Safety switching apparatus with switching element in the auxiliary contact current path

#The present invention relates to a safety switching apparatus and a method for switching on or switching off a technical installation in a failsafe manner, and more particularly, to a safety switching apparatus and method that operate more efficiently in terms of energy consumption and power saving.

#A safety switching apparatus in terms of the present invention is any switching apparatus that is designed to meet the safety standards for industrial machines, such as EN ISO 13849 and/or EN/IEC 62061 or related safety standards. Particularly, a safety switching apparatus in terms of the present invention is designed to meet the requirements of PL d (Performance Level d) according to EN ISO 13849 and/or SIL 2 (Safety Integrity Level) based on EN/IEC 62061. This includes safety relays, safety controllers, and also sensor and actuator modules which are used for controlling and performing safety critical tasks in the field of industrial production environments. For example, safety relays are known which monitor the operating position of an emergency off button or a guard door or, by way of example, the operational state of a light barrier and take this as a basis for disconnecting a load current into a machine or a machine area. Failure of such safety switching apparatuses can have life endangering consequences for machine personnel, for which reason safety switching apparatuses are typically used only when they are certified by relevant supervisory authorities, such as occupational health organizations.

#DE 10 2004 033 359 A1 discloses a prior art system for safeguarding an automatically operating robot. The apparatus comprises a safety switching apparatus which actuates two external switching elements at the output. At the input, the safety switching apparatus is provided with one or more input signals by appropriately connected signal generators. The input signal(s) received is/are supplied to an evaluation and control unit, which is preferably designed to have multichannel redundancy. In the preferred exemplary embodiment, the safety switching apparatus comprises two output relays, the switching position of which is determined by the evaluation and control unit. Each relay has a number of positively guided make and break contacts.

#Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the description below. In the drawing:

#FIG. 1 shows a simplified illustration of a technical installation with an exemplary embodiment of the safety switching apparatus,

#FIG. 2 shows a simplified illustration of a first exemplary embodiment of the novel safety switching apparatus,

#FIG. 1 illustrates a technical installation 10 having an exemplary embodiment of the safety switching apparatus 1 for switching on or off the technical or dangerous installation 10 in a failsafe manner. In this exemplary embodiment, the installation 10 includes, by way of example, a robot 12, the movements of which during working operation present a danger to persons who are in the working area of the robot 12. For this reason, the working area of the robot 12 is safeguarded by means of a protective fence having a guard door 14. The guard door 14 allows access to the working area of the robot 12, for example for maintenance work or for setup work. During normal working operation, the robot 12 is permitted to work only when the guard door 14 is closed, however. As soon as the guard door 14 is opened, the robot 12 must be disconnected or put into a safe state in another manner.

#In order to detect that the guard door 14 is in the closed state, the guard door 14 has a guard door switch mounted on it which has a door portion 16 and a frame portion 18. The frame portion 18 produces a guard door signal on a line 20, said signal being supplied to the novel safety switching apparatus 1 via line 19.

#In this exemplary embodiment, the safety switching apparatus 1 has an I/O portion 24 having a plurality of connections (external or device connections) 25. In some exemplary embodiments, the connections 25a, 25b are connecting terminals or field terminals which are arranged on one housing side of the housing 27 of the safety switching apparatus 1. By way of example, there may be tension spring terminals or screw terminals. In other exemplary embodiments, the connections may be plugs or sockets which contain a plurality of contact elements (pins), with one pin in each case forming one connection. Frequently, M8 sockets having five contact pins are used for connection of signaling devices or other sensors at field level. Accordingly, exemplary embodiments of the novel safety switching apparatus may be or may comprise field devices which are arranged outside a switchgear cabinet in close proximity to the robot 12.