Tape and method for measuring and/or pulling cable

A cable is pulled in a duct or along an overhead support line according to a method and through the use of a tape comprised of warp and weft threads. Indicia printed on the web is used to indicate the length of the course of travel for the cable along which the web extends. The width of the web is sufficient to affix indicia on the surface thereof. The web has an elongation of 10% or less at a break strength which is in excess of 750 pounds of pull force. The pull strength of the woven web is about 2900-3000 pounds. The web is comprised of strands of parallel filaments of yarn consisting of aromatic polyamide fibers. Insulated conductors are incorporated in the tape as two of many warp threads according to a second tape embodiment for conducting a tension signal along the tape. After a length of the course of travel is measured with the tape, one end of the tape is connected to the leading end of a cable while the remaining end of the tape is connected to a winch.

BACKGROUND OF THE INVENTION 
This invention relates to a method and apparatus to pull cable and/or to 
measure the length of a cable-retaining structure, such as an underground 
conduit or overhead support line, incident to the installation of a cable. 
More particularly, the present invention relates to using a tape or web 
comprised of warp and weft threads, preferably with indicia thereon to 
indicate the length of the cable-retaining structure along which the web 
extends. If desired, the tape includes conductors for transmitting a 
tension signal. 
In the placement of underground cables, particularly telephone 
communication cables and electric utility cables, it is desired, and 
usually necessary, to measure the length of a particular duct in which the 
cable is placed or overhead line which is to be used for supporting the 
cable. Sometimes, for example, a cable is provided with connectors prior 
to its placement in the duct or onto an overhead line. A measurement of 
the duct length or length of overhead line is first necessary to procure 
the correct length of preconnecterized cable. It is also necessary to 
measure the length of a duct or support line when placing a cable 
comprised of optical fibers for procuring and installing the cable. 
Careful and cautious handling of a cable made up of optical fibers is 
necessary. The optical fibers of the cable are particularly susceptible to 
fatigue fractures that will occur some time after a tension stress 
excursion beyond the yield point of the optical fiber material. Loss of 
integrity of the fibers may not immediately occur even though the tension 
on one or more of the fibers in a bundle exceeds the yield point of the 
material. Because of this phenomenon, tensioning of a cable comprised of 
optical fibers must be controlled with greater care during pulling in a 
conduit or otherwise installing procedures than is usually necessary when 
installing a cable comprised of metal conductors. As a necessary incident 
to controlling tension on the cable, it is important that the cable or 
line which is used to pull the cable possess sufficient strength and a 
minimum of elongation so that temporary increases and decreases of 
resistance during the cable placing operation will not result in even 
momentary stress excursions on the cable. 
In the past, the length of a cable duct was measured using a tape comprised 
of, for example, a weftless web of parallel fibers adhered together by an 
adhesive. This tape does not possess sufficient strength to permit its use 
for pulling a cable. Therefore, after measuring the duct length, the tape 
was used to introduce a pull line in the duct for the actual cable pulling 
operation. One tape which has been manufactured in the past is made of 
strands of polyamide resin which possess the strength and chemical 
resistance necessary to pull a cable in a duct, but unfortunately, the 
weftless tape is manufactured by adhering parallel threads of polyamide 
resin with glue or resin. When this occurs, the tape lacks sufficient 
strength to even permit its use for pulling a winch line into the duct. 
The tape has almost no further value for accomplishing further procedures 
to install a cable. However, sometimes the tape can be used to install a 
nylon rope which is then used to install a wire line which is, in turn, 
used to install a winch line in a duct to accomplish the cable placement 
operation. In addition to the foregoing, I have discovered that the use of 
resins or glues used in the manufacture of such tapes is detrimental to 
the duct system because the resin or glue adheres to the surface of the 
duct, thus impeding and sometimes preventing subsequent cable pulling 
operations. 
A minimal elongation of a tape or line under a pull force is important for 
achieving accurate measurements of a duct. For example, a nylon rope can 
stretch to over 40% of its free length before breaking. Moreover, when the 
pull line is used for the cable placement operations, the strength of the 
pull line must be adequately large so that if exceeded, the pull line will 
not shear with a dangerous backlash force. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a tape and a method for 
measuring and/or pulling cable in a duct through the use of such tape 
which includes a web comprised of warp and weft threads and preferably 
indicia on the web to indicate the length of a duct along which the web 
extends. 
It is a different object of the present invention to provide a tape and a 
method for using the tape in the pulling of cable in a duct or installing 
cable on an overhead support line in which the tape embodies a 
construction for minimizing elongation to about 10%, preferably 4%, or 
less at a break strength which is in excess of 750 pounds of pull force. 
More particularly, in one aspect of the present invention there is provided 
a tape for use in pulling cable along a course of travel, the tape 
comprising warp and weft threads, the tape having an elongation of 10% or 
less at a break strength which is in excess of 750 pounds of pull force. 
Preferably, the tape further includes indicia to indicate the length of 
the duct or course along which the tape extends, the tape having a normal 
width sufficient to affix the indicia thereon. Means, such as metal wires, 
each covered with a sheathing of insulation, are preferably arranged to 
form warp threads along opposite lateral sides of the tape to conduct a 
tension signal in the direction of the length of the tape. 
The present invention in a further aspect thereof provides a method for 
pulling a cable along a desired course wherein the method comprises the 
steps of selecting a tape comprised of warp and weft threads, the tape 
having indicia at spaced-apart distances to indicate units of length for 
measuring the length of the desired course, feeding the tape from one end 
of the course to the opposite end of the course, using the indicia on the 
tape to measure the length of the course, and using the measurement for 
selecting a desired length of cable to be placed along the course. 
In a still further aspect of the present invention there is provided a 
method for installing a cable along a desired course by the steps of 
selecting a tape comprised of warp and weft threads, feeding the tape 
along the course, coupling the tape to an end of the cable, and pulling 
the cable by the tape along the course. 
In its preferred form, the tape of the present invention has a pull 
strength of about 2900-3000 pounds, and a weight of about 7 pounds per 
1000 feet at a nominal width of 1 inch and a thickness of 1/32nd of an 
inch. The woven form of warp and weft threads provides strands of parallel 
filaments of yarn which preferably consist of aromatic polyamide fibers.

In FIG. 1 of the drawings, there is illustrated an underground conduit or 
duct 10 extending between underground work areas 11 and 12. Usually, an 
array of ducts extends below ground level between work areas 11 and 12. 
The length of the duct which is to be measured by the use of the tape 
according to the present invention may be in excess of 1500 feet. A plug 
13, sometimes referred to in the art as a pig, is secured to the leading 
end of a tape 14, the details of which will be described hereinafter. The 
plug with the tape secured thereto is installed into an exposed opening of 
the duct 10 located in the work area 11. The tape extends through a 
suitable opening in the side wall of a conduit 15 having an adapter nozzle 
16 at one end to fit tightly in the duct. Means 17 supplies a fluid medium 
to the free end of the conduit 15. Such means may comprise an air blower; 
however a supply of pressurized water can be used. The plug is propelled 
along the length of the conduit by energizing means 17. At the discharge 
end of the conduit, the plug is removed from the conduit by workmen and 
the leading end of the tape is positioned into a desired relation with the 
conduit so that a measurement can be taken of a length of the conduit. The 
purpose of this measurement is to determine the necessary length of cable 
which is to be installed in the conduit. Usually, the actual length of the 
conduit is to be determined so that the leading end of the tape is placed 
in registry with the end of the conduit in work area 12. The personnel in 
work area 11 applies tension to the tape under a small force sufficient to 
straighten the tape in the duct while the leading end of the tape is 
anchored or held in place by other personnel in work area 12. 
As will be described in greater detail, indicia preferably in the form of 
incremental markings along the length of the tape provides the means by 
which the workmen can determine the length of the tape which extends along 
the actual duct. After the measurement is completed, the measurement 
information is used for ordering the desired length of cable. The lead 
time between measuring and placing the cable can be 2 to 3 months during 
which time the tape, if it is to be used to pull or install a cable in the 
conduit, is allowed to remain in the underground conduit. Since the tape 
is comprised of an interlocking weave, the tape can safely remain in the 
duct. I have discovered that the woven tape construction is far superior 
to weftless tape using an adhesive to hold the strands thereof together. 
Such an adhesive will break down in the continued presence of subsurface 
water which includes acids or other caustic chemicals. 
A desired length of cable 18 comprised of telephone communication cable or 
an electric utility cable is coiled about an arbor 19 of a supply reel 20. 
The tape and method of the present invention are particularly useful for 
telephone communication cables comprised of a multiplicity of optical 
fibers within a sheathing of plastic material. A connector 21, per se, 
well known in the art, forms part of a cable eye that is attached to the 
leading end of the cable. A tension meter 22 is preferably connected 
closely adjacent the leading end of the cable to form an interconnecting 
element between the cable and a pull line which, in the preferred form of 
the present invention, is comprised of the tape 14. However, when 
extremely high tensions are necessary to install the cable in the duct, 
e.g., in excess of 3000 pounds, it is necessary to thread aircraft cable 
through the duct. This is accomplished by affixing the leading end of the 
aircraft cable to a free end of the tape 14 and then threading the 
aircraft cable to the duct by withdrawing the tape. The free end of tape 
14 or the free end of such aircraft cable is attached to the tension meter 
22. The tape or cable is threaded through a manhole opening 23 for work 
area 12 where it is wrapped about the arbor of a tension reel 24. The 
tension reel is supported on a suitable frame 25. A drive motor 26 is 
connected to rotate the reel 24. A control 27 for motor 26 is used to 
control the tension which is applied to the tape 14. 
To protect and guide the cable during passage from reel 20 into the work 
area 11, it is preferred to thread the leading end of the cable through a 
lubricating collar 28, such as disclosed in U.S. Pat. No. 4,028,473 or 
4,326,605 for discharging a suitable lubricant onto the surface of the 
cable. The cable passes from the lubricating collar 28 along a length of a 
feeder tube which may be used according to the method described in U.S. 
Pat. No. 4,202,530 and that the tube may take the form of the feeder tube 
disclosed in my U.S. Pat. No. 4,296,157. An adapter 29 is used to 
interconnect the discharge end of the feeder tube with the entry end of 
the duct 10. 
After the leading end of the cable is fed through the collar 28 and the 
guide tube, the connector 21 is secured thereto. A connector with the 
in-line tension meter 22 is placed into the entry end of the conduit. The 
adapter 29 can then be engaged with the entry end of the conduit so that 
the guide tube protects the outer surface of the cable as it is drawn from 
the reel 20. This occurs by energizing the drive motor 26. The control 27 
is used to prevent the development of excessive tension on the cable 
during placement in the conduit. Such control is preferably carried out 
through the use of a signal provided by the load meter in a manner 
disclosed in my copending application Ser. No. 346,386, filed Feb. 5, 
1982, now abandoned. To carry out the preferred form of this method, a 
detector 30 is arranged at the discharge end of the conduit to receive a 
signal that is transmitted by the load meter for indicating the magnitude 
of the tension that is applied to the leading end of the cable by the 
tape. The output signal from the detector 30 may be used as the basis for 
adjusting the control 27 during the cable pulling operation. After the 
leading end of the cable emerges from the duct 10 in work area 12, it is 
disengaged from the connector 21 so that the pull tape can be wound 
completely on reel 24. Thereafter, the usual cable splicing operations can 
be carried out with the terminal end of a further cable 31 located within 
the work area 12. 
In view of the foregoing, it is apparent to those skilled in the art that 
cable can be pulled along an overhead support line by employing the tape 
14 to measure the length of the course before procuring and installing the 
cable. Moreover, the cable can be installed on the overhead support line 
by using the tape 14 to form the pull line to move the leading end of the 
cable along the course. 
FIGS. 2-4 illustrate in greater detail the construction of the tape 14 for 
use in pulling a cable along a course from one end to the opposite end 
thereof. The course may comprise an underground duct or an overhead track 
along a support line. The tape has warp threads 39 and a weft thread 38. 
In the preferred form, the warp and weft threads take the form of strands 
of parallel yarn filaments comprised of aromatic polyamide fibers which 
provide a tape pull strength of between 2900-3000 pounds with an 
elongation at a break strength of approximately 4%. An elongation of 10% 
under a pull force of 750 pounds is acceptable within the scope of the 
present invention. The tape is comprised of 20-100 warp ends, but 
preferably 50, of 1500 denier KEVLAR 29 (Trademark by E. I. DuPont). A 
tape made of this material with 50 ends has a very high strength to weight 
ratio without adhesives. At 50 ends, the weight of the tape is about 7 
pounds per 1000 feet, and at 20 ends, the weight of the tape is about 2.8 
pounds per 1000 feet, whereby it can be efficiently transmitted over an 
extended length of a conduit in excess of 1500 feet by the use of a fluid 
medium, such as air, as described hereinbefore. KEVLAR 29 is one of a 
family of aromatic polyamide fibers under the generic name ARAMID with a 
tension strength of 400,000 pounds per square inch and a modulus of 
9,000,000 pounds per square inch. KEVLAR yarn with a denier of 1500 has a 
yield of 2976 yards per pound at 1000 filaments with a zero twist. The 
nominal yarn diameter is 0.0212 inch. The yarn is presently available at 
9000 and 15,000 denier, 4000 and 10,000 filaments, respectively, zero 
twist and 0.052 and 0.067 diameter, respectively. The high strength to 
weight ratio of the tape comprised of warp and weft threads is important 
not only because of the low elongation at break strength, but also to 
insure accurate measurements of a length of the order of 1500 feet. To 
carry out such measurements, indicia is printed, woven or otherwise placed 
on the tape at preselected intervals along its length. The indicia may be 
in English or metric dimensions as desired and in FIG. 2, examples of such 
indicia are indicated by reference numerals 36 and 37. The chemical 
resistance of KEVLAR 29 while excellent is no detriment to printing of 
indicia thereon and it has been found that printing methods and materials 
well known in the art can be used. The chemical resistance of the KEVLAR 
29 material is given in the following table: 
TABLE 
______________________________________ 
CHEMICAL RESISTANCE TO YARN OF 
KEVLAR 29 ARAMID 
Environment Tensile Strength 
(100 hr* exposure at 70.degree. F.; 21.degree. C.) 
Loss % 
______________________________________ 
ACIDS 
Formic (90%) 10 
Hydrochloric (37%) 90 
Hydrofluoric (10%) 12 
Nitric (70%) 82 
Sulfuric (70%) 100 
OTHER CHEMICALS 
Brake Fluid (312 hr) 2 
Greases (MoS.sub.2 and Lithium base) 
0 
Jet Fluid (JP-4) (300 hr) 
0 
Ozone (1000 hr) 0 
Tap Water 0 
Boiling Water 0 
Superheated Water 156.degree. C. (313.degree. F.) 80 hr 
16 
______________________________________ 
*Except where noted. 
Exposure of the aromatic polyamide fibers to intense ultraviolet light for 
over a period of time, for example, 5 weeks has a deteriorating effect to 
the material. However, the tape is usually protected by a duct or the 
outer sheathing against attack by ultraviolet radiation. Adequate 
protection for the tape against exposure can be carried out prior to its 
placement. 
As best shown in FIG. 4, weft thread 38 intersects warp threads 39 at right 
angles, typically in the form of a linen or plain weave. The weft thread 
38 is continuous by the formation of reverse bends in which the weft 
thread at the edge passes over a warp thread; wraps around the outer end 
of the warp thread and returns underneath the warp thread. While only four 
warp threads 39 are shown in FIG. 4, it is to be understood, of course, in 
the preferred embodiment, 50 such warp threads form the tape of the 
present invention. The interlocking weave of the tape assures greater 
strength and overcomes the disadvantages of using glue or resin to bond 
the threads together as well as the attendant problem of deterioration of 
the bonding materials when residing in the conduit over a long period of 
time. Moreover, a tape having resin or glue, even though it may not 
deteriorate, is subject to transfer of the resin or glue to the internal 
wall surface of the duct or overhead cable carriers by rubbing contact 
therewith. This impedes subsequent pulling operations since the glue will 
increase friction with the surface of a cable in rubbing contact with the 
glue residue. I have also found that glue or resin is ineffective to 
prevent separation of high strength threads of tape under high tension, 
particularly at the points where the tape rubs against the wall surfaces 
at bends, particularly in a duct. Moreover, it has been found that a tape 
using glue or resin is not strong enough to pull a winch line when this is 
necessary. The adhesive-tape combination will break if an attempt is made 
to pull the winch line into the duct, thus requiring further procedures to 
accomplish the installation of a winch line. 
In FIGS. 5 and 6, the same reference numerals have been applied to parts 
which are identical to the parts described in regard to FIGS. 1-4 and the 
suffix "A" has been applied to reference numerals identifying parts which 
correspond to the parts already described in regard to these figures. 
In the embodiment of the tape shown in FIG. 5, a weft thread 38 intersects 
warp threads 39 at right angles and forms a tape 14A with a linen or plain 
weave in the same manner as already described in regard to FIG. 4. One or 
more warp threads 39 comprised of aromatic polyamide fibers extends along 
each of the opposite lateral sides of the tape and the next warp thread at 
each lateral side portion is formed by electrical conductors 41. Each 
conductor comprises a metal wire 42 coverd by an outer sheathing 43 of a 
suitable electrically-insulative material. The electrical conductors 41 
take the place of warp threads at opposite lateral sides of the tape and 
extend along the length of the tape for delivering an electrical signal 
from the tension meter 22 to a detector 30A which is illustrated in FIG. 
6. The tension signal may be fed directly to the conductors by connecting 
the bared end portions of the conductors to suitable terminals on the 
tension meter. It is preferred, however, as shown in FIG. 6, to secure an 
end portion of the tape to an eyelet 22A at one end of the tension meter 
by a knot so as to form a trailing end portion which extends along the 
casing of the tension meter. The conductors are connected together to form 
a conductor loop. This arrangement of parts is used when the tension meter 
embodies a transmitter that can induce an electrical signal in the 
conductor loop formed by conductors 41. The electrical signal corresponds 
to the tension imposed on the tension meter when the free end thereof is 
coupled to a cable through an eyelet 22B. The detector 30A is directly 
coupled by the bared end portions of the conductors to indicate the 
magnitude of tension that is applied to the cable by the tape. The output 
signal from the detector 30A may be used as a basis for adjusting the 
control 27 (FIG. 1) during the cable pulling operation. 
Referring, again, to FIG. 5, it will be understood that the conductors 41 
may be arranged to form warp threads at any desired site in the tape and 
do not materially affect the strength and other properties of the tape 
described herein. However, the tape, according to the embodiment of FIG. 
5, will have a slightly greater weight per unit of length as compared with 
the tape described heretofore in regard to FIG. 4 given the same tape 
width. The width of the tape with conductors can be reduced if it is 
necessary when the weight per unit of length is critical. One other aspect 
to the tape of FIG. 5 is the fact that it has increased rigidity as 
compared with the tape of the FIG. 4 embodiment because the strands of 
parallel yarn filaments comprise aromatic polyamide fibers. These fibers 
are more flexible than metal conductors. A tape with metal conductors has 
sufficient flexibility so that it can be propelled along a course defined 
by a conduit or the like. 
The tape of the present invention eliminates the need to install a nylon 
rope according to the prior practice for feeding a wire line through the 
duct for placing the cable therein. It is pointed out that, for example, a 
nylon rope can stretch over 40% of its length before breaking. When 
stretched to its limit, the nylon rope can break with a dangerous backlash 
force which cannot be tolerated in the close working environment of 
underground work areas as commonly utilized for underground cable 
placement operations. Moreover, a nylon rope, for example, cannot be used 
to accurately control the tension imposed on a cable, particularly where 
it is desired to limit the maximum tension to some predetermined value, 
such as 500 pounds. The maximum force which at some instance can be 750 
pounds, if exceeded, produces a static fatigue failure of the fiber optic 
material. Accurate control of tension is not possible when a large amount 
of pulling force is stored as kinetic energy in a stretched nylon rope. 
Although the invention has been shown in connection with a certain specific 
embodiment, it will be readily apparent to those skilled in the art that 
various changes in form and arrangement of parts may be made to suit 
requirements without departing from the spirit and scope of the invention.