Editing Combination lock

{{Short description|Lock using symbols rather than a key}}
{{Use Indian English|date=January 2018}}
{{Use dmy dates|date=November 2020}}
{{More citations needed|date=June 2009}}

[[File:5-digit Wordlock locked with combination Basin and hardened shackle.jpg|thumb|right|A [[Wordlock]] letter combination lock.]]
A '''combination lock''' is a type of [[Lock and key|locking device]] in which a [[sequence]] of symbols, usually numbers, is used to open the lock. The sequence may be entered using a single rotating dial which interacts with several discs or ''cams'', by using a set of several rotating discs with inscribed symbols which directly interact with the locking mechanism, or through an electronic or mechanical keypad. Types range from inexpensive three-digit [[luggage locks]] to high-security [[safe]]s. Unlike ordinary [[padlock]]s, combination locks do not use keys.

[[File:Combination discs.png|frame|Exploded view of the rotating discs. The notches on the disc correspond to the numerals in the correct combination. In this case, the combination is 9-2-4.]]
[[File:Combination unlocked.png|frame|The discs are mounted on one side of the lock, which may in turn be attached to the end of a chain or cable. The other side of the lock, or the other end of the cable, has a pin with several protruding teeth.]]
[[File:Combination locked.png|frame|When the toothed pin is inserted and the discs are rotated to an incorrect combination, the inner faces of the discs block the pin from being extracted.]]
[[File:CombinationLock.jpg|thumb|right|250px|A simple combination 
lock.]]

==History==
The earliest known combination lock was excavated in a [[Ancient Rome|Roman]] period tomb on the [[Kerameikos]], [[Athens]]. Attached to a small box, it featured several dials instead of keyholes.<ref name="Hoepfner (1970)">{{Cite journal
| last = Hoepfner
| first = Wolfram
| title = Ein Kombinationsschloss aus dem Kerameikos
| journal = Archäologischer Anzeiger
| pages = 210–213
| volume = 85
| issue = 2
| year = 1970
}}</ref> In 1206, the [[muslims|Muslim]] engineer [[Ismail al-Jazari]] documented a combination lock in his book ''al-Ilm Wal-Amal al-Nafi Fi Sina'at al-Hiyal'' (''The Book of Knowledge of Ingenious Mechanical Devices'').<ref name=Vallely>Paul Vallely, [https://web.archive.org/web/20080517055128/http://www.independent.co.uk/news/science/how-islamic-inventors-changed-the-world-469452.html How Islamic Inventors Changed the World], ''[[The Independent]]'', 11 March 2006.</ref> Muhammad al-Asturlabi (ca. 1200) also made combination locks.<ref>{{cite book |last1=Canby |first1=Sheila R. |last2=Beyazit |first2=Deniz |last3=Rugiadi |first3=Martina |last4=Peacock |first4=A. C. S. |title=Court and Cosmos: The Great Age of the Seljuqs |date=27 April 2016 |publisher=Metropolitan Museum of Art |isbn=978-1-58839-589-4 |page=188 |url=https://books.google.com/books?id=BPrjCwAAQBAJ&pg=PA188 |language=en}}</ref>

[[Gerolamo Cardano]] later described a combination lock in the 16th century.

U.S. Patents regarding combination padlocks by J.B. Gray in 1841<ref>Permutation padlock. Found in [[Google Books]]. [https://patents.google.com/patent/US2261A/]</ref> and by J.E. Treat in 1869<ref>Improvement in permutation padlocks [[Google Books]].[https://patents.google.com/patent/US93501A/]</ref> describe themselves as improvements, suggesting that such mechanisms were already in use.

Joseph Loch was said to have invented the modern combination lock for [[Tiffany & Co.|Tiffany's Jewelers]] in New York City, and from the 1870s to the early 1900s, made many more improvements in the designs and functions of such locks.<ref>"IMPROVEMENT IN TUMBLERS FOR PERMUTATION-LOCKS" by Joseph Loch, U.S. patent 200070, 5 February 1878.  Found in [[Google Books]]. [https://patents.google.com/patent/US200070A/]</ref> However, his patent claim states: "I do not claim as my invention a tumbler composed of two disks, one working within the other, such not being my invention.", but there is no reference to prior art of this type of lock.

The first commercially viable single-dial combination lock was patented on 1 February 1910 by John Junkunc, owner of American Lock Company.<ref>{{Cite web|url=https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US948280.pdf|title=US948280.pdf|website=docs.google.com|language=en|access-date=2017-04-15}}</ref>

== Types ==

===Multiple-dial locks===
One of the simplest types of combination lock, often seen in low-security [[bicycle]] locks, [[briefcase]]s, and [[suitcase]]s, uses several rotating discs with notches cut into them.  The lock is secured by a pin with several teeth on it which hook into the rotating discs.  When the notches in the discs align with the teeth on the pin, the lock can be opened.

[[File:Masterpadlock.jpg|thumb|left|A single-dial padlock by [[Master Lock]].]] [[File:Stoplock Dismantled.jpg|thumb|right|The component parts of a Stoplock combination padlock.]]

===Single-dial locks===
The [[rotary combination lock]]s found on [[padlock]]s, lockers, or [[safe]]s may use a single dial which interacts with several parallel discs or ''cams''. Customarily, a lock of this type is opened by rotating the dial clockwise to the first numeral, counterclockwise to the second, and so on in an alternating fashion until the last numeral is reached. The cams typically have an indentation or notch, and when the correct [[permutation]] is entered, the notches align, allowing the latch to fit into them and open the lock.

The C. L. Gougler Keyless Locks Company manufactured locks for which the combination was a set number of audible clicks to the left and right, allowing them to be unlocked in darkness or by the vision-impaired.{{citation needed|date=July 2021}}

In 1978 a combination lock which could be set by the user to a sequence of his own choosing was invented by Andrew Elliot Rae.<ref>{{cite web |last1=Rae |first1=Andrew E. |title=Combination lock |url=https://patents.google.com/patent/US4290286A |website=Google Patents}}</ref> At this time the electronic keypad was invented and he was unable to get any manufacturers to back his mechanical lock for lockers, luggage, or brief-cases. The silicon chip locks never became popular due to the need for battery power to maintain their integrity. The patent expired and the original mechanical invention was instantly manufactured and sold worldwide mainly for luggage, lockers, and hotel safes. It is now a standard part of the luggage used by travellers.

===Other designs===
Many doors use combination locks which require the user to enter a numeric sequence on a [[keypad]] to gain entry. These special locks usually require the additional use of electronic circuitry, although purely mechanical keypad locks have been available since 1936.<ref>{{US patent|2029080}}</ref> The chief advantage of this system is that multiple persons can be granted access without having to supply an expensive physical key to each person. Also, in case the key is compromised, "changing" the lock requires only configuring a new key code and informing the users, which will generally be cheaper and quicker than the same process for traditional key locks.

[[electronic lock|Electronic combination locks]], while generally safe from the attacks on their mechanical counterparts, suffer from their own set of flaws. If the arrangement of numbers is fixed, it is easy to determine the lock sequence by viewing several successful accesses. Similarly, the numbers in the combination (but not the actual sequence) may be determined by which keys show signs of recent use. More advanced electronic locks may scramble the numbers' locations randomly to prevent these attacks.

There is a variation of the traditional dial based combination lock wherein the "secret" is encoded in an electronic microcontroller.  These are popular for safe and [[bank vault]] doors where tradition tends towards dial locks rather than keys.  They allow many valid combinations, one per authorized user, so changing one person's access has no effect on other users.  These locks often have auditing features, recording which combination is used at what time for every opening.  Power for the lock may be provided by a battery or by a tiny generator set in operation by spinning the dial.<ref>{{cite web|title=Kaba-MAS X-09 and CDX-09 High Security Locks|url=http://www.kaba-mas.com/pdf/brochures/x_09.pdf|pages=8|date=Dec 2010}}</ref><ref>{{cite web|title=Operating Instruction for the X-09 Type 1F High Security Electronic Lock|url=https://portal.navfac.navy.mil/portal/page/portal/NAVFAC/NAVFAC_WW_PP/NAVFAC_NFESC_PP/LOCKS/PDF_FILES/X-09_Operating_Instructions.pdf|date=December 2010|url-status=dead|archive-url=https://web.archive.org/web/20110728015227/https://portal.navfac.navy.mil/portal/page/portal/NAVFAC/NAVFAC_WW_PP/NAVFAC_NFESC_PP/LOCKS/PDF_FILES/X-09_Operating_Instructions.pdf|archive-date=28 July 2011}}</ref>

==Internal mechanisms ==
* A relock trigger, or internal relocker, is an integral part of the combination lock itself.  It is usually designed to activate when the dial spindle is punched through.  The trigger may consist of a spring-loaded lever or plunger that engages the bolt when the back cover is dislodged from the lock case.  Some combination locks also are equipped with a thermal relock trigger that activates in the event of a torch attack. Nearly all safes made after World War II have relock triggers in their combination locks.

==Manufacturers==
*[[ABUS]]
*[[Master Lock]]
*[[Sargent & Greenleaf]]
*[[Wordlock]]
*Dudley
*[[Conair Corporation|Conair]]
*Kaba Mas
*CJSJ

==See also==
* [[Electronic lock]]
* [[Password]]
* [[Immobiliser]]
* [[Keycard]]

==References==
{{Reflist}}

==External links==
{{Commons category|Combination locks}}
* [http://home.howstuffworks.com/combination-lock.htm How Combination Locks Work] HowStuffWorks.com

{{Locksmithing}}

{{DEFAULTSORT:Combination Lock}}
[[Category:Locks (security device)]]
[[Category:Locksmithing]]

[[de:Schloss (Technik)#Zahlenschloss]]