Patent Application
20150211365
The present invention relates generally to the degradation of natural and man-made surfaces as is common in such fields as road milling, mining and construction. More particularly, the present invention relates to increasing the wear resistance of degradation picks commonly used in such processes. In road milling, for example, degradation picks may be secured to the exterior of a rotating drum and brought into engagement with a road surface to remove a layer of the surface in preparation for applying a new layer. In another example, degradation picks may be secured to links of a chain and brought into engagement with the wall of a mine to remove earthen materials. Such uses can wear down a degradation pick quickly.
Degradation picks often comprise a steel body comprising an attachment shank at one end and a super hard tip at an opposing end. As the steel body wears it may fail prior to the super hard tip, prematurely ending the life of the pick. Increasing the wear resistance of degradation picks may extend the life of such picks and thus reduce the frequency that such picks need to be replaced during operation.
Wear to the steel body is especially pronounced on surfaces facing a direction of impact. For example, degradation picks secured to the exterior of a rotating drum may tend to wear on surfaces facing the direction of rotation since these surfaces are most likely to impact a surface. Additionally, it is known to secure degradation picks adjacent an edge of a rotating drum at an angle offset from a line perpendicular to an axis of rotation of the rotatable drum. This offset may position a super hard cutter beyond the edge of the rotating drum to clear aggregate from side walls of a cut which have a tendency to collapse. While this offset may provide a cleaner side wall, it may also expose an exterior of the steel body to impact from a road surface without protection from the super hard cutter.
Consequently, numerous attempts have been made to increase the wear resistance of degradation picks.
One such system is disclosed in U.S. Pat. No. 4,682,987 to Brady et al. which shows heavy duty industrial, mining and general purpose cutting tools comprising hard surface coatings comprising nickel-chromium metal alloy powder and a flux, usually boron and/or silicon. The hard surface is applied in slurry form, dried and then fused in a furnace.
Another such system is disclosed by U.S. Pat. No. 4,725,098 to Beach, which describes a rotary cutting bit for use in mining and excavating applications incorporating an annular groove about a head portion of the bit immediately rearwardly of where a hard tip of the bit is seated and a hardfacing material deposited in the groove in the form of an annular ring.
Another such system is disclosed by U.S. Pat. No. 7,300,115 to Holl et al., which describes a chisel holder for a road milling machine or the like, having a base element supporting a holding neck, a protrusion connected to the base element upstream of the holding neck when viewed in an advancing direction of the tool and a chip breaker formed on the base element and extending, starting at the holding neck, at least partially over the protrusion.
The prior art shows some advancements in increasing the wear resistance of degradation picks; however, it is believed that there is still a need to develop improved wear resistance apparatuses.
In one aspect of the present invention, a degradation pick for degrading a surface comprises a substantially conical body with a pointed end. The pointed end may comprise a super hard cutting element to increase durability. The super hard cutting element may comprise sintered polycrystalline diamond attached to a carbide substrate. The substrate may be attached to a bolster, and the bolster may be attached to the pointed end of the substantially conical body. A shank may be attached to the substantially conical body opposite the pointed end. At least one cavity may be disposed on an exterior surface of the substantially conical body between the pointed end and the shank. At least one cutter, also comprising sintered polycrystalline diamond attached to a carbide substrate, may be disposed within the cavity.
In some embodiments, the carbide substrate portion of the at least one cutter is disposed within the at least one cavity. The polycrystalline diamond portion of the cutter may protrude from the cavity. In other embodiments, the polycrystalline diamond portion is disposed outside of the at least one cavity.
In various embodiments, the polycrystalline diamond portion may comprise a substantially conical geometry, hemispherical geometry or cylindrical geometry. In some embodiments, the at least one cutter comprises a central axis perpendicular to the exterior surface of the conical body. The central axis of the at least one cutter may be offset from a central axis of the substantially conical body by 5 to 85 degrees.
In some embodiments, the degradation pick further comprises a plurality of cutters. A combination of the plurality of cutters may form between 1 and 40% of a circumference of the substantially conical body. The plurality of cutters may be equally spaced from the pointed end of the substantially conical body.
In some embodiments, a block with a hole therein may be disposed on a surface of a rotatable drum. The shank of the substantially conical body may be disposed within the hole. The hole may sit at an angle offset from a line perpendicular to an axis of rotation of the rotatable drum and the block may be disposed substantially adjacent an edge of the rotatable drum. The angle of the hole may cause the pointed end of the substantially conical body to overhang the edge of the rotatable drum. The angle of the hole may also cause the at least one cutter to be disposed substantially on a line perpendicular to the axis of rotation of the rotatable drum and passing through the edge of the rotatable drum. The at least one cutter may be disposed along a line perpendicular to an axis of rotation of the rotatable drum and in a direction of rotation.
a and 3b are longitudinal section views of other embodiments of degradation picks comprising at least one cutter disposed within at least one cavity.
a, 4b and 4c are perspective views of embodiments of degradation picks comprising various cutter geometries.
Referring now to the figures,
While the plurality of blocks 110 are generally positioned such that the pointed end 130 may face in a direction of rotation, it is known to position blocks substantially adjacent an edge of a rotatable drum at an angle offset from a line perpendicular to an axis of rotation of the rotatable drum. This configuration, which is shown in the magnified view of
The substantially conical body 125 may be made of steel and consequently wear at a faster rate than the super hard tip 135. This may prematurely limit the useful life of a degradation pick because significant wear may not have occurred at the super hard tip 135 when the steel is in need of replacement. To offset extensive wear to the substantially conical body 125 and thus extend the useful life of a degradation pick, at least one cutter 160 may be disposed within a cavity on an exterior surface of the substantially conical body 125.
Embodiments of the present invention may position the at least one cutter 160 substantially on a line perpendicular to an axis of rotation of the rotatable drum 100, passing through the edge of the rotatable drum 100 and/or in a direction of rotation.
The degradation pick 200 further comprises a shank 240 attached to the substantially conical body 205 opposite the pointed end 210. In the embodiment shown, the shank 240 comprises a substantially circular cross-section. However, in other various embodiments, the shank may also comprise a substantially polygonal cross-section or asymmetrical cross-section.
a discloses another embodiment of a degradation pick 300a comprising at least one cavity 350a disposed on an exterior surface 355a of a substantially conical body 305a between a pointed end 310a and a shank 340a. At least one cutter 360a is disposed within the at least one cavity 350a. As shown in the figure, a central axis of the at least one cutter 360a may be perpendicular to the exterior surface 355a of the substantially conical body 305a. As is also shown in the figure, the central axis of the at least one cutter 360a may also be offset from a central axis of the substantially conical body 305a by 5 to 85 degrees. In this formation, the at least one cutter 360a may shield the substantially conical body 305a from wear during a surface degradation operation. The at least one cutter 360a may be removable and replaceable to prolong the life of the degradation pick.
The at least one cutter 360a may comprise polycrystalline diamond 362a attached to a carbide substrate 367a. The carbide substrate 367a may be disposed within the at least one cavity 350a. In various embodiments, the carbide substrate 367a may be brazed or press-fit within the at least one cavity 350a.
In the embodiment shown, the polycrystalline diamond 362a is protruding from the at least one cavity 350a such that the carbide substrate 367a is completely disposed inside the at least one cavity 350a.
b discloses yet another embodiment of a degradation pick 300b comprising at least one cutter 360b disposed within at least one cavity 350b. In the embodiment shown, polycrystalline diamond 362b forming part of the at least one cutter 360b is completely disposed outside of at least one cavity 350b.
a, 4b and 4c disclose various embodiments of degradation picks 400a, 400b and 400c each comprising a plurality of cutters 460a, 460b and 460c disposed within cavities thereon. While
As shown, the polycrystalline diamond may comprise a substantially hemispherical geometry (as shown in
Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.
This patent application claims priority to U.S. Provisional Pat. App. No. 61/758,345 which is incorporated herein by reference for all that it contains.
