Boring or penetrating the earth – Automatic control – Of advance or applied tool weight
Patent
1993-09-24
1995-02-14
Dang, Hoang C.
Boring or penetrating the earth
Automatic control
Of advance or applied tool weight
175 57, 175381, E21B 4400, E21B 1062
Patent
active
053886496
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an apparatus for drilling in soil or rock and a method for regulating its penetration, where the penetration is restricted if one or more drill bits are overloaded.
BACKGROUND OF THE INVENTION
Previously known drilling equipment is described in Finnish Application No. 891706, in which drilling is carried out either by means of a hammering or a rotating tool. The application describes how a hammer furnished with a drill bit and with or without a bit-rotating tool can be backed into its cylinders if the drilling unit is driven too far forward.
The pressure shocks caused by the tool upon drilling are a disadvantage of the above solution, because they disturb the control of backing the whole tool unit. Generally, it is possible to control the backing of the tool only when the drill head is driven on the wall which is being drilled and detection of the whole drill head reading the target is possible as a result of the backing of the tool.
SUMMARY OF THE INVENTION
The present invention enables elimination of possible damage to the single bits and dependable control of the backing of the drill bits. The invention is characterized by the features described in the patent claims.
It can be considered the major advantage of the invention that even in a multi-bit tool the single bits can be controlled individually, their overload detected and, accordingly, the feed motion stopped or feeding force restricted in order to prevent the bits from being damaged. With such a tool it is possible to drill in soft soil very fast and on facing rock, no matter at which angle, even at the reach of one bit only, because, due to its backing capacity, the bit is not damaged. A single bit in a conventional multi-bit tool would not remain undamaged in such a situation since it would then have to sustain the whole feeding force alone.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention is described in detail with reference to the enclosed drawings where:
FIG. 1 is a multi-bit drilling tool;
FIG. 2 is a cross-section of a shock-absorbing cylinder of a bit;
FIG. 3 is a diagram of a hydraulic system; and
FIG. 4 is a diagram of an alternative hydraulic system.
FIG. 1 shows a rotatable tool 1 at the head of which there are several drill bits of different types. As a matter of principle, all the bits are cutting discs 4 which, on cutting soil or rock, move into slow rotation around their shaft while tool 1 is rotated and fed forward. The drill bit rods 5 are at the same time rods of pistons 6 of hydraulic cylinders 7, at the heads of which supporting parts 2,3 for the cutting discs 4 are fixed.
FIG. 2 shows a hydraulic system by means of which the backing of a bit is functioning. From the former cylinder, hydraulic pressure enters into cylinder 7 through back-valve 18. The drill bit and the piston are then in a slightly backed, or rearward position.
1. If feeding is stopped because of overload in this drill bit, the piston is affected by pressure, e.g. adjusted to 100 bar, over valve 18, pushing the piston to its extreme, or forward position. From the other side of the piston, oil escapes through valve 15, the opening pressure of which is, for instance, 120 bar. Due to the considerably smaller cross-sectional area of the piston, pressure can rise even more thereby opening valve 15 and allowing oil to flow to lower pressure. When no oil leaks out through the oil outlet pipe 12, this is a sign that the piston is in a backed position at least in one of the cylinders.
When the piston reaches its extreme position the spindles 13 and 14 open respective valves, so that oil starts to flow through the piston along channel 17 and further along channel 12 to the next cylinder. The piston remains in its extreme position if there is no overload, though the same pressure of ab. 100 bar prevails on both sides of the piston. In the piston, a force remains active which is caused by the cross-sectional ratio and considered proper load for the drill bit. If there was a similar backed situati
REFERENCES:
patent: 1612338 (1926-12-01), Wilson et al.
patent: 2819041 (1958-01-01), Beckham
patent: 2942850 (1960-06-01), Heath
patent: 3924690 (1975-12-01), Shaw
patent: 4386669 (1983-06-01), Evans
Derwent's Abstract, No. 84-80 378/13; 16.06.81.
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