designed to give the piston some rotary movement about its axis

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Pistons; Trunk pistons; Plungers (bellows pistons F16J3/06; piston-rings or seats therefor F16J9/00; ; rotary pistons, e.g. for "Wankel" type engines F01C; specific for combustion engines, i.e. constructed to withstand high temperature or modified for guiding, igniting, vaporising or otherwise treating the charge F02F; ; pumps F04B; floats F16K33/00) > Connection to driving members > designed to give the piston some rotary movement about its axis