Patent ID: 8398051

Claim:
A gate valve actuator, comprising: a stem which is movable linearly in an actuator housing connectable to the gate valve, the stem acting on the gate valve to shift the gate valve between open and closed positions, respectively, wherein the stem is driven by a motor in a first direction into a steady state operation position, and in said position the stem is biased in a second opposite direction towards a shutdown position by a spring member acting on the stem, and a trigger mechanism arranged for holding the spring member in a compressed state in a holding position, the trigger mechanism comprising an electrically controllable trigger which is arranged for release of the spring member in result of de-energizing the electrically controlled trigger, wherein the trigger mechanism comprises at least one latch which is pivotally supported in the actuator housing about a pivot, a first end of the latch being in operative engagement with the stem while the opposite second end of the latch is in operative engagement with the trigger, in the compressed state of the spring member, wherein the trigger mechanism comprises a rod which is movable linearly in the actuator housing, an electrically driven trigger actuator driving the rod into the holding position wherein the rod engages the latch, and a trigger spring by which the rod is withdrawn from the holding position to a withdrawn position upon de-energizing the trigger actuator, and wherein the latch engages the rod indirectly via a locking pin which in the holding position is arrested by the rod to engage a seat formed in the second end of the latch, and which upon withdrawal of the rod is pushed by the latch out from the seat, thereby permitting the latch to pivot out of engagement with the stem.