damaged in the rotary sealing movement 32 a during the sealing process the sealing shafts 70 a must be driven at an angular velocity such that the tangential velocity of the sealing surfaces 30 a corresponds to the velocity of the film tube 18 a in the transport direction 16 a in particular at high velocities of the film tube 18 a this leads to high angular velocities of the sealing shafts 70 a and thus to very short contact times of the sealing surfaces 30 a with the film tube 18 a and short sealing times as a result of the displacement movement 38 a the sealing shafts 70 a can be driven during the sealing process at a lower angular velocity the movement component 34 a in the transport direction 16 a has a lower velocity than the movement of the film tube 18 a in the transport direction 16 a a velocity difference is compensated during the sealing process by the displacement movement 38 a the thereby enabled lower angular velocity of the sealing shafts 70 a during the sealing process leads to a longer contact time of the sealing surfaces 30 a with the film tube 18 a and longer sealing times in particular the sealing time can be adjusted within the limits defined in particular by a maximum deflection 52 a a maximum acceleration and a maximum velocity of the displacement movement 38 a independently of the velocity of the film tube 18 a in the transport direction 16 a the sealing time is here defined by the contact time of the sealing surfaces 30 a with the film tube 18 a and thus by the angular velocity of the sealing shafts 70 a during the sealing process a velocity difference between the resulting.