DD201345B1 - CIRCUIT ARRANGEMENT FOR MONITORING THE AMPLIFIERS AND THE PRESS SAFETY VALVES - Google Patents

Description

a) Title of the invention

Circuit arrangement for monitoring the amplifiers and the press safety valves

b) Field of application of the invention

The invention relates to a circuit arrangement for the simultaneous monitoring of the function of the amplifier and the press safety valves of a two-channel electronic press safety control with two similar, independent control channels and a fed by a frequency generator with a pulsed AC voltage monitoring channel.

c) Characteristic of the known technical solutions

In a known solution of this type (DE-OS 27 21 270. Fig. 1), the input signals for the amplifiers of the press safety valves are formed from the output signals of the two control channels and the monitoring channel. A monitoring of the function of the amplifier and the press safety valves themselves is not provided, so that a faulty behavior of these components is not recognized. In particular, in presses in which the insertion and removal of the parts in the tool is done by hand, the failure of a press safety valve can lead to an unwanted triggering of a press stroke and thus to fatal accidents.

In another known embodiment (DE-OS 27 21 270, Fig. 2), the monitoring of the amplifier function takes place in that the output signals of the amplifier of the two control channels is guided to a control level and

be monitored for coincidence. The press safety valves are not included in the monitoring of the amplifiers. Another disadvantage is the different signal level of 1 and 0 signal of the comparator logic and the device-dependent load voltage when the consumer is switched on and off, which can lead to mis-comparisons with single-channel voltage reduction.

In order to monitor the amplifiers in electronic safety circuits (Strang, E .: Monitoring Devices for Fail-Safe Signal Processing; Technical Messages - AEG-Telefunken 58 (1968) 3, pp. 179-181), it is also known that the output signals of the gate driving the amplifier and the Input signals of the consumer to an integrated into the monitoring channel antivalence Kontroi stage and to check for antivalence.

For electronic press safety controls, galvanic isolation between logic and power unit is required for safety reasons. In order to comply with this galvanic isolation in front of and behind the amplifier, special components, for. Relay, optocoupler, required. A way to monitor the function of consumers themselves, such. As the control of the realization of the required switching positions of the press safety valves is not shown here. The disadvantage of the comparisons leading to comparative comparisons of different signal levels of the comparator logic and consumer voltage, which has already been described in DE-OS 27 21 270, Fig. 2, is also effective here.

In another known press safety control according to DE-OS 27 42, the inclusion of the press safety valves is specified in the monitoring. The press safety valves are assigned by the power unit galvanically isolated limit switches, which monitor the proper functioning of the press safety valves and provide appropriate logical monitoring signals to the safety controller. It is customary (for example DE-AS 25 09 235) to combine the monitoring signals of a plurality of points to be monitored by AND and / or NOR links

 This solution is disadvantageous in that amplifier together with

Press safety valves only consistently with additional material effort and not fully monitored, d. h., It can not be ensured that no input signal can be present without an output signal and in case of failure, the machine is stopped.

d) Object of the invention

By applying the invention, an increase in the safety and reliability of the press safety control is to be achieved with little control technology effort.

e) Presentation of the essence of the invention

The invention has for its object to monitor the function of the amplifier and the press safety valves fail-safe, with no additional components for electrical isolation of logic and power unit are required and only the same signal level to be compared.

According to the invention this is achieved in that in each case the input signals of the amplifier of a control channel and the output signals of the combined by AND gate in a known manner position or air pressure signals of the or the press safety valves of the same control channel are performed on a built-in monitoring channel comparative control stage.

In an expedient variant in which the switching of the press safety valves of the two control channels takes place simultaneously, the output signals of the combined by the AND gate position or air pressure signals of the press safety valves both control channels on a common, integrated into the monitoring channel control level and compared.

f) embodiment

The invention will be explained in more detail below using an exemplary embodiment.

The accompanying drawing shows a schematic representation of the arrangement of the control stages at different switching cycles of the press safety valves.

_ 4 -

A circuit arrangement of the type mentioned consists of the two identically constructed control channels 1, 2 and a self-monitoring. fail-safe monitoring channel. The monitoring channel is constructed in a known manner from series-connected control stages 16, which are acted upon by a frequency generator 15 with a pulse-shaped alternating voltage. For identical signals at the outputs of the control channels 1, 2, the monitoring frequency is controlled by the associated control stage 16. Thus, due to unequal operation of encoders and due to tolerances in the timers conditional short-term signal differences in the control channels 1, 2 are not identified as an error, a turn-off delay 17 is turned on in the frequency evaluation. The output signals of the two control channels 1, 2 are each fed to an intermediate logic 3, 4, the output signals of which together with the error-free through all control stages 16 of the monitoring channel controlled monitoring frequency each form the input signals for an amplifier 5, 6. The amplifiers 5, 6 control the press safety valves 7, 8 for the clutch or brake of the press. The valve piston position or the pressure of the compressed air switched by the press safety valves 7, 8 can be detected by signal transmitters 9, 10, 11, 12 in two states and output in a known manner through AND gates 13, 14 for each valve 7, 8. The different for each control channel 1, 2 intermediate logic 3, 4 is constructed in each case two-channel and is monitored in a known manner by control stages 16 fail-safe.

In order to monitor the function of the amplifiers 5, 6 and the press safety valves 7, 8, the input signals of the amplifiers 5, 1b of a control channel 1, 2 with the output signals of the associated AND gate 13, 14 are each fed to a common control stage 16 and compared with each other, d. The function of the booster 5, 6 and the associated press safety valve 7, 8 of each control channel 1, 2 is monitored independently of the other.

By this circuit order, it is of course also readily possible, if necessary, for each control channel 1, 2 several press safety valves 7, 8 are controlled by one amplifier 5, 6, which can all be monitored independently.

A particular advantage of this solution is that in addition to the monitoring of the function of the amplifier at the same time the proper operation of the press safety valves is detected via the monitoring channel.

Another advantage is also to be seen in that basically always two logic signals are compared with each other and therefore additional components for galvanic isolation of logic and power unit are not required.

Claims (2)

Invention claim: A circuit arrangement for monitoring the amplifiers and the press safety valves of a two-channel electronic press safety control comprising two similar independent control channels and a control circuit consisting of series-connected control stages powered by a frequency generator with a pulsed AC voltage and having outputs for monitoring the press safety valves, characterized in that in each case the input signals of the amplifier (5; 6) of a control channel (1; 2) and the output signals of the position or air pressure signals of the or of the press safety valves (7; 8) of the same combined by AND gate (13; Control channels (1; 2) on a built-in monitoring channel comparative control stage (16) are guided. 2. SchaltungsOrdnung for monitoring the amplifier and the press safety valves according to item 1, characterized in that the output signals of the combined by the AND gate (13; 14) position or air pressure signals of the press safety valves (7; 8) of both control channels (1, 2) on a common, integrated into the monitoring channel control stage (16) are guided and compared. Documents considered: DE-OS 2742 039 (F 16 P 3/20)
DE-AS 2509 235 (F 16 P 3/20) For this 1 page drawing