Читать книгу Essentials of Thermal Processing - Gary Tucker S., Gary S. Tucker - Страница 15

Only when thinner steel cans came into use could the can opener be invented. Before then, canned food used to come with the written instructions: ‘Cut round the top near the outer edge with a chisel and hammer’. The first can openers were primitive claw‐shaped or ‘lever‐type’ design. Robert Yeates, a cutlery and surgical instrument maker patented the first can opener in Great Britain in 1855. It was a wooden handled leaver‐type cutting blade. Three years later, in the USA, Ezra Warner patented another design (Warner et al. 1858). His looked like a bent bayonet. The large curved blade was driven into a can's rim and then forcibly worked around its edge. This first type of can opener was deemed to be too dangerous for ordinary people to use it, and the store assistants opened each can before it was taken away (http://www.wikipedia.org).

Another can opener was invented by William Lyman of the United States in 1870. It had to be pierced into the centre of the end and had a cutting wheel that rolled around the rim of the can end. It was difficult to operate as it had to be adjusted to the size of the end. A breakthrough came in 1925 when a second, serrated wheel was added to hold the cutting wheel on the rim of the can. The basic principle of this opener was the same as is used on the modern can openers. The first electric can opener was introduced in December 1931.

The easy opening end is the ultimate in convenience as far as can openers go. In the 1960s, a pull tab was patented by Ermal C. Fraze owner of the Dayton Reliable Tool Company in Ohio, USA, for aluminium ends for beverage cans. A lot of work then went into the development of an easy opening tinplate end that could withstand the requirements of being retortable and had a good shelf life. By the1980s, these ends were available commercially.