A can opener (also known as a tin opener) is a device used to open metal cans. Although preservation of food using tin cans had been practiced since at least 1772 in the Netherlands, the first can openers were patented only in 1855 in England and in 1858 in the United States. Those openers were basically variations of a knife, and the 1855 design continues to be produced. The first opener employing the now familiar sharp rotating wheel, which runs around the can's rim cutting the lid, was invented in 1870 but was difficult to operate. A breakthrough came

in 1925 when a second, serrated wheel was added to hold the cutting wheel on the rim of the can. This easy to use design has become one of the most popular can opener models.

Around the time of World War II, several can openers were developed for military use, such as the P-38 and P-51. These featured a robust and simple design where a folding knife and absence of a handle significantly reduced the opener size. Electric can openers were introduced in the late 1950s and met with success. The development of new can opener types continues with the recent addition of a side-cutting model.

Invention of cans

Food preserved in tin cans was in use by the Dutch Navy from at least 1772. Before 1800, there was already a small industry of canned salmon in the Netherlands. Freshly caught salmon were cleaned, boiled in brine, smoked and placed in tin-plated iron boxes. This canned salmon was known outside the Netherlands, and in 1797 a British company supplied one of their clients with 13 cans. Preservation of food in tin cans was patented by Peter Durand in 1810. The patent was acquired in 1812 by Bryan Donkin who had later set up the world’s first canning factory in London in 1813. By 1820, canned food was a recognized article in Britain and France and by 1822 in the United States. First cans were robust containers, which weighed more than the food they contained and required ingenuity to open, using whatever tools available. The instruction on those cans read "Cut round the top near the outer edge with a chisel and hammer."

First, lever-type can openers

fulcrum in use". This robust design survives today.

In 1858, another lever-type opener of a more complex shape was patented in the US by Ezra Warner of Waterbury, Connecticut. It consisted of a sharp sickle, which was pushed into the can and sawed around its edge. A guard kept the sickle from penetrating too far into the can. The opener consisted of several parts which could be replaced if worn out, especially the sickle. This opener was adopted by the US Army during the American Civil War (1861-1865); however, its unprotected knife-like sickle was too dangerous for domestic use. A home-use opener named the "Bull's head opener" was designed in 1865 and was supplied with cans of pickled beef named "Bully beef". The opener was made of cast iron and had a very similar construction to the Yates opener, but featured a more artistic shape and was the first move towards improving the look of the can opener. The bull-headed design was produced until the 1930s and was also offered with a fish-head shape.

The Bunker opener

can's rim.The necessity to pierce the can first was a nuisance, and this can opener design has not survived till present days. In 1925, the Star Can Opener Company of San Francisco, California had improved the Lyman's design by adding a second, toothed wheel called "feed wheel", which allowed a firm grip of the can edge. This addition was so efficient that the design has been adopted until present days.

Whereas all previous openers required using one hand, or other means, to hold the can, can-holding openers both hold the can and open it. The first such opener was patented in 1931 by the Bunker Clancey Company of Kansas City, Missouri and was therefore called the "Bunker". It featured the now standard pliers-type handle, grasping which would tightly hold the can, while turning the key would rotate the cutting wheel progressively cutting the lid along the rim. The Bunker company was absorbed by the Rival Manufacturing Company, also of Kansas City, in 1938.

Churchkey

Lagering cellars in the monasteries were locked, as the monks guarded the secrets to their craft The monks carried keys to these lagering cellars on their cinch, or belt. It may have been this key from which the "Church Key" opener got its name. Another motive for assigning the device such an ironic name could have been the fact beer was first canned (for test marketing) in 1933 — the same year Franklin Delano Roosevelt signed the Cullen-Harrison Bill. This act, which predated Repeal of Prohibition, amended the Volstead Act, making 3.2 beer legal. Some experts have posited the term "church key" was a way to "stick it to" the religious organizations who had effected Prohibition in the first place.

Another key opener with completely different design was patented by J. Osterhoudt in 1866. Instead of piercing the can it was used to roll a stripe off the can. It was also called "key", because of resemblance to a door key. Such openers are attached to many small, thin-walled cans nowadays.

Military use can openers

opening a can of K-rations. The P-38 can opener is keychain-sized (about 1.5 inches, 38mm, in length) and consists of a short metal blade that serves as a handle (and can also be used as a screwdriver), with a small, hinged metal tooth that folds out to pierce the can lid. A notch just under the hinge point keeps the opener hooked around the rim of the can as the device is "walked" around to cut the lid out. A larger version called P-51 is somewhat easier to operate. P-38 was developed in 1942 and was issued in the canned field rations of the United States Armed Forces from World War II to the 1980s. The P-38 and P-51 are cheaper to manufacture and are smaller and lighter to carry than most other can openers. The device can be easily attached to a keyring or dog tag chain using the small punched hole.

Official military designations for the P-38 include 'US Army pocket can opener' and 'Opener, can, hand, folding, type I'. As with some other military terms (e.g. jeep), the origin of the term is not known with certainty. The P-38 and P-51 openers share a designation with the P-38 and P-51 fighter planes, however this is coincidental. The most likely origin of the name is much more pedestrian; the P-38 is 38 mm (1.5 in) long. This explanation also holds for the P-51, which measures 51 mm (2.0 in) in length.

P-38s are no longer used for individual rations by the United States Armed Forces, as canned C-rations were replaced by uncanned MREs in the 1980s. They are, however, included with US military "Tray Rations" (canned bulk meals). They are also still seen in disaster recovery efforts and have been handed out alongside canned food by rescue organizations, both in America and abroad in Afghanistan. The original US-contract P-38 can openers were manufactured by J.W. Speaker Corp.

(stamped "US Speaker") and by Washburn Corp. (marked "US Androck"), they were later made by Mallin Hardware (now defunct) of Shelby, Ohio and were variously stamped "US Mallin Shelby O." or "U.S. Shelby Co.".

Standard issue "FRED" can opener of the Australian Defence ForceA similar device that incorporates a small spoon at one end and a bottle opener at the other is currently employed by the Australian Defence Force and New Zealand Army in its ration kits. The Field Ration Eating Device is known by the acronym "FRED". It is also known widely in its derogative term, the "Fucking Ridiculous Eating Device".

Another similar device was included with British Army 'Operational Ration Pack, General Purpose' 24-hour ration pack and 'Composite Ration Pack' rations. At one stage they were manufactured by W.P. Warren Engineering Co. Ltd. The instructions printed on the miniature greaseproof paper bag they were supplied in read: "Their design is similar, but not identical, to the P-38 and P-51 can openers."

Most military use can openers have a very simple design and were and are produced for civilian use in many countries. For example, a small folded openers similar to P-38 and P-51 has been designed back in 1924 and is widely spread in the Eastern European countries.

Electric openers
A modern Krups hand-held electric can openerThe first electric can opener was patented in 1931 and modeled after the cutting-wheel design. Those openers have been produced in 1930s and advertised as capable to remove lids from more than 20 cans per minute without any risk of injury.Nevertheless, they found little success. Electric openers were re-introduced in 1956 by two Californian companies. Klassen Enterprises of Centreville brought out a wall-mounted electric model, but this complex design was unpopular too.

The same year, Walter Hess Bodle invented a freestanding device combining an electric can opener and knife sharpener.He and his family members built their prototype in his garage with daughter Elizabeth sculpting the body design. It was manufactured under the "Udico" brand of the Union Die Casting Co. in Los Angeles and came in the flamingo pink, avocado green, and aqua blue colors of the era. These openers were introduced on the market for Christmas sales and had immediate success.

Modern designs