Abstract: A vacuum bulb is provided, including a sealed chamber; two electrical contacts, which move relative to one another, the chamber including a cylindrical body of a dielectric material and closed at ends thereof by two metal covers, each of the two metal covers being connected to one of the two electrical contacts: and a dielectric coating, which covers an outer surface of the chamber, and includes at least two layers, including an overmolding layer of a synthetic material and an intermediate layer of silicone, the intermediate layer being interposed between the outer surface and the overmolding layer, the intermediate layer being discontinuous and localized on metal portions of the chamber so as to cover at least partially an outer surface of the metal portions, and the silicone includes compressible hollow bodies having a skin of a thermoplastic material.

Abstract: The invention relates to a vacuum bulb (1) including a sealed chamber (4), two electrical contacts (7, 7?) and a dielectric coating (12) which covers the outer surface of the chamber (4). This coating (12) includes at least two layers, an overmoulding layer (14) made of a synthetic material and an intermediate layer (13) made of silicone interposed between the outer surface of the chamber (4) and the overmoulding layer (14). According to the invention, the intermediate layer (13) is discontinuous and localised on the metal portions of the chamber (4) so as to cover at least partially the outer surface of the metal portions, where the silicone of the intermediate layer (13) includes hollow bodies, where these hollow bodies are compressible, and have a skin made of a thermoplastic material. The invention also relates to a switchgear including at least one such vacuum bulb (1), in particular a circuit-breaker pole.