The present invention relates generally to devices for sharpening pencils and more particularly to sharpeners designed for the flattened style of carpenter's pencils.
The need for a sharpening device designed for the sharpening of a carpenter's pencil has long been well known, as sharpening has generally required the use of a utility knife to accomodate the odd shape of the pencil. The difficulty of sharpening this style of pencil with such a sharpening device without leaving wood on the broad sides of the rectangular pencil lead has long presented a major obstacle. For example, in U.S. Pat. No. 5,077,903 a sharpener is presented with dual rotary cutter assemblies arranged to cut two curves in the point. In U.S. Pat. Nos. 4,759,129 and 4,918,816 four cutters and associated gearing are similarly used to achieve the desired sharpening effect on a carpenter's pencil. In U.S. Pat. No. 4,081,010 a cutting blade is driven around the pencil in a complicated “eccentric” motion by means of cams to achieve the required pencil point shaping. All of these references, however, require complex configurations with many blades, gears and motors.
One solution is presented by U.S. Pat. No. 6,092,293 issued to Donaldson for a pencil sharpener and owned by assignee of this application. Donaldson discloses the use of a curved blade or a blade that is bent to define straight sections which enables the blade to more closely form an ideal contour of the contour of the carpenter's pencil as it is rotated. The curved blade removes enough wood to expose a good writing pencil tip but not too much wood resulting in a weak tip that could break with little pressure.
While providing a high quality sharpener that consistently forms good writing pencil tips, the sharpener of Donaldson can be relatively expensive due to the need to form a curved or bent blade. Thus, another more economical alternative solution, while not necessarily providing quite as good a pencil point as disclosed in Donaldson, is desired.
The present invention discloses a simplified and economical solution for a device which will sharpen a carpenter's pencil without the need of providing a curved or bent blade. Particularly, a carpenter's pencil sharpener for cutting a point on a flat pencil has a base enclosure and a centering collar rotatably mounted on the base enclosure. The base enclosure and the centering collar cooperatively generally define a longitudinal central axis. The base enclosure has a pencil contour surface generally matching a desired contour of the pencil. The centering collar positions the pencil generally along the central axis during rotation of the centering collar. A flat blade has a cutting edge positioned along the contour surface at an angle of approximately 10-13 degrees relative to the central axis for cutting against the pencil when the pencil is rotated about the central axis. In other alternatives, the contour surface is generally a right circular cone.
Further aspects of the invention will be discerned with reference to the following detailed description when taken in conjunction with the drawings, in which:
Referring to
The collar 14 further presents an opening 18 for insertion of a carpenter's pencil 23 to be sharpened, and in the preferred embodiment the collar opening 18 is in the form of intersecting rectangular slots 18a/18b (
Within the base enclosure 12 there is a pencil point contour surface 22 defined about central axis 13, the inside shape of which is depicted in
A flat straight blade 26 is generally aligned with an edge 22a of the contoured surface 22, and is held on the base enclosure 12 by pin(s) and/or screw(s). It has been determined that positioning the flat straight blade 26 on an incline at an angle ∀ if 10 to 13° relative to the central axis 13 (best shown in
As best shown in
From the foregoing description, it will be apparent that modifications can be made to the apparatus without departing from the teachings of the present invention. Accordingly, the scope of the invention is only to be limited as necessitated by the accompanying claims.
While preferred embodiments of the present invention have been illustrated in the appended drawing and described in the detailed desciption above, the present invention is not limited thereto but only by the scope and spirit of the appended claims.
This application is a continuation of U.S. patent application No. 10/875,828, filed Jun. 24, 2004, which claims the benefit of U.S. Provisional Patent Application No. 60/482,919, filed Jun. 27, 2003.
Number | Date | Country | |
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60482919 | Jun 2003 | US |
Number | Date | Country | |
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Parent | 10875828 | Jun 2004 | US |
Child | 11670629 | Feb 2007 | US |