US2783968A

US2783968A - Automatic drilling feed control

Info

Publication number: US2783968A
Application number: US555071A
Authority: US
Inventors: Leo A Bell
Original assignee: BELL CORP
Current assignee: BELL CORP
Priority date: 1955-12-23
Filing date: 1955-12-23
Publication date: 1957-03-05
Anticipated expiration: 1974-03-05

Description

March 5, 1957 L. A. BELL AUTOMATIC DRILLING FEED CONTROL Filed Dec. 23, 1955 United States Patent Cl AUTOMATIC DRILLING FEED CONTRUL Leo A. Bell, Odessa, Tex., assignor to Bell Corporation, Odessa, Tex., a corporation of Texas Application December 23, 1955, Serial No. 555,071

16 Claims. (Cl. 254-173) The present invention relates in general to an apparatus for paying out cable into a cable system and, more particularly, to an apparatus for controlling the operation of a feeding means for paying out cable into the cable system in such a manner as to maintain the tension in the cable system substantially constant. While the invention is susceptible of general application, it is particularly applicable to the oil well drilling field and will be considered in such connection herein as a matter of convenience.

The usual oil well drilling rig includes a derrick carrying a crown block from which the traveling block is suspended by a cable system. Connected to the traveling block by a swivel fitting is a kelly which extends downwardly through and is driven by a rotary table, a drill string terminating in a drill bit being connected to the lower end of the kelly so as to be driven thereby. The cable system includes a dead line or dead line section formed by anchoring one end of the cable of the cable system to the structure of the rig, the dead line extending from adjacent the bottom of the derrick to the crown block. The cable system also includes a fast line or fast line section which extends downwardly from the crown block to a draw works at the bottom of the derrick, the fast line being trained around a cable supply drum, hereinafter referred to as the draw works drum, incorporated in the draw works. In drilling a well with such a rig, it is necessary to apply at least a part of the weight of the drill string to the bit to cause the bit to penetrate the formation therebeneath. In order to maintain the desired weight on the bit, it is necessary to pay out cable from the draw works drum into the fast line section of the cable system as drilling progresses, the draw works being provided with cable feeding means for this purpose. While the feeding means may take various forms, it ordinarily is merely a brake which controls rotation of the draw works drum to pay out cable therefrom as drilling progresses, the weight of the drill string automatically producing rotation of the draw works drum upon release of the draw works brake.

With such a drilling rig, the weight applied to the drill bit at any instant is inversely related to the tension in the cable system. In other words, when the cable system is supporting the entire Weight of the drill string and the bit so that none of the weight of the drill string is applied to the bit, the tension in the cable system is a maximum. Conversely, if the entire weight of the drill string is applied to the bit, the tension in the cable system is at a minimum. While the tension in the cable system may be measured anywhere therein to determine the weight applied to the bit, I prefer to utilize the tension in the dead line for the purposes of the present invention as a matter of convenience, although it will be understood that the tension in other portions of the cable system may be utilized without departing from the spirit of the invention.

A primary object of the present invention is to provide an apparatus for controlling the feeding meansforpaying out cable from the draw works drum into the fast line 2,783,968 P atzented Mar. 5, 1957 of the cable system automatically in such a manner as to maintain the tension in the cable system, preferably in the dead line section thereof, substantially constant, for a given drill string length, so as to apply a substantially constant weight to the drill bit. Thus, the feeding means is caused to pay out cable from the draw works drum automatically at a rate proportional to the rate of penetration of the drill bit into the formation therebeneath, which is an important feature of the invention.

An important object of the present invention is to provide an apparatus for controlling the cable feeding means which includes crawler means movable along the fast line section of the cable system, means for energizing the feeding means to pay out cable into the fast line sec-- tion of the cable system in response to downward movement of the crawler means along the fast line toward the feeding means, and means responsive to increasing tension in the cable system, and preferably in the dead line, for energizing the crawler means to produce downward movement thereof along the fast line.

With the foregoing construction, the crawler means moves downwardly relative to the fast line as long as the tension in the cable system is above a predetermined value, corresponding to a weight application to the bit less than the desired value. As the crawler means moves downwardly along the fast line with the fast line stationary, it energizes the feeding means to cause the feeding means to pay out cable, which results in upward movement of the fast line. This causes the fast line to carry the crawler means upwardly again to de-energize the feeding means. Such movement of the crawler means downwardly along the fast line and upwardly with the fast line continues until suflicient cable has been payed out to reduce the tension in the cable system to the desired value, corresponding to the desired weight application to the bit.

Another object of the invention is to provide an apparatus having means for automatically de-energizing the feeding means in response to upward movement of the crawler means away from the feeding means. Another object in this connection is to provide means for de-energizing the feeding means, in response to upward movement of the crawler means away from the feeding means, which includes means for connecting the feeding means to the crawler means.

Another object of the invention is to provide a crawler means or crawler unit which includes a frame, two driving wheels carried by the frame and engageable with one side of the fast line, a third wheel engageable with the opposite side of the fast line intermediate the two driving wheels, and a motor carried by the frame and connected to the two driving Wheels, the motor being controlled by the tension responsive means associated with the cable system, and preferably with the dead line.

Another object is to provide a crawler unit wherein the third wheel mentioned in an idler wheel resiliently biased into engagement with the fast line section of the cable system.

Another object is to provide a crawler unit wherein the idler wheel is readily disengageable from the fast line to permit disengaging the crawler unit therefrom.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be apparent to those skilled in the art in the light of this disclosure, may be attained with the exemplary embodi-.

ment of the invention illustrated in the accompanying drawing and described in detail hereinafter. Referring to the drawing:

Fig. l is a diagrammatic elevational view of an oil well drilling rig incorporating the present invention;

Fig. 2 is an enlarged, fragmentary elevational view showin'gthe lower end of the drilling rig with the invendon-installed therein; and

Fig. 3 is an isometric view of a crawler means or crawler unit of the invention.

In the drawing, the numeral designates a derrick equipped with a crown block 12. Suspended from the crown block 12 by a cable system 14 is a traveling block 16. A kelly 18 is suspended from a swivel fitting 20 carried by the traveling block 16, and connected to the lower end of the kelly is a drill string 22 terminating in a bit 24 for drilling a well bore 26. The keily s8 extends through and is rotated by a rotary table 28 on the floor 30, of the rig, such rotation of the kelly being transmitted to the bit 24 through the drill string 22.

One end of the cable forming the cable system 14 is anchored to the structure of the drilling rig, as by anchoring it to the floor 30 at 32. The section 34 of the cable system between the anchor point 32 and the crown block i2 is stationary or dead during upward and downward movement of the traveling block 16, and is thus referred to as a dead line. The other end of the cable forming the cable system 14 is connected to a cable supply drum or draw works drum 36 incorporated in a draw works 38 mounted on the derrick floor 30. The section 40 of the cable between the draw works drum 36 and the crown block 12 is known as the fast line since it is the fastest moving section of the cable system as cable is reeled onto or payed out from the draw works drum 35. The draw works 28 includes suitable power equipment, not shown, for rotating the draw works drum 36 in a direction to reel in cable when it is desired to raise the traveling block 16 and the drill string 22. For the purpose of paying out cable from the draw works drum 36 into the fast line section 40 of the cable system 14, the draw works 38 provides a suitable feeding means 42, the feeding means being energized to pay out cable whenever it is desired to lower the drill string 22. While the feeding means 42 may be of any suitable type, it conventionally includes means, not specifically shown, controlled by a brake lever 44 for braking the draw works drum 36. The feeding means 42 is energized, in the particular construction illustrated, by moving the brake lever 44 upwardly to release thebraking means controlled thereby, and the feeding means is de-energized by moving the brake lever downwardly to actuate the braking means.

During drilling, it is necessary to apply at least part of the weight of the drill string 22 to the bit 24 to secure penetration of the underlying formation, harder formations requiring hi her bit pressures. As the bit 24 drills downwardly, it is necessary to pay out cable from the draw works drum 36 into the fast line section 4! of the cable system 14 in order to maintain the desired weight on the bit, this being accomplished with the particular feeding means 42 illustrated by moving the brake lever 44 upwardly to release the braking means controlled thereby. In many drilling rigs, the driller controls the weight on the bit 24 manually by manipulating the brake lever 44 with reference to abit pressure gauge, not shown, such gauge being responsive to the tension somewhere in the cable system 14, such as the tension in the dead line 34. As Will now be described, the present invention performs this same function automatically.

Considering the present invention in a general way, it includes means 46 responsive to tension in the cable system l4, and preferably in the dead line 34 as a matter of convenience. As hereinbefore explained, the tension in the dead line 34 is inversely related to the weight appliedto the bit 24 for a given length of the drill string 22. The tension responsive means 46 relays to a control panel 48 a signal indicative of the tension in the dead line 34, the tension responsive means being shown as connected to the control panel 48 by a connecting means 59. The control panel 48 is connected, by a connecting means 52, to a crawler means orcrawler unit 54 which is movable along the fast line 40. The crawler unit 54, as hereinafter described, moves downwardly relative to the fast line 40 whenever the tension in the dead line 34 exceeds a predetermined value so that the load applied to the bit 24 is less than the desired value. A connecting means 56 connects the crawler unit 54 to the brake lever 44 in such a manner that movement of the crawler unit 54 downwardly toward the draw works drum 36 raises the brake lever to energize the feeding means 42, thereby paying out cable from the draw works drum 36 into the fast line section 40 of the cable system 14 to increase the weight applied to the bit 24. Such paying out of cable from the draw works drum 36 results in upward movement of the fast line 40, which carries the crawler unit 54 upwardly away from the draw works drum. A weight 66 connected to the brake lever 44 tends to move the brake lever 44 downwardly to tie-energize the feeding means 42, the weight 60 performing a function to be described hereinafter. In order to limit the amount of cable which can be payed out, a connecting means 53 between the crawlerunit 54 and the brake lever 44 moves the brake lever downwardly to de-energize the feeding means 42 after the crawlerunit has been moved upwardly by the upwardly moving fast line 49 a predetermined distance.

Considering the invention in more detail, the tension responsive means 46 may be of any suitable type and is therefore shown only diagrammatically. For example, it may be of the hydraulic type and may include a diaphragm which'transmits to the control panel 48 a pres sure signal proportional to the tension in the dead line 34, and thus inversely related to the weight on the drill bit 24 for a given length of drill string. In this case, the connecting means 50 comprises a hydraulic line 62.

The control panel 48 may also be of any suitable type and is also shown only diagrammatically for this reason. The control panel receives the signal from the tension responsive means 46 and relays this signal to the crawler unit 54. Preferably, but not necessarily, the signal re lated to the crawler unit 54 is electrical so that the connecting means 52 between the control panel and the crawler unit really constitutes electrical wiring 64. Preferably, the control panel 48 is provided with a knob 66 for adjusting the signal relayed to the crawler unit 54 so as to adjust the weight applied to the bit 24. Also, the control panel is preferably provided with a knob 68 for adjusting the downward speed of the crawler unit relative to the fast line 40 to a value commensurate with the drilling rate. For example, when the drill bit 24 is penetrating the underlying formation very slowly, the crawler unit 54 should-move downwardly relative to the fast line 40 relatively slowly. Similarly when the drilling rate is high, the speed of the crawler unit should be higher, thereby providing for more accurate paying out of cable from the draw works drum 36 in response to increases in the dead line tension above the predetermined value.

Considering the crawler unit 54 in more detail, it includes a frame 70 having therein a notch 72 which receives the fast line 40 when'the crawler unit is applied to the fastline. Mounted on the frame 70 on one side ofthe notch 72 are

standards

74 and 76 carrying

shafts

78 and 80, respectively. The

shafts

78 and 80 are interconnected by a chain 82 trained around

sprockets

84 and 86 on the respective shafts. The shaft 78 is driven by an electric motor 88 which is connected to the control panel 48 by the wiring 64, it being understood that the electric motor 88 merely represents one of the'motor types which could be used.

'Fixe'd on the

shafts

78 and 80 and engaging one side of the fast line 40 at spaced points thereon are pulley-like driving wheels90 and 92, respectively. Engageable with the opposite side of the fast line 40 intermediate the driving wheels-90 and 92 is apulley-like idler wheel 94, the

I wheels 90, 92-and 94 preferably *being' provided with traction knobs"96 to"prevent slipping of the wheelsrelative to the fast line 40. The idler wheel 94 is carried by a yoke 98 having a plunger 100 which extends into a cylinder 102, disengagement of the plunger and the cylinder being prevented by a pin 104 on the plunger movable in longitudinal slots 106 in the cylinder. Within the cylinder 102 is a compression spring 108 which biases the idler wheel 94 into positive engagement with the fast line 40, thereby clamping the fast line between the driving

wheels

90 and 92 on the one hand and the idler wheel 94 on the other to insure driving engagement between the driving wheels and the fast line. The cylinder 102 is pivotally connected to the frame 70 by a hinge 110 in such a manner that the cylinder engages the under side of the frame to prevent upward pivoting of the yokec'ylinder assembly beyond the position shown. However, the yoke-cylinder assembly may be pivoted downwardly from the position shown to disengage the idler wheel 94 from the fast line 40, whereby the crawler unit 54 may be moved laterally to disengage it from the fast line.

The connecting means 56 between the crawler unit 54 and the brake lever 44 includes a cable 112 connected at one end to the brake lever. The cable is trained around a pulley 114 supported by the structure of the derrick 10, and is connected to a sling 116 which, in turn, is connected to the yoke 98 by eyes 118. The connecting means 58 between the crawler unit 54 and the brake lever 44 includes a normally slack cable 120 connected at its upper end to an eye 122 on the base plate 70. The cable 120 is trained around a pulley 124 anchored to the derrick floor 30, and is connected at its other end to the brake lever 44. As will be apparent, the cable 112 pulls upwardly on the brake lever 44 to energize the feeding means 42 as the crawler unit 54 moves down the fast line 40 toward the feeding means. The weight 60 biases the brake lever 44 downwardly to tend to de-energize the feeding means 42. The cable 120 will pull downwardly on the brake lever 44 to deenergize the feeding means 42 in the event that the crawler unit 54 is carried upwardly beyond a predetermined level by upward movement of the fast line 40.

Considering the operation of the invention, it will be assumed that the crawler unit 54 has been installed on the fast line 40 in the manner hereinbefore described and illustrated in the drawing. The driller then adjusts the control knobs 66 and 68 to provide the desired weight on the drill bit 24 for the particular drill string length in use, and to provide the desired rate of movement of the crawler unit 54 relative to the fast line 40, the latter depending upon the drilling speed as hereinbefore explained. Also, the

cables

112 and 120 are connected to the crawler unit 54 and the brake lever 44 as described.

Under the foregoing conditions, as long as the desired weight is applied to the drill bit 24, the motor 88 will be de-energized and the crawler unit will remain stationary relative to the fast line 40. As drilling progresses, the weight applied to the bit 24 decreases with the result that the tension in the cable system 14 increases, since progressively more of the weight of the drill string 22 is transferred from the bit to the cable system. This increase in the tension in the cable system 14 is sensed by the tension responsive means 46, which relays a signal to the control panel 48. When this signal reaches a predetermined magnitude corresponding to the setting of the knob 66, which setting must be changed each time the ,drill string length is changed, the control panel 48 relays a signal to the motor 88, the magnitude of this signal depending upon the setting of the control knob 68. The signal transmitted to the motor 88 results in energization of this motor to rotate the driving

wheels

90 and 92 in a Y direction to move the crawler unit 54 downwardly relative to the fast line 40 and toward the feeding means 42 at a speed dependent on the setting of the knob 68, the setting of this knob being determined by the drilling I speed.

Asthe crawler unit 54 moves downwardly, the cable 112 pulls upwardly on the brake lever 44 until, eventually, the feeding means 42 is energized to pay out cable from the draw works drum 36 into the fast line section 40 of the cable system, thereby decreasing the cable system tension. However, it will be noted that since the crawler unit 54 is mounted on the fast line 40, the upward movement of the fast line resulting from energizing the feeding means 42 causes the crawler unit to move upwardly with the fast line. This upward movement of the crawler unit away from the feeding means 42 permits the weight 68 to move the brake lever 44 downwardly to de-energize the feeding means 42, thereby terminating the paying out of cable from the draw works drum. If the tension in the cable system 14 is still too high, the motor 88 of the crawler unit 54 remains energized and the crawler unit continues to move downwardly relative to the fast line 40, the crawler ultimately re-energizing the feeding means42. Again, the crawler unit 54 is carried upwardly by the upwardly moving fast line 40 to de-energize the feeding means 42 again, this action continuing until the cable tension has been reduced to the desired value, corresponding to the desired weight on the bit 24. Thus, the crawler unit 54 automatically controls the paying out of cable from the draw works drum 36 to maintain the tension in the cable system substantially constant, thereby maintaining the weight applied to the bit substantially constant for a given drill string length, which is an important feature of the invention.

In the event that the weight 60 fails to de-energizc the feeding means 42 for any reason in response to upward movement of the crawler unit 54 away from the feeding means, or in the event that cable is payed out at too high a rate for any reason, the crawler unit 54 will eventually be carried up to the upper limit of its vertical travel. When this occurs, the cable 120 will become taut and will pull downwardly on the brake lever 44 to de-energize the feeding means 42. With this construction, it is impossible for uncontrolled downward movement of the drill string 22 to occur, which is an important feature of the invention.

As will be understood, when the plunger-

cylinder assembly

100, 102 is swung downwardly to disengage the idler wheel 94 from the fast line 40, the crawler unit may be swung aside to render the drilling feed control of the invention inoperative. If desired, the crawler unit 54 may be suspended in the derrick 10 adjacent the fast line 40 by an auxiliary supporting line, not shown, when the invention is not in use.

Thus, the present invention provides an apparatus for controlling automatically the rate at which cable is payed out from the draw works drum 36 in such a manner as to maintain the weight applied to the drill bit 24 substantially constant. The provision of the safety cable 120 prevents any uncontrolled paying out of the cable in the event that any part of the installation becomes inoperative for any reason.

Although I have disclosed an exemplary embodiment of my invention herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims hereinafter appearing.

I claim as my invention:

1. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension, the combination of: crawler means movable along the cable system; means responsive to movment of said crawler means along the cable system for energizing the feeding means so that the feeding means pays out cable into the cable system; and means responsive to tension in the cable system for energizing said crawler means to produce movement thereof along the cable system.

2. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension, the combination of: crawler means movable along the cable system; means r po s v o mov m t. o t e crawler means along the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the cable system; and means responsive to increasing tension in the cable system for energizing said crawler means to produce movement thereof along the cable system toward the feeding means.

3. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension,

the combination of: crawler means movable along the cable system; means responsive to movement of the crawler means along the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the cable system; means responsive to increasing tension in the cable sys term for energizing said crawler means to produce movement thereof along the cable system toward the feeding means; and means responsive to movement of said crawler means away from the feeding means for dc-energizing the feeding means.

4. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension, the combination of: crawler means movable along the cable system; means responsive to movement of the crawler means along the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the cable system; means responsive to increasing tension in the cable systern for energizing said crawler means to produce movement thereof along the cable system toward the feeding means; and means responsive to movement of said crawler means away from the feeding means for de-energizing the feeding means, including means for connecting said crawler means to the feeding means.

5. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension and which includes a fast line section adjacent the feeding means and a dead line section, the combination of: crawler means movable along the fast line section of the cable system; means responsive to movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feeding means so that tie feeding means pays out cable into the fast line section of the cable system, including means for connecting said crawler means to the feeding means; and means responsive to increasing tension in the dead line section of the cable system for energizing said crawler means to produce movement thereof along the fast line section of the cable system toward the feeding I means.

6. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension and which includes a fast line section adjacent the feeding means and a dead line section, the combination of: crawler means movable along the fast line section of the cable system; means responsive to movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the fast line section of the cable system, including means for connecting said crawler means to the feeding means; means responsive to increasing tension in the dead line section of the cable system for energizing said crawler means to produce movement tiereof along the fast line section of the cable system toward the feeding means; and means responsive to movement of said crawler means away from the feeding means for tie-energizing the feeding means.

7. In an apparatus for controlling a feeding means for paying out cable into a cable system which is in tension and which includes a fast line section adjacent the feeding means and a dead line section, the combination of: crawler means movable along the fast line section of the cable system; means responsive to movement of said a l r m a s a n he fast line s at n 0 he sable y e oward v fee in eans, b ne g zi g t e feed; ing means so that the feeding means pays'out'cable into the fast line section of the cable systemfincluding means for connecting said crawler means to the feeding means; means responsive to increasing tension in the dead l ne section of the cable system for energizing said crawler means to produce movement thereof along the fast line section of the cable system toward the feeding means; and means responsive to movement said crawler means away from the feeding means for ie-energizing the feeding means, including means for connecting crawler means to the feeding means. a

8. In an apparatus for controlling the weight applied to a drill bit suspended from a traveling block which, turn, is suspended from a crown block by. a cable system having a dead line section and having a fast line section leading to a draw works drum provided with feeding means for paying out cable from the draw works drum into the fast line section of the cable system, the combination of: crawler means movable along the fast line section of the cable system; means responsive to downward movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feeding means so that the'feeding means pays out cable into the fast line section of the cable system, including means for connecting said crawler means to the feeding means; and means responsive to increasing tension in the dead line section of the cable system for energizing said crawler means to produce downward movement thereof along the fast line section of the cable system toward the feeding means.

9. In an apparatus for controlling the weight applied to a drill bit suspended from a traveling block which, in turn, is suspended from a crown block by a cable sys; tem having a dead line section and having a fast line section leading to a draw works drum provided with feeding means for paying out cable from the drawworks drum into the fast line section of the cable system, the combination of crawler means movable along the fast line section of the cable system; means responsive to downward movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feedingsrneans so that the feeding means pays out cable into the fast line section of the cable system, including means for connecting said crawler means to the feeding means; and means responsive to increasing tension in the cable system for energizing saidicrawler means to produce downward movement thereof along the fast line section of the cable system toward the feeding means.

10. In an apparatus for controlling the weight applied to a drill bit suspended from a traveling block which, in turn, is suspended from a crown block by a cable system having a dead line section and having a fast line section leading to a draw works drum provided with feeding means for paying out cable .from the draw works drum into the fast line section of the cable system, the combination of: crawler means movable along the fast line section of the cable system; means responsive to downward movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the fastlinesection of the cable system, including means for connecting said crawler means to the feeding means; means responsive to increasing tension in the deadline section of the cable system for energizing said crawler means to produce downward movement thereof along the fast line section of the cable system toward the feeding means; and means responsive to upward movement of said crawler means away from the feeding means for de-energizing the feeding means. 7 Y

11. In an apparatus for controlling the weight applied to a drill bit suspended from a traveling block whi'ch,-in turn, is suspended from a crown block by a cable system having a dead line section and having a fast line section leading to a draw Works drum provided with feeding means for paying out cable frcm the draw works drum into the fast line section of the cable system, the combination of: crawler means movable along the fast line section of the cable system; means responsive to downward movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the fast line section of the cable system including means for connecting said crawler means to the feeding means; means responsive to increasing tension in the dead line section of the cable system for energizing said crawler means to produce downward movement thereof along the fast line section of the cable system toward the feeding means; and means responsive to upward movement of said crawler means away from the feeding means for de-energizing the feeding means, including means for connecting said crawler means to the feeding means.

12. Apparatus as defined in claim 1 wherein said crawler means includes two driving wheels engageable with one side of the cable of the cable system and an idler wheel engageable with the opposite side thereof intermediate said driving wheels, said crawler means including a motor connected to said driving wheels.

13. An apparatus as defined in claim 8 wherein said crawler means includes two driving wheels engageable with one side of the cable of the cable system and an idler wheel engageable with the opposite side thereof intermediate said driving wheels, said crawler means including a motor connected to said driving wheels.

14. In combination: feeding means for paying out cable into a cable system in tension; crawler means movable along the cable system; means connecting said crawler means to said feeding means for energizing said feeding means in response to movement of said crawler means along the cable system so that said feeding means pays out cable into the cable system; and means connected to the cable system and responsive to increasing tension therein for energizing said crawler means to produce movement thereof along the cable system.

15. In an apparatus for controlling a feeding means for paying out cable into a cable system, the combination of: crawler means movable along the cable system; means responsive to movement of said crawler means along the cable system for energizing the feeding means so that the feeding means pays out cable into the cable system; and means for energizing said crawler means to produce movement thereof along the cable system.

16. In an apparatus for controlling the weight applied to a drill bit suspended from a traveling block which, in turn, is suspended from a crown block by a cable system having a dead line section and having a fast line section leading to a draw works drum provided with feeding means for paying out cable from the draw works drum into the fast line section of the cable system, the combination of: crawler means movable along the fast line section of the cable system; means responsive to downward movement of said crawler means along the fast line section of the cable system toward the feeding means for energizing the feeding means so that the feeding means pays out cable into the fast line section of the cable system, including means for connecting said crawler means to the feeding means; and means responsive to decreasing weight on the drill bit for energizing said crawler means to produce downward movement thereof along the fast line section of the cable system toward the feeding means.

Seljos Nov. 17, 1953 Allenbough Dec. 15, 1953