Abstract:
A wear-resistant cutting bit for use on a mining or excavating cutting tool is disclosed. The cutting bit utilizes a hardened insert having a narrow base attached to the remainder of the cutting bit. An extended collar of the hardened insert projects from the cutting bit and ends with a generally conical section. The extended collar and narrow base of the hardened insert enable the cutting bits of the present invention to be more wear-resistant and cost-effective than other cutting bits used on mining and excavating equipment.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to mining and excavating tools and, more particularly, is concerned with a cutting bit designed for erosion resistance. 
       BACKGROUND INFORMATION 
       [0002]    Mining and excavating tools often employ drums and the like on which are mounted many cutting bits. Each cutting bit typically has a hard wear-resistant tip made of a material such as tungsten carbide attached to a generally conical steel head of the bit. A problem with such designs is that the softer steel head material erodes during cutting operations. This is commonly referred to as “steel wash”. 
         [0003]    Wear-resistant cutting bits have been developed in order to increase erosion resistance. U.S. Pat. No. 4,725,098 to Beach discloses the deposition of a hard-facing material about the steel nose of a cutting bit. U.S. Pat. No. 5,417,475 to Graham et al. discloses the installation of a ring of hard material on the front surface of a steel nose of a cutting bit. U.S. Pat. No. 6,709,065 to Peay et al. discloses the use of a ledge of hard material mounted near the steel nose of a cutting bit. Published U.S. Application No. 2005/0035649 to Mercier et al. discloses the installation of hard wear rings on a stepped shoulder of a cutting bit. 
         [0004]    Despite these known designs, a need still exists for cutting bits which exhibit improved wear resistance thereby extending the life of the bit and reducing operating costs. 
         [0005]    The present invention has been developed in view of the foregoing. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a wear-resistant cutting bit for use on a mining or excavating cutting tool. The cutting bit utilizes a hardened insert having a narrow base attached to the remainder of the cutting bit. An extended collar of the hardened insert projects from the cutting bit and ends with a generally conical section. The extended collar and narrow base of the hardened insert enable the cutting bits of the present invention to be more wear-resistant and cost-effective than other cutting bits used on mining and excavating equipment. 
         [0007]    An aspect of the present invention provides an insert for a cutting bit comprising a forward most generally conical portion, an extended collar adjacent and rearward of the generally conical portion, the extended collar portion having a diameter and an axial length, a tapered transition segment and a reduced diameter base. 
         [0008]    Another aspect of the present invention provides a cutting bit comprising a forward portion and a shank oriented about a longitudinal axis, the forward portion having a socket, a hardened insert affixed to the socket of the forward portion, the hardened insert comprising a generally conical portion adjacent an extended collar adjacent and transition segment adjacent a reduced diameter base, wherein the reduced diameter base and transition section fit into the socket of the forward portion. 
         [0009]    These and other aspects will become more apparent from the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an exploded, oblique view of a cutting bit and bit holder comprising a base block and sleeve according to one embodiment of the present invention. 
           [0011]      FIG. 2  is a side view of a cutting bit with a section of the nose cut away around the hardened tip. 
           [0012]      FIG. 3  is a side view of a hardened tip according to one embodiment of the present invention. 
           [0013]      FIG. 4  is a side view of a cutting bit with a hardened ring about the forward portion according to one embodiment of the present invention. 
           [0014]      FIG. 5  is a side view of a cutting bit with a hardened ring about the forward portion according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to  FIG. 1 , a cutting assembly  1  is shown. The cutting assembly  1  includes a base block  10  which mounts onto a rotating drum or other piece of equipment. A sleeve  20  fits inside an opening  12  in the base block  10 . Cutting bit  30  inserts into a bore  22  of the sleeve  20 . Sleeve  20  and cutting bit  30  may be secured to the opening  12  and bore  22  through appropriate means known to those skilled in the art, for example, by press fitting, by using a retainer ring or other fastening means. 
         [0016]    Referring now to  FIG. 2 , a more detailed side view of the cutting bit  30  according to one embodiment of the present invention is shown. Cutting bit  30  may have a shank  40  and forward portion  50  separated by a flared collar  60 . The cutting bit  30  may be situated about a longitudinal axis  2 . The cutting bit  30  has an axially forward end  70  and an axially rearward  80  in relation to the longitudinal axis  2 . At the axially forward end  70  of the cutting bit  30  is a hardened insert  100  located into a socket  90  in the forward portion  50  of the cutting bit  30 . 
         [0017]    Hardened insert  100  may be any number of wear materials, including tungsten carbide, titanium carbide and tantalum carbide, aluminum oxide, titanium nitride, cobalt, cubic boron nitride, polycrystalline diamond, and may include other ceramics, and alloys and cermets of these materials. Hardened insert  100  is typically made of cemented tungsten carbide and is brazed into the socket  90  or attached by any other method known to those skilled in the art. 
         [0018]    In the embodiment shown in  FIG. 2 , the shank  40  of the cutting bit  30  has a retainer  42  near the axially rearward end  80 . This retainer  42  provides a seating surface for press fitting the cutting bit  30  into the sleeve  20 . 
         [0019]    Referring now to  FIG. 3 , the hardened insert  100  will now be described in more detail. At the axially forward end  70  the hardened insert  100  has generally conical portion  110  ending at a cutting tip  120 . As used herein the phrase “generally conical” desribes a portion of the cutting tip being shaped like a cone and includes frustoconical and pyramidal shapes. Rearward of the generally conical section  110  is an extended collar  130 . Rearward of the extended collar  130  is an inwardly tapering transition segment  140 . Rearward of the transition segment  140  is a reduced diameter base  150 . The reduced diameter base  150  may be any suitable shape, for example cylindrical and/or conical. As used herein, phrase “reduced diameter” describes a diameter of the base of the hardened insert being of lesser diameter than the diameter of the extended collar of the hardened insert. The reduced diameter base  150  may be about 85% to about 35%, for example about 70% of the diameter of the extended collar  130 . The extended collar  130  may have an extended collar diameter  132  of about 15 mm to about 35 mm, for example about 25 mm. Although, the embodiment in  FIG. 3 , shows a reduced diameter base having a uniform diameter, non-uniform shapes of varying diameter are also contemplated. 
         [0020]    The reduced diameter base  150  enables the forward portion  50  to withstand a significant amount of wear before resulting in cutting bit failure. Forward portion  50  and shank portion are typically made of carbon steel. Still referring to  FIG. 3 , a wear area  52  is illustrated by the phantom line  53 . This is a high wear area  52  in cutting bits. The relatively soft carbon steel of the forward end abrades much faster than the hardened insert  100 . Due to the reduced diameter of the base  150 , the wider extended collar  130  and conical section  110  protect the base  150  and the steel of the forward portion  50  adjacent to the base  150  from much abrasion. This maintains the integrity of the steel and brazing securing the hardened insert for a much longer time than would be achievable with an insert of uniform diameter. 
         [0021]    Hardened inserts  100  typically wear along the generally conical portion  110  at an angle of 90° to 120°, for example 110°. The wear angle, denoted 0, is illustrated in  FIG. 3 . As described above, the hardened insert  100  has an extended collar  130  designed to extend useful life of the cutting bit  30 . The extended collar  130  may be generally cylindrical and has an axial length  134  illustrated in  FIG. 3 . The axial length  134  may be about 5 mm to about 35 mm, for example about 10 mm. As a consequence, the hardened insert  100  is able to wear from the cutting tip  120  position shown in  FIG. 3  through to position A. In most instances, the reduced diameter base  150  allows wear of the cutting bit  30  even beyond position A before the cutting bit  150  ultimately fails. 
         [0022]    In one embodiment of the present invention shown in  FIG. 4 , the cutting bit  200  has a hardened exterior surface placed about the nose  252  of the forward portion  250 . In this embodiment, the hardened exterior surface is a sheath  220  made from cemented tungsten carbide. The nose  252  may be slightly recessed about the periphery of the forward portion  250  to accommodate the sheath  220  or the sheath  220  may be fit over an unrecessed periphery of the nose  252 . The sheath  220  may be affixed to the forward portion  250  by brazing or other known method. 
         [0023]    Another embodiment incorporating a hardened exterior surface about the nose  352  of the forward portion of the cutting bit  300  is shown in  FIG. 5 . In this embodiment, the nose  352  of the forward portion  350  has a wear-resistant exterior comprising a hardfacing weld  354 . In the embodiments shown in  FIGS. 4-5  the exterior of the nose  252 ,  352  has been hardened to at least a hardness 50 RWc. In other embodiments, the forward portion may be made from a hardened or alloy steel to provide wear-resistance. 
         [0024]    In addition to exceptional life, the cutting bits of the present invention have shown an ability to reduce sparking during mining operations. At times, the atmosphere in underground mines can become combustible. It is therefore desirable to reduce ignition sources, such as sparks, in mining equipment. 
         [0025]    Test results demonstrating the performance of the cutting bits according to one embodiment of the present invention have shown a 3:1 improvement in wear. Tests of the cutting bits of the present invention were performed on a single continuous mining machine having two drums. One drum was equipped with standard cutting bits while the second drum was equipped with cutting bits of the present invention. The test setup ensured the standard cutting bits and the cutting bits of the present invention where used under identical conditions, e.g. the material cut, time in operation and rate of cutting. The cutting bits were run until failure. The standard cutting bits lasted for one 8-hour shift while the cutting bits of present invention cut for three 8-hour shifts. 
         [0026]    Some improvement in the life of the bits was expected due to a slight increase in the amount of material used in the inserts of the present invention compared to standard cutting bits. However, a 3:1 increase in cutting bit life exceeded expectation considering a less than 2:1 increase in hardened material was added to the cutting bits. 
         [0027]    Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.