Means for pulling fiber optic cable through a conduit

A means for pulling a length of fiber optic cable through an underground conduit is described wherein a lead puller is positioned at the exit of the conduit and one or more booster pullers are positioned at intermediate positions along the length of the conduit upstream from the exit thereof. The booster puller pulls the cable from the cable entry to the intermediate location and the cable is then fed downstream into the conduit with the lead puller being simultaneously operated to pull the conduit from the intermediate location to the exit. The lead and booster pullers each have a pair of hydraulically operated pinch wheels mounted thereon which may be selectively series connected or connected in parallel to achieve either maximum speed or maximum torque.

BACKGROUND OF THE INVENTION 
This invention relates to an improved method and means for pulling great 
lengths of fiber optic cable through a buried or underground conduit. 
Fiber optic cable is comprised of a bundle of glass fibers or other 
transparent material enclosed within a protective outer sheath. The fiber 
optic cable is normally wound upon reels which are transported to the job 
site by reel haulers, trucks, etc. The fiber optic cable is normally 
pulled through the underground conduit by means of a rope connected at one 
end thereof to the lead end of the fiber optic cable. The rope is normally 
pulled through the conduit by some sort of pulling apparatus. The friction 
of the fiber optic cable being pulled through the conduit has heretofore 
limited the lengths of the cable which could be pulled due to the tension 
limits or strength of the cable. Such pulling limitations resulted in the 
necessity of splicing together shorter lengths of the fiber optic cable 
which is time consuming and expensive. In addition, the transmission 
quality of the cable is affected by a large number of splices. 
An attempt was made to solve the problems associated with pulling long runs 
of fiber optic cable and the same is described in U.S. Pat. No. 4,576,362 
issued to Ralph C. Langston on Mar. 18, 1986. In the Langston apparatus, a 
first cable puller is positioned at the conduit exit with a second pulling 
apparatus being provided at an intermediate access point along the length 
of the conduit through which the cable is being pulled. Both of the 
pulling machines of the Langston patent involve capstan winches. The 
Langston method utilizes a positive pull by the lead puller to tighten the 
cable on the booster capstan drive. The Langston method requires 
approximately sixteen percent of the booster pulling tension to snub the 
cable on the booster capstan. Therefore, a cable that requires 600 pounds 
pull to move must be snubbed with approximately 100 pounds pull to obtain 
proper friction on the booster capstan drive. On an optic fiber cable pull 
of considerable length, any additional drag at the inlet of the conduit 
will be amplified about five times at the outlet. Therefore, a drag of 100 
pounds to snub the booster capstan may require 500 pounds extra pull by 
the lead puller. Therefore, on pulls of considerable length, the effective 
pull required by the lead puller that snubs the cable on the booster 
capstan may be cut to below one-fourth. A further disadvantage of the 
Langston method is that the fiber optic cable must be coiled on the 
booster puller which results in cable twisting when the cable is removed 
from the booster puller.

SUMMARY OF THE INVENTION 
The apparatus of this invention comprises a wheeled frame means having an 
internal combustion engine mounted thereon which is connected to a 
hydraulic pump means. Mounted at the rear of the wheeled frame means is a 
pivotal reel carrier on which may be mounted a fiber optic cable reel as 
desired. Also mounted on the reel carrier are a pair of pinch wheels which 
are rotatably mounted about horizontal axes in such a manner so that the 
peripheries of the pinch wheels are closed adjacent one another. Each of 
the pinch wheels is powered by a hydraulic motor which is operatively 
connected to the hydraulic pump. A valve interconnects the hydraulic pump 
and the hydraulic motors on the pinch wheels so that the pinch wheels may 
be either powered by the hydraulic fluid in series or in parallel. When 
the hydraulic motors are series connected, the pinch wheels will be 
operated at maximum speed. When the hydraulic motors are connected in 
parallel by the valve, the pinch wheels will be operated at less speed 
than when series connected but will have increased torque for pulling 
power. 
When the apparatus is being used to pull rope through the conduit, with one 
end of the rope being connected to the fiber optic cable, the rope is 
wrapped around both of the pinch wheels in a "FIG. 8" pattern and is then 
delivered to rope tender canisters positioned on the wheeled frame means. 
When the apparatus is used as a booster puller at an intermediate access 
point, the fiber optic cable is wrapped around one of the pinch wheels so 
that the pinch wheel will pull the fiber optic cable from the conduit 
entry towards the intermediate access opening. The workman is positioned 
at the booster puller and grasps the cable and thence feeds the cable into 
the downstream portion of the conduit at the intermediate access opening. 
It is a principal object of the invention to provide an improved method and 
means for pulling fiber optic cable through an underground conduit. 
A further object of the invention is to provide a fiber optic cable puller 
having a pair of pinch wheels which are hydraulically connected in series 
or in parallel to achieve either maximum speed or maximum torque depending 
upon the position of the valve connecting the hydraulic motors with the 
hydraulic pump. 
Yet another object of the invention is to provide a method and means for 
pulling fiber optic cable through an underground conduit in such a manner 
so that great lengths of the cable may be pulled without stalling the 
equipment or without damaging the cable, by having an adjustable limit 
which can be set on the puller as to not exceed the allowable tension of 
the cable. 
Yet another object of the invention is to provide a puller which has 
greater pulling power than normally allowed for pulling fiber optic cable 
to be used for pulling "innerduct" through a conduit. 
Still another object of the invention is to provide an apparatus of the 
type described which may be used as a lead puller to pull rope through the 
conduit or which may be used as a booster puller to pull the fiber optic 
cable through the conduit. 
These and other objects will be apparent to those skilled in the art. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The cable reel puller and carrier is illustrated in FIG. 1 and is generally 
designated by the reference numeral 10. Puller 10 includes a wheeled frame 
means 12 having a hitch 14 at the forward end thereof. A pair of 
hydraulically operated stabilizing jacks or stabilizers 16 and 18 (not 
shown) are mounted at the rearward end of the wheeled frame means 12. 
A reel support 20 is pivotally mounted at the rearward end of the wheeled 
frame means 12 for moving the reel support 20 from the transport position 
of FIG. 3 to the pulling position of FIG. 2 by means of the pair of 
hydraulic cylinders 22 and 24. 
Frame means 12 is provided with three rope canister support areas 26, 28 
and 30 (FIG. 1) at its forward end adapted to have rope canisters 32 
mounted thereon and maintained thereon by means of strap assembly 34 as 
best illustrated in FIGS. 2 and 3. 
A rope tender apparatus 36 is mounted on the frame means 12 (FIG. 2) for 
delivering the rope 38 into the interiors of the canisters in a manner 
similar to that described in U.S. Pat. No. 4,465,261. 
The numeral 40 refers to a power source such an internal combustion engine 
which is operatively connected to a hydraulic pump 42. Hydraulic pump 42 
provides hydraulic fluid for the operation of cylinders 22, 24, 16, 18 as 
well as the hydraulic motor on the rope tender 36. Hydraulic pump 42 also 
delivers hydraulic fluid under pressure to the pinch wheels 46 and 48 
which are operatively rotatably mounted on the reel support 20 as best 
illustrated in FIG. 4. As seen in FIG. 4, pinch wheels 46 and 48 are 
operatively rotatably mounted on a frame 50 having a pair of arcuate 
mounting brackets 52 and 54 extending inwardly therefrom which are adapted 
to be selectively pivotally secured to the plates 56 and 58 by means of 
bolts 60, 62 and 64, 66 respectively. As seen in FIG. 5, the pinch wheels 
may be angularly disposed with respect to the vertical by changing the 
relationship of the brackets 52 and 54 with respect to the plates 56 and 
58. 
Plates 56 and 58 are mounted on a frame member 68 which is pivotally 
secured to reel support 20 by bolt assemblies as illustrated in FIG. 4 to 
permit adjustment of the pulling angle. Valve 70 is mounted on the frame 
member 68 between the plates 56 and 58 and is hydraulically connected to 
the hydraulic pump by conduits 72 and 74. Pinch wheels 46 and 48 are 
powered by hydraulic motors 76 and 78 as illustrated in FIGS. 9 and 10. 
FIG. 9 illustrates hydraulic motors 76 and 78 being series connected so 
that the motors 76 and 78 be operated at a maximum speed. When valve 70 is 
shifted from the position of FIG. 9 to the position of FIG. 10, the motors 
76 and 78 are connected in parallel so that the motors 76 and 78 will be 
operated at a slower speed than when series connected but will have a much 
greater torque or pulling power when connected in parallel. As seen in the 
drawings, the pinch wheels 46 and 48 are each provided with a V-shaped 
peripheral gripping portion 80 comprised of portions 80A and 80B which is 
best illustrated in FIG. 6. In FIG. 6, the numeral 38 illustrates the 
pulling rope 38 being received in the pinch groove 80A defined by the 
flanges 82 and 84. The broken lines in FIG. 6 illustrate the position of a 
fiber optic cable 86 being received in portion 80B. The double groove 
angle of the flanges 82 anad 84 permits the proper gripping of the rope 38 
in portion 80A and the cable 86 in portion 80B. In the drawings, the 
numeral 88 refers to an idler wheel adapted to maintain the rope 38 in the 
pinch groove of pinch wheel 48. 
When it is desired to pull a long length of cable 86 through an underground 
conduit 90, an excavation 92 is created in the ground at the location from 
which the cable is to be pulled. For purposes of description, the entry of 
the conduit 90 will be identified by the reference numeral 94 as seen in 
FIG. 12. 
At least one excavation 96 is formed in the ground downstream from 
excavation 92 and the conduit 90 will be cut at 90 and 100 respectively. 
An exit excavation 102 is formed in the ground at the location to which 
the cable is to be pulled. For purposes of description, the numeral 104 
refers to the exit end of the conduit 90. 
A booster puller 10 is positioned adjacent the intermediate excavation 96 
as illustrated in FIG. 12. A suitable cable reel 106 will be positioned at 
the entry excavation. A lead or primary puller 10 is positioned adjajcent 
excavation 102 but does not have to be so positioned until it is required 
to pull the rope 38 from excavation 96 to excavation 102. A length of rope 
38 is then blown or otherwise passed through the that portion of conduit 
90 between excavation 96 and excavation 92. The "tail" end of the rope 38 
is secured to one end of the fiber optic cable 86 wound on the reel 106. 
The lead end of the rope 38 is passed around the pinch wheel 46 as 
illustrated in FIG. 2 and thence passed around the pinch wheel 48 as also 
illustrated in FIG. 2. The lead end of the rope 38 is then positioned in 
the rope tender apparatus 36 so that as the rope 38 is being pulled by the 
pinch wheels 46 and 48, the rope will be deposited in the canisters 30 and 
32. 
Puller 10, at excavation 96, will then be activated so that the pinch 
wheels 46 and 48 will be rotated in opposite directions to pull the rope 
through the conduit 90 between excavations 92 and 96 which will cause the 
conduit 86 to be pulled through the conduit 90 from the entry opening 94 
in excavation 92 to the intermediate excavation 96. When the lead end of 
cable 86 reaches excavation 96, the rope 38 is disconnected therefrom and 
the cable 86 is wrapped around pinch wheel 46 as illustrated in FIG. 11. 
If a rope 38 has not been blown or otherwise passed through the conduit 90 
between excavations 102 and 96, the same is accomplished at this time. The 
tail end of the rope 38 is secured to the lead end of the cable 86 at 
excavation 96 and the rope 38 as seen in FIG. 12. At this time, the puller 
10 at excavation 102 becomes the lead puller and the puller 10 at 
excavation 96 becomes the booster puller. As the cable 86 passes around 
the pinch wheel 46 at excavation 96, the workman controls the slack in the 
cable as required to coordinate the pull speed between the lead puller and 
the booster puller. The workman feeds the cable into the opening 100 as 
illustrated in FIG. 11. Thus, booster puller 10 is pulling the cable 
between the entry excavation 92 and the intermediate excavation 96 while 
the lead puller pulls the cable from the intermediate excavation 96 to the 
exit excavation 102. 
It can therefore be seen that a novel method and means has been provided 
for pulling great lengths of fiber optic cable through an underground 
conduit through the use of a lead puller and one or more booster pullers 
upstream of the lead puller. The valve 70 may be shifted as desired to 
either obtain maximum speed or maximum pulling power depending upon 
whether the hydraulic motors 76 and 78 are series connected or are 
connected in parallel. 
FIG. 8 illustrates an adjustable relief valve 110 which is imposed in the 
hydraulic circuitry between the hydraulic pump and the pull motors 76 and 
78. Valve 110 is adjusted with a conventional tension meter prior to the 
pulling operation so that the hydraulic fluid will by-pass the pull motors 
76 and 78 when the maximum tension is reached so that the motors 76 and 78 
will stall out before the allowable tension is reached in the cable 86. A 
hydraulic gauge 112 is provided in the circuit so that the hydraulic 
pressure to the motors 76 and 78 can be monitored during the pull with the 
indicated pressure being directly related to the pull on the cable. 
If the puller is being used to pull innerduct through a conduit prior to 
pulling cable, the by-pass valve 114 may be operated to by-pass the relief 
valve so that sufficient hydraulic pressure can be supplied to the motors 
76 and 78 to pull the innerduct through the conduit.