2. Apply an appropriate force downward to pass the blade through the tank cover.
3. Gently lift the can cover upward, keep the blade forward, and continuously and forcefully rotate the can cover for one or more turns, so that the can cover can be easily opened.
During the period from 65438 to 2009 in the 1920s, the British explorer William Parry led many polar researchers across Baffin Bay and the long frozen soil to the North Pole. The explorers used a kind of equipment that can ensure their survival in the cold polar environment: canned food. Thin tin cans can prevent the food they bring from going bad. But the trouble is that it is difficult to open these cans when eating. Listen to the canned roast veal, and there will be such instructions: please open it from the top with a hammer and chisel.
18 12 years, Brian Tang Jinfa, a British engineer and papermaker, understood this method of preserving food in metal cans, and it became one of the few products that could not be separated from auxiliary tools. Obviously, Jintang thinks that how to make a set of tools for opening cans is someone else's business.
Early tin cans were much heavier than the food they contained. /kloc-At the beginning of the 9th century, soldiers opened cans with bayonets. Later, during the American Civil War, hungry soldiers shot and opened these cans to eat. In contrast, the first screwdriver used to open cans did not improve much. It takes a sharp tool to drill through the top of the can. People must carefully saw the iron sheet along the circumference of the can lid to expose the food in the can, but it is troublesome and even dangerous to do so. Customers often use their own tools to open these cans, or simply ask the owner for help.
In the late 1950s, when manufacturers could make thinner cans, the design of screwdriver made a breakthrough. 1858, ezra Werner applied for a patent: screwdriver with blade. People can forcibly insert the blade into the tank cover instead of smashing it in, and there is also a small metal guard to ensure that the screwdriver will not go too deep into the tank and prevent the liquid in the tank from spilling out. In addition, the curved blade can grasp the edge of the can lid, thereby removing the lid. Werner is too optimistic to claim that his technology can even be easily and safely operated by children.
But the first screwdriver that was really widely used in the United States was the "bull's head" screwdriver that appeared in the late19th century. It was named after the shape of the cast iron head that fixed the blade of the screwdriver. It has two blades, the short and sharp one can be inserted into the cover, and then the longer one can be cut along the edge of the cover, which is much more convenient than the screwdriver of 1858 Werner. This kind of screwdriver was so popular at that time that we can often see them in antique shops today.
William Lehman applied for a magic wheel knife screwdriver at 1870. However, there are still serious flaws in his design. When in use, one end of the screwdriver must accurately pierce the central part of the cover, and then it will serve as the fulcrum for cutting. In addition, this screwdriver must be adjusted according to the shape of the jar.
1925, Star Paiqi subsidiary in San Francisco added a serrated gear to Lyman's wheel cutting machine, which can run on the lower edge of the cover. At this point, the innovation of screwdriver has entered a new era. When this screwdriver works, it can be opened smoothly by squeezing the lid with two wheels. The electric screwdriver appeared in 193 1, and its working principle is the same as that of the star screwdriver, and it is still used by people.
The technology of opening beverage cans has gone through different paths. Wineries and beverage factories use tin cans instead of glass bottled drinks, not for long-term preservation, but because tin cans are cheap and can be thrown away after use. People usually don't have to open the lid completely. The well-known "church key" screwdriver can open a triangular hole in the bottle cap so that they can sip and drink at the same time.
In the late 1950s, the appearance of ultra-thin aluminum cans enabled people to open cans without special tools. The lid of this can is connected with a small round pull ring, which is easy to open, but it also produces a lot of garbage. For more than ten years, this kind of abandoned pull ring can be seen everywhere, and it was not until the law stipulated that the pull ring must be connected with the lid after opening the can that this phenomenon was stopped.
In recent 70 years, although there is still much room for improvement, the design of screwdriver has not changed much. Ordinary manual screwdriver often causes the lid to fall into the can, leaving the trouble of taking out the sharp metal disc. An unpopular design is to open the can from the lower edge of the lid with a wheel knife to solve this problem. The lid was indeed taken away, but the mouth of the jar left a sharp edge. The old screwdriver for opening cans with a blade has not been completely eliminated. Nowadays, the screwdriver named "john wayne" used by campers is a special accessory of Swiss army knives and other portable knives. Some electric screwdrivers are designed with magnets to attract the cover, while others have many accessories, which can be used for opening bottles, cans or plastic bags, sharpening knives and other purposes.
Perhaps in the next few decades, with the rapid development of information technology, genetic engineering and atomic physics, screwdriver will be more and more perfect, but perhaps with the improvement of food packaging, people no longer need it.