High impact resistant degradation element

In one aspect of the invention, a degradation element includes a substrate bonded to a sintered polycrystalline ceramic. The sintered polycrystalline ceramic has a tapering shape and a rounded apex. The rounded apex has a curvature with a 0.050 to 0.150 inch radius when viewed from a direction normal to a central axis of the degradation element that intersects the curvature. The rounded apex includes the characteristic of when the rounded apex is loaded against a rock formation, the rounded apex fails the rock formation forming a crushed barrier ahead of the rounded apex that shields the rounded apex from a virgin portion of the rock formation while still allowing the rounded apex to penetrate below a surface of the rock formation.

BACKGROUND OF THE INVENTION

The present invention relates generally to a degradation element that may be driven by milling drums, mining drums, drill bits, chains, saws, mills, crushers, impacters, plows, or combination thereof. Specifically, the present invention deals with a degradation element comprising a substrate bonded to a sintered polycrystalline ceramic.

U.S. Patent Publication No. 2004/0065484 to McAlvain, which is herein incorporated for all that it contains, discloses a rotatable point-attack bit retained for rotation in a block bore, and used for impacting, fragmenting and removing material from a mine wall. An improved elongated tool body having at the front end a diamond-coated tungsten carbide wear tip that is rotationally symmetric about its longitudinal axis and contiguous with a second section steel shank at the rear end. The two distinct parts are joined by a high impact resistant braze at ratios that prevent tool breakage. The method of making such a diamond-coated section comprises of 1) placing within a reaction cell, the diamond powder and the carbide substrate and 2) simultaneously subjecting the cell and the contents thereof to temperature and pressure at which the diamond particles are stable and form a uniform polycrystalline diamond surface on the tip of the carbide substrate thus forming a diamond-coated insert providing both cutting edge and steel body protection for increased durability and extended cutting tool life.

U.S. Pat. No. 7,717,523 to Weaver, which is herein incorporated for all that it contains, discloses a cutting pick comprises an elongate shank and a cutting tip mounted to one end of the shank. The cutting tip has a leading end, a trailing end and a mounting portion for mounting to the shank. The tip has a shape such that it diverges outwardly in a direction from the leading end to the trailing end to a portion of maximum diameter. An annular sleeve is attached about the shank adjacent to and in non-contacting relationship with the trailing end of the cutting tip. The maximum diameter of the cutting tip is of greater diameter than the diameter of the inner diameter of the annular sleeve so that the portion of maximum diameter overlies the sleeve radially.

U.S. Pat. No. 6,918,636 to Dawood, which is herein incorporated for all that it contains, discloses the pick includes a radially inner end and a shank to be fixed to the drum to substantially prevent relative movement between the pick and drum. The pick further includes a cutting head having leading and trailing faces intersecting to provide a cutting edge to extend generally parallel to an axis. The leading face in use is inclined by an acute rake angle R to a radius of the axis, with the trailing face being inclined at an acute back clearance angle B to a plane passing through the edge and normal to the radius. The leading face and trailing face being inclined by an acute angle and the shanks when fixed to the drum extends at an acute angle to the radius.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, a degradation element includes a substrate bonded to a sintered polycrystalline ceramic. The sintered polycrystalline ceramic may comprise diamond. The sintered polycrystalline ceramic may have a metal catalyst concentration of less than eight percent and ninety five percent of the interstitial voids comprise a metal catalyst. In some embodiments, the sintered polycrystalline ceramic comprises cubic boron nitride.

The polycrystalline ceramic has a tapering shape and a rounded apex. The rounded apex has a curvature with a 0.050 to 0.150 inch radius when viewed from a direction normal to a central axis of the degradation element that intersects the curvature.

In some embodiments, the sintered polycrystalline ceramic is partitioned by a transition from the tapered shape to the rounded apex. The rounded apex may have a surface area of 0.0046 in2to 0.0583 in2.

The rounded apex may comprise the characteristic of when the rounded apex is loaded against a rock formation the rounded apex fails the rock formation forming a crushed barrier ahead of the rounded apex that shields the rounded apex from a virgin portion of the rock formation while still allowing the rounded apex to penetrate below a surface of the rock formation.

The degradation element may comprise the characteristic that when the rounded apex is loaded against the rock formation along the central axis with 2,000 pounds of load into a rock formation comprising an unconfined compressive strength of 23,000 pounds per square inch (psi), the degradation element indents into the formation 0.018 to 0.026 inches and forms a 0.046 to 0.064 inch deep crater. In this embodiment the rock formation may be Terra Tek Sandstone.

In some embodiments, the degradation element comprises an additional characteristic of when the rounded apex is loaded against the rock formation at a non-vertical angle, the tapering shape is configured to wedge out fragments of the rock formation outside of the crushed barrier.

In some embodiments, the rounded apex is configured to compressively load the crushed barrier and the rock formation. The tapered shape may be configured to wedge up fragments of the rock formation thereby creating a tensile load between the crushed barrier and the surface of the formation.

The degradation element may comprise the characteristic that the degradation element is loaded against the rock formation along the central axis of the degradation element. The degradation element may be configured to be driven by a driving mechanism. The driving mechanism may be a rotary degradation drum; however, the driving mechanism may be a drill bit or a chain.

In some embodiments, the substrate comprises a first attachment end configured for attachment to the sintered polycrystalline ceramic and a second end configured for attachment to a degradation tool. The degradation element and the degradation tool may be rotationally fixed with respect to one another.

FIG. 1discloses an embodiment of a machine100, such as a milling machine. The machine has a forward end101and a rearward end102. An excavation chamber110is attached to the underside103of the machine's frame. The excavation chamber110is formed by a front plate104, side plates105, and a moldboard106. The excavation chamber110encloses a driving mechanism120, which is supported by the side plates. A conveyor107is also supported by the machine. An intake end108of the conveyor enters the excavation chamber110through an opening formed in the excavation chamber110, usually formed in the front plate104, but the opening may be formed in any portion of the excavation chamber110. The driving mechanism120is configured to drop aggregate onto the conveyor proximate its intake end. The conveyor transports the aggregate from the intake end to the output end109.

FIG. 2discloses the driving mechanism120. A degradation element200may be configured to be driven by the driving mechanism120. The degradation element200may be configured to be driven into a rock formation210. The rock formation210may have a compressive strength that resists the degradation element200from failing the rock formation210. The degradation element200may be configured to be driven with a load sufficient to fail the rock formation210. In this embodiment, the degradation element200is configured to be driven by a rotary degradation drum. The rotary degradation drum may be a milling drum.

In some embodiments, the driving mechanism120may be a trenching drum, a trenching chain, a hammer mill, a jaw crusher, a cone crusher, an indenter, an impacter, a excavator bucket, a backhoe, a plow, chisels, or combinations thereof.

FIG. 3adiscloses a degradation tool350and the degradation element200. The degradation element may comprise a polycrystalline ceramic302. The polycrystalline ceramic may have a tapered shape310and a rounded apex311. The degradation element may also comprise a substrate301. The substrate301may comprise a first attachment end340configured for attachment to the sintered polycrystalline ceramic302and a second attachment end341configured for attachment to the degradation tool350. The degradation tool350may comprise a shank351connected to a body352. The degradation element200may be attached to the body352of the degradation tool to form a tip. The degradation element200and the degradation tool350may be rotationally fixed with respect to one another.

FIG. 3bdiscloses the degradation element200. The degradation element200may comprise the substrate301bonded to the sintered polycrystalline ceramic302. The substrate301and the sintered polycrystalline ceramic302may be processed together in a high-pressure, high temperature press. In this embodiment, the sintered polycrystalline ceramic302comprises diamond. In some embodiments the sintered polycrystalline ceramic302comprises cubic boron nitride.

The sintered polycrystalline ceramic302may comprise a metal catalyst concentration of less than eight percent and at least ninety five percent of the interstitial voids comprise a metal catalyst. The metal catalyst may have a greater coefficient of thermal expansion than the ceramic302, so when the ceramic302is subjected to high heat, the heat may cause the metal catalyst to expand faster than the ceramic302, thereby, breaking bonds within and weakening the sintered polycrystalline ceramic302. The sintered polycrystalline ceramic302can also be also weakened by a greater concentration of interstitial voids. Thus, the sintered polycrystalline ceramic302of the present invention, is stronger because of the reduced interstitial voids in the sintered polycrystalline ceramic302.

In some embodiments, the degradation element may have a central axis315that intersects the rounded apex311. Viewing the degradation element200from a direction normal to the central axis315, the tapered shape310may have an outer sidewall320and the rounded apex311may have a curvature321. The curvature321of the rounded apex311may have a 0.050 inch to 0.150 inch radius of curvature. The radius of curvature may be uniform along the curvature321; however, in some embodiment the radius of curvature may vary along the curvature321. Segments of the curvature321may have a radius of curvature greater than 0.150 inches and/or less than 0.050 inches.

In some embodiments, the sintered polycrystalline ceramic302is partitioned by a transition330from the tapered shape310to the rounded apex311. The rounded apex311may have a surface area of 0.0046 in2to 0.0583 in2.

The tapered shape may be a conical shape. The conical shape may have a base radius360that is proximate the substrate301and a tip radius361that is proximate the transition330from the tapered shape310to the rounded apex311. The base radius360may be larger than the tip radius361. In some embodiments, the tapered shape310may comprise a concave shape, a convex shape, a chisel shape, or a combination thereof. Several shapes that may be compatible with the present invention are disclosed in U.S. patent application Ser. No. 12/828,287, which is herein incorporated by reference for all that it discloses. In the preferred embodiment, the tapered shape310is symmetric with respect to the central axis315; however, the tapered shape310may be asymmetric with respect to the central axis315. The chisel shape may be asymmetric with respect to the central axis315.

FIG. 4discloses the degradation element200engaging a rock formation210. The rounded apex311may comprise the characteristic of when the rounded apex311is loaded against a rock formation210, the rounded apex311fails the rock formation210by forming a crushed barrier401ahead of the rounded apex311that shields the rounded apex311from a virgin portion402of the rock formation while still allowing the rounded apex311to penetrate below a surface403of the rock formation.

The virgin portion402of the rock formation may require a specific amount of load to fail. Forces from the load that act on the rock formation210may also act on the rounded apex311. Because the specific geometry of the rounded apex is critical for achieving the best results, protecting the rounded apex from wear may prolong the effective life of the tip. The forces that may wear, and therefore, change the shape of the rounded apex may include impact forces, compressive forces, and abrasive forces. When the polycrystalline ceramic comprises a low metal catalyst and few empty interstitial voids as described above, the tip is well suited to handle both the impact and compressive loads. Thus, the ceramic is more susceptible to abrasive wear. So, when the tip comprises a curvature that is blunt enough to crush the formation ahead of itself, but the apex radius also has a minimal surface area as described above, the tip may penetrate deeply into the formation and still form a crushed zone or barrier401ahead of the tip. The crushed barrier shields the rounded apex311from the abrasive force of the virgin portion402of the rock formation. Testing has shown that the abrasive loads from the virgin rock cause less wear to the rounded apex than wear from the crushed barrier. Thus, the crushed barrier serves to preserve/shield the curvature of the apex from wearing which continues to allow the tip to penetrate and crush simultaneously.

In some embodiments, the degradation element200may comprise the characteristic that the degradation element200is loaded against the rock formation210along the central axis315of the degradation element200. The load may be transferred from the degradation element200to the rock formation210substantially through the rounded apex311in such a manner that the rounded apex311penetrates into the surface403of the rock formation. The geometry of the rounded apex311may be configured to compressively fail the rock formation210immediately ahead of the rounded apex311forming a crushed barrier401that shields the rounded apex311from the virgin portion402of the rock formation.

In some embodiments, the degradation element200may comprise an additional characteristic of when the rounded apex311is loaded against the rock formation210at a non-vertical angle, the tapering shape310is configured to wedge out fragments405of the rock formation outside of the crushed barrier401. The tapered shape310may be configured to push the fragments405out of the rock formation210in a direction substantially perpendicular to the surface403of the rock formation.

In some embodiments, the rounded apex311is configured to compressively load the crushed barrier401and the rock formation210. The tapered shape310may be configured to wedge up fragments405of the rock formation thereby creating a tensile load between the crushed barrier401and the surface403of the formation.

FIG. 5discloses the degradation element200engaging a sandstone rock formation500. The degradation element200may comprise the characteristic that when the rounded apex311is loaded against the sandstone rock formation500along the central axis315with 2,000 pounds of load into the sandstone rock formation500comprising an unconfined compressive strength of 23,000 pounds per square inch (psi), the degradation element200indents into the sandstone rock formation 0.018 to 0.026 inches and forms a 0.046 to 0.064 inch deep crater510. In this embodiment, the sandstone rock formation500may be Sandstone. The indention may be a depth520that the degradation element penetrates into the rock formation. The crater depth521may be the sum of the indention depth and a depth of the crushed barrier.

FIG. 6discloses a drill bit600. In some embodiments, the driving mechanism120is a drill bit600. The degradation element200may be configured to be driven by the drill bit600into the rock formation. The drill bit600may be a roller cone bit, a fixed bladed bit, a waterwell bit, a horizontal bit, a percussion drill bit, or combinations thereof.

FIG. 7discloses another embodiment of a machine100, such as a long wall miner. The machine100may comprise a main frame701on endless tracks702. A conveyor703may be attached to the main frame701. The conveyor703may be configured to transport aggregate away from the excavation site. A moveable arm705may be attached to the main frame701. The movable arm705may move along a track706that runs substantially parallel to the front side of the machine100. The driving mechanism120may be supported by the movable arm705. The driving mechanism120may be guided by the movable arm705to engage the rock formation210in a lateral direction with respect to the main frame701. The driving mechanism120may be an excavation drum.

FIG. 8discloses another embodiment of a machine100, such as a continuous miner. The machine100may comprise a main frame801on continuous tracks802. A turret803may be attached to the topside804of the main frame801. A pair of forwardly directed loading arms805may be attached to the turret803. The driving mechanism120may be supported by the loading arms805. The loading arms805may be configured to lift and lower the driving mechanism120. The driving mechanism120may be a chain. The degradation element200may be configured to be driven by the chain. In some embodiments the driving mechanism120is an excavation drum.