An orifice meter comprising a gate valve type of body with an oval body band clamped between a pair of parallel plates. A gate-like carrier slides between the plates and carries an orifice disc with seal ring surrounding it. The seal rings seal around the flow passage and the orifice disc is large enough...http://www.google.fr/patents/US4370893?utm_source=gb-gplus-shareBrevet US4370893 - Orifice meter with replacable orifice disc
