Top IPC subclasses
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1
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F03D
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3
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Wind motors
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2
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F03B
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2
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machines or engines for liquids
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3
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E04C
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2
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Structural elements; building materials
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4
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F03G
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2
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spring, weight, inertia, or like motorsmechanical-power-producing devices or mechanisms, not otherwi
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5
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E04B
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1
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General building constructions; walls, e.g. partitions; roofs; floors; ceilings; insulation or other protection of buildings
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