CA2364666A1

CA2364666A1 - Improved method and apparatus for cutting and splitting pipe

Info

Publication number: CA2364666A1
Application number: CA002364666A
Authority: CA
Inventors: Randall H. Collier
Original assignee: TRENCHLESS REPLACEMENT SYSTEMS CORP
Current assignee: TRENCHLESS REPLACEMENT SYSTEMS CORP
Priority date: 2001-08-02
Filing date: 2001-12-07
Publication date: 2003-02-02

Abstract

A cutting apparatus is adapted to cut corrugated metal pipe or thin walled pipe regardless of the pipe's concentricity and structural integrity as all required forces are offset internally within the cutting tool. A series of cutting wheels, stepped in stages, are mounted in an opening of a frame which fits over a portion of the pipe wall.
The frame is drawn through the pipe to allow the cutting wheels to cut a specific longitudinal portion of the pipe without relying on or touching other portions of the pipe, thus eliminating the pipe's size and total structural integrity as prereqisites for using the device on the pipe.
Slots on the wheels help rotate the wheels as the frame moves along the pipe.
A guide provides the frame with an area of contact with the pipe wall to allow the cutter apparatus to follow the pipe wall regardless of the pipe's shape. A leading edge of the frame is hardened and sharpened to shear any exterior bolts or bonding used on the pipe. A
sharpened, hardened ripper behind the cutter wheels ensures any uncut metal is severed.
For mobility, the cutter head is attached to a traveling link, connected to a pull string, which allows the head to follow along the pipe wall independently of any irregularities.
A chassis attached to the pull string is adjustable for different diameter pipes to allow for alignment of the cutter apparatus with the pipe wall. An expanding head travels behind the cutting apparatus to spread the cut pipe and make room for a new replacement pipe to be drawn through. The head may have elongate ribs to avoid crinkling of the pipe as it is being spread. One or more cutting tools may be employed to provide a corresponding number of longitudinal cuts through the pipe.

Description

TEM Docket No. 235.5 TITLE: IMPROVED METHOD AND APPARATUS FOR CUTTING AND
s SPLITTING PIPE
FIELD OF THE INVENTION
The present invention relates to a cutting, expanding, and re-piping apparatus that permits the in situ replacement of an existing corrugated metal pipe or thin walled pipe so used for culverts by cutting and expanding the host pipe to permit a re-placement pipe to be drawn through the host pipe. More specifically, the invention is directed for use on corrugated metal piping or thin-wall piping used for culverts under roads where the culvert has deteriorated over time, has lost some of its structural integrity or has partially collapsed, thereby losing its original circular shape.
is BACKGROUND OF THE INVENTION
Existing underground or buried pipe, such as culverts or water and gas mains, are typically replaced for various reasons, such as the impending expiry of the pipe's service life, the failure or deterioration of the existing pipe, and the insufficient size/capacity of 2o the existing pipe. Removal of such "old" pipe is avoided, if possible, to avoid prohibitive excavation costs and other related expenses and inconveniences, such as repaying a road surface and closing the road to vehicular traffic.
Various devices and techniques have therefore been developed for in situ replacement of buried pipe to reduce costs and inconveniences. Examples of such tools 2s to cut through an existing pipe from within, particularly those employing a form of cutting means such as cutting wheels or blades, are shown in US patents 5,098,225 (Rockower et al.) and 6,149,346 (Takamatsu et al.). However, a disadvantage of such prior art cutting tools is that they are dependent upon the concentricity and structural integrity of the pipe since such tools utilize offsetting forces to attain the cut or split. In Rockower and Takamatsu the cutting wheels or bodies will not cut through a longitudinal section of deteriorated pipe unless the cutting wheels/bodies have sufficient radial force s to push through the pipe. For instance, in Rockower, the cutting wheels at the bottom of the cutting tool will not be able to push downwardly and cut through a bottom portion of intact pipe if the opposed ceiling portion of the pipe has deteriorated and does not provide sufficient support for such downward forces. Hence, it is difficult, if not impossible, to expediently and properly split a deteriorated pipe lacking structural integrity with current so cutting tools since the pipe will lose its concentricity and be incapable of supplying the necessary offsetting forces.
In another type of pipe replacement apparatus shown in US patent 5,112,158 (McConnell), a crushing head has circumferentially disposed tapered blades for crushing an existing pipe. Such apparatus will also encounter difficulties with deteriorated pipe 1s because the crushing head will be forced off centre of the pipe and may jam if the blades encounter non-uniform resistance from the deteriorated pipe walls.
What is therefore desired is a novel pipe cutting tool that overcomes the limitations and disadvantages of the existing tools. Preferably, it should be able to cut through a pipe regardless of the pipe's structural integrity. All of the required cutting 2o forces should be offset internally within the cutting tool itself. The same cutting tool should be capable of use for various sizes of pipes, to avoid the cost of stocking various sizes of cutters for different pipes. The tool should be adapted to cut through external culvert obstructions, such as joining clamps, which traditionally have been problematic for conventional tools. Further, a user should have the option of using more than one 25 cutting tool concurrently in a pipe to provide a desired number of longitudinal cuts, so as to easily and quickly adapt to the size and integrity of the pipe, and to the existing soil conditions.

SUMMARY OF THE PRESENT INVENTION
According to the present invention, there is provided in a first aspect a cutting apparatus which is adapted to cut corrugated metal pipe or thin walled pipe regardless of the pipe's concentricity and structural integrity as all required forces are offset internally within the cutting tool. The apparatus accomplishes this with a series of cutting wheels, stepped in stages, mounted in a frame which envelopes one or more portions of the pipe wall and is drawn through the pipe to cut a specific logitudinal portion of the pipe without relying on or touching other portions of the pipe. The present apparatus relies on pressure between its frame and cutting wheels when pulled along the wall of the pipe, thus 1o eliminating the pipe's size and total structural integrity as prereqisites for using the device on the pipe.
In particular, the first aspect of the present device includes a guide for the device's frame which provides several advantages, including:
providing the frame with a larger area of contact with the pipe wall to allow the cutter apparatus to follow the pipe wall regardless of the pipe's shape;
creating a channel for the cutter wheels beyond the diameter of the pipe; and, preventing debris from falling into the cavity of the pipe while cutting the pipe wall.
The leading edge of the frame of the present apparatus is hardened and sharpened 2o to shear any exterior bolts or bonding used to hold pipes together. Behind the cutter wheels is a sharpened, hardened ripper to ensure any uncut metal is severed.
For mobility, the cutter head is attached to a traveling link, connected to a pull string, which allows the head to follow along the pipe wall independently of any irregularities. A
chassis attached to the pull string is adjustable for different diameter culverts to allow for alignment of the cutter apparatus with the pipe wall.
An expanding head travels behind the cutting apparatus to spread the cut pipe and make room for a new replacement pipe to be drawn through.

All of the aforementioned components of the present invention are connected to each other at end of a pull string.
Depending on soil and pipe conditions, one or more cutting tools can be employed at the end of the pull string to provide a corresponding number of longitudinal cuts s through the pipe.
In a second aspect of the invention an improved expanding head provides a more tapered cone head and elongate ribs spaced about the head to facilitate movement through the pipe being replaced. In particular, the improved head should provide for a better distribution of forces exerted when spreading the pipe to avoid undue crinkling and 1o buckling of the pipe.
Further, an alternate cutting apparatus is provided that is particularly suited for silty soils with a considerable rock content. Among other features, the apparatus has fewer cutting wheels which are on average generally larger than those of the aforementioned cutting apparatus. Slots have been added circumferentially about the 15 cutting wheels to urge the wheels to rotate as the cutting apparatus is advanced along the pipe. The guide is made narrower and has bevelled corners to urge dirt and rocks away from the cutting wheels. The channel's length is curtailed to allow a pressure drop in any soil moving through the mouth of the apparatus over the cutting wheels.
Reinforcement plates are added to improve resistance to side loads and better distribute stress zo concentrations behind the throat of the apparatus.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:
z5 Figure 1 shows a cutting, expanding and re-piping assembly according to a first embodiment of the present invention in operation, namely a pull string pulling a cutting tool through an existing culvert, and an expanding head and collar with a new culvert being drawn therewith;
Figure 1 a is a view similar to fig. l showing a shorter coupler for using the cutting tool in an existing culvert of smaller diameter;
s Figure 2 is a more detailed elevational view of the cutting tool of fig. l ;
Figure 2a is a view similar to fig.2 showing the frame of the cutting tool with cutting wheels removed;
Figure 3 is a plan view from above of the cutting tool of fig.2;
Figure 4 is a view from below of the cutting tool of fig.2;
1o Figure 5 is a end view from the front of the cutting tool of fig.2;
Figure Sa is a view similar to fig.5 showing the frame of the cutting tool with the cutting wheels removed;
Figure 6 is a cross-sectional view along line 6-6 of fig.2;
Figure 7 is a detailed elevational view of one of the cutting wheels of the cutting 1s tool of fig.2;
Figure 8 is a cross-sectional view of the cutting wheel of fig.7;
Figure 9 is an end view looking into a culvert with three cutting tools employed therein;
Figure 10 shows a second embodiment of the cutting tool;
2o Figure 11 is a plan view from above of the cutting tool of fig.10;
Figure 12 is a view from below of the cutting tool of fig.10;
Figure 13 is a cross-sectional view along line 13-13 in fig.l0 looking backward along the cutting tool;
Figure 14 is a side elevational view of an improved expanding head;
2s Figure 15 is an end view, from the right side in fig. 14, of the improved expanding head;
s Figure 16 is a detailed elevational view of one of the cutting wheels of the cutting tool of fig.10 showing slots thereabout; and, Figure 17 is a cross-sectional view of the cutting wheel of fig.l6.
s LIST OF REFERENCE NUMERALS IN DRAWINGS
cutting and spreading apparatus 12 existing culvert/pipe 14 centerline of 12 10 16 ground/soil 18 new culvert/pipe pull string 22 chassis portion of 20 24 coupling plate 1s 25 bolts 26 travelling block expanding head/spreader 32 collar cutter of 10 (first embodiment) 20 41 frame of 40 42 nose of 40 44 lower jaws 46 upper lip 47 edge of 46 25 48 mouth guide SOa, SOb plates of 50 52 longitudinal channel 54 throat 56 ripper 58 leading edge of 46 58a, 58b portions of 60 handle 62 bolt holes in 44 70 cutting wheels 70a-7 0e first to last cutting wheel 72 outer perimeter of 70 74 nut and bolt arrangement 76 bore 130 improved spreader 131 head of 130 132 screws 134 ribs (longer) 135 ribs (shorter) 136 nose of 130 137 tail of 130 138 troughs 140 cutter (second embodiment) 141 frame of 140 142 nose 144 lower jaws of 141 2s 146 upper lip of 141 147 downwardly extending portion of 146 148 mouth 150 guide 150a, 150b plates of 150 151 bevelled edges 152 channel s 153 end of 152 154 throat 164 reinforcing plates 170a first cutting wheel 170b second cutting wheel 172 cutting edge 173 slots 174 nut and bolt arrangement 175 tapered edges 176 bore is 177 sloped portions of 172 178 hub portion a DESCRIPTION OF EMBODIMENTS OF THE INVENTION
Figure 1 shows an apparatus for cutting and spreading pipe according to a first embodiment of the present invention, generally designated by reference numeral 10. An important feature of the apparatus is the cutting head 40, which may also be referred to as a "cutting tool", "cutter assembly" or simply a "cutter". The cutter 40 is shown being drawn along the wall of an old, or existing, culvert 12 by a pulling means such as a pull string 20. The existing culvert 12, also referred to herein as a "pipe", may comprise oil/gas pipelines, water lines, sewer pipes, gas mains, and the like, which are buried in the ground 16 or are located above-ground. The cutting tool 40 is best suited for use on 1o metallic pipes that are traditionally difficult to cut, such as corrugated metal pipe.
However, it is also well suited for smooth walled metal pipes and, as will be appreciated later, pipes of different materials.
The expanding head 30 of the present invention shown in fig.l may also be referred to as a "spreader tool" or "spreader". It has a conical head 31 of conventional design and is linked to the pull string 20 for travel behind the cutter 40 through the existing cut culvert to further expand and spread the culvert and surrounding soil as is known in the art. The surface of the head is typically inclined at an angle "A1" of about 15 degrees. The spreader 30 makes room for a new/replacement corrugated culvert/pipe 18. The new culvert 18 is connected behind the spreader 30 via suitable means, such as a 2o collar 32. In addition, the spreader 30 may take other, non-conical shapes, depending on the configuration of the new pipe to be installed.
In an alternate embodiment of the spreader 130 shown in figs.l4 and 15, the device is improved by reducing the angle of inclination "A2"of the cone head 131 to about 7.5 degrees to better distribute pressures between the cone and the culvert and to avoid crinkling of the culvert as it is being spread. A series of spaced elongate ribs 134 and 135 are also fixed to the surface of the head, as by screws 132 to facilitate replacement of ribs in the field if need be. The longer ribs 134 extend along the entire length of the head from its nose 136 to the tail 137, whereas the shorter ribs 135 do not extend to the nose 136 to accommodate the conical shape of the head. Good results have been achieved using bars made of nylon, such as NYLATRON, which keep the cone head from gripping or snagging on the interior surfaces of culverts, which are often galvanized.
s It will be appreciated that bars of other materials may also be suitable.
The troughs 138, or spaces, created between the ribs 134, 135 facilitate movement of soil along the head by providing a means for dirt and other debris to escape from the pipe 12 past the expanding head for deposit outside the new culvert 18 being drawn in.
Referring again to the first embodiment shown in fig.l, the cutter 40, expanding 1o head 30, collar 32 and new culvert 18 are all operatively engaged to the end of the pull string 20 which is located generally along the longitudinal centerline 15 of the old culvert 12. The pull string 20 is pulled at a downstream location of the old culvert by suitable pulling means for exerting adequate force to pull the entire assembly through the ground.
An important feature of the pull string 20 is a triangular coupling plate 24 fixed to the is rigid chassis 22 by suitable means, such as bolts 25. A traveling link 26 is pivotally coupled at one end to the top of the coupling plate 24 and at the other end to the nose of the cutter at 42. As will be appreciated better later, the link 26 provides the cutter 40 with some freedom of movement radially to allow the cutter to follow corrugations and other imperfections and irregularities on the old culvert wall 12. The height of the coupling 2o plate 24, as well as the length of the link 26, may be appropriately varied to fit the cutter in culverts of various sizes/diameters. For example, the shorter ("shallower") coupling plate 24a in fig. l a would be used for a pipe of smaller diameter than the taller plate 24 used for the larger pipe of fig. l .
Another important feature of the present invention is the configuration and 2s function of the cutter, as shown in fig.l and in greater detail in figs.2 to 8. The location of the various features of the cutter relative to each another will be described based on the orientation of the cutter at the top of the culvert as shown in the figures.
It should be understood that the described locations would change for a cutter oriented in a different manner, say upside down on the lower part of the old culvert.
The cutter 40 has a frame 41 (as best seen in figs. 2a and Sa) with a series of metallic cutting wheels, generally indicated by 70 in fig.2, spaced in tandem relationship s along a pair of lower elongate jaws 44 of the frame 41. Although it is contemplated that hardened steel wheels will be most commonly used, wheels made of other suitable materials, such as ceramic, may be employed for other applications. The frame has an opposed upper elongate lip 46 spaced above the jaws 44 to define an elongate longitudinal mouth 48 of suitable size to accept most thicknesses of culvert walls 12.
to Two elongate plates SOa and SOb, one extending transversely from either side of the lip 46, form a frame guide 50 above the mouth 48 along most of its length. The guide 50 provides an enlarged area of contact between the culvert wall and the frame to make it easier for the frame to follow the culvert wall regardless of its shape. The bottom surface of each plate SOa, SOb extends slightly below the edge 47 of the lip to form a longitudinal is channel 52 (best viewed in figs.2 and 5) for the back cutting wheels which extend across the mouth and beyond the radial extent of the culvert's wall. The guide 50 also prevents debris, such as soil from the ground above the pipe, from falling past the cutter into the inner cavity of the culvert being cut open.
The cutting wheels 70, which are individually designated by reference numerals 20 70a to 70e, are rotatably mounted along the jaws 44 by suitable means, such as the nut and bolt/axle arrangement 74 which operationally engages the wheel's bore 76, shown in figs.6-8. The wheels 70a-70e are arranged so that they are stepped in stages upwardly toward the lip 46, and more particularly toward the channel 52, progressively from the mouth's front opening back towards the throat 54. In the first embodiment the outer 25 perimeter 72 of the first cutting wheel 70a (which first engages the wall of the existing culvert wall as it enters the mouth) extends the least distance from the lower jaws 44 into the mouth 48. In contrast, the outer perimeter of the last, or fifth, cutting wheel 70e extends the furthest from the jaws 44 and across the mouth 48 into the channel 52 of the upper lip, in close proximity to the ceiling of the channel. In the first embodiment, the first three wheels 70a-70c are of the same size, but the bolt holes 62 (see fig.2a) are spaced progressively closer to the mouth 48 to bring the perimeter of the cutting wheels s 70a-70c progressively closer to the upper lip. The fourth cutting wheel 70d is of greater diameter than wheels 70a-70c so that its outer perimeter is yet closer to the upper lip than wheel 70c. Finally, the fifth cutting wheel 70e has a greater diameter than wheel 70d to bring its perimeter closest to the frame's upper lip. It will be understood that other configurations of wheel sizes and bolt hole locations are possible to achieve a progressive 1o cut of the pipe wall within the mouth 48, as for example with the second embodiment of the cutter described below.
As the cutter 40 is drawn into contact with the culvert wall, the cutting wheels apply a progressively greater pressure on the wall to cut therethrough. By the time that the last wheel 70e engages the cut being formed in the wall, the wall should be at least 1s nearly or fully severed. As a "fail-safe" precaution, the inclined elongate throat 54 extends from the back of the mouth 48 behind the last cutting wheel 70e to present a hardened, sharpened lower edge, termed a "ripper" 56. The ripper ensures that any uncut culvert wall that might pass the last wheel 70e will be severed as the cutter is pulled through the existing culvert.
2o The leading edge 58 of the lip 46 has an upward pitch from the front to the back of the frame 40, with a steeper nose portion 58a and a more gradually sloped spinal portion 58b. The leading edge is hardened and sharpened for shearing any exterior obstructions that are encountered along the culvert's wall, such as exterior bolts or banding for joining sections of the culvert, and for pushing aside the ground through 2s which the frame 40 may travel. An elongate hole 60 further along the spine toward the back of the frame forms a handle for a user to grip and lift the tool by hand.

A second preferred embodiment of the cutter 140 shown in figs 10 to 13 is particularly suited for use in soils with a substantial content of clay and rocks of various sizes and to cut couplings joining segments of a culvert. The cutter 140 is similar to the cutter 40, and for this reason will not be described again in great detail.
For ease of s reference, the reference numerals used in figs. 10-13 are similar to those used to describe the components of the cutter 40, with the addition of a prefix "1". Some of the differences of the cutter 140 are set out below.
Only two cutting wheels are provided toward the back portion of the mouth 148.
A first cutting wheel 170a rotatably mounted to the lower lip 144 is located ahead of a 1o second cutting wheel 170b of larger diameter rotatably mounted at the back of the mouth adjacent the throat 154. The cutting wheels employed have on average a larger diameter than the wheels 70a-70e in that the first cutting wheel 170a is at least as large as the fifth cutting wheel 70e of the first embodiment. The wheels 170a, 170b are also arranged so that they are stepped in stages upwardly toward the upper lip 146 and the channel 152, 15 progressively toward the back of the mouth 148. The outer perimeter of the last, or second, cutting wheel 170b extends the furthest from the lower jaws 144 across the mouth into the channel 152, whereas the first wheel 170a remains marginally out of the channel 152. Good results have been achieved using a 5.5 inch (about 140 mm) diameter wheel 170a and a 6.5 inch (about 165 mm) diameter wheel 170b.
2o Referring to figs. 16 and 17, the wheels 170a, 170b are further improved by scoring a number of slots 173, or grooves, generally evenly spaced about the circumference of each wheel just below and to either side of the outer perimeter 172, or "cutting edge". Each slot 173 preferably extends from the sloped portion 177 of the cutting edge onto the surface of the radially extending hub portion 178. The slots 173 2s engage the culvert wall as it is being cut to urge the wheel to turn as the cutter is pulled through the culvert. As opposed to having the wheel remain stationary and exposing the same cutting surface to the culvert wall, the present wheels 170a, 170b rotate along the culvert wall for more uniform contact and wear of the cutting edge.
The nut and bolt arrangement 174 (figs. 10-13) has also been altered to provide a shallower transverse profile (as seen in figs.l2 and 13) closer to the lower jaws to help avoid snagging on sharp edges or protruding portions of the culvert. The nuts are flatter and do not extend as far out from the jaws as the nuts 74 of the first embodiment, and the outer edges 175 are tapered and kept as smooth as possible.
The channel 152 does not extend forwarly out of the mouth 148 but is curtailed at 153 by a downwardly extending portion 147 of the lip 146 to lessen the amount of dirt so entering the channel as the cutter is pulled forwardly through the soil.
The lip portion 147 urges rocks and dirt away from the channel 152, and the channel allows a pressure drop in any soil progressing through the open mouth 148 and over the wheels 170a, 170b.
Reinforcing plates 164 behind the throat 154 on either side of the neck of the cutter's frame 141, as shown in fig.l0, help resist side loads and relieve stress concentrations in that area of the frame during operation.
Each of the elongate plates 150a and 150b of the guide 150 have been narrowed (i.e. reduced transversely as viewed in fig.l3), and outwardly sloped beveled edges 151 have been provided near the mouth 148 to urge rocks and dirt away from the cutting wheels 170a, 170b to reduce soil resistance and avoid snagging on rocks. The outside 2o edges 145 of the lower jaws 144 are also provided with outwardly sloped bevels to likewise urge rocks and dirt away from the cutting wheels 170a, 170b.
The jaws 144 have been tapered toward the nose 142 to reduce the weight of the cutter. This tapering is possible due to the reduction in the number of cutting wheels employed and their set back away from the nose area.
As shown in fig.9, more than one cutter tool may be mounted on an existing culvert to provide a corresponding number of longitudinal cuts therethrough.
The number of cutters used will be determined by prior inspection and site conditions, such as the condition of the soil and of the culvert.
An example of the typical operation of the present invention may now be illustrated with reference to the first embodiments of the cutter 40 and spreader 30. Once s one end of a culvert is located and, if need be, excavated to expose the inlet, the cutter's mouth is slid onto the culvert wall and is pushed on as far as it will go until the cutting wheels resist further movement. The pull string 20 should already be passed through to the other end of the culvert where the cutting is to finish, and the nose 42 of the cutter should be attached to a coupling plate 24 and traveling link 26 of suitable size for the 1o diameter of culvert to be cut. The number of cutters to be used is determined based on the earlier mentioned criteria. The spreader 30 is connected to the end of the pull string just behind the cutter, and the new culvert is in turn connected to the spreader via the collar 32. Force is then exerted on the far end of the pull string to draw the cutter longitudinally further onto the culvert wall. The cutting wheels 70 engage the wall with 15 greater force and progressively push the wall toward the upper lip 46, and in doing so the wheels form a cut through the wall, thereby severing the culvert. The cone head then spreads the severed culvert and draws in the new culvert as is known in the art. As the cutter travels along the culvert, the lower lip 44 remains inside the culvert while the upper lip 46 remains outside the culvert. Hence, the frame's leading edge 58 pushes aside the 2o ground and severs any external pipe obstructions that are encountered, such as external bolts.
An important advantage of the cutter 40 is its ability to cut through the culvert wall regardless of the culvert's structural integrity. The cutter does not rely on structural support from other portions of the culvert to counteract cutting forces.
Rather, the 25 upward forces of the cutting wheels 70 on the culvert wall are counteracted, or resisted, by the opposed upper lip 44 of the cutter's frame. Hence, all of the required cutting forces are offset "internally" within the cutter itself.

Another advantage of the present invention is the ability to use the same cutter for various sizes of culverts. As long as the thickness of the culvert wall can be accommodated within the mouth 48 of the cutter, a user need only provide a suitably sized coupling plate 24 and/or travelling link 26 for the choosen culvert.
Hence, a user is s able to avoid the needless cost of stocking various sizes of cutters and of transporting several sizes of cutters to a work site.
Yet another advantage is that the leading edge 58 is adapted to effectively cut through external culvert obstructions which traditionally have been problematic for conventional tools.
1o A further advantage is the ability to use more than one cutter during a single pass through an existing culvert to provide the desired number of longitudinal cuts. Hence the apparatus is easily and quickly adapted at a work site to the size and integrity the particular pipe, as well as the existing soil conditions.
The above description is intended in an illustrative rather than a restrictive sense, 15 and variations to the specific configurations described may be apparent to skilled persons in adapting the present invention to other specific applications. Such variations are intended to form part of the present invention insofar as they are within the spirit and scope of the claims below. For instance, other variations in the number of cutting wheels (other than the sets of two or five described above) might be suitable for certain soil 2o conditions. It should also be appreciated that the cutter may be used individually without the spreader in certain applications, such as for cutting a planar sheet of metal for instance.

Claims

We claim:

1. A cutting apparatus for cutting pipe comprising:
a frame having an opening which envelopes a portion of said pipe;
a series of cutting wheels, stepped in stages, mounted in said frame and extending into said opening to cut a specific logitudinal portion of said pipe without relying on or touching other portions of said pipe;
said frame further having a leading edge hardened and sharpened to shear any exterior bolts or bonding on said pipe; and, a sharpened, hardened ripper located at a terminal end of said frame opening rearward of said cutting wheels for severing any portion of pipe left uncut by said series of cutting wheels.