The Invention
The patent, US407738A, granted to Washington A. Martin of Chicago, Illinois, on July 23, 1889, is for an improved lock and latch mechanism. The primary goal of the invention is to create a latch that cannot be easily forced open with a thin instrument, like a knife blade, a common vulnerability in older locks.
Key Features:
- Square Bolt: The most significant innovation is the use of a square bolt (5) instead of a beveled one. Traditional beveled bolts are automatically retracted when the door closes, but they can also be pushed back by an intruder’s tool. A square bolt cannot be forced back in this manner, making it more secure.
- Automatic Tripping Mechanism: Since a square bolt cannot be pushed back by the door itself, Martin designed a separate “trigger” mechanism to operate it. The lock has a beveled trigger (14) that projects from the lock casing. When the door closes and makes contact with the door jamb, the trigger is forced back.
- Linkage to the Bolt: The trigger is connected to an arm with a pin (13). The trigger’s movement causes the pin to disengage from a lug (10) on the bolt’s inner yoke (7). This releases the bolt, allowing a spring (6) to automatically project it into the strike plate, locking the door.
- Retracting and Unlocking Mechanisms: The patent also describes two ways to retract the bolt:
- By Cam and Knob: A cam (19) and a knob (22) can be turned to force the bolt back and unlock the door.
- By a Key-Operated Lock: The cam’s arbor is forked to engage with a key-operated lock, like a “Yale or any other suitable lock,” allowing for traditional key-based unlocking.
- Retracted Position Hook: When the bolt is retracted, a hook (25) can be pivoted to hold the bolt in that position, so the door can be opened and closed without the bolt engaging, like when people are frequently going in and out.
Significance of the Invention and Inventor
Washington A. Martin’s lock is a clear example of an inventor identifying and solving a common security vulnerability. His invention shows a move toward more sophisticated and secure locking mechanisms.
- Enhanced Security: The invention’s main significance is its direct contribution to security. The shift from a beveled to a square bolt addressed a major weakness in existing locks, providing a more robust and tamper-proof solution for homeowners and businesses. This was particularly important as cities grew and the need for reliable security increased.
- Incremental Innovation: While it’s not a complete reinvention of the lock, the patent is an excellent example of incremental innovation. Martin took existing components—a bolt, springs, and a key mechanism—and rearranged them in a clever way with the addition of a new part (the trigger) to solve a specific problem.
- The “Everyday” Inventor: Washington A. Martin was an individual inventor, assigning a portion of his patent to a partner to commercialize it. This was a common practice in the late 19th century, where thousands of individuals proposed improvements to everyday objects. His patent shows how a single, thoughtful idea could contribute to the overall progress of technology and security.
