Raised state holding mechanism of flap gate for breakwater

A raised state holding mechanism of a flap gate for a breakwater, comprising:

• a door body which has a buoyancy chamber, and a front end side which is supported to freely rise and lower with a rotating shaft on a base end side of the door body as a supporting point;
• a two-folding support rod for immobilizing and supporting the door body when it is raised, the two-folding support rod having one end part connected to the front end part side of the door body to rotate freely, while the other end part thereof is supported so as to rotate freely in a position at a specified distance from a rotating shaft on a side where the door body lowers, the one end part and the other end part having a connecting member between them, wherein a base end side connecting rod on the other end side and a front end side connecting rod on the one end side fold by means of the connecting member;
• a stay which supports the support rod when the door body is in a raised state, one end part of the stay being connected to rotate freely in the middle of the base end side connecting rod of the support rod, and a guider roller being attached to the other end part of the stay to rotate freely,
• a guide rail for guiding the guide roller which moves between the raised position and the lowered position of the door body, together with changes which occur between the two-folded state and the elongated state of the support rod;
• and
• a raising limit stopper which restricts the movement of the guide roller in a raising direction,
• wherein the raised state holding mechanism of a flap gate for a breakwater raises or lowers the door body in an inclined state by supplying air to the buoyancy chamber or by discharging air from the buoyancy chamber, and comprises:
• movable pulleys attached to the ends of both rods of a two-rod double-acting cylinder device, with the other ends of the ropes wound around these two movable pulleys, with one rope in the direction in which the door body rises, while the other rope is in the direction in which the door body lowers, each being attached to its respective guide roller, so that a piston of the double-acting cylinder device moves according to the raising and lowering of the door body, and a stroke sensor which detects the position of the piston is provided to the double-acting cylinder device;
• and
• a hydraulic pathway between an oil tank and the double-acting cylinder device having a raising side oil supply pathway which supplies oil to a raising side oil chamber on the side of one rod where one rope is wound, and a raising side oil discharge pathway which similarly discharges oil from the raising side oil chamber on the side of the one rod, and a lowering side oil supply pathway for supplying and discharging oil in a lowering side oil chamber on the side of the other rod where the other rope is wound, and a shut-off valve being provided in the raising side oil discharge pathway to prevent the discharge of oil from the raising side oil chamber, and a check valve being provided in the raising side oil supply pathway to prevent the discharge of oil from the raising side oil chamber, if a force in a lowering direction acts on the door body during the operation of raising the door body and when raising of the door body is completed, and to prevent lowering of the door body during the operation of raising the door body and when raising of the door body has been completed.