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Chubbs No.3 Bank Lock

Patent & Propriety Locks

This is a complex and extremely rare lock. It was designed for one purpose - to defeat A.C.Hobbs.

Following the Great Exhibition of 1851 Chubbs reputation & public confidence in their products was badly shaken, so I speculate that the decision was taken that Chubbs would offer a range of new locks that was proof against Hobbs' picking techniques and that one of the designs resulted in this pattern of lock. This would seem to be a sound speculation as it is reported that Hobbs said " Mr Chubb has made a lock; the like of which he has never made before ... " by that I take it that Hobbs' meant - one that cannot be picked ! He is said to have been challenged to pick the lock, but declined to try.

No.3 Bank Lock

The lock is unlike any other that Chubbs had made before, there is no detector mechanism, the security of the lock did not reply on detecting, or responding to the overlift of any lever. The image above shows the lock with the bolt thrown and is a right hand lock. This would be an suitable moment for a little background history for this lock. Until a few years ago there was only 1 known example of this pattern of lock, and that was a very 'experimental' version, undoubtably the 1st or early production example. While this one lock was known (currently location unknown) no other example had even been seen or known of. The three black and white photos below are of that 1st known example, the lock is unusual in that in addition to being numbered (s/n : 173662) it is also dated : Oct 20th 1851. My thanks to Mike Fincher for the photos.

Then two sequentially numbered examples were located in Adelaide, Australia where they had been removed from a strongroom in a bank in the early 80's. The two locks were opposite hands. They are slightly different to the above example, but have clearly evolved from it. The other lock is now in another private collection.

The lock contains a number of design elements intended to make it secure. It has 12 levers, a multi-layer curtain, warding, portcullis and sopisticated detent system.

The descriptive quote below is taken from George Prices' famous book of 1856, however there was no engraving of the lock to accompany the text.

" Lock No.3 – For banks Mr. Chubb has introduced what he particularly calls his ‘bank lock’. It contains a barrel with a series of curtains. While the keyhole is open, all access to the tumblers from the keyhole is completely cut off by two sliding pieces of solid metal which fit closely on either side of the barrel. These pieces are acted upon by an eccentric motion, so that when the key is applied to the lock and turned in it, the keyhole is shut up by the revolution of the curtains, and then only do the sliding pieces of metal moves aside to allow the key to act upon the tumblers. These pieces return to their position when the key has passed; therefore, while the key is lifting the tumblers, all communication is cut off from the exterior of the lock by these sliding pieces and the series of curtains. The bolt is made in two pieces, the main bolt never being in contact with the key, which acts only on the talon bolt, and by it transmits the motion to the main bolt. After the action of locking, the talon bolt is partly repelled, and a lever or ‘dog’ connected with it locks into a series of combinations arranged upon the front parts of the tumblers, and holds them securely down, so that none of them can be lifted in the least degree until the talon bolt is thrown forward to release them.

If, therefore, any pressure be applied to this talon bolt to endeavour by its help to ascertain the combinations of the tumblers, it will only the more tightly lock them down, and render the attempt ineffectual. By another contrivance it is rendered impracticable to move a pick or picks round in the lock more than a small distance, unless the tumblers could previously be all lifted to their right positions, which can only be done by the right key. Should one or more of the tumblers be surreptitiously raised by any possible means, they cannot be detained in this uplifted position, for the action of turning back the pick to try to raise another tumbler sets in motion a lever which allows the tumblers already raised to drop to their former position, leaving the operator just as far from the attainment of his object as at the outset."
Here the lock is shown with the top of the curtain and lock cap removed.

The barrel, curtains and two sliding portcullis can be seen, and in the images below I have removed them for clarity.

Here the key (which is not original) is shown in the curtain. The bottom layer covers the bolt throwing step, the next layer protects the lower three levers and the remainder would be covered by the top (removed).

The strength of this lock lies in the sophisticated detent system, which combined with the two part bolt effectively requires that the entire lever pack be set to the correct height before the main bolt stump can be moved against the levers. In order to assist the reader to fully understand the mechanism I list below the sequence of events that occurs as the key is turned.
1 - The bolt is thrown, and the lever pack is locked by the dog / yoke.
2 - Insert the key, with the bit at 6 o'clock. As the key is turned counter clockwise the edge of the top of the curtain contacts the curved bronze bar at around 4 o'clock. The bronze bar is connected to the dog / yoke and it in turn is connected to the 'talon bolt' (see image below).

3 - At 3 o'clock the action of the curtain has moved the portcullis out of the path, and moved the yoke to release the lever pack, and in doing so moved the talon bolt to the right, ensuring that no tension can be placed upon the main bolt & lever gates.
4- Further rotation of the key as far as 1 o'clock will allow the bolt throwing step of the key to enter the talon bolt and in doing so draw the yoke back into the edge of the lever pack. In doing so it will lock the entire lever pack before the talon bolt will begin to touch the main bolt. At this point the levers are all set at their correct (or incorrect) heights, no further adjustment is possible.

5 - At this point any further rotation of the key will not be possible unless all the levers have been lifted to a certain degree. The straight bronze bar above the curtain is connected to a secondary dogging system which is released by a curved spring which can been seen resting under the left side of the levers. If the levers have not all been lifted the bronze bar will prevent any further rotation of the curtain.
6 - If all the levers have been lifted, and are correctly aligned the yoke will continue to enter the outer edge of the levers, the talon bolt will then transmit it's motion to the main bolt which will move the stump against through the lever gates.




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