Spear valve for emptying and filling a pressurised beverage keg

Valve device for the filling and the emptying of a double-walled container totally made of a plastic material such as PET or similar, wherein said container comprises a first container made of a substantially rigid plastic material, and a second container inserted inside said first container and made of a yieldable plastic material, thereby defining a gaseous inner volume between said first container and said second container, and a communicating port for communicating said inner volume with the outside, said port being formed at a neck part of a neck and at a mutual connection region of said first and second container, and an opening for the filling/emptying said container is provided at said neck part of the neck, said valve device being mounted onto said neck part of said neck of said container, and a locking member for the locking of said valve device onto said opening,

• characterized in that said valve device comprises a valve body which includes a first tubular member connected to a second tubular member, the latter connected in a blocked manner onto said opening of the container through said locking member, a third tubular member mounted in an axially movable manner inside said valve body against the thrust of a spring, said third tubular member being able to slide through a pneumatic sealing member arranged at one end part of said first tubular member, said third tubular member having a free end, the arrangement being such that said free end abuts against the thrust of said spring on a port at the central part of said second tubular member.