Tumblers are small objects, usually made of metal, that move within a lock cylinder in ways that obstruct a lock’s operation until an authorized key or combination moves them into alignment. There are several types of tumblers;
they come in a variety of shapes and sizes and move in different ways.
Because tumblers generally provide more security than wards, most locks today use some type of tumbler arrangement either instead of or in addition to wards.
A typical key-operated cylinder consists of a cylinder case (or housing), a plug (the part with a keyway), springs, and tumblers. The springs are positioned in a way that makes them apply pressure to the tumblers. The tumblers are positioned so that when no key is inserted, or when the wrong key is inserted, the spring pressure forces one or more of the tumblers into a position that blocks the plug from being rotated. When the proper key is inserted into the keyway, however, the key moves the tumblers to a position that frees the
plug to turn.
A lock can have more than one cylinder. A key-operated, single-cylinder lock has a cylinder on one side of the door only (usually the exterior side) so that no key is needed to operate it from the other side. Typically, it can be operated from the noncylinder side by pushing a button or by turning a knob, handle, or turn piece. Key-operated, double-cylinder locks require a key on both sides of a door. Many local building and fire codes restrict the use of double-cylinder locks on doors leading to the outside because the locks can make it hard for people to exit quickly during a fire or other emergency.
Types of tumbler locks
There are three basic types of tumblers: lever, disc, and pin. Most lever tumbler locks, such as those used on luggage, brief cases, private mailboxes, and lockers, offer a low level of security. The lever tumbler locks commonly found on bank safe-deposit boxes are specially designed to offer a high level of security. Disc tumbler locks offer a medium level of security. They’re often used on desks, file abinets, and automobile doors and glove compartments. Pin tumbler locks can provide medium to high security, but in general they offer more security than do other types of tumbler locks. Many prison locks and virtually all house locks and high-security padlocks use pin tumbler cylinders. Some automobile door and ignition locks also have pin tumblers.
A special type of pin tumbler lock, called a tubular key lock (or tubular lock), has its tumblers arranged in a circular keyway (Fig. 3.10). It uses a tubular key to push the tumblers into proper alignment. Because of its odd appearance, a tubular key lock is harder for most people to pick open than are standard pin tumbler locks. Sometimes erroneously called “Ace Locks” (which is Chicago Lock Company’s trade name for some of its tubular key locks), tubular key locks are often found on vending machines, laundromat equipment, bicycle locks, and high-security padlocks.
Another type of pin tumbler system is found in interchangeable core (IC) locks. Although they come in the form of deadbolts, key-in-knobs, rim locks, mortise locks, padlocks, and desk and cabinet locks, all locks in an IC system can either use the same key or be master keyed. Some examples of IC locks are shown in Fig. 3.11. The common feature of IC locks is a figure 8-shaped core that houses the tumblers and springs. The cores can be easily removed and replaced (Fig. 3.12). Any IC lock can be re-keyed simply by inserting new cores