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lock and key

 
Columbia Encyclopedia:

lock and key

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lock and key, fastening fitted to an entryway, such as a gate or door, or a container, such as a cabinet, drawer or safe, to keep it closed and/or prevent unauthorized access or use. Locks typically consist of a sliding, pivoted, or rotary bolt protected by a fixed or movable object. A lock may be opened by a mechanical, magnetic, electric, electronic, or electromechanical key or by employing a code or sequence of numbers or letters.

Mechanical Locks

There are two basic types of mechanical locks, each with variations. The oldest and simplest is the warded lock, which is essentially a spring-loaded bolt in which a notch has been cut. The key fits into the notch and slides the bolt backward and forward. The lock takes its name from the fixed projections, or wards, inside the lock and around the keyhole. The correct key has notches cut into it that match the wards, which block the wrong key from operating the lock. The ward lock is the easiest to pick and now is used only for cheap padlocks.

The tumbler lock contains one or more pieces of metal (called tumblers, levers, or latches) that fall into a slot in the bolt and prevent it being moved. The proper key has serrations that raise the metal pieces to the correct height above the slot, allowing the bolt to slide. There are three types of tumbler locks, pin-tumbler, disk-tumbler, and lever-tumbler. Pin-tumbler locks are the most common. The tumblers in this type of lock are small pins. The modern door lock is a compact pin-tumbler cylinder lock of the type developed (1860) by the American inventor Linus Yale. Door locks on automobiles and most high-security locks have pin tumblers. Disk- or wafer-tumbler locks, use flat disks, or wafers, instead of pins. When the proper key is inserted, the disks retract, releasing the bolt. Disk-tumbler locks are often used in desks and file cabinets. Lever-tumbler locks employ a series of different-sized levers resting on a bolt pin to prevent the bolt from moving. When the proper key is inserted, all the levers are raised to the same height, enabling the bolt pin to release the bolt. Lever-tumbler locks are often used in briefcases, safe-deposit boxes, and lockers.

The first of the keyless locks was the combination lock, developed at the beginning of the 17th cent. In it a number of rings inscribed with letters or numbers are threaded on a spindle. To open the lock the rings must be turned to form a code word or number, which causes the slots inside the rings to align and permits the spindle to be drawn out. A variant of the combination lock employs a movable dial with a series of numbers around it in place of the rings. The dial must be turned clockwise and counterclockwise in the proper sequence of numbers to align disk tumblers and open the lock. Once used only for padlocks, combination locks began to be used in safes and strong-room doors during the last half of the 19th cent. The time lock, first used successfully c.1875, has a clock mechanism that is set to permit opening only a certain time.

Electric and Magnetic Locks

Recent lock developments include the magnetic-key lock, in which the pins are actuated by small magnets on the key, which has no serrations. When the key is inserted into the lock, these magnets repel magnetized spring-loaded pins, raising them in the same way that the serrations on a tumbler-type key would. The card-key lock is actuated by a series of magnetic charges; the card-key is popular where security is vital, because a new series may be electronically defined for each new user, without having to change the lock itself. Similarly, electronic card access systems are used in many hotels and office buildings. A special "key" system uses a paperboard or plastic card, on which a code is recorded as a series of holes or bumps, or a microchip or a magnetic strip on which a code is stored. A card reader at the lock location reads the code and sends the information to a computer, which sends a signal to release the bolt if the code is correct. Electronic combination locks similarly use a computer to compare a combination stored in memory with one entered on a keypad; access is permitted if the combinations match. In a biometric entry system the numeric keypad is replaced by a scanner, which captures an individual's fingerprint, palmprint, signature, or other personal characteristic and compares it with that in the computer's memory. Biometric entry systems are most often used in high-security areas, such as nuclear power plants.

In an electromagnetic lock a metal plate is attached to the door and an electromagnet is attached to the doorframe opposite the plate. When the current flows, the electromagnet attracts the plate, holding the door closed, When the flow of current is stopped, the door unlocks. A variation places the plate and electromagnet so that the door is held open when current flows, enabling the door to be closed automatically when the current stops.

Keyless entry systems, which are common in motor vehicles, rely on a keychain fob that contains a remote-control unit consisting of an integrated circuit and a radio transmitter. The fob sends a low-powered radio signal to a receiver in the motor vehicle, and, if the received code is the correct one, the receiver in the vehicle relays the signal to a microprocessor, which opens the lock. The acceptance of such entry systems has led to devices that allow additional functions within the vehicle to be activated remotely.

In other keyless entry systems, radio-frequency identification (RFID) is used. An RFID tag, card, or fob is brought within range of radio waves produced by an RFID reader or interrogator, allowing data to be exchanged; when the microprocessor controlling the lock confirms that the received data is associated with someone allowed entry, the door is unlocked. RFID systems are more commonly used to control entry into buildings or rooms, and the use of a computer to control locks that use RFID allows access to specific areas to be restricted to specific people or at specific times.

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Gale Encyclopedia of Espionage & Intelligence:

Locks and Keys

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Home > Library > History, Politics & Society > Intelligence & Security Encyclopedia

Locks can be either mechanical or electronic, the latter being a modern variation for which a specific numeric code is required to release the locking mechanism. Much more common is a mechanical lock, opened by purely physical means. Locks do not have an independent existence; they must lock something or someone in or out, and they must have a key. The key is based on principles that go back to ancient times, using one of the most rudimentary types of machine known to humankind: the inclined plane.

Historical background. In the history of physics and technology, there are three simple machines: the lever, the inclined plane, and the hydraulic press. The last of these only came into existence during the 1600s, but the first two date to a time before the dawn of civilization. The simplest form of inclined plane is a ramp, which makes it possible to move an object across a vertical distance with a smaller amount of exertion than would be required to lift it straight upward. Other modifications of the inclined plane are wedges, knives, axes, screws, corkscrews, and a key and lock mechanism.

The earliest locks date back to ancient Egypt, and even the more modern variations on lock design that developed in the wake of industrialization still harken back to the design used in the pharaohs' palaces. For example, American locksmith and inventor Linus Yale, Jr., whose name remains an important one in the lock and key industry, based his cylinder lock in the 1860s on the Egyptian design. The latter consisted of a wooden housing containing wooden pegs of varying length, fitted into holes bored into the top of a wooden bolt. Only when a long wooden key with pegs of specific lengths was inserted into the bolt could it be opened.

Basic workings of a lock. Modern locks and keys are made of steel rather than wood, but otherwise the design is not remarkably different from that used to lock doors thousands of years ago. Inside a modern mechanical lock is a row of pins, usually five in number. Each pin has its own cylinder, and when the lock is locked, they hold together two pieces of metal rather as the "teeth" of a belt hold together two sections of a piece of leather. The pins are of varying length, meaning that in order to open the lock, it is necessary to raise them all together so that the bottoms are in alignment.

The solution to this problem is, quite literally, a key, whose serrated edge is actually a row of inclined planes fitted to the configuration of pins inside the lock. The notches on the key are made to push the pins upward just the right amount for each pin, so as to force them all into their respective cylinders and separate the two blocks from one another. The shape of the notches is such that the key can be withdrawn from the lock after use, at which point springs push the pins back downward into their original place.

Mechanical and electronic variations. A variation on this model is Yale's cylinder lock. In this design, the pins are lined up along a larger metal cylinder, which they hold in place inside a cylindrical housing. Inserting the proper key raises the pins and frees the cylinder so that, when it is turned, it rotates and draws back a cam that holds a bolt in place. The bolt is spring-loaded, such that when the key is withdrawn, the spring pushes the bolt back into place, turning the cylinder back to its original position and making it possible to withdraw the key.

There are other variations on the mechanical lock, most notably the old-fashioned lever lock, but the basic principle is the same. By contrast, an electronic lock requires the use of a keypad and a numeric code. The user enters a code, which the machine interprets as a series of binary (on-off) electric pulses. These pulses are bits in a number sequence, which are read by a computer chip. Assuming the sequence matches the one encoded on the chip, the latter sends out an electric signal that opens a mechanical bolt holding the lock in place.

Further Reading

Books

Macaulay, David, with Neil Ardley. The New Way Things Work. Boston: Houghton Mifflin, 1998.

Phillips, Bill. The Complete Book of Locks and Locksmithing. New York: McGraw-Hill, 1995.

Roper, C. A. The Complete Book of Locks and Locksmithing. Blue Ridge Summit, PA: Tab Books, 1983.

Sloane, Eugene A. The Complete Book of Locks, Keys, Burglar and Smoke Alarms, and Other Security Devices. New York: Morrow, 1977.

Wikipedia on Answers.com:

Lock (device)

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Home > Library > Miscellaneous > Wikipedia
"Lock and key" redirects here. For the novel by Sarah Dessen, see Lock and Key.
Padlock
Simple three-disc locking mechanism
from a wooden box recovered from
the Swedish ship Vasa, sunk in 1628

A lock is a mechanical or electronic fastening device that is released by a physical object (such as a key, keycard, fingerprint, RFID card, or security token) or secret information (such as a keycode or password), or combination of more than one of these.

Typically, in pin-tumbler and wafer-tumbler applications, a lock in the rest position is closed. The key has a series of grooves on either side of the key (the key's blade), which limit the type of lock the key can slide into. As the key slides into the lock, the grooves on the blade of the key align with the wards in the keyway allowing or denying entry to the cylinder. Then, a series of pointed teeth and notches on the blade called bittings allow pins or wafers to move up and down until they are in line with the shear line of the inner and outer cylinder, allowing the cylinder or cam to rotate freely inside the lock and the lock to open.

Contents

History of locks

Medieval lock in Kathmandu

Securing one's property has long been a concern of people throughout the world. Beyond hiding the objects or constantly guarding them the most frequently used option is to secure them with a device. Early solutions included knots to either detect, like the Thief knot, or hamper, like the Gordian Knot. Historians are unsure where the first lock was invented, but evidence suggests that locks initially developed independently in the Egyptian, Greek, and Roman civilizations. Wooden locks and keys were in use as early as 4,000 years ago in Assyria.[1] The first known lock with a key is a pin lock. The lock is strung on a rope hanging out of a hole in a door. A cylinder of wood with a hole drilled through its axis is the key, the length of the cylinder being the critical factor. The key is inserted into the hole and the bolt is pushed the correct distance. To lock the door the rope was pulled to extract the key cylinder, simultaneously pulling the bolt closed. This type of lock is still in use in certain parts of the world. Puerto Rico still uses this system[citation needed]. A disadvantage of this lock is that a vandal can push the rope into the hole — an ancient equivalent of putting glue into a lock.

The warded lock is present from the Antiquity. This lock is still used in modern times when the security required is not high and cost is a significant factor. This lock has become the most recognisable lock/key design in the Western world. Lock puzzles were used to obscure the locking mechanism or even provide a non-functioning lock for the thief to waste time on.

In the early 1900s a wooden pin lock with a wood key was discovered in Egypt and is believed to have been used in 250 b.c. [2]

Early improvements in pin locks included increasing the number of pins to increase security, and changing the orientation of the pins to allow the key to provide the unlocking force instead of a rope, thus establishing the principles of the modern pin tumbler lock.

Famous locksmiths

See also: Locksmithing
Chinese lock and key from Yunnan Province, early 20th century
  • Robert Barron patented a double-acting tumbler lock in 1778, the first reasonable improvement in lock security.
  • Joseph Bramah patented the safety lock in 1784. It was considered unpickable for 67 years until A.C. Hobbs picked it, taking over 50 hours.
  • Jeremiah Chubb patented his detector lock in 1818. It won him the reward offered by the Government for a lock which could not be opened by any but its own key.
  • James Sargent described the first successful key-changeable combination lock in 1857. His lock became popular with safe manufacturers and the United States Treasury Department. In 1873, he patented a time lock mechanism, the prototype for those used in contemporary bank vaults.
  • Samuel Segal invented the first jemmy-proof locks in 1916.
  • Harry Soref founded the Master Lock Company in 1921 and patented an improved padlock in 1924 with a patent lock casing constructed out of laminated steel.
  • Linus Yale, Sr. invented a pin tumbler lock in 1848.
  • Linus Yale, Jr. improved upon his father's lock in 1861, using a smaller, flat key with serrated edges that is the basis of modern pin-tumbler locks. Yale developed the modern combination lock in 1862.

Types of locks

A type of padlock side view.
Door with two locks, one in the door knob and a separate deadbolt.
A typical combination lock.
Placement of locks depending on door type
Locks at Hohenzollernbrücke in Cologne, Germany

Locks may be entirely mechanical, or electromechanical. They may be operated by turning some form of removable key, by keying or dialling in a combination which directly or via electromechanical means operates the lock, with some form of magnetic or other card reader, or by moving a part on a safety lock intended to prevent accidental operation rather than to prevent unauthorized access.

Warded lock

The warded lock is one of the earliest types of locks. It said to have been developed in China.

Tumbler locks

Pin-tumbler lock

The Pin tumbler lock is the most widespread lock in the western world.[3] Pin-tumbler locks have been around in some form since 2000 BCE. The Egyptian form of this lock was large, heavy, and made of wood, with pins made of metal, usually bronze, but sometimes iron. This design in its modern form was first patented in 1805 in England. The patent holder was an American named A.O. Stansbury. In the middle of the 18th century, the American locksmiths Linus Yale Sr. and his son, Linus Yale Jr., refined the lock design into the form recognizable today. These early versions of the pin-tumbler lock were expensive to produce, and did not become widely available until mass production became feasible.

Wafer-tumbler lock

The first patent for the wafer lock was issued in the United States in 1868 to P.S. Felter.[4] The wafer lock is relatively inexpensive to produce and is often used in automobiles and cabinetry. This type of lock is generally made of die-cast zinc alloy.

Lever locks

Lever locks were invented in Europe in the 17th century.[5] This is a popular lock type for safes and North American prisons today, as they are generally built of strong materials. They are also used as door locks in some countries. This is the type of lock that replaced the medieval warded lock in the 19th century. Robert Barron of England patented the double-acting lever in 1778. Jeremiah Chubb would follow with his own detector lock in 1818.

Disc tumbler lock

The disc tumbler lock or Abloy lock was invented in 1907, and is widespread in Finland. The mechanism contains no springs and is durable. Picking the lock is too hard compared to alternative means of gaining entry.

Other types

There are also many other types of lock, such as warded locks, tubular locks, electronic locks (itself a huge area) and also many variations of the various types, such as dimple locks, which are a variation on Yale's original cylinder lock in which the pins interact with the side of the key rather than the edge, "laser track" car locks, which are a variation on wafer locks, and some higher security lever locks also include the types of warding found on warded locks.

List of common locks

See also

Footnotes

  1. ^ "Locks.ru". Locks.ru. http://www.locks.ru/germ/informat/schlagehistory.htm. Retrieved 2011-11-03. 
  2. ^ "Old Locks Show Skill Of Craftsmen" Popular Science, September 1937
  3. ^ Pulford 2007, pg. 33
  4. ^ Pulford 2007, pg. 173
  5. ^ Pulford 2007, pg. 317

References

  • Phillips, Bill. (2005). The Complete Book of Locks and Locksmithing. McGraw-Hill. ISBN 0-07-144829-2.
  • Pulford, Graham W. (2007). High-Security Mechanical Locks : An Encyclopedic Reference. Elsevier. ISBN 0-7506-8437-2
  • Alth, Max (1972). All About Locks and Locksmithing. Penguin. ISBN 0-8015-0151-2
  • Robinson, Robert L. (1973). Complete Course in Professional Locksmithing Nelson-Hall. ISBN 0-911012-15-X

External links

Wikimedia Commons has media related to: Locks

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

 
 

 

Copyrights:

Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2012, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.  Read more
$copyright.smallImage.alttext Gale Encyclopedia of Espionage & Intelligence. Encyclopedia of Espionage, Intelligence, and Security. Copyright © 2004 by The Gale Group, Inc. All rights reserved.  Read more
Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Lock (device).  Read more

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