A multi-stage type flow rate switching device is provided which simplifies switching of flow paths and which rarely causes erroneous operation. The multi-stage type flow rate switching device includes a constant flow rate path 2 and a variable flow rate path 3 arranged in parallel between a liquid medicine...http://www.google.es/patents/US5927326?utm_source=gb-gplus-sharePatente US5927326 - Multi stage type flow rate switching device
