Diaphragm pump with compensation means in the hydraulic control chamber

Claim 1

Hydraulically controlled diaphragm pump, comprising a pumping chamber of variable volume of which one wall is constituted by a deformable diaphragm, an intermediate chamber filled with fluid, defined by a fixed enclosure of which one longitudinal end wall is constituted by the said diaphragm whereas another wall is constituted by a piston mounted for sliding inside the said enclosure and adapted to be actuated with a reciprocating movement inside the said enclosure, of pre-determined stroke and frequency, adjustable in relation to the rate of flow required for the pump, a conduit for re-filling the said intermediate chamber connected to a reservoir of fluid, and a controlled member for opening and closing said conduit; according to one of the main features of the invention, the said controlled member is constituted by a valve which cooperates with a fixed seat through which the said conduit reaches into the said intermediate chamber, and which is mounted for sliding on a mobile train comprising a slide rod for said valve, said rod being also mounted for sliding longitudinally inside a support integral with the enclosure of the said intermediate chamber and traversing the said seat, a shoulder integral with the said rod forming a priming means for the valve and a means to hold it on its seat, and an actuating surface integral with the said rod and situated opposite to the said shoulder with respect to the said seat, on which surface the diaphragm can rest in its back position, the said mobile train being returned towards the said membrane in its conduit-closing position, by way of a spring coupled between the said support and the said mobile train, wherein the said rod traverses the said seat, the said element being constituted by an end shoulder of the rod.