Patent Application
20250052154
The invention pertains to a rotatable cutting tool that is useful for the impingement of earth strata such as, for example, asphaltic roadway material, coal deposits, mineral formations and the like. More specifically, the invention pertains to a rotatable cutting tool with a cutting tip and bolster that is useful for the impingement of earth strata that reduces stresses and forces transmitted to the cutting tool during a machining operation, thereby improving performance characteristics for the rotatable cutting tool.
Rotatable cutting tools have been used to impinge earth strata, such as, for example, asphaltic roadway material or ore bearing or coal bearing earth formations, or the like. Generally speaking, these kinds of rotatable cutting tools have an elongate cutting tool body typically made from steel and a hard tip (or cutting insert) affixed to the cutting tool body at the axial forward end thereof. The hard tip is typically made from a hard material such as, for example, cemented (cobalt) tungsten carbide. The rotatable cutting tool is rotatably retained or held in the bore of a tool holder or, in the alternative, in the bore of a sleeve that is in turn held in the bore of a holder.
The holder is affixed to a driven member such as, for example, a driven drum of a road planning machine. In some designs, the driven member (e.g., drum) carries hundreds of holders, wherein each holder carries a rotatable cutting tool. Hence, the driven member may carry hundreds of rotatable cutting tools. The driven member is driven (e.g., rotated) in such a fashion so that the hard tip of each one of the rotatable cutting tools impinges or impacts the earth strata (e.g., asphaltic roadway material), thereby fracturing and breaking up the material into debris.
As can be appreciated, during operation the rotatable cutting tool and the cutting insert are typically subjected to a variety of extreme cutting forces and stresses in an abrasive and erosive environment. The overall total length of the cutting insert, and in particular, the length that the cutting insert extends from the axial forward end of the cutting tool, determines the amount of forces and stresses that are transmitted to the cutting tool during operation. In other words, the more the cutting insert extends from the cutting tool, the larger the forces and stresses that will be generated, which may result in tool failure.
The invention solves the problem of the transmission of excessive forces and stresses to the cutting tool by providing a cutting insert that is at least partially received in a socket of a bolster, wherein the shank portion of the bolster provides a narrow bottom style geometry and the cutting insert provides a tapered geometry that together increases the strength of a braze joint between the bolster and the base portion, thereby reducing forces and stresses transmitted to the cutting tool during a machining operation.
In one aspect of the invention, a rotatable cutting tool comprises a cutting tool body, a bolster and a cutting insert. The cutting tool body has an axial forward end, an axial rearward end, a head portion axially rearward of the axial forward 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 rearward end. The head portion includes a base portion formed with a pocket. The bolster is at least partially received in the pocket. The bolster includes a head portion, a collar portion and a shank portion. The head portion includes a socket formed with a side wall and a radius blend formed with a radius, R2. The shank portion includes a rearwardly tapering frustoconical section, a variably tapered section extending in a rearward direction from the rearwardly tapering frustoconical section, and a cylindrical section extending in the rearward direction from the variably tapered section. The cutting insert is at least partially received in the socket of the bolster. The cutting insert comprises a super hard material bonded to a cemented metal carbide substrate and includes a conical head portion, a collar portion and an axially rearward frustoconical portion. The shank portion of the bolster provides a narrow bottom style geometry and the axially rearward frustoconical portion of the cutting insert provides a tapered geometry that together increases the strength of a braze joint between the bolster and a base portion of the cutting tool body, thereby reducing forces and stresses transmitted to the cutting tool during a machining operation.
In another aspect of the invention, a cutting insert comprises 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.
While various embodiments of the invention are illustrated, the particular embodiments shown should not be construed to limit the claims. It is anticipated that various changes and modifications may be made without departing from the scope of this invention.
Referring to the drawings wherein like reference characters designate like elements, a rotatable cutting tool 10 is generally shown in
The cutting tool body 12 is divided into three principal portions: namely, a head portion 22, a collar portion 24 and a shank portion 26. The most axial forward portion is the head portion 22 that begins at the axial forward end 14 and extends along longitudinal axis X-X in the axial rearward direction. The mediate portion is the collar portion 24 that begins at the juncture with the head portion 22 and extends along the longitudinal axis X-X in the axial rearward direction. The collar portion 24 comprises a tapered neck section 28 followed by a cylindrical collar section 30.
The most axial rearward portion is the shank portion 26 that begins at the juncture with the collar portion 24 and extends along the longitudinal axis X-X in the axial rearward direction. The shank portion 26 comprises a forward cylindrical tail section 32, followed by a mid-section 34, followed by a retainer groove 36, followed by a rearward cylindrical tail section 38 and terminating in a beveled section 40. As is known by 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 the bore of a tool holder (not shown) or the bore of the sleeve carried by a holder.
Referring now to
Referring to
The rearwardly tapering frustoconical side wall 48a, the second transition side wall 48b and the cylindrical side wall 48c has a total length, LPT, along the axis X-X. The rearwardly tapering frustoconical side wall 48a has a length, LP1, along the axis X-X between about 25-50 percent of the total length, LPT. For example, the length, LP1, can be about thirty-three (33) percent of the length, LPT. The transition side wall 48b has a length, LP2, along the axis X-X. The cylindrical side wall 48c has a length, LP3, along the axis X-X between about 50-80 percent of the total length, LPT. For example, the cylindrical side wall 48c has a length, LP3, of about sixty-five (65) percent of the total length, LPT. It should be noted that the length, LP3, of the cylindrical side wall 48c is always larger in magnitude than the length, LP1, of the rearwardly tapering frustoconical side wall section 48a. It should be noted that the length, LP2, of the transition side wall 48b will always be less in magnitude than the length, LP1 of the rearwardly tapering frustoconical side wall section 48a and the length, LP3, of the cylindrical side wall 48c.
A bolster 46 is at least partially received in the pocket 48 of the base portion 44. The bolster 46 is made of a suitable material, such as cemented metal carbide material comprising about 1 to 40 percent concentration of cobalt by weight, preferably 5 to 10 percent. In one aspect, the cutting insert 18 is affixed to the bolster 46.
Referring now to
The shank portion 60 of the bolster 46 includes a rearwardly tapering frustoconical section 60a, a variably tapered section 60b extending in a rearward direction from the rearwardly tapering frustoconical section 60a, and a cylindrical section 60c extending the rearward direction from the variably tapered section 60b to the beveled section 62. The variably tapered section 60b provides a transition between the tapering frustoconical section 60a and the cylindrical section 60c.
In one aspect, the rearwardly tapering frustoconical section 60a of the shank portion 60 is formed with an angle, A3, with respect to the longitudinal axis Y-Y. In one embodiment, the angle, A3, of the first rearwardly tapering frustoconical section 60a is approximately equal to the angle, A1, of the rearwardly tapering frustoconical side wall 48a of the pocket 48. For example, the angle, A3, can be about thirty (30) degrees with respect to the longitudinal axis Y-Y.
In the illustrated embodiment, for example, the bolster 46 has a total length, LBT, of about 1.224 in (31.90 mm). The head portion 56 has a length, LB1, along the longitudinal axis Y-Y of about 0.35 in (8.89 mm), which is about twenty-seven (27) percent of the total length, LBT. The collar portion 58 has a length, LB2, along the longitudinal axis Y-Y of about 0.15 in (3.8 mm), which is about twelve (12) percent of the total length, LBT. The shank portion 60 has a length, LB3, of about 0.724 in (18.39 mm) along the longitudinal axis, Y—Y, which is about fifty-eight (58) percent of the total length, LBT. Thus, the length, LB3, of the shank portion 60 is at least fifty (50) percent of the total length, LBT, of the bolster 46. It will be appreciated that the lengths, LB1, LB2, LB3 and LBT are for illustrative purposes only and the invention can be practiced with any desirable 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.
As shown in
As shown in
After positioned at the desired position within the pocket 48, the bolster 46 is then fixedly attached to the pocket 48 by brazing, and the like. In one embodiment, the bolster 46 is affixed to the pocket 48 by brazing between each dimple 64 and the collar portion 58. It will be appreciated that other means for fixedly attaching the bolster 46 to the base portion 44 may be provided in accordance with the scope of the invention.
Similar to the shank portion 60 of the bolster 48, the conical side wall 20a of the socket 20 also includes a plurality of dimples 64. As shown in
Referring now to
As shown in
As shown in
In the illustrated embodiment, the head portion 72 of the cutting insert 18 has a substantially pointed geometry with an apex 82 having a radius, R3, of between about 0.050 in (1.27 mm) to about 0.125 in (3.175 mm). For example, the apex 82 may have a radius, R3, of about 0.090 in (2.40 mm).
As shown in
As mentioned above, the cutting insert 18 is affixed to the socket 20 of the bolster 46 by brazing, and the like. Because the geometry of the cutting insert 18 generally conforms to the geometry of the socket 20 of the bolster 46, the cutting insert 18 is affixed to the side wall 20a of the socket 20. However, it will be appreciated that the geometry of the cutting insert 18 can vary depending upon the specific application, so long as the collar portion 74 and the axially rearward frustoconical portion 76 conforms to the geometry of the socket 20 of the bolster 46.
As described above, the shank portion 60 of the bolster 46 provides a narrow bottom style geometry and the axially rearward frustoconical portion 76 of the cutting insert 18 provides a tapered geometry that increases the strength of the braze joint between the bolster 46 and the base portion 44 to reduce forces and stresses transmitted to the cutting tool (10) during a machining operation, thereby avoid failures during the machining operation.
The patents and publications referred to herein are hereby incorporated by reference.
Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.
