Rotatable cutting tool with cutting insert and bolster

Abstract

A rotatable cutting tool includes a cutting tool body having a head portion. A bolster is at least partially received in the head portion and includes a socket, a collar portion, and a handle portion. The socket is formed with a conical sidewall and a radius fillet. A hard tip or cutting insert is at least partially received in the socket and includes a conical head portion, a toroidal portion, and an axially rearward frustoconical portion that substantially fits the geometry of the socket of the bolster. The shank portion of the bolster provides a narrow-bottomed geometry, and the axially rearward frustoconical portion of the cutting insert provides a tapered geometry, which together increase the strength of a brazed joint between the bolster and the base portion, thus, forces and stresses transferred to the cutting tool during machining operations are reduced.

Description

Technical Field

[0001] The present invention relates to a rotatable cutting tool that can be used to impact subterranean structures, such as asphalt road material, coal deposits, mineral formations, and the like. More particularly, the present invention relates to a rotatable cutting tool with a cutting tip and a bolster that can be used to impact subterranean structures, which reduces stresses and forces transmitted to the cutting tool during machining operations, thereby improving the performance characteristics of the rotatable cutting tool. Background Art

[0002] Rotatable cutting tools have long been used to impact ground structures such as asphalt road material or strata containing ore or coal. Generally speaking, these types of rotatable cutting tools have an elongated cutting tool body, typically made of steel, and a hard tip (or cutting insert) attached to the cutting tool body at its axial forward end. The hard tip is typically made of a hard material such as cemented (cobalt) tungsten carbide. The rotatable cutting tool is rotatably held or retained in a bore of a tool holder or, alternatively, in a bore of a sleeve, which in turn is retained in a bore of a bracket.

[0003] The brackets are attached to a driven component, such as a driven drum in a road-planning machine. In some designs, the driven component (e.g., drum) carries hundreds of brackets, each of which carries a rotatable cutting tool. Thus, the driven component can carry hundreds of rotatable cutting tools. The driven component is driven (e.g., rotated) in such a way that the hard tip of each rotatable cutting tool impacts or strikes the ground structure (e.g., asphalt road material), thereby fracturing the material and breaking it into fragments.

[0004] As will be appreciated, during operation, rotatable cutting tools and cutting inserts are often subjected to a variety of extreme cutting forces and stresses in abrasive and corrosive environments. The overall length of the cutting insert, and specifically the length that the cutting insert extends from the axial forward end of the cutting tool, determines the amount of forces and stresses transmitted to the cutting tool during operation. In other words, the further the cutting insert extends from the cutting tool, the greater the forces and stresses that will be generated, which can potentially lead to tool failure. Summary of the Invention

[0005] The present invention addresses the problem of transferring excessive forces and stresses to the cutting tool by providing a cutting insert that is at least partially received in a socket of the bolster, wherein the shank portion of the bolster provides a narrow bottom profile geometry and the cutting insert provides a tapered geometry that together increase the strength of the brazed joint between the bolster and the base portion, thereby reducing the forces and stresses transferred to the cutting tool during machining operations.

[0006] In one aspect of the present invention, a rotatable cutting tool includes a cutting tool body, a bolster, and a cutting insert. The cutting tool body has an axial front end, an axial rear end, a head portion axially rearward of the axial front end, a collar portion axially rearward of the head portion, and a shank portion axially rearward of the collar portion and axially forward of the axial rear end. The head portion includes a base portion having a recess formed therein. The bolster is at least partially received in the recess. The bolster includes a head portion, a collar portion, and a shank portion. The head portion includes a socket having a sidewall formed therein and a radius fillet having a radius R2 formed therein. The shank portion includes a rearwardly tapering frustoconical section, a variable tapering section extending in a rearward direction from the rearwardly tapering frustoconical section, and a cylindrical section extending in a rearward direction from the variable tapering section. The cutting insert is at least partially received in the socket of the bolster. The cutting insert comprises an ultrahard material bonded to a cemented metal carbide substrate and includes a conical head portion, a collar portion, and an axially rearward frusto-conical portion. The shank portion of the bolster provides a narrow bottom geometry, and the axially rearward frusto-conical portion of the cutting insert provides a tapered geometry, which together increase the strength of the brazed joint between the bolster and the base portion of the cutting tool body, thereby reducing the forces and stresses transmitted to the cutting tool during machining operations.

[0007] In another aspect of the present invention, a cutting insert includes a conical head portion having a length L1, a collar portion having a length L2, and an axially rearward frustoconical portion having a length L3, wherein the length L3 of the axially rearward frustoconical portion is between about forty percent (40%) and about fifty-five percent (55%) of a total length L4 of the cutting insert. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Although various embodiments of the present invention have been shown, the specific embodiments shown should not be construed as limiting the claims. It is contemplated that various changes and modifications can be made without departing from the scope of the present invention.

[0009] Figure 1 is a side view of a rotary cutting tool having a cutting insert and a bolster according to an embodiment of the present invention;

[0010] Figure 2 It is along Figure 1 a cross-sectional view of the cutting insert, bolster, and head portion of the rotary cutting tool taken along line 2-2;

[0011] Figure 3 is a cross-sectional view of the pocket in the base portion with the bolster and cut insert removed for clarity;

[0012] Figure 4 is an isometric view of a bolster according to an embodiment of the present invention;

[0013] Figure 5 yes Figure 4 side view of the bolster;

[0014] Figure 6 yes Figure 4 A top view of the bolster;

[0015] Figure 7 It is along Figure 6 a cross-sectional view of the bolster taken along line 7-7;

[0016] Figure 8 is a top isometric view of a cutting insert according to an embodiment of the present invention;

[0017] Figure 9 yes Figure 8 a side view of a cutting insert;

[0018] Figure 10 yes Figure 8 a top view of the cutting insert; and

[0019] Figure 11 It is along Figure 10 A cross-sectional view of the cutting insert taken along line 11-11. DETAILED DESCRIPTION

[0020] Referring to the drawings, wherein like reference numerals denote like elements, according to one aspect of the present invention, Figure 1 1 . The rotatable cutting tool 10 is shown generally in FIG. The rotatable cutting tool 10 includes an elongated cutting tool body, generally designated 12. The cutting tool body 12 is typically made of steel, such as a Mn-B steel alloy. The cutting tool body 12 has an axial forward end 14 and an axial rearward end 16. A hard tip or cutting insert 18 is attached (e.g., by brazing, etc.) to a socket 20 in the axial forward end 14 of the cutting tool body 12.

[0021] The cutting tool body 12 is divided into three main parts: namely, a head portion 22, a collar portion 24, and a shank portion 26. The most axially forward portion is the head portion 22, which begins at the axial forward end 14 and extends in the axially rearward direction along the longitudinal axis XX. The middle portion is the collar portion 24, which begins at the junction with the head portion 22 and extends in the axially rearward direction along the longitudinal axis XX. The collar portion 24 includes a tapered neck section 28 followed by a cylindrical collar section 30.

[0022] The axially rearwardmost portion is the shank portion 26, which begins at the junction with the collar portion 24 and extends in the axially rearward direction along the longitudinal axis XX. The shank portion 26 includes a forward cylindrical tail section 32, followed by an intermediate section 34, followed by a retainer groove 36, followed by a rearward cylindrical tail section 38 and terminates in a chamfered section 40. As known to those skilled in the art, the shank portion 26 is the portion of the cutting tool body 22 that carries a retainer 42. The retainer 42 rotatably retains the rotatable cutting tool 10 in a bore of a tool holder (not shown) or a bore of a sleeve carried by a holder.

[0023] Now refer to Figure 1-3 , the head portion 22 includes a base portion 44 attached to the collar portion 24. Figure 2 and 3 As shown, the base portion 44 of the head portion 22 is formed with a recess, generally shown at 48. In one aspect, the recess 48 extends axially along the axis XX from an axial forward end 50 of the base portion 44 rearwardly toward the collar portion 24. The recess 48 is formed with a rearwardly tapered frusto-conical sidewall 48a extending rearwardly (i.e., in an axially rearward direction) from the axial forward end 50, a transition sidewall 48b extending rearwardly from the first rearwardly tapered frusto-conical sidewall 48a, a cylindrical sidewall 48c extending rearwardly from the transition sidewall 48b, and a conical sidewall 48d extending rearwardly from the cylindrical sidewall 48c.

[0024] refer to Figure 3 , the rearwardly tapering frustoconical sidewall 48a forms an angle A1 of between about twenty (20) degrees and about forty (40) degrees relative to the axis XX. For example, in one embodiment, the angle A1 is about thirty (30) degrees relative to the axis XX. The transition sidewall 48b forms an angle A2 that is less than the magnitude of the angle A1. For example, the angle A2 can be between about ten (10) degrees and about twenty (20) degrees relative to the axis XX. It should be noted that the cylindrical sidewall 48c extends generally parallel to the axis XX (i.e., at an angle of zero (0) degrees relative to the axis XX).

[0025] The rearwardly tapering frustoconical sidewall 48a, the second transition sidewall 48b, and the cylindrical sidewall 48c have a total length LPT along the axis XX. The rearwardly tapering frustoconical sidewall 48a has a length LP1 along the axis XX that is between about 25-50 percent of the total length LPT. For example, the length LP1 may be about thirty-three (33) percent of the length LPT. The transition sidewall 48b has a length LP2 along the axis XX. The cylindrical sidewall 48c has a length LP3 along the axis XX that is between about 50-80 percent of the total length LPT. For example, the cylindrical sidewall 48c has a length LP3 that is about sixty-five (65) percent of the total length LPT. It should be noted that the length LP3 of the cylindrical sidewall 48c is always greater in magnitude than the length LP1 of the rearwardly tapering frustoconical sidewall section 48a. It should be noted that the length LP2 of the transition sidewall 48b will always be less in magnitude than the length LP1 of the rearwardly tapering frusto-conical sidewall section 48a and the length LP3 of the cylindrical sidewall 48c.

[0026] Bolster 46 is at least partially received in pocket 48 of base portion 44. Bolster 46 is made of a suitable material, such as a cemented metal carbide material, that includes a cobalt concentration of approximately 1 to 40 percent by weight, preferably 5 to 10 percent. In one aspect, cutting insert 18 is attached to bolster 46.

[0027] Now refer to Figure 4-7 , shows a bolster 46 according to one aspect of the present invention. Bolster 46 has an axial forward end 52 and an axial rearward end 54. Bolster 46 is divided into three main sections; namely, a head section 56, a collar section 58, and a shank section 60 that terminates in a chamfered section 62. The axially forward-most section is head section 56, which begins at axial forward end 52 and extends in an axially rearward direction along longitudinal axis YY. Head section 56 is formed with a large radius R1 of between about 1.5 inches (38.1 mm) and about 3.5 inches (88.9 mm). In one embodiment, for example, radius R1 is about 2.54 inches (69.8 mm). The intermediate section is collar section 58, which begins at the junction with head section 56 and extends in an axially rearward direction along longitudinal axis YY to shank section 60.

[0028] The shank portion 60 of the bolster 46 includes a rearwardly tapering frustoconical section 60a, a variable tapering section 60b extending in the rearward direction from the rearwardly tapering frustoconical section 60a, and a cylindrical section 60c extending in the rearward direction from the variable tapering section 60b to the chamfered section 62. The variable tapering section 60b provides a transition between the tapered frustoconical section 60a and the cylindrical section 60c.

[0029] In one aspect, the rearwardly tapered frusto-conical section 60a of the shank portion 60 forms an angle A3 relative to the longitudinal axis YY. In one embodiment, the angle A3 of the first rearwardly tapered frusto-conical section 60a is approximately equal to the angle A1 of the rearwardly tapered frusto-conical sidewall 48a of the pocket 48. For example, the angle A3 may be approximately thirty (30) degrees relative to the longitudinal axis YY.

[0030] In the illustrated embodiment, for example, bolster 46 has an overall length LBT of approximately 1.224 inches (31.90 mm). Head portion 56 has a length LB1 along longitudinal axis YY of approximately 0.35 inches (8.89 mm), which is approximately twenty-seven percent (27) of the overall length LBT. Ring portion 58 has a length LB2 along longitudinal axis YY of approximately 0.15 inches (3.8 mm), which is approximately twelve percent (12) of the overall length LBT. Handle portion 60 has a length LB3 along longitudinal axis YY of approximately 0.724 inches (18.39 mm), which is approximately fifty-eight percent (58) of the overall length LBT. Thus, length LB3 of handle portion 60 is at least fifty percent (50) of the overall length LBT of bolster 46. It should be understood that the lengths LB1, LB2, LB3 and LBT are for illustrative purposes only and that the present invention may be practiced with any desired lengths LB1, LB2, LB3 and LBT so long as the length LB3 is at least fifty (50) percent of the total length LBT of the bolster 46.

[0031] like Figure 7 As shown, the head portion 56 of the bolster 46 includes a socket 20 for receiving the cutting insert 18. The socket 20 is formed with a rearwardly tapering conical sidewall 20a that terminates in a radius fillet 20b. In one embodiment, the conical sidewall 20a forms an angle A4 of between about twenty (20) degrees and about forty (40) degrees relative to the longitudinal axis YY. In one embodiment, the radius fillet 20b is formed to have a radius R2 within a range of between about 0.060 inches (1.52 mm) and about 0.080 inches (2.03 mm).

[0032] like Figure 4-7 As shown, the bolster 46 is movably connected to the base portion 44 when initially installed in the pockets 48 of the head portion 22. This movably connected is provided by a plurality of dimples 64 formed on the shank portion 60 that engage the pockets 48 of the base portion 44 of the head portion 22. Specifically, the dimples 64 are formed on an axially forward frusto-conical section 60a of the shank portion 60 of the bolster 46. Figure 5As shown, the dimples 64 are equally spaced about the axially forward frusto-conical section 60a of the shank portion 60. In the illustrated embodiment, the axially forward frusto-conical section 60a has a total of five (5) dimples 64 that are equally spaced about seventy-two (72) degrees from one another. However, it should be understood that the present invention is not limited by the number of dimples 64 and that the present invention may be practiced with any desired number of dimples 64, so long as the bolster 46 is properly movably connected to the base portion 44.

[0033] After being positioned at the desired location within pocket 48, bolster 46 is then fixedly attached to pocket 48 by brazing or the like. In one embodiment, bolster 46 is attached to pocket 48 by brazing between each pocket 64 and collar portion 58. It will be appreciated that other means for fixedly attaching bolster 46 to base portion 44 may be provided within the scope of the present invention.

[0034] Similar to the shank portion 60 of the bolster 48, the conical sidewall 20a of the socket 20 also includes a plurality of dimples 64. Figure 6 As shown, the dimples 64 are located in two circumferential rows about the conical sidewall 20a of the socket 20, each row having three (3) equally spaced dimples 64 with an angle A5 of approximately one hundred twenty (120) degrees such that the dimples 64 in one row are circumferentially spaced apart from the dimples 64 in the other row by an angle A6 of approximately sixty (60) degrees.

[0035] Now refer to Figure 8-11 , shows a hard tip or cutting insert 18 according to an embodiment of the present invention. The hard tip or cutting insert 18 has an axial forward end 68 and an axial rearward end 70. The cutting insert 18 is divided into three main sections; namely, a conical head portion 72, a collar portion 74, and an axially rearward frustoconical portion 76 terminating in a chamfered section 77. The axially forward-most section is the head portion 72, which begins at the axial forward end 68 and extends in an axially rearward direction along the longitudinal axis ZZ. The intermediate section is the collar portion 74, which begins at a junction with the head portion 72 and extends in an axially rearward direction along the longitudinal axis ZZ to the axially rearward frustoconical portion 76. The collar portion 74 is divided into two sections: an axially forward first section 74a and an axially rearward second section 74b.

[0036] like Figure 9 As shown, the axially rearward frustoconical portion 76 forms an angle A7 relative to the longitudinal axis ZZ. Generally, the angle A7 is approximately equal to the angle A4 of the socket 20. In one embodiment, the angle A7 is within a range of between about twenty (20) degrees and about forty (40) degrees. For example, the angle A7 can be about twenty-nine (29) degrees.

[0037] In the illustrated embodiment, the axial rearward end 70 is generally planar. However, it should be understood that the present invention is not limited to a planar rearward section 88 and that the present invention may be practiced with any desired geometry, such as tapered, non-planar, etc., so long as the cutting insert 18 is geometrically configured to properly seat within the socket 20 of the bolster 46.

[0038] like Figure 11 As shown, the cutting insert 18 includes a superhard material 78 bonded to a cemented metal carbide substrate 80. The superhard material may be bonded to the substrate via a high pressure and high temperature process. The superhard material 78 may include a ceramic material, diamond, polycrystalline diamond (PCD), natural diamond, synthetic diamond, vapor deposited diamond, silicon bonded diamond, cobalt bonded diamond, thermally stable diamond, polycrystalline diamond with a binder concentration of 1 to 40 weight percent, infiltrated diamond, layered diamond, monolithic diamond, polished diamond, coarse diamond, fine diamond, cubic boron nitride, diamond impregnated matrix, diamond impregnated carbide, non-metallic catalyzed diamond, or combinations thereof. The superhard material 78 may have a thickness of at least 0.100 inches (2.54 mm). As shown in FIG. Figure 8 and 9 As shown, the superhard material 78 is bonded only to the head portion 72 and the axially forward first section 74 a of the collar portion 74 of the cutting insert 18 .

[0039] In the illustrated embodiment, the head portion 72 of the cutting insert 18 has a generally pointed geometry with a radius R3 of between about 0.050 inches (1.27 mm) and about 0.125 inches (3.175 mm) at its apex 82. For example, the apex 82 may have a radius R3 of about 0.090 inches (2.40 mm).

[0040] like Figure 9As shown, the axially rearward frustoconical portion 76 may have a length L1 between about 0.25 inches (6.35 mm) and about 0.35 inches (8.89 mm). For example, the length L1 may be about 0.27 inches (8.27 mm). The collar portion 74 has a length L2 between about 0.07 inches (1.8 mm) and about 0.15 inches (3.81 mm). For example, the collar portion 74 may have a length of about 0.12 inches (3.05 mm). The axially rearward frustoconical portion 76 may have a length L3 of 0.304 inches (7.72 mm). The cutting insert 18 may have an overall total length L4 between about 0.55 inches (13.97 mm) and about 0.75 inches (19.05 mm). For example, the overall total length L4 of the cutting insert 18 may be about 0.694 inches (17.63 mm). Thus, the length L3 of the axially rearward frusto-conical portion 76 may be between about forty percent (40%) and about fifty-five percent (55%) of the total length L4 of the cutting insert 18 .

[0041] As mentioned above, the cutting insert 18 is attached to the socket 20 of the bolster 46 by brazing or the like. Because the geometry of the cutting insert 18 generally matches the geometry of the socket 20 of the bolster 46, the cutting insert 18 is attached to the sidewall 20 a of the socket 20. However, it should be understood that the geometry of the cutting insert 18 may vary depending on the specific application, so long as the collar portion 74 and the axially rearward frusto-conical portion 76 match the geometry of the socket 20 of the bolster 46.

[0042] As described above, the shank portion 60 of the bolster 46 provides a narrow bottom geometry and the axially rearward frustoconical portion 76 of the cutting insert 18 provides a tapered geometry, which increases the strength of the brazed joint between the bolster 46 and the base portion 44 to reduce the forces and stresses transmitted to the cutting tool (10) during the machining operation, thereby avoiding failure during the machining operation.

[0043] Patents and publications mentioned herein are hereby incorporated by reference.

[0044] While presently preferred embodiments have been described, the invention may be otherwise embodied within the scope of the appended claims.

Claims

1. A rotatable cutting tool comprising: a cutting tool body having an axial front end, an axial rear end, a head portion axially rearward of the axial front end, a collar portion axially rearward of the head portion, and a shank portion axially rearward of the collar portion and axially forward of the axial rear end, the head portion including a base portion having a recess formed therein; a bolster at least partially received in the pocket, the bolster comprising a head portion, a collar portion, and a shank portion, the head portion comprising a socket formed with a sidewall and a radius fillet formed with a radius R2, the shank portion comprising a rearwardly tapering frustoconical section, a variable tapering section extending in a rearward direction from the rearwardly tapering frustoconical section, and a cylindrical section extending in the rearward direction from the variable tapering section; and a cutting insert at least partially received in the socket of the bolster, the cutting insert comprising a superhard material bonded to a substrate and including a conical head portion, a collar portion, and an axially rearwardly frustoconical portion, wherein the shank portion of the bolster provides a narrow bottom profile geometry and the axially rearward frusto-conical portion of the cutting insert provides a tapered geometry, which together increase the strength of the brazed joint between the bolster and the base portion, thereby reducing forces and stresses transmitted to the cutting tool during machining operations.

2. The rotatable cutting tool of claim 1 , wherein the superhard material comprises a ceramic material, diamond, polycrystalline diamond (PCD), natural diamond, synthetic diamond, vapor deposited diamond, silicon bonded diamond, cobalt bonded diamond, thermally stable diamond, polycrystalline diamond with a binder concentration of 1 to 40 weight percent, infiltrated diamond, layered diamond, monolithic diamond, polished diamond, coarse diamond, fine diamond, cubic boron nitride, diamond impregnated matrix, diamond impregnated carbide, non-metal catalyzed diamond, or a combination thereof.

3. The rotatable cutting tool of claim 1, wherein the collar portion comprises an axially forward first section and an axially rearward second section.

4. The rotatable cutting tool of claim 3, wherein the superhard material is bonded only to the conical head portion of the cutting insert and the axially forward first section of the collar portion.

5. The rotatable cutting tool of claim 3 , wherein only the axially forward first section of the collar portion of the cutting insert and the axially rearward frustoconical portion of the cutting insert are received within the socket of the bolster.

6. The rotatable cutting tool of claim 1, wherein the head portion of the cutting insert has a generally pointed geometry with an apex having a radius R3.

7. The rotatable cutting tool of claim 1, wherein the head portion of the cutting insert has a length L1, the collar portion of the cutting insert has a length L2, and the axially rearward frustoconical portion of the cutting insert has a length L3.

8. The rotatable cutting tool of claim 7, wherein the length L3 of the axially rearward frustoconical portion of the cutting insert is between about forty percent and about fifty-five percent of the total length L4 of the head portion of the cutting insert.

9. A rotatable cutting tool according to claim 1, wherein the recess is formed with a rearwardly tapered truncated conical side wall extending rearward from the axial front end of the base portion, a transition side wall extending rearward from the rearwardly tapered truncated conical side wall, a cylindrical side wall extending rearward from the transition side wall, and a conical side wall section extending rearward from the cylindrical side wall section.

10. The rotatable cutting tool of claim 1, wherein the rearwardly tapered frusto-conical section of the shank portion of the bolster forms an angle A3 of approximately thirty degrees relative to the longitudinal axis YY of the bolster.

11. A rotatable cutting tool according to claim 1, wherein the socket of the support beam is formed with a rearwardly tapered conical side wall terminating at a radius fillet, and wherein the rearwardly tapered conical side wall forms an angle A4 of between about twenty degrees and about forty degrees relative to the longitudinal axis YY of the support beam.

12. The rotatable cutting tool of claim 11 , wherein the socket of the bolster further comprises a plurality of dimples formed in the rearwardly tapered conical sidewall for engaging the cutting insert when the cutting insert is at least partially received in the socket.

13. The rotatable cutting tool of claim 12, wherein the plurality of dimples are arranged in two circumferential rows about the rearwardly tapering conical sidewall of the socket.

14. The rotatable cutting tool of claim 1 , wherein the bolster further comprises a plurality of dimples formed in the shank portion for engaging the pockets formed in the base portion of the head portion.

15. The rotatable cutting tool of claim 1, wherein the shank portion of the bolster has a length LB3 along the longitudinal axis YY that is at least fifty percent of a total length LBT of the bolster.

16. A rotatable cutting tool according to claim 1, wherein the conical head portion of the cutting insert has a length L1, the collar portion of the cutting insert has a length L2, and the axially rearward frustoconical portion of the cutting insert has a length L3, wherein the length L3 of the axially rearward frustoconical portion is between about forty percent and about fifty-five percent of the total length L4 of the head portion of the cutting insert.

17. The rotatable cutting tool of claim 1, wherein the collar portion of the cutting insert comprises an axially forward first section and an axially rearward second section.

18. The rotatable cutting tool of claim 17, wherein the superhard material is bonded only to the conical head portion of the cutting insert and the axially forward first section of the collar portion of the cutting insert.

19. The rotatable cutting tool of claim 1, wherein the conical head portion of the cutting insert has a generally pointed geometry with an apex having a radius R3.

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