A cutting/expanding tool includes a cylindrical support body having a guide side and a cutting side, a pair of guide rollers mounted in tandem along the longitudinal axis of the support body on the guide side, a cutting wheel mounted between the tandem guide rollers on the cutting side of the support body, and an expander connected rearwardly of the support body. A plurality of cutting wheels may also be provided, each of progressively increasing diameter. A scoring wheel may be mounted forwardly of the cutting wheels to prescore the surface to be cut, so as to facilitate the cutting action, and a deburrer may be mounted rearwardly of all the cutting wheels so as to smooth the cut edge. A method of using the cutting/expanding tool is also described, whereby after the tool has been propelled through a buried main to cut and to expand it, a replacement main is drawn back through the existing main.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a cutting/expanding tool that permits the 
in-place replacement of an existing main by inserting the 
cutting/expanding tool into the main so as to cut the main and expand it, 
thereby permitting a replacement main to be drawn through the existing 
main. 
2. Description of the Related Art 
When it becomes necessary to replace an existing main, for example a gas 
service main and particularly a buried gas main, it is often desirable to 
leave the existing main in place and to use is as a guide for the 
replacement main. In the particular case of a buried main, the location of 
the main, for example under a sidewalk or a street, often makes excavation 
costs prohibitive. Moreover, even if excavation is undertaken, the cost to 
restore the surface of the ground, for example by repaving, often 
contributes substantially to the overall cost of repairing the main. 
Various techniques have therefore been proposed to permit the replacement 
on an existing main without the need for excavating the entire length of 
the main or otherwise disturbing the surface of the ground. According to 
these techniques, the ground at two ends of the existing main is excavated 
to expose those ends. A tool is inserted into the buried main to cut and 
to expand the main in place. A replacement main is drawn through the 
expanded main, leaving the old main in place in the ground. 
U.S. Pat. No. 3,181,302 to Lindsay shows such a tool. As shown in FIGS. 9 
through 11 therein, the tool includes a pipe cutter that pulls a spreader 
assembly. The pipe cutter is formed by two half cylinders which are 
retained in spaced relationship and which support a plurality of cutter 
disks. The disks alternately project upwardly and downwardly from the 
surface of the cylinder halves. With this structure, as the pipe cutter is 
drawn through an existing main, it progressively cuts the main in half 
whereupon the spreader assembly spreads the halves to permit a replacement 
main to be drawn back through the existing main's halves. 
A disadvantage of the cutter/expander tool shown by Lindsay is that it is 
prone to rotational motion which causes unpredictability in the cut. The 
rotational motion is so large that Lindsay provides a rotating bearing to 
accommodate the motion. Moreover, the Lindsay tool cuts the existing main 
into two halves, and separates the two halves with its spreader. With no 
support at the separation between the halves, the soil surrounding the 
existing main easily falls into the cavity left by the cutter/expander 
tool. This soil blocks efforts to insert a replacement main into the 
existing main. 
It has also been considered to use a cutter/expander tool in the form 
illustrated in FIG. 26. As shown there, the tool includes an expander bulb 
1 in the form of an eccentric, generally conical bulb. On the expanding 
side 2, a shearing blade 4 is mounted through suitable means such as bolts 
5. The shearing blade 4 is located at a diameter on the eccentric expander 
bulb which corresponds to the diameter of existing main 11. Means 6 are 
provided on the expander to push or pull (not shown) the tool through the 
main 11. 
Use of the cutter/expander of FIG. 26 has not been found to be 
satisfactory. First, like the cutter/expander of Lindsay, it is not 
possible to control rotation of the tool. Thus, even though the FIG. 26 
tool is inserted into the main with shearing blade 4 down, it may 
eventually rotate to a shearing blade-up position, thereby allowing 
surrounding soil to fall into the existing main and block the insertion of 
a replacement main. Second, the force required to overcome friction and to 
create a cutting force while propelling the tool through the existing main 
is so great as to force the existing main out of the ground. Usually, the 
existing main is forced out of the ground into the excavation ditch at the 
exit end of the tool. Sometimes, however, when the tool binds within the 
existing main, the existing main buckles up through the ground at its 
midpoint, thereby defeating the entire purpose of using the tool. 
Finally, the tool of FIG. 26 is ill-equipped to cut through many different 
couplings and repair points often found on existing mains. As shown, for 
example, in FIG. 1, main 11 can include a significant number of couplings 
and joints along its length. For example, a stainless steel repair sleeve 
12 may have been bolted around the main to repair a leak in the main. The 
main may also include a strap-on T coupling 14 which permits services 15 
to be added at any point along the main. Additionally, to connect separate 
lengths of main together, threaded couplings 17 or compression couplings 
19, may have been used. Such couplings present problems to conventional 
cutting/expanding tools. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to overcome the disadvantages 
found in conventional cutting/expanding tools. 
It is a further object of the present invention to provide a 
cutting/expanding tool which reduces the propensity of the tool to rotate 
within the existing main. 
It is a further object of the present invention to provide a 
cutting/expanding tool which is capable of cutting through various 
couplings and other paraphernalia associated with existing mains. 
It is a further object of the present invention to provide a 
cutting/expanding tool which is capable of cutting an existing main and 
expanding it in place in such a way that the forms a roofed tunnel which 
prevents surrounding soil from falling into the main and thereby 
facilitates the insertion of a replacement main. 
It is a further object of the present invention to provide a 
cutting/expanding tool which operates so as to reduce the force which is 
necessary to propel the tool through the existing main, thereby to ensure 
that the main remains in place during the cutting/expanding process. 
In one aspect of the invention, these objects are achieved through the 
provision of a cutting/expanding tool having a support body with a guide 
side and a cutting side, an expander connected rearwardly of the support 
body, a pair of tandem guide rollers mounted for rotational movement on 
the guide side, and a cutting wheel mounted for rotational motion on the 
cutting side. A scoring wheel may be mounted forwardly of the cutting 
wheel to score the inner surface of the existing main prior to cutting by 
the cutting wheel, thereby to ease the cutting process. The 
rearwardly-connected expander may be shaped in a generally eccentric 
frustro-conical form with the eccentric expanding portions projecting 
toward the cutting side. 
In another aspect of the invention, these objects are achieved by the 
provision of a splitting/expanding method that includes the steps of 
guiding a cutting/expanding tool through a main, the cutting/expanding 
tool having a pair of tandem guide rollers and at least one cutting wheel 
opposed to the guide rollers, scoring the inner surface of the main with 
the guide rollers whereby the guide rollers track through the main 
preventing substantial rotation of the tool, cutting the main with the 
cutting wheel, and expanding the main along the scoring. Preferably, the 
main is replaced by drawing a replacement main through the expanded main, 
the replacement being connected rearwardly of a second, generally 
frustro-conical expander whose largest diameter is larger than the 
diameter through which the existing main has already been expanded in the 
expanding step. 
This brief summary of the invention has been provided so that the nature of 
the invention may be understood quickly. A more complete understanding of 
the invention may be obtained by reference to the following detailed 
description of the preferred embodiment and the accompanying drawings, 
which together form a complete part of this specification.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIG. 2, the cutting/expanding tool includes an elongated, 
generally rod-like support member 11. A screw-eye 12 is bolted to the 
forward end of the support rod to provide means for dragging the tool 
through an existing main. A threaded coupling 14 is provided at the rear 
end of the support rod to permit coupling to expander 15 as will be 
described below. 
The outer diameter of the support rod 11 is chosen in consideration of the 
inner diameter of the existing main. That is, the outer diameter of the 
support rod should be slightly smaller than the inner diameter of the 
existing main. This permits clearance between the two and accommodates 
variations in the inner diameter of the main caused, for example, by 
corrosion, minor bends, etc. 
The length of the support rod 11 is chosen in consideration of the room 
needed to mount the assemblies described below, and further in 
consideration of the leverage needed by expander 15 to expand the cut 
main. That is, the distance between the most rearward cutting wheel 32 and 
expander 15 should be sufficient to allow expander 15 to expand the out 
main with a gradual pitch rather than requiring the expander to expand the 
cut main with a steep pitch. 
A series of generally rectangular cutouts or wells 17 are provided along 
the upper or guide surface of the support rod 11. In each cutout, a guide 
roller 16 is journalled on axis 19 for rotational movement within the 
wells 17. As shown in FIG. 3, the guide roller are spaced one behind the 
other in tandem relationship along the longitudinal axis of support rod 
11. 
A channel 20 is cut at the base of each of wells 17. The channel prevents 
any debris which falls into the well from interfering with the rotation of 
guide rollers 16. That is, debris falling into the well will, for the most 
part, also fall through channel 20. 
A series of wells are also cut into support rod 11 on the surface of the 
rod that is opposed to the guide surface. This surface will hereinafter be 
called the cutting surface. As shown in FIG. 2, each of the wells with the 
exception of the last is progressively larger from the forward end of the 
support rod and extending rearwardly thereof, and each accommodates a 
progressively larger wheel. In particular, the forward end of support rod 
11 includes a first well 21 having a scoring wheel 22 journalled for 
rotational motion around axle 24. The diameter of scoring wheel 22 is 
selected so that it protrudes from the cutting surface of support rod 11 
by a distance which is not sufficient to cut completely through the 
existing main. That is, scoring wheel 22 is designed simply to score the 
inner surface of the existing main and to facilitate later cutting by the 
remaining cutting wheels. 
A first cutter wheel 25 is journalled for rotational movement around axle 
27 within well 26. The cutter wheel 25 and well 26 are arranged rearwardly 
of scoring wheel 22. Preferably, first cutter wheel 25 is also mounted 
rearwardly of the forward most guide roller 16 and forwardly of the 
second, although this is not essential. 
The diameter of first cutter wheel 25 is selected so that it cuts 
completely through the wall of the existing main. In particular, as shown 
in FIG. 2, the diameter of first cutter 25 is larger than that of scoring 
wheel 22. 
A second cutter wheel 29 is mounted rearwardly of the first cutter wheel in 
a similar arrangement around shaft 30 and in well 31. As shown, second 
cutter wheel 29 is of increased diameter with respect to first cutter 
wheel 25 and facilitates cutting larger diameter fittings, for example, 
stainless steel repair sleeve 12 (FIG. 1). 
Third cutter wheel 32 is arranged rearwardly of second cutter wheel 29 and 
journalled for rotational movement around axle 34 within well 35. The 
diameter of third cutter wheel 32 is larger than that of second cutter 
wheel 29, and permits cutting through even larger diameter pieces, such as 
couplers 17 and 19 (FIG. 1). In this case, the diameter of the cutter 
wheel is such that well 35 extends completely through support rod 11. If 
support rod 11 had been adapted for use with a larger main and its 
diameter therefore had been larger, this might not have been required. 
Preferably, third cutter wheel 32 and its associated well is mounted behind 
the second forwardmost guide roller 16. 
Finally, at the most rearward end of support rod 11, a deburrer in the form 
of a deburring wheel 36 is mounted for rotational movement around axis 37 
in well 39. The deburrer is arranged to remove sharp edges from the cut 
edge of the main, thereby to ensure that damage to the replacement main is 
minimized as the replacement main is drawn into the existing main. 
At the most rearward end of support rod 11, threaded coupling 14 is screwed 
into corresponding threaded sleeve 40. Lock screws 41, arranged around the 
periphery of sleeve 40, prevent loosening of this connection. 
A threaded coupling 42, mounted at the most forward end of expander 15, is 
also inserted into sleeve 40, and is held in place there by corresponding 
lock screws 43. 
As shown in FIGS. 2 and 3, expander 15 is a generally solid mass having an 
eccentric frustro-conical shape. The top edge of the expander, 
corresponding to the guide surface of support rod 11, extends 
substantially straight back to the rearward edge of the expander. 
Accordingly, when inserted into a main, this surface simply bears against 
the inner surface of the main. 
On the other hand, the lower surface 44 of the expander, corresponding to 
the cutting surface of rod 11, is inclined downward and is adapted to 
expand the cut main along its cut edge. 
The most rearward portion of the expander 15 is provided with a threaded 
coupling 47 which is adapted to receive means for propelling the 
cutting/expanding tool 10 through the main. 
Each of the foregoing parts is preferably made of material harder than the 
material that it is adapted to cut and to expand. In the preferred 
embodiment, the support rod 11 and each of the guide, scoring, deburring 
and cutter wheels are steel, case hardened to between Rockwell C55 and 
C60. 
FIGS. 4 and 5 show the cutting/expanding tool 10 in use in an existing 
main. As shown in FIG. 4, excavations 50 and 51 have been made at 
respective ends of main 11. A hydraulic propulsion unit designated 
generally at 52 is erected within excavation 51 and is provided with, 
among other things, support plates 53 and 54 against which the hydraulic 
propulsion unit presses. As shown in FIG. 4, sleeve 48 (similar in 
construction to sleeve 40) couples cutting/expanding tool 10 to a rod 49 
which extends back to excavation 51 and which is propelled by hydraulic 
propulsion unit 52. 
While FIG. 4 shows that the cutting/expanding tool is pushed through main 
11, it is also possible to pull the cutting/expanding tool by means of 
screw eye 12. Pulling the cutting/expanding tool is advantageous in that 
it permits the tool to be used in connection with mains which have small 
radius turns. On the other hand, pushing the tool is advantageous in the 
event that gas main 11 moves during the cutting/expanding process into 
excavation 50. In that event, the exposed portion of the main would 
interfere with pulling the tool through the tool, and it would be 
necessary temporarily to stop the cutting/expanding process to remove the 
newly-exposed portion of main 11. On the other hand, if the tool were 
pushed through the main, the newly-exposed portion of the main would not 
interfere at all. 
FIG. 5 is an expanded view of the cutting process. As shown there, each of 
the wheels is configured to perform certain specific functions; these 
configurations are shown in detail in the cross-sectional views of FIGS. 6 
through 13a and 13b. 
The guide rollers are shown in the cross section of FIG. 7. As shown there, 
the first guide roller is configured not to cut through the main, but only 
to form a groove 55 in the inner, upper surface of the main. Trailing 
guide rollers will track in groove 55, and in conjunction with the tandem 
arrangement of the guide rollers will prevent the tool from rotating 
within the main. 
To achieve this, each of the guide rollers 16 is formed with a broad peak 
56. Because of this broad peak, the guide roller is not able to cut 
through the main, and only forms groove 55 as shown in FIG. 5. 
If desired, one or more of the guide rollers may be formed with a cusp 57 
as shown in FIG. 13a. The cusp 57 permits the guide rollers to track more 
faithfully in groove 55, and improves the non-rotational stability of the 
tool. In this regard, it may be desirable to use the guide roller 
configurations shown in FIGS. 7 and 13 in combination. For example, the 
forwardmost guide roller 16 might be configured as shown in FIG. 7 
initially to form groove 55; the trailing guide rollers could then be 
formed as shown in FIG. 13a to assist these latter guide rollers to track 
in groove 55. 
If desired, one of the guide rollers can also include perforating spokes to 
form perforations in the guide groove, thereby to permit any residual 
natural gas or other gaseous ground contents that might be trapped in the 
cut main to escape rather than being stored inside the cut main. A 
suitable perforating guide roller is shown in FIG. 13b. 
FIG. 6 is a cross section of scoring wheel 22. As shown there, the scoring 
wheel includes a cutting edge 60 which enables the scoring wheel to form a 
score 61 as shown in FIG. 5. As described above, however, the diameter of 
the scoring wheel 22 is selected so that score 61 does not extend 
completely through main 11, but only facilitates later cutting by wheels 
25, 29 and 32. 
FIG. 8 is a cross-sectional view of cutter wheel 25. As shown in FIG. 8, 
cutter wheel 25 includes cutting edge 62 and is of sufficient diameter to 
cut completely through main 11. 
FIG. 9 is a cross-sectional view of cutter wheel 29. As shown in FIG. 9, 
cutter wheel 29 includes cutter edge 64 and is of a diameter sufficient to 
extend not only through main 11 but also through additional paraphernalia 
normally found in connection with main 11, such as repair sleeve 12. 
FIG. 10 is a cross-sectional view of cutter wheel 32. As shown in FIG. 10, 
cutter wheel 32 includes cutter edge 65 and is of a diameter sufficient 
not only to cut through main 11 but also to cut through even larger 
diameter paraphernalia found in connection with main 11, such as coupling 
19. 
FIG. 11 is a cross-sectional view of deburring wheel 36. As shown in FIG. 
11, the deburring wheel includes a projection 66 which is adapted to ride 
in the cut 68 in main 11 and to smooth the edges 67 of that cut. This 
smooths the inner edge of the cut, the edge along which the replacement 
main will be drawn, and minimizes damage to the replacement main. 
FIG. 14 shows a perspective view of the expander 15 as it expands the cut 
main 11. As shown there, expanding surface 54 of expander 15 forces the 
cut main downwardly and outwardly. Because of the distance between final 
cutting wheel 32 and expander 15, the main is forced outwardly and 
downwardly with a gradual pitch, thereby lessening the force required to 
expand the main. As shown in cross section in FIG. 12, during the 
expanding, the main is also hinged around groove 55 that was formed by 
guide rollers 16. This hinging action also lessens the force required by 
the expander to expand main 11. 
Because the cutting wheels are located on the lower, cutting surface of 
support rod 11, and because the tandem guide rollers track to prevent 
substantial rotation of the tool, the main is cut at bottom thereof. After 
the expander expands the main, the main acts as a roof to prevent soil 
from falling into the tunnel left by the cutting/expanding tool. Because 
of this roofed tunnel, surrounding soil does not fall and block or 
otherwise impede replacement of the main with replacement main. 
Returning to FIG. 4, hydraulic propulsion unit 52 propels cutter 10 through 
main 11 until it reaches excavation 50. At that point, tool 10 is removed 
from the end of the propulsion rod in preparation for drawing the 
replacement back through the roofed tunnel formed by the existing main. 
FIGS. 15 through 18 are views for explaining this. As shown in FIG. 18, a 
coupler assembly 70 is formed from a solid coupler 71 and a solid shaft 73 
threaded at the end thereof. The coupler 71 is beveled its exposed end and 
includes a pair of through-holes 74 offset perpendicularly from one 
another. Threaded shaft 73 is adapted to be inserted through hole 72 in 
second expander 75. The second expander is shaped in a generally 
frustro-conical form with the aforementioned hole 72 extending 
therethrough and with a recessed portion 76 whose inner diameter is 
designed to accommodate the outer diameter of the replacement main. 
The length of shaft 73 is selected so that when shoulder 73a of the coupler 
assembly bears against the base 76a of recess 76, the threaded portion 
extends out of second expander 75 sufficiently to be engaged with coupler 
sleeve 48. Coupler sleeve 48 is similar to coupler sleeve 40 and is 
provided with pairs of lock bolts around the periphery thereof. The 
threaded rod 73 and coupler sleeve 48 are threaded together and the lock 
bolts are set. 
FIG. 15 to 17 are views for explaining the preparation of replacement main 
80 for connection to coupler assembly 70. As shown in FIG. 15, replacement 
main 80 is inserted into die 48. the die is provided with two pairs of 
throughgoing holes patterned the same as throughgoing holes 74 on coupler 
70. Additionally, die 48 is provided with a pair of spaced, mutually 
perpendicular lock bolts and associated threaded holes. 
As shown in FIG. 16, replacement main 80 is inserted into die 48 and the 
lock bolts are tightened. By drilling through both pairs of throughgoing 
holes, the replacement main is provided with two pairs of throughgoing 
holes 81 that correspond to holes 74 in coupler 70, as shown in FIG. 17. 
As shown in FIG. 19, replacement main 80 is then slipped over coupler 71, 
and bolts 83 are inserted through the through-holes to secure the 
replacement main in place (FIG. 22). 
As shown in FIGS. 20 and 21, the replacement main is then drawn back 
through the roofed tunnel provided by the previously cut and expanded 
existing main. Specifically, as shown in detail in FIG. 22, the second 
expander ensures that there is sufficient clearance for the replacement to 
be drawn through the roofed tunnel without obstruction. In particular, as 
shown in cross section in FIG. 23, existing main 11 is spread by second 
spreader 75 to the extent that replacement main 80 is easily drawn 
therethrough. 
In FIGS. 19 through 23, the process of drawing the replacement main back 
through the existing main has been shown as if it were conducted by 
pulling on hydraulic pusher rod 49. This, of course, is not essential. As 
shown in FIG. 24, it is also possible to feed a cable through the existing 
main and to secure a screw eye assembly to coupler sleeve 48, thereby to 
draw the replacement main back through the existing main 11 with the 
cable. 
FIG. 25 shows the replacement main in place within the existing main. At 
this point, additional excavations can be made, if necessary, to provide 
service access, for example, the access shown at 14 in FIG. 1. 
Those skilled in the art will recognize that modifications to the foregoing 
embodiment may be made without departing from the spirit of the present 
invention. Under certain cutting circumstances, for example, it may be 
possible to dispense with cutting blade 4 and to provide the FIG. 26 tool 
with appropriate tandem guide rollers and cutter wheels. Accordingly, the 
foregoing description should not be construed as limiting the scope of the 
invention, which instead should be measured by reference to the following 
claims.