(51) Int. Cl.: E 21 c, 9/00

E 21 b, 7/04

Federal Republic of Germany

[emblem]

German Patent Office

(52) German Cl: 5 b, 9/00

5 a 7/04

(10) Offenlegungsschrift 2 016 952

(11) [Published Patent Application]

(21) Application number: P 20 16 952.2

(22) Filing date: April 9, 1970

(43) Disclosure date: October 21, 1971

Exhibition priority: --

(30) Union priority

(32) Date: --

(33) Country:

(31) Filing number: --

(54) Title: Drilling Tool Guide

(61) Supplement to: --

(62) Divisional from: --

(71) Applicant: Gräfer, Albrecht, Grad. Mining Eng., Dr. Eng. e.h., 4322 Sprockhövel

Representative according to § 16 of the Patent Act: --

(72) Inventors: Gräfer, Albrecht, Grad. Mining Eng., Dr. Eng. e.h., Pilgrim; Alfred; 4322 Sprockhövel

Notification, pursuant to Art. 7 § 1 para. 2 no. 1 of the law of September 4, 1967 (Federal Law Gazette I, p. 960): --

DT 2 016 952

10.71 109 843/882 5/70

G 208

Dr. Eng. E. h. Albrecht Gräfer

- Grad. Mining Eng. - 4322 Sprockhövel, Wittener Str. 39

Drilling Tool Guide

The invention relates to a device for guaranteeing as vertical a direction as possible during the boring of so-called target boreholes in underground or open pit mining.

The term target borehole is defined in general as a borehole, which is located between two toes or bottoms of a hole, in order to be able to use them at a later date with so-called field extension wells for sliding holes, passage channels or as the exit for blind shaft expansions. The important issue with target boreholes is the ability to reach as accurately as possible the desired end point. The diameter of such target boreholes is generally about 200 m; the length of such target boreholes can range up to 250 m and more.

In order to solve this problem, the current practice is to use predominantly 2 - 5 drill pipes, which are connected downstream of the drilling tool and which exhibit guide bars - so-called drilling guide rods - that are welded on in the longitudinal direction. The outside diameter of the guide bars is adjusted to the diameter of the drilling tool. In the case of material removing drilling tools - for example, cutter heads faced with hard metal or diamond, the usual practice is to select the guide bars so as to be 1 to 2 mm smaller in diameter than the diameter of the drilling tool, in order to prevent the drill pipes with the welded on guide bars from jamming in the drill hole. When roller bits are used that drill holes of varying size, compared to the nominal diameter, in media of varying hardness, the guide bars are selected so that the diameter is 1 to 2 mm greater than the nominal diameter. The latter strategy includes the risk of jamming in the drill hole.

Basically it must be pointed out that the ratio of the diameter of the drilling tool to the diameter of the drill pipe guide bars is largely influenced by the desired course of the borehole.

The smaller the diameter of the guide bars is compared to the drilling tool, the larger is the deviation of the borehole from the desired direction. Even if the diameters are flawlessly matched, the abrasion resulting from the drilling operation will bring about a play-induced enlargement and, thus, an undesired deviation.

In order to remedy this drawback associated with the guide bars with a rigid diameter, one has endeavored to design these guide bars so as to be supported by springs or with other design means in such a way that the guide bars automatically adjust themselves to the largest possible diameter and, thus, limit the difference between the diameter of the borehole and the guide bars to ± 0. In the past the guide bars of the above described type were connected not only rigidly to the drill pipe, so that during the drilling process they rotate along with the drill pipe, but they were also constructed in a pivot mounted manner, so that the guide bars did not carry out the rotational movement of the drill pipes.

None of the aforementioned designs known in the prior art has yielded the desired success, because their construction did not totally satisfy the drilling conditions - in particular, in the case of rapidly alternating types of rock, where it is possible under some circumstances for the individual layers of rock to blow out non-uniformly; and, as a result, there is no perfect engagement surface for the guide bars. In addition, however, the constant alternation between hard and soft layers of rock - in particular, in the carbonaceous rock formations - has a negative influence on the desired drilling direction that to date could not be suppressed with the guide elements known in the prior art.

Therefore, in summary it must be pointed out that to date it has not been possible to bore a straight line borehole over longer distances - for example, 200 m - without conducting expensive directional measurements with a commensurate correction.

The invention described below is based on the problem of remedying the aforementioned drawbacks and of providing a guide, which is intended for the drilling tool, including the downstream drill pipes, and
which automatically corrects the occurring inclination of the drill hole in the event of a deviation from the vertical direction.

The solution to the problem, on which the invention is based, is achieved by a drilling tool guide in the form of a target directed drill pipe, which is characterized in that on deviation from the vertical direction a plumb bob, which is suspended on the center axis of the guide drill pipe so as to be moveable on all sides, activates valves, whereby pressurized drilling fluid causes the guide bar(s) to be pushed radially by way of its (their) assigned adjusting pistons against the wall of the drill hole.

The object of the invention is to provide a spring-load or weight-loaded valve, which opens only after reaching a pre-determined working pressure, in order to maintain a constant working pressure for the activation of the valves in the device.

In order to guarantee the increase in the control sensitivity of the valves, the design provides an unequally legged lever between the plumb bob and the control valves.

Furthermore, the invention proposes that the control movements of the plumb bob be dampened in that it is surrounded by the quiescent drilling fluid.

One embodiment of the invention is shown as a schematic drawing in the attached figures and is described in detail below.

Figure 1 is a longitudinal view of the inventive drilling tool guide with a piston, valve and plumb bob arrangement for underground, upwardly directed target boreholes.

Figure 2 is a cross sectional view along the line A-B of the piston arrangement and design of the valve cone stems.

Figure 3 is a cross sectional view along the line C-D of the plumb bob suspension.

The housing of the drilling tool guide 2 is mounted rotatably on the drill pipe 1. The housing 2 is provided externally with guide ribs 3 for the purpose of accommodating the guide bars 4. The guide bars 4 are held, on the one hand, by threaded bolts 5 against axial displacement. The radial play of the guide bars 4 is guaranteed by spacer sleeves 6 in the area of the threaded bolts 5. In the area of the threaded bolts 5 the cup springs 7 push the guide bars 4 constantly outwards and, thus, against the wall of the drill hole. On the other hand, the guide bars 4 are held by a transverse bolt 8, which is moveable in an oval borehole 9, and, thus, allows and limits the radial movement. The flow of drilling water is returned through the borehole 10 to the drilling tool 11, which is not shown in greater detail. At the same time the valve 12, which is under a calibrated spring force, has to be lifted, as a result of which the availability of a constant drilling water pressure for the purpose of controlling the drilling tool guide is always guaranteed. At the same time the drilling water passes through the boreholes 13 into the annulus 15, which is sealed with collars 14 against the revolving drill pipe 1. The drilling water is conveyed simultaneously over the valve borehole 16 into the cylindrical space below the piston 17. As long as the target borehole runs exactly vertically in the desired direction, all of the pistons 17 are driven simultaneously. The plumb bob 18 is suspended in a cardanic manner on mountings 19 and 20. As soon as the direction of the drill hole begins to slant, the plumb bob 18 swings away and activates via the lever 21 the valve 22, opposing the inclination.

It was pre-determined that the face side of the plumb bob 18 would not be allowed to act directly on the valve 22, since the control sensitivity is supposed to be increased with the high transformation ratio in the lever 21.

In order to damp the oscillations, the annulus 23 is filled with water or the like. If the valve cone 22 is lifted by the plumb bob 18 by way of the lever 21, then the drilling water supply borehole 16 is closed; and the drilling water outlet beyond the profiled valve stem 24 is released. At this point the opposing pistons 17', which continue to be under pressure, can slide back the relieved piston, including the guide bar. At the same time the water escapes over the annulus 23 and the overflow borehole 25 into the environment. Bad Original

It stands to reason that the invention envisages a plethora of design solutions. For example, only 3 or also more pistons than illustrated may be used. Or during the drilling procedure the pistons 17 can also remain unpressurized; and only in the event that the borehole slants, the pistons can be activated on the slanted side by means of a corresponding valve design with the same control system.

Patent Claims

1. Drilling tool guide in the form of a guide drill pipe with a plurality of radially adjustable guide bars, which are mounted on the periphery, characterized in that on deviation from the vertical direction a plumb bob (18), which is suspended on the center axis of the guide drill pipe so as to be moveable on all sides, activates valves (22), whereby pressurized drilling fluid causes the guide bar(s) (4) to be pushed radially by way of its (their) assigned adjusting pistons (17) against the wall of the drill hole.

2. Drilling tool guide, as claimed in claim 1, characterized in that in order to achieve a constant working pressure in the drilling medium in the last drill pipe below the drilling tool, there is a spring-load or weight-loaded valve (12), which opens only after reaching a pre-determined working pressure.

3. Drilling tool guide, as claimed in claims 1 - 2, characterized in that in order to increase the control sensitivity, there is an unequally legged lever (21) between the plumb bob (18) and the control valve (22).

4. Drilling tool guide, as claimed in claims 1 - 3, characterized in that in order to damp the oscillations, the plumb bob (18) is surrounded by the quiescent drilling fluid.

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key to figures

AT = application date

OT = disclosure date

Schnitt = section