JPH0258433B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to an underground drilling drill bit, and more particularly to an arrangement of cutting elements thereof. The most common type of underground drill bit for oil and gas wells is a cutter that rotates about an axis and rolls around the bottom of the wellbore along its path or cut as the bit rotates. . The stub has several rows of teeth that cut through the strata due to the force applied to the stub. The teeth are spaced apart in several rows, and are spaced so that as much soil as possible at the bottom of the borehole is scraped away by one rotation. The conventional underground drill bit is
It includes various features designed to avoid the problem known as "tracking." This tracking problem occurs when the teeth are spaced apart on a rotatable cutter such that each tooth repeatedly passes through the imprint made in the soil by the previous tooth. Therefore, ridges and peaks may be formed in the soil.
As a result, the cutter has its wear and tear accelerated. Each tooth is therefore worn prematurely and unevenly. In bits equipped with hard metal insert teeth that are held in a tight fit within the drilled hole, the supporting metal may wear early in the morning, causing the insert to fall out. A solution to this tracking was introduced on April 10, 1973.
U.S. Patent No. RCOPessier granted on the date
No. 3,726,350 and U.S. patent application Ser. Another solution to the tracking problem is proposed in US Pat. No. 4,187,922, issued to FFPhelps on February 12, 1980. In the invention described above, the inserts are arranged in annular rows and the spacing between each insert is varied to prevent tracking from occurring. In these prior art inserts are arranged in groups, in one group each insert is similarly partitioned, while in other groups the inserts are spaced differently. or the spacing of the inserts in each row is such that the spacing gradually increases from the minimum to the maximum and decreases to the minimum, or the inserts of each pair are spaced apart from each other in the row. The spacing of the inserts is varied in each row so that they are separated by a different spacing than the spacing between all other pairs of inserts. In each of the prior art solutions mentioned above, the inserts are arranged in an annular row.
Each row is separated by a minimum spacing to provide sufficient support metal for the insert. To prevent furrows from forming between each row, one other vine placed in the same cut or path is placed in a staggered pattern to remove soil in areas where furrows would otherwise form. It has columns. Another method is to position the cutter itself offset from the other cutters within the cut, as described in the aforementioned US patent application Ser. No. 043,533. In this case, the bit may rotate off center, which means that the axis of rotation of the bit is displaced from the central axis of the borehole during drilling. One result of such a phenomenon is that ridges also develop between alternating rows of the various cutters. In prior art cutters there are regions with overlapping rows of rings without any space between them. The aforementioned U.S. Patent No.
No. 3,726,350, the cutter has rows of insert halves that are offset from each other. U.S. Pat. No. 2,774,571 discloses the use of the inner end or nose region of each cutter in which inserts are thus arranged. Also, in U.S. Pat. No. 2,230,569, a number of arrangements for cutters with milled teeth, such as a spiral row of teeth, are described. Vertical shaft cutters having spiral rows are also conventionally used. The teeth or inserts are all arranged in several rows in the prior art. The rows may extend circumferentially or perpendicular to the axis of the cutter, with each insert within the row extending only partially around the cutter. It may be. The rows may be parallel to the axis of the cutter or may be spiral as described above. However, all these insert arrangements cannot completely eliminate tracking problems,
Furthermore, it is not possible to completely cover the bottom of one cut with one cutter. The object of the present invention is to have inserts distributed on the surface of the cutter so that only one cutter is used in a selected cut, and the cutting elements are balanced so that the rock can be fractured more efficiently. An object of the present invention is to provide an underground drilling drill bit having a cutter configured to undergo loose wear. Another object of the present invention is to provide an underground drilling drill bit that can avoid tracking even under off-center operating conditions and eliminate the occurrence of annular ridges. be. These objectives are accomplished in the preferred embodiment by spacing the inserts in a distributed pattern that varies widely in spacing rather than rows. In order to provide sufficient strength to the metal fittings supporting the inserts, a minimum distance between the inserts is defined around each insert such that a constraint is imposed on the spacing of the inserts. A maximum distance is also established around each insert to ensure that adjacent traces at the bottom of the borehole overlap. This maximum distance is a function of the nature of the rock and the size of the insert. A boundary area is thus defined around each insert and the inserts are distributed within that boundary area. In locating the inserts in the preferred method, one insert is first placed at any point within a selected area of the cutter shell. The position of the second insert is then selected within a bounded area around the first insert, in a preferred method using a random number generator. A further third insert is disposed in a similar manner within the border area around the second insert. However, the third insert need not be located closer to the first insert than the minimum required distance between the inserts. The positions of subsequent inserts are then selected in a similar manner. The invention will now be described in detail with reference to preferred embodiments and with reference to the accompanying drawings. In the accompanying FIG. 1, a lift drill bit or reamer 11 is shown drilling a shaft 13. This lifting drill bit 11 is adapted to be pulled upwardly into a previously drilled pilot hole 15. Rising drill bit 11
includes a cutter support member or cutter support plate 17 fixed perpendicularly to a cylindrical stem 19. The stem 19 is fixed to a drill pipe (not shown) and has a longitudinal or rotational axis concentric with the axis of the cutter support plate 17. The cutter support plate 17 has a cutter mount 2.
3, a plurality of cutter assemblies 21 are attached. Each cutter mount has two arms 25 spaced apart from each other and facing away from the cutter support plate 17. Arm 25 defines a saddle for receiving cutter assembly 21. The cutter assembly 21 is one inner cutter 27
, some intermediate cutters 29 , and some outer cutters or gauge cutters 31 . It is preferable that the inner cutter 27 and the gauge cutter 31 are the same. Further, in a preferred embodiment, the width of the cutting structure of the inner cutter 27 and the gauge cutter 31 is smaller than the width of the cutting structure of the intermediate cutter 29. Each cutter assembly 21 is a
043533, which includes a cutter shell mounted on a bearing. A cutter shell 33 for the intermediate cutter 29 is shown in cross section in FIG. Each cut shell 33 is generally conical in shape and is cut perpendicular to the axis of rotation 35 to define a frustoconical outer surface in rolling contact with the soil. The inner part 37 of the cutter shell 33 is the stem 19
(see Figure 1), and its outer part 39
The outer diameter is smaller than that of the Each cutter shell 33 has a nose region 41, a middle region 45, and a gauge region 43. The nose region 41 is an annular truncated conical surface formed at the edge of the inner portion 37 . The surface of this nose region 41 is formed at an angle of 54° to the axis of rotation 35.
Gauge area 43 is a truncated conical surface formed at the edge of outer edge 39 . The surface of this gauge area 43 is formed at an angle of 60° with respect to the axis of rotation 35. The intermediate region 45 is cylindrical and has a rotational axis 3
5 adjacent to the gauge region 43. The truncated conical surface 45b is the annular surface 45
a, and in the preferred embodiment is formed at an angle of 7.5° with respect to the axis of rotation 35. Another truncated conical surface 45c is formed between the truncated conical surface 45b and the nose region 41, and this truncated conical surface is formed at an angle of 12.5 degrees with respect to the rotation axis 35. . As used herein, nose region and gauge region refer to surfaces directly connected to the inner and outer portions, respectively, separated by an intermediate cutter and formed at a substantially greater angle to the axis of rotation than the intermediate cutter. defined as something. The intermediate region 45 is a hole drilled perpendicularly to its surface and includes a hard metal insert 49 (first
It includes a plurality of apertures 47 (only one of which is shown) that house the holes (see figure). In a preferred embodiment for intermediate cutter 29, no insert is located in nose region 41 or gauge region 43. The bottom pattern of the insert hole 47 is shown in an exploded view in FIG. 2, which shows the appearance of the bottom of the cut hole when one cutter is rotated once. The left side of FIG. 2 shows a truncated conical surface 45.
Intermediate region 4 at the intersection with nose region 41 of c
It shows the inside of 5. The right side of FIG. 2 shows the outside of the intermediate region 45 at the intersection of the annular surface 45a and the gauge region 43. The inserts in the intermediate region 45 are distributed or irregularly arranged within the limits of the border region so as not to form an annular array. Each insert hole 47 in intermediate region 45 has a border region surrounding the insert. The bounding area of the first selected insert hole 47' is schematically shown in dashed lines in FIG. , and a second loop 55 corresponding to the maximum required distance between the insert centerlines. In the preferred method and apparatus, the first loop 53 and the second loop 55 are concentric and identical for each insert hole 47 located in the intermediate region 45. The minimum required distance is determined empirically by the cutout metal required to hold the insert. The maximum required distance is also determined by the extent to which a typical formation is disturbed by a single insert. Moreover, these minimum required distances and maximum required distances depend on the circumference of the cutter, the shape and size of the insert, and the amount of protrusion of the insert from the cutter shell. The cutter diameter on the inside of the truncated conical surface 45c is 34.279 cm, and the annular surface 45a
The diameter of the cutter is 39.471 cm, the diameter of the insert hole 47 is 1.5875 cm,
In the preferred embodiment where the depth of 47 is 1.270 cm, the minimum required distance between insert centerlines is 2.0664 cm.
cm. Therefore, the radius of the first loop 53 is
It is 2.064cm. Also, the maximum required distance between the insert centerlines is 3.483 cm, so the radius of the second loop 55 is 3.483 cm. In a preferred method of selecting the position of the insert, the position of the first insert hole 47' is arbitrarily selected at any point in the intermediate region 45. Then, in the example of FIG.
7" centerline position of the first loop 53 and second loop 55 of the first insert hole 47', as by a typical computer positioning random number generator.
randomly selected within the area between. "Random"
The term refers to irregular insert positioning without a specific pattern within a specific boundary area. A first loop 53' and a second loop 55' of the border area are then formed around the centerline of the second insert 47'', as shown in dotted lines in FIG. 5. Third insert hole 47
are randomly located within the boundary area of the second insert hole 47''. However, this third insert hole 47 is located closer to the first insert hole 47' than the minimum required distance between the inserts. In FIG. 5, the border area of the second insert hole 47'' which is too close to the first insert hole 47' is shown by hatching. Such an insert hole positioning procedure is such that each subsequent insert location is randomly selected within the boundary area of the previous insert, but closer to any previously selected insert than the minimum required distance between the inserts. This will be done to ensure that nothing happens. And this procedure is intermediate area 45
The process is repeated until the insert positions are determined for all of the positions of the inserts. Due to the spatial limitations of the intermediate region 45, there are some spaces where the distance from the insert is greater than the maximum required distance, but insufficient to place additional inserts without being too close to existing inserts. However, this is acceptable. However, the minimum required distance must always be observed. As mentioned above, the insert location selection procedure may be performed manually or by a computer. In the computerized method, a random number generator is used to select the insert location within the boundary area limits. In a purely mathematical sense, the program is not random, since no repetitions occur in true random selection. The random number generator used in connection with the program generates approximately 50000 before producing a repeating number.
generate a number of This is sometimes called pseudo-random selection. A computer program in the Fortran language is listed at the end of this specification. In this program, the intermediate area 4
5 is an annular surface 45a, truncated conical surfaces 45b and 45c
was assumed to be a conical surface with one angle rather than one with multiple angles. In selecting the insert locations, some of the insert holes 47 will be located close to the edge of the intermediate region 45. This is permissible as long as the cylindrical surface of insert hole 47 is no closer than about 0.0396 cm from the edge of intermediate region 45. If the border region of a previous insert crosses the edge of the intermediate region 45, the insert may be placed only in that portion of the border region inside the intermediate region. According to the above procedure, a cutter can be obtained in which inserts are intentionally avoided from being arranged in rows in the intermediate region 45. The spacing between the inserts is distributed such that there are no groups of three adjacent inserts in which the intersection of the centerline of the insert and the cut surface lies in one plane. Although one or more clusters may occur in the preferred embodiment, the occurrence of such clusters is believed to be rare. FIG. 3 is a graph showing substantially uniform coverage of the cutting structure. This graph was constructed by plotting the relative density of the inserts starting at the nose region 41 and continuing radially outward to the gauge region 43 with the location of each insert.
The relative density of the inserts represents the sum of the linear distances of the inserts passing through a selected plane divided by the circumference of the cutter shell in the selected plane. The plane selected in this case must be perpendicular to the axis of rotation 35 of the cutting shell 33. For example, the nose region 41
At a position 0.5 inch (1.27 cm) from the truncated conical surface 4
A plane passing through 5c and perpendicular to the axis of rotation 35 passes through a number of inserts 49. This plane passes through several inserts and also divides it into two,
It also passes through only part of other inserts. When this plane passes through each insert at the same point as the cutter shell 33, its length of passage is added to the linear distance. Thus, once the straight line distances are added, these distances are divided by the circumference of the cutlet shell at the relevant location to give approximately 1.274 cm from the nose area 41.
The value is 0.28. If the inserts are spaced in annular rows at such points and there is no cutter metal between them, the relative density of the inserts is 1.0 or
It becomes 100%. The first at both side edges of the intermediate region 45
For sections other than 0.25 inch (0.635 cm), the relative density varies between approximately 0.15 and 0.28, preferably not dropping below 0.10, so the insert distribution is fairly uniform. Please note that. This shows that all possible planes extending perpendicular to the axis of rotation 35 divide at least one part of the insert. If annular columns existed, the graph of FIG. 3 would have a value of 0 between each annular column because the plane at these points would not pass through any insert. The attached Table 1 shows the exact position of each insert 49 in the insert hole 47 in the middle region 45 of the cutter with dimensions as described above. "A"
The column marked with indicates the distance along the axis of rotation 35 from the outer part 39 to the point where the insert is placed. Further, the angle α is an angle around the rotation axis 35 of the cutter shell 33 when measured from an arbitrary first point. The distance between any angles α is proportional to the circumferential distance along the intermediate region 45 of the cutter in a plane perpendicular to the axis of rotation 35. Although not essential to the present invention, each insert hole 47 is disposed at a position that differs in distance from the outer portion 39 from all other insert holes to the third decimal place. Further, each insert hole 47 is arranged in a different plane from all other insert holes up to the third decimal place. The positions of the inserts were selected by computer, but not in the numerical order shown in Table 1. That is, the positions of the second inserts selected by the computer do not necessarily correspond to the order of the insert numbers shown in Table 1. Insert No. 3 of Table 1 is Table 1
It does not exist within the boundary area of insert No. 2. Rather, Table 1 lists each insert in order of increasing angle α. Inserts No. 292 to 294 are shown in FIG. 3 so that FIG. 3 corresponds to Table 1. All insert holes 4
7 are bored perpendicularly to the surface on which they are located, except for insert holes passing through the intersection of the annular surface 45a and the truncated conical surface 45b and the intersection of the truncated conical surface 45b and the truncated conical surface 45c. For the insert holes passing through each of the latter holes, they are drilled perpendicular to a surface that includes more than half the diameter of the insert hole. Figure 6 shows inner cutter 27 or gauge cutter 3.
1 (see FIG. 1). These cutters are identical to each other, but differ considerably from the intermediate cutter 29. One reason now is that the gauge cutter 31 requires a very high density insert at its outer edge so that it can cut through the sidewalls of the shaft 13. The inner cutter 27 also requires a row of inserts in its nose region to be able to cut away the edge of the pilot hole 15. In order to be compatible, the inner cutter 27 and the gauge cutter 31 must be formed identically to each other, with several rows of inserts located both in the nose region and near the gauge cutter region. The inner cutter 27 or the gauge cutter 31 has a substantially conical shape and includes a cutter shell 53a cut perpendicularly to its axis of rotation 54. The bearing for the cutter shell 53a is the aforementioned intermediate cutter 2.
It has the same structure as that used in 9. The cutter shell 53a has an inner portion 55a that is closer to the stem 19 (see FIG. 1) than its outer portion 57. Each katsuta shell 53a is
Like the intermediate cutter 29 described above, it has a nose region, an intermediate region, and a gauge region. Nose area 5
Reference numeral 9 denotes a circular truncated conical surface formed at an angle of 35° with respect to the rotation axis 54 at the edge of the inner portion 55a. Gauge area 61 is a circular truncated conical surface formed at an angle of 60° with respect to axis of rotation 54 at the edge of outer portion 57 . The intermediate region 63 has an annular surface 6 formed at an angle of 5° to the axis of rotation 54.
3a adjacent to its gauge region 61. The annular surface 63a is connected to a truncated conical surface 63b, and this truncated conical surface 63b is connected to the first loop 5.
It is formed at an angle of 7.5 degrees to 4. Another truncated conical surface 63c is formed between the nose region 59 and the truncated conical surface 63b at an angle of 20 degrees with respect to the axis of rotation 54. Nose region 59 includes a row of insert holes 65 that are drilled and reamed for receiving inserts 49 (see FIG. 1). Row 65 includes 37 insert holes spaced equidistantly from outer portion 57. In this specification, pitch is defined as the distance between the center lines of the inserts on the surface of the cutter shell 53. The pitch is varied in column 65 to avoid tracking as described in the aforementioned US patent application Ser. No. 043,533. In FIG. 7, row 65 is divided in a counterclockwise direction into a group of increasing pitch (indicated by ) and a group of decreasing pitch (indicated by D). Pitch gradually increases in groups where it increases;
In the group where it decreases, it gradually decreases.
The starred inserts are spaced between the last insert of the last group and the first insert of the first group in row 65. The amount of pitch increase decreases with increasing pitch, and the number of inserts within each group is selected according to several criteria. The minimum pitch is first determined by the required cutter shell metal needed to hold the insert in place. The amount of pitch increase is determined by the degree to which a typical formation is disturbed by a single insert. This value is larger than the diameter of the insert 49, and the diameter of the cutter shell 5
3, the size and shape of the insert, and the protrusion of the insert from the cutter shell. The number of inserts in a group depends on the desired variation from insert to insert. Generally, three to seven inserts are distributed in each group to ensure that the pitch difference from one insert to its adjacent inserts is clear. To calculate the exact position of the inserts, a constant number is calculated that covers the total pitch increase by one less than the number of spaces between inserts in a group. In groups of increasing pitch, any space between insert centerlines is equal to the previous space in the group plus the above constant. Conversely, in the group where pitch decreases,
Any space between insert centerlines is equal to the previous space minus the constant. Preferably, the maximum and minimum spaces used for each group within a column are the same. In FIG. 7, row 65 has nine insert groups, five increasing pitch groups and four decreasing pitch groups. Groups in which two pitches increase and groups in which two pitches decrease are arranged alternately. Each insert group includes five inserts, and four spaces with different pitches are defined between the inserts of each group. In addition, in the area where a group where one pitch decreases is placed after a group where one pitch increases, those groups overlap each other, and the last space of the group where pitch increases is a space where the pitch increases. It is also the space at the beginning of the decreasing group. FIG. 7 shows the relative angular positions of the inserts within row 65, as shown in Table 2. Katsutashiel 53 (see Figure 6) is Katsutashiel 3
Insert 4 of the same size as 3 (see Figure 3)
9 (see Figure 4). However, the cutout shell 53 has different dimensions, and its inner part 55
The length from a to the outer part 57 is 13.970 cm,
The diameter at the inner edge of the gauge cutter 61 is 36.626
cm, and the diameter at the outer edge of the nose region 59 is
It is 36.225cm. Angle α in Figure 7 (unit: °)
begins at 0 on the vertical axis 67 shown. Insert hole 65' arranged on axis 67
is shown as Insert No. 2 in Table 2 and all inserts in column 65 for a particular cutter size have an outer section as shown in column A (in cm) in Table 2. It is 57 to 13.256 cm. The next insert hole 65'' in the row 65 is 1.560 mm from the centerline, or axis 67, of the first insert hole 65'.
Table 2 placed in a position rotated counterclockwise
This is for insert No. 7. Further, the third insert hole 65 is aligned with the axis 67
This is for insert No. 13 of Table 2, which is located at a position of 17.940 degrees from the center line of the insert hole 65', that is, at a position of 9.430 degrees from the center line of the insert hole 65'. Graduation of pitch and position of insert may be determined in this manner using Table 2. Other numbers shown in Table 2 will be explained later.53
It shows the position for other inserts to be placed on top. In FIG. 6, alternating rows 69 of inserts are placed in frustoconical surface 63b near its edge with annular surface 63a. FIG. 8 is an illustration showing the arrangement of inserts similar to FIG. 7, and shows the relative positional relationship between rows 69 and 71. row 69
All of the insert center lines are from the outer part 57.
The center line of the insert on the other side 71 is 4.015 cm from the outer side 57.
It is located at the cm position. Therefore row 69 and row 7
The center lines of the first insert holes are spaced apart along the axis of rotation 54 by 0.744 cm. The diameter of these insert holes is 1.587 cm, so about half of the insert diameters overlap each other. To ensure some degree of overlap, the axial distance between the insert centerlines of rows 67 and 71 should not exceed the diameter of the inserts. The 18 inserts in row 69 are divided into three groups of six inserts each. Each group in column 69 is a group whose pitch decreases when viewed counterclockwise. The locations of these inserts were selected as described above for row 65 and are shown in Table 2. Each group of rows 69 alternates with each group of rows 71 and is circumferentially separated by each group of rows 71. The first insert hole 69' of row 69 is designated as insert number 38 in Table 2 and is located 54.290 degrees from axis 73, which is the same axis as axis 67. The second insert hole 69'' is shown as insert No. 46 located at 63.430° from the axis 73. The 21 insert holes of row 71 are divided into four groups, of which three One group has five inserts and one group has six inserts.The group in row 71 has a uniform pitch between each insert.The group in row 71 has a uniform pitch between each insert. The first insert hole 71' is shown in Table 2 as insert No. 5 located at 4.940 degrees from axis 73. insert placed in position
It is shown in Table 2 as No. 12. In FIG. 6, the inserts of the fourth row 75 are located on the annular surface 63a. The center line of all insert holes in this row 75 is 5.319 mm from the outer part 57.
cm apart. 40 insert holes are arranged in row 75, and these insert holes are 7
The three pitches of individual inserts are divided into increasing groups, with six spaces defined between each insert. The pitches of these groups are calculated in a manner similar to that described above for column 65. Each insert is evenly spaced between these three groups. The exact location of the inserts is shown in Table 2, with all insert holes in row 75 shown in column A under a distance of 2.578 cm. Row 75 for a 1.587 cm diameter insert
The inserts overlap the inserts in row 71 because they are axially spaced only 1.437 cm from alternating rows 71. To allow for such overlap, each insert in alternate rows 71 is spaced between two inserts in row 75. Such overlap prevents interference between row 75 and alternating row 71. In FIG. 6, rows 77 of inserts are located in gauge area 61. In FIG. These inserts (not shown) differ from insert 49 (see FIG. 1) in that they have a flat top surface. These inserts are mounted with their top surfaces flush with the surface of the gauge area 61. Preferably, 39 evenly spaced inserts are arranged in row 77, and these inserts are not shown in Table 2. In FIG. 6, a plurality of insert holes 79 (only one of which is shown) are distributed in the truncated conical surfaces 63b and 63c. The position of the insert hole 79 is selected in the area between the nose area 59 and the boundary area of the rows 59 and 71. The insert hole 79 is also selected within the maximum and minimum limits of the same boundary area as described above for the intermediate cutter 29. The same computer program as described above is used to select the location of this insert hole 79, and numbers are used instead of the dimensions of the intermediate cutter. The positions of all randomly selected inserts in the cutout shell 53 are shown in Table 2. The numerical differences between the computer program for Katsutashiel 33 and the computer program for Katsutashiel 53 are lines 00620, 00630, 00640,
00650 only. Their differences are as follows. Line Katsutashiel 33 Katsutashiel 5 00620 7.074 7.473 00620 8.020 8.024 00620 395 274 00630 169 96 00630 0 21 00640 0 21 00640 9.893 11.0 00650 5 .506 2.894 00650 6.561 4.498 00650 0 18 Also, from line 00660C to 00720C, "C" is displayed in those displays. Not included. Since the boundary area provided by rows 69 and 71 is irregular, there is no circumferential space between rows 69 and 71 and the distributed insert holes 79. That is, any plane perpendicular to the axis of rotation 54 in the intermediate cutter 63 always passes through a portion of at least one insert. The alternating rows 69 and 71 prevent circumferential spaces from existing between these rows and row 75, so that the intermediate cutters 6
3, there is no space in which a plane perpendicular to the axis of rotation 54 can extend without passing through at least a part of the insert. A circumferential space exists in the nose region 59 radially inward from the row 65. The relative density of the insert across the cutter shell 53 is fairly uniform and preferably does not fall below 0.10 as discussed above for the cutter shell 33. In operation, stem 19 (see FIG. 1) is rotated clockwise and raised upwardly. This rotates the cutter assembly 21 and forms an annular passage around the borehole surface 51. The insert 49 disturbs the strata and forms the vertical shaft 13. The underground drill bit according to the invention has various advantages. In the middle part of the borehole, ie between the gauge cutter and the inner cutter, only one cutter is needed to cover the annular portion of the borehole surface. This is because, with the insert arrangement as described above, interference between the insert hole rows, which could occur between rows in the prior art, cannot occur. Higher pressure is allowed to be exerted on each insert without overlapping or staggered placement of the cutters. This is because there are fewer cuts to transmit the force exerted on the bit. The reduced number of stubs thus reduces the maintenance required in drilling the shaft. The face of the shaft is evenly covered, which increases the crushing efficiency and avoids under-excavation due to off-center operating conditions. Since it is not necessary to arrange the cutters in an overlapping manner in the intermediate region, tracking between the cutters is avoided. The combination of distributing the inserts in several rows and varying the pitch of the gauge cutter and inner cutter provides uniform coverage of the borehole surface. By arranging the inserts in several rows, the carbide density in the side wall region of the pilot hole and borehole is increased. Furthermore, by varying the pitch of the inserts in these rows, tracking is avoided. Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various modifications and omissions can be made within the scope of the present invention. This will be obvious to those skilled in the art.

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【table】 [Brief explanation of drawings]

FIG. 1 is a schematic front view, partially in section, of a lift drill bit having cutter assemblies constructed in accordance with the present invention, in particular each cutter assembly is shown to show their relative radial position; It is shown in phantom in the plane of the cross section. FIG. 2 is an illustration showing the insert position of one of the intermediate cutters shown in FIG. 1. FIG. 3 is a graph showing the insert density of one of the intermediate cutters shown in FIG. 1. FIG. FIG. 4 is an illustrative sectional view showing a cutter shell of one of the intermediate cutters shown in FIG. 1. FIG.
FIG. 5 is an illustration showing a method of positioning an insert in accordance with the present invention. FIG. 6 is an illustrative sectional view similar to FIG. 4, showing one cutter shell of the inner cutter or gauge cutter shown in FIG. 1. FIG. 7 is an explanatory view showing the compounding state of one insert row in one of the gauge cutters or inner cutters shown in FIG. 1. FIG. Figure 8 shows the arrangement of two rows of inserts in one of the gauge cutters or inner cutters shown in Figure 1.
This is an illustration similar to the figure. 11... Ascent drill bit, 13... Vertical shaft,
15...Pilot hole, 17...Cut support plate, 19...Stem, 21...Cut assembly,
23...Katsuta mount, 25...Arm, 27
...Inner Katsuta, 29...Middle Katsuta, 31...
...Gauge Katsuta, 33...Katsuta Ciel, 35...
...rotation axis, 37...inner part, 39...outer part,
41...Nose area, 43...Gauge area, 45
... Middle region, 45a ... Annular surface, 45b, 45
c... truncated conical surface, 47... insert hole, 49
...Insert, 51...Drilling hole surface, 53...First loop, 53a...Katsutashiel, 54...
Rotation axis, 55... second loop, 55a... inner part, 57... outer part, 59... nose region, 6
1...Gauge area, 63...Intermediate area, 63a...
...Annular surface, 63b, 63c...Truncated conical surface, 65
...Column, 67...Axis line, 69, 71...Column, 73
... Axis line, 75, 77 ... row, 79 ... insert hole.

Claims (1)

[Claims] 1. A cutter shell 33 in the shape of a truncated cone, which is rotatably attached to an underground drilling drill bit and configured to be rolled along the surface of the stratum to be excavated.
53, and an insert 49 fixed to each of a plurality of holes 47, 79 provided in an annular band portion 45 along the outer circumferential surface of the cutter shell, each of the inserts being fixed to the annular band portion 45 along the outer peripheral surface of the cutter shell. The inserts are spaced apart widthwise and circumferentially at different intervals from each other so as not to form rows in any direction and shape, each of said inserts having a distance between it and the nearest adjacent insert. is between a minimum required distance and a maximum required distance, the minimum required distance and the maximum required distance being determined by the conditions of the cutter and the conditions of the formation, whereby the insert A cutter characterized by being firmly held on the outer circumferential surface of the cutter and configured so that each insert effectively excavates a stratum.