A diaphragm pump, especially a vacuum pump, in which a diaphragm of elastomeric material is clamped at its outer peripheral portion against a peripheral portion of a rigid wall which has, radially inwardly of the clamped portion, a concavely curved spherical surface forming with the diaphragm a pumping...http://www.google.com.au/patents/US3947156?utm_source=gb-gplus-sharePatent US3947156 - Diaphragm pump, particularly for the generation of vacuum
