Handling: hand and hoist-line implements – Hand forks and shovels – Grappling type
Reexamination Certificate
2000-07-12
2001-08-14
Kramer, Dean J. (Department: 2167)
Handling: hand and hoist-line implements
Hand forks and shovels
Grappling type
C294S057000, C294S118000
Reexamination Certificate
active
06273482
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a new and improved manual post hole digger. The improved manual post hole digger permits the user to more conveniently produce a vertical hole with an essentially constant hole diameter through the length of the hole, enabling the user to dig deep holes.
A common type of manual post hole digger is the clamshell post hole digger. Previously known clamshell post hole diggers typically comprise a pair of sharpened shovel blades mounted on pivotally connected elongated handles. The post hole digging is accomplished by thrusting the blades into the ground then spreading the handles apart forcing the shovel blades together gripping the soil. The soil is then removed from the hole and dumped to the side. This process is repeated until a hole of the desired depth is attained.
The principal problem with this type of clamshell post hole digger is, as the hole is dug deeper the handles cannot be spread sufficiently far apart to grip the soil. Therefore, the diameter at the hole opening must be increased as the depth of the hole is increased.
Many attempts have been made to design clamshell post hole diggers which can dig a deep hole without the need to increase the diameter at the opening of the hole. Such diggers are provided by: Luck (U.S. Pat. No. 5,669,648), Alienate (U.S. Pat. No. 5,478,128), Robinson (U.S. Pat. No. 5,427,424), Burnham (U.S. Pat. Nos. 5,320,363, 5,273,331), Arens (U.S. Pat. No. 2,710,765), Rice (U.S. Pat. No. 2,654,626), Sonnenberg (U.S. Pat. No. 2,435,473), Loos, et al. (U.S. Pat. No. 2,230,498), Mayeda, et al. (U.S. Pat No. 2,028,680), McDowell (U.S. Pat. No. 1,888,929) and Theriot (U.S. Pat. No. 1,706,332). These devices are complex and difficult to operate. The devices often contain numerous parts that become worn and damaged from the soil and debris.
There remains a need for a low cost, simply built, reliable, and easy to use clamshell post hole digger.
BRIEF SUMMARY OF THE INVENTION
One objective of the present invention is to provide an improved clamshell post hole digger that enables the user to dig essentially constant diameter holes. Advantageously, the present invention enables the user to use either abduction or adduction to dig deeper post holes without having to increase the diameter of the hole opening as the depth of the hole increases.
The post hole digger of the present invention utilizes a unique cross-handled design which enables the user to close the blades of the post hole digger without having the handles wider than the diameter of the top of the hole.
In a specific embodiment, the present invention comprises the following components, two sharpened shovel blades, two hinge brackets, and two elongated handles. Preferably, on the hinge brackets there are an offset handle mounting plate, shovel blade mounting plate, and an axial pivot point, where the offset handle mounting plate and the shovel blade mounting plate are on opposite sides of the axial pivot point. The elongated handles are secured to the offset mounting plates on the hinge brackets. The shovel blades are secured to the shovel blade mounting plate. The hinge brackets are secured together at the axial pivot point with the shovel blades opposing each other. In a preferred embodiment the shovel blades are made of stainless steel.
The offset configuration allows the elongated handles to be pushed or pulled towards each other and cross without coming into contact. Through this crossing the shovel blades close and the elongated handles stay within the diameter of the hole opening. This enables the user to dig a deeper constant diameter post hole.
A further objective of the present invention is to decrease the user's fatigue. The user can change from abduction to adduction and back to abduction by changing the position of the hands on the elongated handles. The switching from abduction to adduction allows the user to use different muscles and decrease fatigue.
A further aspect of the present invention pertains to markings on one, or both, of the elongated handles which show the depth of the hole. By having ruled handles, the user can easily dig a hole of a desired depth. Thus, one aspect of the present invention is a cross-handled post hole digger with ruled handles. The ruled handles of the present invention can also be used with a standard post hole digger.
Other objectives of the present invention are to provide a low cost, simply built, reliable, and easy to use clamshell post hole digger.
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Kramer Dean J.
Saliwanchik Lloyd & Saliwanchik
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