This application claims priority to German Patent Application No. 10 2018 009 217.9, filed Nov. 23, 2018, the disclosure of which is incorporated by reference herein in its entirety.

The invention relates to a locking device having a guard lock for safety doors.

Such a device is known from DE 10 2010 007 388 A1. These well-known locking devices are commonly used for safeguarding machines and installations, from which a risk emanates in operation, against unauthorized access. Start-up of such machines should only be allowed when the locking device is locked and, where appropriate, issues a “door closed” signal. In addition, renewed access to the machines should only be permitted when the machine no longer poses any risk. This is achieved by means of a so-called guard lock, i.e. the locking device is not released until there is a stop signal or a similar signal from the machine.

A well-known locking device builds the guard lock using a longitudinally displaceable push rod in a housing or frame part, said push rod being configured to lock a control wheel in a defined state. The locking of the safety door can be effected by an actuator being a key, which is fastened on the door part and is inserted into a receptor at the housing or frame part. The actuator turns the control wheel such that the push rod is able to engage an indentation of the control wheel by the force of a spring. This prevents the key from being removed from the receptor. For controlled release of the key once the machine has stopped, the push rod is moved from an engaging position into a release position.

A disadvantage, however, is the need for a control wheel, which is usually located in a first housing part, while the push rod is located in a second housing part. There is therefore an increased space requirement, with the consequence that the well-known locking device cannot be designed to be compact. Furthermore, the key can only be inserted into the receptor in a correct position. A fail-safe guard lock is then not always guaranteed or may require additional mechanical alignment work at the safety door.

From US 2013/0088024 A1 is known a locking device including a plunger. That plunger can move against a biasing force of a compression spring and has a recess to restrict the movement of the plunger.

It is an object of the invention to provide a locking device having a guard lock, which provides high locking forces, is of simple construction and offers a much greater degree of flexibility.

This object is achieved by the features of claim1.

A locking device is provided having a guard lock for a safety door, where the separate actuator comprises a clamping recess as an engagement recess for a locking plunger. The clamping recess and the locking plunger provide a mechanical locking function. The locking plunger is therefore a snap-in plunger. Furthermore, the mechanical catching function provides the possibility of locking. By locking or blocking the locking plunger, the guard locking unit and actuator are mechanically connected to each other. Catch engagement is achieved by a locking plunger driven against biasing force, which in turn runs the actuator into the clamping recess located there.

The guard lock can be achieved via a locking shaft or a locking rod which moves engagement elements, such as, for example, four circumferentially distributed balls, inside the locking plunger, which can take place similar to the ratchet principle. The engagement elements lock the locking plunger towards the locking shaft and thus prevent dipping of the locking plunger. The locking shaft/locking rod can be moved by a bistable solenoid. The position of the locking shaft/locking rod and the associated locking of the locking function can be safely monitored.

In addition to the locking recess, the actuator may contain an electronic identification element, in particular an RFID tag. The position of the RFID tag and thus of the safety device can be reliably detected with an RFID sensor located in the guard lock unit. Consequently a combination of a contactlessly acting sensor (RFID) and a safe-guard lock can be formed to protect a safety device.

The locking device according to the invention then comprises a guard lock unit and an actuator, which has an encodable RFID tag and a locking recess/engagement recess for the locking plunger/engagement plunger. The RFID tag enables to provide the function of a proximity switch with defined behaviour in the event of an error. The locking recess/engagement recess allows the actuator to be continuously inserted at a 180° angle into a head or an actuator slot, which can preferably be designed with openings. The directions of approach are therefore particularly variable and angle-flexible.

Further details of the invention are to be found in the following description and the dependent claims.

