filling chamber 12 by means of corresponding ducts 11 the individual ducts are coupled to each other by means of a ring duct 20 which can be formed by the filling chamber 12 the service fluid in particular oil or in the case of water clutches water can be admitted without pressure or also with pressure in an especially advantageous development the solution according to the invention of filling the core chamber 6 is applied in a hydrodynamic clutch 2 with a closed circuit 21 this closed circuit 21 comprises the working fluid circulation 22 setting up in the torus shaped working chamber 5 and an external part 23 outside of the working chamber 5 which is only connected with the inlet 10 in the torus shaped working chamber 5 and at least one outlet 24 after discharge from the torus shaped working chamber 5 the closed circuit 21 is designed to be pressure sealed and as illustrated in fig2 is alternatively coupleable by means of a junction 25 with resources 26 for filling and or evacuation and resources 27 for generating an influencing pressure factor for the pressure in the closed circuit 21 the hydrodynamic clutch 2 comprises for this purpose a casing 28 allocated to the primary blade wheel 3 which is locked with the primary blade wheel 3 and sealed from the secondary blade wheel 4 by means of a first device for sealing 29 and to a resting case 30 by means of a second device for sealing 31 to achieve a pressure sealed tight closed circuit 21 it.