Abstract:
The present invention relates to impact-type cutting tools used to pulverize and displace road construction materials, aggregate, earth strata, or the like. In particular, the present invention relates to a rotatable tool bit and assembly for use in such impact-type cutting tools, wherein tool bit life is improved and tool bit change-out time is reduced.

Description:
BACKGROUND  
       [0001]     The present invention relates to impact-type cutting tools used to pulverize and displace road construction materials, aggregate, earth strata, or the like. In particular, the present invention relates to a rotatably mounted tool bit and assembly for use in such impact-type cutting tools, wherein tool bit life is improved and tool bit change-out time is reduced.  
         [0002]     Impact-type cutting tools are used in such operations as road recycling, trenching, boring and other mining and road construction operations. The cutting tools generally operate by driving a plurality of cutting tool bits into a surface to but cut/pulverized. A cutting tool bit may be driven by a variety of mechanisms including rotary drum drives, rotary wheel drives, chain drives, augers or others. Regardless of the drive mechanisms employed, a particular cutting tool bit cuts through the aggregate or similar material by impacting a hard cutting tooth of the cutting tool bit on the surface to be cut/pulverized. Commonly, the cutting tool bit is disposed within a mounting block pocket of a particular drive mechanism such that a portion of the bit including the tooth is free to rotate relative to the mounting block pocket. The resultant force of the impact of the cutting tooth on the cutting surface translates into tool bit rotation relative to the mounting block pocket and consequently, rotation of the cutting tooth. Rotation of the cutting tooth is preferable as more uniform tooth wear is sustained during cutting. It is generally recognized that more uniform tooth wear greatly extends the working life of the tooth. As working life is increased, less tool bit change-outs are necessary, thus decreasing time and cost associated bit change-outs.  
         [0003]     Unfortunately, it is often the case that the pulverized particulate or other material is forced between an interface of a cutting tool bit and the mounting block pocket the bit is disposed in. At least two issues arise from the forced introduction of foreign matter into such interfaces. First, rotation of a cutting tool bit relative to the mounting block pocket might be interfered with or arrested, thereby greatly accelerating localized tooth wear. Second, the foreign matter might build up in such a manner as to eject the bit from the mounting block pocket. The second issue can also arise when the tool bit contacts alternating soft and hard cutting surfaces. The impulse force on the tooth and bit can cause either the bit or even the tooth itself to eject or “kick” out of place during operation. Regardless of whether ejection is caused by particulate build-up or varying cutting surface hardness, the extreme forces on the tool bit while displaced can cause tool bit damage or even failure.  
         [0004]     In an attempt to improve bit rotation and reduce kick out, cutting tool bits of prior design have incorporated retaining clips or other means to promote tighter contact between a bit and a mounting block pocket in order to reduce particulate ingression. These clips have been further modified to include “bowed” or spring designs, which seek to dampen transverse impulse forces. For examples of “springs” and “spring clip” designs, see U.S. Pat. Nos. 4,247,150 and 5,018,793. Regrettably, particulate and foreign material along with the impulse forces hereinto described continue to plague the proper operation of cutting tool bits. Additionally, clips of prior design fail to provide a proper grasping surface or similar feature for removal of the clip during tool bit change-out. In this manner, the clips of prior design can be difficult to remove, thereby adding to tool bit change-out time and reducing overall process efficiency.  
         [0005]     As a result, a need exists for a rotatable cutting tool bit assembly that promotes tooth rotation, resists ejection of a tool bit from a corresponding mounting block pocket, and is amenable to tool bit change-out from the mounting block pocket.  
       SUMMARY  
       [0006]     One aspect of the present invention relates to a rotatable cutting tool bit for use with impact-type aggregate cutting tools. In one embodiment, the tool bit comprises a cylindrical shank defining a central longitudinal axis, a bit head connected to the shank and having a mouth opposite the shank, and a cutting tooth mounted within the mouth of the bit head such that the cutting tooth defines a central longitudinal axis. In the preferred embodiment, the central longitudinal axis of the cutting tooth is both parallel to and at an offset from the central longitudinal axis of the shank.  
         [0007]     Another aspect of the present invention relates to a bit assembly of a rotating aggregate cutting machine comprising a mounting block pocket for use with a rotating aggregate cutting machine and a corresponding cutting tool bit. In a preferred embodiment, the mounting block pocket includes a cylindrical passage, in which the tool bit is disposed. The tool bit includes a cylindrical shank defining a leading section and a trailing section, a bit head connected to the leading section of the shank, and a cutting tooth disposed in the bit head. Further, the cutting tooth is preferably free to rotate relative to the mounting block pocket about an axis of rotation. In a preferred embodiment, the ability to rotate is accomplished as the shank of the cutting tool bit is rotatably and transversely secured within the mounting block pocket.  
         [0008]     In another preferred embodiment, the shank is transversely secured via a clip captured within a clip groove formed in the trailing section of the shank. The clip preferably includes a generally annular body defining an open end and a closed end opposite the open end. Further, the closed end forms a sidewall extending from the annular body for grasping and removing the clip. In a related embodiment, a central longitudinal axis of the cutting tooth is offset from the axis of rotation of the cutting tooth. As will be described further in the Detailed Description, this offset promotes tooth rotation, thereby improving tooth life during a cutting operation.  
         [0009]     Yet another aspect of the present invention relates to a method of un-assembling a rotatable bit from a mounting block pocket of an impact-type aggregate cutting machine. The method generally comprises of the steps of: Providing a mounting block pocket for use with an impact-type aggregate cutting machine; Providing a cutting tool bit disposed within the mounting block pocket; Providing a clip captured within a clip groove formed in the cutting tool bit shank; Removing the clip by grasping a sidewall of the clip; and finally, Removing the tool bit from the mounting block pocket. In this manner, the clip may be more readily removed from the tool bit shank as a grasping surface is specifically provided for clip removal.  
         [0010]     By at least the above stated means, the present invention promotes tooth rotation, resists ejection of a tool bit from a corresponding mounting block pocket, and is amenable to tool bit change-out from the mounting block pocket. In short, the present invention embodies a bit assembly having longer cutting tooth life, operating more reliably, and requiring shorter tool bit change-out times. A more detailed description of the invention and its preferred embodiments is presented below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention will be further described with reference to the drawing wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawing, and wherein:  
         [0012]      FIG. 1  is a side view illustration, with portions shown in cross-section, of a bit assembly in accordance with the present invention for use with a rotating aggregate cutting machine.  
         [0013]      FIG. 2  depicts an exploded view of the bit assembly of a rotating aggregate cutting machine of  FIG. 1 .  
         [0014]      FIG. 3  shows a clip having a sidewall for use with the bit assembly of  FIG. 1 .  
         [0015]      FIG. 4  illustrates an alternative embodiment bit assembly in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0016]     In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the FIGS. being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.  
         [0017]     A preferred embodiment of a tool bit assembly  10  in accordance with the present invention is shown in  FIG. 1 . The tool bit assembly  10  includes a tool bit  12  and a mounting block pocket  14  (shown in cross-section). The tool bit  12  can be generally described as including a cylindrical shank  16 , a bit head  18  connected to the shank  16 , and a hard cutting tooth  20  disposed in the bit head  18 . A preferred embodiment of the tool bit assembly  10  also includes a wear sleeve  22  and a clip  24 . Components of the tool bit assembly  10  are described in greater detail below. In general terms, however, the sleeve  22  is positioned over the shank  16 , with the shank  16 /sleeve  22  being mounted within the mounting block pocket  14  and maintained therein by the clip  24 .  
         [0018]     The mounting block pocket  14  (shown in cross-section) is illustrated more clearly in  FIG. 2  and can be of a type commonly known in the art. The mounting block pocket  14  includes a passage  26 , wherein the passage  26  extends through the mounting block pocket  14  from a first open end  28  to a second open end  30 . In an alternative embodiment, the passage  26  can include grooves or other features for lubricant or the like, as such features are well known to those of ordinary skill in the art.  
         [0019]     In a preferred embodiment, the mounting block pocket  14  is constructed of materials and to dimensions that are well known to those of ordinary skill in the art. Such mounting block pockets are readily available from a number of sources, including Fansteel VR/Wesson-Lexington of Lexington, Ky. In one preferred embodiment, the mounting block pocket  14  incorporates an industry standard, 0.780-inch diameter passage  26 .  
         [0020]     The tool bit  12  is illustrated in greater detail in  FIG. 2 , and again includes the shank  16 , the bit head  18 , and the tooth  20 . The shank  16  forms a cylindrical shape having a central longitudinal axis (also referred to as “shank axis”) x. With the one embodiment of  FIG. 2 , the shank  16  defines a leading section  34  and a trailing section  36 . The leading section  34  is connected to the bit head  18  while the trailing section  36  forms an annular clip groove  38  in an exterior surface of the shank  16 . In one preferred embodiment, the trailing section  36  of the shank  16  defines a larger diameter than an adjacent portion of the shank  16 .  
         [0021]     In a preferred embodiment, the shank  16  is 2.2±0.005 inches long and 0.375±0.005 inches in diameter at the leading section  34 ; the trailing section  36  is 0.750±0.005 inches in diameter; the clip groove  38  is 0.187±0.005 inches in width and in depth; and the sleeve  22  is 0.685±0.005 inches in diameter. While a preferred embodiment has been described incorporating the above-detailed dimensions and materials, it is intended that upon reading this Specification, one having ordinary skill in the art would recognize that a variety of shank  16  dimensions and materials suitable for the impact-type cutting tool bit assembly  10  are included within the scope of the present invention. For example, in one embodiment, the shank  16  is formed of steel.  
         [0022]     With the embodiment of  FIG. 2 , the bit head  18  forms a crown  42  and a shoulder  48 . The crown  42  has a central longitudinal axis (also referred to as “crown axis”) b. The crown  42  also forms a mouth  52  (shown by dotted lines), opposite the shoulder  48 , the mouth  52  having a central longitudinal axis (also referred to as “mouth axis”) d. The mouth  52  can be generally described as a cavity sized to accept the cutting tooth  20  (described below). As depicted in  FIG. 2 , the shoulder  48  extends from the leading section  34  of the shank  16  and defines a central longitudinal axis (also referred to as “shoulder axis”) c. In a preferred embodiment, the crown  42  defines a taper from the shoulder  48  toward the mouth  52 . In other embodiments, the bit head  18 , including the crown  42  and the shoulder  48 , incorporate alternative or multiple diameters, tapers, or other features.  
         [0023]     In a preferred embodiment, and in contrast to tool bits known in the art, the crown axis b is parallel to and at an offset from the shoulder axis c. Furthermore, the mouth axis d is coaxial to the crown axis b. As a result of these relative positions, the mouth axis d is also parallel to and offset from the shoulder axis c.  
         [0024]     With the embodiment of  FIG. 2 , the shoulder  48  has a diameter in the range of 1.0-2.0 inches, more preferably in the range of 1.5-1.75 inches, even more preferably approximately 1.5 inches. Additionally, the bit head  18  preferably tapers in diameter 0.3-1.0 inch along a length thereof. The mouth  52  is preferably sized to accept a bullet nose cutting tooth  20  (available from Fansteel VR/Wesson-Lexington of Lexington, Ky.). In one embodiment, the bit head  18  includes a lateral offset in the range of 0.040-0.080 inch, more preferably 0.050-0.070 inch, and even more preferably 0.055-0.065 inch between the crown axis b and the shoulder axis c. In one embodiment, the lateral offset is not less than 0.03 inch. In another embodiment, the lateral offset is approximately 0.06 inch. While a preferred embodiment has been described incorporating the above-detailed dimensions, it is intended that upon reading this Specification, one having ordinary skill in the art would recognize that changes may be made to the above-described bit head dimensions and materials without departing from the scope of the present invention.  
         [0025]     As illustrated in  FIG. 2 , the cutting tooth  20  preferably forms a base  56  and a nose  58  and has a central longitudinal axis (also referred to as “tooth axis”) e. Additionally, the nose  58  forms an impact surface  62 . Those of ordinary skill in the art generally refer to the tooth  20  as a bullet nose tooth (available from Fansteel VR/Wesson-Lexington of Lexington, Ky.). The tooth  20  is preferably formed of tungsten carbide, but can include a variety of materials suitable for aggregate cutting operations. Upon reading and understanding this disclosure, one of ordinary skill in the art would recognize that a variety of tooth designs are appropriately within the scope of the present invention.  
         [0026]     Spring sleeves or wear sleeves are commonly used to protect tool bit shanks from wear. With the preferred embodiment of  FIG. 1 , the wear sleeve  22  covers a portion of the shank  16 . In one embodiment, the wear sleeve  22  is a generally tubular lumen having a slit  39 , through its thickness, the slit  39  running the length of the wear sleeve  22 . Such sleeves are well known in the art and are available from a variety of sources.  
         [0027]     With additional reference to  FIG. 3 , the clip  24  preferably includes a clip body  69  and a sidewall  68 . The clip body  69  is annular in shape having an open end  64  and a closed end  66 . The open end  64  preferably includes a gap in the clip body  69 , but may alternatively be formed by overlapping sections of the clip body  69  which may be forced open to create a gap. In preferred embodiments, the clip  24  includes the sidewall  68  to aid in grasping the clip  24 . With the embodiment of  FIG. 3 , the sidewall  68 , preferably located at the closed end  66 , is generally arcuate in shape, conforming to the overall annular shape of a clip body  69 .  
         [0028]     The sidewall  68  can alternatively incorporate a variety of shapes including flat planes, multiple radii splines, or others. Additionally, the sidewall  68  is preferably located nearer the closed end  66  than the open end  64 . In a preferred embodiment, the clip body  69  is generally planar in a Z-plane with the sidewall  68  extending generally perpendicular to the clip body  69 . In an alternative embodiment, the clip body  69  is generally arcuate in a Z-plane. In yet another embodiment, the sidewall  68  extends at a non-perpendicular angle from the clip body  69 . In a preferred embodiment, the clip  24  defines an inner diameter approximately matching that of the clip groove  38 . Additionally, the sidewall  68  preferably extends at least 0.1 inch, more preferably at least 0.25 inch from the clip body  69 . Upon reading this disclosure, one having ordinary skill in the art would recognize that the clip  24  could define a variety of inner diameters corresponding to a variety of different clip groove  38  ( FIG. 2 ) diameters. Further, the clip body  69  can take a variety of shapes including, but not limited to pretzel shapes (or other such shapes with overlapping ends), square shapes, triangle shapes, and others.  
         [0029]     The interrelation of the tool bit assembly  10  components can be described more clearly by returning to the preferred embodiment of  FIG. 1 . In a preferred tool bit assembly  10 , the cutting tooth  20  is disposed within the mouth  52  (hidden in  FIG. 1 , but see  FIG. 2 ) of the crown  42  of the bit head  18 . In the preferred configuration, the tooth axis e is coaxial to the mouth axis d, which is in turn coaxial with the crown axis b. Further, the crown  42  and the shoulder  48  of the bit head  18  are connected together and the shoulder  48  is in turn connected to the first end  34  of the shank  16 . Additionally, the shank  16  and shoulder  48  are preferably connected together such that the shank axis x and shoulder axis c are coaxial. In this manner, the cutting tooth  20  (otherwise mounted within the mouth  52 ) is offset from the shank axis x. The effect of the offset described above and alternative axes offsets, and combinations thereof, which are encompassed within the scope of the present invention, are described in further detail below.  
         [0030]     The shank  16  is preferably secured within the mounting block pocket passage  26  such that the second end  36  of the shank  16 , including the clip groove  38  (partially covered in  FIG. 1 , but see  FIG. 2 ), protrudes from the second end  30  of the passage  26 . Further, in a preferred embodiment, the shoulder  48  of the bit head  18  contacts the first end  28  of the passage  26 . A virtual gap between interfaces is shown in  FIG. 1  to allow illustration of the interface surfaces. It is to be noted that the contact may be selective, continuous, or combinations thereof. As previously described, the wear sleeve  22  can be disposed over the portion of the shank  16  that is secured within the mounting block pocket  14 . With the embodiment of  FIG. 1 , the clip  24  is captured within the clip groove  38  ( FIG. 2 ) of the shank  16  such that the sidewall  66  of the clip  24  extends in a direction away from the mounting block  14 . Further, the clip body  69  preferably contacts the second end  30  of the passage  26 . It is to be noted that this contact may also be selective, continuous, or combinations thereof.  
         [0031]     As will be described in greater detail below, the above assembly allows the tool bit  12  to rotate, and in fact, promotes rotation of the tool bit  12 , within the pocket  14  while being transversely retained within the mounting block pocket  14 . This, in turn, results in rotation of the cutting tooth  20  relative to the mounting block pocket  14 . Rotation of the cutting tooth  20  is important as the extreme forces associated with cutting operations can lead to a relatively short tooth life. Rotation generally promotes more consistent wearing of the tooth  20 , and in particular, consistent wearing of the impact surface  62  of the tooth  20 .  
         [0032]     One means by which the current invention improves rotation of the tool bit  12  can be described with reference to  FIG. 1 . The tool bit  12 , and particularly the impact surface  62  of the cutting tooth  20 , is caused to impact the strata or aggregate S by imparting a drive force F on the mounting block pocket  14 . The drive force F is shown curved for illustrative purposes of the travel path of the tool bit assembly  10  only as many common drive mechanisms are rotary in nature. It is to be recognized that the drive force F is more accurately depicted with reference to a linear vector.  
         [0033]     It is well known to those of ordinary skill in the art that tool bits of prior design will rotate to some degree upon impacting a cutting tooth with aggregate or strata. Contrary to prior art, it has been surprisingly found that improved rotation of the cutting tooth  20  is accomplished by laterally offsetting the tooth axis e from an axis of rotation W of the tooth  20 . In a preferred embodiment, the shank  16  rotates within the mounting block pocket  14  thus defining an axis of rotation W of the tooth  20  relative to the mounting block pocket  14 . Because the tool bit  12  rotates about the shank axis x, and the tooth axis e is laterally offset from the shank axis x, the tooth axis e is laterally offset from the axis of rotation W of the tooth  20 . Rotation of the tooth  20  relative the mounting block pocket  14  is promoted because the tooth  20  is able to partially, laterally deflect away from the relatively harder strata or aggregate S it encounters during cutting. In other words, the tooth is able to move laterally with respect to the axis of rotation W. For example, over a one-hundred and eighty degree turn, the tooth  20  laterally deflects twice the distance of its offset from the axis of rotation W. The lateral deflection produces a moment M that results in the forced rotation of the tool bit  12 . It should be noted that a similar moment might also be generated by centrifugal forces resulting from the drive force F. In fact, a tooth  20  that has been offset too much from the axis of rotation W can become overly susceptible to centrifugal forces and thereby cease to rotate.  
         [0034]     Surprisingly, if properly offset, not only does the forced lateral deflection of the tooth  20  improve rotation, the lateral deflection also dampens the transverse impulse forces on the tool bit  12  during cutting. As previously mentioned, transverse impulse forces can result in bit failure by causing the bit  12  or tooth  20  to eject or “kick” out. An offset tooth  20  is able to absorb some of the transverse force by laterally deflecting away from the harder strata. Equally surprising, it has been found that the forced rotation of the shank  16  causes foreign material and particulate to be displaced away from the tool bit  12  and mounting block  14  interface, further improving and ensuring tool bit  12  rotation. Thus, an offset between the tooth axis  60  and the axis of rotation W decreases tooth wear and increases time between bit change-outs.  
         [0035]     Although, in a preferred embodiment, the axis of rotation W is defined by the rotation of the shank  16  within the passage  26 , alternative embodiments of the present invention include rotation enabled by other elements of the tool bit  12  rotating relative the mounting block pocket  14 . For example, in an alternative embodiment the bit head  18  is free to rotate about the shank  16  such that the axis of rotation W of the tooth  20  is defined by the rotation of the bit head  18  relative to the shank  16 . In either case, the preferred offset between the tooth axis e and the axis of rotation W of the tooth  20  arises from the offset between the crown axis b and the shoulder axis c, wherein the shoulder axis c and shank axis x are coaxial. However, as will be described in greater detail below, alternative embodiments of the present invention include a variety of configurations to accomplish the offset of the tooth axis e from the axis of rotation W of the tooth  20 .  
         [0036]     The present invention also encompasses a more efficient method of removing a tool bit  12  from a mounting block pocket  14 . A preferred method of removing the tool bit  12  from the mounting block pocket  14  may be described with reference to  FIG. 2 . As previously mentioned, a preferred embodiment of the present invention includes the clip  24  incorporating the sidewall  68  for grasping. In light of this preferred embodiment, removal of the tool bit  12  from the mounting block pocket  14  includes removing the clip  24  from the clip groove  38  by grasping the sidewall  68  and pulling the clip  24  away from the shank  16 . The tool bit  12  can then be removed from the bit pocket  26 . In a preferred embodiment, the sidewall  68  and the open end  64  of the clip  24  are opposite one another. Thus, the sidewall  68  is pulled in a direction opposite the open end  64  during clip  24  removal. Further, the tool bit  12  is removed from the mounting block pocket  14  in a direction of the first end  28  of the mounting block pocket passage  26 .  
         [0037]     As various changes could be made in the above constructions and methods without departing from the scope of the invention as defined in the claims, it is intended that all matter contained in the description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. As such, alternative embodiments are proposed within the scope of the present invention. For example, an alternative embodiment tool bit  212  is illustrated in  FIG. 4 , and includes a shank  216  and a bit head  218 , forming a mouth (hidden in  FIG. 4 ) and maintaining therein a tooth  220 . The shank  216 , bit head  218 , and tooth  220  are highly similar to previous embodiments. However, with the embodiment of  FIG. 4 , a shank axis x′, a shoulder axis c′, and a crown axis b′ are coaxial. A mouth axis d′ and a tooth axis e′ are coaxial and offset from the first group of axes x′, c′, b′ such that the tooth axis e′ is offset from the shank axis x′. Thus, the tooth axis e′ is offset from an axis of rotation W′ of the tooth  220  when the shank  216  is rotatably disposed in a mounting block pocket (not shown). In another exemplary alternative embodiment tool bit not shown, each of the shank axis x′, shoulder axis c′, crown axis b′, mouth axis d′ and tooth axis e′ are parallel and offset from one another such that the tooth axis e′ is offset from the axis of rotation W′ of the tooth  220 . As demonstrated by the description of these alternative embodiments, the present invention embodies a variety of configurations which result in an offset of a central longitudinal axis of a tooth from an axis of rotation of the tooth relative to a mounting block pocket.  
         [0038]     By at least the above stated means, the present invention promotes tooth rotation, resists ejection of a tool bit from a corresponding mounting block, and is amenable to tool bit change-out from the mounting block pocket. In short, the present invention embodies a bit assembly having longer cutting tooth life, operating more reliably, and requiring shorter tool bit change-out times.  
         [0039]     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.