Fail-safe photoelectric detector
US5121975A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 8, 1991 |
| Grant date | Jun 16, 1992 |
| Priority date | — |
| Expiry date | May 8, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/2619
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A control circuit for continually testing a photoelectric detector. The detector includes a light source, and a photoelectric receiver having a predetermined drop-out time, attached to a movable storage carriage, spaced apart and substantially sightaligned. The carriage has a reversible electric motor which is controlled by the control circuit, including at least two relays, the contacts of which are connected in series so that the contacts of both must be closed in order for the motor to be energized. The relay drop-out time is substantially longer than the receiver drop-out time. In the circuit, an inverter is connected between the second coil and the light source. This inverter inverts signals received from the second coil and passes them to the light source so that receipt of a signal at the receiver causes the light source to turn off, in turn causing a loss of signal at the receiver, resulting in the light source turning on. An oscillation is thus established which passses through each component of the monitoring circuit and the detector. The drop-out time of the relays is long enough that the relays stay closed unless the oscillation is stopped, either by a failure of the mo…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.