US 3,944,818 AGranted

Photoelectric guard

AssigneeVisomat-Gerate GmbH

InventorKlaus Bechtel

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Abstract

This invention relates to a protective guard for surrounding hazardous parts of a machine. The guard comprises a photoelectric barrier, connected to a circuit which will shut down the machine both when the photoelectric beam is broken, and also when a part of the photoelectric system fails to operate correctly.

Claims5

Dependent claims

A photoelectric guard barrier comprising:

a pulse generator for providing a train of binary pulses;
a plurality of luminescence diodes connected to said pulse generator so as to emit, respectively, light output pulses in response to the output pulses of said generator;
a plurality of photo-receivers the number of which is equal to the number of said luminescence diodes, each of said photo-receivers being operatively arranged to receive said light output pulses from respective ones of said luminescence diodes and providing output signals representative thereof;
a trigger circuit for each photo-receiver providing a one output when each said photo-receiver senses light and providing a signal above a preselected threshold;
a NAND-gate having one input coupled to the pulse generator and remaining inputs coupled respectively to each said trigger circuit, said NAND-gate providing a O output when said trigger circuits and said pulse generator simultaneously provide a one output;
an OR-gate having one input connected to said pulse generator and remaining inputs connected respectively to each said trigger circuit, said OR-gate providing a one output when either said pulse generator provides a one output or any of said trigger circuits provides a one output;
a master slave flip-flop coupled to said NAND and said OR-gate, a O output from said NAND-gate setting the normal output of said flip-flop into a one state and a one output from said OR-gate resetting the normal output of said flip-flop into the O stage;
said master slave flip-flop providing a one output when all said photo-receivers sense bright from said light output pulses and a O output when all said photo-receivers sense dark during the intervals between said light output pulses;
said flip-flop being neither set nor re-set when light does not reach at least one of said photo-receivers and said generator pulse is present or when at least one photo-receiver senses light and said generator pulse is absent, thereby providing a constant output.

6 more elements

Dependencies are inferred from the claim text.

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Abstract

A photoelectric guard barrier comprising:

a pulse generator for providing a train of binary pulses;
a plurality of luminescence diodes connected to said pulse generator so as to emit, respectively, light output pulses in response to the output pulses of said generator;
a plurality of photo-receivers the number of which is equal to the number of said luminescence diodes, each of said photo-receivers being operatively arranged to receive said light output pulses from respective ones of said luminescence diodes and providing output signals representative thereof;
a trigger circuit for each photo-receiver providing a one output when each said photo-receiver senses light and providing a signal above a preselected threshold;
a NAND-gate having one input coupled to the pulse generator and remaining inputs coupled respectively to each said trigger circuit, said NAND-gate providing a O output when said trigger circuits and said pulse generator simultaneously provide a one output;
an OR-gate having one input connected to said pulse generator and remaining inputs connected respectively to each said trigger circuit, said OR-gate providing a one output when either said pulse generator provides a one output or any of said trigger circuits provides a one output;
a master slave flip-flop coupled to said NAND and said OR-gate, a O output from said NAND-gate setting the normal output of said flip-flop into a one state and a one output from said OR-gate resetting the normal output of said flip-flop into the O stage;
said master slave flip-flop providing a one output when all said photo-receivers sense bright from said light output pulses and a O output when all said photo-receivers sense dark during the intervals between said light output pulses;
said flip-flop being neither set nor re-set when light does not reach at least one of said photo-receivers and said generator pulse is present or when at least one photo-receiver senses light and said generator pulse is absent, thereby providing a constant output.

6 more elements