Product dispenser with deformable bag

Liquid to pasty product dispenser comprising a container inside which is located a bag made from an easily deformable plastic compound, without an air intake, a base carrying a dispensing member being mechanically held with respect to the container, a bottom end of the bag being welded along a band, said bag being formed from a sheath obtained by welding longitudinal edges of a strip along at least one longitudinal band, the peripheral length of the cross section of the sheath being equal to the peripheral length of the base, said longitudinal band of weld intersecting said band of weld at the bottom end at a point which is remote from ends of said band of weld at the bottom end, said longitudinal band of weld welding an inner face of a longitudinal edge of the strip, from which the bag is formed, to the inner face of the other longitudinal edge of the strip located on the same side of the strip as the inner face, said base including a weld surface, and an assembly of the two longitudinal edges of the strip being folded back against an outer surface of the sheath and welded in this position by welding a top end of the bag onto the weld surface of the base, wherein the container (104) is made from a flexible memory material and is associated with a valve (137) located in such a sense that the air present in the container (104) is compressed when an action is exerted on the container for the purpose of dispensing the product contained in the bag (102).