U.S. patent number 3,680,412 [Application Number 04/881,842] was granted by the patent office on 1972-08-01 for joint breakout mechanism.
This patent grant is currently assigned to Gardner-Denver Company. Invention is credited to James R. Mayer, Joe D. Tipton.
United States Patent |
3,680,412 |
Mayer , et al. |
August 1, 1972 |
JOINT BREAKOUT MECHANISM
Abstract
A remotely controlled breakout mechanism grips and loosens
threadably joined connections between sections of a drill string.
The mechanism is coaxial with and movable along the drill string
and includes stationary and rotatable gripping assemblies which are
independently operable for interengagement with splines formed
about the adjacent ends of adjoining string sections. The
stationary gripping assembly holds one section against rotation and
axial movement while the rotatable gripping assembly applies a
thread-loosening torque to the adjoining section. A pressure fluid
power system for the breakout mechanism includes a control which
prevents rotation of the rotatable gripping assembly unless the
jaws thereof have been operated for positive interengagement with
the splines on a section. Another control is responsive to
engagement of the jaws of the stationary gripping assembly for
limiting the joint retightening torque output of a fluid motor
which normally rotates the drill string with full torque output
during drilling operations. The breakout mechanism also serves as a
centralizer for the drill string and as a support for temporarily
suspending the drill string off the hole bottom. The number and
shape of the splines on the end surfaces of the sections are
preselected to provide substantial circumferential engagement with
the jaws of the mechanism and to provide a sufficiently great
number of opportunities for the gripping assemblies to interengage
the splines so that a short-stroke power cylinder can be employed
to operate the rotatable gripping assembly.
Inventors: |
Mayer; James R. (Dallas,
TX), Tipton; Joe D. (Garland, TX) |
Assignee: |
Gardner-Denver Company (Quincy,
IL)
|
Family
ID: |
25379321 |
Appl.
No.: |
04/881,842 |
Filed: |
December 3, 1969 |
Current U.S.
Class: |
81/57.34;
81/57.19; 173/147; 173/159; 175/85; 81/57.16; 81/57.21;
173/164 |
Current CPC
Class: |
E21B
19/20 (20130101); E21B 19/167 (20130101) |
Current International
Class: |
E21B
19/16 (20060101); E21B 19/00 (20060101); E21B
19/20 (20060101); B25b 013/50 (); B25b
017/00 () |
Field of
Search: |
;81/57.16,57.19,57.21,57.15,57.22,57.33,57.34,57.35,57.36 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones, Jr.; James L.
Claims
What we claim is:
1. A fluid actuated breakout mechanism operable for loosening a
threaded joint between a rotatable drill member and a drill string
section from an initially tight condition;
said breakout mechanism including a fluid actuated jaw assembly
having drill string section engaging jaws and drill member engaging
jaws;
a reversible fluid actuated rotary motor providing torque for
rotating said drill member to connect and disconnect said joint;
and
fluid control means responsive to operation of said breakout
mechanism to limit the joint connecting torque output of said motor
to a level less than its joint disconnecting torque output.
2. The invention defined in claim 1, wherein:
said breakout mechanism includes a fluid actuated jaw assembly
operable to engage said drill string section; and
said fluid control means includes a bypass connectable in circuit
with said motor when said drill string section engaging jaws are
engaged.
3. The invention defined in claim 2, wherein:
said fluid control means includes fluid actuated valve means
operable to connect said bypass; and
said valve means and said drill string section engaging jaws are
connected to a common fluid supply valve for simultaneous
operation.
4. Threadably joinable drill string sections each having external
splines formed adjacent opposite ends thereof and a breakout
mechanism for loosening threaded joints between sections of a drill
string, comprising:
upper and lower gripping means;
said upper gripping means being rotatable with respect to said
lower gripping means;
a bore extending through said gripping means for receiving the
splined adjacent ends of two joined sections;
jaw means having plural teeth formed thereon and housed in said
gripping means; and
said jaw means being operable for movement relative to said
gripping means into said bore to effect interengagement of said
teeth with the splined ends of said joined sections.
5. The invention defined in claim 4, wherein:
said jaw means comprise fluid actuated pistons radially disposed
about said bore in cylinder bores interconnected by fluid passage
means.
6. The invention defined in claim 4, together with:
fluid actuated means for operating the jaw means of said upper
gripping means;
fluid actuated cylinder means having a cylinder body connected to
said lower gripping means and an extendable piston rod connected to
said upper gripping means; and
fluid control means in circuit with said jaw means of said upper
gripping means and said cylinder means for sequentially operating
said jaw means of the upper gripping and then said cylinder
means.
7. The invention defined in claim 4, wherein:
said teeth have sloping walls which when extended would intersect
to define an included angle of 60.degree. .
8. The invention defined in claim 4, wherein:
said teeth are spaced apart by at least .125 inch.
9. The invention defined in claim 4, together with:
annular bushings removably attached to the upper and lower gripping
means and disposed adjacent the opposite openings of said bore.
10. The invention defined in claim 9, wherein:
the inside diameter of said bushings are smaller than the diameter
of said bore.
11. The invention defined in claim 4, together with:
means for moving said upper and lower gripping means along the
entire length of a drill string section received in said bore.
Description
BACKGROUND OF THE INVENTION
Remotely controlled mechanisms have been developed heretofore for
making up and breaking out threaded connections between sections of
pipe or rod joined together to form a drill string. Ordinarily the
drill bit is rotated by a drill motor as it is fed into the ground,
consequently, the joints between sections become extremely tight
and substantial forces are required to loosen or break out such
joints as the string is disassembled.
Self-reacting breakout mechanisms which simulate the gripping and
turning actions of a pair of human hands have been disclosed in
U.S. Pat. No. 3,158,213 issued to O'Neill et al and in U.S. Pat.
No. 3,463,037 issued to Johnson.
The Johnson breakout is hinged and openable to receive laterally
the ends of two pipe sections. The adjacent ends of the joined
sections have six circumferentially spaced slots for receiving
single spring applied pawls carried by stationary and rotary
portions of the mechanism. An extendable power cylinder mounted on
the stationary portion is operable to rotate the rotary portion to
loosen the threads.
The breakout disclosed by O'Neill et al is operationally similar to
the Johnson device and is incorporated in a semi-automatic drill
rig as part of a more comprehensive system intended to reduce human
intervention and effort in the drilling operation. Thus O'Neill et
al show a portable drill rig having a tiltable mast which slidably
supports a rotary drill motor, a breakout mechanism carried by the
mast, a suspension means for temporarily supporting the string off
the bottom of the hole, and a pipe transfer and storage device for
swinging pipe sections to and from alignment with the drill string.
The O'Neill breakout includes a stationary jaw assembly, a
rotatable jaw assembly and a guiding jaw assembly for guiding the
upper pipe into the lower pipe during make-up operations. It is
believed that the stationary jaws and rotatable jaws either
frictionally engage with or bite into the walls of the pipe
sections.
While the desirability of employing a remotely controlled,
self-contained breakout mechanism in a semiautomatic drill rig has
been generally recognized by O'Neill et al, substantial problems
remain to be solved in the following areas:
1. Provision of interengaging means formed on the breakout jaws and
on the drill string sections which will assure rapid and positive
engagement between the breakout jaws and the sections without
damaging the sections;
2. Provision of powerful, yet compact drive means for rotating the
rotary jaws for breakout;
3. Provision of a control system which will provide driving
engagement between the rotary breakout jaws and a drill string
section before the rotary jaws are powered for breakout;
4. Provision of remotely controlled means for moving the breakout
mechanism along the entire length of a drill string section to
enable the breakout of connections between the drill motor and a
string section in case a string section is advanced only part way
into the ground;
5. Provision of a control system which will, as a drill string is
being disassembled, automatically coordinate the operation of the
drill motor and the breakout mechanism to provide a snug-tight
connection between the drill motor and the top of that section
joined to the drill motor which will not uncouple when the drill
motor is reversely rotated to spin out a preloosened connection at
the bottom of that section;
6. Provision of a mechanism which will not only serve its intended
breakout purpose, but will also function as a drill string
centralizer during the drilling operation and as a temporary
support for suspending the drill string off bottom as string
sections are removed.
SUMMARY OF THE INVENTION
The broad object of this invention is to provide a drill string
breakout mechanism for a drill rig which coacts with splined drill
string sections and with improved control systems to permit drill
strings to be made up and broken down in a manner which is more
rapid, foolproof, and safe than any heretofore known. More
specifically, this invention is intended to provide structures,
mechanisms and controls for drill string handling which meet the
several above-enumerated shortcomings of the prior art.
BRIEF DESCRIPTIOn OF THE DRAWINGS
FIG. 1 is a front elevational view of a mobile, track-type drill
rig which incorporates the present invention;
FIG. 2 is a partial sectional view of an improved breakout
mechanism shown in FIG. 1;
FIG. 3 is a partial sectional view generally taken along lines 3--3
of FIG. 2;
FIG. 4 is a partial sectional view of a connection between
threadably joined drill string sections;
FIG. 5 is a diagrammatic illustration of the teeth on the drill
string sections and the pistons of the breakout mechanism shown in
FIGS. 2 and 3;
FIG. 6 is a schematic illustration of a fluid power and control
system for the drill rig shown in FIG. 1; and,
FIGS. 7 through 15 are diagrammatic illustrations of a sequence of
operations which may be performed by remote control in the drill
rig shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 of the drawings, the drill rig, generally
designated by numeral 20, is of the track type and is movable from
place to place by powered tracks 22 which support the rig frame 24.
Pivotably supported on the frame 24 is an elongated mast 26 which
in the upright position has a foot 28 which rests on the ground
surface 30. The mast is generally square in transverse cross
section and is fabricated by welding or the like. A pair of
transversely spaced guide channels 32 are secured to the front of
mast 26 and extend the full length of the mast for retaining and
guiding a drill motor, generally shown at 34, and a breakout
mechanism, generally shown at 36. The drill motor 34 is moved up
and down the mast 26 by a fluid operated motor 38 which drives a
chain 40 secured to the drill motor 34 and trained over drive
sprocket 42 and idler sprocket 44. The breakout mechanism 36 is
powered up and down the mast by a fluid operated motor 46 which
drives a chain 48 in a path parallel to the path of chain 40. Chain
48 is trained over drive sprocket 50 and idler sprocket 52 and is
secured to the breakout mechanism 36 by a lug 54 as shown in FIG.
3. A rack, generally shown at 56, for transferring and storing
sections of a drill string is attached to the side of the mast 26
and is powered for lateral movement by a fluid operated motor
58.
In FIG. 1, many conventional components of the rig 20 as well as
fluid supply lines have not been shown since they are not part of
this invention. An operator's control panel 60 is shown on the rig
with handles for operating certain components of the power and
control system of the rig which are illustrated schematically in
FIG. 6.
In order to facilitate the description of the operation of this
invention for assembling and disassembling a multiple section drill
string, the identically constructed pipe or rod sections are
designated by letters A, B, C and D. In FIG. 1, section A projects
from a bore hole 62 and is connected to adjoining section B which
is in turn connected to the projecting shank 64 of the drill motor
34. Sections C and D are stored in the rack 56.
From the foregoing brief description of the drill rig 20, it will
be understood that this rig includes these components:
1. Drill motor 34;
2. Transfer and storage rack 56;
3. Breakout mechanism 36;
4. Drill string sections A-D;
5. power and control system shown in FIG. 6.
These components will be discussed in detail under separate
headings.
DRILL MOTOR
The illustrative drill motor 34 is of the percussion type, i.e. a
fluid actuated hammer, not shown, impacts a shank 64 which projects
from the drill motor front head 66 for threaded engagement with one
of the sections A-D. The hammer impacts are transmitted through the
shank and the drill string to a bit 212 which cuts into an
underlying earth formation to form the bore hole 62 in a well
understood manner. To enhance the cutting action of the bit, it is
rotated during the drilling operation by a fluid actuated motor 68
comprising a subassembly of the drill motor 34. The rotary output
of the rotation motor 68 is coupled to the shank 64 by any suitable
means; and, reference may be had to U.S. Pat. No. 3,082,741 for
details of one suitable construction. Preferably, the rotation
motor 68 may be reversed and operated independently of the drill
motor hammer so that the rotation motor is cooperable with the
breakout mechanism 36 and the transfer and storage rack 56, as will
be hereinafter described, to provide a remotely controlled,
semi-automatic means for assembling, disassembling and storing a
multisection drill string. Motor 34 is provided with a slide 70
which is restrained within and guided by the spaced channels 32;
and, the drive motor 38 and the chain 40 move the drill motor 34 up
and down the mast 26 as desired.
While the illustrative drill motor 34 is of the rotary percussive
type, the scope of this invention is not limited by a particular
drill motor type or construction or by a particular mode of
drilling. For example, a so-called "top drive" drill motor which
reversibly rotates, but does not impact, a drive spindle could be
substituted for motor 34. Moreover, the motive fluid for operating
the drill hammer and the rotation motor 68 can be either hydraulic
fluid or compressed air as desired, although a hydraulic supply is
described hereinafter in connection with FIG. 6.
TRANSFER AND STORAGE RACK
The remotely controlled rack 56 stores drill string sections not in
use and transfers sections to and from coaxial alignment with the
drill motor 34 and the breakout mechanism 36. The vertically spaced
upper and lower rack assemblies 70, 72 include brackets 74, 76
which are rigidly attached to the side of the mast 26 and T-shaped
upper and lower rails 78, 80 which are journaled for lateral
movement by roller assemblies 82, 84. The fluid actuated rack motor
58 reversibly rotates an elongated shaft 86 having pinions at its
ends which coact with gear racks, not shown, formed on the upper
and lower rails 78, 80 whereby rotation of motor 58 and shaft 86 in
one direction moves both rails 78, 80 laterally inwardly with
respect to the mast 26 and rotation in the other direction moves
the rails outwardly. The lower rail 80 carries cuplike receptacles
88 for receiving the threaded lower ends 89 of those sections
stored in rack 56. A locking plate 90 attached to the upper rail 78
has an elongated slot, not shown, opening toward the mast 26 in
line with the longitudinal axis of the drill string. The slot is
dimensioned to receive the reduced diameter neck portion 92 of the
sections A-D and the slot is transversely enlarged at spaced
intervals to permit the normal diameter upper ends 94 of stored
sections to drop down through the locking plate 90. After the lower
end 89 of a section has been seated in a receptacle 88 and the
upper end 94 of the section is disposed in the slot in the locking
plate 90, a power cylinder 96 mounted on the locking plate moves a
clamp member 98 with respect to locking plate 90 to grip the upper
ends 94 of those sections stored in the rack 56 and secures these
sections against rotation for a purpose to be described herein.
Since the transfer and storage rack is only incidentally involved
in the operation of the present invention, only a brief description
has been set forth. For a detailed description of the structural
and functional features of rack 56, reference may be had to
copending U.S. Pat. application Ser. No. 757,950 filed Sept. 6,
1968.
BREAKOUT MECHANISM
The structural details of the breakout mechanism 36 are shown in
FIGS. 2 and 3. As viewed in FIG. 2, the breakout mechanism
comprises an upper rotatable gripping assembly 100 and a lower
stationary gripping assembly 102 which are reversely mounted above
and below and intermediate plate 104. The mounting plate 104 is
rigidly attached at right angles to a U-shaped slide 106 which
carries at either side detachable slide bars 108 which interfit in
mast guide channels 32. As hereinbefore explained, the chain 48 is
attached to a lug 54 extending rearwardly from the slide 106; and,
the chain is powered by motor 46 for raising and lowering the
breakout mechanism 36 along the mast 26.
The mounting plate 104 is generally rectangular and extends
forwardly from the mast 26 so that an aperture 110 near the center
of the plate 104 is aligned with the longitudinal axis of the drill
string.
The jaw or gripping assembly 100 includes a housing 112 having four
angularly spaced stepped bores 114 which open radially through the
housing body into a center bore 116. A cylinder 118 is removably
retained in each of the radial bores 114 by a snap ring 120; and, a
piston 122 operates within each of the cylinders 118 between a
retracted position, shown in FIGS. 2 and 3, and an extended
position wherein the cylindrical rod portion of each piston 122
enters the center bore 116 for a purpose to be explained. The
enlarged head 126 of each piston carries an O-ring 128 to provide a
fluid seal between the head 126 and the interior wall of the
cylinder 118. The pistons 122 are normally biased to the retracted
position by surrounding coiled springs 130 seated between a
shoulder of the stepped bores 114 and the piston heads 126.
Pressure fluid is communicated to and from the rear pressure
surfaces of this piston heads from a flexible supply conduit 132
through a fitting 134 which opens into one of four internal
passages 136 in housing 112 which interconnect the bores 114. The
internal passages 136 open to annular grooves 138 relieved in the
external walls of cylinders 118; and, ports 140 connect the grooves
138 to the interior of the cylinders. When pressure fluid is
supplied to the cylinders 118, the pistons 122 are simultaneously
forced radially inwardly into the central bore 16; and, when
pressure fluid is thereafter exhausted from the cylinders 118, the
return springs 130 urge the pistons 122 radially outwardly from the
central bore 116 to their fully retracted position.
The extreme inner ends of the piston rods 122 are arcuate as viewed
in FIG. 3 and are slotted or serrated at 192 for interengagement
with the splines 144 formed on the lower end 89 of a drill string
section. Splines 145 which are identical to splines 144 are framed
on the end of shank 64 which has male threads which join the shank
to the upper end 94 of a string section. To maintain proper
alignment of the piston splines 192 with either the section splines
144 or the shank splines 145, the piston rods are held against
rotation with respect to the stepped bores 114 by a slot and key
arrangement designated at 146. Further discussion of the piston rod
splines 192 is presented hereinafter in connection with the
detailed description of the sections A-D.
A centralizer bushing 148 of hard, wear-resistant material is
mounted on the housing 112 concentrically with the center bore 116
by means of a flanged retainer ring 150 which is removably secured
to the housing by a plurality of angularly spaced fasteners 152.
The interior diameter of the bushing is smaller than the diameter
of the center bore 116 and is selected to provide a loose running
fit with the exterior surface of a drill string section.
As thus far described, the structural and operational details of
the rotatable jaw assembly 100 and the stationary jaw assembly 102
are identical; therefore, to avoid needless duplication of the
description of the stationary jaw assembly, the suffix letter "a"
will be added to those numerals denoting identical structure
elements incorporated in the stationary jaw assembly 102.
The center bores 116, 116a of the housings 112, 112a are
concentrically piloted with respect to the mounting plate aperture
110 by the interfitting of annular bosses 154, 154a within the
counterbores formed in opposite openings of the aperture 110. The
stationary jaw assembly 102 is fixed against rotation with respect
to plate 104 by means of a plurality of cap screws 156 which clamp
a radially projecting annular flange 158a of the lower housing 112a
to the underside of plate 104. The flange 158 of the upper housing
112 is held in bearing relation against the upper surface of the
plate 104 by an annular retaining ring 160. While the retaining
ring is fixed to the plate 104 by plural cap screws 162, it will be
understood that the housing 114 of the rotatable gripping assembly
100 is free to rotate about the axis of its center bore 116
relative to the retaining ring 160, the plate 104 and the
stationary gripping assembly 102.
The jaw assembly 100 is rotatable with respect to the stationary
jaw assembly 102 through an angle Z from the full line position to
the broken line position as depicted in FIG. 3. Such rotation of
jaw assembly 100 is provided by a double acting power cylinder 164
having a cylinder body 166 pivotally attached to the mounting plate
104 at 168 and having an extendable and retractable piston rod 170
pivotally attached to a lever arm 172 by a clevis and pin
arrangement 174. The inner end of the lever arm 172 is threaded
into a boss 176 projecting from the housing 112. Pressure fluid for
actuating the piston of the power cylinder 164 is communicated to
opposite ends of the cylinder body 166 by flexible conduits 178 and
180. It will be noted that the power cylinder 164 has a short
stroke and is, therefore, relatively small and mountable on the
support plate 104 in a very compact manner without adding
appreciably to the overall size or weight of the breakout mechanism
36.
DRILL STRING SECTIONS
When having reference to FIGS. 2 through 5, numerals indicating
common structural features of all of the string sections A--D will
not include a suffix letter. However, in connection with the
description of the operation of the drill rig 20, as shown in FIGS.
1 and 7 through 15, the sections will be generally designated by
letters A, B, C, and D and numerical references to structural
features of a particular section will be followed by a letter
suffix. For example, see FIG. 1 where the upper end segment of
section B is indicated as 94B.
The sections A-D are identically constructed and, as shown in FIG.
4, comprise an upper end segment 94 and a lower end segment 89
which are preferably attached at opposite ends of an elongated body
segment 182 by some suitable welding operation such as friction
welding. The body segment 182 generally comprises a hardened
thin-walled metal tube having inner and outer diameters uniform
from end to end. The interior of the upper end segment 92 is
provided with female threads 184 which receive mating male threads
186 formed exteriorly on the lower end segment 89. The threads
engage for their full length and the extreme upper end surface of
the upper end segment 94 abuts with an annular shoulder 188 of the
lower end segment 89. A reduced diameter neck portion 92 is
provided to permit the upper segments 94 to be received in the
aforedescribed slot in the locking plate 90 of the transfer and
storage rack 56. Since other types of racking devices could be used
with the rig 20, the neck 90 may not be necessary and represents
only one possible embodiment.
An important feature of this invention is the provision of
serrations or splines 144 and 190 respectively located adjacent the
ends of the lower end segment 89 and the upper end segment 94. The
basic function of these splines is to provide an improved surface
means on the drill string sections whereby the jaw assemblies 100
and 102 can quickly and positively grip the adjacent end segments
of joined drill string section.
The prior art suggests that drill pipes and rods be provided with
flat surfaces relieved in their outer wall which are engageable by
opposed jaws of a wrench. Usually two, four or six flats are
provided for this purpose; and, unless the wrench can be moved
substantially about the perimeter of a string section and can be
easily manipulated with respect to the flats, extreme difficulty is
experienced in engaging the wrench with the flats. This poor
situation is worsened if the wrench is capable of only very limited
angular movement relative to the flats since the angular
opportunities for engaging a six flatted section, for example, are
60.degree. apart. Thus a wrench adapted for gripping a six flatted
section must be capable of rotating 60.degree. with respect to the
section to insure an opportunity for the wrench to fit onto the
flats. An additional increment of wrench rotation must be provided
which at least equals the rotation needed to break out the threads
between sections. The amount of breakout rotation will depend upon
the configuration of the threads and the properties of the thread
material. It is believed that wrench rotation on the order of
60.degree. is unacceptable where the wrench comprises a part of a
self-contained breakout device for a portable drill rig because the
power cylinder must have a relatively long stroke to turn the lever
arm of the wrench through a 60.degree. arc. The restraints imposed
on the physical dimensions and weight of a power cylinder suitable
for use on a breakout mechanism such as that disclosed in this
specification require that the stroke of the power cylinder be as
short as possible.
Several solutions to theproblems noted above in the use of a short
stroke cylinder for rotational power in a breakout mechanism have
been proposed but found unacceptable. One solution involves the
substitution of a rotary drive motor for the power cylinder 164 so
that unlimited wrench rotation is available to align the wrench
jaws with flats or slots as taught by the prior art. It has been
found, however, that sufficiently high starting torque for breaking
out tight joints encountered in a typical drill string cannot be
provided by a rotary drive motor which meets the size and weight
requirements of the application under consideration. It has also
been suggested that the jaws of the wrench have sharp edges which
bite into the outer wall of the drill string sections thereby
eliminating flats altogether. Such biting action will severely
shorten the useful life of a thin-walled section such as sections
A-D if the section material is soft enough to deform. If the
sections are hardened, as is the usual case with percussive drill
strings, the jaws will not bite into the section sufficiently to
hold when loosening torque is applied to the wrench. Still another
solution has been advanced whereby the number of wrench flats on
the sections is substantially increased to increase correspondingly
the opportunities for the wrench to come into alignment with a pair
of flats. In practice any improvement has been severely limited
since increasing the number of flats produces a decrease in the
area of each flat hence a decrease in the effective area of driving
contact between the wrench jaws and the flats.
The present invention effectively uses a short stroke cylinder 164
to rotate the rotatable jaw assembly 100 through an angle Z, shown
in FIG. 3, to achieve assured engagement of the splines 144 on the
lower end segments 89 and splines 145 on the shank 64 with
complementary splines 192 on the end surfaces of the pistons 122.
In the development of the breakout mechanism 36, it has been
discovered that three factors must be considered if a splined or
serrated construction is to be successfully employed with drill
string sections, namely:
1. The size of the angle of rotation Z of the rotatable jaw
assembly 100 as provided by a power cylinder having a short stroke
length applied to a lever arm also of the shortest practical
length.
2. The size of the angle of rotation Y needed to loosen the threads
184, 186 which join adjacent drill string sections. The angle Y may
be referred to as the thread breakout angle and can be calculated
or measured for any given type of threaded joint.
3. The size of the angle X between the splines.
In relating these angles to the design of the breakout mechanism
and the drill string and shank splines, the angle Z must be at
least equal to the sum of angles X and Y if the teeth 196 of the
piston splines 192 are to be provided enough rotative movement to
insure that they will come into engaging alignment with the splines
144 and 145 under the worst conditions of initial misalignment and
will thereafter be rotated through the breakout angle of the joint
threads. As an example, if the angle Z is fixed at 15.degree. by
the design of the breakout mechanism and if the breakout angle of
the threads 184, 186 is known to be 6.degree. , the angular spacing
of the splines 144, 145 and 192 can be no more than 9.degree..
Under these conditions 40 splines could be provided. It will be
understood that for any given breakout angle Y the number of
splines will vary directly as the rotation angle Z is changed. From
a knowledge of this relationship and fixing what has been found to
be a practical design limit on angle Z of 30.degree., the minimum
number of splines for drill strings having a breakout angle of
6.degree. would be 15.
The maximum number of splines has been found to be established by
practical limits on the circumferential spacing between adjacent
splines. If an excessive number of splines are formed on a string
section of a given diameter and wall thickness, the teeth of the
splines are not of sufficient cross section and strength to
withstand the turning forces applied thereto to break out a joint.
Moreover, if the splines are too closely spaced, they will tend to
become clogged with dirt and mud while in the bore hole and the
piston splines 192 cannot interengage. A minimum critical
circumferential spacing between splines has been established as
being .125 inch.
Another feature of the splined string sections and shank disclosed
herein is the slope of the walls of spline teeth. Referring to FIG.
5 it will be seen that the sides of an individual tooth 194 on a
string section slope toward one another and if projected, intersect
to define an included angle R. The teeth 196 of the piston splines
192 are sloped at the same angle R for interfitting engagement with
the splines 144. In order to maximize the engagement between the
teeth 194 and 196, the number of teeth 196 which will engage upon
linear movement of the piston 122 should be made as great as
possible. The limitation on the number of teeth 196 is the maximum
possible size of the angle S which, in turn, can be no greater than
the included angle R defined by the slope of the teeth 194. Thus
the slope of the walls of the teeth on the string section and the
piston surface 142 determines the maximum number of engageable
teeth, the diameter of the pistons 122 and, therefore, the total
area of clamping engagement of the rotation assembly 100 and the
stationary assembly 102 with the drill string sections engaged
thereby. A practical upper limit on the size of angles R and S
occurs when the tooth slope is so great that a tangential rotating
force applied by the teeth 196 of the pistons 122 to the teeth 194
creates a reactance force acting upon the piston teeth 196 which
has a radial force component greater than the opposed force
imparted to the teeth 196 by the pressure fluid acting on the head
128 of each piston 122. If this condition should occur, the teeth
194 and 196 will not stay in rotary driving engagement; and, it is
possible to severely damage these teeth. In a preferred embodiment
of the splines 144, 190 on the pipe sections and the pistons 122,
122a, the included angle R is 60.degree..
POWER AND CONTROL SYSTEM
In the preferred embodiment of the drill rig 20, the hereinbefore
described components and assemblies are powered by and controlled
by a hydraulic system comprised of conventionally constructed
pumps, motors and valves. The pumps P.sub.1, P.sub.2 and P.sub.3
are are mounted on the rig frame and are powered by a suitable
prime mover also carried on the rig frame
The pump P.sub.1 supplies the reversible motor 38 which moves the
drill 34 up and down the mast under the control of the rig operator
by means of a suitable motor control valve, not shown. The pump
P.sub.2 supplies the reversible drill rotation motor 68 which is
remotely controllable by the rig operator by valve means, not
shown. A pilot controlled relief valve V.sub.1 is connected in
parallel with the drill rotation motor 68; and, when opened,
V.sub.1 bypasses fluid around motor 68. V.sub.1 only operates as a
bypass for fluid flow which produces rotation of the motor 68 in
the forward direction i.e., the direction of rotation of the shank
64 which tends to tighten a threaded joint between the shank and
string sections and between sections. The relief valve V.sub.1
opens at a preset fluid pressure, less than the full pressure of
the pump P.sub.2, only when a two-way pressure operated valve
V.sub.2 is opened to connect the pilot portion of V.sub.1 to a
fluid reservoir by means of conduit 198. Thus it will be understood
that valves V.sub.1 and V.sub.2 coact to reduce the torque output
of the drill rotation motor only in the forward direction to limit
the tightness of threaded joints while the reverse or thread
disconnecting torque output is unchanged. In a preferred embodiment
of this control feature of the invention the joint connecting
torque output of the motor 68 is cut to from one fourth to one
third of the joint disconnecting torque output. The purpose of this
control feature will be more clearly understood from the following
description of the operation of the invention.
The pump P.sup.3 supplies valves V.sub.3, V.sub.4, V.sub.5 and
V.sub.6 which are also connected to a reservoir for the pump
P.sub.3.
V.sub.3 is a three-position spring centered valve shown in the
neutral position. V.sub.3 is operated to supply pressure fluid from
pump P.sub.3 to the transfer and storage rack motor 58 for forward
and reverse rotation to effect lateral movement of the rack 56 as
described above.
V.sub.4 is a two-position detented valve shown in the disengaged
position wherein conduits 200 and 202 are connected to the
reservoir of pump P.sub.3. When V.sub.4 is operated to connect
conduits 200 and 202 to the pump P.sub.3, pressure fluid is
supplied to the stationary jaw assembly 102 to force the pistons
122a radially inwardly into gripping engagement with the splines
190. At the same time, pressure fluid is supplied to V.sub.2 which
opens the bypass valve V.sub.1 in the manner described above. When
V.sub.4 is returned to the position shown in FIG. 6, the conduits
100 and 102 are exhausted to the reservoir whereby the springs 130a
return the pistons to their retracted position and valve V.sub.2 is
depressurized thereby blocking the bypassing fluid flow through
V.sub.1.
V.sub.5 is a three-position, spring centered valve shown in the
neutral position. V.sub.5 supplies pressure fluid from pump P.sub.3
to actuate the piston jaws 122 of the rotary jaw assembly 100 and
to extend and retract the double acting cylinder 164 for effecting
rotation of the rotary jaw assembly 100. Conduit 132 communicates
V.sub.5 to the fitting 134 on the housing 112 and has a branch
conduit 180 connected to one end of the cylinder 164. Interposed in
branch conduit 180 is a pressure sensing sequence valve V.sub.7
which is operated to its open position by a build-up of fluid
pressure in the conduit 132 as the pistons 122 of the rotary jaw
assembly engage with shank 64 or with a drill string section. The
conduit 178 connects the other end of the cylinder 164 with
V.sub.5. The sequence valve V.sub.7 provides an important control
feature of this invention by assuring that the pistons 122 have
been extended so that the piston teeth 196 are biased for
interengagement with splines 144 or 145 before pressure fluid is
admitted to the power cylinder 164 to rotate the pistons 122. This
sequence of operations gives the piston teeth 196 their best chance
for engagement with splines 144 or 145 with a very minimum degree
of relative rotation and reduces the chance of damage to these
splines or malfunction of the rotary breakout assembly due to a
failure of the spline teeth to engage prior to actuation of the
power cylinder 164.
V.sub.6 is a three-position, spring centered valve shown in the
neutral position for supplying pressure fluid from pump P.sub.3 to
the reversible motor 46 which powers the breakout mechanism 36 up
and down the rig mast 26.
The manual control handles for valves V.sub.3, V.sub.4, V.sub.5 and
V.sub.6, as well as the handles for control valves, not shown, for
the drill rotation motor 68 and the drill pull-down motor 38, may
be conveniently grouped on the operator's control panel 60. In
FIGS. 1 and 7-15 the pressure fluid conduits for the rig components
described above have not been shown since their location and manner
of installation are merely a matter of design and convenience.
OPERATION
The preferred mode of operation of the drill rig 20 is as follows.
The rig 20 is moved into position at the drilling site and the mast
26 is elevated to the desired angle with respect to the ground
surface 30. As shown in FIG. 7, string section A is initially
stored in the mast 26 with its upper end 94A joined to the drill
motor shank 64 and with its lower end 89A extended through the
breakout mechanism 36 which has been lowered by motor 46 to its
lowermost position for bearing up on the plate 210 of the mast foot
28. The threaded lower end 89A of section A is joined to a drill
bit 212 which is advanced into the ground by the hammering and
rotating action of the drill motor 34 and by the pull-down force
applied to the drill string by the motor 38. The pistons 122, 122a
of the breakout mechanism 36 are retracted and the centralizer
bushings 148, 148a closely surround the body 182A of section A. The
sections B, C, and D are stored in the rack 56 which has been moved
to its outermost lateral position by motor 58.
The drill motor is then actuated to impact and rotate section A and
bit 212 to start the hole 62. The centralizer bushings 148, 148a
serve to restrain section A and the bit 212 from lateral bending
and wandering as the hole is started. The incorporation of this
centralizing function in the breakout mechanism itself is
particularly advantageous since it eliminates the need for a
separate centralizer assembly on the rig. As the drill motor is
advanced by the feed motor 38, the rotation motor 68 may be
operated up to full torque output. When the extreme lower position
of the drill motor 34 is reached, as shown in FIG. 8, the front
head 66 of the drill motor abuts with the retainer ring 150 of the
breakout mechanism 36; and, the shank 64 and upper section end 94A
are automatically aligned for engagement with the breakout pistons
122 and 122a, respectively. The stationary jaw assembly 102 is then
actuated by valve V.sub.4 to cause the piston teeth 196a to engage
with the string section splines 190A whereby section A is held
against rotation and longitudinal movement. When V.sub.4 is
operated to actuate the stationary jaw assembly 102, the valve
V.sub.2 is simultaneously operated to place the bypass valve
V.sub.1 in parallel with the drill rotation motor 68. Valve V.sub.5
is then operated first to supply pressure fluid behind the piston
jaws 122 of the rotary jaw assembly 100 causing jaws 122 to contact
the shank serrations 145 and thereafter to extend the piston rod
170 of the cylinder 164 causing the jaws 122 to rotate the shank 64
through the angle Z, as shown in FIG. 3. As soon as the jaw teeth
196 and shank splines 145 interengage, the cylinder 164 imparts
thread breakout rotation to the shank relative to the nonrotatably
held section A. The valve V.sub.5 is then operated to release the
pistons 122 and to retract the piston rod 170 of the rotation
cylinder 164. The drill rotation motor 68 is then reversed at full
power to completely disconnect or spin out the shank from section
A. The motor 38 then raises the drill motor 34 to the top of the
mast 26 as shown in FIG. 14 so that the rack 56 may be moved in to
the position shown in FIG. 9 whereby the section B is aligned with
the drill motor 34 and the breakout mechanism 36. Drill motor 34 is
then lowered to thread the shank 64 into the upper end 94B of
section B and is then raised again to lift section B so that the
lower end 89B clears the receptacle 88 and the neck 92B is aligned
with the slot in the locking plate 90 whereby the rack 56 can be
laterally retracted to the position shown in FIG. 10. The drill
motor 34 is then lowered and operated to rotate section B to
connect its male threads 186B with female threads 184A of section
A. Valve V.sub.4 is then operated to release the stationary piston
jaws 122a and to take the bypass valve V.sub.1 out of circuit with
the drill rotation motor 68.
The cycle of operations described above is repeated until a
sufficient number of sections have been added to the drill string
to advance the bit 212 to the desired depth.
Not all of the length of a string section need be employed;
therefore, holes may be drilled to depths which are not even
multiples of a section length. In such a case the joint between the
shank 64 and the uppermost section, section B in this case, is
stopped short of the lowermost position of the breakout mechanism
36 as shown in FIG. 10. To disassemble sections A and B, valve
V.sub.6 is operated to actuate the motor 46 to raise the breakout
mechanism 36 up the mast into abutting engagement with the drill
motor 34 as shown in FIG. 11. The stationary breakout assembly 102
is actuated by valve V.sub.4 and the rotary breakout assembly is
then actuated by valve V.sub.5 to loosen the joint between sections
A and B. The rotation motor 68 is then operated in the forward
direction, but at reduced torque output because the bypass valve
V.sub.1 is in circuit with the rotation motor, to retighten the
shank 64 to a snug relation with the upper end 94B of section B.
Thus snug-tight connection between the shank and section B is for a
purpose to be explained hereafter. The breakout mechanism 36 is
lowered against the foot plate 210 and the drill motor raised to
position the joint between sections A and B in proper alignment
with the breakout mechanism, as shown in FIG. 12. The breakout
mechanism is operated to break out the joint between sections A and
B in the manner described above. With the rotatable jaws 122
retracted and the stationary jaws 122a engaged to support section A
off the hole bottom, the rotation motor is reversed to spin out the
joint between sections A and B. This step in the string disassembly
cycle can be performed with complete confidence that the shank will
not uncouple from the top of section B since this joint has
previously been retightened to a snug condition by the reduced
forward torque output of the drill rotation motor 68 while, on the
other hand, the joint between sections A and B has not been
retightened at all from its loosened condition. This feature of the
invention provides a foolproof method of drill string disassembly
which increases the speed and efficiency of drilling operations and
eliminates a heretofore hazardous working condition for the rig
operator. Section B is then raised by the drill motor 34 to align
the neck 92B with the slot in the locking plate 90 of the rack 56.
The rack is moved laterally to receive the section B and the drill
motor 34 is then lowered to seat it lower end 89B in receptacle 88
and to align its upper end 94B with the clamp member 98. Cylinder
96 is then actuated to clamp section B against rotation; and, the
drill rotation motor 6B is reversed at full torque output to
disconnect completely the snug-tight joint between the shank 64 and
the top of section B. Rack 56 is then retracted, as shown in FIG.
14, and the drill motor 34 is lowered to connect the shank 64 with
the upper end 94A of section A which is supported by the breakout
mechanism 36, as shown in FIG. 15. Section A is then withdrawn from
the hole 62 to its stored position in the mast 26, shown in FIG. 7,
to complete the drilling cycle.
* * * * *