Flighting section and tooth holder
The present invention is directed generally to rotary driven cylindrical cutters and scarifiers for use in earth-working, mining, or other in situ disintegration of hard materials. The invention is particularly directed to such rotary driven cylindrical cutters and scarifiers as incorporate means for feeding or excavating the material cut or mined away from its initial location generally to a second material-carrying means. 
     The invention has particular utility in connection with roadway resurfacing machines which include rotary driven cylindrical cutters and appropriate conveying apparatus entirely supported on a mobile ground-engaging vehicular platform. Examples of the prior art are to be found in Hargrave U.S. Pat. No. 2,197,549; Jakob et al U.S. Pat. No. 4,139,318; Ratcliff, Jr. U.S. Pat. No. 4,311,284; and Swisher, Jr. et al U.S. Pat. No. 4,325,580. 
     In general, the roadway mining or planing equipment disclosed in the prior art includes a rotary driven cylindrical comminuting drum which acts to scarify and to mine the top portion of an asphaltic road surface in situ. The rotary driven drum includes flighting on the drum which acts to collect the mined material toward the center of the drum where it can be removed. Often the mined material is then remixed with additional bituminous material and thereafter redeposited as a newly formed smooth asphaltic surface. 
     In some prior art devices of this type, the flighting is itself formed from a plurality of cutting bit support members which are connected to the curved surface of the cutting drum by bolts which pass from the upper surface of the flighting downward into the drum to engage threaded openings in the drum. Alternatively, the bolts may pass through the surface of the drum to engage lock washers and threaded nuts on the interior of the drum. A plurality of the cutting bit supporting members are arranged end-to-end so as to form a substantially continuous helical flighting, the top surface of which is elevated above the curved surface of the drum. The top surface includes angled openings into which conventional cutting bits are received. 
     In use, the abrasive forces, which often include rather high value sudden shocks, are transmitted from the cutting bits into the supporting members and the bolts securing the supporting members to the smooth drum surface. The forces occasionally become large enough to shear the securing bolts, causing the machine to be stopped often for considerable lengths of time. The repair and replacement of the cutting bit supporting member damaged in this manner typically necessitates the use of an easy-out or similar removing tool in the field to remove the portions of the sheared bolts remaining in the drum. This is a time-consuming repair job which results in considerable expense to the road-mining machine operator. 
     In an attempt to avoid the problems presented by the bolt-secured supporting members, other roadway planing devices include a continuous flighting welded in place in helical fashion on the surface of the drum. A plurality of individual cutting bit support blocks are welded to the upper edge of the flighting. The support block includes a recess for receiving a cutting bit of chisel cutter preferably having a tungsten carbide tip or the like. 
     In use, the cutting bits vibrate and otherwise move within the support block recess. Particularly in the presence of abrasive dust from the roadway mining operation, the vibration and movement of the cutting bits act to enlarge the recesses to such an extent that the cutting bit is no longer retained. It then becomes necessary to remove the old support block, usually with the aid of a cutting torch, and to weld a new support block in its place. Again, this repair job is difficult to do in the field and still achieve accurate alignment of the support block on the flighting section. Misalignment of the support block results in undesirable lateral forces on a new cutting bit which in turn results in very fast wear and ultimate failure of the replaced parts. 
     The present invention is intended to avoid many of the difficulties of the prior art by constructing the drum-mounted flighting and tool holders to have particularly advantageous features. The flighting consists of a plurality of helical flighting sections, typically 90° arcs, which are fixed by welding them to the cutting drum. Each flighting section includes a plurality of recesses in one side of the flighting. A plurality of tool holders are removably mounted within the flighting section recesses. Each tool holder includes a bore which receives a typically tungsten carbide-tipped cutting bit. Each helical flighting section has a first wall which contains the recesses for receiving the tool holders and a second opposing wall which does not have the recesses. Both walls are generally perpendicular to the cutting drum so as to define the intended flighting for feeding the excavated material from its initially mined location to a central point where it can be removed by appropriate conveying apparatus. Each of the tool holders generally projects outward beyond the surface of the first wall containing the recesses, and in this manner presents wear points or wear surfaces to be acted upon by the abrasive mine asphaltic road material. Thus, the sideways projecting portions of the tool holders act to protect the flighting section itself so as to extend the life thereof. 
     In use, the cutting bits will vibrate or otherwise move with respect to the tool holders just as in the prior art which will ultimately result in loss of retention of the cutting bit and necessitate replacement of the tool holder. This replacement is easily achieved by the removal of the threaded fasteners holding the tool holder in the recess in the flighting. 
     The replacement of the worn cutting tool holder is simplified in that a recess is provided directly in the flighting to accept a cutting tool holder, thereby assuring its proper positioning and alignment. This also acts to increase the usable life of the cutting bits themselves since proper alignment between the cutting bit and drum is assured. 
    
    
     Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived. The detailed description particularly refers to the accompanying figures in which: 
     FIG. 1 shows a front plan view of a rotary driven cylindrical cutter according to the present invention; 
     FIG. 2 is a sectional view of the cutter shown in FIG. 1, taken along lines 2--2; 
     FIG. 3 is a sectional view of a portion of the rotary cutter shown in FIG. 2, taken along line 3--3; and 
     FIG. 4 is a plan view of the cutter as viewed from the top of FIG. 3. 
    
    
     A rotary driven cylindrical cutter 10 in accordance with the present invention includes a cylinder 12 supported generally at both ends by an appropriate support means 14 and 16 and driven for rotation by a motor not shown through stub shafts 18. Flighting 20, which generally comprises arcuate flighting portions 22, are welded by welds 23 to the outer surface 13 of drum 12 for continuous movement therewith. The rotation of the drum 12 is such that, as shown in FIG. 1, the lower portion of the drum moves out of the plane of the paper and upward toward the top of the drum. It will be seen that with this motion taking place, the flighting 20 acts to drive material contacted by the flighting toward the lateral center 24 of the drum. 
     The rotation of the drum 12 is seen in FIG. 2 to be in the clockwise direction R about axis X while the overall apparatus proceeds in the direction given by arrow A. A plurality of tool holders 26 are removably mounted to the flighting sections 22, and each tool holder includes at its radial outward extremity a cutting tool 28, typically carbide-tipped, which is directed forward in the direction of rotation of the drum. The cutting tools 28 are caused to contact the road surface 30 and, in a known manner, mine a controlled portion of the road surface and thereby leave the surface substantially plane but with a slightly roughened surface texture so as to ensure superior bonding to any subsequently applied new surfacing materials. 
     The flighting 20 has two surfaces 30 and 32 generally perpendicular to the surface 13 of drum 12. The first perpendicular surface 30 is seen to face generally toward the lateral center 24 of drum 42, while surface 32 is seen to face toward end shafts 18 of drum 20. A plurality of recesses 34 are provided on inside surface 30. Each recess 34 is defined by a forward wall 35 and rearward wall 37, both of which are preferably arranged parallel to the axis X of rotation of drum 12. A tool holder 26 is received snugly within recess 34 such that an edge 36 of the tool holder 26 projects beyond the plane of inside surface 30. The tool holder 26 is secured in position by means of screw-threaded fasteners 38 passing through the flighting section 22 from depresesions 37 on the outside surface 32 to engage threads 39 within the tool holder 26. The depressions 37 act to protect the head 41 of the fasteners 38 from damaging contact with the mined material. 
     The tool holder itself includes inclined recess 40 for receiving the butt end of replaceable cutting tool 28 in the conventional manner. The cutting tool 28 is aligned by the recess in the tool holder 26 so as to be forwardly directed on the bottom portion of drum 12 as shown in FIG. 2. 
     Although the invention has been described in detail with reference to preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and as claimed in the following claims.