How does this Chubb Detector Lock operate?

[lorddlm2]

Hi there

I have a Chubb detector lock with its original key, and am very interested to know how this particular version would have prevented and indicated illegal access attempts. I have attached a few images of the actual lock, along with a borrowed image (found on this forum) to show a part of the lock mechanism that I didn't photograph myself.

The lock itself has the serial number 1674333, and I am assuming that it dates to circa 1870?

Im not sure of the terminology, but on the reverse of the lock frontage is a removable disc that has a 'roofed' area where key enters it. This disc has a small ridge in it that engages with a mounted spring.

If anyone can explain how detector part of this lock operates, and what the correct terminology for the components are, I would be very grateful indeed.

[Arcade Al]

The disk part is called the curtain. It's purpose is to make the lock difficult to access with basic picking tools.

On some other locks the curtain also has the function of engaging with and moving the bolt across - these are then known as throwers or bolt-throwers.

[KitBear]

Hi LordDim2

I have taken some pictures showing the operation of the Definitive detector mechanism, the "Round Disc" as Arcade Al put it is called the Curtain, it's purpose is to restrict access to the keyhole when a key or instrument is inserted and turned, it also restricts the amount of movement the picker has to work within the lock.

Your locks levers are in very bad condition, someone in the past has filed all the levers flat to remove the gates, now the lock offers no security at all, the detector function will never work again, the only way to restore it back to normal working condition is to make a new set of levers for it which has to be done by someone with the skills and knowledge for the project.

It's just plain vandalism how some people destroy what they don't know, choking them is just too good in my opinion but it certainly makes you feel better.

Kit

[lorddlm2]

Those photos were great! Thank you for taking the time to post them here - they explained the process better than words could.
After reading your post, I will certainly be getting this lock correctly restored.

[KitBear]

I tried to edit the post after I had posted it but I took too long and exceeded the 10 minute requirement so I apologise.

The "Roofed area" from what you described sounds like what's known as the Talon (2 V Shaped sections on the bolt) and the spring is the curtain retainer which is used to centre the curtain keyhole to the case keyhole to assist key removal.

The detector works as follows:

The user throws the bolt with the key to lock it and leaves.

Let's assume a well equipt thief chooses your lock, and either uses a pick or a false key.

One or more levers are lifted above the lever gate height and so lifting the detector lever with them, the detector lever is now retained by the detector spring in an upright position thereby blocking the bolt from passing through the gate, the thiefs further attempts at picking the lock are now rendered useless, the lock is now completely deadlocked, nothing other than the correct key or destruction will now open it.

The thief now has 2 options, leave and allow the lock to report it's status to the owner or try to pick the lock to reset and leave or continue trying.

The thief leaves and later the owner returns, the owner tries his key but it doesn't open the lock, this tells him that someone has been tampering with his lock.

The owner now turns the key in the lock in the locking direction (as though to lock it again) and the bolt stump moves into the far most gates on the levers.

This action allows the bolt to move forward (usually 2-3mm) which causes the ramp section at the rear of the bolt to raise the spring to release the detector from the upright position.

The lock is now reset and the owner can now unlock the lock as normal.


I would seriously advise you to seek an antique lock professional restorer to repair the lock, it might cost but you will get a quality result, a person taking on the task NEEDS to know what they are doing.

Just out of interest could you please post some more pics of the interior perhaps someone on here could point you in the right direction and even give you an estimate.

Thanks for sharing.

Kit

[KitBear]

I've just thought of someone who could help.

http://www.d-r-lock-restoration-and-repair.com/

his work is first rate, take a look at his previous projects for evidence to his craftsmanship.

Kit

[lorddlm2]

Hi Kit

Sorry I didn't reply earlier. Firstly, thanks so much for this link. I am staggered by some of the keys this locksmith has made. I have never seen anything quite like them.

I have found a retired locksmith, a former Chubb employee during the 1950's. I will show him the lock, but should he have any reservations, I will be sure to call your recommendation.

Your text description was perfectly explained - I now feel that I do understand the mechanism.

Thank you for taking the time to explain all this to me - its much appreciated

[lorddlm2]

I have read the excellent description above, yet I am still having a problem relating this to my particular Chubb Detector lock (shown in the photo below). With my particular lock, exactly how does the detector spring inform the owner that an imposter has tried to gain access? Essentially, where does this spring locate to when tampered with? Once it has relocated itself, what will it prevent from happening?
Any help will be warmly appreciated

[KitBear]

Hi, the retention spring doesn't move, it stays fixed to the backplate, the spring just keeps the detector lever in the raised position above the lever gate therefore preventing the bolt from moving back, in other words, when the detector lever has been raised beyond the gate height the spring will catch the end of the detector lever and will block the bolt stump from passing through it rendering it inoperable thereby informing the owner (due to it no longer working) that someone has tampered with it.

You can test this out for yourself by locking the lock with the key and then lifting one of the levers beyond the gate height, the detector lever will make a click sound and hold the detector lever in the raised up position, you can reset it by either using the key or by using a pen etc.. to lift the detector spring which will allow the detector lever to fall back to rest with the other levers.

Hope this helps

Kit

[lorddlm2]

Hello Kit

Thank you very much for your reply and easy to understand description. I FINALLY understand how this lock works!

You are very kind to take the time to explain this to me