U.S. patent application number 17/397412 was filed with the patent office on 2021-11-25 for pipe extraction assisted by pre-stressed strand.
The applicant listed for this patent is The Charles Machine Works, Inc.. Invention is credited to Robert F. Crane, Mark D. Randa, Steven W. Wentworth.
Application Number | 20210364102 17/397412 |
Document ID | / |
Family ID | 1000005764701 |
Filed Date | 2021-11-25 |
United States Patent
Application |
20210364102 |
Kind Code |
A1 |
Crane; Robert F. ; et
al. |
November 25, 2021 |
Pipe Extraction Assisted By Pre-Stressed Strand
Abstract
A machine for extracting a ductile pipe. The machine has a vise
which can grip the pipe, and a wire clamp. Each of the wire clamp
and vise are supported on a carriage which is movable relative to a
frame. This enables the vise to grip and pull the ductile pipe.
Additionally, a wire strand may be disposed through the pipe from a
far end to the end at which the machine is placed. The wire clamp
allows the machine to pre-stress the strand to improve the
extraction of the ductile pipe.
Inventors: |
Crane; Robert F.; (Nekoosa,
WI) ; Randa; Mark D.; (Oconomowoc, WI) ;
Wentworth; Steven W.; (Scottsdale, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Charles Machine Works, Inc. |
Perry |
OK |
US |
|
|
Family ID: |
1000005764701 |
Appl. No.: |
17/397412 |
Filed: |
August 9, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16866720 |
May 5, 2020 |
11112033 |
|
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17397412 |
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62843878 |
May 6, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16L 1/06 20130101; F16L
55/18 20130101; B66D 3/006 20130101; F16L 1/028 20130101 |
International
Class: |
F16L 1/028 20060101
F16L001/028; B66D 3/00 20060101 B66D003/00; F16L 1/06 20060101
F16L001/06; F16L 55/18 20060101 F16L055/18 |
Claims
1. A method comprising: disposing a wire strand through an existing
pipe, the existing pipe having first and second ends and an
underground section disposed between the first and second ends;
securing the wire strand to a pipe puller at the second end of the
existing pipe; gripping the wire strand with a first wire clamp at
the first end of the existing pipe; while the first wire clamp is
gripping the wire strand, moving the first wire clamp away from the
first end of the existing pipe; after the step of moving the first
wire clamp away from the first end of the existing pipe, securing
the wire strand with a second wire clamp; thereafter, releasing the
grip of the first wire clamp and moving the first wire clamp toward
the first end of the existing pipe; thereafter, gripping the wire
strand with the first wire clamp; and thereafter, moving the
carriage away from the first end of the existing pipe with the wire
strand gripped by the first wire clamp.
2. The method of claim 1, further comprising: subsequently, while
continuing to grip the wire strand with the first wire clamp
gripping the existing pipe with a pipe clamp; and pulling the pipe
with the pipe clamp and the first wire clamp.
3. The method of claim 2 wherein the first wire clamp and pipe
clamp are supported on a carriage, and wherein: the step of pulling
the pipe comprises extending a cylinder to translate the
carriage.
4. The method of claim 2 wherein the first wire clamp comprises
three jaws having a central passage disposed between the three
jaws, and wherein: the step of gripping the wire strand with the
first wire clamp comprises reducing a space between the jaws.
5. A method comprising: disposing a wire through an existing pipe,
the existing pipe having first and second ends and an underground
section disposed between the first and second ends, wherein a first
direction is defined as being from the second end toward the first
end; anchoring the wire to the existing pipe at the second end;
thereafter, pulling the wire in the first direction from the first
end without moving the pipe, thereby stretching the wire; and
thereafter, while maintaining the wire in tension, pulling the
existing pipe and the wire in the first direction from the first
end.
6. The method of claim 5 in which the step of pulling the wire from
the first end comprises: with a first wire clamp, pulling the wire
in the first direction; thereafter, with a second wire clamp,
gripping the wire and holding it in place; and thereafter,
releasing the wire with the first wire clamp.
7. The method of claim 6 further comprising: after releasing the
wire with the first clamp, moving the first wire clamp in a
direction opposite the first direction; and thereafter, pulling the
wire in the first direction prior to the step of pulling the pipe
and the wire in the first direction from the first end.
8. The method of claim 5 in which the step of pulling the existing
pipe and the wire in the first direction from the first end
comprises: gripping the wire with a first wire clamp; gripping the
pipe with a pipe vise; and thereafter, while the wire and the pipe
are gripped, extending an actuator to move the first wire clamp and
the pipe vise in the first direction.
9. The method of claim 8, wherein the pipe vise and first wire
clamp are supported on a carriage.
10. The method of claim 8 in which the step of pulling the wire in
the first direction from the first end without pulling the pipe
comprises: with a first wire clamp, pulling the wire in the first
direction; with a second wire clamp, gripping the wire and holding
it in place; and thereafter, releasing the wire with the first wire
clamp.
11. The method of claim 10 in which the pipe vise and first wire
clamp are supported on a carriage, and the carriage is supported on
a stationary support structure.
12. The method of claim 11 in which at least a portion of the
support structure is interposed between the carriage and the second
wire clamp.
13. The method of claim 5 further comprising: securing a
replacement pipe to the second end of the existing pipe; and
thereafter, extracting the existing pipe and thereby installing the
replacement pipe along substantially the same path previously
defined by the existing pipe prior to its extraction.
14. A method of tensioning a wire prior to extraction of a pipe,
comprising: placing a wire within a pipe, the pipe having a first
end and a second end; at the second end, securing the wire to the
pipe; at the first end, pulling the wire without moving the pipe
until the wire is at a desired tension, wherein the desired tension
is less than the force required to overcome an adhering bond
between the pipe and an underground environment.
15. The method of claim 14 in which the step of pulling the wire
comprises: gripping the wire with a first wire clamp; while
gripping the wire, pulling the first wire clamp without moving the
pipe; thereafter, gripping the wire with a second wire clamp; and
thereafter, releasing the wire with the first wire clamp.
16. The method of claim 15 further comprising: thereafter, moving
the first wire clamp toward the first end of the pipe; thereafter,
gripping the wire with the first wire clamp; and thereafter,
pulling the first wire clamp without moving the pipe.
17. The method of claim 15 wherein the step of gripping the wire
comprises: moving a plurality of jaws toward the wire rope such
that a space between the plurality of jaws is smaller than the
diameter of the wire rope.
18. The method of claim 15 further comprising: providing a pipe
pulling apparatus, the pipe pulling apparatus comprising: a
stationary frame; a carriage movable relative to the stationary
frame; a first wire clamp supported on the carriage; and a second
wire clamp configured for support on the stationary frame; wherein
the step of pulling the wire is performed by the pipe pulling
apparatus.
19. The method of claim 18, further comprising: gripping the wire
with the first wire clamp; with the carriage, pulling the first
wire clamp away from the pipe; supporting the second wire clamp on
the stationary frame such that the second wire clamp is not
permitted to move toward the pipe; gripping the wire with the
second wire clamp; and thereafter, releasing the wire with the
first wire clamp.
20. The method of claim 19 in which the second wire is permitted to
move away from the pipe when supported on the stationary frame.
Description
BACKGROUND
[0001] When small diameter pipes need replacement due to a need for
capacity increase or because of a lack of pipe integrity,
open-trench methods are often used. Apparatus for direct
replacement without trenches are growing, as disclosed in U.S. Pat.
Nos. 7,128,499 and 10,584,807, both issued to Wentworth, and both
of which are fully incorporated by reference herein.
[0002] Direct extraction and replacement of a host pipe offers two
major benefits for both the owner of the pipeline and the public.
Firstly, the method places the new pipe on the exact path of the
existing host pipeline thereby staying within the pipeline
right-of-way as required, as well as increasing the likelihood of
avoiding damage to adjacent closely spaced utilities that may be
parallel in path or cross the path of the host pipe.
[0003] There are two known ways to extract small diameter pipes.
First, one may use the tensile strength of the existing pipe alone
to break the shear strength between the pipe's outer wall and the
surrounding soil, thereby allowing said pipe extraction by pulling
from one end of the pipe. Alternatively, a strand, such as a high
strength wire rope, may be passed through the inside diameter of
the pipe with an obstruction, or "pipe puller" at the far end. When
the strand is pulled from the opposite end, the pipe may be removed
due to the tension supplied by the strand. A combination of these
methods may also be used.
[0004] Both methods complete the installation by pulling a
replacement pipe into the volume previously occupied by the host
pipe; either by attaching the replacement pipe to the tail end of
the host pipe or the tail end of the strand, or by making a second
pull using an additional length of strand to pull on after the host
pipe has been removed from the bore.
[0005] Pulling the pipe depends solely on pipe tensile strength. As
a result, the magnitude of the force that can be applied to extract
the pipe is limited exactly to the host pipe tensile strength. Each
added foot of host pipe length added to the extraction length adds
to the force required to break the shear bond from pipe to soil
which limits the lengths of the extraction that can be
achieved.
[0006] For this reason, a wire rope may be used in some
applications. The strength of the strand adds to the length of pipe
that can be extracted. Even with the improved distance the strand
achieves, it may be advantageous to increase the length of pipe
that can be extracted yet more.
[0007] The maximum magnitude of extraction force occurs during the
initial pulling cycle, when the pipe outer wall is still adhered to
the surrounding soil. Once this adhering bond and its associated
static friction has been broken, the extraction or pulling force
drops considerably, in the range of 50 to 75%. It is during this
initial pulling cycle that the pipes manufactured from low strength
materials such as lead are most likely to fail before the pipe/soil
bond has broken. If the pipe is used without a strand, a broken
pipe will cause the extraction to be unsuccessful. Thus, the strand
enhances the pipe extraction operation, especially during this
initial pulling cycle.
[0008] Pipes manufactured from lower strength materials such as
lead may have tensile strength of less than 1/2 of a ton. Steel
wire rope in a 5/16'' diameter can have a tensile strength as great
as 7 tons. High strength strands can add a substantial extraction
force, especially with low strength or small diameter pipes.
[0009] While the steel pipe does not elastically stretch a
significant amount after long term placement, wound wire rope
strands do stretch. When the two components are loaded in parallel
in a tensile manner, the differences in the stretch rates affect
the magnitude of the load achieved during extraction.
[0010] The success or failure of the extraction process is largely
a function of the tensile or extraction forces that can be applied
to the host pipe. Thus, it is desirable to increase the available
extraction force to enable extraction of low strength pipe.
SUMMARY
[0011] In one aspect, the invention is directed to a pipe
extraction machine. The pipe extraction machine comprises a frame,
a carriage, an actuator, a wire clamp, and a pipe cutter. The
carriage is movable along the frame. The carriage comprises a vise.
The vise comprises a pair of jaws configured to engage a ductile
pipe having a strand extending therethrough. The actuator is
connected to the frame and the carriage or moving the vise along
the frame between first and second positions. The wire clamp is
supported on the carriage and has a plurality of wire jaws. The
wire jaws are disposed about a central opening and configured to
selectively engage a strand.
[0012] In another aspect, the invention is directed to a pipe
extraction machine. The pipe extraction machine comprises a frame,
a carriage and an actuator. The carriage comprises a pipe vise and
a wire clamp. The pipe vise and wire clamp define an axis disposed
therethrough. The actuator moves the carriage along the frame. The
pipe vise and the wire clamp are each configured to selectively and
individually grip a system defining a pipe with an internally
disposed wire.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a diagrammatic representation of a pre-stressing
operation. A strand is placed in an existing pipe. Two clamps are
disposed about the strand. The machine which pulls the pipe and the
strand is removed. In FIG. 1A, the clamps are shown prior to a
wire-stressing stroke.
[0014] FIG. 1B is a diagrammatic representation of the
pre-stressing operation of FIG. 1A. In FIG. 1B, the clamps are
shown after a wire-stressing stroke.
[0015] FIG. 2 is a side plan view of a strand clamp assembly for
use in the operation of FIGS. 1A-1B.
[0016] FIG. 3 is a sectional view of the clamp assembly of FIG. 2
along section line A-A.
[0017] FIG. 4 is an exploded perspective view of the clamp assembly
of FIG. 2.
[0018] FIG. 5 is a top view of a pipe pulling assembly having a
movable carriage within a support frame.
[0019] FIG. 6 is a left side view of the pipe pulling assembly of
FIG. 5.
[0020] FIG. 7 is a back view of the pipe pulling assembly of FIG.
5, with an opening for accepting a pipe and strand visible.
[0021] FIG. 8 is a rear right top perspective view of the pipe
pulling assembly of FIGS. 5-7.
[0022] FIG. 9 is a cutaway side view of the pipe pulling assembly
of FIG. 5, engaged in a wire-stressing operation. In FIG. 9, a wire
is secured in a first wire clamp in a first position.
[0023] FIG. 10 shows the view of FIG. 9, with the carriage advanced
such that the strand has been pulled to the right. A second wire
clamp is held in place by the support frame.
[0024] FIG. 11 shows the view of FIG. 9, with the first wire clamp
moved back for a second stroke, and a pipe clamp surrounding a
pipe. The strand is held in tension by the second wire clamp.
[0025] FIG. 12 shows the view of FIG. 9, with the carriage advanced
such that the pipe and the strand have been pulled to the right.
The second wire clamp is released by the support frame to maintain
tension on the strand.
[0026] FIG. 13 shows a first embodiment of a product pipe puller
apparatus.
[0027] FIG. 14 is a sectional view of the pipe puller apparatus of
FIG. 13 along line C-C.
[0028] FIG. 15 is a second embodiment of a pipe puller
apparatus.
[0029] FIG. 16 is a sectional view of the pipe puller apparatus of
FIG. 15 along line D-D.
DETAILED DESCRIPTION
[0030] With reference now to FIGS. 1A and 1B, a system 10 which
enables the extraction of a pipe is shown. The system 10 will be
disposed at two sides of a buried underground pipe 11. The pipe 11
is disposed in an underground environment 200. Often, each side of
the pipe 11 will have a pit 202 excavated such that materials, such
as pipe extractor 100 (FIGS. 5-8) and other tooling, may be
properly placed. Alternatively, one or both exit points may be
within a basement, or at the surface of the ground.
[0031] The system 10 comprises a buried pipe 11 with first end 11A
and second end 11B. A strand 16, such as a wire rope, is disposed
inside of the pipe 11 and extends from its first end 11A to the
second end 11B. The strand 16 is attached to a pipe puller 13 at
the first end 11A. The pipe puller 13 has a larger effective
diameter than the first end 11A of the pipe 11 and bears against
its face. The pipe puller 13 facilitates attachment between the
strand 16 and a replacement pipe 12. The replacement pipe 12 may be
made of a flexible and strong material such as high density
polyethylene (HDPE). By pulling the replacement pipe 12 as the
buried pipe 11 is extracted, the replacement pipe will closely
align with the path of the extracted, buried pipe.
[0032] The system 10 further comprises a stationary strand clamp 14
and a moving rope jaw 15. The strand clamps 14, 15 may be identical
in structure. The strand clamps 14, 15, as shown best in FIGS. 2-4,
comprise a nut collar 31, a body 32, and internal jaws 35. The nut
collar 31 is selectively positionable within the body 32. As shown,
the nut collar 31 has external threads 37 which mate with lands 38
within the body to enable the selective positioning of the nut
collar 31. The body 32 comprises an internal passage 34 which
cooperates with an internal passage 36 in the nut collar to allow
the strand 16 to pass through, as shown in FIGS. 1A-1B.
[0033] The internal jaws 35 are capable of at least two
configurations, determined by the position of the nut collar 31.
When the nut collar 31 is not fully threaded into the body 32, the
jaws are unsecured within the strand clamp 14. In this first
configuration, a strand 16 (FIGS. 1A-1B) that is disposed within
the internal passage 34 of the body, and thus the jaw aperture 39
(FIG. 4) will not be gripped by the internal jaws 35. A strand
clamp 14, 15 in this configuration can freely slide relative to an
internally-disposed strand.
[0034] When the nut collar 31 is threaded into the body 32, the
internal jaws 35 are pressed into the tapered internal surface of
the internal passage 34 of the body. This causes the jaw aperture
39 to contract, allowing the surface of each internal jaw 35 to
grip or bite an internally disposed strand 16. In this second
configuration, a strand clamp 14, 15 will not move relative to the
strand 16. The internally-disposed surface of each internal jaw 35
may have features which enhance the gripping function of the strand
clamp 14, 15 when in the second configuration, while preventing
obstruction when in the first configuration. Threads or similar
surface features are possible examples.
[0035] When the nut collar 31 is loosened or removed from the body
32, the associated strand clamp 14, 15 moves from the second
configuration to the first configuration, again allowing the strand
16 to pass freely within. The taper angle of the internal passage
34 causes the internal jaws 35 to largely be self-initiating when
moved in a direction d as shown in FIG. 3, with minimal force
required from the nut collar 31 to achieve the second
configuration.
[0036] As shown, the internal passage 34 has a portion which is
complementary to the surface of a conical frustum. Likewise, the
external surfaces of the internal jaws are substantially congruent
to the surface of a cone, such that force applied by the nut collar
31 at the larger opening of the internal passage 34 forces the jaws
35 closer together. Such movement causes the jaws to place the
strand clamp 14, 15 to be placed in the second configuration,
configured to grip an internally-disposed strand 16.
[0037] With reference again to FIGS. 1A and 1B, the system 10 is
shown in two different states. In FIG. 1A, the movable strand clamp
15 is in the second configuration, gripping the strand 16. The
stationary strand clamp 14 is in the first configuration and is not
gripping the strand. Prior to a stroke of the movable strand clamp
15, the distance between the rear face 33 of the movable strand
clamp 15 and the first end 11A of the buried pipe 11 is D.
[0038] In FIG. 1B, the movable strand clamp 15 has pulled to the
right, stretching the strand 16 by a distance S. If further strokes
are required to achieve the desired tension in the strand, the
stationary strand clamp 14 may be placed in the second
configuration to hold the strand 16 in tension. The movable strand
clamp 15 is placed in the first configuration and moved back to the
position shown in FIG. 11A. The movable strand clamp 15 is then
placed in the second configuration and the process repeated.
[0039] Using this method, the extraction force achieved in a
subsequent pulling stroke of the pipe can exceed previous methods.
With the wire rope restrained under high tensile load, achieved by
the stretching step described above, the pipe will be left under an
equivalent compressive load. The second end 11B of the pipe can be
clamped and the summation of the compressive load on the pipe and
the tensile strength of the pipe can be applied to the pipe before
either the pipe yields or the rope breaks.
[0040] This system 10 thus provides a dual load path which enhances
known methods of extracting pipe. The tension on the strand 16
should be held until the first pipe extraction stroke, as described
below, is complete and the pipe has been broken loose from the
surrounding soil. Typically, required pulling force will drop 50 to
75% after the first extraction pulling cycle, and the pipe alone
can withstand the continued (but lower) extraction forces using the
methods discussed in U.S. Pat. Nos. 7,128,499 and 10,584,807.
[0041] While the functions of pre-stressing the strand and
performing the subsequent pipe extraction may be performed by
separate apparatus, a pipe extractor 100 capable of both operations
is shown in FIGS. 5-8. The pipe extractor 100 comprises a
stationary hull or support structure 101 and a movable carriage
102. The carriage 102 is supported on the support structure 101 on
rails 105, which allow the carriage to move along a single axis
which is parallel to a central opening 108 in the pipe extractor
100.
[0042] One or more hydraulic cylinders 103 are shown for moving the
carriage 102. While cylinders 103 are shown, other linear actuators
may be used to move the carriage, such as a rack and pinion
drive.
[0043] A face 106 of the support structure 101 may preferably be
placed against the soil next to the extraction location for the
pipe 11 (FIGS. 1A-1B) and anchored there.
[0044] The carriage 102 comprises a pipe clamp or vise 116, which,
as described in the incorporated references, may include a pair of
opposed jaws having parallel faces, which are forced together in
opposite directions by a cam plate to maintain each of the first
and second jaw in a parallel arrangement, as described in U.S. Pat.
No. 10,584,807, which was previously incorporated by reference.
Alternatively, the vise 116 may have two jaws which pivot relative
to one another and are actuated together by a cylinder, as
described in U.S. Pat. No. 7,128,499.
[0045] The carriage 102 further comprises a pipe shear 104, which
may shear a length of pipe 11 and strand 16 after it has been
removed from its underground location.
[0046] With reference to FIGS. 9-12, the system 10 is shown with a
pipe extractor 100 included. In the view of FIGS. 9-12, the pipe 11
length is shortened for visibility purposes. Further, it should be
understood that the pipe 11 is under a surface of the ground 200,
as shown in FIGS. 1A-1B.
[0047] The strand 16 is disposed within the pipe 11 and connected
to a pipe puller 13. The pipe puller 13 is connected to a product
pipe 12 and bears against the first end 11A of the pipe 11. The
pipe 11 is disposed through the central opening 108 (FIG. 7) of the
pipe extractor 100.
[0048] The pipe extractor 110 further comprises a first pocket 111
attached to a rear face 109 of the support structure 101. The first
pocket 111 is adapted to support and hold the stationary strand
clamp 14 in place. The carriage 102 further comprises a second
pocket no. The second pocket 110 is configured to support and hold
the movable strand clamp 15 in place. The second pocket 110 may be
disposed within the pipe shear 104 or may be between the pipe shear
104 and the vise 116.
[0049] The strand clamps 14, 15 may be secured about the strand 16
by their respective pockets 111, 110. The clamps 14, 15 may be
threaded on to the strand 16 by placing the second pocket no,
movable strand clamp 15, second pocket in and stationary strand
clamp 14 over the end 113 of the strand, in that order. With each
element secured in place, the wire rope end 113 may be placed on a
spool (not shown) to take in slack as the pulling operation
continues.
[0050] In FIG. 9, the second end 11B of the pipe 11 is within the
vise 116 but the vise 116 is not closed. Movable pipe clamp 15 is
placed into the second configuration by tightening the nut collar
31 (FIGS. 1A-4). In FIG. 10, the cylinders 103 actuate to pull the
carriage 102, and consequently the strand 16, towards the rear face
109. The pipe 11 is not gripped and therefore remains in place.
This step may be repeated until the strand 16 is at a desired
tension. Tension is held during the return stroke by placing the
stationary strand clamp 14 in its second configuration. The movable
strand clamp 15 is placed in its first configuration, and the
cylinders 103 retract to move the carriage 102 towards the face
106.
[0051] When the desired tension in the strand is achieved, the vise
116 may be actuated about the second end 11B of the pipe 11, as
shown in FIG. 11. The movable strand clamp 15 is placed in the
second configuration. The second end 11B is clamped or crushed, and
the cylinders 103 move the carriage towards rear face 109. As shown
in FIG. 12, the pipe 11 is dislodged from its position, breaking
adhesion between the pipe 11 and the underground environment in
which it is situated. As shown, the pipe puller 13 pulls
replacement pipe 12 behind it.
[0052] During each stroke of the cylinders 103 to pull the strand
and/or the pipe 11, the stationary rope clamp 14 may be in the
first configuration, such that the strand will pass unencumbered,
or in the second configuration, such that the stationary rope clamp
14 will travel with the strand 16, as shown in FIG. 12.
[0053] If further strokes are desired with the rope in tension, the
pipe extractor 100 may be placed back in the configuration shown in
FIG. 9, with tension held by the stationary pipe clamp 14 during
the return stroke of the cylinders. As discussed above, the vise
116 alone may be suitable for subsequent steps after adhesion
between the underground environment and the pipe 11 is broken.
[0054] Optionally, at this point the pipe 11 and strand 16 may be
sheared by pipe shear 104. If the strand 16 is sheared, the pipe
puller 13 must be attached to the first end 11A of the pipe such
that the installation of the product pipe 12 can continue in
subsequent pipe-thrusting steps.
[0055] With reference to FIGS. 13-16, embodiments of the pipe
puller 13 are shown. As shown in FIGS. 1A-1B and 9-12, the pipe
puller 13 is disposed against the first end 11A of the pipe and
applies extraction load to the pipe. The puller 13 comprises a
pilot nose 26, an expander body 21, a swivel 24 and a carrot puller
23.
[0056] The pilot nose 26 may include self-tapping threads 117
(FIGS. 15-16) which facilitate attachment with the pipe 11.
Rotation may be applied to the nose 26, and thus the threads 117,
through flats 118 (FIG. 15).
[0057] The pipe puller 13 has an internally disposed channel 28
within the expander body 21 and pilot nose 26, within which cable
jaws 32 are situated. The jaws 32 are secured to the strand 16
(FIGS. 1A-1B, 9-12) by tightening nut 22, which attaches to the
internal portion of the expander body 21 with internally disposed
threads 29.
[0058] The expander body 21 is proximate the nose 26. The expander
body 21 has a tapered outer surface, so that soil is expanded away
from the bore left by host pipe 11. Expanding the borehole
facilitates installation of the replacement pipe 12.
[0059] The expander body 21 is attached to the carrot puller 23 by
a swivel joint 24. The swivel joint 24 enables the carrot puller 23
to deflect from the host pipe centerline while being installed. The
swivel joint 24 allows the pipe puller 13 to better follow the same
path as the pipe 11 as replacement pipe 12 is installed and
prevents twisting damage to the product pipe 12 as it is
installed.
[0060] The carrot puller 23 may be of any type typically used in
underground utility installation. As shown, the carrot puller 23
cuts threads with cutting features 25, 27 into the inside surface
of the product pipe 12 as it is rotated. After installation of
puller 23 into product pipe 11, swivel joint 24 may be installed
thereby attaching the product pipe 12 to the strand 16.
[0061] The replacement pipe 12 is pulled in with the pipe puller 13
as described, or a second length of strand 16 may alternatively be
pulled behind the existing pipe 11. The second length of strand may
then be used to pull a replacement pipe 12 into the now-empty path
of the pipe 11.
[0062] Changes may be made in the construction, operation and
arrangement of the various parts, elements, steps and procedures
described herein without departing from the spirit and scope of the
invention as described herein.
* * * * *