| 摘要 |
A piston and cylinder arrangement for opening and closing entrance or exit doors or both in a milking compartment of a fully automated milking system. The piston and cylinder arrangement comprises an elongated cylinder having two pistons connected in tandem to an elongated piston rod. The cylinder is hermetically divided into two cylindrical portions each containing one of the pistons. The piston acts against a liquid in one portion and in the other portion the piston is actuated by pneumatic pressure. The piston rod is extended through the end of the cylinder and is connected to open and close an entrance door. The cylindrical portion containing the liquid has the liquid on both sides of the piston connected by a check-valve and a by-pass valve. To block movement of the pistons, the by-pass valve is retained in a closed position by pneumatic pressure from a supply of pressurized gas for actuating the piston in the pneumatic side of the cylinder. The by-pass valve is a sliding valve urged into an open position by a compression spring when the valve is not closed by pneumatic pressure. Both the by-pass valve and the check valve are disposed external to the cylindrical housing.
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