SAFE 31 3D model
The first safes appeared in England in the XIX century, with an increase in the number of capitalists. It was then that simple chests and cupboards were replaced by cabinets made of steel and equipped with strong locks. They were extraordinarily reliable - before the invention of an acetylene-oxygen burner. After that, two layers of metal were added, additionally paved with copper and a layer of concrete.
At first the safes were locked with a key. Burglars opened them, cracking locks with crowbar or exploding with gunpowder, piled into the keyhole. Mechanical locks were invented - coded with a dial, which was typed on several rotated disks.
Such locks began to open with the use of a medical stethoscope - because when the digit occupied the correct position, there was a slight click. Some have learned to feel the vibration of the door when the lock is clicked. This defect was overcome after the Second World War, when dial dials and locks began to issue a series of additional clicks, which prevented the correct selection of combinations. To implement false clicks, additional slave spring-loaded discs were introduced, which, with each rotation of the dial, produce loud, uneven clicks. Usually in the design of modern mechanical combination locks there are two slave discs of different diameters - which completely overlaps the noise of clicks of the key code elements of the lock
In the 1960s, the robbers began using drills with a diamond bit that moved hydraulically and overcame the concrete. A measure against this is the addition of corundum (solid alumina) to the concrete. Now the most modern tool of the burglar is a welding lamp, creating a temperature of more than 3000 degrees. But if you add graphite to the mixture that fills the walls, then when using this lamp, the mixture begins to smoke heavily, and it is impossible to stay close to the safe. To overcome this protection, robbers recently steal safes without opening them on the spot. With the help of modern hydraulic loading equipment, it is possible to remove even very heavy safes, which are then opened in a convenient place.
Also, a case was recorded when a refrigerator was used to break into a safe. The safe was in it for three days, after which it was smashed by a sledge hammer.