Light barrier for preventing machine accidents including fail safe device

• US 3,360,654 A
• Filed: 04/09/1965
• Issued: 12/26/1967
• Est. Priority Date: 05/06/1964
• Status: Expired due to Term

• Current Assignee: Harro Muller
• Original Assignee: Harro Muller
• Inventors: HARRO MULLER
• Application Number:
  US04/446,987
• Time in Patent Office: 991 Days
• US Class Current: 250/221
• CPC Class Codes: F16P 3/144 using light grids
• CPC Class Codes: G01V 8/26 using mechanical scanning systems
• CPC Class Codes: G08B 13/184 using radiation reflectors

Claims

1. IN AN APPARATUS FOR USE AS A LIGHT BARRIER TO PROVIDE A WARNING INDICATION IN THE EVENT THAT AN OBJECT INTRUDES INTO A GIVEN AREA, SAID APPARATUS HAVING A LIGHT SOURCE, THE IMPROVEMENT COMPRISING:

AREA MONITORING MEANS TO DIRECT A LIGHT BEAM ACROSS SAID AREA AND TO SWEEP SAID AREA REPEATEDLY AT HIGH FREQUENCY WITH THE LIGHT TRAVERSING SAID AREA BEING DIRECTED TO A PHOTOELECTRIC DEVICE WHICH PRODUCES AN ELECTRIC SIGNAL WHICH IS A FUNCTION OF THE LIGHT RECEIVED THEREBY, WITH EACH SWEEP CONSTITUTING A PROTECTIVE CYCLE, SAID MEANS SHUTTING OFF THE LIGHT TO SAID DEVICE FOR A GIVEN PERIOD BETWEEN EACH PROTECTIVE CYCLE TO PRODUCE A MONITORING CYCLE DURING WHICH A DARK PULSE OCCURS;

AND ELECTRICAL MEANS CONNECTED TO SAID DEVICE TO PROVIDE A WARNING INDICATION IN THE EVENT THAT THE LIGHT TO SAID DEVICE IS SHUT OFF DURING A PROTECTIVE CYCLE AND IN THE EVENT THAT A DARK PULSE IS NOT PRODUCED DURING A MONITORING CYCLE.