Boring or penetrating the earth – With storage means for bit lubricant carried by bit or shaft – Rotation of bit actuates lubricant feed means
Reexamination Certificate
2000-10-25
2002-10-08
Schoeppel, Roger (Department: 3672)
Boring or penetrating the earth
With storage means for bit lubricant carried by bit or shaft
Rotation of bit actuates lubricant feed means
C175S372000, C384S093000, C384S095000, C277S307000, C277S400000, C277S402000
Reexamination Certificate
active
06460635
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to providing a reliable bearing and seal system for sealed bearing rotary cone-type rock bits used in hard rock drilling to permit significant increases in the speed and load capability thereof, and more particularly relates to a load responsive elastically flexing bearing design that provides hydrodynamic lubrication of the loaded bearing surfaces in response to relative rotation, thereby permitting the bearing to carry heavier loads at higher speeds while generating less heat than prior art drill bit bearings, and permitting the bearing to be lubricated with liquid oil-type lubricants such as synthetic oils that provide improved compatibility with elastomeric seals compared to the greases presently used in rock bits.
Rotary drilling techniques are used to penetrate into the earth to create wells for obtaining oil and gas. In order to drill through the rock which is encountered in such endeavors, a drill bit is employed at the bottom of a hollow drill string.
A rotary cone-type rock bit is commonly used for such drilling. In such bit designs, rotary cones incorporating patterns of cutting teeth are mounted on support shaft structures at the lower extremity of the drill bit. When the bit is rotated, the rotary cones rotate about the shafts and roll upon the bottom of the bore hole, and the weight of the drill string acting through the cutting teeth causes the rock formation to be broken up into small cuttings. Drilling fluid is circulated down through the drill string and into the bottom of the bore hole to transport the cuttings back to the earth's surface. An example of such well known prior art drill bits is shown in U.S. Pat. No. 5,456,327 to Denton et al.
Thrust and journal bearings are typically employed to transfer the weight of the drill string from the shaft to the rotary cone, and ball bearings are typically employed to retain the rotary cones to the shaft. A grease-type lubricant, pressure balanced to the annulus of the well bore, is provided to lubricate the bearings. Drill bit bearings are expected to operate under very harsh conditions which include elevated temperature, high loading, extreme impact, and complex movement between the rotary cone and the shaft. Due to the severe geometrical constraints the bearings are small. Relative to their small size, these bearings are severely loaded, and the bearing contact stresses reach extremely high levels. As a result, the bearings perform poorly when operated at higher speeds, especially when higher loads are employed, which limits life in hard rock drilling.
Conventional rock bit bearings operate in a boundary lubrication regime, and are lubricated with greases that are heavily loaded with solid lubricants such as graphite, molybdenum disulphide, powdered calcium fluoride, copper particles and various types of soap to help carry the heavy bearing loads. Examples of such greases are described in U.S. Pat. No. 4,358,384 to Newcomb and U.S. Pat. No. 5,015,401 to Landry.
An elastomeric rotary seal is used to establish dynamic sealed relation between the rotary cone and the shaft in order to retain the lubricant and exclude the highly abrasive drilling fluid. Examples of such seals are described in U.S. Pat. No. 3,765,495 to Murdoch et. al. and U.S. Pat. No. 4,610,319 to Kalsi. In addition to the bearings, rotary seals are also a weak link in the reliability and life of the bearing systems employed in high speed rotary cone bits. Firstly, the solid lubricants contained in rock bit bearing greases are highly abrasive to elastomeric rotary seals. Secondly, these seals are prone to wear due to the harsh abrasive drilling fluid environment within which the drill bit operates. Thirdly, as the speed increases, higher heat generation by the bearings and the rotary seal causes thermal degradation of the elastomer material of the seal. These factors, coupled with the higher seal wear rate associated with high speed operation, can lead to early seal failure, permitting abrasive invasion of the bearings, and rapid bearing failure which can in severe cases even lead to loss of the rotary cone down-hole.
In order to replace the drill bit at the end of its useful life, it is necessary to first pull the entire drill string from the well. The downtime associated with the lengthy round trips required for such bit replacement can be a major component of the cost of drilling a well, particularly in wells of great depth. A significant reduction in the cost of oil and gas drilling can therefore be obtained by improving the reliability and life of the bearing and seal system used in rotary cone rock bits.
BRIEF SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a reliable bearing and seal system for use in mechanical equipment subject to high bearing loads, such as sealed bearing rotary cone-type rock bits used in hard rock drilling.
It is another objective of this invention to provide compact hydrodynamically lubricated bearings that lower bearing friction to permit operation under higher loads and higher speeds while minimizing bearing wear, preventing seizure, and remaining effective even as wear occurs at the bearing interface.
It is another objective of this invention to reduce bearing generated heat to prevent heat-related degradation of lubricant, bearings, elastomer seals, and associated components.
It is another objective of this invention to provide a bearing that is capable of providing hydrodynamic lubrication of bearing surfaces while employing a grease-type lubricant containing a high content of solid lubricant particles.
It is another objective of this invention to provide bearings for sealed bearing rotary cone-type rock bits that can operate under high loading in a liquid oil-type lubricant environment, such as a synthetic oil.
It is another objective of this invention to provide a compact bearing that can withstand high shock loads while maintaining low friction operation.
It is another objective of this invention to provide a sealed bearing rotary cone-type rock bit that maintains the integrity of the sealed bearing system seals and bearings by employing a liquid oil-type lubricant such as a high viscosity synthetic oil.
It is another objective of this invention to provide a compact bearing that permits low friction operation over a wide range of loads.
From the standpoint of the basic concept, this invention provides an improved bearing design of generally ring-like form for supporting and guiding a relatively rotatable member. Elastically flexing regions are incorporated into the bearing structure to create undulations in the bearing surface in response to the load and pressure applied to the bearing surface, to create an initial hydrodynamic wedge angle with respect to the mating surface of the relatively rotatable member. The gradually converging geometry created by these undulations promotes a strong hydrodynamic action that wedges a lubricant film of a predictable magnitude into the dynamic interface between the bearing and the relatively rotatable member in response to relative rotation. This film physically separates the dynamic surfaces away from each other, thus minimizing the asperity contact, thus reducing friction, wear and the heat produced by the bearing, while permitting operation at higher load and speed combinations. The bearing of the present invention has a continuous ring shaped body of generally circular form that defines at least one dynamic surface, and defines a plurality of support regions each defining a static face oriented in generally opposed relation with the dynamic face. A plurality of flexing regions are defined by undercut regions between adjacent support regions, it being preferred that the undercut regions be open-ended; i.e. passing completely through the bearing beam-section width from side to side. Each of the flexing regions incorporates a first beam having a first hinge connection with one of the plurality of support regions, and incorporates a second beam having a second hinge connection w
Dietle Lannie L.
Kalsi Manmohan S.
Somogyi Dezso
Andrews & Kurth Mayor, Day, Caldwell & Keeton, LLP
Jackson James L.
Kalsi Engineering, Inc.
Schoeppel Roger
LandOfFree
Load responsive hydrodynamic bearing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Load responsive hydrodynamic bearing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Load responsive hydrodynamic bearing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2934256