Pick with Threaded Shank
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, or within a holder secured within the block.
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.
BRIEF SUMMARY OF THE INVENTIONIn 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.
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.
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.
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.
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.
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.
Claims
1. A degradation assembly, comprising:
- a block secured to a surface; and
- a pick comprising a working end and a shank,
- wherein the shank comprises a continuous external circumference and a shank thread form configured to secure the shank within the block.
2. The assembly of claim 1, wherein the shank comprises an outer surface and the shank thread form is disposed on the outer surface.
3. The assembly of claim 1, wherein the block comprises a bore there through.
4. The assembly of claim 3, wherein the block comprises a block thread form disposed within the bore and the shank thread form is configured to mate with the block thread form.
5. The assembly of claim 4, wherein the shank thread form comprises a buffer pad configured to clean the block thread form as the shank thread form is mated with the block thread form.
6. The assembly of claim 4, wherein the shank thread form and the block thread form are collectively configured to prevent the pick from rotating within the block while in operation.
7. The assembly of claim 4, wherein the shank thread form and the block thread form are collectively configured to tighten due to impacts on the working end while in operation.
8. The assembly of claim 1, wherein the shank comprises a solid cross-section.
9. The assembly of claim 1, wherein the working end comprises a tip comprising a superhard material.
10. The assembly of claim 1, wherein the shank comprises a tapered section configured to taper toward a bottom portion opposite of the working end.
11. The assembly of claim 10, wherein the tapered section is formed between the shank thread form and the working end, and the tapered section is configured to provide an interference fit between the shank and the block.
12. The assembly of claim 10, wherein the shank thread form is disposed on the tapered section.
13. The assembly of claim 10, wherein the tapered section is configured to resist a majority of the working torque between the pick and the block while in operation.
14. The assembly of claim 1, wherein the pick comprises a reduced cross-section between the shank and the working end providing a predetermined area of failure.
15. The assembly of claim 1, wherein the shank is hollow.
16. The assembly of claim 15, wherein the shank thread form is disposed on an internal surface of the shank.
17. The assembly of claim 16, wherein the shank thread form tapers inwardly towards the working end.
18. A degradation assembly, comprising:
- a block secured to a surface;
- a holder secured within the block; and
- a pick comprising a working end and a shank,
- wherein the shank comprises a continuous external circumference and a shank thread form configured to secure the shank within the holder.
19. The assembly of claim 18, wherein the holder comprises a bore there through.
20. The assembly of claim 18, wherein the holder is secured within the block by an interference fit or spring clamp.
Type: Application
Filed: Jan 17, 2012
Publication Date: Jul 18, 2013
Inventors: David R. Hall (Provo, UT), Gary Peterson (Provo, UT), Jeff Jepson (Spanish Fork, UT), Ronald B. Crockett (Payson, UT)
Application Number: 13/351,414
International Classification: E21C 35/19 (20060101); E21C 35/197 (20060101); E21C 35/18 (20060101);