repeat refresh safari use applescript

gistfile1.txt

#!/usr/bin/osascript

tell application "System Events"
  repeat
    if exists process "Safari" then
      tell application "Safari"
        activate
        end tell
        tell process "Safari"
        keystroke "r" using {command down}
      end tell
      delay 60
    else
      exit repeat
    end if
  end repeat
end tell