Pumping apparatus

Claim 1

A single entry centrifugal impeller pump comprising, a volute casing having axial end walls with an inlet orifice in one axial end wall, a peripheral outlet, and a gas exhaust passage in the other end wall; an impeller having an impeller disc mounted for rotation with its rear face adjacent said other axial end wall of the volute casing, and a plurality of impeller blades extending from the front face of the impeller to define an eye of the impeller in communication with said inlet orifice of the volute casing; a liquid reservoir chamber located above and in communication with said gas exhaust passage of the volute casing, said chamber having a first outlet for connection to a gas exhaust means and a second outlet communicating with atmosphere; a float valve mechanism located in said reservoir chamber and having first and second valve members arranged, upon raising of the float within said chamber, respectively to close said first outlet and to open said second outlet; means for discharging liquid from said reservoir chamber to the front side of said impeller when said reservoir chamber is at atmospheric pressure; and means for delaying movement of said float valve mechanism to open said first outlet and close said second outlet in response to a fall of liquid level in said reservoir chamber; said means for delaying movement of said float valve mechanism comprising an air reservoir having an air bleed orifice communicating with said float chamber, and a balancing member coupled to said float valve mechanism and exposed on the one hand to the fluid pressure prevailing upstream of said first outlet and on the other hand to the fluid pressure prevailing in said air reservoir.