Rotary valve actuator

An actuator for operation of a valve provided with a rotatable valve member, said actuator comprising:

• a tubular housing, defined by a longitudinal axis, by a peripheral cylindrical wall and by two opposite end walls, said housing accommodating therein
• a piston, mounted with possibility for reciprocating linear stroke motion along the longitudinal axis in a forward and a backward direction between one end wall and the opposite end wall, said piston is defined by a periphery body portion, which is concentric with the housing and by a first and by a second end, said piston is actuatable from at least one end thereof,
• an operating rod, which is operatively coupled with the piston and is rotatable about the longitudinal axis upon reciprocating stroke motion of the piston, said operating rod is adapted to output a rotation moment to the valve member,
• a cam follower arrangement for transferring the piston reciprocating linear stroke motion into rotation of the operating rod, said arrangement comprises a cam follower means, which is associated with the operating rod and is displaceable along a helical path provided in the piston,
• at least two fixing rods, which are rigidly secured at one end wall of the cylinder vis-à-vis the first end of the piston, said fixing rods extend parallel to the longitudinal axis and enter into respective blind passages provided at the first piston end to allow the linear stroke motion,
• wherein said actuator is provided with at least two additional fixing rods, which are rigidly secured at an opposite end wall of the cylinder vis-á-vis a second piston end, said additional fixing rods extend parallel to the longitudinal axis and enter into respective blind passages provided at the said second piston end to enable the linear stroke motion.