Abstract: The invention relates to a constant force pyrotechnic actuator comprising a pyrotechnic gas generator, a body, a piston capable of moving in the said body under the effect of the gases emitted by the generator, and a pressure regulator member situated inside the piston, the said piston having a front face traversed by a duct making it possible to place in communication the space separating the gas generator and the said piston, and an inner space in which the regulator member is housed. Within said actuator, the piston is extended by a hollow push rod terminating in an enlarged head, the said head having gas discharge ducts, and the inner space of the said rod is in communication with the inner space of the piston in which the regulator member is housed.