This invention relates to a flat key cylinder lock with anti-burglar features particularly for use with master key locking systems according to the preamble of Claim 1.
Known are flat key locks where. in addition to the usual bolt pins and counter-pins slided by the key dents, auxiliary side pins are provided which are slided by the key flanks and provide an added measure of burglar-proof ability.
Locks of this type are known, for example, from German Patent No. 2,003,059, and 1,260,340, in which the auxiliary pins are arranged to extend perpendicularly to the plane of the key. The pin action results from that, on the pins being slided sideways by the key being pushed in, they move out of the plug outer surface to engage in recesses formed in the cylindrical casing in which the plug is received rotatably. The proper key is formed with notches which, on the key being inserted into the lock, enable the auxiliary pins to retract by reaction effect as the plug is rotated. The pin retraction is facilitated by the crowned shape of the recesses.
When a bogus key is used, the notches and pins mismatch, and accordingly, the pins are held in a position of engagement with the recesses and prevent the plug from turning.
The burglar resisting ability of the known auxiliary pins is, in actual practice, rather unreliable because it can be easily overcome by effecting removal thereof lengthwise to the key profile at the areas abutting the auxiliary pins, that is by milling out the key flanks longitudinally, thereby the pins are allowed to slide freely in their seats. Such a deceptively machined key (referred to in the jargon as a "relieved" key) allow unrestricted sliding for the auxiliary pins which are, therefore, free to retract as the plug is rotated.
In fact, as is well known in the art of professional burglars, the relieved bogus key has on the same side thereof either a deceptive continuous longitudinal land formation or a deceptive continuous longitudinal groove formation on the appropriate height of the key determined after a deceptive external exploration of the key channel of the lock to be subjected to burglary.
The published German Patent Application No. 31 23 511 discloses a lock provided with holes for the auxiliary pins perpendicular to the usual pins and counter-pins and having the same or a larger diameter than the latter. With a "relieved" key, the counter-pins, after a 90° rotation, can fit into the holes for the auxiliary pins and make the lock fast. With a non-relieved key, the plug rotation would be hindered by the auxiliary pins being held engaged with the notches in the cylinder casing.
A lock according to the above disclosure has the disadvantage that when the lock is made fast in the rotated position, the bogus key cannot be removed and the lock is rendered unreusable.
The German Patent Application No. 3,014,183, discloses a lock having auxiliary pins cooperating with interference pins or balls that engage recesses in the outer casing to prevent the rotation of the plug.
The auxiliary and interference pins are shaped so as to enable rotation of the plug when the key is inserted but not when it is removed.
AT-B-371 833 generically hints that different types of auxiliary locking units may be used in a lock.
It is the technical aim of this invention to provide a cylinder lock having auxiliary pins which can obviate the drawbacks of the known ones, that is, can resist burglary efforts using deceptively "relieved" keys.
Within the above aim, it is an object of this invention to provide a lock which is suitable for use in locking systems with hierarchically different keys in conformity with a scale comprising multiple levels.
This aim and object are achieved by a cylinder lock as defined in Claim 1, in the preamble of which AT-B-371883 is considered.
Further features and advantages of the invention will become apparent from the following detailed description of some embodiments thereof, with reference to the accompanying illustrative drawing, in which:
With reference to Figure 1, this lock comprises a cylindrical casing 1, on the interior of which a cylindrical plug 2 is set rotatably.
The cylindrical plug 2 is formed, in a known manner no further illustrated herein, with a lengthwise channel or flute 3 having a shaped profile to receive the operating key, as well as with a plurality of holes 4 aligned on a longitudinal plane coinciding with the lock centreplane and accommodating the usual pins or bolt pins which, in cooperation with the counter-pins, are driven by the lock actuating key.
The plug 2 has additional holes 5, 6 formed therein alongside the channel 3 and being oriented in a radial direction.
The hole 6 is part of a first type of auxiliary locking pin unit described below and the hole 5 is part of a second type of auxiliary locking pin unit.
The holes 5, 6 extend in plane containing an axis substantially, but do not necessarily coincide with the axis of the plug 2.
With the lock in the position shown, which is the position with the key disengaged, the holes 5, 6 are aligned with recesses 7, 8 in the form of longitudinal grooves having an arcuate cross-section and being formed on the inner walls of the casing 1.
The hole 5 is in communication with the channel 3 and accommodates a cylindrical pin 9 having each of its opposed ends configured as a spherical cap.
As visible in Fig. 1 pin 9 has an actuation surface portion 9a projecting into the channel 3 and a locking formation 9b normally out of engagement with the recess 7.
A hole 10 is also formed in the plug 2 which intersects the hole 6 orthogonally thereto and opens into the channel 3.
The hole 10 is closed on the side of the casing 1 by a pellet or plug nut 11 force fitted to provide support for a compression spring 12 which penetrates, with its opposed end, a recess formed in a pin 13 guided in the hole 10.
The pin 13 is provided at one end with a flange 14 which, owing to the bias force applied by the spring 12, is held at one end against a shoulder of the hole 10, and at the other end, with a hemispherical head 15 merging with the cylindrical body of the pin 13 through a conical collar 16.
The hemispherical head 15 provides an actuation surface portion normally protruding into the channel 3.
The abutment shoulder for the flange 14 in the hole 10 is positioned such that the hemispherical head 15 partially protrudes into the channel 3. Further, the depth of the hole 6, when combined with that of the recess 8, will equal the diameter of the hole 6, so that it can accommodate a ball 17 of the same diameter.
The ball 17 provides a locking formation normally in engagement with the recess 8 to exert a locking action between plug 2 and casing 1.
It should be noted that, with the flange 14 abutting against the shoulder in the hole 10, the ball 17 prevented from coming out of the hole 6 by the body of the pin 13 blocking access to the hole 10.
In the above description, reference has been made, for reasons of clarity in the drawings, to a single hole 5 formed on one side of the channel 3 and to a single pair of mutually intersecting holes 6, 10 formed on the other side of the same hole. Actually, it is envisaged that, according to the invention on the same side of the channel 3 and at an axial distance from each other, a set of holes comprising at least one hole 5 and respective pin 9 together with a pair of holes 6,10 and respective pins 13 and ball 17,are provided.
It will be understood from the foregoing, that on the same side of the channel 3 two different types of auxiliary locking pin units are provided, i.e. a first type including the radial hole 6, the ball 17, the transverse hole 10 and the pin 13 and on the same side a second type of auxiliary locking pin unit including the radial hole 5 and the pin 9.
The lock just described is operated by means of a key having side notches arranged such that, with the key inserted into the channel 3, each notch faces one hole 5 to receive the pin 9. Furthermore, the key can act with its flanks directly on the pins 13 and push them back into the holes 10 against the bias of the spring 12.
As shown clearly in Figure 1, with the key removed, the plug 2 is inhibited from turning by, in addition to the actions of the pins and counter-pins housed in the holes 4, by the locking action of the ball 17 which cannot retract into the hole 6 owing to the pin 13 blocking it from moving.
On inserting the proper key into the channel 3, the pins 9 retain their freedom of movement due to the provision of corresponding notches on the key which enable the pins 9 to penetrate the channel 3. Simultaneously, the key flanks i.e. actuating land portions thereof push into the holes 10 the pins 13, thereby the ball can move down the conical region 16 and stop against the spherical head 15, thus disengaging from the recess 8. Owing to the pins in the holes 4 being positined by the key dents in the shear plane between the plug 2 and casing 1, the plug 2 may now be turned.
If a bogus "relieved" key is introduced into the channel 3 from either end, there will be at least one pin 13 which retains its position shutting off the ball 17 and, hence, the plug 2.
If the bogus key is not correctly relieved, the inhibiting function is assumed by at least one of the pins 9 being pushed back into the recess 7 to the plug blocking position.
As may be seen, the lock can provide a better safeguard than traditional ones, since the auxili- ary pins not only widen the range of key coding, but also compel any ill-intentioned person surreptitiously attempting to pick the lock to manipulate pins which are difficult to locate.
In practicing the invention, many modifications and variations are feasible especially in respect of the auxiliary pin fashioning.
In the embodiment of Figure 2, the pin 9 is replaced by a ball 18 and a pin 19. The ball 18 is accommodated in a radial hole 20 which intersects the hole 21 perpendicularly wherein the pin 19 is slidable.
Relatively to the lock centreplane in addition to the basic features of the invention the hole 21 is symmetrical to the hole 10 and opens into the channel 3 for the key at a position which need not necessarily be juxtaposed to the hole 10.
The pin 19 is provided with a flange 22 and an annular groove 23 defined by two flaring walls 24. The flange 22, similarly to the flange 14, is urged against a shoulder in the hole 21 by a spring 25 which rests on a plug nut 26 in the hole 21.
With the proper key, the ball 18 will be facing the groove 23 and is free to move in the hole 20, disengaging from the recess 7 and allowing the plug 2 to be rotated.
By contrast, if the key has no notches, the ball 18 will remain in tangent contact with the periphery of the pin 19, while in engagement with the recess 7 and preventing the plug 2 from rotating. As visible from the drawing all actuation formations 9a, 15, 19, are substantially at the same height with respect to the channel 3.
In Figure 3, there is shown a solution wherein the hole 27 accommodating the auxiliary pins is formed through the channel 3 for the key. Thus no plug nuts are required. whilst to prevent the pins from leaving their seats, there are provided axial pins 28 which, by interfering with a side bevel 28a of the auxiliary pins, also prevent them from turning.
In Figure 4, lastly, there is shown an embodiment wherein the cylindrical springs 12 are replaced with leaf springs 29 each inserted into a respective slot 30 cut through the periphery of the plug 2 perpendicularly to its axis and intersects the hole 10 diametrically. The spring 29 has one end secured by a chamfer 31 of the slot and the other end acting on the pin 13 to bias it toward the position of engagement with the channel 3 for the key.
One of the basic features of the inventive locks is that they enable the fabrication of so-called master key systems, wherein the locks may be operated in conformity with hierarchically different levels, in the sense that keys of a hierarchically higher level can operate locks of lower levels, but not vice versa. Diversification may be achieved by intervention on the key flanks and respective side pins. Thus, the highest key in the hierarchy will have notches for receiving the pins 9 and lands for pushing back the pins 13 of all the locks. The lower level locks may have one or more auxiliary pins 9, 13 missing.
The presence of the spring-loaded pins 13 inhibits the fabrication of keys of a higher hierarchical level by "relieving".
The hierarchy to be obtained with the auxiliary pins may be combined with that to be obtained with the usual pins and counter-pins, thereby a much differentiated hierarchical scale can be provided.