Electromagnetically actuated lock

The apparatus is an electromagnetically actuated lock which has a movable part, which is prevented from rotation or displacement by a barring bolt that extends into a recess of the movable part. Locking pins extend into the barring bolt and which locking pins positively lock the bolt in the withdrawn or retracted position when access is authorized and which locking pins also positively lock the bolt in the extended position when access is unauthorized.

BACKGROUND OF THE INVENTION 
The invention relates to an electromagnetic lock as defined in the preamble 
to claim 1. 
In the future use of electronic keys, for example for vehicles, in which 
the user possesses only an encoded key without a mechanical function (key 
bit), it is necessary to also replace the purely-mechanical lock function 
with an electrically-controlled device. 
It is known from U.S. Pat. No. 4,784,415 that an electromagnetic lock is 
provided with a movable part that can be prevented from displacement by a 
barring bolt, with the barring bolt extending into a recess of the movable 
part. At least one locking pin extends into the barring bolt, and the 
locking pin unlocks the barring bolt if access is authorized. Coils that 
can be supplied with current, and in which the locking pin and barring 
bolt form the armature, assure the unlocked or locked state of the barring 
bolt in the event of a power outage. A plurality of locking pins can be 
provided. 
DE-A1 35 05 971 discloses a key for actuating the electromagnetic lock, the 
key containing contact pins or bridges, by means of which the lock is 
rendered operable when the key is fully inserted. 
SUMMARY OF THE INVENTION 
It is the object of the invention to develop a key-lock system that meets 
increased safety requirements due to potential danger during a 
malfunction. 
This object is accomplished by the features described herein.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows an arrangement similar to the operating principle of magnet 
valves. The system has three coils A-C, with associated armatures 2, 3, 4, 
and compression springs F1, F2, F3, which are grouped in a housing (G), 
and a receptacle 5 (bell) for a secure attachment to, for example, the 
jacket tube for a guide spindle 1 of a motor vehicle. 
In the locked state, a barring bolt 2 extends into a recess of a shaft or 
guide spindle 1 illustrated in FIG. 1. The barring bolt 2 is additionally 
held by locking pins 3 and 4. The shaft or guide spindle is thus fixed 
against rotation. Analogously, the device of the invention can also be 
used to stop a longitudinally-movable part 1. 
For unlocking, first the coils B and C are supplied with current to release 
the locking pins. Afterward, the barring bolt 2 is withdrawn from the 
guide spindle 1, and the guidance is enabled, through the supply of the 
coil A with current. The coils B and C are shut off, so the locking pins 3 
and 4 are returned to their inoperative positions, which prevents an 
undesired engagement of the barring bolt 2 with the guide spindle 1. As 
soon as the current through coil A is shut off, the barring bolt 
additionally locks the two locking pins. This provides a three-fold 
protection against unintentional blocking of the guidance. 
For locking the guide spindle 1, the coil A and coils B and C must be 
excited consecutively. Afterward, the current in coil A is shut off first, 
followed by the current in coils B and C. The guidance is in the locked 
state after the barring bolt 2 latches in the recess of the guide spindle 
1. 
The position of the locking pins and the barring bolt can be permanently 
monitored through the measurement of the inductances by the associated 
control electronics. 
FIG. 2 shows the associated electrical circuit. The coils A-C are 
controlled by way of a power output stage L, which for its part detects 
the electrical coil values and conducts them to the process control STG. 
The control signals are generated by the process control as a function of 
the locking-pin and barring-bolt position, on the one hand, and the 
requests from the vehicle, on the other hand. The level of the 
continuous-current supply at Kl.30, the message "ignition on" at Kl. 15 
and the status of the infrared closing system IR are provided as input 
signals. 
For increased security, it is advantageous to provide more than two locking 
pins. 
While the invention has been disclosed in this patent application by 
reference to the details of preferred embodiments of the invention, it is 
to be understood that the disclosure is intended in an illustrative, 
rather than in a limiting sense, as it is contemplated that modifications 
will readily occur to those skilled in the art, within the spirit of the 
invention and the scope of the appended claims