An assembly including a first enclosed volume and a sealed connection device between the first enclosed volume and a second enclosed volume, the first enclosed volume including a first flange and a first door sealingly closing an opening delimited by the first flange, and the second enclosed volume including a second flange and a second door sealingly closing a second opening delimited by the second flange, the second door being secured to the second flange by a bayonet connection, said connection device being mounted on a wall of the first enclosed volume and comprising: - first means for securing the first and second flanges to each other, - second securing and disengaging means intended to sealingly secure the second door and the first door and to disengage the second door from the second flange, the second means including a securing plate mounted movable in rotation on an outer face of the first door about a longitudinal axis and capable of being secured to an outer face of the second door by a bayonet connection, said securing plate being such that a first part of the rotational displacement of the securing plate is intended to secure the first door and the second door and a second part of the rotational displacement of the securing plate is intended to unlock the second door relative to the second flange, - third means for releasing the first door relative to the first flange, - fourth means for opening a passage between the first and the second enclosed volume, - a control ring capable of being rotated about the longitudinal axis, the rotation of said control ring actuating at least the second, third and fourth means, the assembly also including means for immobilising the securing plate relative to the first door in a first position in the absence of the second door and in a second position in the presence of the second door in a state wherein the first door and the second door are secured and the second door is unlocked relative to the second flange, - a first device for actuating said control ring and - a second device for actuating the first securing means. - first means for securing the first and second flanges to each other, - second securing and disengaging means intended to sealingly secure the second door and the first door and to disengage the second door from the second flange, the second means including a securing plate mounted movable in rotation on an outer face of the first door about a longitudinal axis and capable of being secured to an outer face of the second door by a bayonet connection, said securing plate being such that a first part of the rotational displacement of the securing plate is intended to secure the first door and the second door and a second part of the rotational displacement of the securing plate is intended to unlock the second door relative to the second flange, - third means for releasing the first door relative to the first flange, - fourth means for opening a passage between the first and the second enclosed volume, - a control ring capable of being rotated about the longitudinal axis, the rotation of said control ring actuating at least the second, third and fourth means, the assembly also including means for immobilising the securing plate relative to the first door in a first position in the absence of the second door and in a second position in the presence of the second door in a state wherein the first door and the second door are secured and the second door is unlocked relative to the second flange, - a first device for actuating said control ring and - a second device for actuating the first securing means.