Boring or penetrating the earth – Processes – Boring curved or redirected bores
Reexamination Certificate
2002-07-08
2003-07-08
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
Processes
Boring curved or redirected bores
Reexamination Certificate
active
06588516
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to directional boring and, in particular to a system for boring through both soil and solid rock using the same machine.
BACKGROUND OF THE INVENTION
At present, when underground utilities such as natural gas, potable water, or sanitary sewer pipes are placed in rock, trenches are excavated using large hard rock trenching equipment such as the Vermeer T-655, or possibly even shot using explosives. In these conditions, electric, telephone and cable TV lines are normally strung overhead along poles, mostly due to the difficulty and expense of placing them underground. Thus, in many situations, a solid rock formation will cause utility lines to be located above ground due to the difficulty of underground installation. Many such sites involve mixed conditions involving both a solid rock formation for part of the run and soil for the remainder, often at the beginning and end of the run. In such a situation, rock drilling or trenching equipment may lack the capability to bore through the soil to reach the rock formation.
Directional boring apparatus for making holes through soil are well known. The 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. See Malzahn, U.S. Pat. Nos. 4,945,999 and 5,070,848, and Cherrington, U.S. Pat. No. 4,697,775 (RE No. 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. A spade, bit or head configured for boring is disposed at the end of the drill string and may include an ejection nozzle for water to assist in boring.
In one variation of the traditional boring system, a series of drill string rods are 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 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.
Accurate directional boring necessarily requires information regarding the orientation and depth of a cutting or boring tool, which almost inevitably requires that a sensor and transmitting device (“sonde”) be attached to the cutting tool to prevent mis-boring and re-boring. One such device is described in U.S. Pat. No. 5,633,589, the disclosure of which is incorporated herein for all purposes. Baker U.S. Pat. No. 4,867,255 illustrates a steerable directional boring tool utilizing a pneumatic impactor.
Directional boring tools with rock drilling capability are described in Runquist U.S. Pat. No. 5,778,991 and in Cox European Patent Applications Nos. EP 857 852 A2 and EP 857 853 A2. However, although directional boring tools for both rock drilling and soil penetration are known, no prior art device has provided these capabilities in a single machine together with the ability to steer the tool in both soil and rock. The present invention addresses this need.
There is also a need in the art for a directional boring tool for rock drilling and soil penetration that provides a percussion hammer driven by liquid fluids, provides indexing of a device for detecting angular rotation (e.g., a sonde) and provides a method for ON/OFF control of the percussion hammer (e.g., pneumatic or liquid driven). In addition, there is a need for an apparatus that provides improved steerability of the drill head.
SUMMARY OF THE INVENTION
A drill head for an apparatus for directional boring according to the invention includes a holder (or housing) for a device for detecting angular orientation such as a sonde, a pneumatic hammer and a rotary bit assembly connected head to tail with the angular orientation housing at one end and the bit at the other. The drill head may also include a starter rod, which may be connected to the angular orientation detector housing. The bit preferably has a frontwardly facing main cutting surface with a plurality of cutting teeth disposed thereon and a gage tower radially outwardly offset from the main cutting surface having at least one frontwardly facing gage cutting tooth thereon suitable for cutting over an angle defined by less than a full rotation of the bit. The device for detecting angular orientation is in a predetermined alignment with the gage tower so that it determines the orientation of the gage tower relative to the axis of rotation of the drill head. In one preferred embodiment, the main cutting surface is substantially flat and circular and has a series of fluid ejection ports thereon, and the drill head has passages for conducting a drill fluid therethrough to the ejection ports. In another preferred embodiment, the bit has a heel portion on an outer side surface thereof at a position opposite the gage tower, which heel portion slopes inwardly from back to front.
Such a drill head may be used in a method for directional boring according to the invention using a directional boring machine which can push and rotate a drill string having the drill head mounted thereon. Such a method comprises the steps of boring straight through a medium by pushing and rotating the drill head with the drill string while delivering impacts to the bit with the hammer, prior to changing the boring direction, determining the angular orientation of the gage tower using the device for detecting angular orientation, and changing direction during boring by pushing and rotating the bit repeatedly over an angle defined by less than a full rotation of the bit while delivering impacts to the bit with the hammer, so that the drill head deviates in the direction of the cutting action of the gage tower. The medium may be soil, solid rock, or both at different times during the bore. In particular, the steps of boring straight and changing direction can be carried out in both soil and rock during the same boring run using the same bit.
According to a further aspect of the invention, a method is provided for directional boring in mixed conditions including both soil and solid rock. Such a method comprises the steps of boring straight in both soil and rock by pushing and rotating the drill head with the drill string while delivering impacts to the bit with the hammer, prior to changing the boring direction in both soil and rock, determining the angular orientation of the gage tower using the device for detecting angular orientation, changing direction when boring in rock by pushing and rotating the bit repeatedly over an angle defined by less than a full rotation of the bit while delivering impacts to the bit with the hammer, so that the drill head deviates in the direction of the cutting action of the gage tower, and changing direction when boring in soil by pushing the bit with the drill string without rotating it so that the drill head deviates in a direction of the gage tower and away from the heel portion. Since the main cutting face of the drill bit is large and flat, the pushing force of the drill string alone may be insufficient to steer the tool in soft ground without rotation. It is thus preferred to deliver impacts to the bit with the hammer while changing direction in soil. This method of the invention may provide better steering in some ground conditions.
Another aspect of the invention provides a drill head for an apparatus for horizontal directional drilling, comprising: a device for detecting angular orientation; a holder for the device for detecting angular orientation, the device for detecting angular orientation being disposed therein; a hammer driven by a liquid, the hammer arranged and configured to generate percussive blows; and a rotary bit assembly connected to the hammer, the rotary bit assembly arranged and configured for receiving
Albert Rene′ Marcel
Rankin James R.
Runquist Randy R.
Van Houwelingen Mark
Pezzuto Robert E.
Vermeer Manufacturing Company
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