Locking device

A locking device includes a key having a locking code and a device for reading the locking code on the key and comparing it with a predetermined locking code. The key has a grip portion and an elongated information carrier extending outwardly from the grip portion. The key is insertable into an opening in the reading device. Magnetic information elements are provided along the information carrier and reading elements in the reading device read the information elements when the key is inserted. A projection extends outwardly from the information carrier transversely of its elongated direction. An information element is located on the projection and a corresponding reading element is provided within the reading device. The dimension of the projection outwardly from the information carrier is such that only the information element located on the projection can excite its corresponding reading element.

SUMMARY OF THE INVENTION 
The present invention is directed to a locking device including a key and a 
reading device. The key has a grip portion, and an information carrier 
extending from the grip portion on which information elements are arranged 
in a pattern establishing the locking code of the key. The reading device 
contains reading elements which read the locking code on the key and 
compare the locking code as read to a predetermined locking code. 
A locking device of this general type is disclosed in German Pat. No. 21 38 
991. This device is a mechanical lock having tumblers which can be placed 
in the unlocked position by switching magnets in the lock housing when a 
magnetic field of predetermined direction is located in the region of the 
switching magnets by means of the key. The key has two magnets arranged 
next to one another in a plane. The magnets are supported on locking discs 
which can be displaced about axes extending perpendicularly relative to 
the direction of magnetic polarization. By turning the locking discs, the 
angular position of the directions of polarization relative to one another 
can be changed so that the key is coded. This known locking device has the 
disadvantage that the size of the key increases disproportionately when a 
large number of coding variations is required. 
Further, in German Utility Model No. 75 33 052 a flat key is disclosed for 
a cylinder lock. The key contains an insert of magnetizable material. The 
insert is magnetized in certain regions in different polarization 
directions and is read by the reading device of the lock cylinder when the 
flat key is inserted. The number of coding variations possible with this 
particular arrangement is relatively small. In addition, it is difficult 
to recognize when all the information elements have been read so that a 
proper comparison of the locking code as read with the predetermined 
locking code can be performed. 
It is the primary object of the present invention to provide a 
predetermined position of the key relative to the reading device so that 
the position can be detected without error. 
In accordance with the present invention, the information carrier portion 
of the key has an elongated shape and carries the magnetic information 
elements which determine the locking code along its peripheral surface. 
The information carrier portion of the key is inserted into an opening in 
the reading device. In addition to the information elements along its 
peripheral surface, an additional magnetic information element is provided 
on the carrier portion so that it can be read by a separate reading 
element in the reading device which has a susceptibility to a magnetic 
field. This additional information element is located on a projection 
which extends radially outwardly from the peripheral surface of the 
information carrier portion, that is, it extends transversely outwardly 
from the information carrier portion relative to its elongated direction. 
The radial distance outwardly from the elongated axis of the information 
carrier portion is made greater for the information element on the 
projection than for the remaining information elements on the carrier 
portion so that the reading element corresponding to the information 
element on the projection is excited during the insertion of the carrier 
portion only by the information element on the projection. Accordingly, 
the reading element corresponding to the information element on the 
projection, determines whether the key has been completely inserted into 
the reading device, and, if necessary, releases the reading device for 
scanning the locking code or for comparing it with the predetermined 
locking code. 
Preferably, the projection is located at the end of the information carrier 
adjacent to the grip portion. With the projection arranged in this manner, 
it guides the key into the opening in the reading device as the 
information element on the projection approaches the region of the 
corresponding reading element in the reading device. 
In embodiments where the information carrier has the shape of a circular 
cylinder, preferably the projection is inserted into a corresponding 
groove in the reading device. In such an arrangement, the projection 
prevents rotation of the key within the opening in the reading device and, 
in combination with the groove, aligns the information carrier relative to 
the reading device. 
The additional information element located on the projection is 
advantageously located so that it is on the surface of the information 
carrier most remote from its axis. The entire projection can be formed of 
a permanently magnetic material which is magnetized in certain regions on 
the surface of the projection which is directed outwardly away from the 
axis of the information carrier. Alternatively, a separate permanent 
magnet could be positioned on the projection. 
Another advantageous feature involves the provision of a stop surface on 
the end of the projection more remote from the grip portion and a 
complementary stop surface is provided in the reading device. The 
insertion of the key in the axial direction into the reading device can be 
regulated by means of this stop surface on the projection. In place of or 
in addition to the stop surface on the projection, the key can be provided 
with an outwardly projecting shoulder at the intersection of the grip 
portion and the carrier portion. The shoulder is located between the 
projection and the grip portion and abuts against an oppositely directed 
stop surface on the reading device. The shoulder can be formed by an 
increased diameter portion of the grip portion or by a flange projecting 
outwardly from the end of the information carrier adjacent to the grip 
portion. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiment of the invention.

DETAIL DESCRIPTION OF THE INVENTION 
In the drawing a key 1 is illustrated having a grip portion 3 for use in 
handling the key and a circular cylindrical information carrier 5 
extending axially outwardly from the grip portion. Information carrier 5 
includes a plurality of magnetic information elements 7 distributed in a 
pattern along the cylindrical axis of the information carrier and also in 
an angular pattern around the outer circumferential peripheral surface of 
the information carrier. The distribution of the magnetic information 
elements in the pattern establishes a binary locking code for the key in 
which the pattern of the information elements 7 correspond to a bit "1" 
and the vacant spaces in the pattern, that is, the spaces without an 
information element, represent a bit "0". 
The locking code on the key can be read by a reading device 9. The 
information carrier 5 of the key 1 is inserted into a cylindrical opening 
11 in the housing 13 of the reading device with the opening shaped to 
receive the information carrier 5. The reading device has a plurality of 
reading elements 15 susceptible to a magnetic field and arranged axially 
along as well as around the circumferential surface of the opening 11 in 
the pattern of the information elements 7. The reading elements respond 
either to the presence or absence of the information elements 7 in the 
pattern. The reading elements are connected to a comparator 17 which 
compares the locking code as read from the key to a locking code supplied 
from a code generator 19. When the predetermined locking code coincides 
with the locking code read from the key 1, the comparator 17 emits a 
signal at its output 21 which can be utilized for operating the lock, not 
shown. 
The lock may be a central locking system or a theft protection system for a 
motor vehicle. The magnetic information elements 7 can be separate 
permanent magnets inserted into a non-magnetic body on the key. However, 
the key may be formed of a magnetic material which is magnetized in the 
zones in which the information elements are located. The reading elements 
may be Hall probes or reed switches. 
At the end of the information carrier 5 adjacent the grip portion 3, an 
axially extending projection 23 extends radially outwardly from the 
cylindrical periphery of the information carrier 5. The projection 23 
engages, in a form locking manner, in a groove 25 formed in the surface of 
the opening 11 within the housing 13 of the reading device 9. The groove 
25 is adapted to receive the projection 23. The combination of the 
projection 23 and the groove 25 align the information carrier 5 in the 
circumferential direction relative to the reading elements 15 in the 
reading device 9. A shoulder 27 located at the end of the projection 23 
more remote from the grip portion 3, determines the depth of insertion of 
the information carrier into the housing 13. In the fully inserted 
position of the key, the shoulder contacts a countershoulder 29 at the 
inner end of the groove 25. At the end of the information carrier 5, 
located just outside the housing when the key is fully inserted, an 
annular shaped shoulder 31 extends radially outwardly from the cylindrical 
periphery of the information carrier and the shoulder rests against the 
surface of the housing in the inserted position. The shoulder 27 and the 
annular shaped shoulder 31 can be dimensioned so that, in the inserted 
position of the key, they determine either jointly or individually the 
axially position of the key relative to the reading device. At the free 
end of the carrier 5, that is the end opposite the grip portion 3, a 
conically shaped stop head 3 is provided and a groove extends around the 
circumference of the stop head. In the inserted position of the key 1, a 
spring-loaded snap-in member 37, located at the inner end of the opening 
11, engages within the groove 35. The snap-in member 37 can be displaced 
radially relative to the opening 11 permitting the insertion of the head. 
The conical surface of the stop head 33 forms an obliquely extending guide 
surface which deflects the snap-in member 37 out of its path as the key is 
inserted. 
To prevent the comparator 17 from reading and comparing the code on the key 
before the key is fully inserted, the comparator 17 has a release input 39 
connected to an additional reading element 41 which is susceptible to a 
magnetic field. The reading element 41 responds to an additional magnetic 
information element 43 positioned in the projection 23 on the information 
carrier 5. The information element 43 is spaced radially from the axis of 
the information carrier 5 by a greater amount than the remaining 
information elements 7 located along the circumferential periphery of the 
carrier. The radial distance of the information element 43 from the axis 
is selected so that the reading element is actuated only by the 
information element 43 and not by the information elements 7 which precede 
it as the key is inserted into the opening 11. The comparator is released 
only when the key is completely inserted into the housing. If necessary, a 
time delay can be incorporated into the release of the comparator to 
prevent the comparator from being released while the key is still in 
motion. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.