A rotary drill bit for boring a hole through a solid body is disclosed. The drill bit comprises a collar and a penetrating member. At a proximal end, the collar is attachable to a drill shaft. At a distal end, the collar is attachable to the penetrating member. The penetrating member has a connecting end for attachment to the collar and a cutting end for engaging the solid body. A pilot drill is fixedly attached to the cutting end for initiating contact with the solid body.

RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part application of U.S. application Ser. No. 09/601,560 for “Method and Apparatus for Drilling Through a Solid Material” filed Aug. 8, 2000 which was a United States national phase filing from PCT/US99/02202 filed on Feb. 2, 1999 which was a continuation-in-part application of U.S. application Ser. No. 09/018,244 (now U.S. Pat. No. 6,161,633) filed on Feb. 3, 1998. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to a method and apparatus for boring through a solid body. More particularly, the invention relates to an improved rotary drill bit for boring holes with increased efficiency through difficult to penetrate materials.  
         BACKGROUND ART  
         [0003]    There are different drill bits for drilling through a variety of solid materials. Many of these drill bits are designed for particular applications. For instance, drill bits have been designed to drill through wood, metal, and concrete. In order to drill through these different materials, designers have varied the material used to produce the drill bits, the shape of the drill bits, and the speed with which the drill bit is operated.  
           [0004]    One problem existing with many drill bits is the rate at which they will drill a hole is too slow. When the material to be drilled is difficult to penetrate, the process of boring a hole may take as long as several minutes. It is often important to maximize the efficiency at which a hole can be bored into a given material in order to improve manufacturing productivity. Such is the case in drilling tap holes in metal purifying blast furnaces.  
           [0005]    The first step in producing steel sheet which is used in the building and construction industry, the automotive industry, the appliance industry, the electric motor industry, etc., is to produce relatively pure iron from iron ore. This process is carried out within a blast furnace. In order to maximize the productivity of a steelmaking facility, as much pure iron as possible must be produced. Many resources are expended in developing methods and procedures to increase the amount of pure iron which can be produced annually.  
           [0006]    In developing these methods and procedures, every manufacturing variable in the blast furnace process is optimized. One of these variables is the rate at which the blast furnace can be tapped to drain molten iron from the furnace. A typical blast furnace is tapped from seven to twelve times per day seven days per week. The typical blast furnace tap hole takes several minutes to drill. In fact, some tap holes take as long as 15 minutes to drill.  
           [0007]    The rate at which the tap hole is drilled is adversely affected by drill bit “walking.” Walking occurs as the drill bit first meets the material to be drilled, it slides or skids laterally rather than boring into the material. Therefore, drill bit walking prevents the drill operator from initiating the drilling process.  
           [0008]    The drilling process is also slowed by drill bit binding. Binding occurs when loosened debris created in the drilling process builds within the hole. The debris accumulates around the drill bit and freezes the drill bit within the hole preventing the drill bit from rotating within the hole.  
           [0009]    In order to solve some of these problems, certain drill bits have been designed which have air passages. Pressurized air is forced through the passages toward the drill bit/solid body interface to blow the debris away from the drill bit and prevent binding. However, when the hole to be drilled has a substantial length, as is the case with a blast furnace tap hole, the debris continues to build because it cannot escape the hole.  
           [0010]    The present invention is provided to solve these and other problems.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention is directed to a drill shaft connectable to a drilling apparatus at one end a drill bit at an opposing end for boring a hole through solid materials. The drill shaft of the present invention has interchangeable parts and increases the rate at which a hole can be drilled.  
           [0012]    One object of the present invention is to provide a sectional shaft. The shaft includes a drill shaft and an extension shaft. The drill shaft may include an outer sleeve fixedly attached to an end of the shaft. At an opposite end of the shaft, the sleeve is not fixedly attached. The shaft passes through the interior of the sleeve. The sleeve is spaced a distance from the shaft so that the shaft is approximately centered within the sleeve. As pressurized air is introduced through the passage, it passes through the interior of the shaft until the air reaches an outlet between the fixed and free ends of the sleeve. The air then travels down along the shaft through the space between the shaft and the sleeve. The air is then expelled from the space at the free end of the sleeve to blow off debris.  
           [0013]    The extension shaft joins the drill shaft with a drilling apparatus. The extension shaft includes a base unit of a heavy wall rod. The base unit includes a first end threaded for connection to the drilling apparatus and a second end threaded for connection to the drill shaft. Anti-lock nuts are located at the first and second ends. The anti-lock nuts prevent the shaft connections from seizing that results from the torque of the drilling apparatus. The anti-lock nuts also protect the threads on the shafts when molten iron emerges from a blast furnace tap hole. A block maintains the integrity of the threaded connections.  
           [0014]    Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and detailed description of the invention. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    [0015]FIG. 1 is a cross-sectional view of a drill bit of the present invention connected to a drill shaft;  
         [0016]    [0016]FIG. 2 is an exploded view of the cross-sectional view of FIG. 1;  
         [0017]    [0017]FIG. 3 is a view taken along  2 - 2  of FIG. 1;  
         [0018]    [0018]FIG. 4 is a cross-sectional view of a drill bit of the present invention;  
         [0019]    [0019]FIG. 5 is a view taken along  3 - 3  of FIG. 4;  
         [0020]    [0020]FIG. 6 is a view taken along  4 - 4  of FIG. 4;  
         [0021]    [0021]FIG. 7 is a cross-sectional view of an embodiment of the present invention; and  
         [0022]    [0022]FIG. 8 is a cross-sectional view of a sectional shaft of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0023]    While the invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.  
         [0024]    Referring to FIG. 1, a drill bit  10  for boring a hole through a solid body is illustrated. The drill bit  10  of FIG. 1 is shown joined to a shaft  12 . The drill bit  10  comprises a collar  16  removably attached to a penetrating member  20 . This feature allows the collar  16  or the penetrating member  20  to be switched out depending upon the wear to that part or the type of material to be drilled.  
         [0025]    The collar  16  is generally produced from a rigid metallic material. The collar  16  has a cylindrical side wall  24  centered about a longitudinal axis  28 , a proximal end  32  and a distal end  36 . Alternatively, the collar  16  can be produced with a triangular, square, rectangular, pentagonal, hexagonal, octagonal, or other similarly shaped side wall. The side wall  24  has an inner surface  40  and an outer surface  44 . The inner surface  40  defines a chamber  48  for receiving the shaft  12  at the proximal end  32  of the collar  16 . The inner surface  40  is furnished with a first set of reverse threads  52 . The reverse threads  52  are oriented so that a counterclockwise torque fastens and tightens the collar  16  to a corresponding threaded portion  56  of the shaft  12 .  
         [0026]    The penetrating member  20  comprises a cutting end  60  and a connecting end  64 . The connecting end  64  has opposing planar side walls  68  joined by opposing arcuate side walls  72 . The arcuate side walls  72  are furnished with threaded portions  76 . These threaded portions  76  also have a reverse orientation so that the connecting end  64  can be joined to the distal end  36  of the collar  16 .  
         [0027]    Each arcuate side wall  72  has a length which is less than the length of the planar side walls  68 . FIG. 3 shows that this arrangement lends the penetrating member  20  a narrow profile  80 . When the penetrating member  20  is inserted into and threadably attached to the collar  16  there are air gaps  84  on either side of the penetrating member  20 . The purpose of the air gaps  84  will become clear on further description.  
         [0028]    The cutting end  60  is designed to bore through the solid body and is generally suitable for drilling through tough materials such as concrete and/or steel. The cutting end  60  comprises identical first and second spades  88  radiating from a center point  92 . A pilot drill  96  is positioned at the center point  92 .  
         [0029]    The pilot drill  96  is a conical portion centered about the longitudinal axis  28 . The pilot drill  96  blends into the remaining portions of the penetrating member  20  forming a smooth transition region  100 . The pilot drill  96  is the first portion of the drill bit  10  to contact the solid material which is to be drilled. This pilot drill  96  penetrates the body forming an initial pilot hole and aids in guiding the drill bit  10  through the body. In other words, the pilot drill  96  acts as an anti-walk mechanism because as the pilot drill  96  enters the solid body and forms the pilot hole the remaining portions of the drill bit  10  cannot drift out of position. The anti-walk mechanism increases the rate at which a hole can be drilled because less time is wasted aligning the drill bit with the targeted drill area.  
         [0030]    The spades  88  have a pentagonal cross-section. Each spade  88  has a base wall  104 , a pair of side walls  108 , and a pair of angled walls  112 . A portion of each base wall  104  is integrally connected to the connecting end  64  of the penetrating member  20 . The pair of opposing side walls  108  extend perpendicularly from the base wall  104 . A portion of each side wall  108  is integrally connected and coplanar with the planar side wall of the connecting end  64  so that the penetrating member  20  maintains its narrow profile  80  at the cutting end  60 . At an opposite side of the base wall  104 , the angled walls  112  extend from each cutting end  60  side wall  108 . The angled walls  112  form a beveled cutting surface  114  and extend upwardly and inwardly until the angled walls  112  meet forming a cutting edge  116 . Thus, the cutting edge  116  is formed by the union of the pair of angled walls  112 . Thus, each spade  88  has a cutting edge  116 .  
         [0031]    The cutting edges  116  are those portions of the penetrating member  20  that perform the bulk of the drilling. The size of the hole to be bored corresponds roughly to the total length of the cutting edges  116  plus a diameter  120  of the pilot drill  96 . Each cutting edge  116  extends outwardly from the center point  92  and tapers downwardly toward the base wall  104 . The downwardly tapering cutting edges  116  cooperate with the pilot drill  96  to facilitate movement of the solid material and to prevent the drill bit from walking or shifting along the solid material's surface as the hole is being bored.  
         [0032]    The drill bit  10  of the present invention can be employed in conjunction with a solid shaft  12  without having binding occur. Having the cutting edges  116  extend beyond the outer surface  44  of the collar  16  allows debris to be removed from the hole without the use of pressurized air. Therefore, when drilling through a known carcinogenic material, blowing is not needed to avoid drill bit  10  binding. However, the shaft  12  can include a conventional passage  121  to permit pressurized air to be forced through the air gaps  84 .  
         [0033]    In an alternative embodiment shown in FIGS. 4 through 6, pressurized air is forced through a passage  122  which extends partially down the axial length of the shaft  12 . The pressurized air is used to blow off loosened debris of the solid body created during the drilling process that, if allowed to build up, could bind the drill bit  10  as the hole is being drilled. Drill bit binding causes delays in the drilling process. Thus, by blowing off the debris and avoiding drill bit binding, the rate at which a hole can be drilled is increased. The pressurized air also acts to cool the drill bit and shaft and further prevents the drill bit and shaft from annealing.  
         [0034]    In this embodiment, an outer sleeve  124  is fixedly attached to an end of the shaft  12 . At an opposite end of the shaft  12 , the sleeve  124  is not fixedly attached. The shaft  12  passes through the interior of the sleeve  124 . The sleeve  124  is spaced a distance from the shaft  12  so that the shaft  12  is approximately centered within the sleeve  124 . As pressurized air is introduced through the passage  122 , it passes through the interior of the shaft  12  until the air reaches an outlet  126  between the fixed and free ends of the sleeve  124 . The air then travels down along the shaft  12  through the space between the shaft  12  and the sleeve. The air is then expelled from the space at the free end of the sleeve  12  to blow off debris. This arrangement prevents drill bit binding, and the pressurized air also cools the drill bit as it is boring the hole. This arrangement also reduces the amount of debris that goes airborne during blow off.  
         [0035]    The cutting edges  116  extend radially beyond the outer surface  44  of the collar  16 . Thus, the circumference of the hole being drilled is greater than the circumference of the collar  16 . This structure cooperates with the air gaps  84  on either side of the penetrating member  20  and the pressurized air passed through the passage in the shaft  12  to aid in preventing the drill bit  10  from binding up within the hole. As the pressurized air is forced through the passage and the outlet and along the shaft  12 , it is forced out of the free end of the sleeve  124  and blows the debris away as the hole is being drilled. The loosened debris is expelled from the drilling area along the outer surface  44  of the collar  16 . The air gaps  84  help circulate the air within the hole being bored.  
         [0036]    [0036]FIG. 7 illustrates yet another embodiment. In the embodiment illustrated in FIG. 7, the drill shaft  12  is sectioned into a distal end  130  having a fluid pressure port  131 , a solid intermediate section  132 , and a proximal end  134  having a fluid pressure vent  136 . A partial sleeve  138  surrounds the intermediate section  132  and portions of the distal end  130  and proximal end  134 . A disparity in the diameters of the sleeve  138  and the shaft  12  allow the fluid pressure to travel in through the port  131 , down the solid intermediate section  132 , and out the vent at the distal end  130 .  
         [0037]    [0037]FIG. 8 illustrates yet another embodiment of the present invention. In this embodiment, an extension shaft  150  joins the drill shaft  12  with a drilling apparatus (not shown). The extension shaft  150  can be provided or used in combination with any of the previously described drill shafts and is generally of a larger diameter than the shaft  12 . Accordingly, the extension shaft  150  includes a base unit  154  of a heavy wall rod. The base unit  150  may include a central opening or passage  155  for delivering a fluid pressure to the passage of the shaft  12 . The base unit  154  includes a first end  156  threaded, typically rope threaded, for connection to the drilling apparatus and a second end  160  having a receiver housing threaded, typically rope threaded, for connection to the drill shaft  12 . In use, anti-lock nuts  164 ,  166  are located at the first and second ends  156 ,  160 . The anti-lock nuts  164 ,  166  are produced from a hex-shaped rod stock, and threaded, typically rope threaded, for connection to the drill shaft  12  and the extension shaft  150 .  
         [0038]    The anti-lock nut  164  located at the first end  156  is generally tack welded to the first end  156 . The anti-lock nut  166  located at the second end  160  is typically tack welded to the drill shaft  12 . Each of the anti-lock nuts  164 ,  166  include weld dimples  168  located on their respective bearing surfaces to prohibit wear. When the drill shaft  12  and the extension shaft  150  are joined, the anti-lock nut  166  is generally in engagement with the extension shaft  150 . The anti-lock nuts  164 ,  166  act as bearing members to prevent the shaft connections from seizing that results from the torque of the drilling apparatus by providing a bearing surface. The welded dimples  168  also help to prevent seizing of the parts. The anti-lock nuts  164 ,  166  also protect the threads on the shafts  12 ,  150  when molten iron emerges from a blast furnace tap hole. A block maintains the integrity of the threaded connections.  
         [0039]    While specific embodiments have been illustrated and described, numerous modifications are possible without departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying claims.