Patent ID: 9151403
Filing Date: 2015-10-06
Classification: F15B,F16K

Abstract:
1. A valve actuator comprising: a movable control element moveable in a longitudinal direction; a propulsion device for moving said movable control element, the propulsion device comprising a moveable portion moveable in the longitudinal direction having a stroke extending from a first position to a second position; a resilient element, having a stroke extending in the longitudinal direction from a first relatively unloaded position to a second relatively loaded position; and, a transmission mechanism; the resilient element being loaded in the longitudinal direction under action of the propulsion device via the transmission mechanism and being configured to urge the moveable portion of the propulsion device in the longitudinal direction towards the first position via the transmission mechanism when loaded; wherein the transmission mechanism provides a gearing ratio between the moveable portion of the propulsion device and the resilient element; wherein the transmission mechanism is configured to vary the gearing ratio between the moveable portion of the propulsion device and the resilient element within the stroke of the moveable portion of the propulsion device; wherein the transmission mechanism comprises: a pivotable lever arm having one end pivotally coupled around a pivot point to an outer structure of the valve actuator and another end, and further comprising a surface which engages with the moveable portion; and an arm linkage, which arm linkage is pivotally coupled to the lever arm at a separate point on the lever arm between the said one end and another end where said separate point is spaced apart from the said pivot point; wherein movement of the moveable portion in the longitudinal direction causes the lever arm to pivot around the said pivot point which causes the arm linkage to move in the longitudinal direction and which is translated to smaller longitudinal movement of the resilient element.