediate housing (1) , and the first and second crimp members (22,23) are appropriately positioned adjacent each other and at an appropriate distance along the jacket of the fiber optic cable, a tool (not shown) which is preferably identical in form to the securing housing (10) is used to crimp the first crimp member (22) to the jacket. The securing housing (10) is used to crimp second crimp member (23) to the jacket (100) in the same way and simultaneously with the first crimp member (22) .

With specific reference to Figures 8 and 9 of the drawings, there is shown a cross-sectional detailed view of the relative positioning of the securing housing (10) and the first crimp members (22) (on a coupling end (28) of the intermediate housing (1) , the tool relative to the second crimp member (23)), and the inner chamfer (8) of the intermediate housing (1) . Figure 8 shows the crimp member (23) prior to actuation of the crimp and Figure 9 shows the same parts after actuation of the crimp. Actuation of the crimp proceeds as follows: as the securing housing (10) is threaded onto the intermediate housing (1) , the force transmitting element (16) of the securing housing (10) engages a section of the first crimp member (22) having an annularly tapered outer diameter. Further movement of the force transmitting element (10) against the first crimp member (22) pushes the first crimp member along the jacketed cable until it engages the inner chamfer (8) of the intermediate housing (1) . Further axial movement of the force transmitting element (10) in combination with the stationary inner chamfer (8) causes a force vector to be placed on the first crimp member forcing the first gripping edge (30) of the crimp member (22) to grip the jacket (100) of the fiber optic cable. Engagement of the crimp member (22) and the chamfer (8) of the intermediate housing (1) , therefore, initiates and directs the deformation of the first gripping edge (30) of the crimp member (22) . After the first gripping edge (30) of the crimp member (22) has deformed a specific amount, further axial movement of the force transmitting element (16) causes deformation of the second gripping edge (31) of the crimp member (22) . After the securing housing (10) is fully tightened to the intermediate housing (1) , the actuation of the crimp member (22) is completed as shown in Figure (9) of the drawings. This crimp is permanent, even though the securing housing (10) is disengageable from the intermediate housing (1) . In an alternate embodiment of the securing housing (10) , the force transmitting element (16) instead of being radiused is positioned at a 45° angle with respect to the longitudinal axis (9) of the securing housing

(10) and is positioned 90° with respect to the inner chamfer (8) of the intermediate housing (1) . In the embodiment of a 45° annular chamfered force transmitting element (16) , the first and second gripping edges

(30,31) are deformed simultaneously to grip the cable jacket (100) . The radiused force transmitting element

(16) , however, is preferred. With specific reference to Figures 10 and 11 of the drawings, there is shown a cross-sectional detailed view of an alternate embodiment of crimp member (22) as shown prior to and subsequent to actuation of the crimp. The alternate embodiment of the crimp member (22) which includes opposite hingewalls

(26) which intersect at the pivot point (27) reduces the crimping force necessary to deform the first and second gripping edges (30,31) of the crimp member (23) to achieve an appropriate crimp on the jacket (100) of the fiber optic cable. In this configuration, the force required to initiate and complete the deformation of the crimp member (22) is reduced. The strength of the resulting crimp, however, is maintained. For that reason, the alternate embodiment of the crimp member (23) is preferred.

In the assembly operation, both the first and the second crimp members (22,23) are crimped as previously described. After the crimp has been actuated, the deformation of the crimp members (22,23) is maintained rendering the crimp permanent . The crimp is not disengageable from the jacket (100) of the fiber optic cable, even though the securing housing (10) is disengageable from the intermediate housing (1) . During the assembly operation, the securing housing (10) , is partially disengaged so that the threads are backed off from the intermediate housing (1) , although not completely. The tool used to crimp the second crimp member (23), which in a preferred embodiment is identical to the securing housing (10) , is completely removed from the intermediate housing (1) . As one of ordinary skill in the art can appreciate, partial disengagement of the securing housing and removal of the tool causes opposing force transmitting elements (16) , to disengage the first and second crimp member (22,23) .

When both force transmitting elements (16) act to place opposing forces on the first and second crimp members (22,23) respectively, the result is a slight compression of the fiber optic cable jacket (100) between the first gripping edges (30) of first and second crimp members (22,23) respectively. Removal of the forced transmitting elements (16) , and the forces imposed thereby, permit the compressed fiber optic cable jacket (100) to release and return to its original uncompressed length. This permits the intermediate housing (1) to freely rotate about the fiber optic cable jacket. The physical stops (24,25) of the crimp members (22,23), limit the longitudinal movement of the intermediate housing (l) along the fiber optic cable but do not interfere with rotation of the intermediate housing (1) relative to the cable.

After the second crimp (23) is actuated and the tool is removed, the tool is replaced by the mating housing (17) . The attachment section (19) of the mating housing (17) is threaded over the coupling end (28) of the intermediate housing (1) . The inner geometry of the attachment section (19) of the mating housing (17) differs from the inner geometry of the complementary engaging end (11) of the securing housing (10) in that the mating housing (17) does not include a force transmitting element (16) . When the connection between the mating housing (17) and the intermediate housing (1) is complete, there is an area of clearance around the member crimp (23) permitting the mating housing (17) as coupled to the intermediate housing (1) to freely rotate about the fiber optic cable. In a preferred assembly method, a few drops of epoxy are deposited on the threads (6) of the coupling end (28) of the intermediate housing (1) prior to connection with the mating housing (17) . The epoxy on the threads (6) , permanently attaches the intermediate housing (1) to the mating housing (17) . When the securing housing (10) is partially disengaged from the securing end (29) of the intermediate housing (1) , and by virtue of the permanent attachment between the intermediate housing (1) and the mating housing (17) , the connector comprising the securing housing (10) , the intermediate housing (1) and the mating housing (17) is able to rotate freely about the fiber optic cable. The fiber optic connector according to the teachings of the present invention, therefore, is permanently attached to the fiber optic cable while still providing the very important rotational freedom prior to coupling to an enclosure.

Further assembly of the fiber optic cable according to the teachings of the present invention includes attachment of a fiber optic breakout fitting such as the one described in U.S. Patent Application Serial Number (Unknown) which is referred to as The Whitaker Corporation Docket Number 16744 the contents of which are specifically incorporated by reference herein. The breakout fitting as described in the co-pending patent application is a preferred breakout fitting, alternative embodiments however, are acceptable. In order to prevent moisture penetration into the fiber optic connection, four o-rings (32) are positioned in o-ring seats (20,15,7). As one of ordinary skill in the art can appreciate, each o-ring is compressed at a joint between interconnecting elements of the fiber optic connector according to the teachings of the present invention. Sufficient compression of each of these o-rings at the various interconnection points is a sufficient environmental seal to prevent moisture engress into the enclosure to which the fiber optic connector is attached.

The appropriate coupling of the fiber optic connector to an enclosure comprises the following steps: as the intermediate housing (1) /mating housing (17) is free to rotate about the fiber optic cable, threadable attachment can be made between the coupling section (18) of the mating housing (17) and an enclosure (105) to which it is to be connected. As the mating housing (17) is coupled to the enclosure (105) , the securing housing (10) remains either partially or fully disengaged from the intermediate housing (1) . If the securing housing (10) is partially engaged with the intermediate housing (1) , it is also capable of freely rotating about the fiber optic cable in concert with the intermediate housing (1) . When the mating housing (17) is fully coupled to the enclosure, the securing housing (10) is then threaded onto the securing end (29) of the intermediate housing (1) . When the securing housing (10) is tightened against the intermediate housing (1) by the threaded connection, the force transmitting elements (16) engage the first crimp member (22) and press it forward. The slight axial movement of the first crimp member (22) in response to the force applied by the securing housing (10) , slightly compresses the cable jacket (100) between the first and second crimp members (22,23). The slight compression of the cable jacket (100) results in a positive physical and in the case of an armored fiber optic cable conductive contact between the intermediate housing (1) , the strip of armor (104) and the outer perimeter of the jacket (100) . Further tightening of the securing housing (10) to its maximum engagement with the intermediate housing (1) , provides for sufficient clamping of the connector onto the jacket (100) to sufficiently resist rotation of the fiber optic cable relative to the connector.

Advantageously, the completed assembly results in connection between a fiber optic cable and an enclosure having high tensile and compressive strength. The connection is resistant to rotation between the cable and the connector, and in the case of an armored cable, provides a high quality ground from the armor of the fiber optic cable through the connector and to the enclosure. The fiber optic connector according to the teachings of the present invention also provides a reliably terminated and coupled fiber optic cable assembly.

Claims

Claims :

1. A fiber optic connector for terminating a fiber optic cable, the connector housing an intermediate section (1) engageable with a mating housing (17) and a securing housing (10) , a first crimp member (22) for clamping the fiber optic cable wherein the connector is characterized in that: a second crimp member is provided (23) for clamping the fiber optic cable, said first and second crimp members (22,23) having first and second physical stops (24,25) respectively, said intermediate housing (1) being disposed between said first and second crimp members (22,23), said first and second physical stops (24,25) limiting movement of said intermediate housing (1) along said cable when said first and second crimp members are actuated.

2. A fiber optic connector as recited in claim 1 further characterized in that said crimp members (22,23) comprise an annular ring having a non-uniform outer diameter along their length, the area of maximum outer diameter comprising the physical stop.

3. A fiber optic connector as recited in claim 1 further characterized in that said crimp member has a non-uniform inner diameter along its length the area of minimum inner diameter comprising a gripping edge, which grips the fiber optic cable upon actuation of said crimp member.

4. A fiber optic connector as recited in claim 1 further characterized in that said crimp member has a relief area creating a pivot point and providing for a pivotal movement about said pivot point when said crimp member is actuated.

5. A fiber optic connector as recited in claim 1 further characterized in that said crimp member has opposite inwardly angled annular hinge walls that intersect at a pivot point.

6. A fiber optic connector as recited in claim 1 further characterized in that said fiber optic cable comprises a plurality of fibers, fibrous strength members, a jacket, and an armor disposed between said jacket and said strength members, and wherein a strip of armor is retroflexed over said jacket and is captivated between said jacket (100) and said first crimp member (22).

7. A fiber optic connector as recited in claim 6 further characterized in that said armor is further captivated between said jacket 100 and said second crimp member (23) .

8. A fiber optic connector as recited in claim 1 further characterized in that said securing housing (10) has an inner geometry that further comprises a radiused force transmitting element (16) that engages said crimp members (22) to actuate gripping of the cable by said crimp member (22) .

9. A method of terminating a fiber optic cable comprising the steps of: stripping a fiber optic cable jacket to expose strength members, an inner tube and individual fibers positioning a securing housing, a first crimp member, an intermediate housing, a second crimp and a crimping tool over the fiber optic cable jacket, actuating the first and second crimp members by threading said securing housing and said tool to said intermediate housing, partially disengaging said securing housing from said intermediate housing, removing said tool, and threading a mating housing to said intermediate housing.