CA1104553A

CA1104553A - Sealing system for an earth boring cutter

Info

Publication number: CA1104553A
Application number: CA328,493A
Authority: CA
Inventors: Santos Shields
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1978-07-17
Filing date: 1979-05-28
Publication date: 1981-07-07
Also published as: GB2025540A; US4168868A; GB2025540B

Abstract

SEALING SYSTEM FOR AN EARTH BORING CUTTER
Abstract of the Disclosure A sealing system acts as a barrier to the drilling fluid, pulverized cuttings and other materials in the bore-hole preventing the materials from entering the bearing area of an earth boring cutter and retains lubricant inside the bearing area. At least one bearing pin extends from the body of an earth boring bit and a rolling cutter is mounted on the bearing pin. A seal assembly is located between the mouth of the cutter and the bearing pin. The seal assembly includes an "O" ring and a washer ring. The washer ring has a semi-circular or semi-elliptical cross section.

Description

SEALING SYSTEM FOR AN EARTH BORIMG CUTTER
Technical Field The present invention relates to the art of earth boring and, more particularly, to a rotary rock bit with improved means for sealing the bearings of the bit from materials in the ~orehole and retaining lubricant within the bearing area.
Background of the Invention The present in~ention is especially adapted for 10 use with rock bits popularly known as three-cone rotary rock bits; howe~er, its use is not restricted thereto, and the present invention can be used in other types of rotary rock bitss A three-cone rotary rock bit consists of a main bit ~ `
body adapted to be connected to a rotary drill~string. The 15 bit includes three individual rotatable cone cutters mounted on three individual bearing pins extending rom the main bit body. Bearing systems are provided between the cone cutters and the bearing pins to promote rotation of the cutters and means are provided on the outer sur~ace of the cone cutters 20 for disintegrating the earth formations as the bit and the cutters rotate. A sufficient supply of ~mcontaminated lubri-cant must be maintained proximate the bearing systems throughout the lifetime of the bit. Various forms of seals have been provided between the cone cutters and the bearing 25 pins upon which they are mounted to retain lubricant and pre-vent contamination; however, the need for new sealing systems is as acute today as any time in the history o~ rock drill-ing.
A three-cone rotary rock bit must operate under 30 very severe conditions, and the size and geometry of the bit is restricted by the operating characteristics. ~t the same , ....... .. , ~ ~ .

iS3 time, the economics of petroleum procluction demand a longer life-time and improved performance from the bit. In atte~pt-ing to provide an improved bit, new and improved materials have been developed for the cutting structure of the cone cutters. They have provided a longer usel~ul lifetime for the cone cutters. This has resulted in the bearing systems of the bit being often the Eirst to fail during -the drilling operation. Consequently~ a need exists for new and improved bearing systems to extend the useful life-time of the bit and to allow development of other elements that interact with the sealing and bearing system~s. In attempting to improve the bearing systems, various seal systems have been provided to maintain the bearing area free of harmEul materials and retain lubricant. In atte~lpting to provide new sealing systems, great care must be taken that the overall capacity of the bearing systems is not reduced.
Description of Prior Art In U.S. Patent No. 3,397,928 to E. M. Galle ~
patented Augu~t 20, 1968, a seal means for drill bit bearings ~ ~-is shown. The seal means includes a shaft rigidly secured to a drill bit body with a bearing surface formed thereon.
A cutter element is rotatably mounted to said shaft and includes a bearing surface thereon that opposes and engages the bearing surface on the shaft. A resilient packing ring is positioned in a groove in one of the surfaces. The packing ring, the groove and an opposing surface are sized such that upon assembly of the cutter element upon the shaft the cross sectionalthickness of the packing ring is compressed by not less than substantially 10% of this thickness prior - ,

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to assembly of the cutter element upon the shaft.
The presen-t invention provides an improved sealing system for a rotary rock bit tha-t acts as a barrier to the drilling fluid, pulverized cuttings and other materials in the borehole to preven-t the materials from entering -the bearin~ area of the bi-t and retains lubricant within the said bearing area.
The present invention relates to a seal assembly for use in an earth boring bit having a bit body, a bearing shaft extending from the hit body, and a rolling cutter rotatably mounted on the bearing shaft with lubricant between :~ .
the bearing shaft and the roller bearing, the seal assembly being between the roller cutter and the bearing shaft so that the lubricant can produce internal pressure acting on the seal assembly. The seal assembly includes an "O" ring of deformable material positioned around the bearing shaft between the bearing shaft and the roller cutter with the lubricant~con~
tacting the "O" ring with the internal pressure acting on ~ ;
~.
the "O" ring. The seal assembly also has a hard washer ring posltioned around the bearing shaft between the bearing shaft :
and the roller cutter with the "O~" ring contacting the washer ring and the internal pressure acting on the "O" ring forcing the "0" ring onto the washer ring. The washer ring has a substantially semi-circular cross section with a curved side, the curved side contacting the ..o.t ring wherein the internal pressure will cause the "O" ring to deform onto the curved sided of the washer ring.
The unique seal of the present invention ca~ be .
shown to have a number of importan~ features not existing in ', ~ ! ' :
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:

i3 the prior art. It is, however, to be understood that the scope of the present invention is deEined by the claims at the end of this speciEication and a general description oE
the prior art and dis-tinctions thereover is not to be inter-pre-ted as limiting the coverage of the presen-t invention.
Previous "O" ring ~eal conEigurations emplo~ed flat edge bearing surEaces which result in pinching of the "O" ring because it tended to squeeze be-tween two interfaces of -the gland seal components. The present invention provides a small volume annular cavity at top and bottom of the "O"
ring/washer interface for material expansion, rather than into the interface as in the prior art. The above and other features and advantages of the present invention will become apparent upon consideration of the following detailed de-~scription of the invention when taken in conjunckion with the accompanying drawings.
Brief Description of the Drawings Figure 1 is an illustration of an earth boring bit .
constructed in accordance with the present invention. ~
:
Figure 2 is an enlarged view illustrating the seal assembly of the bit shown in Figure 1.
Fi~ure 3 illustrates the pressure loading of the~
seal assembly shown in Figures 1 and 2.
Figure ~ is a cross sectional view of a seal element of the prior art.
De-tailed Description of the Invention Referring now to Figure 1, a sectional view of one arm 18 of a three-cone rotary rock bit 10 is shown. It is to be understood that the structure of the other two arms are -3a-F

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substantially identical to the arm 18. A cutter 14 is rotatably positioned on the journal portion or bearing pin 17 of the arm 18 and adapted to disintegrate the earth ~or-mations as the bit 10 is rotated. The bearing pin 17 pro-jects from the cutter rèceiving surface of the arm 18. Thecutting structure 15 on the surface of c~tter 14 contacts and disintegrates the formations in a ma;nner that is well known in the art. The cutting structure 15 is shown in the form of tungsten carbide inserts. ~Iowever, it is to be 10 understood that other cutting structures such as steel teeth may be used as the cutting structure on the cone cutter 14.
Tha body 13 of the bit 10 includes an upper threaded portion 12 that allows the bit 10 to be connected to the lower end of a rotary drill string (not shown). The 15 bit 10 also includes a central passageway 16 extending along the central axis of the bit to allow drilling fluid to enter from the upper section of the drill string (~not shown) im-mediately above and pass downward to the bottom of the well bore to flush cuttings and drilling debris from the well 20 bore.
~ plurality of bearing systems are located in the bearing area between the cutter 14 and the bearing pin 17.
The bearing systems in the bearing area include an outer friction bearing 19, a series of ball bearings 2Q, an inner 25 friction bearing 21, and a thrust button 22. ~ seal assembly is positioned between the cutter 14 and the bearing pin 17.
The seal assembly includes washer ring 11 and loll ring 35 that act to retain lubricant in the bearing area around the bearing systems and prevent any materials in the well bore 30 from entering the bearing area. Passageways 23 and 24 are provided to allow lubricant to be transmitted to the bearing systems. The passageway 24, as shown, also allows the balls that make up the ball bearing system 20 to be inserted into position after the cone cutter 14 is placed on the bearing 35 pin 18. The series of ball bearin~s 20 ser~es to lock the cone cutter 14 on bearing pin 17. After the balls are in place, a plug 25 is inserted into the passageway 24 and welded therein by weld 26. Plug 25 has a reduced diameter throughout the major portion of its length to allow lubricant . . ~, : :. : :~ ~: :

;53 to be transmitted to the bearing area. The additional passageways 23 extend from passageway 24 to the bearing area to in~ure a suEficient supply of lubricant to bearings 19, 20, 21 and 22.
A bore 30 extends into the body 13 from the surface of the bit body. A passage 31 extends from the bore 30 to the passageway 24. A lubricant reservoir 32 is located in the bore 30. The lubricant reservoir 32 is located between a flexible diaphragm 28 and a reservoir cap 34. An "O" ring 10 seal prevents borehole fluid from by-passing the upper por-tion o~ the reser~oir cap 34 and lubricant within the lubri-cant reservoir 32 from escaping into the borehole. A
retaining ring 33 holds reservoir cap 34 in position in bore 30. The flexible diaphragm 28 prevents lubxicant in 15 the lubricant reservoir 32 from escaping into the bore 30 and fluid in the borehole tha~ hasentered bore 30 through passage 27 from en-tering the lubricant reservoir 32. Lubri-cant within the lubricant reservoir 32 is channeled into the passage 31 through opening 29 and is directed to the bear-20 ings.
Referring now to Figure 2, an enlarged view of aportion of the arm 18, the cone 14 and the seal assembly is shown. The seal assembly is positioned between a surface 36 on the bearing pin 17 and a surface 38 on the cone cutter 25 14. The seal assembly is also positioned bebween a receiving surface 39 on the arm 18 and a surface 37 on the bearing ele-ment 19. The seal assembly provides an improved sealing system that acts as a barrier to the drilling fluid, pulver-ized cuttings and other materials in the borehole to prevent 30 -the materials from entering the bearing area of the bit and retains lubricant within said bearing area. The washer ring 11 is positioned in the mouth of the cutter 14 around the bearing pin 17. The washer ring 11 has a semi-circular or ~, semi-elliptical cross section. The "O" ring 35 is mounted 35 within the cutter mouth inside of the washer ring 11.
The structural details~of an earth boring bit 10 constructed in accordance with the present invention having been described, the operation of the bit 10 will now be con-sidered with reference to Figures 2 and 3. The lubrication .. . .

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;3 system of the bit 10 is filled with a suitable lubricant.
The area within the 1exible diaphra~m 28 provides a reser-voir of lubrican~.. The flexlble diaphragm 28 seals the lower end of the lubricant reservoir and is held in place by the cap 34. The bit 10 will be lowered into a well bore until the cutter 14 contac-ts the earth formations at the bottom of the borehole. The hydrostatic pressure of fluid in the well bore is substantial. The lubrication system of the bit 10 -allows the pressure of fluid in the well bore to be trans-10 mitted to the lubricant reservoir through passage 27 to the lubricant through diaphragm 28. This allows the pressure of lubricant inside the bit and fluid in the borehole to be equalized as the bit 10 is mo~ed through the borehole.
Lubricant from the lubricant reservoir can migrate through 15 passages 31, 24 and 23 and be transmitted to the bearing systems.
The bit 10 i5 rotated and thrust downward, thrust-ing the cutter 14 against the earth formations. Continued rotation with the weight of the drill string apply:Lng a 20 thrust force to the bit 10 causes the cutters to disintegrate the formations and form the desired borehole. Internal pres-sure of lubricant within the bit 10 will tend to force the "o" ring seal 35 outward into the opening 41 between the cutter 14 and the bearing pin 17. As shown in Fi~ure 3, the 25 washer ring 11 prevents the "O" ring 35 f`rom being pinched between the cutter 14 and the bearing pin 17. Previous "O"
ring seal configurations employed flat edge bearing surfaces which result ln pinching of the "O" ring because it tended to squeeze between two interfaces of the gland seal compo-30 nents. The present in~ention provides a small volume annularcavity at top and bottom of the "O" ring/washer interface for material expansion, rather than into the interface as in the prior art.
The cross section of the washer ring 11 is semi-35 circular in the preferred configuration, but may ~lso besemi-elliptical, however the cross section is not l}mited to these two shapes. The ~asher ring may be of other shape hav-ing one flat surfac~ and the remaining surfaces so configured as to provide two annular spaces at top and bottom oE the , : . ` . '~ ' ' washer ring. These spaces provide room into which "O" ring material may be s~ueezed during bit operation. The flat side of the semi-circular washer ring 11 fits against the surEace 39 on the bearing pin 17. The curved surface of the washer ring 11 faces the "O" ring seal 35. As shown in Figure 3, when the internal pressure o~ lubricant within the bit forces the "O" ring seal outward toward the opening 41, the "O" ring seal 35 will become deformed around the curved side oF the washer ring 11. The washer ring therefore does not "see" any ~;
10 sharp corners and is prevented from becoming pinched as in the prior art. The curved surface of the washer ring 11 pro-vides a greater area for the "O" ring 35 to deform around.
The washer ring 11 may be made of plastic, leather, metal or other materials. The "O" ring 35 may be made of any suitable 15 "O" ring material. The washer material should be harder than the "O" ring material.
Referring now to Figure 4, an illustration of the problem encountered with prior art "O" rings will be de-scribed. A prior art "O" ring 40 is shown positioned in the 20 same seal cavity as the seal assembly of the present inven-tion. Internal pressure of lubricant within the bit 10 will tend to force the prior art "O" ring seal 40 outward toward the opening 41 between the rotating cutter 14 and the hearing ,~
pin 17. The prior art "O" ring 40 will deform and attempt 25 to move into the gap 41. Because of the relat~ve rotation between rolling cutter 14 and bearing pin 17, the prior art lloll ring having been pinched into the opening 41 will become damaged during operation. The present invention overcomes this problem by preventing the "O" ring from moving into this 30 pinched configuration.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In an earth boring bit having a bit body, a bearing shaft extending from said bit body, a rolling cutter adapted to be rotatably mounted on said bearing shaft, a lubricant filled reservoir in said bit body and providing lubricant between said bearing shaft and said rolling cutter, and a seal assembly between said rolling cutter and said bearing shaft to prevent lubricant loss from said bit and from internal pressure acting on said seal assembly, the improvement comprising:
said seal assembly including an "O" ring of deformable material positioned around said bearing shaft between said bearing shaft and said rolling cutter with said lubricant contacting said "O" ring and said internal pressure acting on said "O"
ring, and a hard washer ring positioned around said bearing shaft between said bearing shaft and said rolling cutter with said "O" ring contacting said washer ring and said internal pressure acting on said "O" ring forcing said "O" ring onto said washer ring, said washer ring having a substantially semi-circular cross section with a curved side, said curved side contacting said "O" ring wherein said internal pressure will cause said "O" ring to deform onto said curved side of said washer ring.

2. An earth boring bit comprising:
a bit body;
a bearing shaft extending from said bit body;

a rolling cutter rotatably mounted on said bearing shaft, said rolling cutter having a cutter mouth;
lubricant between said bearing shaft and said rolling cutter; and a seal assembly positioned around said bearing shaft within said cutter mouth between said bearing shaft and said rolling cutter to prevent lubricant loss from said bit from internal pressure in said reservoir, said seal assembly including a hard washer ring having a substantially semi-circular cross section positioned within said open mouth, said washer ring semi-circular cross section providing a curved side and an "O" ring of deformable material positioned within said open mouth inside of said washer ring wherein said internal pressure causes said lubricant to force said "O" ring to deform onto said curved side of said curved side of said hard washer ring.

3. The earth boring bit of claim 2 wherein said washer ring curved side is positioned adjacent said "O"
ring.

4. An earth boring bit, comprising:
a bit body;
a bearing pin extending from said bit body;
a rolling cone cutter rotatably mounted on said bearing pin, said rolling cone cutter having a cone mouth;
lubricant between said bearing pin and said rolling cone cutter; and a seal assembly positioned around said bearing pin within said cone mouth and located between said bearing mb/Jo 9 pin and said rolling cone cutter to prevent lubricant loss from said bit from internal pressure in said reservoir, said seal assembly including an "O" ring of deformable material positioned around said bearing pin within said cone mouth and a washer ring of hard material positioned around said bearing pin within said cone mouth, said washer ring having a substantially semi-circular cross section with a curved side, said washer ring positioned within said cone mouth with said curved side facing said "O" ring and said "O" ring positioned inside said washer ring wherein said internal pressure will force said "O"
ring to deform onto said curved side of said washer ring.
5. An earth boring bit, comprising:
a bit body;
a bearing pin extending from said bit body;
a rolling cone cutter rotatably mounted on said bearing pin, said rolling cone cutter having a cone mouth;
lubricant between said bearing pin and said rolling cone cutter: and a seal assembly positioned around said bearing pin within said cone mouth and located between said bearing pin and said rolling cone cutter to prevent lubricant loss from said bit from internal pressure in said reservoir, said seal assembly including an "O" ring of deformable material positioned around said bearing pin within said cone mouth and a washer ring of hard material positioned around said bearing pin within said cone mouth, said washer ring having a semi-circular or semi-elliptical cross section mb/Jo 10

Claim 5...continued.

with a curved side, said washer ring positioned within said cone mouth with said curved side facing said "O"
ring and said "O" ring positioned inside of said washer ring between said washer ring and said lubricant wherein said internal pressure will force said "O" ring to deform onto the curved side of said washer ring.

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