USOO7001081B2
`
`(12) United States Patent
`Cox et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,001,081 B2
`Feb. 21, 2006
`
`(*) Notice:
`
`(54) STRAIN RELIEF BOOT WITH FLEXIBLE
`EXTENSION FOR GUIDING FIBER OPTC
`CABLE
`(75) Inventors: Larry R. Cox, Austin, TX (US); Harry
`A. Loder, Austin, TX (US); Edward B.
`Lurie, Round Rock, TX (US); Mark D.
`Matthies, Austin, TX (US)
`(73) Assignee: 3M Innovative Properties Company,
`St. Paul, MN (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 10/444,122
`(22) Filed:
`May 22, 2003
`(65)
`Prior Publication Data
`US 2004/0234209 A1
`Nov. 25, 2004
`(51) Int. Cl.
`(2006.01)
`G02B 6/36
`(52) U.S. Cl. ........................................................ 385/86
`(58) Field of Classification Search ............ 385/86-87,
`385/134–136, 76,53,56; 439/523,449,
`439/470, 456
`See application file for complete Search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,170,452 A 12/1992 Ott
`5,329,603 A 7/1994 Watanabe et al.
`5,390,272 A 2/1995 Repta
`
`
`
`5,461,690 A 10/1995 Lampert
`5,473,723 A 12/1995 Stockman
`5,781,681 A 7/1998 Manning
`6,134,370 A 10/2000 Childers
`6,374,022 B1
`4/2002 Parmigiani et al.
`6,482,017 B1 11/2002 Van Doorn
`6,554,489 B1
`4/2003 Kent
`2002/0012504 A1
`1/2002 Gillham
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`WO
`
`O 533 496 A1
`O997756 A2
`WO 03/021307 A2
`
`3/1993
`5/2000
`3/2003
`
`OTHER PUBLICATIONS
`US CONEC(R); Concours NPTM (Non-Planar) Optical Cir
`cuits; Product Literature; (C) 2002 US Conec Ltd., US Conec
`Ltd., Hickory NC, USA; 2pp.
`3M Interconnect Solutions; Multi-Fiber Cable Assembly;
`Product Literature; Nov. 21, 2002; Austin, TX; 4 pp.
`International Search Report for PCT/US2004/012269.
`Primary Examiner Javaid H. Nasri
`(74) Attorney, Agent, or Firm-Melanie G. Gover
`(57)
`ABSTRACT
`
`The present invention relates to a fiber optic cable assembly
`including a connector Subassembly having a fiber optic cable
`terminated in a connector, the fiber optic cable having a
`minimum bend radius, and a Strain relief boot attached to the
`connector Subassembly, the Strain relief boot having a core
`portion, a flexible extension with a proximal end and a distal
`end, the proximal end extending from the core portion. The
`flexible extension retains at least a portion of the fiber optic
`cable.
`
`37 Claims, 3 Drawing Sheets
`
`Senko EX1016
`PGR2024-00037
`U.S. Patent No. 7,001,081
`
`

`

`U.S. Patent
`U.S. Patent
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`US 7,001,081 B2
`US 7,001,081 B2
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`Feb. 21, 2006
`Feb. 21, 2006
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`Sheet 1 of 3
`Sheet 1 of 3
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`U.S. Patent
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`U.S. Patent
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`Feb. 21,2006
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`Feb. 21, 2006
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`Sheet 2 of3
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`Sheet 2 of 3
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`US 7,001,081 B2
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`US 7,001,081 B2
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`U.S. Patent
`U.S. Patent
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`US 7,001,081 B2
`US 7,001,081 B2
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`Feb. 21, 2006
`Feb. 21, 2006
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`Sheet 3 of 3
`Sheet 3 of 3
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`1
`STRAIN RELEF BOOT WITH FLEXBLE
`EXTENSION FOR GUIDING FIBER OPTC
`CABLE
`
`FIELD OF INVENTION
`
`The present invention relates to a strain relief boot for use
`with a connector Subassembly to yield a fiber optic cable
`assembly. In particular, the present invention relates to a
`Strain relief boot that allows for routing, bending, and
`flexing of the fiber optic cable used in the cable assembly
`while helping to minimize the possibility that Such routing,
`bending or flexing will violate the minimum bend radius of
`the fiber optic cable.
`
`BACKGROUND
`
`One skilled in the art recognizes that in fiber optic cable
`applications, care is taken not to violate the minimum bend
`radius of the cable, i.e., the radius at which bends in the cable
`should not be exceeded. For example, a fiber optic cable that
`uses a typical 125 micrometer diameter glass/glass fiber has
`a minimum bend radius of about 2.5 to 3.0 cm (about 1
`inch). It is known that bends can increase attenuation
`because bends in the optical fiber change the angles of
`incidence and reflection. Bends can decrease the mechanical
`Strength, i.e., the tensile Strength of the fiber. Bends also
`cause cracks in the optical fiber thereby decreasing its life
`and the life of the fiber optic cable. Thus, a fiber optic cable
`manufacturer usually publishes the minimum bend radius of
`its fiber optic cables.
`Fiber optic cables are used in many applications that
`require routing the cables in a desired direction. For
`example, a fiber optic cable terminated in a cabinet can be
`required to bend through an arc of about ninety degrees
`Shortly after the termination point. Thus, as one skilled in the
`art will recognize, care should be given to the cable routing,
`bending, or flexing at that point to minimize the possibility
`that such routing will violate the minimum bend radius of
`the cable.
`There exists a need for devices that can aid the routing,
`bending, and flexing of a fiber optic cable while Simulta
`neously trying to minimize the possibility that Such routing,
`bending, and flexing will violate the minimum bend radius
`of the fiber optic cable.
`
`SUMMARY
`
`In one aspect, the present invention provides for a fiber
`optic cable assembly comprising (a) a connector Subassem
`bly comprising a fiber optic cable terminated in a connector,
`the fiber optic cable having a minimum bend radius; and (b)
`a Strain relief boot attached to the connector Subassembly,
`the Strain relief boot comprising a core portion; a flexible
`extension having a proximal end and a distal end, the
`proximal end extending from the core portion, and a means
`for retaining at least a portion of the fiber optic cable which
`is disposed along the flexible extension. The flexible exten
`Sion does not have a predetermined bend.
`In another aspect of the invention, the flexible extension
`is a tapered beam having a varying croSS-Sectional area Such
`that the height of the beam at its proximal end is about twice
`the height of the beam at its distal end. The tapered beam at
`the distal end does not come to a sharp point.
`AS further described herein, the flexible extension on the
`Strain relief boot does not have a predetermined curve or
`path to it. That is, the flexible extension, in its original
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`position, is Substantially Straight and not initially curved.
`When a user applies a force to the fiber optic cable, the
`flexible extension will respond to that particular amount of
`StreSS by bending and flexing. The more force applied to the
`fiber optic cable, the more the flexible extension will bend,
`and it will bend at a Substantially constant radius of curva
`ture. If the stress on the fiber optic cable is completely
`relieved, the flexible extension will likely follow the relaxed
`state of the fiber optic cable.
`The above Summary of the present invention is not
`intended to describe each disclosed embodiment or every
`implementation of the present invention. The figures and
`detailed description that follow below more particularly
`exemplify illustrative embodiments. Also, all numbers used
`herein are assumed to be modified by the term “about'.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention can be further described with the figures
`below. Like reference numbers represent Similar items.
`FIGS. 1 to 5 are perspective views of various exemplary
`embodiments of repositionable Strain relief boots in accor
`dance with various aspects of the present invention.
`FIG. 6 is a perspective View of an exemplary non
`repositionable boot in accordance with another aspect of the
`present invention.
`FIG. 7 is a top view of the FIG. 2 embodiment with a
`connector attached.
`FIG. 8 is a perspective view of one exemplary embodi
`ment of a fiber optic cable assembly in accordance with one
`aspect of the present invention.
`FIG. 9 is a side view of an exemplary connector Subas
`Sembly that can be used in the present invention.
`These figures are idealized, not drawn to Scale, and are
`intended only for illustrative purposes.
`
`DETAILED DESCRIPTION
`
`An advantage of one exemplary embodiment of the
`present invention is that one can bend and flex the fiber optic
`cable used in a fiber optic cable assembly So as to direct it
`in a desired direction. In particular, through the use of a
`flexible extension on the strain relief boot, the fiber optic
`cable can bend at a constant radius of curvature, desirably at
`a radius that is greater than the minimum bend radius of the
`cable. The flexible extension also aids in relieving the StreSS
`that would be imposed on the fiber optic cable as it exits the
`core portion of the Strain relief boot by providing a Zone
`where the fiber optic cable can transition out of the Strain
`relief boot. In other words, without the flexible extension,
`the fiber optic cable can bend at nearly a 90° angle as it exits
`the Strain relief boot, which in most cases would exceed the
`minimum bend radius of the cable and damage the optical
`fibers therein.
`Another advantage of one exemplary embodiment of the
`present invention is that the flexible extension is designed,
`through materials Selection and through the dimensions, to
`have a flexural characteristic that coincides with the flexural
`characteristic of the fiber optic cable used. The term “flex
`ural characteristic' means the deflection characteristic of a
`Specified length of material. One can determine the flexural
`characteristic in various ways, and a useful way is described
`as follows. One can take a 5.08 cm (2 inches) length of a
`fiber optic cable, place it horizontally and Secure one end,
`apply a known load (e.g., 1 lb or 0.454 kg) at room
`temperature (23 C.) on the free end of the cable and
`measure the vertical downward deflection of the cable at the
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`3
`free end. From this test, one can have an understanding of
`how much bending or flexing a known length of fiber optic
`cable exhibits under a specified load So as to design an
`approximate flexible extension. If the flexural characteristic
`of the flexible extension is too high, e.g., 50% higher than
`that of the cable, the flexible extension would likely be too
`Stiff and when one tries to apply a StreSS to the fiber optic
`cable assembly, the flexible extension would likely provide
`little to no transition for the cable. Thus, the bent cable will
`most likely exceed the maximum bend radius, possibly
`causing a kink and damaging the optical fibers therein. If the
`flexural characteristic of the flexible extension is too low,
`e.g., 50% lower than that of the cable, the flexible extension
`would likely be too soft thereby providing no support to the
`cable when a stress is applied to it. The term “coincide”
`means generally that the flexural characteristic of the fiber
`optic cable used in the fiber optic cable assembly is similar
`to but does not have to be exactly the same as the flexural
`characteristic of the flexible extension.
`The strain relief boot can be repositionable or non
`repositionable. AS used herein, the term “repositionable
`Strain relief boot' means generally that it can be bent or
`flexed multiple times from its original position, which is
`typically Substantially Straight, to a Second position and then
`back to its original position. A flexible Strain relief boot is
`one that can be bent or flexed multiple times from its original
`position and is considered to be a repositionable boot. In one
`exemplary embodiment after bending or flexing, the repo
`sitionable strain relief boot will remain in its bent position so
`as to direct the fiber optic cable used therein in a desired
`direction. The term “non-repositionable strain relief boot
`means the Strain relief boot has a predetermined path, e.g.,
`it can be curved or it can be Substantially Straight, and it is
`not intended for one to Substantially change that predeter
`mined path.
`FIGS. 1 to 5 represent perspective views of various
`exemplary embodiments of the repositionable Strain relief
`boot. Turning to FIG. 1, repositionable strain relief boot 10
`has core portion 11 and connector mating end 12, which is
`the end that will be attached to some connector Subassembly
`designs to yield a fiber optic cable assembly. Channel 13
`runs through the core portion and the connector mating end.
`A fiber optic cable (not shown) resides in channel 13. In this
`particular embodiment, the channel is tapered, where the
`channel is the widest near the connector mating end. Rib 14
`extends from the Strain relief boot, and as shown here, from
`the core portion of the strain relief boot. The rib could,
`however, extend from the connector mating end portion of
`the strain relief boot as well. More than one rib can be used
`on the core portion and/or on the connector mating end
`portion of the Strain relief boot. In one exemplary embodi
`ment, the rib is formed integrally with the strain relief boot,
`e.g., the rib and Strain relief boot are molded in place. A wire
`(See FIG. 5, wire 52) is disposed in the rib. In one exemplary
`embodiment, the wire is molded in place in the rib so it is
`locked in the rib. The wire bends and flexes as the strain
`relief boot bends and flexes. And, because the wire is molded
`in place with the rib, it will not likely break out of the rib
`unless too much force is applied to the Strain relief boot
`during the bending and flexing process. The Strain relief boot
`has a longitudinal axis, generally denoted as “L” that lies
`along the longitudinal centerline of the Strain relief boot. For
`reference purposes, a Cartesian coordinate System having X,
`y, and Z axes is shown in FIG. 1, where the X-axis represents
`the width of the strain relief boot or the width of the flexible
`extension, the y-axis represents the length of the Strain relief
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`boot or the length of the flexible extension, and the Z-axis
`represents the height of the Strain relief boot or the thickness
`of the flexible extension.
`A plurality of Slits or gaps is disposed on the core portion
`of the strain relief boot. The slits in the core portion and on
`the ribs lie generally perpendicular to the longitudinal axis
`L. While the slits aid in the bending and the flexing of the
`Strain relief boot, they also act as bend limiting features.
`When one bends the Strain relief boot in an arc, i.e., away
`from its original position, the Slits on one side of the core
`portion tend to expand, while the Slits on the opposite Side
`of the core portion tend to close. The Side of the core portion
`that has the longest distance to travel will See an expansion
`of the Slit or gap opening. The amount of slit expansion or
`contraction is one determination of the amount of bending
`the Strain relief boot experiences. AS one skilled in the art
`will recognize, when the Strain relief boot is bent at angles
`of 10 and 45 away from its longitudinal axis in the
`negative Z direction (downwards), the slits disposed on the
`topside of the strain relief boot will expand more at the 45
`angle than at the 10° angle. And, the slits on the bottom Side
`of the strain relief boot will contract more at the 45° angle
`than at the 10° angle. It should be noted that the reposition
`able strain relief boot described in FIGS. 1 to 5 could have
`Some degree of bending in all three dimensions. For
`example, it is possible to twist the Strain relief boot.
`Continuing with FIG. 1, flexible extension 15 has a
`proximal end and a distal end, the proximal end extends
`from the core portion of the strain relief boot. Thus, the
`proximal end of the flexible extension is situated close to or
`nearest the core portion and the distal end is situated farthest
`away from the core portion. Also because the flexible
`extension “extends from the core portion, it does not
`actually lie within any part of the core portion. At least a
`portion of the fiber optic cable is disposed on the flexible
`extension. In one exemplary embodiment, means for retain
`ing the fiber optic cable is disposed on the distal end of the
`flexible extension. A plurality of means for retaining the
`fiber optic cable can reside at any distance along the flexible
`extension. In the exemplary embodiment of FIG. 1, the
`means for retaining the fiber optic cable is a closed loop 16.
`Although flexible extension shown in FIG. 1 lies horizontal
`to the page thus allowing for bending and flexing of the fiber
`optic cable in both the positive and negative Z directions, it
`is within the Scope of the present invention to have the
`flexible extension disposed vertical to the page thereby
`allowing for bending and flexing of the fiber optic cable in
`the positive or negative X direction.
`The flexible extension can generally be described as a
`beam having a varying cross-sectional area. In one exem
`plary embodiment, the flexible extension is a tapered beam.
`A tapered beam provides the advantage that when an injec
`tion molded proceSS is used to make the flexible extension,
`it will be easier to remove a tapered beam from the mold
`than to remove a beam of Substantially constant croSS
`Section. In another exemplary embodiment, the flexible
`extension is a cantilevered tapered beam. In order for the
`beam to bend at a Substantially constant radius of curvature,
`the StreSS imposed along they dimension or the length of the
`beam should be substantially constant. To simplify the
`mathematical relationships between the dimensions of the
`flexible extension and the materials property of the flexible
`extension, the thickness of the flexible extension, i.e., the Z
`dimension, at its distal end is chosen to about one half of the
`thickness of the flexible extension at its proximal end. It
`should be noted that the dimension of the flexible extension
`depends upon the properties of the material used for con
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`US 7,001,081 B2
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`Structing it, Such as, e.g., the Young's modulus, and the
`material properties of the fiber optic cable used. In one
`exemplary embodiment, the length of the flexible extension
`is about one third of the total length of the strain relief boot.
`In another exemplary embodiment, the length of the flexible
`extension was chosen to be 2.54 cm (1 in.), which is
`approximately the length of an arc Subtending an angle of
`45 for a 2.54 cm (1 in.) radius. One skilled in the art will
`recognize that the length of the flexible extension could be
`more than or less than 2.54 cm, depending on the fiber optic
`cable application.
`There are various methods in determining the flexible
`extension design and construction. AS described above, one
`exemplary method involves first determining the flexural
`characteristic of the fiber optic cable. That is, one needs to
`determine the deflection characteristic, e.g., the deflection
`length, of a known length of the fiber optic cable under a
`specified load. For example, if a 5.08 cm (2 in.) cable
`initially lies horizontally with one end fixed and a load of
`one pound is applied to the free end of the cable, one can
`measure the vertical downward deflection of the cable at the
`free end. The 5.08 cm cable can deflect in an arc Such that
`the vertical deflection distance is 1.27 cm (0.5 inch) under a
`load of 0.454 kg (1 lb). The load imposed on the free end of
`the fibershould yield a deflection in the cable that is less than
`the known minimum bend radius of the cable. The deflection
`distance of the fiber optic cable should coincide with the
`deflection distance of the flexible extension. The deflection
`distance “Y” (in cm or in.) can be described by the following
`formula: Y=(PL)+3EI, where P=load imposed on the free
`end of the cable (in lbs or kg), L=length of the beam (in cm
`or in.), E=Young's modulus i.e., the elastic modulus of the
`material used for the beam (in N/m’ or psi), I=moment of
`inertia and
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`which is integral with the core portion, has two closed loops
`26 to function as means for retaining the fiber optic cable.
`FIG. 3 shows a repositionable strain relief boot 30 where
`the flexible extension is a Separate part that extends from the
`core portion. The flexible extension has collar 35 that can be
`attached, e.g., Snapped to the core portion. Although FIG. 3
`shows an open collar, a closed collar can also be used. The
`core portion could optionally have retaining features 37 to
`provide a stop for the collar 35. Alternately, the collar and
`the core portion could be retained by an interference fit. The
`flexible extension also has two open loops 36 to function as
`means for retaining the fiber optic cable. One advantage of
`this particular embodiment is that the fiber optic cable can be
`threaded radially through the two open loops.
`FIG. 4 shows a repositionable strain relief boot 40 having
`a dual member flexible extension 45 with two beams and
`closed loop 46. Because the mathematical relationship that
`describes the moment of inertia “I” for the dual member
`flexible extension could be rather complex, one could use
`finite element analysis to determine, through an iterative
`process, the flexural characteristic of the dual member
`flexible extension. The defined parameters would be P, Land
`Y (derived from the flexural characteristic of the fiber optic
`cable used) and the finite element analysis process could
`Solve for variables Such as b, h, as described above as well
`as “t', the thickness of the loop and “d” the inside and
`outside diameters of the enclosed loop.
`FIG. 5 shows another exemplary repositionable strain
`relief boot 50 similar to that in FIG. 1, except that the
`connector mating end has been removed. This particular
`embodiment can be used for Single fiber optic Systems and
`is particularly suited with the connector subassembly of
`FIG. 9 to yield a fiber optic cable assembly. The connector
`Subassembly 200 of FIG. 9 contains a housing 202, trigger
`204, protective end cap 206 to protect the optical fiber (not
`shown), strands of fiber, such as KEVLAR fiber, 208 which
`have been securely held together by metal crimp ring 210.
`Polymeric protective sheath 214 overlays and protects a
`portion of the fiber optic cable 212. In use, the core potion
`of the strain relief boot would be in contact with wall 202a
`of the connector Subassembly and at least a portion of the
`fiber optic cable 212 would he disposed the flexible exten
`Sion.
`FIG. 6 shows an exemplary non-repositionable Strain
`relief boot 60 having a core portion 61 containing a prede
`termined curve, i.e., a preset curvature that will route the
`fiber optic cable used in substantially a 90 curvature that
`should be greater than the minimum bend radius of the fiber
`optic cable used. The core portion can be Supported by
`reinforcing member 61a. The non-repositionable boot fur
`ther contains connector mating end 62 and flexible extension
`65 having means for retaining fiber optic cable 66 that is
`similar to that of FIG. 1.
`One skilled in the art will appreciate that other designs can
`be used to retain the fiber optic cable. The strain relief boots
`shown in FIGS. 1 to 5 have a tapered core portion with the
`first end being larger than the Second end. It is within the
`Scope of the present invention, however, to use a non
`tapered core portion. The connector mating end is attached
`to the larger end of the tapered core portion and the flexible
`extension extends from the opposite, Smaller end of the
`tapered core portion.
`As shown and described above in FIGS. 1 to 5, rib 14
`resides along the Surface of the core portion of the Strain
`relief boot and in these embodiments, the ribs are Substan
`tially straight and lie to one side of the strain relief boot. It
`is within the Scope of the present invention to have multiple
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`= 1 bh
`= 5 (
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`35
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`where b=width of the beam or the x-dimension (in cm or
`in.), h=height of the beam or the Z-dimension (in cm or in.).
`One can specify a “b’ value and solve the equation for “h”,
`which would be the height of the beam at the proximate end.
`AS Stated, the height of the beam at the distal end is chosen
`to be one half of that of the proximate end. The above stated
`equation is used merely to approximate the dimensions of
`the flexible extension. One skilled in the art will recognize
`that mathematical modeling tools, Such as finite element
`analysis, can be used to help define the dimensions of the
`flexible extension.
`The flexible extensions have the primary function to allow
`the fiber optic cable to be routed, that is, bent or flexed along
`a curvature having a constant radius. It has been learned that
`the addition of the flexible extension extending from the
`core portion of the body in combination with a means for
`retaining the fiber optic cable provide a mechanism by
`which a cable can bend along a constant radius of curvature,
`preferably at a radius that does not violate the minimum
`bend radius of the fiber optic cable. The connector mating
`end of the body is of an appropriate dimension to mate with
`a conventional fiber optic cable assembly, such as a MPT
`connector from US Conec, Hickory, N.C. or an Optical
`Gateway Interface connector from 3M Company, St. Paul,
`Minn.
`Turning now to FIG. 2, repositionable strain relief boot 20
`is similar to that of FIG. 1 except that flexible extension 25,
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`ribs on the core portion and/or the connector mating end
`portion of the strain relief boot and the rib(s) do not have to
`lie along a Straight line. For example, the rib could be a spiral
`Oc.
`The strain relief boot of the present invention can be made
`from a wide variety of polymers. Suitable polymers include,
`but are not limited to HYTREL, a tradename for GE Plastics
`ethylene propylene diene terpolymer. Another Suitable poly
`meric material is polyurethane. The polymeric material
`used, however, should meet the Underwriter's Laboratory
`UL-94 V0 flammability requirements.
`The flexible extension can be made from a wide variety of
`metals and polymers. Suitable polymers include, but are not
`limited to, HYTREL and polyurethane. Again, the polymeric
`material used should meet the UL-94 VO flammability
`requirements. Suitable metals would include but are not
`limited to Stainless Steel, carbon Steel, beryllium copper or
`phosphor bronze.
`The strain relief boot can be manufactured by various
`techniques. Suitable manufacturing techniques include
`injection molding or co-injection molding where multiple
`polymers of different moduli and different flexural charac
`teristics can be used for the flexible extension. One advan
`tage of the co-injection molding would be that it produces a
`flexible extension having varying elastic moduli and flexural
`characteristics.
`The Strain relief boot of the present invention can accom
`modate any type of fiber optic cable Such as Single or
`multifiber cable, which can be Supplied in various shapes,
`Such as, e.g., a round cable, an Oval cable, or a rectangular
`cable. As such, FIGS. 1 to 3 show various exemplary
`embodiments that can accommodate an oval or rectangular
`cable and FIG. 4 show and exemplary embodiment that can
`accommodate a round cable.
`FIG. 7 shows the repositionable strain relief boot of FIG.
`2 attached to a terminated connector. FIG. 8 shows the
`embodiment of FIG. 7 with a connector Subassembly to
`yield fiber optic cable assembly 100. As shown, at least a
`portion of the fiber optic cable 300 is disposed on the flexible
`extension and retained by closed loops 26.
`What is claimed is:
`1. A fiber optic cable assembly comprising:
`(a) a connector Subassembly comprising a fiber optic
`cable terminated in a connector, the fiber optic cable
`having a minimum bend radius, and
`(b) a Strain relief boot attached to the connector Subas
`Sembly, the Strain relief boot comprising a core portion,
`a flexible extension having a proximal end and a distal
`end, the proximal end extending from the core portion,
`and a means for retaining at least a portion of the fiber
`optic cable which is disposed along the flexible exten
`Sion;
`wherein the flexible extension does not have a predeter
`mined bend;
`wherein the strain relief boot is repositionable or non
`repositionable;
`wherein the repositionable or the non-repositionable
`Strain relief boot further comprises a connector mating
`end attached to the end of the core portion that is the
`opposite of the end from which the flexible extension
`extends, and
`wherein the repositionable Strain relief boot has a longi
`tudinal axis along its length and further comprises:
`(c) a plurality of slits in the core portion, the slits disposed
`generally perpendicular to the longitudinal axis, and
`(d) a rib extending from the core portion, the rib having
`a wire disposed therein.
`
`1O
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`15
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`25
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`US 7,001,081 B2
`
`8
`2. The fiber optic cable assembly of claim 1, wherein the
`flexible extension is a tapered beam having a varying
`croSS-Sectional area Such that the height of the tapered beam
`at the proximal end is about twice the height of the tapered
`beam at the distal end.
`3. The fiber optic cable assembly of claim 1, wherein the
`strain relief boot and the flexible extension are formed
`integrally.
`4. The fiber optic cable assembly of claim 1, wherein the
`flexible extension is a removable member comprising a
`collar at its proximal end, the collar being attached to the
`core portion of the strain relief boot.
`5. The fiber optic cable assembly of claim 1, wherein the
`rib is formed integrally with the strain relief boot.
`6. The fiber optic cable assembly of claim 1, wherein the
`wire is molded in place in the rib.
`7. The fiber optic cable assembly of claim 1, wherein the
`means for retaining a fiber optic cable is Selected from a
`group consisting of open loops, closed loops, and combina
`tion thereof.
`8. The fiber optic cable assembly of claim 7 having two
`flexible extensions extending from the core portion of the
`Strain relief boot, the flexible extensions disposed parallel to
`one another.
`9. The fiber optic cable assembly of claim 8, wherein the
`two flexible extensions are connected by at least one closed
`loop.
`10. The fiber optic cable assembly of claim 1, wherein the
`flexible extension is made from a material Selected from a
`group consisting of polymeric material, a metallic material,
`or combination thereof.
`11. The fiber optic cable assembly of claim 10, wherein
`the polymeric material is Selected from the group consisting
`of polyurethane and a terpolymer elastomer made from
`ethylene-propylene diene monomer.
`12. The fiber optic cable assembly of claim 10, wherein
`the polymeric material meets UL-94VO rating requirements.
`13. The fiber optic cable assembly of claim 1, wherein the
`core portion of the Strain relief boot is tapered.
`14. The fiber optic cable assembly of claim 1, wherein the
`length of the flexible extension is about one third of the total
`length of the strain relief boot.
`15. The fiber optic cable assembly of claim 1, wherein the
`flexible extension provides stress relief to the fiber optic
`cable exiting the core portion.
`16. The fiber optic cable assembly of claim 1, wherein the
`flexural characteristic of the flexible extension coincides
`with the flexural characteristic of the fiber optic cable used.
`17. The fiber optic cable assembly of claim 1, wherein
`when a tensile StreSS is applied to the fiber optic cable, the
`flexible extension deflects in Substantially a constant radius
`of curvature in response to that StreSS.
`18. The fiber optic cable assembly of claim 17, wherein
`the constant radius of curvature at which the flexible exten
`Sion deflects is not less than the minimum bend radius of the
`fiber optic cable.
`19. The fiber optic cable assembly of claim 1, wherein the
`fiber optic cable is a single or multifiber cable.
`20. A strain relief boot for use with a fiber optic cable
`having a minimum bend radius, the Strain relief boot com
`prising:
`(a) a core portion; and
`(b) a flexible extension having a proximal end and a distal
`end, the proximal end extending from the core portion;
`and
`(c) means for retaining at least a portion of the fiber optic
`cable which is disposed along the flexible extension,
`
`

`

`US 7,001,081 B2
`
`wherein the flexible extension does not have a predeter
`mined bend wherein the flexible extension does not
`have a predetermined bend;
`wherein the strain relief boot is repositionable or non
`repositionable;
`wherein the repositionable or the non-repositionable
`Strain relief boot further comprises a connector mating
`end attached to the end of the core portion that is the
`opposite of the end from which the flexible extension
`extends, and
`wherein the repositionable Strain relief boot has a