Abstract: On a belt retractor for vehicular seat belt restraining systems having a vehicle and belt sensitive automatic blocking mechanism (26) for the belt reel (12) rotatably mounted in the housing (10) the pawl tooth of a locking pawl (18) first coming into contact with the locking toothing (16) is formed as the control tooth (181). A control link (22) of the locking pawl (18) exhibits a radial stroke which is dimensioned so that the locking pawl (18) is swivelled by the control cam (24) up to first contact of the control tooth (181) with a tooth flank of the locking toothing (16) past which it is further swivelled unsubstantially at the most. After initial contact of the control tooth (181) with a tooth flank of the locking toothing (16) a torque is exerted by rotation of the belt reel on the locking pawl (18) as a result of which the locking pawl (18) is forced to swivel up to positive interlock of the pawl teeth (182, 183) with the locking toothing (16).

Abstract: The piston of a piston/cylinder unit of a belt pretensioner with a pyrotechnic gas generator is characterized in that the piston is made from a first metallic piston part (12) which is firmly connected with the cable (16) and at least one second piston part (14) made of a thermoplastic material, at least one section of which is arranged on the side of the first piston part (12) facing the gas generator and forms a sealing contact with the walls of the cylinder. This arrangement creates the constructional prerequisites for further advantageous developments of the piston as regards the safety of the belt pretensioner. In particular, the piston can be equipped with a sealing lip which releases itself from the inner walls of the cylinder of the piston/cylinder unit when the unit is heated, e.g. in a vehicle fire, and so offers an escape path for the gases in order to avoid the danger of explosion.