Optical fiber cable pulling eye

A pulling eye assembly for optical fiber cables is formed of a housing having a gripping device for gripping the multiple strength members. The first embodiment uses longitudinally extending cavities which communicate with radially directed threaded set-screw holes for receiving epoxy and/or set-screws. In the second embodiment, a pair of collets are used to grip the strength members. In both cases, a crimping sleeve is attached to an end of the cylindrical housing and being crimpably engageable with an outer surface of an optical fiber cable.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to devices used to pull optical fiber cables 
through cable ducts, and more particularly, to such devices for use with 
optical fiber cables having more than one strength member. 
2. Description of the Prior Art 
The use of optical fibers is becoming prevalent in the telecommunications 
and data communications industries, and new building structures are being 
provided with cable ducts for the subsequent installation of optical fiber 
cables. Additionally, the telephone companies have found that the space in 
existing duct systems can be more effectively utilized by the use of 
optical fiber cable because of its small outer diameter, which is 
typically less than 0.90 inch. 
A typical 4-inch duct has installed therein sub-ducts such as, for example, 
three 11/2-inch sub-ducts, or four 1-inch subducts, through which optical 
fiber cable is to be installed. 
A typical optical fiber cable is formed about a central strength member 
which may be formed of either a single steel or a dielectric member or a 
plurality of twisted members. However, newer versions of optical fiber 
cables have multiple strength members running parallel to one another. 
Such multiple strength member cables are produced by a number of 
manufacturers including Alcatel Cable Systems and AT&T. 
Due to the fragile nature of optical fibers, pulling cables through 
pre-installed ducts is a difficult and tedious task. Pulling eye 
assemblies were devised to facilitate the installation of cables through 
ducts. The pulling eyes provided a means for gripping the cable and, in 
particular, the strength components of the cable, so that stresses would 
not be exerted on the optical fibers while the cable was pulled through 
the duct system. 
Due to the small size of the cable ducts, the cable diameter had to be 
maintained at a minimum, as did the diameter of the pulling eye assembly. 
Most existing pulling eyes have too large a diameter and therefore require 
larger duct sizes. In addition, the pulling eye had to be of such size 
that it could pass through bends having a predetermined minimum radius. A 
standard size requirement for pulling eyes is that a cable with an outer 
diameter of 0.7 inch must pass through a 1-inch sub-duct with a 24-inch 
bend radius. 
SUMMARY OF THE INVENTION 
The present invention contemplates a pulling eye assembly to be used for 
pulling multiple strength member optical fiber cable through ducts. The 
pulling eye assembly is designed to protect the optical fiber cable during 
installation. 
The first embodiment of the pulling eye uniquely uses a soft metal crimping 
sleeve having an inner surface adapted to receive the cable diameter. The 
pulling eye has a gripping body attached to the crimping sleeve. At one 
end of the gripping body is an eye which allows for lead line or swivel 
attachment. Extending longitudinally through the gripping body from the 
other end thereof are a plurality of symmetrically located elongated 
cavities dimensionally sized to accept the individual ones of the strength 
members. Once inserted in the cavities, the strength members can be held 
in place by set screws or by epoxy. Once the strength members are gripped 
in place in the gripping body, a number of crimps can be placed on the 
crimping sleeve to engage the outer jacket of the optical fiber cable. 
In the second embodiment, the soft metal crimping sleeve is attached to a 
collet housing. The collet housing is provided with a conical central 
opening for receiving a pair of collets. The pair of collets are also 
provided with a plurality of symmetrically located elongated cavities 
running longitudinally therethrough for receiving the strength members of 
the optical fiber cable. Once the strength members are passed through the 
collet housing and placed in the collets, the collets are driven into the 
conical opening of the collet housing through the use of an eye nut 
thereby forcibly engaging the cable strength members. The eye nut provides 
a means of attaching a lead line or swivel. A tubular housing is 
threadedly disposed over the collet housing and engages the crimping 
sleeve at one end thereof. The crimping sleeve is then crimped onto the 
outer jacket of the cable. 
A primary objective of the present invention is to provide a pulling eye 
assembly which may be used to pull optical fiber cables through cable 
ducts. 
Another objective of the present invention is to provide a pulling eye 
assembly that protects the buffer tubes and optical fibers during 
installation. 
Another objective of the present invention is to provide a pulling eye 
assembly which grips each cable strength member separately. 
Another objective of the present invention is to allow the installation of 
a cable with an outer diameter of up to 0.7 inch into a 1-inch sub-duct 
with a 24-inch bend radius. 
The invention will be more fully understood when reference is made to the 
following detailed description taken in conjunction with the accompanying 
drawings

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1A, therein is illustrated a typical optical fiber 
cable 10 used with the pulling eye assembly of the present invention. The 
optical fiber cable 10 has a plurality of centrally located optical fibers 
12. Carrying the optical fibers 12 is a gel filled plastic buffer tube 14. 
A plurality of radial strength yarn threads 16 extend along the outside of 
the buffer tube 14. A strength and protective member in the form of a 
corrugated steel armor layer 18 may be provided for additional protection 
against possible rodent damage. The armor 18 is usually coated with a thin 
layer of plastic material. A ripcord 20 is used to assist in removal of 
the armor 18. A final polyethylene outer jacket 22 is provided for 
additional cable protection. Embedded within the outer jacket 22 adjacent 
the corrugated armor layer 18 is a pair of diametrically opposed strength 
members 24. 
Referring to FIGS. 2-4, there is shown the first embodiment of the pulling 
eye assembly 26 of the present invention which is generally indicated by 
the numeral 26. The pulling eye assembly 26 primarily consists of a 
gripping body portion 28 and an attached cable crimping sleeve portion 30. 
The crimping sleeve portion 30 is formed of a non-corrosive, malleable, 
electrically conductive metal so it may be crimped over the outer jacket 
22 of the optical fiber cable 10. The gripping body portion 28 has an eye 
aperture 32 which allows for attachment of a lead line or swivel (not 
shown) for pulling the optical fiber cable 10 through the desired conduit. 
There are several symmetrically spaced longitudinally directed cavities 33 
in the gripping body portion 28. Once the optical fiber cable 10 is 
stripped as shown in FIG. 1B with the strength members 24 extending from 
the end thereof, the cable strength members 24 can be slid by the user 
through the open end of the cable crimping sleeve portion 30 and into the 
longitudinally directed cavities 33 to be gripped via set-screws 34, or 
pouring a material such as epoxy (not shown) into the threaded set-screw 
holes 36. When the cable strength members 24 are metallic, the set-screws 
34 would be inserted into the longitudinally directed cavities 33 to clamp 
down on the strength members 24. When the strength members 24 are made of 
a dielectric material such as fiberglass, a material such as epoxy would 
be poured into the set-screw holes 36 and then shorter set-screws would be 
used to push the material into the longitudinally directed cavities 33. 
Once the cable strength members 24 are clamped into place by the epoxy 
and/or set-screws, a number of crimps are placed on the cable crimping 
sleeve portion 30 in order to engage the cable outer jacket 22. 
Turning now to FIGS. 5-8, the pulling eye assembly primarily comprises two 
collets 52 (FIG. 8) which are designed to grip the cable strength members 
24. The collets 52 are tapered and fit into a collet housing 54 which has 
a similar taper. The collet housing 54 is adapted to receive the pair of 
collets 52 (FIG. 8) for gripping the cable strength members 24 of the 
cable 10. The collet holder 52 is formed of a noncorrosive material and 
includes a central cylindrical portion 64 having a conical opening 66 
extending therethrough. Opening 66 is partially conical and partially 
cylindrical. The conical portion is at an end opposite a crimping sleeve 
56 and widens in the direction away from sleeve 56. The cylindrical 
portion has a diameter approximately equal to the minimum diameter of the 
conical portion. The ends of the housing 54 are threaded around the 
exterior to receive a threaded retaining nut 58 and an eye nut 60. The 
tapered fit causes the gripping force on the strength members 24 to 
increase as the cable pulling tension increases. 
The cable crimping sleeve 56 which has an inner diameter slightly larger 
than the cable outer diameter is attached to one end of the collet housing 
54 by means of the threaded retaining nut 58. The eye nut 60 which has an 
eye aperture 62 for lead line or swivel attachment is screwed on the other 
end of the collet housing 54. As the eye nut 60 is tightened onto the 
collet housing 54, the collets 52 also tighten onto the cable strength 
members 24. Once the eye nut 60 has been sufficiently tightened onto the 
collet housing 54, a number of crimps are placed on the crimping sleeve 56 
in order to engage the cable outer jacket 22 of the optical fiber cable 
10. 
During installation of the crimping sleeve 30 or 56 onto the optical fiber 
cable 10, the various layers of the optical fiber cable 10 are stripped 
back appropriate distances to expose the strength members 24 as shown in 
FIG. 1B. The cable is then slid into the crimping sleeve, and the cable 
strength members 24 are slid into the gripping components 33 or 52. The 
strength members 24 are then secured to the pulling eye assembly 26 or 50 
as heretofore stated. The crimping sleeve 30 or 56 is then crimped onto 
the cable jacket 22. 
Thus, the above-described pulling eye assembly provides a unique structure 
that satisfies all of the objectives heretofore set forth. The use of the 
pulling eye assembly allows a multiple strength member cable to be pulled 
through cable ducts while protecting the fibers in the cable. 
The preferred embodiments admirably achieve the objects of the present 
invention; however, it should be appreciated that departures can be made 
by those skilled in the art without departing from the spirit and scope of 
the invention which is limited only by the following claims.