Rudimentary Treatise on the Construction of Locks

by A. C. Hobbs; George Dodd

“If by any means these several instruments can be introduced simultaneously, the barrel keeps them all confined in a very small space, preventing their expansion, and renders it impossible to work them independently of each other; therefore they are of no avail, being incapable of acting as more than a single pick, which is perfectly useless. The barrel and curtain have each been previously used separately in locks, but until patented by Mr. De la Fons in 1846 they had not been used in combination. Neither of them, used separately, is of much use, but when combined they afford a very great security. Locks have been, and still are shewn, containing either the barrel or curtain singly, and as these have been picked, it has been asserted that the improvement now introduced in Chubb’s lock is equally insecure; but a slight examination of the difference in their construction will prove the contrary. Mr. Chubb has purchased the patent-right of this part of Mr. De la Fons’ invention, and applies it to all his locks.

“Lock No. 2.—The next improvement, recently patented by Mr. Chubb, is based upon the assumption that there may be a possibility of overcoming the security of the barrel and curtain as already described (although this assumption is not in the slightest degree admitted), and consists in applying what is called a ‘tumbler-bolt,’ working on a hinge connected with the main bolt. The web of the key does not in any case touch the main bolt in unlocking, but acts only on the tumbler-bolt. All the tumblers must first be lifted, each to its proper position, before the tumbler-bolt will act. Should any pressure be applied to either bolt before the tumblers are all at their exact position, the effect would be to throw the bolts out of gear, and thus effectually to stop the stump of the main bolt from passing through the racks of the tumblers. None of the many plans of picking which have been suggested, such as smoked key-blanks, thin key-bits, &c., would be of the least avail against a lock made on this principle. Different kinds of detectors may be applied to these locks. It is submitted that this lock, retaining all the simplicity and durability which have distinguished Chubb’s lock for so many years, and combining with them these important improvements, affords a complete security against all surreptitious attempts of any nature. Locks on the same principle are being made on the permutation plan, with any number of tumblers, and any number of changes in combination that may be desired.

“It has been suggested that the ‘detector,’ instead of giving additional security to Chubb’s lock, affords a partial guidance to a person attempting to pick it. This objection holds good to a certain extent in these locks as originally made, in which all the tumblers had an equal bearing against the detector-stump; but in the locks as now constructed this objection is entirely obviated, by giving the tumblers an unequal bearing, whereby, if an operator feels the obstruction of the detector-stump, he cannot tell whether the tumbler which he is lifting is raised too high, or not high enough.

“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 key-hole is open, all access to the tumblers from the key-hole 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 key-hole is shut up by the revolution of the curtains, and then only do the sliding pieces of metal move 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.”

Such is the statement with which Messrs. Chubb have favoured us respecting their three new locks. We are willing to admit the enterprising spirit which has led to their production, and the ingenuity which has been bestowed on their construction; but whether they mark a step in advance in the art of lock-making may perhaps admit of doubt. With respect to the lock No. 1, we would remark, that locks with the barrel and curtain combined were made by Mr. Aubin of Wolverhampton in 1833, and that a specimen of such a lock was exhibited on his stand of locks in the Great Exhibition. Locks with the combined barrel and curtain were also made and sold by Mr. Jones of Newark, N.J., as stated at [p. 104].

With respect to the lock No. 2, the object of the tumbler-bolt is evidently intended to produce the same effect as the movable stump in Mr. Hobbs’s protector-lock, [fig. 47], page 100; but with greater complexity in the construction, there is less efficiency in the action of this part of Mr. Chubb’s lock as compared with that of Mr. Hobbs, inasmuch as a pressure of the stump against the tumblers, corresponding with the strength of the spring which holds the bolt in its place, can always be produced, thereby giving friction, and affording indication as to which tumbler it is that is in tight contact with the stump.

With respect to the barrel and curtains of lock No. 3, and all similar contrivances, the object of which is said to be to prevent the entrance into the key-hole of all instruments except the proper key, we would offer the self-evident remark, that the same aperture which admits the key will also admit some other instrument. In the case of Mr. Chubb’s “bank-lock,” it may be questioned whether the revolving curtain, &c. give it any advantage over the other locks already referred to which are furnished with similar contrivances. The effect of the talon-bolt in this lock appears to be the same as that of the false notches, namely, to hold the tumblers in the position in which they were placed when the pressure was applied. Hence, a pressure applied to the talon-bolt affects the parts which come in contact with the key in the act of locking and unlocking; and this circumstance brings the lock under the application of the principle stated at page 99, and thus, if this principle be admitted, may render the security of the lock somewhat questionable.

Various other locks have been brought out since the date of the “lock controversy” in the year 1851. We would gladly notice them all, did they shew novelty of design and mark an advance in the art of the locksmith. We must, however, admire the ingenuity with which Mr. Hobbs’s movable stump has been more or less adopted; but in the attempts to imitate it the objection has not been removed, that it is possible to produce on the tumblers a pressure or friction equal to the strength of the spring which holds the tumblers down.

There is, however, a lock which has lately been introduced to the public, which calls for special notice, on account of the high honours which have been bestowed upon it. We refer to the prize lock of the Society of Arts, London, the invention of Mr. H. J. Saxby of Sheerness, who has received the Society’s medal and the sum of ten guineas as the reward of his ingenuity. The interior of this lock consists of a cylinder with four pins or slides radiating from the centre, and pressed into the key-hole by means of spiral springs. The pins project beyond the periphery of the wheel or cylinder, and into slots in a ring which is affixed to the case of the lock, thereby preventing the cylinder from being turned. On each pin is a notch, so placed that when the proper key is inserted into the key-hole, the notches on the several pins will be brought into a position such as will allow the cylinder to turn. The turning of the cylinder in this, as in the Bramah lock, shoots the bolt.

A lock on precisely the same principle, but more secure in its construction, was described by Mr. Hobbs in a paper read by him before the Society of Arts in January 1852, when diagrams illustrative of the same were exhibited. This paper was not reported at any length in the journal of the Society’s proceedings; but the same paper was read by Mr. Hobbs, March 1, 1852, before the Liverpool Polytechnic Society, and a full report thereof, and a description of the lock in question, is given in the “Transactions” of that Society, from September 1849 to December 1852 (8vo, Liverpool, 1853). This lock is no other than the Yale lock already noticed at page 83, and is thus described at page 196 of the “Transactions:”