Abstract:
The present invention relates to post hole diggers. In particular, the present invention describes a post hole digger that constructs uniform diameter holes. The post hole digger of the present invention is comprised of a pair of handles, digging scoops and a hinge bracket. The hinge bracket translates the movement of the handles into movement of the scoops. The hinge bracket restricts the movement of the handles as digging occurs, allowing for the construction of a relatively straight-sided posthole, essentially removes the tapering of a hole as the hole becomes deeper.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to hole diggers. In particular, the invention describes a posthole digger that makes uniform diameter holes.  
         BACKGROUND OF THE INVENTION  
         [0002]    The post hole diggers generally in use today are the type where the digger is thrust into the ground and the handles are pulled apart to close the blades and scoop out the dirt. As the hole becomes deeper the upper portion of the hole becomes progressively wider. A three-foot deep hole made with a traditional hole digger with a scoop end of only five inches must be opened up ten to eleven inches at the top. The hole created will be tapered which will create a lack of ground support when concrete is used to keep the post in position.  
           [0003]    There are some prior art devices that allow the digging of a posthole of constant diameter. U.S. Pat. No. 6,089,632 to Pickren presents a device wherein the handles cross instead of separating when pulling out dirt. The movement of crossing the handles is counter-intuitive and there is some danger of trapping or pinching ones fingers between the crossing handles. Also the device of the U.S. Pat. No. 6,089,632 patent has an increased number of pieces such as two hinge brackets, mounting plates for handles and shovel blades which renders the device more difficult to repair and maintain.  
           [0004]    The U.S. Pat. No. 5,427,424 to Robinson teaches a device with a single handle also capable of digging a constant diameter shaft. The device has a complex design with many sections and parts. Once more the device is awkward to use and with many parts subject to wear and damage through prolonged use.  
           [0005]    The U.S. Pat. No. 5,320,363 to Burnham discloses a device that digs holes of approximately constant diameter. The Burnham patented device has a center shaft and two side shaft brackets and bracket plates plus a single handle with an actuator lever. The relationship between the single handle and the actuator device does not allow for the increased leverage achieved by the two handles of the instant invention making it more difficult to dig through hard or packed soil and stony ground. It also has multiple parts making maintenance and repair more difficult.  
           [0006]    Lastly, the following two patents U.S. Pat. No. 5,478,128 to Aaland and U.S. Pat. No. 4,042,270 to Weiland are also capable of making post holes of constant diameter. These patents also have numerous parts which can be worn or damaged by use making maintenance and repairs more difficult, Most of the designs in the prior art have many parts that become worn and damaged from use and the debris generated by digging. The number of parts makes repairs more costly and difficult. In addition, several of the designs are awkward to use, especially if user is accustomed to the traditional post hole digger. The present invention seeks to solve the problems present in the prior art while keeping the device simple.  
         OBJECTS OF THE INVENTION  
         [0007]    Accordingly, it is an object of the present invention to design a post hole digger that makes holes of uniform diameter with a minimum number of parts.  
           [0008]    It is an additional object of the present invention to provide a device that make holes using similar motions of the more traditional hole diggers.  
           [0009]    It is a further object of the present invention to provide a device that is durable, easy to use and efficient.  
           [0010]    Further, it is an object of the present invention to provide a device of novel design and construction.  
           [0011]    Lastly it is an object of the present invention to provide a device able to dig deep holes without increasing the diameter of the upper portion of the hole.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention is able to dig a hole five to six inches wide and three to four feet deep without appreciably enlarging the top section of the hole. The present device is comprised of a pair of handles, two metal scoops and a hinge bracket. In an alternative embodiment, the device may comprise two unitary pieces incorporating the handle and scoop into one unit with the units joined by a hinge bracket. The hinge bracket is designed to limit the movement from the elongated handles and to translate the movement to the scoops.  
           [0013]    In a preferred embodiment the scoops are joined together to provide strength and limitation of movement. The digging scoops can be joined together by a bolt or, in a preferred embodiment, one of the scoops may have a fixed protrusion fitted into a slot formed in the second scoop to allow a sliding movement of the first scoop to provide a more secure closing of the scoops during the removal of dirt. The hinge bracket can be located at any point along the handles. Preferentially, the hinge bracket is positioned near the midpoint of the pair of handles or, alternatively, between the midpoint of the handles and the digging scoops. The bracket hinge limits the movement of the handles and translates the handle movement to the digging scoops. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1A a shows a side view of an embodiment of the post hole digger where the scoops are held together by a bolt.  
         [0015]    [0015]FIG. 1B shows a side view of a preferred embodiment of the post hole digger.  
         [0016]    [0016]FIG. 2 shows a top cross section of the hinge bracket.  
         [0017]    [0017]FIG. 3A shows the scoops in a preferred embodiment slidably attached using a bolt-slot sliding union.  
         [0018]    [0018]FIG. 3B depicts a pair of unattached scoops.  
         [0019]    [0019]FIGS. 4A and 4B show the post hole digger of the instant invention and a prior art post hole digger, respectively, in operation digging a hole. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    The preferred embodiment of the present invention will now be described with reference to accompanying drawings. It will nevertheless be understood that no limitations of the scope of the invention is thereby intended, such alterations as scale of the parts, materials used, position of the hinge bracket, color or weight which would fall within the spirit and the scope of the invention described herein.  
         [0021]    [0021]FIG. 1A shows a side view of an embodiment of the post hole digger  14 . The post hole digger  14  is comprised of two handles  8  approximately four to six feet long with a diameter of approximated one inch. Blades  12   a  and  13   a  of scoop  28  are fixedly attached at one end of one of each handle  8 . The handles  8  are wrapped by a hinge bracket  9  attached to the two handles. The hinge bracket  9  has a pin  7  that rotates to translate the minimum motion applied to the handles  8  into movement of the scoops  28  allowing the opening and closing of the scoops  28 . In a preferred embodiment, the hinge bracket is located at a midpoint on the handles with the midpoint defined as the point midway between the top of scoop  28  and the top of the handles. In an alternative preferred embodiment, the hinge bracket  9  may be located between the midpoint and the top of the scoops. In the embodiment shown in FIG. 1A, the scoops are securely joined together by a bolt  29 . In the present invention it is not necessary to have the scoop joined but it is a preferred embodiment to provide strength and restrain movement. It should be recognized that the handle/scoop component can be fabricated into a single unitary part, such as by forging, with two such unitary parts joined using hinge bracket  9  and the scoop attachments noted supra.  
         [0022]    [0022]FIG. 1B shows an alternative preferred embodiment of the post hole digger  14 . As in FIG. 1A the device has a pair of handles, two digging scoops and a hinge bracket. The location and function of the hinge bracket  9  is as in FIG. 1A. At the end of each handle  8  a scoop blade  12  or  13  is fixedly secured. In the upper portion of scoop  12  is fixed bolt  11 . The upper portion of opposite scoop blade  13  has a slot  10  that slides forward and backward on the fixed bolt  11 . The efficiency and closing power of the movement of scoop blades  12  and  13  is enhanced by the sliding of scoop  12  into and away from the fixed scoop  13 .  
         [0023]    [0023]FIG. 2 shows a cross sectional view of the hinge bracket  9  and the handles  8  of the post hole digger. The handles  8  are securely attached to the hinge bracket by a screw  18  that goes through the hinge bracket  9  and at least halfway into the diameter of the handle. It is recognized that other attachment methods are possible such as a nut and bolt combination or adhesive or rivets. The hinge bracket  9  has a bolt  17  going through the middle, between the handles. The bolt  17  rotates to translate a minimum of motion applied to the handles to the opening and closing of the scoops for the removal of dirt from the hole. This allows for the digging of a hole of uniform diameter in which width is slightly larger than the distance between opened scoop  28  without appreciably enlarging the upper portion of the hole. The hinge bracket  9  is preferably made of hardened steel and the handles  8  of wood. It is recognized that other durable materials can be used.  
         [0024]    [0024]FIG. 3A and B show a side view of the scoops attached and separated respectively. In FIG. 3A, the arrow  15  shows the direction in which scoop blade  13  slides on the fixed bolt  11  by the use of slot  10 . The scoop blade  12  is fixed in place while scoop blade  13  is free to slide into or away from scoop blade  13 . The scoops of the post hole digger can be made of any material that is suitable for outdoor use and digging. Preferably the material will be durable, generally non-corroding and substantially lightweight. Some of the materials that may be used include, but are not limited to, wood, fiberglass, aluminum, hardened steel and others. In a preferred embodiment, the scoop blades will be made of hardened steel. The material composing the scoop blades can be varied accordingly to the type of soil being dug such as a loose sandy soil or a hard-packed clay soil. The scoops can be attached to the handle by pressure insertion or by a bolt or a screw or other methods well known in the art.  
         [0025]    [0025]FIG. 3B depicts the scoops in an alternative embodiment. In the alternative embodiment, both scoops are identical. One side of the upper portion scoop blade  6   a  defines a hole  16  through which the fixed bolt  11  will be passed. The opposite side of the upper portion of scoop blade  6   a  defines a slot  10  that will allow for the sliding movement. Once the hole  16  and the slot  10  from each pair of scoop blades  6   a  are aligned, the fixed bolt  11  is passed through both holes  16  and is secured. In a variation two bolts  11  may be used to connect the pair of scoops  6   a  together. In either variation, the top of the bolt is wider than the width of the slot  10  allowing for stable sliding movement and stronger closing power. FIG. 3B also depicts a receiving section  32  formed to receive handle  8 .  
         [0026]    [0026]FIGS. 4A and 4B depicts the post hole digger of the instant invention and a prior art post hole digger, respectively, in operation. In FIG. 4A, it can be appreciated that the hole  19  dug by the post hole digger  14  of the present invention is relatively uniform in diameter from top to bottom in comparison to the hole dug by the prior art post hole digger  27  where the hole  20  is wider at the top than at the bottom. The prior art post hole digger  27  has two scoop blades  26  and  24  and a bolt  25  joining both scoop blades. Both of the scoops are fixed in position by the bolt  25  whereas in the present invention posthole digger  14  has a fixed scoop  12  and a sliding moving scoop  13 . The post hole digger  14  of the present invention also has the hinge bracket  9  to limit the movement of the handles  8 . In contrast, with the prior art post hole digger  27 , as the hole  20  becomes deeper, the movement of the handles  23  becomes wider and more extreme creating a tapered hole rather the more uniform hole  19  fashioned by post hole digger  14  of the instant invention.