Control valves

A valve for controlling fluid flow, comprising

• a hollow body having a flow passage for the fluid;
• a sealing member formed of flexible polymeric material and consisting essentially of a generally radially resilient tubular portion encircled by at least one radially extending flange, the sealing member being supported within the hollow body by said radially extending flange;
• a movable spindle comprising means for occluding the flow passage during operation of the valve and a stem connected to or integral with the occluding means, the spindle passing through the tubular portion of the sealing member with the exterior surface of the spindle adjacent to the interior surface of the tubular portion;
• and
• means for defining at least one generally radially rigid annular ridge extending from one of said adjacent surfaces to contact the other and positioned so that at least during normal operation of the valve it remains displaced axially along said sealing member from the plane of each of said at least one radially extending flange, said ridge being oversized in that it stands proud from the surface from which it extends by an amount greater than the difference between the diameters of said two adjacent surfaces as measured before assembly of the valve, so that in the assembled valve the annular region of said tubular portion overlying said annular ridge, and said annular ridge, and the surface which said annular ridge contacts, are biased together by resilient radial distension of said tubular portion, thereby to provide a gland seal against loss of the fluid from the valve body.