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S&G Disc / Pin Tumbler Hybrid

PostPosted: Tue Jul 24, 2018 7:05 pm
by Patrick Star
So, when searching for another patent, I happened to stumble upon this mechanism, assigned to Sargent & Greenleaf.
It's in US patent 4651546; see https://patents.google.com/patent/US4651546

Basically, it's a hybrid between a disc detainer and a pin tumbler lock.
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Very interesting construction. I certainly haven't seen anything like it before.
Has this ever been produced?

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Tue Jul 24, 2018 7:10 pm
by Riyame
Wow, that is really neat. I have never seen or heard of them making any. There might be some made up to test things but they were never produced AFAIK. Given the date I bet they tried to design a core to go with their high security padlocks but I guess it never passed testing.

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Thu Jul 26, 2018 6:51 am
by macgng
Holy Crap! that's frikin cool man! thanks for finding and sharing that patent! :D

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Thu Jul 26, 2018 3:34 pm
by huxleypig
Awesome concept! Shame we never saw it in reality.

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Thu Jul 26, 2018 5:01 pm
by Patrick Star
In case you haven't read the actual patent, it's actually more interesting than what a glance at the drawings would imply.
If it was just a disc detainer with a pin tumbler stuck on top I'd imagine it'd be quite pickable and impressionable with pretty much standard techniques. But...
By this construction, a more pick-resistant lock is provided since torque cannot be applied to find the shear line, the tumbler discs as well as the other parts being rotatable a full 360° without applying force to the inner cylinder unless all of the tumbler pins are properly aligned with the shear line. Similarly, this renders the lock highly resistant to unauthorized opening of the lock by torquing techniques. Since the key in this lock construction never comes into contact with the tumbler pins and the tumbler discs with the inner cylinder or plug 14 when properly positioned by the appropriate key rotate 360° without applying force, the lock is impression proof.


Reminds me of eg. newer Kwikset Smartkey or certain car locks, where you can't tension the damn thing.

Well, huxleypig probably can with some fancy gadget he built for the purpose :)

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Thu Jul 26, 2018 6:07 pm
by Cheesehead
Patrick Star wrote:In case you haven't read the actual patent, it's actually more interesting than what a glance at the drawings would imply.
If it was just a disc detainer with a pin tumbler stuck on top I'd imagine it'd be quite pickable and impressionable with pretty much standard techniques. But...
By this construction, a more pick-resistant lock is provided since torque cannot be applied to find the shear line, the tumbler discs as well as the other parts being rotatable a full 360° without applying force to the inner cylinder unless all of the tumbler pins are properly aligned with the shear line. Similarly, this renders the lock highly resistant to unauthorized opening of the lock by torquing techniques. Since the key in this lock construction never comes into contact with the tumbler pins and the tumbler discs with the inner cylinder or plug 14 when properly positioned by the appropriate key rotate 360° without applying force, the lock is impression proof.


Reminds me of eg. newer Kwikset Smartkey or certain car locks, where you can't tension the damn thing.

Well, huxleypig probably can with some fancy gadget he built for the purpose :)


Maybe I'm missing something obvious, but how does the key reliably open the lock then? If it can spin freely, why should the pins lining up bind the second cylinder enough to start the lock turning? Once the pins have started to clear the shear line it's no longer a problem because the lock will hold the discs in place to prevent the discs from free-spinning. But I don't understand how to start it.

...The plug sleeve or shell member together with the lower tumbler pin sections and the tumbler discs then all rotate in unison under the force of the key to the unlocking position


I don't see what compels the plug sleeve to rotate together with the tumbler section. Thoughts?

-Tyler

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Fri Jul 27, 2018 1:32 am
by madsamurai
Cheesehead, I was wondering that myself... I think the idea was that the angled flats between 'levels' on the discs pushing against the pins themselves would provide enough to turn the cylinder once the pins were aligned to the shear.

"When the lower pin sections 31 are all properly positioned upon appropriate rotation of the proper key, so that the plane of separation of the upper and lower pin sections becomes aligned with the shear line or shear plane 14a between the sleeve or shell member 14 and the bore 12, the lower pins then transfer force to the inner cylinder tending to rotate it by continued rotation of the key to rotate the plug assembly to the unlocking position, and similar action caused by the pins pushing the side of the inner cylinder upon rotation of the key in the opposite direction return the cylinder to the unlocking position where the lower tumbler pin sections are then positioned axially to place their planes of separation with the upper pin sections out of alignment with the shear plane or interface plane 14a, returning the lock to its locked condition."

My guess is this didn't work as dependably as they hoped, and probably why it never made it to production... Seems to me that any resistance to the inner cylinder being able to turn freely (dirt in the lock or a stuck tailpiece or whatever else) would cause the discs to continue past the alignment point, oversetting or undersetting pins that were at the shear line and allowing the key to freely turn without any effect.

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Mon Jul 30, 2018 6:12 pm
by vde
Brilliant - are they actually produced?

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Sun Aug 05, 2018 5:41 pm
by GWiens2001
Never heard of or seen one of them. But it certainly looks to be highly prone to failure with the lightest amount of dirt or corrosion. Can see why it would not be produced. Probably a concept that they patented in case someone else made one.

Clearly, they were inspired by the Abloy Profile system. Probably figured that the pin tumbler mechanism would be an improvement on the sidebar mechanism.

Perhaps they could make part work like the Yale PKPT padlocks, where once the key was rotated correctly the plug could be pushed in slightly, engaging an outer shell or cam/tailpiece that would operate the locking mechanism. Sort of like the Bowley lock. Then the key would work correctly and reliably.

Just some thoughts and ideas.

Gordon

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Sun Aug 05, 2018 8:48 pm
by Patrick Star
GWiens2001 wrote:Perhaps they could make part work like the Yale PKPT padlocks, where once the key was rotated correctly the plug could be pushed in slightly, engaging an outer shell or cam/tailpiece that would operate the locking mechanism. Sort of like the Bowley lock. Then the key would work correctly and reliably.

Unfortunately I think any lock that has an opening procedure other than "insert key and turn" is out of the question for the mass market.
Even disc detainers which just behave in a slightly different way than usual (in that you can turn a wrong key somewhat before it comes to a stop) can be highly confusing. Once I had to stop an otherwise smart guy before he broke the key off in the lock...

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Mon Aug 06, 2018 4:34 am
by MHM
Wow, that really is an outstanding find. It absolutely reeks of "Let's make our own military padlock core, we can't use Medecos forever". And look at the length of the shaft on that key. S&G can't help themselves, they're a safe lock manufacturer first and foremost and as well as tucking the locking mech way up out of harm's way inside a padlock, I'll bet you they were thinking of inch-thick safe doors as well.

As the other guys have said, it's pretty obvious why it didn't get made. I'd add also that there's no obvious way of keeping the discs at zero rotation to aid the entry of the key, AND with all these extra parts you're multiplying complexity and numbers of parts to the point that the gains in security are far outweighed by the potential for failure and lockouts. The manufacturing tolerances on this thing would have to be epic to get it to function smoothly.

What interests me the most is that S&G even bothered to patent this - it was clearly never going to get made, and patents cost money. Gives you an interesting insight into the corporate culture of the time, and makes you wonder what other patents are out there with S&G's name on them...

Re: S&G Disc / Pin Tumbler Hybrid

PostPosted: Mon Aug 06, 2018 10:42 am
by Patrick Star
MHM wrote:What interests me the most is that S&G even bothered to patent this - it was clearly never going to get made, and patents cost money. Gives you an interesting insight into the corporate culture of the time, and makes you wonder what other patents are out there with S&G's name on them...

When you spend some time browsing patents, you notice that there are lots of things patented that have never been close to seeing commercial production. Not only locks, but essentially every area. Electronics, software (where appliciable), pharmaceuticals, etc. You also - perhaps somewhat more surprisingly - find many patents that would never hold up to a challenge in court (due to prior art, obviousness, etc).
And this goes way back (early 1900s if not earlier) and continues to this day.
I think it's basically a way of making your competitors lives more difficult by filling any potential invention space with patent hazards that at the very least have to be investigated and occasionally also worked around.
And since everyone else is doing it, you'd be at a competitive disadvantage if you didn't.

Since the major cost when patenting something is the lawyers to do the necessary investigation and write the actual patents, you can probably achieve very good economics of scale if you're a major corporation with a fully staffed in-house legal department.

The upside of course is that we get a lot more weird inventions and Rube Goldberg-style locks to study, even if only on paper and described in legalese :)