I tried this:
th = link_to "ID", results_path(sort: "id", search_form: @search_form)
to return the instance @search_form to the controller "results", but that returns a nil variable, but I have to point out that the sort variable accessed on the controller in this way params[:sort] has the correct value, so the path works.
So now I have to return every single attribute by its own and this is the solution that works
th = link_to "ID",
                      :sort => "id",
                      :verweildauer => @search_form.verweildauer,
                      :datenjahr => @search_form.datenjahr,
                      :drgsystem => @search_form.drgsystem,
                      :greatersmallerequal => @search_form.greatersmallerequal,
                      :patients_per_page => @search_form.patients_per_page
then I have to rebuild the object on the controller accessing every single attribute.
How can I directly pass in the @search_form into the controller?
 
    