In this remark of Mr. Kemp's we entirely coincide; and it still applies to all locks hitherto made (1834), that the keys, when in the possession of a workman, may be copied; and, in many, without possession. Mr. Kemp's invention may supply a partial remedy for this defect; but until a complete one is provided, the art of lock-making is imperfect, and no locks are inviolable.
Viewing the subject in this light, it affords the editor of this work much satisfaction to state, that he has in his possession a lock, the key of which cannot be copied; a locksmith possessing no tools by which an exactly similar one can be made; and the machine by which the original one was made, is so arranged as to be deprived of the power of producing another like it The lock is very simple, very strong, and can be very cheaply made. The cost of a complete machine to make them would be about one hundred pounds; with that they might be manufactured at one-half the expense of any patent lock. The inventor is desirous to have the subject brought before the public under a patent, but want of time to devote himself to such an object at present obliges him to lay it aside.
Locks have been made which required that the key should be a powerful magnet; others, in which an unusual and complicated motion must be given to the key; and others, in which an improper key or instrument would fire a pistol, or ring an alarum, as proposed by the Marquis of Worcester.
Of all the various locks that have of late years been introduced to the notice of the public, Mr. Chubb's has obtained the greatest celebrity. Although it possesses but small claims to novelty, it cannot be denied that it combines, in an eminent degree, the qualities of security, simplicity, strength, and durability; and we think that the persevering and business-like manner in which the ingenious inventor has contrived to fix it before the public eye, has contributed in no small degree to the successful "run" it has had. The chief characteristic in this lock, and that which marks it as Chubb's, is the employment of a lever called a detector, which locks the bolt fast upon any of the tumblers being beyond its assigned range, and shows that some person has been attempting to unlock it by a false instrument. In other respects the lock resembles Barron's and Bramah's; and we are disposed to question its boasted superiority ever those admirable inventions for a reason which now forces itself upon our attention.
In Barron's and Bramah's the picker has no means of knowing whether the tumblers are lifted too high or not; but in Chubb's he has only to put the detector hors de combat in the first instance, by a correct thrust from the outside of the door (which might be accurately measured) so as to fix it fast in its place; the detector then becomes a stopper to the undue ascent of the tumblers, and the extent of their range is thereby correctly ascertained: thus it appears to us, the detector might be converted into a director of the means of opening the lock.
In 1829 Mr. Gottlieb took out a patent for improvements in locks, which consisted in the application of a piece of paper over the key-hole, so secured as to prevent its being removed without the introduction of a key passing through it; and hence any attempt to break open the lock would be indicated by the fracture of the paper. The paper is introduced and secured by means of a folding shield with a hole in it, similar to the key-hole, in a lock plate; this shield is kept down by a spring catch, which cannot be disengaged for the introduction of a fresh piece of paper, except by the proper key, which is furnished with a projecting stud on the side of the key-stem, for the purpose of disengaging the shield catch when turned. As a source of further security, the patentee proposes to employ checque-paper, with some design engraved upon it; and by having this paper bound in a checque-book, and a leaf torn oft' when required, so that the paper found in the key-hole at any time being compared with the edge of the leaf in the book, the substitution of another paper would be discovered.
We shall conclude our account of inventions of this class with a short notice of a lock for which Mr. Edwin Cotterill, of Birmingham, recently obtained a patent, and which appears to possess in an eminent degree the advantages of strength, durability, and security.
Figs. 1, 2, 3, 4, represent a door-lock upon Mr. Cotterill's construction; Fig. 1 being a view of the lock with the back plate removed, and Fig. 2 a front view, Fig.3 a back view, and Fig. 4 a section of the revolving barrel, drawn to a larger scale, a is the case of the lock, and b a cylindrical barrel, having a Fig. 4 number of small steel bolts cc, which slide in radiating channels in the face of the barrel, and are pressed towards the centre by spiral springs d d, contained in the barrel; a groove, z z, is cut in the face of the barrel and of the bolts, which, when the bolts are forced outwards by the key, form a continuous circular channel; but when the key is withdrawn, each of the sliders is forced in different degrees towards the centre, so that the solid parts of the bolts intercept the groove in the barrel. In this position of the bolts the barrel is held fast by an immovable circular ring e, which fits into the groove z, and has notches which embrace the bolts, and the barrel is thereby held fast; but when the bolts are forced outward by the key, the groove in the bolts coincides with the notched ring, and the barrel may be turned in either direction, f is an arm or stud fixed to the circumference of the barrel, which first lifts one or more tumblers at g, and then shoots or draws back the lock bolt, by pressing against the horns of the bolt at jj. k is the latch bolt which slides in a channel formed to receive it in the lock bolt; the bolt is pressed outward by two spiral springs, enclosed in two cylindrical cases m m, let into the heel of the bolt, and the bolt is drawn back by a cam n, upon the knob spindle, and acting upon either of the studs, so as to withdraw the bolt by turning the knob in either direction.
The key consists of a cylindrical stem, having a number of inclined grooves cut in the circumference, and acting upon inclines formed on the ends of the bolts. These grooves vary in depth, slope, and the angle they form with the axis of the key, and are cut by a machine, which can be varied whilst working to such an extent, that millions of keys might be cut which should each differ. Two keys only are cut alike, and these are sent with each lock sold; and as the locks are all made to the keys, the liability of one key opening more than one lock is at once obviated. Should an attempt be made to open the lock with a false key, one of the bolts is projected too far, and is retained in that position by a spring catch p, which falls into the groove, so that the true key cannot move the lock, until, by a particular movement of the key, the catch is disengaged.
Figs. 5 and 6 represent a padlock upon the same principle; Fig. 5 being a back view of the lock with the back plate removed, and showing the lock as open; and Fig. 6 being a section of the lock with the barrel removed, to show the manner in which the staple is held when the lock is shut. a is the case of the lock, and 6 the barrel containing the bolts, similar to that already described, and held by a notched ring on the back of the front plate, and therefore not seen in the figure. On the back of the barrel is a portion of a circular ring r, having a gapor space equal to the breadth of the shackle s, and a groove is formed in the shackle to admit the ring. The lock is closed by pushing in the shackle, and turning the barrel by means of the key, so as to bring the gap in the ring downwards, whereby the ring itself is brought into the groove in the shackle, and prevents the shackle being withdrawn; by turning the barrel so as to bring the gap upwards, the shackle is released from the ring, and may be withdrawn, so as to be disengaged from the staple; a stud t on the back of the shackle prevents its being drawn out too far.
The peculiar formation of the sliding shackle affords great strength; and from its closely entwining the staple, it becomes impossible to apply any instrument for the purpose of wrenching it, whilst the cap at the top renders it impervious to wet.