Linus Yale Jr. (April 4, 1821 – December 25, 1868) was an American businessman, inventor, mechanical engineer, and metalsmith. He was a co-founder with millionaire Henry R. Towne of the Yale Lock Company, which became the premier manufacturer of locks in the United States. He was the country's leading expert on bank locks and its most important maker. By the early 20th century, about three-quarters of all banks in America used his bank locks. He is best remembered for his inventions of locks, especially the cylinder lock, and his basic lock design is still widely distributed today, and constitutes a majority of personal locks and safes.
Linus Yale Jr. was born in Salisbury, New York. His ancestors were of the same family as Elihu Yale, the benefactor to and namesake of the well known Yale University. The Yale family of America were all descended from the same ancestor, Thomas Yale, Elihu's only uncle with the Yale name. Thomas Yale was the stepson of Governor Theophilus Eaton.
Yale's father, Linus Yale Sr., opened a lock shop in the 1840s in Newport, New York, specializing in bank locks; he was a successful inventor who specialized in expensive, handmade bank locks and mechanical engineering, and who held eight patents for locks and another half dozen for threshing machines, sawmill head blocks, and millstone dressers.
After some regular education, Yale Jr. joined his father's business and introduced some revolutionary locks that utilized permutations and cylinders. In 1857, he established the Yale & Greenleaf Lock Co. with his future brother-in-law, Congressman Halbert S. Greenleaf, who also financed the venture. In 1858, Yale's father died, and Linus Yale Jr. became more involved with his father's lock company. Yale Jr. was joined in the family business by his cousin, Charles Oscar Yale, who was also a prolific lock inventor with several patents.
Yale opened his own shop about 1860 in Shelburne Falls, Massachusetts, specializing in bank locks. He later founded a company with millionaire Henry Robinson Towne in the South End section of Stamford, Connecticut, called the Yale Lock Manufacturing Company. Throughout his career in lock manufacturing, Yale acquired numerous patents for his inventions and received widespread acclaim from clients regarding his products.
Yale was personal friends and frequent correspondent with the abolitionist Congressman William Morris Davis.
Young Yale developed an early affinity for portrait painting, but about 1850 switched interests to assist his father with improving bank locks and studying mechanical problems. However, his artistic expertise later proved useful, drafting clear and accurate diagrams for his later lock designs.
In the 1860s, around the time he had opened his own shop in Shelburne Falls, Massachusetts, Yale specialized in bank locks. He introduced some combination safe locks and key-operated cylinder locks that were improvements on previously used locks. Possessing admirable skills in mechanics and lock making, Yale created one of the first modern locks that used a pin-tumbler design.
The pin-tumbler design is also known as the cylinder design, and plays significant roles in today's locks and safes. Yale had previously harbored the practical implementation of the tumbler lock for decades, and had sketched the idea in 1844. Yale was convinced that key holes in traditional locks made the locks susceptible to thieves who could use picks, gunpowder explosives, and heat to thwart the locks. This led him to employ permanent dial and shaft designs in his inventions, known as "combination locks" today. Yale's best-known lock design, the cylinder pin-tumbler lock, utilized a key-operated lock concept first conceived in ancient Egypt over 4,000 years ago.
Yale's inventions were so successful and received such critical acclaim that he exhibited several of his lock designs at world's fairs in the United States and overseas, winning a number of awards at these exhibitions.
Throughout his career Yale acquired many patents, mostly related to his inventions of locks and safes, but also including mechanical problems. In 1858, 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 had many inventions to his name throughout his career, thoroughly revolutionizing the locks industry and improving the security of financial institutions. Drawing on the principles first put to use in large wooden locks built by ancient Egyptians, Yale patented a pin tumbler lock for use in banks in 1851; he patented his pin tumbler lock for use in doors in 1863; in 1865 he patented the pin tumbler padlock, which are still widely used today. Yale's model of the padlock was smaller, sturdier, more reliable, and innovative, proving to be a distinction among locks of his day.
In 1851 Yale invented what he referred to as the "Yale Magic Infallible Bank Lock", for safes and bank vaults. This design allowed the 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 keyhole behind it.
Yale stated nine peculiarities for his Yale Magic Infallible Bank Lock that separated it from its peers:
Being without springs, there are none to fail; it is impossible to damage by fire, dampness, or neglect. The design rid itself of the vices of the springs that become rusty or softening by heat or moisture.
The lock has a head that is detached from its key-bits, thus leaving a space between the head and the key-hole, making it virtually impossible to be picked.
When the key is withdrawn, all print or record of its action is obliterated, and no tell-tale left for duplicate keys to be made
Powder proof. No powder can possibly be introduced into the lock itself, which eliminates the threat of gunpowder explosions.