A can opener (also known as a tin opener) is a device used to open metal cans.
The first tin cans, invented in 1810, were heavy-weight containers that required ingenuity to open, using knives, chisels or even rocks. Not until cans started using thinner metal about 50 years later were any dedicated openers developed.
Many variations exist, ranging from simple small and lightweight openers having no moving parts such as the "butterfly" can opener, or those incorporated in many pocket knives, to dedicated electrically-operated kitchen appliances with featuring degrees of automation. Ezra Warner of Waterbury, Connecticut, U.S. was first, in 1858, to patent a can opener. The cutting wheel can opener was invented by William Lyman in 1870. The Star Can Company of San Francisco, California introduced a modified design with a serrated rotating wheel in 1925. The first electric can opener debuted in 1931, modeled after the cutting-wheel design. The 1950s and 1960s saw the variety of canned goods increase. Wall-mounted can openers were introduced with gear-driven cutting wheels operated by a handle. Most featured a magnet to hold the lid once it had become separated from the body of the can, thereby preventing the lid from falling into the contents of the can, as well as the danger of cutting oneself on the sharp edge while trying to extract the severed lid. They were available in a range of colors to match the increasingly brighter kitchen units of the time. In 1968 Sunbeam produced an electric combination can opener/knife sharpener in avocado green.
Electric openers became available in the 1960s, either as wall-mounted or free-standing appliances. The can is placed against the cutting wheel and held in place by a lever. The motor drives the blade around the can, switching itself off automatically once the can is open. Black & Decker currently produce seven types, some with built-in knife sharpeners and bottle openers.
A new style of can opener has recently emerged (US Patent 5,946,811) -- it cuts the rim neatly in half in the plane of the flat end, leaving half of the rim attached to the can and the other half attached to the flat end. No sharp edges are produced on the lid. The driving teeth are very much finer than those of the classical can opener and reside at the bottom of a V-shaped groove which surrounds the rim on three sides at the point of action.