The present invention relates to a structure for fitting a valve seat support ring in a valve port of a valve where the valve port is opened and closed by turning a semi-spherical valve disc.
FIG. 4 illustrates a known valve, in which the numerals 1, 2, 3 and 4 indicate a valve housing, a valve port, a valve stem and a semi-spherical valve disc respectively. Into the left port 2 in FIG. 4, a valve seat holder 5, an annular valve seat 6 and an annular compression spring 7 are inserted in order. By screwing a valve seat support ring 8 into the port 2, the valve seat 6 is forced against the valve disc 4. The numeral 9 indicates a thread, and the numeral 10 indicates a recess on which a tool for screwing the support ring 8 into the port 2 is put.
FIGS. 5 and 6 illustrate another example of a known support ring fitting structure in which the same numerals identify the same members as those in the above example. In this structure, instead of the above thread 9 and recess 10, there are provided a groove 12 and a hole 13 opposite to each other on the inner surface of the port 2 and outer surface of the support ring 11 which is fitted in the port 2 in axially slidable state. Also, on the side end of the support ring 11, there are a plurality of threaded bores 12 axially arranged and communicating with the hole 13.
A ball 15 is inserted into the hole 13, and the support ring 11 is inserted into the port 2. Then, a screw 16 is screwed into each bore 14, which makes the ball 15 pushed out of the hole 13 to insert it into the groove 12, whereby the ring 11 is fitted in the port 2.
However, in the valve as shown in FIG. 4, for long use of the valve, the threaded portion is subject to corrosion and to deposition of substance in fluid, which causes difficulty in removal of the support ring. Further, manufacturing is troublesome and costly, and it requires special tools to assemble and disassemble it.
The ball-having structure in FIGS. 5 and 6 is easy in manufacturing, assembling and disassembling, but the ball is likely to be lost when disassembled. Also, the valve has to be made of special material depending upon use, but it is difficult to obtain a ball made of such material.