Elastic and sliding valvular joint, suitable to work in pre-filled syringes

A pre-filled syringe having a cylindrical wall connected to a base and a moveable plunger which together with the cylindrical wall and the base define an internal chamber for a liquid product to be dispensed, the base being provided with an outlet communicating with a passage for feeding product from the internal chamber between the plunger and base to define a first product chamber between the base and the elastic-sliding valve and a second product chamber between the elastic-sliding valve and the plunger, through the passage to a needle upon movement of the plunger toward the base, the improvement which comprises an elastic-sliding valve positioned within the internal chamber, said elastic-sliding valve comprising a discoidal elastic valve member and a cooperative element wherein one of said discoidal elastic valve member and cooperative element is moveable relative to the other for opening the elastic-sliding valve for communicating product from the internal chamber through the passage upon movement of the plunger toward the base wherein movement of the plunger away from the base results in opening of the elastic-sliding valve member so as to mix the product in the first chamber with the product in the second chamber prior to feeding product through the passage into the needle upon movement of the plunger toward the base.