Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Repair – replacement – or improvement
Reexamination Certificate
2001-09-17
2003-04-22
Lee, Jong-Suk (James) (Department: 3673)
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Repair, replacement, or improvement
C405S174000, C405S184000, C405S184100, C175S053000
Reexamination Certificate
active
06551028
ABSTRACT:
FIELD
The present invention relates to an apparatus for the replacement of underground pipe.
BACKGROUND
Underground pipes are subject to inevitable deterioration and wear and, therefore, must be replaced from time to time. An obvious method for replacing existing underground pipe with replacement pipe is to excavate the entire length of the existing pipe, remove it and place new replacement pipe into the excavation. Excavation of existing pipe is time-consuming, labor-intensive and results in damage to the area surrounding the excavation. In many instances pipes often lie beneath driveways, buildings, or gardens, and property owners are very concerned about any damage that may result thereto. In addition, excavation is often made difficult by the presence of underground utilities.
Accordingly, it is an object of the present invention to provide an apparatus and method for replacing underground pipe requiring minimal excavation.
Other devices and methods have previously been proposed for use in replacement of underground pipes and mains. For example, those disclosed in U.S. Pat. No. 6,171,026 issued to Crane et al.; U.S. Pat. No. 6,092,553 issued to Hodgson; U.S. Pat. No. 5,544,977 issued to Crane et al.; U.S. Pat. No. 4,720,211 issued to Streatfield et al.; and U.S. Pat. No. 4,738,565 issued to Streatfield et al. However, all of the devices and methods disclosed by the above patents suffer from several drawbacks.
Often the earth surrounding underground pipes is extremely hard because it has been compacted or has settled over the years that the pipes have been in the ground. Many of the tools of the prior art, such as those described in U.S. Pat. No. 4,720,211 issued to Streatfield et al., and U.S. Pat. No. 5,098,225 issued to Rockower et al., involve the movement outwards of fragments of the existing underground pipe and expansion of the cavity thereof in order to create a cavity large enough to accommodate a replacement pipe. Obviously, in very compact earth, expansion of the cavity of the existing underground pipe can be very difficult and sometimes impossible. Furthermore, such expansion can damage nearby underground utilities or surface features (e.g. where an existing pipe passes under a sidewalk the sidewalk, may be cracked by expansion of the cavity of the existing pipe). Therefore it is an object of the present invention to provide an apparatus and method for replacing underground pipe that does not cause the expansion of the cavity of the existing underground pipe. It is a further object of the present invention to provide an apparatus and method for replacing underground pipe that does not cause outward movement of fragments of existing underground pipe.
In order to replace existing underground pipe without causing expansion of the surrounding earth, it is often necessary to remove fragments of the existing underground pipe from the cavity of the existing underground pipe. Generally, the prior art tools and methods for replacing underground pipe fracture or cut the existing underground pipe in situ and draw replacement pipe into the cavity of the fractured or cut existing underground pipe. In other words the fragments of the fractured or cut existing underground pipe remain in the ground surrounding the replacement pipe, once it is drawn into place. One exception is the tool described in U.S. Pat. No. 6,171,026 issued to Crane et al., wherein the existing underground pipe is cut in two and the resulting slit pipe is drawn out of the borehole, drawing replacement pipe into place in the process. The method and apparatus of U.S. Pat. No. 6,171,026 is obviously not suitable for use with frangible or fracturable pipe. Accordingly, it is an object of the present invention to provide an apparatus and method for the replacement of both frangible and non-frangible pipes wherein fragments of the existing underground pipe are removed from the cavity thereof, thereby making it possible to replace existing underground pipe without expanding the pipe or the surrounding earth.
SUMMARY OF THE INVENTION
A tapered tool for the replacement of underground pipe is provided that has a nose smaller than the inside diameter of an existing underground pipe, a cylindrical base with an outside diameter at least as large as the outside diameter of the existing underground pipe, and a plurality of breaking members joining the nose to the base such that the breaking members are angled radially outwards from the nose to the base, such that the breaking members are forced against the inside surface of the existing underground pipe and are operative to fracture the existing underground pipe into fragments as the tool is pulled through the existing underground pipe. The edge of the base that is closest to the nose is operative to force the fragments of the existing underground pipe radially inward, such that they pass through the bore of the base.
By forcing the fragments of the existing underground pipe inwards and allowing them to pass through the tool and into the replacement pipe the tool of the present invention makes it possible to replace existing underground pipe without expanding the cavity of the existing underground pipe, thereby protecting surface features and nearby underground utilities that might be damaged by such expansion. This is especially true when the existing underground pipe is found in very hard ground. Such compact earth is not further compressed by the forces applied to expand the cavity of the existing underground pipe but instead transmits the forces directly to, for example, nearby underground utilities.
In an alternative embodiment the breaking members of the tool are curved to form a conical helix. The helical tool rotates about its axis as it is pulled through the existing underground pipe thereby breaking the existing underground pipe in a helical pattern.
In addition, the expansion of the cavity of existing underground pipes found in very hard ground requires the application of greater force and may in some instances be impossible. The use of greater force additionally results in an increased risk of tool breakage. Therefore, by not expanding the cavity of the existing underground pipe, the tool of the present invention makes possible the replacement of existing underground pipes found in very hard ground with the use of less force, with less risk of damage to nearby utilities and surface features and with less risk of tool breakage.
In an alternate embodiment of the tool of the present invention, one side of the tool comprises a curved plate and the other comprises breaking members similar to those of the first embodiment described above. The breaking members fracture the existing underground pipe and the fragments are directed radially inward and pass through the tool as described above. The curved plate results in a more even distribution of force against the side of the existing underground pipe and therefore prevents expansion of the existing underground pipe on that side. In addition, the curved plate prevents fragments and earth from one side of the existing underground pipe from entering the tool. Therefore, the embodiment incorporating a curved plate allows the replacement of existing underground pipe in hard ground while reducing the amount of debris that passes through the tool.
Trenchless pipe replacement tools, such as the tool of the present invention, are often used in conjunction with a pipe guide or other means for drawing replacement pipe into place behind the tool. When used in conjunction with a pipe guide the tool directs the fragments of the existing underground pipe radially inwards and allows them to pass through the tool, through the pipe guide and into the replacement pipe. Therefore, the present invention additionally comprises mechanisms for clearing fragments and earth from the replacement pipe.
A first embodiment of the debris clearing mechanism comprises a sprocket supported on a support member inside the pipe guide. A chain enters the replacement pipe at one end, passes through the replacement pipe to the pipe guide, where it passes
Hall Priddy Myers & Vande Sande
Lee Jong-Suk (James)
LandOfFree
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