Door latching assembly for holding a fluid pressure actuated cassette during use

A fluid processing assembly comprising

• a fluid pressure actuated cassette to pass fluid,
• a holder to hold the cassette in association with a fluid pressure actuator to control passage of fluid through the cassette,
• a door carried by the holder for movement between an opened position to expose the holder and a closed position enclosing the cassette held in the holder,
• an expandable gasket on the door facing the held cassette when the door is in the closed position, the expandable gasket normally resting, when the door is in the closed position, in a relaxed state out of sealing contact with the held cassette,
• an actuator to apply pressure to the expandable gasket to achieve, when the door is in the closed position, an expanded state in sealing contact against the held cassette,
• a latch pin on one of the holder and door, and
• a latch assembly on the other one of the door and holder that makes swinging engagement with the latch pin when the door is in the closed position, the swinging engagement between the latch assembly and latch pin being releasable by application of manual force when the gasket rests in the relaxed state, the swinging engagement between the latch assembly and latch pin being locked against release by application of manual force in response to pressure applied by the gasket when the gasket achieves the expanded state.