Device for mixing an air stream and apparatus for heating and/or air-conditioning the cabin of a motor vehicle comprising this device

A mixing device, for distributing in variable proportions a main air stream, particularly a stream of air flowing through an apparatus for heating and/or air-conditioning the cabin of a motor vehicle, between at least one hot air duct and at least one cold air duct, which device comprises at least one panel comprising at least one perforation arranged in the hot air duct and a shut-off plate that can move between an open position in which it does not cover the perforation in the panel and a shut-off position in which it shuts off the panel, at least one shutter for adjusting the passage cross section of the cold air duct that can move between an open position and a shut-off position, a control mechanism for controlling, in synchronism, the movement of the shut-off plate and the movement of the shutter for adjusting the passage cross section of the cold air duct between their open position and their shut-off position.