DE112010003725T5 - Rotatable cutting tool with hard cutting element - Google Patents

Abstract

A rotatable cutting tool (30) which is designed to strike a substrate while being rotatably retained in a holder bore. The rotatable cutting tool (30) contains a hard cutting member (70, 90, 110) which is fastened in a socket (44) to the axially front end (34) of a cutting tool body (32). The hard cutting member (70, 90, 110) has an axial front functional section (80, 100, 120) which has an initial transverse functional dimension (C, C ', C' ') and further has a base section (86, 98, 118 ) which has a largest transverse base dimension (D, D ', D' '). There is a ratio of the initial transverse function dimension (C, C ', C' ') to the largest transverse base dimension (D, D', D '') in the range between 0.42 and less than 0.48.

Description

CROSS-REFERENCE TO PREVIOUS PATENT APPLICATION

Applicants hereby claim priority for this patent application based on copending US Patent Application Serial No. 12 / 880,377 filed on Sep. 13, 2010, for a ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen and published on Apr. 19, 2010. Copending US Provisional Patent Application Serial No. 61 / 244,228, filed September 18, 2009, for ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen. Furthermore, the Applicant hereby incorporates by reference in its entirety US Serial No. 12 / 880,377, filed September 13, 2010, for a ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen and filed on Sep. 19, 2009 in co-pending US Provisional Patent Application Serial No. 61 / 244,228 for a ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen.

GENERAL PRIOR ART

The invention relates to a rotatable cutting tool, which is usually mounted in a stationary block (or holder) on a rotatable drum. The rotatable cutting tool, which can rotate about its central longitudinal axis, carries a hard cutting insert at the axially forward end thereof. The hard insert is made of a hard material such as (cobalt) tungsten carbide. The rotatable cutting tool engages or encounters a substrate as the drum rotates. The hard insert has a geometry that provides a number of benefits in terms of both the work efficiency of the rotary cutter and the cost of materials for making the rotary cutter.

A rotatable cutting tool typically has a generally elongated, cylindrical geometry. The rotatable cutting tool comprises an elongated steel cutting tool body having an axially forward end and an opposite axially rearward end. The cutting tool body typically carries an assembly or means by which the rotatable cutting tool is rotatably supported by the stationary block or holder on the drum. Exemplary structures suitable for rotatably mounting a rotatable cutting tool to a block or holder include those shown and described herein: U.S. Patent Number 4,201,41 to Beaten et al., U.S. Patent Number 3,519,309 to Engie et al., U.S. Patent Number 3,752,515 to Oaks et al. and U.S. Patent Number 7,380,888 to Ojanen for a rotatable cutting tool with a holding piece with recesses.

A hard cutting member is typically attached to the axially forward end of the cutting tool body, such as by brazing. As mentioned above, the hard cutting member is typically made of a hard material such as cobalt tungsten carbide. U.S. Patent Number 4,389,074 to Greenfield, U.S. Patent Number 5,131,725 to Rowlett et al. U.S. Patent Number 5,429,199 to Sheirer et al., U.S. Patent Number 6,375,272 to Ojanen and U.S. Patent Number 6,478,383 to Ojanen et al. disclose braze alloys heretofore suitable for such a brazing operation and suitable compositions of tungsten carbide.

Heretofore, a hard cutting element suitable for use in rotary cutting tools has exhibited many different geometries. An exemplary geometry is in the U.S. Patent Number 4,497,520 shown and described at Ojanen.

In the case of a street leveling machine, in many cases, the rotatable drum may carry many hundreds of individual blocks or holders. Each individual block or holder carries its own corresponding rotatable cutting tool that can rotate relative to its corresponding block or holder. It is not uncommon for a rotatable drum to carry hundreds of individual rotary cutting tools.

The street leveler drives the rotatable drum to cause it to spin. The orientation of the rotatable cutting tools relative to the drum is such that when the drum is rotated, the drum drives the rotatable cutting tools into the substrate. As the rotatable cutting tools hit the substrate, the substrate typically breaks, resulting in larger pieces of debris and smaller particles and debris. Typically, debris generated in a road leveling operation is very abrasive, causing the rotatable cutting tool to wear.

The rotatable cutting tool may experience wear in a number of ways. The hard cutting member, which is the portion of the rotatable cutting bit that first strikes the substrate, may experience wear. The initial impact of the hard cutting member on the substrate as well as the path of the scree along the hard cutting member can cause this wear. During the cutting operation, the hard cutting member may lose material to the point where it becomes dull and ineffective to accomplish efficient cutting.

Another wear mechanism relates to the braze joint between the hard cutting member and the elongate cutting tool body. During the cutting operation, the braze joint experiences heavy stress due to the continuous intermittent, violent impact of the rotary cutting tool on the substrate material. Over time, the braze joint may experience sufficient stress to fail, whereby the hard cutting member may separate from the cutting tool body. Obviously, if the rotatable cutting tool loses the hard cutting member, the rotatable cutting tool is no longer suitable for the cutting operation.

In addition, during a cutting operation such as a road leveling operation, debris moves along the elongated cutter body. Due to the abrasive nature of the scree, the elongated cutting tool body experiences wear and erosion. As the cutting tool body typically comprises steel, those skilled in the art will characterize this wear phenomenon as "steel wash". The result of "steel scrubbing" is to cause the diameter of the axially forward portion of the cutting tool body to decrease below or axially behind the hard cutting member. Such a reduction in diameter causes this portion of the cutting tool body to assume an hourglass shape. As the cutting operation progresses, the diameter of the axially forward portion of the cutting tool body continues to decrease to a point where it eventually breaks, thereby ending the life of the rotatable cutting tool due to the failure of the cutting tool body.

One way to retard steel has been to increase the size of the base portion of the hard insert. By increasing the size of the base portion, the hard cutting tip provides a greater degree of protection to the axially forward end of the steel cutting tool body. Along with increasing the size of the base portion of the hard insert, there was an increase in the overall geometry of the hard insert. By increasing the overall size of the hard insert, there has been an increase in the cost of materials for the rotatable cutting tool. In addition, by increasing the overall size of the hard insert, the resistance to penetration of the hard insert increases and thus more power or energy is needed to drive the rotatable cutting tool through the layers.

Steel washing has been (or may be) acute in cutting operations where the substrate is soft asphalt. When cutting soft asphalt, the rotatable cutting tool can cut to a depth such that the steel body enters the cut. When this occurs, the erosion or washing of the steel cutting tool body becomes significant, causing the steel cutting tool body to wear to one end of a useful condition before the hard insert wears to the end of a useful state. This can be a disadvantageous condition because the hard cutting insert contains a lot of useful tungsten carbide and yet the rotatable cutting tool is not suitable for cutting.

It is thus highly desirable to provide an improved rotatable cutting tool rotatably supported by an individual block or holder of a rotatable drum of a cutting machine (e.g., a road grader), the hard cutting board containing no amount of useful tungsten carbide at the time, where the steel cutting tool body reaches an end of its useful life. Furthermore, it would be desirable to provide a hard insert that provides protection to the steel cutting tool body and yet does not increase the power or energy required to drive the rotatable cutting tool through the layers.

BRIEF SUMMARY OF THE INVENTION

In one form thereof, the invention is a rotatable cutting tool intended to impact a substrate and adapted to be rotatably retained in the bore of a holder. The rotatable cutting tool includes an elongated cutting tool body having an axially forward end and an axially rearward end with a socket at the axially forward end thereof. The rotatable cutting tool further comprises a hard cutting member abutting the cutting tool body within the Version is attached. The hard cutting member has an axially forward end and an axially rearward end. The hard cutting member has an axially forward functional portion having an initial transverse functional dimension, and further includes a base portion having a largest transverse base dimension. A ratio of the initial transverse functional dimension to the largest transverse base dimension ranges between 0.42 and less than 0.48.

In yet another form, the invention is a hard cutting member for attachment to a cutting tool body. The hard cutting member includes an axially forward end, an axially rearward end, and an axially forward functional portion having an initial transverse functional dimension. The hard cutting member further includes a base portion having a largest transverse base dimension. A ratio of the initial transverse functional dimension to the largest transverse base dimension ranges between 0.42 and less than 0.48.

In yet another form, the invention is a hard cutting member for attachment to a cutting tool body. The hard cutting member includes an axially forward end and an axially rearward end. The axial length is the distance between the axially front end and the axially rear end. The hard cutting member has an axially forward functional portion having an initial transverse functional dimension and a base portion having a largest transverse base dimension. A ratio of the initial transverse functional dimension to the largest transverse base dimension ranges between 0.42 and less than 0.48. A ratio between the axial length and the largest transverse base dimension ranges between 0.75 and less than 0.78.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings which form a part of the present patent application:

1 Figure 11 is a side view of a rotary cutting tool with a hard cutting member at the axially forward end;

2 is a side view of the hard cutting member of 1 wherein a portion of the axially forward end of the steel cutting tool body is broken away and exposing the hard cutting member in the socket and the braze joint between the hard cutting member and the surface defines the socket;

3 is a side view of the hard cutting member of 2 , not shown in the version;

4 is a side view of a second specific embodiment of a hard cutting member and

5 is a side view of a third specific embodiment of a hard cutting member.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Illustrated with reference to the drawings 1 a first specific embodiment of the rotary cutting tool of the invention, generally as 30 designated. The specific embodiments presented herein relate to street leveling tools. It will be understood, however, that the invention applies to other types of cutting tool that are useful in other types of cutting operations. Exemplary operations include, but are not limited to, road planing (or milling), coal mining, concrete cutting, and other types of cutting operations where a cutting tool with a hard cutting member strikes a substrate (e.g., earth strata, paving, road asphalt material, concrete, and the like) the substrate is broken up into pieces of a variety of sizes, including larger pieces or chunks and smaller pieces including dusty particles.

The rotatable cutting tool 30 has a central longitudinal axis AA. In operation, the rotatable cutting tool rotates 30 around the axis AA. The rotatable cutting tool 30 includes an elongate cutter body, generally as 32 referred to, which is usually made of steel. Exemplary compositions of the steel for the cutting tool body include, without limitation, those disclosed in the following document: U.S. Patent Number 4,886,710 at Greenfield and U.S. Patent Number 5,008,073 at Greenfield. The elongated cutting tool body 32 represents a generally cylindrical geometry and has an axially forward end 34 on an axially rear end 36 on.

The elongated cutting tool body 32 contains a head section 38 which has an enlarged transverse dimension at the axially front end 34 relative to the overall transverse dimension of the cutting tool body. The elongated cutting tool body 32 further includes an integral shaft portion 40 having a reduced transverse dimension at the axially rear end 36 relative to the overall transverse dimension of the cutting tool body. The shaft section 40 contains an annular groove 42 at the axially rear end 36 ,

The head section 38 contains a version 44 at the axially front end of the cutting tool body 32 , The version 44 represents a so-called flat-bottomed geometry, wherein the socket 44 a generally circular soil surface 46 and a generally cylindrical surface 48 having. It is understood that other geometries of a socket may be suitable for use with the rotatable cutting tool, provided the geometry of the hard cutting member is the same as that of the socket.

The elongated cutting tool body 32 carries an elongated resilient mount 52 , The resilient mount 52 provides an axial front end 54 and an axially rear end 56 dar. The resilient holder 52 contains a longitudinal slot 58 along the entire longitudinal length thereof. The presence of the slot 58 provides radial compliance to the compliant mount 52 , Although not directly shown, the bracket contains 52 a radially inner projection that is in the groove 42 is received to assist in holding the holder to the shaft of the rotary cutting tool.

A generally circular washer 60 (see solid line illustration), which has a collar 62 which extends in an axially rearward direction surrounds the resilient mount 52 and compresses it radially. Although not shown, the washer contains 60 a central opening. The washer 60 As shown by solid lines, it is in a state prior to insertion of the rotatable cutting tool 30 into the bore of a block or holder. When inserting the rotatable cutting tool 30 into the bore of a block or holder is the washer 60 in an axially forward direction along the surface of the resilient mount 52 until pressed against the rear surface of the enlarged head section 38 strikes.

The rotatable cutting tool 30 also contains a hard cutting member, commonly referred to as 70 is designated by brazing in the socket 44 at the axially front end 34 of the cutting tool body 32 attached. Qualities of (cobalt) tungsten carbide suitable for use herein include those described in U.S. Pat U.S. Patent Number 4,859,543 at Greenfield and the U.S. Patent Number 6,197,084 to Smith.

2 shows that in the version 44 brazed hard cutting link 70 wherein between the hard cutting member 70 and the surfaces that the socket 44 define a braze joint 68 is present. The dimension "B" represents the axial length of the hard cutting member 70 axially in front of the axially front end 34 of the cutting tool body 32 when the hard cutting member 70 within the version 44 of the cutting tool body 32 is attached.

With further reference to the 2 and 3 contains the hard cutting element 70 an axial front end 72 and an axially rear end 74 flat, several spacer humps 76 that is from the rear end 74 protrude. The hard cutting element 70 contains one by parenthesis 80 shown function section. The functional section 80 has a cross-start dimension equal to "C". The hard cutting element 70 also has a base section 86 which has a transverse base dimension "D".

With reference to 4 is a second embodiment of the hard cutting member, generally as 90 indicated. The hard cutting element 90 contains an axial front end 92 and an axially rear end 94 flat, several distance blocks 96 that is from the rear end 94 protrude. The hard cutting element 90 contains one by parenthesis 100 shown function section. The functional section 100 has a cross-start dimension equal to "C". The hard cutting element 90 also has a base section 98 which has a transverse base dimension "D".

With reference to 5 is a third embodiment of the hard cutting member, generally as 110 indicated. The hard cutting element 110 contains an axial front end 112 and an axially rear end 114 flat, several distance blocks 116 that is from the rear end 114 protrude. The hard cutting element 110 contains one by parenthesis 120 shown function section. The functional section 120 has a cross-start dimension equal to "C". The hard cutting element 110 also has a base section 118 which has a transverse base dimension "D".

Table I below shows the dimensions B-B ", C-C" and D-D "of these specific embodiments. Table I. Specific dimensions (in millimeters) for the first, second and third embodiments embodiment Dimension B / B '/ B''(mm) Dimension C / C '/ C''(mm) Dimension D / D '/ D''(mm) Ratio C: D First 14.1 8.54 18.75 0,455 Second 14.46 8.54 18.75 0,455 third 16.46 8.54 18.75 0,455

Table II below shows the dimensions (in millimeters) of various specific embodiments of the hard cutters. Table II Dimensions for the specific embodiments of hard cutting members embodiment Initial diameter of the functional section (mm) Diameter of base section (mm) Ratio of the initial diameter of the functional section to the diameter of the base section A 8.0 19 0.42 B 8.2 19 0.43 C 8.16 18.87 0,432 D 8.4 19 0.44 e 8.6 19 0.45 F 8.54 18.75 0,455 G 8.7 19 0.46 H 8.9 19 0.47 I 9.0 19 0.474 J 8.92 18.61 0.479

It will be understood that, in one sense, the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.42 and less than 0.48. In one range, the ratio of the initial diameter of the functional portion to the diameter of the base portion varies between 0.42 and 0.479. In a narrower range, the ratio of the initial diameter of the functional portion to the diameter of the base portion varies between 0.43 and 0.455. In an even narrower range, the ratio of the initial diameter of the functional section to the diameter of the base section varies between 0.432 and 0.45. A center of the ratio of the initial diameter of the functional portion to the diameter of the base portion is 0.44.

It is understood that the smaller ratio provides for a narrower or smaller axially forward portion of the hard cutting member. As a result, the hard cutting member experiences less resistance. By experiencing less resistance, less power or energy is needed to drive the rotatable cutting tool through the layers.

It is thus apparent that the present invention provides an improved rotatable cutting tool rotatably supported by an individual block or holder of a rotatable drum of a cutting machine (e.g., a road leveling machine), the hard cutting board containing no amount of useful tungsten carbide at the time where the steel cutting tool body reaches an end to its useful life.

The patents and other documents identified herein are hereby incorporated by reference. Other embodiments of the invention will become apparent to those skilled in the art from consideration of the specification or practice of the invention disclosed herein.

It is intended that the specification and samples are merely illustrative and not intended to limit the scope of the invention. The true scope and spirit of the invention are indicated by the following claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

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Claims (14)

A rotatable cutting tool for impacting a substrate and adapted to be rotatably supported in the bore of a holder, the rotatable cutting tool comprising: an elongated cutter body having an axially forward end and an axially rearward end, the cutter body including a socket at the axially forward end thereof; a hard cutting member fixed to the cutting tool body in the socket, and the hard cutting member having an axially forward end and an axially rearward end; wherein the hard cutting member has an axially forward functional portion having an initial transverse functional dimension; the hard cutting member further comprising a base portion having a largest transverse base dimension; and a ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.42 and less than 0.48. The rotatable cutting tool of claim 1, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.42 and less than 0.479. The rotary cutting tool of claim 1, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.43 and less than 0.455. The rotary cutting tool of claim 1, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range of between 0.432 and less than 0.45. A hard cutting member for attachment to a cutting tool body, the hard cutting member comprising: an axially forward end and an axially rearward end; an axially forward functional portion having an initial transverse functional dimension; a base portion having a largest transverse base dimension; and a ratio of the initial transverse functional dimension to the largest transverse base dimension in the range between equal to 0.42 and less than 0.48. A hard cutting member according to claim 5, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.42 and less than 0.479. A hard cutting member according to claim 5, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.43 and less than 0.455. A hard cutting member according to claim 5, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range of between 0.432 and less than 0.45. A hard cutting member for attachment to a cutting tool body, the hard cutting member comprising: an axially forward end and an axially rearward end, wherein an axial length is the distance between the axially forward end and the axially rearward end; an axially forward functional portion having an initial transverse functional dimension; a base portion having a largest transverse base dimension; a ratio of the initial functional dimension to the largest transverse base dimension ranging between 0.42 and less than 0.48, a ratio between the axial length and the largest transverse base dimension ranging between 0.75 and less than 0.78. A hard cutting member according to claim 9, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range of between 0.42 and less than 0.479. A hard cutting member according to claim 9, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range between 0.43 and less than 0.455. A hard cutting member according to claim 9, wherein the ratio of the initial transverse functional dimension to the largest transverse base dimension is in the range of between 0.432 and less than 0.45. A hard cutting member according to claim 9, wherein the ratio of the axial length to the largest transverse base dimension is in the range between equal to 0.76 and less than 0.78. A hard cutting member according to claim 9, wherein the ratio of the axial length to the largest transverse base dimension is in the range between equal to 0.768 and less than 0.771.

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