US3581534A

US3581534A - Changeable combination cylinder lock

Info

Publication number: US3581534A
Authority: US
Inventors: Frank J Testa
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-02-09
Filing date: 1970-02-09
Publication date: 1971-06-01
Anticipated expiration: 1988-06-01

Abstract

A cylinder lock in which the tumbler assemblies can be rotated with respect to one another by means of a combination-change key to change the combination of the lock for various unlocking keys. The tumbler assemblies have mating cam projections and recesses whereby the assemblies can be positioned and rotated with respect to each other.

Description

PA'I'EMED JUH 1 IS?! INVENTOR FRANK J. TESTA BYZOW'MM ATTORNEYS WINDOW LOCK BACKGROUND OF THE INVENTION the lock unit 26 is in one of its locking positions the

tumbler

50, 50 project beyond the cylindrical surface of the plug 34 and into an associated one of the recess 48, 48. The tumblers are adapted for retraction into the plug 34 from their pro- This invention relates in general to locking devices for win- 5 lected position5 3cm)" Ofa P p y 54 inserted in a dows and the like and deals more particularly with an improved locking device for a window ofdouble-hung sash type.

The general aimof the present invention is to provide an improved locking device of the aforedescribed type for locking in a plurality of positions to retain a window in a closed position or to permit the window to be moved freely between closed and partially opened positions.

SUMMARY OF THE INVENTION In accordance with the present invention a window-locking device is provided which includes strike means for mounting on one part of a window and a strike-engaging element for mounting on another part of the window and lockable in a plurality of positions relative to the strike means for selectively locking a window in a closed position or in one or more other positions wherein the window is movable freely between closed and partially opened positions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary elevational view ofa window having double-hung sash showing a locking device embodying the present invention mounted thereon.

FIG. 2 is a fragmentary sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a sectional view through the lock unit taken along the line 3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawing, a locking device embodying the present invention and indicated generally at is shown mounted on a double-hung window which has upper and lower sash indicated at 12 and 14, respectively, slidable in a frame 16 between open and closed positions. The upper sash has a side rail 18 and a bottom crossrail 20 and the lower sash includes a side rail 22 and a top crossrail 24. The two crossrails are in contactwhen the window is in a closed position as it appears in FIG. 1.

The locking device 10 comprises a lock unit indicated generally at 26 mounted on the upper surface of the crossrail 24 and strike plates 28 and 30 fastened to the side rail 18 which cooperate with the lock unit in various locking positions to lock the window in a closed position or to limit its movement between closed and partially opened positions.

Considering first the lock unit 26, the unit generally comprises a casing 32 supporting a rotary or locking element 34 which carries a locking member 36. The casing may be made in various forms but preferably, and as shown, it includes a barrel portion 38 and a generally rectangular base flange 40 which has a rectilinear edge 42 for parallel alignment with the crossrail 24 to aid in positioning the lock unit on the sash 14. A generally cylindrical bore 44 extends through the barrel portion 38 and has an axis 46 disposed in a plane generally parallel to the plane of the base flange. As viewed from above in FIG. 2, the axis 46 is inclined with respect to the rectilinear edge 42 and the plane of the sash. Recesses 48, 48 extend longitudinally of the bore 44 at the top, bottom and opposite sides thereof, respectively, as shown in FIG. 3.

The locking element used in practicing the invention may be of any type suitable to cooperate with the casing in a plurality of locking positions. In the illustrated embodiment 10 the locking element 34 is a conventional cylindrical key plug of disc tumbler type which has an axially spaced series of disc tumblers mounted in radial slots therein, a typical tumbler being indicated at 50 in FIG. 3. A spring 52 is operatively assoeiated with each tumbler 50 to bias the tumbler toward and to resiliently hold it in a projected position as shown. When slot opening through the forward end of the plug. When the tumblers arc retracted the plug 34 may be rotated in the bore 44 by the key 54.

The strikeengaging member 36 is generally L-shaped and is riveted or otherwise suitably secured at one end to the rear end of the plug 34 and serves to retain the plug in assembly with the casing 32. The terminal or free end portion of the member 36 is spaced radially outwardly from the axis 46 and bent rearwardly. It has an arcuately formed radially outwardly facing strike engaging surface 56 and

abutment surface

58 and 60 on opposite sides thereof arranged to engage the upper surface of the base flange 40 which limits rotation of the plug 34 in both a clockwise and a counterclockwise direction.

The number of locking positions may vary. The illustrated device 10 has three locking positions which include an inoperative position and two operative ones. In FIG. 1, the member 36 is shown in 12 o'clock position corresponding to a fully locked position of the window. The

disc tumblers

50, 50 are aligned with recesses 48, 48 at the top and bottom of the bore 44 and biased downwardly into the recess 48 at the bottom of the bore when the key 54 is withdrawn from the plug to retain the lock unit 26 in the latter position. Rotation of the key 54 in a counterclockwise direction from the fully locked position moves the member 36 to a nine Oclock or inoperative position. The abutment surface 58 engages the flange 40 to arrest counterclockwise rotation of the plug when the

tumblers

50, 50 are generally aligned with the recess 48, 48 at the sides of the bore so that the key 54 may be withdrawn to lock the member in its nine oclock position. Rotation of the key in a clockwise direction through an angle of from the inoperative position moves the member 36 to another operating position at three oclock corresponding to another locked condition of the window. Clockwise rotation of the plug 34 is arrested by engagement of the abutment surface 60 with the base flange 40 as best shown in FIG. 3. The key may also be withdrawn from the plug to lock the unit 26 when the locking member 36 is in its three oclock position.

The strike plates 28 and 30 are fastened to the side rail 18 in vertically spaced relation to each other and to the crossrail 20 and preferably extend for some distance inwardly from the rail or toward the center of the window. The lower strike plate has a downwardly facing abutment surface 62 for engaging the arcuate surface 56 on the member 36 when the window is in its closed position and the lock unit is in its fully locked position. The upper strike plate 30 extends inwardly for some distance beyond the lower strike plate 28 and has a downwardly facing abutment surface 64 for engaging the side abutment surface 58 when the member 36 is in its three o'clock position. In the latter position the terminal end portion of the member 36 is disposed transversely inwardly of the inner edge of the lower strike plate 28 so that the member 36 is free to move past the strike plate 28 as the window is moved toward its open position. The inwardly extending free end portion of the upper strike plate 30 is disposed in the path of the element 36 so that the abutment surface 58 ultimately engages the strikeengaging surface 64 to limit the movement of the window toward its fully open position. Thus, when the element 36 is locked in its three oclock position the sash 12 and] 14 are freely movable between their closed position and partially open positions. When the element 36 is in its inoperative position, the terminal end of the element is spaced forwardly of the strike plates 28 and 30 and the sash l2 and 14 are freely movable between their closed and fully opened positions lclaim:

l. A locking device for a window having double'hung sash longitudinally movable relative to each other through a range of positions between opened and closed positions, said device comprising strike means adapted for mounting in fixed posi- BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the field of cylinder locks in which the lock combination can be varied without disassembling the entire lock.

Throughout this specification the term combination" refers to the unlocking formula peculiar to a given set of tumbler assemblies and the corresponding indicia on the particular unlocking key which operates that set of tumbler assemblies. The term cylinder lock" refers to a key-operated mechanism that operates ancillary devices such as a bolt and latch to bring the-bolt and latch into and out of locking engagement.

2. Description of the Prior Art Changeable combination locks are particularly desirable in situations where a number of persons have access to the keys for sufficient periods of time to permit the key profile to be copied. Obviously a copy of a key can be used to open the look as well as the original unlocking key. If, however, the lock combination can be varied from time to time, unauthorized access by means ofa copied key can be significantly thwarted.

Cylinder locks which have changeable combinations are well known in the art. US. Pat. No. 2,766,61 l reveals a cylinder lock which can be disassembled to change the combination. Once the lock is disassembled, one of the tumblers is inverted with respect to the others and the lock is reassembled with a new combination.

It is desirable to be able to vary the lock combination without having to disassemble the entire cylinder assembly. Locks of this type are known from US. Pat. Nos. 2,603,081 2,895,323 and 3,263,461.

US. Pat. No. 3,263,461 is of particular interest in that it discloses a lock frequently used in parking meters wherein the combination can be changed without disassembly. In that patent the tumbler assemblies are rotated with respect to one another by means of a combination-change key to change the combination and thereby adapt the lock to one of a plurality of unlocking keys. However, the prior-art lock of this patent employs sliding tumblers which engage adjacent tumbler assemblies to help prevent relative rotation ofone tumbler assembly with respect to the others if the tumblers should inadvertently slide from their unlocked positions, and this construction results in several significant disadvantages. For example, the tumblers must be returned to a starting or base position before a new combination can be set, thereby requiring the use of several change keys. Also, it can only be mounted horizontally.

SUMMARY OF THE INVENTION The present invention relates to an improved changeable combination cylinder lock. The combination of the lock is changed by means of combination-change keys and is accomplished by changing the relative positions of the tumbler assemblies with respect to one another.

The tumbler assemblies are composed of a carrier element and tumblers bearing indicia of the lock combination. The assemblies and their accessories are serially mounted along a cylinder axis to form the core of the cylinder lock. The assem' blies are normally coupled together by means of axially extending camming portions on the tumbler retainers and the specific locking function is provided by sliding any one of the tumblers within the assemblies into engagement with longitudinal cutouts in the lock casing. A spring element normally biases the camming portions of the adjacent tumbler assemblies into engagement. When the lock combination is to be changed a combination-change key cooperates with the camming portions to rotate the tumbler assemblies with respect to one another.

The camming portions are formed by triangularly shaped teeth which engage mating recesses at the confronting surfaces of adjacent tumbler assemblies. The teeth are positioned apart near the periphery of the assemblies and permit the assemblies to engage one another in two different relative positions to form different lock combinations.

The tumblers themselves slide within the tumbler assem blies and the indicia-bearing portion of the tumblers project within a centrally located keyhole channel formed by the as semblies. Since the assemblies are rotated 180 with respect to one another to vary the locking combination, two tumblers symmetrically located with respect to the central keyhole channel may be carried in each assembly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of my cylinder lock with a key and bolt in position.

FIG. 2 is a cross-sectional view of the assembled cylinder lock installed in a working environment.

FIG. 3 is a cross-sectional view of the cylinder lock between adjacent tumbler assemblies looking toward the bolt with a key in unlocking position.

FIG. 4 is an exploded view of the elements forming the core assembly of my cylinder lock.

FIG. 5 is an end view of the tumbler retainer as viewed from the right in FIG. 4.

FIG. 6 is a view of the tumbler assemblies during a combination-changing sequence.

Like reference numerals are used throughout the drawings where like elements are shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference to FIGS. 1 and 2 shows my cylinder lock, generally designated by numeral 10, with a bolt 12 and an installed key K. As seen in FIG. 2 the lock 10 can be installed in a housing 14 by means ofa collar 16 and jamnut 18. The housing 14 may be that ofa parking meter change box. The bolt 12 is shown in locking position with a latch 20 which would be permanently connected with a fixed portion of the parking meter. The bolt 12 is held to the cylinder lock by means of a nut 22 and rotates with the lock core assembly by means of flats on the stub shaft 24.

The lock 10 is composed basically ofa casing and a core assembly. The casing is formed by a barrel 26 and a cap member 28 crimped on the barrel 26 after the core assembly has been installed. The internal surface 38 of the barrel 26 is cylindrical and includes four longitudinal cutouts 40.

The core assembly is composed of a plurality of tumbler assemblies 30 (letter suffices being used where necessary to distinguish the similar assemblies and their subparts), a thrust plate 32, a thrust spring 34, which takes the form of a fluted washer, and an end plate 36. In the assembled lock the core assembly is essentially sandwiched between the barrel 26 and cap 28 by the thrusting force of spring .34.

The locking function is performed by the tumbler assemblies 30 and cutouts 40. As seen in FIGS. 3 and 4 each tumbler assembly 30 is composed of a tumbler retainer 42 and two symmetrically positioned tumblers 44, 46. The tumblers 44, 46 slide freely within grooves 48, 50 in the retainers 42. The cutouts 40 in the barrel 26 are located in the cylindrical sur face 38 to register in the locking position with the grooves 48, 50 in the retainers 42. The cutouts 40 have the same width as the grooves 48 and 58 in the retainers 42. This positioning and size of the cutouts 40 pennit the tumblers 44, 46 to slide into the cutouts 40 and lock the tumbler assembly 30 to the barrel 26. The tumbler assemblies are coupled together by cams-and recesses as described below and consequently the engagement of any one of the tumblers 44, 46 with the cutouts 40 will prevent rotation of both the lock core assembly and the bolt 12 rigidly fastened to the stub shaft 24 on the inner tumbler assembly 300.

Each of the tumbler retainers 42 includes a centrally located key channel 52 seen in FIG. 3 through which a key K may be inserted to operate the tumblers. The channel in the innermost retainer 42c may be a blind channel since it is not necessary for the key to project entirely through the stub shaft 24 and bolt 12. Each of the tumblers 44, 46 includes a central portion having a key follower 54, 56 respectively. These followers 54, 56 project into the key channel 52 and engage laterally disposed camming grooves cut in opposite faces of the key K. It will be understood that the camming grooves in the key K if properly cut for the tumblers 44, 46 will lift the tumblers out of the cutouts 40 in the barrel 26 as shown in FIG. 3 and will permit the tumbler assembly 30 to rotate with respect to the barrel 26. The positioning of the followers 54, 56 on the tumblers 44, 46 are therefore indicia of the particular combination for unlocking the respective tumblers. With a plurality of tumbler assemblies 30 forming the core assembly it will be necessary that the camming grooves in the appropriate unlocking key be precisely located to lift all of the tumblers out of the cutout 40 when the key is completely inserted. With all tumblers lifted, the key can rotate the core assembly and consequently the bolt 12 with respect to the fixedly mounted barrel 26.

it will be readily understood that a multitude of lock combinations can be formed from this lock design with three or four standard tumblers differing only in the positioning of the followers on the central portions. Thousands of different combinations may be fonned by disassembling the lock, rearranging the tumbler assemblies in different orders and rearranging the tumblers within the various tumbler assemblies.

The combination of the cylinder lock may also be changed without disassembly simply by rotating one tumbler assembly with respect to the others. This rotation is accomplished by means of a combination change key which engages the followers 54, 56 in precisely the same manner as the unlocking keys except that a combination key only engages those tumbler assemblies which must be rotated to change to a particular new combination. For example, if tumbler assembly 30b is to be inverted or rotated 180 with respect to assemblies 30a and 30c, two change keys would be employed. The first change key would engage and lift only the tumblers in assemblies 30a and 30b. This would ermit the assemblies 300 and 30b to be rotated with respect to assembly 300. A second change key would then be used to engage and lift only the tumblers in assembly 30a so that assembly 30a would be rotated back to its original position with respect to assembly 300. The inversion of tumblers 44b, 46b with the followers 54b, 56b will now form a new combination with the adjacent tumblers.

A particularly important feature of my invention is the design of the tumbler assemblies which always permits rotation of the outer tumbler assemblies with respect to the inner tumbler assemblies regardless of the existing lock combination. As seen most clearly in FIG. 4 the retainers 42 include camming tangs 60 in the form of triangularly shaped teeth and mating cam recesses 62 alternately located on the axially confronting surfaces of the retainers. The camming tangs 60 extend axially from the confronting surfaces and are located at positions 180- apart on the cylindrical tumbler retainers 42. The recesses 62 extend axially into the retainers 42 and are similarly positioned 180 apart as most clearly seen in FIG. 5. Tangs 60 and recesses 62 are normally engaged and held engaged by the thrusting force of the thrust spring 34 applied serially through the thrust plate 32 and the retainers 42. When a change key causes one or more of the outer tumbler assemblies to be rotated, the inner assemblies are locked to the barrel 26 by means of the tumblers 44, 46 and camming action of the tangs 60 and recesses 62 causes a slight axial displacement and disengagement of the outer, rotated tumbler assemblies from the inner assemblies. Since the entire core assembly is sandwiched between the barrel 26 and the cap 28, compliance is necessary to permit the axial displacement of a tumbler sembly and is provided by the spring 34.

Reference to FIG. 6 shows the axial displacement of assembly 30a with respect to assemblies 30b and 30c which oc curs during the use of the second change key in the example cited above. As shown, the camming action between tangs 60b and the recess 62a has displaced assembly 30a axially along with the thrust plate 32. The apex of tang 60b will slide on the periphery of assembly 30a until the camming recess 620 have rotated and are aligned with the diametrically opposite tangs.

It will be noted that during relative rotation of the assemblies, spring thrust will cause the tangs 60b to bear against the confronting surface of assembly 3011. To assure that no binding occurs during this step, the confronting surface of assembly 30a is smooth along its periphery except for the recesses 62. For this reason the grooves 48, 50 which guide the tumblers 44, 46 are always located in the same confronting surface which includes the tangs 60. ll is also to be noted that the rotation of the assemblies for combination change is al ways in one direction (clockwise as presently illustrated) and the flat of each tang against the wall of the recess prevents movement in the other direction.

The tumblers 44, 46 are prevented from rotating in the grooves 48, 50 by the flatted sides and the thickness between the axially opposite sides should preferably be less than the depth of the grooves to prevent the tumblers from catching on the recesses 62. Of course, it is possible that the tumblers could be carried in transverse holes lying wholly within the retainers. In such case, the relationship of the tangs and recesses with respect to the tumblers need not be so rigidly defined.

My improved cylinder lock offers several advantages which are not available in the prior-art locks.

Since the position of the tumblers within the tumbler assemblies 30 does not interfere with the rotation of an outer tumbler assembly with respect to the inwardly adjacent assembly, my lock can be mounted in either a horizontal or a vertical position without fear of adjacent assemblies becoming locked together due to a shifting or intentional positioning of one tumbler in an inwardly disposed assembly. The tumblers do not interfere with changing the lock combination because the engagement of adjacent tumbler assemblies is not provided by the tumblers, but instead, by the retainers 42. Another advantage closely associated with the intercoupling by means of the retainers is the fact that changing a given combination requires a smaller number of change keysv For example, if the intercoupling of adjacent tumbler assemblies 30b and 30c were provided by the tumblers 44c, 46c it might be necessary to first disengage the tumblers 44c, 46c from assembly 30b before assembly 30b could be rotated with respect to assembly 30c. This requires at least one additional change key and in other situations more than one additional change key may be required to make the desired combination change.

Additionally, it willbe noted that the camming tangs 60 and recesses 62 normally lock all of the tumbler assemblies 30 together. With any single tumbler engaged in the barrel cutouts 40, the entire core assembly will remain continuously locked to the barrel 26. The interlocking of the various tumbler assemblies eliminates any problems of one assembly inadvertently rotating with respectto another in the event that the tumblers of an outer assembly, for example 30a, become disengaged from the cutouts 40 of barrel 26. It will be understood that such inadvertent rotation might occur during shipping and would change the previously established lock combination to a new and unknown combination. Lock inserts are used in the prior-art devices to prevent such inadvertent rotation of the tumblers; however, with my improved lock such inserts are not essential.

In the prior-art locks which rely upon specially shaped tumblers to engage adjacent tumbler assemblies it is possible that the tumblers can be damaged in the event that the wrong change key is used when setting a new combination. By eliminating the specially shaped tumblers and using springloaded camming portions, such damage is precluded. Furthermore, the shape of my tumblers renders them simple and more economical to manufacture.

lt will be understood that various modifications can be made to the specific structure shown and described. For example, the number of possible lock combinations can be greatly multiplied by using more than just three tumbler assemblies 30. The camming tangs 60 and the mating recesses 62 need not take the form of ratchet teeth but may with equal facility take a symmetric form having two camming surfaces to permit relative rotation of the tumblers in either direction. lf desired, other curved shapes rather than the triangular tooth may be employed provided the cams maintain their locking function.

lclaim:

1. A core assembly for a changeable combination cylinder lock comprising:

a plurality 'of cylindrical tumbler carriers coaxially positioned with respect to one another and serially located along a core axis, the carriers bearing axially confronting surfaces defining mated camming tangs and tang-receiving portions forming disengageable couplings between adjacent carriers;

resilient thrusting means axially contacting at least one carrier for urging the disengageable couplings of the carriers into engagement; and

a lock tumbler located in each tumbler carrier and freely slidable in the carrier in a direction generally transverse to the core axis.

2. The core assembly of claim 1 wherein:

the confronting surfaces of tumbler carriers defining the camming tangs additionally define a nesting groove extending generally transverse to the core axis; and

the lock tumblers in the carriers having confronting surfaces defining the camming tangs are slidably mounted within the nesting groove.

3. The core assembly of claim 2 wherein the tumblers are fitted in close, sliding contact with the nesting grooves and have flat surfaces in contact with the grooves to prevent rotation of the tumblers in the grooves.

4. The core assembly of claim 1 wherein:

the coaxially' positioned tumbler carriers define a centrally located keyhole having a noncircular cross section; and

the freely slidable tumbler includes a central portion bearing indicia of the lock combination and projecting at least partially within the centrally located keyhole.

S. The core assembly of claim 1 wherein:

the camming tangs consist of two ratchet teeth extending from an axially confronting surface of the rotatable retainer and spaced 180 apart near the periphery of the rotatable retainer.

6. An improved cylinder lock having changeable key combinations comprising:

a lock casing having a cylindrical bore with tumbler receiving cutouts;

a plurality of rotatable tumbler retainers positioned coaxially within the cylinder bore of the casing in adjacent relationship and having matched and axially extending camming portions intercoupling adjacent retainers;

cam-engaging means operatively associated with the plurality of tumbler retainers for biasing the camming portions of adjacent retainers into engagement; and

key-operated tumblers slidably mounted within the tumbler retainers and having locking sections shaped to slidingly mate with the tumbler receiving cutouts of the lock casmg.

7. The cylinder lock of claim 6 wherein:

the surface of one retainer confronting with an adjacent retainer includes a tumbler slot of preselected depth in the axial direction and extending lengthwise across the confronting surface; and

the key-operated tumbler within the retainer is slideably mounted in and secured against rotation in the slot and has a thickness in the axial direction less than the preselected depth of the slot.

8. The cylinder lock of claim 6 wherein:

the lock casing includes two pairs of longitudinal tumblerreceiving cutouts, the pairs bein respective] offset by equal amounts on opposite sides 0 a central p ane bisecting the cylindrical bore of the casing;

the rotatable tumbler retainers rotate concentrically about the axis of the cylindrical bore; and

two key-operated tumblers are slidably mounted in parallel relationship within one rotatable retainer and are offset from the center of rotation of the retainer by an amount equal to the offset of the tumbler-receiving cutouts to register with the cutouts in a locking position of the retainer.

9. The cylinder lock of claim 6 wherein:

the rotatable tumbler retainers are generally cylindrically shaped with axially opposed end surfaces; and

the camming portions of the rotatable tumbler retainers include triangularly shaped and axially extending teeth and mating recesses on confronting end surfaces of the tumbler retainers.

10. The cylinder lock of claim 9 wherein:

the cam-engaging means includes a spring element for resiliently biasing the triangularly shaped teeth into engagement with the mating recesses; and

the end surfaces of the tumbler retainers bearing the triangular teeth additionally include a tumbler-guiding groove extending transverse of the cylindrically shaped retainers and having a depth in the axial direction completely accommodating the tumblers within the grooves below the end surfaces whereby the tumblers may slide freely within the grooves of the retainer when the teeth are engaged with the mating recesses.

Claims

1. A core assembly for a changeable combination cylinder lock comprising: a plurality of cylindrical tumbler carriers coaxially positioned with respect to one another and serially located along a core axis, the carriers bearing axially confronting surfaces defining mated camming tangs and tang-receiving portions forming disengageable couplings between adjacent carriers; resilient thrusting means axially contacting at least one carrier for urging the disengageable couplings of the carriers into engagement; and a lock tumbler located in each tumbler carrier and freely slidable in the carrier in a direction generally transverse to the core axis.

2. The core assembly of claim 1 wherein: the confronting surfaces of tumbler carriers defining the camming tangs additionally define a nesting groove extending generally transverse to the core axis; and the lock tumblers in the carriers having confronting surfaces defining the camming tangs are slidably mounted within the nesting groove.

4. The core assembly of claim 1 wherein: the coaxially positioned tumbler carriers define a centrally located keyhole having a noncircular cross section; and the freely slidable tumbler includes a central portion bearing indicia of the lock combination and projecting at least partially within the centrally located keyhole.

5. The core assembly of claim 1 wherein: the camming tangs consist of two ratchet teeth extending from an axially confronting surface of the rotatable retainer and spaced 180* apart near the periphery of the rotatable retainer.

6. An improved cylinder lock having changeable key combinations comprising: a lock casing having a cylindrical bore with tumbler receiving cutouts; a plurality of rotatable tumbler retainers positioned coaxially within the cylinder bore of tHe casing in adjacent relationship and having matched and axially extending camming portions intercoupling adjacent retainers; cam-engaging means operatively associated with the plurality of tumbler retainers for biasing the camming portions of adjacent retainers into engagement; and key-operated tumblers slidably mounted within the tumbler retainers and having locking sections shaped to slidingly mate with the tumbler receiving cutouts of the lock casing.

7. The cylinder lock of claim 6 wherein: the surface of one retainer confronting with an adjacent retainer includes a tumbler slot of preselected depth in the axial direction and extending lengthwise across the confronting surface; and the key-operated tumbler within the retainer is slideably mounted in and secured against rotation in the slot and has a thickness in the axial direction less than the preselected depth of the slot.

8. The cylinder lock of claim 6 wherein: the lock casing includes two pairs of longitudinal tumbler-receiving cutouts, the pairs being respectively offset by equal amounts on opposite sides of a central plane bisecting the cylindrical bore of the casing; the rotatable tumbler retainers rotate concentrically about the axis of the cylindrical bore; and two key-operated tumblers are slidably mounted in parallel relationship within one rotatable retainer and are offset from the center of rotation of the retainer by an amount equal to the offset of the tumbler-receiving cutouts to register with the cutouts in a locking position of the retainer.

9. The cylinder lock of claim 6 wherein: the rotatable tumbler retainers are generally cylindrically shaped with axially opposed end surfaces; and the camming portions of the rotatable tumbler retainers include triangularly shaped and axially extending teeth and mating recesses on confronting end surfaces of the tumbler retainers.

10. The cylinder lock of claim 9 wherein: the cam-engaging means includes a spring element for resiliently biasing the triangularly shaped teeth into engagement with the mating recesses; and the end surfaces of the tumbler retainers bearing the triangular teeth additionally include a tumbler-guiding groove extending transverse of the cylindrically shaped retainers and having a depth in the axial direction completely accommodating the tumblers within the grooves below the end surfaces whereby the tumblers may slide freely within the grooves of the retainer when the teeth are engaged with the mating recesses.