Valves and valve actuation – With material guide or restrictor – Movable or resilient guide or restrictor
Patent
1992-12-30
1994-05-17
Hepperle, Stephen M.
Valves and valve actuation
With material guide or restrictor
Movable or resilient guide or restrictor
251120, F16K 4708
Patent
active
053120850
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a control valve used in a fluid transporting pipe line for adjusting the flow rate, and more particularly to a control valve having an opening and closing function in addition to the flow rate adjusting function for a fluid being transported.
BACKGROUND ART
A control valve in the prior art, for example, as shown in FIG. 13, has the problem that, when controlling at a low opening range, i.e., at the lower limit of the valve rangeability, if the flow rate of a fluid is controlled, a valve plug and a valve seat are locally eroded by the cavitation of the fluid occurring owing to a variation of a pressure condition in the front and rear of the valve, and the amount of fluid leakage on the valve closing is increased by the above cavitation, and thus precise control is difficult, consequently, the control valve fails to operate.
Accordingly, various proposals aimed at preventing fluid leakage owing to the occurrence of the cavitation when the valve is closed have been made. Among the above proposals, an example is disclosed in Japanese Unexamined Patent Publication No. 59-34073. The control valve disclosed in the above publication is designed such that a valve plug having two large and small barrels is provided so as to move up and down in relation to an inner hole comprising a small diameter portion adjacent to a valve seat and a vertical wall portion larger than the small diameter portion, and an increased diameter portion, the hole wall of which is formed in a horn-shape spreading downward so that corrosion of the valve plug and the valve seat owing to the occurrence of the cavitation, and fluid leakage on the valve closing are prevented; also, the flow rate control is carried out in the minimum opening portion defined by the circumferential surface of the large barrel portion or the resting portion and the inner hole, according to the movement of the valve plug.
Nevertheless, in such a conventional control valve, since it is necessary to rub the resting portion and the valve seat portion by lapping so that the interface of the above portions is made conformable, there are problems in that machining is troublesome, high precision is required, and the interface is worn because of repeated opening and closing valve operations, and thus the valve fails to close.
Also, although the flow characteristics of the control valve are obtained by changing the minimum opening portion area defined by the inner hole and the valve plug, the flow characteristics corresponding to its design is not easily obtained because the valve plug is cylindrical and the configuration is liable to be subjected to resistance due to the viscosity of the fluid, and thus it is difficult to increase the range ability.
Furthermore, the conventional diaphragm valve generally has a construction as shown in FIG. 14 of the accompanying drawings, there is no dead space in the interior of the valve when the fluid is flowing and the reliability of its fluid-stopping ability is high, and thus many diaphragm valves are used in super pure water pipe lines in the semiconductor industry to prevent the growth of bacteria, in the bio-industry in the field of medicine and cosmetics, and in all kinds of chemical pipe lines. Further, the prior arts concerning the diaphragm valves and the diaphragms themselves used in the above applications are disclosed in Japanese Examined Utility Model Publication No. 2-3026 and 63-37578, etc. Also, as a substitute for the diaphragm valve, "fluororesin bellows for bellows-seal valve" is disclosed in Japanese Examined Utility Model Publication No. 42-21903. These prior arts use superior techniques in that the growth of bacteria can be prevented as stated above and the fluid stopping ability thereof is very reliable.
Nevertheless, with the constitution of the prior art, since no consideration is given to designing the inherent flow characteristics of the valve, a similar percentage of characteristics or linear flow characteristics essential to general automatic control valves
REFERENCES:
patent: 1538207 (1925-05-01), Niedecken
patent: 2685294 (1954-08-01), Gold et al.
patent: 3572629 (1971-03-01), Clark
patent: 4335737 (1982-06-01), Power
patent: 4355784 (1982-10-01), Cain
patent: 4413645 (1983-11-01), Seabase et al.
patent: 4477054 (1984-10-01), Danby et al.
Kuroki Yasunori
Yokoyama Ikuo
Asahi Yukizai Kogyo Co. Ltd.
Hepperle Stephen M.
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