Flow change-over valve for the blowing of fluids into molten metal vessel

Claim 1

A flow change-over valve for the blowing of fluids into a molten metal vessel comprising a housing provided with an inner body supporting space, an outlet port and at least three inlet ports for different fluids, said at least three inlet ports comprise first, second and third inlet ports, a spherical valve body hermetically fitted into said supporting space, said valve body having upper and lower extension portions disposed axially with respect to said outlet port, said valve body rotatably supported in the housing to perform a changing-over of said inlet passages and provided therein with a main passage communicating with said outlet port and selectively communicating between a respective one of said first, second or third inlet ports, said main passage extending through the upper extension portion of the valve body for communication with the outlet port, said main passage further defining an inlet opening in said valve body for communication with a respective one of said first, second or third inlet ports, and an outlet opening which defines the outlet port, said third inlet port being a purging fluid inlet arranged to communicate with said inlet opening so as to provide a purge fluid flow through said main passage to the outlet port during each rotation of the valve body when changing-over from said first inlet port to said second inlet port and vice versa, hermetic sealing means providing a sealed fluid passage, respectively, between each of said first and second inlet ports and the inlet opening of said valve body, and means for pushing said hermetic sealing means against the valve body so as to prevent leakage, said housing being provided with a shroud-like gap surrounding the valve body, said gap being in communication with the inner periphery of the housing, said gap being in communication with said third inlet port for purging fluid and the inlet opening of said main passage to provide a purge fluid flow when the valve body changes-over from said first inlet port to said second inlet port so as to provide a purge fluid flow through said main passage, and vice versa, to prevent any mixing of different fluids flowing through said first and second inlet ports, the lower extension portion of the valve body being provided with a purge fluid passage for communicating with a second purge fluid inlet, said purge fluid passage extending within said purge fluid passage extending within said lower extension portion to said spherical valve body, said passage communication with said main passage interiorly of said spherical valve body so as to direct purging fluid toward said outlet port, said housing including a purge fluid connection wherein both said purge fluid inlet and said second purge fluid inlet communicate with said purge fluid connection.