Boring or penetrating the earth – Automatic control – Of advance or applied tool weight
Patent
1993-07-22
1994-09-20
Dang, Hoang C.
Boring or penetrating the earth
Automatic control
Of advance or applied tool weight
173 1, 173 4, 175 24, E21B 4400
Patent
active
053481062
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of controlling a rock drilling process, wherein a percussion power and a feed force of a drilling machine are adjusted to optimize the drilling process so that the rotation power of the drill is no more than a preset limit value.
Rock drilling is usually based on a control system in which the driller controls the operation of the equipment on the basis of his practical experience. In such cases, the driller usually sets certain basic values on the basis of the assumed conditions and does not have time to observe possible deviations and to control the operation accordingly. Especially with a drilling equipment comprising several booms, the driller is not able to observe all of them sufficiently efficiently and continuously to be able to control them optimally. This usually results in partially inefficient drilling as well as equipment damages.
In systems based on automatic control of drilling, the feedback and control are effected by using hydraulic actuating means in such a way that one operating parameter, such as percussion, rotation or feed, is controlled on the basis of another parameter so that, for instance, The feed is retarded or the percussion is increased when the force required for rotation increases. In these solutions, the adjustment is based on mere proportioning of certain operating parameters to each other without being able to more accurately set adjusting parameters dependent on the conditions.
U.S. Pat. No. 4,793,421 discloses a programmed automatic control system aimed at optimizing the drilling. This system utilizes two groups of parameters one of which is used to control the maximum rotation rate by sensing means and the other to control the supply of the maximum power to the feed motor. In the US Patent, the maximum values of both rotation and feed are applied until the preset limit values are achieved in either way or the drilling conditions require that the limit values be reset. The system of the US Patent is not directly applicable to rock drilling as it adjusts only rotatory drilling. In addition, the system merely aims at maximizing the rotation power or feed power, while the different drilling stages are not adjusted separately.
U.S. Pat. No. 4,354,233 discloses a solution iin which a computer compares a preset penetration value to an actual penetration value. In this method, the rotation rate and the axial load, i.e. feed, as well as torque and oscillation rate are adjusted. Changes in the adjusting values of the different drilling stages are not taken into account in any way.
U.S. Pat. No. 4,165,789 discloses a method in which the optimization is based on the adjustment of the rotation of the drilling machine and the adjustment of the rotation resistance. The method aims at keeping one parameter constant by adjusting the other parameter. The solution is very simple and does not enable the optimization of the entire drilling process. Moreover, it does not in any way take into account the different adjustments and parameter changes required at the different drilling stages.
U.S. Pat. No. 3,581,830 teaches measuring torque of the drill rod, the feed force being used as an adjusting parameter. The feed force, that is, the feed rate is decreased when the adjustment exceeds a preset value. This U.S. patent merely aims at keeping the torque strain of the drill rod below a certain limit value and it does not in any way teach adjusting or not even aim at adjusting the drilling process by changing the set values as required by the different drilling stages. A common disadvantage of the systems of the above-mentioned patent documents is that they adjust only a part of the drilling process and their parameters are difficult if not impossible to change.
A further disadvantage of the prior art systems is that they typically result in uneconomic drilling as the drilling parameters are inappropriate in one way or another. Systems based on hydraulic control respond rather slowly to sudden changes occurring during the drilling, as a result of which inefficie
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Dang Hoang C.
Tamrock Oy
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