The partial vacuum generated in a vacuum chamber by a suction pump via an air aspirating line and a hose can be changed by admitting leakage air through an air supply line. The supplied amount of leakage air is determined by a relative movement of a regulating groove and a leakage groove in respect to...http://www.google.de/patents/US6290671?utm_source=gb-gplus-sharePatent US6290671 - Regulating device for a breast pump
