US 3039543 A
Description (OCR text may contain errors)
June 19, 1962 G. LOOCKE DEEP DRILLING CONTROL SYSTEM 2 Sheets-Sheet 2 Filed Nov. 12, 1957 0 a W 3 1 w m 3 H m 3 3 5 B m M 3 w 2 3 L 3 W 3 0J 3 a 3 L w I 3 L o f o O 1|! F f --I I E L L a I 0 c m 5 i 3 A 3 g 3 Wm H .Q 9 5 0 a A6 m w M e A 3 w 3 L 0 MJJ u 3 EN Inventor:
GWWA W4 United States Patent Germany Filed Nov. 12, 1957, Ser. No. 695,899 Claims prioritsy, application Germany Nov. 12, 1956 Claims. (Cl. 17 -26) The present invention relates to deep drillings and more particularly to an electric control system for deep drills and deep drilling operations.
Deep drillings particularly those for oil wells, are generally done by a drill bit fastened to the lower end of a drill rod. The latter is driven by a motor at its upper end, the motor being stationed on the surface of the earth.
Recently, an improved drill has been devised, in which the motor is positioned at the lower end of the drill rod above the drill bit. The electric motor directly impels the drill bit whereas the tubular drill rod does not revolve and is only used for removing the drillings from the drilling hole, generally by means of liquid passed through the drill pipe. The drill pipe is suspended into the drilling hole from a derrick and is progressively released in accordance with the advancement of the drill bit in the earth.
The known drilling devices do not speed and efficiency of operation.
In particular, the drilling speed is not adjusted to its optimum degree at any given moment.
The drilling speed (v), i.e. the speed at which the drill bit advances vertically in the earth depends on a plurality of conditioning factors, as, for example, the nature and structure of the ground, the torque of the motor driving the drill, and the quantity of the flushing liquid (generally wash water) which is conveyed through the drill tube in order to remove loose earth, rocks, etc., loosened by the drill bit.
In case of an elevated drilling speed a considerable amount of drillings has to be removed from the drilling hole and hence the quantity of wash fluid must be correspondingly great.
Of course, the total amount of the wash liquid cannot be increased beyond a certain 'amount in view of the limited capacity of the pump or the cross section of the pipe conduits. If the drill speed is even further increased, the amount of the wash liquid becomes insufiicient and is therefore incapable of removing the entire drillings. The drill bit may then get stuck in the loose, unremoved drillings and it may even break.
It is therefore of paramount importance to adjust the drilling speed to the available wash liquid, and to adjust the drilling speed to the various other above named conditioning factors, as the torque capacity of the motor, the structure of the earth.
It has already been suggested in the art to adjust the drilling speed by providing a plurality, for example four, electric motors at the lower end of the drilling rod, which can be switched on and on" together or separately from a control desk above the ground, thereby changing the torque with which the drill bit is impelled.
In the motor casing there is arranged a telephone or microphone detecting the drilling sound and conveying the same to the control desk above the ground, where a listening operator tries to discern from the quality of the received sounds if the drill bit operates in soft or hard ground and correspondingly decides if and how many electric motors have to be switched in or have to be switched oli, respectively, in order to adjust the drilling speed to the prevailing conditions in the drilling hole (see US. patent to Lord 1,666,461).
, It is quite obvious that this manner of control requires attain an optimal 3,339,543 Patented June 19, 1962 great skill and experience on the part of the operator and is still insufiicient and unreliable.
It is an object of the present invention to provide an automatic control system for use with deep drills of the type having the motor mounted at the lower end of the drill rod in the drill hole and directly impelling the drill bit, with the drill rod remaining stationary, which controls the drilling operation of the deep drill so that at each moment of the drilling operation the optimal drilling speed is obtained under the prevailing drilling conditions.
It is another object of the present invention to provide an automatic control system for use with deep drills of the type having the motor mounted at the lower end of the drill rod in the drill hole and directly impelling the drill bit, with the drill rod remaining stationary, which is fully automatic and assures an elficient and reliable control in an uncomplicated manner.
It is a further object of the present invention to provide an automatic control system for use with deep drills of the type having the motor mounted at the lower end of the drill rod inthe drill hole and directly impelling the drill bit, with the drill rod remaining stationary, which guarantees the greatest possible progress of the drilling operation while avoiding damage to the drilling equipment, and particularly the motor and the drill bit.
These objects are achieved by the automatic control system of the present invention for controlling deep drillings, in which the drilling is effected by a drill bit driven by an electric motor provided at the lower end of a drilling rod in the drill hole and in which the drill rod is suspended from a winch above the ground.
According to the present invention, the automatic control is effected by interconnected electrical control systems automatically adjusting the drilling speed to its optimal value, taking into consideration the prevailing drilling conditions.
The control system of the trol systems hereinafter identified as a, b, c.
The control system or controls the drilling speed so that the maximum value of the permissible torque of the motor driving the drill bit is not exceeded.
In the control system b the drilling speed and the quantity of flushing liquid conveyed to the drilling hole are controlled and adjusted to each other so that the necessary quantity of flushing liquid is supplied to the drill hole without undue waste of flushing liquid.
The control system c envisages the situation in which the quantity of the flushing liquid cannot be increased and in which the flushing liquid is now kept at a constant level. The control circuit 0 renders the maximum amount of the flushing liquid, the control reference value factor which controls the drilling speed, so that no more drillings are produced as can be removed by the maximum amount of flushing liquid, control system 0 also ensures that the permissible torque of the motor is not exceeded.
The invention will be better understood upon the following description of the accompanying drawings, wherein FIGURE 1 is a schematic view of a deep drill of the.
type having the motor driving the drill bit disposed at the lower end of the drill rod in the drill hole;
FIGURE 2 is a schematic representation of the switching diagram of the control systems a, b, c' of the control arrangement of the present invention;
FIGURE 3 is a schematic view of one embodiment of the control arrangement for deep drills of the present invention.
Referring now to the drawings somewhat more in detail and turning first to FIGURE 1, the drill rod 2 is suspended from the derrick 1 and bears at its lower invention comprises the conend the electric motor 3 driving the drill bit 4. Since the drill rod 2 is suspended on the suspension wire 5, the electric motor 3 and the drill bit 4 are relieved from some of the weight of the drill rod 2. The suspension wire 5 is guided over a pulley 6 and a winch "7 and can be raised or lowered by the latter in accordance with the drilling speed. Preferably, the winch 7 is driven by a motor. Flushing liquid is pumped into the drill rod 2 at its upper end by pump (not shown in FIG. 1) via the tube 8. The drill rod 2 does not rotate and remains stationary during the drilling. It is only used. for car-rying the electric motor 3 and the drill bit 4 and as a conduit for conveying the flushing liquid to the drilling hole. This Wash liquid has to remove the drillings from the hole.
The control system schematically shown in FIGURE 2 comprises the control circuits at, b, c, which will next be described.
The particular size and construction of the electric motor 3 determines the theoretical torque output which the motor can furnish at a particular voltage, frequency and stator current. This theoretical torque is reproduced by the setting device it as a reference value. The actual torque output of the motor 3 can be ascertained by measuring voltage, frequency and stator current, and these measured values can be used to reproduce the torque; this is carried out in the transforming device 11. In other words, device It} produces a reference value, for example a current indicative for the desired torque and device 11 reproduces the actual torque as produced by motor 3.
The torque exerted by the drill bit, and hence the actual value of the torque of the electric motor 3, depends to a great extent on the load applied to the drill bit. The torque of the electric motor 3 can therefore be varied by turning the winch 7 in one direction or the other so as to raise or lower, respectively, the drill rod 2, thereby increasing or reducing, respectively, the pressure exerted by the latter upon the drill bit 4.
The second important factor is the drilling speed. This factor can be ascertained from the speed v with which the suspension wire 5 is released from the winch. The latter speed can be easily determined by measuring the rotary speed of the pulley 6. A control value corresponding to the measured value of the drilling speed v is formed in the transforming device 12.
A third important factor is the quantity of the flushing liquid. it is measured by a quantitative measuring device 13 an example of which is disclosed in FIG. 3, elements 331, 332 to be explained later.
In the setting device it a predetermined DC. current is provided which represents and corresponds to the reference control value of the torque of the motor 3. The transforming device 11 furnishes a value proportional to the actual value of the torque of the motor. This value is preferably proportional to the active current of the motor in which case both voltage and frequency are also controlled. In the comparing device 14 an error signal is ascertained by comparing the reference value produced in the setting device it} and the actual value of the torque of the motor supplied by the transforming device 11. In accordance with this error signali.e. the difference between the reference value and the actual value of the torque of the motor-the automatic controller 15 is actuated which, in turn, controls the winch 7 via the automatic control circuit (system) a in the following manner:
If the actual value of the torque of the motor 3 is too small, i.e.- less than the reference value, the winch is caused to turn in clockwise direction so as to release an additional portion of the suspension wire 5, thereby increasing the weight of the drill rod 2 and the motor 3 upon the drill bit 4. Due to the increased pressure upon the drill bit, the torque of the latter and the motor is also increased until the actual value of the torque has become equal to the reference value.
If the actual value of the torque is too great, i.e. greater than the reference value of the torque of the motor, the winch 7 is caused to turn in counterclockwise direction so as to reduce the weight of the drill rod acting upon the drill bit 4. Consequently, the torque is reduced until actual value and reference value of the torque have again become equal.
In both instances the change of the torque of the motor varies the value formed by the transforming device 11 correspondingly (see the double arrow behind the winch 7 in the diagram of FIGURE 2).
The quantity of flushing liquid Q to be furnished by the pump 8 depends on the drilling speed v. A suddenly increasing drilling speed v indicates that the drill bit 4 has hit upon ground of a softer structure and therefore produces a greater amount of drillings than before. in this situation the quantity Q of flushing liquid must be increased in order to remove the greater amount of drillings and to prevent the drill bit from getting stuck in the loose gravel. The value of the drilling speed v formed in the transforming device 12 is therefore used as a controlling condition for adapting the amount of the flushing liquid to this new situation. This is done by comparing in a device 17 the value supplied by the transforming device 13 representing the actual value of the quantity Q of flushing liquid with the value supplied by the transforming device 12. The resulting deviation, which is also an error signal, actuates the automatic controller 17 thus inducing the latter to effect a corresponding change of the amount of flushing liquid conveyed by the pump 8. (Control system b.)
If the drilling speed continues to increase, it may occur that the maximum conveying capacity of the pump and the conduits is reached. It is therefore necessary to reduce the drilling speed down to a level corresponding to the maximum available quantity of flushing liquid. The reduction of the torque of the drill bit, which is equivalent to a reduction of the drilling speed, is effected by the automatic control system c. As soon as the maximum value Q of the capacity of pump 8 is reached, a signal is sent by the maximum contact 8 to the pump 8. As the contact 8 closes, the quantity of flushing liquid Q is now established as a controlling condition Whereas the drilling speed now becomes the controlled condition. The transforming device 12 measures the actual value of the drilling speed v and the actual value is compared with the desired value of the drilling speed in the comparing device 16'. The resulting deviation induces the automatic controller 16 to lower, via the setting device 10, the desired value of the torque of the motor 3 down to a level which can be considered assafe in View of the constant quantity of available flushing liquid.
The various control systems just described can be equipped with electrically operated elements, or with hydraulic, electro-hydraulic or electro-pneumatic elements. in the embodiment shown for illustrative purposes in FIGURE 3 electrically operated control elements are used.
The following table shows the correlation between the elements of the circuits illustrated in FIGURES 2 and 3 of the drawings:
FIGURE 2 FIGURE 3 Setting device 10. Field coil 317. Transforming device 11. Field coil 315.
Counting device 310. Generator 309.
Quantitative measuring device 13. Comparing device 14. Automatic controller 15.
Measuring device 331. Amplidyne 314.
Direct current motor 311. Direct current generator 312. Field coil 313.
Field coil 321.
Field coil 325.
Switch relay 333. Potentiometer 334. Rectifier 335.
Comparator 16 Pump controller 17.
FIGURE 3 shows the derrick 301 with the drilling rod 302. The drill rod 302 is suspended by suspension wires 305 running over pulleys 306. At its lower end, the drill rod 302 bears the motor 303 and the drill bit 304 driven by the motor 303.
The suspension wire 305 runs over the pulleys 306 communicating with winch 307. By turning this winch, the drill rod 302 can be lifited or lowered at the desired speed corresponding to the drilling speed of the drill bit. A special motor can be provided which is adapted to lift or lower the drill rod very slowly. Furthermore, there is provided a pump 308 conveying the flushing liquid through the drill rod to the bottom of the drill hole.
A three-phase-current generator 309 supplies the necessary current to the electric motor 303. In the power line between the generator 309 and the motor 333 there is inserted a counting device 310 known per se measuring current and voltage and forming a current impulse proportionate to the actual value of the torque of the motor 303. See for example: St'ztblein-Die Technick der Fernwirkanlagen, Oldenbourg-Berlin 1934, pages 30 to 34. This value, which corresponds to the actual value, is fed to the coil 315 of generator 314 of the amplidyne type.
The winch 307 is driven by a direct current motor 311 fed by a direct current generator 312 having a field coil 313. Current is supplied to this field coil by the above mentioned amplidyne 314. This amplidyne has several field coils. One of its field coils, the above-mentioned field coil 315, is excited by a current corresponding to the actual value of the torque of the electric motor 303.
The further field coil 317 is excited by a constant direct current source which corresponds to the desired value of the torque of the electric motor 333. There is a contact blade 3332 connected in series with coil 317 and pertaining to a relay 333, to be explained later. The torque of the motor is obtained by calculation or by tests in a manner known per se. A field coil 318 of the amplidyne 314 is fed by another amplifying means (e.g. an amplidyne 319).
This amplidyne 319 has a field coil 320 actuated by a constant current and a field coil 321 excited by a current depending on the drilling speed. Thus, amplidyne 319 constitutes a comparator between a reference value (current in coil 320) and a speed responsive signal (current in coil 321). The constant value exciting the field coil 320 is the desired value of the drilling speed and the value exciting the field coil 321 is the actual value of the drilling speed. The current supply to coil 320 is governed by a contact blade 333d, also pertaining to the said relay 333 (infra).
The drilling speed is measured by a tachometer generator 322 coupled with the pulleys 306. Tachometer generators of this type are disclosed, for example, in U.S. Letters Patent No. 2,889,475. The tachometer 322 thus furnishes a direct current which is proportional to the rotating speed of the pulleys 306 and hence to the drilling speed. The voltage of the tachometer is fed to the field coil 321 of the amplidyne 319 via a contact blade 3330.
The pump 308 is driven by the motor 323 which, in turn, is supplied with current by the generator 324. The field coil 325 of this generator is excited by an amplidyne 326. This amplidyne 326 has several field coils. The field coil 328 is excited by a constant DC. voltage via contact blade 333a. The excitation of the field coil 329 depends upon the amount of the flushing liquid. The excitation of the field coil 330 depends upon the drilling speed since this field coil is connected to the tachometer 322 via a contact blade 33311.
The amount of the flushing liquid conveyed by the pump is measured by a suitable measuring device 331 as, for instance, by a venturi meter. The number of revolutions in the venturi meter is proportional to the amount of flushing liquid and measured by the tachometer 332, the voltage of which is supplied to the field coil 329.
326 depends on the amplidyne a portion of the excitation of the exciter amount of flushing liquid conveyed by the pump 308. In other words amplidyne 326 constitutes a comparator for the two signals respectively developed in said coils 329 and 330 and the current flowing in coil 325 can be considered an error signal resulting from the comparison of the flux in coils 329 and 330.
Furthermore, there is provided a threshold switch relay 333 controlling all of the contact blades 333a to 333a in the system shown in FIGURE 3, and operating as threshold or limit switch.
This switch relay 333 is actuated as soon as the pump 308 has reached its maximum number of revolutions and hence the amount of flushing liquid cannot be further increased. This maximum number of revolutions corresponding to the maximum conveying capacity of the pump 308 is a datum given and known by the construction of the individual pump. A current corresponding to this maximum capacity of the pump is formed by the potentiometer 334 which latter is connected with the switch relay 333 via the rectifier 335. Under normal operating conditions the voltage created by the tachometer 332 counteracts the voltage of the potentiometer 334. As long as the tachometer voltage is less than the voltage of the potentiometer 334 the relay 333 is inactive. After the voltage of the tachometer 332 has reached the fixed voltage at the potentiometer 334, the relay 333 is actuated and the relay then opens all those contacts in FIG- URE 3 which are shown as closed (333b, 333a) and it closes all those contacts (333a, 3330, 333d) which are shown in their respective opened positions. Accordingly, coils 321 and 320 are energized and excite amplidyne 319 which now, in turn, energizes coil 318. The current in the latter coil is now the reference value for the current in coil 315 because upon opening of contact 333e, coil 3-17 becomes ineffective.
A tachometer is described, for example, in Elektrische Messung mechanischer Grossen, Springer 1956, 4th edition, pages 198/ 199, and a device for measuring the quantity of liquids is described therein on page 210. A torque measuring device is described on pages 192/193, see also the diagram 260.
An amplidyne which can be used for the purpose of the present invention is described, for example, in U.S. Patent 2,247,166.
Operation The embodiment shown in FIGURE 3 operates in the following manner:
The actual torque as produced by the electric motor 303 is measured in the counting device 310 and fed to the field coil 315. The reference value of the torque is given by the excitation of field coil 317. The deviation 1.e. the error signal which is the diflierence between the two values acts upon the motor 311 via the amplidyne 314 and the field coil 313 of the generator 312. Hence,
the winch 307 is adjusted at such a speed that the maximum of the allowable torque of the motor will not be exceeded.
The flushing liquid which has to supplied by pump 308 is determined by the drilling speed. If there is a greater drilling speed v; thisis indicative of the fact that the drill bit 308 has encountered soft ground and a greater quantity of drillings is obtained. Consequently, the amount of the flushing liquid must be increased correspondingly in order to remove the increased amount of drillings so as to prevent the drill bit from getting stuck in the drillings. The value of the drilling speed .is measured by the tachometer 322 and a corresponding .direct current is supplied to the field coil 330 of the amplidyne 32 6. The amount of the flushing liquid passing into the borehole is measured by the tachometer 332 and a corresponding direct current is fed to the field coil 329. The two factors are thus compared and adjusted to each other in the 326 with a view to make, the driving motor 323 of the pump turn with the required number of revolutions. The situation may occur that the flushing liquid cannot be further increased in view of the maximum capacity of the pump 3% and the cross section of the conduit in the drill rod 302.
The maximum amount of flushing liquid which can be conveyed by the pump to the drilling hole is of course known at the time of installation of the entire system. A corresponding maximum value is formed in the potentiometer 334. As soon as the voltage produced in the tachometer 332 reaches this maximum value the reversing relay 333 responds and closes all contacts which had hitherto been opened and opens all contacts which had hitherto been closed. This means that also the contact 333a in the circuit of the field coil 328 is closed. Thereafter the amplidyne 326 is constantly excited. The contact 33317 in the circuit of the field coil 339 is opened, i.e. there is no longer any influence of the tachometer machine 322 on the amount of flushing liquid conveyed by the pump 3&8. The amount of the flushing liquid now remains on the constant level Q which is expressed by a constant voltage supplied by the amplidyne 326 and resulting in a constant number of revolutions of motor 323 and pump 308.
As soon as reversing relay 333 reponds i.e. in case the maximum quantity of the available flushing liquid Q has been reached, contact 3330 which is in the circuit of the field coil 321, and contact 333 of governing field coil 329 are closed; both coils pertain to amplidyne 319. The voltage supplied by the tachometer 322 and corresponding to the drilling speed now influences amplidyne 319. Simultaneously, contact 333e is opened and winding 317 is rendered ineflective so that winding 318 takes over for flux comparison in amplidyne 314 as stated above.
If the drilling speed deviates from the value represented by the current in coil 328 there will be an error signal due to the flux comparison of the coils 320 and 321 and being effective in amplidyne 319 as comparator. The output of amplidyne 319 resulting from this comparison in turn is fed as a current to coil 3-1-8. This current in 318 produces a flux which is then compared with the flux developed by a current in coil 315, and amplidyne 3. 14 is thereby subjected to a second error signal resulting from such flux comparison. Arnplidyne 314 produces a corresponding output current in coil 313 to regulate the speed of motor 311 so that the speed of motor 311 is brought back to the desired value.
It will be observed that this holds true only as long, as the torque of motor 311 (flux in coil 315) remains constant at a particular value. If the actual torque decreases, the motor 311 is caused to increase the speed of the winch and the drilling speed. An increasing drilling speed in turn causes elements 322, 3&9 and 314 to respond so as to decrease again the drilling speed. Thus, an approximately constant speed level is attained.
It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.
What I claim is:
1. In combination with a deep drill including a drill rod, a drill bit, an electric motor mounted in the lower end of said drill rod and driving said drill bit with said drill rod remaining stationary, a suspension wire for said drill rod, a winch drivingly connected to said suspension wire for raising and lowering said drill rod with said drill bit and said motor, a motor for driving said Winch, a pump for handling a flushing liquid through said drill rod into the bore hole so as to remove the drillings therefrom, an automatic control system comprising: electric circuit means responsive to the drill motor torque and producing a corresponding electric output signal; electric .circuit means producing an electric reference value corresponding to a desired torque; measuring means for the drilling speed and producing an electric output signal corresponding to said drilling speed; measuring means responsive to the amount of fluid passing into said bore hole and producing an electric output signal indicative of said amount of liquid; an electric threshold switch connected to said last mentioned measuring means and responding whenever a predetermined maximum amount of liquid passes into the bore hole; a first electric comparator electrically connected to said two circuit means and producing a first electric error signal corresponding to the difference between said reference value and said torque output signal; control means electrically connecting said comparator and said winch motor and feeding said first error signal to said winch motor for governing its speed in response to said first error signal; a second electric comparator electrically connected to said two measuring means and producing a second electric error signal corresponding to the difference between said two measuring signals; control means electrically interconnecting said second comparator and said pump motor for feeding said second error signal to said pump motor for governing the flow of liquid in response to said second error signal, said threshold switch when responding deactivating the connection between said speed measuring means and said second comparator and deactivating said reference value producing means, when said maximum amount of liquid is reached; and circuit means being responsive to a response of said threshold switch and connected to said first comparator for establishing a drilling speed responsive reference value therein Whenever said maximum amount of liquid is reached.
2. In combination with a deep drill including a drill rod and a pump for handling a flushing liquid through said drill rod into the borehole so as to remove the drillings therefrom; a drill bit; an electric drill motor mounted in the lower end of said drill rod remaining stationary; a suspension wire for said drill rod; a winch drivingly connected to said suspension wire for raising and lowering said drill rod with said drill bit and said motor; a motor for driving said winch; means for producing a measured value corresponding to the actual torque output of said drill motor for a particular voltage current and frequency thereof; means for producing a reference value for the torque of said drill motor at any given time; and control means connected to said winch motor and being responsive to the difference between said measured value and said reference value of said drill motor to cause said winch to position said suspension wire with said drill rod and said drill motor upon said drill bit, thereby adjusting thetorque of said drill motor and said drill bit.
3. In combination with a deep drill including a drill rod, a drill bit, an electric drill motor mounted in the lower end of said drill rod and driving said drill bit with said drill rod remaining stationary, a suspension wire for said drill rod, a control device comprising: a winch drivingly connected to said suspension wire for raising and lowering said drill rod with said drill bit and said motor; a motor for driving said winch; means for producing a measured value corresponding to the actual torque output 'of said drill motor for a particular voltage, current and frequency thereof; means for producing a reference value for the torque of said drill motor at any given time; a comparator connected to said two means and responsive to the difference between said measured value and said reference value and being connected to said winch motor for adjusting the drilling speed in response to said difference of values; a pump for handling a flushing liquid through said drill rod into the bore hole so as to remove the drillings therefrom; an electric motor for said pump; means for measuring the flow of flushing liquid conveyed by said pump and producing an electrical signal corresponding to said flow of liquid; a tachometer generator connected to the supension wire of said drill rod sensing the lowering speed of said drill bit and producing an electrical output signal corresponding to said speed; and
circuit means interconnecting said tachometer generator and said flow measuring means for combining said two signals and producing a common output signal; and electric control means interconnecting said pump motor and said circuit means for causing control of said liquid flow in response to said common output signal so that the liquid flow increases with increasing drilling speed.
4. In combination with a deep drill including a drill rod, a drill bit, an electric drill motor mounted in the lower end of said drill rod and driving said drill bit with said drill rod remaining stationary, a suspension wire for said drill rod, a control system comprising: a winch drivingly connected to said suspension wire for raising and lowering said drill rod with said drill bit and said motor: a motor for driving said winch; means for producing a measured value corresponding to the actual torque of said drill motor for a particular voltage, a current and frequency thereof; means for producing a first reference value for the torque of said drill motor at any given time; first control means interconnecting said winch motor and said two means being responsive to the diiference between. said measured value and said reference value and governing the winch motor and drilling speed, thereby controlling the weight of said drill rod and said drill motor upon said drill bit, and also controlling the torque of said drill motor and of said drill bit; a pump for handling a flushing liquid through said drill rod into the bore hole so as to remove the drillings therefrom; measuring means connected to said pump and being responsive to the maximum flow of flushing liquid conveyed by said pump and deactivating said first reference value producing means upon occurrence of said maximum flow; means connected to said suspension Wire for measuring the drilling speed and producing an electrical signal corresponding to said speed; and a normally inactive second electrical control means operatively connected to said speed measuring means and including means for supplying a second reference value to be compared with said speed responsive signal to generate a third reference value, said second control means being actuated in response to a signal corresponding to the maximum flow as measured by said flow measuring means, said second control means being further connected to said first control means for feeding said third reference value thereto, thereby replacing said first reference value so as to limit the speed of said winch motor and the drilling speed to a value corresponding to the maximum amount of flushing liquid.
5. An automatic control system for a deep drill including an electric motor driven drill bit and means for nonrotatably suspending said motor in a bore hole, said system comprising: measuring means connected to said suspending means and being responsive to the drilling speed and producing a corresponding electric output signal; a motor driven pump for conveying flushing liquid into the bore hole; measuring means connected to said pump and being responsive to the amount of liquid pumped into said bore hole and producing an electric output signal corresponding to the said pumped amount of liquid; an electrical comparator connected to said two measuring means and comparing said two output signals so as to form an error signal; a control means interconnecting said pump motor and said comparator so as to control the flow of flushing liquid in response to said error signal; an electric winch motor drivingly connected to said suspending means for lowering said motor driven drill bit thereby determining the drilling speed; a normally inactive electric control circuit electrically interconnecting said speed measuring means and said winch motor for controlling the speed of said winch motor in response to said drilling speed, said normally inactive control circuit, said winch motor with control circuit, and said drilling speed measuring means defining a closeable feedback loop; and means connected to said liquid measuring means and being responsive to the maximum amount of liquid to be pumped, and when responding activating said control circuit for closing said feedback loop.
References Cited in the file of this patent UNITED STATES PATENTS