The Invention
The patent, US443945A, granted to Washington A. Martin of Chicago, Illinois, on December 30, 1890, is for a mortise lock. This invention is a more complex and refined version of his earlier lock, designed to be more versatile and secure.
Key Features:
- Mortise Lock Design: The lock is designed to be inserted into a mortise (a cavity) in the edge of a door, a common type of lock for securing entryways.
- Rectangular Bolt: The bolt (B) has a rectangular, “quadrilateral” shape, which, like his previous invention, cannot be forced back with a simple tool. This provides a high level of security.
- Spring-Actuated Trigger: The bolt is automatically projected into the strike plate by a spring (C) when the door closes. This is achieved by a unique trigger (E) that projects from the lock’s face. As the door closes and the trigger hits the flat surface of the strike plate, it is pushed back, which in turn releases the bolt.
- Adjustable Trigger for Versatility: A significant improvement is the “swivel end” (
e') on the trigger. This allows the beveled end of the trigger to be adjusted to accommodate doors that open either to the right or to the left. This made the lock a universal product that didn’t need to be custom-made for a specific door. - Tumblers for Key Security: The lock includes a system of tumblers (D), which are a key part of the locking mechanism. The tumblers have recesses that catch a lug on the bolt, locking it in place. Only a key with the correct “bits” can lift the tumblers and allow the bolt to retract.
- Thumb-Bolt and Pawl Mechanism: The lock has a thumb-bolt for inside operation. A lever or pawl (
n) can be used to hold the thumb-bolt in a specific position. This allows the user to leave the door unlocked so it can be opened and closed freely (using the knob), with the trigger still working, but the key-operated tumblers disengaged. - Comprehensive System: The patent describes a complete and highly integrated system, including a key-guide, various springs, and projections all working together to provide multiple modes of operation (locked, unlocked with key, unlocked with thumb-bolt, and freely operational without locking).
Significance of the Invention and Inventor
Washington A. Martin was an African American inventor who made significant contributions to lock technology. This patent is a testament to his expertise and a superb example of a complex, well-engineered device.
- Enhanced Security and Usability: This patent goes beyond simple security and focuses on user convenience and versatility. The adjustable trigger was a clever innovation that made the lock a more marketable and practical product for a wide range of doors. The multiple operational modes (locked, unlocked, and on-the-latch) show a sophisticated understanding of a user’s needs.
- Pioneering Innovator: As an African American inventor, Washington A. Martin faced significant barriers. However, he successfully patented multiple improvements to lock mechanisms, establishing himself as a skilled and inventive designer. His work is part of a larger story of African American inventors who used the patent system to protect their intellectual property and contribute to the industrial and technological growth of the United States.
