Valve Actuator with Degressive Characteristic Spring

摘要

An actuator for a gate valve having a gate has a stem coupled to a gate. A spring is coupled to the stem and has an extended length position while the gate is in a closed position and a contracted length position while the gate is in an open position. The spring has a degressive characteristic such that a graph of a force required to move the gate from the closed position to the open position versus a deflection of the spring is a nonlinear curve with a positive slope that decreases when moving from the closed to the open position. The spring may be an array of wavy springs arranged in nested and in valley-to-crest combinations.