US 5,665,961 A · Photoelectric switch for use with a machine control circuit

Abstract

A photoelectric switch having a rectifier for converting a received AC voltage to a DC voltage, a transparent cover having a user friendly finger rest surface, means for generating a pulsed infrared beam across the finger rest surface, means responsive to the breaking of the pulsed infrared beam by an operator placing at least one finger on the finger rest surface to actuate a relay to generate an output signal, and means for disabling the actuation of the relay in response to the operator removing his finger from the finger rest surface restoring the continuity of the pulsed infrared beam. The photoelectric switch includes fault protection circuits which disable the relay when the AC voltage is below a predetermined voltage, when the ambient infrared background illumination exceeds a predetermined value, or when the means for generating a pulsed infrared beam fails to generate the beam. The photoelectric switch also includes circuits for lighting a fault light when the AC voltage is less than the predetermined voltage, the ambient infrared background illumination exceeds the predetermined limits, and when a contact in the relay welds or becomes stuck in the activated position.

Claims23

Dependent claims

A photoelectric switch for use in conjunction with a machine for performing a machining operation and a control circuit responsive to a pair of said photoelectric switches generating an input signal to activate said machine, said control circuit preventing said machine from performing said machining operation unless said control circuit receives an input signal from both of said photoelectric switches within a predetermined period of time, said machine being actuated by an AC electrical power source providing an AC voltage within a predetermined AC voltage range, each photoelectric switch of said pair of photoelectric switches comprising:

a cover having a contoured finger rest surface;
means for generating a light beam above said finger rest surface, said light beam being occluded by an operator placing at least one finger on said finger rest surface;
a relay having an activated state in which it generates said input signal;
means for activating said relay to said activated state in response to said beam being occluded by said at least one finger being placed on said finger rest surface;
means for deactivating said relay in response to the termination of said occlusion of said light beam;
and
light beam failure means, responsive to said means for generating a light beam when said means for generating a light beam fails, to output a signal to said relay inhibiting the activation of said relay;
wherein said light beam failure means comprises a light emitting failure circuit electrically connected to said means for generating a light beam and to said relay.

5 more elements

A photoelectric switch comprising:

a cover having a contoured finger rest surface;
means for generating a pulsating infrared light beam parallel to said finger rest surface external to said cover, said pulsating infrared light beam being broken by an operator placing at least one finger on said finger rest surface;
a relay having at least one contact for generating an output signal;
means for activating said relay to generate said output signal in response to said infrared light beam being broken by the operator placing at least one finger on said finger rest surface;
means for deactivating said relay to terminate said output signal in response to the termination of said infrared light beam being broken;
high ambient infrared light protection means for inhibiting the activation of said relay in response to the ambient infrared light level exceeding a predetermined value;
and
light beam failure means, responsive to said means for generating a light beam when said means for generating a light beam fails, to output a signal to said relay inhibiting the activation of said relay.

5 more elements

Dependencies are inferred from the claim text.

Photoelectric switch for use with a machine control circuit

Life of this patent

Photoelectric switch for use with a machine control circuit

Life of this patent

Abstract

Claims23