Adjusting device for a vehicle seat with a spindle and an associated spindle nut

The adjusting device (24) has first and second adjusting elements (20, 22), a spindle (26) and a plastic spindle nut (30) round the spindle. The spindle cannot rotate relative to the first adjusting element. The spindle nut can rotate in the second one. Its outer jacket forms a wormwheel engaged with a worm (32) connected to a rotating drive (36).