Boring or penetrating the earth – Processes – Boring horizontal bores
Reexamination Certificate
1998-02-17
2001-09-04
Neuder, William (Department: 3672)
Boring or penetrating the earth
Processes
Boring horizontal bores
C175S295000, C175S299000, C405S184000, C173S011000, C173S013000, C173S152000
Reexamination Certificate
active
06283229
ABSTRACT:
TECHNICAL FIELD
This invention relates to directional boring, particularly to an apparatus and method for bursting an existing pipeline or boring a non-linear hole.
BACKGROUND OF THE INVENTION
Directional and non-directional boring apparatus for making holes through soil are well known. A directional borer generally includes a series of drill rods joined end to end to form a drill string. The drill string is pushed or pulled through the soil by means of a powerful hydraulic device such as a hydraulic cylinder. A spade, bit or chisel configured for boring is disposed at the end of the drill string, which may include an ejection nozzle for water to assist in boring. In general, the direction of boring is controlled by selectively rotating a boring head having an angled face. During rotation, the borer continues straight, whereas when pushed without rotation the boring head moves in the favored direction. See Malzahn U.S. Pat. Nos. 4,945,999 and 5,070,948, and Cherrington U.S. Pat. No. 4,697,775 (RE 33,793). The drill string may be pushed and rotated at the same time as described in Dunn U.S. Pat. No. 4,953,633 and Deken et al. U.S. Pat. No. 5,242,026.
In one variation of the traditional boring system, a series of drill string rods is used in combination with a percussion tool mounted at the end of the series of rods. The rods can supply a steady pushing force to the impact tool and the interior of the rods can be used to supply the pneumatic borer with compressed air. See McDonald et al. U.S. Pat. No. 4,694,913. This system has, however, found limited application commercially, perhaps because the drill string tends to buckle when used for pushing if the bore hole is substantially wider than the diameter of the drill string.
A variety of systems are now known for the installation of underground pipes, particularly for the replacement of an existing deteriorated pipe. In one widely practiced method, a pneumatic impact boring tool is sent through the existing pipeline such that the head of the tool, which may be provided with blades that apply intense local pressure to the existing pipe, fractures or splits the existing pipe. See, for example, Streatfield et al. U.S. Pat. Nos. 4,720,211, 4,738,565 and 4,505,302. A replacement pipe, typically made of plastic such as HDPE, can be drawn along behind the boring tool. This process has proven effective commercially because it bursts the old pipe and replaces it with a new pipe at the same time. However, the system relies on a pneumatic impact tool, which in turn requires an air compressor. Exhaust from the impact tool is vented into the interior of the replacement pipe, which is unacceptable for certain types of pipe installations, such as gas and water lines.
Directional borers are less effective for pipe bursting, especially for hard to burst pipes like cast iron, because the steady pushing force of the drill string lacks the impact power of a pneumatic impact boring tool. Thus, in some instances, a directional borer or winch is used to pull a pneumatic impact tool through an existing pipeline in order to burst the existing pipe and pull in the replacement pipe. These alternatives are effective but require considerable equipment and manual labor. A need remains for a boring system that can avoid the need for a pneumatic impact tool and still provide cyclic impacts suitable for pipe bursting operations, rock breaking, and the like.
SUMMARY OF THE INVENTION
An impact boring tool according to the invention has a tubular housing and a head mounted at a front end of the housing. The head preferably includes a chisel configured for breaking loose rocks and stones encountered in soil. A striker is disposed within the housing for delivering an impact force to the head, either directly or through one or more intervening parts. A trigger mechanism causes the striker to deliver an impact to the head and chisel only when an external force exerted on the impact tool in its lengthwise direction exceeds a predetermined level. This predetermined level generally coincides with a maximum effective amount of pushing or pulling force for moving the tool through the ground, which force is exerted by an external device such as a directional boring machine.
According to a preferred form of the invention, the impact tool includes a head mounted for limited longitudinal movement relative to a housing, a chisel shaft connected to the head, and a trigger shaft engaging the chisel shaft. The trigger shaft initially retains a striker in a rearward position against the action of a striker spring. Upon relative movement between the head and the housing, the trigger mechanism activates to release the striker to apply an impact force to the head through the trigger shaft and chisel shaft.
A directional boring apparatus of the invention includes a drill string, a directional boring machine connected to a rear end of the drill string and capable of forcing the drill string through soil, and an impact boring tool as described above connected to a front end of the drill string. The invention further provides a method of directional boring using such a directional boring apparatus including the steps of pushing (or pulling) the impact tool forward through the ground using the directional boring machine, rotating the drill string while pushing or pulling it to move the tool in a substantially straight forward direction, ceasing rotation of the drill string while pushing or pulling to change the direction of travel of the tool, actuating the trigger mechanism when the pushing force exerted by the drill string exceeds the predetermined level, and re-setting the trigger mechanism after actuating it. The latter operating is preferably done by pulling back on the drill string as described hereafter.
Objects, features and advantages of the invention will become apparent from the following detailed description. It should be understood, however, that the detailed description is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: Re. 33793 (1992-01-01), Cherrington
patent: 2385439 (1945-09-01), Gubbins
patent: 3946819 (1976-03-01), Hipp
patent: 4462471 (1984-07-01), Hipp
patent: 4505302 (1985-03-01), Streatfield
patent: 4694913 (1987-09-01), McDonald
patent: 4720211 (1988-01-01), Streatfield
patent: 4738565 (1988-04-01), Streatfield
patent: 4945999 (1990-08-01), Malzahn
patent: 4953638 (1990-09-01), Dunn
patent: 5010965 (1991-04-01), Schmelzer
patent: 5070948 (1991-12-01), Malzahn
patent: 5139086 (1992-08-01), Griffith, Sr.
patent: 5242026 (1993-09-01), Deken et al.
patent: 5289887 (1994-03-01), Puttmann
patent: 6035954 (2000-03-01), Hipp
Crane Robert F.
Wentworth Steven W.
Earth Tool Company L.L.C.
Neuder William
Philip G. Meyers Intellectual Property Law, P.C.
Walker Zakiya
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