Note: Descriptions are shown in the official language in which they were submitted.
EARTH BORING BIT WITH ECCENTRICALLY
FORMED BEARING SURFACE
Background of the Invention
The present invention relates in general to the
~ art of earth boring and more particularly to a rotary rock
j~ ~ bit with an improved bearing system. The present invention
S is especiaIly adapted for use on that type of rotary rock
bit popularly known as a three cone bit; however, its use
is not restricted thereto and the bearing system of the
present invention can be used in other ~arth boring bits
wherein an improved bearing system is required.
~ A three cone rotary rock bit is adapted to be
connected as the lower member of a rotary drill string. As
the drill string is rotated the bit disintegrates the
` ~ formations to form an earth borehole. The three cone rotary
rock bit includes three individual arms that extend angularly
downward from the main body of the bit. The lower end of
each arm is shaped to form a bearing pin or journal. A
rolling cone cutter is mounted upon each bearing pin (or
journal) and adapted to rotate thereon. The cone cutters
include cutting structure on their outer surface that serves
to disintegrate the formations as the bit is rotated.
A rotary rock bit must operate under very severe
environmental conditions and the size and geometry of the
bit is restricted by the operating characteristics. At
the same time, the economics of petroleum production demand
a longer lifetime and improved performance from the bit.
In attempting to provide an improved bit, new and improved
materials have been developed for the cutting strusture of
the cone cutters thereby providing a longer useful lifetime
for th cutt~rs. This has resulted in the bearing system
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being the first to fail during ~he drilling operation.
Consequently, a need exists for an improved bearing system
to extend the useful lifetime of the bit.
Description of Prior Art
In U. S. Patent ~lo. 3,746,405 to Russell L. Welton,
a well drilling bit lubrication system and seal is shown.
A journal bearing lubrication means and a seal cooperatively
combined therewith to maintain lubrication throughout the
useful life of the roller cutter of a well drilling bit, to
the exclusion of foreign materials entering therein from
the drilling fluids and surrounding earth formations is
shown. A journal bearing o right cylinder form is provided,
characterized by the formation of a strategically pl~ced recess
or recesses therein and all without subtracting from the load
carrying capabilities of the bit, the assembly being retained
in working condition by a single element combined with the
lubrication means and assuring proper axial placement of
the roller cutter.
In U. S. Patent No. 3,890,018 to ~obert D. Clamon,
a rotary rock bit with wiper pad lubrication system is shown.
A system is pro~ided for circulating lubricant into the
loaded contact area between the bearing pin and the rotating
cutter of an earth boring bit. The cutter is mounted to
; rotate about the bearing pin. The cutter includes a cutter
interior surface. At least one wiper pad cavity is located
in the aforementioned interior surface of the cutter. A
wiper pad is positioned in the wiper pad cavity and a
resilient member is positioned beneath the wiper pa~. As
the cutter rotatesl the wiper pad forces lubricant into
the load area between the bearing pin and the interior
surface of the cutter.
In U. S. Patent No. 4,061,376 to Arthur A.
~illaloboz, a rock bit bearing structure is shown. A rock
bit has a rotary cutter cone journaled on a fixed journal
bearing shaft with the radial load being taken by a
cylindrical journal bearing~ The friction bearing portion
of the fixed shaft has a groove extending around the
periphery of the shaft. The groove is filled with a
bearing metal over an arc on the lower load bearing fraction
~0 of the shaft. The remaining unfilled portion of the groove
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ls connected through a lubricant supply passage in the bit
body with a pressure-compensated grease reservoir in the
bit body to supply lubrication to the journal bearing.
According to one aspect of the present invention
there is provided method of constructing a rotary rock bit having
at least one depending arm, the me-thod including the step
pf producing a journal bearing pin extending cantilevered
from the arm, the bearing pin having a central axis and a
cylindrical bearing surface concentric thereto. A circumferent~
ially extending groove is formed in the peripheral bearing
surface of the bearing pin of predetermined extent, less than the
circumferential extent and eccentric to the axis of the bearing
pin. A first intermediate portion of the groove is filled
with a bearing material and thereby providing a pair of
; opposed unfilled gro~ove por-tions on each side thereof. The bearing
material surface is machined to be concentric with the bearing
pin surface, and the unfilled groove portions is provided
with a lubricant composition~ ,
According to another aspect of the present invention
there is provided a rolling cutter earth boring bit having a bit
body with at least one downwardly extending arm,and a journal
bearing pin extending cantilevered from the arm having a cylindrical
periphery forming a bearing surface. In the peripheral surface
of the bearing pin there is a circumferential extending groove
of predetermined extent less than and eccentric to the axis
of the cylindrical bearing surface. A bearing material fills an
intermediate portion of ~e eccentric groove and thereby provides
a pair of unfilled opposed groove portions~ A lubricant composi-
tion is disposed within the opposed groove portions, and a roll-
'~ ing cone cutter is rotatably mounted on the bearing pin~
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The above and other features ancl advantages of thepresent invention will become apparent from a consideration of
the following detailed description of the invention when taken
in conjunction with the drawings.
BRIEF DESCRIPTION OF THE 9RAWINGS
Figure 1 illustrates a rotary rock bit constructed
in accordance with the present invention.
Figure 2 is a sectional view of a rolling cone cutter
of the bit of Figure 1 taken along lines 2-2.
DETAILED DESCRIPTION OF THE INVENTION
.
Referring now to the drawings and to Figure 1 in
particular, shown therein and generally designated by the
reference number 10 is a three cone sealed bearing rotary rock
bit. The bit 10 includes a bit body 11~ including an upper
threaded portion 12. The threaded portion 12 allows the
bit 10 to be connected to the lower end of a rotar~ drill string
(not shown). 9epending from the bi-t body 11 are three sub-
stantially identical arms with the arm 13 being shown in Figure 1.
The lower end of each of the arms is provided with an extended
journal portion and the details of this jounal portion
will be discussed subsequently. Three rotary cone cutters are
rotatably posltioned on the three bearing pins extending from
the arms. The cutter 14
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is shown in Figure 1. Each of the cutters includes cutting
structure on its outer sur:~ace adapted to disintegrate
formations as the bit 10 is rotated and moved downward. The
cutting structure 15 is shown in the ~orm of tungsten carbide
5 inserts. However, it is to be understood that other cutting
structures such as steel teeth may be used as a cutting
structure on the cone cutters.
The bit includes a central passageway extending
along the central axis of body 11 to allow drilling fluid
10 to enter from the upper section of the drill string (not
shown) immediately above and pass downward through three jet
nozzles past the cone cutters. In use~ the bit 10 is
connected as the lower member of a rotary drill string tnot
shown) and lowered into the well bore until the cone
15 cutters engage the bottom o~ the well bore. Upon engagement
with the bottom of the well bore, the drill string is
rotated, rotating bit 10 therewith. Drilling fluid is
forced down through the interior passage of the rotary drill
string by mud pumps located at the surface. The drilling
20 fluid continues through the central passageway of bit 10,
passing through the nozzles past the cutting structure of
the cutters to the bottom of the well bore, thence upward
in the annulus between the rotary drill string and the wall
o~ the well bore, carrying with it the cuttings and debris
25 from the drilling operation.
The bearing system must insure free rotation of
the cone cutters under the severe drilling environmental
conditions. The improved bearing system of the present
invention provides an earth boring bit with a long lifetime
30 and that will withstand the conditions encountered in
drilling a deep well. The elongated lower portion of arm
13 forms a journal 18. The rolling cone cutter 14 is
rotatably mounted on the bearing pin 18. The primary bearing
surface of the bearing pin 18 is provided by forming a
35 groove in the bearing pin and filling a portion of the
groove with bearing material on the load side of the bearing
pin. The groove is eccentric to the bearing pin central
axis. Bearing material is applied in the groove and is
machined to coincide with the bearing pin surface on the
40 loaded side. The unfilled portion of groove sexves as a
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lubricant reservoir in close proximity to the load side
of the journal.
The bearing system of the present invention
insures free rotation of rotatable cutter 14 under the
severe drilling conditions. A series of ball bearings (not
shown) that bridge between raceways 16 and 17 insure that
rotatable cutter 14 is rotatably locked on journal 18. The
rotatable cutter 14 is positioned upon journal 18 and the
series of ball bearings inserted through a bore extending
into arm 13. After the ball bearings are in place, a plug
is inserted in the bore and welded therein. A flexible
seal 9 forms a seal between cutter 14 and journal 18 to
pxevent loss of lubricant or contamination of the lubricant
from materials in the well bore.
Referring now to Figure 2, a sectional view of
bearing pin 18 is shown. The groove 20 is cut in the journal
surface. The groove 20 is eccentric to the central axis 23
; of bearing pin 18 and the journal surface. Beaxing material
19 is applied in the groove 20 and machined to coincide with
the journal surace on the loaded side of the journal 18.
A space 21 for lubricant is provided on each side of the
bearing material 19. The central axis 23 o the bearing pin
18 and the axis 22 used to form the groove 20 are offset
and the groove 20 is eccentric to the bearing pin 18. The
unfilled portion of groove serves as a lubricant reservoir
in close proximity to the load side o the journaI.
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