Flow-regulating device for perfusion-transfusion apparatus

A system of flow-rate regulation for perfusers-transfusers commonly known as visual apparatus, comprising a chamber of transparent synthetic material having an upper portion provided with a perforator for admission of liquid into said chamber, a fixed central tube in said chamber, said tube having an upper inlet for fluid and a lower outlet for the fluid, a cylindrical sleeve surrounding said tube, float means operatively associated with said sleeve and tube for producing closure of said upper inlet of said tube when liquid in said chamber drops below a predetermined level, said sleeve and tube defining an annular passage therebetween, said sleeve having an open lower end through which liquid is admitted and flows upwardly through said annular passage and then downwardly through said upper inlet in said tube with the latter open when the liquid in the chamber is above said predetermined level as detected by said float means, said cylindrical sleeve being freely slidable on said fixed central tube and including a flexible diaphragm which closes said upper inlet of said tube when the liquid in the chamber drops below said predetermined level and said sleeve having an upper end with a cavity located above said flexible diaphragm.