High-security cylinder lock based on bridge tumblers

Abstract

A bridge tumbler lock has tumblers that both slide and pivot, with their motion controlled by pairs of key interfaces. A sidebar is released to permit lock opening movement when all tumblers are in their correct positions. This results in a lock that is resistant to release of information due to partially correct key combinations occurring in the course of a lock picking attempt and thus enables enhanced security in an economical, effective lock construction.

Claims

1. A cylinder lock comprising: (a) a cylinder having an entry passage for key insertion, (b) one or more rotatable substantially flat surfaced tumblers with a shield form substantially planar body portion that, in response to insertion into said passage of a conventional key with upper or lower edge profiled surface, can respond to contact with said surface to slide linearly in a plane and can also rotate, to regulate alignments for enabling cylinder rotation for locking and unlocking, (c) each tumbler having its axis of rotation perpendicular to its direction of sliding and constructed and arranged to have its direction of sliding constrained by a central outward projection from the body portion of the tumbler that is rotatably journaled within a suitable groove in the cylinder.

2. A cylinder lock as in claim 1 wherein; said direction of sliding constraint comprises a projecting pin, and further comprising: (d) a sidebar mechanism for restricting rotation of the cylinder, which is released by a proper alignment of the tumblers, (e) holes in one or both of said tumblers and sidebar and lugs in one or both of said sidebar and tumblers, so as to effect the release of the sidebar when movement of the tumblers places holes and lugs in proper alignment, (f) means for controlling both the linear sliding and rotational motions of the tumblers using pairs of transverse key interface displacements; and (g) means for restricting rotation of the cylinder, which restriction is released by proper alignment between holes and/or lugs on the tumblers and holes and lugs on the sidebar; and wherein a flat interface between tumblers and sidebar lugs, is provided by their configuration and alignment, so as to prevent changes in lock behavior as tumblers and lugs approach correct alignment that would reveal information about the correct alignment.

3. The lock of claim 2 with means for controlling both the sliding linear and rotational motion of the tumblers using pairs of purely transverse key interface displacements.

4. The lock of claim 2 comprising holes in one or more tumblers including a first hole centrally located in the tumbler that receives a sidebar projection pin and is situated in relation to spaced lugs of the tumbler which respond to key surface guiding contact, the tumbler body including one or more further through holes and/or lugs of the tumbler, the relation of the first hole to the further holes and/or lugs being effective to enable the guiding response movement to move such holes or lugs through a wide range of motion to align said one or more further holes of the tumbler with one or more lugs or holes of the sidebar sufficiently to release the sidebar whereby a high number of lock combinations is enabled for increased lock security.

5. The lock of claim 1 with means for controlling both the transverse and rotational motion of the tumblers using pairs of purely transverse key interface displacements.

6. The lock of claim 5 with means for restricting rotation of the cylinder, which is released by proper alignment between holes on the tumblers and lugs on the sidebar.

7. The lock of claim 6 with a flat interface between tumblers and sidebar lugs, so as to prevent changes in lock behavior as tumblers and lugs approach correct alignment.

8. The lock of claim 7 with sidebar lug cross-section effecting resistance to forcing.

9. The lock of claim 8 with a system of one or more inactive decoy holes in the tumblers, producing a change in behavior that mimics the effects of correct alignment between tumblers and lugs, but cannot be accurately distinguished from correct alignment until all tumblers are in either correct or decoy alignment relative to the sidebar.

10. The lock of claim 1 further comprising a flexible interface between the sidebar and housing, so as to deform under excessive force in such a way as to reduce force on the sidebar lugs and thereby prevent unlocking.

11. The lock of claim 1 in combination with a conventional key for sliding in the key way.

12. The lock of claim 1 further comprising a system of decoy holes in the tumblers, producing a change in unlocking behavior that mimics the effects of correct alignment between tumblers and lugs, but cannot be accurately distinguished from correct alignment until all tumblers are in either correct or decoy alignment.

13. The lock of claim 1 comprising holes in one or more tumblers including a first hole centrally located in the tumbler that receives a sidebar projection pin and is situated in relation to spaced lugs of the tumbler which respond to key surface guiding contact, the tumbler body including one or more further through holes and/or lugs of the tumbler, the relation of the first hole to the further holes and/or lugs being effective to enable the guiding response movement to move such holes or lugs through a wide range of motion to align said one or more further holes of the tumbler with one or more lugs or holes of the sidebar sufficiently to release the sidebar whereby a high number of lock combinations is enabled for increased lock security.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an exploded view of the lock mechanism, showing the key, cylinder, housing, tumblers, and sidebar according to an embodiment of the invention shown together with a conventional key and a locking unlocking structure affixed to a portion (cap) of the locking mechanism;

(2) FIG. 2 is a top view, partially cross-sectioned, of the arrangement of tumblers inside the cylinder;

(3) FIG. 3 is a cut-away side view of the arrangement of tumblers inside the cylinder;

(4) FIG. 4a is a close-up isometric view (expanded) of the key-facing side of a tumbler;

(5) FIG. 4b is a close-up isometric view (expanded) of the sidebar-facing side of a tumbler;

(6) FIG. 5 is a partially cross-sectioned view close-up of the top (slide-facing) side of a tumbler;

(7) FIG. 6a shows the interaction between the key and a tumbler;

(8) FIG. 6b shows the interaction between the key and a tumbler when in correct alignment;

(9) FIG. 7a, a partially sectioned top view, shows the interaction between a tumbler and the sidebar in correct alignment;

(10) FIG. 7b, a partially sectioned top view, shows the interaction between a tumbler and the sidebar when in decoy alignment; and;

(11) FIG. 8 shows the position of the sidebar facing plate within the lock housing;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(12) The following described embodiments of the invention comprise a movable cylinder lock (cover all or as a movable cylindrical comprising a lock) and key combination in which the rotation of the cylinder is restricted by a sidebar, which is into a recess in the lock housing. The sidebar has a number of projecting lugs, which fit into recesses in a corresponding number of bridge tumblers.

(13) Each bridge tumbler comprises a plate, preferably flat, with a number of pins on one side (face) of the plate, preferably three and a number of holes on the other. One of these three pins is shorter than the others and fits into a groove in the cylinder, resulting pivot point at which the tumbler can only slide in one direction. The other two pins protrude into a keyway, interfacing with the key, which can be a conventional key as indicated in FIG. 1. Each pair of key positions therefore controls the transverse and rotational motion of the tumbler. The average of the pair determines the transverse position of the tumbler while the difference determines the rotational position. One of the holes on the other side of the tumbler plate is deep enough to allow lugs on the sidebar to enter the tumbler, freeing the sidebar and allowing the lock to rotate. The others are not, and act as decoys to confuse a potential lock picker. As these holes are displaced a significant distance from the tumbler's pivot point, the rotational motion of the tumbler results in an axial displacement of these holes. Freeing the sidebar therefore requires the correct hole to be in the correct axial and transverse position, which can only occur if both of the pair of key positions are correct.

(14) The recess in the lock housing is covered by a grooved plate, forming a vee-shape whereas the recess itself has a rectangular cross-section. When the plate is not deformed by excessive force, its shape forces the sidebar into the cylinder when the lock is rotated. If it is deformed by excessive force, the rectangular cross-section of the underlying recess results in a contact force on the sidebar that is in an azimuthal direction rather than a radial, and consequently fails to deliver sufficient force to push the sidebar into the cylinder. This protects the sidebar lugs from excessive force.

(15) FIG. 1 shows an exploded view of a lock device embodiment. A key 2 is insertable into the cylinder 4 via its keyway 20. A slide 6 covers the top of the cylinder. The cylinder sits inside a housing 8 which has a notch 9 to engage a sidebar (described below). This notch is covered by a plate 10 (see, also FIG. 8 and discussion of it below). A cap 11 secures the cylinder inside the housing. A plurality of tumblers 12 with projecting lugs 14 rest atop the key due to gravity. A sidebar 16 sits in the sidebar well 26 where it is held against the housing by springs 18. The housing or cap has a detent 8a or like projection to activate locking/unlocking protected object (not shown) in response to cylinder rotation when the cylinder is properly rotated and engaged to rotate the housing therewith. Detent 8a is shown on the cap 11 but could be on the housing 8. FIG. 1 also shows the full lock mechanism operation. FIG. 1 also illustrates key 2 as a conventional key i.e., one with flat engagement upper or lower edge for functional engagement with tumblers of the lock. The lock mechanism can be used with other conventional or non-conventional keys.

(16) FIG. 2 is a top view, partially cross-sectioned, of the arrangement of tumblers inside the cylinder 4 with dashed lines indicating features not visible from the top, shows that the tumblers 12 sit in tumbler wells 21. These are connected by slots 22 to the keyway 20. A shallower slot 24 guides the tumbler, restricting its transverse rotational or pivoting motion to a single axis. The sidebar 16 sits in the sidebar well 26, supported by springs 18 that sit in their own wells 19, and a plurality of side bar lugs 30 extend through holes 28 to the tumbler wells, allowing the sidebar to engage the tumblers.

(17) FIG. 3 shows a cut-away side view of the cylinder 4, showing the positions of the tumblers 12 inside the tumbler wells 21. This also provides a view of the slots 22 connecting these to the keyway 20, and the guide slot 24.

(18) FIG. 4a shows a close-up of the key-facing side of the plate-form tumbler 12. On this side there are two long lugs 32 to interact with the key, (item 2 in FIG. 1) and one shorter lug 34 to guide the tumbler. Also shown is the deep hole 36 through the tumbler.

(19) FIG. 4b shows a close-up of the other side, i.e. the sidebar-facing side, of the tumbler 12. On this side are a number of holes. One of them 36 is deep enough to release the sidebar. The other holes 38 are not deep enough to completely release the sidebar, but imitate the behavior of the correct hole if the other tumblers are not correctly aligned. One of the long lugs 32 of the key facing side is also visible.

(20) FIG. 5 shows a top view cross-section of a tumbler 12. This shows the long lugs 32, the short lug 34, the deep hole 36, and one of the shallow holes 38. The other shallow hole is shown with dashed lines as it is behind (under) the other holes.

(21) FIG. 6a shows the interaction between the key surface 25 and tumblers 12. This is accomplished by direct contact with the long tumbler lugs 32, causing a swiveling and sliding tumbler motion as it moves the deep hole 36 as well as the decoy holes 38 relative to the sidebar lug hole 28 and consequently the sidebar lug 30. The short lug 34 is also shown for clarity. It should be noted that that the placement of hole and legs as shown in FIG. 6a is exemplary and not limiting. For example, lugs and holes now shown in tumbler and sidebar placements could be reversed in whole or in part.

(22) FIG. 6b shows the same components as in FIG. 6a in correct alignment established by further movement of the key in the keyway. The deep hole 36 is now in the same position as the sidebar in 30.

(23) FIG. 7 is a partially sectioned top view, showing the interaction between the sidebar 16 and a tumbler 12 when the components are in incorrect alignment. Note that the sidebar lug 30 is able to penetrate into the deep tumbler hole 36. Decoy holes 38 are shown for comparison.

(24) FIG. 7b shows the same components not in correct alignment for unlocking (i.e., in decoy alignment). Note that the sidebar lug 30 is only able to penetrate a short distance into the decoy hole 38.

(25) FIG. 8 shows the position of the sidebar-facing vee-shaped plate 10 relative to the housing 8 and the sidebar-facing notch 9. As noted above, deformation of the plate by excessive force in an azimuthal direction changes the angle of force on the sidebar and thus prevents forcing of the side bar into the cylinder and prevents unlocking.

(26) It should be noted that the large seat surface area of the tumblers and side bar provide resistance to forcing and also present a difficult feel detection prospect for a lock-picker compared to conventional rotatable cylinder locks.

(27) Although the invention has been described with respect to various embodiments, it should be realized these teachings are also capable of a wide variety of further and other embodiments within the spirit and scope of the appended claims.