1. Field of the Invention
The invention relates to a door or protective hood locking control system, which serves as a safety device to protect persons against accidents from automatic motional processes of machines and industrial robots.
2. Discussion of Related Art
Known safety circuits, which also comprise door-monitoring components, are known from an article entitled "Erst bei Storung schalten" (Switch only in the event of a disorder), published in the German publication KEM, January, 1989 on pages 55 to 56.
This article deals with the use of so-called safety relay components which provide compact solutions by saving on wiring and which may be used in the area of protective door monitors and protective door tumblers of machines. Usually such monitoring circuits or tumblers of protective doors serve to protect persons against accidents due to automatic motional processes of machines and installations and also due to industrial robots carrying out certain motional processes. With the increasing complexity of manufacturing processes, such safety circuits for the locking and unlocking of doors or protective hoods can also increasingly serve in machine protection itself against unwanted interruptions of automatic processes. It is possible to differentiate between a plurality of circuits, for example, between the use of two alternately operating monitor switches and the use of two monitoring switches operating in parallel, whose constructions are with or without catches (door tumblers). The locking effect for such door locks is brought about by spring pressure or a magnetic force.
Usually, manually operated push-button switches are used for locking and unlocking doors. Catch magnets may be acted upon as the appropriate current paths become released by further, safety-relevant switches. At the same time, the door position is scanned by an opener or closer which is separate from the locking magnets so as to enable further switching conditions to be derived. Such unlocking or locking circuits for magnets or on some other basis should also contain so-called stoppage monitors in a suitable form, which ensure that unlocking, after which a door or hood can be opened, occurs only when a machine has stopped or at the end of a rotational motion.
Furthermore, protective devices for monitoring creep or rotational motions with normal or increased safety at machines are known from the Offenlegungsschriften 38 37 218 and 39 00 733. The safety circuit, which is described in the German Offenlegungsschrift 39 00 733, relates to a monitoring circuit of modular construction, which, by stringing together additional monitoring circuits, relates also to machines with several axles, which in each case carry out rotational motions.
The safety circuits described in the two German Offenlegungsschriften, 38 37 218 and 39 00 733, are incorporated herein by reference for describing supply of rotational movement signals utilized in a door or protective hood locking control system and for describing their own safety concepts which may be applied to the present invention.
With respect to the usual door-locking control systems for machines, the previously-mentioned stoppage monitors are required. Usually, at least one rotational motion sensor is disposed and serves as a parallel switch or series switch in the locking circuit of the door magnet. The magnet may be activated or the door caused to open only when the stoppage :monitor has established that there is no rotational motion or other motion in the area of the axle that is to be monitored. If such a door locking system is to be constructed redundantly with high safety, then it will require even two such stoppage monitors or stoppage switches, which produce independently of one another the corresponding rotational motion signals and bring them along separate paths into the area of the triggering circuit for the door magnets. This is particularly expensive, since most of the existing security protection circuits for switching off any rotational motion of the machine, for example, over :relay switches in the triggering region of the motors, must anyhow have a system for sensing rotational motions. Under certain circumstances, such a system can also be very expensive.