| 摘要 |
<p>A pneumatic retard, of the type used to achieve time-delayed actuation of water-flow alarms or other devices, has a pneumatic chamber from which air is slowly discharged under the pressure applied by a spring-driven plunger. The chamber has an air discharge valve, which also serves as an inlet valve. When the actuating plunger has been released and has traveled to a position at which much of the air has been exhausted, the discharge valve is opened, releasing the remaining air pressure. This releases the plunger to travel from that point onward with a rapid actuating stroke.</p> |
