simple lift/turn interlocking pins

[98AB49DC5A]

This idea comes completely from corbin. they came up with (I think it's them) a lift/turn pin that uses no sidebar like medeco but instead has the pins interlock. it requires minimal modifications to implement in a conventional cylinder(replace pins / cut groove in plug) and it completely prevents bumping. It might also make picking harder as for the same reason as picked pins would not be loose.

basically they cut a slot in the bottom pin in which a tab on the upper pin sit.
http://www.flickr.com/photos/i_am_subverted/3040679118/
this setup prevents bumping but it wears out fast, and the grooves in the pins are somewhat difficult to mill, I propose a slight modification to the system which could make it easier to manufacture add more differs.

http://www.postimage.org/image.php?v=Ts5sG4i

basically instead of making the groove down the center of the pin you take a chunk off the side . this makes the pin asymmetrical so rather than having two possible disengaging orientations it only has one. Given three possible key cut angles an off center chisel tip would allow two cut positions per pin, plus the rotations, like Medeco biaxials, yielding 6 rotation differs per pin. given that's 6^N times more differs per lock than a conventional pin tumbler.

one way keys would also be possible under this system given a slight modification to the top pins. Some of you may have seen another post that had plug mod which allowed for one way keys
viewtopic.php?f=9&t=15918
I propose to do the same sort of thing, in nearly the exact same way, the top pin's tab would be cut so as to loosely couple it to the bottom pin allowing one cut differ of movement. up by said top pin
one side of it's tab is sloped so as to allow it to take advantage of this loose fit and rise one unit should the key be cut one differ below the proper cut. when the plug has turned back around the top pin falls back into place. The one way key mod described would require only that the top pin be changed and would be very easy to retrofit.

[98AB49DC5A]

I ought to mention that the one way key option would only work against a non clever person. someone who actually understood why it works could simply use a plug spinner. the same problem is present in most brinks function(apparently that's what this feature is called) locks, at least the pin tumble ones. I highly suspect abloy's one way keyed locks are vulnerable in the exact same way(I won't elaborate because that could take another paragraph and I have to get on with this).

anyways here's a diagram of typical brinks function pin tumblers(can you spot the problem in the upper left lock?)

The gradual ramp would make the plug spinner vulnerability less viable but would not work with the two way key unless you bevel the bottom pin. the system I propose for one way keying would be even more vulnerable to the plug spinner vulnerability as the top pin contains the ram and the ramp uses only 2-3 degrees of motion to lift the pin one key differ, not two... so yeah

[mcm757207]

Emhart happens to be my favorite high security lock, but it did however fail the test of time. Wear in the keys causes the pins to sit lower, breaking off the very detailed "dove tail" parts of the pins. Machining of the pins was also problematic causing them to be rather expensive. While your design does seem to be cheaper to produce, on a casual glance, you will still have the longevity problem. Also, just FYI, Emhart only has two rotations (left and right). Master pins come in three types (left, right, and "same").

The one issue I might see with your design is the tendency for some people pull out of the key while rotating it back to 12:00- if done in your lock, unless special milling is done to prevent it I suppose, I feel like the "ledge" might fold in on itself over time.

[Raymond]

In analyzing this newer idea I see some problems.
Cutting the T shaped slot around the plug on the original Corbin-Emhart is simpler than cutting two passes to make the angle on only one side, assuming you even can make that deep of a V cut on only one side. I doubt it.
If someone tried picking and turned the pin 180 degrees, then the correct key would not work until the pin pair was realigned manually.

[98AB49DC5A]

As for wear problems I think that a ball bearing type key retaining system , like the one on abloy locks could reduce wear on the pins caused by the user pulling on the key while turning though there would still be problems

also on the original emhart locks AFAIK the grooves milled in the plug have no special profile. just flat grooves. they don't interlock with driver pins like the bottom pins do. As for the problems with maintaining pin orientation, No ideas there.

[98AB49DC5A]

Extending the irregular shearline around the plug could reduce the problems coused by users pulling on the key while turning. extending the shearline would be fairly simple. two sidebar like slots cut in the lock body could hold semicircular pieces of metal in place in the grooves running in the plug. If someone manages to pick the lock open, or modifies a key so as to be romoveable after turning it, the bottom pins are locked in place until the plug comes back to it's original position preventing a denial of service attack. the half circle segments also lock the key to the plug after it is turned preventing users from wearing the bottom pins by pulling on the key while turning.

I have been considering how to cut the key and pin and I believe I may have a solution that ensures the pin comes to rest at the proper height/rotation allowing for positioning at any angle rather than ensuring one of two positions(Emhart/medeco style key cuts). the pin is cut with an angled flat tip.

Using a conventional key cutting machine that does not create angled cuts two pin rotations are made possible by having the pin come to rest on one of the slopes of the key cut. more pin rotations are possible if the pin comes to rest on an angled surface between peaks. though this would require a key cutting machine that can create angled cuts. such keys could be used in conventional pin tumbler locks as well as in the originally described cylinders allowing for two levels of security.

on a side note, I've modified a single chamber of a lock cylinder (Schlage) wo work with such a pin.by pulling the key out a tiny bit the pin comes to rest on the forward slope of the cut and at the proper angle.(I have no blanks)

[Evan]

As for wear problems I think that a ball bearing type key retaining system , like the one on abloy locks could reduce wear on the pins caused by the user pulling on the key while turning though there would still be problems

also on the original emhart locks AFAIK the grooves milled in the plug have no special profile. just flat grooves. they don't interlock with driver pins like the bottom pins do. As for the problems with maintaining pin orientation, No ideas there.

Just how long do you expect a lock to be in use before it needs to have the wearable parts replaced ?

The problems cited regarding the Emhart locks ALL involve a lack of proper maintenance... You need to periodically replace worn keys with new ones cut to factory specs to ensure continued performance of the locking system...

Same with the pins... High traffic, frequently used lock cylinders should be re-keyed to the same bitting(s) at least every two years to ensure the security of that lock and to prevent unintended key interchange in that cylinder from other keys within that keying system let alone from random stray keys...

Trying to design a lock that will function for years and years with ZERO maintenance will result in a more complicated and expensive mechanism than you actually require to achieve your objectives and will not realistically achieve the security objective as it will not be maintained properly regardless of its mechanical durability...

Locks should be entirely gutted and reassembled with new springs, pins and possibly even replacement of the keyway plug at least every 15 years... This is considered the maximum serviceable lifespan for a keying system when you would scrap what you have in place and create a new keying system anyway to ensure that the locks are still performing according to what they were designed to do...

~~ Evan

[98AB49DC5A]

Really, I had no idea they required maintenance, or replacement of parts. a ball bearing key retension system would be completely unnecessary then. on a positive note the little half circle segments would reduce wear and reduce time between services, possibly to the level of a normal pin tumbler lock.

Now more then ever I appreciate abloy's locks. I wonder whether those ever actually need servicing replacement of parts, whatever? though they aren't as secure as I once thought(see blackbag http://blackbag.nl/?p=1359)