Patent ID: 6158679
Filing Date: 2000-12-12
Classification: G01F,G05D

Abstract:
An orifice for a pressure-type flow rate controller wherein the fluid flow rate Q on a downstream side of the orifice is calculated according to the equation Q=KP1 where K=a constant and P1=a pressure on an upstream side of the orifice with the ratio P2/P1 of pressure P2 on the downstream side of the orifice to the pressure P1 on said upstream side kept below a critical pressure ratio and wherein a means determines the difference between the calculated flow rate Q and a set flow rate Qs and actuates a control valve on the upstream side of said orifice so as to regulate the upstream pressure P1 for bringing the downstream flow rate to said set flow rate, said orifice comprising:a stainless steel plate about 2 to 3 mm in thickness said plate having an inlet taper on an inlet side thereof in the shape of a bugle and a short narrowed straight section adjoining the inlet taper formed by cutting an upstream opening end of a preliminary hole made in said plate;a short inner taper adjoining said narrowed straight section and an enlarged straight section adjoining the short inner taper formed by enlarging a second opening end of the preliminary hole; and,said plate having, on an outlet side thereof, an outlet hole extending toward said enlarged straight section, said outlet hole having a wall which converges toward said enlarged straight section.