Patent ID: 7677528

Claim:
A controller comprising: a casing fixed to an upper part of a main body; a valve rod arranged projecting downward from the casing and moving up and down in a reciprocating manner; an operating shaft arranged in the casing in a freely up and down moving manner; a power transmitting means for amplifying a force applied on the operating shaft and transmitting to the valve rod; a biasing means for biasing the operating shaft downward; and a pressure chamber, formed between a piston arranged on the operating shaft and a partition plate arranged below the piston and fixed to the casing, for moving the operating shaft upward when an operation gas is introduced, wherein the controller further comprises a slow start means for slowly moving the valve rod upward, the slow start means including: the piston having an outer diameter smaller than an inner diameter of the casing and movable in up and down direction with respect to the operating shaft; a pressure spring, arranged between a spring receiver arranged at an upper part of the operating shaft and the piston, for applying an elastic force corresponding to an amount of up and down movement of the piston on the spring receiver and the piston; a diaphragm arranged between an outer peripheral edge of the piston and the upper casing, for partitioning the pressure chamber and a space on an upper side of the piston; an operation gas introducing chamber arranged below the partition plate; a constantly opened communication passage, formed in the partition plate, for communicating the pressure chamber and the operation gas introducing chamber; a flow adjusting valve for adjusting a flow of the operation gas introduced into the constantly opened communication passage; an auxiliary communication passage, formed in the partition plate, for communicating the pressure chamber and the operation gas introducing chamber; and an open-close valve, arranged in the auxiliary communication passage, for opening the auxiliary communication passage when the piston is at the lower most posit on and for closing the auxiliary communication passage when the piston is raised from the lower most position by a predetermined distance and has reached an auxiliary communication shut off position, wherein a male threaded portion is formed on the operating shaft at an upper end of the operating shaft, a female threaded portion for direct threaded engagement to the male threaded portion is formed at an inner periphery of the spring receiver, the spring receiver being screw fit to the operating shaft, supported to the casing in a non-rotatable and up and down movable manner, and the elastic force of the pressure spring being adjustable by the spring receiver moving up and down when the operating shaft is rotated.