Patent Application
20130181501
The present invention relates to picks or bits used to degrade surfaces, specifically to picks or bits used in mining, trenching and road milling operations. It was formerly believed that allowing a pick to rotate within a block may be beneficial in that it may result in a more even wear on the pick rather than having the wear concentrated on one side. To protect the block from wear due to the rotating pick, a bit holder or sleeve was sometimes disposed between the pick and the block. For example, U.S. Pat. No. 5,098,167 to Latham, which is herein incorporated by reference for all that it contains, discloses a sleeve containing a bit for use on a roadway surface reclaiming machine in a removable manner which aids in protecting the block from abrasion. To decrease abrasion between the confronting surfaces of the block and the sleeve, and to increase the useful life of the pick, the sleeve may be threaded into the block in such a manner that contact by abrasive material with the sleeve tightens the connection between the block and the sleeve.
It has since been discovered that diamond enhanced picks may last longer despite uneven wear when non-rotatable. U.S. Pat. Pub. No. 2009/0273225 to Hall et al., which is herein incorporated by reference for all that it contains, discloses a pick shank press fit within a bore of a pick holder. The pick may comprise a diamond enhanced tip and may be rotationally fixed within a bore of the holder. The shank may comprise at least one longitudinal slot extending along the shank from a distal end of the shank. The slot allows the shank to resiliently collapse upon insertion into the bore while still allowing the shank to maintain a press fit while within the bore.
Despite the advancements as shown in the prior art, it is believed that there is still a need to develop better means to rotationally secure picks or bits.
In one aspect of the present invention, a degradation assembly may comprise a block secured to a surface. The degradation assembly may also comprise a pick comprising a working end and a shank. The shank may comprise a continuous external circumference and a shank thread form configured to secure the shank within the block. The shank thread form may be disposed on an outer surface of the shank.
The block may comprise a bore there through. A block thread form may be disposed within the bore and may be configured to mate with the shank thread form. The shank thread form may also comprise a buffer pad configured to clean the block thread form as the shank thread form is mated with the block thread form. The shank thread form and the block thread form may be collectively configured to prevent the pick from rotating within the block while in operation or to tighten due to impacts on the working end while in operation.
The shank may comprise a solid cross-section or the shank may be hollow. When hollow, the shank thread form may be disposed on an internal surface of the shank. In this embodiment, the shank thread form may taper inwardly towards the working end.
The shank may comprise a tapered section. The tapered section may be formed between the shank thread form and the working end and the tapered section may be configured to provide an interference fit between the shank and the block. The shank thread form may be disposed on the tapered section. The tapered section may be configured to resist a majority of the working torque between the pick and the block while in operation. The working end may comprise a tip comprising a superhard material.
The pick may comprise a reduced cross-section between the shank and the working end to provide a predetermined area of failure.
In another aspect of the present invention, a degradation assembly may comprise a block secured to a surface, a holder secured within the block, and a pick comprising a working end and a shank. The shank may comprise a continuous external circumference and the shank thread form may be configured to secure the shank within the holder. In this embodiment, the holder may comprise a bore there through. The holder may be secured within the block by an interference fit or spring clamp.
The accompanying figures further describe the invention.
a is a perspective view of an embodiment of a pick.
b is a cross-sectional view of an embodiment of a pick secured in a block.
a is a perspective view of an embodiment of a pick with a tapered shank.
b is a cross-sectional view of an embodiment of a pick with a tapered shank secured in a block.
a is a perspective view of another embodiment of a pick with a tapered shank.
b is a cross-sectional view of another embodiment of a pick with a tapered shank secured in a block.
a is a cross-sectional view of an embodiment of a pick with a hollow shank.
b is a cross-sectional view of an embodiment of a pick with a hollow shank secured in a block.
a is a perspective view of another embodiment of a pick and holder.
b is a cross-sectional view of an embodiment of a pick and a holder secured in a block.
Referring now to the figures,
The road milling machine 101 may comprise a degradation drum 104. The degradation drum 104 may comprise a plurality of blocks 105 secured to its outer surface. A pick 106 may be secured within each block 105. During normal operation, the degradation drum 104 may rotate causing the picks 106 to engage and degrade the formation 102. In other embodiments of the present invention, blocks may be secured to surfaces of drums, chains, or other moving parts of mining, trenching or road milling machines to cause picks to engage and degrade formations of all types. In some embodiments, each pick may be disposed within a holder, and a holder may be secured within each block.
a discloses an embodiment of a pick 201. The pick 201 may comprise a pick body 204 in between a working end 206 and a shank 202. The working end 206 may directly engage a formation. The working end 206 may comprise a substantially conical shape and a tip 211. The tip 211 may comprise a superhard material selected to reduce wear and extend service life. The superhard material may comprise natural diamond, synthetic diamond, polycrystalline diamond, vapor deposited diamond, cubic boron nitride, diamond impregnated matrix, diamond impregnated carbide, silicon carbide, other superhard material known in the art, or combinations thereof.
The shank 202 may comprise a bottom portion 210. The bottom portion 210 may comprise a continuous external circumference. The shank 202 may comprise a solid cross-section (as shown in this embodiment) or the shank 202 may be hollow. It is believed that a shank 202 comprising a continuous external circumference and solid cross-section may be able to withstand a large amount of load and/or torque without substantially deforming. A shank thread form 205 may be disposed on an outer surface of the shank 202.
b discloses a cross-sectional view of the pick 201 (as shown in
In some embodiments, the shank thread form 205 and the block thread form 209 may be collectively configured to prevent the pick 201 from rotating within the block 207 while in operation. Because the pick 201 may be configured to not rotate within the block 207, due to the nature of thread forms the pick 201 may be also axially fixed within the block 207. In other embodiments, the shank thread form 205 and the block thread form 209 may be collectively configured to tighten due to impacts on the working end 206 while in operation. This may be accomplished by offsetting the position of the working end 206 from a direction of impact such that each impact applies torque to the pick 201 and manufacturing the shank thread form 205 either right-handed or left-handed based on which direction it is offset.
This embodiment further comprises a buffer pad 212 disposed on the shank thread form 205. The buffer pad 212 may clean the mating block thread form 209 as the thread forms rotate with respect to each other. By keeping the thread forms clean, a more secure fit may be possible.
a discloses an embodiment of a pick 301 with a shank 302 comprising a tapered section 303. A pick body 304 may be disposed between a working end 311 and the shank 302. The tapered section 303 may be configured to taper towards a bottom portion 310 opposite of the working end 311. A shank thread form 305 may be disposed on at least a portion of the tapered section 303.
b discloses a cross-sectional view of the pick 301 (as shown in
a discloses another embodiment of a pick 401 comprising a shank 402 and a tapered section 403. A pick body 404 may comprise a substantially larger cross-section than a working end 406 and the shank 402. The tapered section 403 may be configured to taper towards a bottom portion 410 and begin tapering from the largest cross-section of the pick body 404.
b discloses a cross-sectional view of the pick 401 (as shown in
In some embodiments, the pick 401 may comprise a reduced cross-section 413 disposed between the shank 402 and the working end 406. The reduced cross-section 413 may be configured to provide a predetermined area of failure. During working operations that may cause damage to the shank thread form 405, the working end 406 may break-off at the reduced cross-section 413. As the working end 406 breaks off, the pick 401 may no longer engage the formation and the stress on the shank thread form 405 may be relieved.
b also comprises an inset disclosing an embodiment of the shank thread form 405. In the embodiment shown, the shank thread form 405 is a trapezoidal thread form and may comprise a plurality of crests 414, roots 415, flanks 416 and pitches 417. The shank thread form 405 may comprise an angle 418 intermediate adjacent flanks 416. It is desirable that the angle 418 be sufficiently large that substantially all aggregate fall out and not get stuck within the shank thread form 405.
a discloses an embodiment of a pick 501 comprising a working end 506 and a shank 502 wherein the shank 502 is hollow. The shank 502 may comprise an internal surface 519 and a shank thread form 505 may be disposed on the internal surface 519.
b discloses a cross-sectional view of the pick 501 (as shown in
a discloses an alternative embodiment of a pick 901 comprising a shank 902 with a shank thread form 905. The pick 901 may be secured into a pick holder 920.
b discloses a cross-sectional view of the pick 901 (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.
