In a suction control unit used with an endoscope having a channel, a tubular main body has a suction port in the side wall and a bore and in the bore, an inner tube with a through hole communicating with the channel of the endoscope is installed. A sliding tube is located slidably in the axial direction...http://www.google.co.uk/patents/US4794913?utm_source=gb-gplus-sharePatent US4794913 - Suction control unit for an endoscope
