Apparatus for determining the curvature of an elongated hole

Details Apparatus for determining the curvature of an elongated hole Apparatus for determining the curvature of an elongated hole

1997-08-13

1999-08-31

Kim, Robert

Optics: measuring and testing

By particle light scattering

With photocell detection

356352, G01B 902

Patent

active

059460946

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to apparatus for determining the curvature of an elongated hole, such as a drill hole, in rock;
2. Description of the Related Art
Apparatus of this kind find use in ore prospecting operations and in investigating and mapping ore deposits and other types of deposits. It is, of course, important when investigating ore deposits for instance, to be aware of the actual directional extension of the test holes that are drilled to this end, for instance the location of the hole at different depths, in order to effectively map the deposits. Such drill holes will always have curved sections and it is therefore necessary to determine the actual longitudinal extension of the drill hole. In this regard, there has earlier been used an apparatus of the kind taught by SE-C-387698 (7304122-0), wherein an apparatus probe is moved to different longitudinal sections of the hole and is constructed to conform to the curvature of the hole. Curvature or bending of the probe is determined with the aid of a camera which observes an objective in the probe, wherein the relative transversal displacement of the objective caused by curving of the probe constitutes a measurement of the curvature of the drill hole.


SUMMARY OF THE INVENTION

In order to provide an accurate measuring result and, at the same time, to minimize the total cost of the preliminary exploration, the known probe must have a relatively large diameter. Naturally, the diameter of the test drill hole must be correspondingly large, and it is well known that the cost of drilling the test hole increases with increasing hole diameters.
It is therefore generally favourable from the aspect of cost to use narrow drill holes to this end, without detracting from the accuracy to which the curvature of the hole is determined along its length.
It is therefore an object of the present invention to provide an apparatus probe of the aforesaid kind which combines high measuring accuracy with a small but effective diameter.
A further object of the invention is to provide an apparatus which is very flexible, magnetically insensitive, production friendly and temperature independent and which enables measurements to be made at several points along the probe in a simple manner.
These objects are achieved with the present invention.
As will be understood, the invention is not restricted solely to determining the longitudinal extension of drill holes in rock, but can be used more generally to determine the curvature of any form of channel or passageway. In an extreme case, such a channel or passageway may conceivably have the form of a slot, wherein the actual probe may be rigid in the width direction of the slot when it is essentially only necessary to obtain information regarding curvature of the slot solely in a plane at right angles to the width direction of the slot.
According to the invention, an optic fibre section is fitted in or on the probe body at a distance from its bending neutral line, preferably close to the outer surface of the probe body. The optical fibre section is mounted in the length direction of the probe. Consequently, as the probe bends, the optical fibre section will be subjected to a change in length that is representative of the extent to which the probe bends in an axial plane embraced by the optical fibre section and the probe axis. By probe axis is meant its bending neutral line, i.e. the centres of gravity of respective probe cross-section areas. According to the invention, the channel curvature is evaluated by calculating the physical change in distance between two partial reflection devices (e.g. gratings) in an optical fibre, but the curvature is measured optically such that the measuring result will comprise primarily the optical change in distance between the partial reflection devices. It is important to note that this optical change in distance does not solely correspond to the physical change in distance but is also influenced by the fact that the optical properties of the fi

REFERENCES:
patent: 4436419 (1984-03-01), Stetson et al.
patent: 4525818 (1985-07-01), Cielo et al.
patent: 4806012 (1989-02-01), Meltz et al.
patent: 4927232 (1990-05-01), Griffiths
patent: 5301001 (1994-04-01), Murphy et al.
patent: 5528367 (1996-06-01), Putnam et al.

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