Hi Nico,
I haven't tried this out, so I can't guarantee this to work, but you could specify a Timer that goes off every 7.2 seconds. Additionally, you'd create a process that runs on the triggering event with the name of that Timer. This process Assigns a new value of 1 to Schranke1...Schranke6.CurrentCapacity. I'm unsure whether a delay is required for the entities to move through the system, but I'd try adding a Delay of Math.Epsilon after this Assign step, to ensure they do. Then, with a new Assign step, change the CurrentCapacity of Schranke 1 through 6 back to 0.
You may have to change the Initial capacity of all your gates to 0 in the Facility window. Also, make sure you change the Off Shift Rule to finish work that has already started, on all your gates.
Hope this works.
Tom