Photoelectric light curtain using retroreflector

A relatively low-cost photoelectric machine access safety device comprising:

• (a) an integral rectangular support structure with each of three sides having an inside surface enclosing a guarded area through which an associated machine is accessed;
• (b) retrodirective reflective means mounted in a substantially continuous path on each of the three inside surfaces and facing the guarded area;
• (c) integral photoelectric light transmission and receiving means mounted on the inside surface of the fourth side for generating a control signal when transmitted light is not received;
• (d) movable reflector means positioned adjacent the fourth side and adapted to reflect a light beam transmitted by said photoelectric means directly to said retrodirective reflective means at a varying incidence angle and back along the same path directly to said photoelectric means;
• (e) moving means mounted on the fourth side for moving said movable reflector means so that the reflected light beam scans all of the guarded area whereby any body within the guarded area will interrupt the scanning light beam causing said photoelectric means to generate a control signal;
• and
• (f) control means mounted on said support structure and coupled to said photoelectric means and responsive to a control signal for stopping the associated machine accessed through the guard area.

A relatively low-cost photoelectric machine access safety device comprising:

• (a) an integral support structure having an inside surface enclosing a guarded area through which an associated machine is accessed;
• (b) continuous retrodirective reflective means mounted in a path on the inside surface and facing the guarded area;
• (c) photoelectric light transmission and receiving means mounted on said support structure for generating a control signal when transmitted light is not received;
• (d) movable reflector means positioned adjacent said support structure and adapted to reflect a light beam transmitted by said photoelectric means directly to said retrodirective reflective means along an incidence angle and back along the same light path directly to said photoelectric means;
• (e) moving means mounted on said support structure for moving said movable reflector means so that the reflected light beam scans all of the guarded area whereby any body within the guarded area will interrupt the scanning light beam causing said photoelectric means to generate a control signal;
• and
• (f) control means coupled to said photoelectric means and responsive to a control signal for stopping the associated machine accessed through any part of the guard area.