Preparation of a plastic for its extrusion particularly in the form of a gaged bead intended to be used as a seal and interlayer in multiple glazings

An installation for preparing a plastic material of the type having a butyl rubber base, comprising:

• a tank having an open top and containing raw plastic material;
• a cover inserted in said open top, said cover having an outlet orifice, a face of said cover oriented towards said plastic material having a shape such that a sectional area of a volume of the plastic material enclosed by said cover is smaller the closer said plastic material is to said outlet orifice;
• means for heating said cover;
• means for pressing said cover for movement into said tank, whereby the plastic material in said tank is heated and forced through said outlet;
• and
• a plurality of heating appendages formed on said face of said cover and extending toward said plastic material,
• wherein said appendages extend parallel to a direction of movement of said cover, and wherein the length of said appendages increases in inverse correspondence with the distance of said appendages from said outlet, whereby said heating appendages closest to said outlet provide increased heat transfer surface area to the plastic material as compared to ones of said heating appendages further from said outlet.