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SELECT DISTINCT patent.*, YEAR(date) as year FROM patent LEFT JOIN category ON category.patent = patent.patent AND category.type = patent.type WHERE (category.class = '81') AND (category.subclass = '57.4') ORDER BY date ASC, patent, type

Total of 1 patents found where: Class is '81'; Subclass is '57.4';

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T / S Patent Date Description Patentee Category Assigned To
 1952
U 2,582,442 January 15, 1952 Power Wrench Mechanism for Ceramic Filter Presses
A motorized wrench to tighten the screw on the leaves of a clay filter press that can be moved from one press to the other.		 LAPP, Grover W.
 Filter Press Lapp Insulator Co., Inc.

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