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The Puretic power block is a special kind of mechanised winch used to haul nets on fishing vessels. The power block is a large powered aluminium pulley with a hard rubber-coated sheave. While many men were needed for the back-breaking work of hauling a purse seine manually, the same work could be done by fewer men with a power block.〔Schmidt PG (1959) "The Puretic power block and its effect on modern purse seining". In (''Modern Fishing Gear Of The World 1'' ), pp. 400–414. Editor Hilmar Kristjohsson, FAO, Rome.〕 The Puretic power block revolutionized the technology of hauling fishing nets, particularly purse seine nets. According to the Food and Agriculture Organization of the United Nations (FAO), "no single invention has contributed more to the success of purse seine net hauling" than the power bloc, which was "the linch-pin in the mechanization of purse seining".〔FAO: Fishing Equipment: (Power block ) Rome. Retrieved 28 May 2009.〕〔(The Power Block ) ''FishByes'', December 1995.〕 ==History== The power block was invented by a Croatian fisherman, Mario Puratić, and patented in 1953. In English, Puratić is usually spelt Puretic, sometimes Puretich. While he was working as a tuna and sardine fisherman from San Pedro, California, Puratić started thinking about the difficulty of hauling seine nets. The original power block he designed was essentially a simple winch which used a V-shaped roller coated with hard rubber. It was suspended from a davit, and powered from the warp end of the winch by a looping rope. In 1954, the power block was trialled by American purse seiners in the Pacific. They have evolved since then, and nowadays power blocks are powered by hydraulic pumps. Their speed, torque and direction can be remotely controlled from the bridge during operations. As a result, retrieving the net is safer and requires less manual work.〔〔Bardarson, HR (1971) "Deck Equipment for Purse Seining". In ''Modern Fishing Gear Of The World 3'', pp. 283–287, Editor Hilmar Kristjohsson, FAO, Rome. (Download PDF (56MB) )〕 Other important innovations of the same period were the development of synthetic fishing nets and sonar detection devices. The combination of the automated power block hauling synthetic nets with sonar sensing revolutionised the industry.〔 The use of power blocks was found to have further advantages. It is possible to fish in rougher weather with the power block, because the steady force exerted by the net stabilizes the vessel. When deployments are made which miss the schooling fish, the net can be rapidly retrieved and redeployed on the same school. The power block also makes it easy to get nets aboard in emergencies, such as a sudden shift in tides or winds, or shark attacks on the catch and net.〔 On the other hand, the increase in the effectiveness of purse seine fishing led to herring schools choosing to school deeper in the water. Nets that could operate in deeper water needed to be bigger and heavier. That in turn meant bigger vessels, which pushed the smaller herring vessels out of business.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Puretic power block」の詳細全文を読む スポンサード リンク
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