Abstract:
A post hole digger for producing a hole in the ground comprising a first handle pivotally coupled to a second handle and a first blade coupled to the first handle and a second blade coupled to the second handle. The first handle and the second handle extend along a plane defined generally by a longitudinal axis of the first handle and a longitudinal axis of the second handle when the first blade and the second blade are in the open configuration. The first blade and the second blade are generally parallel to the plane and spaced apart from the plane when provided in the open configuration.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
   The present application claims the benefit of and priority as available under 35 U.S.C. §§ 119-21 to the following U.S. patent application (which is incorporated by reference in the present application): U.S. Provisional Patent Application No. 60/461,089 titled “POST HOLE DIGGER” filed Apr. 8, 2003. 

   BACKGROUND 
   The present invention generally relates to post hole diggers. The present invention more specifically relates to a post hole digger that enables a user to conveniently produce a vertical hole in the ground with minimal interference between the post hole digger and the sides of the vertical hole. 
   It is generally known to provide a post hole digger for digging holes within the earth for placement of a post therein. Traditional post hole diggers include two concave blades that face one another to form a cylindrical region generally about six inches in diameter. The blades are pivotally connected to one another proximate the top portion of the blades. Extending from each blade is a fixture or cap supporting a shaft handle extending approximately four feet in height. The blades are spaced apart from one another such that each shaft is proximate the inner surface of each of the blades. By thrusting the blades into the ground, the earth is secured between the blades by moving the upper end of the handles away from one another forcing the blades to pivot about the pivot toward one another. 
   As the hole becomes deeper, the pivoting motion of the blades results in the shafts contacting the edge of the hole proximate the top of the hole. This minimizes the pivoting motion of the blades and thereby reduces the amount of dirt that can be pulled out with each pivoting motion of the shafts. As a result, a user is often forced to widen the width of the hole in order to accommodate the shafts. This can result both in excess effort from the user, as well as an increased use of cement and/or other type of filling for the hole. Further, the use of the fixtures extending from the blades to support the shafts can often interfere with the sight line of the user with respect to the blades, thereby inhibiting free visual access to the hole during use of the post hole digger. Additionally, the traditional wood and plastic handles or shafts are subject to breaking near the fixture that holds them. Further, the nuts and bolts that connect the handles to the fixtures typically loosen during use. 
   Accordingly, it would be advantageous to provide a post hole digger that allows for full pivoting of the blades relative to one another while minimizing the contact between the shafts and the upper edge of the hole. It would also be advantageous to provide a post hole digger that enables a user to dig deeper post holes without having to increase the diameter of the hole opening as the depth of the hole increases. It would also be advantageous to provide a post hole digger that enables a user to close the blades of the post hole digger without having the handles or shafts wider than the diameter of the top of the hole. It would also be desirable to provide a post hole digger having shafts with a configuration that maximizes the sight line of the post hole digger. It would also be desirable to provide a post hole digger having a handle arrangement and blade attachment that minimizes the chances of the handles breaking or loosening during use. 
   It would be advantageous to provide a post hole digger or the like of a type disclosed in the present application that provides any one or more of these or other advantageous features. The present invention further relates to various features and combinations of features shown and described in the disclosed embodiments. Other ways in which the objects and features of the disclosed embodiments are accomplished will be described in the following specification or will become apparent to those skilled in the art after they have read this specification. Such other ways are deemed to fall within the scope of the disclosed embodiments if they fall within the scope of the claims which follow. 
   SUMMARY 
   One embodiment of the invention relates to a post hole digger. The post hole digger comprises a first shaft pivotally coupled at a pivot to a second shaft, the first shaft and the second shaft each comprising an upper end, a lower end, and a central portion having a central axis, and a first blade coupled to the first shaft at the lower end of the first shaft and a second blade coupled to the second shaft at the lower end of the second shaft. The central axis of the first shaft and the central axis of the second shaft generally define a plane when the first blade and the second blade are provided in an open configuration. The first blade and the upper end of the first shaft are located on a first side of the plane when the first blade and the second blade are provided in the open configuration. The second blade and the upper end of the second shaft are located on a second side of the plane when the first blade and the second blade are provided in the open configuration. The upper end of the first shaft and the upper end of the second shaft may be pivoted away from one another to position the blades in a substantially closed configuration. 
   Another embodiment of the invention relates to a post hole digger. The post hole digger comprises a first handle pivotally coupled to a second handle, the first handle and the second handle each having a longitudinal axis, and a first blade coupled to the first handle and a second blade coupled to the second handle. The first blade and the second blade are configured to pivot from an open configuration to a closed configuration by pivoting the first handle and the second handle away from one another. The first handle and the second handle extend along a plane defined generally by the longitudinal axis of the first handle and the longitudinal axis of the second handle when the first blade and the second blade are in the open configuration. The first blade and the second blade are generally parallel to the plane and spaced apart from the plane when provided in the open configuration. 
   Another embodiment of the invention relates to a method of producing a post hole digger. The method comprises providing a first shaft pivotally coupled to a second shaft, the first shaft and the second shaft comprising an upper end, a lower end, and a central portion having a longitudinal axis, and providing a first blade coupled to the first shaft and a second blade coupled to the second shaft. The method comprises configuring the first blade and the second blade to pivot from an open configuration to a closed configuration by pivoting the upper ends of the first shaft and the second shaft away from one another. The method comprises configuring the central portions of the first shaft and the second shaft to extend along a plane generally defined by the longitudinal axis of the first and second shaft when the first blade and the second blade are in the open configuration. The method comprises configuring the first blade and the second blade to be generally parallel to the plane and spaced apart from the plane when provided in the open configuration. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front perspective view of a post hole digger according to an exemplary embodiment. 
       FIG. 2  is a side view of the post hole digger according to an exemplary embodiment. 
       FIG. 3  is a front view of the post hole digger according to an exemplary embodiment. 
       FIG. 4  is a top view of the post hole digger according to an exemplary embodiment. 
       FIG. 5  is a front view of a shaft of the post hole digger according to an exemplary embodiment. 
       FIG. 6  is a side view of the shaft of the post hole digger according to an exemplary embodiment. 
       FIG. 7  is a plan view of a pivot bearing of the post hole digger according to an exemplary embodiment. 
       FIG. 8  is a side view of the pivot bearing of the post hole digger according to an exemplary embodiment. 
       FIG. 9  is a side view of the post hole digger in the closed position according to an exemplary embodiment. 
       FIG. 10  is a side view of a post hole digger according to an alternative embodiment. 
   

   DETAILED DESCRIPTION 
   Before explaining a number of preferred, exemplary, and alternative embodiments of the invention in detail, it is to be understood that the invention is not limited to the details or methodology set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or being practiced or carried out in various ways. It is also to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
   A system (shown as a post hole digger  10 ) for digging holes within the earth (e.g., for the placement of posts, fences, poles, etc.) is shown in  FIG. 1  according to a preferred embodiment. Post hole digger  10  may be operated by a user to dig deeper, more uniform diameter post holes without having to widen the upper portion of the hole. Post hole digger  10  enables a user to close the blades of the post hole digger  10  without having the handles or shaft wider than the diameter of the top of the hole. 
   Referring to  FIG. 1 , post hole digger  10  includes a pair of shafts  12  and a pair of blades  14  attached to shafts  12 . Shafts  12  are pivotally attached at a pivot  16 . Referring to  FIGS. 2 ,  3  and  5 , each shaft  12  includes a grip  18 , a central portion  20 , an upper end  22 , and a lower end  24 . Each shaft  12  further includes an upper transition  26  between grip  18  and central portion  20  and a lower transition  28  extending from the lower end  24  of the central portion  20  of shaft  12 . As shown in  FIGS. 1-3  and  9 , shafts  12  may be attached to pivot  16  along central portion  20  proximate lower transition  28 . According to various alternative embodiments, shafts  12  may be attached to pivot  16  at any suitable point along shafts  12 . The lower end  24  includes an engagement face or surface  30  that is directly connected to each respective blade  14 . According to an exemplary embodiment, engagement surface  30  may be formed by flattening the lower portion of shaft  12 . According to an alternative embodiment, the lower portion of shaft  12  may be cut to provide the beveled profile of engagement surface  30 . 
     FIGS. 2 and 4  show the post hole digger  10  in a non-extended or stowed configuration (e.g., the blades  14  are in an open position). When in the non-extended configuration, and as shown in  FIGS. 2 and 4 , the longitudinal axis of each of central portions  20  of shafts  12  define a plane  32  which also extends through the central axis of pivot  16 . Grip  18  and engagement surface  30  of each shaft  12  are both located on the same respective side of plane  32 . As shown in  FIG. 4 , a second plane  34  is perpendicular to plane  32  and to the central portion of each blade  14 . Second plane  34  extends through each grip or handle  18  as well as through pivot  16  and is perpendicular to the central axis of pivot  16 . Upper and lower transitions  26 ,  28  of each shaft  12  extend from plane  34  at a predefined angle toward central potion  20  (and plane  32 ). 
   According to an exemplary embodiment, as shown in  FIG. 6 , the upper transition  26  may include a compound angle such that handle  18  is spaced a predetermined distance from an edge of the central portion  20  of post hole digger  10 . For example, length  88   a  between the edge of grip  18  and the edge of central portion  20  may be approximately 2 inches. As shown in  FIG. 5 , length  88   b  between the edge of grip  18  and the edge of central portion  20  may be approximately 1 inch. Similarly, lower transition  28  includes a compound angle such that engagement surface  30  is a predetermined distance from an edge of central portion  20  of post hole digger  10 . For example, as shown in  FIG. 6 , length  88   c  between the edge of engagement surface  30  and the edge of central portion  20  may be approximately three inches. As shown in  FIG. 5 , length  88   d  between the edge of engagement surface  30  and the edge of central portion  20  may be approximately one inch. 
   Referring to  FIGS. 2 and 4 , the blades are in the open position. According to an exemplary embodiment, the handles  18  may spaced approximately two to four inches apart from one another when in the open position as shown by length  88   e.  Of course the exact distance between the handles may vary according to various exemplary embodiments. According to an exemplary embodiment, both of the handles fit within a cylindrical plane defined by the shape of the blades  14 . 
   Referring to  FIGS. 7 and 8  pivot  16  will be described in greater detail. Pivot  16  includes a pair of bearings  36 . Each bearing  36  includes a bearing surface  38 . Bearing surface  38  may include either a coating or a separate material  40  being corrosion resistant, non-rusting, and having a low coefficient of friction. Each bearing  36  further includes a pin  42  extending therefrom that is received in a corresponding slot  44  on the other bearing  36 . This pin and slot arrangement limits the rotation of the bearings relative to one another and as a result limits the rotation of blades  14 . Slot  44  allows bearing  36  to pivot a predefined angle from the vertical. According to an exemplary embodiment, slot  44  is configured to allow bearing  36  to pivot between 10 and 35 degrees from the vertical. According to a preferred embodiment, slot  44  is configured to allow bearing  36  to pivot about 20 to 25 degrees from the vertical, and more preferably about 22.5 degrees from the vertical. 
   According to an exemplary embodiment, bearing  36  includes an arcuate inner surface  46  located opposite bearing surface  38  that is proximate shaft  12 . In one embodiment, each bearing  36  is welded to the outer surface of each respective shaft  12  such that inner surface  46  is adjacent shaft  12 . According to an exemplary embodiment, a pivot pin  48  need only extend through bearings  36  and not necessarily through shafts  12 . In an alternative embodiment, pivot pin  48  extends through each shaft  12  and through each opening  50  extending through each bearing  36 . According to various alternative embodiments, it is also possible to both weld bearing  36  to each shaft as well as to have pivot pin  48  extend through the shafts. Regardless of whether the bearing is welded to or mechanically attached to shafts  12 , the bearing surface  38  preferably rotates within plane  34 . 
   Referring to  FIG. 9  post hole digger  10  is shown in a fully closed position (e.g., the post hole digger  10  is located within a hole in the ground). According to an exemplary embodiment, the post hole digger may be configured such that if the hole is six inches in diameter or equal to the distance between blades  14  when the blades are in the open position, then the outside of shafts  12  would contact the upper edge of the hole when the hole is 32 inches deep. According to this embodiment, if the hole is twelve inches in diameter, shafts  12  would contact the upper edge of the hole when the hole is 48 inches deep. 
   To operate the post hole digger  10 , a user grasps and hold grips  18  in the non-extended position shown in  FIGS. 2 and 4 . The user may then thrust the blades  14  into the ground. As shown in  FIG. 9 , the user may move the grips away from one another so that shafts  12  pivot about pivot  16  and blades  14  close and grip the soil therebetween. The user may then lift the post hole digger  10  out of the hole while continuing to pull the grips  18  apart. Once the post hole digger  10  is removed from the hole, the user may move the grips toward one another so that shafts  12  pivot about pivot  16  and blades  14  move apart from one another, thereby releasing the soil from between the blades  14 . 
   According to various exemplary embodiments, the assemblies and components of the post hole digger may be constructed from various different materials. According to a preferred embodiment, the assemblies and components of the post hole digger may be constructed from materials that are durable, substantially non-corroding, and light weight. For example, a variety of plastics (e.g., high-impact), polymers, rubber, etc. may be used for construction or assembly of the grip. Using rubber or plastic offers several advantages including that the grip may be constructed in a variety of different colors, surface finishes, textures, opacity, etc. According to various exemplary embodiments, a variety of suitable materials may be used for other components (such as the shafts and blades) of the post hole digger, including metals, alloys, composites, aluminum, stainless steel, fiberglass, wood, etc. Further, various parts of the post hole digger may be constructed and assembled as a single integrally formed piece or may be constructed and assembled from multiple parts. 
   It is important to note that the construction and arrangement of the elements of the post hole digger as shown in the various embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g. variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter disclosed in this application. For example, referring to  FIG. 10 , a pivot  52  may be located below or proximate the upper edge of blades  14 . Further the lower transition portion  54  may be formed of a separate component that is welded to or mechanically attached to the central portion of the shafts. Accordingly, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In any claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present inventions.