Device and method for tightening a safety belt serving to protect occupants in a vehicle

A belt brake for a safety belt serving to protect occupants in a vehicle, which belt can be wound onto and from a belt drum mounted rotationally about a belt shaft, comprising:

• at least one braking means displaceably mounted longitudinally to the belt shaft, connected to the belt shaft in a rotationally fixed manner and located between a first and a second thrust bearing;
• means, connected to at least the first thrust bearing, for forcibly guiding the first thrust bearing along the belt shaft in response to a winding or an unwinding of the safety belt onto or from the belt drum, to transfer the first thrust bearing from a first position at which the safety belt is wound onto the belt drum and at which an axial distance a1 exists between the braking means and at least one of the first and second thrust bearings, to a second position at which the safety belt is at least partially unwound from the belt drum and at which an axial distance a2 exists between the braking means and the at least one thrust bearing, with a2<a1;
• and
• at least one actuator element which, when actuated in the second position, produces a braking force which acts longitudinally on the belt shaft between the first and second thrust bearings and which is directed towards the at least one braking means.