Patent Application
20070272447
Referring to
Cones 11, 13 and 15 have a plurality of rows of cutting elements, which in this example comprise tungsten carbide inserts pressed into holes drilled in the metal of the cone body. Alternately, the cutting elements could comprise teeth machined in the exterior of the cone body. In the example of
First cone 11 also has a plurality of heel row inserts 19, which are located in a heel area adjoining the gage surface. One of the cones 11, 13, 15 will be provided with the maximum number of heel row inserts, which in this example, comprises heel row 19 of first cone 11. Heel row inserts 19 must have adequate supporting metal of the cone body between each insert 19. The supporting metal and the diameter of the barrel of each insert 19 determine the number of heel row inserts 19 that can be mounted on first cone 11. In this example, there are seventeen heel row inserts 19, but that number can vary.
First cone 11 has an adjacent row 21 of inserts, which is the closest row to the inserts of heel row 19. In this example, each portion of each adjacent row insert 21 is closer to bit axis 12 than any portion of heel row inserts 19. That is, they do not superimpose or overlap each other when rotated into a single sectional plane, as shown in
Like first cone 11, second cone 13 has two rows of gage inserts 27 that are staggered, but that arrangement could vary. Second cone 13 has a plurality of heel row inserts 29 and a plurality of adjacent row inserts 31. In this invention, since first cone 11 was selected to have the maximum number of heel row inserts, either second cone 13 or third cone 15 will be selected to have an adjacent row of inserts with 90% or more of the same number of inserts as first cone heel row 19. In this example, second cone 13 has that row of adjacent inserts 31. Also, second cone adjacent row inserts 31 may have the same diameter and cutting end protrusion as first cone heel row inserts 19.
Adjacent row 31 of second cone 13 is spaced much closer to its heel row 29 than adjacent row 21 is spaced to its heel row 19 of first cone 11. Preferably, second cone heel row inserts 29 and adjacent row inserts 31 are staggered relative to each other, with each adjacent row insert 31 being circumferentially between and farther inward than two of the heel row inserts 29. When rotated into a single plane as shown in
In order to provide adequate support metal for the large number of adjacent row inserts 31, in addition to the staggering, the size of heel row inserts 29 is considerably less than the size of adjacent row inserts 31. The diameters as well as the cutting ends of heel row inserts 29 are less than the diameter and cutting end protrusion of adjacent row inserts 31. Because second cone heel row inserts 29 and adjacent row inserts 31 are staggered, they normally have equal numbers. Second cone 13 also has inner row inserts 33 and one or more nose inserts 35. Inner row inserts 33 are located between adjacent row inserts 21 and inner row inserts 23 of first cone 11.
Third cone 15 has gage surface inserts 37 , which in this example, are located in a single row. In addition, third cone 15 is configured to reduce tracking occurring between first cone heel row inserts 19, second cone heel row inserts 29 and third cone heel row inserts 39. The heel rows 19, 29 and 39 are all at the same distance from bit axis 12 in this embodiment. The number of first cone heel row inserts 19 and second cone heel row inserts 29 is either the same or within 90% of the same as mentioned, thus tracking could occur. To reduce tracking, third cone heel row 39 is provided with a substantially different pitch or distance between axes of inserts than the pitches of first cone heel row inserts 19 and second cone heel row inserts 29. The pitches in heel rows 19 and 29 do not differ significantly, and the pitch in first cone heel row 19 is a minimum amount possible, given the diameter and size of heel row inserts 19. Consequently, the pitch in third cone heel row 39 is made considerably larger, preferably 20 to 50% greater. In this example, there are only fourteen heel row inserts 39, versus seventeen heel row inserts 19 and sixteen heel row inserts 29. Stated another way, there are at least 20 to 50% more inserts in first cone heel row 19 than in third cone heel row 39. In this example, the difference is three divided by fourteen, which is 21.5% more.
In this example, third cone 15 has adjacent row inserts 41 that are staggered with heel row inserts 39 to enhance durability. The innermost portion of each heel row insert 39 is closer to bit axis 12 than the outermost portion of each adjacent row insert 41, creating an overlapping portion as shown in
Adjacent row inserts 41 may have the same diameter and cutting end protrusion as second cone adjacent row inserts 31 and first cone adjacent row inserts 21, and thus, they will also have a pitch that is 20-50% greater than between adjacent row inserts 31 of second cone 13. As shown in
When designing the cutting structure in accordance with this invention, the designer first selects one of the cones 11, 13, 15 to have a maximum number of heel row inserts given a desired protrusion and barrel diameter. In this embodiment, as mentioned, first cone 11 has the maximum number of heel row inserts in its heel row 19. The designer then selects another cone to have adjacent row inserts that are the same size and have at least 90% as many inserts as the maximum heel row 19. In this example, second cone 13 was provided with only one less adjacent row insert 31 than first cone heel row inserts 19. The designer then staggers heel row 29 on second cone 13 with adjacent row inserts 31. In order to provide supporting metal, heel row inserts 29 may be of smaller diameter and may have smaller cutting end protrusion than adjacent row inserts 31.
The designer then designs the third cone to break up tracking in the heel rows of the other cones. The designer does this by use of a third cone heel row 39 having a pitch 20-50% greater than the pitches of first cone heel row 19. In this example, heel row 39 has 21.4% fewer inserts than first cone heel row 19. Adjacent row 41 is staggered with heel row inserts 39, and therefore has also a greater pitch than adjacent row 31, thus breaking up tracking in the adjacent rows 31, 41.
The invention has significant advantages. Increasing the pitch in one of the heel rows resists tracking in the heel row and in one of the adjacent rows resists tracking in the adjacent rows. Providing at least 90 percent as many adjacent row cutting elements as the maximum number in the heel row provides durability for the adjacent row and resists ridge buildup.
While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. For example, although only cones with tungsten carbide inserts as cutting elements are shown, the cones could have cutting elements that comprise teeth machined from the body of the cone.
This claims priority to provisional application 60/808,874, filed May 26, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60808874 | May 2006 | US |
