Abrading – Abrading process – Utilizing nonrigid tool
Reexamination Certificate
1999-07-08
2001-01-09
Morgan, Eileen P. (Department: 3723)
Abrading
Abrading process
Utilizing nonrigid tool
C451S313000, C451S314000, C451S523000, C451S539000
Reexamination Certificate
active
06171177
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a tool and method for facilitating access to optical fibers contained in an optical fiber cable, and more particularly, for removing encapsulating material which encircles optical fibers in an optical fiber cable.
BACKGROUND
Optical fiber is now used in a variety of telecommunication applications because of its small physical size and high bandwidth capacity. Typically, multiple fibers are contained in an optical fiber ribbon or loosely enclosed in a buffer tube, and an optical fiber cable is manufactured to include several buffer tubes or ribbons. A plastic encapsulant surrounds the fibers within a ribbon or tube to protect and insulate the fibers from stress and bending.
Optical fiber cables with enclosed ribbons or tubes are conventionally manufactured and marketed in the form of reels. Oftentimes, during or after initial installation of an optical fiber cable, access to the individual fibers along the length of the fiber cable, commonly referred to as midspan access or entry, is required.
Current midspan access techniques, however, do not provide a means for easy and quick access to fibers with low risk of damage to fibers or fiber coatings. For example, cutting of the encapsulant with a knife blade or pin does not provide for easy control of the depth and position of a cut and often results in undesired cutting of an optical fiber or damage to the coatings on the fibers, which degrades the longevity or reliability of the fibers. In addition, initiating a peel of the encapsulant in the middle of a ribbon is difficult because the encapsulant is often a thin covering over the fibers and has a surface which is smooth and flat and sometimes coated with a water blocking gel.
Other midspan access techniques such as immersing a ribbon or tube in chemicals or heating for reducing the strength of the bond between the fibers and the encapsulant are extremely time consuming and can harm coatings and partially or completely alter or remove ink coloring identification on the fibers. In particular, the use of chemicals often requires post-cleanup of the fibers after access is obtained.
Beasley, William E., “Meeting the Demands of the Local Loop with Improved Ribbon Fiber Midspan Access”, 1994 NFOEC Conference, pp. 401-409, incorporated by reference herein, describes a midspan access technique which requires that, after the outer covering of a cable is removed, two friction pads are placed on either side of a ribbon and forcibly moved against each other to focus the force applied to the pads on a particular span of the ribbon and weaken the bond of the encapsulant to the ribbon in that area. The removal of encapsulant by use of friction pads, however, often results in contact between the friction pads and the fibers which become exposed, thereby risking damage to the fibers or coatings on the fibers.
Therefore, there exists a need for a method and apparatus for accessing encapsulated optical fibers in midspan of an optical fiber cable which overcomes the disadvantages of the prior art techniques described above.
SUMMARY OF THE INVENTION
In accordance with the present invention, a tool for separating optical fibers which are encircled by an encapsulant and included in such optical signal transmission media as an optical fiber ribbon or buffer tube comprises a pair of holders for receiving the encapsulated optical fibers therebetween. At least one of the surfaces of the holders which face each other and receive the encapsulated optical fibers therebetween has abrasive material thereon for engaging the encapsulant. At least one of the holder surfaces is resiliently urged from within the tool in the direction of the other surface, which can be fixed in position or also can be urged toward the other surface, for causing the abrasive material to resiliently engage the encapsulated fibers and to apply a force to the encapsulant fibers that cannot exceed a predetermined maximum.
When the encapsulated fibers are held between the holders, the encapsulated fibers or the tool is moved transversely relative to the direction of the bias which is applied to the at least one holder surface to cause the abrasive material to move against and abrade a desired span portion of the encapsulated fibers. The abrasive material is of a predetermined grit insufficient to remove encapsulant completely from the fibers based on the movement of the abrasive material only once against the span portion. Movement of the abrasive material against the span portion only once will create stress concentrators in the encapsulant, and movement of the abrasive material against the same span portion more than once will cause the abrasive material to scratch off or remove encapsulant which contacts the abrasive material, as well as to create stress concentrators in the encapsulant that remains on the fibers. After only the stress concentrators are created in the encapsulant or there has been substantial removal of encapsulant, the medium can be easily removed from the tool and access to the fibers at a desired midspan portion of the medium is readily available.
In still another aspect of the invention, the tool is constructed to provide that the biasing force on the abrasive material cannot cause the separation distance between the abrasive surfaces to be less than a minimum separation distance. The minimum separation distance avoids contact between the abrasive surfaces and the fibers in the encapsulant. When the biased abrasive material at the at least one holder surface has moved toward the other holder surface such that the minimum separation distance is achieved, substantial or complete removal of the encapsulant at the span portion acted upon by the abrasive surface has occurred.
In a preferred embodiment, the tool includes first and second holders which are pivotally engaged to permit relative movement such that each opposes the other with abrasive material on each surface spaced from and facing the abrasive material on the other surface. Each of the holders includes a floating plate having an abrasive coating or a strip or pad with abrasive material on an inner surface. Shoulder screws couple a plate to its associated holder and a plate includes recesses for receiving the heads of the screws from the opposing plate. The recesses are of a sufficient depth to prevent contact between the heads of the screws on one plate and the opposing plate. A resilient spring or a resilient material such as a foam pad between a plate and its associated holder applies a bias force, which cannot exceed a predetermined maximum, to the plate in the direction of the opposing plate for resiliently holding the encapsulated optical fibers.
In another embodiment, the tool includes a first holder which is coupled to a floating plate having an abrasive coating or a strip or pad with an abrasive material on its inner surface and a second holder which is fixed in place and includes an abrasive material on its inner surface. The abrasives on the respective holders oppose each other when the holders oppose each other. Shoulder screws couple the plate to the first holder. A resilient spring between the plate and the first holder applies a bias force, which cannot exceed a predetermined maximum, to the plate in the direction of the opposing abrasive material on the second holder.
In a further embodiment, the recesses have a depth which is insufficient to prevent contact between the screw heads and the elements defining the recesses. Therefore, the screw heads and such recesses define a minimum separation distance between the abrasive materials when the tool is closed. The spring applies the bias force for resiliently holding the encapsulated optical fibers until the minimum separation distance between the plates is reached.
In still a further embodiment, the tool having at least one floating plate includes a projection on at least one of the plates which extends from the inner surface of the one plate toward the inner surface of the opposing holder or plate. The projection defines a minimum separatio
Brooks L. P.
Morgan Eileen P.
Norris, Mc Laughlin & Marcus
Pirelli Cable Corporation
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