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a closing device. Locks first appeared in the ancient empires of Assyria, Babylonia, and Egypt in about the second millennium B.C. Even the lock designs used in ancient Egypt incorporated elements used in modern locks. In Kievan Rus’, locks of various types were made that provided for the individuality of each lock. Modern locks are classified according to their design and the action of their mechanism as locks with and without tumblers, cylinder locks, and combination locks. Locks may be removable (including padlocks) or stationary, permanently installed (built-in, mortised, or surface-mounted locks).
In locks without tumblers, when the key is turned the crossbar (latch) is checked by a spring-loaded “dog” that enters the groove of the latch plank. The security of the lock is provided mainly by the shaped profile of the keyhole. In tumber locks, the crossbar (latch) consists of a set of differently shaped movable plates (tumblers). The key may be turned only if the projections of the key bit correspond exactly to the edges of certain tumblers. In such locks it is possible to provide various combinations of tumblers— for example, four standard tumblers arranged in certain sequences will yield 24 lock series.
The principle of operation of cylinder locks is analogous to that of tumbler locks, but pins are used instead of tumblers. If the pins fully enter the radial channels of the cylindrical core, the core can be rotated around its axis and the latch can be displaced. To achieve this, the lock’s “own” key must be inserted into the keyhole. If even only one of the notches on the working edge of the key displaces a pin with an error on the order of 0.1 mm, the key will not turn. This apparatus provides the high security of cylindrical mechanisms, which are virtually unique for each lock. The series of a lock is determined by the relative location of the pins; such a series can be expressed by a four-digit or five-digit number marked on the key. The security of cylindrical locks can be improved by changing the profile of the key slot in three dimensions. Combination locks contain not only the usual elements of a lock mechanism but also features to make possible their opening with or without a key by setting levers or rings according to a combination of numbers or letters assigned to the particular lock. In stationary locks, reliability can be improved by the use of two or more keys. The lock mechanism can be connected to a clock, so that the lock may be used only during predetermined time periods. Locks can also be connected to blocking, remote-control, or alarm systems.
In addition to various locks for doors and furniture, specially designed locks are used for other applications (for example, jewelry).
REFERENCEGoberman, G. E., and V. I. Bychkov. Zamki i skobianye pribory. Moscow, 1962.
G. Iu. FILANOVSKII
in navigation, a hydraulic engineering installation that is located between bodies of water with different levels and through which vessels or rafts pass. Locks are built on canals, at hydraulic
engineering complexes on rivers, and in seaports whose water area experiences large-amplitude tides.
A sketch of a lock was discovered in the papers of Leonardo da Vinci. Locks were first built in Western Europe in the 16th century and in Russia—on the Vyshnii Volok Water System—in the 18th century. In the USSR, many large locks have been constructed on numerous navigation canals, at reservoirs, and at hydraulic engineering complexes on the Volkhov, Dnieper, Svir’, Volga, and Kama rivers. A substantial number of large locks have been built in Western Europe and in the USA, for example, on the Ohio, Mississippi, and St. Lawrence rivers.
A lock (Figure 1) consists of chambers, ends, and approaches. A lock chamber, in which vessels to be raised or lowered are held, is formed by two longitudinal walls and a floor. As a rule, the walls and floor are made of reinforced concrete. The chamber is sealed by metal gates located within the upstream and downstream ends. According to the number of successive chambers in a lock, a distinction is made between single locks and flights of locks. The number of chambers in a lock depends on the magnitude of the change in water level and on the relief of the terrain. To increase the traffic capacity of a lock, two or more lanes of chambers are built in tandem.
The main dimensions of lock chambers—that is, their length and width—are chosen when a lock is designed. They depend on the category of the waterway, the amount of freight expected to be handled on the waterway, and the size of the largest vessel, train, or convoy the lock is designed to accommodate at one time. The chambers of the largest locks are up to 33 m wide, up to 400 m long, and—in locks in seaports—from 5 to 15 m deep at the sea entrance. Lock chambers are filled or emptied in a prescribed time, from 5 to 15 min, by means of filling or emptying valves and a culvert system.
The ends of a lock are usually massive headworks. In addition to gates, which maintain the difference in water levels and permit vessels to pass through when the levels of adjacent pools are equalized, the ends contain sluice culverts, equipment for eliminating water turbulence, repair and emergency booms, equipment control mechanisms, and automatic control systems. The approaches to a lock’s upstream and downstream ends comprise canals for sectors of a water area that contain both berthing facilities and facilities for mooring ships waiting to be locked and guiding structures for the safe entry of vessels into the lock.
The process of passing vessels through a lock, called lockage, consists in a sequence of operations that are carried out in accordance with commands issued from a control center. The operations include the opening and closing of gates and valves, the filling of the lock chambers with water, the emptying of the chambers, and the entry and departure of vessels. The number of lockages completed in a day during the continuous operation of a lock determines the traffic capacity of the lock.
REFERENCESMikhailov, A. V. Sudokhodnye shliuzy. Moscow, 1966.
Grishin, M. M. Gidrotekhnicheskie sooruzheniia. Moscow, 1968.
A. V. MIKHAILOV
What does it mean when you dream about a lock?
Locks in a dream may represent an inability to get what one wants, or being kept out. Perhaps some ability is locked up inside and needs to be expressed. Locks can also be symbols of security.