U.S. patent application number 09/750338 was filed with the patent office on 2003-07-03 for loose tube cable having an easily removable buffer tube binder for cable access.
Invention is credited to Dallas, George, Witt, Geoffrey Martin.
Application Number | 20030123822 09/750338 |
Document ID | / |
Family ID | 25017451 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030123822 |
Kind Code |
A1 |
Witt, Geoffrey Martin ; et
al. |
July 3, 2003 |
LOOSE TUBE CABLE HAVING AN EASILY REMOVABLE BUFFER TUBE BINDER FOR
CABLE ACCESS
Abstract
An optical fiber cable comprising a plurality of buffer tubes,
binder wrapped around the buffer tubes, a ripcord disposed between
the buffer tubes and the binder, and a protective outer jacket
covering the buffer tubes. Upon application of a sufficient
outwardly directed pulling force, the ripcord rips both the binder
and the jacket thereby providing access the buffer tubes and
optical fibers therein. The binder is formed of a material which
melts or softens when the jacket is formed by an extrusion process
so that the binder is thereby incorporated into the jacket.
Alternatively, the binder is formed of a material which will adhere
to the jacket when the jacket is formed by an extrusion process and
is easily torn when the jacket is ripped by the ripcord.
Inventors: |
Witt, Geoffrey Martin;
(Hickory, NC) ; Dallas, George; (Hickory,
NC) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037-3213
US
|
Family ID: |
25017451 |
Appl. No.: |
09/750338 |
Filed: |
December 29, 2000 |
Current U.S.
Class: |
385/109 |
Current CPC
Class: |
G02B 6/441 20130101;
G02B 6/4429 20130101; G02B 6/4495 20130101 |
Class at
Publication: |
385/109 |
International
Class: |
G02B 006/44 |
Claims
What is claimed is:
1. An optical fiber cable, comprising: a plurality of buffer tubes
having optical fibers therein; a binder wrapped around said buffer
tubes to hold said buffer tubes together; a first ripcord disposed
between said buffer tubes and said binder; and a jacket
circumscribing said buffer tubes, said binder and said ripcord,
wherein said ripcord rips said binder and said jacket upon
application of an outwardly directed pulling force.
2. The optical fiber cable according to claim 1, further comprising
a second ripcord disposed between said buffer tubes and said
binder, wherein said first and second ripcords are arranged on
opposite sides of said buffer tubes held together by said
binder.
3. The optical fiber cable according to claim 1, wherein said
binder is made of paper, mylar foil, metal foil, or polymer
tape.
4. The optical fiber cable according to claim 1, wherein said first
ripcord is made of aramid, glass, or carbon fibers.
5. An optical fiber cable, comprising: a plurality of buffer tubes
having optical fibers therein; a binder wrapped around said buffer
tubes to hold said buffer tubes together; and a jacket
circumscribing said buffer tubes, wherein said binder is formed of
a material which melts upon application of heat when said jacket is
formed by an extrusion process so that said binder is incorporated
into said jacket.
6. The optical fiber cable according to claim 5, wherein said
material of said binder comprises polypropylene, polyethylene or
copolymers thereof.
7. The optical fiber cable according to claim 5, further comprising
a ripcord disposed between and said binder and said jacket.
8. The optical fiber cable according to claim 5, further comprising
a ripcord disposed between said buffer tubes and said binder.
9. An optical fiber cable, comprising: a plurality of buffer tubes
having optical fibers therein; a binder wrapped around said buffer
tubes to hold said buffer tubes together; and a jacket
circumscribing said buffer tubes, wherein said binder is formed of
a material which adheres to said jacket when said jacket is formed
by an extrusion process.
10. The optical fiber cable according to claim 9, further
comprising a ripcord disposed between said buffer tubes and said
jacket, wherein said ripcord rips said jacket and said binder
adhering to said jacket upon application of an outwardly directed
pulling force.
11. The optical fiber according to claim 9, wherein said material
comprises paper which is textured or coated with an adhesive, mylar
foil, metal foil, polymer tape, elastomeric tape, or cloth tapes
wherein texture allows adhesion to the jacket.
12. An optical fiber cable, comprising: a plurality of buffer tubes
having optical fibers therein; a binder wrapped around said buffer
tubes to hold said buffer tubes together; an armor layer
circumscribing said buffer tubes, and a jacket circumscribing said
armor layer, wherein said binder is formed of a material which
adheres to said armor layer when said jacket is formed by an
extrusion process.
13. The optical fiber cable according to claim 12, further
comprising a ripcord disposed between said buffer tubes and said
armor layer, wherein said ripcord rips said jacket, said armor
layer and said binder adhering to said armor layer upon application
of an outwardly directed pulling force.
14. The optical fiber according to claim 12, wherein said material
comprises paper which is textured or coated with an adhesive, mylar
foil, metal foil, polymer tape, elastomeric tape, or cloth tapes
wherein texture allows adhesion to the jacket.
15. An optical fiber cable, comprising: a plurality of buffer tubes
having optical fibers therein; a binder wrapped around said buffer
tubes to hold said buffer tubes together; and a jacket
circumscribing said buffer tubes, wherein the tensile strength of
said binder is reduced upon application of heat when said jacket is
formed by an extrusion process.
16. The optical fiber cable according to claim 15, wherein said
binder is formed of a material which adheres to said jacket when
said jacket is formed by the extrusion process.
17. The optical fiber cable according to claim 16, wherein said
material comprises a thermoplastic elastomer, polyolifin, or
polymers with weak thermal linkages.
18. The optical fiber cable according to claim 16, further
comprising a ripcord disposed between said buffer tubes and said
jacket, wherein said ripcord rips said jacket and said binder
adhering to said jacket upon application of an outwardly directed
pulling force.
19. An optical fiber cable, comprising: a plurality of buffer tubes
having optical fibers therein; a binder wrapped around said buffer
tubes to hold said buffer tubes together; and an armor layer
circumscribing said buffer tubes, and a jacket circumscribing said
armor layer, wherein the tensile strength of said binder is reduced
upon application of heat when said jacket is formed by an extrusion
process.
20. The optical fiber cable according to claim 19, wherein said
binder is formed of a material which adheres to said armor layer
when said jacket is formed by the extrusion process.
21. The optical fiber cable according to claim 20, wherein said
material comprises a thermoplastic elastomer, polyolifin, or
polymers with weak thermal linkages.
22. The optical fiber cable according to claim 20, further
comprising a ripcord disposed between said buffer tubes and said
armor layer, wherein said ripcord rips said jacket, said armor
layer and said binder adhering to said armor layer upon application
of an outwardly directed pulling force.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a loose tube cable having a
binder which is easily removable when the cable is accessed. In
particular, the present invention relates to a loose tube cable
having ripcord disposed under a binder surrounding a plurality of
buffer tubes for ripping a binder and an outer protective jacket.
This invention also relates to a binder formed of a material which
is weakened or melted by the application of heat when the loose
tube cable is jacketed.
BACKGROUND OF THE INVENTION
[0002] In conventional loose tube cables, buffer tubes are stranded
(helically or reverse helically) around a central strength member
to form a stranded core. The buffer tubes are utilized as the
primary structure for protecting the thin optical fibers contained
within. That is, the buffer tubes house an optical unit such one or
more loose optical fibers or an optical fiber ribbon comprising a
plurality of optical fibers which are held together in a planar
array. The buffer tubes are generally filled with a water blocking
component such as a thixotropic gel which prevents water ingress
but allows for fiber movement during cable expansion or
contraction, or contain a water swellable material which absorbs
water. In addition to the buffer tubes, filler rods may be stranded
around the central strength member in order to provide symmetry in
design for fiber counts lower than that of a full fiber count
cable.
[0003] After the buffer tubes (and filler rods) are stranded around
the central strength member, one or more binders are wrapped around
the buffer tubes in order to hold the buffer tubes in place prior
to extrusion of a cable jacketing material about the stranded core.
The binders are typically tape-like members or filaments made of
polyester and aramide materials and may be helically or
contra-helically applied. Next, the stranded core which is held
together by the binder is wound on a reel at the end of the
stranding line and moved to a jacket line where one or more
ripcords (typically two ripcords which are 180 degrees apart) are
disposed over the stranded core and a plastic material, e.g.,
polyvinyl chloride (PVC), polyethelene, polypropolyene, or
copolymer thereof, is extruded to form a protective outer jacket
around the ripcord and stranded core. Once the cable has been
jacketed, the binders surrounding the buffer tubes are no longer
necessary because the jacket now serves hold the loose tubes in
place.
[0004] The ripcords disposed between the outer jacket and the
stranded core are provided for ripping the outer jacket in order to
access the buffer tubes in the loose tube cable. That is, when it
is necessary to access the optical fibers in the loose tube cable,
e.g., prepare the optical fibers for splicing, the ripcord is
pulled with sufficient force to rip the outer jacket and the
binders are removed from the buffer tubes using a cutting tool.
However, the removal of the binders increases the time required for
accessing the cable and may potentially damage the buffer tubes or
other cable components.
[0005] U.S. Pat. No. 6,088,499 discloses a fiber optic cable which
includes a cable core and a sheath section disposed over the cable
core. The cable core includes a plurality of buffer tubes housing a
plurality of optical fibers, a binder stranded around the cable
core, and a ripcord disposed under the binder. The sheath section
includes two ripcords, armor tape which surrounds the ripcords, and
a jacket which surrounds the armor tape. When it is desired to
access the fiber optic cable, the ripcords in the sheath section
are pulled to rip the armor tape and the jacket to gain access to
the cable core, and then the ripcord in the cable core is pulled to
rip the binder to gain access to buffer tubes and the optical
fibers therein. However, the additional ripcord in the cable core
increases manufacturing costs and is a required step which must be
performed in order to access the cable.
[0006] In view of the disadvantages of conventional loose tube
cables which utilize binders which must be removed in order to
access the buffer tubes and optical fibers therein, it is an object
of the present invention to provide a solution to the problem of
removing binders from fiber optic cables.
SUMMARY OF THE INVENTION
[0007] The present invention is adapted to achieve the foregoing
objects. In accomplishing these objects, a first embodiment of the
present invention provides an optical fiber cable comprising a
plurality of buffer tubes, binder wrapped around the buffer tubes,
a ripcord disposed between the buffer tubes and the binder, and a
protective outer jacket covering the buffer tubes. Upon application
of a sufficient outwardly directed pulling force, the ripcord rips
both the binder and the jacket thereby providing access the buffer
tubes and optical fibers therein.
[0008] According to a second embodiment of the present invention,
there is provide a fiber optic cable comprising a plurality of
buffer tubes, binder wrapped around the buffer tubes, a ripcord,
and a protective outer jacket covering the buffer tubes, wherein
the binder is formed of a material which melts or softens when the
jacket is formed by an extrusion process so that the binder is
thereby incorporated into the jacket.
[0009] According to a third embodiment of the present invention,
there is provided a fiber optic cable comprising a plurality of
buffer tubes, binder wrapped around the buffer tubes, a ripcord,
and a protective outer jacket covering the buffer tubes, wherein
the binder is formed of a material which will adhere to the jacket
when the jacket is formed by an extrusion process and is easily
torn when the jacket is ripped by the ripcord.
[0010] According to a fourth embodiment of the present invention,
there is provided a fiber optic cable comprising a plurality of
buffer tubes, binder wrapped around the buffer tubes, a ripcord,
and a protective outer jacket covering the buffer tubes, wherein
the binder is formed of a material which will adhere to the jacket
and has mechanical properties which will be reduced when the jacket
is formed by an extrusion process, and is easily torn when the
jacket is ripped by the ripcord.
[0011] The above and other features of the invention including
various and novel details of construction and process steps will
now be more particularly described with reference to the
accompanying drawings and pointed out in the claims. It will be
understood that the particular optical fiber cable embodying the
invention is shown by way of illustration only and not as a
limitation of the invention. The principles and features of this
invention may be employed in varied and numerous embodiments
without departing from the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following detailed description, appended claims, and
accompanying drawings, wherein:
[0013] FIG. 1 illustrates a plan view of the fiber optic cable in
accordance with a first embodiment of the present invention;
[0014] FIG. 2 illustrates a sectional view of the fiber optic cable
in accordance with a first embodiment of the present invention;
and
[0015] FIG. 3 illustrates a plan view of the fiber optic cable in
accordance with a second through fourth embodiments of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Referring to FIGS. 1 and 2, a fiber optic cable 10 according
to a first embodiment of the present invention will be described.
The fiber optic cable 10 includes a core section 20 formed by
stranding a plurality of buffer tubes 30 around a central strength
member 40. Each of the buffer tubes 30 includes one or more loose
optical fibers 25 or an optical fiber ribbon (not shown) comprising
a plurality of optical fibers which are held together in a planar
array. Further, each of the buffer tubes 30 is filled with a water
blocking component such as a thixotropic gel which prevents water
ingress, or contains a water swellable material which absorbs
water. In addition to the buffer tubes 30, filler rods (not shown)
may be stranded around the central strength member 40 in order to
provide symmetry in design for fiber counts lower than that of a
full fiber count cable.
[0017] One or more ripcords 35 are disposed lengthwise along on the
core section 20 and a binder 50 is wrapped or stranded around the
core section 20 and the ripcords 35 to hold the stranded buffer
tubes 30 prior to jacketing. During the jacketing operation, the
core section 20 is passed through an extruder head (not shown) to
cover the core section 20 with an outer protective jacket 70 which
surrounds the core section 20 thereby producing the jacketed fiber
optic cable. The ripcords 35 are operative to rip both the binder
50 and the jacket 70 upon application of a sufficient outwardly
directed pulling force. In the preferred embodiment, two ripcords
35 are arranged on opposite sides (i.e., 180 degrees apart) of the
core section 20 so that the cable is perfectly bisected when the
ripcords are pulled. Examples of materials that can be used as
binders include paper which is textured or coated with an adhesive
such as ethylene or propylenne copolymer adhesive, mylar foil,
metal foils (e.g., copper, aluminum or steel), polymer tapes (e.g.,
polyester or polyolefin), elastomeric tapes (e.g., polyolefin,
acrylic, or polyurethane), cloth tapes (e.g., cotton, polyester,
nylon, linen). In addition, the binder 50 may be have optimized
mechanical properties such as slits along the edge to initiate a
tear. The ripcord 35 can be made of polyester, aramid, glass,
carbon fiber or blends of the materials. The jacket material can be
made from polyethylene, polypropylene or copolymers of the two
materials.
[0018] Referring to FIG. 3, a fiber optic cable 110 according to a
second embodiment of the present invention will be described. The
fiber optic cable 110 includes a core section 120 formed by
stranding a plurality of buffer tubes 130 around a central strength
member 140. Each buffer tube 130 includes one or more loose optical
fibers 125 or an optical fiber ribbon comprising a plurality of
optical fibers which are held together in a planar array. Further,
each of the buffer tubes 130 is filled with a water blocking
component such as a thixotropic gel which prevents water ingress,
or contains a water swellable material which absorbs water.
[0019] A binder 150 is wrapped or stranded around the core section
120 to hold the stranded buffer tubes 130 in place so that an outer
protective jacket 170 may be applied which surrounds the core
section 120 and binder 150. As shown in FIG. 3, in the jacketing
operation, one or more ripcords 160 are placed over the binder 150,
and the core section 120 and the ripcords 160 are passed through an
extruder head 180 to cover the core section 120 and ripcords 160
with the outer protective jacket 170 thereby producing the jacketed
fiber optic cable. Alternatively, the ripcords 160 may be placed
under the binder 150 prior to extrusion of the outer protective
jacket 170, as in the first embodiment of the present
invention.
[0020] In accordance with the second embodiment of the present
invention, the binder 150 is formed of a material, such as
polypropylene, polyethylene, and copolymers thereof, which will
melt when the jacket 170 is extruded from the extruder 180 so that
the binder 150 will be absorbed or incorporated into the jacket
170. That is, the binder 150 is formed of a material having a
melting temperature which-is less than temperature of an extruder
(e.g., less than 450 degrees Fahrenheit) which extrudes the jacket
170. The melting temperature of the binder is less than the
temperature of the molten jacket as it is applied to the core
section.
[0021] In accordance with a third embodiment of the present
invention, the binder 150, as discussed above with regards to the
second embodiment, may be formed of a material which adheres to the
jacket 170 when the core section 120 is covered with the outer
protective jacket extruded from the extruder head 180, and is
easily torn or ripped when the jacket 170 is removed via the
ripcords 160. Alternatively, where an armor layer (not shown) is
provided between the jacket 170 and the binder 150, the binder will
adhere to the armor layer. Examples of materials which will adhere
to the jacket 170 or armor layer include paper which is textured or
coated with an adhesive such as ethylene or propylene copolymer
adhesive, mylar foil, metal foils (e.g., copper, aluminum or
steel), polymer tapes (e.g., polyester or polyolifin), elastomeric
tapes (e.g., polyolifin, acrylic, or polyurathane), cloth tapes
wherein texture allows adhesion to the jacket 170 (e.g., cotton,
polyester, nylon, linen).
[0022] In accordance with a fourth embodiment of the present
invention, the binder 150, as discussed above with regards to the
second and third embodiments, may be formed of a material having
mechanical properties that are reduced with heat, causing the
material to soften and adhere to the jacket when the jacket is
extruded to cover the core section 120 so that the binder 150 is
easily torn or ripped when the jacket is removed via the ripcords
160. Alternatively, where an armor layer (not shown) is provided
between the jacket 170 and the binder 150, the binder will adhere
to the armor layer. Examples of materials include thermoplastic
elastomers (crosslinked), polyolifins such as propylene, ethylene
and their copolymers, and polymers with weak thermal linkages such
as polyether linkages.
[0023] As in the second embodiment, the ripcords 160 in the third
and fourth embodiements may be placed over the binder 150 or under
the binder 150 prior to extrusion of the outer protective jacket
170.
[0024] As discussed above, the binder materials of the second
embodiment will work with non-armored cables, where the binder
materials will contact the jacket. The binder materials of the
third and fourth embodiments work with both armored and non-armored
cables. However, with armored cables, the binders must adhere to
the armor layer, by using an adhesive, by softening the binder, or
by softening the coating on the armor (r.f. heating).
[0025] Accordingly, the fiber optic cable in accordance with the
first though fourth embodiments of the present invention eliminate
the need for cutting tools for cutting the binder, or multiple
different ripcords for ripping the binder and the jacket thereby
reducing the time required for accessing the cable as well as the
manufacturing cost.
[0026] Although certain preferred embodiments of the present
invention have been described, the spirit and scope of the
invention is by no means restricted to what is described above. For
example, although the preferred embodiment as been described with
reference to binders for a loose tube cable, the ripcord and binder
materials utilized in the different embodiments of the present
invention can be adapted for use for binders stranded around other
cable components.
* * * * *