US3104864A

US3104864A - Figure

Info

Publication number: US3104864A
Authority: US
Current assignee: FIRST ASSET-BASED LENDING GROUP Inc C/O CONSOLIDATED ASSET MANAGEMENT COMPANY 120 NORTH ROBINSON OKLAHOMA CITY OK 73192
Publication date: 1963-09-24
Anticipated expiration: 1980-09-24

Description

Se t. 24, 1963 .1. o. MELTON ETAL 3,104,364

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 7 Sheets-Sheet 1 INVENTORS JamesdMeZialz h I & from M Car raider BY m w,wgm,p

ATTORNEYS Sept. 24, 1963 J. o. MELTON ETAL ,8

. AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 7 Sheets-Sheet 2 PO-S/T/VE' ACT/01V REZA y HmeAz/uc plesssues GOVEAA/OE INVENTORS James QMeZZozz [7'vi2z M. farperzfer ATTORNEYS Sept. 24, 1963 J. o. MELTON .ETAL ,8

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS 7 Sheets-Sheet 5 Filed March 22, 1961 g aw N.

Mm Ms W: whim um kuSQ Sept. 24, 1963 J. o. MELTYON ETAL 3,104;864

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 '7 Sheets-Sheet 4 INVENTORS P 1963 J. o. MELTON ETAL 3,104,864

AUTOMATICCONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961' 7 Sheets-Sheet 5 HUJIMI'IMJ' 67 7/ 89 9/ 70 f i 95 4: 2:;

@ l y. L5: 28 James 0 Malian [ruin /l Car van is?" BY I g g g g; MM3M,ML{M

TTORNEYS Sept; 24, 1963 J. o. MELTON ETAL 3,104,364

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 7 Sheets-Sheet 6 4L VE' .S'UPPL Y INVENTORS y coA/r/eou E0 James 0. Malian our [ram M. Carpenter A ORNEYS Sept. 24, 1963 J. o. MELTQN Em 3,104,864

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS 7 Sheets-Sheet 7 Filed March 22, 1961 A I an Inn"? Mn 0 3 MM 0a C M ma J w 0 P ATTORNEYS United States Patent 3,104,864 AUTOMATIC CGNTROL DEVHIE FQR DRELLING APPARATUS James 0. Melton, Norman, and Irvin M. Carpenter, Gklah-oma City, Okla, assignors to The Geolograph Company, ()lslahoma City, Okla, a corporation of Oklahoma Filed Mar. 22, 1961, er. No. 97,604 7 Claims. (Cl. 254173) The present invention relates to an apparatus capable of use in connection with a drilling rig and more particularly the present invention relates to certain improvements in an apparatus capable of controlling, in an automatic manner, the weight exerted against the drill bit of a rotary drilling rig, as will hereinafter appear in detail.

The present invention is an improvement over the invention disclosed and claimed in copending application Serial No. 802,968, filed on March 30, 1959, for Control Device For Drilling Apparatus.

The rate of drilling, or the rate of penetration of the drill bit into the ground, will depend primarily upon the hardness of the earth layer which the bit engages; this drilling rate, within certain limits, will also depend upon the load or weight applied to the bit, which in turn depends upon the rate at which the drill string is lowered. Logically enough, it has been ascertained that the feed or lowering rate of the drill string should be correlated with the penetration rate of the drill bit in order to achieve optimum drilling; it has appeared further that the simplest method of effecting this correlation is by measuring and controlling the weight on the drill bit. Therefore, in present day practice, the operator of a conventional drilling rig attempts to sense the weight changes on the bit and, accordingly, feeds off suificient amount of drilling line in order to maintain a substantially constant weight on the bit. The operator accomplishes this result by first watching a weight indicator which is attached to the dead line at the drilling rig; then, as the weight increases beyond a predetermined value, the operator releases a braking means associated with the drilling line so as to feed off the proper amount of additional line. as distinguished from the inventions disclosed and claimed in the present application and the aforementioned copending application.

The invention disclosed in the aforementioned copending application relates to an apparatus of the type described above, and including those elements described above, wherein there is provided a feed control means which is completely automatic. Such a system includes (a) a sensing device which bears against the dead line of the drilling rig and which transmits a pressure proportional to the tension in the dead line; (b) a control unit which is connected to the sensing unit and which provides a pneumatic pressure output responsive and proportional to the pressure transmitted from the sensing device; (c) an air motor connected to the braking mechanism and to the control device for the purpose of releasing and engaging the braking mechanism in response to the pressure at the sensing device; (d) a governor having a friction wheel bearing against the cable drum and operating a valve to deenergize the air motor when the drilling speed becomes excessive; and (e) a plurality of This latter procedure is, of course, entirely manual,

Patented Sept. 24, 1963 intermediate elements adapted to eliminate any ag in response and, at the same time, to provide safety features in the control system itself.

In comparing the present invention with that of the aforementioned copending application, the following main improvements are featured in the present invention:

(1) In the basic system of the prior copending application, the control point :of the governor is manually adjustable; in the present invention this adjustment is made pneumatically and, further, is remotely controlled.

(2) In the prior basic system, it has been discovered that the pressure between the controller and the air motor tends to build up, especially during very slow drilling; the present invention provides an intermittent bleed-oft to prevent this build-up.

(2) In the prior basic system, it has been discovered that there are occasional lags and sticking of valves such that the air motor is not always immediately deenergized when the output pressure decreases from the controller; the present invention provides an additional safety valve operating directly from the controller to deenergize the air motor immediately, and much faster than heretofore attainable, when the output pressure from the controller decreases.

(4) The cont-roller of the present invention has been modified to control the valve referred to in paragraph (3) a new feature of this invention involves the employment of a spring-loaded pivot pin for the flapper, as will hereinafter appear.

Therefore, it is a principal object of the present inven tion to provide an improved system for maintaining the weight on the drill bit substantially constant.

It is another important object of the present invention to provide an automatic control system of the type referred to above wherein the elements constituting the control system may be simply attached, or added, to a conventional drilling rig without requiring any further modifications or changes in the structure of the drilling rig itself.

It is a further object of the present invention to provide an automatic control system of the type referred to above wherein the brake control means is made completely responsive to the change in the tension in the dead line and wherein response lags are minimized or eliminated entirely.

it is a further object of the present invention to provide an automatic control system of the type referred to above wherein safety means are included to cause engagement of the brake when the tension in the dead line exceeds a certain predetermined value due to the passage of the drill :bit into a gas pocket, or due to a break-oil, or other similar condition.

It is a further object of the present invention to provide a system of the type referred to above wherein the control point of the governor is remotely controlled.

It is a further object of the present invention to provide a bleed-oil valve, and operating means therefor, for preventing the pressure from building up between the controller and the air motor, especially during slow drilling.

It is a further object of the present invention to provide a safety valve which results in a more rapid and more positive deenergization of the air motor when the tension in the dead line decreases.

It is a still further object of the present invention to provide a spring-loaded pivot pin for the flapper in the controller.

Other and further objects and advantageous features of the present invention will hereinafter more fully appear in connection with a detailed description of the drawings which:

FIGURE 1 is a view in elevation, partly diagrammatic, showing a conventional drilling rig employing the novel control system of the present invention;

FIGURE 2 is a pneumatic circuit diagram corresponding to the elements illustrated in FIGURE 1;

FEGURE 3 is a sectional view, on an enlarged scale, of the airmotor and its associated quick-release valve and safety Valve shown in FIGURE 1;

FIGURE 4 is a fragmentary side elevation, partly in section, showing the governor employed in the present invention;

FIGURE 5 is a front elevation, on an enlarged scale, showing the details of some of the internal components of the controller illustrated in FIGURES l and 2;

FIGURE 6 is a sectional view, on an enlarged scale, taken along section line 66 of FIGURE 5, showing details of the spring-loaded pivot pin;

FIGURE 7 is a sectional view, on an enlarged scale, taken along section line 77 of FIGURE 5, showing details of the flapper, the nozzle and the internal valve, the latter operating the safety valve; and

FIGURE 8 is a sectional view, on an enlarged scale, of the pneumatic relay shown in FIGURE 2.

Referring to the drawings in detail, FIGURE 1 shows a conventional derrick 1 supporting at its upper end a crown block 2, the latter including two or more conventional pulleys. A cable 3, secured at one end 4 to the frame of the derrick passes around one pulley 5 of the crown block 2, then downwardly and around a pulley 6 in a movable or travelling block 9. From the travelling block the cable 3 passes upwardly and around a second pulley 5 of the crown block. The cable 3 may then pass downwardly to a winding drum 10. As many pulleys (or sheaves) 5 and 6 are included in the crown block and travelling block respectively, to provide the number of lines required to support the load.

The portion of the cable 3 extending from the anchor 4 to the crown block 2 is referred to as the dead line. The portion of the cable 8 extending from the crown block down to the winding drum 10 is referred to as the fast line. Any conventional winding means including a motor, gears, clutches, etc. (which form no part of the present invention) may be employed for the purpose of driving the winding drum 10.

Traveling block 9 is connected to the kelly 12 through a swivel head 13, the kelly 12 extending through a rotary turntable 14; the drill string (not shown) is secured to the lower end of the kelly 12. and carries at its lower end a suitable lbit (not shown) for drilling through the various earth formations.

Adjacent the one end of winding drum 10 there is shown, diagrammatically, a braking mechanism consisting of a brake arm 15 pivotally mounted on a support 16- and a brake band 17 which 'bears against a brake drum 11 secured to one end of the winding drum 10. At the righthand end of the brake arm 15 there is a spring 18 which is of sufiicient size to urge the brake band 17 against the brake drum 11 so as to prevent the winding drum 10 from rotating. If desired, the spring 18 could be replaced by a weight (not shown) of suitable size.

The above described apparatus is essentially conventional and admits of manual operation as is; i.e., the operator can lift up on the right-hand of the brake arm 15 so as to release the brake whenever he feels that it is desirable to increase the weight on the drill bit. The elements which constitute the automatic control system of the present invention, and which will be described hereinafter, may now be added to the above described conventional apparatus without requiring, any further changes or modifications of the existing rig structure. Conversely, after attachment, the elements of the instant automatic control system may be simply removed, or otherwise disabled, and the rig may be operated manually in the prior conventional manner.

In accordance with the present invention, there is provided a weight-sensing mechanism consisting of a hy-.

draulic sensing unit 21 which has a sensing plunger 22 urged against the dead line 3. This sensing unit II also includes a pair of cable guides 23 and 24 through which the cable 3 is permitted to pass. Preferably, one of these cable guides is firmly secured to the cable/the other allowing the cable to slide freely therethrough. Thus, the

sensing plunger 22 contacts the portion of the cable 3' between the two cable guides 23 and 24. A suitable hydraulic fluid is introduced through the sensing device 21 through a suitable fitting (not shown) which is closed when the sensing system is filled to the desired level.

A conduit 28 connects with the sensing device 21 and transmits the fluid pressure therein to a control means,

diagrammatically indicated by the reference numeral .29

port 35 adjacent the brake arm 15. In the simplified.

form of the invention shown in FIGURE 1, the air motor is connected to the output, or controlled pressure, line 33 of the controller 29 through a quick release valve 36, also known per se, Also, as shown in FIGURE 1, the air motor 34 has an arm 33 actuated by the motor and a cable 39 extending from one end of the arm 38 around a pulley li to one end of the brake arm 15 and adjacent the spring 18.

The pulley 40 is mounted on an overhead support 41 which is attached to the upper end of the support 35.

Also shown in FIGURE 1 are the friction wheel of the governor (later to be described) bearing against the flange of the brake drum 11, a safety valve 200, a check valve 171 and a recording unit generally designated by the reference character 300.

FIGURE 2. shows a pneumatic circuit which is designed for completely automatic operation. The various elements, some of which are described in greater detail hereinafter, will be described in connection with the com- 'bination shown in FIGURE 2 as follows:

The air supply which is available at any conventional rig passes into the system through the inlet conduit and to the air scrubber 151. From the air scrubber 15-1, the pressurized air passes through a manual cut-ofi valve 153 and through a pressure regulator-filter 152, which is essentially of conventional design and will not be further described in greater detail. From the pressure regulator 152, the air supply passes through the conduit 30 connect ing with the controller 29 (later to be described in detail). The conduit 1 36 leading to the air clamp 135 also connects with the pressure regulator 152 as shown. Thus, when the system is turned on, pressure is supplied to the air clamp 135 irrespective of what happens to the elements shown at the right in this figure.

The outlet conduit 3-3 from the controller connects with a positive action relay having an outlet conduit 161. The positive action relay is a standard purchased item, known per se, which will not be further described except briefly as follows: The output pressure delivered by the positive action relay from its outlet conduit 16-1, will be equal to, or proportional to, the pressure coming pressure within the conduit33 rises above a predetermined level (for which a suitable setting has been provided internally of the positive action relay), the relay will be tripped internally such that the output pressure at the conduit 161 will be reduced to zero. In other words, this positive action relay is a pneumatic safety device to stop the action of the driller in case of a twist-01f or when drilling into a cavity.

The outlet conduit 161 of relay 160 feeds air under controlled pressure to the pneumatic relay 225, later to be described in detail. Briefly, however, the pneumatic relay 225 supplies air at its outlet conduit 231 at a pressure equal to that supplied from the conduit 161 and, hence, from the controller 29. The pneumatic relay 235 is connected to the pressure regulator 152 by means of a conduit 235. The pressure supplied by the pneumatic relay 225 (as will more clearly appear hereinafter), is equal to the output from the controller 29 but does not draw air directly from the output of the controller. The outlet conduit 231 of the pneumatic relay 235 feeds air under controlled pressure to the one-to-one relay 162 through conduit 163.

The one-to-one relay 162 is known per se and it functions to produce a result similar to that of the pneumatic relay 225. This relay 162 is connected with the high pressure source of air through valve 165, conduit 164 and pressure regulator 154, the latter being connected in parallel with the pressure regulator 152. The outlet conduit 166 of the relay 162 connects with the quick release valve 36. The action of the relay 162 is such that, when there is pressure in the conduit 163, the relay will permit air to pass from the conduit 164 into the outlet conduit 166 at a pressure equal to that in the conduit 163 and for the purpose of operating the air motor 34. The quick release valve 36 connects with the air motor 34 through the T connection 64.

The outlet conduit 231 of the pneumatic relay 225 also connects with another con-duit 170 leading to a check valve v17-1 which opens only in the direction of the arrow in FIGURE 2. The check valve :171 connects with a bleed-0T1 valve 237 through conduit 238. The bleed-ofl? valve, described below, connects with the governor casing 102 by means of a conduit 121 as will appear hereinafter. Conduit 1'21 connects with an internal valve in the governor which vents the air pressure in the conduit 121 to the atmosphere when the speed of the cable drum exceeds a predetermined value. Thus, this decrease in pressure will serve to deenergize the air motor 34.

In connection with slow speed drilling, it has been observed that the pressure on the outlet side of the controller 2-9 tends to build up, for reasons that are not entirely understood. Therefore, the bleed-off valve 237 intermittently opens to the atmosphere to bleed off the excess pressure in the

conduits

121 and 238. The bleed-oft" valve 237 is provided with an actuating arm 239 which, in the position shown in FIGURE 2, provides direct communication between the conduits 12-1 and 238. The outer end of the arm 239 is provided with a roller 240 which engages the teeth of the sprocket wheel 241, the latter being mounted for rotation on the shaft 242 above the bleed-01f valve 237. As the sprocket wheel 241 turns, the various teeth thereon will engage the roller 241) so as to pivot the arm 239 intermittently and in a counterclockwise direction from that shown in FIGURE 2. In the counterclockwise position of the arm 239, the bleed-01f valve 237 will bleed oil? the excess pressure in the

conduits

121 and 238 to the atmosphere. Shaft 242 can be connected to rotate in response to any continuously moving device including, for example, the rotary turntable or to a device which operates in response to the rate of drilling. By way of example, FIGURE 1 shows the

conduits

121 and 238 leading to a recording device 309 which has therein a main shaft (not shown) movable in response to the rate of drilling. The shaft 242 can be appropriately driven by the main shaft referred to above.

A pneumatic means (described in detail hereinafter), is

mounted within the governor 102 for the purpose of varying the control point of the governor. This pneumatic means is connected by means of conduit 143 to another pressure regulator 155 which is connected in parallel with pressure regulators 1'52 and 154. Adjustment of the control on the pressure regulator 155 will determine the control point at which the governor 102 will operate.

As will hereinafter appear, a safety valve 200 connects with the air motor 34 through the T connection 64. This safety valve also connects with the controller 29 by means of the conduit 201. As will hereinafter appear, this safety valve operates in response to a decrease in input pressure from the conduit 28 below a predetermined value to deenergize the air motor immediately. The hydraulic pressure in the conduit 28 is directly proportional to the tension in the dead line 3 and is provided by the hydraulic sensing unit 21. A detailed description of the operation of the entire combination shown in FIGURE 2 will appear hereinafter following the specific disclosure of certain of the elements.

The air motor 34, quick release valve 36 and the safety valve 200, all referred to above, are shown in further detail in FIGURE 3 and will be briefly described as follows:

The air motor 34, which is essentially of a conventional design, comprises a spring loaded plunger 45 which is pivotally attached at its outer end to the arm 33. The

arm 38 is pivotally attached at its lower end to a bracket 46 mounted on the base 47 of the air motor. The air motor also includes an air-tight casing 48 and a bellowstype diaphragm 49, the latter being secured at one end to the inner end of the spring loaded plunger 45. Ring stiifeners 55 are provided to hold the folds of the diaphragm in proper position during expansion and contraction of the diaphragm. A helical spring 51 is located internally of the diaphragm 49 for the purpose of urging the diaphragm and the plunger to the left. The casing 43 is provided with an external opening 52 at which a suitable fitting is located. A threaded horizontal rod 53 is also secured to the right-hand portion of the casing 48 for the purpose of providing limits for the pivotal movement of the arm 38. For this last-mentioned purpose, there are provided nuts 54 and 55 and washers 56 and 57.

The quick release valve 36 includes a plurality of

ports

60, 61, 62 and 63. The port 60 is plugged; the port 61 is connected with the atmosphere; the port 62 is connected to the opening 52 of the casing 48 of the air motor 34 by means of a T connection 64; the remaining port 63 is connected to the source of controlled air pressure by means of a connection 65. The internal portion of the quick release valve 36 includes a flexible and springloaded diaphragm 66 which is shown in its normal condition of repose in FIGURE '3. The diaphragm 66 has the ability to provide controlled air pressure from the line 166 through the port 62 to the air motor 34 when the controlled air pressure is so provided through the. conduit 33. However, when the air pressure in the conduit 33 falls below the pressure previously supplied to the air motor 34, the diaphragm 66 in the quick release valve 36 will move so that the air within the air motor will be permitted to pass backwardly through the quick release valve through the port 61 to the atmosphere. Thus, when the air pressure within the conduit 33 falls below a certain value, the air motor 34 is immediately cut off due to the venting action of thhe quick releasevalve 36. In the absence of the quick release valve 36, there would be a certain amount of lag in the operation of the air motor 34. The safety valve 200 operates briefly as follows: when the controller 29 is operating in response to a hydraulic pressure above a predetermined value from the dead line sensing unit 21, an internal valve in the controller will (in a manner later to be described) direct the full pressure from the regulated air supply to the safety valve 200 through the conduit 201. The safety valve is provided with three

ports

202, 203 and 204; port 202 communicates with the conduit 201; port 203 communicates with the port 52 of the air motor 34 through the T connection 64. A diaphragm 2&5 is mounted in the cavity 2% of the safety valve 200 in such a manner as to close ofi (internally) port 2&3 when the pressure in conduit 291 is equal to the full value of the regulated supply. However, when the pressure falls below this value, the diaphragm 2115 will move downwardly, venting the pressure in the port 253 to the atmosphere, and at the same time, deenergizing the air motor 34. When the hydraulic pressure from the dead line falls below a predetermined value, the internal valve 95 in the controller will cut oif the supply of air to the conduit 201 and, at the same time, will bleed the pressure in this conduit to the atmosphere.

FIGURE 4 shows a governor or safety device employed for the purpose of preventing the drill string from being lowered too fast, as for example, when the drill bit should pass into a gas pocket or the like. The governor includes a friction wheel keyed to a shaft 101. The friction wheel 1% is adapted to bear against the outer peripheral flange of the winding drum 1% (as shown in FIGURES 1, 2 and 4). The casing 162 of the governor also includes a concentrically mounted shaft 1% which is driven by the shaft 191 through suitable gearing inside the casing 102. The gearing is considered as essentially conventional and, hence, is not shown. A cross bar 1% is secured to the shaft 1193 for rotation therewith. A pair of fly weights, generally designated by the reference character 105, are pivotally mounted (as at 1%) adjacent the opposite ends of the cross bar 11%. Each fly weight 195 has an inner arm 1&7 adapted to bear against a flange 1118 of a slidable sleeve 199. At the right-hand end of the casing 102, as it appears in FIGURE 4, a slidable piston 11% is mounted in a cylindrical opening 111.

At the right-hand end of the casing 102, a hollow tubular member 112 threadedly engages a threaded portion 113 of the governor. A short cylindrical member 114 having therein a recess 117 abuts against the right-hand end of the tubular member 112 in such a manner that the recess is in alignment with the bore of the tube. A rotatable coupling 118 is received on the short cylindrical member114 and threadedly engages the right-hand end of the tubular member 112 so as to secure the cylindrical member 114 against it. The piston 110 is provided with an extension in the form of a rod 11$ which projects into the bore of the tube of 112. A cup 125 is mounted on the end of the rod 119 as shown. A helical spring 133 surrounds the right-hand end of the rod 119 so as to bear against the right-hand end of the threaded portion 113 and the bottom of the cup 125. A flexible diaphragm 134,

being cup-shaped in its normal condition of repose is mounted within the cavity (formed by the bore of the tube and the recess 117) in such a manner that its folded edge 141 is received in a suitably shaped recess 142 formed in the mating portions of the tube 112 and the cylinder 114. A conduit 143, which is connected to the source of air pressure in a manner not shown on this figure, threadedly engages a hole in the cylinder 114 and communicates with the recess 117 through the right-angled passageway 144. The left-hand end of the slidable piston 110 is provided with a disc 115. A ball 116 is received within suitably opposed and aligned cavities on the adjacent portions of the disc 115 and the slidable sleeve 1119 as shown.

The upper right-hand put of the housing 162 includes a valve portion 121} to which is connected a conduit 121 containing air under pressure (from a source lat-er to be described). The valve portion 120 also includes a slidable valve stem 122 which is urged towards the left under the action of the spring 123 so as to hold the conical portion 124- of the valve in its corresponding seat.

The pressure of the air in the conduit 14-3 can be varied from the source as desired and this pressure is transmitted to the flexible diaphragm 134 which bears against the cup 125 urging the same toward the left against the action of the spring 133. As will appear below, the value of the pressure from the conduit 143 will determine the A ultimate rotary speed of the winding drum necessary to move the piston 11% towards the right such that the valve 125 will be opened.

It the winding drum 1% were now rotating rapidly, its

If the force transmitted from the slidable sleeve 189 through the ball 116, piston 111i and rod 119 to the cup 125 is sufiicient to overcome the force exerted onthe cup by the membrane 134 (resulting from the pressure of air from the line 143), then the sleeve 1119 and the piston 11%) will be moved to the right. The disc would then bear against the valve stem 122, moving the conical portion 124 away from its seat so as to Vent the pressure in the conduit 121 to the atmosphere through the opening 126. As indicated above, the controlled pressure from the conduit 14-3 will determine the maximum speed required of the winding drum to open the valve I 129; since the conduit 121 connects with the supply of air to the air motor, the opening of the valve will serve to deenergize the air motor so as to cause engagement of the brake.

Casing 152 is pivotally mounted, as at 127, on a pair of vertical standards 12 3 (only one of which is shown in FTGURE 4).

connects with a lug 131 at the lower right-hand portion of the casing N12 and also with a lug 132 on the base 129 so as to urge the casing 162 in a pivotal direction (with respect to the standards 12$) tending to force the friction wheel 1th) out of contact with the peripheral flange on the winding drum 1%.

An air clamp 135 is mounted on the base 129 for the purpose of urging the casing 1% in a pivotal direction opposite to that effected by the spring so as to bring the friction wheel 10% into contact with the peripheral flange of the winding drum 1%. This air clamp is connected to a primary source of pressure through a conduit 136. A vertically movable plunger 137 is mounted withina' central cylindrical chamber 138 in the air clamp 135. A a

short rod 139, connected at its lower end to the center of the plunger 137, projects outwardly through an appropriate holein the air clamp 135. A small vent 149 is also provided in the upper portion of the clamp and leading to the central chamber 138.

When a source of air under pressure is supplied to the conduit 136 and to the central chamber 138, the plunger 137 and the rod 139 will be moved vertically upwards. The rod 139, contacting the lower right-hand portion of the casing 1112, will pivot the casing 192 in a counterclockwise direction, about the pivotal points 127, so as to urge the friction wheel 1 into engagement with the peripheral flange on the winding drum 11 This last described condition represents the operating position ofthe governor shown in FIGURE 4. The base 129 with its appropriate supporting structure is mounted in a position adjacent the winding drum so that the friction wheel 109 can be caused to bear against a peripheral flange of the winding drum 1% in the manner described above.

FIGURES 5, 6 and 7 show the operation of the controller 29. Air under pressure is supplied from the normal source of :air pressure at the rig to the controller 29 through the conduit 31} appearing in FIGURE 5. The hydraulic pressure which effects the control within the controller 29 is conducted to the controller from the diaphragm on deadline through the conduit 28 appearing The vertical standards 12% are secured at their lower ends to a base support 129. Aspring 130' action of the controller will be briefly described as follows:

The Bourdon tube 71] moves in accordance with the fluctuation of hydraulic pressure in the conduit 23 so as to move the flapper 72 about the pivot 71 relative to the nozzle 73.

The nozzle 73 is suitably threaded into a nozzle block 74 which, in turn, is connected to the air supply from the conduit 3%) through the pressure indicator 75 and conduit 76. As best shown in FIGURE 7, the nozzle 73 is threadedly received in the hole 7 9 in the nozzle block 74. The nozzle block 74 is also provided with two

ports

80 and 81 communicating with the hole 79. The port 8i} communicates with the conduit 76 which supplies air to the nozzle, whereas the port 81 communicates with the conduit 78 which conducts the air under controlled pressure away from the nozzle. The nozzle 73 is provided with an internal bore 82 in which is received a plug 83. The plug 83 is provided with a restricted orifice 84 and the nozzle itself is provided with a restricted orifice 85. The portion of the nozzle 73, in the region of the port 81, is provided with a plurality of holes 36. The plug 83 is positioned,

in such a manner that, when the flapper 72 moves away from the nozzle 73, a venturi eifect is created within the nozzle so as to draw a slight suction on the conduit 78, thereby providing a more rapid response.

The action of the flapper 72 against the nozzle 73 will now be described in relation to both FIGURES and 7: when the pressure in the Bourdon tube 7a is at a maximum, the flapper 72 will be moved to its closest position relative to the nozzle 73 and, if desired, even to the extent of closing off the orifice 35; under such a condition, the air passing into the hole 79 of the nozzle block 74 (through the conduit 76 and the port 80) will pass through the orifice $4 of the plug 33, through the holes 86 and outwardly into the conduit 78 through the port 31. Under the latter conditions, the pressure in the conduit 78 will ultimately reach the pressure in the conduit 76. As the pressure in the Bourdon tube decreases, however, the flapper 72 will be moved progressively farther away from the nozzle 73 so that an increasing quantity of air will issue forth from the nozzle 73 through the orifice 85. Thus, the pressure in the conduit 78 will be reduced below the pressure in the conduit 76 by an amount commensurate with the sizes of the

orifices

34 and 85 and in accordance with the distance between the flapper 72. and the nozzle 73.

The nozzle block 74 is mounted on a sub-frame 87 which is pivotally connected to the frame 88 of thecontroller 29 by means of the nut 99, the latter permitting pivotal movement of the subfirame 87 so as to vary the initial position of the flapper 72 relative to the nozzle 73. This pivotal movement of the subframe 87 can be effected by means of the toggle 89 which is pivotally attached adjacent the upper portion of the subframe 8 7, the threaded rod 91 which is attached to the toggle 89, the lug 92 which is attached to the frame 88 of the recorder 29 and the two nuts 93 and 94 which are received on the threaded rod 91 on opposite sides of the lug 92.

The air under controlled pressure from the nozzle block 74 passes from the conduit 73 through the pressure indicator 77 and to the conduit 33 marked Controlled Air Out (inFIGURE 5 As indicated heretofore, the controller 79 is provided with an internal valve 95 which is employed for operating the safety valve 230. As best shown in FIGURE 7, this internal valve. 95 comprises a threaded fitting 96 which is received in a suitable threaded opening 97 in a block 98. The block 98 is mounted on the subframe 87 opposite from the block 74.

The block 98 is also provided with two ports 2% and 299 communicating with the threaded hole 97 and connecting with conduits 2G1 and 99 respectively. Conduit 201 connects with the safety valve 290, as described heretofore, and conduit 99 connects with the conduit 30 through the pressure indicator 75'.

Mounted within the fitting 96 is a pin 210 which is moveable axially of the fitting. The pin 2.10 is provided with a central enlarged portion 211 having convex surfaces on its left-hand and right-hand ends. The internal bore 207 of the fitting 96 is provided with a guide 212 and an insert 213 forming a seat for the right-hand end of the enlarged portion 211. The left-hand end of the bore 207 is provided with a concave surface 215 which constitutes a seat for the left-hand end of the enlarged portion 211.

In the position shown in FIGURE 7, the air supply will pass through the conduit 99, into the hole 97 in the block 98, through the openings in the guide 212, and the insert 213, through the holes 214, and through the conduit 201 to the safety valve 200; under these conditions, the pressure beneath the diaphragm 205, as it appears in FIGURE 3, would be substantially the full value of the regulated supply entering through the conduit 99. With the left-hand end of the member 211 being seated on the surface 215, no air will leak between the pin 210 and the hole through which the pin passes. However, when the pin 210 is moved to the right, there will be suflicient clearance between the parts to permit air to seep between the pin and the hole in the fitting 96 in which the pin is received.

Now, if the pressure from the dead line falls below a predetermined value, the Bourdon tube 70 will move in such a way as to pivot the flapper 72 about the pivot pin 71 so that the lower end of the flapper 73 will come into contact with the pin 210 to move the latter axially toward the right. At this point, the valve portion 211 will seat against the member 213 shutting off the supply of air from the conduit 99 to the conduit 201. At the same time, the 'air which seeps between the pin 210 and the hole in the fitting 96 in which the pin is received, Will reduce the pressure in the line 291 immediately so that the safety valve 200 will per'ate, instantaneously to deenergize the air motor 34.

Assuming that the pressure in the Bourdon tube 70 was suflicien-tly low that the pin 210 would be moved to its extreme right-hand position, if the pressure in the Bourdon tube were lowered still further, there would be a tendency for the flapper 72 to bend or for the pivot pin 71 to bend. Hence, the structure shown in FIGURE 6 is provided to prevent a bending or breaking of the flapper 72 or to prevent a breaking or bending of the pivot pin were it not otherwise mounted. The pivot pin 71, shown in FIGURE 6, is'received in an elongated hole 216 in the block 217. A helical spring 213 having its ends engaging the left-hand end of the pin and the central portion of the block 217 continuously urges the pivot pin 71 towards the right as it appears in FIGURE 6. The subframe 87 is provided with an elongated vertical slot 219'. The block 217 is provided with a corresponding rearwardly projecting portion 229. The projection 22% is adapted to fit into the vertical slot 219. A threaded bolt 221 passes through a suitable hole in the projection 220. By means of the not 222 and washer 223, the block 217 can be adjusted to any vertical position as provided by the movement of the projection 220 within the slot 219.

FIGURE 8 shows the details of a pneumatic relay 225. The port 22 6 connects with the positive action relay 162 through the conduit 161, the positive action relay itself being connected to the output of the controller 29 in a manner described heretofore. As the pressure from the controller increases, air enters the port 226 and acts upon the diaphragm 227 forcing the central shaft 228 toward the right; this movement of the central shaft 228 will cause the inlet valve 229 to open permitting air from the supply to pass into the central chamber 230 from the conduit 23-6. Air from the central chamber will then pass into the conduit 23-1 through port 2 32. Conduit 231 connects with the relay 162 and the check valve 171 as indicated heretofore. The inlet valve 229 will remain open until the pressure in the conduit 231 is equal to 11 the pressure in the conduit 162. When these two forces become equal, the diaphragm 227 and the shaft 228 will return to their normal positions; closing the inlet valve 229. However, if the pressure in the conduit rat decreases thereafter, the pressure in the conduit 231 and in the central chamber 236 will act upon the diaphragm 227 forcing the shaft 228 towards the left so as to open the bleed valve 233, thus allowing the air in the conduit 231 to bleed to the atmosphere. The bleed valve will remain open until the pressures in

conduits

161 and 231 become equal. When these two forces become equal, the diaphragm 227 and the shaft 228 will return to their normal positions, closing the bleed valve 253. An additional diaphragm 234- is provided to support the other end of the shaft 228. An equalizing orifice 235 is provided to equalize the pressure on the opposite sides of the diaphragm 234. The purpose of the relay 225 is to supply air to the air motor ultimately at a pressure equal to the output pressure from the controller 2? Without, at the same time, drawing air directly from the output of the controller.

Operation (1) Referring now to all of the drawings, and in particular to FIGURE 2, it will be assumed that a drilling operation is taking place. It will be assumed'further, that the weight on the drilling bit as reflected by the tension in the dead line 3 is within the minimum and maximum limits of operation. The controller will have its elements approximately in the positions shown in FIG- URE 5. The governor will have its elements in the positions shown in FIGURE 4. The brake will be considered as engaged as represented by the relative positions of the elements shown in FIGURE 3.

(2) From the assumed conditions above, let it now be assumed that the drilling has progressed to the extent that the tension in the dead line 3 has exceeded the maximum predetermined value for the operation of the present invention. Under this latter condition, pressure in the conduit 28 will increase, causing the Bourdon tube 70 to expand so as to move the flapper '72 closer to thenozzle 7d. Movement of the flapper 72 towards the nozzle 73 will decrease the quantity of air coming from the orifice 85 and, in turn, will raise the value of the pressure in the conduit 78 towards the pressure in the conduit 7 6. The increased pressure in the conduit 78 will reflect a similar increase in pressure in the

conduits

33, 161, 231, 163 and 166 to the quick release valve 36, opening the same and energizing the air motor so as to lift the arm of the brake and, thus, permitting the drill string 12 to descend. The drill string will descend until the pressure in the dead line 3 is reduced to a value which will cause a reverse operation of the various elements described and in such a manner as to reengage the brake means. Under normal operating conditions, the brake will be released and reengaged intermittently so as to produce a substantially constant tension in the dead line 3 within the minimum and maximum limits referred to above.

(3) From the conditions described above in paragraph (;1), let us now assume that the drill bit has passed into an air pocket such that it begins to descend at a rapid rate and in such a manner that the tension in the dead line increases to a maximum. The following control and safety deatures will come into operation:

'(a) The speed of the winding drum 10, being excessive, will cause the fly weights 105 to be thrown centrifugally outward opening the valve 124 and reducing the pressure in the air motor so as to reengage the brake;

(b) The flapper 72 will have closed off fully the nozzle 35 in the orifice 73. The output pressure in the conduit 33 from the controller 2% will be at a maximum and this maximum will be above the limit set in the positive-action relay 16%. Thus, the positive-action relay will reduce the pressure in the lines between it and the air motor substantially to atmospheric pressure. ensure that the brake will be reengaged.

(4) It will be assumed that the drill string is descending and that the tension in the line '3 suddenly decreases by a large amount. The Bourdon tube 70' will be contracted to such an extent that the flapper 72 will contact the pin 21% moving the latter towards the right (as it appears in FIGURE 7). Under the latter condition, the air supply from the conduit 99 will be shut off; the pressure in the conduit Zlll will be reduced and the safety valve 2% will open so as to deenergize the air motor 34 and to engage the brake. Not only will the operation of the safety valve 209, in the manner described herein,

assist in the deenergizing of the air motor 34- when the pressure in the dead line decreases extremely rapidly, but also, this safety valve 209, by itself, will serve to deenergize the air motor in the event that one or more of' the valves between controller 29 and the air motor 34 should otherwise become inoperative. Furthermore, if the pressure in the Bourdon tube 70 should become extremely low, the pivot pin '71 would be urged toward the left against the action of the spring 218 so as to prevent possible damage to the flapper '72 or to the pivot pin itself.

(5) Under conditions of extremely slow drilling, it has been observed that the pressure in the conduits leading from the controller 29 to the air motor 34- tends to build up for reasons that remain somewhat obscure. As

indicated heretofore, the sprocket wheel 241 will be rotated by the shaft 242 so as to operate the bleed-off valve 267 so as to prevent the build-up of pressure in conduits 121 and 238 (6) If for any reason, it is desired to change the control point of the governor 102 so as to reflect a ditferent maximum speed of the cable drum 10, the output pressure in the conduit 143 from the pressure regulator can be increased or reduced by adjusting the external control on the pressure regulator 155. This change in pressure in the conduit 143 will like-wise produce a change in pressure within the recess 1 17', the change in pressure in the recess 117 will, of course, be reflected by a change in force exerted by the diaphragm 134 against the right-hand end of the cup 125. Thus, it will appear that the control of the governor 162 can be effected hydraulically and remotely.

Although it has been stated above that the pressure on the outlet side of the controller 29' tends to build-up for reasons that are not entirely undersood, or for reasons that remain somewhat obscure, it is believed that this pressure build-up is due, in part at least, to frictional effects in the various adjusting points and pivots in the controller and in various valves and other moveable members, and to temperature effects as well.

Whereas the present invention has been described in particular relation to the drawings attached. hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, might be made within the spirit and scope of this invention.

What is claimed is:

1. In a drilling rig including a frame, an upper pulley.

block secured to said frame, a lower movable pulley block, upper and lower pulleys rotatably mounted within said pulley blocks, respectively, a drill string supported from said lower block, a rotatable cable drum, a cable wound against said cable drum so as to prevent rotation of the same, the improvementwhich comprises an automatic control system including a weight sensing device containingflhydraulic fluid therein and having a sensing element bearing against said cable, said sensing element being movable in response to the changes in tension in said cable for producing in said sensing device a fluid pressure in said hydraulic fluid proportional to the tension'in said This will also serveto cable, a fluid pressure responsive actuator attached to said brake means and adapted upon energization to release said brake means, a controller connected between said sensing device and said actuator for increasing the fluid pressure in said actuator for energizing said actuator in response to an increase in fluid pressure in said sensing device and so as to release said brake when the tension in said cable exceeds a predetermined value, a quick release valve connected between said controller and said actuator for venting the fluid pressure in said actuator to the atmosphere so as to deenergize said actuator in response to a decrease in output pressure from said controller, a safety valve connected to said actuator, and means connected to said safety valve and responsive to a decrease in pressure in the hydraulic fluid in said sensing device for opening said safety valve to vent the pressure in said actuator to the atmosphere to deenergize said actuator.

2. In a drilling rig including a frame, an upper pulley block secured to said frame, a lower movable pulley block, upper and lower pulleys rotatably mounted within said pulley blocks, respectively, a drill string supported from said lower block, a rotatable cable drum, a cable wound on said cable drum passing around the pulleys of said pulley blocks and secured at one end to said frame whereby the unwinding of said cable drum will cause the drill string to descend, and a brake means normally hearing against said cable drum so as to prevent rotation thereof, the improvement which comprises an automatic control system including a weight sensing device having a sensing element bearing against said cable adjacent the fixed end thereof, said sensing element being movable in response to the changes in tension in said cable, a pressure controller having an inlet connected to a primary source of air under pressure and an outlet supplying air from said primary source at a variable pressure, a movable element mounted in said controller and adapted by its movement to effect said variable pressure at said outlet, means connecting said movable element of said controller with said sensing device and forming a closed fluid circuit, said sensing element, when moving in response to changes in tension in said cable producing a fluid pressure in said closed fluid circuit proportional to the tension in said cable, said means connecting said sensing device with said movable element transmitting the change in fluid pressure caused by the movement of said sensing element to move said movable element in accordance with the change in pressure in said closed fluid cirwit,- the pressure of air at the outlet of said valve thereby varying in accordance with the changes in tension in said cable, an air motor mounted adjacent said brake means and having thereon an arm movable in accordance with pressure in said air motor, a brake cable connected from one end of said arm to said brake means, a quick release valve, said air motor having an inlet connected to the outlet of said controller through said quick release valve, said air motor when the air pressure therein increases in accordance with the increase of air pressure thereto from said controller through said quick release valve moving said arm so as to tension said brake cable and release said brake means, said quick release valve having therein means for venting the pressure within said air motor to the atmosphere when the outlet air pressure from said controller decreases, a safety valve connected to the inlet of said air motor, and a pilot valve mounted in said controller and connecting with said safety valve, said pilot valve being actuated by said movable element in response to a decrease in pressure in said closed fluid circuit so as to open said safety valve to vent the pressure in said air motor to the atmosphere thereby deenergizing said air motor.

3. In a drilling rig including a frame, an upper pulley block secured to said frame, a lower movable pulley block, upper and lower pulleys rotatably mounted within said pulley blocks, respectively, a drill string supported from said lower block, a rotatable cable drum, a cable wound on said cable drum passing around the pulleys of said pulley blocks and secured at one end to said frame whereby the unwinding of said cable drum will cause the drill string to descend, and a brake means nonmally bearing against said cabledrurn so as to prevent rotation thereof; the improvement which comprises an automatic control system including a weight sensing device having a sensing element bearing against said cable adjacent the fixed end thereof, said sensing element being movable in response to the changes in tension in said cable; a pressure controller having therein a nozzle valve and a pivotal flapper; said nozzle valve having an inlet connected to a primary source of air under pressure, an orifice arranged in registry with said flapper, and an outlet supplying air from said primary source at a variable pressure depending upon the movement of said flapper relative to said orifice; an expansible element mounted in said con troller; means connecting said expansible element of said controller with said sensing device and forming a closed fluid circuit; said sensing element, when moving in response to changes in tension in said cable, producing a fluid pressure in said closed fluid circuit proportional to the tension in said cable; a pivot pin mounted in said controller, said flapper being connected at one end to said expansible element and being pivotal about said pivot pin such that the other end of said flapper is movable towards and away from said orifice; said means connecting said sensing'device with said expansible element transmitting the change in fluid pressure caused by the movement of said sensing element to said expansible element for pivoting said flapper relative to said orifice in accordance with the change in pressure in said closed fluid circuit, the pressure of air at the outlet of said valve thereby varying in accordance with the changes in tension in said cable; an air motor mounted adjacent said brake means and having thereon an arm movable in accordance with pressure in said air motor; a brake cable connected from one end of said arm to said brake means; a quick release valve; said air motor having an inlet connected to the outlet of said controller through said quick release valve; said air motor, when the air pressure therein increases in accordance with the increase of air pressure thereto from said controller through said quick release valve, moving said arm so as to tension said brake cable and release said brake means; said quick release valve having therein means for venting the pressure within said air motor to the atmosphere when the outlet air pressure from said controller decreases; a safety valve connected to the inlet of said air motor; and a pilot valve mounted in said controller and connecting with said safety valve, said pilot valve being actuated by said flapper in response to a decrease in pressure in said closed fluid circuit so as to open said safety valve to vent the pressure in said air motor to the atmosphere thereby deenergizing said air motor.

4. Apparatus as set forth in claim 3 including means for mounting said pivot pin slidably and resiliently relative to said controller.

5. In a drilling rig including a frame, an upper pulley block secured to said frame, a lower movable pulley block, upper and lower pulleys rotatably mounted within said pulley blocks, respectively, a drill string supported from said lower block, a rotatable cable drum, a cable wound on said cable drum passing around the pulleys of said pulley blocks and secured at one end to said framewhereby the unwinding of said cable drum will cause the drill string to descend, and a brake means normally bearing against said cable drum so as to prevent rotation thereof, the improvement which comprises an automatic control system including a weight sensing device having a sensing element bearing against said cable adjacent the fixed end thereof, said sensing element being movable in response to the changes in tension in said cable, a pressure controller having an inlet connected to a primary source of air under pressure and'an outlet'supplying air from said primary source at a variable pressure, a movable element mounted in said controller and adapted by its movement to eifect said variable pressure at said outlet, means connecting said movable element of said controller with said sensing device and forming a closed fluid circuit, said sensing element, when moving in response to changes in tension in said cable producing a fluid pressure in said closed fluid circuit proportional to the tension in said cable, said means connecting said sensing device with said movable element transmitting the change in fluid pressure caused by the movement of said sensing element to move said movable element in accordance with the change in pressure in said closed fluid circuit, the pressure of air at the outlet of said valve thereby varying in accordance with the changes in tension in said cable, an air motor mounted adjacent said brake means and having thereon an arm movable in accordance with pressure in said air motor, a brake cable connected from one end of said arm to said brake means, a quick release valve, said air motor having an inlet connected to the outlet of said controller through said quick release valve, said air motor, when'the air pressure therein increases in accordance with the increase of air pressure supplied thereto from said controller through said quick release valve moving said arm so as to tension said brake cable and release said brake means, said quick release valve having therein means for venting the pressure within said air motor to the atmosphere when said air pressure supplied from said controller decreases, a governor mounted adjacent said cable drum, a circumferential flange on said cable drum, a shaft mounted for rotation within said governor, a friction wheel mounted on first shaft and bearing against said circumferential flange, a slidable valve actuator mounted within said governor, means mounted within said governor and movable in accordance with rotary speed of said shaft for moving said valve actuator in a given direction, a valve mounted in said casing of said governor and being opened by said valve actuator when the speed of said shaft exceeds a predetermined value, a conduit connecting said valve in said governor to the output of said controller, whereby, when the unwinding speed of said winding drum exceeds a certain value, the output of said controller will be vented to atmosphere through the valve in said governor, a bleed-off valve in said conduit, and means for intermittently opening said bleed-off valve.

6. In a drilling rig including a frame, an upper pulley block secured to said frame, a lower movable pulley block, upper and lower pulleys rotatably mounted within said pulley blocks, respectively, a drill string supported from said lower block, a rotatable cable drum, a cable wound on said cable drum passing around the pulleys of said pulley blocks and secured at one end to said frame whereby the unwinding of said cable drum will cause the drill string to descend, and a brake means normally bearing against said cable drum so as to prevent rotation thereof, the improvement which comprises an automatic control system including a weight sensing device having a sensing element bearing against said cable adjacent the fixed end thereof, said sensing element being movable in response to the changes in tension in said cable, a pressure controller having an inlet connected to a primary source of air under pressure and an outlet supplying air from said primary source at a variable pressure, a movable element mounted in said controller and adapted by its movement to effect said variable pressure at said outlet, means connecting said movable element of said controller with said sensing device and forming a closed fluid circuit, said sensing element, when moving in response to changes in tension in said cable producing a fluid pressure in said closed flu id circuit proportional to the tension in said cable, said means connecting said sensing device with said movable element transmitting the 1'6" 7 change in fluid pressure caused by the movement of said sensing element to move said movable element in accordance with the change in pressure in said closed fluid circuit, the pressure of air at'the outlet of said valve thereby varying in accordance with the changes in tension in said cable, air motor mounted adjacent said brake means and having thereon an arm movable in accordance with pressure in said air motor, a brake cable connected from one end of said arm to said brake means, a quick release valve, said air motor having an inlet connected to the outlet of said controller through said quick re lease valve, said air motor, when the air pressure therein increases in accordance with the increase of air pressure supplied thereto from said controller through said quick release valve moving said arm so as to tension said brake cable and release said brake means, said quick release valve having therein means for venting the pressure within said air motor to the atmosphere when said air pressure supplied from said controller decreases, a governor mounted adjacent said cable drum,-a circumferential flange on said cable drum, a shaft mounted for rotation within said governor, a friction wheel mounted on said shaft and bearing against said circumferential flange, a slidable valve actuator mounted within said governor, means mounted within said governor and movable in accordance with rotary speed of said shaft for moving said valve actuator in a given direction, a valve mounted in said casing of said governor and being opened by said valve actuator when the speed of said shaft exceeds a predetermined value, a conduit connecting said valve in said governor to the output of said controller, whereby, when the unwinding speed of said winding drum exceeds a certain value, the output of said controller will be vented to atmosphere through the valve in said governor, a bleedoff valve in said conduit, a pivotal arm mounted on said bleed-off valve and operable to open said bleed-oil valve to the atmosphere when said pivotal arm is pivoted in a predetermined direction, a roller mounted on one end of said pivotal arm, a sprocket shaft mounted above said pivotal'arm, means for rotating said sprocket shaft, and

a sprocket wheel mounted on said sprocket and having thereon a plurality of sprocket teeth engageable with said roller for pivoting said pivotal arm intermittently in said given direction so as to reduce the pressure in said conduit intermittently.

7. In a drilling rig including a frame, an upper pulley block secured to said frame, a lower movable pulley block, upper and lower pulleys rotatably mounted within said pulley blocks, respectively, a drill string supported from said lower block, a rotatable cable drum, a cable wound on said cable drum passing around the pulleys of said pulley blocks and secured at one end to said frame, whereby the unwinding of said cable drum will cause the drill string to descend, and a brake means normally bearing against said cable drum so as to prevent rotation 7 thereof, the improvement which comprises an automatic control system including a weight sensing device having a sensing element bearing against said cable adjacent the fixed end thereof, said sensing element being movable in response to the changes in tension in said cable, a pres-- sure controller having therein an inlet connected to a primary source of air under pressure and an outlet supplying air from said primary source at a variable pressure depending upon the movement of said sensing element, the pressure of air at the outlet of said controller thereby varying in accordance with the changes in tension in said cable, an air motor mounted adjacent said brake means and having thereon an arm movable in accordance with pressure in said air motor, a brake cable connected from one end of said arm to said brake means, said air motor having an inlet connected to the outlet of said controller,

said air motor, when the air pressure therein increases in accordance with the increase of air pressure supplied thereto from said controller moving said arm so as to tension said brake cable and release said brake means,

1 7 a governor mounted adjacent said cable drum, a circumferential flange on said cable drum, a shaft mounted for rotation Within said governor, a friction wheel mounted on said shaft and engageable with said circumferential flange, a slida'ble valve actuator mounted Within said governor, operating means mounted in said governor and movable in accordance with the rotary speed of said shaft for moving said valve actuator in a given direction, a valve mounted in said governor and being opened by said valve actuator when the speed of said shaft exceeds a predetermined value, a conduit connecting said valve of said governor to the output of said controller, whereby, when the unwinding speed of said ca'ble drum exceeds a certain value, the output of said controller will be vented to atmosphere through the valve in said governor, resilient means in said governor bearing against said operating means and biasing the same for movement in said given direction, a pneumatic chamber mounted on said governor, means supplying fluid under pressure to said chamber, means for remotely varying the pressure of the fluid supplied to said chamber, and a flexible diaphragm mounted in said chamber bearing against said operating means for exerting a force thereon in opposition to said resilient means.

No references cited.

Claims

1. IN A DRILLING RIG INCLUDING A FRAME, AN UPPER PULLEY BLOCK SECURED TO SAID FRAME, A LOWER MOVABLE PULLEY BLOCK, UPPER AND LOWER PULLEYS ROTATABLY MOUNTED WITHIN SAID PULLEY BLOCKS, RESPECTIVELY, A DRILL STRING SUPPORTED FROM SAID LOWER BLOCK, A ROTATABLE CABLE DRUM, A CABLE WOUND ON SAID CABLE DRUM PASSING AROUND SAID PULLEYS OF SAID PULLEY BLOCKS AND SECURED AT ONE END TO SAID FRAME WHEREBY THE UNWINDING OF SAID CABLE DRUM WILL CAUSE SAID DRILL STRING TO DESCEND, AND A BRAKE MEANS NORMALLY BEARING AGAINST SAID CABLE DRUM SO AS TO PREVENT ROTATION OF THE SAME, THE IMPROVEMENT WHICH COMPRISES AN AUTOMATIC CONTROL SYSTEM INCLUDING A WEIGHT SENSING DEVICE CONTAINING HYDRAULIC FLUID THEREIN AND HAVING A SENSING ELEMENT BEARING AGAINST SAID CABLE, SAID SENSING ELEMENT BEING MOVABLE IN RESPONSE TO THE CHANGES IN TENSION IN SAID CABLE FOR PRODUCING IN SAID SENSING DEVICE A FLUID PRESSURE IN SAID HYDRAULIC FLUID PROPORTIONAL TO THE TENSION IN SAID CABLE, A FLUID PRESSURE RESPONSIVE ACTUATOR ATTACHED TO SAID BRAKE MEANS AND ADAPTED UPON ENERGIZATION TO RELEASE SAID BRAKE MEANS, A CONTROLLER CONNECTED BETWEEN SAID SENSING DEVICE AND SAID ACTUATOR FOR INCREASING THE FLUID PRESSURE IN SAID ACTUATOR FOR ENERGIZING SAID ACTUATOR IN RESPONSE TO AN INCREASE IN FLUID PRESSURE IN SAID SENSING DEVICE AND SO AS TO RELEASE SAID BRAKE WHEN THE TENSION IN SAID CABLE EXCEEDS A PREDETERMINED VALUE, A QUICK RELEASE VALVE CONNECTED BETWEEN SAID CONTROLLER AND SAID ACTUATOR FOR VENTING THE FLUID PRESSURE IN SAID ACTUATOR TO THE ATMOSPHERE SO AS TO DEENERGIZE SAID ACTUATOR IN RESPONSE TO A DECREASE IN OUTPUT PRESSURE FROM SAID CONTROLLER, A SAFETY VALVE CONNECTED TO SAID ACTUATOR, AND MEANS CONNECTED TO SAID SAFETY VALVE AND RESPONSIVE TO A DECREASE IN PRESSURE IN THE HYDRAULIC FLUID IN SAID SENSING DEVICE FOR OPENING SAID SAFETY VALVE TO VENT THE PRESSURE IN SAID ACTUATOR TO THE ATMOSPHERE TO DEENERGIZE SAID ACTUATOR.