Boring or penetrating the earth – Bit or bit element – Bit with leading portion forming smaller diameter initial bore
Patent
1996-08-26
1998-09-08
Neuder, William P.
Boring or penetrating the earth
Bit or bit element
Bit with leading portion forming smaller diameter initial bore
175391, E21B 1028
Patent
active
058031952
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a system, a method and a cutterhead for dry full-area drilling according to the preambles of the independent claims.
A downward-drilling system according to the preamble of claim 1 is known from U.S. Pat. No. 5,199,515. This system operates with compressed air which is injected towards the shaft bottom through a hollow drill string and blow nozzles communicating therewith which are arranged on the cutterhead, as well as with suction air operating through suction nozzles arranged on the cutterhead and riser ducts communicating therewith. The riser ducts serve to remove cuttings which are produced by the rotating, crushing cutterhead and which are transported with the aid of the compressed air towards the suction nozzles and through stationary riser pipes to above ground. The nser ducts and the stationary riser pipes are interconnected by a swivel.
This known system has however proved to involve the risk that the cuttings produced swirl up and are sprayed about by the compressed air and that portions of the swirling cuttings are out of the reach of the suction nozzles. As a result, cuttings and dust will impinge on the shaft wall and adhere to it. This entails that the cutterhead will work material that has already been partially worked, resulting in unnecessary wear to the cutterhead and lower cutting efficiency of the system. Moreover, the shaft walls are sometimes soiled to an unacceptable extent, for example in the case of bedrock depository of spent nuclear fuel.
The object of the invention is to overcome or at least essentially reduce the above-described problems inherent in the prior-art drilling system. Also, the invention aims to provide a constructional simplification of the known system.
According to the invention, these objects are achieved by means of a drilling system, a drilling method and a cutterhead according to the description below.
According to the invention, the use of compressed air is thus dispensed with, the cuttings being removed by suction only. To this end, there is provided at least one suction nozzle at the underside of the cutterhead, the suction nozzle or nozzles each having a suction intake at the periphery of the cutterhead, where a relatively larger amount of cuttings is produced by the cutterhead from the shaft being drilled. The suction intake communicates with a suction channel which is provided in a drill string and which is connected to a vacuum unit above ground. If several suction nozzles are used, which is preferred, they are arranged pairwise substantially along diameters of the cutterhead. Preferably, the cutterhead has a pilot drill bit which is provided with additional suction nozzles, also communicating with said suction channel.
The invention has also proved applicable to tunnel drilling.
The invention will now be described in more detail with reference to the accompanying drawings showing an embodiment thereof.
FIG. 1 shows a cutterhead according to the invention in perspective,
FIG. 2 shows the cutterhead partly in section and partly schematically,
FIG. 3 shows the cutterhead from below.
FIG. 4 shows means for guiding the cuttings in a section taken along line IV--IV in FIG. 2, and
FIG. 5 shows a drill pipe with a suction sleeve.
FIGS. 1-3 show a cutterhead 1 for dry rotary, crushing full-area drilling. The cutterhead has a pilot drill bit 2 on a pilot rod 3, a base head 4 and an adapter 5 for connecting the cutterhead 1 to a drill string 6 (FIG. 5). The roller cutters of the base head 4 and of the pilot drill bit 2 are designated 7 and 8, respectively. The construction described so far is previously known and also comprises stabiliser rollers 8A.
Through the base head 4 and the pilot drill bit 2 extends a suction channel 9 which via a plenum 10 merges into a suction channel 11 arranged in the drill string 6 (FIG. 5). This suction channel is connected to a vacuum unit (not shown) via a separator, such as a cyclone (not shown), for cuttings produced by the cutterhead 1 in the shaft.
At the bottom, the suction channel 9, extend
REFERENCES:
patent: 3314724 (1967-04-01), Tinlin
patent: 4275796 (1981-06-01), Kleine
patent: 5199515 (1993-04-01), Sinclair et al.
patent: 5417292 (1995-05-01), Polakoff
Brolund Stig-.ANG.ke
Haugen Karl Thorbjorn
Kallvik Roland
Lovgren Gert Axel
Kroll-Disab AB
Neuder William P.
Sandvik AB
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