Boring or penetrating the earth – Bit or bit element – Rolling cutter bit or rolling cutter bit element
Reexamination Certificate
2000-09-18
2002-06-18
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Rolling cutter bit or rolling cutter bit element
C175S227000, C384S093000
Reexamination Certificate
active
06405811
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to earth boring bits of the rolling cutter variety. More specifically, the present invention relates to the lubrication of the bearing surfaces of air cooled rolling cutter bits for mining applications, principally drilling blast holes for recovery of minerals.
2. Description of the Related Art
The original rolling-cone rock bit was invented by Howard R. Hughes, U.S. Pat. No. 939,759, and drilled through the hard caprock at the Spindletop field near Beaumont, Texas with relative ease. Since that initial discovery, the rolling-cone rock bit has been widely used and refined by the oil and gas industry.
Earth-boring or rock bits of the rolling-cutter variety are also useful in penetrating earthen formation for purposes other than the production of petroleum. These applications are generally referred to as “mining” applications. A principal application for mining bits is the drilling of blast holes. Blast holes are relatively shallow holes (compared to those drilled for the production of petroleum) in the earth that are used for a variety of purposes, but primarily to insert explosives into the earth for opening subterranean mine cavities.
While petroleum production holes are typically filled with drilling mud during drilling, blast holes use air to accomplish many of the same goals. The air is pumped down the drill pipe into the bit, and returns along the space between the pipe and the hole to the top of the hole. A bit will typically have nozzles that direct the air out of the bit towards the earth being broken up by the cutters so that the debris may be carried up by the air flow to the top of the hole. The bit may also direct some of the air into internal passages to cool the frictional surfaces that are damaged by the extreme heat developed by the drilling action.
Snyder, et al (U.S. Pat. No. 3,820,612) discloses a method for lubricating the bearing surfaces between the cutters and the journal bearings of a typical roller-cone bit. Snyder discloses the introduction of a mixture of water and lubricating additives into the air stream at the top of the hole. As the air travels down the drill pipe and through the internal passages of the bit the air not only cools the bit, it also deposits the lubricating additive thus prolonging bit life. This requires the expensive addition of a water pump and a means for metering out the appropriate amount of water and lubricant to lubricate the bit without clogging up the hole.
Pastusek (U.S. Pat. No. 4,381,824) discloses the use of solid lubricant mounted in the cutter and journal bearing of the bit such that the lubricant is biased into contact with the wear surfaces. The lubricant is biased, using either a spring or air pressure, into the bearing surfaces where the journal and the cone meet. As the lubricant is worn down, the biasing means provides continuous feed of the lubricant. The lubricants disclosed for this use are soft metals such as silver, lead, copper, indium, and tin.
Parish (U.S. Pat. No. 4,386,668) discloses a bit with a liquid lubricant reservoir within the bit wherein the liquid lubricant is pressurized by the compressed air coming down the drill pipe via a piston. There is also a means for releasing excess pressure when the temperatures rise inside the bit and cause the liquid lubricant to expand beyond a predetermined limit. This system requires that the bearing surfaces lubricated by the liquid be sealed from the other bearing surfaces so that the liquid is not simply released into the hole.
BRIEF SUMMARY OF THE INVENTION
A solid lubricant is added to the internal passages of an air cooled bit such that the compressed air erodes the lubricant into the air stream, which then passes through the bearing surfaces between the cutter and the journal. The air stream, laden with ablated solid lubricant particles, both cools the surfaces and deposits the solid lubricant to reduce the friction between these surfaces.
REFERENCES:
patent: 1017935 (1912-02-01), Watres
patent: 3820612 (1974-06-01), Snyder et al.
patent: 4381824 (1983-05-01), Pastusek
patent: 4386668 (1983-06-01), Parish
patent: 4412590 (1983-11-01), Daly
patent: 4428442 (1984-01-01), Steinke
patent: 4805709 (1989-02-01), Johnsey et al.
patent: 5881829 (1999-03-01), Dimond et al.
Bagnell David
Baker Hughes Corporation
Bracewell & Patterson L.L.P.
Halford Brian
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