Abstract
Fire detectors are the most important part of automatic fire alarm systems, and diaphragms are the essential part of the detectors.
Ordinarily they are made of thin phosphor bronze or brass strips. Because the heat treatment is not commonly applied to the strips, after they are punched and corrugated, they show considerable secular change which reduces the reliability of fire detectors.
The authors made diaphragms of extremely thin beryllium copper strips of 0.03mm thickness. And after repeating heat-treatment-tests at various temperatures, the tempering at 300°C for 1～11/2 hour followed by some auxiliary treatments to remove the thermal striction was found most effective for decreasing secular changes of diaphragms. ln the course of these investigations, the authors found also what kind of treatments are most suitable for decreasing the secular changes in the case of phosphor bronze diaphragms.
