LOCK. 



raifes it fo as to remove the catch e from tlie notclies/or^, 

 and then the key enters the notch /■ in the bolt, and moves it. 

 In this, which is the common lock, it will be feen there is no 

 feenrity, except what arifes from the intricacy of the wards 

 F furrounding the key ; for a f.ilfe key, or any other inllru- 

 ment which is of the fame length as n, will, if it can pufs the 

 wards, raife the tumbler and draw back the bolt. Mr. 

 Rowntree has, by applying an ingenious contrivance to this 

 lock, rendered it fo fccnre^ that it will be nearly impofTible 

 to pick or open it with any other than the true key. To 

 the tumbler he has added a piece of metal h,Jigs. 7 and 8, 

 called its_^;;, fixed to its lower fide. When the tumbler 

 is locked in the notches /, j, of the bolt, the fin apj)lics 

 itfelf to a cluftcr of fmiill wheels \, Jigs- 5 and 8, all littcd 

 on one centre pin beneath the tumbler ; the edges of thefe 

 wheels ftop the fin h, and prevent the tumbler being raifed ; 

 but each wheel has a notch i,fg. 8, cut in its circumference, 

 and when they are all placed, fo that every notch is t'jrned 

 to the fide oppofite the fin of the tumbler, and forming one 

 notch through the whole clufi;er of wheels, then the fin is 

 at liberty to enter this notch, allowing the tumbler to rife : 

 'but when the tumbler is down, and the plain edges of all or 

 ■any of the wheels are prefented to the En, the tumblor can- 

 rot be raifed ur.lefs the wheels are firft put into the right 

 pofition above-mentioned : this is done by a number of le- 

 vers Yi-ifys. y and 7, all centred on one pin at i. At the op- 

 pofite end each has a tooth m, entering a notch in the wheel 



XXII. 'Mifccl'any, in which A reprefents the bolt, fitted ta 

 Aide on the metal plate BBC, by palling through a hole in the 

 fide C, which is turned up, as fiiewn \nfg. 3 : the other end 

 of the bolt is guided by paifing under proper grooves in the 

 lower fide of the circular box D D, which is fcrewed to the 

 plate B to confine the bolt down. It contains the whole mc- 

 chanilm of the lock, confilfing of an interior cylinder or bar- 

 rel E E, (hew n in the feftion^/fj . 3 , with its appendagt s in per- 

 fpeftive wjlg. 4. This barrel is fitted to turn round within the 

 box DD, the upper end au being received into a cavity exactly 

 fitting it, and them.iddlccncompancd by a circular ringof llccl 

 plate i i, fcrewed into the box as fiiewn mjig. 3, and one-half 

 ihewn at b,Jig. 4. The ring enters a circular groove formed 

 round the barrel, and thus confines it from having any other 

 motion than a rotation on its axis, and this only by the aid 

 ' of the key R, as will be explained. The barrel has a hole 

 through its centre, which is clofed at bottom by a circular 

 plate F, fcrewed to it, and fupporting the central pin Cr, 

 which occupies the centre of the hole through the barrel : 

 this centre pin guides the key in entering tli; lock. When 

 the barrel E E is turned round by the key, it flioots the bolt 

 A, by an ingenious contrivance, explained 'in Jig 2, an aper- 

 ture being cut through the plute B B C to exinbit it. The 

 plate F, on the lower end of the barrel E, has a pin f pro- 

 jecting from it : this pin enters a curved opening, at a 

 fmall diftance from the centre, and therefore defcribcs a cir. 

 cle when llie barrel is turned round, cut through the bolt A, 



belonging to it, fo that when any lever is preffed outwards as is fliewn by the dark curve F in Jig. 2. In the pofiti m 

 it turns its wheel round. The levers are preflcd towards the there fnewn the belt is withdrawn, and the pin_/', reding 

 key by a fpring n applied to each, and in this ftate they reft againll the folid part of the groove, prevents the barrel hvhg 

 againft a pin fixed in the plate. The wheels are now dif- turned round any farther in the direction from F to / : 



' ' ' ■ but by the application of the key, the barrel may be turned 

 in the other dircftion from y to F, in which ccurfe it pafics 

 round in a circular part of tlie groove, and therefore produces 

 no motion of the bolt A, until the piny" Ilrikes the llraight 



arranged completely, every one prefenting its plain edge to 

 the fin, but every one requiring a different degree of motion 



to bring the notch round to the proper pofition. When the 

 'key is introduced and turned round, it firil operates upon 

 the curved part p q,fg- 5. pf the levers K, and railing 



them, turns all the circles I at once into the proper pofition. 



The key, in turning farther round, operates on the part c c. 



part o- of the groove, and afts againll it to throw the bolt 

 forwards: and when the barrel lu\s made a complete circuit, 

 and the piny is again come to the fame pofition it w«.3 at 



Ji". 6, of the tumbler, now at liberty to move, and by raifing firil, the bolt is fliot out as at f.g. i, and the pin is relling 



it releafes the bolt, and in turning ftill further round, it in the hollow h, which prevents it moving any farther in the 



feizes the notch r of the bolt, as inyfr. 6, and (hoots it. fame direftion. When the barrel is turned back again, the pin 



"The key is cut into fteps of different lengths, as fhewn at /afts againll the notch i and the curved part /■ of the groove, 



•vv, vnjig. R.: each ftep operates on its refpedlive lever K and withdraws the bolt into the pofition of Jig. 2 : now the 



in a different degree, and turns its circle I the proper quan- pin J, either when the bolt is fiiot out or in, is in a right 



titv. The notch at j afts upon the tumbler, and the plain line with the centre of the barrel E, to which it is fixed, 



part t moves the bolt. In this lock there is no poffibility of and the direftion of the bolt's motion. By this means, no 



picking It, for if all the levers except one were raifed the force whatever applied to drive back the bolt can luve the 



proper quantity, that one would detain the tumbler aseffec- leall tendency to turn the barrel round, and flrain the me- 



tually as the whole number; and a falfe key, befides having chanilm which prevents its motion, unlefs the parts are firft put 



the wards as R, mull have all the notches v, v, of tlie exatt into a particular arrangement, by the application of t!ie key. 



depth, neither greater nor lefs, or it will not open the lock, The interior meclianifm mull be explained hj Jig. 4, in which 



even if one alone is incorrcft. If the key is lofl, when a /, m, n, reprefent fmall fteel fiidere, which are fitted into 



new one is made, the maker takes out the levers K and cir- proper grooves or flits, made in the fubilance of the barrel 



cles I, and arranging them in anew order, one upon the other, E. Of thefe there are fix in number, arranged round the 



making the new key to fit the new arrangement, and then barrel, and projecling a little from its exterior furface in the 



the old kev wiU not open the lock ; though none of the fmall part. Thefe Aiders are received in notches _)•, z, in the 



parts are altered, but only their arrangement. The fame fixed Ileal ring b I, before defcribed ; and thus effeilually 



may be done if it be fufpecled that an imprefTion has been detain the barrel at fix points from being turned round, cx- 



frandently taken from the key to make a falfe one by. cept it is firil unlocked by the key R being introduced at 



The locks invented by Mr. .Tofeph Bramah difpiay great the key-hole H, and the Aiders preffed down by it, fo as to 



ingenuity, and dem.and a particular defcription, having been in bring the notches (of which each A:der has one, as at r 



very general ufe for many years pall, and greatly admired. He Jig. ^■) all oppofite the fteel plate ^ i, and then the barrel 



obtained a patent for his invention in 17^*4, andettabhAied a may be turned round. When the key is abfent, the flidcrj 



manufadlory of them, in which he employed a number of inge- are raifed up by a brafs ring v Aiding on the central pin G, 



nious tools and enfines for the fabrication of the different and lifted up by a fpiral fpring co. The key has fix notches 



parts. One of Mr. Bramah's fimplell forms of a lock for a cut in the end of it, as Aiewn at S, which is an end view : 



drawer, or for a door, is reprefcntcd \nf^s, 1, 2, 3, 4, Fiale each notch in the key includes cue of the fix Aiders /, m, n, 



and 



