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BACKGROUND 
       [0001]    This invention relates generally to drilling devices and, more particularly, to an expandable diameter drill bit having a torsion spring for biasing one or more blades outwardly such that a hole being drilled is enlarged. 
         [0002]    Rotary drilling devices are used to bore a generally cylindrical hole into the ground to a depth at which a fluid may be extracted, such as water, oil, natural gas, or the like. Sometimes an existing well needs to be re-drilled, cleaned out, or the diameter expanded. A rotary drill may include one or more blades that scrape or dig into the ground surface as the drill rotates. The blades often wear out, break, or otherwise fail and must be replaced, especially when operated at high speed. Another problem with drilling devices is that a drill bit having one diameter may be used and then replaced with a drill bit having a larger diameter in order to increase the diameter of the well. 
         [0003]    Although existing rotary drilling devices are presumably effective to drill subsurface wells, they are less effective in operating to increase the diameter of the hole. For instance, some expanding diameter drill bits urge their blades outwardly by centrifugal force and, as a result, require high speed rotation which may not be possible in some subsurface conditions or if debris is building up too quickly within a hole. 
         [0004]    Therefore, it would be desirable to have an expandable diameter drill bit having one or more blades that are automatically biased outwardly by respective torsion springs. Further, it would be desirable to have an expandable diameter drill bit having a construction that is less susceptible to blade breakage and more effective in cutting through rock. 
       SUMMARY 
       [0005]    An expandable diameter drill bit according to the present invention includes a cutting blade having a receiving end and a contacting end, the receiving end having a pivot shaft and the contacting end having a tip. A drill bit includes a drill head body having an upper attachment portion and a lower body portion, the lower body portion defining a blade opening for receiving the receiving end of the cutting blade and a bolt receiving hole on each of two opposing sides transverse the blade opening. The drill bit includes a torsion spring having a helical coil, a first blade leg, and a second body leg. The blade bolt passes through the bolt receiving holes and the pivot shaft and is secured into position with a blade bolt set screw. The first blade leg is coupled to the cutting blade with a spring retainer bolt, the second body leg is coupled to the drill head body, and the torsion spring biases the blade outwardly from the drill head body. 
         [0006]    The drill bit  10  may be inserted into a hole with the purpose of expanding the hole diameter as it is lowered therein. The drill bit is spun around such that the blades cut away at the edges of the hole. As the diameter of the hole becomes larger, the oppositely biased torsion springs force the blades outward, thus causing the hole to become even larger. 
         [0007]    Therefore, a general object of this invention is to provide an expandable diameter drill bit for efficiently drilling a well beneath the surface of the Earth. 
         [0008]    Another object of this invention is to provide an expandable diameter drill bit, as aforesaid, in which a pair of blades is pivotally movable between a retracted configuration not extending outwardly from a drill body and an extended configuration extending outwardly from the drill body. 
         [0009]    Still another object of this invention is to provide an expandable diameter drill bit, as aforesaid, in which each cutting blade is naturally biased toward the extended configuration by a respective torsion spring. 
         [0010]    Yet another object of this invention is to provide an expandable diameter drill bit, as aforesaid, in which each cutting blade may be coated with or include materials that cut more effectively through subsurface compositions and debris. 
         [0011]    A further object of this invention is to provide an expandable diameter drill bit, as aforesaid, that cuts more effectively through subsurface compositions and debris. 
         [0012]    A still further object of this invention is to provide an expandable diameter drill bit, as aforesaid, in which each cutting blade includes serrated teeth. 
         [0013]    Other objects and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, embodiments of this invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of an expandable diameter drill bit according to a present embodiment of the present invention illustrated in an expanded configuration; 
           [0015]      FIG. 2 a    is a front view of the expandable diameter drill bit as in  FIG. 1 ; 
           [0016]      FIG. 2 b    is a side view of the expandable diameter drill bit as in  FIG. 2   a;    
           [0017]      FIG. 2 c    is a section view taken along line  2   c - 2   c  of  FIG. 2   b;    
           [0018]      FIG. 2 d    is an isolated view on an enlarged scale taken from  FIG. 2   c;    
           [0019]      FIG. 2 e    is an isolated view on an enlarged scale taken from  FIG. 2   c;    
           [0020]      FIG. 2 f    is an isolated view on an enlarged scale taken from  FIG. 2   c;    
           [0021]      FIG. 3 a    is an exploded view of the expandable diameter drill bit as in  FIG. 1 ; 
           [0022]      FIG. 3 b    is an isolated view on an enlarged scale taken from  FIG. 3   a;    
           [0023]      FIG. 3 c    is an isolated view on an enlarged scale taken from  FIG. 3   a;    
           [0024]      FIG. 3 d    is an isolated view on an enlarged scale taken from  FIG. 3   a;    
           [0025]      FIG. 3 e    is an isolated view on an enlarged scale taken from  FIG. 3   a;    
           [0026]      FIG. 4 a    is a front view of the expandable diameter drill bit according to the present invention illustrated in a retracted configuration; and 
           [0027]      FIG. 4 b    is a side view of the expandable diameter drill bit as in  FIG. 4   a.    
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    An expandable diameter drill bit and method of use will now be described with reference to  FIGS. 1 to 4   b  of the accompanying drawings. The drill bit  10  may generally include a drill head body  100  and a plurality of blades  200  secured to the drill head body  100  with a bolt and set screw combination and held in tension with the drill head body  100  via tension springs  300 . 
         [0029]    With reference to  FIGS. 3 a  and 3 b   , the drill head body  100  serves as the structural support for the expandable blades  200 . The drill head body  100  may have an upper threaded portion  105  for attaching the drill bit to various devices useful for guiding the drill bit underground and a lower body portion  110  for attaching the blades  200  to the drill bit  10 . Although not required, the upper threaded portion  105  may be generally conically shaped as shown in the figures. 
         [0030]    An outside edge  107  of the upper threaded portion  105  may be inserted into, for example, a drill string (not shown). The threaded portion  105  may be configured such that when the drill bit  10  is connected to the drill string and in use the drill bit  10  does not become loosened. Other means for ensuring semi-permanent connection to the drill string (or other guiding device) is contemplated within the scope of the present invention. It shall also be understood that drill bits generally have a shortened lifespan due to the conditions under which they are used, and therefore, as will be appreciated by those skilled in the art, it may be preferable that the drill bit  10  is removable from the drill string (or other guiding device) at the end of its life. 
         [0031]    The upper threaded portion  105  terminates at an inside edge  109  of a top face of the lower body portion  110 . The lower body portion  110  may define blade openings  112  for accepting receiving ends  205  of the blades  200 . The blade openings  205  may be separated by a divider  115  for ensuring proper positioning of the blades  200  and to prevent the blades  200  from rubbing against each other during use. 
         [0032]    Bolt receiving holes  120  in opposing sides of the drill head lower body portion  110  and though the center of the divider  115  may generally correspond to holes  210  (pivot shafts) in receiving ends  205  of the blades  200 . Referring now to  FIG. 3 c   , a threaded end  131  of a blade bolt  130  may be inserted through a first bolt receiving hole  120   a  ( FIG. 4 a   ) in the drill head lower body portion  110 , through the hole  210  (pivot shaft) in the receiving end  205  of a first blade  200 , through the hole in the divider  115 , through the hole  210  (pivot shaft) in the receiving end  205  of a second blade  200 , and through a second bolt receiving hole  120   b  in the drill head lower body portion  110 . A head  132  on the end opposite the threaded end  131  of the blade bolt  130  may subsequently come to rest along an outer perimeter  119  of the first receiving hole  120   a  to keep the blade bolt  130  in its preferred position. 
         [0033]    A channel  133  ( FIG. 3 c   ) may be cut around a perimeter of the blade bolt  130  at a length L of the bolt  130  such that when the bolt  130  is inserted through the drill bit lower body portion  110  as described above, the channel  133  is at a position corresponding generally to the hole in the divider  115 . A blade bolt set screw hole  125  ( FIG. 3 e   ) in one or both outside ends of the divider  115  may receive a blade bolt set screw  135 , which may fit within the channel  133  in the blade bolt  130 . In some embodiments, it may be preferable for the blade bolt set screw  135  to fit within the channel  133  to prevent the blade bolt  130  from shifting laterally but still allow the blade bolt  130  to rotate within the bolt receiving holes  120   a ,  120   b . In other embodiments, it may be desirable for the blade bolt set screw  135  to be tightened such that the blade bolt  135  is prevented from both shifting laterally and rotating. 
         [0034]    The lower body portion  110  may further be equipped with a fluid discharge hole  128 . Fluids are often used to reduce friction, provide buoyancy to the drill string, and remove cuttings from the well bore. As the well bore in which the drill is operating is flooded with fluids, the fluid discharge hole  128  may allow for fluids to be discharged away from the drill head body  100 . 
         [0035]    The blades  200  provide the means by which surface material is displaced to form a hole, and in some particular embodiments, a well bore hole. Each blade  200  may be generally rectangular at the receiving end  205  and culminate at a tip at the surface contacting end  215 . The tip may have a rounded configuration as shown in the drawings although a pointed tip may also be used in other embodiments not shown). An upper corner  212  of the blade at the receiving end  205  may be rounded to facilitate rotation of the blade  200  about the blade bolt  130  while situated inside of the blade openings  112 . 
         [0036]    Outer edges  214  of the blades may be serrated to increase the performance of the blades. Serrated edges may be superior to plain edges because serrated edges tend to grab and cut the material as the blades come into contact with the surface. The blades may be made of any material strong enough to withstand the high forces exerted on the blades as they rotate and cut away at the surface. Exemplary materials include steel, steel alloys, tungsten carbide, cubic boron nitride, et cetera. 
         [0037]    In addition to the blades themselves, the edges may be coated in a material exhibiting superior hardness properties thereby increasing the effectiveness of the blades and the life of the drill. In some embodiments, the edges  214  may additionally or alternately be equipped to receive an insert  220 , such as that shown in  FIG. 3 a   . The insert  220  may also be constructed of a material exhibiting superior hardness properties. Exemplary materials include tungsten carbide, cubic boron nitride, diamond, et cetera. 
         [0038]    It should be noted that the blades may be any desired length based on the requirements of a particular project (e.g., 20″, 25″, 30″, 35″, 40″, 45″, etc.). Additionally, while the embodiments described herein focus on the use of two opposing blades, additional or fewer blades could be used depending on the particular project. 
         [0039]    With reference to  FIG. 2 c   , tension springs  300  may act to keep the blades  200  in tension with respect to the drill head body  100 . The springs  300  may be, for example, helical torsion springs having a central coil  305  with a first blade leg  310  extending along a length of the blade  200  and a second body leg  315  extending toward and attaching to the base  100 . The central coil  305  may fit into a recess  240  in the pivot shaft  210  and the first blade leg  310  may fit into a recess  242  in the blade  200  ( FIGS. 2 e  and 3 d   ). The first blade leg  310  may be secured into place via one or more spring retainer bolts  320  ( FIG. 2 f   ). The second body leg may be inserted into a cavity  140  in the drill head body  100  ( FIG. 2 d   ). 
         [0040]    When the springs  300  are in full tension, the blades  200  are in a retracted position as illustrated in  FIGS. 1 and 2   a . When retracted, such as to about a 4″ diameter, the drill bit  10  may be inserted into a ground hole that is intended to be drilled or enlarged. In a retracted position, the blades  200  may not exhibit any substantial hole-widening capabilities. However, the mechanical energy stored in the springs  300  as a result of the central coil  305  constantly acts to push the blades outward or away from the retracted position.  FIG. 2 a    illustrates the springs  300  pushing the blades  200  outward toward an expanded configuration ( FIG. 1 ). The mechanical energy can thus be altered by modifying the central coil  305  (e.g., increasing the tension or decreasing the tension in the spring). Therefore, as the blades  200  cut away at the interior surface of a hole, the blades may be pushed further outward as a result of the tension springs  300 , thereby increasing the diameter of the hole in the surface. It may be preferable for the blades  200  to extend in opposite directions from each other to obtain the highest possible degree of surface displacement. In an embodiment, a diameter of the blades in the extended configuration may be about 24″ although other diameters would be effective depending on individual blade lengths. 
         [0041]    In use, the drill bit  10  is inserted into a hole with the purpose of expanding the hole diameter. The blades  200  may first be in the retracted configuration so as to fit into the hole as described above. The drill bit  10  is spun around such that the blades  200  cut away at the edges of the hole. As the hole becomes larger (i.e. has a larger diameter), the springs  300  force the blades  200  outwardly, thus causing the hole to become even larger. 
         [0042]    While many methods of manufacturing the drill head body  100  and blades  200  are contemplated within the scope of the present invention, some exemplary methods include die casting, molding, forging, extruding, machining, et cetera. 
         [0043]    Many different arrangements are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention are described herein with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the disclosed improvements without departing from the scope of the present invention. Further, it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. The description should not be restricted to the specific described embodiments.

Summary:
An expandable diameter drill bit includes a cutting blade having receiving and contacting ends, the receiving end having a pivot shaft and the contacting end having a tip. A drill bit includes a drill head body having an upper attachment portion and a lower body portion, the lower body portion defining a blade opening for receiving the receiving end of the cutting blade and a bolt receiving hole on opposing sides transverse the blade opening. The drill bit includes a torsion spring, a first blade leg, and a second body leg. The blade bolt passes through the bolt receiving holes and the pivot shaft and secured with a set screw. The first blade leg is coupled to the cutting blade with a spring retainer bolt, the second body leg is coupled to the drill head body, and the torsion spring biases the blade outwardly from the drill head body.