Pencil sharpener
From Wikipedia, the free encyclopedia
A pencil sharpener (also referred to as Topper in Ireland) 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[when?] 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 an improved mechanical sharpener[1]. Electric pencil sharpeners for offices have been made since at least 1917.[2]
They now come in a wide array of colors and shapes. It is common for traditional sharpeners to have a case around them to collect the shavings. It can be removed for emptying.
[edit] Mechanical sharpeners
A mechanical pencil sharpener is a hand-powered machine. A common, portable variety is usually small and in the shape of a rectangular prism, about 1 x 5/8 x 7/16 inch (2.5 x 1.7 x 1.1 cm) in size with a conical hole on the small end. A sharp blade is mounted in a recess on the largest side such that its sharp edge just enters the cone. The body of the sharpener is often variously contoured, ridged and grooved to make it easier to grip firmly. It has no moving parts. The tip of the pencil is inserted into the hole of the sharpener and twisted, while holding the sharpener motionless. The blade inside the sharpener shaves the wood of the pencil, thus sharpening the tip, while the shavings emerge through a slot along the blade edge. An important feature is a larger clearance hole at the end of the cone allowing sections of the pencil lead which breaks away to be removed with only minor inconvenience. Such sharpeners can be bare or enclosed in a container to collect the shavings. Enclosed sharpeners can be harder to clear in the event of a blockage. The base of such a sharpener is often made of aluminum, magnesium or hard plastic.
A larger, stationary mechanical sharpener can be mounted on a desk or wall and powered by a crank. The pencil is inserted into the sharpener with one hand and the crank is turned 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, with a more precise finish than the simpler blade device. Some such rotary sharpeners have only one burr cylinder. The casing of the sharpener is a repository for the pencil shavings; it needs to be emptied periodically.
[edit] Electric sharpeners
Electric pencil sharpeners work on the same principle as mechanical ones, but the cylindrical cutter is (or cutters are) rotated rapidly by an electric motor.[3] Some electric pencil sharpeners are powered by batteries rather than being plugged into a building's electrical system, 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. Sharpeners that have two holes, one for normal pencils and one for larger art pencils are still fairly common. 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.
Carpenters still use flat pencils, originally intended to give a thicker and stronger lead, but with the same line width. These were traditionally sharpened with tools conveniently to hand, such as planes or sandpaper. Rotating pencil sharpeners are now available for these too, where a rotating plastic collar hold the pencil in position. These work poorly, as the conical point they generate removes all the advantages of the pencil's specialised shape.
Since mechanical pencils dispense the graphite stick progressively as it is used, they do not require sharpening and are not usually made of plastic or metal that and not intended to be sharpened. 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.[citation needed]
[edit] References
- ^ "20 Things You Didn't Know About... Pencils", Discover magazine, May 2007, http://discovermagazine.com/2007/may/20-things-you-didnt-know-about-pencils, retrieved on 2009-04-30
- ^ See photo at the Early Office Museum, which also shows earlier electric sharpeners used industrially.
- ^ Electric Pencil Sharpeners
[edit] External links
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Wikimedia Commons has media related to: Pencil sharpeners |
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Look up pencil sharpener in Wiktionary, the free dictionary. |
- Antique Pencil Sharpeners
- Collector of pencil sharpener (in French and partly in English)
- Dutch Collector of pencil sharpeners
