Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1996-09-13
1998-06-23
Ferensic, Denise L.
Fluid handling
Line condition change responsive valves
Direct response valves
1375274, 137527, F16K 2110
Patent
active
057691169
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a water-hammer-preventive (or "non-water-hammering") check valve placed in a pipeline and capable of safely and reliably preventing water hammer due to the reverse flow of water in the pipeline resulting from a sudden stop of energy supply to a pump during a pumping operation. In this specification, the term "water" is used in its broad sense to denote any kind of fluids, and the terms "upstream", "downstream", "inlet" and "outlet" refer to directions and positions based on the normal flow (not the reverse flow) of a fluid.
BACKGROUND ART
When the action of a check valve placed in a pipeline is unable to follow a sudden change in the flow velocity of a fluid flowing through the pipeline and the valve element of the check valve is seated on a valve seat during the reverse flow of the fluid, water hammer occurs on the downstream side of the check valve sometimes causing serious troubles. Inventions that provide water-hammer-preventive check valves are disclosed in, for example, JP-B Nos. 40-3654, "Water-Hammer-Preventive Pumping Apparatus", 51-25930, "Improvements in Water-Hammer-Preventive Pumping Apparatus", and 63-60274, "Swing Type Water-Hammer-Preventive Check Valve". These inventions will be inclusively designated as "prior inventions". As is generally known, these prior inventions have been widely used. The present invention relates to improvements in the water-hammer-preventive check valves of the prior inventions.
The water-hammer-preventive check valves of the prior inventions were based on a clear technical idea surpassing a hitherto prevalent technical idea of preventing water hammer (symptomatic means using a control means that permits a valve element to be seated on a valve seat when a reverse flow acts on the valve element due to a delay in the valve closing movement and slows the movement of the valve element or using an automatic valve or a surge tank that avoids or buffers pressure rise due to water hammer). More concretely, it is readily inferred from the description in the specifications of the prior inventions that the prior inventions incorporate radical improvements including designing a valve element and the shapes of flow passages around the valve element so that a valve element is seated on a valve seat upon the stoppage of the flow of water flowing in a discharge direction in the line after the exhaustion of the inertia of water after power supply to a pump has been stopped to prevent the reverse flow of water and to remove causes of water hammer positively. A water-hammer-preventive check valve of the prior invention shown in FIG. 8 is constructed to eliminate as many factors that impede the closing motion of a valve element as possible and to enable a valve element to move down by its own weight for a proper closing motion. This water-hammer-preventive check valve corrects some errors, if any, by the action of a weight, a spring or the like and achieves substantially satisfactorily an object of preventing water hammer.
However, persons skilled in the art have been encountered by the following technical problems when carrying out the fundamental techniques of the water-hammer-preventive check valve of the prior inventions. to a valve element to form a single link, the valve element is unable to be seated closely on a valve seat unless parts are formed with high accuracy. when the valve element and an arm member are fabricated simply in two separate links and the arm member is connected to a valve casing, i.e., when the valve element is connected simply to an arm member with a necessary clearance therebetween and the arm member is connected to a valve casing, another problem arises; that is, an end portion of the valve element on the upstream side comes into contact with the valve seat first obliquely sliding along the valve seat due to the flapping of the valve element and, sometimes, the end portion scratches on the valve seat to obstruct the smooth movement of the valve element (such a mode of movement of the valve element wil
REFERENCES:
patent: 945151 (1910-01-01), Blauvelt
patent: 1871536 (1932-08-01), Le Bus
patent: 3098502 (1963-07-01), Deve
patent: 3106220 (1963-10-01), Hose
patent: 3283772 (1966-11-01), Ensign
patent: 3996962 (1976-12-01), Sutherland
patent: 4601309 (1986-07-01), Chang
patent: 5145005 (1992-09-01), Dollison
patent: 5261449 (1993-11-01), Smetters
Yokota Hiroshi
Yokota Shingo
Ferensic Denise L.
Hiroshi Yokota
Kabushiki Kaisha Yokota Seisakusho
Kim Joanne Y.
Shingo Yokota
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