Implements or apparatus for applying pushing or pulling force – Pipe or rod jack – Lifter
Reexamination Certificate
1999-04-05
2001-10-16
Watson, Robert C. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Pipe or rod jack
Lifter
Reexamination Certificate
active
06302376
ABSTRACT:
BACKGROUND
Stakes are used in many applications. In most applications, they are meant as temporary support, and as such need to be removed. Removing the stakes from the ground can be very difficult, as they are driven in to depths over a foot, and the angle at which they are driven into the ground varies from stake to stake. When a stake is pulled out at an angle different from that at which it entered the ground, the remover must overcome the frictional forces of the ground around the stake on the stake surface, and also the lateral forces of the ground as the stake is pulled against it.
There are devices labeled as stake pullers that use the lever arm/fulcrum combination to increase the mechanical advantage and pull out a stake. A recently patented one being the device disclosed in U.S. Pat. No. 5,597,151 to Duncan entitled Stake Puller with Stake Supporting Backplate. This device uses a lever and fulcrum for mechanical advantage, and adds a backplate to the stake-engaging mechanism to try and minimize the bending shear on the stake. This design lists as it's advantages that it can be used for wooden stakes because of the minimized bending shear, and that it may be “pumped”, or reapplied without having to reposition the stake puller between each effort. The problem of bending shear on a stake is only really applicable for a wooden stake; it is not a problem for steel stakes which are becoming the standard. The self touted stability of the fulcrum foot in this disclosure leaves the problem that the stake puller must overcome both the frictional forces of the ground around the stake on the stake surface, and also the lateral forces of the ground as the stake is pulled against it, because pivoting about a stationary fulcrum translates the downward force of the user on the lever arm into a bending force on the stake. The Duncan patent discloses one way to overcome this deficiency, which is to have the user both push down, and pull backward to force the fulcrum to rock on its otherwise stable foot in order to manually compensate for the lateral force exerted by the stake. This makes the stake puller difficult to manipulate, and requires more force by the user.
Even with a stake puller, removing a stake can be quite strenuous. A need exists for a stake puller which is easy to manipulate, and which requires a lesser total force by the user. Such a stake puller would pull a stake out at the angle at which it entered the ground with a simple downward force by the user, to make removal easy and non-strenuous. Such a stake puller would also be effective for removing stakes driven deeply into the ground. There is also a need for a stake puller with a simple stake-engaging mechanism.
SUMMARY OF THE INVENTION
According to an aspect of the invention, a self-translating stake puller for removing a stake, comprising a lever arm having opposing first end and second end, a stake-engaging mechanism attached to the second end of the lever arm, and configured to pivot the stake about the second end, and a fulcrum having a is top end and a bottom end, wherein the top end is pivotally attached to the lever arm between the first end and the second end, such that the fulcrum plane of pivot is generally parallel to the plane of pivot of the stake about the second end, and wherein the bottom end of the fulcrum is of a size and shape such that the fulcrum can rock easily on the bottom end. According to another aspect of the invention, there is a method for removing stakes from the ground by using the stake puller described above.
REFERENCES:
patent: 90559 (1869-05-01), Knott
patent: 441864 (1890-12-01), Black
patent: 762846 (1904-06-01), Rotvold
patent: 793169 (1905-06-01), Arnold
patent: 1139568 (1915-05-01), Olson
patent: 1288223 (1918-12-01), Schmitt
patent: 1911287 (1933-05-01), Pladson
patent: 2099592 (1937-11-01), Barton
patent: 3048368 (1962-08-01), Linabery
patent: 3945611 (1976-03-01), Moodie et al.
patent: 4738433 (1988-04-01), Hoff
patent: 5499795 (1996-03-01), Mathews
patent: 5597151 (1997-01-01), Duncan
Bowen Kathleen K.
Watson Robert C.
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