Motor vehicle lamp with improved ventilating means

Abstract

A lamp especially suitable for use as a headlamp in a motor vehicle. The lamp includes a lamp housing, a lens sealed to the housing and coacting with the housing to define a sealed chamber, and a lightbulb positioned in the chamber and operative to generate light within the chamber for projection through the lens to a location to be illuminated. The lamp further includes a compensator mechanism which is operative in response to variations in chamber temperature to compensatingly vary the chamber volume whereby to maintain an essentially constant pressure in the chamber irrespective of changes in the chamber temperature resulting from ambient temperature changes or from energization and de-energization of the lightbulb. In one disclosed embodiment the compensator mechanism comprises a bellows positioned exteriorally of the chamber and a conduit interconnecting the bellows and the chamber. In another disclosed embodiment the compensator mechanism comprises a collapsible bag positioned in the sealed chamber and vented to atmosphere so that the bag may expand and contract in response to temperature variations. Maintaining a substantially constant pressure in the sealed chamber prolongs the life of the seal between the lamp housing and the reflector and thereby prolongs the useful life of the lamp.