| 摘要 |
Apparatus for raising and lowering the net of a tennis court which is incorporated in the post supporting the net. The apparatus includes a hydraulically operable ram and cylinder device, the ram of which is connected to the cord of the net so that the net is raised when the ram is extended. The ram is extended by a manually operable pump. A valve biassed to the open position is located so that fluid pumped from a reservoir into the cylinder is returned to the reservoir through the valve. The valve is closed to trap fluid in the cylinder to enable the ram to be extended by insertion of appropriate coin in a coin-operable mechanism. Operation of the coin-operable mechanism starts a timing device which is operative to open the valve at a predetermined time, usually one hour, after the valve has been closed. When the valve is opened the ram retracts under the weight of the net and/or the effect of a spring to cause the net to be lowered.
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