Note: Descriptions are shown in the official language in which they were submitted.
- ~266639
CABLE PULLING SYSTEM
The invention relates to a system for
inserting cable into a conduit and more particularly to
an air~powered cable~pulling system.
The increased use of undergro~nd cable
(e.g. telephone, electric and other utility cables)
contained in buried conduit requires improved methods
of moving the cable through sections of conduit which
often exceed 100 feet in length. Presently, this is
accomplished by blowing a lightweight guide line
through the conduit using compressed air. The guide
line is then used to pull a heavier~weight line which
in turn is used to pull heavier rope which is then used
to pull the actual cable through the conduit. This
multistep process takes considerable effort and time.
~5 Typical installations require a four^man crew to work
about two hours to pull a single primary cable through
a 2" diameter conduit 600 feet in length. In addition,
work is frequently delayed due to breaking of the guide
lines and the damaging of sections of the conduit.
2~ In response to the need for improved
cable~pulling equipment, two types of alternative
,
equlpment have been developed over the past several
years While these two types of equipment const1tute
an improvement over the installation method described
above, they are expensive, require specially trained
operators and cannot be used in relatively
~l26~63~
inaccessible locations, e.g., underground vaults,
electrical rooms and back yards. Specifically, in one
type, a rodding machine is mounted on a truck or
trailer and is used to push a 3/8" or 1/2n spring steel
rod through a section of conduit while rotating the rod
at a low rate of speed. Normal payout of the rod is
about 40 to 50 inches per minute. Upon reaching the
end of the conduit, the electrical or communications
cable is attached to the rod which is then pulled back
~ through the conduit.
While this rodding type of equipment is
useful in situations involving badly blistered or
collapsed conduit, it incorporates the following severe
disadvantages:
~5 1. A long set up time (15 to 30 minutes) is
required;
2. Communication between the operator and the
reel~tender is necessary for safe operation,
in order to insure that the rod is stopped
2Q when it clears the receiving-end of the
conduit;
3. The payout of the rod is relatively slow;
4. The equipment cannot be used on conduit
runs containing 24~ radius 90 bends;
5. The equipment cannot be used in relatively
inaccessible areas;
:
6. A specially trained operator is required,
thereby limiting productivity and scheduling;
3a and
7. The equipment is extremely expensive.
:
~2~ g
In a second type of cable-pulling equipment, a
high-volume/low^pressure air blower, mounted on a
teailer, is used to blow a plug~like device (referred
to as a "birdie~) through a conduit by the use of
compressed air, with the birdie carryinq one end of a
steel guide line through the conduit. The steel guide
line extends from a drum which is mounted far free
rotation so as not to impede the progress of the birdie
through the conduit. Once the birdie passes through
; 10 the length of the conduit, the steel guide line is
attached to the electrical or communications cable and
pulled back through the conduit using a hydraulic-
powered winch drum.
The disadvantages of this type of equipment
~5 include the following:
1. The uncontrolled payout (unwinding) of the
steel guidline (frequently at a rate of
over 1000 feet per minute) creates severe
potential safety problems;
2~ 2. A specially trained operator is required;
3. The birdie cannot be blown through partially
collapsed sections of conduit;
4. Because the equipment is mounted on a
trailer, it cannot be used in relatively
inaccessible areas: and
5. The equipment is extremely expensive.
Of the above disadvantages, perhaps the most
severe i9 the uncontrolled unwinding of the steel guide
line and therefore uncontrolled movement of the birdie
through the conduit. In essence, the system operates
as a compressed air gun which "shoots~ the birdie
.:
~Z~i6~3~
through the conduit. The birdie exits the opposite end
of the conduit at a high velocity and can cause severe
damage. The safe operation of this system is dependent
on the operator's ability to stop the freewheeling drum
when the birdie exits the conduit and, as such, is
especially sensitive to operator error.
Accordingly, it is an object of the present
invention to provide an improved cable-pulling system
which overcomes the defects inherent in prior art
systems.
Another object of thb present invention is to
provide a cable pulling system which is relatively
port~ble and therefore useable in otherwise
inaccessible areas.
Still another object of the present invention is
to provide a cable-pulling system the operation of
which results in a substantial savings of labor as
compared to the operation of prior art devices.
A further object of the present invention is to
2a provide a cable~pulling system which is safer than
prior art systems.
A still further object of the present invention
is to provide a cable~pulling system which may be
quickly assembled, used and disassembled.
An additional object of the present invention is
to provide a cable~pulling system which is simple to
operate and does not require a specially trained
::
~266639
operator,
An additional object of the present invention is
to provide a cable pulling system including an improved
birdie capable of maintaining an airtight seal along
irregular sections of conduit.
These and other objects are achieved, in
accordance with the present invention, by rnoving a
; birdie connected to a supply of cable through a length
of conduit with the birdie being formed so as to create
1~ a fluid seal within the conduit. Pressurized fluid
(such as air) is introduced to a first end of the
conduit so as to create a pressurized region within the
conduit between the first end and the birdie, thereby
urging the birdie through the conduit and to the
opposite end thereof. Movement of the birdie is
restricted, however, by the cable which is spooled GUt
only in response to the existence of a threshhold
pressure in the region of the conduit between the first
end and the birdie. Once the birdie exits the opposite
2Q end of the conduit, pressurization is lostj the cable
is no longer spooled out and movement of the birdie is
effectively stopped. As such, a controlled movemént of
the birdie through the conduit is achieved.
An additional feature of the present invention
is the formation of the birdie from a first group of
resilient fluid-impervious discs disposed in
concentric, adjacent relationship, with at least one of
:: ~
t
1~:66639
the discs having a diameter slightly greater than the
inside diameter of the conduit and another of the discs
having a diameter substantially equal to the inside
diameter of the conduit. This first group of discs is
spaced from a second group of resilient fluid
impervious discs which are also disposed in concentric,
adjacent relationship, with at least one of the discs
having a diameter slightly greater than the inside
diameter of the conduit and another of the discs having
a diameter substantially equal to the inside diameter
of the conduit. The birdie so formed provides a
fluid~tight seal with the interior of the conduit
notwithstanding the presence of obstructions or
collapsed sections of conduit.
~5 The above brief description as well as further
objectives, features and advantages of the present
invention will be more fully understood by reference to
the following detailed description of the presently
preferred, but nonetheless illustrative embodi~ents in
2Q accordance with the present invention, when taken in
conjunction with the accompanying drawings, wherein:
Fig. 1 is a fragmentary side elevation of the
cable~pulling system of the present invention;
Fig. 2 is a fragmentary front elevation of the
cable^pulling system of the present invention;
Fig. 3 is a sectional side elevation of the
birdie used in the cable~pulling system of the present
::
:
: s
3L2~639
invention located within a portion of the conduit;
Fig, 4 is a fragmentary sectional side elevation
of an alternate embodiment of the present invention
shown during operation thereof;
Fig, 5 is a fragmentary sectional side elevation
of the portion of the cable~pulling system which is
connected to the conduit: and
Fig. 6 is a fragmentary sectional side elevation
of an alternate embodiment of the portion of the
1~ cable-pulling system which is connected to the conduit.
Referring now to Figs. 1^3, the cable^pulling
system of the present invention may take the form of
the portable unit shown in Figs. 1 and 2 and indicated
generally by the reference numeral 10. The system also
includes a birdie 12 which is shown in Fig. 3 moving
through a section of conduit 14. The portable unit 10
includes an L-shaped dolly formed from a horizontal
platform 16 and vertical uprights 18 and 20 connected
at their upper ends by a crossbar 22. Preferably, the
; 2Q platform 16 and uprights 18 and 20 are formed of
aluminum and welded together. In order to facilitate
mobility of the unit 10, platform 16 supports a pair of
wheels 24 and 26, which are located proximate to
respective uprights 18 and 20, and a pair of remote
casters 28 and 30. In addition, a handle 32 extends
between the upper ends of uprights 18 and 20.; The use
of the wheels 24 and 26 and casters 28 and 30 permit
~: :
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~26663~
the unit 10 to stand upright and be maneuvered in small
areas, such as transformer rooms. In addition, the
unit 10 may be operated as a hand truck by tilting the
unit back on wheels 24 and 26, thereby allowing the
unit to be quickly moved over substantial distances.
A drum 34 mounted on unit 10 carries a supply of
cable 36, preferably steel wire rope, one end of which
i5 secured to the birdie 12 by use of a connector or
clip 38. During operation of the cable-pulling system
the birdie 12 is urged through the conduit 14 pulling
the cable 36 therethrough and payout or unwinding of
the cable 36 from the drum is regulated in order to
control the movement of the birdie 12. Specifically,
the drum 34 is carried on an axle 40 which is rotatably
supported on the unit 10 in a pair of bearings 42 and
44 mounted on respective uprights 18 and 20. Movement
of the axle 40, and therefore movement of the drum 34,
is controlled by a gear 46 mounted on the axle 40 and
driven by the output gear 48 of a pneumatic motor 50
2~ through a chain 52. As such, the winding and unwinding
of the cable 36 from the drum 34 is achieved by ~;
operation of the pneumatic motor 50 which is controlled
by the introduction of compressed air through tubes 54
~ and 56. The motor 50 may be formed with an internal
;~ 25 rotor tnot shown) which is driven by compressed alr and
which in turn drives output gear 48 through a suitable
gear reducer. A four^horsepower air-powered gear motor
,: :
-:
126~639
which would pay out cable at 100 feet per minut~ is
contemplated for use in 2~ and 4" diameter conduit no
greater than 700 feet in length. For 4~, 5~ and 6"
diameter conduit a four-horsepower air powered gear
motor which would pay out cable at 50 feet per minute
(the lower gearing would provide increased pulling
power) is contemplated.
The motor 50 is constructed so that if
pressurized air is supplied to the motor through tube
1~ 54, output gear 48 is driven to cause counterclockwise
movement of the drum 34 and unwinding of the cable 36.
Conversely, pressurized air supplied to the motor 50
through tube 56 results in clockwise movement of the
drum 34 and rewinding of the cable 36 thereon. If
~5 pressurized air is not supplied to the motor 50 through
either tubes 54 or 56, the motor 50 will act as a brake
with respect to the drum 34 to prevent either the
winding or unwinding of the cable 36.
As best seen in Fig. 1, adjustment of the
2a tension of the chain 52 is accomplished by rotation of
a lead screw 58 which is mounted on the platform 16.
Rotation of the lead screw 58 results in movement of
the motor 50 through a connector 60. As best seen in
Fig. 2, in order to insure even winding and unwindlng
of the cable 36 across the drum 34, the drum axle 40
carries a gear 62 which is adapted to drive a rod 64
through a gear 66 which is secured to one end of the
~266639
rod 64 and driven by a chain 68. Rod 64 is mounted for
rotation in bearings 70 and 72, which are secured to
respective uprights 14 and 16, and carries a cable
guide 74. Rod 64 is threaded so that upon rotation
guide 74 is moved back and forth along the rod so as to
evenly wind and unwind the cable 36 from the drum 34.
An air compressor, not shown, is used to provide
the pressurized air necessary for operating the motor
50 and, as will be described below, for moving the
cable 36 through the conduit 14. The air compressor
may be any standard unit capable of providing
high*pressure/low~volume pressurized air, and
compressors having an output of 150 to 175 CFM are
preferred. The compressor supplies pressurized air to
the system through a main supply line 76 which is :
secured to a T^connector 78 which forms part of the ~ :
: : unit 10. Gne outlet of connector 78 supplies air to ~:
the tubes 54 and 56 through an air filter and regulator
: 80, an oil lubricator 82 and a motor control valve 84.
20. Valve 84 permits air pressure to be supplied to tubes
54 and 56 to permit winding and unwinding of the cable: :
~:: : :.
36. Mufflers 86 and 88 are provided for respective ~ :
tubes 54 and 56 through which the respective tubes 54
and 56 exhaust to the atmosphere when not supplying~air --
: to the motor 50. For example, when valve 84 is
~:
operated to supply pressurized air to the motbr~50
: through line 54 in order to permit unwinding of the
`:
:
~266639
cable 36, tube 56 and muffler 88 serve as the exhaust
for the motor. Similarly, when valve 84 is operated to
supply pressurized air through tube 56 to operate the
motor 50 to rewind the cable, tube 54 and muffler 86
serve as the exhaust for the motor. The valve 84 as
well as the lubricator 82 and air filter and regulator
80 are carried on a shelf bracket 90 which extends
between and is connected to uprights 18 and 20.
The other outlet of T connector 78 provides air
lQ through an on/off valve 92 and a tube 94 to a
pressurized air/cable junction assembly 96. Assembly
96 is adjustably connected to crossbar 22 through the
use of a pair of shoulders 98 and 100 which extend
upwardly from the crossbar 22 and which rotatably
support a pair of arms 102 and 104 which are secured to
opposite sides of assembly 96. Both the arms 102 and
104 and shoulders 98 and 100 are formed with
corresponding openings 106 whereby the angular
orientation of the assembly 96 may be fïxed by the
2a insertion of a pin 108 through the corresponding
openings. Shoulders 98 and 100 also rotatably support
a pulley 110 which serves as a guide for the cable 36.
Arms 102 and 104 may support a lineal footage counter, ,_
-
not shown, in the region proximate to the pulley 110
for monitoring the amount of cable unwound from the
drum 34.
Assembly 96 includes a pressure gauge 112 and an
12~;6639
air~pressure escape valve 114 which serves as a safety
feature by preventing extreme pressure build^up in the
system. The cable 36 extends from the pulley 110 and
enters the assembly 96 at one end through an airtight
opening. A conduit extension tube 116 is secured to
the opposite end of the assembly 96 and is adapted to
supply both pressurized air and cable to the conduit 14.
During operation of the cable pulling system the
cable 36 is inserted into the assembly 96 and then
secured to the birdie 12 by use of the clip 38. The
birdie 12 is then inserted into one end of the conduit
extension tube 116, which end is then secured to the
assembly 96. The opposite end of the conduit extension
tube 116 is then secured to the conduit 14 at which
point the cable pulling system is ready for operation.
To institute operation, on/off valve 92 is opened to
supply pressurized air to the conduit extension tube
116 through tube 94 and assembly 96. Since the birdie
12 forms an airtight seal with the interior walls of
2~ the conduit 14 the introduction of pressurized air into
the region of the conduit 14 behind the birdie 12 would
normally urge the birdie through the conduit. However,
movement of the birdie 12 through the conduit 14 can
only be accomplished by the concurrent operation of the
motor 50, through valve 84 and tube 54, to permit
unwinding of the cable 36 from the drum 34. Because of
the use of the T-connector 78, air from the compressor
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~266639
~3
is supplied simultaneously to both the conduit 14,
through on/off valve 92, and to the motor 50 through
motor control valve 84 and tube 54. Initially, the
compressed air will travel to the region of the conduit
behind the birdie 12. Once this area is pressurized,
the compressed air will flow to the motor 50, powering
the motor to rotate the drum 34 and unwind the cable
36, thereby permitting movement of the birdie 12
through the conduit 14.
a The velocity of the birdie 12 through the
conduit 14 is therefore regulated by the action of the
motor 50 spooling out cable 36 from the drum 34. This
is in contrast to the prior art method in which a
high~volume/low~pressure air source is used to "shoot"
a birdie through a conduit in a totally uncontrolled
manner. As long as the birdie 12 remains in the
conduit 14 the entire air system will remain
pressurized and compressed air will continue to be
supplied to the motor 50. Once the birdie 12 has moved
through the entire length of the conduit 14 and exits
the open end of the conduit the air system immediately
: ~ opens and pressurization is lost. As a result, all of :
~ the compressed air supplied by the compressor exits
,~
through the open end of the conduit 14 and no
: 25 compressed air is supplied to the motor 50. In the
absence of a supply of compressed air, motor 50
: immediately brakes the drum 34 to prevent further
,, ~ :
, ~ , . , - , :
~26~3~
14
unwinding of the cable 36. The immediate braking of
the drum 34 serves to stop the birdie 12 as soon as it
exits the open end of the conduit 14. In this manner,.
the birdie 12 does not exit the conduit 14 as an
uncontrolled projectile with the inherent safety
problems, Instead, the birdie exits the conduit 14 and
is immediately stopped by the action of the motor 50
preventing further unwinding of the cable 36 from the
drum 34. As such, movement of the birdie 12 through
and out of the conduit 14 proceeds in a controlled and
safe manner.
once the birdie 12 has pulled the cable 32
through the entire length of conduit 14 and has exited
the conduit at the end remote from the unit 10, the
~5 cable-pulling system may be used to pull the cable 32,
along with telephone, electric or other utility wires,
back through the conduit 14. After the birdie exlts
the end of the conduit 14 remote from the unit 10,
motor control valve 84 is operated to shut of~ the
supply of compressed air to the motor 50 through either
: : tube 54 or 56. On/off valve 92 is then moved to its
: off position to stop the flow of compressed air to the
conduit 14 through tubes 94 and 116. Pin 38 is then ~:
: ~ operated to disconnect the birdie 12 from the cable 36,
: 25 which is then connected to the specific wiring~to be u ~ ~:
pulled through the cable. Once the wiring lS firmly
secured to the cable, valve 84 is operated to~supply
: :
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12Ei66;~9
compressed air to the motor S0 through tube 56, thereby
causing the motor 50 to rotate the drum 34 so as to
rewind the cable 36 thereon. As a result, the cable 36
and the wiring connected thereto are both carefully
pulled through the entire length of conduit 14. Since
compressed air within the conduit 14 is not required
for this operation, conduit extension tube 116 may be
disconnected from the end of the conduit proximate to
the unit 10 so as to permit viewing of the rewinding of
~0 the cable 36 and the pulling of the wiring back through
conduit 14. once the wiring exits the end of the
conduit proximate to the unit 10, the motor control
valve 84 is operated to shut off the supply of
compressed air to the motor 50, thereby stopping
further movement of the drum 34 and cable 36. The
wiring is then disconnected from the cable 36 and the
unit 10 may be taken to the next job.
~ The construction of the birdie 12 is shown in
detail in Fig. 3 and includes a rod 118 which is
;: ~ 2~ threaded at both ends, An eye nut 120 is connected to
; one end of the rod 118 and provides an attachment po1nt
for the clip 38 which carries the cable 36. Located
: ~ proximate to the eye nut 120 is a pair of steel:washers _ :
: 122~and 124 which are spaced apart by three flexible
sealing discs 126, 128 and 130. The discs may be
formed of any flexible, durable, fluid~impervlous
material, such as plastic, rubber with fiber plies,
::
~26663g
neoprene etc , and each disc is shaped so as to conform
to the interior of the conduit 14. Each of the discs,
however, is formed with a different diameter. The
middle disc 128 is formed with a diameter equal to the
diameter of the conduit 14, the first or forward disc
126 is formed with a diameter slightly smaller than the
diameter of the conduit 14 and the last or rearward
disc 130 is formed with a diameter slightly larger than
the diameter of the conduit 14. The discs are
maintained in concentric, adjacent relationship with
each other and with the washers 122 and 124, by the use
of a net 132. The end of the rod 118 remote from the
eye nut 120 is similarly formed with a pair of steel
washers 134 and 136 spaced by three flexible sealing
discs 138, 140 and 142. Nuts 144 and 146 serve to
maintain the washers 134 and 136 and discs 138, 140 and
142 in concentric, adjacent relationship with each
other. The function of these two groups of sealing
discs (126, 128, 130 and 138, 14~ 142) is to insure
: 2~ that the birdie 112 creates a fluid seal (such as an
air seal) with the conduit 14 regardless of whether the
conduit is slightly collapsed, dented or includes
obstructions 148.
: The diameters of respective washers 122 and 134
are greater than the diameters of washers 124 and 136.
Washers 122 and 134 are each located forward o. their
respective discs and serve to define the smallest
'
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~66639
diameter tubing through which the birdie 12 may move.
For example, if the tubing 14 is collapsed or dented to
the extent that its effective diameter is less than the
diameter of washers 134 and 122, the birdie will not
pass through the conduit. As such, washers 122 and 134
should be sized to correspond to the minimum possible
acceptable diameter of the conduit 14. The diameter of
washers 13~ and 124 are smaller than respective washers
134 and 122 in order to permit their respective discs
1~ to freely bend backwardly when the birdie passes
through egg~shaped or collapsed sections of conduit or
over obstructions 148.
The use of the three different*sized discs
insures that the birdie 12 will maintain a seal with
the conduit 14 in situations where the conduit 14 has
been collapsed or dented so as to create an irregular
inner circumference (egg~shaped) having, in some
places, a diameter greater than the original diameter
of the conduit 14. In these situations, the fluid seal
2~ is not lost because the larger diameter discs 130 and
142 expand to the larger diameter and maintain the
seal. In addition, the use of two sets of sealing
discs prevents the loss of fluid seal when the birdie
, ,_
; 12 moves through collapsed or dented sections of
conduit or over an obs~truction 148. Specifically, the
two sets of sealing discs each serve as back-up for~the
other to maintain the fluid seal. For example,~ lf
t
~2~1E;6~
discs 138, 140 and 142 are unable to provide an
effective fluid seal with the conduit 14 upon passing
over obstruction 148, pressurization is not lost since
discs 126, 128 and 130 continue to maintain the
birdie's 12 seal with the conduit 14. As a result, the
birdie 12 continues to travel through the conduit 14
and discs 138, 140 and 142 are moved past the collapsed
or dented section of conduit or over the obstruction
148 and again resume their sealing action. The
birdie's 12 fluid seal with the conduit 14 is similarly
maintained even though the seal provided by the second
set of discs 126, 128 and 130 may be lost when they
move through the collapsed or dented section or over
the obstruction 148. While either set of discs may, at
any time, fail to provide an effective seal, the other
set of discs will serve as a temporary back-up to
maintain the seal between the birdie 12 and the conduit
14.
It will readily be appreciated that each set of
sealing discs may contain more than three individual
discs and that the discs of a set may be formed of
different materials. In addition, should the birdie 12
encounter an obstruction or collapsed section of
conduit 14 which prevents its passage, pressure
build~up in the system will register on the pressure
gauge 112 of unit 10 and eventually trigger
air~pressure escape valve 114, to bleed off pressure so
1266~39
1~
as to prevent any dangerous pressure build~up.
Referring now to Figs. 4 ^ 6 the cable~pulling
system of the present invention may be mounted on a
vehicle, such as the vehicle shown in Fig. 4 and
indicated generally by the reference numeral 150.
Specifically, the portable unit 10 described above and
modified so as not to include the pressurized air/cable
junction assembly 96 may be mounted on the vehicle 150,
havinq a conduit extension tube 152 which corresponds
to conduit extension tube 116 of unit 10, a cable 154
which corresponds to cable 36 of unit 10 and a cable~
guide pulley 156 which corresponds to pulley 110 of
unit 10. The vehicle~mounted unit 150 may be used, for
example, Eor moving the cable 154 through an
underground conduit 158 having one end which opens into
an underground room 160, access to the room being
through a manhole opening 162. the vehicle~mounted
unit 150 is particularly desirable in this type of
application in view of~the difficulty in moving the t
portable unit 10 through the manhole opening 162 and
into the underground room 160. With the vehicle-
mounted unit 150, the rear of the vehicle, from which
the cable 154 and conduit extension tube 152~extend,
may be located directly above the manhole opening 162
with the cable 154 and tube 152 extending down into the
room 160. Additional pulleys and rigging 164 may be
attached to the walls of the room 160 and used to
:
~26G639
properly position the cable 154 with respect to the
open end of the conduit 158.
It will be readily appreciated, however, that an
assembly similar to the pressurized air/cable junction
assembly 96 is required in order to introduce both the
pressurized air from tube 152 and the cable 154 into
the conduit 158. This is accomplished by use of an
airtight chute indicated generally in Fig. 4 by the
reference numeral 166. Chute 166 is connected to the
open end of the conduit 158 and includes an air inlet
168 which i~ connected to tube 152 to supply
pressurized air and a cable inlet 170 which provides an
airtight opening through which the cable 154 may enter
the conduit 158.
The construction of the chute 166 may take many
different forms for various applications, the specific
requirements being that the chute be firmly secured to
the open end of the conduit 158 so as not to Hblow out~
upon the introduction of compressed air and that the
chute include airtight openings permitting entry of
both the cable 152 and the compressed air. Referring
now to Fig. 5, one form of airtight chute is indicated
generally by the reference numeral 172 and is
specifically well~suited for applications in which the
open end of a conduit 174 is flush with a concrete wall
176. Chute 172 includes a tube 178 having a diameter
slightly less than the diameter of the conduit 174 so
9L266~39
that one end of the tube may be inserted therein. The
opposite end of the tube is threaded and adapted to
receive a cap 180 which includes an airtight cable
guide 182. Guide 182 is formed so that movement of the
cable 154 therethrough is accomplished without loss of
compressed air so that the interior of the chute can
remain pressurized. Chute 172 also includes an air
inlet connector 184 to which one end of the conduit
extension tube 152 is secured, as well as an
air~pressure escape valve 186 which serves as a safety
feature by preventing extreme pressure build~up in the
system.
The tube 178 is held in place within the conduit
174 and a fluid seal is effected therebetween through
the use of a seal 188, such as a rubber gasket, which
is disposed between the exterior portion of the tube
178 and the open end of the conduit 174. A washer 190
is placed over the seal 188 and a support bracket 192
contacts the washer l90 to urge the gasket 188 into
sealing engagement with the open end of the conduit
174. Bracket 192 is secured to the wall 176 by the use
of bolts 194 and 196 which are received in expanding
plugs 198 and 200 set in the wall 176.
Referring now to Fig. 6, a chute indicated _'
generally by the reference numeral 202 is particularly
well suited for use in situations where the open end of
; ~ a conduit 204 extends outwardly from a wall and is
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~266~39
22
freely accessible. In this situation, a collar 206 is
cemented or otherwise secured to the end of the conduit
204 and formed with an internally threaded opening 208 ~.
to which chute 202 is secured. Specifically, the chute
202 is formed from a tube 210 having external threads
at both ends thereof for attachment of one end of the
tube to the collar 206 and the other end of the tube to
a cap 212. Cap 212 includes an airtight cable guide
214 which permits movement of the cable 154 into the
conduit 204 without loss of compressed air. Chute 202
is also formed with an air~.inlet connector 216 which
receives the conduit extension tube 152 and permits
compressed air to enter the conduit 204. The chute 202
also includes an air-pressure escapt valve 218 which
serves as a safety feature by preventing extreme
pressure build~up in the system.
Use of either of the chutes 172 or 202, requires
that the chute be secured to the conduit as described ::
above, Respective caps~180 and 214 are then screwed
off and the cable 154 (without the birdie 12 attached
thereto) is threaded through respective guides 182 and ~ .
216.~ The birdie 12 may then be connected to the cable
: 154 and placed in the open end of respective tub~es 178
"_
and 210. The birdie 12 should be pushed past the ~ :
~25 respective airPinlet connectors 184 and 216 by use of a
suitable rod, and may even be pushed into respectlve
conduits 174 and 204. Once the birdie is approprl~ately
: ~ :
r ~ :
~266~3~
23
situated within either respective tubes 174 or 204 or
respective conduits 174 or 204, respective caps 180 and
214 are replaced and the cable~pulling system may then
be operated in the same manner as described for unit 10
to move the birdie 12 through either conduit 174 or
204, pulling the cable 154 therethrough. the chutes
172 and 202 may be removed from the end of the conduit
152 during the re-winding of the cable 154 and the
pulling of wiring back through the conduit 152.
As will be readily apparent to those skilled in
the art, the invention may be used in other specific
forms or for other purposes without departing from its
spirit or central characteristics. The present
embodiments are therefore to be considered as
illustrative and not restrictive, the scope of the
invention being indicated by the claims rather than by
the foregoing description, and all embodiments which
come within the range of equivalence of the claims are
intended to be embraced.
