Valve arrangement especially suitable for preventing introduction of air into vascular systems

An intravenous system comprising a source of intravenous fluid, first catheter means for insertion into the vascular system of a patient, a pump for pumping fluid from said source to said catheter means, second catheter means coupling said pump to said source, said pump including means to terminate said pumping operation upon an opening of one of said catheter means to ambient atmosphere, and flow control means in at least said first catheter means for preventing movement of air therethrough, said flow control means comprising a body provided with an input chamber and an output chamber and further provided with respective orifices respectively coupled to said chambers, and a resilient means associated with said body and adapted for defining with said body a connecting channel between said orifices, but normally being configured to obturate the orifice coupled to the output chamber thereby to obturate the latter said orifice and such that a relative pressure in the output chamber will tend to strengthen the obturating of the latter said orifice whereas a relative positive pressure in the input chamber will tend to open the latter said orifice, said resilient means encircling said body and defining therewith the connecting channel in the form of an annular space, said body being configured to define an annular groove bracketed by shoulders, said resilient means being a tube of resilient material supported on and extending between said shoulders, said control further comprising spring means to urge the tube into the annular groove yieldingly against the orifice coupled to the output chamber without obstructing the orifice coupled to the input chamber so that fluid may pass into the annular groove from the orifice coupled to the input chamber before meeting resistance from said tube.