CA1313382C

CA1313382C - Cutter bit

Info

Publication number: CA1313382C
Application number: CA000606110A
Authority: CA
Inventors: Stephen P. Stiffler; Wayne H. Beach
Original assignee: Kennametal Inc
Current assignee: Kennametal Inc
Priority date: 1988-07-20
Filing date: 1989-07-19
Publication date: 1993-02-02
Anticipated expiration: 2010-02-02
Also published as: EP0428599A1; ATE117049T1; KR900702170A; PL161730B1; CN1028662C; DE68920585D1; DE68920585T2; AU4050089A; CN1040247A; EP0428599A4; WO1990001106A1; JPH03503430A; EP0428599B1; AU617517B2; US4940288A; ES2015173A6

Abstract

ABSTRACT OF THE DISCLOSURE

A cutter bit for use in construction and/or excavation applications is provided having a hard wear resistant tip joined to a steel shank. The wear resistant tip is rotational symmetric about its longitudinal axis and has a rear end having a socket therein in which is bonded a steel protrusion on the forward end of the steel shank. The tip socket and an outer rearmost facing surface on the tip rear end have respective pluralities of first and second dimples formed thereon and protruding therefrom for spacing, centering and aligning the tip on the bit body to facilitate formation of a braze joint of a desired given cross-sectional thickness profile between the tip and bit body.

Description

13~3382 CUTTER BIT

BACKGROUND OF TEE INVENTION

The present invention relates to a cutter bit design for use in construction and excavation. It especially relates to cutter bits having a cemented carbide tip thereon.
In the past, a variety of cutter bit designs have been used in construction and excavation applications. These cutter bits have typically been tipped with a cemented tungsten carbide-cobalt insert which was brazed to the steel shank of the cutter bit.
Both rotatable and nonrotatable bits have been used in these applications. One of the early rotatable cutter bit designs involved a cemented carbide tip having an annular rear surface with a socket therein to which the forward end of the steel shank was brazed. The forward end of the steel shank had an annular forward surface with a forward projection thereon which partially extended into the socket (i.e., the depth of the socket was greater than the height of the forward projection).
The braze joint between the steel and the cemented carbide was thus thickest at the forward end of the steel projection and thinnest at the facing annular surfaces of the cemented carbide and steel~ While rotatable cutter bits of the foregoing design were commercially used, the cemented carbide of the tip was susceptible to fracture ~3~33~2 during usage.
The foregoing design was superseded by rotatable cutter bit designs in which the rear of the carbide was flat, or had a so-called valve seat design, either of 5 which was brazed into a socket in the forward end of the steel (see, for example, United States Patent Nos.
4, 4 9 7, 52 o and 4, 216, 832, and West German Offenlegungschrift No. 2846744).
Examples of cutter bit designs utilizing a 10 socket in the rear of the carbide are shown in South African Patent No. 82/9343; Russian Inventor~s Certificate No. 402655; Published Swedish Patent Application No. 8400269-0 and United States Patent No.
4,547,020.
SUMMARY OF THE INVENTION

The present applicants have designed an improved cutter bit including a cemented carbide tip brazed to its 20 forward end, in which the carbide tip has a socket in which a ferrous (e.g., steel) projection on the forward end of the steel shank or body is received. The desig~
according to the present invention is believed to offer a combination of improved carbide fracture resistance in 25 conjunction with an improved joint strength between the carbide and the steel.
In accordance with the present invention, an improved cutter bit is provided having a ferrous body bonded to a cemented carbide tip. The ferrous body has a 30 longitudinal axis and a forward end. The forward end has a first forwardly facing surface and a second forwardly facing surface in which the second forwardly facing surface is located radially inside of the first forward surface, as well as being located forward of said first 35 forwardly facing surface by a distance, H.
The cemented carbide tip has a first rearwardly facing surface with a socket therein extending forwardly 13~33~

therefrom and having a second rearwardly facing surface located a distance, D, from the first rearwardly facing surface. The distances, H and D, have been sized such that H is greater than D. In addition, the first rearwardly facing surface of the tip is bonded to the first forwardly facing surface of the ferrous body, while the second rearwardly facing surface of the tip is bonded to the second forwardly facing surface of the ferrous body.
In this manner, the bond, or joint, between the carbide and steel, which is preferably provided by brazing, is thicker between the first rearwardly facing surface of the carbide and the first forwardly facing surface of the steel, than that found between the second rearwardly facing surface of the carbide and the second forwardly facing surface of the steel.
Also, in accordance with the present invention, in order to substantially maintain the uniformity of the braze joint thickness around the circumference of the protrusion surface, the improved cutter bit is provided with protruding means in the form of pluralities of first and second dimples. The pluralities of dimples are located between the tip and the body forward end and formed on one thereof and protruding toward the other thereof for engaging the other and placing the tip in a spaced relationship relative to the body for facilitating formation therebetween of the braze joint having the predetermined desired thicknesses.
More particularly, the first dimples are formed on and protrude from the socket of the tip and spaced from one another. Preferably, the first dimples are three in number and circumferentially spaced approximately 120 degrees from each other. The second dimples are formed on and protrude from the first rearwardly facing surface of the tip and spaced from one another. Preferably, the second dimples are four in number and circumferentially spaced approximately 90 -4_ 13133~

degrees from each other.
These and other aspects of the present invention will become more apparent upon review of the drawings, which are briefly described below in conjunction with the 5detailed description of the invention.

BRIBF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an elevational view of one 10embodiment of a cutter bit in accordance with the present invention in partial cross section.
Figure 2 shows an enlarged view of the braze joint shown in cross section in Figure 1.
Figure 3 shows a rear plan view of the rear end 15of the embodiment of the tip shown in Figures 1 and 2.
Figure 4 shows an elevational view of the embodiment of the tip in partial cross section.
Figure 5 shows half of an elevational view of the embodiment of the tip shown in Figure 4.
20Figure 6 shows a view similar to that of Figure 2 but of another embodiment of the tip.
Figure 7 shows à view similar to that of Figure 3 but of another embodiment of the tip.
Figure 8 shows a view similar to that of 25Figure 4 but of another embodiment of the tip.
Figure 9 shows an enlarged longitudinal axial sectional view of still another embodiment of the tip.
Figure 10 shows an enlarged fragmentary longitudinal axial sectional view of still another 30embodiment of the bit body.

DETAILED DESCRIPTION OF THE INVENTION

Shown in Figure 1 is one embodiment of rotatable 35cutter bit 1 having a cemented tungsten carbide-cobalt tip 3 joined to a ferrous metal body 5, here steel, by a braze joint 7. The steel body 5 extends along and is ~3~3~

preferably rotationally symmetric about a longitudinal axis X-X which extends between the forward end 9 and rearward end 11 of the body 5. The rearward end 11 of the steel body 5 may have loosely retained thereon a resilient retainer member 13 for releasably holding the cutter bit rotatable in the bore of a mounting block on a conventional construction or excavating machine (not shown). This and other styles of resilient retainer means useful with the present invention are described in 1~ United States Patent Nos. 3,519,309 and 4,201,421.
The forward end 9 of the ferrous body 5 has a first annular forwardly facing surface 15 which preferably lies in a plane perpendicular to the longitudinal axis. Radially inside of this first forwardly facing surface 15 is a protrusion 17 extending forwardly therefrom. At the forward end of the protrusion 17 is a second forwardly facing surface 19 which preferably lies in a plane perpendicular to the longitudinal axis. The first and second forwardly facing surfaces are joined by an outwardly facing surface 21 which tapers inwardly as it extends forwardly, or is preferably frustoconical in shape, and is rotationally symmetric about longitudinal axis X-X. All sharp inside and outside corners preferably are removed and replaced by fillets or chamfers.
The height, H, of the second surface 19 above the first surface 15 is preferably about 0.178 to O.lg8 inch. More importantly, the height, H, is greater than the depth, D, of a generally complementary shaped socket 23 in the cemented tungsten carbide-cobalt tip 3 so that when the protrusion 17 is brazed to the socket 23 the thickness of the resultant braze joint will be smaller adjacent the second forwardly facing surface 19 than it is adjacent the annular forwardly facing surface 15.
In Figure 2, the foregoing is shown more clearly. The cemented carbide tip 3 has an annular rearmost surface 25 facing the forward end 9 of the steel -6- ~3~33~?~

body, and more particularly, facing the annular forwardly facing surface 15 on the steel body. Located radially inside of, and forward of, annular rearward facing surface 25 is a second rearwardly facing surface 27.
Both surfaces 25 and 27 are preferably planar in nature and preferably lie in a plane perpendicular to longitudinal a~is X-X. Preferably located between, and preferably ~oining, the two rearwardly facing surfaces 25 and 27 is an inwardly facing surface 29 extending forwardly from the annular rearmost surface 25 while tapering inwardly, or preferably of frustoconical shape.
The depth, D, of the socket 23 defined by surfaces 27 and 29 is preferably between 0.170 to about 0.176 inch, but more importantly, the depth, D, of the socket is less than the height, H. The socket and protrusion have been sized such that, in the absence of braze metal, the tip can be seated on the surface 19 of the steel body without touching surface 15 of the steel body.
This results in a braze joint 7 which has an average thickness, T~, between the annular rearwardly facing surface 25 of the tip and the annular forwardly facing surface 15 of the steel body which is greater than the average thickness, T2, between rearwardly facing surface 27 of the tip and forwardly facing surface 19 of the ferrous body. Thickness, Tl, is preferably between about 0.008 to 0.024 inch, and more preferably, between about 0.010 to 0.016 inch thick. Thickness, T2, is preferably between about 0.001 to 0.006 inch, and more preferably, between about 0.002 to 0.004 inch thick. The preferred average braze ~oint thickness, T3, between the inwardly tapering surfaces 29 and 21 on the tip socket and the steel body protrusion 17 are also between about 0.008 to 0.024 inch, and more preferably, between about 0.010 and 0.016 inch. Preferably, Tl and T3 are each at least twice T2 and, more preferably, at least three times T2.
In order to substantially maintain the 13~

uniformity of the braze joint thickness, T3, around the circumference of the protrusion surface 17, it is preferred that protruding means in the form of a plurality of first dimples 31 be located between the tip 3 and the body forward end 9. Preferably, the first dimples 31 are provided on the rearward end of the tip 3, being formed on and protruding from the inwardly tapering surface 29 thereof for engaging the tapering surface 21 on the ferrous body protrusion. In such manner, the first dimples 31 place the tip 3 in a spaced, centered relationship relative to the ferrous body protrusion for facilitating formation therebetween of the braze joint 7 having the above-described cross-sectional thickness profile. Thus, the first dimples 31 are preferably a part of the tip 3, extend radially inwardly from the inwardly tapering surface 29 of the tip socket, and are circumferentially distributed on this surface.
Preferably, there are three of the first dimples 31 located at 120 degrees to each other. These are more clearly shown in the Figure 3 rear plan view of the tip.
Also, as seen in the embodiment of Figs. 6-8, it is desirable to provide a plurality of second dimples 32 in the protruding means. Ordinarily, the first dimples 31 will establish a positive spaced relationship between the tip 3 and body 9 which ensures the desired thickness profile along the braze joint 7. However, the first dimples 31 are subject to cocking and misalignment due to inaccurate placement of the tip 3 on the body 9 or due to the existence of out-of-tolerance conditions of portions of any of the facing surfaces of the tip or body. These second dimples 32 are provided to compensate for such contingencies. The second dimples 32 are formed on and protrude from the rearmost facing surface 25 for placing the tip 3 on the ferrous body end 9 in an aligned and spaced relationship thereto such that their respective axes generally coincide. Preferably, the second dimples are four in number and, as seen in Fig. 7, are -8- ~3133~

circumferentially spaced approximately 90 degrees from each other.
The size of the first and second dimples 31, 32 should be such that, while they assist in assuring substantial uniformity of the braze thickness, T3, they are not so large as to interfere with the maintenance of the required relationships between the braze thicknesses, Tl, T2 and T3. Spherical shape dimples are preferred.
Dimples 31 should have a height of about 0.005 to 0.008 inch above surface 29 to maintain the requirement that T2 is less than T3. By assuring that the foregoing relation exists between T2 and T3, it is believed that tip fracture in use will be minimized while providing a strong, long-lived joint between the tip of the steel body, thereby minimizing tip loss.
In an alternative embodiment (not shown), the annular surfaces 25 and 15 on the tip and steel shank, respectively, may be tilted rearwardly as they extend radially outwardly from the longitudinal axis X-X to thereby form frustoconical surfaces. In such a case, the angle of tilt is less than that of surfaces 21 and 29 and is preferably no greater than 30 degrees from a plane perpendicular to the longitudinal axis X-X. In this embodiment, the depth, D, may be calculated from a plane defined by the rearmost edge of surface 25 which occurs where it meets cylindrical surface 65 (see Figure 4). To be consistent, the height, ~, of the steel protrusion in this situation would be calculated from a plane defined by where surface 15 intersects diameter DR3, the outer diameter of tip surface 65 (see Figure 4).
It is further preferred that a high temperature braze material be used in joining the tip to the ferrous body so that braze joint strength is maintained over a wide temperature range. Preferred braze materials are 35 ~ iHandy Hi-temp 548, Trimet 549, 080 and 655. Handy Hi-temp-548 alloy is composed of 55 +/- 1.0 w/o (weight percent) Cu, 6 +/- 0.5 w/o Ni, 4 +/- 0.5 w/o Mn, 0.15 +/-~3~338~

0.05 w/o Si, with the balance zinc and 0.50 w/o maximum total impurities. The Handy Hi-temp-Trimet 549 is a 1-2-1 ratio Trimet clad strip of Handy Hi-temp 548 on both sides of copper. Further information on Handy Hi-temp 548 and Trimet 549 can be found in Handy & Harman Technical Data Sheet Number D-74. The foregoing braze alloys are manufactured and sold by Handy & Harman Inc., 859 Third Avenue, New York, NY 1002. Handy Hi-temp and Trimet are registered trademarks of Handy & Harman Inc.
Applicants have found that acceptable braze joints have been achieved by using Handy Hi-temp-549 discs which have been shaped into cups, fitted between the socket of the tip and the protrusion of the ferrous body and then brazed by conventional induction brazing techniques which, in addition to brazing the tip to the steel body, also hardens the steel which may be any of the standard steels used for rotatable cutter bit bodies.
After the brazing and hardening step, the steel is tempered to a hardness of Rockwell C 40-45. The cemented carbide tip may be composed of any of the standard tungsten carbide-cobalt compositions conventionally used for construction and excavation applications. Applicants have found that acceptable results in asphalt reclamation have been achieved with a standard tungsten carbide grade containing about 5.7 w/o cobalt and having a Rockwell A
hardness of about 88.2.
The earth engaging surfaces of the tip may have any of the conventional sizes or shapes previously used in the art. However, a preferred design is shown in Figures 1-5 (and also in Figures 6-8). In the design shown, the forward end of the earth engaging surfaces has a spherical nose 45 having a radius RT, joined to a frustoconical surface 50 tapering away from the rotational axis of symmetry, X-X, as it extends rearwardly at an angle 90-AT, to form a maximum diameter, DF at a distance L2 from the forward end of nose 45.
Joined to frustoconical surface 50 is a bell shaped 13~33~

section 55 having an earth engaging concave surface 60 at whose rear end is joined a uniform diameter protective surface 65. The concave surface is formed by a series of concave surfaces 60A, 60B and 60C, each having a different radius of curvature and wherein the radii decrease as one moves rearwardly along the length of the tip ti.e., 60A>60B>60C). While any number of radii, RN, or arcs, AN, may be used, it is preferred that at least three radii (or arcs) be used to form the smooth continuous surface 60, here shown as Rl, R2 and R3, and Al, A2 and A3. The rear end of the concave surface 60 joins cylindrical surface 65 which preferably has a diameter DR3 which is not only greater than DF, but is of sufficient size to completely, or at least substantially cover the entire forward surface of the steel body to which the tip is brazed (i.e., more than 98% of the forward surface diameter). Maximum protection from wear to the forward end of the steel shank is thereby provided by the cemented carbide tip, thus reducing the rate of wear on the forward end 9 of steel body.
The use of the concave surface 60 of variable radius as shown allows a tip to be manufactured having increased length Ll while assuring maximum strength and a substantially even distribution of stresses during use to thereby minimize tip fracture in use.
The internal diameters of the socket DRl and DR2, and its shape, can be selected to provide a substantially uniform wall surface, especially in the zone of the concave section 60. The flat circular surface 27 at the forward end of the socket provides a large area for brazing to the forward end surface of the protrusion on the steel body. This structure, in combination with the thin braze joint thickness at this location, provides assurance that, during use, most significant loads applied to the tip will place the tip in compression rather than tension. Examples of dimensions which applicants have found to be acceptable 1 3 ~

are shown in Table I. These dimensions should be used with the previously provided dimensions relating to the tip socket, steel protrusion and braze joint thicknesses.
TABLE I
EXEMPLARY TIP DIMENSIONS
AttributeRadius DiameterAngle Length (inch) (inch)(degree) (inch) Rl 1.179 R2 1.047 R3 0.363 l 3.708 A2 11.630 A3 53.672 RT 0.125 L1 0.693 L2 0.184 L3 0.070 DF 0.425 DRl 0.285 DR2 0.531 DR3 0.750 As is well known to those of ordinary skill in the art, at the junctures of the various surfaces described on the carbide tip, chamfers, fillets and/or pressing flats may be provided, where appropriate, to assist in manufacturing and/or provide added strength to the structure.
Figures 9 and 10 illustrate respective modified embodiments of the tip 3A and body 5A of the cutter bit.
These embodiments of the tip 3A and 5A are only slightly modified from the embodiments of the tip 3 and body 5 of Figures 2 and 6, so only the differences between the two will be described. The respective outwardly facing .. ~

131~3g~

surface 21 on the protrusion 17 of the body 5 and the inwardly facing surface 29 on the socket 23 of the tip 3 in Figures 2 and 6 are frustoconical in shape; in contrast thereto, the corresponding surfaces 21A and 29A
on the respective protrusion 17A and socket 23A of the body 5A and tip 3A are respectively concave and convex in shape. The convex surface 2sA on the tip socket 23A
has a radius R4 equal to approximately 0.487 inch and is concentric with the radius R3 on the outside surface 55A
of the tip 3A. The radius R3 is the same as before.
Additionally, the radius R5 at the transition 67 between the convex surface 29A and the surface 27 is equal to 0.12 inch. The concave surface 21A on the body protrusion 17A and the transition 69 between the concave surface 21A and the surface 19 complement those of the tip socket 23A. The modification of the configuration of the socket 23 of tip 3 tFigures 2 and 6) having the frustoconical surface 29 to the configuration of the socket 23A of the tip 3A (Figure 9) having the convex surface 29A provides a more uniform thickness in the annular section of the tip surrounding the socket thereby strengthening the material of the tip in this section.
The first dimples 31 are now formed on and protrude from the inwardly facing convex surface 29A of the tip socket 23A for engaging the outwardly facing concave surface 21A
on the body protrusion 17A.
Other embodiments of the invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention -disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A cutter bit comprising:
a ferrous body having a longitudinal axis and a forward end;
a cemented carbide tip;
said cemented carbide tip having:
a rounded foremost portion;
an outwardly tapering second portion rearwardly of said rounded foremost portion;
an annular rearmost surface facing said forward end of said ferrous body and oriented in a first plane perpendicular to said longitudinal axis;
an inwardly facing surface extending forwardly and inwardly from said annular rearmost surface;
and a rearwardly facing surface located radially within said inwardly facing surface and forwardly of said annular surface;
a braze joint joining said rearwardly facing surface, said inwardly facing surface and said annular rearmost surface to said forward end of said ferrous body;
and wherein said braze joint has an average thickness adjacent said rearwardly facing surface which is smaller than the average thickness of said braze joint adjacent said rearmost annular surface.

2. The cutter bit according to Claim 1 wherein said rearwardly facing surface is planar and oriented in a second plane perpendicular to said longitudinal axis.

3. The cutter bit according to Claim 1 wherein said inwardly facing surface is frustoconical in shape.

4. The cutter bit according to Claim 1 wherein said inwardly facing surface is convex in shape.

5. A cutter bit comprising:
a ferrous metal body having a longitudinal axis and a forward end;
a cemented carbide tip;
said cemented carbide tip having:
an annular rearmost surface facing said forward end of said ferrous body;
an inwardly facing surface extending forwardly and inwardly from said annular rearmost surface;
and a rearwardly facing surface located radially inwardly of said inwardly facing surface and forwardly of said annular rearmost surface;
a braze joint joining said rearwardly facing face, said inwardly facing surface and said annular rearmost face to said forward end of said ferrous body;
and wherein said braze joint has an average thickness adjacent said rearwardly facing surface which is smaller than the average thickness of said braze joint adjacent said rearmost annular surface.

6. The cutter bit according to Claim 5 wherein said rearwardly facing surface is planar and oriented in a plane perpendicular to said longitudinal axis.

7. The cutter bit according to Claim 5 wherein said inwardly facing surface is frustoconical in shape.

8. The cutter bit according to Claim 5 wherein said inwardly facing surface is convex in shape.

9. The cutter bit according to Claim 5 further comprising means disposed between said tip and said body and being formed on one thereof and protruding toward the other thereof for engaging the other and placing said tip in a spaced relationship relative to said body for facilitating formation therebetween of said braze joint having the predetermined desired thicknesses.

lo. The cutter bit according to Claim 9 wherein said protruding means includes a plurality of first dimples formed on and protruding from said inwardly facing surface of said tip and being spaced from one another.

11. The cutter bit according to Claim 10 wherein said plurality of first dimples are three in number being circumferentially spaced approximately 120 degrees from each other.

12. The cutter bit according to Claim 10 wherein said protruding means includes a plurality of second dimples formed on and protruding from said rearmost facing surface of said tip and being spaced from one another.

13. The cutter bit according to Claim 12 wherein said plurality of second dimples are four in number being circumferentially spaced approximately 90 degrees from each other.

14. The cutter bit according to Claim 9 wherein said protruding means includes a plurality of second dimples formed on and protruding from said rearmost facing surface of said tip and being spaced from one another.

15. The cutter bit according to Claim 14 wherein said plurality of second dimples are four in number being circumferentially spaced approximately 90 degrees from each other.

16. A cutter bit comprising:
a ferrous body having a longitudinal axis and a forward end;
a cemented carbide tip having:
a first rearwardly facing surface with a socket therein extending forwardly therefrom and having a second rearward facing face located a distance, D, from said first rearwardly facing surface;
said forward end of said ferrous body having a first forwardly facing surface and a second forwardly facing surface;
wherein said second forwardly facing surface is radially inside of said first forwardly facing surface and located forward of said first forwardly facing surface by a distance, H;
wherein said first rearwardly facing surface of said cemented carbide tip is bonded to said first forwardly facing surface of said ferrous body and said second rearwardly facing surface of said cemented carbide tip is bonded to said second forwardly facing surface of said ferrous body;
and wherein H is greater than D.

17. The cutter bit according to Claim 16 wherein said second rearwardly facing surface is planar and wherein said second forwardly facing surface is planar.

18. The cutter bit according to Claim 16 further comprising means disposed between said tip and said body and being formed on one thereof and protruding toward the other thereof for engaging the other and placing said tip in a spaced relationship relative to said body for facilitating placement of said respective surfaces of said tip and body at said desired distances, D and H, from one another.

19. The cutter bit according to Claim 18 wherein said protruding means includes a plurality of first dimples formed on and protruding from said socket of said tip and being spaced from one another.

20. The cutter bit according to Claim 19 wherein said plurality of first dimples are three in number being circumferentially spaced approximately 120 degrees from each other.

21. The cutter bit according to Claim 19 wherein said protruding means includes a plurality of second dimples formed on and protruding from said first rearwardly facing surface of said tip and being spaced from one another.

22. The cutter bit according to Claim 21 wherein said plurality of second dimples are four in number being circumferentially spaced approximately 90 degrees from each other.

23. The cutter bit according to Claim 18 wherein said protruding means includes a plurality of second dimples formed on and protruding from said rearwardly facing surface of said tip and being spaced from one another.

24. The cutter bit according to Claim 23 wherein said plurality of second dimples are four in number being circumferentially spaced approximately 90 degrees from each other.