Abstract: A spring-return, pneumatic actuator includes a casing having therein a cylinder chamber, a housing chamber and a spring chamber and equipped therein with a piston reciprocating by air supplied and discharged from an air supply and exhaust vent on a primary side of the pistons. A piston rod is joined to the piston, and a conversion mechanism is provided for converting a reciprocating motion of the piston into a rotary motion. A spring undergoes a snap action due to the reciprocating motion of the piston, and a communication space chamber is formed via a communication part to have a predetermined volume from a secondary side to the spring chamber. The cylinder chamber has the piston and the piston rod built-in, the housing chamber has the conversion mechanism built-in and the spring chamber has the spring built-in.

Abstract: A spring-return, pneumatic actuator includes a casing having therein a cylinder chamber, a housing chamber and a spring chamber and equipped therein with a piston reciprocating by means of air supplied and discharged from an air supply and exhaust vent on a primary side of the piston, a piston rod joined to the piston, a conversion mechanism for converting a reciprocating motion of the piston into a rotary motion, a spring undergoing a snap action by means of the reciprocating motion of the piston and a communication space chamber formed via a communication part to have a predetermined volume from a secondary side to the spring chamber. The cylinder chamber has the piston and the piston rod built-in, the housing chamber has the conversion mechanism built-in and the spring chamber has the spring built-in.

Abstract: A spring-return type actuator for valves including a piston cylinder mechanism, a movement conversion-transmission means disposed in the piston cylinder mechanism for converting reciprocation of a piston into a rotary motion of a valve drive shaft, a spring mechanism disposed in series relative to the piston cylinder mechanism, and a plurality of tie rods each including a male member having one end thereof attached to a flange portion of one side wall of the spring mechanism and having an external thread portion, and a female member having one end thereof screwed into a flange portion of the other side wall of the spring mechanism and having an internal thread portion helically meshed with the external thread portion of the male member and having a winglike member attached to the outer periphery thereof for engaging the female member with the outer periphery of the spring box to prevent the female member from rotating, and each tie rod having a length set larger than the free length of a spring when assumed i

Abstract: A valve driving apparatus comprising a case proper provided in the interior thereof with a movement conversion-transmission mechanism, a cylinder mechanism freely detachably fixed to one end of the case proper and a piston rod supporting mechanism freely detachably fixed to the other end of the case proper so as to be applicable to any kind of valve merely by the replacement of the mechanisms between which the case proper intervenes.