U.S. patent number 3,716,106 [Application Number 05/167,713] was granted by the patent office on 1973-02-13 for constantly slipping clutch control for rotary drilling.
Invention is credited to Earl A. Peterson.
United States Patent |
3,716,106 |
Peterson |
February 13, 1973 |
CONSTANTLY SLIPPING CLUTCH CONTROL FOR ROTARY DRILLING
Abstract
A drilling system for rotary drilling. A drilling system for the
rotary drilling of well bores utilizing a pair of cooperating
subsystems, one subsystem providing for control of the penetration
rate or weight of the drill bit, the second subsystem controlling
the rotational speed or torque of the drill bit. A drawworks
supporting the drill string is cooperatively engaged to a
continuously slipping clutch to provide precise control over the
vertical motion of the drill string and bit. The rotary drill table
providing rotational power to the drill string and bit is
cooperatively coupled to a continuously slipping clutch to provide
precise control over the rotational motion of the drill string and
attached drill bit.
Inventors: |
Peterson; Earl A. (Long Beach,
CA) |
Family
ID: |
22608504 |
Appl.
No.: |
05/167,713 |
Filed: |
July 30, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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810322 |
Mar 25, 1969 |
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Current U.S.
Class: |
173/1; 173/4;
173/151; 173/178; 175/27 |
Current CPC
Class: |
E21B
19/08 (20130101); E21B 3/06 (20130101) |
Current International
Class: |
E21B
3/00 (20060101); E21B 19/08 (20060101); E21B
3/06 (20060101); E21B 19/00 (20060101); E21b
003/02 (); E21b 019/08 () |
Field of
Search: |
;173/1,4-6,12,151
;175/27 ;254/187A,187 ;64/26 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Parent Case Text
This is a continuation-in-part of my application Ser. No. 810,322
filed Mar. 25, 1969 and now abandoned.
Claims
I claim:
1. A rotary drilling apparatus for controlling the support of a
drill string and the rotation of a rotary drill table
comprising:
a. a drawworks including a drum, a hoisting cable disposed about
said drum, means for sensing the weight on said hoisting cable and
an input shaft to said drawworks, whereby rotation of said input
shaft is adapted to rotate said drum;
b. a first rotational power source;
c. a first continuously slipping clutch interposed between said
first rotational power source and said input shaft of said
drawworks;
d. a second rotational power source; and
e. a second continuously slipping clutch interposed between said
second rotational power source and the rotary drill table whereby
the speed of rotation of the rotary drill table and the tension in
said hoisting cable is controlled.
2. A rotary drilling apparatus as defined in claim 1 wherein said
first and second continuously slipping clutches comprise an inner
hub and outer housing adapted to frictionally rotate with respect
to each other and liquid means for dissipating the frictionally
generated heat therein, and a clutch shaft being secured to said
inner hub.
3. A rotary drilling apparatus as defined in claim 2 wherein said
continuously slipping clutches include a friction disc secured to
said inner hub, friction elements adapted to slidably engage and
rotate within said outer housing, said liquid means for dissipating
heat adjacent to the friction elements, and air actuated expandable
elements secured to said housing and adjacent said friction
elements whereby said friction elements frictionally engage said
friction disc upon actuating said expandable elements.
4. A rotary drilling apparatus as defined in claim 2 wherein said
first rotational power source is coupled to the outer housing of
said first continuously slipping clutch, and said second rotational
power source is coupled to the outer housing of said second
continuously slipping clutch said frictional rotation between said
respective outer housing and said respective inner hub being at a
predetermined differential speed whereby the torque at said clutch
shaft is controlled.
5. A rotary drilling apparatus as defined in claim 4 including
first and second sensing means for respectively outputting indicia
responsive to the load on said hoisting cable and rotation of said
rotary drill table and means for actuating the expandable elements
of said first and second continuously slipping clutches
respectively in response to the output indicia of said first and
second sensing means respectively.
6. In combination with a drilling rig including a drill string and
coupled drill bit, and a rotary drill table adapted to receive and
rotate said drill string, a rotary drilling apparatus
comprising:
a. drawworks including a rigid frame, a drum mounted on a drum
shaft rotatably supported by said rigid frame, a hoisting cable
wound about and secured to said drum an end thereof being coupled
to the drill string;
b. a first power source;
c. a first continuously slipping clutch having an inner hub and
outer housing adapted to frictionally rotate with respect to each
other and liquid means for dissipating the frictionally generated
heat therein, and a clutch shaft being secured to said inner hub
and journeled on said rigid frame, said outer housing being coupled
to said first power source and said clutch shaft being coupled to
said drum shaft;
d. a second power source; and
e. a second continuously slipping clutch having an inner hub and
outer housing adapted to frictionally rotate with respect to each
other and liquid means for dissipating the frictionally generated
heat therein, and a clutch shaft being secured to said inner hub
and coupled to the rotary drill table, said outer housing coupled
to said second power source.
7. A rotary drilling apparatus as defined in claim 6 wherein said
first and second continuously slipping clutches include a friction
disc secured to said inner hub, friction elements adapted to
slidably engage and rotate with said outer housing, said liquid
means for dissipating heat being adjacent said friction elements,
and air actuated, expandable elements secured to said housing and
adjacent said friction elements whereby the friction elements
frictionally engage said friction disc upon actuating said
expandable elements.
8. A rotary drilling apparatus as defined in claim 6 including
first and second sensing means for outputting indicia responsive to
the load on said hoisting cable and the rotation of said rotary
drill table respectively, said first sensing means coupled to the
expandable elements of said first continuously slipping clutch and
said second sensing means coupled to the expandable elements of
said second continuously slipping clutch.
9. For use with a drilling rig including a drill string and coupled
drill bit, a rotary drill table adapted to receive the drill
string, a drawworks having a first continuously slipping clutch
interposed between a power source and a drum of the drawworks, a
hoisting cable secured to the drawworks drum and supporting the
drill string, a second continuously slipping clutch interposed
between the rotary drill table and the power source thereof, a load
sensor interposed in the hoisting cable and the rotation sensor
coupled to said rotary drill table, a method for rotary drilling of
well bores comprising the steps of:
a. sensing the load on the hoisting cable;
b. adjusting the output torque of said first continuously slipping
clutch to a predetermined level in response to the sensed load on
the hoisting cable;
c. sensing the rotation of said drill string; and
d. adjusting the output torque of said second continuously slipping
clutch to a predetermined level in response to the sensed rotation
of said rotary drill table.
10. A method for rotary drilling of well bores as defined in claim
9 including the step of simultaneously adjusting the penetration
rate of and torque on the drill bit in response to the sensed load
and rotation respectively.
11. A method of rotary drilling of well bores as defined in claim 9
including the step of simultaneously adjusting the weight on and
rotation of the drill bit in response to the sensed load and
rotation respectively.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention drilling system is generally related to the
field of well bore drilling apparatus and, more particularly, to
rotary drilling apparatus.
2. Prior Art
With the increasing importance of off-shore and on-shore drilling
of oil and gas wells, the need to improve the control over such
operations has become evident. The problems which are incident to
the drilling of well bores have been known for a great deal of
time. Since the drill bit must penetrate the earth to a great
distance, the weight on the drill bit must be maintained at a
predetermined level in spite of the increased weight added by the
drill pipe as the drill string becomes longer. Even with the use of
drill collars and slip joints, tension in the drill string must be
controlled. Conventional systems disclosed by the prior art
utilized static hoisting equipment to support the weight of the
drill string at the surface. Where the drilling of the well bore is
in an off-shore environment, this apparatus is totally unusable to
compensate for the vertical displacement of wave motion.
Another device disclosed by the prior art to seek to control the
rate of penetration of the drill string or the bit weight utilizes
a fluid coupling to seek to compensate for the added weight of the
drill string and wave motion where the well bore is being drilled
in an ovv-shore environment. The attempt to use a fluid coupling
between the power source and the hoisting apparatus leaves
substantial problems unresolved. The weight of a drill string can
be as high as 400,000 lbs. thereby imposing loads which cannot be
suitably supported by the fluid coupling. In addition, wave action
can cause in-haul and over-haul action on the fast line of the
supporting apparatus which cannot be properly compensated for by a
fluid coupling. In addition, this system disclosed by the prior art
provides no means for controlling the rotational speed or torque on
the drill string and the drill bit. This is necessary to prevent
damage to the bit or the rotary drill table.
Another device disclosed by the prior art utilizes a single power
source coupled to both a hoisting apparatus as well as a rotary
drill table through separate power transmission devices. The power
sources are coupled to the hoisting mechanism and the rotary drill
table through a torque converter. The required torque converter and
transmission present severe operational and equipment problems
which are totally resolved by the present invention. The drawworks
used to support the drill string and the cooperating rotary drill
table are each controlled by continuously slipping clutches adapted
to provide controlled torque to the respective drawworks and rotary
drill table. By appropriate sensors, the drill string can be
supported by the controlled torque of a first continuously slipping
clutch, the rotational torque of the rotary drill table being
controlled by a second continuously slipping clutch. The
combination of the two subsystems provide a method for rotary
drilling which substantially resolves the problems left unresolved
by the apparatus disclosed by the prior art.
SUMMARY OF THE INVENTION
The present invention drilling mechanism constitutes a method for
rotary drilling and apparatus for implementing same. A drawworks
hoist is driven by a continuously slipping clutch to provide
controlled torque on the fast line attached thereto. The
continuously slipping clutch is operated in an overspeed condition
whereby the driving member is rotated at a speed which will permit
compensation for the increased weight of the drill string and for
wave motion where the present invention is utilized in an off-shore
environment. The drill string is supported by the fast line
attached to a drum of the hoist. As additional lengths of drill
pipe are added to the drill string, the load on the fast line will
be increased. In addition, where the well bore being drilled is in
the ocean or other body of water subject to wave motion, the
tension in the fast line is maintained at a predetermined level to
control the penetration rate of or weight upon the drill bit. The
driving member of the continuously slipping clutch is appropriate
to maintain a controlled tension in the fast line irrespective of
whether the drilling vessel is rising or falling with the water
level. The control over this weight is extremely important where
the drilling of the well bore is in an off-shore environment. The
drawworks utilizing the continuously slipping clutch to implement
the first subsystem of the present invention drilling mechanism is
similar to that described in Applicant's U.S. Pat. No.
3,373,972.
The drill string is supported by a kelly disposed through the
rotary drill table, a traveling block supporting the kelly on a
swivel joint. The fast line from the drawworks is carried over a
crown block at the top of the drilling derrick, the traveling block
being supported by the drawworks cable. The rotary drill table is
powered through a continuously slipping clutch permitting precise
control over the rotation of the rotary drill table and therefore
the speed and torque imposed upon the drill bit.
It is therefore an object of the present invention to provide an
improved method for rotary drilling of well bores.
It is another object of the present invention to provide an
apparatus for rotary drilling which can control the bit weight of
the drill string and the torque imposed upon the drilling bit.
It is still another object of the present invention to provide an
improved apparatus for rotary drilling utilizing continuously
slipping clutches.
It is yet another object of the present invention to provide a
method of rotary drilling whereby the penetration rate and rotation
of the drill bit can be precisely controlled.
The novel features which are believed to be characteristic of the
invention, both as to its organization and method of operation,
together with further objectives and advantages thereof will be
better understood from the following description considered in
connection with the accompanying drawing in which a presently
preferred embodiment of the invention is illustrated by way of
example. It is to be expressly understood, however, that the
drawing is for the purpose of illustration and description only,
and is not intended as a definition of the limits of the
invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a side, elevation view of a drilling platform embodying a
supporting drawworks and power source for a rotary drill table in
accordance with the present invention.
FIG. 2 is a top plan view of the drawworks hoist of FIG. 1
utilizing a continuously slipping clutch assembly in accordance
with the present invention.
FIG. 3 is a side, elevation view, shown in partial cross-section,
of a clutch assembly taken through line 3--3 of FIG. 2.
FIG. 4 is a top plan view of the rotary drill table of FIG. 1
powered in accordance with the present invention.
DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT
An understanding of the cooperative relationship of subsystems of
the present invention can be best gained by reference to FIG. 1
wherein a side, elevation view of the drilling derrick and
associated equipment is shown, the drilling derrick being generally
designated by the reference numeral 10. For the purpose of example,
drilling derrick 10 is shown mounted upon drilling barge 11,
drilling barge 11 being anchored in an aqueous environment 12 such
as the ocean. Although it is within the scope of the present
invention to utilize the present invention method of rotary
drilling on on-shore applications, the advantages of the present
invention are most fully realized where the apparatus for
implementing the present invention is utilized in the off-shore
drilling of well bores. Barge 11 is shown held in a substantially
stationary condition above well bore 13 by anchor lines 14 or other
appropriate stabilizing means. Drawworks 15 and a power unit 16
capable of producing controlled tension in the fast line or
hoisting cable 17 are mounted upon the deck of barge or other
floating structure 11. Hoisting cable 17 is supported by crown
block 18 at the top of derrick 10, the traveling end of hoisting
cable or fast line 17 carrying traveling block 19 and hook 20. The
dead line of hoisting cable 17 is terminated at a stationary point
such as on derrick 10, weight sensor 21 being disposed in the dead
line for determining the weight imposed upon drill bit 22.
Hook 20 supports swivel joint 23 which is typically supplied with
drilling fluid through mud hose 24 connected to a mud pump which is
not shown. Kelly joint 25 depends downwardly from swivel joint 23
through a kelly bushing in the center of rotary drill table 26.
Drill string 27 is coupled to the lower end of kelly 25 and extends
through water 12 into well bore 13. Drill bit 22 is connected to
the lower end of drill string 27 for providing the penetration of
well bore 13.
Rotary table 26 is powered through shaft 28 by power unit 29, power
unit 29 providing means for precisely controlling the rotation or
torque imposed upon bit 22. Power unit 29 will be described in
greater detail hereinbelow.
As stated, an object of the present invention is to provide means
for controlling any combination of penetration rate and bit weight
on one hand and rotational speed or torque of bit 22 on the other.
In addition, the present invention method of rotary drilling
provides means for controlling the parameters of rotary drilling as
stated along with allowing for motion compensation arising out of
wave or tidal action of ocean 12. Referring now to FIG. 2, an
understanding of drawworks 15 and power unit 16 can be best gained.
Fast line 17 is typically hauled in and hauled out through the
power provided by motors 40 and 41. Although the scope of the
present invention embodies the use of any number and type of
suitable power sources, motors 40 and 41 typically comprise series
wound DC motors typically having a power output of 700 horsepower
each. The output shaft of motor 40 is coupled to input shaft 42 by
way of shaft coupling 43. Shaft coupling 43 is a conventional
device used to mechanically connect axially aligned shafts. The
output shaft of motor 41 is coupled to input shaft 42 at shaft
coupling 44. As stated above, shaft coupling 44 is a conventional
coupling device. Shaft couplings 43 and 44 will mechanically couple
the torque output of motors 40 and 41 to input shaft 42. The
elements of drawworks 15 are supported by a fixed frame, shaft 42
being rotatably mounted or otherwise journeled in suitable bearings
45 and 46.
The rotational power imposed upon input shaft 42 is transmitted to
the remainder of drawworks 15 by drive sprockets 47 and 48
concentrically disposed about input shaft 42 substantially adjacent
bearings 45 and 46 respectively. Drive sprockets 47 and 48 are
typically chain drive sprockets, but they can be any other suitable
torque transmitting devices such as pulleys. Drive sprockets 47 and
48 concurrently supply power to jack shaft 49, gear tooth clutch 50
selecting either sprocket 51 or sprocket 52, the power of both
motors 40 and 41 being transmitted through the selected sprockets
51 or 52. Although drive sprocket 48 is shown to be substantially
equal in size to drive sprocket 47, the number of drive sprockets
48 will typically exceed the number of drive sprockets 47 to
provide additional torque transmitting capacity.
Drive sprocket 47 is coupled to driven sprockets 51 by chain 53 and
drive sprockets 48 are coupled to driven sprockets 52 by chain 54.
Sprockets 51 and 52 are rotatably mounted upon jack shaft 49, each
being selectively coupled to shaft 49 by gear tooth clutch 50 which
is in itself concentrically disposed upon jack shaft 49 and secured
thereto. Although the scope of the present invention is broad
enough to implement gear tooth clutch 50 by any suitable power
transmission device, gear tooth clutch 50 is preferably a two speed
gear tooth clutch transmission. Where gear tooth clutch 50 is a two
speed transmission, use of motors 40 and 41 produces four operating
modes based upon selected speed and torque output. As will be
discussed below, the use of power unit 16 provides an additional
operating mode which provides the improved characteristics of the
present invention.
One end of shaft 49 is journeled in suitable bearing 55, the end of
shaft 49 depending beyond bearing 55 having concentrically mounted
thereon sprockets 56 and 57. Sprockets 56 are coupled to sprockets
78 by way of chain drive 79. Sprockets 78 are secured to the
housing of high-speed drum clutch 58. Although high-speed drum
clutch 58 can be implemented through the use of conventional
clutches, high-speed drum clutch 58 is preferably an air-actuated
clutch providing for positive engagement between the driving and
driven elements thereof. Actuation of high-speed drum clutch 58 is
provided by a conventional roto-coupling 59 through which the
activating air line for engaging and disengaging high speed drum
clutch 58 is directed. When high-speed drum clutch 58 is engaged,
the torque output thereof will appear upon shaft 60 thereby being
transmitted to drum 61 and fast line 17. Drum 61 is keyed or
otherwise secured to shaft 60 in a conventional manner, the manner
of securing drum 61 to shaft 60 not being part of the present
invention. Shaft 60 is journeled in suitable bearing 62 and 63 of
the fixed frame.
Power is transmitted to low-speed drum clutch 64 in a similar
manner to that utilized to transmit power to high-speed drum clutch
58. The second end of shaft 49 is journeled in suitable bearing 65
of the fixed frame, the end of drive shaft 49 extending beyond
bearings 65 having concentrically secured thereto sprockets 66.
Sprockets 66 are coupled to sprockets 67 by chain drive 68,
sprockets 66 being secured to the clutch housing or driving member
of low-speed drum clutch 64. Torque transmitted through low-speed
drum clutch 64 is supplied to shaft 60, to drum 61 and to fast line
17. Although the scope of the present invention embodies any number
of suitable, conventional clutches to implement low-speed drum
clutch 64, low-speed drum clutch 64 is preferably implemented
through the use of an air actuated, ventilated disc clutch. Control
lines for supplying air actuation to low-speed drum clutch 64 is
axially disposed through shaft 60 at roto-coupling 69. Drum 61 is
equipped with a conventional supplemental braking system
referencing the movement of drum 61 to the fixed frame.
Since the drilling of a well bore typically requires the use of an
additional hoist for raising or lowering a variety of devices into
the well bore, sandline drum 70 is secured to shaft 71, shaft 71
being journeled in suitable bearing 72 and 73 of the fixed frame.
Sprockets 57 axially disposed adjacent sprockets 56 on jack shaft
49 are coupled to sprockets 74 via chain drive 75. Sprockets 74 are
concentrically disposed upon and secured to shaft 71. The drilling
of a well bore typically requires a number of operations whereby
the drill string is pulled out and reinserted for changes of the
drill bit. Since the drill string is typically comprised of a
series of coupled drill pipes, catheads 76 and 77 are axially
disposed at opposite ends of shaft 71, each of catheads 76 and 77
being used for the alternate purpose of the make-up or break-up of
the drill string.
As stated, an object of the present invention is to provide means
whereby the penetration rate or weight upon drill bit 22 can be
controlled. As shown in FIG. 2, power unit 16 is coupled to
drawworks 15 to provide alternate means for providing tension in
fast line 17. Sprockets 80 are concentrically disposed upon and
secured to shaft 81, shaft 81 being journeled in suitable bearing
82 of the fixed frame. Sprockets 83 are concentrically secured to
input shaft 42 adjacent sprockets 47, sprockets 80 being coupled to
sprockets 83 via chain drive 84. The driven elements of clutch 85
are coupled to shaft 81, the housing of clutch 85 being secured to
sprockets 86. Sprockets 86 are coupled to sprockets 87 via chain
drive 88, sprockets 87 being secured to the output shaft of
independent power source 89, typically being a DC, series wound
motor.
Clutch 85 is one capable of operating in a continuously slipping
mode whereby there is a controllable differential speed between the
input and output of clutch 85. Sprockets 86 are connected to and
impart rotational power to drive ring 90 which is secured to the
housing of clutch 85. Sprocket 86 and drive ring 90 are rotatably
mounted upon shaft 81. Although it is within the scope of the
present invention to implement clutch 85 by a number of
conventional mechanically engaging clutches, clutch 85 is
preferably an air actuated, water cooled disc clutch capable of
operating in a continuously slipping mode wherein there is a
controlled differential speed between the hub and housing and
therefore the driven friction disc and driving friction elements of
the clutch. In this form of the present invention, actuation and
cooling of clutch 85 is accomplished through the use of
roto-coupling 91.
An understanding of the manner in which controlled tension may be
maintained in fast line 17 can be best gained by reference to FIG.
3 wherein an enlarged cross-sectional, side elevation view of
clutch 85 is shown. As stated, it is within the scope of the
present invention to implement continuously slipping clutch 85
through the use of torque transmitting clutches having heat
dissipation characteristics suitable to permit significant speed
differentials between the input and output friction elements of the
clutch. It is preferred that an air actuated, liquid cooled disc
clutch be used to implement clutch 85. Referring now to FIG. 3,
clutch 85 comprises a substantially cylindrical like housing 100,
axial surface 101 therefore being secured to longitudinal surface
102 of drive ring 90, housing 100 being secured to drive ring 90 by
conventional bolts 103. Shaft 81 is rotatably mounted in suitable
bearings 82. Drive ring 90 is comprised of hub 104, an end thereof
being radially extended into ring portion 105, ring portion 105
being secured to clutch housing 100. Drive ring 90 is rotatably
mounted upon shaft 81, drive ring 90 being journeled on suitable
bearings 106. Sprockets 86 are radially secured to a portion of hub
104 of drive ring 90, sprockets 86 as shown in FIG. 3 having two
sets of sprocket teeth for receiving chain drive 88 (FIG. 2).
Sprockets 86 can be mounted upon hub 104 by any suitable means.
Slidingly adjacent the inner axial surface of housing 100 is
friction plate carrier 107, friction plate carrier 107 being
adapted to receive driving friction element 108. Friction element
109 is secured to an interior receiving surface of housing 100
adjacent the surface of friction disc 110 and opposite friction
element 108. Annularly disposed within driving friction plate
carrier 107 and adjacent driving friction element 108 is annular
channel 111. Annularly disposed within housing 100 adjacent
friction element 109 is annular channel 112. Annular channels 111
and 112 are adpated to receive sufficient liquid, typically water,
for dissipating heat created by the frictional engagement of
friction elements 108 and 109 and friction disc 110. Friction disc
110 is securely mounted by spline teeth 113 on clutch hub 114 which
in turn is keyed or otherwise secured to shaft 81.
In order to engage clutch 85, air is introduced to expandable
element 115 by appropriate fittings through shaft 81 from
roto-coupling 91 (not shown). Friction plate carrier 107 is
slidably engaged to the interior wall of housing 100 to axially
move along the axis of shaft 81 through the alternative action of
expandable element 115 and return spring 116. Friction plate
carrier 107 has no rotational motion with respect to housing 100
while permitting axial movement with respect thereto. Air is
introduced for expanding expandable element 115 at air coupling 92
and liquid coolant is introduced at roto-coupling 91 to provide an
inlet and outlet for the coolant disposed within annular channels
111 and 112, connections to roto-coupling 91 not shown.
In order for clutch 85 to operate as a continuously slipping
clutch, clutch 85 must be fully capable of fully dissipating the
heat horsepower generated by the frictional engagement between
driving friction elements 108 and 109 and friction disc 110. When
the present invention method of rotary drilling operates drawworks
15 to maintain fast line 17 in a controlled tension mode, clutch 85
will be engaged. Drive power is supplied by rotating sprockets 86
which in turn causes a given rotational speed and torque to be
applied to housing 100 and friction plate carrier 107. The degree
of tension in fast line 17 is dependent upon the magnitude of the
frictional engagement between driving friction elements 108 and 109
and driven friction disc 110. Air is introduced into expandable
element 115 which in turn will cause friction plate carrier 107 to
be slidably moved. Since friction element 109 is substantially
stationary, driven friction disc 110 will be frictionally engaged
between the opposing surfaces of friction elements 108 and 109. By
providing a controlled speed differential between driving friction
elements 108 and 109 and friction disc 110, the torque imposed upon
shaft 81 will be imparted to shaft 60 (FIG. 2) thereby maintaining
a controlled tension in fast line 17. During the controlled tension
mode of rotary drilling, high-speed and low-speed drum clutches 58
and 64 respectively will be disengaged.
In order to provide a complete rotary drilling system as stated,
FIG. 4 illustrates a portion of rotary drill table 26 and the power
thereto as provided by power unit 29. Power unit 29 drives rotary
drill table 26 via shaft 28. Shaft 28 is coupled to rotary drill
table 26 via a conventional pinion gear (not shown) thereby
changing the axis of rotation by 90.degree.. Referring now to FIG.
4, rotary drill table 26 has disposed therein a receiving orifice
for providing the rotational force in kelly joint 25 (FIG. 1).
Shaft 28 through appropriate pinion gears has mounted thereon
sprockets 120, shaft 28 being rotatably mounted in suitable
bearings 121 of the frame of power unit 29. Sprockets 120 are
coupled to sprockets 122 which are mounted upon shaft 123 journeled
in suitable bearings 124 of the fixed frame of power unit 29. Shaft
123 is coupled to the hub of clutch 125 in the same manner as shaft
81 is coupled to clutch hub 114 in FIG. 3. The clutch housing of
clutch 125 is coupled to ring gear 126 upon which is concentrically
disposed and secured thereto sprockets 127. Ring gear 126 is
rotatably mounted upon shaft 123 by suitable bearings in the manner
shown in FIG. 3. Power is delivered to sprockets 123 and chain
drive 129 which is mounted upon the output shaft 130 of motor 131.
Chain drive 129 transmits power to sprockets 127 and therefore to
clutch 125. Although it is within the scope of the present
invention to utilize a conventional motor for motor 131, motor 131
is typically implemented through the use of a DC, series wound
motor. In the same manner as described with respect to clutch 85,
clutch 125 is adapted to be operated in a continuously slipping
mode. Clutch 125 is preferably an air actuated, liquid cooled disc
clutch wherein air is introduced at air coupling 132, the water
inlet and outlet being at roto-coupling 133.
As stated, it is an object of the present invention to provide
means for controlling the rotational speed or torque of rotary
drill table 26 and therefore the rotational speed and torque at
drill bit 22. When there are no means for precisely controlling the
rotational speed or torque at drill bit 22, encountering material
which is exceptionally hard will cause failure in the power system
of the rotary drill table or at the least damage to the pinion
gears which couple the power to the rotary drill table. Clutch 125
is capable of providing a predetermined speed differential between
the driving and driven elements of clutch 125, the input speed
provided to the driving elements by motor 131 being directly
related to the torque output of clutch 125 based upon the
frictional engagement of clutch 125. Where the rotational speed or
torque imposed upon drill bit 22 is sensed in a conventional
manner, control over the air actuation of clutch 125 can be
accomplished to precisely control the torque or speed of drill bit
22. Since the clutch 125 can dissipate the heat horsepower
generated by the continuously slipping clutch between the driving
and driven elements of the clutch, precise control can be
maintained over the pertinent parameters without the inherent time
delays, errors and inadequate capacities inherent in the devices
disclosed by the prior art.
The operation of the total rotary drilling system as provided by
the present invention can be best understood by again referring to
FIG. 1. Where the weight of drill string 27 is being increased by
the addition of portions of drill pipe as well bore 13 becomes
deeper, the weight upon drill bit 22 can similarly increase unless
drawworks 15 in conjunction with power unit 16 control or otherwise
supports a greater portion of the weight of drill string 27. Sensor
21 and the dead line portion of the hoisting cable will provide an
accurate indication of the weight of drill string 27 and therefore
the weight imposed upon drill bit 22. As the weight of drill string
27 is increased, sensor 21 will initiate increased actuation of
clutch 85 and power unit 16 to provide increased torque output of
clutch 85 and therefore provide increased tension in fast line 17
to support a greater amount of the weight which would otherwise be
imposed upon drill bit 22. In the event the penetration rate of
drill bit 22 is the pertinent parameter, appropriate use of the
output of sensor 21 can adjust torque output of clutch 85 to
provide for precise control thereof. A complete rotary drilling
system does not exist unless the rotational speed or torque at
drill bit 22 is controlled. Conventional sensors can be utilized at
rotary table 26 to determine the torque imposed upon kelly 25 and
therefore the torque or speed at drill bit 22 is also known. Use of
the output of the sensors at rotary drill table 26 will provide for
maintaining the appropriate torque output of clutch 125 by
adjusting the air actuating elements of clutch 125. The two
subsystems comprise a total cooperating system for implementing an
improved method for rotary drilling which substantially surpasses
the methods and apparatus for implementing same as disclosed by the
prior art. Since the increased need and use of off-shore drilling
techniques has substantially increased the cost of the output of
the well, the present invention apparatus and method of rotary
drilling provide increased efficiency and economy in the drilling
of well bores.
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