A brake mechanism comprises a belt wheel shaft (1), a large belt wheel (2) and a bracket (3) with a motor (9). The large belt wheel (2) is rotatably connected to the bracket (3) through the belt wheel shaft (1) and is axially fixed, and the large belt wheel (2) is linked with the output end of the motor (9). A brake block (4) and a spring (5) are arranged on the large belt wheel (2). A friction member (6) is arranged on the bracket (3). The brake block (4) is movably connected to the large belt wheel (2) and is capable of moving between separated or contact positions with the friction member (6). The distance between the part, in contact with the friction member (6), of the brake block (4) and the axis (1) of the large belt wheel (2) is greater than that between the part, in contact with the brake block (4), of the friction member (6) and the axis (1) of the large belt wheel (2). The spring (5) produces elastic force for enabling the brake block (4) to get close to the friction member (6). The brake mechanism is controlled by using the centrifugal force, the rotation speed of the motor (9) is stable, the downtime reduction time is stable, the brake force is produced by the brake block (4) after the motor (9) is stopped and the time required by the brake tool is stable, so that the brake process is stable.Linvention porte sur un mécanisme de frein qui comporte un essieu de courroie (1), une grande roue de courroie (2) et un support (3) ayant un moteur (9). La grande roue de courroie (2) est reliée de façon rotative au support (3) par lintermédiaire de lessieu de courroie (1), et est fixée de façon axiale et la grande roue de courroie (2) est reliée à lextrémité de sortie du moteur (9). Un bloc de frein (4) et un ressort (5) sont agencés sur la grande roue de courroie (2). Un élément de frottement (6) est agencé sur le support (3). Le bloc de frein (4) est relié de façon mobile à la grande roue de courroie (2), et peut se déplacer entre des positions séparée ou en con
