Abstract: A liquified gas dry-cleaning machine having a cleaning vessel with a chamber for containing a wash bath and items to be cleaned, a removable door for sealing the cleaning chamber during a dry-cleaning operation, and a locking ring for retaining the door in closed position. A door opening and closing apparatus is provided which includes a pivot frame for moving the door in an arced path of movement into and out of closed position with the cleaning vessel. The door and locking ring have respective locking lugs with a specifically designed geometry for enabling arced movement of the door into and out of the closed position and for centering the door in aligned relation to the cleaning chamber as an incident to such movement. The locking lugs further have mating locking surfaces designed for point contact in a manner that minimizes stress concentrations at n the roots of the locking ring lugs.