Cutlery – Blades – Toothed or waved
Reexamination Certificate
1999-08-14
2002-03-19
Watts, Douglas D. (Department: 3724)
Cutlery
Blades
Toothed or waved
C030S144000, C030S514000
Reexamination Certificate
active
06357122
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hand tool for cutting drywall.
BACKGROUND OF THE INVENTION
Drywall, also known as plaster board or as sheet rock, is generally prepared for installation as a wall overlay at building construction sites by cutting large standard-sized units of drywall into dimensions that fit the particular on-site requirements. Drywall is made of a gypsum composition and is firm and resistant to penetration and crumbles in the particular areas where sawed. The task of sawing is generally accomplished by a special hand saw. Because of the nature of drywall, the drywall saw has offset cutting teeth of various configurations known in the art that do not bind during the cutting. The cutting teeth are specially adapted to remove crumbled drywall material during the sawing operation. When a first cut at the top edge or side edge of the drywall sheet cannot accomplish the sizing task at hand, an initial cut must be made through a particular area of the drywall, in which case a special tool is required to create a keyhole through a selected area of the drywall to allow subsequent access by the drywall saw.
Drywall saws presently known in the art do not have the capability of penetrating the flat side of a drywall.
A drywall saw with a sharp point is described in U.S. Pat. No. 5,448,833 issued to Coon on Sep. 12, 1995. An embodiment of the hand saw therein shown in
FIGS. 10 and 11
shows a blade with saw teeth on the underside cutting surface and a sharpened edge
38
functioning as a knife on the opposed topside surface. Although the purpose of the knife edge therein is only to be used as an all purpose knife,
FIG. 6
therein describes a pointed tip
13
that is enhanced in
FIGS. 10 and 11
that could be used to penetrate a drywall slightly with either a thrusting motion or with a more powerful plunging motion by a user gripping the handle of the knife in a gripping mode with the fingers over the top of the handle. Nowhere does the Coon patent describe such a use for its drywall saw.
The Coon invention is unable to create a keyhole in the drywall because the underside of the Coon blade is flat and would exert resistant pressure against the drywall during an imagined power stroke with the user using a plunging, downwardly arced motion. During such an attempted plunging motion, assuming a user exerted maximum power by a finger overgrip position relative to the handle, the path of the blade would arc when striking with force against the drywall, whether the drywall is vertical or horizontal. Thus the flat surface bottom surface of the Coon hand saw would be pressured against the surface of the drywall during such an imagined plunging motion after initial entry of the point of the hand saw rather than the upper sharp knife edge of the saw. Thus, the Coon embodiment does not do away with the necessity of having a second tool to create a keyhole entry for secondary penetration by the drywall saw.
SUMMARY OF THE INVENTION
It is therefor an object of the present invention to provide a hand saw for cutting drywall that also can be used to penetrate a sheet of dry wall at a selected position in order to make a hole through the sheet of drywall that will accept the blade of the hand saw for subsequent sawing of the drywall for sizing in accordance with a required dimension.
In accordance with this object and other objects that will become apparent in the course of this disclosure, there is provided a hand saw for penetrating and cutting drywall, comprising a handle, an elongated blade having generally opposed blade top and bottom edges, the blade top edge being flat and said blade bottom edge having saw teeth for cutting drywall, the blade having an inner end and an opposed free end area, the inner end being attached to the handle and the free end area having a tapered sharpened cutting edge extending from the blade bottom edge at the offset saw teeth to the blade top edge. The sharpened cutting edge is formed by a pair of inwardly tapered flat surfaces of the blade between the blade top and bottom edges at the free end area that converge at the sharpened cutting edge. A pointed tip is defined by the blade flat top side, the tapered sharpened cutting surface and the pair of converging flat surfaces. A hand stop is connected to the top side of the handle. The blade bottom edge is slightly tapered upwardly relative to the blade top edge between the handle and the free end area at the sharpened cutting edge.
The present invention will be better understood and the objects and important features, other than those specifically set forth above, will become apparent when consideration is given to the following details and description, which when taken in conjunction with the annexed drawings, describes, illustrates, and shows preferred embodiments or modifications of the present invention and what is presently considered and believed to be the best mode of practice in the principles thereof.
Other embodiments or modifications may be suggested to those having the benefit of the teachings therein, and such other embodiments or modifications are intended to be reserved especially as they fall within the scope and spirit of the subjoined claims.
REFERENCES:
patent: 1171241 (1916-02-01), Potter
patent: 4907344 (1990-03-01), Hahn
patent: 5448833 (1995-09-01), Coon
patent: 5687484 (1997-11-01), Hahn
patent: 5692308 (1997-12-01), Di Libero
Lackenbach Siegel
Vaughan & Bushnell Manufacturing Company
Watts Douglas D.
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