Implements or apparatus for applying pushing or pulling force – Miscellaneous
Reexamination Certificate
2002-05-30
2004-01-27
Watson, Robert C. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Miscellaneous
C254S02600E
Reexamination Certificate
active
06682048
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to cams for use with prying and pulling tools.
More specifically, this invention relates to cams as described above wherein the cam serves to provide a prying or pulling tool, with a moving pivot point that serves to enable the tool to pry or pull in a substantially straight line.
More specifically this invention relates to a cam for use with claw hammers and pry bars to enable the pulling and prying to be accomplished in substantially a straight line.
When pulling a nail or other fastener by means of a claw hammer or a crow bar or other nail pulling or prying means it is advantageous to use a prying means that has a fulcrum near to the pulling or prying point and a long handle for the user to apply a significant mechanical advantage. This mechanical configuration results in the prying or pulling arm of the lever moving through an arc having a short radius while the handle or effort arm rotates through an arc of large radius.
When the fulcrum or pivot point lies along a line perpendicular to the desired direction of pull, the rotation of the prying or pulling means causes the prying or pulling point to rotate upward and towards the fulcrum. When pulling nails from boards this results in the bending of the nail and the elongation of the nail hole.
When prying boards away from a surface or when pulling nails, it is desirable to do so with a pull that is straight and in line with the long axis of the nail or other fastener.
Heretofore, carpenters and other workers who have occasion to pry or pull fasteners out of engagement with a structure have employed a small block of wood or other means to raise the location of the pivot above the level of the object being pried or pulled so that rotation of the pulling or prying point was away from the fulcrum initially and towards the fulcrum as the rotation of the prying or pulling point was moved to a location above the pivot point. The result was a pull or pry that is closer to a straight pry or pull along the long axis of the fastener being pulled or pried than would have occurred had the alternate fulcrum not been used.
The holding of the block or fulcrum in place presents problems when working on a vertical or overhead surface. The availability of a suitable fulcrum close at hand in these work locations also presents problems.
It is an object of this invention to provide a cam that provides a fulcrum that moves upward as the pull or pry progresses.
It is further an object of this invention to provide the cam described above with a handle to facilitate positioning and repositioning the cam and for carrying the cam on a belt or a loop on the workman's clothing.
It is further an object of this invention to provide the cam as described above wherein the cam and handle combination can serve multiple additional utilities.
DESCRIPTION OF THE RELATED ART
The patent art contains numerous examples of means for achieving an approximately straight pull on a fastener.
U.S. Pat. No. 4,260,135 to Dickey teaches a tool rest made from neoprene rubber that protects the work surface from damage while affording a moving pivot for a claw hammer to remove a fastener in an approximate straight line perpendicular to the work surface.
U.S. Pat. No. 1,485,863 to McLain teaches a ramped fulcrum attached to a tool for pulling railroad spikes from ties in an approximately straight pull vertical to the tie.
U.S. Pat. No. 830,072 to Houlihan teaches a nail extractor that attaches to a claw hammer and provides a moving fulcrum to provide the greatest leverage when the nail is fully imbedded.
It can be seen from this prior art that the art has been aware of a need to apply a pulling force along the axis of a fastener to be pulled from a work surface and to protect the surface from marring in the process.
While the prior art can be seen to recognize some of the problems solved by this invention and to offer partial solutions to those specific problems, the art cannot be said to anticipate the instant invention or to suggest it to one skilled in the art.
BRIEF DESCRIPTION OF THE INVENTION
A nail-pulling cam having a planer base and a convexly curved upper surface and a handle extending from the curved upper surface.
REFERENCES:
patent: 830072 (1906-09-01), Houlihan
patent: 1485863 (1924-03-01), McLain
patent: 2449861 (1948-09-01), Renner
patent: 4260135 (1981-04-01), Dickey
patent: 4993429 (1991-02-01), Krinsky
patent: 5230115 (1993-07-01), Hollister et al.
Johnson Russell L.
Watson Robert C.
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