Abstract:
A rotatable cutting tool for use in impinging earth strata such as, for example, asphaltic roadway material, coal deposits, mineral formations and the like. The rotatable cutting tool includes a cutting tool body having a through coolant channel and a two-piece head portion, e.g., the head portion of the cutting tool body having a base portion and a nose portion with a hard tip cutting insert affixed to the nose portion. The through coolant provides for cooling the hard tip cutting insert during operation of the cutting tool. In addition, the through coolant also provides for suppressing dust created by the rotatable cutting tool during operation.

Description:
BACKGROUND OF THE INVENTION 
     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 present invention pertains to a rotatable cutting tool that is useful for the impingement of earth strata wherein the cutting tool body possesses improved design so as to provide for improved 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 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 planing 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. In addition, during a machining operation the cutting insert becomes heated. The heat spreads quickly through the cutting insert. The cutting insert reaches, in a very short time, a range of temperatures within which the resistance to plastic deformation of the cutting insert material decreases. When large cutting forces act on the cutting insert, this phenomenon entails a risk that the cutting insert will be subject to plastic deformation, in particular, in the proximity of the cutting edge, where insert breakage can result. In order to diminish the risk of plastic deformation, an efficient system for cooling the cutting insert would be desirable, whereby the working temperature of the insert can be regulated within desired limits. 
     As is also known during use of the rotatable cutting tool, a substantial amount of dust may be generated, e.g. coal dust during a mining operation. When the dust becomes air borne, it becomes a risk for humans and equipment in the immediate area. For example, the dust can be inhaled by humans (health risk) or the dust can be ignited by mining activities causing an explosion (safety risk). In order to reduce or minimize health and/or safety risks, an efficient system that reduces or minimizes the amount of dust that is generated would be desirable. 
     The present invention has been developed in view of the foregoing. 
     SUMMARY OF THE INVENTION 
     The present invention provides a rotatable cutting tool for use in impinging earth strata such as, for example, asphaltic roadway material, coal deposits, mineral formations and the like. The rotatable cutting tool includes a cutting tool body having a through coolant channel and a two-piece head portion, e.g., the head portion of the cutting tool body includes a base portion and a nose portion with a hard tip cutting insert affixed to the nose portion. The through coolant provides for cooling the hard tip cutting insert during operation of the cutting tool. In addition, the through coolant also provides for suppressing dust created by the rotatable cutting tool during operation. 
     An aspect of the present invention is to provide a rotatable cutting tool for use in impinging earth strata wherein the rotatable cutting tool comprises a cutting tool body and a hard tip affixed to the cutting tool body. The cutting tool body includes an axial forward end for receiving the hard tip and 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 affixed to the collar portion and a nose portion movably connected to the base portion. The cutting tool body defines an internal coolant channel extending axially from the axial rearward end through the shank portion, the collar portion and through at least part of the base portion of the head portion. The nose portion of the head portion is positioned adjacent to the internal coolant channel that extends through the base portion of the head portion. In one aspect of the invention, the base portion defines a pocket for receiving at least a part of the nose portion. In another aspect of the invention, the pocket is in fluid communication with the internal coolant channel. In yet another aspect of the invention, the nose portion includes at least one flute formed on a surface thereof. 
     Another aspect of the present invention is to provide a rotatable cutting tool for use in impinging earth strata wherein the rotatable cutting tool comprises a cutting tool body and a hard tip affixed to the cutting tool body. The cutting tool body includes an axial forward end for receiving the hard tip and 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 that defines a pocket, wherein the head portion further includes a nose portion that is at least partially received in the pocket of the base portion and is rotatably connected to the base portion. The cutting tool body defines a coolant channel that is in fluid communication with the pocket of the base portion. In one aspect, the nose portion defines at least one rotational flute. 
     A further aspect of the present invention is to provide a rotatable cutting tool body with a central longitudinal axis, the rotatable cutting tool body comprising a head portion, a shank portion, and a collar portion mediate of and contiguous with the head portion and the shank portion. The head portion includes a base portion and a nose portion. The cutting tool body further comprises an axial forward end adjacent to the nose portion of the head portion and an axial rearward end adjacent to the shank portion. Means for rotatably connecting the nose portion to the base portion are provided. The cutting tool body also comprises an internal coolant channel extending axially from the axial rearward end through the shank portion, the collar portion, and through at least a portion of the head portion. In one aspect of the invention, the nose portion of the head portion is positioned adjacent an axial forward end of the internal coolant channel that extends through at least a part of the head portion. In another aspect, the base portion defines a pocket for receiving at least a part of the nose portion. In yet another aspect of the invention, the pocket is in fluid communication with the internal coolant channel. In another aspect of the invention, the nose portion includes at least one rotational flute formed on a surface thereof. 
     These and other aspects of the present invention will be more fully understood following a review of this specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded, perspective view of a rotatable cutting tool, in accordance with an aspect of the invention. 
         FIG. 2  is a side elevational view of the rotatable cutting tool, shown in  FIG. 1 , as assembled, in accordance with an aspect of the invention. 
         FIG. 3  is an end elevational view of the rotatable cutting tool shown in  FIGS. 1 and 2 , in accordance with an aspect of the invention. 
         FIG. 4  is a nose portion of a rotatable cutting tool, in accordance with an aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “coolant” generally refers to any liquid, gas, or other material that is suitable for use with the present invention as described herein. In one aspect, the coolant may be a liquid such as, for example, water. In another aspect, the coolant may be, for example, an air-water mixture, oil, or carbon dioxide. 
     Referring to  FIGS. 1 and 2 , there is illustrated a rotatable cutting tool, generally designated as  20 , in accordance with an aspect of the invention. Rotatable cutting tool  20  comprises an elongate cutting tool body, generally designated as  22 . The cutting tool body  22  is typically made of steel such as those grades disclosed, for example, in U.S. Pat. No. 4,886,710 to Greenfield, which is hereby incorporated by reference. 
     Still referring to  FIGS. 1 and 2 , the cutting tool body  22  has an axial forward end  24  and an axial rearward end  26 . A hard tip or insert  30  is affixed (such as by brazing or the like) in a socket  31  in the axial forward end  24  of the cutting tool body  22 . Hard insert  30  is typically made from cemented carbide such as, for example, cemented (cobalt) tungsten carbide wherein U.S. Pat. No. 6,375,272 to Ojanen, which is hereby incorporated by reference, discloses examples of acceptable grades of cemented (cobalt) tungsten carbide. The geometry of the hard insert  30  can vary depending upon the specific application. U.S. Pat. No. 6,375,272 to Ojanen discloses an exemplary geometry for the hard insert. It should be appreciated that as an alternative to the socket, the axial forward end of the cutting tool body may present a projection that is received within a socket in the bottom of the hard tip. This alternate structure can be along the lines of that disclosed, for example, in U.S. Pat. No. 5,141,289 to Stiffler, which is hereby incorporated by reference. 
     The cutting tool body  22  is divided into three principal portions; namely, a head portion  32 , a collar portion  38  and a shank portion  44 . These portions will now be described. 
     The most axial forward portion is the head portion  32 . The head portion  32  begins at the axial forward end  24  and extends along longitudinal axis X-X in the axial rearward direction. 
     The mediate portion is the collar portion  38 . Beginning at the juncture with the head portion  32  and extending along the longitudinal axis X-X in the axial rearward direction, the collar portion  38  comprises a tapered neck section  40  followed by a cylindrical collar section  42 . 
     The most axial rearward portion is the shank portion  44 . Beginning at the juncture with the collar portion  38  and extending along the longitudinal axis X-X in the axial rearward direction, the shank portion  44  comprises a forward cylindrical tail section  46 , followed by a mid-section  48 , followed by a retainer groove  50 , followed by a rearward cylindrical tail section  52  and terminating in a beveled section  54 . As is known by those skilled in the art, the shank portion  44  is the portion of the cutting tool body  22  that carries the retainer (not illustrated). The retainer rotatably retains the rotatable cutting tool in the bore of a tool holder (not illustrated) or the bore of the sleeve carried by a holder. While the retainer can take on any one of many geometries, a retainer suitable for use with this cutting tool body is shown and described, for example, in U.S. Pat. No. 4,850,649 to Beach et al., which is hereby incorporated by reference. 
     Still referring to  FIGS. 1 and 2 , the head portion  32  includes a two-piece construction, in accordance with an aspect of the invention. Specifically, the head portion  32  includes a base portion  54  that is affixed to the collar portion  38 . The head portion  32  also includes a nose portion  56  that is movably connected to the base portion  54 . In one aspect of the invention, the hard tip  30  is affixed to the nose portion  56 . 
     As illustrated in  FIGS. 1 and 2 , the base portion  54  of the head portion  32  defines a pocket, generally designated by reference no.  58 . In one aspect, the pocket  58  can have a substantially circular cross-section and extend axially along axis X-X from an axial forward end  60  of the base portion  54  rearwardly toward the collar portion  38 . A groove  62  (see  FIG. 2 ) is formed in the base portion  54  circumferentially about the pocket  58 . 
     At least a part of the nose portion  56  is received in the pocket  58 . The nose portion  56  is movably connected to the base portion  54 . In one aspect of the invention, the movable connection is provided by a mounting clip  64 , e.g., a spring clip that is attached to the nose portion  56  and includes a plurality of dimples  66  that are received in the groove  62 . The mounting clip  64  is retained on the nose portion  56  by positioning the mounting clip  64  in an elongated notch  68  formed circumferentially about the nose portion  56 . In one aspect of the invention, the described configuration of the mounting clip  64  with dimples  66  that cooperate with groove  62  provides for the nose portion  56  to be rotatably connected to the base portion  54 . Thus, it will be appreciated that the nose portion  56  is allowed to move independently with respect to the base portion  54 . In addition, it will be appreciated that other means for movably connecting the nose portion  56  to the base portion  54  may be provided in accordance with the scope of the invention. 
     Referring to  FIGS. 2 and 3 , the cutting tool body  22  defines a coolant channel  70  that extends axially along axis X-X from the axial rearward end  26  through the shank portion  44 , through the collar portion  38 , and through at least part of the base portion  54  of the head portion  32 . In one aspect of the invention, the coolant channel  70  has a substantially circular cross-section. In another aspect of the invention, the coolant channel  70  is formed on an internal portion of the cutting tool body  22  and an axial forward end  71  of the coolant channel  70  is in fluid communication with the pocket  58  of the base portion  54 . This configuration provides for the nose portion  56  of the head portion  32  to be positioned adjacent to the internal coolant channel  70  that extends through at least a part of the base portion  54  of the head portion  32 . 
     In operation of the rotatable cutting tool  20  of the invention, a coolant is passed through the internal coolant channel  70  in the direction indicated by arrows  72 . The coolant passes from the coolant channel  70  to the pocket  58  of the base portion  54 . Once the coolant reaches the pocket  58 , the coolant is able to contact the nose portion  56  which, as described, is movably mounted within the base portion  54 . It will be appreciated, therefore, that due to the nose portion  56  being movably connected relative to the base portion  54 , that the nose portion  56  does not have a snug or interference fit that would prevent the coolant from passing over the nose portion  56  and moving toward the axial forward end  60  of the base portion  54 . Once the coolant passes the axial forward end  60  of the base portion  54 , it continues to flow toward the axial forward end  24  of the nose portion  56  and toward the hard tip cutting insert  30 . Advantageously, the coolant provides for cooling the hard tip  30  during a cutting operation of the rotatable cutting tool  20 . This provides for the working temperature of the hard tip  30  to be regulated within desired limits during a cutting operation in order to increase the useful life of the hard tip  30 . 
     In addition, it will be appreciated that providing for the coolant to pass through the cutting tool body  22  and reach an axial forward end  24  thereof, provides for the coolant to act as a dust suppressant for dust that may be generated during a particular cutting operation using the rotatable cutting tool  20 . 
     As shown in  FIGS. 1 and 2 , the nose portion  56  may have one or more flutes  74  formed on a surface of the nose portion  56 , in accordance with an aspect of the invention. Advantageously, the flutes  74  provide for the coolant that contacts the nose portion  56  to engage the flutes  74  and to rotate the nose portion  56  with respect to the base portion  54 . The increased rotation of the nose portion  56  due to the flutes  74  interacting with the coolant provides for increased life for the hard tip  30  by providing for more uniform wear of the hard tip  30 . 
       FIG. 4  illustrates an alternate embodiment of a nose portion  156 , in accordance with an aspect of the invention. Nose portion  156  includes a hard tip  130  affixed thereto, similar to the arrangement set forth and described herein in  FIGS. 1 and 2 . However, the nose portion  156  includes a substantially smooth outer surface  176 , i.e., the outer surface  176  does not include flutes formed thereon. The nose portion  156  is still rotatably mounted with respect to a base portion (not shown in  FIG. 4 ) to provide for relative movement between the nose portion  156  and the corresponding base portion. 
     Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.