Boring or penetrating the earth – Automatic control – Of advance or applied tool weight
Reexamination Certificate
1998-12-08
2001-04-03
Schoeppel, Roger (Department: 3672)
Boring or penetrating the earth
Automatic control
Of advance or applied tool weight
C175S106000, C175S203000, C175S319000, C175S434000
Reexamination Certificate
active
06209662
ABSTRACT:
The present invention relates to a method of and apparatus for controlling diamond drill feed and is particularly concerned with computer controlled system.
BACKGROUND OF THE INVENTION
Core drilling with a diamond drill consists of rotating a tubular rod string and diamond bit at high speed (normally up to approx. 1800 rpm) and feeding a drill string into a rock formation. Diamonds impregnated in the matrix of the bit cut the rock resulting in a core entering the hollow drill rods as the bit advances. This core is retrieved by methods such as wirelining or reverse circulation, and retained for analysis. Water is pumped down the inside of the drill string (outside the drill string if using reverse circulation) in order to clear the cuttings from the bit, and keep the bit cool. The exposed diamonds on the bit wear and become dull, and thus require sharpening. Sharpening the bit is done in the hole and involves stripping a part of the matrix off the bit in order to expose new diamonds. This drilling and sharpening is a continual process until the bit is worn out and must be replaced. All the rods must be pulled out of the hole to replace the bit, and reinserted with a new bit.
Conventionally, diamond drilling has been done with manually operated hydraulic machines using a pressure controlled feed system. More recently, some attempts have been made to control the drilling process using microprocessors and electrically controlled actuators. To our knowledge, all of these attempts have involved using electric actuators to replace the handle on otherwise manually controlled pressure control valves. This approach may not allow a microprocessor to be used to its full potential in the control of the drilling process. Some of the most important inherent difficulties in these systems include poor positioning accuracy and poor response time to changing load conditions in the hole, as would occur when penetrating through rock formation transitions or faults, and sharpening the bit, particularly in deep hole conditions.
U.S. Pat. No. 4,157,231 discloses a hydraulic drilling unit for precision machine drilling, which uses a modulating servo valve to adjust a feed rate under computer control, but in the positive direction only. Because this patent does not provide a holdback force to compensate for the length and weight of a diamond drill string, it can not be applied to a diamond drill.
U.S. Pat. No. 5,449,047 discloses a computer control system for blast hole drilling, which also uses unidirectional modulation. Again, because it does not provide a holdback force to compensate for the length and weight of drill string, it is not appropriate for a diamond drill. Further, this patent teaches that the drill rate of penetration should be reduced when passing through less dense material or voids.
Germany Patent No. 94 02 360 discloses a computer control system for auger drilling, which also uses unidirectional modulation. Again, because it does not provide a holdback force to compensate for the length and weight of drill string, it is not appropriate for a diamond drill.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved method and apparatus for controlling the drilling process on a diamond drill.
In accordance with an aspect of the present invention there is provided an apparatus for controlling a diamond drill, wherein, during operation, a bi-directional hydraulic drive, having a head end and a rod end, is coupled to the drill string of the diamond drill allowing either holdback or pulldown forces to be applied thereto, the apparatus comprising: (a) position sensor means adapted to be coupled to said diamond drill for generating a position signal; (b) computing means, including means for setting a desired rate of drill penetration, for determining a feed rate control signal in response to said position signal and said desired rate of drill penetration; and (c) valve means for controlling hydraulic flows to said bi-directional hydraulic drive which, in use, is coupled to said diamond drill, to apply either holdback or pulldown forces to the latter, in response to said feed rate control signal to approximate the desired rate of drill penetration, thus accommodating for a varying length and weight of drill string.
In accordance with a further aspect of the present invention there is provided a method of controlling a diamond drill, wherein a bi-directional hydraulic drive is coupled to the diamond drill to apply pulldown or holdback forces thereto, the method comprising the steps of: (a) pre-setting a desired rate of drill penetration; (b) sensing a position of said drill and generating a position signal in response thereto; (c) computing a feed rate control signal in response to said position signal and said pre-set desired rate of penetration; and (d) applying the pulldown or holdback forces to said drill during a drilling operation in response to said feed rate control signal to approximate the desired rate of drill penetration.
A further embodiment of the invention includes a hydraulic drive head, a hydraulic feed cylinder coupled to the drive head for changing the position of the drive head, a feed control apparatus including a linear position sensor coupled to the feed cylinder for generating a position signal, a positioning module for generating a feed control signal in dependence upon the position signal, a flow control valve having two hydraulic ports for connecting to the feed cylinder and responsive to the feed control signal for controlling flow rate of the two hydraulic ports, a plurality of operation sensors coupled to the diamond drill for generating operation status signals, a plurality of input modules for receiving the operation status signals and converting them to digital operation status signals and a programmable logic controller connected to the plurality of input modules for modifying the feed control signal in dependence upon the digital operation status signals.
A still further embodiment of the invention includes a hydraulic drive head, a hydraulic feed cylinder coupled to the drive head for changing the position of the drive head, a feed control apparatus including a linear position sensor coupled to the feed cylinder for generating a position signal, an integrated programmable logic controller including positioning means, input means and logic means, said positioning means for generating a feed control signal in dependence upon the position signal, a flow control valve having two hydraulic ports for connecting to the feed cylinder and responsive to the feed control signal for controlling flow rate of the two hydraulic ports, a plurality of operation sensors coupled to the diamond drill for generating operation status signals, said input means for receiving the operation status signals and converting them to digital operation status signals and said logic means connected to said input means for modifying the feed control signal in dependence upon the digital status signals.
A feed system controlling flow rate to the feed cylinder offers many advantages over the conventional drill as well as over those using microprocessors to control pressure control valves.
The foregoing and other objects of the invention are accomplished by utilizing a microprocessor controlled closed loop positioning system-to control the rate of penetration (ROP) at the desired level.
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“Introducing the Line
Atlas Copco Canada Inc.
Biebel & French
Schoeppel Roger
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