Wafer tumbler lock
This article needs additional citations for verification. (February 2008) |
A wafer tumbler lock is a type of
Early development
The earliest record of the wafer tumbler lock in the United States is a patent from 1868 by Philo Felter. Manufactured in
By 1878, Yale Lock had purchased Shepardson's company, The United States Lock Company, as well as Felter's American Lock Manufacturing Company.[2] For the next 35 years, production of wafer tumbler locks languished in the U. S. And while Felter and Shepardson had designed their wafer tumbler locks for a variety of applications such as drawer and desk locks as well as padlocks and door locks, the wafer tumbler locks made during this era were mainly used for doors in mortise locks and night-latches.
Emil Christoph developed a wafer tumbler lock in 1913 which used a double-bitted key. His patent was assigned to King Lock of Chicago, a new lock manufacturer. By 1915 Briggs & Stratton Corporation was using King wafer tumbler locks in their ignition switches. In 1919, Briggs & Stratton applied for a switch patent using a wafer tumbler lock of their own design, which used a double-bitted key. Five years later, Edward N. Jacobi of Briggs & Stratton filed for a patent for a five-wafer, single-bitted wafer tumbler lock. The first recorded use of this lock was for an automobile, the 1924 Hupp Eight.
In the UK, this type of lock was introduced by Josiah Parkes & Sons of Willenhall in 1929, who supplied them initially to the Wilmot Breeden company. Early units were stamped with a patent number on the keys, although it is not clear whether this referred to a U.S. patent or one taken out by JPS themselves. Wilmot Breeden combined leaf-tumbler barrels with parallel innovations in pressure diecasting and chromium-plating and thus became the major manufacture of vehicle body hardware in the UK nearly fifty years, supplying all of the country's vehicle manufacturers apart from Rolls-Royce and Bentley who remained with pin-tumbler designs. Early WB key-types were branded 'MRA', 'NAX', and 'MRN', the latter being used universally until 1945. British competitors copied WB patterns, even duplicating the exact cut of their keys, necessitating changes to 'FA', 'FP', and 'FS', each having some variation in fluting, or key-section. All these barrels used single-sided keys until a 'double-entry' pattern was developed for Ford in 1962, and this quickly became the standard with motor manufacturers until the advent of higher-security barrels in 1968. The first of these was 'NH', with ten tumblers arranged five per side, which was required to meet new motor industry standards for security. Subsequently WB's more advanced 'WR' series also had ten tumblers but with an asymmetrical key. Development ceased with the effective demise of WB in 1982.[citation needed]
Design
In a
A rectangular hole is cut into the center of each wafer; the vertical position of the holes in the wafers vary, so a key must have notches corresponding to the height of the hole in each wafer, so that each wafer is pulled in to the point where the wafer edges are flush with the plug, clearing the way for the plug to rotate in order to open the lock. If any wafer is insufficiently raised, or raised too high, the wafer edge will be in one of the grooves, blocking rotation.
Types and wafer arrangements
Wafer tumbler lock configurations vary with manufacturer. The most common is the single-bitted, five-wafer configuration[3] most commonly found on desk drawers, cabinets, key switches, lockers, cash boxes and electrical panels.
Some wafer tumbler locks use a stack of closely spaced wafers designed to fit a specific contour of a double-sided key and work on the principle of a carpenter's
Wafer tumbler locks can use single-bitted or double-bitted keys. Though wafer arrangements within the plug may vary, such as automotive locks, where the wafers are arranged in opposed sets, requiring a double-bitted key, the operating principle remains the same.
Crushable wafer tumbler lock
At one time, several manufacturers made a "crushable wafer tumbler"
Vulnerabilities
Most wafer tumbler locks with poor tolerances can be opened with a set of jigglers or try-out keys. These sets of keys are designed with the most common patterns of key available. The key is inserted into the lock like a normal key, and a turning force is applied whilst the key is raked back and forth until the lock opens.
References
- ^ Hennessy, Thomas F. (1997) [1976]. Locks and Lockmakers of America, Revised 3rd Edition. Locksmith Publishing Corp.
- ^ Yale and Towne Catalogue #10. Yale and Towne Manufacturing Co. 1880.
- ^ "Most Common Type Of Wafer Tumbler Lock Configuration |". 2023-02-18. Retrieved 2023-02-20.
- ^ Practical Course in Modern Locksmithing. Nelson-Hall Publishing Co. 1943.