Patent Publication Number: US-7210745-B2

Title: Retainer for cutting bit

Description:
BACKGROUND 
   Cutting bit assemblies for such applications as mining or road milling typically comprise a cutting bit, sometimes referred to as a cutting pick or cutting tool, rotatably mounted within a support block. The support block is, in turn, mounted onto a drum or other body, typically by welding, which is, in turn, driven by a suitable drive means. When a number of such support blocks carrying cutting bits are mounted onto a drum, and the drum is driven, the cutting bits will engage and break up the material (e.g., earth strata) to be mined or removed. The general operation of such a mining machine or construction machine (e.g., a road planing machine) is well known in the art. 
   Heretofore, various retainers have been proposed or used to mount a cutting bit, rotatable or otherwise, within a support block. 
   As one example of such a retainer, U.S. Pat. No. 4,505,058 to Peterson shows a retainer having two legs. This retainer is to be used in conjunction with a support block having a recess with specially configured sidewalls that cooperate with the bends in the retainer legs to hold the retainer in place. 
   As another example, U.S. Pat. No. 4,883,129 to Lonn et al. shows another retainer that overlaps a cutting bit shank and a support block along substantially the entire length of the retainer. This retainer provides a single, continuous shear zone along its entire length. 
   As still another example, U.S. Pat. No. 6,428,110 to Ritchey et al. discloses a retainer used to retain a cutting bit in a holder. The retainer is stamped out of a piece of sheet steel and is received within an annular grove adjacent to the axial rearward end of the cutting bit. Although this retainer functions in a satisfactory fashion, certain drawbacks occur because the retainer is stamped from sheet steel. 
   One drawback connected with the stamped retainer of U.S. Pat. No. 6,428,110 is the presence of jagged portions along all or part of the peripheral edge of the retainer. This jagged portion can occur due to tearing or shearing of the material (e.g., steel) during the stamping process. The presence of the jagged portion results in a less than desirable surface finish for the retainer. It would thus be desirable to provide a retainer that presents a surface that does not have jagged portions along its peripheral edge, but instead, has a smooth surface finish along its peripheral edge. 
   Another drawback connected with the stamped retainer of U.S. Pat. No. 6,428,110 is the presence of so-called “fall off” on the exterior edge of the projections (or ears) that project in a radial outward direction from the retainer body. More specifically, this “fall off” exists when the exterior edge of the projection is not substantially perpendicular to the front or rear surface of the retainer, but instead, has an angled orientation with respect to such surfaces. It would be desirable to provide a retainer that presents projections (or ears) that do not exhibit this “fall off”, but instead, has projections that have an exterior edge that is generally perpendicular to the front and rear surfaces of the projection (or ear). 
   Still another drawback connected with the stamped retainer of U.S. Pat. No. 6,428,110 is the fact that the grain direction of the steel is dependent upon the direction in which the sheet steel is fed into the stamping press. The grain direction of the steel can run either parallel or perpendicular to the mouth opening of the retainer. It would thus be desirable to provide a retainer that has a consistent grain direction that runs in a direction that is generally parallel to the central longitudinal axis of the retainer body so that the grain direction in the retainer is consistent from part-to-part. 
   SUMMARY OF THE INVENTION 
   In one form thereof, the invention is a retainer for use in conjunction with a cutting bit wherein the cutting bit includes a shank that contains a recess therein. The retainer includes a generally cylindrical retainer body that has opposite ends and a central longitudinal axis. The retainer body has a generally arcuate shape that defines an arc between the opposite ends thereof. The retainer body further includes at least one ear that projects in a radial outward direction. The retainer body is made from a material that has a grain that runs in a direction generally parallel to the central longitudinal axis of the retainer body. 
   In still another form, the invention is a method of making a retainer for use in conjunction with a cutting bit wherein the cutting bit includes a shank that contains a recess wherein the steps comprising: providing a generally straight elongate retainer body having opposite ends and a central longitudinal axis, the retainer body being made from a material having a grain that runs in a direction generally parallel to the central longitudinal axis of the retainer body; bending the straight elongate retainer body into an arcuate shape; and swaging the arcuate retainer body so as to form at least one ear that projects in a radial outward direction. 
   In yet another form, the invention is a cutting bit assembly comprising a cutting bit that has an elongate cutting bit body with an axial forward end and an axial rearward end. The cutting bit body contains a groove adjacent the axial rearward end thereof. The cutting bit assembly further includes a holder that has a central bore that has a forward end and a rearward end. The cutting bit is positioned within the central bore of the holder so as to extend past the rearward end of the bore thereby exposing the groove. A retainer is received within the groove. The retainer comprises a generally cylindrical retainer body that has opposite ends and a central longitudinal axis. The retainer body has a generally arcuate shape defining an arc between the opposite ends thereof. The retainer body further includes at least one ear projecting in a radial outward direction. The retainer body is made from a material having a grain that runs in a direction generally parallel to the central longitudinal axis of the retainer body. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The following is a brief description of the drawings that form a part of this patent application: 
       FIG. 1  is an exploded isometric view of a cutting bit assembly including a cutting bit, a holder (or support block) and a specific embodiment of a retainer; 
       FIG. 2  is a side view of the cutting bit assembly as illustrated in  FIG. 1 , but with the components, including the cutting bit, the holder and the retainer, assembled together; 
       FIG. 3  is a cross-sectional view taken along section line  3 — 3  of  FIG. 2  showing the retainer and the shank of the cutting bit 
       FIG. 4  is a front view of the retainer as illustrated in  FIG. 1  wherein the grain direction is shown as running in a direction that is generally parallel to the central longitudinal axis of the retainer body; 
       FIG. 5  is a rear view of the tool used to install and remove the retainer wherein the retainer is shown as being positioned in the magnetic notch of the tool so that the retainer may be installed on the cutting bit; 
       FIG. 6  is a rear view of the tool used to install and remove the retainer wherein the prongs of the tool are aligned with the opposite ends of the retainer so that the retainer may be removed from the recess in the shank of the cutting bit; 
       FIG. 7A  is an isometric view of a piece of cylindrical wire that will be made into the retainer wherein the grain of the material is along the central longitudinal axis of the cylindrical wire; 
       FIG. 7B  is an isometric view of the cylindrical wire of  FIG. 7A  after being bent (or formed) around a cylindrical mandrel (not illustrated) so that the cylindrical wire takes on an arcuate (or generally circular) shape; 
       FIG. 7C  is an isometric view of the cylindrical wire of  FIG. 7B  after it has been subjected to a swaging step that forms the ears that project in a radial outward direction from the retainer body; and 
       FIG. 8  is a cross-sectional view of the retainer of  FIG. 7C  taken along section line  8 — 8  in  FIG. 7C . 
   

   DESCRIPTION OF A SPECIFIC EMBODIMENT 
   Referring to the drawings,  FIGS. 1 and 2  show a cutting bit assembly  10  that comprises a cutting bit  12 , a support block  14  and a retainer  16  according to the invention. The cutting bit  12  has an elongate cutting bit body that has a forward end  15  and a rearward end  17 . The cutting bit body also has a cylindrical shank  18  that contains an annular groove or recess  20  therein adjacent to the rearward end  17  of the cutting bit body. As described hereinafter, the groove  20  is adapted to receive the retainer  16 . 
   The support block  14  has a cylindrical bore  22  that receives the shank  18  of the cutting bit  12 . The bore  22  has a forward end (not illustrated) and a rear end  23 . The support block  14  has a base  24  that can be welded or otherwise attached to a track pad  26  of a trenching machine (not illustrated) used to break up material (e.g., earth strata). 
   When the trenching machine drives the track pad, the cutting bit  12  will engage and break up material to be broken and mined or otherwise removed. Alternatively, the support block  14  may be welded or otherwise attached to a driven rotatable drum (not illustrated) or any other suitable component of a mining machine or a road planing machine wherein during operation the cutting bits engage and break up the earth strata such as coal in the case of a mining machine or asphaltic material in the case of a road planing machine. 
   Referring to  FIGS. 3 ,  4  and  7 C, the retainer  16  has a generally cylindrical retainer body  30  that is generally circular in cross-section. The retainer body  30  comprises a segment of a cylindrical wire that has been cut to a specific length and then fashioned into the retainer  16  as described hereinafter. The retainer body  30  presents a generally circular (or arcuate) geometry and has first and second opposite ends  34  and  36 . The arcuate retainer body  30  defines an arc preferably extending through an angle “A” of at least one hundred eighty degrees. In the specific embodiment shown in the drawings, the arcuate retainer body  30  defines an arc extending through an angle “A” (see  FIG. 3 ) of about two hundred seventy degrees. 
   When taken in conjunction with its cooperation with the annular groove  20  in the shank  18  of the cutting bit  12 , the retainer body  30  also defines a continuous shear zone  38  preferably, but not always necessarily, along the entire length of the arc as defined by angle “A”. Referring especially to  FIG. 3 , the term “shear zone” as used in this patent application means that portion of the retainer body  30  that overlaps both the shank  18  and the support block  14  when the retainer  16  is installed on (i.e., carried in the annular groove  20  in) the shank  18 . Preferably, the continuous shear zone  38  extends through an angle in the range of between about thirty degrees to about three hundred degrees. More preferably, the continuous shear zone  38  extends through an angle of at least about one hundred eighty degrees, and has first and second ends that are the same as (i.e., coextensive with) the first and second ends  34  and  36 , respectively, of the retainer body  30 . 
   In the specific embodiment illustrated in  FIG. 3 , the continuous shear zone (illustrated by bracket  38 ) extends through an angle of about two hundred seventy degrees, and shear zone  38  has first and second ends that are the same as (or coextensive with) the first and second ends  34  and  36 , respectively, of the retainer body  30 . Alternatively, even though not illustrated, applicant contemplates that one or both ends  34  and  36  of the retainer body  30  may extend beyond one or both ends, respectively, of the continuous shear zone  38 . 
   Referring especially to  FIGS. 3 ,  4 ,  7 C and  8 , the retainer body  30  further includes one or more protruding portions (or ears)  40  that extend in a radial outward direction from the exterior surface of the retainer body  30 . When the retainer  16  is received within the groove  20 , these ears  40  extend in a radial direction past the shank  18  of the cutting bit  12  so as to be exposed and accessible for engagement by an installation tool  46  (as described hereinafter in conjunction with  FIGS. 5 and 6 ) or the like. While the ears  40  may take on any suitable configuration, each protruding ear  40  is preferably a solid projection, and even more specifically, each ear  40  presents a generally rectangular shape. Each ear  40  also has an axially extending outer peripheral surface  42  that may be engaged by the installation tool  46 . Installation tool  46  is along the lines of the installation tool for the TR1 and TR2 retainers shown in a Kennametal advertisement entitled “TR1 and TR2 Retainers and Installation Tools” [B03-22(0.2)F3]. Another example of an installation tool is the puller that is shown and described in U.S. Pat. No. 6,428,110 to Ritchey et al., wherein such patent to Ritchey et al. is hereby incorporated by reference herein. 
   Referring to  FIGS. 5 and 6 , in order to use the retainer  16  of this invention, the cylindrical shank  18  of the cutting bit  12  is inserted into the bore  22  of the support block  14  such that the axial rear end of the shank  18  extends past the rear end of the bore  22  so that the recess  20  is exposed. The cutting bit  12  is now ready to receive the retainer  16 . 
   In order to install the retainer  16  in the recess  20 , as illustrated in  FIG. 5 , the retainer  16  is positioned on the puller  46  so that the retainer  16  is in the magnetic notch  50 . The notch  50  engages at least one of the ears  40  of the retainer  16 . The magnetic notch  50  holds the retainer  16  in place during the installation operation. Typically, the operator then strikes the rear end  52  of the installation tool  46  with a hammer with sufficient force so as to seat the retainer  16  in the recess  20 . 
   When the retainer  16  is installed in the groove  20  contained in the shank  18 , the retainer  16  contacts the surfaces that define the annular recess  20  to impede transverse movement of the retainer  16  relative to the shank  18 . Alternatively, the retainer  16  may be installed on the shank  18  in any suitable manner. 
   In order to remove the retainer  16  from the recess  20 , as illustrated in  FIG. 6 , the prongs  54  of the installation tool  46  are aligned against the opposite ends of the retainer  16 . The operator then strikes the rear end  52  of the installation tool  46  so as to exert a force on the retainer  16  that is large enough to remove the retainer  16  from the recess  20 . Another method to remove a retainer from a recess in the shank of the cutting bit is shown and described in U.S. Pat. No. 6,429,110, which has already been incorporated by reference herein. Alternatively, the retainer  16  may be removed from the recess  20  in any suitable manner. For example, one of the ears  40  may be grasped by a suitable tool, such as a pair of pliers, so as to pull the retainer  16  away from the recess  20 . 
   Because the continuous shear zone (illustrated by bracket  38 ) preferably extends the entire length of the retainer body  30 , the retainer  16  has significant strength and durability characteristics. Furthermore, the engagement of the retainer  16  by the installation tool  46  enables the retainer  16  to be easily installed on and removed from the shank  18  as described hereinabove. 
   It can thus be seen that during operation, the cutting bit  12  is free to rotate relative to the holder  14  and thereby function to engage and break up the earth strata. However, it is also apparent that the retainer  16 , which is received within the groove  20 , securely retains the cutting bit  12  within the bore  22  of the holder  14 . It is also apparent that the retainer  16  can be easily installed and removed through the use of the puller  46  or some other suitable tool so as to decrease the amount of downtime experienced by the machine operator during the replacement of the cutting bits. 
   In regard to method of making the retainer  16  and referring to  FIGS. 7A through 7C , the retainer body  30  is made from a piece of generally cylindrical wire, i.e., the wire has a generally cylindrical cross-section and a central longitudinal axis L—L. One suitable material from which the retainer  16  is made is 1050 spring steel.  FIG. 7A  shows that the grain “G” of the material (e.g., steel) that comprises the wire runs in the same direction as (or is generally parallel to) the central longitudinal axis L—L of the cylindrical wire. 
   Referring to  FIG. 7B , the cylindrical wire shown in  FIG. 7A  is then bent (or formed) over a cylindrical mandrel (not illustrated) so as to form the basic annular (or circular) geometry of the retainer  16 . It can be appreciated that the direction of the grain “G” of the retainer  16  is always along the central longitudinal axis L—L of the retainer body  30 . As a result, the direction of the grain “G” in the retainer body  30  will be uniform from part to part. 
   Referring to  FIG. 7C , the ears  40  are then swaged or formed from the annular retainer body  30  as shown in  FIG. 7B  so as to result in the retainer  16  as illustrated in  FIG. 7C . In regard to the swaging step, the material that forms the ears  40  comes from the retainer body  30 . As a result, the ear  40  originates at a point slightly radial inward of the surface of the retainer (see  FIG. 8 ) and terminates at its outer edge  42  at a point radial outward of the exterior surface (see  FIG. 8 ). As is illustrated in  FIG. 8 , the ear  40  originates at a point that is a distance “B” radial inward of the retainer surface and terminates a distance “C” from the retainer surface. 
   Referring especially to  FIGS. 7C and 8 , there is a notch  48  at each location where the ears  40  project from the retainer body  30 . This notch  48  is due to the fact that during the swaging step, the material that comprises the ear  40  was taken from the retainer body  30  thereby leaving the notch  48 . 
   It can be seen that the surface of the retainer body  30  is smooth and consistent since the retainer body  30  is made from a cylindrical wire. Although not intended to be restrictive, the surface roughness (R a ) of the cold drawn wire is equal to about 125 microinches. Further, it can be seen, especially by  FIG. 8 , that the outer edge  42  of each ear  40  is generally perpendicular (see angle “D”) to the front surface  50  and rear surface  52  of the ear  40 . 
   The fact that the outer edge  42  is perpendicular to the front and rear surfaces of the ear  40  results in a more consistent engagement between the ears  40  and the notches in the puller  46  as compared to a stamped retainer wherein there is “fall off” at the outer edge of the ears. Further, the fact that the surface of the retainer  16  is smooth and consistent results in a more consistent engagement of the retainer  16  by the puller  46  as compared to the stamped retainer that has jagged edge portions. A more consistent engagement between the retainer and the puller provides for more efficient and improved installation and removal of the retainer  16 . 
   The fact that the retainer  16  made from a cylindrical wire that has a grain “G” that runs in a direction generally parallel to the central longitudinal axis of the retainer body results in better consistency between each part as compared to a retainer that is stamped from sheet steel. It is desirable to provide a method that makes the retainer  16  with a part-to-part consistency that has heretofore not been available. 
   It can thus be appreciated that the present invention defines a retainer that exhibits new and improved properties. More specifically, the retainer of the present invention present a surface that does not have jagged edges, but instead, has a smooth surface finish. Further, the retainer presents projections (or ears) that do not exhibit the “fall off”, but instead, are generally perpendicular to the surface of the face of the projection (or ear). Finally, the retainer that has a consistent grain direction wherein the grain runs in a direction along the length, i.e., along the central longitudinal axis, of the retainer body. This feature provides an improved part-to-part consistency in the manufacture of the retainers. 
   The patents and other documents identified herein are hereby incorporated by reference herein. 
   While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. 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. Various changes may be made without departing from the spirit and scope of the invention, which is indicated by the following claims.