Flow measuring device for liquids bearing entrained solids

Claim 1

A flow measuring device comprising a flow tube having sequentially disposed inlet, converging and throat sections, wherein said inlet and throat sections each have substantially uniform diameters, and first and second pressure sensing means communicating with said inlet and throat sections, respectively, for sensing the pressures therein, at least one of said first and second pressure sensing means comprising a tubular housing portion which is mounted on said flow tube so that it communicates with the interior thereof, a pressure sensing diaphragm element received in said housing portion so that it communicates with the interior of said flow tube for sensing the pressure in the adjacent section thereof, said housing portion and said diaphragm element being constructed so that said diphragm element is slidable in sealed relation in said housing portion between a first position wherein it is disposed adjacent said flow tube and a second position wherein it is spaced outwardly therefrom, and means receivable in said housing portion when said diaphragm element is in the second position thereof for providing a sealed obstruction between said diaphragm element and said flow tube, said housing having a pressure tap therein, said pressure tap being positioned between said obstruction means and said diaphragm element when said diaphragm element is in the second position thereof so that when said obstruction means is withdrawn from said housing portion said pressure tap communicates with the interior of said flow tube through said housing portion.