PROBLEM TO BE SOLVED: To provide a spring return type pneumatic actuator capable of obtaining stable output even when mounted on a large-sized rotary valve while preventing complication of overall structure and increase of the number of parts, and smoothly converting straight reciprocating motion of a piston rod into rotary motion by suppressing a lateral load when the piston rod is operated by the elastic force of a spring.;SOLUTION: The spring return type pneumatic actuator includes: a housing section 1 incorporating a conversion mechanism 6; a cylinder section 2 incorporating a piston 26; and a cartridge section 3 incorporating the spring 18. In this actuator, the outer end surface of the spring 18 is held by a substantially disk-like spring retainer 38, which is fixed to the end of the piston rod 7. At least two pieces of center bars 43 are arranged in parallel to the piston rod 7 in the cartridge section 3 and the lateral load of the piston rod 7 is held by supporting the spring retainer 38 by the center bars 43.;COPYRIGHT: (C)2012,JPO&INPIT
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