Non return valve and a proceeding to form a non return valve system to be fasten together inside a receptacle intended to contain air or liquid

A method of forming a non-return valve having a holding device for a discharge pipe, when the discharge pipe is in the holding device, a material of the non-return valve being extended and flattened and having seals at an opening channel so that trash cannot come into the opening, comprising:

• joining two portions of the material, which comprises a plastic or a rubber and which lie planarly against each other, by two weld lines that form the opening channel between themselves;
• applying a weld line on each side of the opening channel for joining a third portion of the material to form a holder on one side of the opening channel for applying a device in a form of a thin resilient sheet material in said holder;
• folding a portion of the material and applying a weld line transversely over the non-return valve comprising an insert in a shape of a polytetrafluoroethylene film tape in the opening channel, so that the folded portion forms the holding device for the discharge pipe, a second portion of the material forming part of the non-return valve, also constituting a gripping device for use upon filling and emptying of a container;
• forming the non-return valve and a container by mutually joining the non-return valve to a the container by a sealing weld and to a polytetrafluoroethylene film tape insert in the opening channel;
• and
• removing the polytetrafluoroethylene film tape after which emptying and filling of the container can be effected.