Patent Publication Number: US-2011068616-A1

Title: Rotatable cutting tool with hard cutting member

Description:
CROSS-REFERENCE TO EARLIER PATENT APPLICATION 
     This patent application is a continuation of co-pending provisional U.S. Patent Application Ser. No. 61/244,228 filed Sep. 19, 2009 for ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen. Applicant hereby claims priority on such U.S. Patent Application Ser. No. 61/244,228 filed Sep. 19, 2009 for ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen. Further, applicant hereby incorporates by reference herein the entirety of such U.S. Patent Application Ser. No. 61/244,228 filed Sep. 19, 2009 for ROTATABLE CUTTING TOOL WITH HARD CUTTING MEMBER by Randal W. Ojanen. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention pertains to a rotatable cutting tool, which typically mounts in a stationary block (or holder) on a rotatable drum. The rotatable cutting tool, which is rotatable about its central longitudinal axis, carries a hard cutting insert at the axially forward end thereof. The hard cutting insert is of a hard material such as, for example, cemented (cobalt) tungsten carbide. The rotatable cutting tool engages or impinges a substrate upon the rotation of the drum. The hard cutting insert exhibits a geometry that provides a number of benefits both in the operational efficiency of the rotatable cutting tool and the cost of materials to manufacture the rotatable cutting tool. 
     A rotatable cutting tool typically presents a generally elongate, cylindrical geometry. The rotatable cutting tool comprises an elongate steel cutting tool body, which has 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 rotatable carried by the stationary block or holder on the drum. Exemplary structures useful for the rotatable attachment of a rotatable cutting tool to a block or holder include those shown and described in U.S. Pat. No. 4,201,41 to Den Besten et al., U.S. Pat. No. 3,519,309 to Engle et al., U.S. Pat. No. 3,752,515 to Oaks et al., and U.S. Pat. No. 7,380,888 to Ojanen for a Rotatable Cutting Tool having Retainer with Dimples. 
     A hard cutting member typically affixes, such as by brazing, to the axial forward and of the cutting tool body. As mentioned above, typically, the hard cutting member is made from a hard material like cemented cobalt tungsten carbide. U.S. Pat. No. 4,389,074 to Greenfield, U.S. Pat. No. 5,131,725 to Rowlett et al., U.S. Pat. No. 5,429,199 to Sheirer et al., U.S. Pat. No. 6,375,272 to Ojanen, and U.S. Pat. No. 6,478,383 to Ojanen et al. disclose braze alloys that have heretofore been suitable for such a brazing operation and suitable compositions of cemented tungsten carbide. 
     Heretofore, a hard cutting member suitable for use in a rotatable cutting tools have exhibited many different geometries. One exemplary geometry is shown and described in U.S. Pat. No. 4,497,520 to Ojanen. 
     In the case of a road planing machine, the rotatable drum can in many cases carry hundreds of individual blocks or holders. Each individual block or holder carries its own corresponding rotatable cutting tool, which is rotatable relative to its corresponding block or holder. It is not unusual that a rotatable drum will carry hundreds of individual rotatable cutting tools. 
     The road planing machine powers the rotatable drum so as to cause it to rotate. The orientation of the rotatable cutting tools with respect to the drum is such so that upon rotation of the drum, the drum drives the rotatable cutting tools into the substrate. Upon the rotatable cutting tools impinging the substrate, the substrate typically breaks thereby forming larger chunks of debris, as well as smaller particles and pieces of debris. Typically, the debris generated in a road planing operation is highly abrasive which causes the rotatable cutting tool to experience wear. 
     The rotatable cutting tool can experience wear in a number of ways. The hard cutting member, which is the portion of the rotatable cutting bit that first impinges the substrate, can experience wear. The initial impact of the hard cutting member against the substrate, as well as the travel of the debris along the hard cutting member, can cause this wear. Over the course of the cutting operation, the hard cutting member can lose material to the point where it becomes dull and ineffective to accomplish efficient cutting. 
     Another wear mechanism pertains to the braze joint between the hard cutting member and the elongate cutting tool body. Throughout the course of the cutting operation, the braze joint experiences severe stresses due to the continual intermittent violent impingement of the rotatable cutting tool against the substrate material. Over the course of time, the braze joint can experience sufficient stress so as to fail thereby allowing the hard cutting member to separate from the cutting tool body. Obviously, if the rotatable cutting tool loses the hard cutting member, the rotatable cutting tool is no longer useful for the cutting operation. 
     Further, during a cutting operation such as, for example, a road planing operation, debris travels down the elongate cutting tool body. Due to the abrasive nature of the debris, the elongate cutting tool body experiences wear and erosion. Since the cutting tool body typically comprises steel, those in the pertinent art characterize this wear phenomenon as “steel wash”. The result of “steel wash” is to cause the axial forward portion of the cutting tool body beneath or axially behind the hard cutting member to reduce in diameter. Such a reduction in diameter causes this portion of the cutting tool body to take on an hourglass shape. As the cutting operation continues, the axial forward portion of the cutting tool body continues to reduce in diameter to a point where it eventually breaks thereby ending the useful life of the rotatable cutting tool due to the failure of the cutting tool body. 
     One way to retard steel was has been to enlarge the size of the base portion of the hard cutting insert. By enlarging the size of the base portion, the hard cutting insert provides a greater amount of protection to the axial forward end of the steel cutting tool body. Along with enlarging the size of the base portion of the hard cutting insert, there has been an enlargement of the overall geometry of the hard cutting insert. By enlarging the overall size of the hard cutting insert, there has been an increase in the cost of materials for the rotatable cutting tool. Further, by enlarging the overall size of the hard cutting insert, resistance to the penetration of the hard cutting insert increases, and thus, more power or energy is needed to drive the rotatable cutting tool through the strata. 
     Steel wash has been (or can be) particularly acute in cutting operations in which the substrate is soft asphalt. In cutting soft asphalt, the rotatable cutting tool may cut to a depth such that the steel body enters the cut. When this occurs, the erosion or wash of the steel cutting tool body becomes significant whereby the steel cutting tool body wears to an end of useful condition prior to the hard cutting insert wearing to an end of useful condition. This can be a disadvantageous condition because the hard cutting insert contains an amount of useful cemented tungsten carbide, and yet, the rotatable cutting tool is not useful for cutting. 
     It would thus be highly desirable to provide an improved rotatable cutting tool, which is rotatably carried by an individual block or holder of a rotatable drum of a cutting machine (e.g., a road planing machine), wherein the hard cutting insert does not contain an amount of useful cemented tungsten carbide at the time the steel cutting tool body reaches an end of useful life condition. Further, it would be desirable to provide a hard cutting insert that provides protection to the steel cutting tool body and yet does not increase the power or energy necessary to drive the rotatable cutting tool through the strata. 
     SUMMARY OF THE INVENTION 
     In one form thereof, the invention is a rotatable cutting tool that is for impingement upon a substrate and adapted to be rotatably retained within the bore of a holder. The rotatable cutting tool includes an elongate cutting tool body, which has an axial forward end and an axial rearward end with a socket at the axial forward end thereof. The rotatable cutting tool further has a hard cutting member, which is affixed to the cutting tool body within the socket. The hard cutting member has an axial forward end and an axial rearward end. The hard cutting member has an axial forward functional portion which has a starting transverse functional dimension, and further has a base portion which has a maximum transverse base dimension. There is a ratio of the starting transverse functional dimension to the maximum transverse base dimension ranging between equal to 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 comprises an axial forward end, an axial rearward end, and an axial forward functional portion, which has a starting transverse functional dimension. The hard cutting member further has a base portion, which has a maximum transverse base dimension. A ratio of the starting transverse functional dimension to the maximum transverse base dimension ranges between equal to 0.42 and less than 0.48. 
     In still another form, the invention is a hard cutting member for attachment to a cutting tool body. The hard cutting member comprises an axial forward end and an axial rearward end. The axial length is the distance between the axial forward end and the axial rearward end. The hard cutting member has an axial forward functional portion, which has a starting transverse functional dimension, and a base portion which has a maximum transverse base dimension. A ratio of the starting transverse functional dimension to the maximum transverse base dimension ranges between equal to 0.42 and less than 0.48. A ratio between the axial length and the maximum transverse base dimension ranges between equal to 0.75 and less than 0.78. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following is a brief description of the drawings that form a part of this patent application: 
         FIG. 1  is a side view of a rotatable cutting tool with a hard cutting member at the axial forward end; 
         FIG. 2  is a side view of the hard cutting member of  FIG. 1  wherein a portion of the axial forward end of the steel cutting tool body is broken away showing the hard cutting member in the socket and the braze joint between the hard cutting member and the surface that defines the socket; 
         FIG. 3  is a side view of the hard cutting member of  FIG. 2  shown not in the socket; 
         FIG. 4  is a side view of a second specific embodiment of a hard cutting member; and 
         FIG. 5  is a side view of a third specific embodiment of a hard cutting member. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Referring to the drawings,  FIG. 1  illustrates a first specific embodiment of the rotatable cutting tool of the invention, generally designated as  30 . The specific embodiments illustrated herein pertain to road planing tools. However, one should appreciate that the invention has application to other kinds of cutting tool useful in other kinds of cutting operations. Exemplary operations include without limitation road planing (or milling), coal mining, concrete cutting, and other kinds of cutting operations wherein a cutting tool with a hard cutting member impinges against a substrate (e.g., earth strata, pavement, asphaltic highway material, concrete, and the like) breaking the substrate into pieces of a variety of sizes including larger-size pieces or chunks and smaller-sized pieces including dust-like particles. 
     Rotatable cutting tool  30  has a central longitudinal axis A-A. In operation, rotatable cutting tool  30  rotates about the axis A-A. Rotatable cutting tool  30  includes an elongate cutting tool body generally designated as  32 , which typically is made of steel. Exemplary compositions of the steel for the cutting tool body include without limitation those disclosed in the following document: U.S. Pat. No. 4,886,710 to Greenfield, and U.S. Pat. No. 5,008,073 to Greenfield. Elongate cutting tool body  32  presents a generally cylindrical geometry, and has an axial forward end  34  and an axial rearward end  36 . 
     Elongate cutting tool body  32  includes a head portion  38 , which has an enlarged transverse dimension adjacent the axial forward end  34  relative to the overall transverse dimension of the cutting tool body. The elongate cutting tool body  32  further includes an integral shank portion  40 , which has a reduced transverse dimension, adjacent the axial rearward end  36  relative to the overall transverse dimension of the cutting tool body. The shank portion  40  contains an annular groove  42  adjacent the axial rearward end  36 . 
     The head portion  38  contains a socket  44  at the axial forward end of the cutting tool body  32 . The socket  44  presents a so-called flat-bottom geometry wherein the socket  44  has a generally circular bottom surface  46  and a generally cylindrical surface  48 . One should appreciate that other geometries of a socket may be suitable for use with the rotatable cutting tool provided that the geometry of the hard cutting member corresponds to that of the socket. 
     The elongate cutting tool body  32  carries an elongate resilient retainer  52 . Resilient retainer  52  presents an axial forward end  54  and an axial rearward and  56 . Resilient retainer  52  contains a longitudinal slit  58  along the entire longitudinal length thereof. The presence of the slit  58  provides a radial resiliency to the resilient retainer  52 . Although not directly shown, retainer  52  includes a radially inward projection that is received within the groove  42  so as to assist with the retention of the retainer on the shank of the rotatable cutting tool. 
     A generally circular washer  60  (see solid line illustration), which has a collar  62  extending in an axial rearward direction, surrounds and radially compresses the resilient retainer  52 . Although not illustrated, washer  60  contains a central aperture. Washer  60  as illustrated by solid lines is in a condition prior to the insertion of the rotatable cutting tool  30  into the bore of a block or holder. Upon the insertion of the rotatable cutting tool  30  into the bore of a block or holder, the washer  60  is forced in an axial forward direction along the surface of the resilient retainer  52  until it abuts against the rearward surface of the enlarged head portion  38 . 
     Rotatable cutting tool  30  further includes a hard cutting member generally designated as  70  affixed by brazing within socket  44  at the axial forward end  34  of the cutting tool body  32 . Grades of cemented (cobalt) tungsten carbide suitable for use herein include those disclosed in U.S. Pat. No. 4,859,543 to Greenfield and U.S. Pat. No. 6,197,084 to Smith. 
       FIG. 2  shows the hard cutting member  70  brazed into the socket  44  wherein there is a braze joint  68  between the hard cutting member  70  and the surfaces that define the socket  44 . Dimension “B” represents the axial length of hard cutting member  70  axially forward of the axial forward end  34  of the cutting tool body  32  when the hard cutting member  70  is affixed within the socket  44  of the cutting tool body  32 . 
     Still referring to  FIG. 2  and to  FIG. 3 , hard cutting member  70  includes an axial forward end  72  and an axial rearward end  74 , which is flat has a has plurality of spacer bumps  76  that project from the rearward end  74 . Hard cutting member  70  includes a functional portion shown by bracket  80 . Functional portion  80  has a transverse starting dimension equal to “C”. Hard cutting member  70  further has a base portion  86 , which has a transverse base dimension “D”. 
     Referring to  FIG. 4 , there is shown a second embodiment of the hard cutting member generally designated as  90 . Hard cutting member  90  includes an axial forward end  92  and an axial rearward end  94 , which is flat has a has plurality of spacer bumps  96  that project from the rearward end  94 . Hard cutting member  90  includes a functional portion shown by bracket  100 . Functional portion  100  has a transverse starting dimension equal to “C′”. Hard cutting member  90  further has a base portion  98 , which has a transverse base dimension “D”. 
     Referring to  FIG. 5 , there is shown a third embodiment of the hard cutting member generally designated as  110 . Hard cutting member  110  includes an axial forward end  112  and an axial rearward end  114 , which is flat has a has plurality of spacer bumps  116  that project from the rearward end  114 . Hard cutting member  110  includes a functional portion shown by bracket  120 . Functional portion  120  has a transverse starting dimension equal to “C″”. Hard cutting member  110  further has a base portion  118 , which has a transverse base dimension “D′”. 
     Table I below sets forth 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 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Dimension 
                 Dimension 
                 Dimension 
                 Ratio of 
               
               
                 Embodiment 
                 B/B′/B″ (mm) 
                 C/C′/C″ (mm) 
                 D/D′/D″ (mm) 
                 C:D 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 First 
                 14.1 
                 8.54 
                 18.75 
                 0.455 
               
               
                 Second 
                 14.46 
                 8.54 
                 18.75 
                 0.455 
               
               
                 Third 
                 14.46 
                 8.54 
                 18.75 
                 0.455 
               
               
                   
               
            
           
         
       
     
     Table II below sets forth the dimensions (in millimeters) of various specific embodiments of the hard cutting members. 
     
       
         
           
               
             
               
                 TABLE II 
               
             
            
               
                   
               
               
                 Dimensions for the Specific Embodiments Hard Cutting Members 
               
            
           
           
               
               
               
               
            
               
                   
                 Starting 
                   
                 Ratio of the Starting 
               
               
                   
                 Diameter of 
                 Diameter of 
                 Diameter of Functional 
               
               
                   
                 Functional 
                 the Base 
                 Portion to the Diameter 
               
               
                 Embodiment 
                 Portion (mm) 
                 Portion (mm) 
                 of the Base Portion 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 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 
               
               
                   
               
            
           
         
       
     
     There should be an appreciation that in one sense, the ratio of the starting transverse functional dimension to the maximum transverse base dimension ranging between equal to 0.42 and less than 0.48. In one range, the ratio of the starting 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 starting diameter of the functional portion to the diameter of the base portion varies between 0.43 and 0.455. In a still narrower range, the ratio of the starting diameter of the functional portion to the diameter of the base portion varies between 0.432 and 0.45. A mid-point of the ratio of the starting diameter of the functional portion to the diameter of the base portion is equal to 0.44. 
     There should be an appreciation that the smaller ratio provides for a narrower or smaller axial forward portion of the hard cutting member. By doing so, 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 strata. 
     It thus becomes apparent that the present invention provides an improved rotatable cutting tool, which is rotatably carried by an individual block or holder of a rotatable drum of a cutting machine (e.g., a road planing machine), wherein the hard cutting insert does not contain an amount of useful cemented tungsten carbide at the time the steel cutting tool body reaches an end of useful life condition. 
     The patents and other documents identified herein are hereby incorporated by reference herein. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. It is intended that the specification and samples are illustrative only and are not intended to be limiting on the scope of the invention. The true scope and spirit of the invention is indicated by the following claims.