adding time signatures on every line

Hi there,
I would like to create a score with exercices. Each line would be a new exercice and therefore I would like to put the time signatures at he beginning of every line. But when I do, it automatically puts it also at the end of the previous line, after the final barline.
I already divided the entire score in systems of 4 measures but it doesn't help.
Does someone have an ide how I could do that?
Thanks in advance for your help.