Device for dispensing a fluid product comprising a metering valve

A device for dispensing a fluid product, comprising a reservoir containing the fluid product and a metering valve comprising a valve body containing a metering chamber, a valve shut-off element sliding axially in said valve body between an rest position and a dispensing position, in order to dispense the contents of said metering chamber, said valve shut-off element being urged towards its rest position by a valve spring, said fluid product comprising a liquid formulation made up of one or more active principle in suspension and/or in solution in a liquefied propellant, said reservoir containing a follower-piston which separates said reservoir between an upper reservoir part connected to said metering valve and a lower reservoir part isolated from said metering valve by said follower-piston, characterized in that said reservoir contains a piston spring which axially urges said follower-piston towards said metering valve, said follower-piston being adapted for axially sliding in said reservoir in a sealed manner after each actuation, in order to compensate for the volume of each dose dispensed, said follower piston being pushed axially downwards by said fluid product when it is filled in said reservoir, such that said follower-piston compresses said piston spring and the air arranged in said reservoir lower part until the pressures are balanced between said upper part of the reservoir containing said fluid product in liquid form and said lower part of the reservoir containing the air and said compressed piston spring.