Does this lock exist?

[jonwil]

I have a lock idea in my head and want to know if it exists (or if its even possible).
The lock would be a double cylinder deadbolt (or something similar with a bolt that goes into the door frame and cant be pushed back like a latch bolt can) and take 2 keys, key A and key B.
When the lock is in the unlocked position, it could be locked by key A or key B.
When the lock has been locked by key A, it can be unlocked by key A, unlocked by key B or further locked by key B.
When the lock has been locked by key B, it can only be unlocked by key B.

Does a lock that works like this exist?
It doesn't matter if its using 2 separate key holes on each side or a single key hole that both keys go into but it needs to work such that if its locked on one side by key B, it cant be unlocked on the other side by key A (regardless of whether it is in the unlocked state or has first been locked from either side by key A)
It must also not use any electricity of any sort in its operation.

[mseifert]

I haven't heard of such a lock, but to me it sounds like you would need some kind of transponder key. Similar to the way a car key recognizes a key and adjusts the seats, mirrors, etc.. It would maybe just activate a solenoid, depending on which key was inserted, allowing the cylinder to turn.

[Squelchtone]

Jonwil, I might understand better if you could give a real world example of where and how such a lock would be used and by what parties? A store employee and a store manager? An apartment renter and a landlord?

Thanks
Squelchtone

[jonwil]

Thinking about this some more, one way you could do exactly what I am suggesting is to have a pair of deadbolts in the door. One is set up so that it can be locked/unlocked with both key A and key B (via master keying or similar). The other is set up so it can only be locked with key B.

Then someone with key A (either inside or outside) can lock the key A deadbolt and the door is locked but can be unlocked any time with key A or key B from either side. If someone with key B locks the key B deadbolt, the door cant be unlocked with key A at all from either side, only with key B. Nothing electrical required at all.

I dont actually have a specific use in mind for this, its just a random idea I had in my head

[ltdbjd]

I want to make sure I understand. Key B always works. Key A always works, except that it won't unlock anything locked by key B. If the lock is already locked by key A, key B can be used to disable Key A from unlocking it (it would be as if it was originally locked by Key B). Is this correct?

I'm thinking about two different things. One I'll have to look up because I don't know much about them and have never seen one, but it's a lock that has two keyways on its face. One is hidden. That might work something like you are talking about but again, I'll have to look into its function. I don't even know what they are called.

Another thought something along the lines of what we use at work. We use ASSA Moguls that are masterkeyed. However they go one step further. There is a small slot cut out of the plug on one side of one chamber. This allows two keys to operate the lock, however one key can turn the plug both directions, the other key will only be able to turn the plug one direction.

Perhaps something similar can be incorporated into what you are trying to accomplish. Not a solution yet, but maybe something to explore.

[jimu57]

Sounds like Medeco Maxum deadbolt.

[Evan]

This is sounding very close to being a Folger Adams Mogul master ring cylinder for low security detention situations where the prisoner is given a change key which can open the locked door when the deadbolt is not thrown, but can not use their key to throw the deadbolt because of a pin installed in the master ring which prevents the cylinder tailpiece from being able to rotate 360 degrees. The correctional officer's master key operates at the master ring and can lock/unlock the deadbolts to secure the cell.

~~ Evan

[FancyPants]

Personally, I'm not sure if I understand this fully, but it almost sounds to me like this could be achieved through a mechanism similar to a master keyed SFIC? I'm just imagining that instead of a control, you have an secondary bolt. I just got home from work and I'm super dazed so I can't fully think it through, so somebody tell me if I'm dumb.

[sisk]

Doesn't Abloy make something along those lines? I vaguely remember seeing a video about an Abloy that had a guest key that could be disabled by someone with the primary key. It's a pretty vague memory so I could be mistaken.

[mh]

Thinking about this some more, one way you could do exactly what I am suggesting is to have a pair of deadbolts in the door. One is set up so that it can be locked/unlocked with both key A and key B (via master keying or similar). The other is set up so it can only be locked with key B.

Yes.
Having this as a mechanical feature in only one lock - doesn't exist IMHO if you insist on the part where you can change the state of the outside lock from the inside.
It does exist if you are willing to insert key B on both sides of the lock to change the state.

[FarmerFreak]

When the lock is in the unlocked position, it could be locked by key A or key B.
When the lock has been locked by key A, it can be unlocked by key A, unlocked by key B or further locked by key B.
When the lock has been locked by key B, it can only be unlocked by key B.

Does a lock that works like this exist?

Yes. But I forgot what the term for it was called.

Here is how it works. Uses a 6 pin tumbler lock cylinder. It has two bibles in it instead of one. One of the bibles only has the first 5 chambers. Key A has extra material after the 6th cut, Key B has the 6th cut on the very tip of the key.

If the cylinder is lined up with the bible with six chambers, both keys can enter and work the lock. If the cylinder is lined up with the 5 chamber bible, Key A cannot exit or enter the cylinder all the way because the 6th pin cannot be lifted. Since there is no material past the sixth cut on key B, it can enter and exit the cylinder without issue.

[Raymond]

In the "Open Source" area, Check out this post: "Modified Cylinder Rekey System" on 9-29-2010."

[mh]

In the "Open Source" area, Check out this post: "Modified Cylinder Rekey System" on 9-29-2010."

Link: viewtopic.php?f=25&t=49064

[Evan]

When the lock is in the unlocked position, it could be locked by key A or key B.
When the lock has been locked by key A, it can be unlocked by key A, unlocked by key B or further locked by key B.
When the lock has been locked by key B, it can only be unlocked by key B.

Does a lock that works like this exist?

Yes. But I forgot what the term for it was called.

Here is how it works. Uses a 6 pin tumbler lock cylinder. It has two bibles in it instead of one. One of the bibles only has the first 5 chambers. Key A has extra material after the 6th cut, Key B has the 6th cut on the very tip of the key.

If the cylinder is lined up with the bible with six chambers, both keys can enter and work the lock. If the cylinder is lined up with the 5 chamber bible, Key A cannot exit or enter the cylinder all the way because the 6th pin cannot be lifted. Since there is no material past the sixth cut on key B, it can enter and exit the cylinder without issue.

@FarmerFreak:

Sounds like a lockout function cylinder to me. User keys only function at the primary pull point, the supervisor key which has the special row of upper pins/springs, usually at 15 degrees out of normal, has only 5 chambers and uses a specially cut key with the steeples removed between bittings on the 5th and 6th bitting on the key and the 6th bitting and the tip of the key so it can be inserted and removed under the bottom pin without being able to lift it above the shear line of the cylinder in that last space.

~~ Evan