Method for overburden drilling, casing shoe and casing tube for

Boring or penetrating the earth – Tool removable or insertable through or around driving or...

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Details

267273, 285908, E21B 1708

Patent

active

055424830

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention refers to a method for overburden drilling with simultaneous loading of casing tube, a casing shoe and a casing tube for the method and a coupling element for casing tubes designed to be used with the method.


DESCRIPTION OF THE BACKGROUND ART

When drilling in soil, a central pilot drill bit is used together with a reamer drill bit so arranged that it can be thrown out eccentrically in relation to the pilot drill bit and expand the hole drilled by it. Thereby the bore will be of a dimension enough to give room not only for the pilot drill bit with the reamer drill bit in its inner position but also for a casing tube brought down in the hole at the same time as the hole is drilled. The casing tube is driven downwards with the drill bit through a casing shoe welded to the end of the casing tube and influenced by the percussive drill hammer. The casing tubes usually consist of three meters in length of steel welded together as drilling and the tube is driven downwards to a suitable extent.
One problem when dealing with the casing tubes is their weight. One further problem is the possibility of corrosion, which in some cases causes the exchange of them to plastic tubes after the drilling, a circumstantial and laborious procedure.


SUMMARY OF THE INVENTION

One object of the present invention is to eliminate the exchange of casing tubes and one further object is to facilitate the handling of casing tubes during drilling. These and other objects are fulfilled by using casing tubes of plastic material from the beginning, which in turn according to the invention is made possible by a special design of the casing shoe and of coupling elements for the casing tubes giving a strong anchoring in the plastic material.
Still one further object of the present invention is to achieve a joint of the casing tubes of plastic material in a simple way. This can be done by joining metal elements to the ends of the casing tubes in the some way as the casing shoe, the metal elements supporting tube couplings, for example of the threaded type.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described more in detail referring to the drawings which are given by way of illustration only, and thus are not limitative of the present invention, and in which:
FIG. 1 shows schematic and partly broken through an example of a known design of the parts at the drill bit of a machinery for simultaneous drilling and casing of the bore;
FIGS. 2 and 3 shows partly in section the design of a casing shoe according to the invention in two embodiments; and
FIG. 4 shows casing tubes with tube couplings according to the invention.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The drill bit in FIG. 1 consists in a known manner of a pilot drill bit 1, a reamer drill bit 2 and a guide 3 for a percussive drill hammer (not shown). The drill bits 1 and 2 and the guide 3 can be rotated and axially influenced by the percussive drill hammer. A casing shoe 5 consists of an upper part 6 and a lower part 7, both cylindrical. The inside diameters of parts 6 and 7 are alike and adapted to the outside diameter of the lower part of the guide 3. The outside diameter of the upper part 6 of the casing shoe is adapted to the inside diameter of the casing tube while the outside diameter of the lower part 7 is substantially the same as the outside diameter of the casing tube 4. The upper part 6 of the casing shoe is ended upwards with a shoulder 8, against which the guide 3 transfers the percussions of the hammer through a corresponding shou

REFERENCES:
patent: 3033919 (1962-05-01), Aschinger
patent: 4168393 (1979-09-01), Silva
patent: 4926909 (1990-05-01), Salinas
patent: 5110382 (1992-05-01), Terry et al.

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