Rudimentary Treatise on the Construction of Locks

CHAPTER VII. AMERICAN LOCKS.

The lock-manufacture in America has undergone some such changes as in England. The insufficiency of wards to the attainment of security has been for many years known; and the unfitness of even tumblers to attain this end, without auxiliary contrivances, has been fully recognised for a dozen years back. In this, and in other mechanical arts, the American machinists depended primarily on the invention of the artisans in the mother country, rather than on those of any continental European state. But the development of the art in the United States has not been wanting in originality; the varieties of locks have been very numerous, and many of them exceedingly ingenious. It is not necessary, however, to describe or depict any of those of simple form. The warded locks of different countries very much resemble each other; the intricate warded locks made in France in the last century have long fallen into disuse, in consequence of the general conviction that no arrangement of wards, however intricate, can afford the degree of security required in a good lock. It will be more to the purpose, therefore, to proceed at once to a notice of those American locks which, during the last few years, have acquired some celebrity; first, however, noticing one of older date.

Stansbury’s lock, invented in the United States about forty years ago, may be regarded as a modification of the Egyptian lock. It had a bolt, case, and key-hole somewhat similar to those of modern locks; but there were peculiarities of construction in other respects. There was a revolving plate, pierced with a series of holes, and having a bit or pin which moved the bolt. On the lock-case were a series of springs, each having a pin at one end; and the arrangement was such that, when the bolt was locked or unlocked, each pin would be pressed into some one of the holes. Like as in the Egyptian lock (figs. 1 to 4), each pin had to be pushed out, and all of them simultaneously, to allow the plate to turn and move the bolt. The key was made with a barrel and bit; and on the front end of the bit was a series of pins corresponding in position with the holes in the plate. The mode of locking or unlocking was as follows: the key was inserted in the key-hole, and turned to a certain position; it was then pressed in with some force, until the pins on the key met those in the plate; when the latter, yielding to the pressure, left the plate free to turn and move the bolt. Modifications of the Egyptian lock, more or less resembling this, have been brought out in some variety on both sides of the Atlantic; but scarcely any have equalled in simplicity the curious wooden relic of by-gone ingenuity in the art of lock-making.

A lock made a few years ago by Mr. Yale, in the United States, somewhat resembles the Bramah lock in having a cylinder or barrel, or rather two concentric cylinders, one working within the other. These cylinders are held together by pins which pass through them both into the key-hole. On the back of the inner cylinder is a pin that fits into a slot in the bolt, and moves it whenever the cylinder is turned. The pins that hold the cylinders together are each cut in two; the pieces of the various pins differing in lengths as irregularly as possible. The key is so peculiarly formed, that, on inserting it in the key-hole, it thrusts the pins radially outwards; each pin being pushed just so far that the joint of the pin shall coincide with the joint between the two cylinders. The inner cylinder can then be turned, by which the bolt is locked or unlocked. If, by the use of a false key, any pin be pushed in too far, it will be as ineffectual in opening the lock as if it were not thrust in far enough; and some of these locks having been made with as many as forty pins, the chances are very numerous against the right combination being hit upon. There is a combination of something like the Egyptian with something like the Bramah lock, here attempted.

One of the principal constructions adopted in America a few years back for bank-locks is that of Dr. Andrews of Perth Amboy, in New Jersey. It was up to that time (1841) believed that the best locks, both of England and America, were proof against any attempts at picking derived from knowledge obtained by inspection through the key-hole; but there still remained the danger that the sight of the true key, or the possession thereof, for only a few minutes, would enable a dishonest person to produce a duplicate. It was to contend against this difficulty that Dr. Andrews directed his attention; and he sought to obtain the desired object by constructing a lock, the interior mechanism of which could be changed at pleasure. The lock of his invention is furnished with a series of tumblers and a detector. The tumblers are susceptible of being arranged in any desired order; and the key has movable bits which can be arranged so as to correspond with the tumblers. When the lock is fixed in its place, no change can be made in the tumblers, and consequently only one arrangement of the bits of the key will suit for the shooting and withdrawing of the bolt. The owner can, however, before the fixing of the bolt, adopt any arrangement of tumblers and bits which he may choose. But though the tumblers cannot be actually re-arranged in any new order within the lock while the latter is fixed, yet by an ingenious contrivance the tumblers can be so acted upon as to render the lock practically different from its former self. The purchaser receives with his lock a series of small steel rings, each ring corresponds in thickness with the thickness of some one of the bits of the key; so that, by suitable adjustment, any one of the bits may be removed from the key, and a ring be substituted in its place. The effect of this substitution is, that the particular tumbler which corresponds with the ring is not raised by it; it is drawn out with the bolt, as if it were part of the bolt itself. Supposing the lock to be locked by this means, the original key would not now unlock it; for one of the tumblers has now been displaced, and can only be re-adjusted by the same ring which displaced it. If an attempt be made to open the lock by the original key, or by the key in its original adjustment, a detector is set in action, which indicates that a false key or other instrument has been put into the lock. One, or more than one, of the bits may be removed from the key, and rings be substituted, and consequently one or more of the tumblers may be disturbed in this peculiar way; so that the lock may change its character in all those permutating varieties which are so observable in most “safety-locks.” The shape of the tumblers is, of course, such as to facilitate this action; they have each an elongated slot, and also two notches; when a tumbler is raised by one of the bits of the key, one of the notches closes around a stump fitted into the case of the lock, and prevents the tumbler from being moved onward with the bolt; but when a ring has been substituted for a bit on the key, the tumbler cannot be raised at all; it is carried onward by a stump on the bolt.

Dr. Andrews is also the inventor of a lock which he terms the snail-wheel lock. In this lock a series of revolving discs, or wheels, taking the place of the tumblers, are mounted on a central pin, on which the pipe of the key is inserted. Each disc has a piece cut out of it, into which the bit of the key enters, and in turning round moves the discs according to the various lengths of the steps on the key. On the outer edge of each disc is a notch, and by the turning of the key all these notches are brought into a line, so that a moveable tongue, or toggle, attached to the bolt, falls into the notches; the key is then turned the reverse way, by which means the bolt is projected.

About the time when Dr. Andrews invented his first lock, Mr. Newell, of the firm of Day and Newell of New York, constructed a lock which possessed the same distinctive peculiarity as that of Andrews, viz. that the key might be altered any number of times without rendering it necessary to remove the lock or change its internal mechanism. This was brought about, however, in a different manner. Instead of having, as in the Andrews lock, a two-fold movement to every tumbler, Mr. Newell employed two sets of tumblers, the one set to receive motion from the other, and having different offices to fill, to be acted upon by the key in respect to the first series, and to act upon the bolt in respect to the second. Calling these two sets primary and secondary, the action of the lock may be briefly described as follows. A primary tumbler being raised to the proper height by the proper bit in the key, raises the corresponding secondary tumbler; the secondary tumbler is held up in a given position during the locking, while the primary becomes pressed by a spring into its original position. It results from this arrangement that the bolt cannot be unlocked until the primary tumbler has been raised to the same height as before, so as to receive the tongue of the secondary tumbler. And as this is the case in respect to any one primary and its accompanying secondary tumblers, so is it the case whether each set comprises four, five, or any other number. The key may be altered at pleasure, and will in any form equally well shoot the bolt; but the lock can only be unfastened by that arrangement of key which fastened it.

It is, however, desirable to trace the course of improvements more in detail, because every successive change illustrates one or other of the several properties required in a good lock. Messrs. Day and Newell’s lock was not finally brought to an efficient form without many attempts more or less abortive. Mr. Newell conceived the idea of applying a second series of tumblers, so placed as to be acted on by the first series. Each of these secondary tumblers had an elongated slot, such that a screw could pass through all of them; the screw having a clamp to overlap the tumblers on the inside of the lock. The head of the screw rested in a small round hole on the back of the lock, so placed as to form a secondary key-hole, to which a small key was fitted. There was thus a double system of locking, effected in the following way: when the large key had been applied, and had begun to act on the primary tumblers, the small key was used to operate on the clamp-screw, and thus bind all of the secondary tumblers together, ensuring their position at the exact heights or distances to which the primary key had caused them to be lifted. The bolt was then free to be shot, and the first series of tumblers reverted to their original position.

But such an arrangement has obvious inconveniences. Few persons would incur the trouble of using two keys; and besides this, there were not wanting certain defects in the action and reaction of the several parts; for if the clamp-screw were to be left unreleased, the first series of tumblers would be upheld by the second series in such a way that the exact impression of the lengths of the several bits of the key could be obtained through the key-hole while the lock was unlocked or the bolt unshot. To remedy one or both of these evils was the next object of Mr. Newell’s attention. He made a series of notches or teeth in each of the secondary tumblers, corresponding in mutual distance with the steps or bits of the key; and opposite these notched edges he placed a dog or lever, with a projecting tooth suitable to fall into the notches when adjusted properly in relation to each other. When the key was used, the primary tumblers were raised in the usual way, and acted on the secondary tumblers; these latter were so thrown that the dog-tooth caught in the notches and held them fast, thereby rendering the same service as the clamp-screw and the small key in the former arrangement. No other relative position of the bits of the key could now unlock the lock.

Still, improvement as it was, this change was not enough; Mr. Newell found that his lock, like all the locks that had preceded it, was capable of being picked by a clever practitioner; and candidly admitting the fact, he sought to obtain some new means of security. He tried what a series of complicated wards would do, in aid of the former mechanism; but the result proved unsatisfactory. His next principle was to provide a number of false notches on the abutting parts of the primary and secondary tumblers, with alterations in other parts of the apparatus. The theory now depended upon was this, that if the bolt were subjected to pressure, the tumblers would be held fast by false notches, and could not be raised by any lock-picking instrument. To increase the security, a steel-curtain was so adjusted as to cover, or at least protect, the key-hole. Great anticipations were entertained of this lock, but they were destined to be negatived. A clever American machinist, Mr. Pettit, accepted Messrs. Day and Newell’s challenge (500 dollars to any one who could pick this lock); he succeeded in picking the lock, and thus won the prize.

Once again disappointed, Mr. Newell re-examined the whole affair, and sought for some new principle of security that had not before occurred to him. He had found that, modify his lock how he might, the sharp-eyed and neat-fingered mechanician could still explore the interior of the lock in such a way as to find out the relative positions of the tumblers, and thus adapt their means to the desired end. How, therefore, to shut out this exploration altogether became the problem; how to make a lock, the works of which should be parautoptic—to coin a word from the Greek, which should signify concealed from view. The result of his labours was the production of the American bank-lock now known by that name. The details of this lock may now conveniently be given.

fig. 40. The American Parautoptic lock; bolt unshot.

fig. 41. The same with the bolt shot.

In fig. 40 the lock is represented in its unlocked state, with the cover or top-plate removed; the auxiliary tumbler and the detector-plate are also removed. In fig. 41 it is represented as locked, with the cover and the detector-plate also removed, and the auxiliary tumbler in its place. In these two figures, the same letters of reference apply to the same parts, unless otherwise stated. B B is the bolt; T¹ are the first series of movable slides or tumblers; s shews the tumbler-springs; T² the secondary series of tumblers; and T³ the third or intermediate series—these latter coming between the first and secondary series; P P are the separating plates between the several members of the first series of tumblers; s¹ are the springs for lifting the intermediate tumblers. On each of the secondary tumblers T² is a series of notches, corresponding in mutual distance with the difference in the lengths of the movable bits of the key. It thence happens that, when the key is turned in the lock to lock it, each bit raises its proper tumbler, so that some one of these notches shall present itself in front of the tooth t in the dog or lever L L. When the bolt B is projected by the action of the key, it carries with it the secondary tumblers T², and presses the tooth t into the notches; in so doing, it withdraws the tongues d from between the jaws j j of the intermediate tumblers T³, and allows the first and intermediate tumblers to fall to their original position. By the same movement, the secondary tumblers T² become held in the position given to them by the key, by means of the tooth t being pressed into the several notches, as shewn in the closed state of the lock (fig. 41). Now let us see what results if any attempt be made to open the lock with any arrangement of key but that by which it has been locked. In such case, the tongues d will abut against the jaws j j, preventing the bolt from being withdrawn; and should an attempt be made to ascertain which tumbler binds and requires to be moved, the intermediate tumbler T³ (which receives the pressure), being behind the iron wall I I, which is fixed completely across the lock, prevents the possibility of its being reached through the key-hole; and the first tumblers T are quite detached at the time, thereby making it impossible to ascertain the position of the parts in the inner chamber behind the wall I I. K is the drill-pin, on which the key fits; and C is a revolving ring or curtain, which turns round with the key, and prevents the possibility of inspecting the interior of the lock through the key-hole. Should, however, this ring be turned to bring the opening upwards, a detector-plate D, fig. 42, is immediately carried over the key-hole by the motion of a pin p¹ upon the auxiliary tumbler T⁴, which is lifted by the revolution of the ring C, thereby effectually closing the key-hole. As an additional protection, the bolt is held from being unlocked by the stud or stump S bearing against the detector-plate; and, moreover, the lever l l holds the bolt, when locked, until it is released by the tail of the detector-plate pressing the pin p¹; l¹ is a lever which holds the bolt on the upper side, when locked, until it is lifted by the tumblers acting on the pin p¹; X are separating-plates between the intermediate tumblers T³; u u¹ are the studs for preserving the parallel motion of the different tumblers.

fig. 42. The detector plate of the Parautoptic lock.

Fig. 43 represents the key in two different forms, or with the bits differently arranged. Either form will lock the lock, but the other will not then unlock it. The end of the key is represented in fig. 44, shewing the screw which fixes the bits in their places. The bits for a six-bitted key are shewn separately in fig. 45.

fig. 43. Key of the Parautoptic lock.

fig. 44. End view of the key.

fig. 45. Separate bits of the key.

In 1847 the parautoptic lock was exhibited at Vienna before the National Mechanics’ Institute of Lower Austria; and towards the close of the year Mr. Belmont, consul-general of Austria at New York, placed in the hands of Messrs. Day and Newell a letter, a diploma, and a gold medal, forwarded by the Institute. The letter was from the president of the Institute to Mr. Newell, and was couched in the following terms:

“The Institute of Lower Austria, at its last monthly session, has passed the unanimous resolution to award to you its gold medal, as an acknowledgment of the uncommon superiority of the combination-lock of your invention; and this resolution was ratified in its general convention held on the 10th instant.

“Whilst I, as president of this Institute, rejoice in seeing the services which by this invention you have rendered to the locksmith’s art thus appreciated and recognised, I transmit to you, enclosed, the said medal, together with the documents relating to it; at the same time availing myself of this opportunity to assure you of my esteem.

“Colloredo Mannsfeld.

“Vienna, May 31st, 1847.”

The diploma and the medal were similar to other honorary distinctions of the same class, and need not be described here; but the report of the special committee may be given, as it expresses the opinions of the Viennese machinists on the relative principles by which safety is sought to be obtained in different kinds of locks.

REPORT

Of a Special Committee on the new Parautoptic Permutation Lock of the American Newell, made known to the Lower Austrian Institute by the Councillor, Professor Reuter, and on the motions relating to it made by the same and accepted by the Institute. Presented at the monthly meeting, April 6th, 1847, by Mr. Paul Sprenger, Aulic Councillor on Public Works, &c. &c.

Gentlemen:—At our last monthly meeting, Mr. Reuter, Aulic Councillor and Secretary of the Institute, directed your attention to a newly invented lock of Mr. Newell, of North America, which was represented as excelling all other changeable combination-locks hitherto known, and as being without a rival.

The Special Committee which was intrusted with the examination of this lock, and of the motions made by the said Secretary, and accepted by the Institute, has conferred on me the honour of making you acquainted with the results of its investigations.

The attention of your committee was chiefly occupied with the three questions proposed by the said Aulic Councillor in relation to the lock in question:

First: Whether the idea of Mr. Newell was of any practical value for already existing and still-to-be-invented combination-locks;

Secondly: Whether the idea was of sufficient importance to be published and minutely described in the transactions of the said Institute; and

Thirdly: Whether the merits of the inventor were of sufficient importance to entitle him to a distinction from the said Institute.

The deliberations on the first question, viz. the newness of the idea, and of its practical value, would of necessity enlist the particular attention of your committee, especially since by far the greater number of its members are by their avocation called upon to be interested in the execution of all kinds of locks.

It is therefore the unanimous opinion of your committee, that the idea of the American Parautoptic Combination-Lock is entirely new and without example.

The combination-locks with keys have, with few exceptions, such an arrangement that a determinate number of movable parts (the so-called combination-parts) must by the turning of the key be raised or lifted into a certain position, if it is desired to project the bolt, or, what is the same thing, to lock it out; consequently these parts, or, as they are technically termed, tumblers, could not be transposed or changed, from the circumstance that the key-bit was one solid piece, with various steps or notches adapted to the several tumblers, and one impression from it destroyed the security of the lock.

In order, however, to add more security to such a combination-lock, and to make the key, in case it should be lost, or any counterfeit made from a wax impression, useless for an unlawful opening of the lock, another step was taken: the key-bit was made to consist of several bits or movable parts, in such a manner that the owner of the lock was enabled to change the bits, and to form, as it were, new keys different from the former. But since the bolt of the lock can only be projected whilst the combination parts or tumblers are in a certain position, which position depends upon the order of the bits in the key, it is evident that the owner, when changing the key, must at the same time make a corresponding change in the position of the tumblers in the lock itself, before the lock can be of any use for the newly changed shape of the key, which rendered it troublesome, and impracticable for the purpose designed, from the fact that no positive change could be made in the lock, without taking it from the door, and then taking the tumblers out of the case, to change them in a suitable form for the key.

This principle of changing the lock is rarely adhered to, as few men understand the machinery of a lock sufficiently to undertake the task; and this circumstance rendered the lock quite as insecure as the former one described.

Another step toward the perfection of combination-locks consisted in this, that the key remains unaltered whilst the combination parts of the lock can, before it is locked, be brought into different positions by means of movable plates on the frame of the lock. These plates were arranged by hand to certain figures, and depended on the memory for adjustment at each time the bolt was to be locked out or in, the key operating only on the bolt, to move it back and forth when the plates were set in proper positions for the purpose; and should the owner forget the arrangement of the plates, after projecting the bolt, his key is of no use to him, and he must resort to the skill of the locksmith to gain access.

The same case may occur in the far less perfect ring-lock of Reynier, which is operated without keys, and is opened by means of the rings being turned in a particular position; on these rings are usually stamped letters, which, by introducing some word readily suggested to the memory, thus point out the relative position of the rings.

But although in case of these ring-locks the owner is enabled to produce a change in the rings in such a manner that the opening of the lock can, as it were, only become possible by rightly arranging the altered position of the letters, still this lock of Reynier’s does not possess that safety and perfection which could have insured it universal application.

M. Crivelli, formerly professor at Milan, has given a minute description of the imperfection of ring-locks generally, in the annals of the Imperial Royal Polytechnic Institute.

It is the unanimous conviction of your committee that the American Lock of Newell surpasses, in the ingenuity displayed in its construction, all other locks heretofore known, and more especially in this, that the owner can, with the greatest facility, change at pleasure the interior arrangement of his lock to a new and more complex one, at every moment of his life, simply by altering the arrangement of the bits in the key, and this is accomplished without removing the lock or any part of it from its position on the door.

Its operation is as follows:—At the closing or locking of the lock, whilst the bolt is projecting, the movable combination parts assume precisely the position prescribed to them by the key, according to the particular arrangement of its bits at the time the key is turned.

The combination parts do not consist in one set of tumblers only, such as are found in all other locks, but there are three distinct sets or component parts fitting into each other. When the bolt is projected, it dissolves the mutual connexion of the constituent pieces, and carries along with it such as are designedly attached to it, and which assume the particular positions given them by the key in its revolution. These parts are rendered permanent in their given form by means of a lever adapted for the purpose, while the parts not united with the bolt are pressed down by their springs to their original places.

If now the bolt is to be returned again, i. e. if the lock is to be unlocked, then the constituent pieces or tumblers which are in the original state must, by means of the key, be again raised into that position in which they were when the lock was closed, as otherwise the constituent parts attached to the bolt would not lock in with the former, and the bolt could not be returned. Nothing, therefore, but the precise key which had locked the lock can effect the object.

This idea in itself, considered by your committee, is as ingenious as it is new, and is accompanied by a perfection in its execution which reflects the highest honour on Mr. Newell, the inventor and manufacturer of the lock.

The lock is built strong and solid, and the several parts are admirably adapted to the functions which they are designed to perform. The walls of steel or iron which separate the security parts from the tumblers, and the cylinder which revolves with the key, present formidable barriers to all descriptions of pick-locks, and render the lock a most positive and reliable security. The tumblers consist of rolled very smooth steel plates, in which the fire-crust has not been filed away, partly in order that the lock might not need oiling, as all these parts are very smooth, and partly that the combination pieces might not easily rust, a thing to which the adhering fire-crust is not favourable. The springs, which by the turning of the key must be raised together with the tumblers, are attached to levers, and press upon the latter at their centre of gravity, in consequence of which all crowding towards either side is prevented, and the key can be turned with facility, in spite of the many combination parts which it has to raise; and the springs themselves are by their positions so little called into action, that their strength can never be impaired by use.

The lock has also another very complete arrangement in the detector-tumbler, which is attached to the cap or covering of the lock. This tumbler, on turning the key either way, closes the key-hole, and not only prevents the use of false instruments in the lock, but detects all attempts at mutilating its interior parts.

This lock is especially useful for locking bank-vaults, magazines, counting-houses, and iron-safes, in which valuable effects, money, or goods are to be deposited for safe keeping. When it is considered that the bits of the key belonging to this lock can be transferred into every possible form within its limits, and since the construction of the lock admits of every combination of the slides resulting from the changes of the key, therefore the lock in question is, in every respect, deserving of the appellation given to it by the Secretary of the Institute, namely, the Universal Combination Lock; and justly so, when we consider that the ten bits attached to the key admit of three millions of permutations, and upward; consequently forming that number of different kinds of keys and locks.

If we consider further, that we need not be limited to the given bit, but that others can be applied, differing in their dimensions from the former; and again, if we consider that from every system arising from a difference in their relative dimensions, a large number of new keys differing from each other will result, and that this can be effected in a space scarcely occupying a square inch,—then we cannot refrain from confessing that the human mind, within this small space, has shewn itself to be infinitely great.

After this preliminary and general exposition, your committee can answer the three questions propounded to them the more briefly, as the locks heretofore known have all been noticed.

To question first.—On the practical value of the invention of Mr. Newell, your committee were unanimous and positive that the principle on which it is based should be preserved.

To question second.—For this reason the committee deemed it desirable that a drawing and description of the American lock in question should be published in the Transactions of the Institute of Lower Austria.

To question third.—With regard to the claims of the inventor, Mr. Newell, to an honorary distinction from the Institute of Lower Austria, the committee recommend that he be presented with a Diploma of honourable mention and a Gold Medal.

The members of your committee, consisting mostly of fellow-tradesmen of Mr. Newell, experience great satisfaction in the fact that it has fallen to their lot to vote to their colleague on the other side of the ocean an acknowledgment of his successful ingenuity, and they close the Report with the request that the Institute will transmit to Mr. Newell of New York, in North America, the Diploma and Gold Medal, together with a copy of this Report, according to the motion of the Aulic Councillor and Professor Reuter.

[An exact copy of the original Report as preserved in the archives of the National Mechanics’ Institute of Lower Austria.]

DR. SCHWARTZ,
Assistant Secretary of the Institute.

There are other circumstances connected with the American bank-lock, in relation to events both in the United States and in England, to which attention will be directed in a subsequent chapter.

The English patent for Messrs. Day and Newell’s lock, dated April 15, 1851, runs as follows: “The object of the present improvements is the constructing of locks in such manner that the interior arrangements, or the combination of the internal movable parts, may be changed at pleasure according to the form given to, or change made in, the key, without the necessity of arranging the movable parts of the lock by hand, or removing the lock or any part thereof from the door. In locks constructed on this plan the key may be altered at pleasure; and the act of locking, or throwing out the bolt of the lock, produces the particular arrangement of the internal parts which corresponds to that of the key for the time being. While the same is locked, this form is retained until the lock is unlocked or the bolt withdrawn, upon which the internal movable parts return to their original position with reference to each other; but these parts cannot be made to assume or be brought back to their original position, except by a key of the precise form and dimensions as the key by which they were made to assume such arrangement in the act of locking. The key is changeable at pleasure, and the lock receives a special form in the act of locking according to the key employed, and retains that form until in the act of unlocking by the same key it resumes its original or unlocked state. The lock is again changeable at pleasure, simply by altering the arrangement of the movable bits of the key; and the key may be changed to any one of the forms within the number of permutations of which the parts are susceptible.”

The “claims” put forth under this patent are the following:—

“1. The constructing, by means of a first and secondary series of slides or tumblers, of a changeable lock, in which the particular form or arrangement of parts of the lock, imparted by the key to the first and secondary series of slides or tumblers, is retained by a cramp-plate.

“2. The constructing, by means of a first and secondary series of slides or tumblers, of a changeable lock, in which the peculiar form or arrangement of parts of the lock, imparted by the key, is retained by means of a tooth or teeth, and notches on the secondary series of slides or tumblers.

“3. The application to locks of a third or intermediate series of slides or tumblers.

“4. The application of a dog with a pin over-lapping the slide or tumblers, for the purpose of holding-in the bolt when the lock is locked or unlocked.

“5. The application of a dog operated on by the cap or detector-tumbler for holding the bolt.

“6. The application of a dog for the purpose of holding the internal slide or tumbler.

“7. The application to locks of curtains or rings, turning and working eccentrically to the motion of the key, for preventing access to the internal parts of the lock.

“8. The application to locks of a safety-plug or yielding-plate, at the back of the chamber formed by such eccentric revolving curtain or ring.

“9. The application to locks of a strong metallic wall or plate, for the purpose of separating the safety and other parts of the lock from each other, and preventing access to such parts by means of the key-hole.

“10. The application to locks of a cap or detective tumbler, for the purpose of closing the key-hole as the key is turned.

“11. The constructing a key by a combination of bits or movable pieces, with tongues fitted into a groove and held by a screw.

“12. The constructing a key having a groove in its shank to receive the detector tumbler.”

fig. 46. Movable stump.

When the American locks became known in England, Mr. Hobbs undertook the superintendence of their manufacture, and their introduction into the commercial world. Such a lock as that just described must necessarily be a complex piece of mechanism; it is intended for use in the doors of receptacles containing property of great value; and the aim has been to baffle all the methods at present known of picking locks, by a combination of mechanism necessarily elaborate. Such a lock must of necessity be costly; but in order to supply the demand for a small lock at moderate price, Mr. Hobbs has introduced what he calls a protector lock. This is a modification of the ordinary six-tumbler lock. It bears an affinity to the lock of Messrs. Day and Newell, inasmuch as it is an attempt to introduce the same principle of security against picking, while avoiding the complexity of the changeable lock. The distinction which Mr. Hobbs has made between secure and insecure locks will be understood from the following proposition, viz. “that whenever the parts of a lock which come in contact with the key are so affected by any pressure applied to the bolt, or to that portion of the lock by which the bolt is withdrawn, as to indicate the points of resistance to the withdrawal of the bolt, such a lock can be picked.” Fig. 47 exhibits the internal mechanism of this new patent lock. It contains the usual contrivances of tumblers and springs, with a key cut into steps to suit the different heights to which the tumblers must be raised. The key is shewn separately in fig. 48. But there is a small additional piece of mechanism, in which the tumbler stump shewn at s in figs. 46 and 47 is attached; which piece is intended to work under or behind the bolt of the lock. In fig. 47, b is the bolt; t t is the front or foremost of the range of six tumblers, each of which has the usual slot and notches. In other tumbler-locks the stump or stud which moves along these slots is riveted to the bolt, in such manner that, if any pressure be applied in an attempt to withdraw the bolt, the stump becomes pressed against the edges of the tumblers, and bites or binds against them. How far their biting facilitates the picking of a lock will be shewn further on; but it will suffice here to say, that the movable action given to the stump in the Hobbs lock transfers the pressure to another quarter. The stump s is riveted to a peculiarly-shaped piece of metal h h (fig. 46), the hole in the centre of which fits upon a centre or pin in a recess formed at the back of the bolt; the piece moves easily on its centre, but is prevented from so doing spontaneously by a small binding spring. The mode in which this small movable piece takes part in the action of the lock is as follows: when the proper key is applied in the usual way, the tumblers are all raised to the proper heights for allowing the stump to pass horizontally through the gating; but should there be an attempt made, either by a false key or by any other instrument, to withdraw the bolt before the tumblers are properly raised, the stump becomes an obstacle. Meeting with an obstruction to its passage, the stump turns the piece to which it is attached on its centre, and moves the arm of the piece p so that it shall come into contact with a stud riveted into the case of the lock; and in this position there is a firm resistance against the withdrawal of the bolt. The tumblers are at the same moment released from the pressure of the stump. There is a dog or lever d, which catches into the top of the bolt, and thereby serves as an additional security against its being forced back. At k is the drill-pin on which the pipe of the key works; and r is a metal piece on which the tumblers rest when the key is not operating upon them.

fig. 47. Hobbs’s Protector Lock.

fig. 48. The key.

Another lock, patented by Mr. Hobbs in 1852, has for its object the absolute closing of the key-hole during the process of locking. The key does not work or turn on its own centre, but occupies a small cell or chamber in a revolving cylinder, which is turned by a fixed handle. The bit of the movable key is entirely separable from the shaft or stem, into which it is screwed, and may be detached by turning round a small milled headed thumb-screw. The key is placed in the key-hole in the usual way, but it cannot turn; its circular movement round the stem as an axis is prevented by the internal mechanism of the lock; it is left in the key-hole, and the stem is detached from it by unscrewing. By turning the handle, the key-bit, which is left in the chamber of the cylinder, is brought into contact with the works of the lock, so as to shoot and withdraw the bolt. This revolution may take place whether the bit of the movable key occupy its little cell in the plate or not; only with this difference—that if the bit be not in the lock, the plate revolves without acting upon any of the tumblers; but if the bit be in its place, it raises the tumblers in the proper way for shooting or withdrawing the bolt. It will be understood that there is only one key-hole, namely, that through which the divisible key is inserted; the other handle or fixed key working through a hole in the cover of the lock only just large enough to receive it, and not being removable from the lock. As soon as the plate turns round so far as to enable the key-bit to act upon the tumblers, the key-hole becomes entirely closed by the plate itself, so that the actual locking is effected at the very time when all access to the interior through the key-hole is cut off. When the bolt has been shot, the plate comes round to its original position, it uncovers the key-hole, and exhibits the key-bit occupying the little cell into which it had been dropped; the stem is then to be screwed into the bit, and the latter withdrawn. It is one consequence of this arrangement, that the key has to be screwed and unscrewed when used; but through this arrangement the key-hole becomes a sealed book to one who has not the right key. Nothing can be moved, provided the bit and stem of the key be both left in; but by leaving in the lock the former without the latter, the plate can rotate, the tumblers can be lifted, and the bolt can be shot.

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