| 摘要 |
A drain valve for installation in a floor has a generally tubular housing having an open upper end and an open lower end and laterally closed side walls therebetween. A bottom plate closing the lower housing end is formed with a throughgoing lower hole and is formed around the lower hole with an upwardly directed lower valve seat. A top plate closing the upper housing end is formed with a throughgoing upper hole and is formed around the respective hole with a downwardly directed upper valve seat. A floatable valve body in the housing between the plates is movable between an upper position fitted in and blocking the upper seat and clear of the lower seat and a lower position fitted in the lower seat and clear of the upper seat. Thus, flow only is possible through the housing in an intermediate position of the ball clear of both of the seats.
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