Grip for pulling fiber optic cable

A grip for cable, especially fragile cable such as fiber optic cable having a fragile connector at one end thereof. The grip comprises an elongated, hollow protective sheath with an open rearward end for receiving the connector therein, a pulling device coupled at the forward end of the sheath by means of a forwardly tapered nose piece and an open mesh sleeve coupled at the rearward end of the sheath for engaging the cable upon a longitudinal stretching thereof which radially reduces the sleeve around the cable. The pulling device comprises a shaft journalled for free rotation on the nose piece by ball bearings mounted in the nose piece to allow the sheath to rotate about its longitudinal axis as it is being pulled. A portion of the sheath body is made flexible to facilitate its movement through curved conduits and other curved passageways and the mesh sleeve is detachably coupled to the rearward end of the sheath to facilitate the manual detachment of the sleeve for ease of loading the connector into the rearward end of the sheath.

FIELD OF THE INVENTION 
The present invention relates to a grip for pulling fragile cable and 
especially fiber optic cable having one or more fragile connectors at the 
end thereof. The grip includes an elongated, hollow protective sheath open 
at a rearward end to receive the connector end of the cable, a pulling 
device coupled at the forward end of the sheath for pulling the sheath, 
and a mesh sleeve coupled at the rearward end of the sheath for gripping 
the cable. A portion of the sheath is made flexible to facilitate its 
movement through conduits and other passageways. The mesh grip is 
detachably coupled to the rearward end of the sheath to permit its manual 
removal and facilitate access to the rearward end of the sheath. 
BACKGROUND OF THE INVENTION 
Cable grips for pulling, holding and supporting elongated objects such as 
cables, ropes and the like are well known in the art. These grips 
typically comprise an open mesh sleeve formed from braided or interwoven 
metallic wire strands which may be expanded radially by longitudinal 
compression to enable them to readily receive the cable and radially 
contracted by longitudinal stretching to frictionally engage the periphery 
of the cable. Tensile forces tending to separate the grip from the cable 
or to move the grip along the cable produce a firmer gripping of the 
cable. 
Such grips are suitable for the fairly rugged electrical cable, but 
significant problems arise when the cable to be pulled is fragile. An 
example of the latter is fiber optic cable which comprises a flexible 
jacket encasing a single optical fiber or a bundle of optical fibers 
therein. Such fragile cable can be easily crushed or its optical 
characteristics can be distorted if the radial compressive forces on the 
cable are localized and become too great. Also, the optical fiber can be 
easily broken when subjected to excessive bending forces. In addition, it 
is typical to have pre-assembled on the end of fiber optic cable one or 
more fragile optical connectors receiving one or a bundle of optical 
fibers therein and secured by an epoxy resin and a crimp. This fragile 
connector is highly susceptible to crushing radial compressive forces as 
well as longitudinal tensile forces which could easily snap the connector 
from the cable. Moreover, the facial end of the connector must be 
protected from damage which would deleteriously affect its optically 
finished surface. 
Moreover, fiber optic cable is much smaller in diameter than the typical 
electrical cable. These small diameters in most cases are much less than 
the conventional wire mesh grips can adequately hold. Also, the fiber 
optic connector at the end of the fiber optic cable has a much larger 
outside diameter than the cable so that a conventional grip selected to 
fit and adequately grip the cable cannot expand enough to accept the 
larger connector diameter or diameters. Conversely, a grip designed to 
receive a large diameter connector cannot compress enough to grip the 
smaller cable diameter. A typical example is a connector with a 0.5 inch 
outer diameter and a cable with a 0.073 inch outer diameter. 
A method presently used to protect a fiber optic cable connector during 
pulling comprises wrapping the connector in a layer of foam rubber and 
then inserting this into a plastic sleeve which in turn is inserted into 
an oversized wire mesh grip. This method, however, is expensive and time 
consuming since conventional wire mesh grips are relatively stiff, thereby 
creating extreme difficulty in inserting the small and flexible cable with 
a connector attached. In addition, after assembly of this combination, the 
holding capability of the oversized wire mesh is marginal and may allow 
slippage of the cable and pulling out of the pre-assembled connector. 
In addition to these qualifications, a grip for pulling fiber optic cable 
must adequately grip the cable and not damage the cable or the connector. 
There are four basic cable configurations that must be contended with by 
the grip designer. The first is a cable by itself, containing one or a 
plurality of fiber optic cables all without preassembled connectors. This 
provides only one rather uniform diameter for the grip to contend with. 
A second configuration involves a single fiber optic cable with a 
preassembled connector, with both the cable and the connector diameter 
being within the grip diameter range so that the grip can be compressed 
longitudinally and therefore expand sufficiently in the radial direction 
to accept the combined cable and connector and also then be stretched 
longitudinally to thereby reduce the radius of the wire mesh into a 
sufficient gripping engagement of the cable. 
A third cable configuration involves a single fiber optic cable with a 
preassembled connector where the connector size is beyond the expansion of 
the wire mesh that is made to suit the cable diameter. Lastly, a fourth 
basic cable configuration involves a plurality of fiber optic cables with 
preinstalled conconnectors where the connector diameter build-up is beyond 
the expansion capability of the wire mesh. 
In my copending U.S. patent application Ser. No. 213,856 filed Dec. 8, 1980 
and assigned to the same assignee as the instant application, there is 
disclosed a cable grip which is especially suitable for pulling fiber 
optic cables and provides the necessary protection to the fragile 
connector ends of such cables by means of a tubular protective sheath. The 
particular embodiment of the sheath disclosed in that patent application 
is one of a rigid metal body formed of, for example, metal tubing. While 
this particular embodiment of a sheath body provides excellent protection 
for the fiber optic connector inserted therein, for certain installations 
involving angled or curved conduits through which the cable must be 
pulled, a sharp curvature of the conduit walls may pose an obstruction to 
the passage of an elongated rigid tubular member. 
SUMMARY 
Accordingly, it is an object of the present invention to provide a hollow, 
elongated sheath having an open, rearward end for receiving and protecting 
the connector end of a fiber optic cable insertable therein, wherein a 
portion of the sheath is substantially flexible in directions transverse 
to its longitudinal axis facilitate its bending around curved conduit 
walls and the like. 
Another object of the present invention is to provide a mesh grip for 
pulling cable and especially fiber optic cable with at least one fiber 
optic connector at the end thereof, wherein the grip is readily detachable 
from an end of a hollow, open-ended sheath protecting the fiber optic 
connector to facilitate the insertion of the cable connector end into the 
end of the sheath. 
Another object of the present invention is to provide a grip that protects 
the end of a fragile cable by a flexible, encasing sheath body which 
utilizes predetermined lengths of commercially available flexible metallic 
conduit as the sheath body, thereby facilitating the manufacture of the 
grip. 
The foregoing objects are attained in accordance with the instant invention 
by providing an elongated grip for pulling fragile cable comprising a 
hollow protective sheath having a forward end and a rearward end and 
formed in part by a cylindrical midsectional body having a longitudinal 
axis. The body is designed to be substantially flexible to bending in 
directions transverse to its longitudinal axis so that the sheath can be 
snaked through curved conduit walls and other passageways. The sheath body 
may be formed from several lengths of commercially available longer 
lengths of flexible metallic conduit or hose which is sold by several 
manufacturers. Characteristically, this type of conduit sheath is also 
smooth, pliable and compressible to some extent; all features which make 
its use particularly suitable for certain pulling grip applications. The 
rearward end of the sheath is open for the reception of the fragile cable 
therein. 
A tensioning device is rotatably coupled to the forward end of the sheath 
and wire mesh cable gripping sleeve is readily detachably coupled at its 
forward end to the sheath. The readily detachable coupling allows quick 
manual removal of the sleeve from the sheath thereby facilitating on-site 
loading of a cable connector into the sheath. The detachable coupling of 
this invention may also be used on formed rigid tubing sheaths, such as 
disclosed in my aforementioned copending patent application in lieu of 
swaged couplings which are not normally detachable from the sheath body. 
Advantageously, the forward end of the sheath is provided with an inwardly 
tapered lead for creating an opening for the fiber optic when pulled 
through a conduit containing a number of existing cables. The pulling 
device comprises an eyelet rotatably connected at the forward end of the 
sheath by a low-friction ball bearing to efficiently alleviate torsional 
stresses on the encased fragile cable during a pulling operation. 
Other objects, advantages and salient features of the present invention 
will become apparent from the following detailed description which, taken 
in conjunction with the annexed drawings, discloses preferred embodiments 
of the present invention.

DETAILED DESCRIPTION OF THE INVENTION 
A grip constructed in accordance with the present invention has particular 
application to gripping fragile cables and as seen in FIG. 1 comprises a 
protective sheath 12, a pulling eyelet 14 coupled to one end of the 
sheath, and a braided or woven open mesh sleeve 16 detachably coupled to 
the opposite end of the sheath 12. 
The mesh sleeve 16 is typically formed from a plurality of interwoven 
metallic wire strands and is split along the longitudinal axis A--A of the 
grip as seen in FIG. 1 for receiving a cable (not shown) which is to be 
gripped by the strands. To enclose the grip about a cable placed therein, 
the two loop edges may be drawn together about the longitudinal axis A--A 
and interconnected by a strand 19. When the sleeve is compressed along its 
longitudinal axis A--A, it increases in size radially to receive a 
conventional fragile cable with one or more fragile connectors at the end 
thereof. Once suitably placed therein, the sleeve 16 can be axially 
stretched which results in a reduction of its size radially into a 
gripping action on the fragile cable. 
The fragile cable may be, a fiber optic cable comprising a flexible, 
resilient jacket encasing a plurality or bundle of individual, hollow 
glass tubes constituting the optical fibers. The fragile connector is 
basically a cylindrical member having an internal cylindrical bore for 
receiving the optical fiber therein, these fibers typically being secured 
thereto by epoxy as well as a crimp surrounding a short fragile tube 
extending from the main cylindrical member of the connector. A cable of 
this type is described in my copending patent application, Ser. No. 
340,900 filed Jan. 20, 1982 and assigned to the same assignee as the 
instant invention and as is known to those working in the fiber optic art, 
the facial end of the connector is optically finished to receive and 
transmit the optical signals in the tybes and hence, should be protected 
from extraneous foreign matter and impacts with obstructions when it is 
pulled through conduits, passageways and the like. 
As seen in FIGS. 1 and 3, the protective sheath 12 is comprised of a hollow 
tubular body 21 having a substantially cylindrical interior chamber 22 
which has a forward end 23 and a rearward end 24. The diameter of the 
chamber 22 may be large enough to enclose one or more fiber optic cables 
having a cluster of two or more connectors attached to one end of each 
cable. 
In accordance with this invention, the sheath body 21 is preferably 
comprised of a flexible hose or conduit which will pass more easily 
through conduits and passageways which include curvatures such as elbows 
or bends therein or for any applications where the ability of the sheath 
to bend or flex in directions transverse to the longitudinal axis is a 
desired or required feature. 
The sheath body may be readily formed from a length A--A of commercially 
available flexible conduit. Such conduit is characterized as having an 
outer sleeve or covering composed of a synthetic rubber-like plastic 
material 25 which is resilient, smooth and compressible, and a corrugated 
inner flexible metallic tube 26 which is concentric about the axis A--A. 
The tube 26 is conveniently formed by helically winding a longitudinally 
corrugated metal strip onto a mandrel such that the adjacent edges of the 
strip overlap one another to form a continuous, helically seamed joint 
concentric about the axis A--A. The helical joint forms an internal 
helical groove or female thread which may be threadedly engaged by 
circumferentially threaded members having male threads thereon of the same 
pitch and hand as that of the female conduit thread. This feature of the 
metallic conduit is used herein to effect threaded connections between the 
sheath body 21 and the opposite nose and mesh ends of the sheath. In 
addition, the body 21 may be obtained by cutting off desired sheath 
lengths from one or more rolls of commercially-available conduit of 
appropriate internal diameter. Such ready availability of a suitable 
component for a major part for the sheath facilitates manufacture of the 
grip for any desired application. 
The forward end 23 of the sheath includes an inwardly tapered conical nose 
26 which is threadedly coupled to the forward end of the sheath body 21 by 
an externally threaded hollow ferrule 27. The nose is subjected to 
components of tensile force and is formed of a rigid metal or plastic 
material which can resist such component forces. Formed in the rearward 
end of the nose 26 (FIGS. 1 and 4) is an interior cylindrical cavity 35. 
This cavity is concentric with the longitudinal axis A--A of the nose 26 
and is also concentric with a cylindrical bore 37 extending through the 
nose 26 which is concentric with the axis A--A. The nose is provided with 
a smooth exterior surface to facilitate its movement through conduits, 
passageways and openings and past other cables which may be contained 
therein. 
The eyelet 14 is formed of a rigid material such as steel, having a shaft 
31 mounted in the cylindrical bore 37 for free rotation concentric with 
the longitudinal axis A--A. One or more roller bearings 38 are mounted in 
the cavity and the shaft 31 is rotatably mounted in the bearing 38 against 
forwardly directed components of tensile forces by a locking cap nut 40 
threadedly connected to the threaded distal end 41 of the shaft 31 and 
abutting the rearward bearing journal 39 of the bearing 38. With the 
eyelet 14 attached to a rope, line or other pulling means, the nose 26 can 
unwind relatively freely while under tensile loading as a result of 
turning movements imparted to the sheath by a torsionally-stressed fiber 
optic cable or by the pulling line. The forward journal 43 of the bearing 
38 is seated against the bottom wall of the cavity 35 adjacent the bore 37 
so the nut 40 and the eyelet shaft 31 cannot be pulled forwardly and away 
from the sheath 12 under tensile loading. As a buffer against significant 
frictional engagement between the eyelet 14 and nose 26, an annular disc 
42 composed of a low-frictional material, such as nylon, is mounted 
concentrically on the shaft 31 between those parts. 
The nose 26 (FIG. 4) is formed with a radially inwardly stepped, 
circumferential shoulder 28 which extends inwardly from the nose 
circumference the entire thickness of the sheath body 21 and additionally 
slightly further inwardly thereof. The shoulder 28 commences the rearward 
part of the nose comprising the externally threaded hollow ferrule or 
coupling 27. The ferrule 27 has a circumferentially threaded end 29 and an 
internal chamber 30 of substantially cylindrical shape concentric with the 
bearing cavity 35. The chamber 30 has an internal diameter which is 
slightly less than the internal diameter of the sheath body 21 to 
accommodate, if necessary, the lead end of the cable inserted into the 
sheath 12. 
The threaded end 29 of the ferrule 27 is typically comprised of a 
continuous helical male thread having three or four thread convolutions 48 
of the same pitch and hand as the internal female thread convolutions 49 
formed by the continuous metal corrugations of the sheath body and may be 
of a modified Acme screw type. The outer or pitch diameter of the male 
thread convolutions 48 is only slightly less than the root diameter of the 
female thread convolutions 49 of the corrugations with which they mate so 
that a relatively tight threaded connection can be effected between the 
two threads. The nose 26 is rotated about the longitudinal axis A--A in an 
appropriate direction until three or more male thread convolutions 48 are 
engaged by the female thread convolutions at which point, the shoulder 28 
is displaced axially into abutment with an inwardly extending flange 51 of 
an end cap 52 to secure the end cap 52 in position between the nose and 
sheath body. To facilitate manual turning of the nose 26, an annular 
circumferential strip can be knurled as indicated by numeral 53. 
As seen in FIG. 2, the mesh sleeve 16 has a lead end 55 and a tail end 56, 
the mesh lead end 55 thereof being concentrically positioned with respect 
to the longitudinal axis A--A. 
The end 55 is comprised of a hollow, metal ferrule 56 having a hollow, 
threaded end 58 typically formed by a helical thread having three or four 
circumferential helical thread convolutions 59 for engaging three or four 
of the rearwardmost female thread convolutions 49 at the rearwardmost end 
of the sheath body 10. Because of the female thread provided by these 
usually has a substantially constant pitch and internal diameter 
throughout the entire length of the sheath body, the threaded end 58 of 
the ferrule 56 may be formed with a male thread of the same pitch and hand 
as on the nose ferrule 27. 
To provide an abutting shoulder essentially equivalent to the shoulder 28, 
the forwardmost end of a cylindrical knurled collar 60 extends far enough 
inwardly to abut a flange 63 of an end cap 65 when the ferrule is rotated 
in an appropriate direction to threadedly engage the three or four female 
thread convolutions. 
An annular collar 70 is mounted on the smooth, exterior surface of rearward 
section 71 of the ferrule 56, the sleeve ends being sandwiched between the 
exterior surface of the section 71 and the interior surface of the collar. 
The collar 70 rigidly couples the sleeve to the ferrule 56 by means of a 
swaging operation and extends longitudinally far enough inwardly to abut 
the end cap 65 when the proper threaded connection is made between the 
female thread on the sheath body and the male thread on the ferrule 56. So 
as not to pose any outwardly extending obstruction on the grip, the outer 
diameter of the collar 70 is slightly less than the outer diameter of the 
end cap 65. 
As mentioned briefly hereinabove, forward and rearward ends of the sheath 
body are each constrained against radially outward expansion by the 
cylindrical cup-shaped end caps 52 and 65, respectively. The end caps 52 
and 65 are essentially identical in size and shape and the inner diameter 
of each cap is slightly greater than the outer diameter of the respective 
ends of the sheath body so that the sleeves fit tightly over the ends of 
the resilient and the radially expandable sheath material at the sheath 
body ends to prevent any appreciable, radially outward displacement or 
buckling of these sheath ends and the underlying metallic corrugations. 
Such radially outward displacement of the sheath body ends. might otherwise 
develop when radially-outwardly directed components of forces are 
developed and applied against the internal thread surfaces of the 
corrugations by the inclined ferrule thread convolutions bearing 
thereagainst when the grip is pulled longitudinally. The radially, 
inwardly-extending flanges 51 and 66 of the caps 52 and 65 respectively, 
are formed with circular concentric openings both concentric with the 
longitudinal axis A--A of the sheath body. The internal diameter of the 
openings in both flanges 51 and 66 is equal to the internal diameter of 
the sheath body so that the flanges abut the outermost edges of the metal 
corrugations to constrain the metal corrugations against longitudinal 
displacement caused by the ferrules exerting outwardly directed forces 
against these corrugations in response to grip pulling. 
To permit longitudinal insertion of each threaded ferrule end through its 
corresponding end cap, the internal diameter of the opening at the cap 
flanges 51 and 66 is also made slightly greater than the root diameter of 
the ferrule threads. The male threads can then be rotated past the flanges 
51 and 66 of the end caps into threaded engagement with the ferrule 
threads in the sheath body. The end caps 52 and 65 will be fixed to the 
sheath body and, in turn, constrain the metal corrugations against both 
longitudinal and radial separations and displacements. As mentioned above, 
to hold the end caps 52 and 65 in forceful abutting relationships with the 
opposite hollow ends of the sheath body, the flanges 51 and 66 are abutted 
by the shoulder 28 and the collar 61, respectively, provided on the 
ferrules 27 and 56, respectively. 
In the illustrated embodiment of this invention, the mesh sleeve 16 is 
split throughout substantially its entire length, having a series of 
opposed loops defining the split in the sleeve. This embodiment is 
advantageously used for a plurality of cables with a plurality of 
connectors at the end thereof which are beyond the regular expansion 
diameter of a closed sleeve. The split could also extend up to the collar 
61. 
With the loops separated, a plurality of fragile cables and connectors can 
be maneuvered through the ferrule 56 and into the sheath 12 via the 
rearward open end of the sheath and received therein. The split sleeve 16 
is wrapped around the cables extending from the sheath 12 and closed, for 
example, by strand 19 lacing up the opposed series of loops defining the 
opposed edges of the slit in the sleeve. After lacing is accomplished, the 
sleeve 16 can be axially stretched which results in a radial compression 
thereof into a gripping engagement with the cables received therein. The 
strand 19 can be of any suitable material such as a flat braided polyester 
and is advantageously laced by using a conventional lacing needle. The 
sleeve 16 may be partly double braided near the ferrule 56 and partly 
single braided toward its trailing end to enhance the gripping of the 
small sized cables in the mesh. The sheath may have a large enough 
internal diameter to accommodate at least three connectors in any 
positional arrangement. 
With partially or fully closed mesh grips, a smooth, tubular feed tube may 
be used to facilitate the process of inserting the cable longitudinally 
through the sheath. Since the ferrule 56 can be detached by counter 
rotation from the rearward end of the sheath body, the detachment of the 
mesh grip from the sheath body 21 allows the feed tube to pass completely 
through the frontward open end of the mesh sleeve and the ferrule 56 
leaving the connectors free to be manually grasped and inserted into the 
rearward end of the sheath. The reattachment of the ferrule 56 in the 
sleeve by appropriate rotation reestablished the threaded union of the 
grip. Although the sheath body 21 is disclosed herein as formed of a 
substantially flexible material a sheath formed of a rigid material may 
also be provided with a detachable coupling which may be a locking or 
threaded connection with a detachable coupling, as disclosed herein, to 
facilitate the process of loading of the cable connectors into the 
protective sheath body portion, as will be apparent. 
While one advantageous embodiment has been chosen to illustrate the 
invention, it will be understood by those skilled in the art that various 
changes and modifications can be made therein without departing from the 
scope of the invention as defined in the appended claims.