Refillable fluid product dispenser

A refillable fluid dispenser comprising:

• a dispenser head including a fluid pump;
• a reservoir of variable volume;
• and a filling valve that is connected to the reservoir;
• the fluid pump being provided with a dip tube that passes through the reservoir, a slidable member including a movable piston that slides in sealing contact around the dip tube so as to cause the volume of the reservoir to vary, the slidable member being movable between a pushed-in position in which the slidable member is situated in the proximity of the fluid pump, and an extended position in which the slidable member is spaced apart from the fluid pump, the reservoir defining a maximum volume in its pushed-in position, and a minimum volume in its extended position, such that the volume of the reservoir increases when the slidable member is pushed in around the dip tube towards the fluid pump, the dip tube being provided with a stationary piston that slides in sealing contact in a movable cylinder that is formed by the slidable member, the movable piston sliding around the dip tube between the fluid pump and the stationary piston, the reservoir being defined axially between the movable piston and the stationary piston, and radially between the dip tube and the movable cylinder;
• the dispenser further comprises an air pump of variable volume, having a volume that varies inversely with the volume of the reservoir, so as to create resistance to the variation in volume of the reservoir.