US3203284A

US3203284A - Power wrench and power slip

Info

Publication number: US3203284A
Application number: US208497A
Authority: US
Inventors: Robert F Norrick
Original assignee: Joy Manufacturing Co
Current assignee: Joy Manufacturing Co
Priority date: 1962-07-09
Filing date: 1962-07-09
Publication date: 1965-08-31
Anticipated expiration: 1982-08-31

Description

1, 1965 R. F. NORRICK 3,203,284

POWER WRENCH AND POWER SLIP Filed July 9, 1962 5 Sheets-Sheet 1 INVENTOR; ROBERT F. NORRICK BYZJ/ ATTORNEY Aug. 31, 1965 R. F. NORRICK POWER WRENCH AND POWER SLIP 5 Sheets-Sheet 2 Filed July 9, 1962 INVE NTOR I ROBERT F- NORR'CK ATTORNEY g- 1965 R. F. NORRICK 3,203,284

POWER WRENCH AND POWER SLIP Filed July 9, 1962 5 Sheets-Sheet 3 FIG-3.

as 10 w I 34 36 I 1 I i'i 72 Q, I 73 a 7 39 67 35 fj as 73 5o 34 h. a l

29 FIG. 4. [2T9 so 32 28 i 1 I 3 (5) 36 l l @H it D INVENTORL ROBERT F- NORRICK BY %%%M ATTORNEY Aug. 31, 1965 R. F. NQRRICK POWER WRENCH AND POWER SLIP 5 Sheets-Sheet 4 Filed July 9, 1962 FIG. 5.

INVE NTOR:

ROBERT E NORRICK ATTORNEY Aug. 31, 1965 Filed July 9, 1962 FIG.9.

R. F. NORRICK POWER WRENCH AND POWER SLIP 5 Sheets-Sheet 5 POWER WRENCH SOL. B

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EE%/= E INVENTORi ROBERT E NORRIC K ATTORN EY United States Patent 3,293,284 POWER WRENQH AND POWER SLIP Robert F. Norrick, Michigan City, Inch, assignor to Joy Manufacturing Company, Pittsburgh, Pa., :1 corporation of Pennsylvania Filed July 9, 1962, Ser. No. 208,497 3 Claims. (Cl. 81-54) This invention relates to a power wrench and slip mechanism and more particularly to a power wrench and slip mechanism which makes and breaks the tool joints of the drill pipe in a blast hole drilling machine.

In blast hole drilling equipment the coupling and the uncoupling or the so called making and breaking of the tool joints of the drill string is usually eifected by pipe gripping tongs, wherein the lower pipe section is usually gripped and held against rotation by a back-up tong and the upper break out or make up tong. After the tool joint is broken, or during coupling of the tool joint, a conventional spinning device, or the rotary drive and pull down mechanism of the drilling apparatus may serve rapidly to rotate or spin the upper pipe section in a manner well known in the art. Thus, during running of the drill pipe out of the hole, the pipe section below the joint to be broken is gripped and held against rotation while the upper pipe section is rotated to loosen the joint and conversely, during the running of the drill pipe into the hole the upper pipe section is rotated to tighten or make the joint while the lower pipe section is gripped and held against rotation :and the latter running function is usually accomplished by inverting or reversing the upper and lower tongs to eflect coupling or making of the joint instead of uncoupling or breaking thereof. The present invention contemplates improvement over known types of joint coupling and uncoupling tongs or mechanisms.

Various known forms of devices have been provided for effecting these make and break operations. The present invention contemplates improvements over such known devices in that the tool joints may be made and broken in an improved and more efi'ective manner.

An object of this invention is to provide a new and improved tonging mechanism.

A further object of this invention is to provide a new and improved power wrench and power slip mechanism.

A further object of this invention is to provide a new and improved power wrench and slip mechanism embodying a novel arrangement of fluid operated cylinders for actuating the pipe gripping jaws.

A further object of this invention is to provide a new and improved tonging mechanism that is integral with the derrick.

A further object of this invention is to provide a new and improved make and break drill rod joint mechanism which is reliable and safe.

A further object of this invention is to provide a new and improved make and break mechanism which effectively cooperates with shoulders on the drill rod to facilitate the making and breaking of a drill string joint.

These and other objects will more fully appear in the accompanying drawings in which are shown for purposes of illustration one form of which the invention may assume in practice and in which:

FIG. 1 is a simplified front elevational view of the derrick showing the rotary pull down mechanism, an indexable rod handling unit, a power wrench mechanism and a power slip unit;

FIG. 2 is a plan view of the power wrench mechanism showing dogs engaged with recesses in the drill pipe;

FIG. 3 is a plan view of the power slip unit 28 mounted in the derrick showing the power slip in engaged position with the drill pipe;

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FIG. 4 is a plan view of the power slip unit 28 mounted in the derrick showing the mechanism in disengaged position;

FIG. 5 is a side elevational view of an elongated drill rod;

FIG. 6 is a perspective view of the upper portion of a drill rod;

FIG. 7 is a cross sectional view of the drill rod taken along lines 77 of FIG. 5;

FIG. 8 is a cross sectional view of the drill rod taken along lines 8-8 of FIG. 5;

FIG. 9 is a schematic hydraulic circuit diagram of the power wrench and power slip mechanism;

FIG. 10 is a schematic electrical circuit diagram of the power wrench and hydraulic slip mechanism.

Referring to FIG. 1 there is shown an elongated vertically extending mast or derrick 10 upon which derrick 10 is slidably mounted a rotary drive and pull down mechanism 12. For a more complete description of the rotary drive and pull down mechanism 12, reference is made to copending application Serial No. 140,068, filed September 22, 1961 assigned to the same assignee.

Derrick 10 has a pair of laterally spaced vertically eX- tending chains not shown which are suitably located in the forward portion of the derrick with the respective upper and lower end portions of the chains being secured to the respective upper and lower forward edges of the derrick 10 whereby the chains support the derrick legs and guide the movement of the rotary drive and pull down unit 12.

The rotary drive and pull down unit 12 comprises one electric motor 13 and one variable speed, reversible, hydraulic motor 14, for rotary drive and pull down functions respectively, mounted upon and rotatably connected to remotely controlled

transmissions

16 and 17 respectively. It is to be realized that reference to hydraulic or electric motors does not preclude the use of the other. The motors 13 and 14 are connected to the respective transmissions through suitable gearing to accomplish the rotary drive and pull down functions associated with the drilling operation. The output drive means of the rotary drive transmission 16 is suitably connected to the gear case 12 which is connected to a drive coupling 19 which has a suitable threaded connection 20 for threaded connection to the upper end portion of a drill rod 50. The pull down hydraulic motor 14 is drivingly connected to pull down transmission 17 which has suitable output means drivingly connected to the gear case 12 which is engaged with the chain (not shown). Rotation of the respective drive motor 14 through the transmission 17 will cause a reaction upon the chain such as to raise or lower the rotary drive and pull down unit 12 in accordance with the direction of rotation of the output means. In order to provide additional guide and support means for the rotary drive and pull down unit 12 with respect to the derrick 10, each forward side edge portion of the rotary drive and pull down unit 12 has a pair of vertically spaced guide bracket members 21 which engage longitudinally extending guide portions of the derrick 10 to maintain the aligned relationship of the rotary drive and pull down unit 12 with respect to the derrick 10.

A rod handling unit 23 provides storage means for drill rods 50 such that whenever a drill rod is to be added to the drill string, the rod handling unit 23 is swung into position to align a drill rod 50 below the threaded connection 20 of the rotary drive and pull down unit 12. The rod handling unit 23 is preferably designed to store four drill rods so that, with one drill rod 50 set up for drilling, three drill rods 50 are stored in the rod handling unit 23. The rod handling unit 23 is swingable about a pivot tube 24 located in the derrick 10 whereby the rod handling unit 23 is positioned beneath the rotary drive and pull down unit 12 with the respective drill rod 50 to be coupled to the drive coupling 19 in alignment therewith. Suitable means such as a hydraulic cylinder suitably pivots the rod handling unit 23 into and out of position.

A power wrench mechanism 26 (FIGS. 1 and 2) and a power slip unit 28 (FIGS. 1, 3 and 4), used in conjunction with each other to connect and disconnect the drill rod joints during the drilling operation, are mounted in the lower portion of the derrick below the rod handling unit 23. The power slip unit 28 comprises a pair of lever arms 30 pivotally mounted intermediate their ends on pins 32 which pins 32 are journaled on a U-shaped support plate 29 integral with the lower portion of the derrick 10. The rearward portion of each lever arm 30 is pivotally connected to one end of a link 34 respectively, such that the other end of each link 34 is also pivotally connected to a common movable member 35. A hydraulic cylinder 36 has its cylinder end pivotally mounted to a bracket 37 which is suitably fixed to the side portion of the derrick 10 while the rod end of hydraulic cylinder 36 is suitably connected to the movable member 35 such that upon pressurization of the head end of the hydraulic cylinder 36 the rod end thereof is caused to move leftwardly as shown in FIG. 4 thereby moving the movable member 35 leftwardly, which through the link connections 34 to lever arms 30, causes the rearward portion of the respective lever arms 30 to be pivoted inwardly toward each other about pivot pin 32 thereby causing a separation or outward movement of the forward end portion of the lever arm 30 to release "the key located thereon in a manner to be described.

The forward end portion of each lever arm 30 is arcuately recessed as at 39 which recess 39 is provided with a rectangular shaped slot 40 which accommodates a key 42 suitably connected thereto or cast integral within the center thereof so that upon pivotal movement of the forward end portion of lever arm 30 about pin 32, the respective forward end portions of the lever arm 30' are moved toward each other, such that the respective key 42 engages a notch on a drill rod 50 to be described to prevent the movement of such drill rod.

Power wrench mechanism 26 comprises an annular hub 43 suitably rotatably mounted on the forward portion of the derrick above the power slip unit 28. The axis of the bore of the annular hub 43 is in longitudinally aligned relationship with the axis of the drive coupling 19 of the rotary drive and pull down unit 12. Annular hub 43 has a plurality of circumferentially spaced dogs 44 pivotally mounted thereon as at '45 wherein the pivotal connection 45 of the dogs 44 is such as to be equidistant from the axis of the central bore thereof and equidistant from each other. The end portion of each dog 44 adjacent the respective pivotal connection 45 is pivotally connected to a hydraulic cylinder 47, which cylinder 47 has its cylinder end suitably pivotably connected to the rim portion of the annular hub 43 as at 48. Actuation of the hydraulic cylinders 47 pivots the dogs 44 about their pivotal connection 45 into engagement with the drill rod 50 such that counterclockwise rotation of the annular hub 43 causes the outer end portions of the dogs 44 to engage the recesses in the drill rod to be described. As shown in FIG. 2 the plan view of the lower portion of the derrick 10 which houses the power wrench mechanism 26 has a hydraulic cylinder 52 suitably rigidly mounted in the righthand corner portion thereof. The rod end 53 of hydraulic cylinder 52 extends rearwardly (upwardly as viewed in FIG. 2) from the forward portion of the cylinder 52 and has a bracket 54 suitably mounted thereon. Bracket 54 has a pair of

sheaves

55 and 56 suitably mounted thereon, with sheave 56 being mounted on the intermediate portion thereof and sheave '55 being mounted on the outer end thereof. A chain 58 has one end suitably secured to the intermediate lateral portion of derrick 10 and is reeved about the .intermediately located sheave 56 which is mounted on bracket 54, thence towards the hydraulic cylinder 52, thence around the forward circumferential portion of annular hub 43 and secured to a bracket 59 which bracket 59 is secured to the outer portion of annular hub 43. A bracket 61 rotatably supporting a guide sheave 6%, is suitably fastened to the rearward portion of the derrick 10 substantially on the same plane as the power wrench mechanism 26. A cable 62 has its one end connected to an adjustable support member 64 suitably mounted on the righthand rearward end portion of derrick 10 as shown in plan view in FIG. 2. Cable 62 is then wound about sheave 55 located on bracket 54 and thence rearwardly around the rearward portion of guide sheave 60 and thence for connection to bracket 59 on the annular hub 43. Actuation of hydraulic cylinder 52 causes the outward movement of the rod end 53 as well as the sheave 56 thereby causing the clockwise rotation of sheave 56 which thereby moves chain member 58 outwardly relative to the fixed connection to the lateral portion of the derrick 10 thereby causing the counterclockwise rotation of the annular hub 43 which in turn carries the dog members 44 therewith such that if the hydraulic cylinders 47 were simultaneously actuated, the forward endportion of the dogs 44 would engage slots in the drill rod 50 which would cause a rotation of the drill rod on continued rotation of the annular hub 43. In a similar manner a pressurizing of hydraulic cylinder 52 to cause retraction of the rod end of the cylinder 52 will move guide sheave 56 downwardly while simultaneously moving sheave 55 via bracket 54 downwardly (as viewed in FIG. 2) towards the hydraulic cylinder 52 such that the sheave 55 exerts a downward pressure on the cable 62 causing a counterclockwise rotation of sheave 55, and a clockwise rotation of annular hub 43. The retraction of the hydraulic cylinders 47 causes the withdrawal of the dogs 44 from the respective annular grooves of the drill rod.

The drill rods of the present invention comprises a number of similarly constructed rods; however, only one will be described in detail. Drill rod 50 (FIGS. 5-8) comprises a cylindrical tubular rod 66 having a central bore 67 extending longitudinally therethrough. Rod 50 has an upper female threaded joint 68 and a lower male threaded joint 69. The upper end portion of drill rod 50 is suitably circumferentially recessed as at 70 and is additionally provided with a pair of diametrically opposed recesses 71 which recesses 71 prevent counterclockwise rotation while permitting clockwise rotation as will be apparent. Each recess 71 has a pair of planar side surfaces 72 and 73 which are normal to each other. Respective side surfaces 72 are parallel to each other and parallel to the longitudinal axis of bore 67. Side surfaces 73 are generally parallel to each other. The lower end portion of rod 50 has a pair of diametrically spaced recesses 75 on the outer surface thereof, wherein each recess 75 has a pair of vertically disposed

surfaces

76 and 77 that are normal to each other to define a shoulder therebetween.

The control circuit for the power slip unit 28 and power wrench mechanism 26 is shown in FIGS. 9 and 10 wherein a pump P1 pumps presurized fluid via conduit 82 to a spring biased power slip valve 80, which valve 80 is controlled by solenoid A such that with the solenoid A deenergized, the power slip valve 80 connects pressurized conduit 82 to'the head end of the power slip cylinder 36 maintaining the power slip arms 30 in the inoperative or disengaged position. Energization of solenoid A actuates power slip valve 30 to connect presurized conduit 82 to the rod end of power slip cylinder 36 to actuate the power slips in a manner described above wherein the lever arms 30 are pivoted to grasp the drill rod 50. The power wrench 26 is controlled by a control valve 81 which re ceives pressurized fluid from a pump P-2 via conduit 83. Control valve 81 in its normal position maintains the

power wrench cylinders

47 and 52 in their selected posis tions of extension or retraction as will be apparent. Control valve 81 is actuated either by solenoids B or C wherein energization of solenoid B actuates power wrench control valve 81 to connect pressurized conduit 83 to the rod end of hydraulic cylinders 47 such that the dogs 44 (FIG. 2) are retracted to their outermost position in the annular hub 43 and cylinders 52 retracted such that hub 43 is in the most extreme clockwise position. Energization of solenoid C actuates power wrench valve 81 to connect the pressurized conduit 83 to the head end of the hydraulic cylinders 47 and the hydraulic cylinders 52 such that the dogs 44 are pivoted inwardly for engagement with a shoulder on the drill rod joints. Upon extension of such cylinders 47 bypass valve 85 thereafter directs pressurized fluid via conduit 86 to the head end of hydraulic cylinder 52 which causes the rotation of annular hub 43. With the dogs 44 engaged with the notches in the drill rod, extension of the hydraulic extension cylinder 52 causes the joint to be unscrewed. Solenoids A, B and C (FIG. are suitably controlled by manually operated switches 90, 91 and 92, respectively.

With a rotary drive and pull down mechanism 12 in the fully retracted position, such that the pull down mechanism 12 is at its uppermost position in a derrick 10, and there are no drill rods 50 coupled to the drive coupling 19,

the rod handling unit 23 upon proper actuation of switches is indexed by suitable swing cylinders to pivot the rod handling unit 23 about the main post 24, such as to align one of the drill rods 50 in the rod handling unit 23 into axial alignment with the spindle 20 and drive couplings 19. Upon lowering of the rotary drive and pull down unit 12, spindle 20 will engage the threads 68 on the upper portion of the drill rod 50. Rotation of the spindle 20 through the drive coupling 19 via rotary drive motor 13 threadedly connects the drive coupling 19 to the drill rod 50 in alignment therewith. The rotary drive and pull down unit 12 is then raised with the drill rod 50 connected thereto high enough that the lower end portion of the drill rod 50 clears the top of the rod cup. Through proper manipulation of switches disclosed in copending application, Serial No. 140,068, the upper portion of the indexable rod handling unit 23 is opened to permit the release of the drill rod 50 held by the spindle 20 while the indexable storage rack 23 is indexed out and away from the central portion of the derrick to provide clearance space for the manipulation and the reciprocable movement of the rotary drive and pull down unit 12.

When the uppermost drill rod is drilled into the ground substantially to the full length of its travel, the top end of the drill rod 50 is positioned so that the

respective recesses

70 and 71 are lined up with power slip arms 30. The power slip unit 26 is normally in the open position and the power slip cylinder 36 is normally extended to keep the power slip arm 30 disengaged from the drill rod 50. Energization of solenoid A connects pressurized conduit 82 to the rod end of the power slip cylinder 36 cansing the retraction of the piston therein which pivots power slip arms 30 toward each other to engage the

recesses

70 and 71 on the upper end of the drill rod 50. Normally the key 42 does not engage a recess 71 on the drill rod, but as the drill rod 50 is then rotated in a reverse direction by the overhead drive unit 12 the key 42 on the power slip arms 30 jumps into place in the recess 71 in the female joint giving a sharp blow to the joint and causing it to unscrew. The drill rod 50 is then held against further turning by the engagement of slip key 42 seated in the recesses 71 so that the spindle can then be disconnected from the drill rod by further rotation. The overhead drive and pull down unit 12 is then moved to the top of the derrick 10 to pick up the next drill rod 50 out of the rod rack handling unit 23. The next drill rod 50 is then added to the drill rod 50 being held by the power slip unit 28 by feeding a male joint into a female joint while simultaneously turning the upper drill rod 50 with the overhead drive and pull down unit 12. As soon as the joint is connected, the power slip unit 28 is opened by deenergization of solenoid A, the drilling operation resumes.

At the completion of a drilled hole, the joint between the top two drill rods is raised to where the

angular recesses

70 and 71, on the lower of the two drill rods line up with the power slip arms 30 of the power slip unit 28 so that upon energization of solenoid A pressurized conduit 82 is connected to the rod end of the power slip cylinder 36 to actuate the power slip arms 30 and key 42 into engagement with the recesses 70 and '71 on the drill rod. Energization of solenoid C by the power wrench control switch 92 actuates power wrench valve 81 which causes the pressurized conduit 83 to conduct pressurized fluid via suitable conduits to the head end of dog cylinders 47 to force the extension of the four dogs 44 on the annular hub 43 into engagement with the drill rod 50. Upon actuation of hydraulic cylinder 52, the annular hub 43 of power wrench mechanism 26 is caused to rotate about the axis of the drill rod 50 in a counterclockwise direction and the four dogs 44 are forced against the drill rod 50 by the extension of the dog cylinders 47 so that as the wrench continues to rotate the dogs 44 engage the recesses 75 of the drill rod such as to unscrew the upper drill rod from the lower drill rod. If the power wrench cylinder 52 reaches the end if its stroke before the joint is broken, the hydraulic cylinder 52 can be retracted by energization of solenoid B which causes power wrench valve 81 to connect the rod end of cylinder 52 to the pressurized conduit 83 whereby the power wrench rotates clockwise and returns to its starting position; however, in this instant the dogs 44 will not cause the drill rod 50 to rotate since the dogs 44 are also in their retracted position. It is necessary to continue advancing and retracting the power wrench 26 until the drill rods 50 are turned to the point where the key 42 on the power slip arm 30 will engage the notches 71 on the female joint at the connection being unscrewed. When this occurs the lower rod is held against further rotation and the power wrench can then exert enough torque to the upper rod to cause it to unscrew from the lower rod. As soon as the joint is loosened the overhead drive and pull down unit 12 is then used to finish unscrewing the joints, The upper rod is now ready to be loaded into the rod rack handling unit 23 while the remaining rods are left hanging in a drilled hole while they are being supported by the power slip mechanism 28. The drill rod 50 which has been disconnected is now raised up by the overhead drive and pull down mechanism 12 so that the rod handling unit 23 can be positioned under it. The rods disconnected must now be removed from the spindle and this is done by means of a notch on the bottom of the drill rod cooperating with a spring loaded dog in the rod cup. The spring biases the dog into engaement with the bottom end portion of the rod. After the drill rod 50 has been lowered into the cup, the overhead drive unit 12 is operated in a reverse direction to cause the rod 50 to turn until the spring loaded dogs in the rod cup engage the notches in the lower end portion of the drill rod to cause the rod to be held stationary while the spindle unscrews itself from a drill rod. After this joint is disconnected, the rack is moved back to its storage position so that the overhead drive and pull down mechanism 12 can be moved down to pick up the remaining rod 50 hanging in the drilled hole. Successive joints are disconnected in the same manner as described above.

A preferred embodiment of this invent-ion having been described and illustrated it is to be realized that modifications therein can be made without departing from the broad spirit and scope of this invention. It is therefore respectfully requested that this invention be interpreted as broadly as possible and be limited only by the prior art.

What I claim is:

1. A drill rod power wrench comprising a rotatable head portion supported by a frame, said head portion having an opening therein for receiving a drill rod with the longitudinal axis thereof substantially coincident with the axis of rotation of said head portion, said head portion having a plurality of pivotally mounted arms having end portions swingable into and away from said opening, a first power operated means mounted on said head portion connected to said arms for swinging said arms, a fluid operated extensible cylinder mounted on said frame operatively connected to said head port-ion by an elongated flexible element secured to the periphery of said head portion for rotating said head portion independently of said first power operated means, a pair of cooperating levers having opposable surfaces pivotally mounted on said frame and positioned below said rotatable head, said levers swingable by second power operated means to engage said opposable surface with such drill rod, and a projection mounted on said opposable surface of at least one of said levers for engaging notches on said first drill rod spaced from notches on a second such drill rod threadedly secured to said first drill rod engaged by said pivotally mounted arms whereby said levers hold stationary a drill rod while said arms mounted on said rotatable head rotate said second drill rod to threadedly disengage said second drill rod from said first drill rod.

2. A drill rod power wrench as set forth in claim 1 wherein said second power operated means has linkage means for moving said levers into self-locking operative positions whereby said linkage means maintain said projections on said lever in self-locking notch engaging position.

3. A drill rod power wrench mechanism comprising rod with the central axis thereof substantially coincident a rotatable head portion supported by a frame, said head portion having an opening therein for receiving a drill with the axis of rotation of said head portion, said head portion having a plurality of pivotally mounted arms having end portions swingable toward and away from said central axis, all of said end portions having respective surfaces substantially radial to said axis of rotation facing in a given direction of rotation about said axis of rotation and positionable within the axially extended outline of said opening when said end portions are swung toward said central axis, a first power operated means mounted on said head portion connected to said arms for swinging said arms, second power operated means mounted on said frame operatively connected to said head portion by an elongated flexible element secured to the periphery of said head portion for rotating said head portion independently of said first power operated means, a pair of cooperating levers having opposable surfaces swingably mounted on said frame independently of said head portion and positioned below said head portion, said levers swingable by third power operated means to swing said opposable surfaces within said axially extended outline, and a notch engaging projection mounted on at least one of said opposable surfaces.

References Cited by the Examiner UNITED STATES PATENTS WILLIAM FELDMAN, Primary Examiner.

Claims

1. A DRILL ROD POWER WRENCH COMPRISING A ROTATABLE HEAD PORTION SUPPORTED BY A FRAME, SAID HEAD PORTION HAVING AN OPENING THEREIN FOR RECEIVING A DRILL ROD WITH THE LONGITUDINAL AXIS THEREOF SUBSTANTIALLY COINCIDENT WITH THE AXIS OF ROTATION OF SAID HEAD PORTION, SAID HEAD PORTION HAVING A PLURALITY OF PIVOTALLY MOUNTED ARMS HAVING END PORTIONS SWINGABLE INTO AND AWAY FROM SAID OPENING, A FIRST POWER OPERATED MEANS MOUNTED ON SAID HEAD PORTION CONNECTED TO SAID ARMS FOR SWINGING SAID ARMS, A FLUID OPERATED EXTENSIBLE CYLINDER MOUNTED ON SAID FRAME OPERATIVELY CONNECTED TO SAID HEAD PORTION BY AN ELONGATED FLEXIBLE ELEMENT SECURED TO THE PERIPHERY OF SAID HEAD PORTION FOR ROTATIN SAID HEAD PORTION INDEPENDENTLY OF SAID FIRST POWER OPERATED MEANS, A PAIR OF COOPERATING LEVERS HAVING OPPOSABLE SURFACES PIVOTALLY MOUNTED ON SAID FRAME AND POSITIONED BELOW SAID ROTATABLE HEAD, SAID LEVERS SWINGABLE BY SECOND POWER OPERATED MEANS TO ENGAGE SAID OPPOSABLE SURFACE WITH SUCH DRILL ROD, AND A PROJECTION MOUNTED ON SAID OPPOSABLE SURFACE OF AT LEAST ONE OF SAID LEVERS FOR ENGAGING NOTCHES ON SAID FIRST DRILL ROD SPACED FROM NOTCHES ON A SECOND SUCH DRILL ROD THREADEDLY SECURED TO SAID FIRST DRILL ROD ENGAGED BY SAID PIVOTALLY MOUNTED ARMS WHEREBY SAID LEVERS HOLD STATIONARY A DRILL ROD WHILE SAID ARMS MOUNTED ON SAID ROTATABLE HEAD ROTATE SAID SECOND DRILL ROD TO THREADEDLY DISENGAGE SAID SECOND DRILL ROD FROM SAID FIRST DRILL ROD.