Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1998-09-29
2001-04-17
Lorin, Francis J. (Department: 1775)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C156S049000, C156S304500, C264S259000
Reexamination Certificate
active
06217809
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to optical cable, and more particularly, to the dieletric strength tape utilized as a strength member in optical cable.
BACKGROUND OF THE INVENTION
Optical cable is widely used as a communication medium in both public and private communication networks. Optical cable comprises glass or plastic fibers that are relatively fragile, and require strength members for protection from tensile stress during processing, installation, and servicing. It is known that excess tensile stress may cause the optical characteristics of the fibers to change, resulting in transmission loss. Accordingly, a variety of different strength system designs for optical cables have been proposed for the protection of the transmission integrity of the fibers contained therein.
Strength system designs typically include the use of rigid strength rods or flexible members made from materials such as steel, KEVLAR® (a registered trademark of E. I. du Pont de Nemours and Company), epoxy/aramid, epoxy/glass, etc. The rigid strength members may form the core of an optical cable, wherein the optical fibers are packaged into one or more plastic buffer tubes that are stranded around the strength member. Alternatively, fiber bundles or ribbons may be disposed in the central portion or core of the optical cable, wherein the strength members are disposed outside the core, typically embedded within the optical cable jacket.
An improved strength member which provides advantageous strength and flexibility characteristics has been developed by Lucent Technologies, Inc. The improved strength member comprises a strength tape that wraps around a core fiber bundle. The strength tape includes a plurality of strands that are woven together into a linear strength tape, as described in greater detail below.
However, there exist practical limits to the maximum length of the strength members utilized in an optical cable. Depending upon the type of strength members utilized, the maximum length of the strength members may be less than the desired length of the optical cable. The maximum length of the strength members may be limited by numerous factors such as material characteristics, fabrication techniques, size and weight considerations, etc.
One technique for extending the length of a strength member is to splice two strength members together so that the combined length is suitable for the particular optical fiber cable being manufactured. A strength member splice has to meet specific requirements in order to be an acceptable method for extending the length of the strength member. For instance, the splice may be required to meet predetermined benchmarks for strength, stiffness, aging, size, and outgassing. In addition, it is desirable to be able to splice strength members on-line during manufacture of the optical cable, and therefore, the method should take a minimum amount of time to complete, and be user friendly.
Therefore, a need exists in the industry for splicing techniques for strength members, such as strength tapes, wherein the physical length of the strength members is less than the desired length of the optical cable. Preferably, the splicing technique is compatible with the manufacturing process of the optical cable so that the splice can be made on-line.
SUMMARY OF THE INVENTION
A method for splicing a strength tape having longitudinally extending strands comprises the trimming or patterning of the strands of the respective ends that are to be joined so that the ends can be mated together in a meshing arrangement. An adhesive film is interposed between the two ends and then cured under the application of heat and pressure for a predetermined period of time. The resulting splice has essentially the same physical dimensions of the strength tape, and similar stiffness characteristics to that of the strength tape. Further, the strength of the splice is more than sufficient for use in an optical cable. Because the complete splice process can be completed in less than 4 to 5 minutes, the splice can be performed on-line with the use of a strength tape accumulator, which is particularly advantageous.
In accordance with an illustrated embodiment of the present mention, a method for splicing dielectric strength tape utilized in an optical cable as a strength member comprises the steps of placing a first end of a first strength tape in mating alignment with a second end of a second strength tape, placing a bonding agent adjacent to the first end and the second end, and curing the bonding agent to complete the splice between the first end and the second end. In order to place the first end and the second end in a mating alignment, the strands of the first strength tape and second strength tape may be selectively cut so the first end and the second end conform to one another. That is, the first end and the second end may be patterned so that the first end and second end align in a meshing arrangement.
The bonding agent placed adjacent to the first end and second end preferably comprises a heat activated, dry film adhesive. The adhesive film may be placed between the first and second ends, or alternatively, on either side of the aligned first and second ends. In addition, a first segment of adhesive film may be placed adjacent to the terminating point of the first end and a second segment of adhesive film may be placed adjacent the terminating point of the second end to further secure the terminating points of the respective ends.
The bonding agent may be cured by the application of a predetermined time-temperature-pressure process treatment. This may be achieved through the use of a splice tray within which the first end and second end are placed in mating alignment. Preferably, a release agent is deposited between the strength tape and the splice tray in order to facilitate removal of the splice following the curing of the bonding agent.
In accordance with another illustrated embodiment of the invention, a method of splicing dielectric strength tape utilized in an optical cable comprises the steps of trimming the first end of the first strength tape and trimming the second end of the second strength tape so that the first end and the second ends form mating ends. The first end is placed in a splice tray and an adhesive film is placed over the first end within the splice tray. The second end is placed over the adhesive film in the splice tray so that the first end and second end are in mating alignment. The splice tray may then be closed and the adhesive film is cured so as to complete the splice between the first end and second end. The curing process may comprise applying a heat and pressure processing treatment to the first and second ends in the splice tray for a predetermined period of time preferably approximately 40-55 seconds. The heat and pressure processing treatment preferably comprise temperatures of approximately 440-450° F., and 3900-4100 lbs. of force. Following the heat and pressure process treatment, the splice may be removed from the splice tray and the adhesive film flashing removed. The depositing of a release agent between the strength tapes and the splice tray may enhance the removal of the splice from the splice tray.
The step of trimming the first end and second end may comprise trimming alternating strands of the respect first and second ends. The strands may be trimmed such that the lengths of the trimmed strands are substantially equal, and different from the length of the untrimmed strands. Alternatively, the strands may be trimmed such that the respective alternating strands have different lengths. Accordingly, the mating interface between the first end and the second end may be perpendicular to the direction of the strands, diagonal to the directions of the strands, or symmetrically staggered in the direction of the strands.
Other features and advantages of the present invention will become apparent to one skilled in the art upon examination of the following drawings and detailed description. It is intended that all such features and advantages be
DeFabritis Raymond P.
Small, Jr. Richard D.
Solis Carlos F.
Tabaddor Priya L.
Alston & Bird LLP
Lorin Francis J.
Lucent Technologies - Inc.
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