Boring or penetrating the earth – Bit or bit element – Bit with leading portion forming smaller diameter initial bore
Patent
1992-07-10
1993-11-09
Bui, Thuy M.
Boring or penetrating the earth
Bit or bit element
Bit with leading portion forming smaller diameter initial bore
175292, E21B 1032
Patent
active
052594696
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a drilling tool for percussive and rotary drilling in advance of a trailing casing tube, in which tool a pilot bit via an intermediate eccentric shaft is carried by a guide body, which is rotatably centered in and by the mouth of said casing tube on the rotational axis of said tool during drilling, and is coupled to drive means in said casing tube for actuation of said tool, a tubular reamer has an eccentric protruding portion carrying on one axial face thereof hard metal button inserts, and the reamer is pivotally mounted on said eccentric shaft between on the one hand a projected position, in which said eccentric portion with the button inserts thereon are adapted to ream up the hole from the initial diameter produced by said pilot bit to the full diameter of the hole enabling the casing tube to be advanced thereinto, and, on the other hand, a retracted position, in which the drilling tool can be passed through said casing tube.
The drive means usually comprise a drill string which within a string of interconnected casing tubes carries a downhole drill for direct actuation of the drilling tool by way of impacts and rotation as described for example in U.S. Pat. No. 3,848,683 (FIGS. 6-8) or, when tophammer drive is practiced, has the drill string directly coupled to the tool for actuation thereof. The latter drive is exemplified by U.S. Pat. No. 3,753,470 (FIGS. 1-3). In both drilling applications tools provided with hard metal button inserts of cemented tungsten carbide have been in extensive use for more than a decade. One such drilling tool is described in U.S. Pat. No. 4,440,244.
In drilling with tools of the above type normally the reamer element is subjected to the heaviest load and has a shorter operational life as compared to the other tool elements. It is generally expected that in the average two reamers will be worn out for each expended pilot bit, and two pilot bits for each guide body. It is therefore important that attempts to increase the operational life be directed primarily to the reamer so as to prolong the useful time cycle between servicing and change of worn tool elements.
It is an object of the invention to increase in drilling tools of the above type the life expectancy of the reamer primarily by improving the grouping and rock crushing action of its button inserts. Another object is to gain by the chosen rock breaking action that the produced rock debris tends to become more coarse in grain. Another object in connection therewith is to enable the produced coarser rock cuttings to be removed by more efficient flushing whereby secondary crushing of the debris by the inserts is reduced. A further object is to improve reamer work and flushing during drilling of tough clayey ground. These objects are attained by the features stated in the appended claims.
An embodiment of the invention and a modification thereof will be described hereinafter with reference to the appended drawings, wherein
FIG. 1 shows, partly in section, the drilling tool in its drilling position in front of a casing tube to be driven down concurrently.
FIG. 2 shows the tool of FIG. 1 in retracted position while being passed through the casing tube.
FIG. 3 shows the forward portion of the tool in FIG. 1 seen from the rear.
FIG. 4 shows a somewhat enlarged side view of the reamer in FIG. 3.
FIG. 5 shows on a still larger scale a view from below of the reamer in FIG. 1 seen on the line 5--5 thereof.
FIG. 6--8 are sections in the scale of FIG. 4 seen on the respective lines 6--6, 7--7, and 8--8 in FIG. 5.
FIG. 9 shows enlarged a modified embodiment of the reamer depicted in a side view similar to FIG. 3.
FIG. 10 is a view showing the modified reamer of FIG. 9 from below in a presentation similar to FIG. 5 but also indicating in section the eccentric shaft carrying the reamer.
In analogy with the above cited patent references, the drilling tool in FIG. 1 comprises a pilot bit 11, a reamer 15 and a guide body 18. In practicing tophammer drilling the slightly modified guide body thus would b
REFERENCES:
patent: 3753470 (1973-08-01), Lagerstrom et al.
patent: 3848683 (1974-11-01), Persson
patent: 4440244 (1984-04-01), Wiredal
patent: 4770259 (1988-09-01), Jansson
patent: 5009271 (1991-04-01), Maric et al.
patent: 5040621 (1991-08-01), Lof
Lof Uno S.
Stjernstrom Karl-Axel
Bui Thuy M.
Munson Eric Y.
Stone Mark P.
Uniroc Aktiebolag
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