Patent Abstract:
An improved bit holder with its mating bit block is disclosed utilizing a slight taper in the bit block bore, and a tapered shank on the bit holder that includes a second larger diameter tapered distal segment that combines with an axially oriented slot through the side wall of the bit holder shank to allow a substantially larger interference fit between the distal tapered shank segment and the bit block bore than previously known. When inserting the bit holder in the bit block bore, the distal first tapered segment resiliently collapses to allow insertion of that segment into the bit block bore. A second shank tapered portion axially inwardly of the first distal tapered portion. The dual tapered shank allows the insertion of the bit holder in the bit block with an interference fit that provides a secure mounting of the bit holder in the bit block.

Full Description:
This application is a divisional of Ser. No. 09/500,983 filed Feb. 15, 2000, now U.S. Pat. No. 6,371,567, which is a continuation in part of Ser. No. 09/273,690 filed on Mar. 22, 1999, now U.S. Pat. No. 6,364,420. 
    
    
     This invention relates generally to road surface removal or reclaimer-stabilizer equipment and mining equipment, and more particularly, to cutter bit holders and bit blocks used in such road milling, mining, and trenching equipment. 
     BACKGROUND OF THE INVENTION 
     Cutter bits are utilized in road, off-road and mining machinery on the perimeter and across the width of a rotary drum or on the outside of a continuous chain or the like where the bits are moved through an orbit which is intercepted by the face of the material being removed or recycled. Road milling equipment removes the defective surface of a road and smooths the top of all or selected portions of the road surface. The bits include a tip and a shank. The shank is received and may axially rotate in a bit holder which is secured onto a bit block that, in turn, is mounted on the drum. Each of the bits has a hardened tip, preferably made of tungsten carbide or such other hardened material that acts to remove a portion of the surface it contacts. By using a sufficient number of these bits around the outer surface of a rotating drum, a large amount of surface may be worked. Any surface being worked generally has a hardness which can be measured or anticipated prior to the removal operation. However, such road surfaces, or surfaces being removed have hardened irregularities running therethrough. The toughness or hardness of the irregularities may result in the breakage of the bits and holders as they are being run over such irregularities. 
     Additionally, a need has developed for providing ease of removability of bits in their bit holders, especially when the bit becomes worn and in need of replacement. U.S. Pat. No. 5,374,111 discloses an undercut flange at the bottom of a base of a bit that allows a pry bar to be wedged between that flange and the top of the bit block (no bit holder in this patent) to help remove a bit from a bit block. It would be desirable to provide a more efficient means for allowing the removal of a bit from a bit holder or a bit block. 
     Additionally, tightening a small fastener on the bottom of a bit holder to hold it in the bit block concentrates friction forces on a small area of the nut top face and the bottom of the bit block. It would be desirable to spread those friction forces over a larger area and avoid the use of a nut to retain the bit holder on the bit block. 
     Further, a need has developed for a truly quick-change type of bit holder that may easily and quickly be both inserted in the bit block and removed therefrom. 
     It is, therefore, an object of the present invention, generally stated, to provide an improved means for quickly mounting and/or removing a bit holder from its associated bit block. 
     Another object of the present invention is the provision of an improved means for mounting a bit holder in a bit block without the use of retaining nuts, clips or the like. 
     A further object of the invention is the provision of retaining a bit holder in a bit block by means of a resilient interference fit between the holder and the block. 
     Another object of the invention is the provision of an improved means for providing for breakage of inexpensive replaceable parts when road resurfacing equipment and mining equipment bits encounter very hard irregularities in the surface being milled or mined. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel are set forth with particularity in the attached claims. The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which like numerals refer to like parts, and in which: 
     FIG. 1 is a side elevational view of a bit block, bit holder and bit assembly constructed in accordance with the present invention; 
     FIG. 2 is an exploded side elevational view of the assembly shown in FIG. 1; 
     FIG. 3 is a side elevational view of a second embodiment of a bit holder constructed in accordance with the present invention; 
     FIG. 4 is a top plan view of the bit holder shown in FIG. 3; 
     FIG. 5 is a side elevational view of a second embodiment of a bit block for retaining the bit holder shown in FIGS. 3 and 4; 
     FIG. 6 is a top plan view of the bit holder shown in FIG. 5; 
     FIG. 7 is a side elevational view of the second embodiment including a bit, bit holder and bit block assembly; 
     FIG. 8 is a bottom plan view of the second embodiment shown in FIG. 7; 
     FIG. 9 is a side elevational view of a third embodiment of a bit holder constructed in accordance with the present invention. 
     FIG. 10 is a top plan view of the bit holder shown in FIG. 9; 
     FIG. 11 is a side elevational view of the third embodiment bit holder being manually hammered into its bit block; 
     FIG. 11 a  is a side elevational view of the third embodiment bit holder being manually hammered out of its bit block; 
     FIG. 12 is a side elevational view of a fourth embodiment combination bit block/bit holder utilizing a long bolt and bottom nut to press fit the bit holder onto the bit block. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-2, a bit mounting assembly, generally indicated at  20 , constructed in accordance with the present invention, includes a bit, generally indicated at  21 , which is mounted on a bit holder, generally indicated at  22 , which, in turn, is secured on a bit block, generally indicated at  23 . The bit block  23  is one of a plurality of such blocks mounted around the outside of the generally circular drum (not shown) or on a movable chain or track (not shown). 
     Referring to FIG. 2, the bit, generally indicated at  21 , includes a forward end  24 , and a shank  25  or rear end thereof. The forward end  24  includes a hardened nose  26 , preferably made of tungsten carbide or a like material, a middle tapered portion  27  including a reduced diameter area  27   a  and a bottom flange portion  28  which is made so as to rest on the bit holder, generally indicated at  22 . A spring steel retaining clip  30  is positioned over the shank  25  of bit  21  and is shaped so that when the bit  21  is inserted in the bit holder  22 , the retaining clip  30  will secure the bit therein while allowing it to rotate from external forces. 
     The bit holder  22 , constructed in accordance with the present invention, includes a generally flat annular leading surface  31  on which the rear side of the bit flange  28  rests when inserted therein. Adjacent the annular leading surface  31  is a middle or tapered portion  32  that ends in an enlarged flange portion  33 . In the preferred embodiment of the invention, a plurality of notches, flats or indents  32   a-d  extend radially inwardly of the middle tapered portion from top surface  31  toward the flange  33 . The back side  34  of flange  33  is an annular flat surface which rests on the bit block  23  when mounted thereon, and includes one aspect of the present invention to be discussed below. Rearwardly adjacent the flange portion  33  is a reduced diameter cylindrical shank portion  35  and a shoulder portion  36  which may vary in length depending on its function, an undercut portion  37  is next to the shoulder portion  36 , and the bit holder terminates in a threaded portion  38  adjacent the distal end  44  thereof. If the nose  26  of bit  21  hits a hard discontinuity, bit  21  will fail first, the bit holder in this embodiment may be engineered to fail next across reduced diameter section  37 . The configuration allows the bit holder to tumble out of bit block bore  49  after failure. 
     Also shown in FIG. 2 is a bore  40  that extends axially through bit holder  22  from a countersink  41  in communication with the front face  31 , through the tapered portion  32 , the flange portion  33  and a substantial portion of the shank  35 ,  36  where it narrows at chamfer  42  to a smaller diameter bore  43 . Bore  43  extends the remainder of the bit holder to its distal end  44 , or it may be increased in diameter partly along its length to decrease the cross sectional reduced diameter section  37 , if desired. The length of the bore  40  is determined partly by the length of the shank  25  on bit  21 . The shank  25  fits within bore  40 , and is retained therein by the spring steel retainer  30 . If the bit  21  should break at reduced diameter portion  29  adjacent the bottom flanged portion  28 , a rod, punch, etc. (not shown) may be inserted into the bottom of the bore to push the shank out of the holder. 
     The bit block  23  consists of a base portion  45  that mounts to a drum, chain, or track (not shown) and an angled bit holder mounting portion  46  extending from the base  45  that includes a top face  47 , and a bottom recessed slot  48  which provides the opposing ends for a bore  49 , which may be tapered, and a reduced bridging portion  51  extending from a bottom of bore  49  to the recessed slot  48 . Bore  49  is sized to receive the cylindrical shank  35  of the bit holder  22  with the annular flat surface  34  on the bottom of the flange portion  33  resting on the top surface  47  of the bit block mounting portion  46 . In one important aspect of the present invention, the surface area of contact between flange bottom  34  and bit block top  47  is much greater than the surface area of contact between the top  52   a  of nut  52  and nut contacting surface on slot  48  and will be discussed in greater detail below. The threaded portion  38  adjacent the distal end  44  of bit holder  22  extends through the reduced passageway  51  where a nut  52  may be threaded thereon by rotating the bit holder until its top surface  52   a  engages the surface of the recessed slot  48  to retain the bit holder  22  on the bit block  23 . 
     Referring to FIG. 1, the distal end of a pneumatically operated chisel is shown in dotted line at  55 , inserted in one of the notches  32 C as more fully shown in FIGS. 3 and 4. The notches  32   a - 32   d,  constructed in accordance with the present invention, allow for the quick removal of the bit  21  from the bit holder  22  by applying a force having a substantial axial component thereto to the bottom side of the bit flange  28 . In the preferred embodiments there may be two, three or four notches or indents  32   a-d  (FIG. 2,  32 - d  not shown) on the bit holder  22  positioned at 120 degree or 90 degree intervals, respectively, around the circumference thereof. Each notch may be straight vertically or slightly wider at surface  31  and narrows as the notch descends toward flange  33 . While the use of the punch  55  on one notch is usually sufficient to remove the bit, the punch may be utilized sequentially in differing notches to balance the axial force, if necessary, to move the bit  21  out of the bit holder  22 . 
     Referring to FIGS. 3-8, a second embodiment of the bit holder and bit block constructed in accordance with the present invention is shown and described. Beginning at FIG. 3, a second embodiment of the bit holder, generally indicated at  60 , is constructed to be a press fit into the bit block, generally indicated at  61 , shown in FIG.  5 . The mounting of the bit holder  60  on the bit block  61  is accomplished without the aid of a retaining nut, such as shown at  52  in the first embodiment, a spring retaining clip or other fastening device utilized on the bottom of the bit block  61 . 
     Referring to FIGS. 3 and 4, similarly to bit holder  22 , the bit holder  60  has a flat annular leading surface  62 , a middle tapered portion  63  behind the flat annular leading surface  62  that also includes a pair of notches  64 - 65 , 120 degrees apart and having the same function as the notches  32   a-d  in the first embodiment and an annular groove  63   a  whose depth is calculated to insure that, in case of the bit hitting a hard discontinuity, the bit holder will break at groove  63   a  rather than the bit block  61  separating at its weldment to the drum or chain. Additionally, the rear of the middle tapered portion  63  is an enlarged flange portion  66  including an annular flange backside  67  similar to that shown in the first embodiment  22 . A locator pin  69  extending from the flange back side  67  fits loosely into a clearance hole  69   a  on bit block top surface  85  (FIG. 5) for limiting the rotation of holder  60  when mounted on the bit block  61 . If the bit holder breaks, the pin  69  falls out of hole  69   a  and does not damage the bit block  61 . To the rear of the annular flange backside is the shank portion of the bit holder, generally indicated at  68 . An undercut  70  between the annular flange backside  67  and the shank portion  68  assures that stress points are avoided between the shank and the enlarged flange portion when the bit holder  60  is mounted in the bit block  61 . This undercut  70  also provides a breaking point if undercut  63   a  is not used. 
     Flange  66  is annular in that a bore  71  runs axially through the bit holder in a more straight forward hollow cylindrical manner than the bore  40  which extends through the bit holder  22  of the first embodiment. The leading edge of bore  71  includes a countersink  72  adjacent the flat annular leading surface  62  of the bit holder to receive a similarly shaped shank portion  25  on the bit  21  shown in FIG.  2 . 
     In an important aspect of the present invention, a slot  81  extends through the sidewall of the shank portion from the rear semi-annular face  77  to a rounded front slot termination  82 . An interference fit between the outside of tapered shank portion  73  and the like tapered bore  80  of the bit block  61  is greater than the interference fit possible if slot  81  was not in the shank portion. For example, a 1½ inch diameter shank without a slot would ordinarily have about 0.001-0.003 inch interference. With slot  81 , the same size shank may have about 0.005-012 inch interference in the portion including the slot  81 . As the distal end  77  of the shank portion  68  is positioned in the tapered bore  80  of bit block  61 , the slot allows the now C-shaped portion of the shank to contract its outer diameter radially to ease the insertion of the bit holder in the bit block bore  80 . This slotted portion of the shank  81  allows the C-shaped portion of the shank to act as a very strong radial spring, similarly to a hollow spring steel roll pin. The portion of shank  68  forward of slot  82  provides a 360 degree radial interference fit with the bit block bore  80 , and may be greater than, equal to, or less than an interference fit at the portion of the shank at  101 . The length of the slot  81  with respect to the length of the shank portion  68  may be varied depending upon the application proposed for the bit, bit holder and bit block assembly in order to optimize the operation of same. The slot  81  may, when desired, extend all the way to the rear annular flange back side  67  of the front tapered shank portion of the bit holder  60 . The longer the slot, the less spring action force of shank  68 . A smaller width slot provides a greater spring force. The taper for the shank  73  and bore  80  is preferably 1 degree on each side, but may be more or less, such as 2 to 4 degrees per side or ¼ to ¾ degree per side, if desired. The smaller taper such as 1 degree has a longer length of interference fit engagement and produces more radial pressure for the same axial force exerted upon it than a two degree taper for the same press fit values. 
     Referring to FIGS. 5 and 6, bit block  61  is similar to bit block  23  with the exception that the bit block bore  80  is tapered on the order of about 1 to 4 degrees per side or 2 to 8 degrees of included angle, unlike straight bore  49 . A second locator pin  89  may be mounted in a bore  89   a  to extend slightly into the bore  80  of the bit block  61 . In use pin  89  is about ½ inch in diameter and extends into slot  81  of the bit holder slot about {fraction (3/16)} inch to keep the bit holder  60  from rotating in the bit block  61  and to align the slot  81  in the bit block. A clearance hole  69   a  on top flat surface  85  allows the locator pin in  69  (FIG. 3) to be positioned loosely therein. An annular slot  87  is formed across the bottom portion of the bit block tail surface  88 , otherwise, bit block  61  is very similar to bit block  23  in construction. 
     Referring to FIGS. 7 and 8, the bit  21  and the second embodiments of the bit holder  60  and bit block  61  are shown in assembled condition with the exception of the modification in the bit block  61  to provide a slot  85  positioned in the outer portion of bit block  61  to more easily allow the insertion of tools in the rear of the bit block  61  to drive the bit  21  from the bit holder  60 . 
     FIG. 8 shows the bottom of the assembly including the flat planar mounting pad  86  which mounts to the rotating wheel or moving track on which the assembly is positioned. As one can see from FIGS. 7 and 8 there is no bolt, retaining pin or other retaining means to maintain the bit holder in the bit block. Additionally, force may be applied to the distal end surface  77  of the bit holder  60  to drive the bit holder out of the bit block  61 . As with the first embodiment of the present invention, the notch  65  in the front tapered portion of the bit holder  60  allows a chisel (not shown) or other such device to apply force on the back side-of the bottom flanged portion  28  of bit  21  to drive the bit out of the bit holder. Again, no bolts, retaining pins, retaining rings or the like are necessary between the bit holder  60  and the bit block  61 . 
     Referring to FIGS. 9 and 10, a third embodiment of the bit holder of the present invention, generally indicated at  90 , is similar to the second embodiment bit holder  60  with two exceptions to be discussed below. The forward portion of the bit holder  90  including the leading flat annular surface  91 , a cylindrical front collar portion  92 , the middle tapered portion  93  and the enlarged flange portion  94  perform similar functions to the forward portion of the bit holder of the second embodiment  60 . Also, a pair of notches  95 ,  96  perform an identical function to the notches  64 ,  65  of the second embodiment. The forward portion of the bit holder of the third embodiment is somewhat more compact axially than the second embodiment. Another difference in the third embodiment of the present invention is the construction of the shank portion, generally indicated at  97 . 
     The shank portion  100  is also tapered as is the shank portion  68  in FIG. 3 with approximately 1 degree of taper per side as shown at T 1  in FIG.  9 . The shank portion also includes an undercut section  98  between the back side  94   b  of the enlarged flange portion and the shank portion  97  to avoid sharp areas of stress when mounting the bit holder  90  in a bit block such as that shown at  61 . This portion of the shank could also be designed in either embodiment using a radius at  98  and providing sufficient relief at countersink  120  (FIG. 5) in bit block  61 . In an important aspect of the third embodiment of the present invention, the tapered outermost surface of the shank is divided into a front tapered portion  100  and a rear tapered portion  101 . In this third embodiment  90 , shoulder  102  is formed between the front tapered portion  100  and the rear tapered portion  101 . The distal portion of the shank  77  (FIG. 7) is constructed identically to that of the second embodiment with a rear face  103  a distal chamfer  104  a cylindrical tail portion  105 , a transition chamfer  106  and rear tapered portion  101 . Likewise, the bit holder of the third embodiment may include a central bore  107  therethrough and a slotted portion  108  (FIG. 10) similar to the slot  81  (FIG. 3) of the second embodiment  60 . Slot  108  allows for a greater interference fit between rear taper  101  and bit block bore  80  (FIG.  5 ). In the third embodiment  90 , the shoulder  102  reduces the interference fit on opposing sides from about 0.009 at  101  to about 0.002 inch between the frontal portion of slot  108  and undercut  98 . The rear taper  101  and the front taper  100  are preferably identical, in this embodiment 1 degree. However, these tapers can vary as discussed previously above. 
     Identical smaller tapers give a longer taper contact at each end of the shank. If the angle of the taper at portion  100  is greater than the angle of the taper at portion  101 , the axial length of contact between taper portion  100  and bore  80  of block  61  will be lessened. Also, a convex surface may be substituted for the tapers  100  and  101  with the result being less surface contact between the holder shank  100 ,  101  and block bore  80 . 
     The shoulder  102  assures that the portion of the front taper  100  immediately adjacent the shoulder  102  does not touch the bore  80  of the bit block  61  as the bit holder is driven into the bit block. As the bit holder is further driven into the bit block and the diameter of front taper  100  increases until interference contact is made adjacent the forward end of taper  100  where the 100 percent circumferential surface is located The slot  108  decreases in width mostly in press fit zone  101  to allow the bit holder to be driven into the bit block. The position at which the front taper  100  achieves an interference fit with the bit block bore  80  is approximately that position shown in FIG. 11, i.e., about ¼ to ⅝ inch. The interference fit between the taper portions  100 - 101  and bore  80  maintain the bit holder in fixed mounted position in bore  80 . The use of pin  89  which extends through bore  89   a  into the bore  80  (and slot  108  when the holder is inserted in the block) assures that proper alignment and minimal rotation occurs between the holder  90  and the bit block  61 . However, when using greater interference fit on taper portion  101 , no pin may be required in certain applications. 
     Referring to FIGS. 11 and 11 a,  a means for mounting the bit holders of the present invention in their respective bit blocks is shown at FIG. 11, and a means for demounting or removing the bit holders from their respective bit blocks is shown at FIG. 11 a.  In FIG. 11, the bit holder  90  or bit holder  60  are substantially driven into the bit block  61  with the use of a first drive pin, generally indicated at  105 , that includes an elongate shank portion  106  having a slip fitting cylindrical distal end  120  which loosely fits in the bore  107  (FIG. 10) of the bit holder. A reduced shaft portion  121  may be positioned mediate the distal slip fitting cylindrical portion  120  and an enlarged cylindrical portion stop member  122  including an annular face  123  thereon adapted to matingly engage the front annular flat surface  91  of the bit holder. An enlarged head portion  117  absorbs the blows of a hammer  118 , which strikes the same to drive the press fit shank portion  97  (FIG. 9) of the bit holder  90  into the bore  80  of the bit block  61 . The slip fitting distal cylindrical portion  120  and the annular face  123  of the drive pin  105  assures that the bit holder  90  will be accurately positioned-to drive same into the bore  80  of the bit block  61  without harming any potential annular inserts, such as shown at  163  in FIG. 12 positioned at the upper flat annular surfaces of either the bit holder or the bit block. The hardened inserts, being more brittle than the softer ductile material of the remainder of the bit block  61  and bit holder  90  will be more likely to be damaged during insertion of the bit holder  90  in the bit block  61  if a non-close fitting drive pin were used rather than the preferred embodiment drive pin  105 . 
     Referring to FIG. 11 a,  a second drive pin, generally indicated at  130 , is utilized to remove or drive out the bit holder  90 , or bit holder  60  of the present invention from the bit block  61 . Drive pin  130  includes an enlarged head portion  131  for accepting the blows of the hammer  118  previously mentioned. The shaft portion  132  includes a slightly reduced diameter distal end  133  having a semispherical tip  134  of larger diameter than the bore  107  of the bit holder  90 . 
     In operation, the semispherical distal tip  134  is  10  positioned on the central bore  107  of the bit holder  90  at a countersink  77   a  (FIG. 7) on its rearward distal end  103 . Since the semispherical end  134  is larger in diameter than the central bore  107 , it allows the drive pin  130  to be positioned in other than a coaxial position with the central bore  107  of the bit holder  90 . Countersink  77   a  provides for additional engagement between the distal end of the tool  130  and the bit holder. This provides positioning the drive pin around combinations of bit, bit holders and bit blocks mounted adjacent the bit holder that is being removed from its respective bit block. The hammer  118  striking the enlarged end  131  of the drive pin provides an axially oriented component of force to drive the press fit bit holder  90  outwardly of the bore  80  of the bit block  61 . When needed an anti-seize grease is applied to the mating parts for easier assembly and disassembly. 
     Referring to FIG. 12, a second means of inserting the bit holder  160  into the bit block  61  is shown. This second insertion means includes a threaded bolt, generally indicated at  110 , including a threaded portion  111 , which extends through the bore  180  of the bit holder  160  and out the distal end thereof. A specialized nut  112  is threaded on the threaded distal end of the bolt  110  until contact is made with the rear of the bit block. Then, nut  112  is retained in a non-rotating position by a wrench or by means between the nut and the back side slot  115  of the bit block  61 . Then the hexagonal front bolt portion  113  of the bolt is rotated with the threads  111  engaging the internal threads on the nut  112  such that the hex head  113  drives the front face  162  of the bit holder, and thus the remainder of the bit holder  160 , into the bit block  61  until the back side annular flange  67  (FIG. 3) seats on the front face  85  of the bit block  61 . The front face  162  of bit holder  160  includes a hardened frustoconical tungsten carbide insert  163  disclosed in U.S. patent application Ser. No. 09/121,726. 
     While four embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the true spirit and scope of the present invention. It is the intent of the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.

Technology Classification (CPC): 4