Drilling Apparatus

Abstract

A control system for hole-drilling equipment in which a rotary drill bit and stem is rotated at a predetermined speed and the downward force exerted upon the rotary drill bit is controlled in accordance with a signal derived from the torque required to rotate the drill stem at a constant speed and a signal proportional to a desired drilling rate. Further signals proportional to the actual drilling rate and the penetration rate of the drill stem may also be utilized in relative adjustable combinations so as to provide optimum efficiency of operation.

Description

This invention relates generally to automatic drilling apparatus and is more particularly directed to automatic drilling apparatus of the class wherein a rotary drilling bit is operatively controlled so that its speed remains constant as determined by the torque requirements for effecting such speed so as to control the downward pressure upon the drill bit, such control may further include other predetermined factors which may exist as dynamic factors or which may be predetermined in accordance with known experience and drilling factors.

The present invention contemplates the use of well-known portable drilling apparatus which is normally supplied with a tower for generally, vertically slidably receiving and rotatably disposing a drill stem assembly having a drill bit at its lower end. A controllable speed motor is adapted to supply the rotary motion and suitable controllable means are provided for effecting a downward pressure upon the drill stem and thence upon the drill bit. Suitable means are provided for sensing the torque required to maintain a constant speed of rotation of the drill stem. A signal proportional to the torque is then compared with a further signal, the magnitude of which may be selected on the basis of experience. A comparison of the two signals provides a resultant signal which is then utilized to control, through suitable motor drive means, a downward pressure upon the drill stem so that the most efficient, maximum drilling rate may be obtained through strata of various and differing composition as might be encountered in drilling a hole into the earth, for whatever reason desired.

It is therefore an object of my invention to provide drilling apparatus of improved efficiency.

A further object of my invention is to provide drilling apparatus having increased speed of operation.

Another object of my invention is to provide drilling apparatus which automatically compensates for the encounterance of materials of divergent characteristics.

These and other objects of my invention will become apparent from the appended specification, claims and drawing in which the sole FIGURE illustrates a schematic and diagrammatic representation of drilling apparatus incorporating the principles of my invention.

Referring now to the drawing, there is shown a drill rig 10 disposed on a surface 19 of the earth. Drill rig 10 includes a vertically upwardly extending tower assembly 11 which rotatably and vertically slidably supports a drill stem assembly 12 having a drilling bit 13 affixed at its lower end. Drill stem 12 and drill bit 13 are shown extending vertically downwardly through a plurality of layers of materials of varying and divergent composition as represented by reference characters 14, 15, 16, 17, and 18. Such layers may consist, for example, of soft dirt, sand, sandstone, limestone, taconite and the like and experience has proven that such layers may generally be comprised of alternate soft and hard material of varying degrees, each of which may be penetrated by a suitable drill under appropriate circumstances, but none of which present conditions under which one mode of operation of drilling apparatus will efficiently, or even satisfactorily, penetrate.

Shown schematically on the drawing is a rotary drive motor 20 which may be disposed at the top end of tower 11 and is connected through suitable drive means (not shown) to rotate the drill stem that is rotatably, slidably disposed in tower 11. Associated with drive motor 20 is a suitable means (also not shown) which supplies an electrical signal proportional to the torque being supplied to drive motor 20 and thence to drill stem 12 to rotate the same. Such means might comprise a resistance in series with suitable electrical connections for an electric drive motor, the current being generally proportional to the torque required. The resistor might be connected to suitable electrical utilization apparatus shown in the form of an adjustable signal combiner 25, through a connecting means 21.

A second motor, indicated by reference character 22 is shown in the form of a hydraulic motor which is provided with a suitable drive connection 23 to exert a downward force upon drill stem 12. A suitable drive connection 23 might, for example, take the form of chain members (not shown) which are pulled downwardly by the rotation of hydraulic motor 22 to, in turn, exert a downward force upon drill stem 12. Drill stem 12 is also provided with a suitable means (not shown) for generating or providing a penetration rate signal of drill stem 12 into the earth as it proceeds in its intended drilling operation. Such a source may suitably be connected at the upper end of tower 11 and in cooperation with drill stem 12 to provide a signal (proportional to the rate of descent of drill stem 12) that is connected to adjustable signal combiner 25 through connecting means 24.

Signal combiner 25 is provided with a control knob 38 which may be used to effectively proportionally combine the signals appearing on conductors 21 and 24 to vary their relative effect upon the output of signal combiner 25 which appears at conductor 27 that is in turn connected to a first signal comparator 26. Signal comparator 26 is also connected to an adjustable command signal source 28 having a know 39 for providing a suitable reference signal.

Comparator 26 compares the signals comparing on conductors 27 and 29 and provides an output signal of polarity, or sense, and magnitude proportional to the difference between the two signals appearing at the inputs thereof. A second signal comparator 30 is connected to the output of first signal comparator 26 through conductor 31. Comparator 30 also has an input signal supplied by a pressure transducer 32 that is connected in the hydraulic line supplying hydraulic fluid under pressure to hydraulic motor 22. Transducer 32 supplies an electrical signal through conductor 33 to second signal comparator 30. A signal of suitable sense and magnitude is supplied to a hydraulic control valve 34 through signal connector 35. Hydraulic control valve 34 is operative in response to the sense and magnitude of the signal to control the fluid of hydraulic fluid under pressure from hydraulic pump 37 to hydraulic motor 22 to thereby control the force applied in a downward direction to drill stem 12. Hydraulic motor 22 is shown connected to a suitable tank 36 through a hydraulic connection and valve 34 is likewise shown connected to tank 36 through a suitable hydraulic connection.

It is anticipated that the drill rig 10 might conveniently take the form of a Bucyrus-Erie Company Model 60-R Blast Hole Drill to which the principles of my invention may suitably be applied by those skilled in the art. Rotary drive motor 20 might conveniently incorporate the principles of the well-known Ward-Leonard Motor Control System for effecting a predetermined constant rotational speed as determined by the desires of an operator. Having the principles of my invention in mind, the characteristics of adjustable signal combiner 25 and adjustable command signal generator 28 may suitably be determined by those skilled in the art to which my invention pertains. Hence, no detailed presentation of apparatus has been set forth nor has such apparatus been supplied for first and second signal comparators 26 and 30, the penetration rate signal appearing on conductor 24, pressure transducer 32 or hydraulic servo valve 34. All of these components are readily available to those skilled in the art and the exact nature of such devices may vary from individual to individual and are best left to the selection of the independent designer where he is familiar with the operational characteristics of the apparatus.

OPERATION

In operation, drill rig 10 is disposed over the location at which it has previously been determined, a hole is to be drilled into the earth through surface 19. Motor 20 is energized to rotate at a predetermined speed, nominally 60 r.p.m., although this may vary dependent upon the experience and knowledge of the operator of the strata through which the hole is to be drilled. Assuming that know 38 on first signal combiner 25 is positioned so as to eliminate any effect from penetration rate signal 24, a signal proportional to the torque required to rotate drill stem 12 appears at conductor 21 and thence through signal combiner 25 to conductor 27 connected to first signal comparator 26. According to a predetermined value, again, to some extent dependent upon the experience and knowledge of the operator of the apparatus, knob 39 on adjustable command signal source 28 is set at a predetermined value which affects the level of signal applied through conductor 29 to the input of first signal comparator 26.

The signals appearing at conductors 27 and 29 are compared to provide an output signal at conductor 31 of a sense and magnitude proportional to any difference appearing between the signal proportional to the torque supplied by motor 20 and the signal provided by adjustable command signal source 28.

This resultant signal is compared with the signal supplied by pressure transducer 32 which supplies an electrical signal proportional to the downward force exerted upon drill stem 12 by motor 22 at conductor 33. This signal is compared with the signal appearing at conductor 31 to provide a further resultant signal of given sense and magnitude which causes servo valve 34 to operate in such a manner as to increase or decrease the flow of hydraulic fluid to motor 22 to increase or decrease the downward force upon drill stem 12 as dictated by the sense of the resultant signal determined in second comparator 30. A feedback path is indicated by a dotted line extending from servo valve 34 to second comparator 30 to illustrate a simple well known feedback arrangement to suitably control the operation of servo valve 34.

The operation of pump 37 and tank 36 in connection with suitable hydraulic fittings supplied intermediate all of the hydraulic components are believed straightforward and easily ascertainable by one skilled in the art and hence have not been identified by reference characters nor has the exact nature of the apparatus or operation been described except in terms of function, since the requirements may easily be fulfilled by the use of the illustrated or other hydraulic components well known to those skilled in the art.

In a further mode of operation, the effective combination of the torque signal appearing at conductor 21 and the penetration rate signal appearing at conductor 24 may be varied according to the position of adjustment knob 38 on adjustable signal combiner 25.

Claims

Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

1. In apparatus of the class above described, the combination comprising;

a. a drill stem slidably rotatably disposed on a mounting therefor, said drill stem including drill means at one end thereof;

b. drive means, including speed controlling means, disposed on said mounting and operatively connected to rotate said drill stem;

c. means connected to said drill stem and drive means for providing a first signal proportional to the torque output thereof;

d. a second source of signal, said second source of signal being adjustable;

e. first comparator means connected to said first and second signals for providing a third signal proportional to the deviation of said first signal from a predetermined value;

f. further drive means, including control means therefor, connected to said drill stem to drive said drill stem along the axis slidably disposed on said mounting; and

g. said control means including means for providing a fourth signal proportional to the force exerted upon said drill stem by said further drive means and means for controlling the energization of said further drive means in accordance with said third and fourth signals.

2. The apparatus of claim 1 in which the second signal is proportionally related to the formation in which the drill stem is operative.

3. The apparatus of claim 1 in which the fourth signal is of substantially constant magnitude with respect to the first signal.

4. The apparatus of claim 3 in which the first signal includes a further signal proportional to the rate of motion of the drill stem with respect to the longitudinal axis of the mounting.

5. The apparatus of claim 1 in which the first signal includes a further signal proportional to the rate of motion of the drill stem with respect to the longitudinal axis of the mounting.

6. The apparatus of claim 5 in which the second signal is proportionally related to the formation in which the drill stem is operative.

7. The apparatus of claim 5 in which the first signal is of substantially constant magnitude.

8. The apparatus of claim 5 in which means are provided for variably combining the first and further signal.

9. The apparatus of claim 8 in which the second signal is proportionally related to the formation in which the drill stem is operative.

10. The apparatus of claim 8 in which the first signal is of substantially constant magnitude.