VALVE CASING FOR USE IN A BUTTERFLY VALVE

摘要

This invention is intended to solve the problem that a valve casing for use in a butterfly valve formed by press working, which is advantageous from the standpoint of productivity, thickness and weight, has a serious disadvantages such as breakage or deformation, lowering in sealing performance: due to releasing of the seal ring with ageing when the valve is mounted on pipe line and clamped from both sides. A valve casing according to this invention has a double structure composed of an inner shell and an outer shell. The inner shell comprises a cylindrical part defining a bore- and seal-ring receiving portions formed on both ends with diameters larger than the cylindrical part, substantially forming a S-shape in section. The outer shell surrounds the inner shell to define a space. The inner shell and the outer shell are attached to each other at both ends of the valve casing.