Efficient degradation of materials is important to a variety of industries including the asphalt, mining, construction, drilling, and excavation industries. In the asphalt industry, pavement may be degraded using picks, and in the mining industry, picks may be used to break minerals and rocks. Picks may also be used when excavating large amounts of hard materials. In asphalt milling, a drum supporting an array of picks may rotate such that the picks engage a paved surface causing it to break up. Examples of degradation assemblies from the prior art are disclosed in U.S. Pat. No. 6,824,225 to Stiffler, US Pub. No. 20050173966 to Mouthaan, U.S. Pat. No. 6,692,083 to Latham, U.S. Pat. No. 6,786,557 to Montgomery, Jr., U.S. Pat. No. 3,830,321 to McKenry et al., US. Pub. No. 20030230926, U.S. Pat. No. 4,932,723 to Mills, US Pub. No. 20020175555 to Merceir, U.S. Pat. No. 6,854,810 to Montgomery, Jr., U.S. Pat. No. 6,851,758 to Beach, which are all herein incorporated by reference for all they contain.
The picks typically have a tungsten carbide tip, which may last less than a day in hard milling operations. Consequently, many efforts have been made to extend the life of these picks. Examples of such efforts are disclosed in U.S. Pat. No. 4,944,559 to Sionnet et al., U.S. Pat. No. 5,837,071 to Andersson et al., U.S. Pat. No. 5,417,475 to Graham et al., U.S. Pat. No. 6,051,079 to Andersson et al., and U.S. Pat. No. 4,725,098 to Beach, U.S. Pat. No. 6,733,087 to Hall et al., U.S. Pat. No. 4,923,511 to Krizan et al., U.S. Pat. No. 5,174,374 to Hailey, and U.S. Pat. No. 6,868,848 to Boland et al., all of which are herein incorporated by reference for all that they disclose.
In one aspect of the invention, a degradation pick comprises a bolster disposed intermediate a shank and an impact tip. The shank comprises an outer diameter and first and second ends. The shank is coupled to the bolster through the first end and the second end is adapted for insertion into a central bore of a holder attached to a driving mechanism. The shank comprises a hollow portion disposed within the outer diameter and between the first and second ends. The hollow portion may comprise an opening that is disposed in the second end. In some embodiments the hollow portion may comprise a length that is at least as great as the outer diameter. The outer diameter may be between 0.5 and 2 inches.
The impact tip of the degradation pick may comprise an impact surface with a hardness greater than 4000 HK. The impact surface may comprise a material selected from the group consisting of diamond, polycrystalline diamond, cubic boron nitride, refractory metal bonded diamond, silicon bonded diamond, layered diamond, infiltrated diamond, thermally stable diamond, natural diamond, vapor deposited diamond, physically deposited diamond, diamond impregnated matrix, diamond impregnated carbide, cemented metal carbide, chromium, titanium, aluminum, tungsten, or combinations thereof.
A steel body may be disposed intermediate the first end of the shank and the bolster of the degradation pick. The steel body may be brazed to the bolster. The bolster may comprise a cemented metal carbide. In some embodiments the bolster may be a carbide core that is press fit into the steel body. Other embodiments may comprise a first end of the shank that is press fit into the bolster. The second end of the shank may be disposed within a central bore of a holder. The central bore may comprise a closed end proximate a driving mechanism.
A lubricant reservoir may be disposed at least partially within the hollow area of the shank of the degradation pick. The lubricant reservoir may be pressurized. The lubricant reservoir may comprise a pressurization mechanism selected from the group consisting of springs, coiled sprigs, foam, closed-cell foam, compressed gas, wave springs, and combinations thereof. An O-ring may be disposed proximate a distal surface of the holder and may substantially retain a lubricant within the holder. The O-ring may be disposed intermediate the bolster and the distal surface. In some embodiments the O-ring may be disposed intermediate the shank and an inner surface of the bore.
The degradation pick may be part of an asphalt milling machine, a trenching machine, a coal mining machine, or combinations thereof.
a is a cross-sectional diagram of an embodiment of a degradation assembly.
Referring now to
Referring now to
As can be seen in
In one aspect the bolster 200 of the degradation pick 101 can comprise tungsten carbide. The bolster 200 may also comprise one or more cemented metal carbides including carbides of tungsten, titanium, tantalum, molybdenum, niobium, cobalt and combinations thereof.
The impact tip 201 of the degradation pick 101 comprises an impact surface 307 with a hardness greater than 4000 HK. The impact surface 307 may comprise a material selected from the group consisting of diamond, polycrystalline diamond, cubic boron nitride, refractory metal bonded diamond, silicon bonded diamond, layered diamond, infiltrated diamond, thermally stable diamond, natural diamond, vapor deposited diamond, physically deposited diamond, diamond impregnated matrix, diamond impregnated carbide, cemented metal carbide, chromium, titanium, aluminum, tungsten, or combinations thereof. In some embodiments the impact surface 307 may be sintered onto a carbide substrate 308. The carbide substrate 308 may be brazed to the bolster 200 with a high-strength braze.
The braze material may comprise a melting temperature from 700 to 1200 degrees Celsius; with one representative embodiment having a melting temperature ranging from about 800 to about 970 degrees Celsius. The braze material may comprise silver, gold, copper nickel, palladium, boron, chromium, silicon, germanium, aluminum, iron, cobalt, manganese, titanium, tin, gallium, vanadium, phosphorus, molybdenum, platinum, or combinations thereof. The braze material may also comprise 30 to 62 weight percent palladium, with one representative embodiment ranging from about 40 to 50 weight percent palladium. Additionally, the braze material may comprise 30 to 60 weight percent nickel, and 3 to 15 weight percent silicon; preferably the braze material may comprise 47.2 weight percent nickel, 46.7 weight percent palladium, and 6.1 weight percent silicon.
Active cooling during brazing may also be utilized during the manufacture of some embodiments, since the heat from brazing may leave some residual stress in the bond between the carbide substrate 308 and the impact surface 307. The farther away the impact surface 307 is from the braze interface, the less thermal damage is likely to occur during brazing. Increasing the distance between the brazing interface and the impact surface 307, however, may increase the moment on the carbide substrate 308 and increase stresses at the brazing interface upon impact.
As further shown in
The shank 202 may comprise a hard material such as steel, hardened steel, or other materials of similar hardness. Furthermore, the material forming the shank 202 may be work-hardened in order to provide resistance to cracking or stress fractures due to forces exerted on the pick 101 by the paved surface 104 or the holder 102. The shank 202 may be work-hardened by shot-peening the shank, chrome plating the shank, enriching the shank with nitrogen and/or carbon, or other methods of work-hardening.
The second end 204 of the shank 202 may be rotatably held in the holder 102 by a retaining ring 310 adapted to fit in an inset portion of the holder 102, such that the degradation pick 101 is allowed to rotate within the holder 102 and the pick 101 and holder 102 may wear generally evenly. Additionally, the first end 203 of the shank 202 may also include one or more recesses or grooves to provide compliance to the first end 203. A sleeve (not shown) may be also disposed loosely around the shank 202 and placed within the holder 102, which may allow the sleeve to retain the shank 202 while still allowing the shank 202 to rotate within the holder 102. In another aspect the shank 202 may also include a spring (not shown) adapted to pull down on the shank 202. This may provide the benefit of keeping the degradation pick 101 snugly secured within the central bore 205 of the holder 102.
A lubricant 311 may be inserted into the central bore 205 of the holder 102 so that the lubricant may be disposed intermediate the outer surfaces of the shank 202 and the inter surfaces of the holder 102. In the illustrated embodiment a lubricant reservoir 312 is disposed entirely within the hollow portion 209 of the shank 202. The lubricant reservoir may comprise a lubricant selected from the group consisting of grease, petroleum products, vegetable oils, mineral oils, graphite, hydrogenated polyolefins, esters, silicone, fluorocarbons, molybdenum disulfide, and combinations thereof. A filling port 313 is disposed proximate the second end 204 of the shank and to allow lubricant 311 to be inserted into the reservoir 312, and can also include a check valve to prevent the lubricant 311 from exiting the reservoir 312 through the second end 204.
In
In the present embodiment the lubricant reservoir 312 includes one or more generally tubular lubricant exit pathways 315 that extend radially outward from the inner diameter 304 to the outer diameter 305. The exit pathways 315 may connect to the central bore 205 at a passage opening 213. The pressure from the pressurization mechanism 314 may force the lubricant 311 through the exit pathways 315 and into a space between the shank 202 and the holder 102. O-rings 207, 208 may be disposed proximate the first and second ends 203, 204 of the shank to form first and second seals 210, 211, respectively. The first and second seals 210, 211 may substantially retain the lubricant 311 between the shank 202 and the holder 102 to decrease friction and allow the pick 101 to rotate more easily. The decreased friction may allow for better wear protection of areas in contact with the holder 102, such as the shank 202 or the base of the bolster 200. An enclosed region 212 may be disposed intermediate the first and second seals 210, 211 and may comprise a volume disposed intermediate the inner surfaces of the holder 102 and the outer surfaces of pick shank 202. In the embodiment illustrated in
Referring now to another representative embodiment of the degradation pick 101a illustrated in
In
When the pressurized lubricant 311 is disposed in the enclosed region 212a, the lubricant 311 may exert pressure on the second seal 211a and the retaining ring 310a. This pressure may exert a force on the degradation pick 101a represented by an arrow 321. The force may pull a lower surface 322 of the pick 101a towards a distal surface 402 of the holder 102a. In some embodiments the pressurized lubricant 311 may maintain substantial contact between the lower surface 322 and the distal surface 402 by maintaining a substantially constant pressure on the retaining ring 310a. The force 321 on the pick 101a may retain the pick 101a in the holder 102a while still allowing the pick 101a to rotate with respect to the holder 102a.
Referring now to
In
As can be seen in
Alternatively, and as shown in the degradation pick 101e of
In the degradation pick 101f illustrated 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 application is a continuation-in-part of application Ser. No. 11/844,586, filed on Aug. 24, 2007, now U.S. Pat. No. 7,600,823, which is a continuation-in-part of application Ser. No. 11/829,761, filed on Jul. 27, 2007, now U.S. Pat. No. 7,722,127, which is a continuation-in-part of application Ser. No. 11/773,271, filed on Jul. 3, 2007, which is a continuation-in-part of application Ser. No. 11/766,903, filed on Jun. 22, 2007, which is a continuation of application Ser. No. 11/766,865, filed on Jun. 22, 2007, which is a continuation-in-part of application Ser. No. 11/742,304, filed on Apr. 30, 2007, now U.S. Pat. No. 7,475,948, which is a continuation of application Ser. No. 11/742,261, filed on Apr. 30, 2007, now U.S. Pat. No. 7,469,971, which is a continuation-in-part of U.S. patent application Ser. No. 11/464,008, filed on Aug. 11, 2006, now U.S. Pat. No. 7,338,135, which is a continuation-in-part of application Ser. No. 11/463,998, filed on Aug. 11, 2006, now U.S. Pat. No. 7,384,105, which is a continuation-in-part of application Ser. No. 11/463,990, filed on Aug. 11, 2006, now U.S. Pat. No. 7,320,505, which is a continuation-in-part of application Ser. No. 11/463,975, filed on Aug. 11, 2006, now U.S. Pat. No. 7,445,294, which is a continuation-in-part of application Ser. No. 11/463,962, filed on Aug. 11, 2006, now U.S. Pat. No. 7,413,256, which is a continuation-in-part of application Ser. No. 11/463,953, filed on Aug. 11, 2006, now U.S. Pat. No. 7,464,993. Said application Ser. No. 11/829,761 is a continuation-in-part of application Ser. No. 11/695,672, filed on Apr. 3, 2007, now U.S. Pat. No. 7,396,086, which is a continuation-in-part of application Ser. No. 11/686,831, filed on Mar. 15, 2007, now U.S. Pat. No. 7,568,770. All of these applications are herein incorporated by reference for all that they contain.
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