Tumbler lock

Application filed January 13, 1928. Serial No. 80,992,

This invention has for its object to effect certain improvements in the art of manufacturing tumbler locks whereby, the lock parts may be inexpensively manufactured of g such uniformity that they are interchangeable and so accurately proportioned that, when assembled., the tumbler ends lie flush with the cylindrical surface of the lock cylinder, making unnecessary the usual expen10 sive hand operation of filing the tumblers flush with the lock cylinder and obviating damage to the lock cylinder incident thereto.

More or less hand work and machining has heretofore been necessary in the manu15 facture of tumbler locks with the result that slight variations were unavoidable and, notwithstanding the exercise of the greatest care, some hand filing of protruding tumbler ends was necessary to permit tne lock 20 cylinder to snugly fit within the bore of the lock-case and work without catching. This hand filing has constituted an important item in the cost of manufacture of such locks and the roughened surfaces of the tumbler 25 ends and of the lock cylinder due thereto have been objectionable both on account of the unsightly appearance of otherwise wellexecuted work and on account of impairment of the smooth working conditions of the 3Q locks. _s

With this invention machining and hand work are eliminated, avoiding the objections above noted, reducing the cost of manufacture, and improving the appearance as well ³⁵ as the smooth operation of the locks.

Another object of the invention is to so design the lock cylinder as to make it suitable for production by die casting whereby 40 the desired uniformity of dimensions may be obtained and still afford sufficient strength.

Another object of the invention is to provide a lock with a lock cylinder of frangible 45 material and so constructed that, upon an attempt to force the lock, it will fracture without releasing its locking engagement and its fractured state will baffle fiirther attempts.

With the above and other objects in view 50 the invention consists in the tumbler lock and method of producing same as herein claimed and all equivalents.

Referring to the accompanying drawings in which like characters of reference indicate the same parts in different views. 55

Fig. 1 is a longitudinal sectional view of a lock cylinder with its key and tumblers constructed in accordance with this invention;

Fig. 2 is a detailed view of a set of stand- 60 ardized interchangeable tumblers therefor;

Fig. 3 is a front view of the lock cylinder;

Fig. 4 is a transverse sectional view thereof on the plane of line 4—4 of Fig. 1;

Fig. 5 is a bottom view of the lock cylin- 65 der;

Fig. 6 is a transverse sectional view on the plane of line 6—6 of Fig. 5, and

Fig. 7 is a sectional view of the lock containing such lock cylinder and showing the W fracture of the lock cylinder as when an attempt is made to force the lock.

In these drawings, 10 indicates a lock cylinder, which is die cast for uniformity of dimensions, particularly as to the distance y ⁷⁵between the bottom wall of the key slot 11 and the upper cylindrical surface oi the lock cylinder.

The key 12 fitting in this key slot 11 and engaging the key bearing surfaces formed 80 at the ends thereof is provided with the usual shoulders 13 to engage the stop shoulders 14 of the key slot to determine the operative position and its serrated upper edge forms key bits 15 of various heights, where the usual 85 regularly spaced slide tumblers 16 engage with spring pressure holding the key seated on said key bearing surfaces.

As it is not feasible in a die casting to make the tumbler slots separate, a longitudinally 9θ extending diametrical cored slot 17 is formed through the lock cylinder with opposite grooves 18 in its side walls, within which the tumblers slide. The tumblers have openings 19, through which ^he key passes, as usual, ⁰⁵and in order that they may bear with pressure on the serrated edge of the key, each is. provided with a spring 20 housed within the cylinder in cylindrical recesses 21 and engaged by an outwardly projecting arm 22. To ^loc

1,789,757 avoid weakening the structure, the several spring recesses 21 are arranged alternately on opposite sides of the opening 17 and said recesses extend in one direction to the sur5 face of the cylinder. In order to position the spring 20 as close as possible to the center line of the tumbler slide, its recess 21 is made to open directly into the opening 17 and this materially reduces the length of the guide lu groove 18 on this side of the tumbler, but compensation is provided for the interruption of the guide, groove 18 by extending the arm 22 into a guide groove 23 in the wall of the recess, thus giving the tumbler slide op15 posite edge bearings at both ends to prevent it from binding and also lateral bearings on both sides of both ends and at both edges to prevent lateral displacement by the pressure of the key in passing therethrough. The 20 spring recesses 21 open directly to the opening 17 with parallel side walls and the springs 20 are seated in the closed ends thereof and are located as close as possible to the edge of the tumbler slides but are prevented from fric23 tional engagement therewith by pairs of beads 24 which project from the side walls of the recesses for a short distance.

The spring pressure of the tumbler slides upon the upper serrated edge of the key 30 forces the lower straight edge of the key into bearing engagement with the bottom wall of the key slot 11 at both ends thereof, which, . as before stated, is in predetermined definite relation to the cylindrical surface of the lock 35 cylinder and forms the base line from which the key bits 15 are dimensioned. The tumblers 16, preferably sheet, metal stampings, are formed in sets of different standardized . sizes, one set being shown in Fig. 2 as con40 sisting of the three sizes A, B and C. While the outer dimensions of these tumblers are the same and the size of the openings 19 are the same, the distance from the upper end of the opening to the upper end of the tumbler 45 differs in the different sizes, such distance for tumbler A being indicated as a', that for tumbler B as δ', and that for tumbler C as o'.

. Not only are the effective dimensions of 50 the tumblers thus standardized and made uniform for all tumblers of a given size, but the bit heights of the key are also standard- , ized, a uniform dimension from the base line formed by the bottom straight edge of the ⁵⁵ ν\*°· ^tum^^er bearing surface of the key bit being always the same for tumblers of a given size. Thus all key bits for A tumblers have the bit height dimension a complementary to tumbler diinension a' so that the two oo together equal the dimension y of the lock cylinder, and all key bits for tumblers B have the dimension δ complementary to tumbler dimension δ' so that the two together equal the dimension y of the lock cylinder, and all key bits for tumblers C have the dimension c complementary to tumbler dimension c’ so that the two together equal the dimension y of the lock cylinder. In this manner any A tumbler, when assembled in position to engage an A size key bit, will have both ends ₇₀exactly register with the surface of the lock cylinder and, when the key bit formula is followed in placing the tumblers in the lock cylinder, perfect registration of all tumblers necessarily follows and there is no occasion ₇₅for filing tumblers and for marring the smooth surface of the lock cylinder in doing so.

Such results are incapable of accomplishment in quantity production with lock cylin- ₈₀ders made with machining or hand work so that the die casting of lock cylinders is essential to the maintenance of the uniform dimensions necessary for the purpose.

Although guards 25 may be used at the en- ₈5 trance to the key slot, as usual, to require a key of particular sectional shape, provision has been made to facilitate the entry of the key by providing the key with a pointed end having the downwardly directed cam surface 90 to guide it into proper bearing engagement with the bottom of the key slot at the far end of the opening 17 and with the upwardly directed cam surface for lifting the tumblers and, in order that the key may not bind by 95 being inserted in an angular position influenced by the pressure of the spring-pressed tumblers, one or. more bridges 26 are formed across the opening 17 connecting with and forming oblique extensions of the walls of _Iootumbler grooves 18, as best seen in Fig. 5. It is found in practice that these bridges 26 may be so arranged without interfering with the coring of the.lock cylinder die. The bridges 26 terminate just below the level of the bottom 105 of the key slot but serve to lift the key when engaged by the downwardly directed cam on the end of the key should the key be inserted in an inclined position and thus prevent binding and facilitate the insertion of the key. nu Also upper guide shoulders 27 are formed at both ends of the key slot to insure the proper seating of the key by their engagement with a longitudinally extending shoulder 28 on the key itself. . _Ila

The lock cylinder of this invention may be used in a lock-case of any type and may effect a locking engagement in any well known manner but one type of lock is shown in Fig. 7, wherein the lock-case 29 forms a part of the 120 dead-bolt of. a transmission lock for automobiles,. the lock cylinder 10 being confined therein by a hard metal cap 34 and serving to operate a spring-pressed locking bolt 30 by having a wrist-pin or cam projection 31 on 125 its end engaging a slot in said locking bolt. In this view is shown the protective feature of the die cast lock cylinder of this invention whereby the forcing of the lock is prevented owing to the frangible nature of the die cast- 130

1,789,767 ing and the weakening thereof by the coring to produce the opening 17 with the tumbler grooves and the spring recesses. With the tumblers 16 engaged in the tumbler slots of ₅ the lock-case,'as when the mechanism is locked, an attempt to force the lock by means of a tool such as a screw-driver 32 driven into the key slot of the lock cylinder and turned by means of a wrench 33, will cause the lock 10 cylinder to fracture transversely at about the plane of the uppermost tumbler or the plane of the sectional view shown in Fig. 4. The loose upper end of the lock cylinder will then turn freely without affecting the lower por15 tion of the lock cylinder, which remains locked by the tumblers to prevent the release of the mechanism controlled by the lock.

While the lower straight edge of the key and the bottom of the key slot against which it 2q bears and is held by the pressure of the spring tumblers are defined as constituting the base or reference line from which the parts are dimensioned for accurate complementary matching the tumblers to the key bits, it is 25 obvious that, atty other reference surfaces on the key and lock cylinder may be employed provided they are held in bearing contact by the pressure of the spring-pressed tumblers.