Locking ring actuator for a pressure retaining closure

A closure assembly comprising:

• a door hingedly mounted to a pipe, vessel, or hub extending therefrom, said pipe, vessel, or hub having a round opening with a circumferential groove therein;
• an arcuate locking ring movably retained proximate an outer perimeter of an outer surface of said door being suitable to contract to a radius less than a radius of said round opening exterior of said groove and being suitable to expand wherein an outer portion of said locking ring extends into said groove;
• and
• a locking ring actuator having cylinder with a piston slidably positioned therein, said piston having a piston rod extending axially upward therefrom with a portion extending beyond said cylinder when said piston is proximate a lower portion of said cylinder, an upper cylinder bracket mounted to said portion of said piston rod extending beyond said cylinder, a lower cylinder bracket mounted proximate the bottom of said cylinder, a slider rod having a first end portion mounted to said lower bracket and a second end portion slidingly engaging said upper bracket, a ring actuating arm pivotally connected to said upper bracket and secured proximate an end of said arcuate locking ring, and a ring actuating arm pivotally connected to said lower bracket and secured proximate the other end of said arcuate locking ring wherein said locking ring expands and contracts radially upon actuation of said locking ring actuator and wherein said locking ring actuator moves with said locking ring expansion and contraction.