Earth Drilling Machine

Abstract

A travelling support frame is mounted for up and down travel by two parallel guide columns secured at their lower ends to a base frame. A portion of the traveling frame projects laterally of the drive columns and supports two drive motors, two reducing gearing assemblies, a collector gearing assembly and drive head means. The traveling frame and equipment carried thereby are moved up and down by triangularly arranged thrust ram means, each comprising a downwardly opening, upwardly projecting, piston chamber having a lower mounting portion originally secured to the traveling frame and a downwardly directed piston having a lower mounting portion secured to the base frame. The drive head includes a breakout wrench having a plurality of laterally swinging wrench jaws moved in and out by linear fluid motors. The wrench jaws have radially inwardly directed wrench portions which are like spanner wrenches. The free end of each wrench jaw makes abutting contact with a shank portion of the adjacent wrench jaw, so that in use the wrench jaws brace each other and form a compression ring surrounding the engaged drill pipe. The drill head includes a tool joint component which is movable axially a limited amount relative to the traveling cross frame. A connector rod connects this tool joint component to the piston of a linear fluid motor supported axially above the drill head. Fluid is introduced into the motor below the piston for the purpose of counterbalancing the weight of the drill head and any drill pipe connected thereto. A holding wrench is located below the turning wrench. It comprises a plurality of wrench jaws pivotally mounted for lateral swinging movement, a surrounding control ring, and individual links interconnected between each wrench jaw and the control ring. The control ring is rotated by linear fluid motors. Rotation in one direction causes the links to move the wrench jaws radially inwardly into a position of engagement with holding wrench receiving portions on drill pipe, and movement in the opposite direction causes the links to move the wrench jaws radially outwardly in space relationship from the drill pipe.

Parent Case Text

This is a division, of application Ser. No. 75,020, filed Sept. 24, 1970.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to earth boring or drilling machines. It particularly relates to mechanism for counter-balancing the weight of the drill stem and other rotary components, to turning and holding breakout wrenches, and to mechanism for supporting and vertically moving the rotary drilling equipment.

2. Description of the Prior Art

The present invention relates to an earth boring or drilling machine of the same basic type as disclosed in U.S. Pat. No. 3,220,494, granted on Nov. 30, 1965 to Robert E. Cannon et al., in U.S. Pat. No. 3,454,114, granted July 8, 1969 to Leland B. Poage, in U.S. Pat. No. 3,490,546, granted Jan. 20, 1970 to John S. Hattrup et al., and in U.S. Pat. No. 3,463,247, granted Aug. 26, 1969 to Harold T. Klein. In other words, like each of the machines of the above-identified patents, the machine of the present invention is a precision earth drilling machine which includes rotary drilling equipment mounted for precision movement up-and-down along a plurality of elongated base supported guide columns by traveling cross frame which is hydraulically raised and lowered. The machine of the present invention is a larger capacity machine, adapted for delivering much higher torque than any of the machines shown by the aforementioned patents.

Drilling machines of the present invention are characterized by high torque breakout apparatus for the sectional drill stem which is used with the machine, and by drilling equipment which includes hydraulic means for counter-balancing the weight of the drill stem and certain components of the drilling equipment.

Known but quite different systems for decoupling threaded sections of a drill stem are shown by U.S. Pat. No. 3,181,630, granted May 4, 1965 to Robert S. Coburn; by U.S. Pat. No. 3,239,016, granted Mar. 8, 1966 to Emmett L. Alexander; by U.S. Pat. No. 3,291,225, granted Dec. 13, 1966 to Charles D. Foran; by U.S. Pat. No. 3,446,284, granted May 27, 1969 to Norman D. Dyer and Roy L. Van Winkle; and by U.S. Pat. No. 3,460,638, granted Aug. 12, 1969 to Stuart C. Millsapps, Jr.

Known prior but quite different systems for hydraulically counterbalancing the weight of a drill stem are shown by U.S. Pat. No. 1,781,707, granted Nov. 18, 1930 to Waldo Sheldon, and by U.S. Pat. No. 3,151,686, granted Oct. 6, 1964 to Archer W. Kammerer.

SUMMARY OF THE INVENTION

The drill stem weight counterbalancing equipment of the present invention includes a linear fluid motor which is mounted on a frame portion of the drilling machine substantially in line with the drilling axis. A tension member is interconnected between the piston of such motor and a floating drill head which is threadable to the sections of drill pipe. This drill head and a power drive mechanism therefor are carried together on a traveling cross frame.

According to the invention, the drill head is surrounded by a remotely controllable breakout wrench adapted to grip each section of drill pipe at a location axially inwardly of the drill pipe from its threaded connection with the drill head. The drilling equipment also includes a holding wrench located at a wrench table spaced axially from the drill head on the drilling axis. In use the pipe section second from the drill head is held by this holding wrench mechanism and the drill head is rotated in reverse for "breaking," i.e. "loosening," the threaded joint between the first and second sections of pipe. If the threaded joint between the first section of pipe and the drill head breaks first, the breakout wrench is activated to engage the first section of pipe and the drill head is again reversed for loosening the threaded connection between the first two sections. In addition to counterbalancing the weight of the drill stem and portions of the drilling equipment the linear fluid motor automatically moves the floating drill head axially in response to thread travel during the breakout procedure.

In addition to new and improved breakout system, and to unique apparatus for counterbalancing drill stem and drilling equipment weight, the present invention relates to an improved high torque breakout wrench and an improved high torque holding wrench. It also relates to improvements in the hydraulic thrust ram system used for raising and lowering the traveling cross frame which carries the rotary drilling equipment.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing like letters and numerals refer to like parts, and:

FIG. 1 is an isometric view taken from above and looking towards one side and the front of a drilling machine constructed according to the present invention, showing the drilling apparatus in a partially raised position;

FIG. 2 is a view like FIG. 1, but showing the drilling apparatus in a lowered position;

FIG. 3 is a fragmentary, somewhat schematic front elevational view of breakout mechanism for the drill pipe and a fluid motor type counterbalancing system for the drill head and drill pipe.

FIG. 4 is an enlarged scale view partially in section and partially in elevation of the breakout apparatus shown by FIG. 3, with both the holding and driving wrenches in retracted positions;

FIG. 5 is a view similar to FIG. 4, but showing the holding wrench engaging the second section of pipe from the drill head and the drill head uncoupled from the tool joint at the upper end of the upper drill stem section;

FIG. 6 is a view similar to FIGS. 4 and 5, but showing the turning wrench engaged with the upper section of drill pipe, and the threaded tool joint at the lower end of the upper length of pipe decoupled;

FIG. 7 is a view similar to FIGS. 4-6, but typifying a situation wherein on reverse rotation of the drill head, for random breaking of the threaded joints, the lower threaded joint breaks first, such view showing the lower joint completely coupled;

FIG. 8 is an enlarged scale elevational view, with some parts in section, of the counterbalancing fluid motor and an internal parts position indicating mechanism associated therewith;

FIG. 9 is a cross-sectional view taken through the drill head above the turning wrench, substantially along line 9--9 of FIG. 3;

FIG. 10 is a cross-sectional view taken through the machine immediately above the holding wrench, substantially at the level indicated by line 10--10 in FIG. 3;

FIG. 11 is a view partially in elevation and partially in longitudinal section of a length of drill pipe;

FIG. 12 is a cross-sectional view taken through the recesses formed in the drill pipe for receiving portions of the turning wrench jaws; and

FIG. 13 is a cross-sectional view taken through the holding wrench flats, substantially along line 13--13 of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring more specifically to the several figures of the drawing, the illustrated embodiment is shown to comprise a lower or base frame assembly 10 including a base plate 12 and a generally U-shaped main frame 14 upstanding from the plate 12. Frame 14 includes upstanding wall portions forming a pair of sockets 16 which occupy near corner positions on the plate 12. The lower end portions of a pair of parallel guide columns 18 are received in the sockets 16 and are rigidly secured to the base frame thereby. A fixed cross frame 20 rigidly interconnects the upper ends of the guide columns 18.

The guide columns 18 support and guide a movable or traveling cross frame 22. Traveling cross frame 22 includes vertically spaced apart upper and lower guide sleeves 24, 26 which surroundingly engage the columns 18. A lower portion of the traveling cross frame 22 extends laterally from the sleeves 26 into a position over the base frame assembly 10. It includes wall means 28 forming a housing for a bearing assembly (FIG. 3). A second housing 30 extends laterally from the upper guide sleeves 24 into a position above the housing 28. Housings 28, 30, sleeves 24, 26 and the interconnecting parts of traveling cross frame 22 are structurally integrated into a single rigid frame assembly.

The upper housing 30 contains collector gearing 32 having a pair of inputs 34 and a single output 36. A pair of drive motor assemblies are bolted to the housing 30, and each has an output shaft which is coupled to one of the inputs of the collector gearing. In preferred form the motor assemblies comprise an electric motor 38 and a planetary type reduction transmission 40, such as the type shown by FIG. 7 of the aforementioned U.S. Pat. No. 3,454,114.

Traveling cross frame 22 is raised and lowered by a plurality of thrust rams 41. According to the invention, each thrust ram 41 comprises a hollow piston chamber or "cylinder," designated 42, and a piston 44. In the illustrated embodiment the closed ends of the piston housings 42 are directed upwardly and the open ends are directed downwardly. Mounting sockets 46 of split form receive the lower end portions of the housings 42 and firmly secure them to the traveling cross frame 22. Pistons 44 include upwardly directed head portions (not shown) and lower end mounting portions 48 which are secured to the lower frame 10. Mounting portions 48 are received between vertical plate portions of the frame member 14 and are secured to such plate portions by mounting pins 50.

Thrust rams 41 are essentially identical to the thrust rams shown by the aforementioned U.S. Pat. No. 3,454,114. Accordingly, further details of these thrust rams 41, including the means for supplying and exhausting a motive fluid to and from them, will not be specifically described herein. Rather, reference is made to U.S. Pat. No. 3,454,114, the contents of which are expressly incorporated herein by this reference.

As shown by FIGS. 1, 2 and 10, the guide columns 18 and two of the thrust rams 41 are spaced apart in a quadrangular pattern, with the guide columns 18 being relatively close to corner portions of the base frame assembly 10 on one side of such base frame 10 and the two thrust rams 41 being in the corner portions on the other side of base frame assembly 10. The third thrust ram 41 is located generally between the guide columns 18 and forms a triangular pattern with the other two thrust rams 41. The drilling axis is located substantially at the center of forces within the triangle. The upper ends of the cylinders 42 are interconnected by a generally triangular shaped traveling head frame 52.

Reference is now made to FIG. 3 of the drawing. The output member 36 of the collector gearing 32 is shown to be drivingly connected to a rotary drive housing 54 supported for rotation on the traveling cross frame 22 by upper and lower sets of combination bearings 56, 58. The expression "combination bearing" is used herein to mean a bearing which carries both axial and radial loads. A drive head 60 is received in a lower portion of the rotary housing 54. A plate 62 having axial splines on its periphery is connected to the upper end of drill head 60. These mesh with corresponding internal axial splines 64 carried by the inner side wall of housing 54. The peripheral splines on plate 62 and the splines 64 serve to drivingly connect the housing 54 to the drill head 60 for rotational drive but permits the drive head 60 to travel axially a limited amount relative to the housing 54.

A support stem 66 is rigidly connected at its lower end to the drill head 60 and extends upwardly therefrom. Stem 66 includes a swivel joint at 68. The swivel joint 68 connects the upper and lower portions of the stem 66 together so that they move together axially. The portion of stem 66 below swivel joint 68 rotates with the drill head 60. The portion of the support stem 66 above swivel 68 does not rotate. A piston rod 70 rigidly connects the non-rotating portion of support stem 66 with a piston head 72. Piston head 72 is mounted for linear up and down travel within a piston housing or cylinder 74 of a linear motor 76 which is mounted on top of the traveling head frame 52. The primary function of linear motor 76 is for counterbalancing the weight of the drill head assembly and the drill stem connected thereto. However, it also plays a part in the drill stem breakout technique of the present invention, as will hereinafter be described in detail.

Drill head 60 includes a drilling fluid passageway 78 extending axially through it. This passageway 78 extends from the drill head 60 upwardly through support stem 68, the swivel coupler 68, and an upper branch part 80 of support stem 66. The branch part 80 extends upwardly through an opening 82 in plate 54. Opening 82 is sufficently large that the branch part 80 is free to move axially up and down during axial travel of the support stem 66.

As best shown by FIG. 8, a radial support arm 84 extends laterally from the piston 70 below head frame 52. The outer end of arm 84 is connected to the lower end of a movable core 86 mounted for axial travel within the tubular housing 90 of a variable voltage transformer 88. Housing 90 includes an electrical coil 92 which surrounds the path of rod 86. Change in the axial position of core 86 changes the voltage output of transformer 88. Since core 86 is structurally coupled to the drill head 60 through the piston rod 70 and the support stem 66, the change in resistance of variable voltage transformer 88 gives an indication of the internal position of the drill head 60 and the other internal components connected thereto. Variable voltage transformer 88 may be in an electrical circuit (not shown) which includes a direct read out device. In some installations a variable resistor may be used in place of the variable voltage transformer.

The lower end of drill head 60 is a tool joint component 94 connectible to a complementary tool joint component 96 at the upper end of each section 98 of the drill stem 100. In the illustrated embodiment tool joint component 94 is a threaded "box" and tool joint component 96 is a threaded "pin."

The illustrated form of drill pipe 98 is of composite form. It is shown to comprise a double box major section 102 and a double pin minor section or "sub" 104. At least the box type tool joint component 106 at the lower end of section 102 has threads which complement and will engage the threads of each pin component 96.

As best shown by FIGS. 11-13, each length of drill pipe 98 includes a triangular pattern of axially elongated recesses 108. As shown by FIG. 12, shouldered portions 110 are located circumferentially between the recesses 108.

The recesses 108 are provided for receiving wrench jaw portions of a breakout wrench. A second set of recesses or "flats" are provided on each length 98 axially inwardly of the recesses 108 and are designated 112. The base surfaces of recesses 112 are preferably flat chord surfaces.

As shown by FIGS. 3-9, the drill head assembly includes an axial lower extension 114 of drive housing 44 which carries a breakout wrench mechanism 116, hereinafter sometimes referred to as the "turning wrench."

Referring to FIGS. 5-7 and 9, the turning wrench 116 comprises a drum like carrier 118 which is rigidly secured to and is rotated by the extension 114. A plurality of short posts 120 project downwardly from the lower end of carrier 118. An open centered plate 122 is secured to the posts 120, such as by bolts 124. Three circumferentially spaced apart wrench jaws 126 are pivotally mounted on the carrier 118 for swinging movement radially in and out relative to the position of the drill stem 100. Each jaw 126 includes an outer end portion which is received between a pair of the posts 120. Pivot pins 128 fit through openings formed in the outer end portions of the wrench jaws 126 and the wrench jaws 126 move relative to the pins 128. The pivot pins 128 extend between the plate 122 and the carrier 118. A linear fluid motor 130 is associated with each wrench jaw 126 for moving the same into and out from its wrenching positions. The linear motors 130 are interconnected between connectors 132 on the wrench jaws 126, near the free ends thereof, and connectors 134 secured to the carrier 118. Pivotal connections are provided at 136 and 138 so that extension and retraction of the pistons 140 in motors 130 will cause the wrench jaws 126 to swing laterally of the drill pipe axis 140 between the wrenching positions depicted by solid lines in FIG. 9 and the retracted or inactive positions depicted by broken lines in FIG. 9 with respect to the upper wrench jaw 126 only.

The wrench jaws 126 are of the spanner wrench type. Each includes a radially inwardly directed recess 142 which is bounded at each of its circumferential ends by a generally radially extending wrench surface, designated 144, 146 in FIG. 9.

When the wrench jaws 126 are in their operative positions the shouldered portions 110 of the drill pipe are received in the recesses 142.

Each wrench jaw 126 has an inner shank portion 148 which is in tight load transferring engagement with an end surface 150 of an enjoining wrench jaw 126.

In FIG. 9 the turning wrench 116 is shown in the process of being rotated counterclockwise. The wrench surfaces 146 engage radial surfaces on the wrench sections 110. The loading on the wrench jaws 126 is such that the wrench jaws want to swing further inwardly. This means that compressive loads are transferred from each wrench jaw 126 to the next where contact is made at surfaces 148, 150; the wrench jaws 126 are mutually self-bracing. Together the wrench jaws 126 cooperate to define a compression ring which surrounds the engaged portion of the drill pipe.

Referring now to FIGS. 1, 3-7 and 10, the base member 12 carries a holding wrench assembly 152 in axial alignment with the turning wrench 116. An opening 154 is provided in table 12 in axial alignment with the opening 156 in turning wrench plate 122. Three wrench jaws 158 are pivotally connected to the table 12 by pivot pins 160. Wrench surfaces 162 are formed on radial inner portions of the wrench jaws 158. In the illustrated embodiment the surfaces 162 are essentially flat surfaces and when the wrench 152 is in its operative position the surfaces 162 form a triangular pattern which corresponds to the triangular pattern of the pipe surfaces 112. In this operative position the wrench jaw surfaces 162 are contiguous the pipe surfaces 112.

The wrench jaws 158 are surrounded by a control ring 164. The ring 164 includes three radially inwardly extending enlarged portions 166 in which are formed recesses 168 for receiving the rounded end portions of control links 170. Similar recesses 172 are formed in radial outer portions of the wrench jaws 158 to receive the opposite rounded ends of the control links 170. The guide means for the control ring 164 includes three brace blocks 174. These brace blocks 174 are circumferentially spaced equal distances apart and are located such that when the turning wrench 152 is in its operative position they are radially aligned with the control links 170 and with the mating pairs of wrench surfaces 162, 112. In such operative position the control links 170 are substantially radially oriented.

A pair of linear fluid motors 176 are interconnected between the table 12 and the control ring 160. Pivotal connections 178, 180 are provided at the opposite ends of the motors 176 so that there is freedom of movement of the motors 176 as the control ring 164 turns.

In operation, the motors 176 are operated in unison to rotate the ring 164. In FIG. 10 the left side motor 176 is extended, the right side motor 176 is retracted, and the wrench jaws 158 are swung inwardly into holding engagement with the drill pipe. The control links 170 are radially disposed so that the radially outwardly directed forces imposed on them by the drill pipe 100 through the wrench jaws 158 is transmitted by the control links 170 to the brace blocks 174 which are rigidly secured to the table 12. Thus, the control ring 164 does not have to by itself carry the loads imposed on the wrench jaws 158 during the breakout or joint loosening operation.

The breakout technique will now be described:

Let it be assumed in the drilling operation depicted by FIGS. 4-7 that the traveling frame 22 and the drilling head 60 carried thereby are in the process of being moved upwardly along the guide columns 18, and the drill stem 100 is being withdrawn from the drill hole. When the upper or first section 98 is wholly above the wrench table 12 and the holding wrench receiving depressions 112 of the second section 98 are in position at the wrench table 12 to receive the holding wrench jaws 158, axial movement of the traveling frame 22 is stopped (FIG. 4). The control ring 164 is then rotated to place it in the position shown by FIG. 10, with the wrench jaws 158 engaging the recesses 112. The portion of the drill stem 100 below the first section 98 is then restrained or anchored against both rotational and downward axial or gravitational movement.

The drill head 60 is then reversed, i.e., rotated in a tool joint loosening direction, for the purpose of randomly loosening one of the tool joints at the opposite ends of the upper section 98. The threaded connection between the major and minor parts 102, 104 of the composite section 98 are secured against separation by an epoxy bonding agent or by a different thread design. FIG. 5 relates to the situation when the upper tool joint loosens first. For the sake of clearer illustration, in FIG. 5 the upper section 98 is shown to be physically separated from the drill head 60. However, in the breakout operation the tool joint components 94, 96 are not completed separated, but rather the joint is merely loosened.

Assuming that the randomly loosening operation caused the upper joint to loosen first, and the threaded joint between components 94, 96 is not totally separated but is merely maintained loosely joined, the fluid motors 130 are operated to move the turning wrench jaws 126 into engagement with the shouldered portions 110 between the recesses 108 (FIG. 9). After this has been done the drill head 60 is again rotated in the thread loosening direction. The portion of the drill stem 100 below the upper section 98 is still retained by the holding wrench 152. During such rotation the wrench jaws 126 transmit torque from the drill head 60 to the upper section 98, resulting in a loosening of the threads at the lower tool joint 106, 96. With the tool joints at both ends of the upper section 98 now loosened, the upper section 98 can be easily unscrewed and removed from the drill stem 100. After this is done the drill head 60 is lowered and coupled to the next pipe section by loosely screwing together its box component 94 and the upstanding pin 96 of the next section 98. The drill head 60 is then raised, with the weight of the drill stem 100 being carried by the loosely engaged threads of the loosely made-up tool joint, until such next section is in a position for removal wholly above the holding wrench table 12, and the holding wrench receiving depressions 112 of the following section 98 are at the holding wrench station of the table 12. The breakout wrench 116 is again operated to engage the new upper section 98, and the drill head 60 is rotated in reverse as before to loosen the threaded tool joint at the wrench table 12. This sequence of steps is repeated with the subsequent sections until all sections of the drill stem 100 have been removed from the drill hole.

During loosening of a threaded tool joint allowance must be made for thread travel. Otherwise, thread damage will occur. According to the invention, sufficient fluid pressure is maintained in the counterbalancing linear motor 76 below the piston head 72 to bias the drill head 60 upwardly. Thus, the drill head 60 and the drill pipe 98 connected thereto progressively moves upwardly as decoupling at joint 106, 96 proceeds.

The recesses 108 are axially elongated and the turning wrench jaws 126 are positioned therein such that there is always axial clearance above and below the wrench jaws 126. This is important because the weight of the drill stem 100 must be carried by the linear motor 76 and none of it by the wrench jaws 126.

If during the initial reversal of the drill head 60, to cause a random loosening of the tool joints, the lower joint loosened first, then an added stage must be added to the technique in order to effect loosening of the tool joint between the upper section 98 and the drill head 60. This stage (not shown) involves maintaining the loosened lower tool joint components coupled, so that their threads may carry the weight of the drill stem 100, then retracting the holding wrench jaws 158, and then lowering the drill head 60, with the drill stem 100 attached, downwardly until the holding wrench receiving depressions 112 of the upper section 98 are at the holding wrench station of table 12. The holding wrench jaws 158 are then moved inwardly and used to support the drill stem 100 and prevent its rotation. The drill head 60 is then rotated in the joint loosening direction until the threaded tool joint 94, 96 is loosened. When this happens the joint components are maintained loosely coupled so that the threads can carry the weight of the drill stem 100. The drive head 60 is then raised to locate the upper pipe section 98 in a proper position for removal. The holding wrench 152 is reinserted on the second pipe section 98 and the first section 98, now having both of its tool joints loosened, is easily unscrewed from the second section 98 and from the drill head 60, and is then removed from the drill stem 100.

Claims

What is claimed is:

1. A drill pipe wrench, comprising:

support means situated at least partially about a drill pipe path,

a plurality of circumferentially spaced apart wrench jaws,

means pivotally connecting said wrench jaws to said support means for in and out swinging movement about circumferentially spaced apart axes situated radially outwardly from the drill pipe path which axes are in parallelism with each other and with the drill pipe path,

means for swinging the wrench jaws inwardly together or outwardly together,

said wrench jaws each having a radially inwardly facing wrench portion for engaging an external portion of a drill pipe section, and

said wrench jaws each having specially configured outer end and inner shank portions, wherein when the wrench jaws are swung inwardly into a wrenching position the said outer end portion of each wrench jaw is in load transferring contact with the said inner shank portion of the next wrench jaw, and all wrench jaws cooperate to define a compression ring which surrounds the said wrench portions, whereby the wrench jaws are mutually self-bracing.

2. The drill pipe wrench of claim 1, wherein each wrench jaw is in the nature of a spanner wrench and its wrench portion comprises a radially inwardly facing recess bounded at each of its circumferential ends by a generally radially extending wrench surface.

3. The drill pipe wrench of claim 1, wherein said means for swinging the wrench jaws inwardly together or outwardly together comprises a linear fluid motor for each wrench jaw, interconnected between the wrench jaw and said support means, and control means for operating the said linear fluid motors in unison.

4. The drill pipe wrench of claim 1, wherein said support means is rotatable.

5. The drill pipe wrench of claim 4, further comprising a threaded tool joint on said support means and rotatable therewith, said tool joint being coaxial with the drill pipe path and being spaced on such path axially of the said wrench jaws.

6. The drill pipe wrench of claim 5, wherein each wrench jaw is in the nature of a spanner wrench and each wrench portion comprises a radially inwardly facing recess bounded at each of its circumferential ends by a generally radially extending wrench surface.

7. The drill pipe wrench of claim 6, comprising three wrench jaws which are equally spaced apart.

8. For use in drilling apparatus of a type including a drill head having a threaded box component which rotates with the drill head and is mounted to move axially within said head, and a breakout wrench on said drill head comprising a plurality of circumferentially spaced apart wrench jaws positioned about the axis of the threaded box, and spaced axially outwardly from said threaded box, means pivotally connecting the wrench jaws to said drill head for in and out swinging movement about circumferentially spaced apart axes situated radially outwardly from the axis of the threaded box, which axes are in parallelism with each other and with the axis of the threaded box, means for swinging the wrench jaws inwardly together or outwardly together, said wrench jaws each having radially inwardly facing wrench portions, a drill pipe section comprising:

a tubular body having a threaded pin at one end thereof which is threadable into the threaded box carried by the drill head and a threaded box at the opposite end for connecting said section to another section of drill pipe, and a set of breakout wrench jaw receiving recesses spaced axially inwardly of the pipe section from said threaded pin, said set comprising a plurality of recesses equal in number to the wrench jaws, said recesses being sized to receive the wrench portions of said wrench jaws, each said recess having a pair of end surfaces and a pair of load carrying side surfaces which substantially lie in axial planes and which make torque transferring contact with the wrench portions of said wrench jaws, and each said recess being axially elongated enough so that during axial travel of the pipe section to accommodate thread travel at the box end of the pipe section, the two end surfaces of the recesses remain free of load transferring contact with the breakout wrench jaws.

9. A drill pipe section according to claim 8, further comprising a set of holding wrench receiving recesses spaced axially inwardly of the pipe from the breakout wrench jaw receiving recesses, said holding wrench recesses including both axial load carrying end surfaces and torque transferring chord surfaces.

10. Drilling apparatus comprising:

a drill head comprising a threaded box component which rotates with the drill head and is mounted to move axially within the head, means connected to said box component which carries the weight of said box and any drill pipe connected thereto, and a breakout wrench comprising a plurality of circumferentially spaced apart wrench jaws positioned about the axis of the threaded box, and spaced axially outwardly from said threaded box, means pivotally connecting the wrench jaws to said drill head for in and out swinging movement about circumferentially spaced apart axes situated radially outwardly from the axis of the threaded box, which axes are in parallelism with each other and with the axis of the threaded box, said wrench jaws having radially inwardly facing wrench portions, means for selectively swinging the wrench jaws inwardly together and outwardly together and means mounting the drill head box component for sufficient axial movement in response to thread travel at the box end of the pipe section to accommodate the resulting axial movement of pipe section; and

a drill pipe section comprising a tubular body having a threaded pin at one end thereof which is threadable into the threaded box carried by the drill head and a threaded box at its opposite end for connecting said section to another section of drill pipe, and a set of breakout wrench jaws receiving recesses spaced axially inwardly of the pipe section from said threaded pin, said set comprising a plurality of recesses equal in number to the wrench jaws, said recesses being sized to receive the wrench portions of said wrench jaws, each said recess having a pair of end surfaces and a pair of load carrying side surfaces which substantially lie in axial planes and which make torque transferring contact with the wrench portions of said wrench jaws, and each said recess being axially elongated enough so that during axial travel of the pipe section to accommodate thread travel at the box end of said section, the two end surfaces of the recesses remain free of load transferring contact with the breakout wrench jaws.