Pick Resistant Cylinder Lock

Abstract

A pick resistant, key operated, cylinder type lock having a key plug rotatable within a cylindrical shell and having a plurality of segmented pin tumblers movable radially relative to the axis of rotation of the key plug. The pin tumblers each have inner and outer pin sections separated by a plane of separation adapted to be alined by a proper key with the shear line between the plug and the cylindrical casing, and a plurality of additional redundant lines of separation along the inner section of each pin tumbler. An additional locking member is coupled to each of the pin tumblers and has leg portions projecting into openings in the casing and plug, and provides one or more additional lines of separation at the shear line between the plug and casing, to be alined with the shear line when the pin tumblers are positioned by the key at the proper positions.

Description

BACKGROUND AND OBJECTS OF THE INVENTION

The present invention relates in general to cylinder locks, and more particularly to key-operated pin tubler cylinder locks having special provision for protecting the same against unauthorized entry by the usual lock picking procedures.

One of the common types of key locks which have come into wise use is the type known as a cylinder lock. Such cylinder locks comprise a lock body or casing having a cylindrical bore opening through the front surface of the lock body which rotatably houses a key plug or lock plug having a key way or key slot opening through the front surface of the plug and extending substantially the axial length of the plug. A series of parallel tumbler bores are formed in the plug and lock body along axes extending radially of the axis of rotation of the plug and lying in a common plane when the plug is in locked position. These pin tumbler bores house coil springs and sectioned or segmented locking pins each comprising an inner section lying entirely within the plug portion of the tumbler pin bore having an end surface extending into the keyway to be contacted by the shaped edge of the key, and an outer section which extends into the portion of the tumbler bore lying in the outer lock body. The inner pin section is in axially aligned abutment with its associated outer pin section with the outer pin section normally extending across the shear line or boundary zone between the plug and the lock casing, thus restraining the plug against rotation. However, a key of proper contour will elevate the pins proper distances to locate the line of separation between the inner and outer pin sections in alinement with the shear line between the plug and lock casing, permitting rotation of the plug and the bolt connected with the plug to unlock the closure protected by the lock.

Due to the conditions which arise in the construction of the lock parts under customary manufacturing tolerances, it is possible to effect minute rotary displacement of the plug from its normal locked position to thereby cause the cylindrical surface portions of the plug bounding the tumbler pin bores to form a slight offset shoulder or ledge at the shear line between the plug and the surface of the plug-accommodating bore, which will catch and support the edge of the lower ends of the outer pin sections when the tumbler pins are elevated. This property of the locks is taken advantage of in lock picking procedures by applying a special wrench to the plug to force or stress the plug in an angular direction about its axis of rotation and then manipulate the tumbler pin by a pick inserted into the keyway to individually lift them until the outer pin sections catch on the shoulder or ledge formed when the plug is thus stressed. When all of the outer pin sections have been thus caught in the elevated position, the plug can be turned through the appropriate arc to unlock the lock without the use of a key.

Various means have been proposed for increasing the security of such cylinder locks against picking. These means have variously included secondary apparatus for preventing even slight relative rotation of the plug in the lock casing so that the conventional lock picking techniques of applying the torque to the plug and hanging the outer sections of the tumbler pins is prevented. These have included mechanisms blocking access to the keyway except when they are in a particular position which prevents slight relative rotation of the plug and lock casing.

An object of the present invention is the provision of a novel keyoperated pin tumbler cylinder lock construction, having a lock mechanism which resists unlocking of the lock by the usual lock picking procedures.

Another object of the present invention is the provision of a novel cylinder type key lock wherein each of the pin tumblers are provided with a plurality of lines of separation, together with means associated with each of the pin tumblers which restrain the key plug against rotation for all but one of the plural planes of separation of each tumbler pin.

Another object of the present invention is the provision of a novel key operated pin tumbler cylinder lock wherein the portion of each pin tumbler in the rotatable key plug is segmented to provide a plurality of transverse planes of separation at different axial positions along each pin, together with associated locking members movable along axes paralleling each tumbler pin axis in flanking relation thereto which normally locks the key plug against rotation and releases the key for rotation only when one of the plurality of planes of separation between the segments of each tumbler pin is aligned with the shear line between the key plug and the wall of the plug-accommodating bore in the cylinder lock casing.

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

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a front elevation view of a key operated pin tumbler cylinder lock embodying the present invention;

FIG. 2 is a vertical longitudinal section view thereof, taken along the line 2--2 of FIG. 1;

FIG. 3 is a vertical transverse section view taken along the line 3--3 of FIG. 2; and

FIG. 4 is an interrupted perspective view of the cylinder lock, with an intermediate portion broken away to reveal the construction of the locking mechanism.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several Figures, the cylinder lock of the present invention is indicated generally by the reference character 10 and comprises a lock body or casing 11 of substantially conventional configuration including a lower cylindrical lock case portion 12 and an upwardly extending ridge portion 13 aligned with the medial vertical longitudinal plane of the lock casing. The cylindrical lock case portion 12 has a longitudinally disposed cylindrical bore 14 opening through the front face or surface 15 of the lock body. The rearmost end portion of the bore 14 may have a constricted bore portion opening through the rear face of the lock body, in accordance with conventional practice. A cylindrical key plug or barrel 16 conforming closely to the diameter and curvature of the bore 14 is received in the bore for rotation about the axis thereof and has a front face which is projected slightly forwardly from the front face 15 of the lock casing, and the plug may have a constricted rear portion projecting through the constricted bore portion of the lock case to an exposed position rearwardly of the lock case to be coupled by suitable conventional means with a conventional bolt (not shown). The cylindrical plug 16 is provided with the usual key slot or keyway 17 having an entrance end at the front face of the plug 16.

The ridge portion 13 of the lock casing is provided with a longitudinally spaced, parallel, series of pin-accommodating bores 20 for housing the tumbler pin assemblies. Each of the bores 20 have their axes extending radially of the axis of rotation of the plug 16 in a common plane, usually a vertical plane including the axis of rotation of the plug, and the key 16 is provided with a series of similar bores 21 extending from the periphery of the plug 16 to substantially the center of the key slot 17. The bores 21 are adapted to be aligned axially with the bores 20 when the key 16 is in locked position. The bores 20 and 21, in the usual fashion, support and guide a series of tumbler pin assemblies 22, each made up of an outer tumbler pin section 23 lying principally in the bores 20 in the lock case, and an inner pin section 24 made up of a plurality of pin segments 24a lying wholly or principally within the bore 21 in the key plug 16. The tumbler pin assemblies 22 made up of the outer pin section 23 and the segments forming the inner pin section 24 are biased continuously to a bottomed condition within their respective bores, biased toward the center of the key slot 17, by the coil springs 25 within the bores 20 continuously urging a resiliently biasing force against the upper ends of the outer pin sections 23. The coil springs 25 may be held in the bores 20 by any conventional means, such as by the cover plate 26 fixed in the recess 13a in the top of the ridge portion 13, or by headless screws threaded into threaded top sections of the bores 20. The plane of separation between the outer pin section 23 and the uppermost of the pin segments 24a forming the inner pin section is spaced radially inwardly from the shear line or zone between the cylindrical surface of the key plug 16 and the plug-accommodating bore 14 so that this shear line occurs at an intermediate portion of the outer pin section 23. Thus, the plurality of planes of separation between the pin segment 24a of each tumbler pin assembly and between the uppermost of these pin segments and the outer pin section 23 form rendundant tumbler pin separation surfaces which may be caught against the shoulder or ledge formed when the key plug is stressed by the usual lock picking procedures, and thus the person attempting to pick the lock is unable to determine which of the separation planes is the correct one for unlocking the lock.

Associated with each of the tumbler pin assemblies 22 is a U-shaped tumbler member or locking member 27 having a cross piece or top portion 28 extending transversely to and slidable in an associated vertical slot 29' extending along the upper portion of each bore 20, with the center portion of the cross piece 28 bearing against the top end of the outer tumbler pin section 23. A pair of laterally spaced legs 29 depend from the cross piece through slots 30 in the cylindrical portion 12 of the lock case and into recesses 31 in the confronting portions of the key plug 16. As illustrated in the drawings, the slots 30 in the shell or cylindrical lock case portion 12 and the recesses 31 in the key plug 16 for accommodating the locking legs 29 are somewhat larger than the cross-section of the legs 29 to provide some clearance so that the slight rotation of the key plug which is achieved when it is stressed in accordance with usual lock picking procedures will not bring any shoulder surface at the shear line between the plug and the case into contact with the legs 29, thus avoiding the catching of the locking members which is essential to unauthorized picking of the lock. As illustrated, the U-shaped locking members 27 may be resiliently biased upwardly to the normal positions occupied by them when the lock is in locked condition by axially slidably cylidrical pins 32 seated in elongated cylindrical bores 33 in the plug 16 communicating with the recesses 31 and housing coil springs 34 which bear upwardly against the pins 32 urging them into upwardly biasing engagement with the bottom surfaces of the locking member legs 29.

It will be apparent that in order to unlock the lock, the appropriate key which is inserted into the keyway 17 of the key plug 16 must lift the tumbler pin assemblies 22 an appropriate distance to aline the plane of separation between a pair of the pin segments 24a or between one of such pin segments and the outer pin section with the shear line between the plug 16 and the lock case 11, and must also aline the bottom ends of the locking member legs 29 with this shear line before the plug 16 is released for rotation to the unlocking position. There are no shoulder or ledge formations which can be formed adjacent and brought into contact with the legs 29 because of the clearance provided by the slots 30 and recesses 31 relative to the legs 29, by which a person attempting to pick the lock can determine the appropriate distance to elevate the associated tumbler pin to achieve the proper setting of the tumbler pin and associated lock member. Although the person attempting to pick the lock can, by stressing the plug 16, produce shoulder or ledge formations which can catch the tumbler pin assemblies 22 at the various planes of separation between the pin segments 24a or between the uppermost pin segment and the outer pin segment 23, there are a plurality of such line of separations provided for each tumbler pin so that the person using the pick has no way knowning which one of the plural separation lines for each tumbler pin is the proper one to elevate the locking member legs 29 to proper unlocking position. In the illustrated embodiment, five of such planes of separation are provided for each tumbler pin assembly 22, although it will be appreciated that a different number of planes of separation for each tumbler pin assembly can be used, without altering the underlying principal of operation. In fact, each tumbler pin assembly can be made up entirely of a stack of pin segments such as the pin segments employed for the inner pin section of the specifically described embodiment.

Claims

What is claimed is:

1. A cylinder lock adapted to be unlocked by a key, comprising a lock casing having a forwardly opening, axially elongated cylindrical bore therein a cylindrical key plug rotatably disposed in said bore for rotation about the bore axis having a key slot therein and a cylindrical surface closely conforming to and located immediately adjacent the bounding surface of said bore defining a shear line at the interface therebetween, said lock casing and key plug each having mating bore sections alinable along pin axes intersecting the shear line at the locked position of the plug to form tumbler bores, tumbler pin assemblies in each of said tumbler bores each including a rigid pin locking segment resiliently biased to a normal position extending into both said bore sections crossing said shear line and a plurality of inner pin segments in the plug bore section defining plural planes of separation for each pin assembly spaced radially inwardly of the shear line, and locking members for the respective pin assemblies coupled for reciprocative movement with the associated pin assemblies along paths generally paralleling and laterally spaced from the associated pin axes and each having a rigid elongated locking leg crossing said shear line to block rotary movement of the plug from said locked position, said casing and plug having recesses alinable at the locked position of the plug to receive said legs of said locking members, and said legs having end surfaces positioned to aline with said shear line when the pin assemblies are moved to a release position alining selected planes of separation defined by said pin segments with the shear line to release the plug for rotation to unlocked position.

2. A cylinder lock as defined in claim 1, wherein said plug has elongated bores alined with said legs along the paths of movement of the legs communicating with the recesses for said legs, and axially movable pin members in said last-mentioned bores resiliently biased toward the end surface of the adjacent leg and having an end surface to aline with said shear line when said pin assemblies are disposed at said release position.

3. A cylinder lock as defined in claim 1, wherein said locking segment of each pin assembly is the radially outermost pin portion extending through a major portion of the casing bore section to a plane of separation with the next adjacent pin segment spaced radially inwardly of the shear line toward the axis of rotation of the plug, and said pin segments defining several additional planes of separation therebetween for each pin assembly spaced radially inwardly of the outermost pin portion.

4. A cylinder lock as defined in claim 2, wherein said locking segment of each pin assembly is the radially outermost pin portion extending through a major portion of the casing bore section to a plane of separation with the next adjacent pin segment spaced radially inwardly of the shear line toward the axis of rotation of the plug, and said pin segments defining several additional planes of separation therebetween for each pin assembly spaced radially inwardly of the outermost pin portion.

5. A cylinder lock as defined in claim 1, wherein said locking members each comprise an integral U-shaped member having a cross-piece centrally abutting the locking segment of its associated pin assembly for movement therewith axially of its bore and a pair of depending legs laterally flanking the associated pin assembly each extending across the shear line into said plug to form a pair of said leg members for each pin assembly.

6. A cylinder lock as defined in claim 2, wherein said locking members each comprise an integral U-shaped member having a cross-piece centrally abutting the locking segment of its associated pin assembly for movement therewith axially of its bore and a pair of depending legs laterally flanking the associated pin assembly each extending across the shear line into said plug to form a pair of said leg members for each pin assembly.

7. A cylinder lock as defined in claim 3, wherein said locking members each comprise an integral U-shaped member having a cross-piece centrally abutting the locking segment of its associated pin assembly for movement therewith axially of its bore and a pair of depending legs laterally flanking the associated pin assembly each extending across the shear line into said plug to form a pair of said leg members for each pin assembly.

8. A cylinder lock as defined in claim 4, wherein said locking members each comprise an integral U-shaped member having a cross-piece centrally abutting the locking segment of its associated pin assembly for movement therewith axially of its bore and a pair of depending legs laterally flanking the associated pin assembly each extending across the shear line into said plug to form a pair of said leg members for each pin assembly.

9. A cylinder lock as defined in claim 5, wherein said lock casing includes a cylindrical shell portion having said cylindrical bore housing said plug and a ridge portion projecting radially from the shell portion having the casing bore sections therein housing said pin locking segments, coil springs in said casing bore sections for urging said pin assemblies axially inwardly toward the axis of rotation of the plug, said ridge portion of the casing having lateral slots transversely intersecting the casing bore sections, and the crosspieces of said locking members extending through said slots into abutment with ends of the pin locking segments interposed between the latter and said coil springs.

10. A cylinder lock as defined in claim 6, wherein said lock casing includes a cylindrical shell portion having said cylindrical bore housing said plug and a ridge portion projecting radially from the shell portion having the casing bore sections therein housing said pin locking segments, coil springs in said casing bore sections for urging said pin assemblies axially inwardly toward the axis of rotation of the plug, said ridge portion of the casing having lateral slots transversely intersecting the casing bore sections, and the crosspieces of said locking members extending through said slots into abutment with ends of the pin locking segments interposed between the latter and said coil springs.

11. A cylinder lock as defined in claim 1, wherein said pin assemblies are all disposed with said pin axes located in a common plane along a radius of the axis of rotation of the key plug, and said leg members being disposed with their axes paralleling said pin axes spaced laterally from said common plane.

12. A cylinder lock as defined in claim 2, wherein said pin assemblies are all disposed with said pin axes located in a common plane along a radius of the axis of rotation of the key plug, and said leg members being disposed with their axes paralleling said pin axes spaced laterally from said common plane.

13. A cylinder lock as defined in claim 1, wherein said pin assemblies are all disposed with said pin axes located in a common plane along a radius of the axis of rotation of the key plug, and said leg members being disposed with their axes paralleling said pin axes in a pair of planes laterally flanking said common plane along opposite sides thereof.

14. A cylinder lock as defined in claim 2, wherein said pin assemblies are all disposed with said pin axes located in a common plane along a radius of the axis of rotation of the key plug, and said leg members being disposed with their axes paralleling said pin axes in a pair of planes laterally flanking said common plane along opposite sides thereof.