A history of locks is easy to research, but finding the exact origins of a deadlatch is a bit more challenging. In fact, I couldn’t do it. Other than learning that Hai Chaig from Hong Kong patented an adjustable deadlatch in 1990, the closest I got was a patent obtained by the Schlage Lock Co. in 1952 that describes a deadlocking plunger for the purpose of preventing retraction of latch bolt by unauthorized means when the spring projected plungers are held in a retracted position by the surface of strike plate.
I think that refers to a deadlatch. There isn’t a locksmith out there who hasn’t wondered what was going on inside the housing of that little contraption. When a deadlatch malfunctions and won’t allow the main latch to retract (and the door is stuck shut), you can try to pull the hinges, but more likely will end up breaking the deadlatch apart piece by piece and removing it through the bored 2 1/8” hole.
Deadlatches are “sealed” at the factory. They don’t come apart, ever. After many years in the trade, my curiosity finally got the better of me, so I got out my Dremmel tool and cut the covers off some of them.
Studying the internal parts, I came to several dissatisfying conclusions. First, there isn’t a practical or reliable way to overcome a malfunctioning deadlatch. Do what you’ve been doing.
Second, a deadlatch would be impossible to reassemble. I can’t imagine how they manufacture them. Although I can see how the parts work to create a deadlatch situation, it’s amazing that they do work given how many times they’re used. We’ve all seen old Schlage D deadlatches that work like new even after a million openings.
The three deadlatches I disassembled all used completely different designs. Take one apart yourself and see if you can find the subtle way in which these brilliant little devices work. Don’t worry. You’ll never have to put it back together!
Michael C. Tritel, the owner of Lively Locks & Dead Bolts, can be emailed at [email protected]
