Method for applying an extruded seal to a surface

A method for applying a sealant to a surface of an object by an extruder having an annular channel communicating with an annular outlet, comprising the steps of:

• supplying a continuous flow of synthetic plasticised material through the annular channel as far as the annular outlet, said annular channel having a longitudinal axis, said annular outlet being configured so that an outlet direction of the synthetic plasticised material has at least one radial component that is normal to said longitudinal axis;
• continuing to supply said continuous flow, making an annular portion of the synthetic plasticised material exit the annular outlet, with the annular outlet in an open position, by pressurizing the synthetic plasticised material upstream of the annular channel;
• subsequently closing the annular outlet so that said exited annular portion is separated from the synthetic plasticised material that remains inside the annular outlet;
• performing opening and closing cycles of the annular outlet to form at each cycle at least one annular dose;
• separating the annular dose that has exited the annular channel from the rest of the material remaining inside the annular channel;
• depositing the annular dose that has exited the annular channel on the surface, wherein the annular dose that has just exited adheres to the surface and is then separated from plasticized material remaining in the annular channel;
• and
• compression forming the annular dose on the surface to form a seal, wherein in a closing position of said annular outlet,
• an annular plug surface of a tubular wall interacts with an annular plug seat of a core to close said annular outlet forming said annular dose with the synthetic plasticised material that has exited said annular outlet,
• said annular plug surface is in contact with said annular plug seat with a radial width of contact measured in a direction that is normal to said longitudinal axis and that is greater than zero and less than 0.2 mm,
• said tubular wall has an annular internal distal surface that is contiguous with said annular plug surface inside said annular channel and that is spaced away from said core, and
• at least a portion of said annular internal distal surface facing axially in a direction that is parallel to said longitudinal axis toward an internal surface of said core that is contiguous with said annular plug seat within said annular channel to define in said closing position an annular gap that is interposed between said internal distal surface and said internal surface within said annular channel.