Bit holders and bit blocks for road milling, mining and trenching equipment

Abstract

Improvements in bits, bit holders and bit blocks used in road resurfacing equipment and mining and trenching equipment provide for improved rotatable bit holders in the bit block, ease of removability of bits from bit holders and for predetermined points of desired failure of any member of the combination if the bit should encounter a hard discontinuity while performing its work.

What is claimed:  
     
         1 . A bit assembly for use in road milling and mining equipment including a bit having a hardened distal end connected to a shank portion and means including a shank receiving bore for mounting said bit on said equipment, an improvement comprising, 
 reduced cross section means on one of said bit and said means for mounting said bit on said equipment for providing a predetermined area of failure for when said bit contacts a hard discontinuity in material it encounters.    
     
     
         2 . The bit assembly as defined in  claim 1  wherein said means for mounting said bit on said equipment include, 
 a combination bit holder/bit block including a base having a bottom mounting surface and a bit mounting portion extending therefrom including a shank receiving bore therethrough, and  
 said reduced cross section means include a slot positioned partially through at least one of said base and said bit mounting portion.  
 
     
     
         3 . The bit assembly as defined in  claim 1  wherein said means for mounting said bit on said equipment include, 
 a generally annular bit holder including a bit mounting portion, a shank portion, and a threaded distal end, said annular bit holder having a bore axially therethrough for insertion of a bit therein,  
 a reduced diameter portion of said annular bit holder positioned between said shank portion and said threaded distal end.  
 
     
     
         4 . The bit assembly as defined in  claim 3  wherein said reduced cross section means include, 
 an increased diameter portion of said bore extending axially through said bit holder.  
 
     
     
         5 . The bit assembly as defined in  claim 1  wherein said means for mounting said bit on said equipment include, 
 a generally annular bit holder including a bit mounting portion, a shank portion, and a threaded distal end, said annular bit holder having a bore axially therethrough for insertion of a bit therein,  
 and said reduced cross section means include, 
 a plurality of notch means positioned in spaced orientation around an outside of said bit mounting portion in communication with a top surface thereof also for providing access to an underside of a bit flange on said bit mountable on said bit mounting portion.  
 
 
     
     
         6 . The bit assembly as defined in  claim 1  wherein said bit includes a hardened leading nose portion, a tapered middle portion subjacent said nose portion, an enlarged radial flange subjacent said middle portion and a shank subjacent said radial flange, and 
 said reduced cross section means include 
 a reduced diameter portion of said bit positioned mediate said tapered middle portion and said radial flange.  
 
 
     
     
         7 . A bit holder for retaining a bit therein as a part of a bit assembly, said bit holder comprising, 
 a generally frustoconical bit mounting portion including a top surface, a mediate portion tapering outwardly from said top surface and a radial flange defining the bottom thereof, a shank portion extending axially from said radial flange terminating in a fastening portion adjacent a distal end of said shank portion, an axial bore in communication with and extending inwardly from said top surface adapted for mounting said bit therein, and    discontinuity means extending radially inwardly from an outer surface of said mediate portion in communication with said top surface for providing access to an underside of any bit mounted on said bit holder and resting on said top surface thereof to aid in any removal of a bit from said bit holder.    
     
     
         8 . The bit holder as defined in  claim 7  wherein said discontinuity means include 
 a plurality of vertical notches positioned in even spatial relation around said mediate portion of said bit mounting portion.  
 
     
     
         9 . The bit holder as defined in  claim 7  wherein said bit holder is rotatable on any bit block on which it is mounted, and further including 
 tool means for adjusting a radial orientation of said bit holder on said bit block.  
 
     
     
         10 . The bit holder as defined in  claim 9  wherein said tool means include 
 a socket member including a cylindrical outer wall, a hollow generally cylindrical inner wall, and an end wall across one end of said socket member having a wrench receiving hole therethrough, said hollow generally cylindrical inner wall including  
 detent means extending radially inwardly therefrom for providing complementary mating engagement with said indent means.  
 
     
     
         11 . The bit holder as defined in  claim 7  wherein said bit holder is rotatable on any bit block on which it is mounted and is securable on said bit block in a plurality of rotational positions thereon.  
     
     
         12 . In a bit assembly for use in road milling and mining equipment, 
 said bit assembly including 
 a generally annular bit holder including a bore therethrough and a bit shank receiving portion including a top surface, a tapered portion subjacent said top surface, and a radially extending flange portion subjacent said tapered portion, a shank portion subjacent said radially extending flange portion, and a threaded portion defining an opposing end thereof,  
 a bit block having a body including a base for mounting said block on an external member, and a holder mounting portion including a flat top surface having a holder receiving bore extending inwardly from said top surface through said holder mounting portion and a bottom of said holder mounting portion including a recess means thereon in communication with said holder receiving bore, and  
 a threaded fastener,  
 an improvement comprising  
 said threaded fastener being mountable on said recess in a non-rotatable manner and engageable with said threaded portion of said bit holder, said bit shank receiving portion including discontinuity means on said outer surface thereof for enabling an external member to rotate said bit holder on said holder mounting portion to thread said threaded portion thereof on said threaded fastener.  
   
     
     
         13 . The bit assembly as defined in  claim 12  wherein said discontinuity means include 
 a plurality of indents on said radially extending flange positioned in spaced relation at least partially therearound.  
 
     
     
         14 . The bit assembly as defined in  claim 12  wherein said discontinuity means include, 
 a plurality of indents on said tapered portion of said bit holder shank receiving portion positioned in spaced relation at least partially therearound and being in communication with said top surface thereof.  
 
     
     
         15 . The bit assembly as defined in  claim 12  wherein the mounted rotational orientation of said bit holder on said bit block includes a plurality of substantially discrete positions equal to the number of external faces on said threaded fastener.  
     
     
         16 . The bit assembly as defined in  claim 12  wherein the mounted rotational orientation of said bit holder on said bit block includes a plurality of substantially equally spaced positions whose arcuate separation is equal to 360 degrees divided by the number of external faces on said threaded fastener.  
     
     
         17 . The bit assembly as defined in  claim 12  wherein 
 a depth of said recess is less than the thickness of said threaded fastener, and  
 said threaded fastener being demountable from said recess while still being retained on said threaded portion of said bit holder for changing the arcuate orientation of said fastener on said recess.  
 
     
     
         18 . The bit assembly as defined in  claim 12  wherein forces resisting rotation of said bit holder on said bit block include 
 the friction between contacting areas on a bottom of said bit holder radial flange and said top surface of said bit block, roughen the mating surfaces providing improved drag against loosening rotation between the two,  
 the friction between contacting areas on a bottom of said bit block and a top surface on said threaded fastener,  
 tensile forces tending to stretch said shank of said bit holder, and  
 friction between contacting surfaces of said threaded end on said bit holder and said threads on said threaded fastener.  
 
     
     
         19 . The bit assembly as defined in  claim 12  wherein forces resisting rotation of said bit holder on said bit block include 
 the friction between contacting areas on a bottom of said bit holder radial flange and said top surface of said bit block, roughen the mating surfaces providing improved drag against loosening rotation between the two.