| 摘要 |
<p>A time delay valve of flexible material to be supported in an opening in a wall and having a body member provided with a recess permitting the use of a tool to position the valve in the opening in the wall from one side of the wall with the recess also accommodating displaced material during the time that the valve is being installed. The valve has an enlarged head which closes the opening and flexes away from the wall to open and permit relatively free fluid flow. A metering groove extends radially of an annular sealing surface formed on the perimeter of the head to restrict and delay fluid flow when the valve is in a closed position relative to the wall.</p> |
