 Project (NCRMP) along the coastal line of Odisha to give early warning on the risk in impending natural calamities like tsunami, cyclone and flood.
During the launch, Patnaik also announced the programme for preparations of Village Disaster Management Plans (VDMPs) in 7000 villages in the first phase to build resilient community and to undertake a study on the vulnerability of landslides in Gajapati district of Odisha for taking preventive measures against loss of lives and property due to disasters in future.
Other than EDWS, NCRMP also includes satellite-based mobile data voice by terminals (SBMDVT), digital mobile radio (DMR), a mass messaging system to be operated from the state emergency operation centre and a universal communication interface to allow interoperability among different communication technologies.
Oct 19, 1984 - Dresser Industries, Inc.
In accordance with an illustrative embodiment of the present invention, a thrust bearing member is positioned between the rolling cutter or cone and the bearing pin of a rock bit and comprises wound wire such as a closed spiral coil spring that provides spaced-apart bearing surfaces with open areas therebetween. The flexibility of the spiral spring tends to spread the load between several bearing areas to thereby reduce concentrations of stress and the occurrence of localized high temperatures and wear, and the spacing of the bearing surfaces provides wear and contamination particle traps as well as lubricant reservoirs, to significantly increase the useful life of the bearing.
This invention relates generally to journal or friction bearing structures, and specifically to a new and improved thrust bearing for a rolling cone rock bit or roller rock cutter used in drilling well bores.
A typical friction or thrust bearing used in rock bits, as shown for example in U.S. Pat. No. 4,330,158, has opposed bearing surfaces formed on opposed axial surfaces of the bearing pin and cone. The surfaces oppose and engage one another as the bit is turned on bottom under load applied by the drill collar string to which the bit is attached. Due to heavy loads that are imposed on the bearings during normal drilling operations, significant amounts of friction and heat are generated which limit the bearing life. Of course it is desirable that the bearing life equal or exceed the life of the cone cutting structure, so that the drill string will not have to be tripped to change the bit before the cutting structure has been worn out.
The usual approach to design of bearings of this type has been to maximize the nominal bearing surface areas within the confines of the structural integrity of the rolling cutters or cones, with the objective of presenting larger and more dispersed contact areas at the load-bearing points. Such bearing structures are susceptible to early damage by contaminant particles or by small particles of metal dislodged as a result of the wearing process which adhere to the bearing surfaces and greatly accelerate the wearing process toward catastrophic failure. There is a need for trapping such particles so that they do not remain between rubbing bearing surfaces. Yet another shortcoming of prior structures is that the plain bearing surfaces have not been sufficiently lubricated to provide for maximum bearing life in the somewhat hostile environment in which drill bits are used. Although grooves in solid bearing members have been suggested heretofore, such structures have limited compliance and are easily worn and damaged at areas of localized concentration of stress and localized high temperatures.
A general object of the present invention is to provide a new and improved thrust bearing structure of the type described having a significantly improved bearing life.
Another object of the present invention is to provide a new and improved rock bit journal bearing that includes open areas for trapping debris particles so that such particles do not interfere with movement between opposed bearing surfaces.
Another object of the present invention is to provide a new and improved rock bit thrust bearing constructed and arranged to provide large spaces adjacent to engaged bearing surfaces for the storage of lubricant and supply thereof to contacting bearing surfaces to reduce wear.
Another object of the present invention is to provide a new and improved rock bit journal bearing constructed and arranged to provide a wiping action of one bearing member over the other to evenly distribute lubricant and thereby reduce wear.
Still another object of the present invention is to provide a new and improved journal bearing structure having spaced bearing surfaces formed by wound wire capable of accommodating some degree of misalignment of parts.
These and other objects are attained in accordance with the concepts of the present invention through the provision of a thrust bearing structure, particularly useful in a rock bit, where at least one of the opposed bearing members comprises wound wire forming spaced surface areas in actual contact with the surface of the other bearing member. The cross-sectional shape of the wire, which can take numerous forms, is designed such that between the spaced bearing surface areas there are provided recessed regions which form lubricant reservoirs as well as traps for debris such as particles that are dislodged from the bearing surfaces during operation, or which enter the bearing as contamination.
In one embodiment, the wound wire is in the form of a helical coil spring that is mounted in an interior bore of the cone to provide a thrust bearing. The cross-sectional outline of the coils of the spring is defined by axially outer side walls that engage companion side walls of adjacent coils, and axially inner side walls that converge toward one another to provide axially spaced, inwardly facing bearing surfaces in actual contact with the outer thrust surface of the bearing pin. The helical space defined between the inclined inner wall surfaces of adjacent coils provides large areas for containment of lubricant as well as large trap spaces for loose particles. The helical form of the wire spring bearing provides a pumping action as the cutter rotates on the bearing pin so that lubricant is moved radially along the bearing, and so that the bearing contact areas are constantly changing during such rotation. Also, passages may be provided leading to the lubricant reservoir. Means are provided for preventing rotation of the coil spring with respect to the cone within which it is positioned.
As previously mentioned, the wound wire can have numerous cross-sectional shapes provided that two principal conditions are met: the surface areas thereof which are in actual contact with opposed surfaces of the other bearing member are spaced apart in order to reduce the bearing contact area; and areas or regions are provided between such spaced bearing surface areas for trapping debris particles and for the circulation of a cooling fluid or the presence of lubricant, which could be of the solid form. In general, if one envisions a radial thrust bearing as including a stationary member and a rotating member, with the rotating member having a wound wire form, the rotating member will be in continuous contact with the stationary member at points which an instant before contact were exposed to lubricant. The points of contact on the stationary member are, therefore, continuously changing and moving radially along the stationary member. Such movement of the points of contact allows utilization of the entire bearing surface area of the stationary member and the distribution of wear evenly across its area even though the bearing surface contact area at any instant has been substantially reduced. Another benefit of this wiping action of the rotating member over the stationary member is the displacement or pumping of lubricant which can take place to and from the lubricant reservoir or other parts of a rock bit through suitable lubricant passages. A principal advantage of such lubricant circulation is the reduction of wear and bearing operating temperatures, thereby prolonging the life of a rock bit. Of course the direction of lubricant circulation is determined by the right or left hand winding of the spring coils and by the direction of relative rotation between the bearing members. Moreover it will be recognized that the coiled form of the wire bearing provides a certain amount of self-aligning capability to maintain a substantial contact area and avoid point loads or points of high stress concentration, local high temperatures, and localized wear over the life of the bearing. The inherent flexibility of the coil tends to distribute the load among several separated bearing areas, since each coil turn can be considered to have a degree of freedom for independent motion in the axial and circumferential directions. It also should be noted that since coil springs are readily available and somewhat inexpensive items, the present invention provides a very cost effective bearing structure compared to prior art structures and techniques for making drill bit bearings where special hard metal inlays and hard facings have resulted in higher bit costs.
FIG. 3 is an end view of the bearing pin shown in FIG. 1, with the cone removed.
Referring initially to FIG. 1, the depending arm 10 of a drill bit body has an inwardly extending journal bearing pin 12 formed integrally therewith. A rotary cutter element or cone 13 is rotatably mounted on the bearing pin 12, and has a suitable cutting structure indicated generally at 14 on its outer periphery. The cutting structure 14 can have milled teeth as shown, or tungsten carbide inserts, or any other cutter elements capable of penetrating the rock and making hole as the drill bit is turned on bottom by the drill string. Of course the typical rock bit has a plurality of such arms, pins and cones, however a single assembly has been illustrated for purposes of explaining the structure and operation of the present invention. The cone 13 is retained on the bearing pin 12 by suitable means such as a plurality of balls 15 that are inserted through a ball passageway 16 and into position between opposed annular raceways or grooves 17 and 18 formed in the bearing pin 12 and the cone 13, respectively. A ball plug 19 subsequently inserted into the passageway 16 and secured to the arm 10 functions to retain the balls 15 in the raceways. Of course other means of cone retention may be employed. A passage 20 that leads from a lubricant chamber 21 to the ball passageway 16 enables a supply of lubricant to reach the annular area 22 between the central region 23 of the ball plug 19 and to be communicated past the head 24 of the plug to the various clearances and bearing surfaces between the pin and cone. These passages and a suitable pressure transmitting element (not shown) located in the reservoir 21 and an O-ring seal 55 enable the pressure of the lubricant to be substantially equalized with that of the drilling fluid outside the drill bit body