Electricity: measuring and testing – Of geophysical surface or subsurface in situ – For small object detection or location
Reexamination Certificate
2000-09-12
2002-05-28
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
For small object detection or location
C175S045000
Reexamination Certificate
active
06396275
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an underground boring technique, especially one which is intended to install underground utility cables, and more particularly to a specific technique for using locate point measurements in predicting the depth of a boring tool at a forward point along a particular path of movement of the boring tool.
Installing underground utility cable using a steerable boring tool is well known in the art. Various examples are described in continuing Mercer U.S. Pat. Nos. 5,155,442, 5,337,002 and 5,444,382 and pending U.S. application Ser. No. 442,481, filed May 16, 1995 which is a continuation of Mercer U.S. Pat. No. 5,444,382 (collectively referred to herein as the Mercer Patents), all of which are incorporated herein by reference. An example of the prior art Mercer technique is best illustrated in
FIG. 1
herein which corresponds to FIG. 2 in the Mercer Patents. For purposes of clarity, the reference numerals used in the Mercer Patents have been retained herein for like components.
As seen in
FIG. 1
, an overall boring machine
24
is positioned within a starting pit
22
and includes a length of drill pipe
10
, the front end of which is connected to the back end of a steerable boring head or tool
28
. As described in the Mercer Patents, the boring tool includes a transmitter or sonde for emitting a dipole magnetic field
12
which radiates in front of, behind and around the boring tool, as illustrated in part in
FIG. 2. A
first operator
20
positioned at the starting pit
22
is responsible for operating the boring machine
24
, that is, he or she causes the machine to let out the drill pipe, causing it to push the boring tool forward. At the same time, operator
20
is responsible for steering the boring tool through the ground. A second locator/monitor operator
26
is responsible for locating boring tool
28
using a locator or receiver
36
. The boring tool is shown in
FIG. 1
being guided around an obstacle
30
at a generally constant depth beneath a reference surface
32
until it reaches a termination pit
34
. The locator/monitor operator
26
holds locator
36
and uses it to locate the surface position directly above tool head
28
. Once operator
26
finds this position, the locator
36
is used to determine the depth tool head
28
. Using the particular locator of the present invention, operator
26
can also determine the orientation (yaw, pitch and roll) of tool head
28
and other information pertinent to the present invention, as will be described hereinafter. This information is passed on to operator
20
who uses it to steer the boring tool to its target.
As stated above, the overall arrangement illustrated in
FIG. 1
may be used to install underground utility cable. After the boring tool reaches termination pit
34
, the cable is connected to the drill pipe and pulled into position within the ground as the drill pipe is pulled back through the underground tunnel to starting pit
22
. Once the utility cable is so installed, it would be quite desirable to have a record of where it is actually located within the ground, even if the terrain of the ground changes with time. As will be seen hereinafter, the present invention fulfills this desire in an uncomplicated and reliable way using much of the technology described in the Mercer Patents.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, a method is disclosed as part of an overall process in which a boring tool, for example boring tool
28
is moved through the ground within a given region along a particular path in an orientation which includes pitch. A locating signal is transmitted from the boring tool which signal exhibits a field defined forward point within a reference surface which field defined forward point is vertically above an inground forward point on the particular path through which the boring tool is likely to pass. The method establishes a predicted depth of the boring tool at the inground forward point by first identifying the field defined forward point. The signal strength of the locating signal is then measured at the field defined forward point as being representative of the depth of the boring tool at an inground upstream point which is the current location of the boring tool. With the boring tool at the upstream inground point, the pitch of the boring tool is determined. Using the measured signal strength and the determined pitch, the predicted depth of the boring tool is determined for the inground forward point based on the boring tool moving along an approximately straight path to the inground forward point.
In one aspect of the present invention, an arrangement is disclosed in which a boring tool, for example boring tool
28
, is moved through the ground within a given region along a particular path in an orientation which includes pitch. A locating signal is transmitted from the boring tool which exhibits negative locate points at the surface of the ground. A portable locator measures a signal strength of the locating signal at one of the negative locate points with the boring tool at a particular point. The pitch of the boring tool is then determined while the locator is positioned at the negative locate point. Using the measured signal strength and the determined pitch, the portable locator establishes the depth of the boring tool beneath the surface of the ground.
In another aspect of the present invention, the locating signal exhibits a flux orientation point defined by a particular orientation of flux lines at the surface of the ground. A locating arrangement is provided for determining the depth of the boring tool. The portable locator includes (i) at least one antenna for use in identifying the flux orientation point, (ii) an arrangement configured for measuring a signal strength of the locating signal at the flux orientation point using the one or more antennas, (iii) a pitch sensing arrangement for determining the pitch of the boring tool, and (iv) a processing section configured for using the measured signal strength at the flux orientation point and the determined pitch to establish the depth of the boring tool.
In another aspect of the present invention, the locating signal exhibits a flux orientation point defined by a particular orientation of flux lines at the surface of the ground. A locating arrangement is provided for determining a positional relationship between the boring tool and a portable locator. The portable locator includes (i) at least one antenna for use in identifying the flux orientation point, (ii) an arrangement configured for measuring a signal strength of the locating signal at the flux orientation point using the one or more antennas, (iii) a pitch sensing arrangement for determining the pitch of the boring tool, and (iv) a processing section configured for using the measured signal strength and the determined pitch to establish the positional relationship between the boring tool and the portable locator. In one feature, depth of the boring tool is determined as part of the positional relationship.
REFERENCES:
patent: 5155442 (1992-10-01), Mercer
patent: 5337002 (1994-08-01), Mercer
patent: 5444382 (1995-08-01), Mercer
patent: 5633589 (1997-05-01), Mercer
patent: 5767678 (1998-06-01), Mercer
Radiodetection Limited, Monitoring the Progress of Horizontal Boring Tools, Apr. 1990, Radiodetection Limited Tradeshow Handout, (Date/Page#'s Not Available).
Digital Control Incorporated
Patidar Jay
Pritzkau Michael
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