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Locking Mechanisms

Linus Yale, inventor of a popular and effective lock that uses a pin-tumbler cylinder design, was born in Salisbury, New York, on April 4, 1821. As a youngster, Yale possessed a great deal of mechanical skill and ingenuity. His father, Linus Yale Sr., was a successful inventor, having created sawmill head blocks and a millstone process. The older Yale was also interested in new lock designs, and spent much of his time on bank locks. In the 1840s he created one of the first modern locks that used a pin-tumble design. He opened the Yale Lock Shop in Newport, New York, in 1847.

The younger Yale, meanwhile, who was artistically talented, had begun serious studies in portrait-painting. In 1850 he decided a career in painting wasn't for him and began devoting time to mechanical problems. His father died sometime around this period and Yale became more involved in his father's lock shop. Eventually he set up his own lock business in Shelburne Falls, Mass. He had become convinced that key holes in traditional locks made the locks susceptible to thieves who could use picks, gunpowder or other explosives. This led him to employ permanent dial and shaft designs in many of his newer locks, such as used in what most know as "combination locks" today. In 1851, he invented the "Yale Infallible Bank Lock" for safes and vaults. The design allowed its owner to change its combination and would also allow the key to secure the lock while being hidden away from the exterior of the door by a hardened steel plate, which covered the key-hole behind it. He patented the device, thereby securing his place as an authority on all matters pertaining to locks and safes.

Yale's best-known lock design, however, was for a cylinder pin-tumbler lock. The basic concept was used in ancient Egypt around 4,000 years ago, in locks that were very large (up to two feet long) and made out of wood. The design has a main barrel which is drilled so it has usually five or six cylindrical slots that are set close together in a line. A metal pin, or "tumbler," fits closely to the walls of each of the slots. A second metal pin, or "driver," sits above the tumbler and is pushed down on the tumbler by a very small coil spring, which is permanently compressed as it sits inside the lock's enclosed case. Though similar to the pin-tumbler lock his father had invented years earlier, Yale's lock used a smaller, flat key with serrated edges like the ones we still use today. When inserted into the lock, the key pushes the bottom pins into the right position, which allows the user to turn the key and unlock the lock. Yale patented his cylinder pin-tumbler lock in 1861. Later he perfected the mechanism known as the "clock lock" and invented the double lock, which placed two locks within one case to be operated by the same or different combinations.

Yale exhibited several of his lock designs at world's fairs in the United States and overseas and won a number of awards at these exhibitions. In October 1868, he and Henry Robinson Towne founded the Yale Lock Manufacturing Company in Stamford, Connecticut, to produce cylinder locks. The company's name was later changed to The Yale and Towne Manufacturing Company, which eventually became part of NACCO Industries.

Though locks were his specialty, throughout his career Yale worked on solutions to other mechanical problems as well. In 1858, for example, he patented a device for adjusting at a right angle the joiners' square. In 1865 he patented a tool for reversing the motion of screw-taps. In 1868 he received two patents for improvements in mechanics' vises. Yale died in New York on December 25, 1868.

[May 2002]