Jeremiah Chubb and the Detector Lock (1818)

Background

Grace's Guide records Jeremiah Chubb's birth in 1793 at Braemore (Breamore) in Hampshire, son of Charles Chubb. According to Wikipedia's company history, the family business was begun by his brother Charles as a ship's ironmonger in Winchester and moved to Portsmouth in 1804. Jeremiah was working with Charles there as a ship's outfitter and ironmonger when the detector lock was invented (Wikipedia, "Chubb detector lock").

The live page gives Jeremiah's dates as 1793–1872. Grace's Guide records his death in 1847 at Winchester, Hampshire. This article follows Grace's Guide and flags the difference for review.

The 1817 Burglary and the Competition

In 1817 a burglary at Portsmouth Dockyard was carried out with false keys. The government responded by announcing a competition for a lock that could be opened only with its own key. Jeremiah Chubb's answer was the detector lock, which he patented in 1818. It won him the £100 reward on offer (Wikipedia, "Chubb detector lock"). Grace's Guide says the lock "was soon recognised as the best of its kind."

The Detector Principle

The detector lock was a lever lock in the line of Robert Barron's 1778 design. Wikipedia says Chubb built on earlier work by Barron and Joseph Bramah. The original version had four levers. The correct key lifts each lever to the right height so that the bolt can move.

The new part was a re-locking device that Chubb called a regulator. If any lever was pushed higher than the correct key would lift it, as happens when someone probes with a pick or tries a wrong key, the regulator tripped. The lock then stayed jammed in the locked position. In the original design, only a special regulator key could reset it. Later designs could be reset by the owner's own key turned in a different direction (Wikipedia).

The jam did two jobs. It frustrated the attempt, because whoever was trying had to reset the detector before trying again. It also told the owner, the next time the proper key failed to work normally, that someone had interfered with the lock. Wikipedia's summary: the lock "frustrates unauthorised access attempts and indicates to the lock's owner that it has been interfered with."

Improvements

Wikipedia says the basic principle stayed the same while the design was refined. In 1824 Charles Chubb patented an improvement that removed the need for a special regulator key to reset the lock. By 1847, work by Jeremiah, Charles, Charles's son John, and others had produced a six-lever version. Grace's Guide records Jeremiah and Charles as joint patentees of improvements to safes in 1839.

The Business

The sources agree that the business moved into Wolverhampton and the Black Country lock trade, but they give different dates and details:

• Grace's Guide's company page says Chubb moved into locksmithing in Wolverhampton in 1818. Wikipedia's company article says the same.
• Grace's Guide's page on Jeremiah says the brothers' first Wolverhampton venture was not successful. Jeremiah went to France and then America, and he returned to Britain in 1828. In the meantime Charles carried on making and selling the locks in Portsea and opened offices in London. Charles then set up a lock factory in Temple Street, Wolverhampton, in 1830.
• Wikipedia's detector-lock article instead says the brothers started Chubb Locks in 1820 and moved to Willenhall, with a factory in Temple Street.

Grace's Guide adds that in 1823 the company received a special licence from George IV. It later became the sole supplier of locks to the General Post Office and a supplier to the prison service. Its safe works opened in Glengall Road, Old Kent Road, London, in 1837. For the 1851 Great Exhibition, the firm designed a secure display case for the Koh-i-Noor diamond.

1851: Hobbs and the Six-Lever Lock

By the time of the Great Exhibition, the detector lock had been unpicked for more than thirty years. Wikipedia says a number of people tried and failed before Alfred Charles Hobbs became the first to pick the six-lever Chubb lock, in 1851. The Linda Hall Library describes Hobbs moving on to the Chubb lock after his long effort on the Bramah challenge lock. It adds that Chubb's sales were not hurt by the episode and, if anything, were helped. See Alfred Hobbs and locksport for the wider story.

Legacy

The detector lock added a new idea to lock design: a lock that reacts to an attack, not one that simply resists it. A lock that locks itself further when tampered with, and leaves evidence that someone tried, is still a recognisable goal in high-security design. For modern approaches, see high-security locks, Abloy, and pin tumbler lock.

Related Topics

• Lever Tumbler Lock
• Robert Barron
• Joseph Bramah
• Alfred Hobbs
• Safe
• Notable Figures

Sources