| 摘要 |
A failsafe limit switch with automatic reset for a rolling fire door is usable together with a rolling door with a brake. There is a movable plunger between a secured position and a triggered position which compresses a spring as it moves from its triggered position to its secured position. A movable catch between the engaged position and the released position holds the plunger in the secured position when the catch is in the engaged position under the impetus of the spring when the catch is in the released position. When the catch is in the released position, it also closes the contacts of a normally open switch; and if the catch is in the engaged position, it allows the contacts of the switch to open. The switch is wired in series with a solenoid; the movable arm of the solenoid acts to move the plunger from the triggered position to the secured position when the solenoid is energized. A collar constrained against rotation is threadably mounted on a shaft, the linear position of the collar with respect to the catch is a function of the angular position of the shaft. For a specific angular rotation of the shaft, the collar contacts and releases the catch. |
