I think I have a concept that is feasible to build. After contemplating sliding mechanisms for a while, I started wondering if it could be done with pinned/rotating joints instead. I believe it can.
Basically, each row of drawers has an associated “drive bar” which spans the entire row, and all of the drive bars rotate in unison. Each drawer has an associated “actuator” which is rotated by the drive rod. The actuators are all identical, but each drawer is programmed as “Must be OPEN”, “Must be CLOSED”, or “Magic Drawer” by installing the appropriate “key” on the drawer. The magic drawers, of course, are the ones that are unlocked by moving all the other drawers into the appropriate position.
- Unlocked without linkage.JPG (39.83 KiB) Viewed 3402 times
In the illustration above, we see a side view of a column of drawers. The red squares are the drive rods, seen from their end, and they rotate about the carcase-mounted pins shown in black. We’ll add a parallelogram linkage later, so that all the drive rods rotate in unison. The grey things are the actuators, and they are shown square-drive keyed onto the drive rods. The yellow things are the keys. They are fastened to the side of the drawer box, and they determine the behavior of the drawers. I envision both the actuators and keys being quite thin – perhaps 1/8” or so, depending on material selection.
I placed the keys on the sides of the drawer boxes because that is where I think they can be packaged into the smallest space. So the drawer slides (perhaps dovetail slides) would have to go on the bottom of the drawer.
It’s not shown in the illustration, but I’d put a cover plate on the outside of the keys, for two reasons. One, it would capture the actuator side-to-side. Thus the actuator can simply float on the drive rod, minimizing any tolerance issues. Two, it would hide the key, so someone can’t figure out the code simply by opening the drawers and inspecting all the keys.
The next illustration shows all the drawers in the position that unlocks the magic drawer. In these positions, no key will block its associated actuator from lifting, and so a spring or counterweight will rotate the drive rods counterclockwise, lifting all the actuators and unlocking the magic drawer. But if even one drawer is in the wrong position, the drive rods can’t rotate, and the magic drawer stays locked.
- Locked without linkage.JPG (39.13 KiB) Viewed 3402 times
This design has a few bonus features:
1) There is no restriction on the number of rows or columns of drawers. As a matter of fact, the drawers do not even have to be in regular columns.
2) You can “program” the drawers in any combination you want. You can even have multiple “magic drawers”.
3) You can program a drawer as a “Don’t Care” by not installing any key.
4) If you want, you can design keys with additional behaviors. For example, you could key a drawer such that it has to be
half-open in order to unlock the magic drawer(s).
5) This one may or may not be a “bonus”. But as designed, the code is determined by the drawers themselves. Suppose that each drawer was labeled with a letter. You could shuffle the drawers about (swapping them into different cubbies) as much as you like, but the letter code would not be changed by this shuffling.
And that’s about it, except for adding the parallelogram linkages to the drive rods. In the illustrations below, I have them shown in blue, oriented toward the front of the carcase. This permits longer links with proportionally better pin-slop tolerance, without having to grow the carcase rearward. I would probably place the parallelogram linkage against the side of the carcase. Possibly on both sides of it, if I was concerned about drive-rod twisting.
- Locked with linkage.JPG (44.9 KiB) Viewed 3402 times
- Unlocked with linkage.JPG (39.14 KiB) Viewed 3402 times
There's lots of ways to skin a cat!
Back to the drawing board! I'm not OCD enough to think of opening all the drawers at once. Or maybe I'm too OCD to do that!
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