US1859814A

US1859814A - Automatic drilling control

Info

Publication number: US1859814A
Application number: US477727A
Authority: US
Inventors: Ralph D Wyckoff
Original assignee: GULF PRODUCTION Co
Current assignee: GULF PRODUCTION Co
Priority date: 1930-08-25
Filing date: 1930-08-25
Publication date: 1932-05-24
Anticipated expiration: 1949-05-24

Description

May 24, 1932- R. D. wYcKoFF 1,859,814

AUTOMATIC DRILLING CONTROL Filed Aug. 25, 1950 5 Sheets-Sheet 1 aurea okf/PAT//v Pon/ff? sup/aa y koi May 24, 1932.

C0 7' ROL POWER R. D. WYCKOFF AUTOMATIC DRILLING CONTROL Filed Aug. 25, 1930 5 Sheets-Sheet 2y May 24, 1932.

R. DAWYCKOFF AUTOMATIC DRILLING" CONTROL Filed Aug. 25. 1930 5 Sheets-Sheet 3 Patented May 24, 1932 UNITED STAT-Es PATENT oFElcE RALPH D. WYCKOFF, F IPITTSBURGH, PENNSYLVANIA, ASSIGNOB T0 GULF PRODUC- TION COMPANY, OF HOUSTON, TEXAS, A. CORPORATION OF TEXAS works.

AUTOMATIC DRILLING CONTROL Application Bled August 25, 1930. Serial No. 477,727.

My invention relates to an automatic drilling control and has todo, more particularly, with the control of rotary drilling equipment for oil wells and the like.

The primary object of my invention is to provide, in a rotary drilling apparatus, novel means for automa ically regu ating the feed pressure of the drilling bit by controlling the drill stem Weight suspended bythe draw It is a further object of my invention to provide, in a rotary drilling apparatus, means or automatically maintaining the drill bit at constant feed pressure, in spite of considerable variation in the torque demand upon the rotating means, yet which will, upon an excessive torque demand, effect a decrease in the feed pressure, and partial retrieval of the bit as well, if such excessive torque demand be of prolonged duration.

It is a further object of my invention to provide an automatic control device for rotary drilling aparatus which is selective and may be set to regulate the bit feed pressure in accordance with either the torque demand upon the stem rotating means, the suspended drill stem wei ht, or both.

A further o ject of my invention is to provide anveilicient, comparatively simple inexpensive, and light weight apparatus or ac'- complishing the above objects, which may be readily installed for use with existing conventional drilling equipment with'a minimum of modification thereof.

Further objects, and objects relating to details and economies of construction vand "operation, will definitely appear from the detailed description to follow. In one instance, I accomplish the objects of my invention by the devices and means described in the following specification. .My invention is clearly defined and pointed out in the ap ended claims. A structure constituting a pre erred embodiment of my invention is illustrated in the accompanying drawings, forming a part of vthis specification, in which:

Figure l is an elevational view of conventional rotaryl drilling equipment as set up for control by apparatus' embodying my inven- I tion;

Fig. 2 is a plan view of a preferred form of my automatic controlling apparatus for use with the drilling equipment shown in Fig. 1, the hoist power unit in this instance being an electric motor independent of the power unit. used for turning the drill stem;

Fig. 3 is a plan view of a sli htly modified form of my invention in w ich the hoist power is derived from the main power unit Whlch turns the drill stem,l i

Fig. 4 is a view of a preferred form of weight indicator element adapted for use with apparatus constituting a preferred embodiment of my invention, a portion ofV the housing of which is broken away to disclose the internal construction;

Fig. 5 is a diagram of the weight indicator element and the Whealtstone bridge and contacth making galvanometer to be used therewit i Fig. 6 is a cross sectional view of a torque indicator element adapted for use with the in Fig. 6, showing the electrical connections;

Fig. Sis a diagram of the torque indicator and the VVheatstone bridge and contact making galvanometer to be used therewith; and

Fig. 9 is a plan view of the torque indicator element assembled with the rotary table of the drilling equipment.

Like referencev numerals denote like parts throughout the several views.

It is a well known fact that an oil well may be drilled more satisfactorily when .the weight on the bit and the torque applied to the bit are held within certaln limits, dependent upon the type and condition of the formation being drilled. Such control isz in general, conducive to less breakage of drilling equipment, faster drilling, and strai hter holes The production of straighter ho es is of particular importance both in economy of ferential drive between the drill stem rotat- ,ing member and the draw works, so arranged inverse proportion of total torqle demand and feed pressure upon the bit.

n this connection, it should be pointed out that the feed ressure of the bit against the formation being drilled is due to, and directly proportional to, that portion of the total drill stem weight not suspendedv by the draw works; and that decreasing the suspended weight increases the bit pressure accordingly. Conventional draw works consist of a swivel attached to the upper end of the drill stem permitting rotation of the stem without interference from the falls and tackle supporting the stem through the swivel. One free line of the tackle, known as the deadline, is anchored, the other free line being windable upon the hoisting drum which effects lifting and lowering of the drillstem and thus controls the suspended weight and feed pressure as above explained.

There are, however, certain conditions commonly encountered in drilling in which the tot-al torque applied at the top of the drill stem does not represent the torque on the bit itself. Thus, friction of the drill stem on the side of the bore hole does not represent torque on the bit, and the driller may wish to.

eliminate the torque control under such conditions, but retain the weight control. Further, under other conditions, control in accordance with indicated torque alone is the most satisfactory. lfVith the existing autoneat-ic equipment such selection is impossible, since only the ratio of weight to torque may be changed, it, therefore, bein0 necessary to resort to manual operation if control in accodance with either factor, singly, is desire ln general, my invention consists in employing suitable weight and torque responsive devices, which, for lack of a better term, I shall designate as indicators, these being sovconnected to the drilling equipment, either by electrical or mechanical means, as to control the feeding pressure of the bit against the formation being drilled. This may be accomplished through the medium of a slow speed driving mechanism coupled to the main hoist drum, or to a special drum to which the dead line is attached, or by other means effecting variation inl the suspended drill stem weight. In the preferred embodiment of my invention, a slow speed hoist drum is substituted for the usual dead line anchor, and is rotated by a reversible electric motor driving through a worm reduction gearing. This type of reduction gearing is irreversible, that is, may be turned only by the motor, thus preventing rotation of the drum and motor due to the strain imposed by the tensioned line. Control apparatus for the motor comprises a reversing switch having an intermediate olf position, a selective relay for actuating said switch, and suitable weight and torque 1ndicators electrically connected to said relays. For the purpose o permitting selection of the most desirable actor for control, that is, torque, or wei ht, or a combination of both, a selector switch is' provided intermediate the indicators an the relays. l

Referring to the numbered parts of the drawings in which I have shown a preferred embodiment of my invention, the drill stem l0, having a bit 11, is su ported at its upper end b the swivel 12 w lich in turn is su porte lby the usual falls and tackle broad y designated as 13. One free end of the tackle is wound upon the main hoist drum 14, while the other, commonly known as the dead line, is anchored to and wound upon a slow speed drum 15. A conventional rotary table 16 is employed for rotating drill stem and an indicating device 18 for indicating the torque demand is applied thereto. This indicator may be of any suitable type, mechanical or electrical, and, if an electric motor be employed for driving the table, a Wattmeter in the power circuit thereof will serve the purpose. A weight indicator 1'? of any suitable type is provided for indicating the suspended drill stem Weight, and is preferably installed below the falls and tackle i3 to eliminate errors and necessary computations due to the varying length and Weight of the tackle during the feeding of one length of drill stem.

Referring to Fig. 2 which shows, diagrammatically, a preferred form of controlling apparatus, there is provided a reversible electric motor 19, driving the hoist 15 through a reduction gearing 20, which is preferably of the irreversible worm type and, therefore, serves the additional function of a drum check, preventing unreeling of thc line due to strain imposed thereon by the suspended drill stem weight. A switch is provided for controlling the motor and is preferably of the type having a normally balanced switch arm 21 bearing

contacts

1, 2, and 3 to which are connected the several leads of the motor power supply (not shown). The leads from the motor terminals 23, 24 and 25 are branched and are connected to two oppositely disposed and reversely arranged sets of contacts 23, 24:, 25, and 24h, 23", 25", the former set when engaged by

switch arm contacts

1, 2, 3, respectively, causing operation of the motor in a direction to effect unreeling of the hoist line, the latter set, when engaged by

switch arm contacts

1, 2, and 3, causing the motor to turn in the reverse direction to effect reeling of the line. For thus selectively actuating the switch arm 21 by means of an electric current, a pair of solenoids 26 and 27 are provided having terminals 28 and 29 and a common terminal 30. The switch arm is centralfro ly mounted upon a rockable member 31 which in turn is balanced upon the fulcrum 32.

Y From each end of the rockable member 31 cores 33 and 34 depend into the ends of the 5- solenoids 26 and 27, respectively. It will be ,seen that energization of solenoid 26 will attract core 33 and rock the switch arm 21 from oP position until

contacts

1, 2 and 3 engage contacts 23, 24 and 25". Conversely,

the energization of solenoid 27 will attract core 34 and move the switch arm in the opposite direction causing engagement of

contacts

1, 2 and 3 with contacts 24", 23b and 25". The

switch is of such construction that it automaticallyreturns to its intermediate or oi position upon de-energiza-tion of solenoids 26 and 27.

The Weight and torque indicators 17 and 18 are provided with contacts, and indication of unsatisfactory conditions are set up by the closin of respective electrical circuits thereby. he indicators-are so constructed as to be readily adjustable, as for example b resettin 'the contacts thereof in accor ance with t esize and ty of drill bit employed, the strength of the rill stem, the formation being drilled, and the total drill stem weight. In the arrangement shownin Fig. 1, a new setting of the Wei ht indicator is necessary each time a lengt of drill stem is added, y since the indication is of suspended drill stem weight, and the effective weight on the bit is that portion of the total drill stem weight not suspended by the draw works. In Figs. 4 and'5 there is disclosed what I deem to be a preferred form of Weight'indicator whichy well adapted for use as a part' is particularl of my contro apparatus. The indicator element 17m comprises a ltension link17a having shoulders 176, a carbon pile telemeter element 170 of the type disclosed in U. S. Patent, No. 1, 528,627, and a housing 17d enclosing the reduced portion of the link17a and the telemeter 17o, and having collars 17 e which prevent separation of the parts of the link 17a in the event of rupture of the reduced portion of the link 17 a. The telemeter 17 c of indicator element 17 w is in series with the variable resistance 171l and battery 17e and is connected to the terminals of a Wheatstone bridge 17g which in turn is connected to the contact making alvanometer 17 s which makes connection o terminal with terminal 38 in the event of a. condition of inadequate bit feedin pressure, and connection with terminal 39 1n the event of a condition of excessive bit feedin pressure. In Figs. 6 to 9 there is disclose what I regard tobe a preferred form of vtorque indicator element18w especially well adapted for use as a part of my control apparatus. It comprises a tension bar 18a similar to the tension ar 17a of my wei ht indicator, a carbon pile telemeter 186, a earing block 18o adapt- 5 ed for disposition about the pinion shaft 16a of the rotary table 16, and a housin 18d within which the bar 18a, telemeter 18 and block 180 are housed. The block 180, under variations in torque stress moves slightly longitudinally in the housing 18d due to changing thrust of the pinion 166 against the ring gear 16o of the rotar table and the tension of the chain 16d. ar 18a is accordingly elongated and shortened, which variations in length are transmitted by telemeter 186 as variations in current Ifrom battery 188. Variable resistance l8r, battery 18s, and telemeter 186 are in series and are connected to the Wheatstone bridge 18w which in turn is connected to the contact making galvanometer 182, as shown in Fig.l 8. Galvanometer 18s connects terminal 36 with terminal 40 in the event of a condition of excessive torque of a condition' of ,low torque. Terminal 35 of the weight indicator and ter- 9e minal 36 of the torque indicator are jointly connected to one terminal'of the battery 37. Should there occur a condition of excessive torque demand, insuicient torque demand,` excessive weight upon the drill bit, or inade- 90 Yquate weight upon the drill bit,

indicator terminals

40, 41, 39, or 38, respectively, would be electrically connected with said lbatter terminal by the indicating device involve through

terminal

35 or 36.

Due to the limited size of the contact ele'- ments in most sensitive circuit -closing indicators, the power carried by the primary indicating circuits is of necessity, "too low' for direct actuation oi the switch arm 21, and must be translated. For this purpose, in the embodiment illustrated, I employ a selective relay mechanism having relays 46, 47 48 and 49, the

terminals

42, 43, 44, and of which are respectively connected to the

terminals

38, 39, 40, and 41 of. the indicators. Tor ue responsive relays 48 and-49 are provi ed with a common lead connected to one end of an auxiliary coil 50, the other end of which is connected to terminal 51.. Weight re- 110 sponsive relays 46 and 47 are provided with a common lead connected to terminal 52.

Terminals

51 and 52 are jointl connected to the opposite side of battery 37

fi'om terminals

35 and 36, thus completing the several indi- 115 eating circuits through the indicators` A relay arm 53 ismounted intermediate the

relays

46, 47, 48 and 49, and has, pivotally at- A tached thereto a core portion 54 subject to attraction by the auxiliary coil whenever, 120 and as long as, there exists an unsatisfactory indicated torque condition. Springs 55 are provided for maintaining the arm 53 in normal central position 'when not drawn toward coil 50. Contactors 56 and 59, movable by 125 the relays 46 and 49, respectively,'are connected to a common terminal 60. Contactors 57 ,and 58, movable b relays 47 and 48, respectively, are connecte to a' common terminal 61.l

Contactors

56, 57, 58, or 59 are 130 movable into engagement with contacts 62 on the relay arm 53 in accordance with conditions of inade nate weight upon the drill bit, excessive weig it upon the drill bit, excessive torque demand or insufficient torque demand, res ectively.

source of control power (not shown) is connected to terminal 63 of the relay arm and terminal of the switch operatin solenoids, thus completing the switch actuating circuits through the relays. When torque sensitive relays 48 or 49 are energized, coil 50, being in series therewith, draws relay arin 53 away from weight responsive contact'ors '56 and 57. Contacter 56 or 57, though projected by its weight responsive relay 46 or 47, is arrested in its extent of movement by stop 66 or 67 and can not engage contants 62when arm 53 is under attraction by coil 50. In this manner, should torque and weight conditions be out of harmony, that is, should there simultaneously occur a condition of excessive torquedemand when the drill stem weight on the bit is subnormal, or should the torque demand below though the weight upon the bit is above nor mal, the torque indication 'would be given the. control in preference to the weightindication.

For the purpose of' permitting selection of either the torque indication or the weight indication as the sole control factor; or for the purpose of temporarily disconnecting the automatic control in favor of the usual manual control, a selector 68 is rovided.

p This device is essentially a multip e switch vce connected in the conductors connecting the

relay terminals

42, 43, 44, and 45 with the

indicator terminals

38, 39, 40, and 41, and in the conductor connecting one terminal of the battery 37 with the indicator terminals 85 and 36. By adjustment of the selector arm toone or the other of its several' settings, theA oontinuity of any one or several of the indicating circuits may be interrupted, thus selecting, for purposes of control, those indications the circuits of which are unbroken. If it be desired to temporarily employ manual control, the batter 37 may be disconnected from the' indicators y the selector, thus eliminating the automatic control' as an entirety. y A further refinement *consists in the 'provision of a speed control 69 for the motor, whereby the winding rate ofthe drum 15 may be controlled and smootliei action be provided. It is also` desirable to provide the drum 15 with av brake 70 whereby anchorage of the line may be effected. This is of ad` vantage, particularly. gearing is employed with the, worm gearing 20 for more rapidly raising the traveling blocks of the falls-13 when adding a new len h of drill stem.

n theevent that the indicating devices are sensitive to normal rapid fluctuations, a

when a change speed:

time-lag device or devices should be'provided either in the indicators, the relays or some other portion of the control circuit for preventing any but variations of reasonably long duration from operating the hoist equipment.

With the selector 68 set for control in accordance with either the torque indication or the weight indication, singly, the operation of the control apparatus should be obvious. The selected indicator having been ad'usted to limits in accordance with safe and e cient stresses, when a condition in excess of, or below, the set value occurs, the proper indicating circuit is closed, the respective relay is energized, the respective control circuit is closed by the relay contact moved the motor switch is closed in accordance with the indication, and the drum 15 is turned to reel `or unreel the line suspending a portion of the drill stein weight, thus decreasin or increasing the feed pressure upon the liit and bringing the conditions back to normal. When -the normal operating condition is reached, the closed indicating1 circuit is opened by the indicator, the control circuit is opened by the relay, the switch arm 21 returns to normal oil position, the hoist drum 15 is stopped, and the line is automatically anchored by the drum and its irreversible worm gearing 20. v

With the selector set for control in accordance with indications both of torque and of suspended weight, the operation is similar, being subject to indications in excess of, or below, the predetermined settings of either indicator. However, it sometimes happens that the indications of torque demand and suspended drill stem weight are not in harmony, both being greater than, or both less than, the normal safe and efficient set values. It is for proper operation under such abnormal conditions that the auxiliary coil 50 is provided in the torque indicating circuits. As long as a condition of unsatisfactory torque demand, high or'low, exists, the relay arm 58 will be drawn to aposition out of possible contact by weight responsive contactors,

56 and 57, thus automatically eliminating the weight indication, temporarily', as a control factor. Such operation permits settings of the torque indicator contacts such that when excessive torque is required, the drill stern is slightly lifted or retreived, lessening the feed pressure on the bit, and further, when the torque demand becomes too low, the drill stem is slightly `lowered, increasing the feed pressure on the bit. It is also contemplated, in this connection, to place auxiliary contacts on `the relay4 arm 53, wherby circuits operating warning or signal devices may be closed, thus callingthe o erators attention to the existence of the a normal conditions.

In Fig. 3, I have disclosed a slightly modified embodiment of my invention which is particularly adapted for use in oil fields in mounted thereon a pair of opposed bevel gears 74 and 75 which are engaged at oppositel sides with the gear 71 and, therefore, rotate upon thc'shaft 73 in opposite directions. Attac ed to land housed between said gears 74 and 75, are provided a pair of spaced electromagnetic clutch elements 76 and 77 which rotate with their respective gears. In the space between the electromagnetic clutch elements 76 and 77 and keyed to shaft 73, but

freely slidable axially thereon, is provided disk member 78 which is magnetically clutched by element 76 to cause rotation of shaft 73 in one direction, or by element 77 to cause rotation in the reverse direction. Should neither element 76 nor element 77 be energized, gears 74 and 75 rotate freely and no movement of shaft 73 takes place.

The windings of electromagnetic elements 76 and 77 are connected by any well known expedient, such as collector rings and brushes, to a set of

terminals

79, 80, 81 and 82. Terminals 7 9 land 81 are connected toterminals 61 and 60, respectively, of the relays.

Terminals

80 and 82 of the clutch windings are jointly connected to one lead from a source (not shown) of clutch operating current, the other lead therefrom being connected to terminal 63 of the relays, thus completin the clutch operating circuits through the re ays. The relays, selector, and indicators are identical, structurally, with those fully described in connection with the embodiment illustrated in Fig. 2 and need not be again described in connection with the clutch form of the invention illustrated in Fig. 3. When employing a clutch of this type, simple direct current may be employed for energization of its magneticv elements 7 4 and 75 and no switch such as shown in the embodiment illustrated at Fig. 2 is required, the clutch operation and direction being controlled directly by the

contactors

56, 57, 58 and 59 of the relays.

Shaft 73 is coupled to a worm gearing and hoist such as shown at 20 and 15 of Fig. 2 and feed pressure upon the bit may thus be accurately controlled. Movement of relay contactors 56 or-59, responsive to conditions of low feed pressure and low torque respective- 1y, connect the magneticv element 76 to the clutch operating power supply. cause disk 78 to engage gear 74 and rotate shaft 73 to increase the feed pressure uponlthe drill bit.

' M 'ovement of relay contactors 57 or 58, re-

-; sponsive to conditions of high feed pressure 'and high torque demand respectively, connect the magnetic elementA 77 to the clutch -operating power suppl cause disk 78 to en a gear 75 and rotatedhaft 7 3 in the revers rection to decrease the feed pressure upon the drill bit.

It will be observed that I have provided a selective control apparatus for regulating the feed pressure of a rotary drill bit in accordance with either the torque demand upon the drill stem, or the suspended drill stem weight, or both. My control apparatus is readily capable of adjustment to operate in accordance with safe and eiiicient values for different sizes and forms of drill stems and bits and for various earth formations.

My control apparatus may be set to maintain a substantially constant feed pressure upon the bit regardless of normal varying4 torque demands, yet in the event of an excessive torque demand, will give the torque indication exclusive control, causing reduction in feed pressure; or if such excessive demand be prolonged, effecting partial retrievement ofthe drill bit. Similarly, my control apparatus may be so set that a torque demand very far below that indicative of eiicient drilling will automatically exclude the weight indication as a control factor and permit the feed pressure to be increased to the point where an eicient torque demand is effected.

I- have provided a rotary drill control apy paratus which is extremely sensitive and flexible and by which the drill bit can be maintained at values more closely approximating the optimum than heretofore possible either by manualor automatic devices.

Another feature of my invention is that the apparatus is light in weight, and may be easily transported to and installed in new locations. My apparatus employs no expensive high power, heaVy-duty motors, heavy differentials, cumbersome and exposed chains, sprocket-s, and other parts requiring special mountings and accurate aliner'nents. My apparatus is comparatively compact, the selector, relay and motor switch being capable of .mounting in a single case, close to, or remote from, the indicators and the draw works.

`The motor for driving the slow speed hoist may be of low power, operating through a reductionv worm gearing by direct drive, and the gear ratio may be readily changed to permit ra id lifting of the disconnected travcling bloc s during addition of a new length of drill stem. ifa special slow speed hoist drum be employed as disclosed, the main hoist drum is available for emergency use, which is a further advantage.

While the preferred embodiment disclosedy employs an electric motor for driving the slow speed hoist, it is to be understood that my invention contemplates the substitution thereforof any suitable power device or of a reversing gear and clutch driven from the main power -unit which drives the-rotary table or otherequipment. Such an adaptation is necessary in fields in which electricity is not available as a source of power. Similarly, other means for reeling or tensioning the drill stem suspending line ma be lsubstituted for the slow speed hoist closed without departing from the spirit of my invention. The rela and switch constructions are also capable o constructional modification', the function of the parts disclosed being attainable by other equivalent constructions.

l am aware that,'in several other particulars, the apparatus herein disclosed ma be changed considerably without departing rom the spirit of m invention. I, therefore, claim my invention broadly as indicated by the appended claims.

lVhat I claim is:

1. A full-automatic Well drilling apparatus comprising a drill stem, a bit thereon, means for rotating-the drill stem, means for suspending a portion of the weight of the drill stem to decrease or increase the feeding pressure uponthe bit, meansv sensitive to the 1nstant torque upon the drill stem, which means effects operation of said suspending means to regulate the feeding pressure upon the bit in accordance with redetermined torque limits of safety and e cient drilling, and means effecting operation of said suspending means to maintain the feeding pressure at a substantially constant predetermined value, said last mentioned means being so associated for control of said suspending means as to be operative onl when such operationl is not in coniiict wit the operation of the suspending means by said torque sensitive means.

2. A full-automatic well drilling apparatus comprising a drill stem, a bit thereon, means for rotating the drill stem means for suspending a portion of the welght of the drill stem to decrease or increase the bit feeding pressure against the formation being drilled, and means for controlling said drill stem weight suspending means to maintain a predetermined feeding pressure upon said bit so long as the torque set upA in the drill stem is Within safe limits, but cansinor instantaneous lifting of said drill stem in idle event of an excessive torque demand regardless of the feeding pressure then existent upon the bit. I

3.' A full-automatic well drilling apparatus comprising a drill stem, a bit thereon,

' means for rotating the drill stem, means for suspending a portion of the Weight'of the drill stem to decrease or increase the -bit feeding pressure against the formation be-l in drilled, and means for controlling said drlll stem weight suspending means to maintain a predetermined feeding pressure upon said bit so long as the torque set up in the drill stem is within safe limits, but causing instantaneous lifting of said drill stem in the event of an excessive torque demand regardrum disless of the feeding pressure then existent upon the bit, said controlling means comprising weight sensitive control means, torque sensitive control means2 and means for rendering said weight sensitive cont-rol means ineffective so longas an abnormal torque condition exists.

41. An automatic control apparatus for use with earth drilling equipment employing a drill stem and bit, means for rotating the drill stem, means for suspending a portion of the weight of the drill stem, and a power drive for said weight suspending means; power drive control means comprisin an electric control circuit which when close causes the power drive to increase the suspended drill stem weight, contactor means subject to actuation in accordance with instant factors of torque upon the stem rotating means and suspended drill stem weight, which contactor means normally control continuity of said electric control circuit in accordance with,

both of said instant factors to normally maintain the feeding pressure upon the bit and the torque upon the drill stem within pre-l determined safe and efficient limits, and means for eliminating the feedin pressure as a control factor when there exists simultaneously during the drilling, a conflicting condition of excessive torque and inadequate feeding pressure.

5. An automatic control apparatus for use with earth drilling equipment employing a drill stem and bit, means for rot-ating the drill stem, means for suspending a portion of the weight of the drill stem, and a power drive for said weight suspending means; power drive control means com rising an electric control circuit which w en closed causes the power drive to increase the suspended drill stemweight, contactor means subject to actuation in accordance with instant factors of torque upon the stem rotating means and suspended drill stem weight, which contactor means normally control continuity of said electric control circuit in accordance with both of said instant factors to normally maintain the feeding ressure upon the bit and the tor ue upon t e drill stem within predetermine safe and eicient limits, and means for eliminating the feedlng pressure as a control factor when there exists simultaneously during the drilling, a conflicting condition of excessive torque and inadequate feeding pressure, or a conflicting condition of high feeding pressure and very low torque.

6. An automatic control apparatus for use with earth drilling equipment employing a drill stem and bit, means for rotating the drill stem, means for suspending a portion of the weight of the drill stern, and a reversible power drive for said weight suspending mea-ns; power drive control means comprising a circuit controlling operation of said 'iso ' 15 7. An automatic control apparatus for use with earth drilling equipment employingk a drill stem and bit, means for rotating the ldrill stem, means for suspending a portion of the weight of the drill stein, and a reversible power drive for said weight suspending means; power drive-control means comprising a pair of electric control circuits, one of'which when closed'causes said power drive to increase the suspended drill stem weight, the other of which when closed causes the power drive to decrease the suspended drill stem weight, contacter meansrendered 0perative by a condition of excessive torque or excessive feeding pressure in the equipment for closing the first mentioned of said con-A trol `circuits, contactor means-rendered operative by a condition of low torque or inadequate feeding pressure for closing the 'other ofsaid control circuits, and means for eliminating the feeding pressure as a control factor when there exists simultaneously during the drilling a conflicting condition of excessive torque and inadequate feeding pressure. 40 8. An automatic control apparatus for use vwith earth drilling equipment employing a drill stem and bit, means for rotating the drill stem, means for suspending a portion of the weight of the drill stem, and a reversiblepower drive for said weight suspending means; comprising a pair of electric control circuits, one of which when closed causes said power drive to increase the suspended drill stem weight, the other of which when closed causes the power drive to decrease the suspended drill stem weight, contactor means rendered operative by a condition of excessive torque or excessive feedin pres- 05 mentioned of said control circuits, contactor means rendered operative by a condition of low torque or inadequate feeding pressure for closing the other of said control circuits, andmeans for eliminating the feeding pressure as a control factor when there exists simultaneously during the drilling, a conflicting condition of excessive torque and inadequate feeding pressure, lor a conflicting condition of high feeding pressure and very low torque. G5 9. An automatic control apparatus for use sure in the equipment for closing t e first with earth drilling equipment employing a drill stem and bit, means for rotating the drill stem, and` means for suspending a portion of the drill stem weight to regulate the bit feeding pressure, which comprises means sensitive to the weight suspended, means sensitive to the torque demand upon said stein rotating means, a reversible motor operating the weight suspending means, a, switch for the motor, and selective relay means responsive to and energized by said weight and said torque sensitive means for actuating said switch in accordance with variations in torque demand and suspended weight, said relay having the characteristic of being preferentially responsive to variations in torque demand.

RALPH -D wYcKoFF.

Anu