Cylinder lock and key in which at least one tumbler is magnetically biassed

Abstract: In a cylinder lock, one ore more tumblers (11) of the rotatable cylinder (6) are subjected to magnetically operative biassing means (20, 21).

Description: The Present invention relates to a cylinder lock and key, of the type indicated in the pre-characterizing portion of claim 1. In conventional locks, the biassing means are constituted by coil springs arranged within the holes of the fixed body wherein the counter-tumblers are movable, so as to push the counter-tumblers against the respective tumblers, towards the axis of the rotatable cylinder. These locks enable a burgler to determine the profile of the key which can open the lock, by inserting a tool within the key hole and pushing the tips of the lock tumblers by this tool, against the action of the above mentioned coil springs. A cylinder lock and key of the type indicated in the pre-characterizing portion of claim 1 is disclosed in DE-A-2 201 281. The object of the present invention is that of proposing a new type of lock which has a higher degree of safety with respect to the conventional locks of the above indicated type. In view of achieving this object, the invention provides a lock having all the features of claim 1. Naturally, it is possible to provide one or more tumblers of the lock and, if desired, even all the tumblers of the lock, with magnetically operative biassing means. According to an embodiment, the above mentioned first permanent magnet is arranged within the respective hole of the fixed body between the respective counter-tumbler and an end wall of the hole. Alternatively, the first permanent magnet may be arranged within the respective hole of the fixed body between the respective counter-tumbler and the respective tumbler. In order to improve the magnetic efficiency, preferably the tumbler and/or the respective counter-tumbler are made of ferromagnetic material. The second permanent magnet is fixed within a seat formed in the key on a surface opposite to that which is for cooperating with the tumblers of the rotatable cylinder. In case at least one of the tumblers of the rotatable cylinder has biassing means of the conventional type constituted by a coil spring arranged within the hole of the respective counter-tumbler, according to the invention the counter-tumblers associated with magnetically operative biassing means have a greater length than the counter-tumbler associated with coil spring biassing means. In this manner, a lock of conventional type can be transformed into a lock according to the invention with no modification to the geometry of the fixed body. Due to the above mentioned features, when the key is not introduced into the lock, the first permanent magnet is not biassed towards the axis of the rotatable cylinder. Therefore it is impossible for a non-authorized person to introduce a tool into the key axial passage and press this tool against the tip of the above mentioned tumbler in order to determine the profile of the key which can open the lock. Thus, the lock according to the invention has a higher degree of safety with respect to the known locks. Further features and advantages of the invention will become apparent from the description which follows with reference to the annexed drawings, given purely by way of non limiting example, in which: figure 1 is a perspective diagrammatic view of the lock according to the invention, with the associated key, figure 2 is a cross-sectional view taken along line II-II of figure 1, figure 3 shows the cross-section of figure 2 in a different operative condition, and figure 4 shows a variant of figure 2. In figure 1, reference numeral 1 designates a cylinder lock associated with a door frame 2 and adapted to cooperate with a key 3. As shown in figure 2, the lock 1 is a cylinder lock, comprising a lock fixed body 4 having a cylindrical cavity 5 where a cylinder 6 is rotatably mounted. In the case of the illustrated example, the fixed body 4 of the lock is of the type including two body sections (only one of which is visible in the drawings) arranged symmetrically with respect to a plane 7. The body section which is not shown in the drawings is identical and symmetrical to that shown. However, it is clearly apparent that the invention can be applied to any configuration of the fixed body. Also, in the case of the illustrated example, the two body sections are connected to each other by a bridge-like portion 8 in which a threaded hole 9 is formed for engagement of a screw (not shown) for securing the body 4 to the lock supporting structure 2. The details of construction are not shown herein since they can be made in any known way and since they do not fall within the scope of the present invention. The same applies to the rotatable pawl mounted onto cylinder 6, which occupies the gap 10 between the two body sections defined by the bridge-like portion 8. According to the conventional art, the rotatable cylinder 6 is provided with a plurality of locking tumblers 11 which are slidably mounted within radial holes 12 formed in the cylinder 6 and opening on an axial passage 13 formed in the rotatable cylinder 6 and adapted to receive the active portion 14 of the key. As shown in figure 1, in the case of the example described herein, the active portion 14 of the key 3 has a substantially flattened shape with a rectangular cross-section, and the passage 13 has a similar shape, with a general plane perpendicular to the plane containing the axes of the tumblers 11. Reference numeral 15 designates a plurality of counter-tumblers which are slidably mounted, according to the conventional art, within holes 16 which are formed in the fixed body and open on the cylindrical cavity 5 of the lock. The holes 16 are adapted to become aligned with the radial holes 12 of the rotatable cylinder 6 at a given angular position of the latter. The tips of the tumblers 11 facing towards passage 13 which is for receiving the key are for cooperation with cavities 17 formed on a first face 14a of the active portion 14 of the key 3, so that when this active portion 14 is fully received within passage 13, the tumblers 11 are each brought to an axial position which does not prevent the free rotation of the rotatable cylinder 6 within cavity 5 of the fixed body 4. Also in the case of the illustrated example, all the tumblers 11 of the lock, except for one of them, are radially biassed towards the axis of the rotatable cylinder 6 by coil springs 18 which are interposed within the respective holes 16 between the respective counter-tumblers 15 and a closing element 19 which defines an end wall of the hole. However, according to the invention, one of the tumblers 11 is not subjected to the action of a coil spring. In this case, between the respective counter-tumbler 15 (which has a greater length than the other counter-tumblers 15) and the closure element 19 there is interposed a permanent magnet 20, in form of a circular disk, and a second magnet 21 is fixed within a seat 22 formed on the face 14b of the active portion 14 of key 3, opposite to face 14a having cavities 17, so that when the key 3 is received within passage 13, magnet 21 draws magnet 20, so that the counter-tumbler 15 and the tumbler 11 associated with magnet 20 are biassed against the key. In order to improve the magnetic efficiency, the tumbler 11 and the counter-tumbler 15 which are associated with magnet 20 are preferably constituted of ferro-magnetic material. Figure 3 of the annexed drawings shows the condition of the lock when the key is introduced, with magnet 20 which, being drawn by magnet 21, keeps tumbler 11 associated therewith against the key. When the key is withdrawn, the tumbler 11 associated with magnet 20 is no longer biassed towards passage 13, so that it is free to fall within the respective hole 16. Therefore, if a burgler introduces a tool into passage 13, he is not able to press this tool against the above mentioned tumbler, since the latter is not biassed by any spring. For this reason, therefore, the lock according to the invention has a higher safety degree than the known locks. Figure 4 shows a variant in which magnet 20 is interposed between the respective tumbler 11 and the respective counter-tumbler 15. Naturally, it is possible to replace the biassing spring 18 with the magnet 20 and to provide a cooperating magnet 21 on the key for more than one tumbler of the lock and, if desired, for all lock tumblers. Furthermore, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and illustrated purely by way of example.

Claims: Cylinder lock and key, comprising: a lock fixed body or stator (4), having a cylindrical cavity (5), a cylinder or rotor (6), rotatably mounted within the cylindrical cavity (5) of the fixed body (4) and having an axial passage (13) for introduction of a key (3), a plurality of locking tumblers (11) which are slidably mounted within radial holes (12) of the rotatable cylinder (6) which open on said axial passage (13), said tumblers being adapted to be engaged at one end thereof by a key (3) having a predetermined profile so as to arrange themselves to a position in which they enable a free rotation of the rotatable cylinder (6) within the fixed body (4), a plurality of counter-tumblers (15) slidably mounted within holes (16) which are formed in the fixed body (4) of the lock, and open on the cylindrical cavity (5) of said fixed body (4), said holes (16) for the counter-tumblers (15) being adapted to become aligned with the holes (12) of the tumblers (11) in the rotatable cylinder (6) at a given angular position of the latter, and means (18; 20, 21) for biassing the tumblers (11) radially towards the axis of the rotatable cylinder (6) when the latter is at said given angular position, wherein in the case of at least one of said tumblers (11), said means for biassing the tumbler (11) radially towards the axis of the rotatable cylinder (6) are magnetically operative biassing means (20, 21) characterized in that : said magnetically operative biassing means comprise a first permanent magnet (20) arranged within the hole (16) of the fixed body (4) where the respective counter-tumbler is movable, and a second permanent magnet (21) associated with said key (3) and adapted to draw the first permanent magnet (20) towards the axis of the rotatable cylinder (6) when the key is received in the rotatable cylinder (6), so that the first permanent magnet (20) biasses the respective tumbler (11) against the key (3), said key (3) has a flattened active portion (14) and said axial passage (13) has a similarly flattened shape with a general plane perpendicular to a plane containing the axes of the radial holes (12) of the rotatable cylinder (6), said active portion (14) of the key (3) having a first face (14a) with cavities (17) adapted to cooperate with the tips of the tumblers (11) of the lock, each second permanent magnet (21) is fitted within a seat (22) formed in the key on a substantially planar face (14b) opposite to said first face (14a). Lock and key according to claim 1, characterized in that the first permanent magnet (20) is arranged in the respective hole (16) of the fixed body (4) between the respective counter-tumbler (15) and an end wall (19) of the hole(16). Lock and key according to claim 1, characterized in that the first permanent magnet (20) is arranged in the respective hole (16) of the fixed body (4) between the respective counter-tumbler (15) and the respective tumbler (11). Lock and key according to claim 1, in which for at least some of the tumblers (11) of the rotatable cylinder (6) the biassing means are of the conventional type constituted by a coil spring (18) arranged within the hole (16) of the respective counter-tumbler (15), characterized in that the counter-tumblers (15) associated with the magnetically operative biassing means have a greater length than the counter-tumblers (15) associated with coil spring biassing means (18). Lock and key according to any of the previous claims, characterized in that each tumbler (11) associated with a magnetically operative biassing means is made of ferro-magnetic material. Lock and key according to any of the previous claims, characterized in that each counter-tumbler (15) associated with magnetically operative biassing means is made of ferro-magnetic material. Cylinder lock and key according to claim 1, characterized in that the magnetically operative biassing means comprises two permanent magnets which repel each other, arranged within the hole (16) of the fixed body (4) when the respective counter-tumbler is movable.

Inventors: MOTTURA SERGIO, MOTTURA, SERGIO
Applicants: MOTTURA SERRATURE DI SICUREZZA, MOTTURA SERRATURE DI SICUREZZA S.P.A.
Application year: 1999
Main classification: E05B47
IPC codes: E05B27, E05B47