Safety switch arrangement

Details Safety switch arrangement Safety switch arrangement

1996-11-04

1998-07-07

Leja, Ronald W.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Feeder protection in distribution networks

361 86, H02H 300

Patent

active

057778345

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a safety switch arrangement according to German Patent Application P 44 41 070.0-32.
The dual-channel safety switch arrangement described therein has actuators which include switch-like means comprising semiconductor elements. In contrast to relays, these semiconductor elements have no contacts that are subjected to wear.
A computer unit is provided in each evaluation channel for performing the function check of the actuator, with each computer unit being connected to the actuator by way of two bidirectional supply lines. The computer units, which are preferably configured as controllers, can be disposed upstream of the actuators as standard products; this practice is inexpensive and does not require an additional outlay for circuitry. Computer units are already integrated into a number of sensors for the purpose of controlling the sensor functions. In this case, the computer units can additionally perform the functions necessary for the safety switch, further reducing the circuitry outlay for the sensor.
The computer units are connected by way of a bidirectional supply line so that they can be monitored.
The complete actuation and function monitoring of the actuators is effected centrally in the computer units. To physically separate the function monitoring from the transmission of the sensor signals, separate, bidirectional supply lines are provided from the computer unit to the actuator for transmitting the switching pulses of the sensor and for transmitting test pulses for function monitoring; this increases the operating reliability of the arrangement. The bidirectional supply lines do not only transmit the switching pulses and test pulses to the actuator, but also receive an acknowledgement message from it. Also contained in the acknowledgement message is additional information regarding whether the functions of the actuator and the supply lines are error-free. Based on the different acknowledgement messages, errors that may occur can be localized and classified quickly and reliably.
To perform function checks of the safety switch arrangement, the computer units change the switching states for a short time, and the acknowledgement messages are checked in the computer units to determine whether the functions of the evaluation channels and the actuators are error-free. This change in the switching states is effected for such a short time that the operating state of the working means does not change; in other words, the function check does not impair the operation of the working means. A further advantage of this arrangement is that the function check parameters can be set easily with the computer units.
The object of the invention is to increase the scope of the function check with the least possible circuitry outlay.


SUMMARY OF THE INVENTION

The operating voltages of the computer units are checked by the voltage-monitoring unit, which is guided to the switches in the supply lines leading to the actuators; erroneous control signals originating in the computer units due to overvoltages or undervoltages, which can lead to a dangerous breakdown of the switches, can be discovered in the process.
The function monitoring can advantageously be performed in such a way that the read-back windings no longer need to be guided back to both computer units, which reduces the circuitry outlay. The sensor is advantageously connected to each computer unit by way of a dual-channel supply line, so the signals traveling from the sensor to the computer unit can be monitored.
A further advantage is that the function check is performed independently of the sensor signal state.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below in conjunction with the drawings.
FIG. 1 is a circuit diagram of the safety switch arrangement,
FIG. 2 is a circuit diagram of the actuator, and
FIG. 3 is a timing diagram of the signal states of the bidirectional supply lines.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a safety switch arrangement 1 for s

REFERENCES:
"Multiple-Input Over-Voltage, Under-Voltage Window Comparator for Computer Power Supplies". In: IBM Technical Disclosure Bulletin, vol. 29, No. 10, Mar. 1987, p. 4516.

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