Tue Mar 17, 2015 2:10 am
La Gard / Saint Blaise Time Lock Teardown
So I picked up a La Gard time lock case with two Saint Blaise (A.K.A. STB) 114E movements off eBay for a ridiculously low price. I've never seen, touched, or otherwise had anything to do with a time lock, so I had to read up a bit. A time lock is a secondary lock installed on the inside of a safe or vault that has redundant timers. These timers are, for historical reasons, called "movements", much like in a mechanical watch. The desired amount of hours and minutes is set into each movement and they remain locked until that number of hours and minutes elapses. They must be redundant (two or more) because if you only had one and it failed to unlock (say, if the battery died) you would be forced to destructively enter the safe/vault. The size and shape of the locks/housings have been pretty much standardized for about 100 years and movements from various manufacturers can be installed as "drop-in" replacements if they match the lock/housing you use. Because of this size and shape backwards compatibility there are interesting holdovers of mechanical design on newer electronic movements. For instance, you still set the timer with a winding key rather than a keypad or a menu and buttons. Here is the lock with a small screwdriver shown for a size reference. This shows the unlocked position.
You set the movements by first turning the peg about a full turn to the left. You can feel resistance from winding a spring and you can see the unlock cam rotating to the left-hand side of the movement. The movement is now armed. Then you turn the peg to the right which sets the amount of time that must elapse. The number of minutes increases in increments of 15. There are a lot of details about a movement such as the maximum number of hours you can set, whether or not you can change the set number of hours/minutes once it’s been entered, etc. based on the specific model in use, but this is the basic procedure.
You then lock the entire device by pressing down the center button. This causes the spring loaded cross-shaped arm to slip to the left, engaging a notch in the center button. Until the arm is forced out of the way by one of the cams on the movements the button will not slide back up. The winding down of either of the two movements causes the arm to be shoved to the right, allowing the button to spring back up and the device is now unlocked. Here it is in the locked position with both movements armed.
Looking at a side view, you can see that there is an open chamber for a bolt to slide through. When the locking button is depressed, a metal plug slides into the chamber preventing a bolt from sliding through the chamber and unlocking the safe or vault.
Here you can see the chamber in the unlocked position and the locked position.
And here is the reverse of the lock with the front cover and rear mounting plate removed exposing the locking arm (which is engaged by the center button) and the black spring mechanism containers which are actually part of the movements, not the case.
That's it for now. Next I'll begin dismantling the movement itself.
You set the movements by first turning the peg about a full turn to the left. You can feel resistance from winding a spring and you can see the unlock cam rotating to the left-hand side of the movement. The movement is now armed. Then you turn the peg to the right which sets the amount of time that must elapse. The number of minutes increases in increments of 15. There are a lot of details about a movement such as the maximum number of hours you can set, whether or not you can change the set number of hours/minutes once it’s been entered, etc. based on the specific model in use, but this is the basic procedure.
You then lock the entire device by pressing down the center button. This causes the spring loaded cross-shaped arm to slip to the left, engaging a notch in the center button. Until the arm is forced out of the way by one of the cams on the movements the button will not slide back up. The winding down of either of the two movements causes the arm to be shoved to the right, allowing the button to spring back up and the device is now unlocked. Here it is in the locked position with both movements armed.
Looking at a side view, you can see that there is an open chamber for a bolt to slide through. When the locking button is depressed, a metal plug slides into the chamber preventing a bolt from sliding through the chamber and unlocking the safe or vault.
Here you can see the chamber in the unlocked position and the locked position.
And here is the reverse of the lock with the front cover and rear mounting plate removed exposing the locking arm (which is engaged by the center button) and the black spring mechanism containers which are actually part of the movements, not the case.
That's it for now. Next I'll begin dismantling the movement itself.
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