Abstract:
Bit holders and combination bit/bit holders with shortened quick change shanks that are selectably retainable in complementary base block bores that are likewise shortened for providing added spacing at the rear of base blocks. When a plurality of such base blocks are mounted in close proximity on a drum or endless chain, the added spacing provides ease of holder replacement and easy access at the rear of the bit holder base block bore.

Description:
[0001]    This application claims priority to provisional patent application Ser. No. 62/100,724, filed Jan. 7, 2015, to the extent allowed by law. 
     
    
       [0002]    This invention relates to bit holders and combination bit/holders that are usable in connection with a shortened, generally 1½ inch depth bit holder block bores including a tailing curved segment beyond the 1½ inch annular bore of a bit holder block. 
       BACKGROUND OF THE INVENTION 
       [0003]    Applicant is the inventor of the “quick change” bit holder/bit holder block combination that enables a bit assembly to have its bit holder retained in the bit holder block without the use of threaded nuts or spring clips holding the bit holder shank in the bit holder block bore. This invention is shown and discussed in applicant&#39;s U.S. Pat. Nos. 6,371,567, and 6,585,326 and RE44,690. 
         [0004]    After the creation of the retainerless bit holder shank, applicant realized that the combination of a like tapered shank together with its corresponding bit holder block bore, when retained by an excessive interference fit made possible by an axial slot in the hollow shank, resulted in the greatest interference force being positioned adjacent the top of the terminus of the slotted distal tapered portion of the bit holder shank. The increased interference between the bit holder block bore and bit holder shank caused the minute radial and circumferential collapsing of the bit holder shank adjacent the axial oriented slot. The collapse became more prominent toward the distal end of the shank resulting in somewhat less radial and circumferential force being applied toward that distal end by the bit holder block bore. After the time of the conception of the invention found in the &#39;567 and &#39;326 patents, the positioning of greatest holding force between the bit holder shank and bitholder block bore adjacent the top of slot was utilized in an effort to ease the insertion of the bit holder in the bit holder block bore. That greatest portion of force to insert the bit holder shank was positioned at the last ¼ to ¾ inch of the insertion of the shank of the bit holder in the bit holder block bore. Additional holding force was added adjacent the top of the shank with a standard annular interference fit with the corresponding top portion of the bit holder block bore. These two greatest holding force positions, when added to the holding force positioned adjacent the remainder of the distal tapered portion of the shank resulted in the 3,000 to 15,000 lbs. necessary to insert and retain a lubricated shank in the bit holder block bore. These axial insertion forces are derived when preferably a molybdenum disulfide type lubricant is smeared on the shank of the holder. At least double the axial removal force is required when no lubricant is used. 
         [0005]    In road milling machinery, bit assemblies are generally positioned around the outside of a cylindrical drum that is dimensioned to rotatably fit within the confines of the underside of a road milling machine. In an effort to create the smoothest road milling, bit assemblies have been mounted in staggered positions in spiral or chevron form on the drum to decrease the axial dimensions between adjacent cutting tips of bit assemblies. As a result of this spiral or chevron orientation and the positioning of many bit assemblies on a current milling drum, the spacing behind each bit assembly has been reduced to the point where access to the rear of each bit assembly is severely limited. This rear access is necessary in order to drive out shanks of broken bits, shanks of broken bit holders, and conical bits. The shorter bit holder shank and the shorter bit holder block bore now provide this access. 
         [0006]    When increasing the rear access to the distal end of the shank by shortening the axial shank length and by shortening the axial length of the bit holder block bore, the holding force previously there is reduced. That shank to bit holder block bore retention force must be re-established. 
         [0007]    A need has developed to provide an improved bit holder/bit holder block bore assembly wherein the holding force between a bit holder shank and a bit holder block bore may be positioned axially along the bit holder shank as desired, rather than as previously positioned on the aforementioned portions of the shank. Additionally, increased access to the rear of the bit holder block is desirable for easing the ability to drive the bit holder shank and bit shanks out of its bit holder block from the rear thereof. 
       SUMMARY OF THE INVENTION 
       [0008]    The Invention resides in a shortened bit holder shank having a taper that is less than the taper or cylindrical portion of a bit holder block bore. Additionally, the invention resides in a bit holder block bore having a shortened bit block bore portion with a tailing arcuate bore segment behind the annular bore portion thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention may best be understood from the following detailed description of currently preferred embodiments thereof taken in conjunction with the accompanying drawings wherein like numerals refer to like parts, and in which: 
           [0010]      FIG. 1  is a side elevational view of a combination bit holder and bit holder block constructed in accordance with the present invention; 
           [0011]      FIG. 2  is a fragmentary cross sectional diagram, taken along line  2 - 2  of  FIG. 1  showing the interference between the bit holder shank and the bit holder bore in the present invention; 
           [0012]      FIG. 3  is a side elevational view of a first embodiment of a long shank bit holder positioned in a bit holder block of the present invention; 
           [0013]      FIG. 4  is a side elevational view of a second embodiment of a long shank bit holder positioned in a bit holder block of the present invention; 
           [0014]      FIG. 5  is a side elevational view of a bit holder having a shortened shank with a bulbous distal section of the bit holder shank; 
           [0015]      FIG. 6  is a front elevational view of a modification of the bit holder shown in  FIG. 5  wherein the bulbous section of the shank is of lesser bulbous degree; 
           [0016]      FIG. 7 a    is a side elevational view of a combination bit/bit holder with a shortened shank in accordance with the present invention and a diamond tip formed as a unitary structure; 
           [0017]      FIG. 7 b    is a side elevational view of a bit/bit holder combination having a diamond tip and a long shank shown as mounted in a bit holder block constructed in accordance with the present invention; 
           [0018]      FIG. 8 a    is a side elevational view of a bit/bit holder having a shortened shank constructed in accordance with the present invention wherein the tip of the bit/holder has an enlarged diameter tip insert mounted therein, all mounted in a bit holder block constructed in accordance with the present invention; and 
           [0019]      FIG. 8 b    is a side elevational view of the bit/holder of a modification of the bit/holder constructed in accordance with the present invention having a long shank, all mounted in a bit holder block constructed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    Referring to  FIGS. 1-2 , a combination of a short shank bit holder  10  mounted in a bit holder block  11  constructed in accordance with the present invention includes a bit holder having an upper body portion  12  and a lower generally 1½ inch long shank portion  13  depending from the bottom of the body portion thereof. The upper body portion  13  is about 2 inches in axial height making it longer than the shank  13 , the first holder to be so dimensioned. The shank is generally hollow and cylindrical approximating 1½ inches in diameter, 1½ inches in length, and includes an axially aligned elongate slot  14  through the wall of the shank extending upwardly from the distal end  15  of the shank to a terminus  16  subjacent a radially extending annular flange  17  about 2⅝ inches in diameter, defining the bottom of the body portion  12  of the bit holder  10 . The width of the slot  14  may be varied from about ⅛ inch to about ¾ inch depending on the amount of elastic deformation required to produce the desired holding force between the shank  13  and the bit holder block bore or a base block bore  18 . In this embodiment, the bit holder shank includes an upper annular portion  20  ( FIG. 2 ) sized to have a conventional interference fit of about 0.001-.005 inch greater than the corresponding bit holder block bore or base block bore  18  adjacent the top  21  of the bit holder block. 
         [0021]    A central reduced diameter portion  22  ( FIG. 2 ) of the shank  13  depends from the upper previously mentioned enlarged portion  20 . The upper terminus  16  of the slot  14  is generally, although not always, positioned in this central reduced diameter  22  zone. In this embodiment of the invention, a lower tapered portion  23  extends from the bottom of the upper reduced diameter portion  22  to a position adjacent a distal end  15  substantially annular flange of the bit holder shank  13 . This tapered portion  23 , to be discussed in more detail below, includes what is termed herein “a reverse taper portion.” This reverse taper portion is, with respect to any taper or straight cylindrical bit holder block bore  18 , also to be discussed in greater detail below. The distal, mainly annular, flange  15  is a reduced diameter portion defining about the last ¼ inch length of the shank  13  and is annular with the exception of the slotted portion  14  discussed previously. 
         [0022]    This shortened, reverse taper, shank  13  on the bit holder is an improvement over the shortened bit holder shank shown in applicant&#39;s co-pending provisional application 61/944,676 filed Feb. 26, 2014, the written and drawing contents of which are incorporated herein by reference. 
         [0023]    The bit block  11  shown in  FIGS. 1, 3-4  incorporating the present invention includes a drum mounting portion  24  having a generally flat, or somewhat concave arcuate, base  25  including a plurality of mounting holes  26 - 26  or apertures therein for mounting the base on a drum (not shown). In this embodiment, the plane of the base  25  intersects the center line  27  of a bit holder  10  mounted in the bit holder block  11  at an acute angle thereto. The bit holder block body further includes a forward end adjacent portion  24  of the bit block  11  that in this preferred embodiment includes a peaked center line  28  together with sloped surfaces on either side of the center line (only one shown), aiding in directing material to be removed by the bit assembly from whatever substrate the milling machine is operating on. 
         [0024]    Outwardly of the drum standoff mounting portion  24  of the bit holder block  11  is a generally annular bit holder receiving portion  30  including a flat annular surface defining the top  21  thereof on which the bottom annular flange  17  of the bit holder body  12  is positioned generally contiguous therewith. The annular bit holder mounting portion  30  extends to an outer generally semicircular portion and includes a bit holder block bore  18  which, in this embodiment, has a continuous constant taper surface extending from its top flat annular surface  21  past a bottom semi-annular surface  31  about 1½ inches axially from the top annular surface and further including an arcuate concave surface portion  32  extending below the bottom of the annular bit holder block bore mounting portion  30  at a constant tapered angle continuation of the bit holder block bore that extends from that bottom surface, at  32 , toward the bottom of the bit block mounting portion. 
         [0025]    In this preferred embodiment, the bit holder block bore  18  is a constant taper, or straight cylindrical bore and extends from the top surface  21  through to the bottom of the concave block mounting portion shown at C. It will also be understood that some bit holder block bores  18  may be divided into multiple portions wherein the taper of the top portion of the bit holder block bore is greater than the taper or semi-cylindrical portion of a bottom section of the bit holder block bore. This holder  10  and holder block bore  18  relationship can be opposite in taper and achieve the same results. Additionally, the bottom of the annular bit holder receiving portion of the bit holder block bore includes a slot, whose interiormost outline is shown in dotted line at D that extends from the outermost bottom portion of the bit block bore at C to provide increased access to the rear of the bit holder block bore  18  for use of a tool to drive a broken bit shank or bit from the bit holder bore. 
         [0026]    As stated in applicant&#39;s provisional application Ser. No. 61/983,291, filed Apr. 23, 2014, entitled “Improvements in Rear of Base Block” the inclusion of a cut out portion  31 ,  32  of the rear of the base holder mounting portion  30  of the base block  11  shown at surface C shortens the annular bit holder receiving portion of the bit holder base block from approximately 2⅝ inches in axial dimension to about 1½ inches in axial dimension, increasing the open area behind the bit holder block that allows an easier access to the rear of the bit holder block for a removing tool or punch bar or other shape extractor (not shown). The written contents and drawings of the aforementioned provisional application entitled “Improvements in Rear of Base Block” are incorporated herein. 
         [0027]    Referring to  FIG. 2 , a fragmentary silhouette of the shank of the bit holder shown in  FIG. 1  is shown contrasted to the dimensions of the bit holder block bore shown in  FIG. 1  as they appear in overlapping relation showing the relative dimensions of each with respect to the other. The outline of the bit holder shank is shown at line B while the outline of the bit holder block bore is shown at line A. The outline of the bit holder is shown beginning at an axially extending tire portion  33  through the bit holder body annular flange  17  to a generally rounded annular undercut  34  extending to the top of the bit holder shank. This top of the bit holder shank includes the larger upper portion  20  disclosed above, the central reduced annular portion  22  and the bottom reverse taper portion  23  extending to the generally reduced diameter annular flange defining the distal end  15  of the shank. 
         [0028]    The bit holder shank line A starts at annular flange  17  adjacent the top of the bit holder shank portion  17  of the bit holder and extends from that undercut  34  at a continuous angle to the bottom of the annular portion  15  of the bit holder shank. As shown most clearly at the bottom of the upper portion  20  of the bit holder shank  13 , there is a standard interference between the bit holder shank upper portion  20  and the bit holder block bore, Line A. It should be noted that this upper portion may also be tapered to conform with the angle of taper of the top of the bit holder block bore to provide an annular surface interference rather than an annular line interference. 
         [0029]    From adjacent the upper portion  20  of what is termed the reverse taper portion  23  of the bit holder shank  13  to the bottom  15  thereof, there is an interference with the bit holder block bore, Line A, that increases toward the bottom end  15  of the tapered bit holder shank portion, i.e., in this preferred embodiment from about 0.015 inch on a diameter at the top to about 0.035 inch on a diameter at the bottom portion of the shank  15 . This “reverse taper” only has to be a less tapered portion than that of the adjacent bit holder block bore, Line A. In other words, if the taper of the bit holder block bore Line A is 1 degree per side, the reverse taper of the bit holder shank  13  would only have to be something less than that, i.e., ½ degree per side. If the bit block holder bore is cylindrical, the reverse taper portion of the bit holder shank would only have to be a negative taper of ½ degree, 1 degree, etc. per side. 
         [0030]    It should be noted that “reverse taper” in this connection means a differing slope between the distal slotted portion  16  of the bit holder shank  13  and the corresponding shank engaging portion of the bit holder block bore, Line A. As shown in  FIG. 2 , the difference in slope increases as one approaches the distal end  15  of the shank. The specific numbers are not as important as the relationship between the surfaces shown most clearly in outline in  FIG. 2 . The invention distributes the circumferential and radial loads, between the shank and bit holder block bore in the approximate ¾ inch distance of interference sufficiently to hold the shank  13  in the bore  18  during use. 
         [0031]    The reason for the reverse taper  23  is to move the position at which a greater interference force is exerted at the distal end  15  of the shank than could be achieved with the same interference angles between the shank of the holder and the base block bore. As noted above, in previous versions of the “quick change” bit holder and bit holder block assembly, the taper or cylindrical portions of the bit holder shank and bit holder block bore were identical in configuration and it resulted in the greatest interference being adjacent the top of the slotted portion of the shank. By using a lesser taper on the bit holder shank than that of the bit holder block bore, the area of greatest interference or holding force between the bit holder block bore and the bit holder shank may be moved lower on the shank near distal end  15  and also may be spread over a greater axial length than that utilized in the prior art. The 5,000 to 20,000 pounds axial force necessary to insert the bit holder  10  in the bit holder block bore  18  may be modified as needed along the reverse taper portion  23  as desired. The reverse taper of the shank yields a nearly equivalent radial retention force as the axial insertion force. However, the retention force increases as impact forces tend to improve mating surface tension. 
         [0032]    The recognition that previously known interference fits between a slotted bit holder shank and a bit holder block bore was obtained adjacent the top of the tapered portion and near the top of the slot of the bit holder shank has enabled applicant to realize that the axial length of the shank may be decreased from approximately 2⅝ inches in length to about 1½ inches in length with the same retention force: 1) as long as the reverse taper improvement is utilized in the interfering portion of the bit holder shank  23  and the bit holder block bore  18 , or 2) if similar shank/bore tapers are used with increased interference from that disclosed in applicant&#39;s prior U.S. Pat. Nos. 6,371,567 and 6,585,326 on the order of 0.019 to 0.033 inches of diametrical interference and as long as the tensile and the compressive strength of the bit holder shank is increased by about 20% above the same values used in the reverse taper shank parameters, same taper can yield workable results. This decreased axial length of the bit holder shank and the bit holder block bore enables the bit holder block bore to be axially reduced in length to provide space for additional access of a bit removing tool (not shown) to the rear  31 ,  32  of the bit holder block. 
         [0033]    As shown in  FIG. 3 , when a bit holder having a shortened 1½ inch long shank, shows sufficient wear that it needs to be replaced, it may not only be replaced with another bit holder having a 1½ inch long shank ( FIG. 4 ), but in accordance with applicant&#39;s invention, it may be replaced by what may be termed a standard “quick change” bit holder  40  having a 2⅝ inch long shank. Bit holder block bore  18  enlarge after extended use may also necessitate use of the longer shank bit holder  40 . In this application, the bottom tapered portion  42  of the bit holder shank  41  extends not only in the bottom portion of the 1½ inch long fully annular bit block bore  18 , but also impinges against the continuing concave segment surface  43  of the bit holder block bore  18  extending below the back face C ( FIG. 1 ) of the annular portion of the bit holder block  11  toward the bottom of the bit holder block mounting portion  25  at a constant angle thereto. This additional interference bore portion or segment  43  will provide added retaining force between the bit holder block  11  and the bit holder shank  41  to retain the new shank therein even though the top of the bit holder block bore  18  may be enlarged by repeated pounding and use of the road milling machine (not shown) to an extent no longer permitting use of a shorter shank bit holder  10  ( FIG. 1 ). 
         [0034]    Referring to  FIG. 4 , a modification of the invention shown in  FIG. 3  is utilized at  45  with the bit block  11  shown in  FIG. 3  and provides a bit holder that has its upper body portion  46  identical to that shown in  FIG. 3 . A shank portion  47 , while similar to that of the 2⅝ inch long shank shown in  FIG. 3 , that has a portion of the lower interference section of the shank  47  preferably 180 degree segment of the bit holder shank removed at  48  to provide added access for an extractor tool (not shown) or punch to be utilized when extraction of the bit holder  45 , broken bit shank, or bit is removed from its mounting in the bit holder block bore  18 . 
         [0035]    By positioning the portion of the bit holder shank  47  ( FIG. 4 ) having the slot  14  therein away from the concave tail portion  43  of the bit holder block bore  18 , and by removing the outermost portion of the bit holder shank, the inner portion  47   a  of the bit holder shank is capable of providing increased interference sufficient to maintain the bit holder  45  in the shortened bit block bore  18 . By utilizing the reverse taper at  51 , defined as a taper less than the taper or cylindrical bit block bore, the position of interference force may be located anywhere along the bottom interference portion of the bit holder shank as desired. This allows not only greater use of bit holders, but allows additional longevity for bit holder blocks  11  even after the upper portion of the bit holder block bore  18  has been enlarged by repeated usage. 
         [0036]    Differing Shape Bit Holder Shanks 
         [0037]    Referring to  FIG. 5 , a second embodiment of the bit holder  55  having a shortened shank  56  thereon, constructed in accordance with the present invention, includes a bit holder body  57  substantially identical to that of the first embodiment shown in  FIG. 1  and a shortened bit holder shank  56  about 1½ inches in axial length that has a top larger radial portion  58  and a reduced diameter central portion  60  substantially identical to the first embodiment shown in  FIG. 1 . However, the lower interference portion  61  of the bit holder shank includes a generally bulbous substantially annular section, with the exception of the axial slot  62  which forward end is positioned forward of the interference section as desired to provide sufficient interference between the bit holder block bore and the bit holder shank  61 . 
         [0038]    Referring to  FIG. 6 , a third embodiment  65  of the present invention is shown which is substantially identical to the second embodiment of the invention, with the exception that the lower interference portion  63  of the bit holder shank  64  is created in a flatter bulbous shape which is outwardly extending, although greater axially extending than that shown at  61  in  FIG. 5 . This modification of the bit holder shank  64  would have about equal radial retention force as that of the second embodiment  55  shown in  FIG. 5 . 
         [0039]    Bit/Holders Utilizing Diamond Tips and Shanks in Accordance with the Present Invention. 
         [0040]    Referring to  FIGS. 7 a  and 7 b   , a fourth embodiment  65  and modification  66  of the present invention includes a bit/holder unitary assembly having a bit holder body  67 ,  68 , respectively, in combination with a tungsten carbide base insert diamond coated or combination diamond and cobalt incorporated matrix tip insert  70 ,  71 , respectively, mounted on a tungsten carbide base  72 ,  73 , respectively, that is in turn mounted in the top cylindrical portion of a bit holder body  65 - 66 . The dimensions of the unitary tip, tungsten carbide base, and steel body portions are substantially identical to that utilized with a combination bit and bit holder body previously utilized in the trade (U.S. Pat. No. 8,118,371). The diamond coated insert  70 ,  71  is about 0.565 inch in diameter. This identical height of the bit/holder top portion  67 ,  68  provides use when mounted on a bit block on a road milling machine (not shown. 
         [0041]    In  FIG. 7 a   , the bit/holder unitary structure further includes a reverse taper shortened shank  74  similar to that shown in  FIGS. 1 and 5-6  as mounted in a bit holder block  11  constructed in accordance with the present invention as shown in  FIG. 1 . The shortened bit holder shank  74  of  FIG. 7 a    includes, as in  FIG. 1 ) not only a top increased diameter portion and a central reduced diameter portion, but a lower reverse taper interference portion and a distal reduced diameter generally annular portion as described above with  FIG. 1 . 
         [0042]    As shown most clearly in  FIG. 7 a   , this embodiment provides increased access to the rear of a bit holder block  11  to provide ease of access for extraction of the bit/holder from the bit holder block bore when desired. 
         [0043]      FIG. 7 b    discloses a bit/holder  68  having a top portion substantially identical to that shown at  67  in  FIG. 7 a    with a diamond coated or a diamond tip with a diamond cobalt matrix  71 , a tungsten carbide base  73 , and a top holder body portion  68  together with a quick change slotted shank  75  having an axial length approximating 2⅝ inches that includes a top increased diameter portion, a central reduced diameter portion and a bottom reverse taper portion  76 . The bottom reverse taper portion  76  not only provides interference with the 1½ inch long annular bit holder block bore, but also provides interference with the inner concave tail or continuing taper portion  43  in  FIG. 4  of the bit holder block bore extending onto the back of the block mounting portion. This bit/holder  66  will be utilized when the bit holder block bore has been enlarged sufficiently that a shortened shank on a bit/holder  65  such as shown in  FIG. 7 a    will not be sufficiently retained in the bit holder block bore. 
         [0044]    Referring to  FIG. 8 a   , a fifth embodiment  80  of the bit/holder of the present invention is shown including an enlarged diameter tip  81  having a base greater than ⅝ inch in diameter (shown as ¾ inch in diameter) which is mounted on a vertical extension of the steel body  82  that is surrounded by a tungsten carbide annular ring  83 . The steel body includes an upper generally cylindrical portion and a lower diametrically enlarged base or tire portion  84  of the body that, as shown in the previous embodiment, sits on the top of a bit holder block receiving portion  21 . 
         [0045]    As with the embodiment shown in  FIG. 7 a   , the embodiment shown in  FIG. 8 a    includes a shortened reverse taper slotted shank  85  constructed in accordance with the present invention generally as shown in  FIG. 1  and which may also include shanks such as shown in  FIGS. 5 and 6 . 
         [0046]    Referring to  FIG. 8 b   , a bit/holder  90  constructed in accordance with the present invention includes a top tip  91  and body portion  92  substantially identical to that shown in  FIG. 8 a    with a reverse taper standard length shank  93  about 2⅝ inches in length that may be utilized in connection with the bit holder block  11  of the present invention. When the bore of the bit block is worn sufficiently, it would not retain the shorter shank bit/holder therein. The 2⅝ inch length shank  93  shown in  FIG. 8 b    would, as the previous embodiments have, include an upper enlarged diameter portion, a central decreased diameter portion, and a lower reverse taper portion  94  that provides interference not only with the bottom of the bit holder block bore  18  ( FIG. 1 ) but also with the concave tail  43  ( FIG. 4 ) or segment of the bit holder block bore  43  extending onto the block mounting portion. As with the previous embodiments, as long as the taper of the taper portion of the shank is less than that of the bit holder block bore taper or cylindrical segment, increased interference force may be positioned anywhere along the shank as desired so as to retain the shank  93  in the bit holder block bore. 
         [0047]    While five embodiments have been shown and described, it will be understood by 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.