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US 4,291,359 AGranted
Safety circuit for a potentially dangerous machine monitored by light
AssigneeErwin Sick GmbH Optik-Elektronik
InventorGerhard Dieterle
Life of this patent
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AssigneeErwin Sick GmbH Optik-Elektronik
InventorGerhard Dieterle
Estimating the term…
A safety circuit for a potentially dangerous machine monitored by light and which works in an operating cycle. A safety circuit is described which utilizes a series of relays each of which is switched from an energized to a de-energized condition once during each working cycle of the machine so that each of the relay contact also opens and closes during the working cycle. In this way each relay contact is tested. The relays are so interconnected that if one contact should stick it will interrupt the sequence and will ensure the potentially dangerous machine e.g. a press is rendered inactive. Circuits are given for both hand fed and automatic machines which are monitored by a light barrier or curtain. For the hand fed machine the cycle is initiated by the operator reaching through the light barrier to insert an object into the machine. For an automatically fed machine the test cycle is initiated by a switch automatically activated once per cycle.
Safety circuit for a potentially dangerous machine monitored by light, especially a machine having a drive circuit and which operates in a cycle between a dangerous position and a non-dangerous position and which is made safe by a light barrier or light curtain against intervention, said safety circuit including a first main relay which is energized when the region being monitored is free and which has a make contact located in the drive circuit of the machine, said safety circuit also comprising:
Safety circuit for a potentially dangerous machine monitored by light, especially a machine having a drive circuit and which operates in a cycle between a dangerous position and a non-dangerous position and which is made safe by a light barrier or light curtain against intervention, said safety circuit including a first main relay which is energized when the region being monitored is free and which has a make contact located in the drive circuit of the machine, said safety circuit comprising a test circuit including a series of further relays, each having a plurality of compulsorily guided contacts at least one of each of which is disposed in the energizing circuit of at least one of the other relays whereby, during one working cycle of the machine, each relay is switched at least once from an energized to a de-energized condition whereby all relay contacts are switched in sequence at least once from an open to a closed position and wherein the interconnection of the relay contacts prevents a further cycle of machine operation if said sequence is interrupted due to one of the following causes:
Dependencies are inferred from the claim text.