Pencil sharpener
From Wikipedia, the free encyclopedia
A pencil sharpener (also referred to as pencil parer) is a device for sharpening a pencil's point by shaving one end. Pencil sharpeners exist in both electric and hand-powered forms.
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[edit] History
Pencils were in use before the development of devices specifically to sharpen them. Previously, they were sharpened by shaving with a knife. Pencil sharpeners made this task much easier and gave a more uniform result. Some specialized types, such as a Carpenter's Pencil are still usually sharpened with a knife, due to their flat shape, though recently a fixed-blade device with a rotatable collar has become available.
Bernard Lassimone, a French mathematician, applied for the first patent (French patent #2444) on pencil sharpeners, in 1828. In 1847, Therry des Estwaux invented the manual pencil sharpener. Although John Lee Love invented the portable sharpener originally made for artists. One source claims that the Hammacher Schlemmer Company of New York offered the world's first electric pencil sharpener, as designed by Raymond Loewy, sometime in the early 1940s. (Source - about.com)
[edit] Mechanical sharpeners
A mechanical pencil sharpener is hand-powered.
A common, portable variety is usually small, about 1 inch (2.5 cm) in size, and has no moving parts though this is not always so. One inserts the tip of the pencil into one of the holes, and twists the sharpener or the pencil while holding the other motionless. A blade inside the sharpener shaves the wood of the pencil, thus sharpening the tip. Such sharpeners can be bare or enclosed in a container to collect the shavings. The base of such a sharpener is often made of aluminium, magnesium (presumably to prevent an iron or steel blade from rusting), or hard plastic.
There are also larger stationary mechanical sharpeners, powered by a crank. These are often screwed or bolted to a wall or desk. One inserts the pencil into the opening with one hand and turns the crank with the other. This rotates a set of cylindrical burrs in the mechanism, set at an angle to each other; this quickly sharpens the pencil. The casing of the sharpener is a repository for the pencil shavings; it needs to be emptied periodically. This type of mechanism was long the standard in offices, schools, and libraries before electric sharpeners became common, and these sturdy devices are still found.
[edit] Electric sharpeners
Electric pencil sharpeners work on the same principle as mechanical ones, but the blade is rotated rapidly by an electric motor. Some electric pencil sharpeners are powered by batteries, rather than by electrical plugs, making them more portable.
[edit] Specialized pencil sharpeners
Specialized sharpeners are available that operate on non-standard sizes of pencil, such as large art pencils used in primary schools and carpenters' rectangular pencils. Some mechanical sharpeners have a large hole with a rotating disk in front of it that has several holes of different sizes.
Sharpeners of similar design for use on wax crayons are also available, and often included in boxes of crayons. These often have plastic blades for the softer wax.
Since mechanical pencils dispense the graphite stick progressively as it is used, they do not require sharpening and are usually made of some unsharpenable material such as plastic or metal. Such pencils are sometimes called "self-sharpening pencils." However, prolonged writing periods often cause one side of the graphite to become lopsided and dull. Specialized versions of "pencil sharpener", known as graphite pointers are available for drafters or other mechanical pencil users that demand constantly-sharp points.
There exist knives designed for pencil-sharpening, though they are used rarely in the United States. They resemble narrow razor blades.
