Patent ID: 8590560
Filing Date: 2013-11-26
Classification: E03F,Y10T

Abstract:
1. An opening/closing device comprising: a gate that receives a flow of a fluid, and can fall toward a downstream side of the flow; a fall prevention unit that prevents the gate from falling by supporting the gate; a support release unit that releases a support for the gate by the fall prevention unit; a first float that is arranged on the upstream side of the gate, and is constructed to have a lesser value of specific gravity than the fluid; a surfacing-prevention unit that prevents the first float from surfacing; a second float that is arranged on the upstream side of the gate, is arranged above the first float, and is constructed to have a lesser value of specific gravity than the fluid; and a surfacing-prevention release unit that releases, resulting from surfacing of the second float, the prevention of the surfacing of the first float by the surfacing prevention unit, wherein the support release unit is activated resulting from surfacing of the first float.