Underreamer having cutter arm position indication

#This invention relates to underreaming and chambering tools and more particularly to an arrangement for remotely indicating the position of movable cutter arms on the tool.

#Rotary drills are commonly used for earth boring operations. Such drills are employed in oil and gas wells as well as in mining operations. Often it is desirable to enlarge the diameter of a hole drilled at some point a substantial distance below the surface. In oil and gas wells this is commonly referred to as underreaming, whereas in mining it is commonly referred to as chambering. For ease of explanation, both operations are generally referred to herein as underreaming.

#To effect underreaming operations a variety of underreamers, hole openers, and the like have been devised. With some devices the underreamer can only be installed on the drill string when underreaming operations are taking place. This requires removal of the drill string each time a change is made from straight drilling to underreaming or vice versa.

#These and other features and advantages of the present invention will be appreciated as the same become better understood by reference to the following detailed description of the presently preferred embodiment when considered in connection with the accompanying drawings wherein:

#FIG. 1 is a longitudinal cross-section of the lower underreamer portion with the cutter arms extended and embodies the present invention;

#FIG. 2 is a longitudinal cross-section similar to FIG. 1 with the cutter arms retracted;

#FIGS. 1 and 2 illustrate in side view and partially in section a combined underreamer and latching selector sub constructed according to the principles of the present invention. As illustrated in the present and preferred embodiment, the underreamer has a lower generally tubular shaped outer body portion 10 which may be connected to a lower portion of a drilling string by a conventional threaded female joint 12. The lower portion of the drill string (not shown) typically includes a conventional drill for forming a hole or bore in the earth as the drill string is rotated. Such drills are conventional, forming no part of the present invention, and are not further described herein. The drill is usually coupled directly to the underreamer. Also provided is an upper generally tubular shaped inner body portion 14. The upper body portion contains a threaded male joint 13 for connecting to the lower portion of an upper drill string (not shown). The upper and lower body portions 10 and 14 form longitudinally telescoping upper and lower body portions as they move relative to each other in a longitudinal direction.

#The lower portion of the upper body portion 14 slides along the interior wall of the tubular shaped lower body portion 10. Low friction ring and seal bearings 16 are spaced apart longitudinally in grooves formed around the circumference of the lower portion of the upper body portion 14. Although the invention is not limited thereto, NYLATRON (a registered trademark) GS type bearings made by the Polymer Corporation are used. Significantly the ring and seal bearings 16 form virtually frictionless bearing surfaces on the interior wall of the lower portion 10. This is quite important as it allows the upper telescoping portion 14 to be easily rotated relative to the lower portion 10 while the portion 10 is only held by friction in a hole being bored.

#A splined connector 20 with two separable circular portions is provided in between the telescoping upper and lower body portions 14 and 10 at the tubular shaped portions thereof. Significantly, the splined connector 20 has a first and a second engaged position. Each position has a different angular and a different longitudinal engaged position for the splined connector and hence the upper and lower telescoping portions 14 and 10.