Abstract:
An improved bit assembly for road milling, mining, and trenching equipment includes a streamlined tip assembly that is a combination of conical and cylindrical in shape and devoid of protrusions or annular indentations that might impede the flow of removed material over and around the bit assembly or provide space for removed material to become clogged or imbedded on the tip assembly. The assembly further includes a generally cylindrical spacer that allows a bit removal tool access to the bottom of the assembly to aid in bit removal.

Description:
This invention relates generally to road surface removal or reclaimer-stabilizer equipment and mining equipment and more particularly to bit assemblies including bits, bit holders and bit blocks that are more efficient in their cutting and passage of the cut material around the bit assembly. This application is a divisional of Ser. No. 09/825,601 filed Apr. 04, 2001, now U.S. Pat. No. 6,685,273, which is a continuation-in-part of Ser. No. 09/500,983 filed Feb. 15, 2000, now U.S. Pat. No. 6,371,567 issued Apr. 16, 2002. 

   BACKGROUND OF THE INVENTION 
   Bit assemblies 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 smoothes the top of all or selected portions of the road surface. The bits utilized 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. 
   The bit assembly including the bit, bit holder and bit block, act on the portion of the surface it is removing to separate that surface from the underlayment and as the drum rotates, passed that surface over the outside of the bit assembly. The milling of concrete and macadam surfaces required a substantial power output to operate the drum or continuous chain or the like. With the use of such a substantial power output to operate the heavy milling machinery, a need has developed to provide a more efficient bit assembly that utilizes less power to perform the same function as machines fitted with prior art bit assemblies. 
   In O&#39;Neill et al, U.S. Pat. No. 4,915,455, a substantially frustoconical bit is mounted upon a block that provides a large mostly flat forward leading surface that impedes the flow of macadam or concrete therearound and provides a barrier to movement of the bit on additional portions of the surface to be milled. 
   Additionally, a need has developed for providing ease of removability of bit holders in their bit blocks, especially when portions of or all of the assembly 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 to help remove a bit from the bit block. It would be desirable to provide more efficient means and multiple means for allowing the removal of a bit holder from a bit block. Additionally, heretofore known bit holders have been retained in bit blocks by the use of threaded nuts or retainer rings. A need has developed to provide means to mount the shank portion of a bit holder in a bit block without the need of a fastener on the distal end of the bit holder shank to retain same in the bit block. 
   Further, a need has developed for a truly quick-change type of bit holder that may easily and quickly be 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 a more efficient bit assembly that requires less power to run when mounted on road milling equipment than heretofore known bit assemblies while providing longer lasting useful life of operation. 
   A further object of the present invention is the provision of multiple means for 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 present invention is the provision of an easily mounted tool on the bit holder that facilitates the removal of the bit holder from the bit block at the front of the leading surface of the bit holder without the need for a large amount of access to the rear of the bit block. 

   
     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 exploded view of a bit assembly constructed in accordance with the present invention; 
       FIG. 2  is a fragmentary cross-sectional view with certain modifications taken substantially along line  2 — 2  of  FIG. 1  with the items of  FIG. 1  shown in mounted position on each other; 
       FIG. 3  is a bottom ¾ perspective view of a second embodiment of the invention showing a bit holder mounted in a bit block; 
       FIG. 4  is a top ¾ end perspective view of the second embodiment of the present invention; 
       FIG. 5  is a front ¾ perspective view of the second embodiment of the present invention; 
       FIG. 6  is an upper side perspective view of the second embodiment of the present invention; 
       FIG. 7  is a top plan view of a third embodiment of a bit holder of the present invention; 
       FIG. 8  is a side elevational view of the third embodiment bit holder of the present invention; 
       FIG. 9  is a front end elevational view of the third embodiment of the bit holder of the present invention; 
       FIG. 10  is a top plan view of a fourth embodiment of a bit holder of the present invention; 
       FIG. 11  is a front end elevational view of the fourth embodiment of a bit holder of the present invention; 
       FIG. 12  is a side elevational view of a tool to facilitate removal of a bit holder from a bit block; 
       FIG. 13  is a cross-sectional view similar to  FIG. 2  showing a second embodiment of the plunger of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a bit, bit holder and bit block assembly, generally indicated at  15 , constructed in accordance with the present invention, includes a bit, generally indicated at  16  and a spacer, generally indicated at  17 , together with a bit holder, generally indicated at  18  and a bit block, generally indicated at  20 . 
   The bit  16  includes a hardened tip  21 , usually made of tungsten carbide. The base of tungsten carbide tip  21  (not shown) resides in a pocket (not shown) in the front face  22  of a frustoconical forward portion  23  of bit  16 . At the rear of the frustoconical portion  23  is a cylindrical front portion base  24 . In this embodiment, the cylindrical base  24  performs a function which is analogous to prior art known as a “tire portion” of the bit because in that prior art the outside of the base portion has a rounded shape similar to the outside of a donut or tire. Aft of the cylindrical base  24 , the tip narrows to a cylindrical shank  25 , which, in this embodiment, includes a C-shaped retainer  26  therearound and a cylindrical shank portion base  27  defining the rear end of the bit. 
   The spacer  17  is shaped similarly to the shank portion  25 – 27  of bit  16  in that it includes opposed cylindrical ends  28 ,  30  and a slightly narrowed cylindrical shank portion  31  mounted therebetween having a C-shaped retainer  32  positioned therearound. At the outside of the opposed cylindrical end  30  is a spherical indent  33  whose purpose will be discussed in more detail below. 
   In this embodiment of the present invention, the bit holder, generally indicated at  18 , is termed a bulbous shaped bit holder as the front generally conical portion includes a middle section having a convex outline. The leading portion of the generally conical front section of bit holder  18  includes a cylindrical nose  34 , having a flat annular face  35  from which a central bore  36  extends axially all the way through the bit holder. A plurality of notches  37 – 37  (one shown) adjacent the front face  35  of the bit holder, provide an access area to the cylindrical base  24  of the tip  16  into which a prying tool may be positioned to force out the base  24  of the bit  16  when the bit shank  25  and spacer  17  are mounted in the bore  36  of the bit holder  18 . Rearwardly adjacent the nose  34  is the bulbous portion  38  of the generally frustoconical front section of the bit holder  18 . Rearwardly of the bulbous section  38  is the cylindrical base  40  which performs a similar function in the bit holder  18  that the cylindrical base  24  performs in the bit  16 . 
   Aft of the base  40  of the conical front portion of bit holder  18  is the shank  41 . The shank portion  41  includes an upper shoulder  42  which is slightly larger diameter than the middle shank portion  41 , and a second enlarged portion  42   a  of shank  41  immediately adjacent the distal end  43  thereof. A slot, whose forward end is indicated at  44  extends from the end of upper shoulder portion  42  through the distal end  43  of the shank  41  thus providing a C-shape for the perimeter of the shank  41  allowing it to expand and contract diametrically for a force fit into the bit block, generally indicated at  20 . A pin  45  is mounted in a bore  46  180 degrees around shank  41  from the slot  44 . The pin  45  assures that the spacer  17  will not fall out of the bottom of bit holder bore  36  in the bit holder  18  when it is mounted therein. 
   In another important aspect of the present invention, the bit block  20  includes a base mounting portion  47  having a base  48  which is mountable on the outside of a drum (not shown) which is a part of road milling equipment. The front or leading portion of the mounting section  47  includes a pair of rearwardly angled shoulders  50 — 50  (only one shown). Adjacent the mounting section  47  which holds the bit block on the drum is a generally annular cylindrical bit holder mounting portion  51  having a central bore  52  positioned therethrough from a top surface  53  to a bottom distal portion  54  of the bit block  20 . Adjacent the bottom portion  54  and opposite the mounting portion  47  is a slot  55  which increases the accessibility of a tool to the rear of the bit block and into the bore  52  of the bit block  20  at the rear  54  thereof. Also, immediately above slot  55  is a cylindrical bore  56  which may have a pin (shown in  FIGS. 3 and 5  at  56   a ). Pin  56   a  extends into the slot  44  of the bit holder, thus preventing rotation of same when mounted in the bit block. As is evident from the exploded view, the shank portion  41  of the bit holder  18  is press fit into the bore  52  of the bit block  20  and retained therein. Further, the spacer  17  and the shank portion  25  of bit  16  are mountable through the front end  35  of the bit holder  18  and are retained therein by C-shaped retainers  26  and  32 . Additionally, the spacer is retained in its mounted position by pin  45 . 
   Referring to  FIG. 2 , the mounting relation between the bit block  20 , bit holder  18 , spacer  17  and bit  16  is shown in cross section.  FIG. 2  is modified from a straight cross section of the assembly as shown in  FIG. 1  in that the slot  44  of bit holder  18  and the slot  55  of bit block  20  are not seen so that the mounting relation between the bit block and bit holder may be shown in more detail. Additionally, the upper shoulder  42  of the bit holder is not shown so that the relationship between the lower shoulder  42   a  and the bit block bore  52  may be shown. 
   As is shown most clearly in  FIG. 2 , the lower raised shoulder  42   a  of the shank portion  41  of the bit holder  18  is press fit into the bore  52  of bit block  20 . The press fit between the two is on the order of four times the ordinary press fit between a cylindrical male member and an annular bore because the C-shape cross section of the shank is resilient with the addition of slot  44  therein. This allows the lower shoulder  42   a  to be positioned in bore  52  with such a substantial press fit that neither a retaining nut nor retaining ring is necessary to maintain the bit holder in the bit block. However, because of vibration and potential rotation of the bit holder in the bit block, a pin  56   a  ( FIG. 5 ) is mounted through bore  56  into the slot  44  ( FIG. 1 ) of the bit holder shank in order to maintain the bit holder and bit block in correct non-rotating mounted orientation. As additionally shown in  FIG. 2 , the bit  16  and spacer  17  are mounted in the central bore  36  of bit holder  18  and retained therein by C-shaped retainer clips  26  and  32 . As shown most clearly in  FIG. 2 , the semi-cylindrical indent  33  in the spacer  17  provides for the insertion of a tool through the backside of bore  36  which will accommodate punching out the spacer  17  and the bit  16  from the back of the assembly. 
   As also shown most clearly in  FIG. 2 , in an important aspect of the present invention, the profile of the bit, bit holder and bit block maintains either a cylindrical outline or a conical outline although the conical outline may be slightly concave or convex also, to provide a smooth efficient aerodynamic outer surface which in this case does not have air passing by it, but has macadam or concrete passing by it. This smooth outer surface of the bit  16 , bit holder  18  and bit block  20  also benefits from the opposed shoulders  50  at the leading surface of the bit block  20 . The aim in providing this efficient aerodynamic profile is to both provide longer life for the assembly and the portions thereof, and to provide for more efficient separation of the macadam or concrete and passage of same by the assembly, thus requiring less power to run the road milling equipment and also providing longer life for the assembly  15  when performing its function. Generally, the lack of sharp edges and the lack of cylindrical outcroppings along the surface, or indents along the surface, provide fewer areas for macadam or concrete to sharply impact the surface or become imbedded thereon, thus assuring a more efficient and longer work life for the assembly  15  and the parts thereof. 
   In operation, prior art road milling bit, bit holder and bit block assemblies normally operate for between three and four hundred hours before the parts wear out or a failure occurs in at least one part of the assembly. Applicant&#39;s bit, bit holder and bit block assembly have been operated for more than 1000 hours without serious deterioration of the assembly or failure of parts thereof. Also, the use of the assembly  15  of the present invention on road milling equipment has provided a milling system which consumes less gasoline per hour to operate. While gas consumption of the road milling equipment varies depending on depth of cut, temperature, surface to be milled, etc., over a long period of time, it is believed that the bit assembly of the invention yields about a 10 percent improvement over prior art bit assemblies. 
   Referring to  FIGS. 3–6 , a second embodiment of the present invention is shown utilizing the bit block  20  of the first embodiment together with a concave style bit holder, generally indicated at  60 . Bit holder  60  differs from bit holder  18  not only in that it is concave in its conical leading portion, but also because it has a hardened annular insert  61  preferably made of tungsten carbide positioned at its leading surface. Since the hardened insert  61  extends towards the outside of the concave, but generally conical forward surface  62  of the front portion of bit holder  60  to provide structural strength, there are no notches in the concave surface  62 . With this embodiment, the bit  16  (not shown) would be driven out of the bit holder  60  for replacement by inserting a rod to tool (not shown) in the bottom of bore  63  of the bit holder (shown most clearly in  FIG. 3 ) until it is stopped by semi-spherical indent  33  of spacer  17  ( FIG. 2 ) where a hammer struck on the end of the tool will drive the bit  16  outwardly of the bit holder  60 . The use of a hardened insert  61  has been shown to increase the work life of the bit holder  60  by providing a tougher mounting for the bit  16  in the bit holder  60 . 
     FIGS. 4 and 6  tend to show the increased efficiency obtained by utilizing opposed shoulders  50 — 50  to direct macadam away from the forward portion  50   a  and third shoulder  50   b  of the bit block mounting portion. Also, as mentioned previously, and shown in  FIGS. 3 and 5 , the pin  56   a  is aligned with the slot  64  in the shank of bit holder  60  to prevent rotation of the bit holder  60  in the bit block  20  when mounted therein. Additionally,  FIG. 3  shows the accessibility of the shank  65  on bit holder  60  through the rear  54  of the bit block  20 . Shown most clearly in  FIGS. 3–6 , the forward facing surfaces of the bit holder  60  and bit block  20 , with the exception of leading surface  50   a  for strength of part reasons, all extend rearwardly and outwardly to provide a smooth, efficient deflecting surface for material separated from the macadam or concrete by the bit  16 . 
   Referring to  FIGS. 7 ,  8  and  9 , a third embodiment of a bit holder is shown generally at  70 . Bit holder  70  is similar to the bit holder  18  in that it is a steel front bulbous type having a slotted shank. The steel cylindrical flange front  71  includes an annular steel face  72  similar to the first embodiment. The bulbous frustoconical portion  73  extends rearwardly beyond the cylindrical nose and includes a pair of notches  74 ,  75  therein that provide tool access to the back of a bit for easing removal of the bit from the bit holder. 
   At the rear of the bulbous frustoconical portion  73  is the cylindrical base  76 . In one important aspect of the present invention, the base  76  includes a rectangular notch  77  that extends radially inwardly from the outside of the circumference of cylindrical base  76  and is also in communication with the back face  76   a  of the cylindrical base. When the bit holder  70  is mounted in the bit block, such as  20 , notch  77  will allow access of a tool therein to provide a prying method for removing the bit holder from the bit block. This is especially important if, for some reason, access to the back of the bit holder is not obtainable. A prying tool positioned in notch  77  would provide for removal of the bit holder out of the bit block until after the upper shoulder  78  of shank portion  79  is free of the top of the bit block, thus easing removal of the bit holder from the bit block. 
   Referring to  FIGS. 10 and 11 , a fourth embodiment of the bit holder of the present invention, generally indicated at  80  is a steel nosed bit holder similar to that shown in  FIG. 1 , i.e., a bulbous style frustoconical nose bit holder, with the exception that the notches  82 ,  83  are round in outline rather than rectangular as shown in the first embodiment  18 . The frustoconical portion at the front of the bit holder  80  includes the cylindrical nose  84 , bulbous frustoconical portion  85  and cylindrical base  86 . Rearwardly of the base, the shank portion  87  includes an upper shoulder  88  similar to that shown in the first embodiment. However, the remainder of shank  87  differs from the shank  41  of the first embodiment in two ways. First, instead of having a slot extending from the edge of upper shoulder  88  to the distal end  89  of the shank, the fourth embodiment of the present invention includes a pair of diametrically opposed slots  90 — 90  from the upper shoulder  88  to the forward edge of the distal end  89  such that the distal end  89  is still annular in shape rather than C-shaped as in the first embodiment  18 . The second difference in the shank portion between the first embodiment and the fourth embodiment, is that the lower shoulder portion  91  is moved forwardly on the shank to be at a position to bisect the opposed slots  90 — 90 . In this embodiment, the pair of opposed slots take away stiffness from the annular shank such that the lower shoulder portions  91  are resilient similar to the lower shoulder portion  42   a  of the first embodiment even though the distal end  89  of the shank is continuously circular or annular in shape. The press fit of the lower shoulder  91  in the bore  52  of the bit block  20  is similar to that of the lower shoulder  42   a  of the bit holder  18  in that it is a greater interference fit than that found in typical male-female member press fits, thus providing for ease of secure mountability of the bit holder  80  in the bore  52  of bit block  20 . As with the other embodiments, no nut or retainer is necessary to hold the bit holder in the bit block. Also, pin  56   a  fits in either of the slots  90 — 90 . 
   Referring to  FIG. 12 , a tool for aiding removal of the bit holder  18  from the bit block  20  is generally indicated at  95 . Tool  95  includes an elongate bolt  98  having a hex head  96 , a shank  100  that extends through the bore  36  ( FIG. 1 ) of the bit holder  18  and out the distal end  43  thereof where a hex head nut  99  may be turned on the threads at the distal end of the shank portion  100  of bolt  98 . An enlarged radially extending flange  101  has a central bore  102  through which the bolt shank  100  is passed prior to inserting the bolt through the bit holder bore  36  ( FIG. 1 ). The large flat surface  101  on the rearward side of annular flange  101  provides ample room for positioning the tool thereagainst or striking a hammer thereto to remove the bit holder  18  from the bit block  20  without needing a large amount of access to the rear of the bit block  20  other than room to fit nut  99 . 
   Referring to  FIG. 13 , a second embodiment of spacer or plunger, generally indicated at  105 , performs the same function as spacer  17 , is cylindrical in outline and slidingly fits in the central bore  106  of bit holder  107 . Spacer of plunger  105  includes an elongate infernal slot  108  extending mediate the front end  110  and rear cupped end  111  thereof. A perpendicular bore  112  radially through the shank sidewall  113  secures a pin  114  that extends into slot  108  to limit the movement of the spacer in the bore. An additional notch  115  in spacer  105  provides for removing the spacer from the bit holder  107  by driving the pin into the notch. Unlike spacer  17 , spacer  105  does not need a retainer  32  to keep it mounted in its respective bit holder bore. Thus, an improved road milling bit assembly spacer, bit holder and bit block have been shown and described together with three additional embodiments of the bit holder and a bit holder removing tool. The bit assembly in being efficiently smooth and lacking in substantial annular discontinuities around the bit provides an efficiency of use when the bit separates either macadam or concrete and also provides for an efficient passage of such material around the bit assembly that lessens wear on the assembly and requires less power to drive the assembly through the macadam or concrete while also providing greater bit assembly life and requiring less fuel per hour to drive the assembly than heretofore known bit assemblies. 
   While five differing embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that many 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.