Synchronizing device for a planet gear

Synchronising arrangement in a planetary gear (1), including an axially movable ring gear (22), two coupling rings (9,16) which are each situated on their respective side of the planetary gear (1) and with which the ring gear (22) may alternatively be coupled for various gear positions, and at least two synchronising rings (14,20), at least one of them being between each coupling ring and the planetary gear, which synchronising rings are not only rotatable in a limited manner relative to the ring gear (22) but also have external locking teeth (30,31) which during gearchange movement lock the ring gear's axial movement and connection to the respective coupling ring (9,16) before synchronous rotation is achieved, and the ring gear (22) has at its ends internally arranged locking devices (28) for transfer of axial force from the ring gear to the respective synchronising ring so as, during gear changing, to cause contact between friction surfaces on the respective synchronising ring and coupling ring, characterised in that the ring gear (22) has two grooves (26,27) running round its inside, one at each end of the ring gear, that a substantially annular locking device (28) capable of being compressed in the radial direction is arranged in each groove (26,27) and that a groove (32,33) which runs round the outside and is intended for such a locking device (28), and in which the locking device can move when the ring gear (22) moves, is arranged in the respective synchronising ring (14,20).