US2807954A - Combination lock - Google Patents

Description

Oct. 1, 1957 H. c. MILLER 2,807,954

7 COMBINATION LOCK Filed July 6, 1954 3 Sheets-Sheet l 36 I m" Mmnnnun R Q 3/ I K lllln %M33 6 INVENTOR IIIII I V I 0 L W v BY TTORNEYS Oct. 1, 1957 H. c. MILLER 2,807,954

COMBINATION LOCK Filed July 6, 1954 5 Sheets-Sheet 2 @5. y 0 f ll 0 V Z4 32 5 4 6/ A 59 "U 55' 56 44 55 I I/ 1 U .5, 52 ,1 .4 6'0 2a INVENTOI? ATTORNEYS H. C. MILLER COMBINATION LOCK Oct. 1, 1957 3 Sheets-Sheet 5 Filed July 6, 1954 INVENTOR @12 7 I. W101 ATTORNEYS United States Patent 2,807,954 COMBINATION LOCK Harry C. Miller, Rochester, N. Y. Application July 6, 1954, Serial No. 441,526

9 Claims. (Cl. 70 -333 The present invention relates in general to improvements in permutation locks, commonly referred to as combination locks, and more particularly to combination locks having provisions for resisting detection of the combination of the lock and opening of the same by unauthorized persons.

This application is directed to improvements in the com bination lock disclosed in my earlier Patent No. 2,575,674, granted November 20, 1951.

Locks of the type commonly referred to as combination locks depend for their operation upon the alignment of a plurality of disk-like rotatably supported elements, commonly called tumblers, in a preselected manner to permit retraction of a reciprocating bolt from its projected position. The tumblers are each provided with a peripheral recess, commonly termed a gate, which are to be disposed in registry with each other and in preselected alignment with a fence normally disposed in overlying spaced relation with the tumbler peripheries and supported on a fence lever controlling movement of the bolt. The security of such locks is dependent upon the fact that the number of orders or permutations of the possible relative positions of the tumbler gates before all of the gates come into registry to permit retraction of the bolt is so large that the chance of these gates being aligned by a person not familiar with the combination is negligible.

The tumblers are indirectly spaced from the rotatable dial through the medium of a driving cam which conventionally is provided with a driving pin projecting from one face of the driving cam to engage a rotatable flyer associated with the rearmost tumbler which in turn engages a stop on the tumbler to drive the same. The remaining tumblers are driven by driving pins projecting from their adjacent tumbler disposed in the direction of the driving cam. Conventionally, the fence lever is pivoted to the bolt and is provided with a nose which normally rests upon the driving cam periphery in a position supporting the fence out of contact with the tumbler peripheries. In order to retract the bolt by rotation of the driving cam there is provided in the driving cam a special gate which receives the fence lever nose when the tumbler gates are aligned with the fence to shift the fence lever and the bolt coupled thereto.

Because of the difliculty in mass production manufacture, it is impossible in a practical sense to manufacture all of the parts, including the tumblers, to such close tolerances that there will be the same slight difference in the space between the outer edges of the difierent tumblers and the fence. Accordingly, by very careful manipulation of the driving cam to progressively shift the tumblers through preselected degrees of rotation and dispose the driving cam gate below the fence lever nose, the fence lever may be allowed to drop against the edge of the highest tumbler and through successive manipulations the position of the gate may be detected by skilled persons through senses of touch'or hearing then by continuing to manipulate the driving earn the gates of the successively lower tumblers can be aligned with the fence until the 2,807,954 Patented oet. 1, 1957 2 correct combination is found and the is broken.

To resist this method of breaking the security of combina'tion locks, the combination lock disclosed in my above-mentioned earlier Patent No. 2,575,674. provided a reciprocally slidable plate on the rear face of the driving cam having arcuately curved opposite ends register.

ing with the circular path of the driving cam periphery and disposed normally in a position to present an effective uninterrupted driving cam periphery to the fence lever nose and bar entry of the fence lever into the driving cam gate. A spindle was coaxially supported within a bore provided within the driving cam arbor having a knob disposed outwardly of the dial by which the sliding plate could be shifted to a position exposing the driving cam gate to the fence lever, in which position one end portion of the sliding plate projected beyond the driving cam periphery. Arcuate stop members having arcuate inner faces disposed closely adjacent to the driving cam .pe-

riphery were provided on the rear cover plate of the lock housing to engage the projecting portion of the sliding plate when the driving cam gate was exposedto limit rotation of the driving cam. a

While this mechanism has greatly increased the difliculty of breaking the security of the lock by unauthorized personnel, tests have revealed that after a long period of manipulation of the driving cam with the end of the sliding plate opposite the driving cam gate projected slightly beyond the driving cam periphery so that its arcuate surface merely bears upon the inner curved faces of the stop members, the arcuate face of this portion of the sliding plate may be worn away to the point where the driving cam can be rotated freely with the sliding plate shifted out 'of its locking position a suflicient distance to expose the entrance of the driving cam gate to the fence lever nose. When this conditionis reached, the slight drop of the fence lever into the barely exposed entrance to the driving cam gate may be sufficient to bring the fence into light contact with the tumblers to permit detection of the location of the tumbler gates.

An object of the present invention, therefore, is the provision of a combination lock of the type having means for holding the fence out of engagement with the tumblers during adjustment of the tumblers, wherein the tumblers are disengaged from driving connection with the driving cam when the fence is conditioned to contact the tumblers. Another object of the present invention is the provision of a novel combination lock having associated with retractable means for selectively exposing and closing the driving cam gate to operative association with the fence lever a mechanism to disconnect the driving cam from the tumblers when the driving cam gate is in exposedcondition.

Another object of the present invention is the provision of a novel combination lock of the type having means preventing engagement of the fence with the tumblers during rotation of the tumblers, wherein the driving'connection between the driving cam and tumblers is destroyed when function'of said means is impaired.

' Another object of the present invention is the provision of an improved combination lock of the type having reciprocable means normally closing the'driving cam'gate to hold the fence'out of contact withthe tumblers, wherein the driving connection between the driving 'cam and tumblers is destroyed when the reciprocable means is worn to a sufficient degree to impair its driving cam gateprotecting function.

Another object of the present invention is the provi-' sion of a novel combination lock of the type having a sliding-protecting plate normally positioned to prevent operative 'engagement'of the fence lever with the driving cam gate and shiftable toa position projecting a portion security of the lock of the plate beyond the driving cam periphery to expose the gate to the fence lever, wherein driving means for intercoupling the driving cam with the tumblers is carried by said. plate and is decoupled from said plate when the projecting portion of the plate is worn sutficiently to 1mpair the protecting function of the plate.

Other objects, advantages and capabilities of the present invention will become apparent from the following detail description taken in conjunction with the accompanying drawings showing one preferred embodiment of the invention.

In the drawings:

Figure 1 is a vertical transverse section view of a combination lock embodying the present invention.

Figure 2 is a rear elevation of the combination lock with the lock housing cover plate removed and the reciprocating slide shown in gate-closing position.

Figure 3 is a rear elevation of the combination lock with the lock housing cover plate removed and the reciprocating slide positioned to expose the driving carn gate to the fence lever.

Figure 4 is a detail rear elevation of the reciprocating slide.

Figure 5 is an elevation of the inner face of the lock housing cover plate.

Figure 6 is an elevation of the inner fly.

Figure 7 is an exploded perspective view of the driving cam and gate-closing mechanism.

Referring to the drawings wherein like reference characters designate corresponding parts throughout the several figures, there is illustrated a conventional combination lock modified in such a manner as to permit the application of an embodiment of the present invention. The combination lock comprises a substantially rectangular lock housing member 10 having a hollow boss 11 projecting in opposite directions from the front wall thereof and through a door 12. Secured to the threaded outer end of the hollow boss 11 is a conventional escutcheon plate 13.

Rotatably supported within the hollow boss 11 is a drive spindle 14 threaded at its outermost end to a dial knob 15 having aflixed thereto a conventional dial 16 supported to rotate within the recess of the escutcheon plate 13. The inner end of the driving spindle 14 is threaded to receive an internally threaded portion of a tubular boss 17 projecting from a driving cam 18, the driving cam being keyed to the driving spindle 14 by means of a suitablespline not shown.

A plurality of tumblers, generally indicated by the reference characters 19, 20 and 21, are supported to rotate freely upon the portion of the hollow boss projecting within the lock housing 10, each of the tumblers being of the conventional type designed to be changed by means of a combination resetting key to vary the combination of the lock, and to this end comprising an inner hub 22 on each of which are supported a pair of annular disks 23, 23' having a tumbler gate or recess 24 therein. The outer annular disks 23, 23' are selectively locked against rotation relative to their supporting hubs 22 by means of conventional locking arms carried by the annular disks 23, 23' and engaging peripheral serrations or teeth on the hubs 22 to hold the annular disks in fixed position.

Conventional fiys 25 and 26 consisting of annular rings having an outwardly radiating projection thereon are provided between the outermost and intermediate tumblers 21 and 20 and between the intermediate and innermost tumblers 20 and 19 to rotate in annular recesses provided in the adjacent faces of the inner hubs 22 of the tumblers 21 and 20. The radial projections of the fiys engage stops in the adjacent tumblers to provide a lost motion driving connection between the tumblers operatively associated with each fly. The innermost tumbler 19 is provided with a special fly 27, as illustrated in detail in Figure 6 having an annular ring 28 to surround and ride freely on the hollow boss 11 and an outwardly radiating projection 29 terminating in a triangular tip having inclined converging faces producing a cam surface 30, the faces being inclined, in the preferred embodiment, at external angles of 130 degrees each with the medial radial plane of the projection 29.

The lock is provided with a bolt 31 which is adapted to slide in a suitable guideway formed in one wall of the housing 10, the bolt 31 being operated by a fence lever 32 pivotally attached thereto by means of a screw 33. The fence lever 32 is continuously resiliently urged toward the tumblers by means of a suitable spring 34 and is provided with a laterally projecting arm 35, commonly referred to as a fence, which projects along an axis parallel to the axis of the driving spindle 14 and overlies the peripheries of all the tumblers 19, 20 and 21. The fence 35 is adapted to be received in the gates 24 of the tumblers when the tumbler gates are disposed in registry upon operation of the dial knob 15 to establish the combination. The downward rotation of the fence lever 32 when the fence enters the gates permits the shoulders 36 on the free end of the fence lever 32 to fall free of the depending boss 37 on the top wall of the lock housing 10 and permit the fence lever to be shifted laterally beyond the boss 37 to withdraw the bolt 31 from its projected position.

The driving cam 18, as more particularly shown in Figure 7, is provided with a recessed peripheral portion 38 extending over approximately 75 to degrees of the circumference of the driving cam, in the center of which recessed portion is a driving cam gate 39 adapted to receive the nose 40 of the fence lever 32. As will be obsewed from the detailed illustration of the driving cam 18 in Figure 7, the driving cam gate 39 has a pair of diverging walls, one forming an inclined slightly convex wall for controlling the movement of the fence lever nose 40 into the driving cam gate and therefore the speed of approach of the fence 35 toward the tumbler peripheries, and the other wall forming a shoulder for cooperating with a complementary shoulder on the fence lever nose 40 by which the fence lever 32 is shifted to retract the bolt 31 upon rotation of the driving cam in a counterclockwise direction as viewed in Figures 2 and 7.

Projecting from opposite portions of the rearmost face of the driving cam 18 are a pair of guide blocks 41 having guide grooves 42 formed in the adjacent surfaces thereof to support a slide 43 for rectilinear movement along a diametrical axis of the driving cam 18. The length of the slide 43 corresponds to the maximum diameter of the driving cam 18 and, as will be observed from Figure 7, is provided with opposite ends 44 and 45 which are arcuately curved to correspond with the projected circular path of the periphery of the driving cam 18 so as to present, when the slide 43 is in the position illustrated in Figure 2, an uninterrupted driving cam periphery to the nose 40 of the fence lever 32.

The slide 43 is provided with a recessed portion 46 at its lower end 45 designed to receive a driving pin 47 projecting forwardly and rearwardly of the slide 43 and having a pair of integral supporting arms or wings 48 projecting laterally of the pin, which in the preferred embodiment, are approximately .037 of an inch in thickness. These arms 48 are designed to be received in complementary lateral extensions 49 of the recess 46 and soldered, as indicated at 50, to the portions of the slide 43 bounding the recess extensions 49.

The driving pin 47 is provided with a triangular tip 51 having inclined cam faces adapted to cooperate with the cam faces 30 on the projection 29 of the rearmost fiy 28 and impart rotation to the fly 28 upon rotation of the driving cam 18 when the slide 43 is disposed with its arcuate ends 44 and 45 forming a continuation of the circular periphery of the driving cam. A recessed bushing 52 is also provided on the slide 43 and houses a spring pressed ball check 52' cooperating with the spherrcallyconcave socket 53 in the driving cam 18 to resrhently hold the slide 43 in gate-closing position.

The slide 43 is provided with a central irregular opening 54 whose walls are shaped to cooperate with the tang portion 55 of a slide cam 56 which is fixed on the end of an inner spindle 57 projecting through the axial bore in the hollow driving spindle 14 and dial knob and terminating in an auxiliary knob 58 seated in a recess 15' in the forward end of the dial knob 15. Engagement of the tang portion 55 of the slide cam 56 with the shoulder 59 and concavely curved wall portion '60 of the slide openrng 54 when the slide cam 56 is rotated in a counterclockwise direction as viewed in Figure 2 forces the slide 43 diametrically of the driving cam 18 to the position Illustrated in Figure 2 wherein the upper arcuately curved end 44 of the slide 43 is disposed below the driving cam gate 39 exposing the driving cam gate to receive the fence lever nose 40. Rotation of the tang portion 55 of the slide cam 56 in a clockwise direction as viewed in Figure 2 brings the tang 55 into engagementwith the shoulder 61 and arcuately curved wall 62 bounding the opening 54 to shift the slide 43 back to the position llustrated in Figure 2 wherein the ball check 52' seats 1n its complementary socket 53 and the arcuate ends 44 and '45 form continuations of the circular periphery of the driving cam 18.

The rear cover plate of the lock housing, indicated by the reference character 65, as illustrated in Figure 5, 1s provided with a pair of arcuate stop members 66 and 67 having their inwardly facing surfaces 68 coaxial with the driving cam and spaced slightly from the driving cam periphery. These surfaces 68, in the preferred embodiment herein illustrated, are provided with flutings or cylindrical grooves 69 extending along axes parallel to the medial axis of the tumblers, but they may be either slightly roughened or provided With serrations. The stop members 66 and 67 terminate in stop shoulders 70 positioned to engage the end portion 45 of the slide 43 when projected beyond the periphery of the driving cam 18 to limit rotation of the driving cam to approximately 50 degrees, this being the approximate rotation required when the fence lever nose 40 is seated in the driving cam recesses 39 to effect full retraction of the bolt.

The rear cover plate 65 is also provided with an arcuate groove 71 extending along an arcuate path coaxial with the driving cam and a connecting radial entrance portion 72 extending about a radius of the driving earn, the recess 71 being adapted to receive the rearwardly projecting portion of the driving pin 47 to permit the slide 43 to be shifted diametrically from its gateclosing position when the dial and driving cam are positioned at one selected dial reading and hold the slide plate 43 against return to gate-closing position during rotation of the driving cam through the are permitted by the stop shoulders 70 of the stop members 66, 67. A cylindrical recess 73 in the rear cover plate 65, with which the radial entrance portion 72 connects, receives the driving pin 47 when the slide 43 is in gate-closing position, the wall of the recess 73 preventing shifting of the slide 43 when the driving pin 47 is out of radial alignment with the radial entrance portion 72.

'The provision of the driving pin 47 on the reciprocating slide 43 so that the pin 47 is shifted radially out of intercepting position with respect to the projection 29 on the rearmost fiy 28 destroys the driving connection between the driving cam 18 and the rearmost tumbler 19 when the slide 43'is shifted to gate-opening position so that the tumblers cannot be shifted when the driving cam gate is to any extent exposed to receive the fence lever nose 40 and thereby permit the fence to contact the tumblers.

Further, if an attempt is made to disable the mechanism for preventing engagement of the fence with the tumbler peripheries during rotation of 'the' y forcibly rotating the dial with the end 45' of the slide 43 shifted into frictional contact with the stop member surfaces 68 to wear down the end 45, the arms 48 of the driving pin will be equally worn. Before the slide 43 is worn sufliciently to perrrrit rotation of the driving cam with the slide 43 shifted to expose any of the gate 39, the driving pin arms 48 will have been worn through and the solder joints supporting the driving pin on the slide 43 will be broken. Thus the driving pin 47 will fall away from the slide and further adjustment of the tumblers will be prevented.

The combination lock is manipulated in the conventional manner to position the tumbler gates in registry with each other and in alignment with the fence by rotating the dial knob 15 and dial 16 three complete revolu-' tions in a counterclockwise direction to bring .a preselected dial marking in alignment with the index mark on the escutcheon plate 13, then two complete turns in a clockwise direction to bring another dial marking into alignment with the fixed index mark, and then another complete revolution in. a counterclockwise direction to align the third dial number with the index mark. During this manipulation of the dial knob and dial, the slide 43 is in the position illustrated in Figure 2 of the drawing wherein the arcuate ends 44 and 45 of the slide complete the circular periphery of the driving cam 18 and present an eifective uninterrupted periphery to the fence lever nose 40. The forwardly projecting portion of the driving pin 47 when the slide 43 is in this position engages the projection 29 of the inner fly 27 to rotate the fly 27 and through it the rearmost tumbler 19, the intermediate and outer fiys 26 and 25 being picked up by pins projecting from the inner and intermediate tumblers 19 and 2 upon subsequent complete revolutions of the driving cam 18 to adjust the tumblers 20 and 21.

When the tumbler gates have been thus aligned with the fence 35, the dial is rotated in a clockwise direction to bring the Zero mark into alignment With the fixed index mark on the escutcheon plate 13. In this position, the driving pin 47 is in radial alignment with the entrance porion 72 of the guide recess 71 in the rear cover plate 65, and the driving cam gate 39 is disposed immediately below the fence lever nose 40. The auxiliary knob'58 on the dial knob 15 is then rotated through 180 degrees, bringing the tank portion of the slide cam 56 into progressive engagement with the surfaces 59 and of the slide opening 54 to shift the slide 43 into the position illustrated in Figure 3. In this position, the driving pin 47 is fully inserted within the radial entrance portion 72 of the guide recess 71 where it is free to shift through the arcuate portion of the guide recess, and the upper arcuate end 44 of the slide 43 is disposed below the apex of the driving cam gate 39. If the tumbler gates 24 were aligned in position ot receive the fence 35, the fence lever would then fall under the resilient bias of the spring 34 to seat the fence lever nose 40 in the driving 0am gate 39 to effect retraction of the fence lever 32 and bolt 31 upon further clockwise rotation of the dial knob 15 within the limits permitted by the arcuate portion of the guide recess 72 and the stop surfaces positioned to intercept the projecting portion of the slide 43.

When the driving cam '18 is rotated upon counterclockwise rotation of the dial knob 15 from its unlocking position, the fence lever 32 and bolt 31 are shifted to project the bolt from the lock housing while the shoulder 36 of the fence lever 32 is disposed below the boss 37 on the top wall of the housing, and the shoulder 36 clears the boss 37, the fence lever is raised to the position illustrated in Figure 2 of the drawings by the camming action of the arcuately curved wall of the driving cam gate 39 on the fence lever nose 40. With the zero marking on the dial 16 aligned with the fixed index mark, the auxiliary knob 58 may then be returned through degrees to its original position shifting the tang portion 55 of the slide cam 56 into progressive engagement with the 7 surfaces 61 and 62 of the slide opening 54 to return the slide to the position wherein its arcuate ends again form continuations of the driving cam periphery so as to close the driving cam gate 38 against entrance of the fence lever nose 40 therein.

Because of the triangular shape of the faces 51 and of the driving pin 47 and fly 28, the full return of the driving pin 47 along a radial axis from within the guide recess 71 will not be prevented when the projection 29 of the fly 28 is in alignment with the entrance 72 of the guide recess since the faces are inclined and the fly projection 29 will be cammed to one side or the other of the driving pin 47. Were the opposing faces of these two members flat, the driving pin 47 might become jammed against the outer face of the fly projection 29 thus preventing full return of the slide to covering relation with the driving cam gate.

As explained above, any attempt to break the security of the lock by wearing away the .arcuate lower end of the slide against the inner surfaces of the stop members 66 and 67 will be thwarted by the present construction. The thickness of the lateral extensions 48 of the driving pin 47 is substantially equal to the amount of wear of the end 45 that would be required to permit full rotation of the driving cam 18 with enough of the gate 39 exposed above the slide end 44 to permit the fence to be dropped into contact with the tumbler peripheries. By the present construction, such a degree of Wear of the lower end 45 of the slide 43 will wear away the soldered joint supporting the driving pin 47 on the slide 43, disable the lock and prevent any further manipulation of the tumblers. While the provision of the flutings or grooves 69 on the inner faces of the stop members 66 and 67 insures the decoupling of the driving pin from the slide during this attempted wearing of the slide, this particular feature is not essential but may be displaced by serrations or any other irregular surface formations.

While but one particular embodiment of the invention has been particularly shown and described, it is apparent that various modifications may be made in the invention without departing from the spirit and scope thereof, and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the appended claims.

I claim:

1. A combination lock comprising selectively adjustable tumblers each having a peripheral recess, a bolt, spindle means having fixed thereto a driving cam, a fence lever pivotally connected to said bolt, said fence lever having a nose for engaging the periphery of said driving cam and a laterally extending fence arranged transversely of said tumblers overlying the peripheries thereof, said driving cam having a peripheral recess for receiving said fence lever nose to permit said fence to engage said tumbler recesses when the latter are adjusted in registry therewith for moving said bolt, means movable radially of said driving cam for bridging the peripheral recess therein to prevent movement of said fence lever to engage said fence with the tumbler peripheries, means extending through said spindle means for shifting said bridging means from bridging relation with said driving cam recess, means fixed on said bridging means for driving the adjacent one of said tumblers on rotation of said driving cam, said driving means being disengaged from driving relation with said adjacent tumbler when said bridging means is shifted out of said bridging relation.

2. A combination lock comprising selectively adjustable tumblers each having a peripheral recess, a bolt, a hollow spindle having fixed thereto a driving cam, a fence lever pivotally connected to said bolt, said fence lever having a nose adapted to lie over and engage the periphery of said driving cam and a laterally extending fence arranged transversely of said tumblers overlying the peripheries thereof, said driving cam having a peripheral recess for receiving said fence lever nose to permit said fence to engage said tumbler recesses when the latter are adjusted in registry with said fence for moving said bolt, a slide member supported on and movable radially of said cam, said slide having an arcuate surface for bridging said peripheral recess in said driving cam to prevent entry of said fence lever nose therein, a shaft extending through said hollow spindle, means operably associated between said shaft and said slide member for moving the latter radially of said driving cam, and a lost motion driving connection between said slide member and the adjacent tumbler including a driving member fixed on said slide, said driving member being shifted radially of said cam out of operative driving relation with said adjacent tumbler when said slide member is shifted out of said bridging relation.

3. A combination lock comprising selectively adjustable tumblers each having a peripheral recess, a bolt, a hollow spindle having fixed thereto a driving cam, a fence lever pivotally connected to said bolt, said fence lever having a nose adapted to lie over and engage the periphery of said driving cam and a laterally extending fence arranged transversely of said tumblers overlying the peripheries thereof, said driving cam having peripheral recess for receiving said fence lever nose to permit said fence to engage said tumbler recesses when the latter are adjusted in registry with said fence for moving said bolt, a slide member supported on and movable radially of said cam, said slide having an arcuate surface for bridging said peripheral recess in said driving cam to prevent entry of said fence lever nose therein, a shaft extending through said hollow spindle, means operably associated between said shaft and said slide member for moving the latter radially of said driving cam, and a lost motion driving connection between said slide memher and the adjacent tumbler including a fly mounted on said adjacent tumbler coaxial with said adjacent tumbler and having a projecting finger thereon, and a driving pin fixed on said slide and projecting therefrom at a position disposed radially of the axis of said tumblers to engage said fly finger upon rotation of said driving cam and shift said adjacent tumbler, said driving pin being shifted radially of said cam when said slide member is shifted out of said bridging relation to position said pin for rotation in a circular path concentric with said tumbler axis and out of intercepting relation with said 4. In a combination lock, the combination recited in claim 3 wherein the mutually adjacent portions of said driving pin and fly finger are provided with triangular cam surfaces to effect lateral camming of the fly finger upon interengagement of said cam surfaces during radial return of said driving pin from said shifted position.

5. A combination lock comprising selectively adjustable tumblers each having a peripheral recess, a bolt, a hollow spindle having fixed thereto a driving cam, a fence lever pivotally connected to said bolt, said fence lever having a nose adapted to lie over and engage the eriphery of said driving cam and a laterally extending fence arranged transversely of said tumblers overlying the peripheries thereof, said driving cam having a peripheral recess for receiving said fence lever nose to permit said fence to engage said tumbler recesses when the latter are adjusted in registry with said fence for moving said bolt, a bridging slide supported on and movable radially of said cam, said slide having an arcuate surface for bridging said peripheral recess in said driving cam to prevent entry of said fence lever nose therein when said slide occupies a selected bridging position, a shaft ex tending through said hollow spindle, means operably associated between said shaft and said slide for moving the latter radially of said driving cam to shift said arcuate surface out of bridging relation with said driving cam recess, means disposed at a fixed station adjacent the driving cam having wear surfaces positioned to be engaged by an edge of said slide when the slide is displaced from precise registry with said bridging position, a driving pin, means comprising a readily destructible supporting connection between said driving pin and slide, said driving pin projecting from said slide and driving one of said tumblers upon rotation of said driving cam and being disengaged from said one of said tumblers when said slide is displaced a preselected distance from said bridging position, said supporting connection being located at said edge of said slide to expose the same to rapid Wear destruction by said wear surfaces upon rotation of said driving cam beyond preselected limits when said slide is displaced from said bridging position.

6. A combination lock comprising selectively adjustable tumblers each having a peripheral recess, a bolt, a hollow spindle having fixed thereto a driving cam, a fence lever pivotally connected to said bolt, said fence lever having a nose adapted to lie over and engage the periphery of said driving cam and a laterally extending fence arranged transversely of said tumblers overlying the peripheries thereof, said driving cam having a peripheral recess for receiving said fence lever nose to permit said fence to engage said tumbler recesses when the latter are adjusted in registry with said fence for moving said bolt, a bridging slide supported on and movable radially of said cam, said slide having an arcuate surface for bridging said peripheral recess in said driving cam to prevent entry of said fence lever nose therein, a shaft extending through said hollow spindle, means operably associated between said shaft and said slide for moving the latter radially of said driving cam to shift said arcuate surface out of bridging relation with said driving cam recess and project a portion of said slide member beyond said driving cam periphery, a driving pin having a supporting connection with said slide spaced from the axis of said driving pin at a free edge of the projecta'b'le portion of said slide member, said driving pin projecting from said slide to drive one of said tumblers upon rotation of said driving cam, said supporting connection being formed of a material which is readily subject to wear destruction to release the driving pin from the slide when the connection is worn to a preselected extent and wear means located adjacent the periphery of the driving cam to engage and wear the projecting portion of said slide when said driving cam is rotated beyond preselected limits for destroying the supporting connection between said driving pin and said slide when the projecting portion of said slide has been worn to a preselected extent.

7. A combination lock comprising selectively adjustable tumblers each having a peripheral recess, a bolt, a hollow spindle having fixed thereto a driving cam, a fence lever pivotally [connected to said .bolt, said fence lever having a nose adapted to lie over and engage the periphery of said driving cam and a laterally extending fence arranged transversely of said tumblers overlying the peripheries thereof, said driving cam having a peripheral recess for receiving said fence lever nose to permit said fence to engage said tumbler recesses when the latter are adjusted in registry with said fence for moving said bolt, a bridging slide supported on and movable radially of said cam, said slide having a pair of oppositely arranged arcuate surfaces of radii equal to the radius of the driving cam periphery, said arcuate surfaces being spaced diametrically to coincide with the circular periphery of said driving cam with one of said arcuate surfaces bridging said driving cam peripheral recess to prevent entry of said fence lever nose therein, a shaft extending through said hollow spindle, means operably associated between said shaft and said slide for moving the latter redially of said driving cam to shift said bridging arcuate surface out of bridging relation with said driving cam recess and project the opposite arcuate surface portion beyond the driving cam periphery, stop means having inner surfaces conforming to the circumference of said driving cam to engage said projecting portion and limit rotation of said driving cam, aind a driving pin associated with said slide for driving one of said tumblers upon rotation of said driving cam, said driving pin having a pair of laterally extending legs having wear surfaces thereon, means forming a readily destructi ble supporting connection between said driving pin legs and said slide for supporting said driving pin on said slide with said wear surfaces disposed to receive the same wear as said projecting slide portion, said supporting connection being broken when said driving pin legs are worn through to release said driving pin from said slide.

8. In a combination lock, the combination recited in claim 7 wherein the arcuate surface of said slide to be projected beyond the driving cam periphery is recessed to accommodate said driving pin legs and position the wear surfaces thereof in alignemnt with said arcuate surface, and a light soldering connection is provided between the radially inwardly disposed portions of said legs and the facing portions of said slide recess to be worn through when the projecting arcuate surface of said slide is worn a distance equal to the thickness of said legs and thereby release said driving pin from said slide.

9. The combination recited in claim 8 wherein said inwardly facing surfaces of said stop means are provided with recesses enhancing abrasive action of said inwardly facing surfaces on the projected arcuate surface of said slide when the same is rotated in contact therewith.

References Cited in the file of this patent UNITED STATES PATENTS 94,156 Weimar Aug. 24, 1869 821,548 Streeter et al May 22, 1906 940,936 Le Myre Nov. 23, 1909 1,946,376 Whiting Feb. 6, 1934 2,575,674 Miller Nov. 20, 1951

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