Bearing separator and sealing system for rock bit

The bearing capacity of a rotary rock bit is increased by providing a bearing separator and sealing system which maintains the cylindrical roller bearings in proper alignment without interfering with the integrity of the seal. A spacer unit is positioned around the bearing pin of the rock bit between the cutter member and the bearing pin. The spacer unit includes an annular body with a plurality of separator elements cantilevered from said annular body extending toward the outer end of the bearing pin. The cylindrical rollers are alternately positioned between the separator elements. The annular body of the spacer unit is located in the cone mouth of the cutter member. A seal member is located in the cone mouth of the cutter member between the rock bit body and the annular body of the spacer unit.

BACKGROUND OF THE INVENTION 
The present invention relates to the art of earth boring and more 
particularly to an improved sealed bearing rotary rock bit. The present 
invention is especially adapted for use in that type of rotary rock bit 
popularly known as a three-cone bit; however, its use is not restricted 
thereto, and the present invention can be used in other types of rotary 
rock bits. 
A three-cone rotary rock bit is adapted to be connected as the lowest 
member of a rotary drill string. As the drill string is rotated, the bit 
disintegrates the earth 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 spindle or bearing pin. A cone cutter is mounted 
upon each bearing pin and adapted to rotate thereon. Individual bearing 
systems promote rotation of the cone cutter. These bearing systems have 
traditionally been roller bearings, ball bearings, friction bearings, or a 
combination of the aforementioned bearings. In order to extend the 
lifetime of the bearing systems a lubricant is maintained in the bearing 
area. A seal in the mouth of the cone cutter retains the lubricant in the 
bearing area. The cone cutters include cutting structure on their outer 
surfaces that serve to disintegrate the formations as the bit is rotated. 
The rotary rock bit must operate under very severe 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 structure of the cones, thereby providing a longer useful lifetime 
for the cones. This has resulted in the bearing systems often being the 
first to fail during the drilling operation. Consequently, a need exists 
for an improved sealed bearing system to extend the useful lifetime of the 
bit. 
In addition to rotational forces experienced by the bit, the bit is 
subjected to a thrust load during operation. The weight of the drill 
string and in some instances the downward force applied by the rotary 
drilling equipment apply a substantial thrust load to the bit. The thrust 
load in combination with the rotational forces tend to force the rollers 
into a position askew to the longitudinal axis of the bearing pin. Wear of 
the roller bearing races tends to exaggerate the skewing problem. The load 
experienced by the bearing system tends to be the greatest near the base 
of the cone. The base of te cone contains the gage cutting structure and 
the gage cutting structure encounters the most difficult cutting loads 
during the drilling operation. 
DESCRIPTION OF PRIOR ART 
In U.S. Pat. No. 3,102,601 to D. P. Worth, assigned to Phillips Petroleum 
Company, patented Sept. 3, 1963, an improved drill bit is shown. 
Specifically, the improvement relates to providing a drill bit having 
therein means for releasing drilling fluid at and for predetermined 
intervals from the face of a tooth on the cutter in order to thereby blow 
the detritus broken loose from the formation away from the cutter. It is 
preferred to use a compressed gas such as air for the drilling fluid that 
is released from the face of the tooth, but grit-free liquids may also be 
used. The radial loads are carried by the outboard bearings 40 and the 
inboard bearings 42. The inboard radial bearing comprises the roller 
bearings 42 spaced apart by the retainer 43. In some installations it may 
be possible to omit the spacers 41 and 43. 
In U.S. Pat. No. 3,235,316 to J. R. Whanger, assigned to Hughes Tool 
Company, patented Feb. 15, 1966, a journal bearing for a rock bit is shown 
with alternating surface areas of wear-resistant and anti-galling 
materials. The bearing system disclosed in this patent includes grooves in 
one of the rotatable members and a soft metal having anti-galling 
characteristics positioned in the grooves. 
In U.S. Pat. No. 3,601,456 to Myron D. Becker, patented Aug. 24, 1971, an 
antiskew device for ensuring proper alignment of roller bearings in roller 
cutter earth drilling bits is disclosed. The antiskew device aligns the 
roller bearings as they enter the race area where greatest force is 
applied to ensure that the force is applied equally along the surface of 
the roller bearings. 
In U.S. Pat. No. 3,720,274 to H. F. McCallum, assigned to Dresser 
Industries, Inc., patented Mar. 13, 1973, intermdiate thrust elements are 
positioned between the cutters and the bearing pins of an earth boring 
bit. Each intermediate thrust element is located between a thrust surface 
on a bearing pin and a thrust surface on the associated cutter. The 
intermediate thrust elements aid stabilization of the rotating cutter, 
promote cutter rotation and extend the lifetime of the bit. 
In U.S. Pat. No. 3,784,264 to G. C. Jackson, Jr., assigned to Dresser 
Industries, Inc., patented Jan. 8, 1974, an earth boring bit bearing 
system is shown. The bearing surface of one relatively rotatable member of 
a friction bearing is grit blasted to give it a roughened surface. A 
reservoir containing lubricant having entrained particles of anti-galling 
material is connected to the friction bearing and serves as a source of 
anti-galling material. Particles of the anti-galling material are picked 
up by the roughened surface and a film of anti-galling material formed on 
the bearing surface. 
When reviewing non-analogous prior art, a substantial variety of designs of 
bearing systems will be noted. For example, in U.S. Pat. No. 71,973 to 
John A. Burnap, patented Dec. 10, 1867, an improvement in pulley-block 
including an open ended bearing cage is shown and in U.S. Pat. No. 
3,582,164 to William Derner, patented June 1, 1971, a powdered metal 
bearing cage is shown. 
SUMMARY OF THE INVENTION 
The present invention assists in achieving a more uniform load distribution 
in a rock bit bearing during the drilling operation. The invention lowers 
contact stress by reducing misalignment between the rollers and the 
bearing races and preserves the integrity of the seal. The rollers are 
guided in such a way as to insure that the axes of the rollers remain 
parallel to the axis of the bearing pin and aligned with the bearing races 
to prevent skewing of the rollers during the drilling operation. The 
present invention also prevents the rollers from sliding against the seal 
or each other. The rollers are spaced symmetrically around the periphery 
of the bearing pin to help achieve a more uniform load distribution. Heat 
is dissipated from the bearing surfaces and the lubricant to assist in 
reducing the operating temperature of the bearing. A separator unit with 
cantilevered separator elements projecting between the rollers provides a 
more compatible material for the rollers to slide against and protects the 
seal. The above and other features and advantages of the present invention 
will become apparent from a consideration of the following detailed 
description of the invention when taken in conjunction with the drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings and to FIG. 1 in particular, a sectional view 
of one arm of a sealed bearing rotary rock bit generally designated by the 
reference number 10 illustrating the present invention is shown. As 
illustrated, the arm 11 depends from the main body 12 of the bit 10. The 
bit 10 includes an upper threaded portion that allows the bit 10 to be 
connected to the lower end of a rotary drill string (not shown). The lower 
end of arm 11 is provided with an extended journal portion 13. A rotary 
cone cutter 14 is rotatably positioned upon the extended journal portion 
of arm 11. The cutter 14 includes cutting structure 15 on its outer 
surface adapted to disintegrate formations as the bit 10 is rotated and 
moved downward. The cutting structure 15 is shown in the form of tungsten 
carbide inserts. However, it is to be understood that other cutting 
structures such as steel teeth may be used as the cutting structure on the 
cone cutter 14. 
The bit 10 includes a central passageway extending along the central axis 
of the bit 10 to allow drilling fluid to enter from the upper section of 
the drill string (not shown) immediately above and passed downward to the 
bottom of the well bore to flush cuttings and drilling debris from the 
well bore. A plurality of bearing systems are located in bearing area 
between the cutter 14 and the bearing pin 13. The bearing systems in the 
bearing area include a series of roller bearings 16, a series of ball 
bearings 17, a friction bearing 18, and a thrust button 19. A seal 20 is 
positioned between the cutter 14 and the arm 11. 
The seal 20 retains lubricant in the bearing area around the bearings 
systems and prevents any material in the well bore from entering the 
bearings. A bearing cage 21 with cantilevered separator elements is 
positioned around the bearing pin 13. The separator elements are 
positioned between each of the rollers 16. 
The lubrication system of the bit 10 includes a passage 22 that extends 
through the bearing pin 13 to the bearing area to allow lubricant be 
transmitted to the bearings systems. A passage 23 connected to the passage 
22 allows the make up of the ball bearing system 17 by allowing the balls 
to be inserted into position after the cone cutter 14 is placed on the 
bearing pin 13. The series of ball bearings 17 serve to lock the cone 
cutter 14 on bearing pin 13. After the balls are in place, a plug 24 is 
inserted into the passage 23 and welded therein by a weld 25. The plug 24 
has a reduced diameter throughout the major portion of its length to allow 
lubricant to be transmitted to the bearing area. Additional passages 
extend from passage 23 to the bearing area to insure a sufficient supply 
of lubricant to bearings 16, 17 and 18, and 19. 
A lubricant reservoir is located in the bit body 12 to provide a supply of 
lubricant to the bearings. A flexible diaphragm 26 is positioned in the 
lubricant reservoir and encloses the reservoir to retain a supply of 
lubricant in the lubricant area. The area 27 within the reservoir bore but 
outside of the diaphragm 26 is vented to the dome of the bit by a 
passageway 28 that connects the lower end of the lubricant reservoir with 
the dome of the bit. The upper end of the lubricant reservoir is closed by 
a cap 29 and locked in place in the bit body 12 by a snap ring 30. An 
O-ring seal 31 is positioned around the cap 29 to retain lubricant in the 
lubricant reservoir. A free-breathing porous filter plug 32 extends 
through the flexible diaphragm 26. The free-breathing porous filter plug 
32 provides fluid communication between lubricant in the lubricant area of 
the reservoir and fluid from the bore hole that has entered pressure 
equalizing portion of the lubricant reservoir. The plug 32 is in the form 
of compressed metal particles positioned within an open metal cylinder. 
Referring now to FIG. 2, the seal 20, bearing cage 21 and rollers 16 are 
shown in an exploded view. The bearing cage 21 includes cantilevered 
separator elements 33 that extend away from the seal 20. The separator 
elements 33 include concave surface portions that mate with the external 
surface of the cylindrical rollers 16. The separator elements 33 are 
self-aligning and tend to guide the rollers 16 and hold their axes 
parallel to the axis of the bearing pin 13. The annular body of the 
bearing cage 21 is positioned proximate the seal 20 with the cantilevered 
separator elements 33 extending toward the outer end of the bearing pin 
13. This insures that the rollers 16 will not slide against the seal 20. 
The seal is thus protected and the lubricant is retained within the bit 10 
without contamination. 
The rollers 16 are hardened steel rollers of high wear resistance. In prior 
art rotary rock bits, the rollers were in contact with each other and in 
contact with other elements of hardened steel having high wear resistance. 
The sliding contact between the hardened steel rollers could create an 
undesirable condition that on occasions, would result in the eventual 
destruction of the rollers and ultimate failure of the bit. Since the 
surfaces of the adjcent hardened steel rollers that were in sliding 
contact would be moving in opposite directions and at a substantial 
relative speed, the sliding friction developed would be substantial. 
The separator elements 33 of the present invention provide an element for 
the rollers 16 to slide against that does not add to the sliding motion. 
In addition, the separator elements 33 provide a material for the rollers 
16 to contact that may be more compatible with the hardened steel rollers 
than in prior art bits. For example, the separator elements 33 are of a 
different metal than the hardened steel rollers 16. The separator elements 
33 extend away from the seal 20 and the roller bearings 16 do not come 
into contact with the seal 20. 
The structural details of a rotary rock bit 10 constructed in accordance 
with the present invention having been described, the operation of the bit 
10 will now be considered with reference to FIGS. 1 and 2. The bit 10 is 
connected as the lowest element of a rotary drill string by engaging the 
bit 10 with the drill string by the threaded connection. The bit 10 is 
rotated and thrust downward, thrusting the cutters against the earth 
formations. Continued rotation with the weight of the drill string 
applying a thrust force to the bit 10, causes the cutters to disintegrate 
the formations and form the desired borehole. The combination of rotary 
and thrust forces acts to tend to cause the rollers 16 to attempt to 
become askew to the central axis of the bearing pin 13 and the bearing 
races. The separator elements 33 of the bearing cage 21 serve to prevent 
the rollers 16 from becoming skewed and provides a material that may be 
more compatible with the material of the rollers than when the rollers are 
in direct contact with each other. 
The lubrication system of the bit 10 is filled with a suitable lubricant 
and the area above the flexible diaphragm 26 is completely filled with 
lubricant. The flexible diaphragm 26 seals the lower end of the lubricant 
reservoir and is held in place by the lower portion of the cap 29. The bit 
10 is lowered into a well bore until the cutter 14 contacts the earth 
formation at the bottom of the borehole. The hydrostatic pressure of fluid 
in the well bore is substantial and a pressure differential between the 
pressure of the lubricant inside of the bit 10 and the pressure fluid in 
the borehole will ordinarily develop. The lubrication system of the bit 10 
allows the pressure of fluid in the well bore to be transmitted to the 
lubricant in the lubricant reservoir and the pressures are equalized as 
the bit 10 is moved through the borehole. Lubricant from the lubricant 
reservoir passes through passages 22 and 23 and is transmitted to the 
bearing systems including roller bearings 16 and separator elements 33 to 
extend the useful lifetime of the bit. The seal 20 is located between the 
body of the bearing cage 21 and the body of the bit 10. The seal 20 is 
thus protected and the useful lifetime of the bit 10 is extended.